Homogeneous model studies on the ammoxidation of propylene to acrylonitrile.

摘要

The Grasselli mechanism for the heterogeneous catalytic ammoxidation of propylene is well accepted by many in the field. However, the mechanism still remains as a proposal without the support of conclusive chemical evidence.; In this homogeneous model study, several allyl- and benzylimido complexes of Mo(V), Mo(VI), and W(VI) are synthesized. Complexes Mo{dollar}sp{lcub}rm v{rcub}{dollar}(NAll)Cl{dollar}sb3{dollar}(PPh{dollar}sb3)sb2{dollar} and Mo{dollar}sp{lcub}rm v{rcub}{dollar}(NAll)Cl{dollar}sb3{dollar}(OPPh{dollar}sb3)sb2{dollar} are structurally characterized. The presence of allyl- and benzylimido complexes of Mo(VI) in solution are demonstrated from their reactions with PPh{dollar}sb3{dollar} and OPPh{dollar}sb3{dollar} to form reduced Mo(V) complexes. When one equiv of {dollar}sp{lcub}rm t{rcub}{dollar}BuLi is added to W{dollar}sp{lcub}rm VI{rcub}{dollar}(NAll)Cl{dollar}sb4{dollar}(THF) in benzene, one {dollar}beta{dollar}-H is abstracted via dehydro-halogenation reaction, forming the allylideneamido tungsten(IV) complex, CH{dollar}sb2{dollar}=CH-CH=N=W{dollar}sp{lcub}rm IV{rcub}{dollar}Cl{dollar}sb3{dollar}(THF){dollar}sb2{dollar}. The transformation of an allyl- or benzylimido ligand to acrylonitrile or benzonitrile is achieved from the reaction of pyridine with virtually all the allyl or benzylimido complexes of Mo(V), Mo(VI) and W(VI) synthesized in this dissertation.; The formation and structure of a novel nitrido-bridged dimer with allylpyridinium counterion, (py{dollar}cdot{dollar}All) ((py){dollar}sb2{dollar}Cl{dollar}sb3{dollar}MoNMoCl{dollar}sb3{dollar}(py){dollar}sb2{dollar}), is described in Chapter III. Cleavage of C-N bond is proposed during the formation of the dimer complex.; The successful extension of the homogeneous model for the ammoxidation of propylene to the polyoxometalate systems is described in Chapter IV. This chapter also features another important development: direct functionalization of polyoxometalates.; Mono- and penta-functionalized polyoxoanions, (Mo{dollar}sb5{dollar}O{dollar}sb{lcub}18{rcub}{dollar}(MoNTol-p)) {dollar}sp{lcub}2-{rcub}{dollar} and (Mo{dollar}sb6{dollar}O{dollar}sb{lcub}14{rcub}{dollar}(NTol-p){dollar}sb5{dollar}) {dollar}sp{lcub}2-{rcub}{dollar} are synthesized quantitatively from the condensation reactions of ({dollar}sp{lcub}rm t{rcub}{dollar}Bu{dollar}sb4{dollar}N) {dollar}sb2{dollar} (Mo{dollar}sb6{dollar}O{dollar}sb{lcub}19{rcub}{dollar}) with TolN=PPh{dollar}sb3{dollar} and are structurally characterized. Reaction of (Mo{dollar}sb6{dollar}O{dollar}sb{lcub}18{rcub}{dollar}) {dollar}sp{lcub}2-{rcub}{dollar} with 0.5 equiv of 1,4-Ph{dollar}sb3{dollar}P=NC{dollar}sb6{dollar}H{dollar}sb4{dollar}N=PPh{dollar}sb3{dollar} is explored. Analyses of the product indicated that both (Mo{dollar}sb5{dollar}O{dollar}sb{lcub}18{rcub}{dollar}(MoNC{dollar}sb6{dollar}H{dollar}sb4{dollar}NPPh{dollar}sb3{dollar}-1,4)) {dollar}sp{lcub}2-{rcub}{dollar} and (Mo{dollar}sb5{dollar}O{dollar}sb{lcub}18{rcub}{dollar}(MoNC{dollar}sb6{dollar}H{dollar}sb4{dollar}NMo)Mo{dollar}sb5{dollar}O{dollar}sb{lcub}18{rcub}{dollar}) {dollar}sp{lcub}4-{rcub}{dollar} are produced.; Acrylonitrile(4%) and Benzonitrile(15%) are produced from the reactions of (Mo{dollar}sb6{dollar}O{dollar}sb{lcub}19{rcub}{dollar}) {dollar}sp{lcub}2-{rcub}{dollar} with AllN=PPh{dollar}sb3{dollar} and BzN=PPh{dollar}sb3{dollar}, respectively. Formation of (Mo{dollar}sb5{dollar}O{dollar}sb{lcub}18{rcub}{dollar}(MoNTol-p)) {dollar}sp{lcub}2-{rcub}{dollar} and in-situ {dollar}sp1{dollar}H NMR monitoring of the reaction of (Mo{dollar}sb6{dollar}O{dollar}sb{lcub}19{rcub}{dollar}) {dollar}sp{lcub}2-{rcub}{dollar} with AllN=PPh{dollar}sb3{dollar} in py-D{dollar}sb5{dollar} give strong evidences for the formation of an allylimido intermediate, (Mo{dollar}sb5{dollar}O{dollar}sb{lcub}18{rcub}{dollar}(MoNTol-p)) {dollar}sp{lcub}2-{rcub}{dollar}during the format