Reactivity by Design—Metallaoxetanes as Centerpieces in Reaction Development

Dauth, Alexander; Love, Jennifer A.

doi:10.1021/cr100388p

Cited by 47 publications

(72 citation statements)

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“…On the basis of our previous work in the field of Rh I (olefin) oxygenation reactions, [11] the most likely monooxygenated species in this mixture (NMR) are (different isomers of) the 2-metallaoxetane [12] species 3 a, its ring-closed analogue 3 b, and the allyl-b-alkyl-hydroxide species 3 c (Scheme 2). On the basis of our previous work in the field of Rh I (olefin) oxygenation reactions, [11] the most likely monooxygenated species in this mixture (NMR) are (different isomers of) the 2-metallaoxetane [12] species 3 a, its ring-closed analogue 3 b, and the allyl-b-alkyl-hydroxide species 3 c (Scheme 2).…”

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Stereospecific Carbene Polymerization with Oxygenated Rh(diene) Species

et al. 2012

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Stereospecific Carbene Polymerization with Oxygenated Rh(diene) Species

et al. 2012

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“…1 The classic example of a nickelaoxetane in the literature is a report by de Pasquale on the formation of cyclic carbonates from epoxides and CO 2 . 2 The nickelaoxetane is proposed to arise from the oxidative addition of nickel(0) to the epoxide.…”

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Synthesis of 2-Nickela(II)oxetanes from Nickel(0) and Epoxides: Structure, Reactivity, and a New Mechanism of Formation

et al. 2015

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2-Nickelaoxetanes have been frequently invoked as reactive intermediates in catalytic reactions of epoxides using nickel, but have never been isolated or experimentally observed in these transformations. Herein, we report the preparation of a series of well-defined nickelaoxetanes formed via the oxidative addition of nickel(0) with epoxides featuring ketones. The stereochemistry of the products is retained, which has not yet been reported for nickelaoxetanes. Theoretical calculations support a bimetallic ring-opening/closing pathway over a concerted oxidative addition. Initial reactivity studies of a nickelaoxetane demonstrated protonolysis, oxidatively induced reductive elimination, deoxygenation, and elimination reactions when treated with the appropriate reagents.

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“…9 Several metal-catalyzed reactions that are believed to proceed via 2-metallaoxetanes D3(formally) C− O activated epoxideshave been reported and we refer to a recent review for details. 10 The products of C−C activation, 3-platinaoxetanes F2, have been prepared independently on other routes. 11,12 Related reactions of strained alkanes, however, in particular of cyclopropanes, have been studied both experimentally and theoretically.…”

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Selective Carbon–Carbon Bond Activation of Oxirane by a Bisphosphine Pt(0) Complex—A Theoretical Study

et al. 2015

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Platinum(0) complexes with the chelate ligand bis(di-tert-butylphosphino)methane, t Bu 2 P-CH 2 -P t Bu 2 (dtbpm), generated in solution from appropriate precursors, are the only known transition metal species that selectively activate epoxides (oxiranes) by inserting the Pt fragment into their carbon−carbon bond. The mechanism of this unprecedented reaction is studied theoretically using the random phase approximation. We find that the reaction is kinetically controlled and is caused by the formation of a monocoordinate (dtbpm-κ 1 P)Pt(0) fragment rather than a (dtbpm-κ 2 P)Pt(0) chelate complex. Insertion into epoxide C−C bonds occurs without energy barrier. Conceivable competing reactions, oxirane C−O and C−H activation, both proceed via formation of a σ-complex, followed by small but significant barriers for insertion steps. A reversible formation of the σ-complexes would perfectly explain the observed reactivity. For an irreversible formation, we find that intramolecular rearrangement of these σ-complexes toward C− C activation products is faster than both C−O and C−H activation. In principle, the same reactivity should be expected for other monocoordinated platinum(0) phosphine complexes. However, only the specific properties of dtbpm cause the subsequent, rapid, and irreversible closing of the chelate ligand yielding stable, square-planar Pt(II) C−C activation products. ■ INTRODUCTIONPlatinum complexes with the small bite-angle, bulky, and very electron-rich ligand bis(di-tert-butylphosphino)methane t Bu 2 P-CH 2 -P t Bu 2 (dtbpm) show a unique reactivity toward epoxides: they selectively activate the C−C-bond. The stable neopentyl hydride complex (dtbpm-κ 2 P)Pt(Np)H (A2) reductively eliminates neopentane already under ambient conditions and reacts with various epoxides to the corresponding 3-platinaoxetanes F2 (see Scheme 1). 1−3 Kinetic measurements show 1 that the rate of these reactions corresponds precisely to that of a first-order elimination of neopentane from A2 both in absence and in the presence of epoxides and is practically independent of the solvent used (ΔG ‡ ≈ 100 kJ/mol). This suggests a two-step process where neopentane is first eliminated in the rate-determining step and the generated [(dtbpm)Pt(0)] fragment (C1 or C2) reacts with epoxides in a very fast consecutive step.Reactions with substituted epoxides of defined stereochemistry (cis-and rac-trans-2,3-dimethyloxirane) show that the reaction to the corresponding 3-platinaoxetanes F2 occurs under retention of stereochemistry. This excludes free rotation around the C−O bonds on the reaction itinerary, which one would expect for a nonconcerted insertion of the metal fragment into the C−C bond via radical or zwitterionic processes. From experimental evidence, one would therefore deduce a concerted mechanism. 1 The elimination of neopentane from (dtbpm-κ 2 P)Pt(Np)H (A2) in the absence of epoxides or other substrates occurs at approximately the same rate and results in dimerization of [(dtbpm)Pt(0)], giving a dtbpm-ligand bridged dinuclear...

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Reactivity by Design—Metallaoxetanes as Centerpieces in Reaction Development

Cited by 47 publications

References 343 publications

Stereospecific Carbene Polymerization with Oxygenated Rh(diene) Species

Stereospecific Carbene Polymerization with Oxygenated Rh(diene) Species

Synthesis of 2-Nickela(II)oxetanes from Nickel(0) and Epoxides: Structure, Reactivity, and a New Mechanism of Formation

Selective Carbon–Carbon Bond Activation of Oxirane by a Bisphosphine Pt(0) Complex—A Theoretical Study

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