Disilaferracycle Dicarbonyl Complex Containing Weakly Coordinated η²‑(H-Si) Ligands: Application to C–H Functionalization of Indoles and Arenes

Well-defined iron complex-mediated catalytic C-3-selective silylation of indole derivatives and stoichiometric C–H bond functionalization of arenes were achieved using an iron dicarbonyl complex containing the disilaferracycle moiety [<i>o</i>-(SiMe₂)₂C₆H₄]­Fe­(CO)₂­[<i>o</i>-{η²-(H-SiMe₂)₂}­C₆H₄] (<b>1</b>). Facile liberation of the η²-(H-Si) groups in <b>1</b> was the key to effective promotion of these reactions

Disilametallacycles as a Platform for Stabilizing M(II) and M(IV) (M = Fe, Ru) Centers: Synthesis and Characterization of Half-Sandwich Complexes and Their Application to Catalytic Double Silylation of Alkenes and Alkynes

A series of group 8 half-sandwich disilametallacycles, (η⁶-arene)­M^II(Me₂SiC₆H₄SiMe₂)­L and (η⁶-arene)­M^IV(H)₂(Me₂SiC₆H₄SiMe₂) (M = Fe, Ru) in the formal oxidation states of M­(II) and M­(IV) were synthesized and characterized. Both the M­(II) and the M­(IV) oxidation states were effectively stabilized by the disilametallacycle skeleton, and facile interconversion between (η⁶-arene)­M^II–dinitrogen, (η⁶-arene)­M^II–carbonyl, and (η⁶-arene)­M^IV–dihydride complexes bearing a disilaferracycle framework was accomplished. These M­(II) and M­(IV) complexes can easily generate coordinatively unsaturated 16e disilametallacycles, (η⁶-arene)­M^II(Me₂SiC₆H₄SiMe₂), by dissociation of L or H₂, and stoichiometric and/or catalytic double silylation of alkenes and alkynes was realized thorough this 16e intermediate

Disilametallacycles as a Platform for Stabilizing M(II) and M(IV) (M = Fe, Ru) Centers: Synthesis and Characterization of Half-Sandwich Complexes and Their Application to Catalytic Double Silylation of Alkenes and Alkynes

A series of group 8 half-sandwich disilametallacycles, (η⁶-arene)­M^II(Me₂SiC₆H₄SiMe₂)­L and (η⁶-arene)­M^IV(H)₂(Me₂SiC₆H₄SiMe₂) (M = Fe, Ru) in the formal oxidation states of M­(II) and M­(IV) were synthesized and characterized. Both the M­(II) and the M­(IV) oxidation states were effectively stabilized by the disilametallacycle skeleton, and facile interconversion between (η⁶-arene)­M^II–dinitrogen, (η⁶-arene)­M^II–carbonyl, and (η⁶-arene)­M^IV–dihydride complexes bearing a disilaferracycle framework was accomplished. These M­(II) and M­(IV) complexes can easily generate coordinatively unsaturated 16e disilametallacycles, (η⁶-arene)­M^II(Me₂SiC₆H₄SiMe₂), by dissociation of L or H₂, and stoichiometric and/or catalytic double silylation of alkenes and alkynes was realized thorough this 16e intermediate

Disilametallacycles as a Platform for Stabilizing M(II) and M(IV) (M = Fe, Ru) Centers: Synthesis and Characterization of Half-Sandwich Complexes and Their Application to Catalytic Double Silylation of Alkenes and Alkynes

A series of group 8 half-sandwich disilametallacycles, (η⁶-arene)­M^II(Me₂SiC₆H₄SiMe₂)­L and (η⁶-arene)­M^IV(H)₂(Me₂SiC₆H₄SiMe₂) (M = Fe, Ru) in the formal oxidation states of M­(II) and M­(IV) were synthesized and characterized. Both the M­(II) and the M­(IV) oxidation states were effectively stabilized by the disilametallacycle skeleton, and facile interconversion between (η⁶-arene)­M^II–dinitrogen, (η⁶-arene)­M^II–carbonyl, and (η⁶-arene)­M^IV–dihydride complexes bearing a disilaferracycle framework was accomplished. These M­(II) and M­(IV) complexes can easily generate coordinatively unsaturated 16e disilametallacycles, (η⁶-arene)­M^II(Me₂SiC₆H₄SiMe₂), by dissociation of L or H₂, and stoichiometric and/or catalytic double silylation of alkenes and alkynes was realized thorough this 16e intermediate

Disilametallacycles as a Platform for Stabilizing M(II) and M(IV) (M = Fe, Ru) Centers: Synthesis and Characterization of Half-Sandwich Complexes and Their Application to Catalytic Double Silylation of Alkenes and Alkynes

A series of group 8 half-sandwich disilametallacycles, (η⁶-arene)­M^II(Me₂SiC₆H₄SiMe₂)­L and (η⁶-arene)­M^IV(H)₂(Me₂SiC₆H₄SiMe₂) (M = Fe, Ru) in the formal oxidation states of M­(II) and M­(IV) were synthesized and characterized. Both the M­(II) and the M­(IV) oxidation states were effectively stabilized by the disilametallacycle skeleton, and facile interconversion between (η⁶-arene)­M^II–dinitrogen, (η⁶-arene)­M^II–carbonyl, and (η⁶-arene)­M^IV–dihydride complexes bearing a disilaferracycle framework was accomplished. These M­(II) and M­(IV) complexes can easily generate coordinatively unsaturated 16e disilametallacycles, (η⁶-arene)­M^II(Me₂SiC₆H₄SiMe₂), by dissociation of L or H₂, and stoichiometric and/or catalytic double silylation of alkenes and alkynes was realized thorough this 16e intermediate

Non-Precious-Metal Catalytic Systems Involving Iron or Cobalt Carboxylates and Alkyl Isocyanides for Hydrosilylation of Alkenes with Hydrosiloxanes

A mixture of an iron or a cobalt carboxylate and an isocyanide ligand catalyzed the hydro­silylation of alkenes with hydro­siloxanes with high efficiency (TON >10³) and high selectivity. The Fe catalyst showed excellent activity for hydro­silylation of styrene derivatives, whereas the Co catalyst was widely effective in reaction of alkenes. Both of them catalyzed the reaction with allylic ethers. Chemical modification and cross-linking of silicones were achieved by choosing the right catalyst and reaction conditions

Radical-Organometallic Hybrid Reaction System Enabling Couplings between Tertiary-Alkyl Groups and 1‑Alkenyl Groups

Suzuki–Miyaura couplings of tertiary-alkyl moieties are accomplished in the presence of a copper catalyst, in which quaternary carbons possessing various functional groups can be synthesized via a radical reaction. Mechanistic studies revealed that 1-alkenylcopper^I plays an important role in this coupling reaction. We expect that the radical-organometallic combined process will become one of the best options for the synthesis of quaternary carbons

Combinatorial Approach to the Catalytic Hydrosilylation of Styrene Derivatives: Catalyst Systems Composed of Organoiron(0) or (II) Precursors and Isocyanides

(COT)₂Fe and the open ferrocenes (MPDE)₂Fe (MPDE = η⁵-3-methylpentadienyl) and (DMPDE)₂Fe (DMPDE = η⁵-2,4-dimethylpentadienyl) were found to function as catalyst precursors for the hydrosilylation of alkenes in the presence of auxiliary ligands. Screening trials determined that the optimal catalyst system was composed of (COT)₂Fe and adamantyl isocyanide, allowing the selective hydrosilylation of styrene derivatives with trisubstituted hydrosiloxanes and a polydimethylsiloxane bearing Me₂SiH moieties as the end groups. Under the appropriate conditions, the dehydrogenative silylation side reaction was completely suppressed, and the reaction TON exceeded 5000

Syntheses of Substituted 1,4-Disila-2,5-cyclohexadienes from Cyclic Hexasilane Si₆Me₁₂ and Alkynes via Successive Si–Si Bond Activation by Pd/Isocyanide Catalysts

Palladium-catalyzed reactions of dodecamethylcyclohexasilane [(SiMe₂)₆] (<b>1</b>) with alkynes led to efficient preparation of 1,1,4,4-tetramethyl-1,4-disilacyclohexadienes (<b>3</b>). The reactions were best catalyzed by Pd(0) species generated from Pd₂(dba)₃·CHCl₃ and 1-isocyanoadamantane (AdNC). Terminal and internal alkynes bearing aryl and alkyl substituents could be used as substrates, and the reaction allowed gram-scale preparation of <b>3</b>. A dimethylsilylene (Me₂Si:) species, generated by activation of Si–Si bonds in <b>1</b> by Pd(0) species, was involved in the reaction mechanism. The DFT calculations suggest that oxidative addition of Si–Si bonds in <b>1</b> to Pd­(CNAd)₂ species is followed by extrusion of a Me₂SiPd­(CNAd) intermediate. Reaction of the resulting palladium-coordinated silylene with an alkyne forms a silacyclopropene, which dimerizes to give <b>3</b>. The extrusion is accompanied by ring contraction of <b>1</b> to generate (SiMe₂)₅, which also contributes to formation of <b>3</b> and (SiMe₂)₄ by the Pd(0)-catalyzed reaction with an alkyne. Extrusion of Me₂SiPd­(CNAd) and ring contraction generated more than five Me₂Si: species from (SiMe₂)₆ (<b>1</b>)

Theoretical Study of the Catalytic Hydrogenation of Alkenes by a Disilaferracyclic Complex: Can the Fe–Si σ‑Bond-Assisted Activation of H–H Bonds Allow Development of a Catalysis of Iron?

The mechanisms associated with the hydrogenation of alkenes catalyzed by the iron complex Fe­(<i>cis</i>-CO)₂{<i>o</i>-(SiMe₂)₂C₆H₄}₂(H)₂ (<b>1</b>) were investigated by DFT calculations. The complex <b>1</b> has a structure in which the iron center is bonded to four silicon atoms and two hydrides. Secondary Si···H···Si interactions were also observed. The exchange of a 1,2-bis­(dimethylsilyl)­benzene ligand with ethylene and hydrogen gives a disilaferracycle bearing η²-(CH₂CH₂) and η²-H₂ ligands. The catalytic cycle initiated from the disilaferracycle involves cleavage of a H–H linkage assisted by an Fe–Si bond to form Fe–H and η¹-(H–Si) moieties (step 1), hydrogen migration from the Fe–H group to the η²-(CH₂CH₂) ligand which accomplishes the insertion of ethylene into the Fe–H bond (step 2), and reaction of the resulting β-agostic ethyl moiety with the η²-(H–Si) group to form ethane on the iron atom (step 3). The octahedral geometry of <b>1</b> as well as the presence of π-acidic CO ligands and Fe–Si σ-bonds contributes to all of the catalytic intermediates and the transition states being in the low-spin state. Steps 1 and 3 correspond to the σ-complex-assisted metathesis (σ-CAM) mechanisms proposed by Perutz and Sabo-Etienne, suggesting that these mechanisms can assist in the design of iron-based hydrogenation catalysts operating under mild conditions