Synthesis and structure of mono-, bi- and trimetallic amine-bis(phenolate) cobalt(II) complexes

Kerton, Francesca M. and Das, Uttam K. and Bobak, Julia and Fowler, Candace and Hann, Sarah E. and Petten, Chad F. and Dawe, Louise N. and Decken, Andreas and Kozak, Christopher M. (2010) Synthesis and structure of mono-, bi- and trimetallic amine-bis(phenolate) cobalt(II) complexes. Dalton Transactions, 39 (23). pp. 5462-5477. ISSN 1477-9234

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Abstract

A series of cobalt(II) amine-bis(phenolate) complexes has been prepared and characterized. The protonated tripodal tetradentate ligand precursors; dimethylaminoethylamino-N,N-bis(2-methylene-4-tert-butyl-6-methylphenol), H2[O2NN¢]BuMeNMe2, dimethylaminoethylamino-N,N-bis(2-methylene-4,6-di-tert-butylphenol), H2[O2NN¢]BuBuNMe2, diethylaminoethylamino-N,N-bis(2-methylene-4,6-di-tert-amylphenol), H2[O2NN¢]AmAmNEt2 and 2-pyridylamino-N,N-bis(2-methylene-4,6-di-tert-amylphenol), H2[O2NN¢]AmAmPy; were reacted with cobaltous acetate tetrahydrate under varying conditions to afford a range of monometallic, bimetallic and trimetallic species. An unusual four coordinate complex Co[O2NN¢]AmAmNEt2 containing CoII in a trigonal monopyramidal environment was structurally characterized, whereas using a less sterically demanding ligand a series of five coordinate complexes Co[O2NN¢]BuBuNMe2(L) (L = H2O, CH3OH, (CH3)2C=O, propylene oxide) containing CoII in a trigonal bipyramidal environment was prepared. A new angular structural parameter related to t is defined, where t¢ may be used to compare complexes with trigonal monopyramidal structures. In contrast, ligands containing a pendant pyridyl donor afford dimeric species including {Co(m-CH3OH)[O2NN¢]AmAmPy}2. In the absence of base and in the presence of excess cobaltous acetate, trimetallic complexes were isolated containing a central CoII in an octahedral environment coordinated to four CH3OH and two bridging acetate ligands between two Co[O2NN¢] fragments with CoII in a trigonal bipyramidal setting. The paramagnetic CoII complexes reported were also characterized by UV-vis spectroscopy, mass spectrometry, cyclic voltammetry and magnetic measurements.

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