(<i>p</i>-cymene)Ruthenium(II)(diphenylphosphino)alkyne Complexes: Preparation of (μ-Cl)(μ-PPh₂C⋮CR)-Bridged Ru/Pt Heterobimetallic Complexes

The neutral complexes [(η6-p-cymene)RuCl2(PPh2C⋮CR)] (R = Ph 1, tBu 2, (4-CH3)C6H4 3, (4-C⋮CPh)C6H4 4, (4-CN)C6H4 5) have been synthesized by reacting [(p-cymene)RuCl2]2 with the respective alkynylphosphine. Treatment of 1−5 with AgOTf or TlPF6 and the corresponding PPh2C⋮CR allows the preparation of cationic bis(diphenylphosphino) compounds [(η6-p-cymene)RuCl(PPh2C⋮CR)2]X (X = OTf; R = Ph 6, tBu 7, (4-CH3)C6H4 8, (4-C⋮CPh)C6H4 9, X = PF6; R = (4-CN)C6H4 10). All complexes have been characterized by analytical and spectroscopic methods, by cyclic voltammetry, and in several cases (3 and 7) by X-ray crystallography. Reactions of both neutral (1−4) and cationic (6−8) complexes with [cis-Pt(C6F5)2(thf)2] (thf = tetrahydrofuran) gave heterobimetallic neutral [(η6-p-cymene)ClRu(μ-Cl)(μ-1κP:η2-PPh2C⋮CR)Pt(C6F5)2] (R = Ph 11a, tBu 12a, (4-CH3)C6H4 13a, (4-C⋮CPh)C6H4 14a) and cationic [(η6-p-cymene)(PPh2C⋮CR)Ru(μ-Cl)(μ-1κP:η2-PPh2C⋮CR)Pt(C6F5)2](OTf) (R = Ph 15, tBu 16, (4-CH3)C6H4 17) derivatives stabilized by a mixed Cl/PPh2C⋮CR bridging system. The molecular structures of 12a and 17 have been confirmed by X-ray diffraction. However, the neutral complexes 11−14 existed in solution as a mixture of isomers [(η6-p-cymene)ClRu(μ-Cl)(μ-1κP:η2-PPh2C⋮CR)Pt(C6F5)2] (a) and [(η6-p-cymene)(PPh2C⋮CR)Ru(μ-Cl)2Pt(C6F5)2] (b), respectively.