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

Dalton Transactions Pub Date: 2010-05-17 DOI: 10.1039/C002843F

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[double bond, length as m-dash]O, propylene oxide) containing CoII in a trigonal bipyramidal environment was prepared. A new angular structural parameter related to τ is defined, where τ′ may be used to compare complexes with trigonal monopyramidal structures. In contrast, ligands containing a pendant pyridyl donor afford dimeric species including {Co(μ-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.

Graphical abstract: Synthesis and structure of mono-, bi- and trimetallic amine-bis(phenolate) cobalt(ii) complexes
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