Donor−acceptor interactions within analogously substituted Lewis acid−base adducts of the type Et3Al−E(SiMe3)3 and t-Bu3Al−E(i-Pr)3 (E = P, As, Sb, Bi) were investigated in the solid state, on the basis of single-crystal X-ray structure analyses, and in solution by temperature-dependent NMR spectroscopy. In addition, density functional theory computations (B3LYP/SDD) were performed to analyze molecular structures and to derive dissociation energies (D e) of the R3Al−ER‘3 adducts. The thermodynamic stability of these depends both on the electronic strength of the Lewis acid and base, which is influenced by the central group 13 and 15 elements and their substituents R and R‘, and on steric interactions between the Lewis acid and base. Such repulsive interactions are decisive for the stability of adducts containing small central elements such as P and large substituents such as i-Pr and t-Bu. Comparisons between central structure parameters (Al−E and Al−C(H) bond distances; C(H)−Al−C(H) bond angles) and D e values of several adducts show that the Al−E bond length does not necessarily display the thermodynamic stability of an adduct, while the Al−C(H) bond distance and C(H)−Al−C(H) bond angles are useful structural parameters to estimate the stability of an adduct in the solid state.

Reactions between distibanes of the type Sb 2 R 4 and trialkylalanes and -gallanes R′ 3 M in 1:2 stoichiometry yield eight bisadducts of the type [Sb 2 R 4 ][MR′ 3 ] 2 (R ) Me, R′ ) t-Bu, M ) Al 1, Ga 2; R ) Et, M ) Al, R′ ) Me 3, Et 4, t-Bu 5; M ) Ga, R′ ) Me 6, Et 7, t-Bu 8), which were characterized by multinuclear NMR studies and elemental analysis. In addition, 1, 2, 5, and 8 are the first structurally characterized neutral main group Lewis acid-distibane bisadducts. 1-8 are unstable in solution toward the formation of heterocycles of the type [R 2 SbMR′ 2 ] x . [Me 2 SbGa(t-Bu) 2 ] 3 (9) and [Et 2 SbGa(t-Bu) 2 ] 2 (10) have been isolated and their solid state structures determined by single-crystal X-ray diffraction.

Group 13-group 13 donor-acceptor complexes Cp*M-Al(t-Bu) 3 (M ) Al 1, Ga 2, In 3) and Cp*M-Ga(t-Bu) 3 (M ) Al 4, Ga 5, In 6) were obtained from reactions between [Cp*M] x (M ) Al, x ) 4; Ga, In, x ) 6) and M(t-Bu) 3 (M ) Al, Ga). 3, 4, and 6 represent the first compounds containing dative In(I)-Al(III), Al(I)-Ga(III), and In(I)-Ga(III) bonds. 1-6 were characterized by elemental analyses, mass and multinuclear NMR spectroscopy ( 1 H, 13 C), and single-crystal X-ray analysis (except for 5).Supporting Information Available: Tables of bond distances, bond angles, anisotropic temperature factor parameters, and fractional coordinates for 1, 2, 3, 4, and 6. This material is available free of charge via the Internet at http://pubs.acs.org. OM0606946

Two trialkylbismuthines BiR3 (R = Me 1, i-Pr 2) were structurally characterized by single crystal X-ray diffraction. Single crystals were grown using an IR-laser-assisted technique. 1 forms short intermolecular Bi•••Bi interactions in the solid state, which were further investigated through quantum chemical computations with ab initio coupled cluster and dispersion-corrected density functional methods.