Light-Induced Metastable Linkage Isomers of Ruthenium Sulfur Dioxide Complexes (original) (raw)

2003, Inorganic Chemistry

The irradiation of ruthenium−sulfur dioxide complexes of general formula trans-[Ru II (NH 3 ) 4 (SO 2 )X]Y with laser light at low temperature results in linkage isomerization of SO 2 , starting with η 1 -planar S-bound to η 2 -side S,O-bound SO 2 . The solid-state photoreaction proceeds with retention of sample crystallinity. Following work on trans-[Ru-(NH 3 ) 4 Cl(η 1 -SO 2 )]Cl and trans-[Ru(NH 3 ) 4 (H 2 O)(η 1 -SO2)](C 6 H 5 SO 3 ) 2 (Kovalevsky, A. Y.; Bagley, K. A.; Coppens, P. J. Am. Chem. Soc. 2002, 124, 9241−9248), we describe photocrystallographic, IR, DSC, and theoretical studies of trans-[Ru II (NH 3 ) 4 (SO 2 )X]Y complexes with (X ) Cl -, H 2 O, or CF 3 COO -(TFA -)) and a number of different counterions (Y ) Cl -, C 6 H 5 SO 3 -, Tos -, or TFA -). Low temperature IR experiments indicate the frequency of the asymmetric and symmetric stretching vibrations of the Ru-coordinated SO 2 to be downshifted by about 100 and 165 cm -1 , respectively. Variation of the trans-to-SO 2 ligand and the counterion increases the MS2 decay temperature from 230 K (trans-[Ru II (NH 3 ) 4 (SO 2 )Cl]Cl) to 276 K (trans-[Ru II (NH 3 ) 4 (SO 2 )(H 2 O)](Tos) 2 ). The stability of the MS2 state correlates with increasing σ-donating ability of the trans ligand and the size of the counterion. Quantum chemical DFT calculations indicate the existence of a third η 1 -O-bound (MS1) isomer, the two metastable states being 0.1−0.6 eV above the energy of the ground-state complex. (1) Coppens, P.; Fomitchev, D. V.; Carducci, M. D.; Culp, K.