Polyoxometalate clusters as building blocks

The successful bridging of two hexamolybdate anions by an organodi-imido ligand has been achieved. The reaction between two equivalents of ((n-Bu){dollar}rmsb4Nrbracksb2lbrack Mosb6Osb{lcub}19{rcub}rbrack{dollar} and an organic diisocyanate occurs in pyridine with the evolution of CO{dollar}sb2{dollar} and formation of ((n-Bu){dollar}rmsb4Nrbracksb4lbrack (Mosb5Osb{lcub}18{rcub}{dollar})MoN-Z-NMo(Mo{dollar}rmsb5Osb{lcub}18{rcub})rbrack{dollar} complexes (Z p-C{dollar}rmsb6Hsb4,{dollar} 1a; p-C{dollar}rmsb6Hsb3CHsb3{dollar}, 1b; trans-1,4-cyclohexyl, 1c).; The electronic spectra and electrochemical analysis suggest electronic communication between the two hexamolybdate clusters for the aryldi-imido complexes, 1a and 1b. The electronic spectra show a significant bathochromic shift for the ligand HOMO to metal LUMO charge transfer transition. While most imido hexamolybdate systems display a bathochromic shift, it is much more significant for the two aryldi-imido systems than in other systems indicating substantial orbital stabilization by coordination of the second hexamolybdate cluster to the diimido system. Cyclic voltammetry experiments reveal three reduction processes for 1a and 1b, which also suggest electronic communication between the two hexamolybdate clusters.; The trans-cyclohexyldi-imido system was structurally characterized and reveals that the two hexamolybdate cages are coordinated to the diimido ligand at terminal positions and are poised in a diaxial arrangement on the cyclohexyldi-imido bridge.; Extending these procedures for the bis(hexamolybdate) systems to generate multiply linked oligo- and poly(hexamolybdate) diimido networks was investigated and preliminary results are presented.; Ferrocenyl isocyanate was synthesized and reacted with ((n-Bu){dollar}rmsb4Nrbracksb2lbrack Mosb6Osb{lcub}19{rcub}rbrack{dollar} in pyridine, giving CO{dollar}sb2{dollar} evolution and formation of the first ferrocenylimido system ((n-Bu){dollar}rmsb4Nrbracksb2lbrack Mosb6Osb{lcub}18{rcub}{dollar}(NFc)). Ferrocenylimido hexamolybdate represents the first case in which an oxidizable donor is covalently attached to a polyoxometalate acceptor. The electronic spectrum of ((n-Bu){dollar}rmsb4Nrbracksb2lbrack Mosb6Osb{lcub}18{rcub}{dollar}(NFc)) displays an unique absorption at {dollar}rmlambdasb{lcub}max{rcub}=536 nm (varepsilon=1500){dollar} assignable to the intramolecular charge transfer from the metal centered Fe{dollar}rmsp{lcub}II{rcub}{dollar} to hexamolybdate cluster. Cyclic voltammetry experiments reveal two reduction processes assignable to the cluster and an oxidation process assignable to the ferrocenylimido ligand. Preliminary experiments to induce columnar stacking were investigated, as well as experiments to generate the charge separated donor-acceptor complex.