Synthesis and Structure of New (Polyphosphane)ruthenium Complexes with the Hemilabile Ligand 2‐(Diphenylphosphanyl)‐1‐methyl‐1H‐imidazole − An Unexpected Rearrangement of [RuCl2(PN)(PPh3)2

Abstract

AbstractSeveral RuII complexes containing the potentially bidentate ligand 2‐(diphenylphosphanyl)‐1‐methyl‐1H‐imidazole [PPh2MeIm (PN)] have been synthesised and characterised. Reaction of the ligand with [RuCl2(PPh3)3] in different molar ratios led to the formation of the complexes trans,mer‐[RuCl2(PPh3)2(κ2‐P,N−PPh2MeIm)] (1), fac‐[RuCl(PPh3)(κ2‐P,N‐PPh2MeIm)2]Cl (2a), mer‐[RuCl(PPh3)(κ2‐P,N‐PPh2MeIm)2]Cl (2b), fac‐[RuCl(κ1‐P‐PPh2MeIm)(κ2‐P,N‐PPh2MeIm)2]Cl (3a), and mer‐[RuCl(κ1‐P‐PPh2MeIm)(κ2‐PN‐PPh2MeIm)2]Cl (3b). Complex 1 evolves in solution to 2a, 2b and the dinuclear species [(PPh3)(κ1‐P‐PPh2MeIm)ClRu(μ‐Cl)2Ru(PPh3)(κ1‐P‐PPh2MeIm)Cl] (4a), [(PPh3)ClRu(μ‐Cl)2(μ2‐P,N‐PPh2MeIm)2Ru(PPh3)Cl] (4b), and [(PPh3)(κ2‐P,N‐PPh2MeIm)ClRu(μ‐Cl)2Ru(PPh3)(κ2‐P,N‐PPh2MeIm)Cl] (4c). It is proposed that the formation of the dinuclear derivatives involves an Ru−N bond‐breaking step that demonstrates the hemilabile behaviour of the ligand. When 2 equiv. of the PN ligand were added to [RuCl2(cod)(bpzm)] [cod = 1,5‐cyclooctadiene, bpzm = bis(pyrazol‐1‐yl)methane], the complex cis‐P‐[RuCl2(κ1‐PPh2MeIm)(κ2‐PPh2MeIm)] (5) was formed as the only product. The derivatives [Ru(κ2‐PPh2MeIm)3]X2 [(X = PF6 (6), BF4 (7)] were obtained upon treatment of [RuCl2(arene)]2 (arene = p‐cymene, benzene) with 2 equiv. of the corresponding silver salts and the PN ligand. Both the fac (6a, 7a) and mer (6b, 7b) forms were obtained. Two new hydride complexes were also synthesised: mer‐[RuHClL2(κ2‐PPh2MeIm)] [L = PPh3 (8) or κ1‐PN (9)] by reaction of the PN ligand with [RuHCl(PPh3)3] or [RuHCl(cod)(bpzm)], respectively. The molecular structure of 4b and fac‐7a was solved by an X‐ray diffraction study. Complex 4b has a dinuclear structure with two chloride bridges and two head‐to‐tail PN bridges. The derivative fac‐7a is mononuclear. Both enantiomers — Δ and Λ — were observed in the same unit cell. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)