Late transition-metal complexes of [Ph2P(O)NP(E)Ph2]- (E=S or Se) with a P,N-hybrid ligand: synthesis and structure

Abstract

The unsymmetrical ligands [Ph₂P(O)NP(E)Ph₂]^- (E=S or Se) adopt a range of ligation modes (O,E-chelate, E-monodentate and as a non-co-ordinating anion) upon reaction with selected late transition-metal tertiary phosphine complexes. Hence treatment of cis-[PtCl₂(PPh₃)₂] with K[Ph₂P(O)NP(E)Ph₂] in methanol gave the expected six-membered O,E-chelate complexes [Pt(PPh₃)₂{Ph₂P(O)NP(E)Ph₂-O,E}]⁺ isolated as their hexafluorophosphate salts. When [Pt(Ph₂PC₆H₄NH₂-P,N)₂]Cl₂ was allowed to react under analogous conditions the monocationic mixed complexes [Pt(Ph₂PC₆H₄NH-P,N)(Ph₂PC₆H₄NH₂-P,N)][Ph₂P(O)NP(E)Ph₂] were obtained in excellent yields (>90%). Reaction of [Pd(Ph₂PC₆H₄NH₂-P,N)₂]Cl₂ with K[Ph₂P(O)NP(S)Ph₂] (1:2 molar ratio) gave a mixture of three products identified by ³¹P-{¹H} NMR as [Pd(Ph₂PC₆H₄NH-P,N) (Ph₂PC₆H₄NH₂-P,N)][Ph₂P(O)NP(S)Ph₂], [Pd(Ph₂PC₆H₄NH-P,N){Ph₂P(O)NP(S)Ph₂-O,S}] (P trans to O) and Ph₂PC₆H₄NH₂. Alternatively the neutral compound [Pd(Ph₂PC₆H₄NH-P,N){Ph₂P(O)NP(S)Ph₂-O,S}] was synthesised in moderate yield from [PdCl₂(Ph₂PC₆H₄NH₂-P,N)] and two equivalents of K[Ph₂P(O)NP(S)Ph₂]. Chloride metathesis of [Pt(X)Cl(Ph₂PC₆H₄NH₂-P,N)] (X=CH₃ or Cl) with K[Ph₂P(O)NP(E)Ph₂] gave a series of platinum(II) complexes [Pt(X){Ph₂P(O)NP(E)Ph₂-E}(Ph₂PC₆H₄NH₂-P,N)] (P trans to E) in which the anion adopts an E-monodentate co-ordination mode. The gold(I) complexes [AuCl(PPh₃)] and [AuCl(Ph₂PC₆H₄NH₂)] undergo smooth substitution reactions with K[Ph₂P(O)NP(E)Ph₂] to give [Au{Ph₂P(O)NP(E)Ph₂-E}(PPh₃)] and [Au{Ph₂P(O)NP(E)Ph₂-E}(Ph₂PC₆H₄NH₂)] respectively. All new compounds have been characterised by a combination of multinuclear NMR [¹H, ³¹P-{¹H} and ¹⁹⁵Pt-{¹H}], IR spectroscopy and elemental analyses. The molecular structures of four examples have been determined by single-crystal X-ray crystallography and furthermore reveal intra- and inter-molecular PE···H–N hydrogen bonding arrangements. There is also evidence for π-delocalisation within the E–P–N–P–O backbone.