Coinage Metal Complexes of a Boron-Substituted Soft Scorpionate Ligand

An improved synthesis of lithium phenyltris(methimazolyl)borate, Li[PhTmMe], (methimazole = 1-methylimidazole-2-thione) is described, and the structure of the methanol-solvated [Li(OHMe)4][PhTmMe] has been determined. The
syntheses and characterization of complexes [M(PhTmMe)(PR3)] (M = Cu, Ag, Au; R = Et, Ph;) are reported, and
the complexes [Cu(PhTmMe)(PPh3)], [Ag(PhTmMe)(PEt3)] and [Au(PhTmMe)(PEt3)] are crystallographically characterized,
showing a progression from pseudo-tetrahedral geometry (copper, S3P coordination) to trigonal planar geometry
(silver, S2P coordination) to linear geometry (gold, SP coordination). In addition, the copper(I) and silver(I)
triphenylphosphine complexes of the adventitiously formed phenylhydrobis(methimazolyl)borate ligand, [M(PhBmMe)(PPh3)], have been crystallographically characterized, showing both species to have a trigonal planar primary
coordination sphere, with a secondary M···H−B interaction. Finally, reaction of copper(II) chloride with Li[PhTmMe]
results in formation of a compound analyzing as [CuII(PhTmMe)Cl], although its extreme insolubility and marked
instability have precluded its complete characterization. Attempts to prepare this by ultra-slow diffusion of the
reactants through solvent blanks has led to isolation of a mixed-valence copper(I/II) methimazolate cluster, [CuI10CuII2(mt)12Cl2] and a copper(I) dimeric complex [Cu2(PhTmMe)2], indicating that copper(II) ions oxidatively decompose
the phenyltris(methimazolyl)borate anion.