Platinum–phosphorus bond lengths and nuclear magnetic resonance coupling constants in complexes of tri(n-alkyl)- and tricyclohexylphosphines. Crystal and molecular structure of trans-di-iodobis(trimethylphosphine)platinum(II)

Abstract

The crystal and molecular structure of trans-[Ptl₂(PMe₃)₂] has been determined. Crystals are monoclinic, space group P2₁/n, with a= 8.845(6), b= 10.298(8), c= 7.936(5)Å, β= 95.12(4)°, and Z= 2. Intensities have been measured by diffractometer and the structure solved by the heavy-atom method and refined to R 0.041. The crystal comprises discrete centrosymmetric molecules wrth only small deviations from square-planar co-ordination [Pt–P 2.315(4) and Pt–I 2.599(2)Å]. The intramolecular H ⋯ I distances are longer than in trans-[PtI₂{P(C₆H₁₁)₃}₂]. The configuration of the cyclohexyl groups of the P(C₆H₁₁)₃ ligands is determined by H ⋯ H interactions and leads to strong H ⋯ I interactions between hydrogen atoms on two α-carbon atoms and the Iodide ligands, with consequent lengthening of the Pt–P and Pt–I bonds in trans-[PtI₂{P(C₆H₁₁)₃}₂]. The coupling constants ¹J(Pt–P) for trans-di-iodo(tricyclohexylphosphine) complexes are larger than expected, probably due to large |Ψ_Pt,6s(0)|²/(³ΔE) terms for complexes with bonds lengthened by steric repulsions.