166111-00-8Relevant academic research and scientific papers
Synthesis, Cycloaddition, and Cycloreversion Reactions of Mononuclear Titanocene-oxo Complexes
Nguyen, Trang T.,Kortman, Gregory D.,Hull, Kami L.
, p. 1713 - 1725 (2016)
Titanocene-oxo complexes of the type Cpx2Ti=O(L) (Cpx = pentamethylcyclopentadienyl; tetramethylcyclopentadienyl; L = pyridine or derivatives) are synthesized from the corresponding titanocene-ethylene complexes via oxidation with pyridine N-oxides or styrene oxide. These oxo complexes react with alkynes, nitriles, and α,β-unsaturated carbonyls to form titanacycles, which undergo exchange reactions with organic substrates or react with 4-dimethylaminopyridine to regenerate the titanocene-oxo. Mechanistic experiments support a dissociative mechanism in which the first step is rate-determining retrocycloaddition followed by trapping of the reactive [Cpx2Ti=O] species. In the case of the retro-[4+2]-cycloaddition from dioxatitanacyclohexene complexes, a Hammett study gives ρ values of -1.18 and -1.04 for substituents on two different phenyl rings on the metallacycles, suggesting positive charge buildup and a slightly asynchronous cycloreversion in the rate-determining step.
Facile C-H, C-F, C-Cl, and C-C Activation by Oxatitanacyclobutene Complexes
Nguyen, Trang T.,Bertke, Jeffery A.,Gray, Danielle L.,Hull, Kami L.
supporting information, p. 4190 - 4193 (2015/09/22)
Aryl ketones react readily with oxatitanacyclobutenes bearing pentamethylcyclopentadienyl ligands to form unique titanocene complexes resulting from Cp modification and C-H activation. An intermediate in this reaction is intercepted with various functional groups to form carbonyl insertion, C-F activation, and cyclopropane ring-opening products.
Cycloaddition and cycloreversion reactions of a monomeric Ti(IV) oxo complex with terminal and internal alkynes. A reversible oxametallacyclobutene/hydroxoacetylide interconversion
Polse,Andersen,Bergman
, p. 5393 - 5394 (2008/10/08)
The synthesis and structure of Cp*2Ti(O)(pyr) (Cp* = η5-C5Me5; pyr = pyridine) (1) were described recently. We report here on the [2 + 2] cycloaddition of 1 with terminal alkynes and yhe novel rearrangement of the resulting oxametallacyclobutenes to hydroxoacetylide complexes. in at least one case the arrangement is reversible, and we have obtained information on its mechanism. We have carried out experiments designed to investigate the mechanism of the oxametallacycle-to-hydroxoacetylide rearrangement.
