83634-57-5Relevant academic research and scientific papers
Photoinduced ring-opening metathesis polymerization (PROMP) with photochemically generated Schrock-type catalysts
Van der Schaaf,Hafner,Muhlebach
, p. 1845 - 1847 (2008/10/09)
A new type of photopolymerization (depicted on the right) relies on well-defined, early transition metal complexes. Schrock-type catalysts are photochemically generated from di- or trialkyl tungsten complexes. The photoactivity and latency of the new cata
Five-coordinate tungsten(VI) phenylimido alkylidene complexes and isolated precursors, containing a chelating arylamine ligand: Molecular structure of W(C6H4CH2NMe2-2)(=CHSiMe 3)(CH2SiMe3)(=NPh)
Van Der Schaaf, Paul A.,Grove, David M.,Smeets, Wilberth J. J.,Spek, Anthony L.,Van Koten, Gerard
, p. 3955 - 3963 (2008/10/08)
With monoanionic 2-[(dimethylamino)methyl]phenyl, an aryl ligand in which a potentially chelating tertiary amine group is present, five-coordinate tungsten(VI) phenylimido alkylidene complexes and their alkyltungsten(VI) precursor complexes have been isolated. For example, use of this potentially intramolecular coordinating ligand makes it possible to synthesize the tungsten(VI) alkylidene complex W(C6H4CH2NMe2-2)(=CHSiMe 3)(CH2SiMe3)(=NPh) (5) via a simple one-step reaction from an easily accessible trialkyltungsten phenylimido precursor. Introduction of π-electron donor substituents, such as tert-butoxide and 3,5-dimethylphenoxide ligands, allows isolation and characterization of the respective alkylidene precursor complexes; e.g. W(C6H4CH2NMe2-2)(CH 2SiMe3)2(=NPh)(OCMe3) (7). Complex 7 is unstable at elevated temperatures and decomposes via intramolecular Hα-abstraction reactions. Reaction of 5 with tert-butyl alcohol affords a 1,2-addition of the alcohol at the alkylidene function and subsequent formation of 7; the same reaction with triphenylsilanol results in the instantaneous formation of the new alkylidene complex W(C6H4CH2NMe2-2)(=CHSiMe 3)(=NPh)(OSiPh3) (6), in which the alkyl group is replaced by the silanol group. The analytically pure alkylidene complexes 5 and 6 are inert toward linear olefins but react with aldehydes and ketones in a Wittig-type reaction. The olefin products of the reaction with the aldehydes are obtained as a cis/trans mixture in which the trans isomer is predominant. With cyclic olefins very fast ring opening metathesis polymerization (ROMP) reactions take place; cyclic olefins in which two double bonds are present, such as norbornadiene and dicyclopentadiene, produce cross-linked polymers, whereas reaction with norbornene leads to selective formation of cis-polycyclopentenamers. The five-coordinate structure of 5 that results from intramolecular W-N coordination has been proven in the solid-state (X-ray diffraction) and in solution (NMR) spectroscopy). Crystals of 5 are monoclinic, space group P21/a with unit-cell dimensions a = 17.950(3) A?, b = 16.633(4) A?, c = 19.472(4) A?, β = 115.48(2)°, final R = 0.0661, and Rw = 0.0653.
