Probing Mesitylborane and Mesitylborate Ligation Within the Coordination Sphere of Cp*Ru(PiPr3)+: A Combined Synthetic, X-ray Crystallographic, and Computationa

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• 作者：Kevin D. Hesp ; Felix O. Kannemann ; Matthew A. Rankin ; Robert McDonald ; Michael J. Ferguson ; Mark Stradiotto
• 刊名：Inorganic Chemistry
• 出版年：2011
• 出版时间：March 21, 2011
• 年：2011
• 卷：50
• 期：6
• 页码：2431-2444
• 全文大小：1173K
• 年卷期：v.50,no.6(March 21, 2011)
• ISSN：1520-510X

文摘

The reaction of Cp*Ru(PⁱPr₃)Cl (1) with MesBH₂ (Mes = 2,4,6-trimethylphenyl) afforded the mesitylborate complex Cp*Ru(PⁱPr₃)(BH₂MesCl) (2, 66%). Exposure of 2 to the chloride abstracting agent LiB(C₆F₅)₄路2.5OEt₂ provided [Cp*Ru(PⁱPr₃)(BH₂Mes)]⁺B(C₆F₅)₄^{鈭?/sup> (3, 54%), which features an unusual 畏2-B-H monoborane ligand. The related borate complex Cp*Ru(PiPr₃)(BH₃Mes) (5, 65%) was prepared from 1 and LiH₃BMes. Attempts to effect the insertion of unsaturated organic substrates into the B鈭扝 bonds of 3 were unsuccessful, and efforts to dehydrohalogenate 2 using KOtBu instead afforded the mesitylborate complex Cp*(PiPr₃)Ru(BH₂MesOH) (6, 48%). Treatment of 1 with benzyl potassium generated an intermediate hydridoruthenium complex (7) resulting from dehydrogenation of a PiPr fragment, which in turn was observed to react with MesBH₂ to afford the mesitylborate complex Cp*(P(iPr)₂(CH₃CCH₂))Ru(BH₃Mes) (8, 47%). Crystallographic characterization data are provided for 2, 3, 5, 6, and 8. A combined X-ray crystallographic and density functional theory (DFT) investigation of 3 and 5, using Natural Bond Orbital (NBO) and Atoms in Molecules (AIM) analysis, revealed that 3 and 5 are best described as donor鈭抋cceptor complexes between a Cp*(PiPr₃)Ru+ fragment and a bis(畏2-B-H) coordinating mesitylborane(borate) ligand. Significant 蟽-donation from the B鈭扝 bonds into the RuII center exists as evidenced by the NBO populations, bond orders, and AIM delocalization indices. In the case of 3, the vacant p orbital on boron is stabilized by Ru鈫払 蟺 back-donation as well as by resonance with the mesityl group.}