Tri- and tetra-amine complexes

The medium-ring cyclic triamines, 1,4,7-triazacyclononane (tacn), 1,4,7-triazacyclodecane (tacd), 1,4,8-triazacycloundecane (tacud), and 1,5,9-triaza-cyclododecane (tacdd) have been synthesized and the cobalt complexes [Co(tacn)2]Br3, [Co(tacd)2]Br3,H20 and [Co(tacud)BrCl2] isolated. It has been suggested that the structures are of the sandwich type [viz. (95) and (96) ] and, for this reason, the reporter looks forward to publication of X-ray structural analyses. 

The structures of( — )589-frans and (— )5g9-cis-a-[Co(N02)2(L-3,8-diMetrien)] CIO4 (3,8-diMetrien = 3,8-dimethyltriethylenetetramine) have been reported. The Co—N distances of the tetramine are 1.98 A for the trans-isomer and 

Kobayashi, F. Marumo, and Y. Saito, Inorg. Nuclear Chem. Letters, 1971, 7, 111. 

958 A (average) for the ds-a-isomer. Potential energy minimization calculations have been carried out for the three isomers and the strain energy was found to decrease in the sequence cis-a trans ds-[3. The electronic 

A series of optically active linear tetradentate ligands, which have been stereospeeifically synthesized, have been used to prepare complexes with a trans-[CoN Cl2] core and both five- and six-membered chelate rings, in an attempt to correlate the sign of the Cotton effect with the known chiralities of compounds. How ever, a complete correlation was not possible. The synthesis, resolution, and properties of some oxalato, malonato, and diacido complexes of Co with the stereospecific flexible tetramine ligands 5-Me-3,2,3-tet and NA -bis-(2-picoyl)-l-methyl-1,2-diaminoethane (picpn) have been reported. The stereospecificity is demonstrated by comparison of the optical rotation of the ligand prepared via an asymmetric synthesis with that of the ligand isolated from a resolved complex. The stereochemistry of the complexes has been deduced.  

---