11 research outputs found
Heterobimetallic rutheniumâzinc complexes with bulky N-heterocyclic carbenes: syntheses, structures and reactivity
The rutheniumâzinc heterobimetallic complexes, [Ru(IPr)2(CO)ZnMe][BArF4] (7), [Ru(IBiox6)2(CO)(THF) ZnMe][BArF4] (12) and [Ru(IMes)â(PPh3)(CO)ZnMe] (15), have been prepared by reaction of ZnMe2 with the ruthenium N-heterocyclic carbene complexes [Ru(IPr)2(CO)H][BArF4] (1), [Ru(IBiox6)2(CO)(THF)H][BArF4] (11) and [Ru(IMes)(PPh3)(CO)HCl] respectively. 7 shows clean reactivity towards H2, yielding [Ru(IPr)2(CO) (Âż2-H2)(H)2ZnMe][BArF4] (8), which undergoes loss of the coordinated dihydrogen ligand upon application of vacuum to form [Ru(IPr)2(CO)(H)2ZnMe][BArF4] (9). In contrast, addition of H2 to 12 gave only a mixture of products. The tetramethyl IBiox complex [Ru(IBioxMe4)2(CO)(THF)H][BArF4] (14) failed to give any isol- able RuâZn containing species upon reaction with ZnMe2. The cyclometallated NHC complex [Ru(IMes)â (PPh3)(CO)ZnMe] (15) added H2 across the RuâZn bond both in solution and in the solid-state to afford [Ru(IMes)â(PPh3)(CO)(H)2ZnMe] (17), with retention of the cyclometallati
Activation of aromatic CâC bonds of 2,2â-bipyridine ligands
4,4â-Disubstituted-2,2âČ-bipyridine ligands coordinated to Mo and Re cationic fragments become dearomatized by an intramolecular nucleophilic attack from a deprotonated N-alkylimidazole ligand in cis disposition. The subsequent protonation of these neutral complexes takes place on a pyridine carbon atom rather than at nitrogen, weakening an aromatic CâC bond and affording a dihydropyridyl moiety. Computational calculations allowed for the rationalization of the formation of the experimentally obtained products over other plausible alternatives.Financialsupport from Ministerio de EconomĂa y Competitividad/FEDER (grant CTQ2015-70231-P) and Principado de Asturias (grant GRUPIN14-103) is gratefully acknowledged. J.D.thanks COMPUTAEX for granting access to LUSITANIA supercomputing facilities.Peer Reviewe
Organocatalytic Michael Addition of Unactivated α-Branched Nitroalkanes to Afford Optically Active Tertiary Nitrocompounds
The direct, asymmetric conjugate addition of unactivated α-branched nitroalkanes is developed based on the combined use of chiral amine/ureidoaminal bifunctional catalysts and a tunable acrylate template to provide tertiary nitrocompounds in 55â80% isolated yields and high enantioselectivity (e.r. up to 96:4). Elaboration of the ketol moiety in thus obtained adducts allows a fast entry to not only carboxylic and aldehyde derivatives but also nitrile compounds and enantioenriched 5,5-disubstituted Îł-lactams.We thank the Basque Government (EJ, grant IT1583-22) and Agencia Estatal de InvestigaciĂłn (grants PID2019-109633GB and PID2022-137153NB-C21/AEI/10.13039/501100011033) for financial support. A.G.-U. thanks EJ; B.L. thanks the Navarra Government, and M.E.-V. thanks UPNA (PJUPNA18-2022). Authors also thank SGIker (UPV/EHU/ERDF, EU) for providing NMR, HRMS, and X-ray resources
The role of neutral Rh(PONOP)H, free NMe2H, boronium and ammonium salts in the dehydrocoupling of dimethylamine-borane using the cationic pincer [Rh(PONOP)(η2-H2)]+ catalyst
The Ï-amine-borane pincer complex [Rh(PONOP)(η1-H3B·NMe3)][BArF4] [2, PONOP = Îș3-NC5H3-2,6-(OPtBu2)2] is prepared by addition of H3B·NMe3 to the dihydrogen precursor [Rh(PONOP)(η2-H2)][BArF4], 1. In a similar way the related H3B·NMe2H complex [Rh(PONOP)(η1-H3B·NMe2H)][BArF4], 3, can be made in situ, but this undergoes dehydrocoupling to reform 1 and give the aminoborane dimer [H2BNMe2]2. NMR studies on this system reveal an intermediate neutral hydride forms, Rh(PONOP)H, 4, that has been prepared independently. 1 is a competent catalyst (2 mol%, âŒ30 min) for the dehydrocoupling of H3B·Me2H. Kinetic, mechanistic and computational studies point to the role of NMe2H in both forming the neutral hydride, via deprotonation of a Ï-amine-borane complex and formation of aminoborane, and closing the catalytic cycle by reprotonation of the hydride by the thus-formed dimethyl ammonium [NMe2H2]+. Competitive processes involving the generation of boronium [H2B(NMe2H)2]+ are also discussed, but shown to be higher in energy. Off-cycle adducts between [NMe2H2]+ or [H2B(NMe2H)2]+ and amine-boranes are also discussed that act to modify the kinetics of dehydrocoupling
Correction: Heterobimetallic ruthenium-zinc complexes with bulky N-heterocyclic carbenes: syntheses, structures and reactivity (vol 48, pg 4176, 2019)
Correction for âHeterobimetallic rutheniumâzinc complexes with bulky N-heterocyclic carbenes: syntheses, structures and reactivityâ by Maialen Espinal-Viguri et al., Dalton Trans., 2019, 48, 4176â4189, DOI: 10.1039/C8DT05023F
Regiochemistry control by bipyridine substituents in the deprotonation of reI and MoII N-alkylimidazole complexes
Compounds containing N-alkylimidazoles (N-RIm) and 4,4'-disubstituted 2,2'-bipyridines (4,4'-R'2 bipy) coordinated to cationic {Mo(η3 -C4 H7 )(CO)2 } and {Re(CO)3 } fragments undergo deprotonation of the C2-H group of the N-RIm ligands in their reactions with KN(SiMe3 )2 . The resulting internal nucleophile adds either to one pyridyl ring, which becomes dearomatized and can undergo ring opening in the subsequent reaction with excess MeOTf, or to the metal center, yielding imidazol-2-yl complexes, which in turn add HOTf or MeOTf, affording N-heterocyclic carbene complexes. Which pathway is followed is dictated by the metal and the nature of the imidazole (R) and bipyridine (R') substituents. For ReI compounds, addition to pyridine is found with R'=tBu and OMe, whereas for R=Me and R'=NMe2 , imidazolyl formation is preferred. Coordination of 4,7-Cl2 -1,10-phenanthroline to MoII favors C-C coupling, in contrast to the analogous parent bipy or phenanthroline complexes, for which formation of the imidazol-2-yl complexes had been found. DFT calculations showed the theoretically expected products in each case, and following their predictions new types of products were obtained experimentally.Financial support from Ministerio de Economia y Competitividad/FEDER (grant CTQ2015-70231-P), Ministerio de Ciencia, Innovacion y niversidades (grant PGC2018-097366-B-100) and Principado de Asturias (grant GRUPIN14-103, and Severo Ochoa predoctoral fellowship to S.F.) is gratefully acknowledged.Peer reviewe
Organocatalytic Michael Addition of Unactivated 뱉Branched Nitroalkanes to Afford Optically Active Tertiary Nitrocompounds
The direct, asymmetric conjugate addition of unactivated
α-branched
nitroalkanes is developed based on the combined use of chiral amine/ureidoaminal
bifunctional catalysts and a tunable acrylate template to provide
tertiary nitrocompounds in 55â80% isolated yields and high
enantioselectivity (e.r. up to 96:4). Elaboration
of the ketol moiety in thus obtained adducts allows a fast entry to
not only carboxylic and aldehyde derivatives but also nitrile compounds
and enantioenriched 5,5-disubstituted Îł-lactams
Ligands with 1,10-phenanthroline scaffold for highly regioselective iron-catalyzed alkene hydrosilylation
Catalytic Transfer Deuteration and Hydrodeuteration: Emerging Techniques to Selectively Transform Alkenes and Alkynes to Deuterated Alkanes
Increasing demand for deuterium-labeled organic molecules has spurred a renewed interest in selective methods for deuterium installation. Catalytic transfer deuteration and transfer hydrodeuteration are emerging as powerful techniques for the selective incorporation of deuterium into small molecules. These reactions not only obviate the use of D2 gas and pressurized reaction setups but provide new opportunities for selectively installing deuterium into small molecules. Commercial or readily synthesized deuterium donors are typically employed as easy-to-handle reagents for transfer deuteration and hydrodeuteration reactions. In this minireview, recent advances in the catalytic transfer deuteration and hydrodeuteration of alkenes and alkynes for the selective synthesis of deuterated alkanes will be discussed