INTRAMOLECULAR CONDENSATION-REACTIONS OF S-METHYLMETHIONINE COORDINATED TO COBALT(III)

The sulfonium salt [(en)2CoO2CCH(NH2)(CH2)2S(CH3)2]3+ (en = ethane-1,2 -diamine), prepared by methylation of the thioether group of N, 0-coor dinated methionine, undergoes a set of complex, intramolecular condens ations, oxidations, and rearrangements in aqueous base to give a novel pentadentate cobalt(III) complex (c. 20%) of the 1,9-diamino-4-hydrox y-3,7-diazanonane-4-boxylate ion (dhnc). Its structure has been determ ined by X-ray crystallographic analysis as trans(O,O)-[Co(dhnc)(OH2)] (ClO4)2.2H2O. The crystals were monoclinic, space group P2(1)/c with a 9.053(2), b 29-437(7), c 7.661(1) angstrom, beta 106.63(1)-degrees, a nd Z 4; 2383 data with I greater-than-or-equal-to 3sigma(I) were refin ed to conventional R factors of 0.046 and 0.060. Investigations concer ning the mechanism for the formation of this complex are described.