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[(PPh<sub>2</sub>CH<sub>2</sub>)<sub>2</sub>(SiC<sub>4</sub>H<sub>6</sub>)]

The reaction of the lithium salt of chlorodiphenylphosphine with 1-chloro-1-phenylsilacyclopent-3-ene (<b>1</b>) and 1,1-dichlorosilacyclopent-3-ene (<b>2</b>) gave good yields of 1-((diphenylphosphino)methyl)-1-phenyl-1-silacyclopent-3-ene (L) (<b>3</b>) and 1,1-bis((diphenylphosphino)methyl)-1-silacyclopent-3-ene (L‘) (<b>4</b>). Both molecules were obtained as white solids characterized by NMR. Red and red-violet diamagnetic square-planar complexes <i>trans</i>-NiCl<sub>2</sub>L<sub>2</sub> and <i>cis</i>-NiCl<sub>2</sub>L‘ were obtained by reacting NiCl<sub>2</sub>·6H<sub>2</sub>O with <b>3</b> and <b>4</b>, respectively. Substitution of two PPh<sub>3</sub> in CpRuCl(PPh<sub>3</sub>)<sub>2</sub> by <b>4</b> gave CpRuCl(L‘) (<b>7</b>) in good yield. Orange crystals of <b>7</b> 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°. <b>7</b> 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.