| Research Abstract |
The objects of this research are development of novel C-H bond activation of functionalized organic substances using group 7 and 8 transition metal complexes and its application to selective organic syntheses. In this research, new rhenium, iron, and ruthenium complexes, which can smoothly produce reactive coordinatively unsaturated species, are successfully prepared. They are ReH(C_2H_4)_2(PMe_2Ph)_3 (1), ReH(N_2)(PMe_2Ph)_4 (2), [MnMe_2(dmpe)_2]^+[AlMe_4]^- (3), [MnMe_2(dmpe)_2]^+[BPh_4]^- (4), RuH_2(PPh_3)_4 (5), Ru(C_2H_4)(PPh_3)_3 (6), Fe(N_2)(depe)_2 (7), Complexes 2,5, and 6 react with active hydrogen compounds to give hydride complexes having an enolate anionic ligand. Enolate complexes derived from alpha-cyanocarboxylates have direct coordination of the cyano group to the metal leaving a highly nucleophlic enolate moiety. These complexes smoothly react with aldehydes and acrylonitrile to give aldol reaction and Michael addition products respectively. In contrast, enolate compl
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exes, which are produced by the reaction of 5 and 6 with 2,4- pentanedione, do not react with these compounds. All these complexes 2,5,6 and the enolate complexes thus prepared as well as Ru(cod)(cot)/PR_3 system act as selective catalysts of these reactions. These results indicate that the enolate complexes isolated in this research are active reaction intermediates, and support the unusually high selectivity of the ruthenium and rhenium catalyzed aldol and Michael type reactions.
On the other hand, the C-H bonds of alkenecarboxylates oxidatively add selectively to ruthenium(0) to give new hydridoalkenyl and hydrido-pi-allyl type complexes, depending on the esters employed. In the latter case, dienecarboxylate type complexes are gradually formed by the beta-hydrogen elimination from a sigma-allyl intermediate. The regeiselectivity in these CH bond activation reactions can be understood by the thermodydamic stability of the ruthenim products.
Unusual olefin metathesis reaction between coordinated alpha-cyanocinnamate on rhenium and tetracyanoethylene takes place under ambient conditions. The reaction is considered as the first example of olefin metathesis of functionalized olefins. Less
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