Group 9 Metal–Metal Bonds

Chifotides, Helen T.; Saha, Barna; Patmore, Nathan J.; Dunbar, Kim R.; Bera, Jitendra K.

doi:10.1002/9783527673353.ch9

Cited by 11 publications

(19 citation statements)

References 185 publications

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“…0.1 Å in comparison to those observed for the PNpy ligands on metal dihalide complexes in Table . , This elongation is consistent with an η 2 -imine ligand where significant electron density is transferred from the metal center. , The Co–Co distances of ca. 2.9 Å are well above the range for bonding . The robustness of the dimers was further demonstrated by their nonreactivity toward PPh 3 , as monitored by 1 H and 31 P NMR spectroscopy over the course of 12 h.…”

Section: Resultsmentioning

confidence: 80%

Cobalt Phosphino-α-Iminopyridine-Catalyzed Hydrofunctionalization of Alkenes: Catalyst Development and Mechanistic Analysis

et al. 2016

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A family of CoCl2(PNpy) complexes were prepared, where PNpy = 2-iminopyridyl-phosphine ligands derived from aminoalkyl and aminoaryl phosphines and 2-keto- and 2-formylpyridines. Reduction of CoCl2(PNpy) complexes in the presence of PPh3 gave CoH(PNpy)(PPh3) and CoMe(PNpy)(PPh3), which were active for hydrofunctionalization of alkenes. According to DFT calculations, the CoMe(PNpy)(PPh3) complexes are best described as Co(II) derivatives of the anion [PNpy]−, with a labile PPh3 coligand. Metalation of Na[Ph2PC2NHpy] gave the dimers [CoCl(Ph2PC2NHpy)]2. Monomeric complexes catalyze hydrosilylation of 1-octene with Ph2SiH2, with the CoCl2(iPr2PC3NHpy)/2NaBEt3H system exhibiting the highest rate and selectivity for anti-Markovnikov product. In situ NMR studies established the following: (i) silanes protonolyze catalyst precursors to give the Co-silyl complexes Co(SiR3)(Ph2PC6H4NPhpy)(PPh3), (ii) alkenes compete with PPh3 to give Co(SiHPh2)(Ph2PC6H4NPhpy)(η2-alkene), (iii) ethylene inserts into the Co–Si bond to give Co(CH2CH2SiR3)(Ph2PC6H4NPhpy)(PPh3).

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Section: Resultsmentioning

confidence: 80%

Cobalt Phosphino-α-Iminopyridine-Catalyzed Hydrofunctionalization of Alkenes: Catalyst Development and Mechanistic Analysis

et al. 2016

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“…Dirhodium(II) complexes of the tetracarboxylate type have been widely utilized in the discovery and development of valuable synthetic methodologies. − Especially, dirhodium(II) complexes-catalyzed multicomponent reactions (MCRs) involving electrophilic trapping of metal-associated onium ylide intermediates generated in situ from metal carbenoids with various nucleophiles have emerged as a powerful protocol for construction of structurally complex and diverse molecules (Scheme a) . Trapping of onium ylides by nucleophilic addition to aldimines, carbonyls, activated alkenes (Michael acceptors) and so on, as well as a few examples via the formal S N 1 pathway, have been reported. − Despite the recent progress and the great significance of allylic group in organic synthesis, the introduction of allylic moiety as the third component through allylic metal intermediate remains a formidable challenge in dirhodium(II)-catalyzed MCRs (Scheme a).…”

Section: Introductionmentioning

confidence: 99%

Dirhodium(II)/Xantphos-Catalyzed Relay Carbene Insertion and Allylic Alkylation Process: Reaction Development and Mechanistic Insights

et al. 2021

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Although dirhodium-catalyzed multicomponent reactions of diazo compounds, nucleophiles and electrophiles have achieved great advance in organic synthesis, the introduction of allylic moiety as the third component via allylic metal intermediate remains a formidable challenge in this area. Herein, an attractive three-component reaction of readily accessible amines, diazo compounds, and allylic compounds enabled by a novel dirhodium(II)/Xantphos catalysis is disclosed, affording various architecturally complex and functionally diverse α-quaternary α-amino acid derivatives in good yields with high atom and step economy. Mechanistic studies indicate that the transformation is achieved through a relay dirhodium(II)-catalyzed carbene insertion and allylic alkylation process, in which the catalytic properties of dirhodium are effectively modified by the coordination with Xantphos, leading to good activity in the catalytic allylic alkylation process.

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“…Elementary oxidative addition and reductive elimination processes are more favored on a bimetallic platform than on a single-metal entity . Metal–metal singly bonded dirhodium(II,II) systems are the most prominent catalysts for a wide variety of organic reactions . Although the reactions almost exclusively take place at one of the axial sites, the second metal plays a significant role.…”

Section: Introductionmentioning

confidence: 99%

Acceptorless Dehydrogenation of Alcohols on a Diruthenium(II,II) Platform

et al. 2016

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The diruthenium(II,II) complex [Ru 2 (L 1 )(OAc) 3 ]Cl (1), spanned by a naphthyridine-diimine ligand and bridged by three acetates, has been synthesized. The catalytic efficacy of complex 1 has been evaluated for the acceptorless dehydrogenation (AD) of alcohols and for the dehydrogenative coupling reactions of alcohols with Wittig reagents. The diruthenium(II,II) complex is an excellent catalyst for AD of a diverse range of alcohols, and it is shown to be particularly effective for the conversion of primary alcohols to the corresponding aldehydes without undesired side products such as esters. Triphenylphosphonium ylides in a one-pot reaction with alcohols afforded the corresponding olefins in high yields with excellent E selectivity. The liberated dihydrogen gas was identified and measured to be 1 equiv with respect to alcohol. Deuteration studies with PhCD 2 OH revealed the absence of isotope scrambling in the product, indicating the involvement of a Ru-monohydride intermediate. Kinetic studies and DFT calculations suggest a low-energy bimetallic β-hydride elimination pathway where rate-limiting intramolecular proton transfer from alcohol to metal-bound hydride constitutes the dehydrogenation step. The general utility of metal−metal bonded compounds for alcohol AD and subsequent coupling reactions is demonstrated here.

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Group 9 Metal–Metal Bonds

Cited by 11 publications

References 185 publications

Cobalt Phosphino-α-Iminopyridine-Catalyzed Hydrofunctionalization of Alkenes: Catalyst Development and Mechanistic Analysis

Cobalt Phosphino-α-Iminopyridine-Catalyzed Hydrofunctionalization of Alkenes: Catalyst Development and Mechanistic Analysis

Dirhodium(II)/Xantphos-Catalyzed Relay Carbene Insertion and Allylic Alkylation Process: Reaction Development and Mechanistic Insights

Acceptorless Dehydrogenation of Alcohols on a Diruthenium(II,II) Platform

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