Mercury- and Cadmium-Assisted [2 + 2] Cyclodimerization of tert-Butylselenium Diimide

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• 作者：Aino J. Karhu ; J. Mikko Rautiainen ; Raija Oilunkaniemi ; Tristram Chivers ; Risto S. Laitinen
• 刊名：Inorganic Chemistry
• 出版年：2015
• 出版时间：October 5, 2015
• 年：2015
• 卷：54
• 期：19
• 页码：9499-9508
• 全文大小：533K
• ISSN：1520-510X

文摘

The complexes [MCl₂{N,N鈥?^tBuNSe(渭-N^tBu)₂SeN^tBu}] [M = Cd (1), Hg (2)] were obtained in high yields by the reaction of tert-butylselenium diimide Se^IV(N^tBu)₂ with CdCl₂ or HgCl₂ in tetrahydrofuran. Recrystallization of 1 and 2 from acetonitrile (MeCN) afforded yellow crystals of 1路MeCN and 2路MeCN, respectively. Isomorphic 1路MeCN and 2路MeCN contain an unprecedented dimeric selenium diimide ligand, which is N,N鈥?chelated to the metal through exocyclic imido groups. In addition to the complexes 1 and 2, the ⁷⁷Se NMR spectra of acetonitrile solutions of 1路MeCN and 2路MeCN indicated the presence of the dimeric ^tBuNSe(渭-N^tBu)₂SeN^tBu, monomeric Se^IV(N^tBu)₂, and cyclic selenium imides. Density functional theory calculations at the PBE0/def2-TZVPP level of theory were used to assign the ⁷⁷Se resonances of the dimer. A comparison of Gibbs energies of formation of some metal dichloride complexes [MCl₂{N,N鈥?Se^IV(N^tBu)₂}] and [MCl₂{N,N鈥?^tBuNSe(渭-N^tBu)₂SeN^tBu}] (M = Zn, Cd, Hg) indicated that the formation of complexes containing a dimeric selenium diimide ligand is favored over those containing a monomeric ligand for the group 12 metals. In the case of the group 10 metal halogenides (M = Ni, Pd, Pt), the Gibbs energies of the complexes with monomeric Se^IV(N^tBu)₂ ligands are close to those containing dimeric ^tBuNSe(渭-N^tBu)₂SeN^tBu ligands. A plausible reaction pathway with a low activation energy involves the initial formation of [MCl₂{N,N鈥?Se^IV(N^tBu)₂}] (M = Zn, Cd, Hg), which then reacts with another molecule of Se(N^tBu)₂, leading to the final [MCl₂{N,N鈥?^tBuNSe(渭-N^tBu)₂SeN^tBu}] complex. Without the presence of group 12 metal halogenides, the [2 + 2] cyclodimerization of Se^IV(N^tBu)₂ is virtually thermoneutral, but the activation energy is relatively high, which accounts for the kinetic stability of ^tBuNSe(渭-N^tBu)₂SeN^tBu in solution. A minor byproduct, [Cd₇Cl₁₄{N,N鈥?Se^II(NH^tBu)₂}₆]路4CH₂Cl₂, was identified by X-ray crystallography as a heptanuclear cluster with selenium(II) diamide ligands N,N鈥?chelated to the cadmium centers.