Spectroscopic study of phosphine selenide complexes of Au(I) and X-ray structure of [(cyclohexyl)₃PSeAuBr]

The X-ray structure determination of the complex, [(cyclohexyl)₃PSe-AuBr], revealed a triclinic space group P-1, with a = 9.7654(7), b = 10.9441(9), c = 11.2064(9) Å, α = 117.076(6)°, β = 99.076(6)°, γ = 95.417(6)°, V = 1034.07(14) ų and Z = 2. The Au(I) atom in this complex has a linear coordination with Se1 atom at 2.3776(9) Å on one side and Br1 at 2.3843(9) Å at the trans position making the Se1-Au1-Br1 angle of 177.97(4)°. The P1 atom in the phosphine has tetrahedral geometry. All three cyclohexyl groups are in their usual boat conformation. The phosphorus atom of the triphenylphosphine is approximately perpendicular to the Se1 - Au1 - Br1 linkage with P1 - Se1 - Au1 angle of 99.19(6)°. The Δδ in the ³¹P NMR of the free ligands and their corresponding L - Se - Au - Br (L - Se = trialkyl/arylphosphine selenides) complexes, and the changes in the P - Se bond frequencies in the FTIR upon complexation, are indicative of the bonding of the ligand to Au(I) through selenium. There is a strong corelation between the chemical shifts of the ³¹P NMR and the C - P - C angle in the phosphines.