Carbenerhodium(I) complexes of the half-sandwich-type: reactions with electrophiles

Bleuel, Elke; Schwab, Peter; Laubender, Matthias; Werner, Helmut

doi:10.1039/b008354m

Cited by 24 publications

(23 citation statements)

References 20 publications

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“…We note that a cationic rhodium complex, isoelectronic to 36 with the h 3 -PhCHC 6 H 5 unit in an exo position, has been prepared by protonation of [(h 5 -C 5 H 5 )Rh(CPh 2 )(PiPr 3 )] with HBF 4 . [45] With regard to the mechanism of formation of 35, we assume that a carbene(hydrido)ruthenium(ii) compound [(h 5 -C 5 H 5 )RuH( CPh 2 )(PPh 3 )] is formed initially, which, after insertion of the carbene unit into the Ru À H bond, generates an Ru ± CHPh 2 species. Final rearrangement of the diphenylmethyl moiety from h 1 to h 3 would yield the product.…”

Section: Introductionmentioning

confidence: 99%

“…The yellow, slightly air-sensitive microcrystalline solid with an analytical composition corresponding to 35 was, after chromatographic purification on basic Al 2 O 3 , isolated in 63 % yield. Particularly diagnostic of the coordination of a substituted h [ 45] With regard to the mechanism of formation of 35, we assume that a carbene(hydrido)ruthenium(ii) compound [(h 5 -C 5 H 5 )RuH( CPh 2 )(PPh 3 )] is formed initially, which, after insertion of the carbene unit into the Ru À H bond, generates an Ru ± CHPh 2 species. Final rearrangement of the diphenylmethyl moiety from h 1 to h 3 would yield the product.…”

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confidence: 99%

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Synthesis, Molecular Structure, and CC Coupling Reactions of Carbeneruthenium(II) Complexes with C₅H₅Ru(CRR′) and C₅Me₅Ru(CRR′) as Molecular Units

Braun

Münch

Windmüller

et al. 2003

Chemistry A European J

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The ethene derivatives [(eta(5)-C(5)R(5))RuX(C(2)H(4))(PPh(3))] with R=H and Me, which have been prepared from the eta(3)-allylic compounds [(eta(5)-C(5)R(5))Ru(eta(3)-2-MeC(3)H(4))(PPh(3))] (1, 2) and acids HX under an ethene atmosphere, are excellent starting materials for the synthesis of a series of new halfsandwich-type ruthenium(II) complexes. The olefinic ligand is replaced not only by CO and pyridine, but also by internal and terminal alkynes to give (for X=Cl) alkyne, vinylidene, and allene compounds of the general composition [(eta(5)-C(5)R(5))RuCl(L)(PPh(3))] with L=C(2)(CO(2)Me)(2), Me(3)SiC(2)CO(2)Et, C=CHCO(2)R, and C(3)H(4). The allenylidene complex [(eta(5)-C(5)H(5))RuCl(=C=C=CPh(2))(PPh(3))] is directly accessible from 1 (R=H) in two steps with the propargylic alcohol HC triple bond CC(OH)Ph(2) as the precursor. The reactions of the ethene derivatives [(eta(5)-C(5)H(5))RuX(C(2)H(4))(PPh(3))] (X=Cl, CF(3)CO(2)) with diazo compounds RR'CN(2) yield the corresponding carbene complexes [(eta(5)-C(5)R(5))RuX(=CRR')(PPh(3))], while with ethyl diazoacetate (for X=Cl) the diethyl maleate compound [(eta(5)-C(5)H(5))RuCl[eta(2)-Z-C(2)H(2)(CO(2)Et)(2)](PPh(3))] is obtained. Halfsandwich-type ruthenium(II) complexes [(eta(5)-C(5)R(5))RuCl(=CHR')(PPh(3))] with secondary carbenes as ligands, as well as cationic species [(eta(5)-C(5)H(5))Ru(=CPh(2))(L)(PPh(3))]X with L=CO and CNtBu and X=AlCl(4) and PF(6), have also been prepared. The neutral compounds [(eta(5)-C(5)H(5))RuCl(=CRR')(PPh(3))] react with phenyllithium, methyllithium, and the vinyl Grignard reagent CH(2)=CHMgBr by displacement of the chloride and subsequent C-C coupling to generate halfsandwich-type ruthenium(II) complexes with eta(3)-benzyl, eta(3)-allyl, and substituted olefins as ligands. Protolytic cleavage of the metal-allylic bond in [(eta(5)-C(5)H(5))Ru(eta(3)-CH(2)CHCR(2))(PPh(3))] with acetic acid affords the corresponding olefins R(2)C=CHCH(3). The by-product of this process is the acetato derivative [(eta(5)-C(5)H(5))Ru(kappa(2)-O(2)CCH(3))(PPh(3))], which can be reconverted to the carbene complexes [(eta(5)-C(5)H(5))RuCl(=CR(2))(PPh(3))] in a one-pot reaction with R(2)CN(2) and Et(3)NHCl.

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Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

Synthesis, Molecular Structure, and CC Coupling Reactions of Carbeneruthenium(II) Complexes with C₅H₅Ru(CRR′) and C₅Me₅Ru(CRR′) as Molecular Units

Braun

Münch

Windmüller

et al. 2003

Chemistry A European J

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“…This unique regioselectivity has been attributed to the stabilizing effect of a p-benzyl interaction available only to the branched isomer 3. [2] p-Benzyl complexes of a variety of transition metals [10][11][12][13][14][15] including rhodium [16][17][18][19][20][21] have been isolated, however, there is no empirical evidence to definitively ascribe the regioselectivity in the rhodiumcatalyzed hydroboration to this interaction.…”

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confidence: 99%

Regioselectivity of the Rhodium‐Catalyzed Hydroboration of Vinyl Arenes: Electronic Twists and Mechanistic Shifts

et al. 2007

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Any substituent does it: The hydroboration of vinyl arenes with pinacol borane (HBPin) and cationic rhodium complexes selectively placed the boron proximal to the aryl rather than phenyl ring, regardless of whether this ring bears electron‐donating or electron‐withdrawing substituents. In competition experiments between styrene and various vinyl arenes, preferential hydroboration also occured at the substituted arene (see scheme). Hammett plots indicate a break in the mechanism.

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“…However, the observation of 26 and observations from our group, [31][32][33][34] and others, 10,21,22,25,26 that H (and other groups) can migrate from their original locus on a metal to the perfluorocarbene carbon in the presence of a coordinating anion, in some cases with complete preservation of stereochemistry at C and at Ir, calls into question whether the HCl adducts formed here are those resulting from a kinetic controlled addition, or whether an initial protonation at Ir, followed by H-migration to C is a viable pathway. However, the observation of 26 and observations from our group, [31][32][33][34] and others, 10,21,22,25,26 that H (and other groups) can migrate from their original locus on a metal to the perfluorocarbene carbon in the presence of a coordinating anion, in some cases with complete preservation of stereochemistry at C and at Ir, calls into question whether the HCl adducts formed here are those resulting from a kinetic controlled addition, or whether an initial protonation at Ir, followed by H-migration to C is a viable pathway.…”

Section: Addition Reactions Of Perfluoroalkylcarbene Complexes With Hclmentioning

confidence: 52%

“…For example, addition of HCl to compounds 1 (Scheme 2) (R = Me, Ph, i Pr), 21,22 afforded addition products 2 consistent with the carbene carbon being nucleophilic. Such additions to half sandwich carbene compounds has been explored by several groups.…”

Section: Introductionmentioning

confidence: 99%

Synthesis, structure, and reactivity of iridium perfluorocarbene complexes: regio- and stereo-specific addition of HCl across a metal carbon double bond

et al. 2015

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Reductive activation of an α-fluorine in the perfluoroalkyl complexes Cp*(L)(i)Ir-CF2RF using Mg/graphite leads to perfluorocarbene complexes Cp*(L)Ir[double bond, length as m-dash]CFRF (L = CO, PMe3; RF = CF3, C2F5, C6F5). New complexes E-Cp*(PMe3)Ir[double bond, length as m-dash]CFC2F5 and E-Cp*(CO)Ir[double bond, length as m-dash]CFC6F5 have been characterized by single crystal X-ray diffraction studies, and a comparison of metric parameters with previously reported analogues is reported. Experimental NMR and computational DFT (B3LYP/LACV3P**++) studies agree that for Ir[double bond, length as m-dash]CFRF complexes (RF = CF3, CF2CF3) the thermodynamic preference for the E or Z isomer depends on the steric requirements of ligand L; when L = CO the Z-isomer (F cis to Cp*) is preferred and for L = PMe3 the E-isomer is preferred. When reduction of the precursors is carried out in the dark the reaction is completely selective to produce E- or Z-isomers. Exposure of solutions of these compounds to ambient light results in slow conversion to a photostationary non-equilibrium mixture of E and Z isomers. In the dark, these E/Z mixtures convert thermally to their preferred E or Z equilibrium geometries in an even slower reaction. A study of the temperature dependent kinetics of this dark transformation allows ΔG(‡)298 for rotation about the Ir[double bond, length as m-dash]CFCF3 double bond to be experimentally determined as 25 kcal mol(-1); a DFT/B3LYP/LACV3P**++ calculation of this rotation barrier is in excellent agreement (27 kcal mol(-1)) with the experimental value. Reaction of HCl with toluene solutions of Cp*(L)Ir[double bond, length as m-dash]CFRF (L = CO, PMe3) or Cp*(CO)Ir[double bond, length as m-dash]C(CF3)2 at low temperature resulted in regiospecific addition of HCl across the metal carbon double bond, ultimately yielding Cp*(L)Ir(CHFRF)Cl and Cp*(CO)Ir[CH(CF3)2]Cl. Reaction of HCl with single E or Z diastereomers of Cp*(L)Ir[double bond, length as m-dash]CFRF gives stereospecific cis-addition to give single diastereomers of Cp*Ir(L)(CHFRF)Cl; addition of HCl to several different E/Z ratios of Cp*(L)Ir[double bond, length as m-dash]CFRF affords ratios of diastereomeric products Cp*(L)Ir(CHFRF)Cl identical to the original ratio of starting material isomers. The addition of HCl is therefore demonstrated to be unambiguously regio- and stereo-specific. The observed product regiochemistry of addition of HCl to Ir[double bond, length as m-dash]CF2, Ir[double bond, length as m-dash]CFRF, and Ir[double bond, length as m-dash]C(CF3)2 ligands is the same and is not dependent on the ground state energy preference (singlet or triplet) for the free perfluorocarbene. DFT calculations on model HCl addition reactions indicate that this regiochemistry is strongly preferred thermodynamically, but predict that in H(δ+)-Cl(δ-) addition to Cp(PH3)Ir[double bond, length as m-dash]CF2, H(δ+) attack at Ir has a lower energy transition state, while for Cp(PH3)Ir[double bond, length as m-dash]CFCF3 and Cp(PH3)Ir[double bond, lengt...

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Carbenerhodium(I) complexes of the half-sandwich-type: reactions with electrophiles

Cited by 24 publications

References 20 publications

Synthesis, Molecular Structure, and CC Coupling Reactions of Carbeneruthenium(II) Complexes with C₅H₅Ru(CRR′) and C₅Me₅Ru(CRR′) as Molecular Units

Synthesis, Molecular Structure, and CC Coupling Reactions of Carbeneruthenium(II) Complexes with C₅H₅Ru(CRR′) and C₅Me₅Ru(CRR′) as Molecular Units

Regioselectivity of the Rhodium‐Catalyzed Hydroboration of Vinyl Arenes: Electronic Twists and Mechanistic Shifts

Synthesis, structure, and reactivity of iridium perfluorocarbene complexes: regio- and stereo-specific addition of HCl across a metal carbon double bond

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Carbenerhodium(I) complexes of the half-sandwich-type: reactions with electrophiles

Cited by 24 publications

References 20 publications

Synthesis, Molecular Structure, and CC Coupling Reactions of Carbeneruthenium(II) Complexes with C5H5Ru(CRR′) and C5Me5Ru(CRR′) as Molecular Units

Synthesis, Molecular Structure, and CC Coupling Reactions of Carbeneruthenium(II) Complexes with C5H5Ru(CRR′) and C5Me5Ru(CRR′) as Molecular Units

Regioselectivity of the Rhodium‐Catalyzed Hydroboration of Vinyl Arenes: Electronic Twists and Mechanistic Shifts

Synthesis, structure, and reactivity of iridium perfluorocarbene complexes: regio- and stereo-specific addition of HCl across a metal carbon double bond

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Synthesis, Molecular Structure, and CC Coupling Reactions of Carbeneruthenium(II) Complexes with C₅H₅Ru(CRR′) and C₅Me₅Ru(CRR′) as Molecular Units

Synthesis, Molecular Structure, and CC Coupling Reactions of Carbeneruthenium(II) Complexes with C₅H₅Ru(CRR′) and C₅Me₅Ru(CRR′) as Molecular Units