Barybin Mikhail V., Ellis John E., Pomije Marie K., Tinkham Mary L., Warnock Garry F.
Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455.
Inorg Chem. 1998 Dec 14;37(25):6518-6527. doi: 10.1021/ic980752i.
Reductive carbonylations of NbCl(4)(THF)(2), THF = tetrahydrofuran, mediated by sodium naphthalene in 1,2-dimethoxyethane, DME, or sodium anthracene in THF, provide Nb(CO)(6) as the tetraethylammonium salt in 60% or 70% isolated yields, respectively, the highest known for atmospheric pressure syntheses of this metal carbonyl. Corresponding reductions involving PF(3) give about 40% yields of [Et(4)N][Nb(PF(3))(6)], which in the past was only accessible by a photochemical route. Electrochemical data for Nb(CO)(6) and Nb(PF(3))(6) are compared and show that the PF(3) complex is almost 1 V more difficult to oxidize than the CO analogue. Protonation of Nb(PF(3))(6) by concentrated sulfuric acid yields a volatile, thermally unstable species, which has been shown by (1)H NMR and mass spectral studies to be the new niobium hydride, Nb(PF(3))(6)H. Previously unpublished (93)Nb and (13)C NMR studies corroborate prior claims that the sodium metal reduction of Nb(CO)(6) in liquid ammonia affords Nb(CO)(5)(-), the only known Nb(III-) species. The first details of this synthesis and those of Nb(CO)(5)H(-), Nb(CO)(5)SnPh(3)(-), Nb(CO)(5)NH(3), and Nb(CO)(5)(CNtBu) are presented.
在1,2 - 二甲氧基乙烷（DME）中，由萘钠介导的NbCl₄(THF)₂（THF = 四氢呋喃）的还原羰基化反应，或在四氢呋喃中由蒽钠介导的反应，分别以60%或70%的分离产率提供[Nb(CO)₆]⁻的四乙基铵盐，这是该金属羰基化合物常压合成中已知的最高产率。涉及PF₃的相应还原反应得到约40%产率的[Et₄N][Nb(PF₃)₆]，过去只能通过光化学途径获得。比较了[Nb(CO)₆]⁻和[Nb(PF₃)₆]⁻的电化学数据，结果表明PF₃配合物比CO类似物氧化难度大近1 V。用浓硫酸对[Nb(PF₃)₆]⁻进行质子化反应生成一种挥发性、热不稳定的物种，通过¹H NMR和质谱研究表明其为新的氢化铌Nb(PF₃)₆H。此前未发表的⁹³Nb和¹³C NMR研究证实了之前的说法，即在液氨中用金属钠还原[Nb(CO)₆]⁻可得到[Nb(CO)₅]₃⁻，这是唯一已知的铌（III - ）物种。本文介绍了该合成方法以及[Nb(CO)₅H]₂⁻、[Nb(CO)₅SnPh₃]₂⁻、[Nb(CO)₅NH₃]⁻和[Nb(CO)₅(CNtBu)]⁻合成方法的首次详细信息。
