Single site derivatives of a plenary Keggin polyoxometalate

The preparation of the series of salts of the mixed-metal Keggin polyoxometalates (LMO) {dollar}sp{lcub}4-{rcub}{dollar} (L = {dollar}alpha{dollar}-{dollar}rm PWsb{lcub}11{rcub}Osb{lcub}39{rcub}{dollar}; M = V, Nb, Ta) with the tetrabutylammonium cation was carried out in non-aqueous solvents. The exchange of the terminal MO oxygen in the latter two ions with water is catalysed by protons and was used to prepare {dollar}sp{lcub}17{rcub}{dollar}O labelled compounds.; Four monochalcogenidosubstituted derivatives (LMQ) {dollar}sp{lcub}4-{rcub}{dollar} (M = Nb or Ta, Q = S or Se) were synthesized by chalcogen for terminal MO oxygen exchange with bis(trialkylsilyl) chalcogenides. Three of them (M = Nb, Q = S, Se; M = Ta, Q = S) are resistant to water in organic solution.; The entire series of (LNbOEMe{dollar}sb3rbracksp{lcub}3-{rcub}{dollar} ions (E = C, Si, Ge, Sn, Pb) was prepared from the (LNbO) {dollar}sp{lcub}4-{rcub}{dollar} ion. The (LNbOEMe{dollar}sb3rbracksb{lcub}3-{rcub}{dollar} derivatives can be cleaved with simple ions under mild conditions. The last three of them are stable in the presence of water and can exchange their NbOE oxygen with it.; The formation, structure and reactivity of the condensed ((LNb){dollar}rmsb2Orbracksp{lcub}6-{rcub}{dollar} polyoxometalate show that it can be considered to be an anhydride of the (HONbL) {dollar}sp{lcub}3-{rcub}{dollar} acid. Reactions of this anhydride with alcohols, silanols, hexamethyldisiloxane and related tin compounds were used to prepare several alkyl, silyl and stannyl single site derivatives of the title ion.; Another series of polyoxometalate complexes ((LNbO){dollar}sb2{dollar}ZCp{dollar}sb2rbracksp{lcub}6-{rcub}{dollar} (Z = Ti, Zr, Hf) derived from the (LNbO) {dollar}sp{lcub}4-{rcub}{dollar} ion was synthesized and studied. These metallocene complexes act as polyoxometalate transfer reagents with respect to R{dollar}sb3{dollar}SiX (R = Me, X = Cl, Br, I; R = i-Pr, X = Cl) and are of potential use for the activation of halide ligands.; The first conjugate between a polyoxometalate and an iron porphyrin with a formula (LNbOFeTPP) {dollar}sp{lcub}3-{rcub}{dollar} (TPP = tetraphenylporphine) was prepared and characterized. Its X-ray structure reveals a bent Nb-O-Fe bridge connecting the two subunits.