Mixed-sandwich (Cp*/(HMB))Ru complexes containing bis(methimazolyl)(pyrazolyl)borate (Cp* = η 5-C 5Me 5, HMB = η 6-C 6Me 6)

Abstract

Reaction of the scorpionate salt Li[HB(mt) 2(pz)] (mt = N-methyl-2-mercaptoimidazol-1-yl, pz = pyrazolyl) with the organometallic complexes [Cp*RuOMe] 2 (Cp* = η 5-C 5Me 5) (1) and [(HMB)RuCl 2] 2 (HMB = η 6-C 6Me 6) (2) gave the 18-electron Ru(II) complexes [Cp*Ru(κ 3-H,S,S′)-{HB(mt) 2(pz)}] (3) and [(HMB)Ru(κ 3-H,S,S′)-{HB(mt) 2(pz)}](4B)PF 6 in moderate yields. In the absence of the PF 6 - anion, [(HMB)Ru(κ 2-S,S′- {HB(mt) 2(pz)})(Cl)] [4C] was isolated as a coproduct with (4B)Cl. These complexes are the first examples of organoruthenium(II) complexes containing bis(methimazolyl)(pyrazolyl)borate ligands. Isomers of 4B were observed in solution, and the isomerization process was studied using variable-temperature 1H NMR spectroscopy. The reactivity of 3 toward O 2 and CO was investigated, and in the process we isolated the first Ru(IV) peroxo complex containing a poly(methimazolyl)borate ligand, [Cp*Ru(κ 2-S,S′-{HB(mt) 2(pz)}) (η 2-O 2)] (5), and a CO adduct, [Cp*Ru(κ 2-S,S′-{HB(mt) 2(pz)})(CO)] (6), respectively. The oxidation process was reversible, but treatment of 5 with CO converted it irreversibly to 6. All the new compounds were fully characterized, including by X-ray diffraction analyses. Cyclic voltammetric studies were also conducted for complexes 3, 5, and 6. © 2012 American Chemical Society.