The Crystal and Molecular Structures of the 3,5-Dimethylpyrazolylgallium dimethyl dimer, [Me2Ga·N2C5H7]2, and the Hydroxy-bridged Species, [Me2Ga(OH)(N2C5H7)GaMe2·2N2C5H8]

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Abstract
Crystals of the 3,5-dimethylpyrazolylgallium dimethyl dimer [Me2Ga·N2C5H7]2 (1a) are monoclinic, a = 8.660(3), b = 13.776(1), c = 8.443(2) Å, β = 112.45(2)°, Z = 2, space group P21/c, and crystals of the hydroxy-bridged species [Me2Ga(OH)(N2C5H7)GaMe2·2N2C5H8] (1b) are monoclinic, a = 28.778(3), b = 9.098(3), c = 20.222(2) Å, β = 100.72(1)°, Z = 8, space group C2/c. Both structures were solved by Patterson and Fourier methods and were refined by full-matrix least-squares methods to final R values of 0.071 and 0.045 for 1443 and 2746 reflections with I ≥ 3σ(I) respectively. Molecules of 1a lie on crystallographic centers of symmetry, the central Ga—(N—N)2—Ga ring being almost planar as a result of steric interactions between gallium-methyl groups and those on the 'pyrazolyl' rings. The mean Ga—N and Ga—C distances are 1.993 Å and 1.962 Å respectively. Compound 1b was formed by the attack of moisture on the strained dimer 1a. The central feature is a five-membered Ga2N2O ring, with two 3,5-dimethylpyrazoie molecules hydrogen-bonded to it (N—H … O, O—H … N, 2.851 and 2.892 Å) and to each other (N—H … N, 2.907 Å). The five-membered ring adopts a slightly distorted envelope conformation, the angle between the Ga2N2 and N2O moieties being 13.9°. The mean Ga—N and Ga—O distances are 1.989 and 1.934 Å respectively.

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