Coordination chemistry of ditopic carbanionic N-heterocyclic carbenes

Waters, Jordan B.; Goicoechea, José M.

doi:10.1016/j.ccr.2014.09.020

Cited by 90 publications

(46 citation statements)

References 129 publications

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“…The P-C bond lengths (P-C1 1.8437(9) Å, P-C28 1.8205(10) Å, P-C34 1.8249(10) Å) are in the expected range of a P-C single bond (1.83 Å) involving a tri-coordinate phosphorus atom. This can be explained by the stronger σ-donor abilities of the carbon atom in the 5-position compared to the 2-position, 15 1 Molecular structures of cations 9b + and 10b + of the respective triflate salts; hydrogen atoms, solvate molecules and anions are omitted for clarity and thermal ellipsoids are displayed at 50% probability; selected bond lengths (Å) and angles (°) for 9b + : P-C1 1.8437(9), P-C28 1.8205(10), P-C34 1.8249(10); C1-P-C28 107.15(4), C1-P-C34 100.59(4), C28-P-C34 101.71(4) and 10b + : P-C2 1.831(4), P-C28 1.827(4), P-C34 1.830(4); C2-P-C28 100.22 (16), C2-P-C34 103.41 (16), C28-P-C34 103.52 (17). The molecular structure of cation 10b + is depicted in Fig.…”

Section: Resultsmentioning

confidence: 99%

Cationic 5-phosphonio-substituted N-heterocyclic carbenes

et al. 2016

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2-Phosphanyl-substituted imidazolium salts 2-PR2(4,5-Cl-Im)[OTf] (9a,b[OTf]) (4,5-Cl-Im = 4,5-dichloro-1,3-bis(2,6-di-isopropylphenyl)-imidazolium) (a: R = Cy, b: R = Ph) are prepared from the reaction of R2PCl (R = Cy, Ph) with NHC 8 (4,5-dichloro-1,3-bis(2,6-di-isopropylphenyl)-imidazolin-2-ylidene) in the presence of Me3SiOTf. 5-Phospanyl-substituted imidazolium salts 5-PR2(2,4-Cl-Im)[OTf] (10a,b[OTf]) are obtained in quantitative yield when a slight excess of the NHC 8 is used. 5-Phosphonio-substituted imidazolium salts 5-PR2Me(2,4-Cl-Im)[OTf]2 (14a,b[OTf]2) and 5-PR2F(2,4-Cl-Im)[OTf]2 (16a,b[OTf]2) result from methylation reaction or oxidation of 10a,b[OTf] with XeF2 and subsequent fluoride abstraction. According to our quantum chemical studies the Cl1 atom at the 2-position at the imidazolium ring of dication 14b(2+) carries a slightly positive charge and is therefore accessible for nucleophilic attack. Accordingly, the reaction of 14a,b[OTf]2 and 16a,b[OTf]2 with R3P (R = Cy, Ph) affords cationic 5-phosphonio-substituted NHCs 5-PR2Me(4-Cl-NHC)[OTf] (17a,b[OTf]) and 5-PR2F(4-Cl-NHC)[OTf] (18a,b[OTf]) via a SN2(Cl)-type reaction. A series of transition metal complexes such as [AuCl(5-PPh2Me(4-Cl-NHC))][OTf] (19[OTf]), [CuBr(5-PPh2Me(4-Cl-NHC))][OTf] (20[OTf]), [AuCl(5-PPh2F(4-Cl-NHC))[OTf] (21[OTf]) and [RhCl(cod)(5-PPh2Me(4-Cl-NHC))][OTf] (23[OTf]) are prepared to prove the coordination abilities of carbenes 17b[OTf] and 18b[OTf]. The isolation of a rare example of a tricationic bis-carbene silver complex [Ag(5-PPh2Me(4-Cl-NHC))2][OTf]3 (22[OTf]3) is achieved by reacting 14b[OTf] with Cy3P in the presence of AgOTf. NHC 17b[OTf] represents a very effective dehydrocoupling reagent for secondary (R2PH, R = Ph, Cy, (i)Bu) and primary (RPH2, R = Ph, Cy) phosphanes to give diphosphanes of type R4P2 (R = Ph, Cy, (i)Bu) and oligophosphanes R4P4, R5P5 (R = Ph, Cy), respectively. Methylation of 17b(+) and subsequent deprotonation reaction with LDA affords the cationic NHO (N-heterocyclic olefin) 35(+) of which the gold complex 36(+) is readily accessible via the reaction with AuCl(tht).

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Section: Resultsmentioning

confidence: 99%

Cationic 5-phosphonio-substituted N-heterocyclic carbenes

et al. 2016

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“…More recently our group has also used a similar approach for the synthesis of a NHC complexes of Ga and Fe, where the normal C2 position of the carbene is blocked by a methyl group , . Carbanionic NHCs can be prepared by several methods including chemical reduction and metal‐mediated C–H activation, however deprotonative metallation appears to be one of the most versatile approaches …”

Section: Introductionmentioning

confidence: 99%

Heavier Alkali‐metal Gallates as Platforms for Accessing Functionalized Abnormal NHC Carbene‐Gallium Complexes

Uzelac

Kennedy

Hernán‐Gómez

et al. 2016

Zeitschrift anorg allge chemie

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By sequentially treating the unsaturated carbene IPr (IPr = 1,3-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene) with heavier alkalimetal alkyls NaR or KR (R = CH2SiMe3) and GaR3, novel heteroleptic gallates 1 and 2 have been prepared. Incorporating anionic NHC ligands, these bimetallic complexes react selectively with electrophilles to afford neutral abnormal NHC Ga complexes under mild conditions.

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“…All 1 H and 13 C chemical shifts are reported in parts per million (ppm) relative to TMS, with the residual solvent peak serving as internal reference [51]. 31 P NMR spectra are referenced to 85% H 3 PO 4 as external standard. ESI mass spectra were acquired on a Thermo Scientific LCG Fleet.…”

Section: Methodsmentioning

confidence: 99%

“…In particular, our groups described several NHC Ru catalysts for the transfer hydrogenation (TH) of ketones in 2-propanol [24][25][26]. Current advances in carbene chemistry focus on the development of unusual coordination geometries of the carbene ligand, and apart from abnormal carbenes [27,28], imidazolyl-derived anionic dicarbenes (N-heterocyclic dicarbenes, NHDCs) have recently attracted significant interest [24,[29][30][31][32]. These compounds inherently allow the synthesis of bimetallic structures bearing two main-group elements [29,30,[32][33][34][35][36] or one main-group element and one transition metal [37][38][39][40][41], and examples featuring two transition metal centers are almost exclusively homobimetallic [42][43][44][45][46][47][48].…”

Section: Introductionmentioning

confidence: 99%