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Geometrical and Linkage Isomers of [OsCl 2 (dmso) 4 ] − The Complete Picture
Author(s) -
Alessio Enzo,
Serli Barbara,
Zangrando Ennio,
Calligaris Mario,
Panitalia S.
Publication year - 2003
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200300132
Subject(s) - chemistry , osmium , linkage isomerism , chloroform , isomerization , solvent , dimethyl sulfoxide , population , ruthenium , metal , cis–trans isomerism , crystallography , stereochemistry , organic chemistry , catalysis , demography , sociology
The isomerisation between the three known isomers of the [OsCl 2 (dmso) 4 ] complex — trans ‐[OsCl 2 (dmso‐ S ) 4 ] ( 1 ), cis , fac ‐[OsCl 2 (dmso‐ S ) 3 (dmso‐ O )] ( 2 ), and cis ‐[OsCl 2 (dmso‐ S ) 4 ] ( 3 ) — has been investigated by NMR spectroscopy, X‐ray crystallographic analysis, and DFT calculations. We show that the two dmso‐linkage isomers 2 and 3 equilibrate slowly at room temperature in solutions of both dimethyl sulfoxide (DMSO) and light‐protected chloroform. Although crystals of 2 precipitate from DMSO solutions, crystals of 3 were obtained from chloroform solutions. Compound 2 isomerises to 1 after exposure to sunlight, while 1 transforms into 2 in hot DMSO solution. The molecular energies were calculated by DFT methods, which show that in the gas phase there are small differences in the total energies ( E t ), with 1 exhibiting the lowest energy, in contrast with its low population in solution. This result indicates that the stability of each isomer in solution is not simply determined by E t , but that the solvent plays an important role. In fact, quantum chemical calculations for the isomerisation process 1 ⇄ 2 show a marked increase in the equilibrium constant with increasing the solvent polarity. The calculation of the metal−dmso binding energies, in combination with the X‐ray data, shows a significantly higher strength of Os−S bonds with respect to Ru−S bonds, which explains the different behaviour of otherwise analogous osmium−dmso and ruthenium−dmso complexes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)