Structural and spectroscopic studies on copper, silver and gold complexes of mixed phosphathia ligands and their chalcogenide derivatives

Abstract

Reaction of [Cu(MeCN)₄]PF₆ or AgBF₄ with 1 molar equivalent of Ph₂P(E)(CH₂)₂SZS(CH₂)₂(E)PPh₂[Z =(CH₂)₂, E = S (L^1b) or Se (L^1c); Z =(CH₂)₃, E = none (L^2a), S (L^2b) or Se (L^2c); Z =o-C₆H₄, E = none (L^3a), S (L^3b) or Se (L^3c)] in degassed acetone followed by addition of diethyl ether yielded the mononuclear complexes [ML]X (M = Cu, X^–= PF₆^–; M = Ag, X^–= BF₄^–) in high yield. The gold(I) species [AuL]PF₆ were obtained by reaction of L (= L^1b, L^1c, L^2b, L^2c or L^3a–L^3c) with 1 molar equivalent of [AuCl(tht)](tht = tetrahydrothiophene) and TlPF₆. All of these products have been characterised by ¹H, ³¹P-{¹H}(and in some cases ⁷⁷Se-{¹H} and ¹⁰⁹Ag) NMR and IR spectroscopy, FAB or electrospray mass spectrometry and microanalyses. The data indicate four-co-ordination for all of the copper(I) and silver(I) species and this assignment has been confirmed by single-crystal structure determinations on three copper(I) examples. Spectroscopic studies on [AuL]PF₆ indicated linear two-co-ordination on average, via the phosphine, phosphine sulfide or phosphine selenide functions as appropriate. Variable-temperature ³¹P-{¹H}(and ⁷⁷Se-{¹H}) studies showed that the chalcogenide complexes are considerably more labile in solution than the phosphathia ligand complexes. Crystal structure determinations on [CuL^3a]⁺, [CuL^1c]⁺, [AgL^1c]⁺ and [CuL^2b]⁺ each showed the metal ion co-ordinated to all four donor atoms of a single ligand in the solid state, giving an overall distorted-tetrahedral stereochemistry. In the case of [CuL^1c]⁺ there is a slight lengthening of the P–Se bond length compared to that of the unco-ordinated form of L^3c. Syntheses for the new pro-ligands are also detailed.