SYNTHESIS, CRYSTAL-STRUCTURE, VIBRATIONAL -SPECTRA, AND NORMAL-COORDINATE ANALYSIS OF K-2[OSCL5(CO)]CENTER-DOT-H2O

The X-ray structure determination of K-2[OsCl5(CO)]. H2O (monoclinic, space group P2(1)/c a=13.600(2), b=7.122(1), c=22.186(11)Angstrom, bet a=98.66(3)degrees, Z=8) revealed two crystallographic independent bat very similar complex anions [OsCl5(CO)](2-) with rough C-4v point symm etry. Due to the stronger trans influence of the carbonyl group the bo nd lengths in the Cl-Os-CO axis Os-Cl=2.449(2), 2.430(2) Angstrom are langer as compared with the octahedron basis Os-Cl=2.340-2.370 Angstro m. The water of crystallization is coordinated to potassium (K-OH2=2.6 25-2.815 Angstrom). Using the molecular parameters the IR and Raman sp ectra are assigned by normal coordinate analysis. The valence force co nstants are f(d)(CO)=15.30, f(d)(OsC)=3.88, f(d)(OsCl)=1.81, f(d)(OsCl )=1.36, f(d)(OH)=7.65, 7.82, 7.79 mdyn/Angstrom. The strengthening of the Os-C bond by stronger back donation of the Os-III(d(5)) complex in comparison with the isostructural Os-IV(d(4)) compound is discussed.