Complexes of hybrid ligands. Synthesis, reactions, and structures of platinum complexes derived from a diphenylphosphino-substituted fluorinated tertiary alcohol

Article abstract of DOI:10.1021/ic00251a008

The synthesis of a number of platinum(II) complexes of the hybrid ligand Ph₂PCH₂C(CF₃)₂OH (HL¹) is described. The ligand interacts with Pt²⁺ in two ways: either unidentate and neutral, coordinating through phosphine, or bidentate and uninegative, (L¹)^-, coordinating through phosphine and alkoxide to form a five-membered chelate ring. Complexes prepared include cis- and trans-[PtCl₂(HL¹)₂], cis- and trans-[PtCl(L¹)(HL¹)], cis-[Pt(L¹)₂], cis-[PtCl(L¹)(PR₃)], trans-[Pt(CH₃)(L¹)(HL¹)], and the platinum(IV) complex [PtCl₂(L¹)₂]. Complete crystal and molecular structural determinations have been made on two complexes. trans-[PtCl₂(HL¹)₂] is monoclinic, space group P2₁/n, with a = 16.934 (2) A, b = 10.320 (1) A, c = 10.198 (2) A, β = 90.32 (1)°, V = 1782.2 (9) A³, and Z = 2. Least-squares refinement on F of 232 variables using 3234 observations converged at a conventional agreement factor of 0.039. cis-[Pt(L¹)₂] (CHCl₃ solvate) is monoclinic, space group P2₁/c, with a = 20.036 (3) A, b = 10.133 (1) A, c = 19.517 (3) A, β = 109.69 (1)°, V = 3731 (2) Aβ³, and Z = 4. Least-squares refinement on F of 313 variables using 3030 observations converged at a conventional agreement factor of 0.045. Ligand profiles are calculated from the structural data, and monodentate HL¹ is assigned a cone angle of 159°; the -CH₂C(CF³)₂OH substituent on phosphorus has a bulk comparable to that of tert-butyl or -C₆F₅. The C-OH bond length in coordinated HL¹ is 1.388 (7) A, significantly less than those found in unfluorinated alcohols. It is concluded that the bulk of neutral HL¹ stabilizes the trans isomer of [PtCl₂(HL¹)₂], while the effect of antisymbiosis is dominant in determining the geometry of complexes where the ligand is bidentate. Mechanisms for the formation and interconversion of the complexes are suggested.