Methylation of zinc(II), cadmium(II), and lead(II) by a trans-dimethylcobalt complex

Witman, Mark W.; Weber, James H.

doi:10.1021/ic50164a012

Cited by 21 publications

(7 citation statements)

References 2 publications

(2 reference statements)

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“…6 Similar alkyl transmetallations have been reported in non-catalytic systems between alkyl−Co(dmgBF 2 ) 2 Py and inorganic nickel, 8 and proposed for bioorganometallic 9 and catalytic processes. 10 This alkyl transfer does not appear limited to nickel: vitamin B12-mimetics (such as Co(salen) derivatives) can undergo alkyl transfer to palladium, 11 rhodium, 12 other cobalt, 13 platinum, 14 gold, 15 chromium, 16 and zinc 17 salts and organometallic species. Yet despite the apparent generality of this transformation, there is a paucity of preparative cross-coupling methods that leverage this reactivity.…”

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confidence: 99%

Branch-Selective Addition of Unactivated Olefins into Imines and Aldehydes

et al. 2018

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Radical hydrofunctionalization occurs with ease using metal-hydride atom transfer (MHAT) catalysis to couple alkenes and competent radicalophilic electrophiles. Traditional two-electron electrophiles have remained unreactive. Herein we report the reductive coupling of electronically-unbiased olefins with imines and aldehydes. Iron-catalysis allows addition of alkyl-substituted olefins into imines through the intermediacy of free-radicals, whereas a combination of catalytic Co(Salt-Bu,t-Bu) and chromium salts enable a branch-selective coupling of olefins and aldehydes through the formation of a putative alkyl chromium intermediate.

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confidence: 99%

Branch-Selective Addition of Unactivated Olefins into Imines and Aldehydes

et al. 2018

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“…Analogous precipitates were not observed in the reaction of CH3Co(BDM 1,3pn)+ and Pb2+ or in the 1:1 anaerobic reaction of I and Pb2+. 18 This precludes the presence of 1:1 lead-complex adducts that have been observed in the reactions of RCo(chel) with excess Hg2+.10 Nevertheless, the titration data (Figure 2), the methane evoution profile (Figure 5), and the formation of CH4 upon the dissolution of the precipitate in H30+ strongly suggest that CH3Pb(z'-C3H70) is at least a major product of the reaction.…”

Section: Resultsmentioning

confidence: 99%

“…In a recent paper we described the results of a detailed study on the 1:1 reactions of I with Zn2+, Cd2+, and Pb2+ in i-C3H7OH. 18 We reported that I reacts nearly instantaneously with a stoichiometric amount of all three metal ions to give quantitative yields of the corresponding monomethylcobalt derivative, CH3Co(BDM 1,3pn)+, and surprisingly stable organometallic products of the type CH3M+ (eq 2). These fast (CH3)2Co(BDMl,3pn) + M2t-> CH3Co(BDMl,3pn)+ + CH3M+ (2) Despite the ready cleavage of the Co-C bond by Hg2+, Cr2+, and Tl3+ a surprising number of other electrophilic reagents including H30+, CH3Hg+, Zn2+, Cd2+, Pb2+, and Al3+ are unreactive toward monoalkylcobalt chelates.14 Consequently, we became interested in studying the reactions of the trans-dimethyl complex (CH3)2Co(BDM 1,3pn) (structure I)…”

Section: Introductionmentioning

confidence: 99%

Formation of transient dimethylzinc, dimethylcadmium, and dimethyllead species via methylation of zinc(2+), cadmium(2+), and lead(2+) by a trans-dimethylcobalt complex

Witman¹,

Weber²

1977

Inorg. Chem.

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The methylation reactions in ¡'-C3H7OH of Zn2+, Cd2+, and Pb2+ by an excess of the PYm-dimethylcobalt complex, (CH3)2Co(BDMl,3pn), are discussed. (BDMl,3pn is a mononegative, tetradentate dioxime diimine ligand formed by the condensation of 2 mol of 2,3-butanedione and 1 mol of 1,3-propanediamine.) With a 2:1 complexmetal ratio a very rapid reaction forms CH3Co(BDM 1,3pn)+ and CH3M+ (M2+ = Zn2+, Cd2+, and Pb2+). Then in a slower reaction CH3M+ reacts with a second mole of (CH3)2Co(BDM 1,3pn) to form unstable (CH3)2M species. These compounds rapidly react yielding CH4 and a variety of nonvolatile products such as [CH3Cd(i-C3H70)]4. The progress of the reactions was followed by the absorbance decrease of (CH3)2Co(BDMl,3pn) and a GC analysis of CH4.

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“…The overall second-order rate constant, kK, for protonation and release of methane in trans-[(CH 3 ) 2 Co((DO)(DOH)pn)] is 68 M -1 s -1 (see Table 2), in satisfactory agreement with the previously reported value of 40 M -1 s -1 at 25 • C and 0.10 M (LiClO 4 ) ionic strength. 31 The curvature in Fig. 5 is too small to allow a detailed study of the temperature and pressure dependence of both K and k. We, therefore, selected a low [H + ] (≤ 0.025 M) where eqn (9) reduces to k obs = kK[H + ], to study the temperature and pressure dependence of the overall second-order rate constant (see Table 2).…”

Section: R Co Hdmgmentioning

confidence: 99%

Mechanistic behaviour of alkylcobaloximes and imino-oxime complexes related to vitamin B12

et al. 2009

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The ligand substitution reactions of complexes of the type trans-[(R)Co(Chel)S](+/0) with L, where chel = (DO)(DOH)pn = 2,2'-(1,3-diaminopropanebis(2-methyl-3-butanone)oxime), R = CH(3), L = imidazole, pyrazole, 1,2,4-triazole and 1-methylimidazole, and S = water and MeOH, and chel = (Hdmg)(2) = bis(dimethylglyoximate), R = CH(2)Cl, CH(2)Br, and CH(2)I, L = thiourea and pyridine, and S = water, were studied in detail as a function of temperature and pressure. The reported activation parameters (DeltaH, DeltaS and DeltaV) support the operation of a dissociative interchange (I(d)) mechanism. Complexes of the type trans-[RCo(Hdmg)(2)L] (R = CH(2)Cl, CH(2)Br, and CH(2)I; L = H(2)O and Py) were fully optimized at the B3LYP/LANL2DZp level, and the structural data support the mechanistic assignment based on the reported activation parameters. For the reaction of trans-[(CH(3))(2)Co((DO)(DOH)pn)] with acid, the activation parameters (DeltaH, DeltaS and DeltaV) were found to be 37 +/- 1 kJ mol(-1), -86 +/- 3 J mol(-1) K(-1) and -18.9 +/- 0.7 cm(3) mol(-1), respectively, and support a protonation mechanism.

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Methylation of zinc(II), cadmium(II), and lead(II) by a trans-dimethylcobalt complex

Cited by 21 publications

References 2 publications

Branch-Selective Addition of Unactivated Olefins into Imines and Aldehydes

Branch-Selective Addition of Unactivated Olefins into Imines and Aldehydes

Formation of transient dimethylzinc, dimethylcadmium, and dimethyllead species via methylation of zinc(2+), cadmium(2+), and lead(2+) by a trans-dimethylcobalt complex

Mechanistic behaviour of alkylcobaloximes and imino-oxime complexes related to vitamin B12

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