Amine-functionalised aminophosphines: synthesis, reversible co-ordination to platinum and use in heteronuclear dimer formation

Abstract

Amine functionalised aminophosphines Ph₂PN(R)CH₂CH₂NMe₂ (R = H L¹ or Me L²) were prepared from the reaction of PPh₂Cl with NHRCH₂CH₂NMe₂ in the presence of the base n-butyllithium (L¹) or triethylamine (L²). Reaction of two equivalents of L^1,2 with [PtCl₂(cod)] gave the complexes cis-[PtCl₂L₂] (L = L¹1 or L²2), which were shown to be fluxional with one of the amine groups reversibly co-ordinating to displace a chloride. Removal of a chloride in 1 by metathesis gave cis-[PtCl(L¹-P)(L¹-P,N)]PF₆3 which was not fluxional on the NMR timescale. Reaction of one equivalent of L² with [PtCl₂(cod)] gave the complex cis-[PtCl₂(L²-P,N)] 4 in which L² is acting as a bidentate ligand. The reaction of L² with [{Pt(dmba)(μ-Cl)}₂] (Hdmba = N,N-dimethylbenzylamine) gave [Pt(dmba)Cl(L²)] 5, which exists as a mixture of the two geometric isomers. Reaction of 5 with TlPF₆ gave [Pt(dmba)(L²-P,N)]-PF₆6 as a single isomer in which the phosphorus atom is co-ordinated trans to the N,N-dimethylbenzylamine nitrogen atom. Complex 2 reacts with CoCl₂·6H₂O and ZnCl₂ to give cis-[(L²-P,N)ClPt(μ-L²)MCl₃] (M = Co 7 or Zn 8). The zwitterionic structure of 7 was confirmed by a single-crystal X-ray analysis, which showed no metal–metal interaction between the platinum and cobalt centres.