Crystal structure and thermal decomposition study of the [Ba₂Ni(NO₂)₆]·4H₂O compound

Abstract

Crystalline complexes of types; Cu..J.X4(PR3)4. Cu2X2(PR3)3 and CuX(PR3h have been observed to display cubic, rhombohedral and monomeric motifs, respectively, in which copper(I) displays three and four coordination. The stoichiometry of the complexes observed with various PR 3 ligands may be understood in terms of the cone angle subtended by the PR3 group. When excited in the UV, these complexes may show emission in the visible range. For Cu4X4(PR3)4 complexes, a change from X=ioclicle to X=bromicle leads to quenching of the visible emission. Those complexes (X=I) crystallizing with an internal tlu•ee fold symmetry element emit in the 470-520 nm range whereas those with an intemal twofold axis emit at lower energy (575-615 nm) when excited at 300 nm. The presence of an aromatic ring in the phosphine ligand leads to quenching of the visible emission for complexes of the type: Cu2X2(PR3)3. Two allotropes offormula CuBr[P(cyclohexane)}h crystallize in different space groups depending upon the solvent. The fom1 crystallized from hexane is found in space group C2/c with a 2-fold symmetry axis within the monomeric unit. When crystallized from benzene, space group P2 1 /n is adopted and there is no intemal symmetry element. The two forms display m<L'i:imum emission at 460 and 400 nm. respectively. Packing differences are also noted. ab initio calculations lead to an understanding of the emission behavior of these complexes. PS08.01.14 ON STRUCTURES OF 4X•SX'•4Y•Y'•80H 2 0 AND 4X•X'•2Y•Y'•46H 2 0 CLATHR!\TE HYDRATES. E.A.