CHARACTERIZATION OF GALLIUM-NITROGEN ADDUCTS BY X-RAY STRUCTURAL AND NMR SPECTRAL STUDIES. CRYSTAL STRUCTURE OF [(PhMe2CCH2)2GaCI]2 AND OF ITS MONOMERIC t-BUTYLAMINE ADDUCT, (PhMe2CCH2)2GaCI[NH2(t-Bu)]

Abstract

The nature of (PhMe₂CCH₂)₂GaCl]₂ and its adducts with NH₂(t-Bu) and NH₂(n-Pr) have been investigated. (PhMe₂CCH₂)₂GaCl]₂ crystallizes in the monoclinic space group P2₁/c with a=11.2495(16)Å, b = 21.4977(32)A, c = 7.8337(15)Å, β = 93.489(14)°, V= 1891.0(5)ų and D(calcd.)= 1.305 Mg/m³ for Z = 2. The structure was refined to R(F) = 4.2% for 1672 reflections above 6sgrave](F). The molecule has perfect C_i symmetry, a planar Ga(μ-Cl)₂Ga core and an expanded C(α)-Ga-C(α) angle of 137.9(3)° between the neophyl ligands. (PhMe₂CCH₂)₂-GaClNH₂(t-Bu)] crystallizes in the monoclinic space group P2₁/n with a = 6.4023(10) A, b= 17.4274(25) A, c = 22.2389(38) Å, β = 94.939(13)°, V= 2472.2(7)ų and D(calcd.) = 1.225 Mg/m³ for Z = 4. This structure was refined to R(F) = 3.9% for 1700 reflections above 6sgrave](F). The crystal structure is stabilized by intermolecular Cl … H-N hydrogen bonds and the central Ga(III) atom has a distorted tetrahedral geometry. A benzene solution of (PhMe₂-CCH₂)₂GaClNH₂(t-Bu)] is in equilibrium with (PhMe₂CCH₂)₂GaCl]₂NH₂(t-Bu)] and free amine according to ¹HNMR studies. In contrast to this, a solution of (PhMe₂CCH₂)-GaCl₂NH₂(t-Bu)] is in equilibrium with (PhMe₂CCH₂)GaCl₂]₂NH₂(t-Bu)], free (PhMe₂-CCH₂)-GaCl₂]₂ and free amine. Solutions of (PhMe₂CCH₂)₂GaCINH₂(n-Pr)] and (PhMe₂CCH₂)GaCl₂NH₂(n-Pr)] show no evidence for similar equilibria.