Hetero-dehydrocoupling of silanes and amines by heavier alkaline earth catalysis

Hill, Michael S.; Liptrot, David J.; MacDougall, Dugald J.; Mahon, Mary F.; Robinson, Thomas

doi:10.1039/c3sc51797g

Cited by 106 publications

(107 citation statements)

References 82 publications

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“…This dehydrocoupling mechanism is reminiscent of that described for analogous B(C 6 F 5 ) 3 catalyzed reaction in the classic work from Piers and coworkers (29), which subsequently further illuminated and expanded by the groups of Oestreich (30), Brook (31), Rubinsztajn (32), and Paradies (33). In the context of dehydrocoupling, it is also important to note the pioneering work from the Tilley and Manners research groups, who exploited transition metal catalysts for this purpose (34,35), whereas Hill et al (36) described Zn, Mg, Ca, and Sr catalyzed preparations of amino silanes and Baba and coworker (37) have used InBr 3 to dehydrocouple silanes and carboxylic acids (Table 1 and Fig. 1).…”

Section: Resultsmentioning

confidence: 99%

Metal-free transfer hydrogenation of olefins via dehydrocoupling catalysis

Pérez

Caputo

Dobrovetsky

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

145

111

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A major advance in main-group chemistry in recent years has been the emergence of the reactivity of main-group species that mimics that of transition metal complexes. In this report, the Lewis acidic phosphonium salt [(C 6 F 5 ) 3 PF][B(C 6 F 5 ) 4 ] 1 is shown to catalyze the dehydrocoupling of silanes with amines, thiols, phenols, and carboxylic acids to form the Si-E bond (E = N, S, O) with the liberation of H 2 (21 examples). This catalysis, when performed in the presence of a series of olefins, yields the concurrent formation of the products of dehydrocoupling and transfer hydrogenation of the olefin (30 examples). This reactivity provides a strategy for metalfree catalysis of olefin hydrogenations. The mechanisms for both catalytic reactions are proposed and supported by experiment and density functional theory calculations. fluorophosphonium A wide range of commodity chemicals, petrochemicals, pharmaceuticals, materials, and foods depend on industrial-scale hydrogenation reactions. Catalysts for this process are based on both heterogeneous transition metals materials and homogeneous transition metal complexes. Indeed, it was the discovery of Sabatier (1) in the early 20th century that revealed the utility of amorphous Ni and other metals in hydrogenation processes. Following the dawn of organometallic chemistry in the 1960s, homogeneous catalysts were developed principally based on precious metals (2-4). Although subsequent modifications and optimizations have led to numerous highly selective and efficient catalyst technologies, concerns over cost, natural abundance, and toxicity have prompted efforts to uncover catalysts based on "earth-abundant" elements. The principal targets in these efforts have been the first-row transition metals. Indeed, the groups of Chirik (5, 6), Morris (7), Beller (8), and others (9) have developed remarkably active and selective catalysts based on Fe.Strategies to develop reduction methods using organic or main-group-based reagents have also been explored. For example, use of Hantzsch esters (10), Birch reduction of arenes (11), or the use of B or Al hydrides are effective, albeit stoichiometric reductions. More recently, the advent of "frustrated Lewis pairs" (FLPs) have led to the discovery that combinations of sterically encumbered donors and acceptors act as catalysts for the reductions of imines, enamines, silylenol ethers, olefins, and alkynes (12).To uncover hydrogenation strategies using earth-abundant elements, we have focused our efforts on Lewis acidic phosphorus species. Although Gudat (13), Burford and coworker (14), Yoshifuji (15), and Bertrand and coworker (16), among others, have reported phosphenium cations that demonstrate Lewis acidity, Radosevich and coworkers (17) have exploited the reaction of the unique planar P(III) species with ammoniaborane to give a P(V)H 2 derivative that effects the subsequent reduction of diazobenzene. Although the acidity of P(V) has been exploited previously in ylide reagents (18), Diels-Alder reactions catalysis (19), and add...

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Section: Resultsmentioning

confidence: 99%

Metal-free transfer hydrogenation of olefins via dehydrocoupling catalysis

Pérez

Caputo

Dobrovetsky

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

145

111

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“…[9,10] Conscious efforts have been made to obtain aw ide variety of composition and nuclearity ranging from mononuclear terminal hydrides [10e,g,-j,u,w] to clusters. [10t] Apart from being models for hydrogen-storage materials,s ome of the hydrides have been identified as key intermediates in catalytic reactions,s uch as hydroboration, [10m, 11] hydrosilylation, [12] CO homologation, [12c,d] and dehydrogenative coupling between amine and hydroborane, [13] amine and hydrosilane, [14] and TEMPO and hydrosilane. [10t] Apart from being models for hydrogen-storage materials,s ome of the hydrides have been identified as key intermediates in catalytic reactions,s uch as hydroboration, [10m, 11] hydrosilylation, [12] CO homologation, [12c,d] and dehydrogenative coupling between amine and hydroborane, [13] amine and hydrosilane, [14] and TEMPO and hydrosilane.…”

Section: Scopementioning

confidence: 99%

Molecular Magnesium Hydrides

2017

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Solid magnesium hydride [MgH ] has been pursued as a potential hydrogen-storage material. Organic chemists were rather interested in soluble magnesium hydride reagents from mid-20th century. It was only in the last two decades that molecular magnesium hydride chemistry received a major boost from organometallic chemists with a series of structurally well-characterized examples that continues to build a whole new class of compounds. More than 40 such species have been isolated, ranging from mononuclear terminal hydrides to large hydride clusters with more than 10 magnesium atoms. They provide not only insights into the structure and bonding of Mg-H motifs, but also serve as models for hydrogen-storage materials. Some of them are also recognized to participate in catalytic transformations, such as hydroelementation. Herein, an overview of these molecular magnesium hydrides is given, focusing on their synthesis and structural characterization.

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“…[10] Elsewhere,w ea nd others have shown that oxophilic,d 0 metal complexes provide competent precatalysts to dehydrocouple hydrosilanes and amines. [11][12][13][14] Barium compounds in particular catalyze the coupling of diamines and di(hydrosilanes). [14a,b] We present here an extension of this work to the barium-mediated production of polycarbosilazanes.T he rapid and controlled syntheses of either linear or cyclic polymers by dehydropolymerization of p-xylylenediamine (represented as H 2 N^^NH 2 )a nd diphenylsilane, together with detailed characterizations,a re reported (Scheme 1).…”

mentioning

confidence: 99%

Tailored Cyclic and Linear Polycarbosilazanes by Barium‐Catalyzed N−H/H−Si Dehydrocoupling Reactions

et al. 2016

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Ba[CH(SiMe3 )2 ]2 (THF)3 catalyzes the fast and controlled dehydrogenative polymerization of Ph2 SiH2 and p-xylylenediamine to afford polycarbosilazanes. The structure (cyclic versus linear; end-groups) and molecular weight of the macromolecules can be tuned by adjusting the Ph2 SiH2 /diamine feed ratio. A detailed analysis of the resulting materials (mol. wt up to ca. 10 000 g mol(-1) ) is provided.

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Hetero-dehydrocoupling of silanes and amines by heavier alkaline earth catalysis

Cited by 106 publications

References 82 publications

Metal-free transfer hydrogenation of olefins via dehydrocoupling catalysis

Metal-free transfer hydrogenation of olefins via dehydrocoupling catalysis

Molecular Magnesium Hydrides

Tailored Cyclic and Linear Polycarbosilazanes by Barium‐Catalyzed N−H/H−Si Dehydrocoupling Reactions

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