- Hydrogallation reactions involving the monoalkynes H5C 6-C≡C-SiMe3 and H5C6- C≡C-CMe3 - cis/trans isomerisation and substituent exchange
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Phenyl-trimethylsilylethyne, H5C6-C≡C-SiMe 3, reacted with different dialkylgallium hydrides, R2Ga-H (R = Me, Et, nPr, iPr, tBu), by the addition of one Ga-H bond to its C≡C triple bond (hydrogallation). The gallium atoms attacked selectively those carbon atoms, which were also attached to trimethylsilyl groups. The cis arrangement of Ga and H across the resulting C=C double bonds resulted only for the sterically most shielded di(tert-butyl)-gallium derivative, while in all other cases spontaneous cis/trans rearrangement occurred with the quantitative formation of the trans addition products. The diethyl compound Et 2Ga-C(SiMe3)= C(H)-C6H5 (2) gave by substituent exchange the secondary prod-ucts EtGa[C(SiMe3)=C(H)- C6H5]2 (7, Z,Z) and Ga[C(SiMe3)= C(H)-C6H5]3 (8). Interestingly, compound 8 has two alkenyl groups with a Z configuration, while the third C=C double bond has the cis arrangement of Ga and H (E configuration). The reversibility of the cis/trans isomerisation of hydrogallation products was observed for the first time. tert-Butyl-phenylethyne gave the simple addition product, R 2Ga(C6H5)=C(H)-CMe3 (9), only with di(n-propyl)gallium hydride.
- Uhl, Werner,Claesener, Michael,Haddadpour, Sima,Jasper, Beate,Tiesmeyer, Ines,Zemke, Sarina
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- Syntheses and crystal structures of dialkylgallium hydrides - Dimeric versus trimeric formula units
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Dialkylgallium hydrides (R = Me, Et, iPr, iBu, neopentyl) were obtained on two different synthetic routes. The dimethyl and diethyl compounds were formed by the reaction of LiH with the corresponding dialkylgallium chlorides via lithium dialkyldihydridogallate intermediates, which so far have not been isolated in a pure form. On the second route, trialkylgallium compounds were treated with [GaH3·NMe2Et] to yield the dialkylgallium hydrides by a substituent exchange reaction. The dimethyl, diethyl and diisopropyl compounds are trimeric in solution. That trimeric structure was verified for the diisopropyl derivative by a crystal structure determination. Di(neopentyl)gallium hydride has a dimeric structure in solution and in the solid state.
- Uhl, Werner,Cuypers, Lars,Geiseler, Gertraud,Harms, Klaus,Massa, Werner
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- Organo Group-13 Metal Complexes of d-Block-Elements, III. First Volatile Organogallio Cobalt Compounds
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In non-coordinating solvents, salt elimination between sodium tetracarbonylcobaltate and bulky alkylgallium chlorides yields almost quantitatively the novel volatile cobalt-gallium-complexes of formula (CO)4CoGaR2(L) .The synthesized compounds were identified by means of 1H-, 13C-, 31P-NMR, MS, and infrared ν(CO) data.Additional, 3a was characterized by an X-ray single-crystal analysis.The ?(Co-Ga) bond length is 257.8(3) pm.Those bonds are highly reactive and rapidly cleaved due to electrophilic or nucleophilicattack. 3a, b are used as candidates to generate intermetallic Co/Ga films by the procedure of low-pressure MOCVD. Key Words: Organogallium complexes / Cobalt-gallium bonds / MOCVD
- Fischer, Roland A.,Behm, Joachim
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- Reactions of Ga2Br4*2dioxane with (Trimethylsilyl)methyllithium and Neopentyllithium - Synthesis and Molecular Structure of Lithium Tetraalkylgallanates(III) with Li-C-Ga Bridges.
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Ga2Br4*2dioxane reacts with (trimethylsilyl)methyllithium or neopentyllithium to yield in n-pentane/diethyl ether solution besides elemental gallium exclusively the disproportionation product trialkylgallane.In pure n-pentane the dioxane adducts of the corresponding lithium tetraalkylgallanates (R= -CH2SiMe3 2; R= -CH2CMe3 4) are formed. 2 and 4 are also synthesized by the reaction of GaBr3 with alkyllithium in the molar ratio 1:4.The crystal structure of 2 shows a dioxane-brideged dimer and Li-C-Ga bridges with lithium probably bound by the C-H ?-bonds of the cental carbon atom.
- Uhl, Werner,Klinkhammer, Karl-Wilhelm,Layh, Marcus,Massa, Werner
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p. 279 - 284
(2007/10/02)
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