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Lehnherr D.,University of Alberta | Hallani R.,University of Kentucky | McDonald R.,University of Alberta | McDonald R.,X ray Crystallography Laboratory | And 2 more authors.
Organic Letters | Year: 2012

The synthesis of three heptacyclic heteroacenes is described, namely anthra[2,3-b:7,6-b′]bis[1]benzothiophenes (ABBTs). A stepwise sequence of aldol reactions provides regiochemical control, affording only the syn-isomer. The ABBTs are characterized by X-ray crystallography, UV-vis absorption, and emission spectroscopy, as well as cyclic voltammetry. Field effect transistors based on solution-cast thin films of ABBT derivatives exhibit charge-carrier mobilities of as high as 0.013 cm 2/(V s). © 2011 American Chemical Society. Source

Wells K.D.,University of Alberta | McDonald R.,X ray Crystallography Laboratory | Ferguson M.J.,X ray Crystallography Laboratory | Cowie M.,University of Alberta
Inorganic Chemistry | Year: 2011

The reaction of [RhOs(CO)3(μ-CH2)(dppm) 2]- [CF3SO3] (dppm = μ-Ph 2PCH2PPh2) with 1,3,4,5-tetramethylimidazol- 2-ylidene (IMe4) results in competing substitution of the Rh-bound carbonyl by IMe4 and dppm deprotonation by IMe4 to give the two products [RhOs(IMe4)(CO)2(μ-CH2)- (dppm)2][CF3SO3] and [RhOs(CO) 3(μ-CH2)(μ-κ1:η2- dppm- H)(dppm)] [3; dppm-H = bis(diphenylphosphino)methanide], respectively. In the latter product, the dppm-H group is P-bound to Os while bound to Rh by the other PPh2 group and the adjacent methanide C. The reaction of the tetracarbonyl species [RhOs(CO)4(μ-CH2)(dppm) 2][CF3SO3] with IMe4 results in the exclusive deprotonation of a dppm ligand to give [RhOs(CO)4(μ- CH2)(μ-κ1:κ1-dppm-H)(dppm)] (4) in which dppm- H is P-bound to both metals. Both deprotonated products are cleanly prepared by the reaction of their respective precursors with potassium bis(trimethylsilyl)amide. Reversible conversion of the μ-κ1: κ2-dppm-H complex to the μ-κ1: κ1-dppm-H complex is achieved by the addition or removal of CO, respectively. In the absence of CO, compound 3 slowly converts in solution to [RhOs(CO)κ(μ-κ1:κ1: κ1-Ph2PCHPPh2CH2)(dppm)] (5) as a result of dissociation of the Rh-bound PPh2 moiety of the dppm-H group and its attack at the bridging CH2 group. Compound 4 is also unstable, yielding the ketenyl- and ketenylidene/hydride tautomers [RhOs(CO)3(μ-κ1:κ2-CHCO)(dppm) 2] (6a) and [RhOs(H)(CO)3(μ-κ1: κ1-CCO)(dppm)2] (6b), initiated by proton transfer from μ-CH2 to dppm-H. Slow conversion of these tautomers to a pair of isomers of [RhOs(H)(CO)3(μ- κ1: κ1:κ1-Ph2PCH(COCH)PPh 2)(dppm)] (7a and 7b) subsequently occurs in which proton transfer from a dppm group to the ketenylidene fragment gives rise to coupling of the resulting dppm-H methanide C and the ketenyl unit. Attempts to couple the ketenyl- or ketenylidene-bridged fragments in 6a/6b with dimethyl acetylenedicarboxylate (DMAD) yield [RhOs(κ1-CHCO)- (CO) 3(μ-DMAD)(dppm)2], in which the ketenyl group is terminally bound to Os. © 2011 American Chemical Society. Source

MacDougall T.J.,University of Alberta | Llamazares A.,University of Alberta | Kuhnert O.,University of Alberta | Ferguson M.J.,University of Alberta | And 2 more authors.
Organometallics | Year: 2011

The methylene-bridged complex [IrOs(CO)4(μ-CH 2)(dppm)2][CF3SO3] (dppm = μ-Ph2PCH2PPh2) (3) can be synthesized by the addition of diazomethane to [IrOs(CO)5(dppm)2][CF 3SO3] (1) or [IrOs(CO)4(dppm) 2][CF3SO3] (2). Reaction of 3 with dimethyl acetylenedicarboxylate (DMAD) leads to the insertion of the alkyne into the iridium-carbon bond, yielding both [IrOs(CO)4(μ- κ1:κ1-C(CO2CH3)= C(CO2CH3)CH2)(dppm)2][CF 3SO3] (5) and [IrOs(CO)3(μ- κ1:κ1-C(CO2CH3)= C(CO2CH3)CH2)(dppm)2][CF 3SO3] (6), each of which can be obtained as the exclusive product under either CO or an Ar purge, respectively. Hexafluorobutyne (HFB) fails to react with 3, but reacts with [IrOs(CO)3(μ-CH 2)(dppm)2][CF3SO3] (4) yielding [IrOs(CO)3(μ-κ1:κ1-C(CF 3)=C(CF3)CH2)(dppm)2][CF 3SO3] (7). Reaction of 7 with diazomethane results in the insertion of a second methylene unit into the iridium-carbon bond, yielding [IrOs(CO)3(μ-κ1:κ1-CH 2(CF3)C=C(CF3)CH2)(dppm) 2][CF3SO3] (9), which can be characterized by NMR spectroscopy only at low temperatures owing to deinsertion of the iridium-bound methylene group at ambient temperature. Compound 6 also reacts with diazomethane but in this case results in the formation of a new carbon-oxygen bond between the newly introduced methylene unit and a carbonyl oxygen of the inserted DMAD fragment. This bond formation is accompanied by carbon-hydrogen bond activation of the original osmium-bound methylene group, yielding [IrOs(CO)3(μ-H)(μ-κ1: κ1:κ1-CH2OC(OCH3)= CC(CO2CH3)=CH)(dppm)2][CF3SO 3] (8). Attempts to insert a methylene unit into the iridium-carbon bond of the alkyne-bridged complexes [IrOs(CO)3(μ- κ1:κ1-RC=CR)(dppm)2][CF 3SO3] (R = CO2Me (12), CF3 (13)) yields the C3-bridged complex [IrOs(CO)3(μ- κ1:κ1-CH2(CF3)C=CCF 3)(dppm)2][CF3SO3] (14) in the case of 13, but no further methylene incorporation is observed. Compound 12 reacts with diazomethane to give a number of unidentified products under a variety of conditions. The reactivities of the aforementioned complexes are compared to that of related late metal combinations. © 2011 American Chemical Society. Source

Mobarok M.H.,University of Alberta | Oke O.,University of Alberta | Ferguson M.J.,University of Alberta | Ferguson M.J.,X ray Crystallography Laboratory | And 3 more authors.
Inorganic Chemistry | Year: 2010

The reaction of 1 equiv of primary silanes, SiH 3R (R = Ph, Mes), with [RhIr(CO) 3(dppm) 2] yields mono(silylene)-bridged complexes of the type [RhIr(H) 2(CO) 2(μ-SiHR)(dppm) 2] (R = Ph or Mes), while for R = Ph the addition of 2 equiv yields the bis(silylene)-bridged complexes, [RhIr(CO) 2(μ-SiHPh) 2(dppm) 2]. The kinetic isomer of this bis(silylene)- bridged product has the phenyl substituent axial on one silylene unit and equatorial on the other, and in the presence of excess silane this rearranges to the thermodynamically preferred "axial-axial" isomer, in which the phenyl substituents on each bridging silylene unit are axial and parallel to one another. The reaction of 1 equiv of diphenylsilane with [RhIr(CO) 3(dppm) 2] produces the mono(silylene)-bridged product, [RhIr(H) 2(CO) 2(μ-SiPh 2)(dppm) 2], and the subsequent addition of silane in the presence of CO yields the silyl/silylene product [RhIr(H)(SiPh 2H)(CO) 3(κ 1-dppm)(μ-SiPh 2)(dppm)]. The reaction of [RhIr(CO) 3(dppm) 2] with 2 equiv of SiH 2Me 2 yields the analogous product [RhIr(H)(SiMe 2H)(CO) 3(κ 1-dppm)(μ-SiMe 2)(dppm)]. Low-temperature NMR spectroscopic observation of some key intermediates, such as [RhIr(H)(SiH 2Ph)(CO) 2(μ-CO)(dppm) 2], formed during the formation of the mono(silylene)-bridged species provides evidence for a mechanism involving initial Si-H bond activation at Rh, followed by the subsequent Si-H bond activation at Ir. The Si-H bond activation of a second equivalent of silane seems to be initiated by dissociation of the Rh-bound end of one diphosphine. The reaction of diphenylsilane with the cationic complex [RhIr(CH 3)(CO) 2(dppm) 2][CF 3SO 3] gives rise to a different reactivity pattern in which Si-H bond activation is initiated at Ir. In this case, the cationic silyl-bridged species, [RhIr(CH 3)(CO) 2(κ 1:η 2- SiHPh 2)(dppm) 2][CF 3SO 3], contains an agostic Si-H interaction with Rh. In solution, at ambient temperature, this complex converts to two species, [RhIr(H)(COCH 3)(CO)(μ-H)(μ- SiPh 2)(dppm) 2][CF 3SO 3] and [RhIr(CO) 2(μ-H)(μ-SiPh 2)(dppm) 2] [CF 3SO 3], formed by the competing methyl migration to CO and reductive elimination of methane, respectively. In the diphenylsilylene dihydride product, a weak interaction between the bridging silicon and the terminal Ir-bound hydride is proposed on the basis of NMR evidence. © 2010 American Chemical Society. Source

Slaney M.E.,University of Alberta | Anderson D.J.,University of Alberta | Ferguson M.J.,University of Alberta | Ferguson M.J.,X ray Crystallography Laboratory | And 3 more authors.
Journal of the American Chemical Society | Year: 2010

We report the selective activation of carbon-fluorine bonds in trifluoroethylene using the diiridium complex [Ir 2(CH 3)(CO) 2(dppm) 2][OTf] (1). Coordination of trifluoroethylene in a bridging position between the two metals in 1 results in facile fluoride ion loss in three different ways. Attack by strong fluorophiles such as Me 3SiOTf and HOTf results in F - removal from one of the geminal fluorines to give the cis-difluorovinyl-bridged product [Ir 2(CH 3)(OTf)(CO) 2(μ-κ 1: η 2-C(F)=CFH)(dppm) 2][OTf]. A second activation can also be accomplished by addition of excess Me 3SiOTf to give the fluorovinylidene-bridged product [Ir 2(CH 3)(OTf)(CO) 2(μ-C 2FH)(dppm) 2][OTf] 2. Interestingly, activation of the trifluoroethylene-bridged precursor by water also occurs, yielding [Ir 2(CH 3)(CO) 2(κ 1-C(H)=CF 2)(μ-OH)(dppm) 2][OTf], in which the lone vicinal fluorine is removed, leaving a geminal arrangement of fluorines in the product. A [1,2]-fluoride shift can also be induced in the trifluoroethylene-bridged precursor upon the addition of CO to give the 2,2,2-trifluoroethylidene-bridged product [Ir 2(CH 3)(CO) 3(μ-C(H)CF 3)(dppm) 2][CF 3SO 3]. Addition of hydrogen to the cis-difluorovinyl-bridged product results in the quantitative elimination of cis-difluoroethylene, while its reaction with CO yields a mixture of cis-difluoropropene and 2,3-difluoropropene by reductive elimination of the methyl and difluorovinyl groups with an accompanying isomerization in the case of the second product. Finally, protonation of the 2,2,2-trifluoroethylidene-bridged product liberates 1,1,1-trifluoroethane, in which one hydrogen (H +) is from the acid while the other hydrogen (H -) is derived from activation of the methyl group. © 2010 American Chemical Society. Source

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