Isomeric Mono‐ and Bis[(phosphane)gold(I)] Thiocyanate Complexes

Abstract

The solid-state IR spectrum of Me(3)PAuSCN shows two signals in the range of the C-N stretching vibrations at 2075 and 2113 cm(-1). On the basis of thoroughly tested quantum chemical ab initio calculations (MP2 level of theory) these signals have been assigned to the two isomeric forms Me(3)PAuNCS and Me(3)PAuSCN. The molecular structures, the vibrational frequencies, and the relative energies of the two species have been calculated and the results compared with the experimental IR data. Treatment of Me(3)PAuSCN with equimolar quantities of [(Me(3)P)Au](+)[SbF(6)](-) in CH(2)Cl(2) at -78 degrees C gives the dinuclear reaction product [C(7)H(9)Au(2)NP(2)S](+)[SbF(6)](-) in high yields. A comparison of results of ab initio calculations and IR data suggest that at least three isomeric cationic species [(R(3)PAu)(2)NCS](+), [(R(3)PAu)(2)SCN](+) and [(R(3)PAu)SCN(AuPR(3))](+) are present, the second and third being the predominant components. The structures and vibrational frequencies of all three species have been calculated. The relative energies in the gas phase and in solution are discussed and compared with the corresponding data of the experimental IR spectra.