Cobaloximes with Mixed Dioximes of Glyoxime and Diphenylglyoxime: Synthesis, Characterization, CV, X-ray Studies, and Crystal Packing B. D. Gupta,* R. Yamuna, and Debaprasad Mandal Department of Chemistry, Indian Institute of Technology, Kanpur, India 208016 ReceiVed October 23, 2005 Fourteen complexes of inorganic and alkyl cobaloximes with mixed dioximes of the type (R/X)Co- (gH)(dpgH)Py have been synthesized and characterized by 1 H and 13 C NMR and UV. The spectral data are interrelated, and a good correlation is found between Δδ 1 H(Py R ) with δ 1 H(gH), δ 13 C(CdN gH ), and δ 13 C(CdN dpgH ) indicating the ring current throughout the Co(dioxime) 2 + metallabicycle. All the spectroscopic data and CV show dependence on the field effect. The X-ray structure and crystal packing in ClCo(gH)(dpgH)Py, C 2 H 5 Co(gH)(dpgH)Py, and C 8 H 17 Co(gH)(dpgH)Py have been studied. ClCo- (gH)(dpgH)Py shows a right-handed helix. Introduction Cobaloximes, 1 proposed as model of B 12 coenzyme about 4 decades ago, represent a unique class of compounds in organo- metallic and bioinorganic chemistry, and because of their rich coordination chemistry and potential applications in organic synthesis, they have now acquired an independent research field. 2 Many papers have appeared in the recent past that describe the spectral and structural properties of cobaloximes. The reported trends are related to the mutual cis and trans influence of the ligands, as reflected in their NMR chemical shifts. 3-5 The studies describe the correlation of 1 H NMR chemical shifts of axial ligands B with those of the equatorial ligands and also include the multilinear correlation of 1 H NMR chemical shifts of B with the Co f dioxH charge-transfer band. 5 The spectral correlations initially were interpreted by Marzilli on the basis of cobalt anisotropy 3a-f,4c,6 and then by Lo ´pez on the basis of ring current formalism 5 and recently by us using the field effect (total effect of cobalt anisotropy and ring current). 7 Most of the information is on cobaloximes with dmgH as the equatorial ligand, and studies with other dioximes such as gH, 8a,b chgH, 8c dpgH, 8d,e and dmestgH 7 are few. We have recently reported the synthesis and cis-trans influence studies in mixed dioxime cobaloximes. 9 Despite the reduced ring current and cobalt anisotropy in these complexes, the spectral data fitted well as per our model. The cis influence order was found to be dmestgH > dpgH > dmgH-dpgH > chgH-dpgH > dmgH > gH > chgH. The study on the gH complexes, however, was hampered * To whom correspondence should be addressed. Tel: +91-512- 2597046. Fax: +91-512-2597436. E-mail: bdg@iitk.ac.in. (1) Cobaloximes have the general formula RCo(L)2B, where R is an organic group σ-bonded to cobalt. B is an axial base trans to the organic group, and L is a monoanionic dioxime ligand (e.g. glyoxime (gH), dimethylglyoxime (dmgH), 1,2-cyclohexanedione dioxime (chgH), di- phenylglyoxime (dpgH), and dimesitylglyoxime (dmestgH)). (2) (a) Giese, B. Radicals in Organic Synthesis: Formation of Carbon- Carbon Bonds; Pergamon Press: Oxford, U.K., 1986. (b) Scheffold, R.; Rytez, G.; Walder, L. 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