Microwave Study of the CVD Precursor Trimethylamine-Alane, (CH3)3NAlH3: Rotational Spectra, 27Al and 14N Nuclear Quadrupole Coupling Constants, and Molecular Structure

Warner, H. E.; Wang, Y.; Ward, Charlotte; Gillies, C. W.; Interrante, L. V.

doi:10.1021/j100098a016

Cited by 24 publications

(19 citation statements)

References 22 publications

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“…Fitting the rotational and quadrupole coupling constants yielded B = 2796.9697(7) MHz, χ zz (Al) = 28.30(1) MHz, and χ zz (N) = −2.77(1) MHz. The quadrupole coupling constants are in good agreement with those of the well-known “inverse“ isomer H 3 Al-N(CH 3 ) 3 . However, these results should be used with some care.…”

Section: Resultssupporting

confidence: 72%

Structure of Ammonia Trimethylalane (Me₃Al-NH₃): Microwave Spectroscopy, X-ray Powder Diffraction, and ab Initio Calculations

et al. 1999

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The structural parameters of the ground-state geometry of Me3Al-NH3 calculated by various ab initio methods (HF, B3LYP, and MP2) are presented. For the two isotopomers Me3Al-14NH3 and Me3Al-15NH3, the rotational transitions J = 1 ← 0 and J = 2 ← 1 were investigated by Fourier transform microwave spectroscopy (4−12 GHz). All transitions showed a complicated hyperfine structure consisting of a large number of lines, so that only partial assignment of the experimental data was possible. The best fit was achieved for the J = 1 ← 0 transition of the 15N-marked sample (Me3Al-15NH3), for which 17 of 42 observed components could be assigned by assuming a symmetric top with one quadrupole nucleus (27Al) and three internal methyl group rotors. The combination of microwave spectroscopy and the calculated geometry of Me3Al-NH3 at the MP2(fc)/6-311G(2d,2p) level resulted in an Al−N bond length of 2.066(1) Å as the best estimate for the experimental value. These results are compared with those of the well-known isomer H3Al-NMe3 (Warner, H. E.; et al. J. Phys. Chem. 1994, 98, 12215. Atwood, J. L.; et al. J. Am. Chem. Soc. 1991, 113, 8183. Almenningen, A.; et al. Acta Chem. Scand. 1972, 26, 3928. March, M. B. C.; et al. J. Phys. Chem. 1995, 99, 195). The solid-state structure of Me3Al-NH3 was solved from X-ray powder diffraction data. The compound crystallizes in the orthorhombic space group Ama2 with four molecules per unit cell. There are significant differences between the structure of ammonia trimethylalane in the gas phase and in the solid state. The main differences could be understood on the basis of Onsager's theory using SCRF calculations (B3LYP/6-311++G(2d,p)) (Foresman, J. F.; Frisch, Æ. Exploring Chemistry with Electronic Structure Methods, 2nd ed.; Gaussian, Inc.: Pittsburgh, PA, 1996. Onsager, L. J. Am. Chem. Soc. 1936, 58, 1486).

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Section: Resultssupporting

confidence: 72%

Structure of Ammonia Trimethylalane (Me₃Al-NH₃): Microwave Spectroscopy, X-ray Powder Diffraction, and ab Initio Calculations

et al. 1999

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“…[53] In both AlMes 3 and Al(NTMS 2 ) 3 , the value of the asymmetry parameter, h Q , is very close to zero. This is the result of the high axial symmetry of the 27 Al EFG tensor, which has the largest component, V 33 , oriented along the three-fold rotational axis of the molecule, and V 11 and V 22 oriented in the AlC 3 or AlN 3 planes (that is, j V 33 j > j V 22 j % j V 11 j ).…”

Section: Solid-state Nmr Spectroscopymentioning

confidence: 86%

“…Analytical simulations (Figure 3) [15] and techniques such as NQR and gas-phase microwave spectroscopy have been utilized to measure C Q ( 27 Al) values between 25 and 45 MHz in a variety of systems, including alkylaluminum derivatives, [51,52] trimethylamine alanes, [53] and aluminum isocyanide. [53] In both AlMes 3 and Al(NTMS 2 ) 3 , the value of the asymmetry parameter, h Q , is very close to zero.…”

Section: Solid-state Nmr Spectroscopymentioning

confidence: 99%

Ultra‐wideline ²⁷Al NMR Investigation of Three‐ and Five‐Coordinate Aluminum Environments

et al. 2006

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Ultra-wideline 27Al NMR experiments are conducted on coordination compounds with 27Al nuclei possessing immense quadrupolar interactions that result from exceptionally nonspherical coordination environments. NMR spectra are acquired using a methodology involving frequency-stepped, piecewise acquisition of NMR spectra with Hahn-echo or quadrupolar Carr-Purcell Meiboom-Gill (QCPMG) pulse sequences, which is applicable to any half-integer quadrupolar nucleus with extremely broad NMR powder patterns. Despite the large breadth of these central transition powder patterns, ranging from 250 to 700 kHz, the total experimental times are an order of magnitude less than previously reported experiments on analogous complexes with smaller quadrupolar interactions. The complexes examined feature three- or five-coordinate aluminum sites: trismesitylaluminum (AlMes3), tris(bis(trimethylsilyl)amino)aluminum (Al(NTMS2)3), bis[dimethyl tetrahydrofurfuryloxide aluminum] ([Me2-Al(mu-OTHF)]2), and bis[diethyl tetrahydrofurfuryloxide aluminum] ([Et2-Al(mu-OTHF)]2). We report some of the largest 27Al quadrupolar coupling constants measured to date, with values of C(Q)(27Al) of 48.2(1), 36.3(1), 19.9(1), and 19.6(2) MHz for AlMes3, Al(NTMS2)3, [Me2-Al(mu-OTHF)]2, and [Et2-Al(mu-OTHF)]2, respectively. X-ray crystallographic data and theoretical (Hartree-Fock and DFT) calculations of 27Al electric field gradient (EFG) tensors are utilized to examine the relationships between the quadrupolar interactions and molecular structure; in particular, the origin of the immense quadrupolar interaction in the three-coordinate species is studied via analyses of molecular orbitals.

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“…Wiberg et al originally proposed that the molecule existed as a dimer, 19 whereas subsequent vibrational spectroscopic studies by several groups have provided compelling evidence that the molecule is monomeric, with C 2v symmetry in the gas and liquid states. 73,82,84,85 Atwood et al conducted single-crystal X-ray diffraction experiments and determined the structure of AlH 3 •TMA to be dimeric, 60 albeit highly disordered. However, ab initio MO calculations corroborated this conclusion.…”

Section: Paper Dalton Transactionsmentioning

confidence: 99%

Lewis base complexes of AlH3: prediction of preferred structure and stoichiometry

et al. 2013

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The structures adopted by a range of complexes AlH3·nL, (n = 1 or 2), have been explored in detail to identify the factors that determine the value of n, and whether a monomeric or dimeric arrangement is preferred for the 1 : 1 complexes. Single-crystal X-ray diffraction, vibrational and NMR spectroscopies, and thermal analysis data have been collected, DFT calculations have been performed for AlH3·nL species, and pK(a) values have been collated for a series of amine and phosphine ligands L. The pK(a) of the ligand L exerts an important influence on the type of complex formed: as the basicity of L increases, a monomeric structure is favoured over a dimeric arrangement. Dimeric amine complexes form if pK(a) < 9.76, while monomeric complexes are preferred when pK(a) > 9.99. The steric requirements of L also influence the structural preference: bulky ligands with large cone angles (>163°) tend to favour formation of monomers, while smaller cone angles (<125°) encourage the formation of dimeric or 1 : 2 adducts. The steric bulk of the ligand appears to be more important for phosphine complexes, with smaller phosphines being unable to stabilise the complex at ambient temperatures even through dimerisation. Raman spectroscopy and DFT calculations have been particularly helpful in elucidating the stoichiometric preferences of complexes that have been contentious; these include AlH3·NMe2Et, AlH3·NMe3 and AlH3·nEt2O.

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Microwave Study of the CVD Precursor Trimethylamine-Alane, (CH3)3NAlH3: Rotational Spectra, 27Al and 14N Nuclear Quadrupole Coupling Constants, and Molecular Structure

Cited by 24 publications

References 22 publications

Structure of Ammonia Trimethylalane (Me₃Al-NH₃): Microwave Spectroscopy, X-ray Powder Diffraction, and ab Initio Calculations

Structure of Ammonia Trimethylalane (Me₃Al-NH₃): Microwave Spectroscopy, X-ray Powder Diffraction, and ab Initio Calculations

Ultra‐wideline ²⁷Al NMR Investigation of Three‐ and Five‐Coordinate Aluminum Environments

Lewis base complexes of AlH3: prediction of preferred structure and stoichiometry

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Microwave Study of the CVD Precursor Trimethylamine-Alane, (CH3)3NAlH3: Rotational Spectra, 27Al and 14N Nuclear Quadrupole Coupling Constants, and Molecular Structure

Cited by 24 publications

References 22 publications

Structure of Ammonia Trimethylalane (Me3Al-NH3): Microwave Spectroscopy, X-ray Powder Diffraction, and ab Initio Calculations

Structure of Ammonia Trimethylalane (Me3Al-NH3): Microwave Spectroscopy, X-ray Powder Diffraction, and ab Initio Calculations

Ultra‐wideline 27Al NMR Investigation of Three‐ and Five‐Coordinate Aluminum Environments

Lewis base complexes of AlH3: prediction of preferred structure and stoichiometry

Contact Info

Product

Resources

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Structure of Ammonia Trimethylalane (Me₃Al-NH₃): Microwave Spectroscopy, X-ray Powder Diffraction, and ab Initio Calculations

Structure of Ammonia Trimethylalane (Me₃Al-NH₃): Microwave Spectroscopy, X-ray Powder Diffraction, and ab Initio Calculations

Ultra‐wideline ²⁷Al NMR Investigation of Three‐ and Five‐Coordinate Aluminum Environments