Interaction of Trimethylaluminum and Trimethylgallium with the Acetate Ion. Synthesis and Crystal Structures of [N(CH₃)₄][Al₂(CH₃)₆CH₃COO] and Rb[Ga₂(CH₃)₆CH₃COO]

The crystal structures of the closely related compounds [N(CH₃)₄][Al₂(CH₃)₆CH₃COO] and Rb[Ga₂(C—H₃)₆CH₃COO] have been determined from single-crystal X-ray diffraction data collected by counter methods. The former compound crystallizes in the orthorhombic space group Pnma with unit cell parameters a = 10.202 (3) Å, b = 10.300 (3) Å, c = 18.772 (5) Å, and ρ (calcd) = 0.93 g cm⁻³ for Z = 4, whereas the latter compound crystallizes in the triclinic space group P1̄ with a = 8.986 (3) Å, b = 9.243 (3) Å, c = 9.281 (3) Å, α = 93.27 (4)∘, β = 90.83 (4)∘, γ = 103.61 (4)∘, and ρ (calcd) = 1.66 g cm⁻³ for Z = 2. Least-squares refinement gave final R values of 0.086 and 0.077 for 973 and 2125 independent observed reflections, respectively. Both aluminum and gallium atoms are tetrahedrally coordinated, with M—O distances averaging 1.871 (4) Å for M = Al and 2.069 (1) Å for M = Ga and the corresponding M—C distances averaging 1.94 (2) and 2.00 (1) Å, respectively.