1370548-66-5Relevant academic research and scientific papers
Mapping the elimination of water from hydroxyvinylidene complexes of ruthenium(II): Access to allenylidene and vinylvinylidene complexes in a stepwise fashion
Smith, Elizabeth J.,Johnson, David G.,Thatcher, Robert J.,Whitwood, Adrian C.,Lynam, Jason M.
, p. 7407 - 7417 (2014/04/03)
Reaction of hydroxyvinylidene complexes [Ru(κ1-OAc) (κ2-OAc)(=C=CHC{OH}R1R2)(PPh 3)2] (R1 = R2 = Ph; R1 = R2 = Me; R1 = Ph, R2 = Me) with [CPh 3]BF4 results in the formation of the cationic carbene species [Ru(κ2-OAc)(OC{Me}OCC{H}=CR1R 2)(PPh3)2]BF4. In these complexes, the κ1-acetate ligand has changed its binding mode in order to stabilize the resulting cationic species. The carbene complexes may be deprotonated, although the outcome of the reaction depends markedly on the substituent present. In the case in which R1 = R2 = Ph, the hydrogen on the β-carbon of the organic ligand is removed to afford an allenylidene complex [Ru(κ1-OAc)(κ2-OAc)(=C=C= CPh2)(PPh3)2]. An examination of the structural and spectroscopic parameters for the allenylidene complex indicates that the electronic influence of this ligand is very similar to the corresponding vinylidene and isonitrile analogues. In the cases where R1 = R 2 = Me and R1 = Me, R2 = Ph deprotonation occurs at a methyl group to afford vinylvinylidene complexes [Ru(κ1-OAc)(κ2-OAc)(=C=C{H}-CR 2=CH2)(PPh3)2] (R2 = Me, Ph). No interconversion between vinylvinylidene and allenylidene complexes was observed. The overall process is analogous to a formal E1-type elimination in which the cationic carbene complex may be viewed as a stabilized carbocation intermediate. A DFT study provided insight into selectivity of the deprotonation step indicating that the greatest relative difference in energy between all the possible isomers of the vinylvinylidene and allenylidene complexes was ca. 20 kJ mol-1. Interconversion between the two forms of the complex by a [1,3]-hydrogen shift appears to be unlikely due to the higher energy of the corresponding transition state; hence the selectivity in the formation of the vinylvinylidene complexes may be due the site of deprotonation being kinetically controlled. An alternative mechanism for this interconversion between vinylvinylidene and allenylidene complexes in cationic half sandwich metal complexes is proposed, which proceeds via a deprotonation/reprotonation pathway.
Ruthenium acetate complexes as versatile probes of metal-ligand interactions: Insight into the ligand effects of vinylidene, carbene, carbonyl, nitrosyl and isocyanide
Welby, Christine E.,Eschemann, Thomas O.,Unsworth, Christopher A.,Smith, Elizabeth J.,Thatcher, Robert J.,Whitwood, Adrian C.,Lynam, Jason M.
, p. 1493 - 1506 (2012/06/16)
Reaction of cis-Ru(2-OAc)2(PPh3) 2 with two-electron donor ligands L results in the formation of complexes trans-[Ru(1-OAc)(2-OAc)L(PPh3) 2] (L = CO, NO+, CNtBu). Vinylidene complexes (L = C=CHR) may be prepared from the corresponding reaction with terminal alkynes HC=CR, and species containing hydroxyvinylidene ligands (L = C=CHCR1R 2{OH}) may be prepared from related reactions with propargyl alcohols HC=CCR1R2{OH}. Treatment of cis-Ru(κ2- OAc)2(PPh3)2 with ω-alkynols HC=C(CH 2)nOH (n = 2-4) results in the formation of oxacyclocarbene complexes [L = CCH2(CH2)nO]. An analysis of the spectroscopic data and the structural metrics (as determined by X-ray crystallography) of this series of complexes allows for the relative donor/acceptor properties of the ligand L to be evaluated. This comparison indicates that the vinylidene ligand behaves in a similar fashion to the isocyanide ligand. The complex cis-[Ru(2-OAc)2(PPh 3)2] acts as a precursor for the formation of the complexes trans-[Ru(1-OAc)(2-OAc)L(PPh3) 2] where L is a two-electron donor, σ-donor/π-acceptor ligand. The structural and spectroscopic data of these species provide insight into the relative electron demand of the ligands L.
