The crystal and molecular structures of selected organic and organometallic compounds and an algorithm for empirical absorption correction

Karcher, Barbara
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The crystal and molecular structures of four selected organic and organometallic compounds have been determined by X-ray diffractometery. A brief description of the structural results for each compound is given below;Cr(CO)(,5)(SCMe(,2)) crystallizes in the monoclinic space group P2(,1)/a with a = 10.468(8), b = 11.879(5), c = 9.575(6) (ANGSTROM), and (beta) = 108.14(9)(DEGREES). The coordination around the chromium atom is essentially octahedral. The Cr-C distance (1.835(12) (ANGSTROM)) opposite the Me(,2)CS group is significantly shorter than the remaining Cr-C distances (average value: 1.898(2) (ANGSTROM)). The chromium atom deviates from the plan described by the Me(,2)CS moiety by only 0.2 (ANGSTROM). The Cr-S-C angle is 120.8(4)(DEGREES); the C=S distance is 1.618(8) (ANGSTROM);PSN(,3)C(,6)H(,12) crystallizes in the monoclinic space group P2(,1)/n with a = 10.896(1), b = 11.443(1), c = 7.288(1) (ANGSTROM), and (beta) = 104.45(1)(DEGREES). Strain in this tris(dialkylamino)phosphate forces the nitrogens into a pyramidal configuration, with average bond angles of 109(DEGREES). Each of the five-membered rings in this structure contains a carbon atom which is puckered toward the sulfur and out of the nearly planar arrays of the remaining ring atoms. A new data collecting technique was used successfully on this crystal to increase the average diffracted X-ray intensity: the X-radiation was filtered only when a (beta)-peak was calculated to be within the scan range of an (alpha)-peak;(RhO(,4)N(,4)C(,48)H(,56))('+)(BC(,24)H(,20))('-)(.)1.5NC(,2)H(,3) crystallizes in the triclinic space group P1 with a(' )=(' )17.355(8), b = 21.135(10), c = 10.757(5) (ANGSTROM), (alpha) = 101.29(5), (beta) = 98.36(5), and (gamma) = 113.92(4)(DEGREES). Contrary to earlier speculation, the large diisonitrile ligands in this compound do not bridge two rhodium atoms within the cell. Each Rh cation complex is a monomer;MoP(,2)O(,10)C(,16)H(,22) crystallizes in the monoclinic space group P2(,1)/c with a = 12.220(3), b = 9.963(2), c = 20.150(6) (ANGSTROM), and (beta) = 103.01(3)(DEGREES). The molybdenum atom occupies the axial position of the six-membered ring of each of the two phosphorinane ligands. This confirms that the coordination process occurs with the retention of the configuration at the phosphorus;An empirical absorption correction program was written based on the method described by North et al.('1). A strong reflection at (chi) = 90(DEGREES) is measured at 10(DEGREES) intervals in (phi) to approximate the variance in transmittance with (phi). In many cases, this absorption correction is shown to be better than analytical results based on crystal measurements with 10% error;('1)North, A. C. T; Phillips, D. C; Mathews, F. S. Acta Cryst. 1968,A24, 351.

Chemistry, Physical chemistry