Synthesis and Structural Diversity of Barium (N,N-Dimethylamino)diboranates

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• 作者：Scott R. Daly ; Brian J. Bellott ; Mark A. Nesbit ; Gregory S. Girolami
• 刊名：Inorganic Chemistry
• 出版年：2012
• 出版时间：June 18, 2012
• 年：2012
• 卷：51
• 期：12
• 页码：6449-6459
• 全文大小：558K
• 年卷期：v.51,no.12(June 18, 2012)
• ISSN：1520-510X

文摘

The reaction of a slurry of BaBr<sub>2sub> in a minimal amount of tetrahydrofuran (THF) with 2 equiv of Na(H<sub>3sub>BNMe<sub>2sub>BH<sub>3sub>) in diethyl ether followed by crystallization from diethyl ether at 鈭?0 掳C yields crystals of Ba(H<sub>3sub>BNMe<sub>2sub>BH<sub>3sub>)<sub>2sub>(Et<sub>2sub>O)<sub>2sub> (1). Drying 1 at room temperature under vacuum gives the partially desolvated analogue Ba(H<sub>3sub>BNMe<sub>2sub>BH<sub>3sub>)<sub>2sub>(Et<sub>2sub>O)<sub>xsub> (1鈥?/b>) as a free-flowing white solid, where the value of x varies from <0.1 to about 0.4 depending on whether desolvation is carried out with or without heating. The reaction of 1 or 1鈥?/b> with Lewis bases that bind more strongly to barium than diethyl ether results in the formation of new complexes Ba(H<sub>3sub>BNMe<sub>2sub>BH<sub>3sub>)<sub>2sub>(L), where L = 1,2-dimethoxyethane (2), N,N,N鈥?N鈥?tetramethylethylenediamine (3), 12-crown-4 (4), 18-crown-6 (5), N,N,N鈥?N鈥?tetraethylethylenediamine (6), and N,N,N鈥?N鈥?N鈥?pentamethylethylenetriamine (7). Recrystallization of 4 and 5 from THF affords the related compounds Ba(H<sub>3sub>BNMe<sub>2sub>BH<sub>3sub>)<sub>2sub>(12-crown-4)(THF)路THF (4鈥?/b>) and Ba(H<sub>3sub>BNMe<sub>2sub>BH<sub>3sub>)<sub>2sub>(18-crown-6)路2THF (5鈥?/b>). In addition, the reaction of BaBr<sub>2sub> with 2 equiv of Na(H<sub>3sub>BNMe<sub>2sub>BH<sub>3sub>) in the presence of diglyme yields Ba(H<sub>3sub>BNMe<sub>2sub>BH<sub>3sub>)<sub>2sub>(diglyme)<sub>2sub> (8), and the reaction of 1 with 15-crown-5 affords the diadduct [Ba(15-crown-5)<sub>2sub>][H<sub>3sub>BNMe<sub>2sub>BH<sub>3sub>]<sub>2sub> (9). Finally, the reaction of BaBr<sub>2sub> with Na(H<sub>3sub>BNMe<sub>2sub>BH<sub>3sub>) in THF, followed by the addition of 12-crown-4, affords the unusual salt [Na(12-crown-4)<sub>2sub>][Ba(H<sub>3sub>BNMe<sub>2sub>BH<sub>3sub>)<sub>3sub>(THF)<sub>2sub>] (10). All of these complexes have been characterized by IR and <sup>1sup>H and <sup>11sup>B NMR spectroscopy, and the structures of compounds 1鈥?b>3, 4鈥?/b>, 5鈥?/b>, and 6鈥?b>10 have been determined by single-crystal X-ray diffraction. As the steric demand of the Lewis bases increases, the structure changes from polymers to dimers to monomers and then to charge-separated species. Despite the fact that several of the barium complexes are monomeric in the solid state, none is appreciably volatile up to 200 掳C at 10<sup>鈥?sup> Torr.