PHOSPHOLE COMPLEXES OF COPPER(I) HALIDES - INVESTIGATIONS OF STRUCTURE AND BONDING BY X-RAY CRYSTALLOGRAPHY, INFRARED-SPECTROSCOPY, AND CP MAS P-31 NMR-SPECTROSCOPY

A series of complexes of 1-phenyl-3,4-dimethylphosphole (DMPP) and 1-phenyldibenzophosphole (DBP), of the type [L(n)CuX]m (n = 1, m = 4, L = DMPP, DBP; n = 2, m = 2, L = DMPP; n = 3, m = 1, L = DMPP, DBP; X = Cl, Br, I) have been prepared and characterized. The structure of [(DMPP)CuI]4 has been determined by X-ray crystallography. It crystallizes in the space group C2/c with a = 21.058 (4) angstrom, b = 12.059 (2) angstrom, c = 23.425 (7) angstrom, beta = 111.50 (2)-degrees, and Z = 4. The structure was refined by least-squares methods with R(F) = 0.037 for 2845 unique reflections with I/sigma(I) greater-than-or-equal-to 3.0. The complex crystallizes as a tetramer [(DMPP)CuI]4 with the cubane structure which has previously been observed for 1:1 complexes of PPh3 and other phosphine and amine ligands with copper(I) halides. In this structure each of the four copper atoms is tetracoordinated through bonds to the P atom of the phosphole ligand and the three bridging iodine atoms, which are in turn tricoordinated. The complex lies on a crystallographic C2 axis. The average bond lengths in the P4Cu4I4 core are Cu-P = 2.253, Cu-I = 2.684, and Cu-Cu = 2.933 angstrom, and the average bond angles are Cu-I-Cu = 65.92, I-Cu-I = 109.35, and P-Cu-I = 109.55-degrees. The structures of the other members of the series were deduced from their far-IR and cross-polarization magic-angle-spinning (CP/MAS) P-31 NMR spectra. Thus all of the 1:1 complexes (n = 1) are shown to have the tetrameric cubane structure. The 2:1 complexes exist only for the L = DMPP case. The X = Cl complex has an ionic structure [(DMPP)4Cu]+[CuCl2]-, which represents a new structure type for adducts of copper(I) halides with neutral ligands. Halogen-bridged dimeric structures, [(DMPP)2CuX]2, are proposed for the 2:1 X = Br, I complexes. The 3:1 complexes have mononuclear [L3CuX] structures.