Cyclic Carbene Complexes Research Articles

Mononuclear osmium(II) complexes bearing (S,S)-iPr-pybox and (R,R)-Ph-pybox ligands

The complexes trans-[OsCl2(L){(S,S)-iPr-pybox}] ((S,S)-iPr-pybox = 2,6-bis[4′-(S)-isopropyloxazolin-2′-yl]pyridine; L = CNBn (3), CNCy (4) and MeCN (7)) and trans-[OsCl2(L){(R,R)-Ph-pybox}] ((R,R)-Ph-pybox = 2,6-bis[4′-(R)-phenyloxazolin-2′-yl]pyridine, L = CNBn (5), CNCy (6) and MeCN (8)) have been stereoselectively synthesized from the complexes trans-[OsCl2(η2-C2H4)(R-pybox)] (R = (S,S)-iPr (1), (R,R)-Ph (2)), via substitution of ethylene, under reflux or microwave irradiation conditions. The complex trans-[OsCl2(η2-MeO2CCCCO2Me){(S,S)-iPr-pybox}] (9) has been analogous prepared from complex 1. The activation of terminal alkynes and alkynols by olefin complex 1, under toluene reflux conditions, has been achieved to give vinylidene trans-[OsCl2{CC(H)Ph}{(S,S)-iPr-pybox}] (10), allenylidene trans-[OsCl2(CCC(R)Ph){(S,S)-iPr-pybox}] (R = Ph (11), H (12)) and cyclic carbene complexes trans-[OsCl2(▪){(S,S)-iPr-pybox}] (13).

Amino-Substituted Butatrienes: Unusual η1 Ligands Formed by an Unusual Reaction

The reaction of the bis(amino)allenylidene complex [(CO)5W═C═C═C(NMe2)2] with diethyldiazomethane yields two products, a cyclic carbene complex (2) by 1,2-addition of Et2C−N2 to the Cα−Cβ bond of the allenylidene ligand and the η1-butatriene complex [(CO)5W{C[C(NMe2)2]═C═CEt2}] (3). Complex 2 slowly eliminates N2 and rearranges into 3. In contrast, only η1-butatriene complexes, [(CO)5M{C[C(NMe2)XR]═C═C(R′)2}], are isolated from the reaction of diazoalkanes (R′)2C−N2 (R′ = Me, Et, nPr) with alkoxy(amino)allenylidene complexes [(CO)5M═C═C═C(NMe2)OR] (M = Cr, W; R = Me, Et, (−)-menthyl) or with the (alkylthio)(amino)allenylidene complex [(CO)5W═C═C═C(NMe2)SnPr]. These new η1-butatriene complexes are related to Cα phosphine adducts of allenylidene complexes such as [(CO)5W{C(PMe3)═C═C(NMe2)Ph}] (17) and might be regarded as Cα carbene adducts. However, the PMe3 substituent in 17 is not replaced when 17 is treated with an N-heterocyclic carbene. Vice versa, the “carbene” substituent “C(NMe2)OEt” in the η1-butatriene complex [(CO)5Cr{C[C(NMe2)OEt]═C═CEt2}] is not replaceable by PMe3. Free N-heterocyclic carbenes do not add to the Cα atom of the allenylidene complex [(CO)5W═C═C═C(C6H4NMe2-p)2] but instead to the Cγ atom, giving the dipolar neutral alkynyl complexes [(CO)5W−C≡CC(C6H4NMe2-p)2L] (L = SIMe, SIMes). DFT calculations on the reaction mechanism indicate that a cyclic carbene complex and two isomeric η2-butatriene complexes are intermediates in the reaction pathway to form η1-butatriene complexes. The structure of two representative examples of η1-butatriene complexes and of one Cγ carbene adduct has been established by X-ray structure analyses.

Intramolecular Cyclization of Ruthenium Vinylidene Complexes with a Tethering Vinyl Group: Facile Cleavage and Reconstruction of the C−C Double Bond

Protonation of ruthenium acetylide complexes [M]-*C*CCPh2CH2CH=CH2 (2a, [M] = (eta5-C5H5)(P(OPh)3)(PPh3)Ru; 2a', [M] = (eta5-C5H5)(dppp)Ru; *C = 13C-labeled carbon atom) with HBF4 in ether produces [[M]=*C=CHCH2CPh2*CH=CH2][BF4] (4, 4') exclusively via a metathesis process of the terminal vinyl group with the *C=*C of the resulting vinylidene group. For 4 in methanol, bond reconstruction of the two labeled *C atoms readily takes place via a retro-metathesis process followed by a cyclization of the resulting vinylidene ligand giving the cyclic carbene complex 5, which is fully characterized by single-crystal X-ray diffraction analysis. The protonation of 2a in MeOH is followed by a cyclization, also giving 5. Deuterium-labeling study indicates that the C-C bond formation of this cyclization proceeds simultaneously with the formation of 4 consistent with facile cleavage and reconstruction of C=C bonds. For comparison, complex 4 in alcohol yields, besides 5, the corresponding alkoxycyclohexene 6. Formation of 6 from 4 also involves a skeletal rearrangement with reconstruction of the C=C bond. Interestingly, [[Ru']=*C=C(Me)CH2CPh2*CH=CH2][BF4] (8') originally from a complex with two connected labeled carbon atoms also undergoes reestablishment of the *C=*C bond yielding the cyclic allenyl complex 9'. 13C-labeling studies clearly reveal the reestablishment of two C=C double bonds in the transformation of both 4 to 5 and 8' to 9'. The proposed mechanism implicates a cyclobutylidene intermediate formed either via a regiospecific [2+2] cycloaddition of two double bonds in the ruthenium vinylidene 4 or via a cyclization of 4 giving a nonclassical ion intermediate followed by a 1,2-alkyl shift.

Solvent-Assisted New Reaction Pathways for the (THF)W(CO)5-Promoted endo- and exo-Cycloisomerization of 4-Pentyn-1-ol: A Theoretical Investigation

New solvent-assisted mechanistic routes were located for the (THF)W(CO)5-promoted endo- and exo-cycloisomerization of 4-pentyn-1-ol using the B3LYP/6-31G (with the LANL2DZ relativistic pseudopotential for W) theory level. A mixed model was used by explicitly including a THF molecule as a component of the reactive system and taking into account the effect of bulk solvent by means of the PCM-UAHF method. This THF molecule plays a crucial role by making the endo route leading to the cyclic carbene complex the most favorable one because of an important catalytic effect. These new mechanisms allow a satisfactory rationalization of experimental facts.

The Sensitive Balance between Five-Coordinate Carbene and Six-Coordinate Carbyne Ruthenium Complexes Formed from Ruthenium Vinylidene Precursors

The reaction of the dichloro(vinylidene)ruthenium compounds [RuCl2(CCHR)L2] (R = Ph or tBu and L = PCy3 or PiPr3) (1a−d) with [H(OEt2)2]BArf (BArf- = [B{C6H3(CF3)2-3,5}4]-) resulted in the attack of the proton at the Cβ carbon atom of the vinylidene ligand and afforded the corresponding cationic, five-coordinate carbyneruthenium complexes [RuCl2(⋮CCH2R)L2]BArf (2a−d) in almost quantitative yields. The protonation of the carboxylato derivatives [RuCl(κ2-O2CR)(CCHPh)(PiPr3)2] [R = H (3a), CH3 (3b), or Ph (3f)] with [H(OEt2)2]BArf led to the formation of the five-coordinate cyclic carbene complexes [RuCl{C(CH2Ph)OC(O)R}(PiPr3)2]BArf [R = H (6a), CH3 (6b), or Ph (6f)], which are formed via nucleophilic attack of the carboxylato ligand to a cationic carbyneruthenium intermediate. The protonation of the related vinylidene compounds [RuCl(κ2-O2CR)(CCHPh)(PiPr3)2] [R = CH2F (3c), CHF2 (3d), CF3 (3e), C6H4NO2-4 (3g), C6H4NO2-2 (3h), C6F5 (3i), and C6H3(NO2)2-2,4 (3j)] with [H(OEt2)2]BArf gave an equilibrium mixture of the carbyne [RuCl(κ2-O2CR)(⋮CCH2Ph)(PiPr3)2]BArf (5c−e, 5g−j) and the isomeric, cyclic carbene complexes [RuCl{C(CH2Ph)OC(O)R}(PiPr3)2]BArf (6c−e, 6g−j). The position of this equilibrium significantly depends on the basicity of the carboxylato ligand. The six-coordinate cyclic carbene complexes [Ru(κ2-O2CR1){C(CH2Ph)OC(O)R2}(PiPr3)2]BArf [R1 = R2 = CHF2 (7a), CF3 (7b); R1 = CF3, R2 = H (7c)] were obtained on protonation of the precursors [Ru(κ1-O2CR1)(κ2-O2CR2)(CCHPh)(PiPr3)2] (4a−c) with [H(OEt2)2]BArf. Both 7a and 7b undergo a fluxional process in solution resulting in a κ1/κ2 interconversion of the carboxylato groups. The crystal and molecular structures of 2b, 5e, and 6a were determined by X-ray crystallography.

Efficient Synthetic Routes to Terminal γ-Keto−Alkynes and Unsaturated Cyclic Carbene Complexes Based on Regio- and Diastereoselective Nucleophilic Additions of Enolates on Ruthenium(II) Indenyl Allenylidenes

Ruthenium(II) indenyl allenylidene complexes [Ru{CCC(R1)Ph}(η5-C9H7)(PPh3)2][PF6] (R1 = Ph (1), H (2)) regioselectively react with lithium enolates LiCH2COR2 (R2 = Ph, iPr, Me, Fc, (E)-CHCHPh) at the Cγ atom to yield the neutral σ-alkynyl derivatives [Ru{C⋮CC(R1)Ph(CH2COR2)}(η5-C9H7)(PPh3)2] (3a−e, 4a−d). Protonation of 3a−e and 4a−d with HBF4·Et2O affords the cationic vinylidene derivatives [Ru{CC(H)C(R1)Ph(CH2COR2)}(η5-C9H7)(PPh3)2][BF4] (5a−e, 6a−d), which can be easily demetalated, by treatment with acetonitrile, to yield the terminal γ-keto-substituted alkynes HC⋮CC(R1)Ph(CH2COR2) (7a−e, 8a−d) and the nitrile complex [Ru(N⋮CMe)(η5-C9H7)(PPh3)2][BF4] (9). The addition of lithium enolates LiCH2COR (R = Ph, iPr, Me) on the optically active allenylidene complex [Ru{CCC(C9H16)}(η5-C9H7)(PPh3)2][PF6] (12; C(C9H16) = (1R)-1,3,3-trimethylbicyclo[2.2.1]hept-2-ylidene) proceeds in a regio- and diastereoselective manner, affording σ-alkynyl derivatives [Ru{C⋮CC(C9H16)(CH2COR)}(η5-C9H7)(PPh3)2] (13a−c). The X-ra...

Reversible α-elimination in the conversion of N–CH3 to N–CHIr by double C–H activation

2-Dimethylaminopyridine (pyNMe2; py = 2-pyridyl) reacts with [H2Ir(OCMe2)2L2]+ (L = PPh3) to give a cyclic carbene complex [H2Ir(CHN(Me)py)L2]+via an oxidative addition, reversible α-elimination sequence.

Synthesis of alkynyl, cyclic carbene and vinylidene osmium(II) complexes: first indenyl half-sandwich osmium(II) complexes

The reaction of [OsCl(η5-C9H7)(PPh3)2]1 with 3,3-dimethylbut-1-yne and NaPF6 in refluxing methanol gave the vinylidene complex [Os{CC(H)But}(η5-C9H7)(PPh3)2][PF6]2a and with HCCSiMe3 and NH4PF6 in refluxing methanol gave the unsubstituted vinylidene complex [Os(CCH2)(η5-C9H7)(PPh3)2][PF6]2b. 2-Oxacyclo-pentylidene and -hexylidene complexes [Os{[graphic omitted]H2}(η5-C9H7)(PPh3)2][PF6](n= 1 3a or 2 3b) have been prepared by reaction of 1 with HCC(CH2)nCH2OH. Reaction of 1 and hex-5-yn-1-ol afforded the hydroxyvinylidene complex [Os{CC(H)(CH2)3CH2OH}(η5-C9H7)(PPh3)2][PF6]4 and with 1-ethynyl-1-cycloalkanols in the presence of NaPF6 in refluxing methanol it gave regioselectively the alkenylvinylidene complexes [Os{CC(H)[graphic omitted]H2}(η5-C9H7)(PPh3)2][PF6](n= 1 5a, 2 5b or 3 5c). Deprotonation of the vinylidene complexes 2a, 2b and 5a–5c with potassium tert-butoxide yielded the neutral alkynyl complexes [Os(CCR)(η5-C9H7)(PPh3)2](R = But6a or H 6b) and [Os{CC[graphic omitted]H2}(η5-C9H7)(PPh3)2]7a–7c respectively. Methylation of complex 6a with MeOSO2CF3 yielded the vinylidene complex [Os{CC(Me)But}(η5-C9H7)(PPh3)2][CF3SO3]8.

Photochemical intermolecular C–H and C–F insertion of rhodium into pentafluoroanisole to generate a metallacycle; conversion to a cyclic carbene complex

Irradiation fo [(η5-C5H5)Rh(PMe3)(C2H4)] in pentafluoroanisole generates the metallacycle[(η5-C5H5)Rh(PMe3)[graphic omitted]F4]; reaction of this complex with 1 equiv. of Ph3C + PF6- at 220 K generates [(η5-C5H5)Rh(PMe3)[graphic omitted]F4]PF6.

Zweikernige Mangan- und Rheniumkomplexe mit gemischt aliphatischen-aromatischen Kohlenwasserstoffbrücken / Dinuclear Manganese and Rhenium Complexes with Mixed Aliphatic-Aromatic Hydrocarbon Bridges

The symmetrically hydrocarbon-bridged complexes (OC)5M-(CH2)n+1-X-(CH2)n+l-M(CO)5 [n = 1, X = 1,4-C6H4, M = Mn (2a), M = Re (3a); n = 2, X = 1,4-C6H4, M = Mn (2b), M = Re (3b); n = 1, X = 1,3-C6H4, M = Mn (5a), M = Re (6a); n = 2, X = 1,3-C6H4, M = Mn (5b), M = Re (6b); n = 1, X = 1,2-C6H4, M = Mn (8a), M = Re (9a); n = 2, X = 1,2-C6H4, M = Mn (8b), M = Re (9b)] are obtained by the reaction of the bistriflates X[(CH2)„-CH2-OSO2CF3]2 [X = 1,4-C6H4, n = 1 (la), n = 2 (lb); X = 1,3-C6H4, n = 1 (4a), n = 2 (4b); X = 1,2-C6H4, n = 1 (7a), n = 2 (7b)] with the carbonyl metalates [M(CO)5]- (M = Mn, Re) in THF and dimethyl ether, respectively. According to an X-ray structural analysis 8a crystallizes in the triclinic space group P1̅ with Ζ = 2. Depending on the solvent, the reaction of 7 a with [Mn(CO)5]~ affords also the cyclic carbene complex 10a. The behavior of the manganese compounds toward CO has been investigated exemplarily in the case of 8a and leads to the diacyl complex 1,2-C6H4[CH2CH2C(O)Mn(CO)5]2 (11). Upon reaction with Na2CO3/CH3OH 11 is converted to give the corresponding diester 1,2-C6H4[CH2CH2C(O)OCH3]2 (12).

A comparison of some complexes of the type eq-[Mn 2(CO) 9L], where L is a cyclic carbene ligand with a five- or six-membered ring and the molecular structures of two complexes containing six-membered carbene rings

Two new five-membered ring cyclic carbene complexes eq-[Mn 2(CO) 9L] (where L= CCH 2CH(CH 3)CH 2O or CC(CH 3) 2CH 2CH 2O ) have been prepared and characterized. Thermal analysis and 1H/ 2D exchange experiments are compared for several five- and six-membered ring cyclic carbene complexes of the type eq-[Mn 2(CO) 9L]. The X-ray crystal structures of the six-membered ring carbene complexes eq-[Mn 2(CO) 9L] (where L= CCH 2CH 2CH 2CH 2O and CCH 2CH 2CH 2CH(CH 3)O ) have been determined and are compared with the known structures of the related five-membered ring complexes.

Synthese und reaktivität kohlenwasserstoffüberbrückter komplexe von Mangan, Rhenium, Molybdän und Wolfram

The hydrocarbon-bridged complexes M(CH 2) n M (M = Mn(CO) 5: n = 5 ( 2b), 10 ( 2c); M = Re(CO) 5: n = 5 ( 3b), 10 ( 3c); M = (η 5-C 5H 5)Mo(CO) 3: n = 5 ( 4b), 10 ( 4c); M = (η 5-C 5H 5)W(CO) 3: n = 10 ( 5c)) are obtained by reaction of the bistriflates Y(CH 2) n Y (Y = F 3CSO 3, n = 5 ( 1b), 10 ( 1c)) with the carbonyl metalates [M(CO) 5] − (M = Mn ( 2), Re ( 3)) and [(η 5-C 5H 5)M(CO) 3] − (M = Mo ( 4), W ( 5)) in diethyl ether and THF, respectively. Depending on the solvent, the reaction of 1b with 2 also affords the cyclic carbene complex 2d. The action of SO 2 and CO, respectively, on the complexes 2a- c and 4b, c results in the formation of the sulfinato-S complexes [(η 5-C 5H 5)(OC) 3MoSO 2(CH 2) n O 2SMo(CO) 3(η 5-C 5 H 5)] ( n = 5 ( 4b′), 10 ( 4c′)) and the diacyl-bridged compounds [(OC) 5MnC (O)(CH 2) n (O)CMn(CO) 5] ( n = 3 ( 2a′), 10 ( 2c′)). According to an X-ray structural analysis, the monoacyl complex [(OC) 5MnC(O)(CH 2) 3Mn(CO) 5] ( 2e) crystallizes in the orthorhombic space group Cmca with Z = 4, the acyl function being disordered. 1H NMR spectroscopic investigations indicate a hindered rotation about the C αC β-σ bond in 2b,c and 3b,c.

Reactions of electrophiles with neutral cyclic carbene complexes of iron

Reactions of the two benzannelated ferracyclopentadienes with two electrophiles ― anhydrous protic acid and trimethylsilyl triflate ― have been studied

Synthesis of dimanganese nonacarbonyl cyclic carbene complexes and molecular structures of two of them

The reactions of Br(CH 2 ) 3 Br, BrCH 2 CH 2 CH(C-H 3 )Br, Br(CH 2 ) 4 Br, and BrCH 2 CH 2 CH 2 CH(CH 3 )Br with Na-[Mn(CO) 5 ] yield the dimanganese cyclic carbene complexes [(CO) 5 MnMn(CO) 4 L] (where L=CCH 2 CH 2 CH 2 O, CCH 2 CH 2 CH(CH 3 )O, CCH 2 CH 2 CH 2 CH 2 O, and CCH 2 CH 2 CH 2 CH(CH 3 )O, respectively). The structures of the first two of these complexes have been determined by X-ray crystallography, and this confirms that the cyclic carbene ligand occupies an equatorial position. IR, 1 H and 13 C NMR, and mass spectra are reported and discussed for these carbene complexes

Organische Synthesen mit Übergangsmetallkomplexen, 46. Alkenylcarben‐Chrom‐ und ‐Wolframkomplexe; Protonierung und Aktivierung durch Elektronen‐ziehende Substituenten

Organic Syntheses via Transition Metal Complexes, 46. — Alkenylcarbene Chromium and Tungsten Complexes; Proton Addition and Activation by Electron‐Withdrawing SubstituentsAlkenylcarbene complexes LnMC(OEt)‐CHC(R)NMe2[1, LnM  Cr(CO)5, W(CO)5; R  H, CH3, C6H5] add HBF4 in ether to give novel cationic carbene complexes [Ln MC(OEt)‐CH2‐C(R)NMe2]BF4 (3) by protonation at C‐2 of the C‐CC ligand. The addition of HBF4 to 7 leads to the formation of the cyclic carbene complexes 8. Structures of 3 and 8 are assigned spectroscopically. X‐ray data are reported for 8a. Protonation of 1 and 7 results in a strong deshielding of the carbene carbon atoms, which parallels an increase of reactivity at the MC bonds. An activation of the MC bond has also been achieved by electron‐withdrawing substituents like N‐acyl groups. We report on the first synthesis of [β‐(acylamino)‐alkenyl]carbene complexes 13, which are more reactive than β‐(aminoalkenyl)carbene complexes 7.

Amine, imine, and aminocarbene complexes of platinum(II)

Solutions of the chloride-bridged binuclear platinum complexes [Pt2(µ-Cl)2Cl2L2](L = PMe2Ph or PBu3) readily react with the amines NH2Ph, 4-NO2C6H4NH2, 3-MeOC6H4NH2, NHPh2, or NH2Me to produce trans-[PtCl2(am)L] in the presence or absence of phenylethyne. The imines PhCHNPh, PhCHNMe, 2-MeC6H4CHNPh, or Ph2CNH also react with [Pt2(µ-Cl)2Cl2L2] to produce the analogous N-bonded imine complexes, but reactions of the amines NHEt2 or NH2But with the binuclear compounds lead to additional platinum-containing compounds resulting from ligand redistribution reactions. The complexes of NH2Ph, 4-NO2C6H4NH2, 3-MeOC6H4NH2, and NHPh2 react with phenylethyne over several days at ambient temperature to yield aminocarbene complexes cis-[PtCl2{C(NR1R2)CH2Ph}L](R1R2= H, Ph; H, C6H4NO2-4; H, C6H4OMe-3; or Ph2). Treatment of the imine complexes or any of the other amine complexes with PhCCH, however, led only to decomposition. 2-Aminophenylethyne reacts rapidly with [Pt2(µ-Cl)2Cl2L2] to produce the cyclic carbene complex cis-[PtCl2{[graphic omitted]H}L] in only 1 h, and although the amine-N complexes were observed in solution as transients they were not isolated. Treatment of the carbene complexes with tertiary phosphine, L, leads to cationic complexes trans-[PtCl{C(NR1R2)CH2Ph}L2]Cl. Both the uncharged and cationic aminocarbene compounds are less reactive than their alkoxycarbene analogues, and show no reaction with Cl– and little tendency towards H/D exchange with CD3OD. Hydrogen-1, 13C, and 31P n.m.r. spectroscopic parameters for the complexes are reported and related to the likely solution conformations.

ChemInform Abstract: Synthesis of New Fischer‐Type Carbene Complexes: Characterization andReactions of Titanoxycarbene‐Metal Complexes Derived from (η5‐C5Me5)2Ti(C2H4) and Metal Carbonyls.

AbstractThe biscyclopentadienyl ethylene‐titanium (I) is coupled with the carbonyl complexes (II) to give the cyclic carbene complexes (III).

Cyclic carbene complexes of the type cis-MI[ [formula omitted]H 2](CO) 2(η-C 5H 5) (M = Mo, n = 2 OR 3; M = W, n = 2): their syntheses and reactions of the molybdenum systems with LiEt 3BH

Treatment of [M(CNMe)(CO) 2(η-C 5H 5)] − with I[CH 2] n+1 I provides the cyclic carbene species cis-MI[ CN(Me)(CH 2) n C H 2](CO) 2(η-C 5H 5) (M = Mo, n = 2 or 3; M = W, n = 2), the molybdenum examples of which undergo reaction with LiEt 3BH, so forming the compounds cis- ▪(CO) 2(η-C 5H 5).

Übergangsmetall-Carben-Komplexe, CXXXIII [1] Darstellung, spektroskopische Daten und Molekülstrukturen neuartiger Eisencarben-Komplexe/Transition Metal Carbene Complexes, CXXXIII [1] Preparation, Spectroscopic Data and Molecular Structures of Novel Iron Carbene Complexes

The reaction of Fe(CO)5 with LiNiPr2 and subsequent treatment with Et3OBF4 results in the formation of (CO)4 Fe[C(NiPr2)OC2H5] (1). As a second product the cyclic carbene complex (2) is formed.

Synthesis and Structure of (CO)4W[C(NEt2)PMePh], A Novel Cyclic Carbene Complex

AbstractThe complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 488. DOI:10.1002/anie.198304880