Pentacoordination at Germanium by Transannular Bonding of Sulfur or Oxygen in an Eight-Membered Ring: An Experimental and Theoretical Study

Treatment of LnGeCl4n with D(C6H4SH)2 in the presence of nBuLi leads to the formation of the stable compounds D(C6H4S)2GeL1L2 (for D = S, L1 = Cl, L2 = Ph, 1 and L1 = L2 = Ph, 3; for D = O, L1 = Cl, L2 = Et, 4 and L1 = L2 = Ph, 5). The S(C6H4S)2Ge(Ph)Br compound (2) has been synthesised by halogen exchange from 1 and potassium bromide. X-ray structure determinations of complexes 15 reveal that the germanium atom acts as an acceptor atom displaying an intramolecular transannular interaction with the chalcogen D atom. The geometry of the pentacoordinate Ge atom in the title compounds is described as distorted trigonal bipyramidal with a 6431?% distortion displacement. The D?Ge (D = S, O) hypercoordinate interaction was studied by DFT methods using correlation consistent basis sets and relativistic ECP for Ge. NBO analysis showed that this interaction can be explained in terms of the interplay of covalent and Coulombic interactions.