150747-63-0Relevant academic research and scientific papers
Synthesis of tungsten vinyl alkylidene complexes via the reactions of WCl2(NAr)(PX3)3 (X = R, OMe) precursors with 3,3-disubstituted cyclopropenes
Johnson, Lynda K.,Grubbs, Robert H.,Ziller, Joseph W.
, p. 8130 - 8145 (1993)
Several WCl2(NAr)(PX3)3 complexes were synthesized, including WCl2(N-2,6-C6H3Me2)(PEt 2Ph)3 (1), WCl2(NPh)[P(OMe)3]3 (2), WCl2(N-2,6-C6H3Me2) [P(OMe)3]3 (3), and WCl2[N-2,6-C6H3(i-Pr)2] [P(OMe)3]3 (4). NMR spectroscopic data for these complexes and a single-crystal X-ray diffraction study of 4 supported a meridional arrangement of the three PX3 ligands, all lying cis to the apical imido ligand. The lability of one PX3 ligand in complexes 1-4 was demonstrated by reactions with ethylene and phenyl- and diphenylacetylene to give the corresponding π-acceptor (L) complex WCl2(L)(NAr)(PX3]2. In solution, some of the WCl2(L)(NAr)(PX3)2 complexes, especially those with P(OMe)3 ligands, were in equilibrium with WCl2(L)(NAr)(PX3) and free PX3; complete removal of 1 equiv of PX3 was achieved upon addition of CuCl. Complexes 1-4 and also WCl2(NPh)(PMePh2)3 reacted with 3,3-diphenylcyclopropene and 4,8-dioxaspiro[2.5]oct-1-ene (referred to subsequently as diphenyl- and ketalcyclopropene) to give a number of η2-cyclopropene complexes and/or vinyl alkylidene complexes. Concentrated diethyl ether solutions of the reactants and use of the sterically smaller tungsten precursors enabled the clean formation of the η2-cyclopropene complexes W(η2-cyclopropene)Cl2(NAr)(PX3) 2. Spectroscopic data and a single-crystal X-ray diffraction study of W(η2-diphenylcyclopropene)Cl2(NPh) [P(OMe)3]2 indicated an octahedral geometry in which the two mutually trans PX3 ligands and the cyclopropene occupy equatorial positions cis to the apical imido ligand and the substituents of the cyclopropene lie syn to the imido ligand. The η2-cyclopropene complexes were converted to the corresponding vinyl alkylidene complexes W(=CHCH=CR2)Cl2(NAr)(PX3)2 thermally, photochemically, and chemically (catalysis by HgCl2). For the reactions of the sterically more bulky tungsten precursors with cyclopropenes, direct isolation of the vinyl alkylidene complexes was possible. A crystal structure of an alkoxide derivative W(=CHCH=CPh2) [N-2,6-C6H3-(i-Pr)2] [OCMe(CF3)2]2[P(OMe)3] confirmed the formation of a diphenylvinyl alkylidene ligand with an s-trans arrangement of the double bonds. In addition to an s-trans isomer, the ketalvinyl alkylidene ligand also formed two different s-cis isomers with one oxygen atom of the ketal ring chelating to tungsten. A crystal structure showed that, in one of these isomers, the ketal ring has been opened by a chloride ligand from tungsten, and a mechanism is proposed for this rearrangement.
Combinatorial screening of an in situ generated library of tungsten oxyhalide and imido complexes for olefin metathesis
Romer, Duane R.,Sussman, Victor J.,Burdett, Ken,Chen, Yu,Miller, Kami J.
supporting information, p. 551 - 557 (2015/01/08)
A series of substituted tungsten(VI) halides with general formula WECl4 (E = O or 'NR (imido)) were screened via a high throughput study to identify potential new olefin metathesis catalysts. The tungsten species were treated with a series of aluminum alkyl activators and modifier ligands to generate active catalyst species in situ. Ring-opening metathesis polymerization (ROMP) of cyclooctene was used as a primary screen to identify potential metathesis catalysts and active catalysts were subjected to a secondary screen to evaluate tolerance toward polar functional groups. Several combinations from the high throughput campaign yielded active metathesis catalysts for the ROMP of cyclooctene. However, none of the catalysts examined in this study exhibited any evidence of significant polar functional group tolerance as determined by the results of the secondary cyclooctene/butyl acetate screen.
