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X-ray crystallographic studies of five group III compounds

University of British Columbia

The structures of five compounds of group III elements have been determined by single crystal X-ray diffraction, three boron compounds, one aluminum compound, and one gallium compound: 1» B,B-diphenylboroxazolidine (2-atninoethyl diphenyl-borinate) , C14H16BNO. 2. B ,B-bis (p-f luorophenyl) boroxazolidine , C14H14BF2NO. 3. 4 ,4-dimethyl-2,2-diphenyl-1,3-dioxa-4-azonia-2-bor-anatacyclopentane, C15H18gBNO2. 4. N-methyldiethanolaminogallane dimer, C10H24Ga2N2O4 5. (pentahaptocyclopentadienyl) hydridomolybdenum-μ-di-me th ylaluminum-μ-[ methylaluminum-di- iju.-pentaha_p_to-(monohapto)cyclopentadienyl)dimethylaluminum] (pentaha]3-tocyclopentadienyl)hydridomolybdenum, C25H35Al3Mo2. Crystals of B,B-diphenylboroxazolidine are monoclinic, a = 13.840(1), b = 8.9169(5), c = 10.170(1) A, = 98.85 (1)° , Z = 4, space group P21/n. The structure was determined by direct methods, and refined by electron-density and full-matrix least-squares procedures to R 0.041 for 1458 reflexions. The five-membered boroxazolidine ring is in the half-chair conformation. Bond angles in the ring range from 99.7 for OBN to 110.1° for BOC. Bond lengths are as follows: mean B-C, 1.616(2), B-H, 1 .653 (3), B-0, 1.484(3), C-N, 1 .485 (3), C-O, 1.413(3), mean C-C (aromatic) , 1 .392(11 ), and C-C, 1.505(4) A. The structure consists of discrete molecules linked by 0...H-N hydrogen bonds (2,874(2) A) to form continuous spirals about the 21 axes. Crystals of B,B-bis (p-fluorophenyl)boroxazolidine are orthorhomfcic, a = 13.442 (4), b = 10.214(3), c = 9. 823 (2) ft, Z = 4, space group P212121. The structure was solved by direct methods, and refined by electron-density and full-matrix least-squares procedures to R 0.047 for 1234 reflexions. The five-membered boroxazolidine ring is in a distorted half-chair conformation , Bond angles in the ring range from 99.9(2) for OBH to 108.2(2)° for BOC. Bond lengths are: mean B-C, 1.621:, (3), B-N, 1.652 (4), B-O, 1.471(4), C-N, 1.491(4), C-0, 1.4 18(4), mean C-F, 1.371(1), mean C-C (aromatic) , 1 .390 (13), and C (sp3) -C (sp3) , 1.494 (6) A. The structure consists of discrete molecules each linked to six others by an extensive network of O...H-N (0...N = 2.941(3) A), F...H-N (F...N = 3.171(4) A), and F...H-C (F...C = 3.318(5) A) hydrogen bonds. Crystals of 4,4-dimethyl-2,2-diphenyl-1,3-dioxa-4-azonia-2-boranatacyclopentane are orthorhombic, a = 17.043 (3), b= 6.289 (1), c= 13.024 (2) A, Z= 4, space group Pna2i. The structure was determined by direct methods, and was refined by full-matrix least-squares procedures to R 0,071 for 1100 reflexions. Bond angles in the five-membered ring , which has a distorted half-chair conformation, range from 101.5(4) for OBO to 107.1(4)° for NOB. Bond lengths are: mean B-C, 1.632 (8), B-0, 1.506(7) and 1.556 (8), N-0, 1.409(5), C-O, 1. 378 (9), C-N, 1.467-1.509(7-10), mean C-C(aromatic), 1.395(25)A. The structure consists of discrete molecules separated by normal van der Waals distances. Crystals of the N-methyldiethanolaminogallane dimer are orthorhomfcic, a = 19.112(4), b = 9.947(2), c = 7.709(2) A, Z = 4, space group P212121 . The structure was determined by Patterson and Fourier synthesis and was refined by full-matrix least-squares procedures to a final R of 0.056 for 1477 reflexions. The structure provides the first known crystallographic example of pentacoordinate gallium, the dimerization of HeH (CH2CH2O)2GaH occurring via the formation of a four-membered Ga2O2 ring. The coordination about the gallium is distorted trigonal bipyramidal with an angle of 151.2(4)° between the axial substituents. The mean bond distances are: Ga-N, 2.192(5), and Ga-O, 2.018(2) for axial ligands; Ga-O, 1.847(2), 1.960 (8), and Ga-H, 1.41(4) for equatorial ligands; O-C, 1.419(14), C-N, 1.470(7), C-C, 1.520 (12), and C-H, 1.00 (13) A. The molecule has C2 symmetry to within experimental error. There are possible C-H...0 hydrogen bonds (C...O, 3.13 (1)-3.44 (1) A) in the structure. Crystals of the hydridomolybdenum complex, C25H35Al3MO2, are orthorhombic, a = 19.398 (4) , b = 14.438 (9) , c = 9.0 35 (2) I, Z =4, space group P212121, The structure was determined by Patterson and Fourier syntheses, and refined by full-matrix least-sguares procedures to R 0.066 and Rw 0.063 for 1213 reflexions. The molecular structure exhibits several unusual features: C5H4 groups which are pentahapto to the molybdenum atoms and are involved via the unique carbon atom in multicentre bonding to two aluminum atoms, one of which occurs as an Al(Me)2 unit and the other an AlMe unit which also bridges the two molybdenum atoms. The third aluminum atom is probably involved in a Mo-H-Al (Me)2-H-Mo linkage. Mean bond distances are: Mo-Al, 2.659 and 2.974, Al-C(terminal) , 2.00, Al-C (bridge), 2.05 and 2.33, Mo-C (cyclopentadienyl) , 2. 285, and C-C (cyclopentadienyl) , 1.389 A.

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2010-02-01

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http://hdl.handle.net/2429/19531

Chemistry

University of British Columbia

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