A redox series of gallium(III) complexes: ligand-based two-electron oxidation affords a gallium-thiolate complex.

We have prepared a series of gallium(III) complexes of the redox active iminopyridine ligand (IP). Reaction of GaCl(3) with iminopyridine ligand (IP) in the presence of either two or four equivalents of sodium metal resulted in the formation of deep green (IP(-))(2)GaCl (1), or deep purple [(DME)(3)Na][(IP(2-))(2)Ga] (2a), respectively. Complex 1 is paramagnetic with a room temperature magnetic moment of 2.3 μ(B) which falls to 0.5 μ(B) at 5 K. These observations indicate that two ligand radicals comprise a triplet at room temperature which becomes a singlet due to antiferromagnetic coupling at low temperature. Complex 2 is diamagnetic. Cyclic voltammograms recorded on 0.3 M Bu(4)NPF(6) THF solutions of [Na(THF)(6)][(IP(2-))(2)Ga](-) (2b) indicate that oxidation of 2b occurs in two two-electron steps at -1.31 V and -0.54 V vs. SCE. The observation of two-electron redox events indicates that electronic coupling through the gallium(III) center is minimal and that the two IP ligand on 2b are oxidized concurrently. Oxidation of 2 with one equivalent of MeS-SMe afforded the two-electron oxidized product (IP(-))(2)Ga(SMe) (3). This complex has an electronic structure analogous to 1. Accordingly, both 1 and 3 are deep green in color and magnetic susceptibility measurements performed on 3 confirm the triplet character of the complex at room temperature. Electron paramagnetic resonance experiments on 1 and 3 display a quartet signal at g = 2.0 which confirmed the triplet nature of the compounds, and a half field signal consistent with the integer spin state.

[1]  R. D. Britt,et al.  A redox series of aluminum complexes: characterization of four oxidation states including a ligand biradical state stabilized via exchange coupling. , 2011, Journal of the American Chemical Society.

[2]  K. Lyssenko,et al.  Reversible addition of alkynes to gallium complex of chelating diamide ligand. , 2010, Journal of the American Chemical Society.

[3]  K. Dawson,et al.  Disproportionation and radical formation in the coordination of "GaI" with bis(imino)pyridines. , 2010, Dalton transactions.

[4]  O. Maslova,et al.  Reduction of Disulfides with Magnesium(II) and Gallium(II) Complexes of a Redox‐Active Diimine Ligand , 2009 .

[5]  M. Galanski,et al.  An electrochemical study of antineoplastic gallium, iron and ruthenium complexes with redox noninnocent alpha-N-heterocyclic chalcogensemicarbazones. , 2008, Inorganic chemistry.

[6]  Connie C. Lu,et al.  Neutral bis(alpha-iminopyridine)metal complexes of the first-row transition ions (Cr, Mn, Fe, Co, Ni, Zn) and their monocationic analogues: mixed valency involving a redox noninnocent ligand system. , 2008, Journal of the American Chemical Society.

[7]  P. Fanwick,et al.  Multi-electron activation of dioxygen on zirconium(IV) to give an unprecedented bisperoxo complex. , 2007, Journal of the American Chemical Society.

[8]  A. F. Heyduk,et al.  C-C bond-forming reductive elimination from a zirconium(IV) redox-active ligand complex. , 2006, Journal of the American Chemical Society.

[9]  H. Schlegel,et al.  Structural and electronic behavior of unprecedented five-coordinate iron(III) and gallium(III) complexes with a new phenol-rich electroactive ligand. , 2006, Inorganic chemistry.

[10]  G. Yap,et al.  The insertion of carbodiimides into Al and Ga amido linkages. Guanidinates and mixed amido guanidinates of aluminum and gallium. , 2005, Inorganic chemistry.

[11]  P. Power,et al.  Dimeric gallium oxide and sulfide species stabilized by a sterically encumbered beta-diketiminate ligand. , 2001, Inorganic chemistry.

[12]  P. Jutzi,et al.  Differing Reactivities of Cp*Ga toward Diazabutadienes: Synthesis of Novel 1-Galla-2,5-diazoles and of the Known Radical Ga[But-DAB]2 , 2001 .

[13]  Glenn D. Whitener,et al.  Synthesis, Structure, and Coordination Chemistry of a Tridentate, Six-Electron-Donor Amidinate Ligand , 1999 .

[14]  É. Schmidt,et al.  A CARBENE ANALOGUE WITH LOW-VALENT GALLIUM AS A HETEROATOM IN A QUASI-AROMATIC IMIDAZOLATE ANION , 1999 .

[15]  M. Leskelä,et al.  Synthesis and X‐ray Structures of New Mononuclear and Dinuclear Diimine Complexes of Late Transition Metals , 1999 .

[16]  E. M. Gordon,et al.  The preparation and structural characterization of three structural types of gallium compounds derived from gallium(II) chloride , 1997 .

[17]  R. Culp,et al.  Ring Systems Containing Anionic and Cationic Gallium Centers: Structural and Bonding Considerations. , 1996, Inorganic chemistry.

[18]  A. Barron,et al.  Gallium and indium compounds of sulphur donor ligands: Pyridine-2-thiolates and diphenylthiophosphinates , 1996 .

[19]  George A. Koutsantonis,et al.  Alane– and gallane–sulfur donor chemistry: synthesis of AlH3·NMe(CH2CH2)2S, {AlH2[µ-N(CH2CH2)2S]}2 and MH(SCH2CH2NEt2)2(M = Al or Ga) , 1996 .

[20]  A. Decken,et al.  Gallium-Containing 6.pi.-Electron Ring Systems , 1995 .

[21]  W. Kaim,et al.  Bis(1,4-di-tert-butyl-1,4-diazabutadiene)gallium is not a gallium(II) compound , 1991 .

[22]  C. Raston,et al.  Reactions of gallium hydrides with 1,4-di-t-butyl-1,4-diazabutadiene; subvalent and hydrometallation products , 1990 .

[23]  P. Hitchcock,et al.  Synthesis and X-ray crystal structure of the first homoleptic main group diazadiene complex, bis(1,4-di-t-butyl-1,4-diazabuta-1,3-diene) gallium , 1989 .

[24]  J. Ziller,et al.  Synthesis of 1,3-diphenyltriazenide complexes of aluminium, gallium and indium: Crystal structure of tris(1,3-diphenyltriazenido)aluminium(III) , 1989 .

[25]  A. W. Addison,et al.  Synthesis, structure, and spectroscopic properties of copper(II) compounds containing nitrogen–sulphur donor ligands; the crystal and molecular structure of aqua[1,7-bis(N-methylbenzimidazol-2′-yl)-2,6-dithiaheptane]copper(II) perchlorate , 1984 .

[26]  W. Kaim.  Koordinationsverbindungen des reduzierten Pyrazins mit Alkylderivaten von Bor, Aluminium, Gallium und Indium / Coordination Complexes of Reduced Pyrazine and Alkyl Derivatives of Boron, Aluminum, Gallium, and Indium , 1981 .