Mechanism of deuterium-hydrogen exchange in the photoisomerization of cobalt complex

The 3-cyanopropyl(-CH2CH2CH2CN) group bonded to the cobalt atom in cobaloxi me complexes is isomerized to the 1-cyanopropyl{-CH(CN)CH2CH3} group with r etention of the single crystal form by photo irradiation. When the dideuter ated 3-cyanopropyl group (-CH2CH2CD2CN) was used, the crystal structure ana lysis by neutron diffraction revealed that the produced 1-cyanopropyl group was not {-CD(CN)CHDCH3} but the disordered {-CD(CN)C(H1/2D1/2)(2)CH3} grou p. This indicates that the reaction proceeds through the 1-cyanopropyl grou p and that the olefinic molecule and the cobalthydride may exist in the int ermediate stages of the reaction. (C) 1999 Elsevier Science Ltd. All rights reserved.