Synthesis and structure of mono-, bi- and trimetallic amine-bis(phenolate) cobalt(ii) complexesElectronic supplementary information (ESI) available: Crystallographic data for 1(CH3COCH3), 1(CH3OH), 1(C3H6O), 1(CH3OH-H2O) 2, 3(CH3OH), 4, 5 and 6 (cif format). Ball-and-stick model of 3, additional magnetic and electrochemical data (pdf). CCDC reference numbers 766019-766027. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c002843f

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), H 2 [O 2 NN′] BuMeNMe2 , dimethylaminoethylamino- N , N -bis(2-methylene-4,6-di- tert -butylphenol), H 2 [O 2 NN′] BuBuNMe2 , diethylaminoethylamino- N , N -bis(2-methylene-4,6-di- tert -amylphenol), H 2 [O 2 NN′] AmAmNEt2 and 2-pyridylamino- N , N -bis(2-methylene-4,6-di- tert -amylphenol), H 2 [O 2 NN′] 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[O 2 NN′] AmAmNEt2 containing Co II in a trigonal monopyramidal environment was structurally characterized, whereas using a less sterically demanding ligand a series of five coordinate complexes Co[O 2 NN′] BuBuNMe2 (L) (L = H 2 O, CH 3 OH, (CH 3 ) 2 C&z.dbd;O, propylene oxide) containing Co II 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-CH 3 OH)[O 2 NN′] AmAmPy } 2 . In the absence of base and in the presence of excess cobaltous acetate, trimetallic complexes were isolated containing a central Co II in an octahedral environment coordinated to four CH 3 OH and two bridging acetate ligands between two Co[O 2 NN′] fragments with Co II in a trigonal bipyramidal setting. The paramagnetic Co II complexes reported were also characterized by UV-vis spectroscopy, mass spectrometry, cyclic voltammetry and magnetic measurements. The nuclearity of the title complexes can be controlled by subtle tuning of sterics in the tetradentate ligands and the reaction conditions.