101471-31-2Relevant academic research and scientific papers
Formation of tungstenacyclobutadiene complexes containing a proton in the ring and their conversion to deprotio tungstenacyclobutadiene complexes
Freudenberger, John H.,Schrock, Richard R.
, p. 1411 - 1417 (2008/10/08)
The reaction between W(C-t-Bu) [OCH(CF3)2]3(dme) (dme = 1,2-dimethoxyethane) and tert-butylacetylene or phenylacetylene yields the tungstenacyclobutadiene complexes W(C-t-BuCHCR)(HFIP)3 (R = t-Bu or Ph; HFIP = hexafluoroisopropoxide). In the presence of triethylamine and dme the R = Ph species is converted into a deprotio tungstenacyclobutadiene complex, W(C3-t-BuPh)(HFIP)2(dme). Addition of dme to W(C-t-BuCHCR)(HFIP)3 results in formation of W(C3-t-BuR)(HFIP)2(dme) in equilibrium with W(C-t-BuCHCR)(HFIP)3. Addition of phenylacetylene to W(CPh) (HFIP)3(dme) yields only W-(C3Ph2) (HFIP)2(dme). Addition of tert-butylacetylene to W(C-t-Bu)(DIPP)3 (DIPP = 2,6-diisopropylphenoxide) yields isolable red W(C-t-BuCHC-t-Bu) (DIPP)3 that slowly and irreverisbly is converted in solution into W(C3-t-Bu2)(DIPP)2. The reaction is greatly accelerated by addition of triethylamine or LiDIPP; it is believed that the base removes the ring proton directly. The pyridine adduct W(C3-t-Bu2)(DIPP)2(py) has been fully characterized. W(C3-t-Bu2) (DIPP)2 reacts with excess tert-butylacetylene to give a compound with the formula W(C5H-t-Bu3)(DIPP)2 that can be isolated as its monopyridine adduct. The planar C5H-t-Bu3 ligand system is formed (it is proposed) by regiospecific reaction of tert-butylacetylene with the W-Cα bond in the deprotio tungstenacyclobutadiene complex. The alkylidene-like carbon atom in W(C5H-t-Bu3)(DIPP)2 can be protonated by CF3CO2H or PhCO2H to give complexes of the type W(C5H2-t-Bu3)(DIPP)2(RCO 2). The chemistry of the analogous DMP complexes (DMP = 2,6-dimethylphenoxide) is analogous to that of the DIPP complexes. Isolated characterized complexes include W(C-t-BuCHC-t-Bu)(DMP)3, W(C3-t-Bu2)(DMP)2(py), W(C5H-t-Bu3)(DMP)2(py), W(C-t-BuCHC-t-Bu)(DMP)2Cl, and W(C3-t-Bu2)(DMP)2.
