Group 2 Mediated Dehydrocoupling

Liptrot, David J.

doi:10.1007/978-3-319-21036-0

Cited by 4 publications

(4 citation statements)

References 40 publications

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“…After 3 h at 80 °C, ∼90% of 2a was transformed to a new species revealing a 31 P singlet at 62.3 ppm, which is very close to that of 3b , suggesting the formation of the nickel(II) phenyl product [(MesNH)SiP 2 ]Ni(Ph) ( 3a ; (MesNH)SiP 2 = [(2,4,6-Me 3 C 6 H 2 NH)Si(2-P i Pr 2 C 6 H 4 ) 2 ] − ). Several examples of transition-metal-mediated Si–N coupling were previously known in the literature; − however, non-dehydrogenative Si–N coupling is relatively unexplored, and such coupling generally utilizes silylenes. − Without utilizing silylenes, the Tobita group reported the insertion of pyridine into a Fe–Si bond. , The Wright group also reported the Si–N coupling of an aminopyridine and a chlorodiphenylsilyl anion in a ruthenium complex, followed by a subsequent formal HCl liberation . The Osakada group introduced nitriles to (Et 3 P) 2 Pt(μ-η 2 -SiHPh 2 )Pd(PEt 3 ) to generate a platinacyclopentane possessing both Si–N and Si–C bonds …”

Section: Resultsmentioning

confidence: 99%

A Silyl-Nickel Moiety as a Metal–Ligand Cooperative Site

Kim

Park

et al. 2019

Inorg. Chem.

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Nickel(II) complexes supported by a diphosphinosilyl ligand, [PhSi(2-P i Pr 2 C 6 H 4 ) 2 ] − (PhSiP 2 ), reveal unusual metal−ligand cooperativity (MLC). While (PhSiP 2 )-Ni(NHMes) (2a) was cleanly isolated at room temperature, a nickel triisopropylphenylamido species, (PhSiP 2 )Ni(NHTrip) (2b), slowly transformed into a nickel(II) phenyl species, [(ArNH)SiP 2 ]Ni(Ph) (3b), where (ArNH)SiP 2 − = [(NHTrip)Si(2-P i Pr 2 C 6 H 4 ) 2 ] − . The X-ray crystallographic data of 3b exhibit a Si−N bond generated from Si−N coupling between the silyl moiety and amino group, along with cleavage of a Si−C bond. Because substoichiometric amounts of π-acidic ligands, such as isocyanide, enhance the conversion rate of 2 to 3 (k obs = 0.28 vs 0.44 h −1 ), this reaction may involve reductive elimination (RE) and oxidative addition (OA) operating at the silyl-nickel moiety. This is further supported by the fact that the presence of excess π-acidic ligands results in the generation of demetalated ligands (ArNH)PhSiP 2 (4) having both Si−N and Si−Ph bonds and the nickel(0) species. Theoretical evaluations also agree on such a pathway. Interestingly, the reaction of a nickel phenyl species (3) with gaseous carbon dioxide (CO 2 (g)) produces a nickel(II) carbamato complex, (PhSiP 2 )Ni(OC(O)NHAr) (6), which may involve a RE−OA process occurring at a nickel center. Although 2 and 3 might be in equilibrium, the reaction of 3 with CO 2 does not follow this pathway. Instead, a CO 2 interaction induces RE at the silyl-nickel moiety, followed by amide group transfer, to give a carbamato product, 6, based on our experimental and theoretical evaluations. These results highly support that group transfer involving MLC can be managed via a RE−OA pathway at the silyl-nickel(II) moiety.

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Section: Resultsmentioning

confidence: 99%

A Silyl-Nickel Moiety as a Metal–Ligand Cooperative Site

Kim

Park

et al. 2019

Inorg. Chem.

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“…Activation of E−H bonds (E=H, C, Si, B) by transition metals attracts a high research interest and is an actively developing area related to main group elements, organometallic and catalytic chemistry . In particular, the Si−H bond activation catalyzed by transition metal, rare‐earth metal and alkaline‐earth complexes has extensively been investigated because of its importance for the protection of reactive functional groups . Recently, the catalytic metal‐free Si−H activation and hydrosilylation as well as dehydrocoupling under rather mild conditions have been reported.…”

Section: Introductionmentioning

confidence: 99%

Comprehensive Insight into the Hydrogen Bonding of Silanes

Voronova

Golub

Павлов

et al. 2018

Chemistry An Asian Journal

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The interaction of a set of mono-, di- and trisubstituted silanes with OH proton donors of different strength was studied by variable temperature (VT) FTIR and NMR spectroscopies at 190-298 K. Two competing sites of proton donors coordination: SiH and π-density of phenyl rings-are revealed for phenyl-containing silanes. The hydrogen bonds SiH⋅⋅⋅HO and OH⋅⋅⋅π(Ph) are of similar strength, but can be distinguished in the ν range: the ν vibrations appear at lower frequencies while OH⋅⋅⋅π(Ph) complexes give Si-H vibrations shifted to higher frequency. The calculations showed the manifold picture of the noncovalent interactions in hydrogen-bonded complexes of phenylsilanes. As OH⋅⋅⋅HSi bonds are weak, the other noncovalent interactions compete in the stabilization of the intermolecular complexes. Still, the structural and electronic parameters of "pure" DHB complexes of phenylsilanes are similar to those of Et SiH.

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“…7 Notably, Harder and co-workers realized that the silylamide group sufficiently stabilizes highly reducing calcium hydride clusters, 26 which partially rationalizes the high activity of {Ca[N(SiMe 3 ) 2 ] 2 } 2 for catalytic hydrogenation, 27−29 hydroelementation, 30,31 and dehydrocoupling reactions. 5,32,33 The rich coordination chemistry of {Ca[N(SiMe 3 ) 2 ] 2 } 2 and its derivatives has been extensively studied using multidentate anionic spectator ligands (e.g., β-diketiminates), with illuminating insights into their bonding and reactivities. 24,34−41 isolation of highly reactive molecular calcium hydrides, 3,42 alkyls, 43,44 aryls, 45 and low-valent complexes.…”

Section: ■ Introductionmentioning

confidence: 99%

“…As a synthon, {Ca[N(SiMe 3 ) 2 ] 2 } 2 has enabled access to diverse organocalcium reagents, including the modestly ether-stable dimethylcalcium whose difficult synthesis and purification puzzled organometallic chemists for more than six decades . Notably, Harder and co-workers realized that the silylamide group sufficiently stabilizes highly reducing calcium hydride clusters, which partially rationalizes the high activity of {Ca[N(SiMe 3 ) 2 ] 2 } 2 for catalytic hydrogenation, − hydroelementation, , and dehydrocoupling reactions. ,, …”

Section: Introductionmentioning

confidence: 99%

Carbene–Calcium Silylamides and Amidoboranes

et al. 2022

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The stereoelectronic effects of N-heterocyclic carbene (NHC) and cyclic(alkyl)(amino) carbene (CAAC) coordination to calcium silylamides and amidoboranes have been investigated. The straightforward complexation of a sterically unencumbered NHC (i.e., N,N′-diisopropyl-2,3-dimethylimidazol-2-ylidine) and {Ca[N(SiMe3)2]2}2 or (THF)2Ca[N(SiMe3)2]2 in equimolar amounts afforded (NHC)Ca[N(SiMe3)2]2 (2) or (NHC)(THF)Ca[N(SiMe3)2]2 (4), respectively. Spectroscopic analyses reveal negligible electronic differences in 2 and 4, and the latter can be desolvated under prolonged vacuum. Similarly, CAAC complexation to {Ca[N(SiMe3)2]2}2 afforded (CAAC)Ca[N(SiMe3)2]2 (5) as the first crystallographically characterized CAAC–Ca coordination complex, but this compound is thermally unstable and rapidly decomposes to intractable mixtures. The reaction of {Ca[N(SiMe3)2]2}2 and HNMe2BH3 afforded the bis(amidoborane) [Ca(NMe2BH3)2] n (6), which does not react with bulky carbenes but readily complexes with unencumbered NHCs with subsequent non-innocent participations in calcium-mediated amine borane dehydrocoupling. Significantly, (NHC)2Ca(NMe2BH3)2 (7) decomposes under mild heating (50 °C, 16 h) to form [CaH2] n and the hydride-rich complex [(NHC–BH2NMe2)Ca(NMe2BH3)2]2 (8). Compound 8 was independently prepared from the reaction of 6 and NHC–BH2NMe2 and is remarkably thermally stable in refluxing benzene (85 °C, 24 h). In the absence of carbenes, the dehydrocoupling of 6 and HNMe2BH3 afforded (THF)2Ca(NMe2BH3)(NMe2BH2NMe2BH3) (9), but subsequent reactions with NHC resulted in the immediate abstraction and migration of Me2NBH2 toward the formation of 8.

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Group 2 Mediated Dehydrocoupling

Cited by 4 publications

References 40 publications

A Silyl-Nickel Moiety as a Metal–Ligand Cooperative Site

A Silyl-Nickel Moiety as a Metal–Ligand Cooperative Site

Comprehensive Insight into the Hydrogen Bonding of Silanes

Carbene–Calcium Silylamides and Amidoboranes

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