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

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)(m-SePPh2Me)]2(OTf)2 (3a) and [Ag(PPh2Me)(m-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.