Bismuth Compounds Containig Bismuth-Group 14 Element bonds and Their Reactions Using Transition Metal Complexes

Usage of bismuth reagents in organic synthesis is very limited so far, while their usefulness is becoming clear recent years. Bismuth is one of the least toxic heavy element and its compounds have been used as excellent remedies against gastric disorders nearly 150 years. Therefore bismuth reagents meet the recent requirement for safe and environmentally friendly chemicals. This review article mainly deals with 1) synthetic method of organyl-, silyl-, germyl , and stannylbismuth compounds, 2) transition metal complexes containing trivalent bismuth ligands and 3) application of organobismuth compounds to organic synthesis using transition metal complex catalysts. Bismuth forms trivalent and pentavalent organyI compounds. For silyl-, germyl-, and stannylbismuth compounds, only trivalent species have been synthesized. Among trivalent organic compounds of group 15 elements, bismuth compounds have the weakest donor ability, which comes from higher s-character of its unshared electron pair. Hence relatively few numbers of transition metal complexes with trivalent bismuth ligands are known. Bismuth-carbon bond is very weak compared with other group 15 element-carbon bonds. Transition metal complexes can easily cleave and transform bismuth-carbon bond. Palladium-, rhodium- and copper-catalyzed reactions of organobismuth compounds have been reported.