Diphosphinito-bridged ruthenium(II) and rhodium(III) complexes with stereogenic metal centers

Abstract

The bis-4-phosphinito ligands [(p-Ph2POC6H4)2X] (X=O, 1; X=CMe2, 2; X=S, 3) react with [Ru(η6-p-cymene)Cl2]2 to form the binuclear complexes {[Ru(η6-p-cymene)Cl2]2[μ-(p-Ph2POC6H4)2X]} (X=O, 4; X=CMe2, 5; X=S, 6) in good yields as red air stable solids. The crystal structures of 4–6 were determined by X-ray analysis. In acetonitrile and in the presence of AgPF6 (1:1 equiv. with respect to Ru), complexes 4–6 undergo substitution to yield the cationic complexes {[Ru(η6-p-cymene)Cl(CH3CN)]2[μ-(p-Ph2POC6H4)2X]}[PF6]2 (X=O, 7; X=CMe2, 8; X=S, 9), whose stability in solution is very limited. The acetonitrile ligand in complexes 7–9 can be easily replaced by carbon monoxide; the products {[Ru(η6-p-cymene)Cl(CO)]2[μ-(p-Ph2POC6H4)2X]}[PF6]2 (X=O, 10; X=CMe2, 11; X=S, 12) can only be detected in solution under a CO atmosphere and have limited stability. The reaction of [Rh(η5-C5Me5)Cl2]2 with ligands 1–3 results in the formation of the complexes {[Rh(η5-C5Me5)Cl2]2[μ-(p-Ph2POC6H4)2X]} (X=O, 13; X=CMe2, 14; X=S, 15), which have been isolated as red–orange air stable solids. The cationic complexes {[Rh(η5-C5Me5)Cl(CH3CN)]2[μ-(p-Ph2POC6H4)2X]}[PF6]2 (X=O, 16; X=CMe2, 17; X=S, 18), in which the metal atoms are stereogenic centers, have been obtained from the corresponding complexes 13–15, by treatment in CH3CN with AgPF6, and have been characterized only in solution by 31P{1H} NMR spectra and conductivity measurements. On reaction with ligands 1–3, [Rh(η5-C5H5)(CO)2] was converted into the binuclear phosphinito-bridged complexes {[Rh(η5-C5H5)(CO)]2[μ-(p-Ph2POC6H4)2X]} (X=O, 19; X=CMe2, 20; X=S, 21). The reactions of the binuclear complex {[Rh(η5-C5H5)(CO)]2[μ-(p-Ph2POC6H4)2S]} (21) with CH3I, S-(+)-1-bromo-2-methylbutane and racemic PhCH(CH3)Br were also studied. The products were the corresponding acyl derivatives. The reaction of 21 with neat CH3I easily afforded the complex {[Rh(η5-C5H5)(COCH3)I]2[μ-(p-Ph2POC6H4)2S]} (23), whose structural determination by X-ray analysis is also reported.