Dawson type heteropolyanions. 1. Multinuclear (phosphorus-31, vanadium-51, tungsten-183) NMR structural investigations of octadeca(molybdotungstovanado)diphosphates .alpha.-1,2,3-[P2MM'2W15O62]n- (M, M' = Mo, V, W): syntheses of new related compounds

The mixed binary anions dimolybdopentadecatungstodiphosphate, 1,2-(P{sub 2}Mo{sub 2}W{sub 15}O{sub 61}){sup 10{minus}}, hexadecatungstodivanadodiphosphate, 1,2-(P{sub 2}V{sub 2}W{sub 16}O{sub 62}){sup 8{minus}}, and the ternary molybdotungstovanadophosphates 1,2-3-(P{sub 2}Mo{sub 2}VW{sub 15}O{sub 62}){sup 7{minus}} and 1-2,3-(P{sub 2}MoV{sub 2}W{sub 15}O{sub 62}){sup 8{minus}}, derived from the Dawson anion {alpha}-(P{sub 2}W{sub 18}O{sub 62}){sup 6{minus}} by formal substitution in one polar W{sub 3}O{sub 13} group, have been synthesized. All the octadeca(molybdotungstovanado)diphosphates {alpha}-(1,2,3)-(P{sub 2}MM{prime}{sub 2}W{sub 15}O{sub 62}){sup n{minus}} (M, M{prime} = Mo, V, W) were characterized by electrochemistry and multinuclear ({sup 31}P, {sup 51}V, {sup 183}W) solution NMR techniques. The reactivity of 4-P{sub 2}MW{sub 17} toward alkaline degradation to get P{sub 2}MW{sub 14} is discussed on this basis: vanadium(V) in the 4-location directs the departure of the W{sub 3}O{sub 13} in the other half-anion (16-18-locations) whereas molybdenum(VI) ha no directing effect. The {sup 183}W chemical shifts are discussed also in relation with the nature and the location of the substituting atoms; although considerably remote from the polar substituted site, the tungsten atoms in the opposite polar group are generally as well affected (shielded) as those directly bound ({mu}-oxo junction in the same polar group) to the substituted atom (deshielded), even in the case of the isocharge W {yields} Mo replacement. 22more » refs., 7 figs., 5 tabs.« less