Steric properties of sulfoxide ligands. Synthesis and crystal structure of mer-[RuCl3(Ph2So)3]

Abstract

Solid and circular cone angles and ligand profiles have been calculated for some sulfoxides, showing that S-bonded ligands are markedly bulkier than O-bonded ligands. An application of the cone angles to complexes of Ru^II and Ru^III showed that the bonding mode of sulfoxides appears to be the result of a balance between electronic and steric effects. The complex mer-[RuCl₃(dpso)₃](dpso = Ph₂SO) has been synthesized and structurally characterized: triclinic, space group P, Z= 2 with a= 10.315(3), b= 13.093(4), c= 15.692(5)Å, α= 102.98(2), β= 106.79(1), γ= 102.17(2)°. Two of the three sulfoxides are O- and one is S-bonded. One dpso-O is trans to dpso-S, while the other is trans to Cl. The co-ordination bond distances are consistent with the trans-influence order O < Cl < S. Strain-energy and conformational-entropy terms of three isomers of mer-[RuCl₃(dpso)₃] have been evaluated through molecular mechanics calculations. The energy difference of 7.6 kcal mol^–1 between the characterized complex and the linkage isomer with two trans dpso-S ligands indicates that the isomer isolated is probably favoured thermodynamically and suggests that the interligand steric interactions play an important role in the isomer stability.