Molecular titanium nitrides: nucleophiles unleashed.
Molecular titanium nitrides: nucleophiles unleashed.
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DOI：
10.1039/c6sc03422e
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发表时间：
2017-02-01
期刊：
影响因子：
8.4
通讯作者：
Mindiola DJ
中科院分区：
文献类型：
--
作者：
Grant LN;Pinter B;Kurogi T;Carroll ME;Wu G;Manor BC;Carroll PJ;Mindiola DJ
本文介绍了一种罕见的分子氮化钛的反应性研究。理论和核磁共振光谱的结合提供了这些氮化物的键合描述，反阳离子K+的作用，以及它们高度向下场15N核磁共振光谱位移的起源。在这篇文章中，我们提出了一种罕见的钛盐的反应性研究，以[μ2-K(OEt2)]2[(PN)2TiN]2 (1) （PN - = N-（2-（二异丙基膦）-4-甲基苯基）-2,4,6-三甲基苯胺）的形式产生一系列亚胺基团，包括罕见的例子，如甲基限制，硼限制，磷限制和亲本亚胺。对于后者，使用各种弱酸可以使我们将（PN）2TiNH中NH基团的pK a范围缩小到26-36之间。叠氮化物前体（PN）2TiN3可以通过还原促进消除N2生成配合物1，而配合物（PN）2TiNNTi(PN)2(2)和强还原剂不能实现N2的还原分裂。当1与ClC(O)tBu和OCCPh2分别形成NCtBu和KNCCPh2，以及末端氧配合物（PN）2TiO时，也可以观察到完整的n原子转移反应，并对其进行了表征。结合固态15N核磁共振（MAS）和理论研究，我们了解了反阳离子在二聚体1、单体[K(18-crown-6)][(PN)2TiN]和离散盐[K(2,2,2- kryptofix)][(PN)2TiN]中的屏蔽作用，以及从二聚体到单体再到终端氮化物（离散盐）时高度下场15N核磁共振的起源。利用MO分析和量子化学分析相结合的方法对屏蔽张量进行了分析，发现15N核磁共振谱中15N共振的上场位移与K+诱导的氮化钛官能团的电子结构变化有关。
Reactivity studies of a rare example of a molecular titanium nitride are presented. A combination of theory and NMR spectroscopy provide a description of the bonding in the these nitrides, the role of the counter cation, K+, as well as the origin of their highly downfield 15N NMR spectroscopic shifts. In this contribution we present reactivity studies of a rare example of a titanium salt, in the form of [μ2-K(OEt2)]2[(PN)2TiN]2 (1) (PN– = N-(2-(diisopropylphosphino)-4-methylphenyl)-2,4,6-trimethylanilide) to produce a series of imide moieties including rare examples such as methylimido, borylimido, phosphonylimido, and a parent imido. For the latter, using various weak acids allowed us to narrow the pK a range of the NH group in (PN)2TiNH to be between 26–36. Complex 1 could be produced by a reductively promoted elimination of N2 from the azide precursor (PN)2TiN3, whereas reductive splitting of N2 could not be achieved using the complex (PN)2TiNNTi(PN)2 (2) and a strong reductant. Complete N-atom transfer reactions could also be observed when 1 was treated with ClC(O)tBu and OCCPh2 to form NCtBu and KNCCPh2, respectively, along with the terminal oxo complex (PN)2TiO, which was also characterized. A combination of solid state 15N NMR (MAS) and theoretical studies allowed us to understand the shielding effect of the counter cation in dimer 1, the monomer [K(18-crown-6)][(PN)2TiN], and the discrete salt [K(2,2,2-Kryptofix)][(PN)2TiN] as well as the origin of the highly downfield 15N NMR resonance when shifting from dimer to monomer to a terminal nitride (discrete salt). The upfield shift of 15Nnitride resonance in the 15N NMR spectrum was found to be linked to the K+ induced electronic structural change of the titanium-nitride functionality by using a combination of MO analysis and quantum chemical analysis of the corresponding shielding tensors.