An improved synthesis of the prototype polyoxoanion−organometallic-support system, P 2 W 15 Nb 3 O 62 9 -, as its organic solvent-soluble all-[( n -C 4 H 9 ) 4 N] + salt is described. The improvements result in a 30% faster procedure which also provides a 60% increase in yield of [( n -C 4 H 9 ) 4 N] 9 P 2 W 15 Nb 3 O 62, 2 . One key improvement in this synthesis is a pH titration of protonated [( n -C 4 H 9 ) 4 N] 5 H 4 P 2 W 15 Nb 3 O 62, 1, using [( n -C 4 H 9 ) 4 N]OH and phenolpthalein indicator, which leads to fully deprotonated 2 the key synthon required for clean support of organometallic cations onto the P 2 W 15 Nb 3 O 62 9 - polyoxoanion's “Nb 3 O 9 3 - ” cap. The material obtained from this procedure is of the highest purity (≥95%) seen to date as judged by 31 P NMR spectroscopy. [( n -C 4 H 9 ) 4 N] 9 P 2 W 15 Nb 3 O 62 has been further characterized by 1 H, 13 C, 17 O, and 183 W NMR spectroscopy as well as IR spectroscopy and complete elemental analysis. Also reported are control experiments that (i) confirm the identical reactivity of 2, obtained by either the procedure reported herein or by our previously published accounts, with organometallic cations such as [Ir I (1,5-COD)] +, [Rh I (1,5-COD)] + and [Rh III (C 5 Me 5 )] 2+, (ii) show that the pH titration employed herein may be used to cleanly deprotonate polyoxoanions containing varying degrees of protonation, (iii) show that trace amounts of excess OH - present in P 2 W 15 Nb 3 O 62 9 - prevent clean organometallic cation-support reactions, and (iv) show that 31 P NMR titration of P 2 W 15 Nb 3 O 62 9 - using [(1,5-COD)Ir] + is an effective and simple method of determining the purity of P 2 W 15 Nb 3 O 62 9 - .
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Weiner et al. (1996) studied this question.
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