Bonding data for rhodium-nitrogen bonds affected by the trans-influence ofsulfito ligands

Optical vibrational spectra of the rhodium compounds Na[Rh(SO3)(2)(NH3)(4)] . 2H(2)O (1) and Na-0.75(NH4)(0.25)[Rh(SO3)(2)(NH3)(4)].3.5H(2)O (2), both also in deuterated form ((1D) and (2D)) were measured at ambient and low te mperatures and discussed considering results of X-ray structure analyses. I n 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 RhN2 group which is unaffected and appropriate as an int ernal reference system for the estimation of the trans-influence. Lengths a nd the more sensitive force constants of the different Rh-N bonds and their relative changes are discussed as measures for the trans-influence. (C) 20 01 Elsevier Science B.V. All rights reserved.