Functionalization of η1,η2-Bridging Cyaphide (C⋮P)-Ligands: Trinuclear η1,η1,η2-Bridging Cyaphide and Dinuclear Bridging Isocyaphide (C⋮PR) Complexes of Platinum

The oxidative addition reaction of Pt(PEt 3 ) 4 with Cl 2 C PN(SiMe 3 ) 2 at low temperature (−50 °C) forms the η 1 -phosphavinyl complex cis -Cl(Et 3 P) 2 Pt[C(Cl) PN(SiMe 3 ) 2 ] (Ia), which isomerizes to the trans -isomer (Ib) upon warming to 0 °C; the structure of Ib was determined by X-ray diffraction studies. Complex Ib reacts with Pt(PEt 3 ) 2 Cl 2 in the presence of 3 equiv of sodium benzophenone to generate the bridging, dinuclear η 1,η 2 -cyaphide complex Cl(Et 3 P) 2 Pt(μ-η 1,η 2 -C⋮P)Pt(PEt 3 ) 2 (II) in good yield, providing a much simpler and higher yield preparation of II, which was synthesized and characterized previously by a more circuitous route. Compound II reacts with 0.5 equiv of [Cl 2 Pt(PEt 3 )] 2 or with 1 equiv of W(CO) 5 (THF) to generate the trinuclear metal−cyaphide complexes Cl(Et 3 P) 2 Pt[μ-η 1,η 1,η 2 -C⋮P{Pt(PEt 3 )(Cl) 2 }]Pt(PEt 3 ) 2 (III) and Cl(Et 3 P) 2 Pt[μ-η 1,η 1,η 2 -C⋮P{W(CO) 5 }]Pt(PEt 3 ) 2 (IV), respectively, in which the lone pair of electrons on the C⋮P phosphorus atom is coordinated to a Pt(PEt 3 )(Cl) 2 fragment in the former and to a W(CO) 5 fragment in the latter; the structure of IV was determined by X-ray diffraction studies. Compound II also reacts with MeI to form the methyl isocyaphide complex (Cl)(Et 3 P)Pt(μ-C PMe)Pt(PEt 3 ) 2 (I) (Vc), in which the cyaphide (C⋮P - ) ligand is converted to a methyl isocyaphide (C⋮PMe) ligand in a semibridging coordination mode. When compound II is reacted with MeOTf, the product is the cationic isocyaphide complex [(Cl)(Et 3 P) 2 Pt(μ-η 1,η 2 -C⋮PMe)Pt(PEt 3 ) 2 ](OTf) (Va), which is likely coordinated in an η 1,η 2 -bridging mode. Compound Va reacts with NaI to form Vc, which suggests that Va forms as an intermediate before Vc in the reaction of II with MeI.