Co-ordination chemistry of a P,O-donor ligand: synthesis of new complexes of Ru, Rh and Ir containing Ph2PNHP(O)Ph2 or [Ph2PNP(O)Ph2

Abstract

Methylation of the monooxide Ph2PNHP(O)Ph2(HL) with MeI in tetrahydrofuran afforded [{Ph2P(Me)NP(O)Ph2}2H]I which contains a symmetrical hydrogen bond, whereas benzylation with PhCH2Br gave [Ph2P(CH2Ph)NP(OH)Ph2]Br. The compound HL can be complexed, as a monodentate P-bound ligand, to various, metal centres (RuII, RuIV, RhIII and IrIII). These compounds are excellent precursors for the construction of new five-membered metallacycles containing either M–P–N(H)–P–O or M–P–N–P–O rings. Treatment of [Ir{Ph2PNHP(O)Ph2-P,O}(cod)][BF4](cod = cycloocta-1,5-diene) with an excess of MeI gave the oxidative addition compound [IrI(Me){Ph2PNHP(O)Ph2-P,O}(cod)][BF4] in which a cis configuration of the iodide and methyl ligands is tentatively assigned. Deprotonation of it with NEt3 gave the known neutral iridium(III) complex [IrI(Me){Ph2PNP(O)Ph2-P,O}(cod)]. All compounds were characterised by a combination of 31P-{1H} and 1H NMR spectroscopy, IR spectroscopy and microanalysis. The solid-state structures of [{Ph2P(Me)NP(O)Ph2}2H]I, [Ph2P(CH2Ph)NP(OH)Ph2]Br, [Rh{Ph2PNHP(O)Ph2-P,O}(cod)]-[BF4]·0.33CHCl3 and [RuCl{Ph2PNP(O)Ph2-P,O}(η6-p-MeC6H4Pri)] have been elucidated by X-ray crystallography. The two complexes contain the P,O-chelating ligand Ph2PNHP(O)Ph2 and [Ph2PNP(O)Ph2]– respectively. With the exception of the rhodium complex the P–N–P–O fragments all show π-electron delocalisation.