Bis- and tris-phosphinostannane gold complexes featuring Au → Sn dative interactions: Synthesis, structures, and DFT calculations

Abstract As part of our interest in the coordination chemistry of heavy Group 14 elements, we have synthesized complexes of general formula [( o -(Ph 2 P)C 6 H 4 ) 2 SnClPh]AuX (X = Cl ( 2 -Cl), X = Br ( 2 -Br), and X = I ( 2 -I)) in which the chlorostanane unit acts as a σ-acceptor ligand toward gold. The existence of a Au → Sn dative bond is evidenced by a trigonal bipyramidal geometry about the tin atom as well as a distorted square planar geometry about the gold center. While the measured Au–Sn bond distances are crystallographically indistinguishable in this series, theoretical investigations reveal that the strength of the Au → Sn interaction increases in the order 2 -I  2 -Br  2 -Cl. These results suggest that the Au → Sn interaction is affected by the ligands around gold. Lastly, we also report the tripodal complex [( o -(Ph 2 P)C 6 H 4 ) 3 SnCl]AuSnCl 3 ( 4 ) in which the gold atom is concomitantly coordinated to a Z-type tin ligand and an X-type tin ligand.