Gallium monoiodide: Difference between revisions

Gallium monoiodide
Identifiers
CAS Number	15605-68-2;
3D model (JSmol)	Interactive image;
ChemSpider	9138803;
PubChem CID	10963591;
	InChI InChI=1S/Ga.HI/h;1H/q+1;/p-1 Key: LRPWSMQGXLANTG-UHFFFAOYSA-M;
	SMILES [Ga]I;
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

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Gallium monoiodide is an inorganic gallium compound with the formula GaI or Ga₄I₄. It is a pale green solid and mixed valent gallium compound, which can contain gallium in the 0, +1, +2, and +3 oxidation states. It is used as a pathway for many gallium-based products. Unlike the gallium(I) halides first crystallographically characterized,^[1] gallium monoiodide has a more facile synthesis allowing a synthetic route to many low-valent gallium compounds.

Synthesis

In 1990, Malcolm Green synthesized gallium monoiodide by the ultrasonication of liquid gallium metal with iodine in toluene yielding a pale green powder referred to as gallium monoiodide.^[2] The chemical composition of gallium monoiodide was not determined until the early to mid-2010s despite its simple synthesis.

In 2012, the pale green gallium monoiodide was determined to be a combination of gallium metal and gallium(I,III) iodide, having the chemical composition [Ga⁰]₂[Ga⁺][GaI₄⁻].^[3] However, in 2014, it was found that the incomplete reaction of gallium metal with iodine yielded gallium monoiodide with this chemical composition. Gallium monoiodide synthesized with longer reaction times for complete reaction had a different chemical composition [Ga⁰]₂[Ga⁺]₂[Ga₂I₆^2-].^[4]

The resultant gallium monoiodide is highly air sensitive, but stable under inert atmosphere conditions for up to a year at -35 ˚C.^[4]

Characterization

When gallium monoiodide was first produced, it was proposed that gallium monoiodide is a combination of gallium metal, Ga₂I₃ and Ga₂I₄ based on the characteristic Raman spectra of these constituents.^[5] This hypothesis was confirmed as two variants of gallium monoiodide were determined to have the chemical compositions [Ga⁰]₂[Ga⁺][GaI₄⁻], simplified as Ga₂I₄·2Ga, and [Ga⁰]₂[Ga⁺]₂[Ga₂I₆^2-], simplified as Ga₂I₃·Ga.^[4]^[3]

When the incompletely reacted product was probed by NMR spectroscopy, it showed the presence of liquid gallium metal rather than solid gallium metal.^[3] When probed by ¹²⁷I NQR,^[4] it showed the presence of Ga₂I₄ and further confirms the [Ga⁰]₂[Ga⁺][GaI₄⁻] assignment.^[6] Raman spectroscopy has also confirmed this composition assignment.^[4]^[7] All of the evidence from other spectroscopic methods, and power x-ray diffraction patterns, validates the assignment of [Ga⁰]₂[Ga⁺][GaI₄⁻] for the incompletely reacted gallium monoiodide variant.

When the completely reacted product was probed by ¹²⁷I NQR, it showed the presence of Ga₂I₃.^[4] Raman spectroscopy has also confirmed this assignment, as it aligned with those from a Ga₄I₆ reference.^[4]^[7] Finally, power x-ray diffraction supports that this gallium monoiodide variant matches that of characteristic Ga₂I_3, which is different from that of GaI₂.^[4]

[Ga⁰]₂[Ga⁺][GaI₄⁻] converts to [Ga⁰]₂[Ga⁺]₂[Ga₂I₆^2-] over time.^[4]

Reactivity

The fact that two different gallium monoiodide variants can be accessed provides some insight into how such a wide range of reactivities can be accessed.

Gallium monoiodide is used as a precursor for a variety of reactions. Early-on, gallium monoiodide was shown to produce alkylgallium diiodides via oxidative addition by reacting liquid gallium metal and iodine in the presence of an alkyl iodide.^[1]^[2]^[8] Since then, other organogallium complexes have been synthesized, as well as Lewis base adducts and gallium based clusters.^[8]

Gallium Lewis base adducts

Gallium monoiodide reacts with various monodentate Lewis bases to form Ga(II), Ga(III), or mixed valent compounds, as well as gallium-based dimers and trimers. For example, gallium monoiodide can react with primary, secondary, and tertiary amines, secondary or tertiary phosphines or ethers to form Ga(II)-Ga(II) dimers.^[2]^[8]^[10] Gallium monoiodide can also react with triphenylphosphine (PPh₃) to form Ga(III)I₃PPh₃.^[2] It also reacts with the less sterically hindered triethylphosphine (PEt₃) to form a Ga(II)-Ga(I)-Ga(II) mixed valent complex with datively coordinated PEt₃ ligands.^[8]^[10] These reacts are believed to be a disproportionation, as gallium metal is produced in these reactions.^[9]

Gallium monoiodide reacts with triphenylstibine to produce an SbPh₃ fragment datively bonded to a GaPhI₂ fragment.^[11] The difference in reactivity between PPh₃ and SbPh₃, a heavy atom analogue of PPh₃, can be attributed to a weaker Sb-C bond, allowing for transfer of a phenyl group from antimony to gallium. This suggests that gallium monoiodide can be used as a reducing agent as well.^[8]^[11]

N-heterocyclic carbenes reacts with gallium monoiodide, it forms a complex with a sterically hindered isopropyl ligand.^[9] However, gallium monoiodide reacts with diazabutadienes and subsequent reduction by potassium metal to form Ga analogs of N-heterocyclic carbenes.^[8] Other Ga-based carbenes can be produced from gallium monoiodide precursor using Li(NacNac).^[8]

Gallium monoiodide reacts with multidentate Lewis bases, such as bipyridine, phenyl-terpyridine, and bis(imino)pyridine ligands to form Ga(III) complexes.^[8]^[12] Crystallographically, the bipyridine derivative has a distorted octahedral geometry, with a Ga–N bond length of 2.063 Å. The phenyl-terpyridine derivative adopts a distorted trigonal bipyramidal geometry where the two equatorial Ga–N bonds (as drawn) are longer than the axial Ga-N bond, with 2.104 Å and 2.007(5) Å, respectively. The average Ga-N bond length (2.071 Å) is similar to that of a neutral GaCl₃(terpy) Lewis base adduct (2.086 Å).^[13] The bis(imino)pyridine derivative has a distorted square-based pyramidal geometry. Like for the phenyl-terpyridine derivative, the equatorial imino Ga-N bonds (2.203 Å) are longer than the axial pyridyl Ga-N bond (2.014(7) A˚).^[12] Despite these similar reactivities and bond characteristics, when gallium monoiodide was reacted with imino-substituted pyridines (RN=C(H)Py), unique reactivity was observed. Reductive coupling of the imino-substituted pyridines formed diamido-digallium(III) complexes.^[12] These reactions display the ability of gallium monoiodides to form new C-C bonds.

Gallium heterocycles

Gallium monoiodide can also be used as a precursor to form gallium-based heterocycles. Reactions with diazabutadienes, {RN=C(H)}₂, can form monomers or dimers based on the substituents on the diazabutadienes. More sterically hindered substituents such as Bu^t have resulted in the formation of Ga(II) dimers, whereas reactions with alkyl or aryl substituted diazabutadienes have formed Ga(III) monomers.^[8] Two equivalents of gallium monoiodide can be reacted with phenyl-substituted 1,4-diazabuta-1,3-dienes to form a Ga heterocycle with a diazabutadiene monoanion.^[14] EPR spectroscopy has revealed that the diazabutadiene fragment is a paramagnetic monoanionic species rather than an ene-diamido dianion or a neutral ligand.^[14] Thus, gallium monoiodide undergoes a disproportionation reaction to form a Ga(III) complex with deposition of a Ga(0) metal.^[8]^[14] Upon further reaction with a 1,4-dilithiated diazabutadiene, this Ga heterocycle forms a new complex with the diazabutadiene monoanion fragment datively bonded (Ga-N bond lengths 1.9678(13) Å) to the Ga center and an ene-diamido dianion covalently bonded (Ga-N bond lengths 1.8831(13) Å) to the Ga center.^[14] The geometry about the Ga center suggests that the electrons in the two diazabutadiene systems do not delocalize across the entire complex.

One very important reactivity of this Ga(III) heterocycle is its ability to access gallium analogues of N-heterocyclic carbenes upon reduction with potassium metal.^[15] Although a gallium analogue of N-heterocyclic carbenes had been synthesized previously,^[16] having access to heavier analogues of N-heterocylic carbenes from a synthetically more facile gallium monoiodide route has opened new avenues in coordination chemistry, such as access to new Ga-M bonds.^[17]^[18]^[19]

Gallium monoiodide can also be used to access six-membered Ga(I) heterocycles that have parallels to gallium analogues of N-heterocyclic carbenes. These neutral Ga(I) heterocycles can be synthesized by reacting gallium monoiodide and Li[nacnac].^[18]^[20]

GaCp and GaCp*

Another interesting reaction with gallium monoiodide has been the facile access to half-sandwich complexes, GaCp* and GaCp. Schnöckel first accessed hexameric GaCp* using more synthetically difficult routes.^[21] However, Jutzi and coworkers showed that GaCp*, a heavily employed ligand for transition metal complexes, can be accessed more simply by reacting gallium monoiodide with a potassium salt of the desired ligand.^[22] To avoid benzyl iodide side products, both the gallium monoiodide and the GaCp* ligand have been synthesized in benzene rather than toluene.^[8]^[22] Using this methodology, both Cp*Ga and (C₅Me₄Et)Ga have been synthesized cleanly under more practical reaction conditions.

Furthermore, Schenk and coworkers showed that GaCp, which is less sterically hindered than GaCp*, can also be accessed using a gallium monoiodide precursor. This ligand can be synthesized with a metathesis reaction of NaCp with gallium monoiodide.^[23] This GaCp ligand has been used to access a GaCp₂I complex with datively bonded GaCp. This complex showcases an uncommon donor-acceptor Ga-Ga bond. GaCp can also be used to access a Lewis acid B(C₆F₅)₃ complex with a datively bonded GaCp.^[23] For both of these two complexes, the GaCp* analogues have been synthesized and x-ray crystallography has supported that, as expected, GaCp* is a slightly stronger donor than GaCp.

Like GaCp*, GaCp can also coordinate to transition metal complexes such as Cr(CO)₅(cyclooctene) or Co₂(CO)₈ to yield CpGa–Cr(CO)₅ or (thf)GaCp{Co(CO)₄}₂.^[24] For CpGa–Cr(CO)₅, the Ga-Cr bond length (239.6 pm) is similar to that for a GaCp* analogue (240.5 pm). For this complex, the trans effect is also observed, where the Cr-CO bond trans to the GaCp ligand is contracted (186 pm) relative to the cis Cr-CO bonds (189.5 pm). While GaCp can act as a terminal ligand similar to GaCp*, it was determined that GaCp analogues react faster than their GaCp* counterparts. This can be attributed to the lower steric bulk of GaCp, and Naglav and coworkers have suggested that working at lower temperatures can help access stable complexes with GaCp ligands.^[24]

Unlike reactivity with Cr(CO)₅(cyclooctene), reactivities of GaCp* and GaCp with Co₂(CO)₈ diverge significantly.^[24] Dicobalt octacarbonyl, or Co₂(CO)₈, exists in various isomeric states. One such isomer contains two bridging CO ligands. When GaCp* reacts with Co₂(CO)₈, two equivalents of CO gas are released, forming (CO)₃Co[μ₂-(η₅-GaCp*)]₂-Co(CO)₃. This is a derivative of the dicobalt octacarbonyl complex where the bridging CO moieties are replaced by bridging GaCp* moieties.^[25] On the other hand, GaCp enables oxidative addition to Co₂(CO)₈ to form (thf)GaCp{Co(CO)₄}₂, where gallium has sigma interactions to two Co(CO)₄ units. The average Ga–Co bond length is 248.5 pm and gallium is in a formally +3 oxidation state in this new complex.^[25] Overall, straightforward synthesis of GaCp from a gallium monoiodide precursor has many merits in expanding the scope of transition metal chemistry with lower valent species.

Gallium clusters

A variety of gallium clusters have also been synthesized from a gallium monoiodide precursor. Many gallium-based clusters have been previously synthesized from GaX precursors as prepared by Schnöckel and coworkers.^[28] However, new clusters have also been prepared with the more easily accessible gallium monoiodide starting material. These clusters have often been isolated as salts with bulky silyl or germyl anions, such as [Si(SiMe₃)₃]⁻.^[8] An example of an isolated gallium cluster is [Ga₉{Si(SiMe₃)₃}₆]⁻, which has a pentagonal bipyramidal polyhedral structure. It is synthesized by reacting gallium monoiodide with Li(thf)₃Si(SiMe₃)₃ in toluene at -78 ˚C.^[8]^[27] This reaction has been shown to access a wide array of products, which may be attributed to the wide range of gallium monoiodide compositions that have been subsequently probed by Malbrecht and coworkers. Of these products, [Ga₉{Si(SiMe₃)₃}₆]⁻ is especially unique because Ga was found to have a very low average oxidation state (0.56) and also because this cluster has fewer R substituents than polyhedron vertices.^[27] Other clusters that been isolated via similar reaction pathways include [Ga₁₀{Si(SiMe₃)₃}₆], which is a conjuncto-polyhedral cluster, and a closo-silatetragallane anion, which contains three 2-electron-2-center and three 2-electron-3-center bonds.^[8]^[29]^[26] Interestingly, this latter species can only be synthesized when sub-stoichiometric quantities of I₂ are utilized to access a "Ga₂I₃" intermediate species.^[26] This is equivalent to reacting liquid gallium metal and iodine to pre-completion, which, as explained above, accesses the [Ga⁰]₂[Ga⁺]₂[Ga₂I₆^2-] variant of gallium monoiodide. This highlights the versatility of the gallium monoiodide precursor in accessing a wide range of gallium-based complexes.

Gallium monoiodide can also form cluster-type compounds with transition metals precursors. One example is the reaction between gallium monoiodide and (2,6-Pmp₂C₆H₃)₂Co, (Pmp = C₆Me₅), which yields a nido-type cluster.^[30] This molecule has been described as being similar to a cubane, where the corners are metal and bridging iodine atoms, with one corner removed. This is a particularly unique Co-GaI cluster due to its unusual geometry for transition metal compounds containing heavy group 13 atoms such as gallium. The bond critical points and bond paths, as computed with QTAIM analysis, support that while there are Co-Ga bonds, there are no Ga-Ga bonds.^[30]

Finally, gallium monoiodide has been able to form clusters with heavy gold atoms by acting as a reducing reagent when combined with GaCp* and LAuX (i.e. AuI(PPh₃) or AuCl(PPh₃)).^[8]^[32] This cluster contained the first crystallographically confirmed Ga-Au bonds. Based on the bond critical points of the Ga-Au and Au-Au bonds of this cluster, as well as NBO analysis of atomic charges, it was determined that this cluster could be best described as a Au₃ cluster ligated by Ga ligands. In addition, NBO analysis showed that the charge on the galliums within the GaCp* ligands were much higher than the charge on the Au atoms and the charge on the gallium atoms within the GaI₂ motifs. This suggests that non-bridging Ga-Au bonds are highly polarized, whereas the µ-bridging Ga-Au bonds are more non-polar covalent in character.^[32] While gallium cluster chemistry has been explored in great detail, being able to access clusters with the more tractable gallium monoiodide precursor may allow the discovery of new species that cannot be accessed from other GaX precursors.

References

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^ ^a ^b ^c ^d Naglav, Dominik; Tobey, Briac; Schnepf, Andreas (2013). "Application of GaCp as a Ligand in Coordination Chemistry: Similarities and Differences to GaCp*". European Journal of Inorganic Chemistry. 2013 (24): 4146–4149. doi:10.1002/ejic.201300401. ISSN 1099-0682.
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^ ^a ^b ^c Anandhi, U.; Sharp, Paul R. (2004). "A Gallium-Coated Gold Cluster". Angewandte Chemie International Edition. 43 (45): 6128–6131. doi:10.1002/anie.200461295. ISSN 1521-3773. PMID 15549757.

[:0-1] Dohmeier, Carsten; Loos, Dagmar; Schnöckel, Hansgeorg (1996). "Aluminum(I) and Gallium(I) Compounds: Syntheses, Structures, and Reactions". Angewandte Chemie International Edition in English. 35 (2): 129–149. doi:10.1002/anie.199601291. ISSN 1521-3773.

[:2-2] Green, Malcolm L. H.; Mountford, Philip; Smout, Geoffrey J.; Speel, S. Robert (1990-01-01). "New synthetic pathways into the organometallic chemistry of gallium". Polyhedron. 9 (22): 2763–2765. doi:10.1016/S0277-5387(00)86809-6. ISSN 0277-5387.

[:1-3] Widdifield, Cory M.; Jurca, Titel; Richeson, Darrin S.; Bryce, David L. (2012-03-16). "Using 69/71Ga solid-state NMR and 127I NQR as probes to elucidate the composition of "GaI"". Polyhedron. 35 (1): 96–100. doi:10.1016/j.poly.2012.01.003. ISSN 0277-5387.

[:4-4] ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ Malbrecht, Brian J.; Dube, Jonathan W.; Willans, Mathew J.; Ragogna, Paul J. (2014-09-15). "Addressing the Chemical Sorcery of "GaI": Benefits of Solid-State Analysis Aiding in the Synthesis of P→Ga Coordination Compounds". Inorganic Chemistry. 53 (18): 9644–9656. doi:10.1021/ic501139w. ISSN 0020-1669. PMID 25184621.

[:3-5] Wilkinson, M.; Worrall, I. J. (1975-07-01). "Synthesis of alkylgallium diiodides". Journal of Organometallic Chemistry. 93 (1): 39–42. doi:10.1016/S0022-328X(00)94142-1. ISSN 0022-328X.

[6] Okuda, Tsutomu; Hamamoto, Hiroshi; Ishihara, Hideta; Negita, Hisao (1985-09-01). "79Br and 127I Nuclear Quadrupole Resonance of Mixed Valency Compounds Ga2X4(X=Br, I)". Bulletin of the Chemical Society of Japan. 58 (9): 2731–2732. doi:10.1246/bcsj.58.2731. ISSN 0009-2673.

[:5-7] Beamish, J. C.; Wilkinson, M.; Worrall, I. J. (1978-07-01). "Facile synthesis of the lower valent halides of gallium, Ga2X4 (X = chloride, bromide, iodide) and tetragallium hexaiodide". Inorganic Chemistry. 17 (7): 2026–2027. doi:10.1021/ic50185a069. ISSN 0020-1669.

[:6-8] ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ ^o ^p ^q Baker, Robert J.; Jones, Cameron (2005-04-11). ""GaI": A versatile reagent for the synthetic chemist". Dalton Transactions (8): 1341–1348. doi:10.1039/B501310K. hdl:2262/69572. ISSN 1477-9234. PMID 15824768.

[:7-9] Baker, Robert J.; Bettentrup, Helga; Jones, Cameron (2003). "The Reactivity of Primary and Secondary Amines, Secondary Phosphanes and N-Heterocyclic Carbenes towards Group-13 Metal(I) Halides". European Journal of Inorganic Chemistry. 2003 (13): 2446–2451. doi:10.1002/ejic.200300068. ISSN 1099-0682.

[:8-10] Schnepf, Andreas; Doriat, Clemens (1997-01-01). "A simple synthesis for donor-stabilized Ga2I4 and Ga3I5 species and the X-ray crystal structure of Ga3I5·3PEt3". Chemical Communications (21): 2111–2112. doi:10.1039/A703776G. ISSN 1364-548X.

[:9-11] Cameron Jones; Christian Schulten; Andreas Stasch (2005-04-01). "[Gal2Ph(SbPh3)]: A Rare Tertiary Stibane-Gallium Complex Formed via a Reductive Sb-C Bond Cleavage Reaction". Main Group Metal Chemistry. 28 (2): 89–92. doi:10.1515/MGMC.2005.28.2.89. ISSN 0792-1241. S2CID 101459028.

[:10-12] Baker, Robert J.; Jones, Cameron; Kloth, Marc; Mills, David P. (2004-02-03). "The reactivity of gallium(I) and indium(I) halides towards bipyridines, terpyridines, imino-substituted pyridines and bis(imino)acenaphthenes". New Journal of Chemistry. 28 (2): 207–213. doi:10.1039/B310592J. ISSN 1369-9261.

[13] Beran, G.; Carty, A. J.; Patel, H. A.; Palenik, Gus J. (1970-01-01). "A trans-effect in gallium complexes: the crystal structure of trichloro-(2,2′,2"-terpyridyl)gallium(III)". Journal of the Chemical Society D: Chemical Communications (4): 222–223. doi:10.1039/C29700000222. ISSN 0577-6171.

[:18-14] Pott, Thomas; Jutzi, Peter; Kaim, Wolfgang; Schoeller, Wolfgang W.; Neumann, Beate; Stammler, Anja; Stammler, Hans-Georg; Wanner, Matthias (July 2002). "Reactivity of "GaI" TowardN-Substituted 1,4-Diazabuta-1,3-dienes: Synthesis and Characterization of Gallium Heterocycles Containing Paramagnetic Diazabutadiene Monoanions". Organometallics. 21 (15): 3169–3172. doi:10.1021/om0200510. ISSN 0276-7333.

[15] Baker, Robert J.; Farley, Robert D.; Jones, Cameron; Kloth, Marc; Murphy, Damien M. (2002-10-03). "The reactivity of diazabutadienes toward low oxidation state Group 13 iodides and the synthesis of a new gallium(I) carbene analogue". Journal of the Chemical Society, Dalton Transactions (20): 3844–3850. doi:10.1039/B206605J. ISSN 1364-5447.

[16] Schmidt, Eva S.; Jockisch, Alexander; Schmidbaur, Hubert (1999-10-01). "A Carbene Analogue with Low-Valent Gallium as a Heteroatom in a quasi-Aromatic Imidazolate Anion". Journal of the American Chemical Society. 121 (41): 9758–9759. doi:10.1021/ja9928780. ISSN 0002-7863.

[17] Baker, Robert J.; Jones, Cameron; Mills, David P.; Murphy, Damien M.; Hey-Hawkins, Evamarie; Wolf, Robert (2006-12-14). "The reactivity of gallium-(I), -(II) and -(III) heterocycles towards Group 15 substrates: attempts to prepare gallium–terminal pnictinidene complexes". Dalton Transactions (1): 64–72. doi:10.1039/B511451A. ISSN 1477-9234. PMID 16357962.

[:19-18] Baker, Robert J.; Jones, Cameron (2005-09-01). "The coordination chemistry and reactivity of group 13 metal(I) heterocycles". Coordination Chemistry Reviews. 36th International Conference on Coordination Chemistry, Merida, Mexico, July 2004. 249 (17): 1857–1869. doi:10.1016/j.ccr.2004.12.016. ISSN 0010-8545.

[19] Jones, Cameron; Rose, Richard P.; Stasch, Andreas (2007-07-10). "Synthesis and characterisation of zinc gallyl complexes: First structural elucidations of Zn–Ga bonds". Dalton Transactions (28): 2997–2999. doi:10.1039/B706402K. ISSN 1477-9234. PMID 17622416.

[:20-20] Hardman, Ned J.; Eichler, Barrett E.; Power, Philip P. (2000-01-01). "Synthesis and characterization of the monomer Ga{(NDippCMe)2CH} (Dipp = C6H3Pri2-2,6): a low valent gallium(I) carbene analogue". Chemical Communications (20): 1991–1992. doi:10.1039/B005686N. ISSN 1364-548X.

[21] Loos, Dagmar; Baum, Elke; Ecker, Achim; Schnöckel, Hansgeorg; Downs, Anthony J. (1997). "Hexameric Aggregates in Crystalline (Pentamethylcyclopentadienyl)gallium(I) at 200 K". Angewandte Chemie International Edition in English. 36 (8): 860–862. doi:10.1002/anie.199708601. ISSN 1521-3773.

[:14-22] Jutzi, Peter; Schebaum, Lars Oliver (2002-07-15). "A novel synthetic route to pentaalkylcyclopentadienylgallium(I) compounds". Journal of Organometallic Chemistry. 654 (1): 176–179. doi:10.1016/S0022-328X(02)01429-8. ISSN 0022-328X.

[:15-23] Schenk, Christian; Köppe, Ralf; Schnöckel, Hansgeorg; Schnepf, Andreas (2011). "A Convenient Synthesis of Cyclopentadienylgallium – The Awakening of a Sleeping Beauty in Organometallic Chemistry". European Journal of Inorganic Chemistry. 2011 (25): 3681–3685. doi:10.1002/ejic.201100672. ISSN 1099-0682.

[:16-24] Naglav, Dominik; Tobey, Briac; Schnepf, Andreas (2013). "Application of GaCp as a Ligand in Coordination Chemistry: Similarities and Differences to GaCp*". European Journal of Inorganic Chemistry. 2013 (24): 4146–4149. doi:10.1002/ejic.201300401. ISSN 1099-0682.

[:17-25] Jutzi, Peter; Neumann, Beate; Reumann, Guido; Stammler, Hans-Georg (1998-03-01). "Pentamethylcyclopentadienylgallium (Cp*Ga): Alternative Synthesis and Application as a Terminal and Bridging Ligand in the Chemistry of Chromium, Iron, Cobalt, and Nickel". Organometallics. 17 (7): 1305–1314. doi:10.1021/om970913a. ISSN 0276-7333.

[:12-26] Linti, Gerald; Köstler, Wolfgang; Piotrowski, Holger; Rodig, Alexander (1998). "A Silatetragallane—Classical Heterobicyclopentane or closo-Polyhedron?". Angewandte Chemie International Edition. 37 (16): 2209–2211. doi:10.1002/(SICI)1521-3773(19980904)37:16<2209::AID-ANIE2209>3.0.CO;2-3. ISSN 1521-3773. PMID 29711437.

[:11-27] Köstler, Wolfgang; Linti, Gerald (1997). "Synthesis and Structure of a Tetragallane [R4Ga4I3]− and a Polyhedral Nonagallane [R6Ga9]". Angewandte Chemie International Edition in English. 36 (23): 2644–2646. doi:10.1002/anie.199726441. ISSN 1521-3773.

[28] Schnepf, Andreas; Schnöckel, Hansgeorg (2002). "Metalloid Aluminum and Gallium Clusters: Element Modifications on the Molecular Scale?". Angewandte Chemie International Edition. 41 (19): 3532–3554. doi:10.1002/1521-3773(20021004)41:19<3532::AID-ANIE3532>3.0.CO;2-4. ISSN 1521-3773. PMID 12370894.

[29] Kehrwald, Michael; Köstler, Wolfgang; Rodig, Alexander; Linti, Gerald; Blank, Thomas; Wiberg, Nils (2001-03-01). "Ga10[Si(SiMe3)3]6, [Ga10(SitBu3)6]-, and [Ga13(SitBu3)6]-Syntheses and Structural Characterization of Novel Gallium Cluster Compounds". Organometallics. 20 (5): 860–867. doi:10.1021/om000703p. ISSN 0276-7333.

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@@ Line 12: / Line 12: @@
 '''Gallium monoiodide''' is an inorganic [[gallium]] compound with the formula '''GaI''' or Ga<sub>4</sub>I<sub>4</sub>. It is a pale green solid and mixed valent gallium compound, which can contain gallium in the 0, +1, +2, and +3 oxidation states. It is used as a pathway for many gallium-based products. Unlike the [[Gallium halides|gallium(I) halides]] first crystallographically characterized,<ref name=":0">{{Cite journal|last1=Dohmeier|first1=Carsten|last2=Loos|first2=Dagmar|last3=Schnöckel|first3=Hansgeorg|date=1996|title=Aluminum(I) and Gallium(I) Compounds: Syntheses, Structures, and Reactions|url=https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.199601291|journal=Angewandte Chemie International Edition in English|language=en|volume=35|issue=2|pages=129–149|doi=10.1002/anie.199601291|issn=1521-3773}}</ref> gallium monoiodide has a more facile synthesis allowing a synthetic route to many low-valent gallium compounds.
-== Synthesis ==
+==Synthesis==
 In 1990, [[Malcolm Green (chemist)|Malcolm Green]] synthesized gallium monoiodide by the [[Sonication|ultrasonication]] of liquid gallium metal with iodine in [[toluene]] yielding a pale green powder referred to as gallium monoiodide.<ref name=":2">{{Cite journal|last1=Green|first1=Malcolm L. H.|last2=Mountford|first2=Philip|last3=Smout|first3=Geoffrey J.|last4=Speel|first4=S. Robert|date=1990-01-01|title=New synthetic pathways into the organometallic chemistry of gallium|url=http://www.sciencedirect.com/science/article/pii/S0277538700868096|journal=Polyhedron|language=en|volume=9|issue=22|pages=2763–2765|doi=10.1016/S0277-5387(00)86809-6|issn=0277-5387}}</ref> The chemical composition of gallium monoiodide was not determined until the early to mid-2010s despite its simple synthesis.
@@ Line 19: / Line 19: @@
 The resultant gallium monoiodide is highly air sensitive, but stable under inert atmosphere conditions for up to a year at -35 ˚C.<ref name=":4" />
-== Characterization ==
+==Characterization==
 When gallium monoiodide was first produced, it was proposed that gallium monoiodide is a combination of gallium metal, Ga<sub>2</sub>I<sub>3</sub> and Ga<sub>2</sub>I<sub>4</sub> based on the characteristic [[Raman spectroscopy|Raman spectra]] of these constituents.<ref name=":3">{{Cite journal|last1=Wilkinson|first1=M.|last2=Worrall|first2=I. J.|date=1975-07-01|title=Synthesis of alkylgallium diiodides|url=http://www.sciencedirect.com/science/article/pii/S0022328X00941421|journal=Journal of Organometallic Chemistry|language=en|volume=93|issue=1|pages=39–42|doi=10.1016/S0022-328X(00)94142-1|issn=0022-328X}}</ref>
 This hypothesis was confirmed as two variants of gallium monoiodide were determined to have the chemical compositions [Ga<sup>0</sup>]<sub>2</sub>[Ga<sup>+</sup>][GaI<sub>4</sub><sup>−</sup>], simplified as Ga<sub>2</sub>I<sub>4</sub>·2Ga, and [Ga<sup>0</sup>]<sub>2</sub>[Ga<sup>+</sup>]<sub>2</sub>[Ga<sub>2</sub>I<sub>6</sub><sup>2-</sup>], simplified as Ga<sub>2</sub>I<sub>3</sub>·Ga.<ref name=":4" /><ref name=":1" />
@@ Line 29: / Line 29: @@
 [Ga<sup>0</sup>]<sub>2</sub>[Ga<sup>+</sup>][GaI<sub>4</sub><sup>−</sup>] converts to [Ga<sup>0</sup>]<sub>2</sub>[Ga<sup>+</sup>]<sub>2</sub>[Ga<sub>2</sub>I<sub>6</sub><sup>2-</sup>] over time.<ref name=":4" />
-== Reactivity ==
+==Reactivity==
 The fact that two different gallium monoiodide variants can be accessed provides some insight into how such a wide range of reactivities can be accessed.
 Gallium monoiodide is used as a precursor for a variety of reactions. Early-on, gallium monoiodide was shown to produce alkylgallium diiodides via oxidative addition by reacting liquid gallium metal and iodine in the presence of an alkyl iodide.<ref name=":0" /><ref name=":2" /><ref name=":6">{{Cite journal|last1=Baker|first1=Robert J.|last2=Jones|first2=Cameron|date=2005-04-11|title="GaI": A versatile reagent for the synthetic chemist|url=https://pubs.rsc.org/en/content/articlelanding/2005/dt/b501310k|journal=Dalton Transactions|language=en|issue=8|pages=1341–1348|doi=10.1039/B501310K|pmid=15824768|hdl=2262/69572|issn=1477-9234|hdl-access=free}}</ref> Since then, other [[Organogallium chemistry|organogallium complexes]] have been synthesized, as well as [[Lewis acids and bases|Lewis base]] adducts and gallium based clusters.<ref name=":6" />
-=== Ga Lewis base adducts ===
+===Gallium Lewis base adducts===
 [[File:GaI Lewis base adduct.png|thumb|Reaction pathways of various gallium monoiodide Lewis base adducts. Reactions were conducted in toluene at - 78 ˚C.<ref name=":7">{{Cite journal|last1=Baker|first1=Robert J.|last2=Bettentrup|first2=Helga|last3=Jones|first3=Cameron|date=2003|title=The Reactivity of Primary and Secondary Amines, Secondary Phosphanes and N-Heterocyclic Carbenes towards Group-13 Metal(I) Halides|url=https://chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/ejic.200300068|journal=European Journal of Inorganic Chemistry|language=en|volume=2003|issue=13|pages=2446–2451|doi=10.1002/ejic.200300068|issn=1099-0682}}</ref> (L = phosphines, ethers, amines).<ref name=":6" /><ref name=":7" /> Image adapted from Baker and coworkers.<ref name=":6" />]]
 Gallium monoiodide reacts with various monodentate [[Lewis acids and bases|Lewis bases]] to form Ga(II), Ga(III), or mixed valent compounds, as well as gallium-based dimers and trimers. For example, gallium monoiodide can react with primary, secondary, and tertiary [[amines]], secondary or tertiary [[phosphines]] or [[ethers]] to form Ga(II)-Ga(II) dimers.<ref name=":2" /><ref name=":6" /><ref name=":8">{{Cite journal|last1=Schnepf|first1=Andreas|last2=Doriat|first2=Clemens|date=1997-01-01|title=A simple synthesis for donor-stabilized Ga2I4 and Ga3I5 species and the X-ray crystal structure of Ga3I5·3PEt3|url=https://pubs.rsc.org/en/content/articlelanding/1997/cc/a703776g|journal=Chemical Communications|language=en|issue=21|pages=2111–2112|doi=10.1039/A703776G|issn=1364-548X}}</ref> Gallium monoiodide can also react with [[triphenylphosphine]] (PPh<sub>3</sub>) to form Ga(III)I<sub>3</sub>PPh<sub>3</sub>.<ref name=":2" /> It also reacts with the less sterically hindered [[triethylphosphine]] (PEt<sub>3</sub>) to form a Ga(II)-Ga(I)-Ga(II) mixed valent complex with datively coordinated PEt<sub>3</sub> ligands.<ref name=":6" /><ref name=":8" /> These reacts are believed to be a [[disproportionation]], as gallium metal is produced in these reactions.<ref name=":7" />
@@ Line 45: / Line 45: @@
 [[File:GaI polydentate Lewis base adduct.png|center|thumb|400x400px|Reaction pathways with gallium monoiodide and polydentate Lewis bases form Ga(III) salts (R = Ar, Bu<sup>t</sup>; Ar = C<sub>6</sub>H<sub>3</sub>Pr<sup>i</sup><sub>2</sub>-2,6; Py = 2-pyridyl). Reactions were conducted in toluene at - 78 ˚C. Only the bis(imino)pyridine derivative was reacted at 25 ˚C. All complexes have been crystallographically characterized. Image adapted from Baker and coworkers.<ref name=":10" />]]
-=== Ga heterocycles ===
+===Gallium heterocycles===
 Gallium monoiodide can also be used as a precursor to form gallium-based heterocycles. Reactions with diazabutadienes, {RN=C(H)}<sub>2</sub>, can form monomers or dimers based on the substituents on the diazabutadienes. More sterically hindered substituents such as Bu<sup>t</sup> have resulted in the formation of Ga(II) dimers, whereas reactions with alkyl or aryl substituted diazabutadienes have formed Ga(III) monomers.<ref name=":6" /> Two equivalents of gallium monoiodide can be reacted with phenyl-substituted 1,4-diazabuta-1,3-dienes to form a Ga heterocycle with a diazabutadiene monoanion.<ref name=":18">{{Cite journal|last1=Pott|first1=Thomas|last2=Jutzi|first2=Peter|last3=Kaim|first3=Wolfgang|last4=Schoeller|first4=Wolfgang W.|last5=Neumann|first5=Beate|last6=Stammler|first6=Anja|last7=Stammler|first7=Hans-Georg|last8=Wanner|first8=Matthias|date=July 2002|title=Reactivity of "GaI" TowardN-Substituted 1,4-Diazabuta-1,3-dienes: Synthesis and Characterization of Gallium Heterocycles Containing Paramagnetic Diazabutadiene Monoanions|url=https://pubs.acs.org/doi/pdf/10.1021/om0200510|journal=Organometallics|volume=21|issue=15|pages=3169–3172|doi=10.1021/om0200510|issn=0276-7333}}</ref> [[Electron paramagnetic resonance|EPR spectroscopy]] has revealed that the diazabutadiene fragment is a [[Paramagnetism|paramagnetic]] monoanionic species rather than an ene-diamido dianion or a neutral ligand.<ref name=":18" /> Thus, gallium monoiodide undergoes a [[disproportionation]] reaction to form a Ga(III) complex with deposition of a Ga(0) metal.<ref name=":6" /><ref name=":18" /> Upon further reaction with a 1,4-dilithiated diazabutadiene, this Ga heterocycle forms a new complex with the diazabutadiene monoanion fragment datively bonded (Ga-N bond lengths 1.9678(13) Å) to the Ga center and an ene-diamido dianion covalently bonded (Ga-N bond lengths 1.8831(13) Å) to the Ga center.<ref name=":18" /> The geometry about the Ga center suggests that the electrons in the two diazabutadiene systems do not delocalize across the entire complex.
 [[File:Ga heterocycles.png|center|thumb|600x600px|Ga heterocycles formed from the reaction of gallium monoiodide with 1,4-diazabuta-1,3-dienes. R = 2,6-dimethylphenyl; 2,4,6-trimethylphenyl; 2,6-diisopropylphenyl. For the 1,4-dilithiated diazabutadiene reagent, R = 2,6-dimethylphenyl. Image adapted from Pott and coworkers.<ref name=":18" />]]
@@ Line 54: / Line 54: @@
 [[File:Ga 6-member NHC new.png|center|thumb|400x400px|Reaction of gallium monoiodide (slurry) and Li[nacnac] in a dry ice/acetone bath to access a Ga(I) heterocycle. Excess potassium metal can be added to circumvent a Ga(II) derivative of the six-member Ga(I) heterocycle.<ref name=":20" /> Ar = Dipp. Image adapted from Baker and coworkers.<ref name=":19" />]]
-=== GaCp and GaCp* ===
+===GaCp and GaCp*===
 Another interesting reaction with gallium monoiodide has been the facile access to half-sandwich complexes, GaCp* and GaCp. Schnöckel first accessed hexameric GaCp* using more synthetically difficult routes.<ref>{{Cite journal|last1=Loos|first1=Dagmar|last2=Baum|first2=Elke|last3=Ecker|first3=Achim|last4=Schnöckel|first4=Hansgeorg|last5=Downs|first5=Anthony J.|date=1997|title=Hexameric Aggregates in Crystalline (Pentamethylcyclopentadienyl)gallium(I) at 200 K|url=https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.199708601|journal=Angewandte Chemie International Edition in English|volume=36|issue=8|pages=860–862|doi=10.1002/anie.199708601|issn=1521-3773}}</ref> However, Jutzi and coworkers showed that GaCp*, a heavily employed ligand for transition metal complexes, can be accessed more simply by reacting gallium monoiodide with a potassium salt of the desired ligand.<ref name=":14">{{Cite journal|last1=Jutzi|first1=Peter|last2=Schebaum|first2=Lars Oliver|date=2002-07-15|title=A novel synthetic route to pentaalkylcyclopentadienylgallium(I) compounds|url=http://www.sciencedirect.com/science/article/pii/S0022328X02014298|journal=Journal of Organometallic Chemistry|language=en|volume=654|issue=1|pages=176–179|doi=10.1016/S0022-328X(02)01429-8|issn=0022-328X}}</ref> To avoid benzyl iodide side products, both the gallium monoiodide and the GaCp* ligand have been synthesized in benzene rather than toluene.<ref name=":6" /><ref name=":14" /> Using this methodology, both Cp*Ga and (C<sub>5</sub>Me<sub>4</sub>Et)Ga have been synthesized cleanly under more practical reaction conditions.
@@ Line 63: / Line 63: @@
 Unlike reactivity with Cr(CO)<sub>5</sub>(cyclooctene), reactivities of GaCp* and GaCp with Co<sub>2</sub>(CO)<sub>8</sub> diverge significantly.<ref name=":16" /> [[Dicobalt octacarbonyl]], or Co<sub>2</sub>(CO)<sub>8</sub>, exists in various isomeric states. One such isomer contains two bridging CO ligands. When GaCp* reacts with Co<sub>2</sub>(CO)<sub>8</sub>, two equivalents of CO gas are released, forming (CO)<sub>3</sub>Co[''μ''<sub>2</sub>-(''η''<sub>5</sub>-GaCp*)]<sub>2</sub>-Co(CO)<sub>3</sub>. This is a derivative of the [[dicobalt octacarbonyl]] complex where the bridging CO moieties are replaced by bridging GaCp* moieties.<ref name=":17">{{Cite journal|last1=Jutzi|first1=Peter|last2=Neumann|first2=Beate|last3=Reumann|first3=Guido|last4=Stammler|first4=Hans-Georg|date=1998-03-01|title=Pentamethylcyclopentadienylgallium (Cp*Ga): Alternative Synthesis and Application as a Terminal and Bridging Ligand in the Chemistry of Chromium, Iron, Cobalt, and Nickel|url=https://doi.org/10.1021/om970913a|journal=Organometallics|volume=17|issue=7|pages=1305–1314|doi=10.1021/om970913a|issn=0276-7333}}</ref> On the other hand, GaCp enables oxidative addition to Co<sub>2</sub>(CO)<sub>8</sub> to form (thf)GaCp{Co(CO)<sub>4</sub>}<sub>2</sub>, where gallium has sigma interactions to two Co(CO)<sub>4</sub> units. The average Ga–Co bond length is 248.5 pm and gallium is in a formally +3 [[oxidation state]] in this new complex.<ref name=":17" /> Overall, straightforward synthesis of GaCp from a gallium monoiodide precursor has many merits in expanding the scope of transition metal chemistry with lower valent species.
-=== Gallium clusters ===
+===Gallium clusters===
 [[File:Ga clusters.png|thumb|Examples of Ga clusters synthesized from variants of gallium monoiodide starting materials. R = Si(SiMe<sub>3</sub>)<sub>3</sub>. For the [Ga<sub>9</sub>{Si(SiMe<sub>3</sub>)<sub>3</sub>}<sub>6</sub><nowiki>]</nowiki><sup>−</sup> cluster, the polyhedral vertices are all Ga. Reactions were conducted in toluene at -78 ˚C. Image adapted from (top) Linti and coworkers<ref name=":12" /> and (bottom) Kostler and coworkers.<ref name=":11" />]]
 A variety of gallium clusters have also been synthesized from a gallium monoiodide precursor. Many gallium-based clusters have been previously synthesized from GaX precursors as prepared by Schnöckel and coworkers.<ref>{{Cite journal|last1=Schnepf|first1=Andreas|last2=Schnöckel|first2=Hansgeorg|date=2002|title=Metalloid Aluminum and Gallium Clusters: Element Modifications on the Molecular Scale?|url=https://onlinelibrary.wiley.com/doi/abs/10.1002/1521-3773%2820021004%2941%3A19%3C3532%3A%3AAID-ANIE3532%3E3.0.CO%3B2-4|journal=Angewandte Chemie International Edition|language=en|volume=41|issue=19|pages=3532–3554|doi=10.1002/1521-3773(20021004)41:19<3532::AID-ANIE3532>3.0.CO;2-4|pmid=12370894|issn=1521-3773}}</ref> However, new clusters have also been prepared with the more easily accessible gallium monoiodide starting material. These clusters have often been isolated as salts with bulky silyl or germyl anions, such as [Si(SiMe<sub>3</sub>)<sub>3</sub>]<sup>−</sup>.<ref name=":6" /> An example of an isolated gallium cluster is [Ga<sub>9</sub>{Si(SiMe<sub>3</sub>)<sub>3</sub>}<sub>6</sub>]<sup>−</sup>, which has a pentagonal bipyramidal polyhedral structure. It is synthesized by reacting gallium monoiodide with Li(thf)<sub>3</sub>Si(SiMe<sub>3</sub>)<sub>3</sub> in toluene at -78 ˚C.<ref name=":6" /><ref name=":11">{{Cite journal|last1=Köstler|first1=Wolfgang|last2=Linti|first2=Gerald|date=1997|title=Synthesis and Structure of a Tetragallane [R4Ga4I3]− and a Polyhedral Nonagallane [R6Ga9]|url=https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.199726441|journal=Angewandte Chemie International Edition in English|volume=36|issue=23|pages=2644–2646|doi=10.1002/anie.199726441|issn=1521-3773}}</ref> This reaction has been shown to access a wide array of products, which may be attributed to the wide range of gallium monoiodide compositions that have been subsequently probed by Malbrecht and coworkers. Of these products, [Ga<sub>9</sub>{Si(SiMe<sub>3</sub>)<sub>3</sub>}<sub>6</sub>]<sup>−</sup> is especially unique because Ga was found to have a very low average oxidation state (0.56) and also because this cluster has fewer R substituents than polyhedron vertices.<ref name=":11" /> Other clusters that been isolated via similar reaction pathways include [Ga<sub>10</sub>{Si(SiMe<sub>3</sub>)<sub>3</sub>}<sub>6</sub>], which is a conjuncto-[[Polyhedral skeletal electron pair theory|polyhedral cluster]], and a closo-silatetragallane anion, which contains three 2-electron-2-center and three [[Three-center two-electron bond|2-electron-3-center bonds]].<ref name=":6" /><ref>{{Cite journal|last1=Kehrwald|first1=Michael|last2=Köstler|first2=Wolfgang|last3=Rodig|first3=Alexander|last4=Linti|first4=Gerald|last5=Blank|first5=Thomas|last6=Wiberg|first6=Nils|date=2001-03-01|title=Ga10[Si(SiMe3)3]6, [Ga10(SitBu3)6]-, and [Ga13(SitBu3)6]-Syntheses and Structural Characterization of Novel Gallium Cluster Compounds|url=https://doi.org/10.1021/om000703p|journal=Organometallics|volume=20|issue=5|pages=860–867|doi=10.1021/om000703p|issn=0276-7333}}</ref><ref name=":12">{{Cite journal|last1=Linti|first1=Gerald|last2=Köstler|first2=Wolfgang|last3=Piotrowski|first3=Holger|last4=Rodig|first4=Alexander|date=1998|title=A Silatetragallane—Classical Heterobicyclopentane or closo-Polyhedron?|url=https://onlinelibrary.wiley.com/doi/abs/10.1002/%28SICI%291521-3773%2819980904%2937%3A16%3C2209%3A%3AAID-ANIE2209%3E3.0.CO%3B2-3|journal=Angewandte Chemie International Edition|language=en|volume=37|issue=16|pages=2209–2211|doi=10.1002/(SICI)1521-3773(19980904)37:16<2209::AID-ANIE2209>3.0.CO;2-3|pmid=29711437|issn=1521-3773}}</ref> Interestingly, this latter species can only be synthesized when sub-stoichiometric quantities of I<sub>2</sub> are utilized to access a "Ga<sub>2</sub>I<sub>3</sub>" intermediate species.<ref name=":12" /> This is equivalent to reacting liquid gallium metal and iodine to pre-completion, which, as explained above, accesses the [Ga<sup>0</sup>]<sub>2</sub>[Ga<sup>+</sup>]<sub>2</sub>[Ga<sub>2</sub>I<sub>6</sub><sup>2-</sup>] variant of gallium monoiodide. This highlights the versatility of the gallium monoiodide precursor in accessing a wide range of gallium-based complexes.
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 Finally, gallium monoiodide has been able to form clusters with heavy gold atoms by acting as a reducing reagent when combined with GaCp* and LAuX (i.e. AuI(PPh<sub>3</sub>) or AuCl(PPh<sub>3</sub>)).<ref name=":6" /><ref name=":13">{{Cite journal|last1=Anandhi|first1=U.|last2=Sharp|first2=Paul R.|date=2004|title=A Gallium-Coated Gold Cluster|url=https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.200461295|journal=Angewandte Chemie International Edition|volume=43|issue=45|pages=6128–6131|doi=10.1002/anie.200461295|pmid=15549757|issn=1521-3773}}</ref> This cluster contained the first crystallographically confirmed Ga-Au bonds. Based on the [[Atoms in molecules|bond critical points]] of the Ga-Au and Au-Au bonds of this cluster, as well as [[Natural bond orbital|NBO analysis]] of atomic charges, it was determined that this cluster could be best described as a Au<sub>3</sub> cluster ligated by Ga ligands. In addition, NBO analysis showed that the charge on the galliums within the GaCp* ligands were much higher than the charge on the Au atoms and the charge on the gallium atoms within the GaI<sub>2</sub> motifs. This suggests that non-bridging Ga-Au bonds are highly polarized, whereas the µ-bridging Ga-Au bonds are more non-polar covalent in character.<ref name=":13" /> While gallium cluster chemistry has been explored in great detail, being able to access clusters with the more tractable gallium monoiodide precursor may allow the discovery of new species that cannot be accessed from other GaX precursors.[[File:Ga-Au cluster.png|center|thumb|400x400px|Ga-Au cluster formed by dropwise addition of LAuX to a mixture of GaCp*/"GaI" (excess) in dichloromethane. Image adapted from Anandhi and coworkers.<ref name=":13" />]]
-== See also ==
+==See also==
 * [[Gallium(III) iodide]]
 * [[Persistent carbene]]
-== References ==
+==References==
 {{Reflist}}