Reactivity of TpMe2-containing hydride-iridafurans with alkenes, alkynes, and H2

The TpMe2-containing hydride-iridafurans 2a,b (TpMe2 = hydrotris(3,5-dimethylpyrazolyl)borate) cleanly reacted with ethylene to give the bicyclic derivatives 6a,b. Formation of the latter complexes is a reversible process, and it is proposed to occur by an electrocyclic ring closure that takes place between C2H4 and the 16e unsaturated intermediates A, resulting from hydride migration to the α carbon of the metallacycle. Similar reactions were observed with a variety of alkynes RC≡CR (R = H, Ph, CO2Me) and R′C≡CH (R′= CO2Me, Ph, CMe3), with the regioselectivity observed for the latter substrates depending on the nature of R′. In the case of Me3SiC≡CH the structure of an unexpected byproduct indicates that an alkyne–vinylidene rearrangement has taken place on the metal coordination sphere during the reaction, and this observation suggests that in the mechanism of all these coupling processes the corresponding π adducts are active intermediates. Finally, complexes 2a,b reacted with H2 to give products derived from the hydrogenation of their alkenyl arms.Ministerio de Ciencia e Innovación CTQ2010-17476. Consolider Ingenio 2010 CSD 2007-0006Junta de Andalucía FQM-119, P09-FQM-483

Formation of β-Metallanaphthalenes by the Coupling of a Benzo-Iridacyclopentadiene with Olefins

We have synthesized a new type of metallaaromatic complexes, namely the hydride-β-iridanaphthalenes TpMe2tiebar above startr(H)[C(CH2R′)-C6H4-o-C(R)═tiebar above endC(R)] (benzo-3-H,CH2R′), by reaction of the benzo-iridacyclopentadiene TpMe2tiebar above startr[C6H4-o-C(R)═tiebar above endC(R)](OH2) (benzo-1-OH2) (TpMe2 = hydrotris(3,5-dimethylpyrazolyl)borate, R = CO2Me) with olefins of the type CH2═CHR′ (R′ = H, Me, C6H4-p-Me, OPh). These reactions are proposed to take place with the initial coordination of the olefin and isomerization to a carbene form and subsequent insertion into the Ir–C(phenylic) bond and a final α-H elimination. The reaction with ethoxyethylene does not afford the corresponding derivative but rather gives a mixture of three, isolable, compounds, which are proposed to derive from three different types of insertion of the olefin, one of them a typical 1,2-insertion and the other two as (different) carbenes. The related reactions of the iridacyclopentadiene TpMe2tiebar above startr[C(R)═C(R)-C(R)═tiebar above endC(R)](OH2) (1-OH2) are also discussed. For different combinations of precursor and olefin, we have observed differences in the regio- and stereochemistry of the insertions.Peer reviewe

Preparation and characterization of a monocyclopentadienyl osmium−allenylcarbene complex

5 pages, 3 schemes, 1 table, 1 figure.-- Supporting Information Available: http: //pubs.acs.org.The dihydride−dihydrogen complex [OsH2(η5-C5H5)(η2-H2)(PiPr3)]BF4 (1) reacts with phenylacetylene to give the allenylcarbene derivative [Os(η5-C5H5){CPh(η2-CHCCHPh)}(PiPr3)]BF4 (2) via the π-phenylacetylene intermediate [Os(η5-C5H5)(η2-PhCCH)(PiPr3)]BF4 (3). The reactions of 2 with NaOMe and LiCCPh afford 3:1 mixtures of two hydride−osmaindene isomers of formula OsH(n5-C5H5)(C(C=CPh)=CHC6H4)(piPr3)(4 and 5) instead of the expected osmabenzyne complex.Financial support from the MEC of Spain (Projects CTQ2005-00656 and Consolider Ingenio 2010 CSD2007-00006)) and Diputación General de Aragón (E35) is acknowledged. Y.A.H. thanks the Spanish MEC for his grant.Peer reviewe

Reduction and C(sp2)-H bond activation of ketones promoted by a cyclopentadienyl-osmium-dihydride-dihydrogen complex

The dihydride-dihydrogen complex [OsH2(η5-C 5H5)(η2-H2)(PiPr 3)]BF4 (2) has been prepared by addition of HBF 4·OEt2 to OsH3H3(η 5-C5H5)(PiPr3) (1), and its reactions with benzylideneacetone, methyl vinyl ketone, acetophenone, and benzylideneacetophenone have been studied. The reaction with benzylideneacetone leads initially to [OsH2(η5-C5H 5){κ1-OC(CH3)CH=CHPh}-(P iPr3)]BF4 (3), which in dichloromethane is converted to the hydroxyallyl derivative [OsH-(η5-C 5H5){η3-CH2C(OH)CHCH 2Ph}(PiPr3)]BF4 (4). Complex 4 releases 4-phenylbutan-2-one, and the resulting metallic fragment activates a Cβ(sp2)-H bond of a new molecule of benzylideneacetone to give [OsH(η5-C5H 5){C(Ph)CHC(O)CH3}(PiPr3)]BF 4 (5), which affords Os(η5-C5H 5){C(Ph)CHC(O)CH3}(PiPr3) (6) by deprotonation with NaOCH3. The reaction of 2 with methyl vinyl ketone gives ethyl methyl ketone and [OsH(η5-C5H 5){CHCHC(O)-CH3}(PiPr3)]BF 4 (9). The latter can also be obtained from Os(η5- C5H5)Cl{η2-CH2=CHC(O)-CH 3(PiPr3) (7) via the intermediate [Os(η5-C5H5){CH2CHC(O)CH 3}(PiPr3)]BF4 (8). Treatment of 9 with NaOCH3 leads to an equilibrium mixture of Os(η5- C5H5){CHCHC(O)CH3}-(PiPr 3) (10) and the hydride-vinylidene OsH(η5-C 5H5){=C=CHC(O)CH3}(PiPr3) (11). The reaction of 2 with acetophenone gives 1-phenylethanol and the orthometalated derivative [OsH(η5-C5H5){C 6H4C(O)CH3}(PiPr3)] BF4 (13), which is deprotonated with NaOCH3 to give Os(η5-C5H5){C6H 4C(O)CH3 (14), while the reaction of 2 with benzylideneacetophenone leads to [OsH(η5-C5H 5){C(Ph)CHC(O)Ph}(PiPr3)]BF4 (15), which yields Os(η5-C5H5){C(Ph)CHC(O)Ph} (PiPr3) (16) by deprotonation. Complexes 3, 10, and 13 have been characterized by X-ray diffraction analysis. © 2005 American Chemical Society.Financial support from the MCYT of Spain (Proyect BQU2002-00606) is acknowledged. Y.A.H. thanks the Spanish MCYT for his grant.Peer Reviewe

One-pot dehydrogenative addition of isopropyl to alkynes promoted by osmium: Formation of γ-(η3-allyl)-α-alkenylphosphine derivatives starting from a dihydride−dihydrogen−triisopropylphosphine complex

10 pages, 1 table, 4 schemes, 1 figure.-- Supporting Information Available: http://pubs.acs.org.The dihydride−dihydrogen complex [OsH2(η5-C5H5)(η2-H2)(PiPr3)]BF4 (1) reacts in acetone with 1-phenyl-1-propyne and 2-butyne to give the γ-(η3-allyl)-α-alkenylphosphine derivatives [OsH(η5-C5H5){κ4-(P,C,C,C)-CH2C[CH2C(CH2)PiPr2]CHR}]BF4 (R = Ph (2), CH3 (3)), by means of one-pot tandem processes of four reactions. The stable intermediates have been isolated and characterized. In acetone, complex 1 dissociates H2 and coordinates the solvent to afford [OsH2(η5-C5H5)(κ1-OCMe2)(PiPr3)]BF4 (4), which reacts with a molecule of 1-phenyl-1-propyne or 2-butyne to form [OsH(η5-C5H5)(η3-CH2CHCHR)(PiPr3)]BF4 (R = Ph (5), CH3 (6)), containing the CHR group cisoid disposed to the phosphine and the R substituent anti to Cmeso. In dichloromethane, complexes 5 and 6 evolve to the thermodynamic isomers 7 and 8, containing the CHR group cisoid disposed to the hydride and the R substituent syn to Cmeso. The reactions of 5 and 6 with a second molecule of the respective alkyne lead to the corresponding Z-olefin and [Os(η5-C5H5){η2-(Z)-CH(CH3)CHR}{κ3-(P,C,C)-[CH2C(CH3)]PiPr2}]BF4 (R = Ph (9), CH3 (10)). The isopropenyl group of the phosphine of 9 and 10 undergoes coupling with a third alkyne molecule to give 2 and 3.Financial support from the MEC of Spain (Project CTQ2005-00656) and Diputación General de Aragón (E35) is acknowledged. Y.A.H. thanks the Spanish MEC for his grant.Peer reviewe

Reactions of a dihydride-osmium(IV) complex with aldehydes: Influence of the substituent at the carbonyl group

4 pages, 4 figures.The reactivity of the dihydride−acetone complex [OsH2(η5-C5H5)(κ1-OCMe2)(PiPr3)]BF4 (1) toward cinnamaldehyde, isovaleraldehyde, and benzaldehyde has been investigated. In addition to the reduction of the aldehydes, three different reaction patterns have been observed, which depend on the alkenyl, alkyl, and aryl nature of the substituent at the carbonyl group. As a result, the complexes [Os(η5-C5H5)(CO)(η2-PhCHCH2)(PiPr3)]BF4 (2), [Os(η5-C5H5)(CO)2(PiPr3)]BF4 (3), and [OsH(η5-C5H5){C6H4C(O)H}(PiPr3)]BF4 (6) have been isolated and characterized, including the X-ray structure of 2.Financial support from the MEC of Spain (Projects CTQ2005-00656 and Consolider Ingenio 2010 CSD2007-00006) and Diputación General de Aragón (E35) is acknowledged. Y.A.H. thanks the Spanish MEC for his grant.Peer reviewe

Aldehyde-Assisted Hydrogen Transfer during the Formation of Hydride-Iridafurans from Alkynes and Aldehydes

The bis(ethylene) IrI complex [Tpmath imageIr(C2H4)2] (1; Tpmath image=hydrotris(3,5-dimethylpyrazolyl)borate) reacts with two equivalents of aromatic or aliphatic aldehydes in the presence of one equivalent of dimethyl acetylenedicarboxylate (DMAD) with ultimate formation of hydride iridafurans of the formula [Tpmath imageIr(H){C(R1)[DOUBLE BOND]C(R2)C(R3)O}] (R1=R2=CO2Me; R3=alkyl, aryl; 3). Several intermediates have been observed in the course of the reaction. It is proposed that the key step of metallacycle formation is a C[BOND]C coupling process in the undetected IrI species [Tpmath imageIr{η1-O-R3C([DOUBLE BOND]O)H}(DMAD)] (A) to give the trigonal-bipyramidal 16 e− IrIII intermediates [Tpmath imageIr{C(CO2Me)[DOUBLE BOND]C(CO2Me)C(R3)(H)O}] (C), which have been trapped by NCMe to afford the adducts 11 (R3=Ar). If a second aldehyde acts as the trapping reagent for these species, this ligand acts as a shuttle in transfering a hydrogen atom from the γ- to the α-carbon atom of the iridacycle through the formation of an alkoxide group. Methyl propiolate (MP) can be used instead of DMAD to regioselectively afford the related iridafurans. These reactions have also been studied by DFT calculations.Peer Reviewe

Reactivity of TpMe2-containing hydride-iridafurans with alkenes, alkynes, and H2

© 2014 American Chemical Society. The TpMe2-containing hydride-iridafurans 2a,b (TpMe2 = hydrotris(3,5-dimethylpyrazolyl)borate) cleanly reacted with ethylene to give the bicyclic derivatives 6a,b. Formation of the latter complexes is a reversible process, and it is proposed to occur by an electrocyclic ring closure that takes place between C2H4 and the 16e unsaturated intermediates A, resulting from hydride migration to the carbon of the metallacycle. Similar reactions were observed with a variety of alkynes RC¿CR (R = H, Ph, CO2Me) and RC¿ CH (R= CO2Me, Ph, CMe3), with the regioselectivity observed for the latter substrates depending on the nature of R. In the case of Me3SiC¿CH the structure of an unexpected byproduct indicates that an alkyne-vinylidene rearrangement has taken place on the metal coordination sphere during the reaction, and this observation suggests that in the mechanism of all these coupling processes the corresponding adducts are active intermediates. Finally, complexes 2a,b reacted with H2 to give products derived from the hydrogenation of their alkenyl arms.Peer Reviewe

C-N bond formation by O2-mediated dehydrogenative coupling of phenyl and NH-pyridylidene ligands on TpMe2 Irlll complexes

H,D pick and mix: The pyridylidene compounds [TpIr(C6H5) (CN(H) C4(R)H3)] (R=H, Me, and Ph) react with O2 to form mixtures of two complexes (see scheme). One of them, 4, contains a newly formed CN bond as the result of an oxidative dehydrogenation. During a mechanistic study on its formation, an unexpected H,D scrambling has been disclosed.Peer Reviewe

Iridafurans by Coupling of Alkynes and Aldehydes on a TpMe2Ir System. Facile Demethoxycarbonylation of a β-CO2Me Substituent

4 páginas, 2 figuras, 6 esquemas.The reaction of TpMe2Ir(C2H4)2 (TpMe2 = hydrotris(3,5-dimethylpyrazolyl)borate) with 1 equiv of DMAD (DMAD = dimethyl acetylenedicarboxylate) and 1 equiv of an aromatic aldehyde cleanly yields iridafuran derivatives, characterized by spectroscopy and X-ray analysis. These derivatives experience a stepwise selective hydrolysis−decarboxylation of the CO2Me group located at the β-carbon of the metallacycle, which proceeds through two isolable intermediates: a water adduct of an iridaenolate and an iridium carboxylate bicyclic species.Financial support (FEDER contribution) from the Spanish MICINN (Grants CTQ2007-62814 and Consolider Ingenio 2010 CSD 2007-0006) and the Junta de Andalucía (FQM119, P09-FQM-4832) is acknowledged.Peer reviewe