Synthesis and reactivity of Pt II complexes containing the orthometallated ligand [C6H4-2-PPh2C(H)COCH2PPh3]

Abstract

The reaction of PtCl₂(NCPh)₂ with the ylide [Ph₃PC(H)COCH₂PPh₃]ClO₄ (1:1 molar ratio, refluxing CHCl₃) affords trans-[PtCl₂(NCPh){C(H)PPh₃C(O)CH₂PPh₃}]ClO₄1. However, the reaction of PtCl₂ (CH₂Cl₂, r.t.) or PtCl₂(NCMe)₂ (2-methoxyethanol, reflux) with the ylide [Ph₃PC(H)COCH₂PPh₃]ClO₄ (1:1 molar ratio) affords the orthometallated [Pt{C₆H₄-2-PPh₂C(H)COCH₂PPh₃}(μ-Cl)]₂(ClO₄)₂, 2, as a mixture of diastereoisomers 2a–d. Treatment of 2 with PPh₃ (1:2 molar ratio) affords [PtCl{C₆H₄-2-PPh₂C(H)COCH₂PPh₃}(PPh₃)](ClO₄), 3, as a single geometric isomer. The reaction of 2 with AgClO₄ (1:2 molar ratio) in NCMe gives the solvato complex [Pt{C₆H₄-2-PPh₂C(H)COCH₂PPh₃}(NCMe)₂](ClO₄)₂, 4, while the reaction of 2 with Tl(acac) (1: 2 molar ratio) gives [Pt{C₆H₄-2-PPh₂C(H)COCH₂PPh₃}(acac)](ClO₄), 5. The dicationic complexes [Pt{C₆H₄-2-PPh₂C(H)COCH₂PPh₃}(dppe)](ClO₄)₂, 6, and [Pt{C₆H₄-2-PPh₂C(H)COCH₂PPh₃}(phen)](ClO₄)₂, 7, can be obtained by reaction of 2 with AgClO₄ followed by addition of the appropiate ligand (1: 2:2 molar ratio). The reaction of 6 with NaH gives [Pt{C₆H₄-2-PPh₂C(H)COCHPPh₃}(dppe)](ClO₄), 8, while the reaction of 4 with PPh₃ and NaH gives [Pt{C₆H₄-2-PPh₂C(H)COCHPPh₃}(PPh₃)₂](ClO₄), 9. Complexes 8 and 9, which contain a “free ylide” functionality, react with ClAu(tht) to give [Pt{C₆H₄-2-PPh₂C(H)COCH(AuCl)PPh₃}(dppe)](ClO₄), 10, and [Pt{C₆H₄-2-PPh₂C(H)COCH(AuCl)PPh₃}(PPh₃)₂](ClO₄), 11. In the heterobimetallic complexes 10 and 11 the ylide ligand acts as a C,C,C-terdentate ligand and, in spite of the presence of two chiral centers, only one diastereoisomer (as the mixture of two enantiomers) is observed. All complexes were characterized on the basis of their spectroscopical and analytical parameters.