Single-crystal polarized electronic spectra of the compounds tetra-Greek letter mu-acetatodimolybdenum(II), tetrakis-Greek letter mu-(trifluoroacetato)-dimolybdenum(II), potassium-diaquo-tetra-Greek letter mu-sulfatodiplatinum(III), and the X-ray diffraction crystal structure of tetra-Greek letter mu-acetatodimolybdenum(II)·potassium chloride

摘要

The opportunity to examine both the 100 and 001 crystal faces of very thin crystals of tetra-(mu)-acetatodimolybdenum(II)(u271) resulted in the determination of the spatial orientation of the transition moment for the lowest energy transition of this compound. The orientation of this transition moment (TURN)34(DEGREES) away from the molecular z-axis as well as other supporting evidence, led to the assignment of 21,700 cm(u27-1) origin in the 6K spectra as the (delta)(---u3e)(delta)(u27*), (u271)A(,1g)(---u3e)(u271)A(,2u), electric-dipole allowed transition;Although only the 010 crystal face of tetrakis-(mu)-(trifluoroacetato)-dimolybdenum(II)(u272) was examined spectroscopically, the similarity between the crystal structure and the crystal spectra for this compound and those for Mo(,2)(O(,2)CCH(,3))(,4) has led to a similar assignment for the 22,070 cm(u27-1) peak in the 6K spectra of Mo(,2)(O(,2)CCF(,3))(,4) as (delta)(---u3e)(delta)(u27*), (u271)A(,1g)(---u3e)(u271)A(,2u), electric-dipole allowed;From the proposed MO diagram for potassium diaquo-tetra-(mu)-sulfatodiplatinum(III)(u273), the three observed z-polarized bands are assigned under D(,2h) symmetry as the following electric-dipole allowed transitions: 22,400 cm(u27-1) band, M-O(sigma)(u27*)(---u3e)M-O(sigma)(u27*), (u271)b(,1g)(---u3e)(u271)a(,u); 26,300 cm(u27-1) band, M-M(delta)(---u3e)M-M(delta)(u27*), (u271)a(,g)(---u3e)(u271)b(,u); 29,100 cm(u27-1) band, M-M(delta)(---u3e)M-M, M-OH(,2)(sigma)(u27*), (u271)a(,1g)(---u3e)(u271)b(,1u). A weak, apparently x,y polarized band at (TURN)25,600 cm(u27-1) is attributed to a spin forbidden triplet transition;X-ray diffraction data were collected for a crystal of the compound tetra-(mu)-acetatodimolybdenum(II)(.)potassium chloride(u274) on the Ames Laboratory automated four-circle diffractometer, and the structural data were refined by utilizing standard programs written for that purpose;The data collected for Mo(,2)(O(,2)CCH(,3))(,4)(.)KCl yielded the following preliminary results:; a = 9.601(2)(ANGSTROM) (alpha) = 90(DEGREES) Z = 4; b = 12.799(3)(ANGSTROM) (beta) = 97.59(3)(DEGREES) Volume - 1457.4(5)A(u273); c = 11.641(2)(ANGSTROM) (gamma) = 90(DEGREES);Examination of extinction conditions for certain reflections ledto the conclusion that the compound crystallized in a c-centeredmonoclinic cell; possible space groups were C2/c, C2/m, Cm, Cc,and C2. The fact that only hOl reflections with l = 2n were observedverified the space group was C2/c. The atom positions were refinedby computer least-squares fitting to an agreement factor of 3.3%.The Mo(,2)(O(,2)CCH(,3))(,4) molecules and chlorine atoms were found to sit;on inversion sites, with the potassium atoms resting on two-fold axes;(u271)Mo(,2)(O(,2)CCH(,3))(,4).(u272)Mo(,2)(O(,2)CCF(,3))(,4).(u273)K(,2)Pt(,2)(SO(,4))(,4)(.)2H(,2)O.(u274)Mo(,2)(O(,2)CCH(,3))(,4)(.)KCl.