Chemistry of bis(dihydrogen) ruthenium complexes and of their derivatives

This review is devoted to the chemistry of bis(dihydrogen) complexes. Only a few bis(dihydrogen) complexes have been characterized, among which the three that have been isolated in our group, namely RuH2(H-2)(2)(PCy3)(2) 1 and LRuH(H-2)(2) (L=hydridotris(3,5-dimethylpyrazolyl) borate, Tp*, 65; L = hydridotris(3-isopropyl-4-bromo-pyrazolyl)borate Tp', 66). The first part will present in detail the synthesis and characterization of RuH2(H-2)(2)(PCy3)(2). Its reactivity, as well as its use as catalyst precursor, will be extensively reviewed. The second part of this review deals with the chemistry of the hydridotris(pyrazolyl)borato ruthenium complexes. The different reactivity of these two classes of compounds is dominated by the nature of the eta(2)-H-2, coordination. The nucleophilic character of the hydride and dihydrogen ligands in 1 allows substitution and hydrogen transfer reactions, whereas the reactivity of 65 and 66 is dominated by the electrophilic character of the hydride and dihydrogen ligands. (C) 1998 Elsevier Science S.A. All rights reserved.