| Abstract: | Preparation, Vibrational Spectra, and Normal Cooordinate Analysis of mer-[OsCl3I(NCS)2c]2? and Crystal Structures of two Modifications of mer-(Ph4As)2[OsCl3I(NCS)2c] By treatment of cis-/trans-[OsCl4I2]2? or fac-[OsCl3I3]2? with (SCN)2 in dichloromethane mixtures of different linkage isomers are formed, from which mer-[OsCl3I(NCS) ]2? has been isolated by ion exchange chromatography on diethylaminoethyl cellulose. With tetraphenylarsonium ions mer-(Ph4As)2[OsCl3I(NCS)2c] crystallizes in two different modifications. From acetone solution the high-temperature form α precipitates above ?10°C, the low-temperature form β below, ?65°C. The X-Ray structure determinations on single crystals of α-mer-(Ph4As)2[OsCl3I(NCS)2c] (triclinic, space group P 1 , a = 10.245(5), b = 11.690(5), c = 22.027(5) Å, α = 83.650(5)°, β = 85.734(5)°, γ = 72.566(5)°, Z = 2) and β-mer-(Ph4As)2[OsCl3I(NCS)2c] (triclinic, space group P 1 , a = 10.959(5), b = 11.122(5), c = 21.745(5) Å, α = 97.677(5)°, β = 92.339(5)°, γ = 104.712(5)°, Z = 2) reveal the ordering of the complex anions, which significantly differ in their geometry. The via N coordinated thiocyanate groups exhibit Os? N? C angles of 172.7° and 173.3° (α) and of 164.4° and 175.4° (β). Using the molecular parameters of the X-Ray determinations the low temperature (10 K) IR and Raman spectra of the (n-Bu4N) salt of the complex anion are assigned by a normal coordinate analysis based on a modified valence force field. The valence force constants are fd(OsN) = 1.66 and 1.64 mdyn/Å. Taking into account the trans influence a good agreement between observed and calculated frequencies is achieved. |
