Synthesis, crystal structures and vibrational spectra of linkage isomeric pentabromorhodanoosmates(IV)

By treatment of (n-Bu4N)(2)[OsBr5I] with (SCN)(2) in dichloromethane the li nkage isomers (n-Bu4N)(2)[OsBr5(NCS)] and (n-Bu4N)(2)[OsBr5(SCN)] are forme d which have been separated by ion exchange chromatography on diethylaminoe thyl cellulose. X-ray structure determinations on single crystals of (n-Bu4 N)(2)[OsBr5(NCS)] (monoclinic, space group P2(1)/n, a = 10.955(5), b = 11.6 49(5), c = 35.478(5) Angstrom, beta = 91.92(1)degrees, Z = 4) and (CH2Py2)[ OsBr5(SCN)] (monoclinic, space group P2(1)/n, a = 12.244(2), b = 10.134(3), c = 15.882(4) Angstrom, beta = 107.91(2)degrees, Z = 4) have been performe d. The thiocyanate group is coordinated with the Os-N-C angle of 168 degree s for N bonding and the Os-S-C angle of 110 degrees for S bonding. Based on the molecular parameters of the X-ray determinations the IR and Raman spec tra of both linkage isomers are assigned by normal coordinate analysis. The valence force constants are f(d)(OsN) = 1,81 and f(d)(OsS) = 1,42 mdyn/Ang strom.