Reactivity of a Dititanium Bis(pentalene) Complex toward Heteroallenes and Main-Group Element–Element Bonds

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• 作者：Alexander F. R. Kilpatrick ; Jennifer C. Green ; F. Geoffrey N. Cloke
• 刊名：Organometallics
• 出版年：2017
• 出版时间：January 23, 2017
• 年：2017
• 卷：36
• 期：2
• 页码：352-362
• 全文大小：601K
• ISSN：1520-6041

文摘

The reactivity of the Ti═Ti double bond in (μ,η⁵:η⁵-Pn^†)₂Ti₂ (1; Pn^† = 1,4-{SiⁱPr₃}₂C₈H₄) toward isocyanide and heteroallene substrates, and molecules featuring homonuclear bonds between main-group elements (E–E) has been explored. Reaction of 1 with methyl isocyanide or 1,3-N,N′-di-p-tolylcarbodiimide resulted in the formation of the 1:1 adducts (μ,η⁵:η⁵-Pn^†)₂Ti₂(μ,η²-CNMe) (2) and (μ,η⁵:η⁵-Pn^†)₂Ti₂(μ-C{N(4-C₆H₄CH₃)}₂) (3), respectively, which are thermally stable up to 100 °C in contrast to the analogous adducts formed with CO and CO₂. Reaction of 1 with phenyl isocyanate afforded a paramagnetic complex, [(η⁸-Pn^†)Ti]₂(μ,κ²:κ²-O₂CNPh) (4), in which the “double-sandwich” architecture of 1 has been broken and an unusual phenyl-carbonimidate ligand bridges two formally Ti(III) centers. Reaction of 1 with diphenyl dichalcogenides, Ph₂E₂ (E = S, Se, Te), led to the series of Ti–Ti single-bonded complexes (μ,η⁵:η⁵-Pn^†)₂[Ti(EPh)]₂ (E = S (5), Se (6), Te (7)), which can be considered the result of a 2e^– redox reaction or a 1,2-addition across the Ti═Ti bond. Treatment of 1 with azobenzene or phenyl azide afforded [(η⁸-Pn^†)Ti]₂(μ-NPh)₂ (8), a bridging imido complex in which the pentalene ligands bind in an η⁸ fashion to each formally Ti(IV) center, as the result of a 4e^– redox reaction driven by the oxidative cleavage of the Ti═Ti double bond. The new complexes 2–8 were extensively characterized by various techniques including multinuclear NMR spectroscopy and single-crystal X-ray diffraction, and the experimental work was complemented by density functional theory (DFT) studies.