Gallium complexes borates

These complexes are the first examples of multifunctional catalysts and demonstrate impressively the opportunities that can reside with the as yet hardly investigated bimetallic catalysis. The concept described here is not limited to lanthanides but has been further extended to main group metals such as gallium [31] or aluminum [32]. In addition, this work should be an incentive for the investigation of other metal-binaphthyl complexes to find out whether polynuclear species play a role in catalytic processes there as well. For example, the preparation of ti-tanium-BINOL complexes takes place in the presence of alkali metals [molecular sieve ( )]. A leading contribution in this direction has been made by Kaufmann et al, as early as 1990 [33], It was proven that the reaction of (5)-la with monobromoborane dimethyl sulfide leads exclusively to a binuclear, propeller-like borate compound. This compound was found to catalyze the Diels-Alder reaction of cyclopentadiene and methacrolein with excellent exo-stereoselectivity and enantioselectivity in accordance with the empirical rule for carbonyl compounds which has been presented earlier. 

Gallium(III) complexes, 129 amines, 129 amino acids, 141 arsenates, 135 borates, 134 borohydrides, 141 bromates, 135 carbonates, 134 caiboxylates, 135 chlorates, 135 citrates, 136 cyanides, 129 dithiocarbamates, 138 ethers, 136 fluorides, 138 germanates, 134 hydrides, 140 iodates, 135 p-ketoenolates, 134 lactates, 136 mixed halides, 139 molybdates, 135 nitrates, 135 peptides, 141 perchlorates, 135... 

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