Preparation of tetraalkylformamidinium salts and related species as precursors to stable carbenes

Alder, Roger W.; Blake, Michael E.; Bufali, Simone; Butts, Craig P.; Orpen, A. Guy; Schütz, Jan; Williams, Stuart J.

doi:10.1039/b104110j

Cited by 75 publications

(52 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Recently, Herrmann et al reported on an acyclic bis(di-2-propylamino)carbene, originally synthesized by Alder et al, [23,24] and its ligand properties. This NHC proved to be the most basic so far reported.…”

Section: àmentioning

confidence: 98%

1,3‐Dialkyl‐ and 1,3‐Diaryl‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene Rhodium(i) and Palladium(II) Complexes: Synthesis, Structure, and Reactivity

Mayr

Wurst

Ongania

et al. 2004

Chemistry A European J

237

114

View full text Add to dashboard Cite

The synthesis of novel 1,3-diaryl- and 1,3-dialkylpyrimidin-2-ylidene-based N-heterocyclic carbenes (NHCs) and their rhodium(i) and palladium(II) complexes is described. The rhodium compounds bromo(cod)[1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene]rhodium (7), bromo(cod)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)rhodium (8) (cod=eta(4)-1,5-cyclooctadiene, mesityl=2,4,6-trimethylphenyl), chloro(cod)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)rhodium (9), and chloro(cod)[1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene]rhodium (10) were prepared by reaction of [[Rh(cod)Cl](2)] with lithium tert-butoxide followed by addition of 1,3-dimesityl-3,4,5,6-tetrahydropyrimidinium bromide (3), 1,3-dimesityl-3,4,5,6-tetrahydropyrimidinium tetrafluoroborate (4), 1,3-di-2-propyl-3,4,5,6-tetrahydropyrimidinium bromide (6), and 1,3-di-2-propyl-3,4,5,6-tetrahydropyrimidinium tetrafluoroborate, respectively. Complex 7 crystallizes in the monoclinic space group P2(1)/n, and 8 in the monoclinic space group P2(1). Complexes 9 and 10 were used for the synthesis of the corresponding dicarbonyl complexes dicarbonylchloro(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)rhodium (11), and dicarbonylchloro[1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene]rhodium (12). The wavenumbers nu(CO I)/nu(CO II) for 11 and 12 were used as a quantitative measure for the basicity of the NHC ligand. The values of 2062/1976 and 2063/1982 cm(-1), respectively, indicate that the new NHCs are among the most basic cyclic ligands reported so far. Compounds 3 and 6 were additionally converted to the corresponding cationic silver(i) bis-NHC complexes [Ag(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(2)]AgBr(2) (13) and [Ag[1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene](2)]AgBr(2) (14), which were subsequently used in transmetalation reactions for the synthesis of the corresponding palladium(II) complexes Pd(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(2) (2+)(Ag(2)Br(2)Cl(4) (4-))(1/2) (15) and Pd[1,3-bis(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene)(2)]Cl(2) (16). Complex 15 crystallizes in the monoclinic space group P2(1)/c, and 16 in the monoclinic space group C(2)/c. The catalytic activity of 15 and 16 in Heck-type reactions was studied in detail. Both compounds are highly active in the coupling of aliphatic and aromatic vinyl compounds with aryl bromides and chlorides with turnover numbers (TONs) up to 2000000. Stabilities of 15 and 16 under Heck-couplings conditions were correlated with their molecular structure. Finally, selected kinetic data for these couplings are presented.

show abstract

Section: àmentioning

confidence: 98%

1,3‐Dialkyl‐ and 1,3‐Diaryl‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene Rhodium(i) and Palladium(II) Complexes: Synthesis, Structure, and Reactivity

Mayr

Wurst

Ongania

et al. 2004

Chemistry A European J

237

114

View full text Add to dashboard Cite

show abstract

“…The precursors 1a and 1c [5i], 1,3-di-tert-butylimidazolin-2-ylidene (2b), 1,3-di-cyclohexylimidazolin-2-ylidene (2c), 1-diphenylbenzyl-3-methylimidazolium tetrafluoroborate (2d) [16], 6-chloro-7,9-dimethylpurinium tetrafluoroborate (4) [17], 1,3,7,9-tetramethylxanthinium tetrafluoroborate (5) [18], 1-isopropyl-4,5-dihydro-1H-1,2,4-triazole (6) [19] and 3,4,5,6-tetrahydro-1,3-bis(isopropyl)pyrimidinium tetrafluoroborate (12) [20] were prepared according to the literature. 1 H, 13 C and 31 P NMR spectra were recorded on a JEOL-JMX-GX 270 or 400 MHz spectrometer at room temperature and referenced to the residual 1 H and 13 C signals of the solvents or 85% H 3 PO 4 as an external standard ( 31 P).…”

Section: General Commentsmentioning

confidence: 99%

A straight forward in situ preparation of NHC-substituted phosphapalladacycles

Frey

Schütz

Herrmann

2006

Journal of Organometallic Chemistry

Self Cite

View full text Add to dashboard Cite

“…After the preparation of a free acyclic carbene 2a, bis(diisopropylamino)carbene, by Alder et al [13][14][15], the first metal-complexes of rhodium and iridium could be synthesized via the free carbene by Denk and Herrmann [16] (Fig. 2).…”

Section: Introductionmentioning

confidence: 99%

Structural investigations of metalcarbonyl complexes with acyclic diamino carbenes

Frey

Herdtweck

Herrmann

2006

Journal of Organometallic Chemistry

View full text Add to dashboard Cite

Preparation of tetraalkylformamidinium salts and related species as precursors to stable carbenes

Cited by 75 publications

References 18 publications

1,3‐Dialkyl‐ and 1,3‐Diaryl‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene Rhodium(i) and Palladium(II) Complexes: Synthesis, Structure, and Reactivity

1,3‐Dialkyl‐ and 1,3‐Diaryl‐3,4,5,6‐tetrahydropyrimidin‐2‐ylidene Rhodium(i) and Palladium(II) Complexes: Synthesis, Structure, and Reactivity

A straight forward in situ preparation of NHC-substituted phosphapalladacycles

Structural investigations of metalcarbonyl complexes with acyclic diamino carbenes

Contact Info

Product

Resources

About