Zheng, YQ; von Schnering, HG; Chang, JH; Grin, Y; Engelhardt, G; Heckmann, G
A mixture of polymeric CW6Cl16 (1) and molecular CW6Cl18 (2) is formed in a reproducible reaction by heating purchased WCl4 (contaminated by e.g. C6H2Cl4) in closed silica tubes at 925 K / 915 K. The direct synthesis of 1 from W, WCl5 and CCl4 succeeds at 1030 K / 870 K, but an optimized way to 2 was not yet found (low yield e.g. from W, WCl6 and graphite or from W, WCl6 and C6O6; 975 K / 965 K). The black crystals of I and 2 become greenish-gray after grinding and they are not sensitive to hydrolysis and oxidation. I is diamagnetic with chi(mol) = -865.10(-6) cm(3) mol(-1) and shows numerous FIR bands. I decomposes thermally (870-1060 K) to W and W2C. The C-13 NMR chemical shift of solid 1 is observed at +264 ppm. Compound 2 is soluble in DMSO and the green solution shows characteristic absorptions at 12900, 16500 and 24400 cm(-1) (C-13 NMR: delta = 279.9). The crystal structure of 2 represents a hcp arrangement of isolated triprismo-hexatungsten clusters [((CW6Cl12i)-Cl-tpr)Cla(6)(a)] with (6) over bar m2 symmetry (d(W-W) = 2.743 Angstrom (6x), 2.930 Angstrom (3x); (d) over bar (W-Cl-i) = 2.361 Angstrom, 2.434 Angstrom; d(W-Cl-a) = 2.377 Angstrom; d(W-C) = 2.157 Angstrom). In the structure of I the same central units are interconnected via four Cla-a bridging ligands to form 2D puckered layers (2)(infinity)[((CW6Cl12i)-Cl-tpr)(Cl2Cl4/2a-a)-Cl-a] ((d) over bar (W-W) = 2.658 Angstrom (6 X), 3.020 Angstrom (3 X); (d) over bar (W-Cl-i) = 2.389 Angstrom, 2.456 Angstrom; (d) over bar (W-Cl-a) = 2.389 Angstrom; (d) over bar (W-Cla-a) = 2.548 Angstrom; (d) over bar (W-C) = 2.15Angstrom). Crystal data: 1, CW6Cl16, orthorhombic, Pnma (62), oP92; a = 16.637Angstrom, b = 12.958 Angstrom, c = 9.797 Angstrom, Z = 4; 2094 hkl, R(F) = 0.036. 2, CW6Cl18, hexagonal, P (6) over bar 2c (190), hP50; a = 8.923 Angstrom, c = 17.503 Angstrom, cla = 1.962, Z = 2; 942 hkl, R(F) = 0.048.