Triethylenetetramine complexes

A series of diaquatetraaza cobalt(III) complexes accelerated the hydrolysis of adenylyl(3 -50adenosine (ApA) (304), an enhancement of 10 -fold being observed with the triethylenetetramine complex (303) at pH 7. The pentacoordinated intermediate (305), which is formed with the complex initially acting as an electrophilic catalyst, then suffers general acid catalysis by the coordination water on the Co(III) ion to yield the complexed 1,2-cyclic phosphate (306), the hydrolysis of which occurs via intracomplex nucleophilic attack by the metal-bound hydroxide ion on the phosphorus atom. Neomycin B (307) has also been shown to accelerate the phosphodiester hydrolysis of ApA (304) more effectively than a simple unstructured diamine. 

The Ni(II) complex of a 16-membered macrocycle, 2,7-dimethyl-3,6 -(1,1 - (2,2 - biimidazole) -1,3,6,8,11,14 - hexaazacyclohexadeca -1,7 -diene, 22, was synthesized by Schiff base condensation of the Ni(II)-triethylenetetramine complex and 1,1 -diacetyl-2,2 -bisimidazole (29). The Ni(II) complex formed square-planar geometry with iodide or perchlorate anions and an octahedral structure with chloro or bromo ligands. 

Similar results were obtained when tetraethylenepentamine was replaced with triethylenetetramine. However, in this case the ligand does not deprotonate. The sixth octahedral position was occupied by hydroxide, and the complex was isolated as the perchlorate, [FeL(OH)] (0104)2. Somewhat related reactions have been carried out in which triethylenetetramine complexes of copper(II) or nickel(II) were treated with acetone (57, 38). 

The closely related triethylenetetramine complexes show a d - to l -/3 inversion (66, 67) similar to that expected (Figure 5). Although the investigators suggested complete inversion in the second step (67)—the opposite of the ethylenediamine complexes—their data on direct hydrolysis suggest considerably more inversion for the two-step reaction than for the second step alone. No configurational change was noted for the isomer reaction (65). 

Closely related to this is the much later work of Eishin Kyuno and Laurence Boucher (14), who studied the reactions of the triethylenetetramine complex, [Co(trien)Cl2]Cl. The complex cation of this substance exists in three stereoisomeric forms... 

The synthesis of the Ni(n) complex of the 13-membered (anionic) macrocycle (78) is also achieved using an in situ procedure (Cummings Sievers, 1970) in which triethylenetetramine, acetic acid, acetylacetone, and nickel acetate are heated in water at the reflux. Addition of iodide ion and adjustment of the pH of the solution to approximately 10, leads to crystallization of the Ni(n) complex of the required cyclized product (78) as its iodide salt. The reaction type has been extended to include Cu(ii) as the template metal (Martin, Wei Cummings, 1972) and has also been... 

The aliphatic N4 ligand triethylenetetramine =l,4,7,10-triazadecane (trien) is strongly basic and forms only high-spin complexes with iron(II). If the two terminal amino groups are replaced by imine functions such as pyridine (1) the ligand field strength is increased sufficiently that low-spin or spin crossover iron(II) complexes can be made. 

A series of complexes of the type ML(SCN) (C104)2-, (M - Zn, Cd, or Hg x = 1 or 2) has been prepared where L is en and its tetramethyl derivative, diethylenetriamine and its pentamethyl derivative, triethylenetetramine and its hexamethyl derivative, and bis(ethylenediamine). The complexes are either monomeric with four-, five- or six-coordinate metal, or polymeric containing bridging thiocyanate the perchlorate is always ionic. The thiocyanate is generally bonded through nitrogen to zinc and cadmium (and through sulfur to mercury).181... 

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