Synthesis and characterization of cyclam complexes of rhodium(III)

Abstract

A series of complexes of the type Rh(cyclam)X2+ and Rh(cyclam)XYn+ have been prepared and characterized, where cyclam represents 1,4,8,11-tetraazacyclotetradecane and X and Y represent OH−, H2O, Cl−, Br−, I−, N3−, NCS−, and NO2−. The infrared and electronic spectra are discussed with respect to assignment of the cis and trans isomers, the linkage isomers, and the Rh–ligand stretching frequencies above 250 cm−1. The thermodynamic trans effect is related to shifts in the Rh–ligand stretching frequencies. The intensities of the d–d transitions are related to distortion of the octahedral field to support the cis and trans assignments, and compared to show the decrease in bond constraint for propylene linkages in place of ethylene. Steric constraint accounts for the single case of stereoisomerization by cis-Rh(cyclam)I2+.