Imido–hydrido complexes of Mo(IV): catalysis and mechanistic aspects of hydroboration reactions

Imido–hydrido complexes (ArN)Mo(H)(Cl)(PMe3)3 (1) and (ArN)Mo(H)2(PMe3)3 (2) (Ar = 2,6-diisopropylphenyl) catalyse a variety of hydroboration reactions, including the rare examples of addition of HBCat to nitriles to form bis(borylated) amines RCH2N(BCat)2. Stoichiometric reactivity of complexes 1 and 2 with nitriles and HBCat suggest that catalytic reactions proceed via a series of agostic borylamido and borylamino complexes. For complex 1, catalysis starts with addition of nitriles across the Mo–H bond to give (ArN)Mo(Cl)(NvCHR)(PMe3)2; whereas for complex 2 stoichiometric reactions suggest initial addition of HBCat to form the agostic complex Mo(H)2(PMe3)3(η3-NAr-HBcat

Catalytic hydroboration by an imido-hydrido complex of Mo(IV)

The imido-hydrido complex (ArN)Mo(H)(Cl)(PMe3)3 catalyses a variety of hydroboration reactions, including the first example of catalytic addition of HBCat to nitriles to form the bis(borylated) amines RCH2N(BCat)2. The latter species easily undergoes chemoselective coupling with aldehydes R0C(O)H to yield imines RCH2NQC(H)R

Catalytic hydroboration by an imido-hydrido complex of Mo(IV)

The imido-hydrido complex (ArN)Mo(H)(Cl)(PMe3)3 catalyses a variety of hydroboration reactions, including the first example of catalytic addition of HBCat to nitriles to form the bis(borylated) amines RCH2N(BCat)2. The latter species easily undergoes chemoselective coupling with aldehydes R0C(O)H to yield imines RCH2NQC(H)R

Multiple coupling of silanes with imido complexes of Mo

The bis(imido) complexes (tBuNv)2Mo(PMe3)(L) (L = PMe3, C2H4) react with up to three equivalents of silane PhSiH3 to give the imido-bridged disilyl silyl Mo(VI) complex (tBuN){μ-tBuN(SiHPh)2}Mo(H)(SiH2Ph)- (PMe3)2 (3) studied by NMR, IR and X-ray diffraction. NMR data supported by DFT calculations show that complex 3 is an unusual example of a silyl hydride of Mo(VI), without significant Si⋯H interaction. Mechanistic NMR studies revealed that silane addition proceeds in a stepwise manner via a series of Si–H⋯M agostic and silanimine complexes whose structures were further elucidated by DFT calculation

Multiple coupling of silanes with imido complexes of Mo

The bis(imido) complexes (tBuNv)2Mo(PMe3)(L) (L = PMe3, C2H4) react with up to three equivalents of silane PhSiH3 to give the imido-bridged disilyl silyl Mo(VI) complex (tBuN){μ-tBuN(SiHPh)2}Mo(H)(SiH2Ph)- (PMe3)2 (3) studied by NMR, IR and X-ray diffraction. NMR data supported by DFT calculations show that complex 3 is an unusual example of a silyl hydride of Mo(VI), without significant Si⋯H interaction. Mechanistic NMR studies revealed that silane addition proceeds in a stepwise manner via a series of Si–H⋯M agostic and silanimine complexes whose structures were further elucidated by DFT calculation

Hydrodefluorination of Fluoroaromatics by Isopropyl Alcohol Catalyzed by a Ruthenium NHC Complex. An Unusual Role of the Carbene Ligand

The NHC (NHC = N-heterocyclic carbene) complex Cp*­(IPr)­RuH₃ catalyzes hydrodefluorination of aromatic fluorides at 70 °C with isopropyl alcohol as the reducing reagent. The reaction is selective for aromatic fluorides, as almost negligible C­(sp³)–F bond reduction takes place. The activity decreases from more to less fluorinated substrates, but polyaromatic monofluorides, such as 1-fluoronaphthalene and 6-fluoro-2-methylquinoline, can also be reduced in moderate to good yields. Kinetic studies are consistent with a mechanism based on elimination of NHC and reversible substrate coordination, followed by coordination of the alcohol