Date of Award
Program or Major
Doctor of Philosophy
The comparative study of the mono- and tricyclic triamine complexes based on twelve-membered rings and the group 6 and group 10 metals has been initiated. The four ligands used in this study were 1,5,9-triazacyclododecane ( (12) aneN$\sb3$), 1,5,9-trimethyl-1,5,9-triazacyclododecane (Me$\sb3$ (12) aneN$\sb3$), 1,5,9-triazacyclododecane orthoformamide (orthoformamide) and 1,5,9-triazacyclododecane orthoacetamide (orthoacetamide). Complexes with zero-valent group 6 metal (Cr, Mo, W) tricarbonyls were characterized and the single-crystal X-ray structures determined for each ligand-molybdenum tricarbonyl complex. Complexes with nickel(II), palladium(II) and platinum(IV) have been characterized and the single-crystal X-ray structure of orthoacetamide PdCl$\sb2$ has been determined. The tricyclic orthoamides have been found to be less effective ligands than their monocyclic counter-parts. With respect to the zero-valent group 6 metals the order of ligand strength has been determined to be (12) aneN$\sb3\ >$ Me$\sb3$ (12) aneN$\sb3\ >$ orthoacetamide $>$ orthoformamide.
As with other substituted cyclic triamines Me$\sb3$ (12) aneN$\sb3$ displays an effectively large cone-angle limiting the coordination of nickel(II) and palladium(II). The all trans configuration observed in the orthoamide complexes forces ring conformations which, like Me$\sb3$ (12) aneN$\sb3$, also display large cone-angles. The orthoacetamide limits the coordination of palladium(II) and both of the orthoamides force steric compression of the OC-Mo-CO bond angles in the tricarbonyl complexes. On the basis of structural changes in orthoacetamide upon complexation with molybdenum(0) tricarbonyl and with palladium(II) dichloride the electron donation of orthoacetamide as a bidentate ligand to the stronger Lewis acid is equal to the tridentate donation to the molybdenum(0).
VanKouwenberg, Steven Paul, "The synthesis and characterization of transition metal complexes of triazacyclododecane and its tri-n-methyl and orthoamide derivatives" (1989). Doctoral Dissertations. 1602.