Synthesis of Group 13 Element Metallacarboranes and Related Structure–Reactivity Correlations

David M. Schubert, Marc A. Bandman, William S. Rees, Carolyn B. Knobler, Paul Lu, Wonwoo Nam, M. Frederick Hawthorne

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Abstract

Synthesis, reactivity, and structural characterization studies of a number of group 13 metallacarborane species are described. These include studies of the icosahedral aluminacarborane closo-3-Et-3,l,2-AlC2B9H11 (1a). Compound 1a reacts with Lewis bases to form adducts of the type 2L-1a (L = Lewis base). The reaction of 1a with excess PEt3 results in the rapid formation of endo-10-{AlEt(PEt3)2}-7,8-C2B9H11 (3). The novel sandwich species commo-3,3ʹ-Al[{exo-8,9-(μ-H)2-AlEt2-3,1,2-AlC2B9H9)}(3,l,2-AlC2B9H11)] (4) results from thermal dimerization of 1a. The related sandwich anions [commo-3,3ʹ-Al(3,1,2-AlC2B9H11)2]- ([5]-) and [commo-3,3ʹ-Ga(3,l,2-GaC2B9H11)2]- ([6]-) have been prepared. The full details of the synthesis and structural characterization of σ-bonded species nido-6,9-(μ-AlEt-(OEt2))-6,9-C2B8H10 (8), [A1(η2-6,9-C2B8H10)2]- ([10]-), and [Al(η2-2,7-C2B6H8)2]- ([11]-) are reported. The metallacarboranes 3, 4, [5]-, [6]-, 8, [10]-, and [11]- were characterized by a combination of spectroscopic techniques and by single-crystal X-ray diffraction studies. Crystallographic parameters are as follows: 3, P21/n, a = 9.722 (3) Å, b = 16.135 (4) Å, c = 16.984 (5) Å, β = 90.246 (9)°, V = 2652 Å3, Z = 4, R = 0.064, Rw = 0.082 for 3394 independent reflections with I > 3σ(I); 4, P21/n, a = 7.122 (2) Å, b = 27.668 (8) Å, c = 11.629 (3) Å, β = 96.246 (5)°, V = 2288 Å3, Z = 4, R = 0.065, Rw = 0.075, GOF = 2.39 for 2137 independent reflections; Tl[5]·2/3C7H8, P1, a = 11.347 (2) Å, b = 11.748 (2) Å, c = 12.708 (2) Å, α = 92.429 (6)°, β = 90.876 (6)°, γ = 93.343 (5)°, V = 1689 Å3, Z = 3, R = 0.057, Rw = 0.054, GOF = 1.57 for 1941 independent reflections; Tl[6], P1, a = 6.9564 (6) Å, b = 11.0466 (9) Å, c = 12.0287 (10) Å, α = 102.088 (2)°, β = 95.484 (2)°, γ = 94.687 (3)°, V = 894 Å3, Z = 2, R = 0.041, Rw = 0.054, GOF = 2.03 for 2733 independent reflections; 8·1/2C6H6, A1, a = 13.964 (3) Å, b = 15.966 (4) Å, c = 8.550 (2) Å, α = 92.227 (8)°, β = 86.689 (7)°, γ = 102.060 (8)°, V = 1862 Å3, Z = 4 (reduced cell: a = 8.552 Å, b = 8.909 Å, c = 13.967 Å, α = 99.172°, β = 93.323°, γ = 116.428°, V = 930.9 Å3, Z = 2), R = 0.061, Rw = 0.081, GOF = 2.85 for 2338 independent reflections; [(PPh3)2N][10], P21/c, a = 16.378 (3) Å, b = 18.781 (3) Å, c = 14.806 (3) Å, β = 90.197 (5)°, V = 4554 Å3, Z = 4, R = 0.078, Rw = 0.088, GOF = 2.0 for 2128 independent reflections; [Na][11], P21, a = 10.035 (2) Å, b = 12.433 (3) Å, c = 11.690 (3) Å, β = 111.019 (7)°, V = 1367 Å3, Z = 4, R = 0.049, Rw = 0.059, GOF = 2.08 for 2156 independent reflections. The compound Tl[5]·2/3C7H8 contains the thallium(I)–arene complex Tl(η6-MePh). Compounds 1a and 4 were shown to catalyze the exchange of carborane B–H and arene C–D bonds as well as the polymerization of selected olefins under mild homogeneous conditions. Bonding and the varying degrees of distortion from idealized closo and commo geometries displayed by 3,4, [5]-, and [6]- are discussed. Species 8, [10]-, and [11]- contain Al–C σ-bonded aluminum–carborane connectivities. Compound 8 exhibits rapid exchange of aluminum-coordinated ether in solution, and the compound nido-6,9-(μ-A1Et-(C4H8O))-6,9-C2B8H10 (9) was prepared by ether exchange of 8 in tetrahydrofuran/toluene. Anion [11]- undergoes rapid enantiomer interconversion in solution at room temperature.

Original languageEnglish
Pages (from-to)2046-2061
Number of pages16
JournalOrganometallics
Volume9
Issue number7
DOIs
StatePublished - 1990

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