New group 11 complexes with metal–selenium bonds of methyldiphenylphosphane selenide: a solid state, solution and theoretical investigation

Abstract

Reactions between methyldiphenylphosphane selenide, SePPh₂Me, and different group 11 metal starting materials {CuCl, [CuNO₃(PPh₃)₂], AgOTf, [AgOTf(PPh₃)] (OTf = OSO₂CF₃), [AuCl(tht)], [Au(C₆F₅)(tht)] and [Au(C₆F₅)₃(tht)] (tht = tetrahydrothiophene)} were performed in order to obtain several new species with metal–selenium bonds. The new complexes [CuCl(SePPh₂Me)] (1), [AgOTf(SePPh₂Me)] (2), [AuCl(SePPh₂Me)] (5), [Au(C₆F₅)(SePPh₂Me)] (6) and [Au(C₆F₅)₃(SePPh₂Me)] (7) were isolated and structurally characterized in solution by multinuclear NMR spectroscopy (¹H, ³¹P, ⁷⁷Se and ¹⁹F where appropriate). Solid products were isolated also from the reactions between SePPh₂Me and [CuNO₃(PPh₃)₂] or [AgOTf(PPh₃)], respectively. NMR experiments, including low temperature ¹H and ³¹P NMR, revealed for them a dynamic behaviour in solution, involving the transfer of selenium from PPh₂Me to PPh₃. In case of the isolated silver(I) containing solid an equilibrium between, respectively, monomeric [AgOTf(PPh₃)(SePPh₂Me)] (3) and [AgOTf(PPh₂Me)(SePPh₃)] (4), and dimeric [Ag(PPh₃)(μ-SePPh₂Me)]₂(OTf)₂ (3a) and [Ag(PPh₂Me)(μ-SePPh₃)]₂(OTf)₂ (4a) species was observed in solution. In case of the isolated copper(I) containing solid the NMR studies brought no clear evidence for a similar behaviour, but it can not be excluded in a first stage of the reaction. However the transfer of selenium between the two triorganophosphanes takes place also in this case, but the NMR spectra suggest that the final reaction mixture contains the free triorganophospane selenides SePPh₂Me and SePPh₃ as well as the complex species [CuNO₃(PPh₃)₂], [CuNO₃(PPh₂Me)₂] and [CuNO₃(PPh₃)(PPh₂Me)] in equilibrium. Single-crystal X-ray diffraction studies revealed monomeric structures for the gold(I) 6 and gold(III) 7 complexes. In case of compound 6 weak aurophilic gold(I)⋯gold(I) contacts were also observed in the crystal. DFT calculations were performed in order to understand the solution behaviour of the silver(I) and copper(I) species containing both P(III) and P(V) ligands, to verify the stability of possible dimeric species and to account for the aurophilic interactions found for 6. In addition, the nature of the electronic transitions involved in the absorption/emission processes observed for 6 and 7 in the solid state were also investigated by means of TD-DFT calculations.