Diphenyl(phenylethynyl)phosphine d6 [Rh(III), Ir(III), Ru(II)] Complexes:  Preparation of Homo (μ-Cl)2 and Hetero (μ-Cl)(μ-PPh2C⋮CPh) Bridged d6−d8 Compounds

The novel P-coordinated diphenyl(phenylethynyl)phosphine complexes [Cp*MCl2(PPh2C⋮CPh)] [M = Rh 1, Ir 2] have been prepared by the bridge splitting of [Cp*MCl2]2 with PPh2C⋮CPh. Treatment of 1 and 2 with AgTfO and PPh2C⋮CPh affords the corresponding cationic compounds [Cp*MCl(PPh2C⋮CPh)2](OTf) [M = Rh 3, Ir 4, OTf = triflate], respectively. The analogous neutral Ru(II) derivative [Cp*RuCl(PPh2C⋮CPh)2] 5 has been obtained by reaction of PPh2C⋮CPh and the binuclear complex [Cp*RuCl2]2 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 Cα···Cα 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(phenylethynyl)phosphine] (3−5) complexes toward [cis-Pt(C6F5)2(THF)2] has been explored. Treatment of 1 with 1 equiv of [cis-Pt(C6F5)2(THF)2] in CH2Cl2 affords the doubly chloride bridged [(PPh2C⋮CPh)Cp*Rh(μ-Cl)2Pt(C6F5)2] 6. In contrast, the analogous iridium derivative [Cp*IrCl2(PPh2C⋮CPh)] 2 reacts with [cis-Pt(C6F5)2(THF)2], leading to a mixture of isomers [(PPh2C⋮CPh)Cp*Ir(μ-Cl)2Pt(C6F5)2] 7a and [Cp*ClIr(μ-Cl)(μ-κP:η2-PPh2C⋮CPh)Pt(C6F5)2] 7b (7a/7b ≈ 2.5:1). Similar cationic [(PPh2C⋮CPh)Cp*M(μ-Cl)(μ-κP:η2-PPh2C⋮CPh)Pt(C6F5)2](OTf) [M = Rh 8, Ir 9] and neutral [(PPh2C⋮CPh)Cp*Ru(μ-Cl)(μ-κP:η2-PPh2C⋮CPh)Pt(C6F5)2] 10 hetero-bridged complexes are formed by treatment of the bis[diphenyl(phenylethynyl)]phosphine (3−5) complexes with [cis-Pt(C6F5)2(THF)2] in CH2Cl2. The structure of 10 has been confirmed by a single-crystal X-ray diffraction analysis