The synthesis and characterization of transition metal complexes of triazacyclododecane and its tri-n-methyl and orthoamide derivatives

Publication Year:
1989
Usage 4
Downloads 4
Repository URL:
https://scholars.unh.edu/dissertation/1602
Author(s):
VanKouwenberg, Steven Paul
Tags:
Chemistry; Inorganic
thesis / dissertation description
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).