Synthesis and Structure of New (Polyphosphane)ruthenium Complexes with the Hemilabile Ligand 2‐(Diphenylphosphanyl)‐1‐methyl‐1 H ‐imidazole − An Unexpected Rearrangement of [RuCl 2 (PN)(PPh 3 ) 2 ]

Several Ru II complexes containing the potentially bidentate ligand 2‐(diphenylphosphanyl)‐1‐methyl‐1 H ‐imidazole [PPh 2 MeIm (PN)] have been synthesised and characterised. Reaction of the ligand with [RuCl 2 (PPh 3 ) 3 ] in different molar ratios led to the formation of the complexes trans , mer ‐[RuCl 2 (PPh 3 ) 2 (κ 2 ‐ P , N −PPh 2 MeIm)] ( 1 ), fac ‐[RuCl(PPh 3 )(κ 2 ‐ P , N ‐PPh 2 MeIm) 2 ]Cl ( 2a ), mer ‐[RuCl(PPh 3 )(κ 2 ‐ P , N ‐PPh 2 MeIm) 2 ]Cl ( 2b ), fac ‐[RuCl(κ 1 ‐ P ‐PPh 2 MeIm)(κ 2 ‐ P , N ‐PPh 2 MeIm) 2 ]Cl ( 3a ), and mer ‐[RuCl(κ 1 ‐ P ‐PPh 2 MeIm)(κ 2 ‐ PN ‐PPh 2 MeIm) 2 ]Cl ( 3b ). Complex 1 evolves in solution to 2a , 2b and the dinuclear species [(PPh 3 )(κ 1 ‐ P ‐PPh 2 MeIm)ClRu(μ‐Cl) 2 Ru(PPh 3 )(κ 1 ‐ P ‐PPh 2 MeIm)Cl] ( 4a ), [(PPh 3 )ClRu(μ‐Cl) 2 (μ 2 ‐ P , N ‐PPh 2 MeIm) 2 Ru(PPh 3 )Cl] ( 4b ), and [(PPh 3 )(κ 2 ‐ P , N ‐PPh 2 MeIm)ClRu(μ‐Cl) 2 Ru(PPh 3 )(κ 2 ‐ P , N ‐PPh 2 MeIm)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 [RuCl 2 (cod)(bpzm)] [cod = 1,5‐cyclooctadiene, bpzm = bis(pyrazol‐1‐yl)methane], the complex cis ‐ P ‐[RuCl 2 (κ 1 ‐PPh 2 MeIm)(κ 2 ‐PPh 2 MeIm)] ( 5 ) was formed as the only product. The derivatives [Ru(κ 2 ‐PPh 2 MeIm) 3 ]X 2 [(X = PF 6 ( 6 ), BF 4 ( 7 )] were obtained upon treatment of [RuCl 2 (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 ‐[RuHClL 2 (κ 2 ‐PPh 2 MeIm)] [L = PPh 3 ( 8 ) or κ 1 ‐PN ( 9 )] by reaction of the PN ligand with [RuHCl(PPh 3 ) 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)