Organo Ruthenium鈥揘ickel Dithiolates with Redox-Responsive Nickel Sites

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• 作者：Geoffrey M. Chambers ; Raja Angamuthu ; Danielle L. Gray ; Thomas B. Rauchfuss
• 刊名：Organometallics
• 出版年：2013
• 出版时间：November 11, 2013
• 年：2013
• 卷：32
• 期：21
• 页码：6324-6329
• 全文大小：370K
• 年卷期：v.32,no.21(November 11, 2013)
• ISSN：1520-6041

文摘

Described is a new family of RuNi dithiolates featuring geometrically flexible Ni centers, which enable both acid鈥揵ase and redox chemistry, behavior that is characteristic of the hydrogenases. Treatment of Ni(pdt)(dxpe) with (cymene)₂Ru₂Cl₄ affords the salt [(cymene)Ru(Cl)(pdt)Ni(diphos)]Cl (pdt^{2鈥?/sup> = 1,3-propanedithiolate, diphos = dppe = 1,2-bis(diphenylphosphino)ethane ([1Cl]Cl) and diphos = dcpe = 1,2-bis(dicyclohexylphosphino)ethane ([2Cl]Cl)). Cyclic voltammetry revealed that in CH₂Cl₂ solution [1Cl]Cl reduces irreversibly near 鈭?.6 V vs Fc0/+ followed by the appearance of a reversible 1e鈥?/sup> couple assigned to the [1]0/+ couple. Reduction of [1Cl]Cl and [2Cl]Cl with cobaltocene produced the neutral derivatives (cymene)Ru(pdt)Ni(diphos) ([1]0, [2]0). Crystallographic characterization of these compounds revealed short Ru鈥揘i distance of 2.5539(5) ([1]0) and 2.600(3) 脜 ([2]0). The 2e鈥?/sup> reduction of these chlorides converts the Ni site from square planar to tetrahedral, highlighting the flexibility of the Ni center in these complexes. Variable-temperature NMR studies show that [1]0 and [2]0 are dynamic by virtue of ring flipping in the RuNi(pdt) core. Complexes [1]0 and [2]0 are basic: their conjugate acids, [H1]+ and [H2]+, exhibit pK_aPhCN values of 18.94 and 21.65, respectively. Crystallographic characterization of [H1]+ as its aryl borate salt revealed an unsymmetrical Ru鈥揌路路路Ni interaction and confirmed that the Ni center converted from tetrahedral to square planar, again demonstrating the flexibility of this site.}