Synthesis of Heterobridged (μ-C⋮CR)(μ-X) (X = PPh₂, PPh₂O) Platinum−Rhodium or Platinum−Iridium Dimers

The synthesis and full characterization of a series of heterobimetallic mixed-bridge alkynyl/phosphido platinum−rhodium and alkynyl/phosphinite platinum−rhodium and platinum−iridium complexes is presented. Treatment of trans-[Pt(C6F5)(C⋮CR)(PPh2H)2] [2; R = t-Bu (a), Ph (b)] [generated through the rupture of the homobridged trans,sym-[Pt(μ-κCα:η2-C⋮CR)(C6F5)(PPh2H)]2 (1) with PPh2H] or cis-[Pt(C⋮CR)2(PPh2H)2] with rhodium acetylacetonate species [Rh(acac)L2] (L2 = COD, 2CO) in acetone produces the corresponding alkynyl/diphenylphosphido-bridged complexes trans,cis-[(C6F5)(PPh2H)Pt(μ-κCα:η2-C⋮CR)(μ-PPh2)RhL2] [L2 = COD (3), 2CO (4a)] and cis,cis-[(C⋮CR)(PPh2H)Pt(μ-κCα:η2-C⋮CR)(μ-PPh2)RhL2] [L2 = COD (5), 2CO (6a)]. The related mixed alkynyl/phosphinite complexes [{(PPh2O)2H}Pt(μ-κCα:η2-C⋮CR)(μ-κP,κO-PPh2O)ML2] [ML2 = RhCOD (7), Rh(CO)2 (8), IrCOD (9)] can be prepared by reacting [Pt(C⋮CR){(PPh2O)2H}(PPh2OH)] with [M(acac)L2] (M = Rh, Ir). The molecular structure of 6a, determined by X-ray diffraction, shows that the alkynyl ligand is σ-bonded to platinum and η2-bonded to the rhodium center with a platinum−rhodium distance of 3.142(1) Å. Complex 6a (C38H39O2P2PtRh) crystallizes in the triclinic system, space group P1̄: a = 11.427(2) Å, b = 12.882(2) Å, c = 14.692(2) Å, α = 99.098(14)°, β = 108.339(12)°, γ = 113.11(2)°, V = 1787.2(4) Å3, and Z = 2.