Bonding data for rhodium–nitrogen bonds affected by the trans-influence of sulfito ligands

Abstract

Optical vibrational spectra of the rhodium compounds Na[Rh(SO 3) 2(NH 3) 4]·2H 2O ( 1) and Na 0.75(NH 4) 0.25[Rh(SO 3) 2(NH 3) 4]·3.5H 2O ( 2), both also in deuterated form (( 1D) and ( 2D)), were measured at ambient and low temperatures and discussed considering results of X-ray structure analyses. In both compounds the complex anions adopt cis-configuration with a bent RhN 2 fragment underlying the trans-influence of S-coordinated sulfito ligands and a quasi-linear RhN 2 group which is unaffected and appropriate as an internal reference system for the estimation of the trans-influence. Lengths and the more sensitive force constants of the different Rh–N bonds and their relative changes are discussed as measures for the trans-influence.