The synthesis of metal coordination polymers using lessons learned from monomeric Werner complexes: chromium(III) β-diketone polymers

Abstract

Whereas the synthesis of linear metal coordination polymers that are soluble in organic solvents has proven quite difficult to achieve, such polymers can be prepared using the chemical intuition gained from the reactions of simple Werner coordination complexes. The problems of (1) keeping conjugated metal coordination systems from precipitating before the attainment of long polymer chains, (2) obtaining long metal coordination polymer chains with inert metal ions that do not react fast enough to allow long chains through normal substitution reactions, and (3) obtaining inert metal coordination polymeric chains from labile metal ions have all been solved by standard coordination chemistry reactions. This paper details some methods we have used to overcome these problems plus it reports new chromium(III) polymers that are obtained in deference to problem (2) above. Whereas Fourier-transform nuclear magnetic resonance studies of end groups do not allow molar mass measurements for these paramagnetic systems, viscosity comparisons with analogous cobalt(III) coordination polymers, where FTNMR results are obtainable, indicate that the number-average molar masses of these chromium(III) systems are of the order of 15,000.