Coinage metal complexes of a boron-substituted soft scorpionate ligand

An improved synthesis of lithium phenyltris(methimazolyl)borate, Li[PhTm^Me], (methimazole = 1-methylimidazole-2-thione) is described, and the structure of the methanol-solvated [Li(OHMe)₄][PhTm ^Me] has been determined. The syntheses and characterization of complexes [M(PhTm^Me)(PR₃)] (M = Cu, Ag, Au; R = Et, Ph;) are reported, and the complexes [Cu(PhTm^Me)(PPh₃)], [Ag(PhTm^Me)(PEt₃)] and [Au(PhTm^Me)(PEt ₃)] 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(PhBm^Me)(PPh ₃)], 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[PhTm^Me] results in formation of a compound analyzing as [Cu ^II(PhTm^Me)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, [Cu^I₁₀Cu^II₂(mt)₁₂Cl ₂] and a copper(I) dimeric complex [Cu₂(PhTm ^Me)₂], indicating that copper(II) ions oxidatively decompose the phenyltris(methimazolyl)borate anion.