PREPARATION, CRYSTAL-STRUCTURE AND NORMAL-COORDINATE ANALYSIS OF LINKAGE ISOMERIC PENTACHLORORHODANOOSMATES(IV)

By treatment of [OsCl5I](2-) with (SCN)(2) in dichloromethane the linkage isomers [OsCl5(NCS)](2-) and [OsCl3(SCN)](2-) are formed which have been separated by ion exchange chromatography on diethylaminoethyl cellulose. The X-ray structure determination on single crystals of (Ph(4)As)(2)[OsCl5(NCS)] (monoclinic, space group P2(1)/a, a = 18.872(2), b = 11.6024(2), c = 22.786(1), beta = 109.057(1)degrees, Z = 4) and (Ph(4)As)(2)[OsCl5(SCN)] (monoclinic, space group P2(1)/a, a = 19.057(2), b = 11.306(2), c = 22.612(1), beta = 106.64(2)degrees, Z = 4) reveals the complete ordering of the complex anions. The thiocyanate group is located above one of the Cl ligands of the equatorial plane with the Os-N-C angle of 166.1 degrees for N bonding and the Os-S-C angle of 109.9 degrees for S bonding. The IR and Raman spectra of both linkage isomers known from literature are assigned by normal coordinate analysis based on the general valence force field using the molecular parameters of the X-ray determination. The valence force constants are f(d)(OsN) = 1,81 and f(d)(OsS) = 1,32 mdyn/Angstrom. Taking into account increments of the trans influence a good adjustment between observed and calculated frequencies is achieved.