Synthesis, Characterization, and Biomimetic Chemistry of cis-Oxosulfidomolybdenum(VI) Complexes Stabilized by an Intramolecular Mo(O)S···S Interaction

The reactions of jade-green Tp*Mo^IVO(S₂PR₂) [Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate; R = Et, Prⁱ, Ph] with propylene sulfide produce ochre-red The complexes have been characterized by microanalysis, mass spectrometry, cyclic voltammetry, spectroscopy (IR, NMR, UV−vis, and X-ray absorption), and X-ray crystallography. The distorted-octahedral isopropyl and phenyl derivatives feature a tridentate fac-Tp* ligand, a terminal oxo ligand, and a unique five-membered ring moiety formed by a weak, intramolecular, bonding interaction between the MoS1 and (uncoordinated) S3P moieties. The MoS1 [2.227(2) Å (R = Prⁱ) and 2.200(2) Å (R = Ph)] and S1···S3 distances [2.396(3) Å (R = Prⁱ) and 2.383(2) Å (R = Ph)] are indicative of a π-bonded MoS1 unit and a weak (bond order ca. ¹/₃) S1···S3 interaction; the solid-state structures are maintained in solution according to S K-edge X-ray absorption data. The complexes react with excess cyanide to form thiocyanate and Tp*MoO(S₂PR₂), under anaerobic conditions, or Tp*MoO₂(S₂PR₂), under aerobic conditions; the latter models the production of thiocyanate and desulfo molybdenum hydroxylases upon cyanolysis of molybdenum hydroxylases. The complexes react with triphenylphosphine to give Tp*MoO(S₂PR₂) and SPPh₃, with cobaltocene or hydrosulfide ion to produce [Tp*Mo^VOS(S₂PR₂)]^-, and with ferrocenium salts to yield [Tp*Mo^VO(S₃PR₂)]⁺; in the last two reactions, Mo(V) is produced by direct or induced internal redox reactions, respectively. The presence of the Mo(O)S···S interaction does not radically lengthen the MoS bond in the complexes or preclude them from reactions typical of unperturbed oxosulfidomolybdenum(VI) complexes.