Search

The silylation of a phosphine of OsH6(PiPr3)2 is performed via net-metathesis between Si−C(spn) and H−C(sp3) σ-bonds (n=2, 3). Complex OsH6(PiPr3)2 activates the Si−H bond of Et3SiH and Ph3SiH to give OsH5(SiR3)(PiPr3)2, which yield OsH4{κ1-P,η2-SiH-[iPr2PCH(Me)CH2SiR2H]}(PiPr3) and R−H (R=Et, Ph), by displacement of a silyl substituent with a methyl group of a phosphine. Such displacement is a first-order process, with activation entropy consistent with a rate determining step occurring via a highly ordered transition state. It displays selectivity, releasing the hydrocarbon resulting from the rupture of the weakest Si-substituent bond, when the silyl ligand bears different substituents. Accordingly, reactions of OsH6(PiPr3)2 with dimethylphenylsilane, and 1,1,1,3,5,5,5-heptamethyltrisiloxane afford OsH5(SiR2R′)(PiPr3)2, which evolve into OsH4{κ1-P,η2-GeH-[iPr2PCH(Me)CH2SiR2H]}(PiPr3) (R=Me, OSiMe3) and R′−H (R′=Ph, Me). Exchange reaction is extended to Et3GeH. The latter reacts with OsH6(PiPr3)2 to give OsH5(GeEt3)(PiPr3)2, which loses ethane to form OsH4{κ1-P,η2-GeH-[iPr2PCH(Me)CH2GeEt2H]}(PiPr3)., Financial support from the MCIN/AEI/10.13039/501100011033 (Projects PID2020-115286GB-I00 and RED2018-102387-T), Gobierno de Aragón (Group E06_20R and LMP23_21), FEDER, and the European Social Fund is gratefully acknowledged. E. R. thanks the MCIN for her FPI contract (PRE2018-085398, “ESF investing in your future”).

Molecular phosphorescent heteroleptic bis-tridentate iridium(III) emitters have been prepared via η1-arene intermediates. In the presence of 4.0 mol of AgOTf, the complex [(IrCl{κ3-N,C,N-(pyC6HMe2py)})(μ-Cl)]2 (1; pyC6H2Me2py=1,3-di(2-pyridyl)-4,6-dimethylbenzene) reacted with 9-(6-phenylpyridin-2-yl)-9H-carbazole (PhpyCzH) and 2-phenoxy-6-phenylpyridine (PhpyOPh) to give [Ir{κ3-N,C,N-(pyC6HMe2py)}{κ3-C,N,C′-(C6H4pyCzH)}]OTf (2) and [Ir{κ3-N,C,N-(pyC6HMe2py)}{κ3-C,N,C′-(C6H4pyOPh)}]OTf (3). The X-ray diffraction structures of 2 and 3 reveal that the carbazolyl and phenoxy substituents of the C,N,C′ ligand coordinate to the metal center to form an η1-arene π bond. Treatment of 2 and 3 with KOtBu led to the deprotonation of the coordinated carbon atom of the η1-arene group to afford the molecular phosphorescent [5t+4t′] heteroleptic iridium(III) complexes [Ir{κ3-N,C,N-(pyC6HMe2py)}{κ3-C,N,C′-(C6H4pyCz)}] (4) and [Ir{κ3-N,C,N-(pyC6HMe2py)}{κ3-C,N,C′-(C6H4pyOC6H4)}] (5). These complexes are green emitters that display short lifetimes and high quantum yields of 0.73 (4) and 0.87 (5) in the solid state., Financial support from the Spanish Ministerio de Economía y Competitividad (MINECO) (Projects CTQ2014-52799-P, Red de Excelencia Consolider CTQ2016-81797-REDC), the Gobierno deAragón (E35), Fondo Europeo de Desarrollo Regional (FEDER), and the European Social Fund (FSE) is acknowledged.

A novel osmium-catalyzed cyclization of o-alkynyl phenethylamines to give 3-benzazepines is reported. The procedure allows the straightforward preparation of a broad range of dopaminergic 3-benzazepine derivatives. Mechanistic investigations revealed that the process takes place via osmacyclopropene intermediates, which were isolated and characterized by X-ray crystallography., This research was supported by the MICINN (projects CTQ2011-28258, CTQ2014-52799-P, and CTQ2014-51912REDC), Xunta de Galicia and the European Regional Development Fund (projects GRC2014/032 and EM 2012/051), the DGA (E-35), and the European Social Fund (SFE). A.A.-P.and C.G.-R. thank the Spanish MICINN for a pre-doctoral FPI fellowship and Juan de la Cierva Contract (JCI-2011-09946), respectively.

Communication.-- Titulo del pdf: Making Easier the β-Lactam Fragmentation via Metal-Assistance: Mechanistic Insight., The mechanism of OsH6(PiPr3)2-mediated fragmentation of a 4-(2 pyridyl)-2-azetidinone has been investigated by DFT calculations. The addition of the C4-H bond of the substrate to OsH2(PiPr3)2 allows the active participation of an osmium lone pair in the B-type b-lactam fragmentation process. This new mechanism makes the N1-C4/C2-C3 fragmentation of the lactamic core thermally accessible through a stepwise process., Financial support from the Spanish MINECO and FEDER (Projects CTQ2013-46459-C2-01-P, CTQ2014-52799-P, CTQ2014-54071-P, and CTQ2014-51912-REDC), the DGA (E35), and the European Social Fund (FSE) is acknowledged

A novel osmium-catalyzed cyclization of o-alkynyl phenethylamines to give 3-benzazepines is reported. The procedure allows the straightforward preparation of a broad range of dopaminergic 3-benzazepine derivatives. Mechanistic investigations revealed that the process takes place via osmacyclopropene intermediates, which were isolated and characterized by X-ray crystallography.

Palladium acetate reacts with 1-benzyl-3-(2-hydroxy-2-phenylethyl)-1H- imidazolium chloride to give the corresponding bis(carbene)palladium(II) complex 5 [(NHC)2PdCl2] by direct metalation. The X-ray diffraction structure of the complex is reported. In the presence of NaOH solution (50 % H2O, w/w) in air and under microwave irradiation, the bis(NHC)pallalium(II) complex 5 is an active precatalyst for the Hiyama coupling of aryl halides with trialkoxy(aryl)silanes, providing biaryls and heterobiaryls. For some deactivated aryl bromides and for aryl chlorides, the corresponding cross-coupling reactions require tetrabutylammonium bromide (TBAB) as additive. The fluoride-free Hiyama reactions are performed with low (NHC)palladium loadings (0.1 mol-%). The active catalyst can also be prepared in situ from Pd(OAc)2 and the corresponding imidazolium salt 4. © 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim., Financial support from the Ministerio de Ciencia e Innovación (MICINN) of Spain (Project Nos. CTQ2007-65218, CTQ2008- 00810, Consolider Ingenio 2010 CSD2007-00006), the Generalitat Valenciana (PROMETEO/2009/0349 and FEDER), the Diputación General de Aragón (E35), and the European Social Fund is acknowledged.

A nice ring: The title compounds are easily prepared by dehydrative cyclization of terminal alkynals in the presence of osmium, iridium, and rhodium precursors (see scheme). Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim., Financial support from the MICINN of Spain (project numbers CTQ2008-00810 and CTQ2008-06557), and the Consolider Ingenio 2010 (CSD2007-00006), The Diputacion General de Aragón (E35), Xunta de Galicia, and the European Regional Development Fund (2007/XA084 and INCITE08PXIB 209024PR), and the European Social Fund is acknowledged. M.B. and L.E. thank the Spanish MICINN and Fundación Fundayacucho (Venezuela), respectively, for predoctoral grants.

Catalyst (I), readily available from the imidazolium salt and Pd(O-Ac)2, is isolated as an air-stable greyish solid, which exists in solution at room temperature as a mixture of diastereomers.

The previously unnoticed Ru complex activates the title reaction which proceeds under mild conditions and is fully diastereoselective.

Complex [(η6-p-cymene)OsCl(IPr)]OTf (1; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolylidene; OTf = CF3SO3) reacts with NaOH to give [(η6-p-cymene)Os(OH)(IPr)]OTf (2), which under hydrogen atmosphere affords [(η6-p-cymene)OsH3(IPr)]OTf (3). The hydride ligands of 3 undergo exchange coupling, decreasing the H−H coupling constant from 206 to 74 Hz in the temperature range 213−178 K. Complex 3 is also obtained in a two-step procedure involving the reaction of 2 with NaBH4 to give (η6-p-cymene)OsH2(IPr) (4) and the protonation of the latter with HOTf. Attempts to obtain 4 directly from 1 or (η6-p-cymene)OsCl2(IPr) (5) are unsuccessful. In both reactions (η6-p-cymene)OsHCl(IPr) (6) is formed. Complex 2 also reacts with methanol and 2-propanol. At −30 °C, the reaction with the first of them leads to [(η6-p-cymene)Os(OMe)(IPr)]OTf (7), while with the second one, [(η6-p-cymene)OsH{κ1-OC(CH3)2}(IPr)]OTf (8) is obtained. Complex 2 is a catalyst precursor for the hydrogen transfer from 2-propanol to aldehydes, which ...