Quadridentate imine condensates

Species. This behavior is shown by a relatively small class of (mainly) 4- or 5-coordinated cobalt(II) complexes of quadridentate imine condensates (47, 60, 61, 62, 63), dimethylglyoxime (58), a,p,y,h-... 

The synthesis of quadridentate imine chelates usually requires the combination of two equivalents of the carbonyl compound and a diamine, as in the formation of complexes of ligands (6),17 18 (7)19 and (8).20,21 In similar fashion, thermodynamic template reactions allow the very effective synthesis of quinquedentate and sexadentate metal complexes of ligands such as (9),22 (10),23 (ll),24 (12)25 and (13).26 Condensation of 1,1,1-tris(aminomethyl)ethane with pyridine-2-carbaldehyde alone yields... 

The reaction must take place after the condensation of two CH3CHO molecules adjacent to each other on different ethylene-diamine residues. For one, the CH3 group has to be syn to the Co(III) ion and in the other anti. The syn methyl is deprotonated in the basic medium and the carbanion produced attacks the imine carbon of the other aldimine. The result is a quadridentate where the chiral C center has been formed stereospecifically by the way the imines are oriented through the chelates. Commencing with A-[Co(en)20x]+, only one isomer should be observed. 

The intramolecular condensation of monodentate aminomethylcarbonyl ligands, NH2CH2COR (R = H, Me, Ph), with quadridentate amines such as tren[tris(2-aminoethyl)amine] and tren(l,8-diamino-3,6-diazaoctane) bound to cobalt(III) has been studied. Chloride bound to the pentamine cobalt(III) directs the condensation to the amine site trans to it by base-catalyzed removal of a proton on the amine. The resultant carbinol amine complexes give imines (15), according to Eq. (4), which can be isolated and then reduced by BH4 to the fully saturated amine complexes without significant reduction of the Co(III) center. 

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