Co−C Bond Reactivity and Cis Influence Relationship in Benzylcobaloximes with Glyoxime and Dimesitylglyoxime

Abstract

Benzyl cobaloximes, ArCH 2 Co(dioxime) 2 Py, with two different dioximes, glyoxime (gH) and dimesitylglyoxime (dmestgH), have been synthesized and characterized by 1 H and 13 C NMR and UVvis spectroscopy. The dioxy adducts, ArCH 2 (O 2 )Co(dioxime) 2 Py, were prepared by the insertion of molecular oxygen into the Co-C under photochemical conditions. The rate of insertion depends upon the nature of the dioxime and follows the order dmestgH . dpgH > chgH > dmgH > gH. The steric cis influence of the dioximes on the Co-C bond also follows the same order. The study also suggests that the interactions between the axial benzyl group and the dioximes have significant influence on the Co-C bond reactivity. Such interactions are also seen in the molecular structure of [C 6 H 4 CH 2 Co(gH) 2 -(4-t BuPy)] and in the dioxy complexes 4-CN-C 6 H 4 CH 2 (O 2 )Co(dmestgH) 2 Py and 2-naphthylCH 2 -(O 2 )Co(dmestgH) 2 Py. On the basis of the results we have supported the cage mechanism for the oxygen insertion into the Co-C bond.

Benzyl cobaloximes with thiodioximes: Synthesis, structure and reactivity

“…The diamond diagram is shown in Fig. 5 and the selected bond lengths and bond angles are presented in Table 4 do not differ significantly from the previously reported values of oxygen inserted cobaloximes [28], [35,36]. The important observation is that the strain in 3c decreases after oxygen insertion since a and d values reduce to þ1.105 and þ0.007 Å respectively in 4.…”

“…Yield ¼ 68e75%. The oxygen insertion rate studies were carried out following the procedures outlined in our earlier paper [28] and the reported rate constants value is an average of the 2e3 trials in each case. 3.…”

“…We have, in the recent past, studied the reactivity of the CoeC bond by measuring the rate of oxygen insertion in organocobaloximes [28]. Since the cleavage of the CoeC bond is the key step in this reaction and the effect of cis-influence is felt most on the CoeCH 2 bond, these two processes, cis-influence and rate of insertion, are related to each other and follow the same order [16].…”

Reactivity studies of aryl cobaloximes with molecular oxygen and electrophiles

“…The complexes 4 and 5 are air-stable, yellow crystalline solids, soluble in CH 2 Cl 2 , CHCl 3 acetone, CH 3 OH and CH 3 CN. The new aryl cobaloximes (4 and 5) have been characterized by elemental analyses, NMR and also by X-ray crystallography.…”

Oxygenation of a benzyl ligand in SNS-palladium complexes with O2: acceleration by anions or Brønsted acids

“…[1][2][3][4][5][6] The insertion of O2 into a M-C(sp 3 ) bond in transition-metal alkyl complexes have been investigated, mainly limited to first-row metals such as Cr, 7 Fe, 8,9 and Co. [10][11][12] In the case of second and third-row late transition metals, only methylperoxopalladium 13 and platinum [14][15][16] complexes have been successfully captured. On the other hand, the reactions of several late transition-metal alkyl complexes with O2 produce oxygenated organic compounds.…”