Crystal and molecular structures of bis[dimethylbis-(1-pyrazolyl)gallato]copper(II) and bis[dimethylbis-(3,5-dimethyl-1-pyrazolyl)gallato]copper(II)

Abstract

Crystals of (I)[{Me₂Ga(pz)₂}₂Cu], (pz = pyrazolyl, N₂C₃H₃), are monoclinic, a= 8.522(3), b= 18.091(5), c= 7.463(3)Å, β= 105.90(4)°, space group P2₁/c. Z= 2. Crystals of (II)[{Me₂Ga(dmpz)₂}₂Cu], (dmpz = 3,5-dimethylpyrazolyl. N₂C₅H₇), are monoclinic, a= 16.645(4), b= 12.964(1), c= 14.344(4)Å, β= 104.69(2)°, space group I2/a, Z= 4. Both structures were determined from diffractometer data by Patterson and Fourier syntheses, and refined by full-matrix least-squares methods to R 0.057 [(I). 1692 observed reflexions] and 0.047 [(II), 1995 observed reflexions]. The [{Me₂Ga(pz)₂}₂Cu] molecule is in a pseudo-chair conformation with the two six-membered Ga–(N–N)₂–Cu rings in boat conformations. The copper atom lies on a crystallographic centre of symmetry in the middle of a planar arrangement of four nitrogen atoms. Mean dimensions are: Cu–N, 1.987. Ga–N 1.975, and Ga–C 1.962 Å; N–Ga–N 92.6, and N–Cu–N (chelate angle) 92.6°. Steric requirements of the ligands in [{Me₂Ga(dmpz)₂}₂Cu] necessitate adoption of pseudotetrahedral geometry about the central copper atom, with dihedral angle 71.9° between the two N–Cu–N co-ordination planes, and an almost planar arrangement for the Ga–(N–N)₂–Cu six-membered rings. Mean dimensions are: Cu–N 1.959, Ga–N 1.996, and Ga–C 1.972 Å; N–Ga–N 103.3 and N–Cu–N (chelate angle) 104.9°.