Rh(1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD) tetrafluoroborate, an unsymmetrical Rh-homoazallylcarbene: synthesis, X-ray structure and reactivity in carbonyl arylation and hydrosilylation reactions

Imlinger, Nicolas; Wurst, Klaus; Buchmeiser, Michael R.

doi:10.1016/j.jorganchem.2004.11.057

Cited by 55 publications

(12 citation statements)

References 51 publications

(66 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…To shed light on the origin of the upfield shift of the carbene carbon atom NMR signals in our tilted structures, we performed DFT NMR calculations . We initially tested the computational setup to reproduce the crystallographic geometry and the experimental chemical shift, δ C , of twelve monodentate and chelating NHC–M complexes described in the literature (see Figure S11 in the Supporting Information) plus the free NHC ligand 1 b and the corresponding protonated form, 1 b⋅ H + . We selected these compounds because they represent pairs of related complexes presenting linear and bent NHC−M bonds, for which the crystallographic structure and 13 C NMR data are available.…”

Section: Resultsmentioning

confidence: 99%

Unusual NHC–Iridium(I) Complexes and Their Use in the Intramolecular Hydroamination of Unactivated Aminoalkenes

Sipos

Skelton

et al. 2016

Chemistry A European J

View full text Add to dashboard Cite

N-heterocyclic carbene (NHC) ligands with naphthyl side chains were employed for the synthesis of unsaturated, yet isolable [(NHC)Ir(cod)](+) (cod=1,5-cyclooctadiene) complexes. These compounds are stabilised by an interaction of the aromatic wingtip that leads to a sideways tilt of the NHC-Ir bond. Detailed studies show how the tilting of such N-heterocyclic carbenes affects the electronic shielding properties of the carbene carbon atom and how this is reflected by significant upfield shifts in the (13) C NMR signals. When employed in the intramolecular hydroamination, these [(NHC)Ir(cod)](+) species show very high catalytic activity under mild reaction conditions. An enantiopure version of the catalyst system produces pyrrolidines with excellent enantioselectivities.

show abstract

Section: Resultsmentioning

confidence: 99%

Unusual NHC–Iridium(I) Complexes and Their Use in the Intramolecular Hydroamination of Unactivated Aminoalkenes

Sipos

Skelton

et al. 2016

Chemistry A European J

View full text Add to dashboard Cite

show abstract

“…Analysis of the 1 H NMR spectra of complexes 3 Me E recorded at 25 8C, clearly revealed that the characteristic swing of the unsaturated Rh center between the mesityl groups, already observed for 2 R , is still operative here (as also the case for other cationic derivatives of closely related NHCs). [21] Again, this dynamic chemical exchange could not be frozen by lowering the temperature down to À80 8C, and is thus responsible for the observed averaging of 1 H and 13 C NMR spectra of the two isomeric forms. In principle, the strong attachment of an electrophile to one of the remote oxygens should reduce the symmetry of the ligand from C 2v to C s point group.…”

Section: A C H T U N G T R E N N U N G {Malo-nhc}a C H T U N G T R E mentioning

confidence: 99%

Electronic Tuning of a Carbene Center via Remote Chemical Induction, and Relevant Effects in Catalysis

César

Lugan

Lavigne

2010

Chemistry A European J

110

View full text Add to dashboard Cite

The present report develops the idea that an N-heterocyclic carbene incorporating a remote anionic functionality--here, a malonate group--as a backbone component of its heterocyclic framework, can be "post-functionalized" directly from its transition-metal complexes, upon simple addition of a variety of electrophiles interacting directly with the malonate group in the outer coordination sphere. From a palette of selected electrophilic reagents, it was thus possible to modulate the electronic donor properties of the carbene center over a rather broad range. Both the zwitterionic complex [Rh{malo-NHC}(cod)] and the cationic derivatives [Rh{malo-NHC(E)}(cod)](+) (where "malo-NHC(E)" represents the ligand modified by a selected electrophile "E") were used as pre-catalysts in two types of catalytic reactions, namely, the polymerization of phenylacetylene and the hydroboration of styrene. The results indicate that, in both cases, the zwitterionic species is by far the best catalyst, whereas a decrease in the ligand donicity induced by the added electrophile results in a concomitant reduction of catalytic activity. Apparent deviations to such a trend in the case of the hydroboration of styrene were rationalized in terms of an interaction between the reactive catecholborane substrate and the remote functionality of the N-heterocyclic carbene leading to an in situ modification of the nature of the active species. These observations serve as a useful basis to define the scope and limitations of the present conceptual approach in catalysis.

show abstract

“…The catalyst amounts were 0.001 mol.%± 0.002 mol.%, complete conversion being observed in 1 ± 3 h. Ionic rhodium complex 66a exhibits high activity in the hydrosilylation of alkynes, styrenes and cyclic ketones. 294 High yields were obtained in the presence of 0.05 mol.% catalyst in 12 h.…”

Section: Scheme 74mentioning

confidence: 97%

“…In this case, the selectivity of the catalytic reaction shifts towards the formation of ketones. 294 In a similar reaction, rhodium complexes 62 with benzyl substituents (see Scheme 76) exhibit high activity and selectivity in the formation of alcohols, the yields being 70% ± 95%. 328…”

Section: Vi2h Arylation Of Carbonyl Compoundsmentioning

confidence: 99%

Development of new methods in modern selective organic synthesis: preparation of functionalized molecules with atomic precision

Ananikov¹,

Khemchyan²,

Іvanova³

et al. 2014

Russ. Chem. Rev.

View full text Add to dashboard Cite

Rh(1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD) tetrafluoroborate, an unsymmetrical Rh-homoazallylcarbene: synthesis, X-ray structure and reactivity in carbonyl arylation and hydrosilylation reactions

Cited by 55 publications

References 51 publications

Unusual NHC–Iridium(I) Complexes and Their Use in the Intramolecular Hydroamination of Unactivated Aminoalkenes

Unusual NHC–Iridium(I) Complexes and Their Use in the Intramolecular Hydroamination of Unactivated Aminoalkenes

Electronic Tuning of a Carbene Center via Remote Chemical Induction, and Relevant Effects in Catalysis

Development of new methods in modern selective organic synthesis: preparation of functionalized molecules with atomic precision

Contact Info

Product

Resources

About