Unusual Oxidation of Phosphines Employing Water as the Oxygen Atom Source and Tris(benzene-1,2-dithiolate)molybdenum(VI) as the Oxidant. A Functional Molybdenum Hydroxylase Analogue System

DFT Study on the Interaction of Tris(benzene-1,2-dithiolato)molybdenum Complex with Water. A Hydrolysis Mechanism Involving a Feasible Seven-Coordinate Aquomolybdenum Intermediate

In the present work, the reactivity of the tris(benzene-1,2-dithiolato)molybdenum complex ([Mo(bdt)₃]) toward water is studied by means of the density functional theory (DFT). DFT calculations were performed using the M06, B3P86, and B3PW91 hybrid functionals for comparison purposes. The M06 method was employed to elucidate the reaction pathway, relative stability of the intermediate products, nature of the Mo-S bond cleavage, and electronic structure of the involved molybdenum species. This functional was also used to study the transference of electrons from the molybdenum center toward the ligands. The reaction pathway confirms that [Mo(bdt)₃] undergoes hydrolysis, yielding dihydroxo-bis(benzene-1,2-dithiolato)molybdenum complex ([Mo(OH)₂(bdt)₂]) and benzenedithiol. The reaction takes place through seven transition structures, one of them involving an aquo seven-coordinate molybdenum intermediate stabilized by a lone pair (LP) LP_O→LP_Mo hyperconjugative interaction. This heptacoordinate species allows understanding of the observed oxygen atom exchange between water and tertiary phosphines mediated by these complexes. Calculations also show that [Mo(C₂H₄S₂)₃] and [Mo(OH)₂(C₂H₄S₂)₂] have d² and d⁰ electronic configuration, and hence an electron pair must be transferred during the course of the hydrolysis. The frontier molecular orbital (FMO) analysis concludes that the electron pair is transferred in the rupture of the second Mo-S bond, from the occupied donating Mo d_x²-y² orbital to the unoccupied C₂H₄(SH)₂ S-C σ* ligand orbital. This result is supported by the bond dissociation energy calculations, which demonstrate that the neutral dissociation of the second Mo-S bond is energetically the more favorable.

Amino acid-derived N-heterocyclic carbene palladium complexes for aqueous phase Suzuki–Miyaura couplings

Five palladium complexes featuring N-heterocyclic carbene ligands derived from sustainable precursors have been synthesized and applied in aqueous Suzuki–Miyaura couplings.

Electronic Structure of Neutral and Monoanionic Tris(benzene-1,2-dithiolato)metal Complexes of Molybdenum and Tungsten

The reaction of 3 equiv of the ligand 2-mercapto-3,5-di-tert-butylaniline, H2[LN,S], or 3,5-di-tert-butyl-1,2-benzenedithiol, H2[LS,S], with 1 equiv of [MoO2(acac)2] or WCl6 (acac=acetonylacetate(1-)) in methanol or CCl4 afforded the diamagnetic neutral complexes [MoV(LN,S)2(L*N,S)]0 (1), [MoV(LS,S)2(L*S,S)] (2), and [WV(LS,S)2(L*S,S)] (3), where (L*N,S)- and (L*S,S)- represent monoanionic pi-radical ligands (Srad=1/2), which are the one-electron oxidized forms of the corresponding closed-shell dianions (LN,S)2- and (LS,S)2-. Complexes 1-3 are trigonal-prismatic members of the electron-transfer series [ML3]z (z=0, 1-, 2-). Reaction of 2 and 3 with [N(n-Bu)4](SH) in CH2Cl2 under anaerobic conditions afforded paramagnetic crystalline [N(n-Bu)4][MoV(LS,S)3] (4) and [N(n-Bu)4][WV(LS,S)3] (5). Complexes 1-5 have been characterized by X-ray crystallography. S K-edge X-ray absorption and infrared spectroscopy prove that a pi-radical ligand (L*S,S)- is present in neutral 2 and 3, whereas the monoanions [MV(LS,S)3]- contain only closed-shell dianionic ligands. These neutral species have previously been incorrectly described as [MVI(L)3]0 complexes with a MoVI or WVI (d0) central metal ion; they are, in fact MV (d1) (M=Mo, W) species: [MoV(LS,S)2(L*S,S)] and [WV(LS,S)2(L*S,S)] with a diamagnetic ground state St=0, which is generated by intramolecular, antiferromagnetic coupling between the MV (d1) central ion (SM=1/2) and a ligand pi radical (L*S,S)- (Srad=1/2).