Reactivity of Molybdenum and Rhenium Hydroxo-Carbonyl Complexes toward Organic Electrophiles

摘要

The hydroxo compounds [Re(OH)(CO)_3(N-N)] (N-N=bipy, 2a; Me_2-bipy, 2b) were prepared in a biphasic H_2O/CH_2C1_2 medium by reaction of [Re(OTf)(CO)_3(N-N)] with KOH. In contrast, when anhydrous CH_2C1_2 was used, the binuclear hydroxo-bridged compound [{Re(CO)_3-(bipy)}_2(mu,-OH)]OTf (3-OTf) was obtained. Compound [Re(OH)(CO)3-(Me_2-bipy)] (2b) reacted with phenyl acetate or vinyl acetate to afford [Re-(OAc)(CO)_3(Me_2-bipy)] (4) and phenol or acetaldehyde, respectively. The reactions of [Mo(OH)(eta~3-C_3H_4-Me-2)(CO)_2(phen)] (1), 2a, and 2b toward several unsaturated organic electrophiles were studied. The reaction of 1 with (p-tolyl)isocyanate afforded an adduct of N,N'-di(p-tolyl)-urea and the carbonato-bridged compound [{Mo(eta~3-C_3H_4-Me-2)(CO)_2-(phen)}_2(mu-eta~1(O),eta~1(O)-CO_)] (5). In contrast, the reaction of 2a with phenylisocyanate afforded [Re(OC(O)NHPh)(CO)_3(bipy)] (6); this results from formal PhNCO insertion into the O-H bond. On the other hand, compounds [Mo[SC(O)NH(p-tolyl)](eta~3-C_3H_4-Me-2)(CO)_2(phen)] (7), [Re[SC(O)NH(p-tolyl)](CO)_3(Me_2-bipy)] (8a), and [Re[SC(O)NHEt](CO)_3(Me_2-bipy)] (8b) were obtained by reaction of 1 or 2b with the corresponding alkyl or aryl isothiocyanates. In those cases, RNCS was inserted into the M-O bond. The reactions of 1, 2a, and 2b with dimethylacetylenedicar-boxylate (DMAD) gave the complexes [Mo[C(OH)-C(CO_2Me)C(CO_2Me)-O](eta~3-C_3H_4-Me-2)(CO)(phen)] (9) and [Re[C(OH)C(CO_2Me)C(CO_2Me)O](CO)_2(N-N)] (N-N-bipy, 10a; Me_2-bipy, 10b). The molecules of these compounds contain five-membered metallacycles that are the result of coupling between the hydroxo ligand, DMAD, and one of the CO ligands. The new compounds were characterized by a combination of IR and NMR spectroscopy, and for [{Re-(CO)_3(bipy)}_2(mu-OH)]BF_4 (3-BF_4), 4, 5, 6, 7, 8b, 9, and 10b, also by means of sinele-crvstal X-rav diffraction.