Syntheses and Characterization of Nickel(II) and Ruthenium(II) Complexes with the Novel Phosphine Ligands 1-((Diphenylphosphino)methyl)- 1-phenyl-1-silacyclopent-3-ene and 1,1-Bis((diphenylphosphino)methyl)-1-silacyclopent-3-ene. Crystal Structure of CpRuCl[(PPh₂CH₂)₂(SiC₄H₆)]

The reaction of the lithium salt of chlorodiphenylphosphine with 1-chloro-1-phenylsilacyclopent-3-ene (1) and 1,1-dichlorosilacyclopent-3-ene (2) gave good yields of 1-((diphenylphosphino)methyl)-1-phenyl-1-silacyclopent-3-ene (L) (3) and 1,1-bis((diphenylphosphino)methyl)-1-silacyclopent-3-ene (L‘) (4). Both molecules were obtained as white solids characterized by NMR. Red and red-violet diamagnetic square-planar complexes trans-NiCl₂L₂ and cis-NiCl₂L‘ were obtained by reacting NiCl₂·6H₂O with 3 and 4, respectively. Substitution of two PPh₃ in CpRuCl(PPh₃)₂ by 4 gave CpRuCl(L‘) (7) in good yield. Orange crystals of 7 contain monomeric pseudooctahedral ruthenium(II) centers surrounded by a Cl atom, a Cp ligand, and the two phosphorus atoms of the 1,1-bis((diphenylphosphino)methyl)-1-silacyclopent-3-ene ligand. The silacyclopentene ring adopts a puckered ground state configuration with a puckering angle of 10°. 7 can be described as a spirannic compound with roughly perpendicular Ru−P(1)−C(10)−Si−C(20)−P(2) and Si−C(6)−C(7)−C(8)−C(9) rings.