| The oxo-imido molybdenum(VI) dithiocarbamate complex MoO- (Ntol)L(,2) (tol=p-tolyl; L=S(,2)CNEt(,2)) reacts with 0.5 equivalents of Ph(,3)P or EtPh(,2)P to produce the dinuclear Mo(V) complex Mo(Ntol)L(,2) (,2)O and the corresponding phosphine oxide. An oxo-bridged structure for the dinuclear complex is indicated by IR and ('17)O NMR studies. The visible spectrum of the dinuclear complex displays an intense absorption at 533 nm that does not obey the Lambert-Beer Law: this observation is interpreted in terms of an equilibrium produced via Mo-O bond scission in the dimer.; Additionally, the molecular structure of the dimethylacetylene- dicarboxylate adduct of bis(diethyldithiocarbamato)(p-tolylimido)- molybdenum(IV), Mo(Ntol)(DMAC)(S(,2)CNEt(,2))(,2), is described. The complex represents a rare example of an unsaturated organic mole- cule ligated to an organoimido species. The complex crystallizes in space group P2(,1)/c with the following parameters: a = 17.680(3), b = 8.860(1), c = 20.497(3)(ANGSTROM), (beta) = 106.97(1)(DEGREES), Z = 4. Least-squares refinement based on all 4039 unique intensities converged to R = 0.042 and R(,w) = 0.054. The complex displays a distorted pentagonal bipyramidal structure.; Metathetical substitution reactions involving V(Ntol)Cl(,3) afford alkoxide, aryloxide, and alkyl derivatives of (p-tolylimido)vanadium(V) of the form V(Ntol)Z(,n)Cl(,3-n) (Z = O('t)Bu, O-2,6-C(,6)H(,3)Me(,2), CH(,2)SiMe(,3); n = 1, 2, 3). The successful synthesis of the trimethylsilyl species are critically dependent on the nature of the alkylating agent employed. The molecular structure of the chlorobis(dimethylphenoxide) complex is consistent with an eighteen-electron configuration about the vanadium atoms.; ('51)V NMR studies have been performed on a series of (p-tolyl- imido)vanadium(V) complexes of the general form V(Ntol)Z(,n)Cl(,3-n) (Z = O('t)Bu, 0-2,6-C(,6)H(,3)Me(,2), CH(,2)SiMe(,3); n = 1, 2, 3). In accord with the previously established "Inverse Halogen Dependence" of V(V) nuclei, increasing electronegativity of the substituent Z is manifested in increased shielding of the ('51)V nucleus. The energies of electronic transitions observed in the visible and near IR regions of these species' spectra have been correlated with their ('51)V chemical shifts.; The reaction of two equivalents of MoCl(,4)(THF)(,2) with N(,3)-C(,6)H(,4)- N(,3) yields the novel Mo(VI) diimido bridged dimer, (THF)Cl(,4)MoN- C(,6)H(,4)NMoCl(,4)(THF). The Mo(V) and Mo(IV) diimido bridged dimers can be prepared via reduction of the Mo(VI) and Mo(V) dimers respectively, yielding (PMe(,3))(,2)Cl(,3)MoNCD(,6)H(,4)NMoCl(,3)(PMe(,3))(,2) and (PMe(,3))(,3)Cl(,2)MoNC(,6)H(,4)NMoCl(,2)(PMe(,3))(,3). These diimido bridged dimers exhibit significant differences in reactivity compared to analogous monomeric systems. |
