Synthesis, crystal structures, vibrational spectra, and normal coordinate analyses of the tetrahalogene-bis-pyridine-osmium(III) complexes cis-(n-Bu4N) [OsCl4Py2] and trans-(n-Bu4N) [OsX4Py2], X = Cl, Br

By reaction of (n-Bu4N)(2)[OsX6], X = Cl, Br, with pyridine and (n-Bu4N)[BH4] tetrahalogeno-bis-pyridine-osmium(III) complexes are formed and purified by chromatography. X-ray structure determinations on single crystals have been performed of cis-(n-Bu4N) [OsCl4Py2] (1) (triclinic, space group P (1) over bar, a = 9.4047(9), b = 10.8424(18), c= 17.007(2)Angstrom, alpha=71.833(2), beta=81.249(10), gamma=67.209(12)degrees Z=2), trans-(n-Bu4N)[OsCl4Py2] (2) (orthorhombic, space group P2(1)2(1)2(1), a = 8.7709(12), b = 20.551(4), c = 17.174(4) Angstrom, Z=4) and trans-(n-Bu4N)[OsBr4Py2] (3) (triclinic, space group P (1) over bar, a=9.132(3), b=12.053(3), c=15.398(2)Angstrom, alpha= 95.551(18), beta= 94.12(2), gamma = 106.529(19)degrees, Z = 2). Based on the molecular parameters of the X-ray structure determinations and assuming C-2 point symmetry for the anion of 1 and D-2h point symmetry for the anions of 2 and 3 the IR and Raman spectra are assigned by normal coordinate analysis. The valence force constants of 1 are in the Cl-Os-Cl axis f(d)(OsCl)=1.58, in the asymmetrically coordinated N'-Os-Cl-. axes f(d)(OsCl.)=1.45, f(d)(OsN')=2.48, of 2 f(d)(OsCl) = 1.62, f(d)(OsN) = 2.42 and of 3 f(d)(OsBr) =1.39 and f(d)(OsN) = 2.34 mdyn/Angstrom.