Pyrimidinium betaïnes (1), readily accessible via a straightforward modular synthesis from formamidine and monosubstituted malonic acid, are deprotonated by nBuLi (or KHMDS) to give the stable carbene species [2]Li+ (abbreviated as maloNHC). The latter represents archetype of subgroup N-heterocyclic carbenes incorporating malonate remote anionic functional group within their heterocyclic backbone. While playing dual role monodentate 2 e− L type donor noncoordinating charge carrier X, such...

The present report discloses a modular synthetic route to new type of anionic N-heterocyclic carbene ligand incorporating an enolate group as reactive backbone component its heterocyclic framework. presence such unit facilitates further tailoring the ligand, even after complexation transition metals, with concomitant tuning electronic donor properties center. Simple acylation formamidine Ar-NH-CH═NAr (1a,b) (a: Ar = mesityl (Mes); b: 2,6-diisopropylphenyl (DIPP)) by chloroacetyl chloride...

The 4-hydroxyimidazolium salt, readily prepared in two steps by acylation of a formamidine and quaternization the second nitrogen, affords, after deprotonation, anionic imidazol-2-ylidene-4-olate, which can be complexed to transition metal still subsequently functionalized at O or C backbone atom outer coordination sphere metal.

Abstract A challenging synthetic modification of PEPPSI‐type palladium pre‐catalysts consisting a stepwise incorporation one and two amino groups onto the NHC skeleton was seen to exert sequential enhancement electronic donor properties. This appears be positively correlated with catalytic performances corresponding complexes in Buchwald–Hartwig amination. is illustrated, for example, by quantitative amination 4‐chloroanisole morpholine within 2 h at 25 °C mol % catalyst/substrate ratio or...

Deprotonation of the MnI NHC-phosphine complex fac-[MnBr(CO)3 (κ2 P,C-Ph2 PCH2 NHC)] (2) under a H2 atmosphere readily gives hydride fac-[MnH(CO)3 (3) via intermediacy highly reactive 18-e NHC-phosphinomethanide fac-[Mn(CO)3 (κ3 P,C,C-Ph2 PCHNHC)] (6 a). DFT calculations revealed that preferred reaction mechanism involves unsaturated 16-e mangana-substituted phosphonium ylide P=CHNHC)] b) as key intermediate able to activate non-classical mode metal-ligand cooperation implying formal λ5...

A one-pot two-step procedure was developed for the alkylation of amines via reductive amination aldehydes using molecular dihydrogen as a reductant in presence manganese pyridinyl-phosphine complex pre-catalyst. After initial condensation step, reduction imines formed situ is performed under mild conditions (50-100 °C) with 2 mol% catalyst and 5 tBuOK 50 bar hydrogen. Excellent yields (>90%) were obtained large combination (40 examples), including aliphatic amino-alcohols.

A 95% yield in the cross metathesis of acrylonitrile with a model olefin is achieved at 25 degrees C only 3 mol % new air-stable ruthenium catalyst 1f shown enclosed structural diagram. Even more remarkable are performances its boosted version 1g incorporating an electron-withdrawing group. Both these enhanced versions Hoveyda readily available from Grubbs second generation precatalyst upon reaction styrenyl ether end group which has been functionalized by ester function. The latter acts as...

Abstract Reaction of N , N′ ‐dimesitylformamidine with dimethylmalonyl dichloride in dichloromethane the presence an excess triethylamine gives 2‐chloro‐4,5‐dioxohexahydropyrimidine 1 . The corresponding diamidocarbene 3 is generated situ by further deprotonation KHMDS at –40 °C and identified trapping S 8 to give fully characterized (including X‐ray structure) sulfur adduct 4 It also reacts [RhCl(cod)] 2 yield NHC complex [RhCl( )(cod)] ( 5 ) (characterized structure). donor properties were...

Abstract The present report develops the idea that an N‐heterocyclic carbene incorporating a remote anionic functionality—here, malonate group—as backbone component of its heterocyclic framework, can be “post‐functionalized” directly from transition‐metal complexes, upon simple addition variety electrophiles interacting with group in outer coordination sphere. From palette selected electrophilic reagents, it was thus possible to modulate electronic donor properties center over rather broad...

Abstract Easily available manganese(I) N‐heterocyclic carbene (NHC) complexes, Cp(CO) 2 Mn(NHC), obtained in one step from industrially produced cymantrene, were evaluated as pre‐catalysts the hydrosilylation of carbonyl compounds under UV irradiation. Complexes with NHC ligands incorporating at least mesityl group led to most active and selective catalytic systems. A variety aldehydes (13 examples) ketones (11 efficiently reduced mild conditions [Cp(CO) Mn(IMes) (1 mol%), Ph SiH (1.5...

An elusive free 4-(isopropylamino)imidazol-2-ylidene is engaged in a tautomeric equilibrium with its mesoionic tautomer, 4-(isopropylamido)imidazolium, which displays the typical reactivity of cyclic diaminocarbene; once coordinated to Rh(I) centre, it undergoes smooth 4e(-) oxidation backbone yield an amido-amidino-carbene, weak electron donor viable only complexed form.

Abstract Manganese(I) catalysts incorporating readily available bidentate 2‐aminopyridinyl‐phosphine ligands achieve a high efficiency in the hydrogenation of carbonyl compounds, significantly better than parent ones based on more elaborated and expensive tridentate 2,6‐(diaminopyridinyl)‐diphosphine ligands. The reaction proceeds with low catalyst loading (0.5 mol%) under mild conditions (50 °C) yields up to 96%. magnified image

The backbone-functionalized anionic carbenes maloNHC (1R; malonate backbone) and imidNHC (2; imidate were generated in situ from their respective zwitterionic precursors treated with FeCp(CO)2I to afford the complexes {FeCp(CO)2(1R)} (3R; 59–84% yield), {FeCp(CO)2(2)} (4; 77% respectively. Methylation of complex 3Me takes place at one backbone oxygen atoms give cationic adduct [FeCp(CO)2(1MeMe)](OTf) ([5Me](OTf); 96% whereas methylation 4 nitrogen atom produce [FeCp(CO)2(2Me)](OTf)...

Manganese(I) complexes [(Cp(CH2)nNHCMes)Mn(CO)2] (2a, n = 1; 2b, 2) bearing Cp tethered NHC ligands have been prepared in good yield from [CpMn(CO)3] and N-mesitylimidazole as main components, using a novel synthetic strategy based on the anchoring of an imidazolium moiety to coordinated ligand, followed by intramolecular photochemical CO substitution for pendent generated situ upon addition base. The catalytic performances 2a–b hydrosilylation 2-acetonaphthone with Ph2SiH2 were found be...

Abstract The synthesis and characterization of original NHC ligands based on an imidazo[1,5‐ a ]pyridin‐3‐ylidene (IPy) scaffold functionalized with flanking barbituric heterocycle is described as well their use tunable for efficient gold‐catalyzed C−N, C−O, C−C bond formations. High activity, regio‐, chemo‐, stereoselectivities are obtained hydroelementation domino processes, underlining the excellent performance (TONs TOFs) these IPy‐based in gold catalysis. reactions 1,6‐enynes give rise...

Abstract Systematic modification of the chelating NHC‐phosphine ligand (NHC = N ‐heterocyclic carbene) in highly efficient ketone hydrogenation Mn(I) catalyst fac ‐[(Ph 2 PCH NHC)Mn(CO) 3 Br] has been performed and catalytic activity resulting complexes was evaluated using acetophenone as a benchmark substrate. While variation phosphine NHC moieties led to inferior results than for parent system, incorporation phenyl substituent into methylene bridge improved performance by ca . times...

The trifunctional ligands (R)-1-(diphenylphosphino)-2-((1R,2S,5R)-menthoxy)-1-(2-pyridyl)ethane (2R), (S)-1-(diphenylphosphino)-2-((1R,2S,5R)-menthoxy)-1-(2-pyridyl)ethane (2S), and (S)-(phenyl(2-anisyl)phosphino)(2-pyridyl)methane (3) have been synthesized, as well the corresponding RuCl2(PPh3)(L) complexes. complexes RuCl2(PPh3)(2R) (5) RuCl2(PPh3)(2S) (6) were isolated mixtures of two isomers, 5a 5b 6a 6b, respectively. In each these 2 are η3-(P,N,O) bound. They differ by position...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTransformation of the bis(diphenylphosphino)methane ligand on triruthenium nonacarbonyl framework. Synthesis and characterization ruthenium complexes Ru3(CO)9(.mu.3-.eta.3-P(C6H5)CH2P(C6H5)(C6H4)), Ru3(CO)9(.mu.-H)(.mu.3-.eta.2-P(C6H5)CH2P(C6H5)2), Ru3(CO)10(.mu.-.eta.2-P(C6H5)CH2P(C6H5)(C6H4))Noel Lugan, Jean Jacques Bonnet, James A. IbersCite this: J. Am. Chem. Soc. 1985, 107, 15, 4484–4491Publication Date (Print):July 1, 1985Publication History...

The new anionic heterocycle imidNHC (4,6-dioxo-1,3,5-triazin-2-ylidene-5-ide), combining a carbene and an imidate, was readily prepared through coupling reaction between 1,3-dimesityl formamidine N-phenoxy carbonyl isocyanate followed by deprotonation. donor properties of this switchable ligand were determined, whereas its ambidentate nature established the directed construction exotic stacked polymetallic architectures. Detailed facts importance to specialist readers are published as...

The series of upgraded Grubbs/Hoveyda second-generation catalysts (H2IMes)(Cl)2Ru═C(H)(C6H4OR) (E2 (71% yield), R = CH(Me)(C(O)OMe); M2 (58% CH(C(O)OMe)2; Kme2 (88% CH2C(O)Me; Ket2 (63% CH2C(O)Et); C2 C(Me)CN) were prepared by the reaction Grubbs catalyst (H2IMes)(Cl)2Ru(CHPh)(PCy3) (G2) with appropriate ortho-substituted ether H(Me)C═CHC6H4OR in presence CuCl as a phosphine scavenger. X-ray structures these complexes reveal that terminal oxygen ester, ketone, or malonate group installed...

Abstract The backbone substitution of the standard 1,3‐bis(2,6‐diisopropylphenyl)‐2 H ‐imidazol‐2‐ylidene (IPr) ligand by dimethylamino groups was previously shown to induce a dramatic improvement in catalytic efficiency corresponding Pd–PEPPSI (pyridine‐enhanced pre‐catalyst preparation, stabilization, and initiation) pre‐catalysts N‐arylation reactions. Herein, thorough structure/activity study towards rationalizing this beneficial effect has been described. In addition reported IPr...

The mesoionic 5-acetylimidazolium-4-olate serves as precursor for an anionic, hybrid NHC, "IMes-acac", consisting of fused diaminocarbene and acetylacetonato units, whose respective coordination abilities are evaluated by the formation a series representative copper(I) complexes illustrating ambidentate character ligand.

Abstract Crystal structure determinations on the hydrated forms of complexes M 2 UO (dipic) , = H, Rb, Cs, dipic dipicolinate pyridine‐2,6‐dicarboxylate, all which show strong solid‐state luminescence from uranyl centre, have as a common feature extended π‐stacking arrays ligands. Comparisons with related but non‐luminescent indicate that these stacking may be associated efficient energy transfer “antennae” to unit. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Distorting the ν(CO) response: Weak Cipso⋅⋅⋅CO and Hortho⋅⋅⋅CO interligand interactions within MnI aryloxycarbene complexes are seen to induce a significant redshift of corresponding IR stretching frequencies, revealing that position such bands may not unequivocally correlate with intrinsic electron-donicity ancillary ligands. Detailed facts importance specialist readers published as "Supporting Information". Such documents peer-reviewed, but copy-edited or typeset. They made available...