Reactions of Ruthenium Vinylidene and Acetylide Complexes Containing Trichloromethyl Groups: Preparation of Cyclobutenonyl Complex by Solid State Photolysis and the Applications in Catalytic Reactions under Air Atmosphere
Date Issued
2009
Date
2009
Author(s)
Wu, Chung-Yeh
Abstract
New reactions were observed for the cationic gamma-hydroxyvinylidene complex [Ru2]=C=CHC(OH)(CCl3)2+ (2, [Ru2] = Cp(PPh3)2Ru). A rare chloroform elimination was observed when 2 was treated with n-Bu4NOH yielding the neutral acetylide complex [Ru2]−C≡CC(=O)CCl3 (3). Then solid state photoinduced isomerization of 3 generated the ruthenium perchlorocyclobutenonyl complex [Ru2]−C4Cl3O (4) in high yield. This transformation is analyzed by DFT calculation and complex 4 is found 4.22 kcal/mol more stable in Gibbs free energy than complex 3. In the coupling reaction of 4 with 2-methyl-1-buten-3-yne the four- membered ring ligand is transferred to enyne to give the substituted eta3-butadienyl complex 5 containing the cyclobutenonyl group. This coupling product could be removed from the metal by HCl. Deprotonation of 2 gave the gamma-hydroxyacetylide complex [Ru2]−C≡CC(OH)(CCl3)2 (9). In the photolysis of 9, phosphine dissociation is followed by addition of HCl yielding the neutral vinylidene complex Cl[Ru1]=C=CHC(OH)(CCl3)2 (10, [Ru1] = Cp(PPh3)Ru). Complex 4 is an efficient catalyst for the trimerization of DMAD in aqueous solution as well as in organic solvent. Also, an efficient one-pot intermolecular [2+2+2] cycloaddition of 2 equiv. of DMAD and 1 equiv. of various biaryl alkynes under mild condition by an easy-to-handle complex 4 in unpurified solvents of regent grade quality. The 2:1 cycloaddition products (14, 15 and 16) were afforded in high chemoselectivity and good yield without any additives under air atmosphere. Stepwise cross-trimerizations catalyzed by 4 were also carried out for three diynes and one triyne compounds in two or three steps, respectively, to afford the polycyclic compounds all in high yields. If the catalytic reaction is carried out in the presence of excess styrene, coupling of DMAD with styrene yielded a conjugated diene compound PhCH=CHC(CO2Me)=CHCO2Me (17). Hydrolysis of 4 yielded the cyclobutenedionyl complex (6) which is a more stablecatalyst for the trimerization of alkyne in aqueous medium. Solid state structures of 3, 4, 5, 6, 8, 10, 14hs, 14ha, 16p, 20 and 27 are determined by single crystal X-ray diffraction analysis.
Subjects
solid state reaction
photoisomerization
ruthenium
four-membered ring ligand
[2 + 2 + 2] cycloadditon reactions
alkene-alkyne coupling
air-stable catalyst
Type
thesis
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