Vibrational spectra of trimethyl gallium species in relation to the force field and methyl group internal rotation

McKean, D.C.; McQuillan, Geoffrey P.; Duncan, J.L.; Shephard, N.; Munro, Brian; Fawcett, V.; Edwards, Howell G. M.

doi:10.1016/s0584-8539(87)80019-3

Cited by 11 publications

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“…The substantial 13 C shift of the band at 528.7 cm -1 signals its origin in what is essentially the ν(Ga−C) mode. The frequency is comparable with, but somewhat lower than, the mean value of 561 cm -1 reported for the ν(Ga−C) modes in (CH 3 ) 3 Ga . The final feature to be assigned to CH 3 GaH and lying at 475.5 cm -1 is associated with the skeletal bending vibration δ(C−Ga−H), on the grounds of its minimal 13 C shift.…”

Section: Discussionsupporting

confidence: 59%

“…Of the fundamentals involving the internal motions of the CH 3 Ga fragment, only those arising from the a ‘ CH 3 rocking and a ‘ Ga−C stretching modes were observed, these being calculated to be among the four most intense features in IR absorption. The location of ρ(CH 3 ) (a ‘ ) at 752.9 cm -1 (supported by both the 13 C and deuterium shifts) may be compared with the mean value of 755 cm -1 found for the corresponding modes of (CH 3 ) 3 Ga …”

Section: Discussionmentioning

confidence: 90%

“…The mean frequencies for the corresponding modes in (CH 3 ) 3 Ga are ca. 1440 and 1207 cm -1 , respectively . The assignment of the metal−carbon stretching mode, ν 3 (a 1 ), to the remaining absorption at 476.2 cm -1 is guided by its substantial 13 C shift (11.5 cm -1 ) and by the suggestion of 69 Ga/ 71 Ga splitting amounting to ca.…”

Section: Discussionmentioning

confidence: 99%

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Matrix Photochemistry of Gallium and Indium Atoms (M) in the Presence of Methane: Formation and Characterization of the Divalent Species CH₃MH and Univalent Species CH₃M

et al. 2000

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IR and UV/vis spectroscopic measurements have been used to chart the reactions set in train by irradiating methane-doped argon matrices containing gallium or indium atoms, first with light having λ ) 200-400 nm, and subsequently with broad-band UV-visible light. Assignments of the IR absorption bands are made and their carriers characterized on the basis of D and 13 C substitution and by comparison either with the vibrational properties of related molecules or with those forecast by DFT calculations. Photoexcitation at λ ) 200-400 nm results in insertion of the group 13 metal atom into a C-H bond to form the angular monomethylmetal hydride molecule, CH 3 MH (M ) Ga, In). This product is not photostable but decomposes on exposure to radiation with λ ) 200-800 nm to give the first sighting of CH 3 M, the simplest organic derivative of Ga(I) and In(I) to be characterized to date. The vibrational properties of the species CH 3 MH and CH 3 M are compared with those of related molecules and analyzed for the light they shed on the characters of the M-C and M-H bonds.

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Section: Discussionsupporting

confidence: 59%

Section: Discussionmentioning

confidence: 90%

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Matrix Photochemistry of Gallium and Indium Atoms (M) in the Presence of Methane: Formation and Characterization of the Divalent Species CH₃MH and Univalent Species CH₃M

et al. 2000

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“…Under ambient conditions, the trimethyl derivatives of the group 13 elements range from a gas (BMe 3 ), through a liquid (AlMe 3 and GaMe 3 ), to a low-melting solid (InMe 3 and TlMe 3 ) . On the evidence of mass and vibrational spectroscopic and electron diffraction measurements, the vapors of all but the aluminum compound consist of monomeric MMe 3 molecules (M = B, Ga, In, Tl), each with a trigonal-planar MC 3 skeleton and more or less freely rotating methyl groups. ,,,− In contrast, the analogous aluminum species, AlMe 3 , is found in appreciable concentrations only at elevated temperatures and/or low pressures; , otherwise, the dimer Me 2 Al(μ-Me) 2 AlMe 2 prevails throughout the condensed and vapor states . Increasing the atomic number of the group 13 element results in an overall rise in melting and boiling points consistent with the expected strengthening of van der Waals interactions.…”

Section: Resultsmentioning

confidence: 99%

“…Warming the mixture to room temperature caused a vigorous reaction to occur. After the mixture was stirred for 90 min to ensure completion of the reaction, the volatile products were vaporized in vacuo and fractionated via traps held at 222, 178, and 77 K. Trimethylgallium was collected at 178 K and was authenticated by the IR spectrum of the vapor …”

Section: Methodsmentioning

confidence: 99%

Polymorphism in the Crystal Structures of the Group 13 Trimethyls

et al. 2003

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Crystal structures have been determined for trimethylboron, BMe 3 , and for a new polymorph of trimethylgallium, GaMe 3 ; in addition, the crystal structure of trimethylthallium, TlMe 3 , has been redetermined. The BMe 3 crystal structure represents a new structural type for the group 13 trimethyl derivatives in the solid state. In contrast to its heavier analogues, it consists of layers containing only very weakly interacting BMe 3 molecules. GaMe 3 forms a ladder-like pseudo-polymer via long gallium-to-methyl intermolecular interactions with Ga‚‚‚C distances in the range 3.096(3)-3.226(4) Å. This is compared with a recently reported crystal structure of a polymorph, which, like InMe 3 and TlMe 3 , is characterized by the formation of pseudo-tetramers. The effects of crystallization and secondary interactions have been analyzed by comparison with related crystallographic, gas-phase electron diffraction, and spectroscopic studies of these and other trimethyl derivatives of the group 13 elements. The energetic differences between polymorphs of BMe 3 , GaMe 3 , and InMe 3 have been explored by plane wave DFT calculations. The energy differences between the BMe 3 -like layered structure and the InMe 3 -like pseudo-tetrameric structure are calculated to be -1.7, +3.6, and +10.4 kJ mol -1 for BMe 3 , GaMe 3 , and InMe 3 , respectively. IntroductionThere are three different structures that are observed for the group 13 trimethyl derivatives in the crystalline state. One is the dimeric form observed for trimethylaluminum, 1 in which methyl groups participate in strong metal-metal bridges, with C-Al interaction distances commensurate with those of terminal Al-C bonds. Methyl bridging is also observed in a second structural type featured by the derivatives with Ga, In, and Tl, but the interaction distances are substantially longer than the primary metal-carbon bonds. Prior to this study, crystal structures had been determined for GaMe 3 , 2 InMe 3 , 3,4 and TlMe 3 ; 5 here we describe crystal structure determinations of a new polymorph of GaMe 3 and a redetermination of the structure of TlMe 3 . The third structural type is represented by BMe 3 . As we show below, this crystal structure consists of layers in which the molecules interact by weak van der Waals, or possibly electrostatic, interactions. The longstanding debate over the nature and geometry of the bridging methyl groups in Al 2 Me 6 has recently been resolved in a neutron powder diffraction study at 4.5 K, 6 and in this paper we limit our attention to the second and third structural types.We have also investigated theoretically the energetic differences between polymorphs of BMe 3 , GaMe 3 , and InMe 3 in which the molecules form layers (as in the observed structure of BMe 3 ) or weak methyl bridges (as in InMe 3 ). Polymorphism has been described as the supramolecular equivalent of molecular isomerism. 7 Traditional ab initio modeling procedures (notably GAUSSIAN) simulate isolated molecules, but while this style of calculation is suitable for studying gaseous...

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Vibrational Spectra of Organometallics

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Vibrational spectra of trimethyl gallium species in relation to the force field and methyl group internal rotation

Cited by 11 publications

References 19 publications

Matrix Photochemistry of Gallium and Indium Atoms (M) in the Presence of Methane: Formation and Characterization of the Divalent Species CH₃MH and Univalent Species CH₃M

Matrix Photochemistry of Gallium and Indium Atoms (M) in the Presence of Methane: Formation and Characterization of the Divalent Species CH₃MH and Univalent Species CH₃M

Polymorphism in the Crystal Structures of the Group 13 Trimethyls

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Vibrational spectra of trimethyl gallium species in relation to the force field and methyl group internal rotation

Cited by 11 publications

References 19 publications

Matrix Photochemistry of Gallium and Indium Atoms (M) in the Presence of Methane: Formation and Characterization of the Divalent Species CH3MH and Univalent Species CH3M

Matrix Photochemistry of Gallium and Indium Atoms (M) in the Presence of Methane: Formation and Characterization of the Divalent Species CH3MH and Univalent Species CH3M

Polymorphism in the Crystal Structures of the Group 13 Trimethyls

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Matrix Photochemistry of Gallium and Indium Atoms (M) in the Presence of Methane: Formation and Characterization of the Divalent Species CH₃MH and Univalent Species CH₃M

Matrix Photochemistry of Gallium and Indium Atoms (M) in the Presence of Methane: Formation and Characterization of the Divalent Species CH₃MH and Univalent Species CH₃M