(a) NMR spectroscopic data for [HAl(BH₄)₂]_n are consistent with the compound existing in two forms in solution. One form is probably a dimer and the other, a higher oligomer. Each species possesses one boron environment, and in the ¹¹B NMR spectrum, each species exhibits a binomial quintet. The chemical shift of the signal for each species in the 27Al NMR spectrum suggests an octahedral environment for the Al atom. Suggest a structure for the dimer [HAl(BH₄)₂]₂ which is consistent with these observations and comment on whether the data indicate a static or dynamic molecule.

(b) The elemental analysis for an adduct A is 15.2% B, 75.0% Cl, 4.2% C and 5.6% O. The ¹¹BNMR spectrum of A contains two singlets (δ—20.7 and +68.9 ppm) with relative integrals 1 : 3; the signal at δ—20.7 ppm is characteristic of a B atom in a tetrahedral environment, while that at δ+68.9 ppm is consistent with trigonal planar boron. In the IR spectrum, there is a characteristic absorption at 2176 cm⁻¹. Suggest an identity for A and draw its structure.