938170-63-9Relevant academic research and scientific papers
A π-basic rhenium center that effects cyclohexene isomerization to a β-agostic carbene ligand
Ozerov, Oleg V.,Watson, Lori A.,Pink, Maren,Caulton, Kenneth G.
, p. 9604 - 9605 (2003)
The molecule (PNPR)Re(H)4 (PNPR = (R2PCH2SiMe2)2N, R = iPr or cyclohexyl) reacts at 20 °C with 2 mol of cyclohexene to form equimolar cyclohexane and (PNPR)Re(H)2[=C(CH2)5]. This product is characterized by 1H, 13C, and 31P NMR and by X-ray diffraction as having one CH2 hydrogen (from a carbon located β to Re) donating to the metal ( agostic CH ). This interaction occurs in preference to PNPR amide nitrogen π-donation. DFT calculations confirm this agostic interaction, and show that the (PNPR)Re(H)2 fragment indeed reverses the greater stability of free olefin vs free carbene. Copyright
Operationally unsaturated pincer/rhenium complexes form metal carbenes from cycloalkenes and metal carbynes from alkanes
Ozerov, Oleg V.,Watson, Lori A.,Pink, Maren,Caulton, Kenneth G.
, p. 6003 - 6016 (2008/02/02)
Operationally unsaturated (i.e., 16/18-electron) (PNPR)Re(H) 4, where PNPR is N(SiMe2CH2PR 2)2, is reactive at 22°C with cyclic olefins. The first observed products are generally (PNPR)Re(H)2- (cycloalkylidene), with hydrogenated olefin as the product of hydrogen abstraction from the tetrahydride. The tetrahydride complex with R = 1Bu generally fails to react (too bulky), that with R = cyclohexyl suffers a (controllable) tendency to abstraction of 3H from one ring, forming an η3-cyclohexenyl compound, and that with R = iPr generally gives the richest bimolecular reactivity. The cyclic monoolefins studied show distinct reactivity, C6 giving first the carbene and then coordinated cyclohexadiene, C5 giving carbene, then diene, and then η5-C5H5, C8 giving carbene and then η2-cyclooctyne, and C12 giving an η3-allyl. Norbornene gives a π-complex of the norbornene in thermal equilibrium with its carbene isomer; at 90°C, hydrocarbon ligand Cα-Cβ bond cleavage occurs to give, for the first time, a carbyne complex from an internal olefin. Two compounds synthesized here have the formal composition (PNPR)Re + olefin , and each of these is capable of dehydrogenating the methyl group of a variety of alkanes at 110°C to form (PNP)ReH(≡CR).
