Reactions of monoazadienes with metal carbonyl complexes. 14. Pseudo-allyl complexes from monoazadienes and cobalt carbonyl [Co2(CO)8] by activation of dihydrogen under mild conditions

Abstract

The reaction monoazadienes (MAD, a-g) with Co{sub 2}(CO){sub 8} under H{sub 2} atmosphere, affording the new pseudo-({alpha}-aminoallyl) complexes Co(CO){sub 3}{l_brace}RC(H)C(H)C(H)NHR`{r_brace} (la-g), provides an example of activation of dihydrogen under mild conditions (293 K, 1.2 bar H{sub 2}). Complexes 1 have also been prepared by the reaction of HCo(CO){sub 4}(CO){sub 12} with MAD under H{sub 2}. The electron-donating properties of the {alpha}-amino substituent in 1, inducing an increase of electron density at Co and asymmetry in the allyl-bonding, has been studied by IR, {sup 1}H, {sup 13}C, and {sup 59}Co NMR, and an X-ray crystal structure determination of 1a (R, R` = Me, p-Tol). Crystals of 1a are monoclinic, spacegroup P2{sub 1}/c with cell constants {alpha} = 9.304 (1) A, b = 20.585 (3) A, C = 7.613 (1) A, {Beta} = 90.80 (2){degrees}, Z = 4. A total of 1091 reflections have been used in the refinement, resulting in a final R value of 0.068. Concerning the mechanism of H{sub 2} activation, a radical pathway is proposed by which the observed quantitative yields of 1a/b(R` = aryl) and the moderate yields of 1c-g(R`=alkyl) can be explained. Also {alpha}, {Beta}-unsaturated aldehydes appear to be suitable substrates in the H{sub 2} activationmore » reaction with Co{sub 2}(CO){sub 8}, but the products are very unstable and could be characterized only partly. 60 refs., 4 figs., 7 tabs.« less