Reactions of Terphenyl-Substituted Digallene AriPr4GaGaAriPr4 (AriPr4 = C6H3-2,6-(C6H3-2,6-iPr2)2) with Transition Metal Carbonyls and Theoretical Investigation of the Mechanism of Addition

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• 作者：Madison L. McCrea-Hendrick ; Christine A. Caputo ; Christopher J. Roberts ; James C. Fettinger ; Heikki M. Tuononen ; Philip P. Power
• 刊名：Organometallics
• 出版年：2016
• 出版时间：February 22, 2016
• 年：2016
• 卷：35
• 期：4
• 页码：579-586
• 全文大小：482K
• ISSN：1520-6041

文摘

The neutral digallene Ar^iPr₄GaGaAr^iPr₄ (Ar^iPr₄ = C₆H₃-2,6-(C₆H₃-2,6-ⁱPr₂)₂) was shown to react at ca. 25 °C in pentane solution with group 6 transition metal carbonyl complexes M(CO)₆ (M = Cr, Mo, W) under UV irradiation to afford compounds of the general formula trans-[M(GaAr^iPr₄)₂(CO)₄] in modest yields. The bis(gallanediyl) complexes were characterized spectroscopically and by X-ray crystallography, which demonstrated that they were isostructural. In each complex, the gallium atom is two-coordinate with essentially linear geometry, which is relatively rare for gallanediyl-substituted transition metal species. The experimental data show that the gallanediyl ligand :GaAr^iPr₄ behaves as a good σ-donor but a poor π-acceptor, in agreement with prior theoretical analyses on related systems. In addition, the monogallanediyl complex Mo(GaAr^iPr₄)(CO)₅ was synthesized by reacting Ar^iPr₄GaGaAr^iPr₄ with two equivalents of Mo(CO)₅NMe₃ in THF solution. The mechanism of the reaction between Ar^iPr₄GaGaAr^iPr₄ and Cr(CO)₆ was probed computationally using density functional theory. The results suggest that the reaction proceeds via an intermediate monogallanediyl complex, Cr(GaAr^iPr₄)(CO)₅, that can be generated via two pathways, one of which involves the dimeric Ar^iPr₄GaGaAr^iPr₄, that are possibly competing. Ar^iPr₄GaGaAr^iPr₄ was also shown to react readily under ambient conditions with Co₂(CO)₈ to give the monosubstituted dicobalt complex Co₂(μ-GaAr^iPr₄)(μ-CO)(CO)₆ by X-ray crystallography. The :GaAr^iPr₄ unit bridges the Co–Co bond unsymmetrically in the solid state. No evidence was found for incorporation of more than one :GaAr^iPr4 unit into the dicobalt complex.