CYCLIC TRIMERIC HYDROXY, AMIDO, PHOSPHIDO, AND ARSENIDO DERIVATIVES OF ALUMINUM AND GALLIUM - X-RAY STRUCTURES OF [T-BU2GA(MU-OH)]3 AND [T-BU2GA(MU-NH2)]3

Reaction of t-Bu3Al with PH3 or AsH3 produces cyclic trimeric complexes of formula [t-Bu2Al(mu-EH2)]3 (E - P (1), As (2), which were identified by their IR, NMR, and mass spectra. From infrared data the angle H-P-H and angle H-As-H angles are calculated to be 97 (3) and 105 (3)-degrees, respectively. The adduct t-Bu3GaNH3 (3) may be isolated from mixtures of t-Bu3Ga and NH3 at room temperature. Heating 3 to 160-degrees-C results in the formation of [t-Bu2Ga(mu-NH2)]s (4), whose cyclic trimeric structure was confirmed in the solid state by X-ray crystallography. The analogous mu-ND2 complex 5 can be prepared by substituting ND3 for NH3. Reaction of t-Bu3Ga with H2O in pentane solution at 25-degrees-C gives the cyclic trimer [t-Bu2Ga(mu-OH)]s (6) in 90% yield. The deuterium-labeled compound [t-BU2Ga(mu-OD)]3 (7) may be prepared in a similar fashion using D2O. Compound 6 is also formed by the hydrolysis of [t-Bu2Ga(mu-PH2)]3, [t-Bu2Ga(muAsH2)] 3, and [t-BU2Ga(mu-As(t-Bu)H)]3. The cyclic trimeric structure of 6 was confirmed by X-ray crystallography, which showed a planar Ga3O3 ring with t-Bu groups extending above and below the plane. Crystal data for 4: C24H60N3Ga3; M(n) = 600.03; rhombohedral space group R3cBAR; a = 10.443 (2) angstrom; c = 50.836 (13) angstrom; V = 4801 (5) angstrom3; Z = 6, D(calc) - 1.250 g cm-3; mu(Cu Ka) = 11.26 cm-1; 932 unique reflections over the range of 2 < 2theta < 110-degrees (omega/2theta scan mode) were measured; 652 unique observed reflections were used in the refinement with I > 3sigma(I); R and R(w) = 0.0310 and 0.0329, respectively. Crystal data for 6: C24H57Ga3; M(n) = 602.17; rhombohedral space group R3cBAR; a = 10.362 (2) angstrom; c = 50.927 (10) angstrom; V = 4735.89 (15) angstrom3; Z - 6, D(calc) - 1.262 g cm-3; A(Mo Kalpha) = 13.4 cm-1, 11 17 reflections over the range 3.0 less-than-or-equal-to 20 less-than-or-equal-to 50.0-degrees (0/2theta scan mode) were measured; 610 reflections with I > 3sigma(I) were used in the refinement; R and R(w) = 0.044 and 0.0548, respectively.