Preparation, crystal structures, vibrational spectra, and normal coordinate analysis of four linkage isomeric trichlorotrirhodanoosmates(IV)

By treatment of fac-[OsCl3I3](2-) with (SCN)(2) in dichloromethane the linkage isomers fac-[OsCl3(NCS)(3)](2-) (1), mer-[OsCl3(NCS)(2)(c)(SCN)](2-) (2), mer-[OsCl3(NCS)(SCN)(2)(t)](2-) (3), and mer [OsCl3(NCS)(SCN)(2)(c)](2-) (4) are formed which have been separated by ion exchange chromatography on diethylaminoethyl cellulose. X-Ray structure determinations have been performed on single crystals of fac-(Ph(4)As)(2)[OsCl3(NCS)(3)] (triclinic, space group <P(1)over bar>, a = 12.142(5), b = 13.233(5), c = 19.300(5) Angstrom, alpha = 98.642(5)degrees, beta = 100.509(5)degrees, gamma = 112.514(5)degrees, Z = 2), mer-(Ph(4)As)(2)[OsCl3(NCS)(2)(c)(SCN)]. acetone (triclinic, space group <P(1)over bar>, a = 11.707(5), b = 13.238(5), c = 19.048(5) Angstrom, alpha = 75.960(5)degrees, beta = 88.981(5)degrees, gamma = 69.999(5)degrees, Z = 2), mer-(Ph(4)As)(2)[OsCl3(NCS)(SCN)(2)(t)] (triclinic, space group P1, a = 10.6861(12), b = 11.6587(5), c = 12.5232(5) Angstrom, alpha = 112.069(8)degrees, beta = 95.052(8)degrees, gamma = 92.559(7)degrees, Z = 1) and mer-(Ph(4)As)(2)[OsCl3(NCS)(SCN)(2)(c)]. 2acetone (triclinic, space group <P(1)over bar>, a = 11.444(5), b = 14.661(5), c = 15.830(5) Angstrom, alpha = 75.790(5)degrees, beta = 80.273(5)degrees, gamma = 75.205(5)degrees, Z = 2). The complex anions are completely ordered. The via N or S coordinated thiocyanate groups are located nearly direct above one of the cis-positioned Cl ligands with Os-N-C angles of 169.1 degrees, 171.5 degrees, 175.7 degrees (1), 175.6 degrees, 178.6 degrees (2), 172 degrees (3), and 173.1 degrees (4) and Os-S-C angles of 106.2 degrees (2), 106.1 degrees, 106.6 degrees (3), 105.1 degrees, and 108.2 degrees (4). Using the molecular parameters of the X-Ray determinations the low temperature (10 K) IR and Raman spectra of the (n-Bu(4)N) salts of all four linkage isomers have been assigned by normal coordinate analyses based on a modified valence force field. The valence force constants are f(d)(OsN) = 1.71 (1), 1.46 and 1.62 (2), 1.69 (3), and 1.61 (4), f(d)(OsS) = 1.27 (2), 1.36 (3), 1.32, and 1.49 mdyn/Angstrom (4). Taking into account increments of the trans influence a good agreement between observed and calculated frequencies is achieved.