四配位铱（I）单氢化物：可逆的二氮结合、键活化和去质子化。

Four-coordinate iridium(I) monohydrides: reversible dinitrogen binding, bond activations, and deprotonations.

机构信息

Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, Mail Code 0358, La Jolla, California 92093-0358, USA.

出版信息

J Am Chem Soc. 2010 Jul 7;132(26):8921-3. doi: 10.1021/ja1037808.

DOI:10.1021/ja1037808

PMID:20550129

Abstract

Detailed herein are synthetic, spectroscopic and reactivity studies for two isolable four-coordinate iridium(I) monohydride complexes of the simple formulation HIrL(3). Such complexes have been postulated as reactive species in several transformations, but definite evidence for their existence has remained elusive. To stabilize these complexes, the methyleneadamantyl substituted phosphine ligand P(CH(2)(1)Ad)(i-Pr)(2) (abbreviated L(mAd)) was employed because of the resistance of the adamantane cage toward cyclometalation reactions. Treatment of the dihydride-chloride complex, H(2)IrCl(L(mAd))(2) with PhMgBr under N(2) afforded the square planar complex HIr(N(2))(L(mAd))(2). Contrastingly, treatment of H(2)IrCl(L(mAd))(2) with Li[HBEt(3)] under N(2) generates the trihydride complex H(3)Ir(L(mAd))(2), which possesses an agostic interaction between the L(mAd) ligand and the Ir center. Dissolution of HIr(N(2))(L(mAd))(2) in Et(2)O or C(6)D(12) rapidly establishes an equilibrium mixture with the cyclometalated complex H(2)Ir(kappa(2)-P,C-L(mAd))(L(mAd)). Despite the equilibrium between HIr(N(2))(L(mAd))(2) and H(2)Ir(kappa(2)-P,C-L(mAd))(L(mAd)), addition of 2 equiv of H(2) or 1 equiv of H(2)O to the mixture cleanly generates the pentahydride complex H(5)Ir(L(mAd))(2) or the dihydride hydroxide complex H(2)Ir(OH)(L(mAd))(2), respectively. Sequential addition (n)BuLi and 12-crown-4 (12-c-4) to a HIr(N(2))(L(mAd))(2)/H(2)Ir(kappa(2)-P,C-L(mAd))(L(mAd)), mixture provides the salt [Li(12-c-4)(2)][HIr(kappa(2)-P,C-L(mAd))(L(mAd))], which contains another four-coordinate Ir(I) monohydride. (31)P{(1)H} NMR studies provide evidence that four-coordinate HIr(N(2))(L(mAd))(2) is deprotonated en route to [Li(12-c-4)(2)][HIr(kappa(2)-P,C-L(mAd))(L(mAd))]. [Li(12-c-4)(2)][HIr(kappa(2)-P,C-L(mAd))(L(mAd))] deprotonates both H(2)N(2,6-(i-Pr)(2)C(6)H(3)) and HOC(6)F(5) under an N(2) atmosphere to regenerate HIr(N(2))(L(mAd))(2)/H(2)Ir(kappa(2)-P,C-L(mAd))(L(mAd)) equilibrium mixtures.

摘要

本文详细介绍了两种可分离的四配位铱（I）单氢化物配合物 HIrL(3) 的合成、光谱和反应性研究。此类配合物被假定为几种转化中的反应性物种，但一直难以确定其存在的明确证据。为了稳定这些配合物，采用了亚甲基金刚烷取代的膦配体 P(CH(2)(1)Ad)(i-Pr)(2)（缩写为 L(mAd)），因为金刚烷笼对环金属化反应具有抗性。用 PhMgBr 处理二氢化物-氯化物配合物 H(2)IrCl(L(mAd))(2) 在 N(2)下，得到了平面正方形配合物 HIr(N(2))(L(mAd))(2)。相比之下，用 Li[HBEt(3)] 在 N(2)下处理 H(2)IrCl(L(mAd))(2)，会生成三氢化物配合物 H(3)Ir(L(mAd))(2)，其具有 L(mAd)配体和 Ir 中心之间的螯合相互作用。将 HIr(N(2))(L(mAd))(2)溶解在 Et(2)O 或 C(6)D(12)中，会迅速与环金属化配合物 H(2)Ir(kappa(2)-P,C-L(mAd))(L(mAd)) 建立平衡混合物。尽管 HIr(N(2))(L(mAd))(2)和 H(2)Ir(kappa(2)-P,C-L(mAd))(L(mAd)) 之间存在平衡，但向混合物中加入 2 当量的 H(2)或 1 当量的 H(2)O，可以分别生成五氢化物配合物 H(5)Ir(L(mAd))(2)或二氢化物氢氧化物配合物 H(2)Ir(OH)(L(mAd))(2)。将 nBuLi 和 12-冠-4（12-c-4）连续加入到 HIr(N(2))(L(mAd))(2)/H(2)Ir(kappa(2)-P,C-L(mAd))(L(mAd))混合物中，会得到盐 [Li(12-c-4)(2)][HIr(kappa(2)-P,C-L(mAd))(L(mAd))]，其中含有另一种四配位 Ir(I)单氢化物。(31)P{(1)H}NMR 研究提供的证据表明，四配位 HIr(N(2))(L(mAd))(2)在形成 [Li(12-c-4)(2)][HIr(kappa(2)-P,C-L(mAd))(L(mAd))]的过程中发生去质子化。[Li(12-c-4)(2)][HIr(kappa(2)-P,C-L(mAd))(L(mAd))]在 N(2)气氛下使 H(2)N(2,6-(i-Pr)(2)C(6)H(3))和 HOC(6)F(5)都发生去质子化，从而重新生成 HIr(N(2))(L(mAd))(2)/H(2)Ir(kappa(2)-P,C-L(mAd))(L(mAd))平衡混合物。