No abstract

The 63Cu nuclear quadrupole resonances have been observed in (CuX)nLm (X=Cl, Br, I; L=triphenylphosphine; n:m=1:1, 2:3, 1:2). Two characteristic frequency ranges were observed: the resonance frequencies of the three-coordinated Cu atoms are far above those of the four-coordinated.

730, J a p a n ) Summary 8lBr N.q.r. spectroscopy has revealed a drastic structural change in the (C,H,NH)SbBr, crystal; above 253 K the SbBr,-anion has the trigonal bipyramid structure, whereas below 253 K the axial bonds become asymmetric and the SbBr,-anion is more reasonably described as SbBr,-Br-a t 77 K.

The crystal structure of the Cu2Br2(PPh3)3·1.5C6H6 complex has been determined by three dimensional X-ray analysis. The crystals are monoclinic, and the space group is P21/c, with unit-cell parameters of a=14.122 (3), b=19.573 (4), c=25.985 (7) Å, β=128.99 (1)°, and Z=4. In the Cu2Br2(PPh3)3 molecule, one copper atom is three-coordinate, and the other, four-coordinate.

Zeeman effects of 63Cu and 81Br NQR spectra of bis(triphenylphosphine)copper(I) bromide, CuBr(PPh3)2, have been studied at room temperature. The asymmetry parameters and the quadrupole coupling constants (e2Qq⁄h) have been found to be 0.113 and 64.58 MHz for 63Cu and 0.518 and 105.91 MHz for 81Br. The large asymmetry parameter of the 81Br NQR line is caused by the π-bonding character of the copper-bromine bond. The bonding scheme between the copper and bromine atoms is discussed on the basis of the obtained directions of the electric field gradient axes.