Lewis-base adducts of group 11 metal(I) compounds. 32. Steric effects in the 2:1 adducts of (2-methylphenyl)diphenylphosphine with copper(I) halides

Abstract

Solid-state 31P NMR spectra, far-infrared spectra, and single-crystal X-ray structure determinations have been recorded for (2-methylpheny1)diphenylphosphine (PPh2-o-tol) and its mononuclear 2: 1 adducts with copper(1) halides, (PPh2-o-tol)2CuX. The solid state ,IP NMR spectrum of the ligand shows a single sharp resonance at -18 ppm with respect to 85% H3P04. The spectra of the 2:l adducts show two sets of overlapping asymmetric quartets for the chloride and bromide and a single broad quartet for the iodide, indicating the presence of at least two crystallographically distinct ligands in the first two compounds and one in the third. Average chemical shift values (ppm) are as follows: C1, -1 1; Br, -11; I, -15. The asymmetry in the line spacing for each quartet is consistent with a trigonal coordination geometry around the copper atom. Far-infrared spectra of each of the metal complexes in the range 50-400 cm-' show strong bands that are assigned to terminal metal-halogen stretching vibrations: Cu-Cl, 290 cm-I; Cu-Br, 220 cm-I; Cu-I, 200 cm-'. The parent ligand crystallizes in the monoclinic space group P2,/c with a = 10.713 (5) A, b = 8.726 (5) A, c = 16.573 (6) A, fi = 90.77 (3)O, and 2 = 4. All three copper structures crystallize in the monoclinic space group C2/c. The CI and Br structures are isomorphous with one complete molecule of (PPh2-o-tol)2CuX comprising the asymmetric unit. For X = CI, a = 22.413 (15) A, b = 16.034 (4) A, c = 19.092 (2) A, @ = 107.04 (4)O, and 2 = 8; for X = Br, a = 22.348 (7) A, b = 16.033 (8) A, c = 19.526 (5) A, fi = 108.73 (2)O, and 2 = 8. However, for X = I, a = 18.665 (5) A, b = 10.006 (2) A, c = 19.764 (5) A, fi = 115.29 (2)O, and Z = 4, with the two ligands related by symmetry and the Cu-I bond sited on the 2-fold rotation axis. For X = CI, Cu-P, Cu-P, Cu-X, and P-Cu-P = 2.241 (2) A, 2.257 (2) A, 2.205 (2) A, and 126.96 (7)O respectively; for X = Br, the values are 2.240 (2) A, 2.255 (2) A, 2.336 (1) A, and 127.89 (7)O, respectively; and for X = I, Cu-P, Cu-I, and PCu-P = 2.255 (1) A, 2.507 (1) A, and 126.36 (7)O, respectively. Both Cu-P and Cu-X distances are similar to the corresponding values for (PPh3)2CuX compounds. However, as a consequence of changes in steric profile, the conformational structure of each ligand about the Cu-P bonds with respect to Cu-X is significantly different.