Trifluorosulfane Ligand as an Analogue of the Nitrosyl Ligand: Highly Exothermic Fluorine Transfer Reactions from Sulfur to Metal in the Chemistry of SF3 Metal Carbonyls of the First Row Transition Metals

The variety of known very stable PF3 metal derivatives analogous to metal carbonyls suggests the synthesis of SF3 metal derivatives analogous to metal nitrosyls. However, the only known SF3 metal complex is the structurally uncharacterized (Et3P)(2)Ir(CO)(Cl)(F)(SF3) synthesized by Cockman, Ebs-worth, and Holloway in 1987 and suggested by electron counting to have a one-electron donor SF3 group rather than a three-electron donor SF3 group. In this connection, the possibility of synthesizing SF3 metal derivatives analogous to metal nitrosyls has been investigated using density functional theory. The [M]SF3 derivatives with [M] = V(CO)(5), Mn(CO)(4), Co(CO)(3), Ir(CO)(3), (C5H5)Cr(CO)(2), (C5H5)Fe(CO), and (C5H5)Ni analogous to known metal nitrosyl derivatives are all predicted to be thermodynamically disfavored with respect to the corresponding [M](SF2)(F) derivatives by energies ranging from 19.5 kcal/mol for Mn(SF3) (CO)(4) to 5.4 kcal/mol for Co(SF3)(CO)(3). By contrast, the isoelectronic [M]PF3 derivatives with [M] = Cr(CO)(5), Fe(CO)(4), Ni(CO)(3), (C5H5)Mn(CO)(2,) (C5H5)CO(CO), and (C5H5)Cu are all very strongly thermodynamically favored with respect to the corresponding [M](PF2)(F) derivatives by energies ranging from 64.3 kcal/mol for Cr(PF3)(CO)(5) to 31.6 kcal/mol for (C5H5)Co(PF3)(CO). The known six-coordinate (Et3P)(2)Ir(CO)(Cl)(F)(SF3) is also predicted to be stable relative to the seven-coordinate (Et3P)(2)Ir(CO)(Cl)(F)(2)(SF2). Most of the metal SF3 complexes found in this work are singlet structures containing three-electron donor SF3 ligands with tetrahedral sulfur coordination. However, two examples of triplet spin state metal SF3 complexes, namely, the lowest energy (C5H5)Fe(SF3)(CO) structure and a higher energy Co(SF3)(CO)(3) structure, are found containing one-electron donor SF3 ligands with pseudo square pyramidal sulfur coordination with a stereochemically active lone electron pair.