Late transition-metal complexes with the heterofunctional phosphine Ph2PNHP(O)Ph2
Abstract
The complexes [MCl(cod)(HL)](M = Rh or Ir), [PdCl(η3-C3H5)(HL)], [PdCl(L–L)(HL)], trans-[RhCl(CO)(HL)2] and [AuCl(HL)] have been synthesised by reaction of either [{M(µ-Cl)(cod)}2](M = Rh or Ir; cod = cycloocta-1,5-diene), [{Pd(µ-Cl)(η3-C3H5)}2], [{Pd(µ-Cl)(L–L)}2](L–L = C12H12N, C10H8N or C9H12N), [{Rh(µ-Cl)(CO)2}2] or [AuCl(tht)](tht = tetrahydrothiophene) with Ph2PNHP(O)Ph2(HL). In all these complexes the ligand is monodenate P-bound. Chloride abstraction from [PdCl(C12H12N)(HL)] or [PdCl(η3-C3H5)(HL)], using Ag[BF4], gave the cationic compounds [Pd(C12H12N)(HL)][BF4] or [Pd(η3-C3H5)(HL)][BF4] in which the ligand HL is P,O-chelated. Removal of the amine proton in metal complexes of HL (monodenate P-bound) with KOBut afforded a new class of neutral metallacycles incorporating either an MP2NO or M2P4N2O2 framework based on the [Ph2PNP(O)Ph2]–(L–) ligand. Reaction of [{Pd(µ-Cl)-(C9H12N)}2] with 4 equivalents of HL in methanol at ambient temperature yielded the neutral palladium(II) complex [PdCl{Ph2PNP(O)Ph2-P,O}(Ph2POMe)] in which one HL ligand has undergone P–N bond scission. The reaction of the iridacycle [Ir(cod){Ph2PNP(O)Ph2-P,O}] with Mel was shown to proceed with cis addition affording the iridium(III) metallacycle [IrI(Me)(cod){Ph2PNP(O)Ph2-P,O}]. All compounds described have been characterised by a combination of 31P-{1H} NMR spectroscopy, microanalysis and in some cases by 1H NMR and IR spectroscopy. The molecular structures of four complexes have been determined by single-crystal X-ray diffraction. The metallacycles shown π-electron delocalisation in the P–N–P–O fragment.