Über Aromatenkomplexe von Metallen, LXV. Die Isomerenverteilung bei der Friedel‐Crafts‐Acetylierung des π‐Toluol‐chrom‐tricarbonyls und des freien Toluols

Herberich, Gerhard E.; Fischer, Ernst Otto

doi:10.1002/cber.19620951134

Cited by 36 publications

(11 citation statements)

References 17 publications

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“…Complexation of arenes has a marked effect on their reaction properties. , Since the metal is net electron withdrawing, binding arenes to metals has the effect of activating them toward nucleophilic attack while deactivating them with respect to electrophilic attack. We are aware of only three types of electrophilic aromatic substitution reactions that occur with metal-bound arenes: (1) protonation, (2) Friedel−Crafts acetylation, − and (3) addition of iminium salts .…”

Section: Discussionmentioning

confidence: 99%

Stereoelectronic Factors That Influence Kinetic and Thermodynamic Sites of Protonation of (η⁶-Arene)molybdenum(phosphine)₃Complexes

et al. 1999

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We have previously reported (J. Am. Chem. Soc. 1995, 117, 12639) the arene complex (η 6 -C 6 H 6 )Mo(TRIPOD) (1), where TRIPOD ) 1,1,1-tris(diphenylphosphinomethyl)ethane, is protonated upon addition of 1 equiv of D + to yield the metal-hydride [(η 6 -C 6 H 5 D)Mo-(TRIPOD)H] + (1H + -d 1 ) via exo addition of D + to the arene ligand followed by migration to the metal of the endo proton of the putative η 5 -cyclohexadienyl complex [(η 5 -C 6 H 6 D)Mo-(TRIPOD)] + (1 ‡ ). The opposite isotopomer is obtained when (η 6 -C 6 D 6 )Mo(TRIPOD) (1-d 6 ) is employed to give [(η 6 -C 6 D 5 H)Mo(TRIPOD)D] + (1D + -d 6 ). Our recent investigation of the electronic structure of 1 and its one-electron oxidized derivative [(η 6 -C 6 H 6 )Mo(TRIPOD)] + (1 + ) suggested the mechanism of protonation is not driven entirely by electronic factors; steric factors are likely important for indirect protonation of 1. Consistent with that conclusion, we report herein that some other phosphine derivatives are protonated directly at the metal center. Thus, under the same reaction conditions the monodentate phosphine derivatives (η 6 -C 6 D 6 )Mo(PR 3 ) 3 , where PR 3 ) PPh 2 Me (3-d 6 ), PPhMe 2 (4-d 6 ), and PMe 3 (5-d 6 ), are protonated directly at the metal 0%, 20%, and 40% of the time, respectively. The remainder of the protonations take place via the aforementioned indirect protonation of the arene ligand. Surprisingly, (η 6 -C 6 D 6 )Mo(TRIPHOS) (2-d 6 ), where TRIPHOS ) bis(2-diphenylphosphinoethyl)phenylphosphine, reacts with H + by direct protonation of the metal center 80% of the time to give a C 1 -symmetric kinetic hydride [(η 6 -C 6 D 6 )Mo(TRIPHOS)H] + (2 K H + -d 6 ). The other 20% of the time 2-d 6 reacts via the arene mechanism to give [(η 6 -C 6 D 5 H)Mo(TRIPHOS)D] + (2 K D + -d 6 ). The two enantiomeric forms of 2 K H + are observed to be in rapid equilibrium (k ) 6.4 × 10 3 s -1 at -87°C). Compound 2 K H + eventually isomerizes (k ) 6.1 × 10 -4 s -1 at -60°C) to the C s -symmetric thermodynamic hydride [(η 6 -C 6 H 6 )Mo-(TRIPHOS)H] + (2 T H + ). We conclude from the crystal structures of 1-4, tracer studies, and electronic structure calculations of the five derivatives 1-5 presented herein that indirect protonation does not represent a general mechanism for this class of compounds. In addition to electronic factors that favor direct protonation of the metal center from an equatorial trajectory, subtle steric demands of the phosphine ligands play an important role in dictating whether a proton initially attacks the arene ligand or the metal of 1-5. The semiempirical PM3(tm) method may be used to map metal-based frontier orbitals of the complexes 1-5 onto plots of their surface electron densities, thereby revealing sterically accessible metal electron density. Such plots provide straightforward models that predict the mechanisms of protonation.

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Section: Discussionmentioning

confidence: 99%

Stereoelectronic Factors That Influence Kinetic and Thermodynamic Sites of Protonation of (η⁶-Arene)molybdenum(phosphine)₃Complexes

et al. 1999

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“…Compound, colour, and analysis (%) C,H4)]PF6, mixture of isomers (23) and (24, [Mo(q-C6H7)(dmpe)(PMe3)(v (27) [Mo( q-C,H ,)(dmpe)( PMe,)Me] + (29) [Mo(q-C,H 6E t-mdo)(dmpe),] PF, Orange C, 36.6 (37.0); H, 6.6 (6. PFfJ (32) [ Mo(dmpe),(q-C,H ,Me-2-Et-6-endo)] PF, (33) [Mo(dmpe),(q-C,H,Me-1 -Et-6-endo)]PF6 Orange C, 37.9 (38.…”

Section: Table I (Continued)mentioning

confidence: 99%

“…I ): H, 7.5 (6.9) N.m.r. data ('H, "C, and 'P) 7, PCH,], 1.65 [d, 3 H, J(P-H) 7.5, PCH,], 2.35 (m, 1 H, H'), 3.34 (9, 1 H, H'), 4.92 (br t, 1 H, H2), 5.05 (t, 1 H, H"), 6.05 (m, 1 H, H3); (24) (minor isomer), 0.88 [d, 3 H, J(P-H) 8, PCH,], 1.37 1.76 [d, 3 H, J(P-H) 8, PCH,], 2.23 (m, 1 H, H', H6, H7, or =CH2), 2.43 (d, 1 H, HI, H6, H7, or =CH2), 2.54 (br s, 1 H, H', H6, H7, or =CH2), 3.15 (4, 1 H, H5), 4.57 (br s, 1 H, H'), 5.38 (t, 1 H, H"), 5.72 (m, 1 H, H3)b*4 ,'Pat -35OC: (23), -3.79[dd,1 P,J(P-P)42.3,69.3],30.50[dd,lP,J(P-P)11.3,42.3],44.30 [d, 3 H, J(P-H) 7.5, PCH,], 1.51 [d, 3 H, J(P-H) 7, PCH,], 1.56 [d, 9 H, J(P-H) 8, P(CH,)J, [dd, 1 P, J(P-P) 69. 4,11.3]; (a), -12.92 [dd, 1 P, J(P-P) 70.7,33.6], 32.14 [dd, 1 P, J(P-P) 33.…”

Section: Table I (Continued)mentioning

confidence: 99%

“…4,11.3]; (a), -12.92 [dd, 1 P, J(P-P) 70.7,33.6], 32.14 [dd, 1 P, J(P-P) 33. 5, 25.33, 43.43 [dd, 1 P, J(P-P) 25.6, 71.01 Fully 'H-coupled 13C at -30 OC: (23), 26.9 [t, J(C-H) 131, C"], 32.0 [t, J(C-H) 155 CH,], 40.9 [Complex m, 12 H, P(CH,)J, 5.04 [d, 6 H, J(P-H) 3, C6H6Ib J'(P-H) 9, P(CH,),], 1.65 [vt, 6 H, J(P-H) 9, P(CH,),], 1.80-1.95 (m, 4 H, PCH2CH,P), 5.18 -0.29 [td, 3 H, J(P-H) 11.6 and 3, MoCH,], 1.53 [d, 9 H, J(P-H) 7, P(CH,),], 1 . 6 1 .…”

Section: Table I (Continued)mentioning

confidence: 99%

“…Yield 0.07 g, 55%. Format ion of [ 1,2-Bis( dime t hy1phosphino)e thane] (q -cyclehexadienyl)(q-ethylene)(trimethylphosphine)molybdenum Hexajluorophosphate, a Mixture of Conformational Isomers, (23) and (24).-A solution of compound (1) in C2H,]acetone (0.15 mol 1-I) was transferred to an n.m.r. sample tube, and chilled in liquid nitrogen.…”

Section: (Q -Et H Y1benzene)h Ydrido [O-phen Y Lenebis( Dime Thy Lars...mentioning

confidence: 99%

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Mechanism of the reaction of [Mo(η-C₆H₆)(Me₂PCH₂CH₂PMe₂)(η-C₂H₄)H]⁺with PMe₃giving [Mo(η-C₆H₅Et)(dmpe)(PMe₃)H]⁺: metal-to-ring migration of an ethyl group

Bunting¹,

Green²,

Newman³

1988

J. Chem. Soc., Dalton Trans.

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Non-S.I. units employed: eV z 1.60 x J, atm = 101 325 Pa. Results and DiscussionSynthesis of New Compounds.-The study of the mechanism of reaction ( 2 ) necessitated the synthesis of several new compounds which will be described before the mechanistic studies. The analytical, mass, n.m.r., and i.r. spectroscopic data which characterise the new compounds are given in Table 1. These data are not discussed further except where the interpretation is not straightforward. The structures proposed for the new compounds are shown in the Schemes 1 4 .The q-toluene analogue of (l), namely [Mo(q-c,H,Me)-(dmpe)(q-C2H4)H]PF,, (4), was prepared in 60% yield by reduction of [Mo(q-C,H, Me)(dmpe)(q-C,H,)] PF, using sodium amalgam in the presence of ethylene, followed by the addition of aqueous NH,PF,.Treatment of compound (1) with trimethyl phosphite, carbon monoxide, or isocyano-2,6-dimethylbenzene gives the compounds trans-[M~(q-C,H,)(drnpe)(P(oMe)~}H]PF,, (5), t~Uns-[MO(~-C,H,)(dmpe)(co)H]PF,, (6), and tranS-[MO(q-C,H,)(dmPe)(2,6-Me,C,H,NC)HIPF,, (7), respectively (See Scheme 2). The formation of (5) is discussed in more detail below.[Mo(q-C6H6)(dmpe)(q-C2H4)HIPF6

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A

1997

Reaktionen Der Organischen Chemie

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Über Aromatenkomplexe von Metallen, LXV. Die Isomerenverteilung bei der Friedel‐Crafts‐Acetylierung des π‐Toluol‐chrom‐tricarbonyls und des freien Toluols

Cited by 36 publications

References 17 publications

Stereoelectronic Factors That Influence Kinetic and Thermodynamic Sites of Protonation of (η⁶-Arene)molybdenum(phosphine)₃Complexes

Stereoelectronic Factors That Influence Kinetic and Thermodynamic Sites of Protonation of (η⁶-Arene)molybdenum(phosphine)₃Complexes

Mechanism of the reaction of [Mo(η-C₆H₆)(Me₂PCH₂CH₂PMe₂)(η-C₂H₄)H]⁺with PMe₃giving [Mo(η-C₆H₅Et)(dmpe)(PMe₃)H]⁺: metal-to-ring migration of an ethyl group

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Über Aromatenkomplexe von Metallen, LXV. Die Isomerenverteilung bei der Friedel‐Crafts‐Acetylierung des π‐Toluol‐chrom‐tricarbonyls und des freien Toluols

Cited by 36 publications

References 17 publications

Stereoelectronic Factors That Influence Kinetic and Thermodynamic Sites of Protonation of (η6-Arene)molybdenum(phosphine)3Complexes

Stereoelectronic Factors That Influence Kinetic and Thermodynamic Sites of Protonation of (η6-Arene)molybdenum(phosphine)3Complexes

Mechanism of the reaction of [Mo(η-C6H6)(Me2PCH2CH2PMe2)(η-C2H4)H]+with PMe3giving [Mo(η-C6H5Et)(dmpe)(PMe3)H]+: metal-to-ring migration of an ethyl group

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Stereoelectronic Factors That Influence Kinetic and Thermodynamic Sites of Protonation of (η⁶-Arene)molybdenum(phosphine)₃Complexes

Stereoelectronic Factors That Influence Kinetic and Thermodynamic Sites of Protonation of (η⁶-Arene)molybdenum(phosphine)₃Complexes

Mechanism of the reaction of [Mo(η-C₆H₆)(Me₂PCH₂CH₂PMe₂)(η-C₂H₄)H]⁺with PMe₃giving [Mo(η-C₆H₅Et)(dmpe)(PMe₃)H]⁺: metal-to-ring migration of an ethyl group