Diphenyl(phenylethynyl)phosphine d [Rh(III), Ir(III), Ru(II)] complexes: Preparation of homo (μ-Cl) and hetero (μ-Cl)(μ-PPhC≡CPh) bridged d-d compounds

The novel P-coordinated diphenyl(phenylethynyl)phosphine complexes [Cp*MCl(PPhC≡CPh)] [M = Rh 1, Ir 2] have been prepared by the bridge splitting of [Cp*MCl] with PPhC≡CPh. Treatment of 1 and 2 with AgTfO and PPhC≡CPh affords the corresponding cationic compounds [Cp*MCl(PPhC≡CPh)](OTf) [M = Rh 3, Ir 4, OTf = triflate], respectively. The analogous neutral Ru(II) derivative [Cp*RuCl(PPhC≡CPh)] 5 has been obtained by reaction of PPhC≡CPh and the binuclear complex [Cp*RuCl] in the presence of Zn as the reductor. The molecular structures of 1 and 3-5 have been determined by single-crystal X-ray diffraction. The alkynyl fragments in cations 3 and 4 and in the neutral ruthenium derivative 5 are eclipsed, but the C⋯C interligand distances are longer than the minimal separation necessary (3.2-3.4 Å) to promote alkynyl coupling. The reactivity of these mono (1, 2) and bis[diphenyl(phenylethyny])phosphine] (3-5) complexes toward [cis-Pt(CF)(THF)] has been explored. Treatment of 1 with 1 equiv of [cis-Pt(CF)(THF)] in CHC1 affords the doubly chloride bridged [(PPhC=CPh)Cp*Rh(μ-Cl)Pt(CF)] 6. In contrast, the analogous iridium derivative [Cp*IrCl(PPhC≡CPh)] 2 reacts with [cis-Pt(CF)(THF)], leading to a mixture of isomers [(PPhC≡CPh)Cp*Ir(μ-Cl)Pt(CF )] 7a and [Cp*ClIr(μ-Cl)(:ηPPhC ≡CPh)Pt(CF)] 7b (7a/7b ≈ 2.5:1). Similar cationic [(PPhC≡CPh)Cp*M(μ-Cl)(P:η-PPhC≡CPh)Pt(CF)](OT f) [M = Rh 8, Ir 9] and neutral [(PPhC≡CPh)Cp*Ru(μCl)(P:η-PPhC≡CPh)Pt(CF)] 10 hetero-bridged complexes are formed by treatment of the bis[diphenyl(phenylethynyl)]phosphine (3-5) complexes with [cis-Pt(CF)(THF)] in CHC1. The structure of 10 has been confirmed by a single-crystal X-ray diffraction analysis.