Search

The complex [OsCp{κ3-P,C,C-PiPr 2[C(CH3)î=CH2]}(CH3CN)]PF 6 (1) reacts with (2-pyridyl)methylenecyclopropane, at room temperature, to give initially the cyclobutylidene derivative [Os(η5-C5H5)(î=CCH2CH 2CH-o-C5H4N){PiPr 2[C(Me)î=CH2]}]PF6 (2), as a result of the ring expansion of the alkylidenecyclopropane unit. Over time complex 2 rearranges into the cyclobutene derivative [Os(η5-C 5H5){η2-C(î=CHCH2CH 2)-o-C5H4N}{PiPr2[C(Me) î=CH2]}]PF6 (3). The reaction of 1 with (2-pyridyl)methylenecyclopropane at room temperature also affords the phosphinomethanide metallacycle [Os(η5-C5H 5){κ4-P,Ca,Cb,N-P iPr2[Ca(Me)CH2CH)(C bCH2CH2-o-C5H4N]}]PF 6 (4) as a minor product, which becomes the major product of the reaction at 45 C. This osmacyclopentane results from the C-C coupling of the isopropenyl substituent of the phosphine ligand and the organic substrate. In acetone at 75 C, the reaction of 1 with (2-pyridyl)methylenecyclopropane leads to the 2-alkylidene-1-osmacyclobutane [Os(η5-C5H 5){κ3-N,Ca,Cb-C a(CH2CbH2)(î=CH-o-C 5H4N)}{PiPr2[C(Me)î=CH 2]}]PF6 (5), as a consequence of the oxidative addition of one of the C(sp2)-C(sp3) bonds of the cyclopropane unit of the substrate to the osmium atom, along with 6, a diastereomer of 4. Complexes 3-5 have been characterized by X-ray diffraction analysis. DFT calculations suggest that all of the reaction products are derived from a common key 1-osma-2-azacyclopent-3-ene intermediate (D)., Financial support from the Spanish MICINN (Projects CTQ2011-23459, SAF2010-20822-C02, and Consolider Ingenio 2010 (CSD2007-00006)), the Diputación General de Aragón (E35), the Xunta de Galicia INCITE09 209 084PR, GRC2010/12, and the European Social Fund (FEDER) is acknowledged. L.S. thanks the Xunta de Galicia for a grant.

A Y-shaped tris-NHC ligand has been obtained and coordinated to palladium, affording metal complexes with novel topological properties. The tris-NHC ligand is capable of coordinating the two metals, affording two different coordination environments. The X-ray molecular structure of two of the complexes are reported. The three new Pd complexes provide good activity in the hydroarylation of alkynes, although we did not find any clear evidence about the benefits of using the dimetallic palladium species in the catalytic outcomes.

Novel enantiomerically pure cyclopentadienyl- and indenyl-functionalized N-heterocyclic carbene ligands have been prepared by reaction of a chiral imidazole tosylate derivative with the corresponding cyclopentadienyl and indenyl lithium salts. Coordination of the Cp-functionalized NHC ligand to iridium and rhodium allowed the preparation of enantiomerically pure chelating cyclopentadienyl-functionalized Ir(III) and Rh(III) metal complexes. In contrast, the indenyl-functionalized NHC coordinates to iridium in a monodentate fashion, giving an Ir(I)-NHC complex containing a dangling indene group.

Racemic 2,3-dihydro-1-phenylbenzo[b]phosphole was obtained by reduction of 1-phenylbenzo[b]phosphole-1-oxide, itself derived by ring-closing metathesis of phenylstyrylvinylphosphine oxide. The title compound was then reoxidized under asymmetric Appel conditions. Comparison of the sense and degree of the stereoselectivity to those obtained with an open-chain analogue indicated that the ring system does not affect the selectivity of the process. This in turn strongly suggests that the stereoselection is not related to pseudorotamer preferences in putative phosphorane intermediates. Science Foundation Ireland

The synthesis of a series of new pyrazole-based binucleating compartmental ligands, 3,5-bis(R2R3N)-(4-R1)-pyrazoles L1H L6H (L1H, R1 = H, R2 = Me, R3 = 2-py- (CH2); L2H, R1 = Ph, R2 = Me, R3 = 2-py(CH2); L3H, R1=H, R2 = Cy, R3 = 2-py(CH2); L4H, R1 = Ph, R2 = Cy, R3 = 2-py(CH2); L5H, R1 = Ph, R2, R3 = 2-py(CH2), L6H, R1 = Ph, R2 = Me, R3 = 8-quin), together with the X-ray crystal structure of L3H is reported. After deprotonation and subsequent reaction with 2 equiv of [CuI(CH3CN)4](BF4) and PMe3, L3H forms the stable binuclear CuI complex [L3{Cu(PMe3)}2](BF4) (1). The analogous reaction with L6H and 2 equiv of tert-butyl isonitrile affords [L6{Cu(CNtBu)}2](BF4) (2). 1 and 2 represent the first examples of binuclear CuI pyrazolate complexes of the type [LCuI 2]X that have been characterized by their X-ray crystal structures. With respect to the planes spanned by the pyrazolate backbone, 1 shows a cis orientation of the PMe3 ligands, whereas 2 exhibits a trans arrangement of the tBuNC ligands. L1H L6H are shown to react with 4 equiv of mesitylcopper and stoichiometric amounts of dioxygen, leading to the formation of the unusually stable organocopper frameworks 3 8. These complexes follow a general structural principle that is best described by the heteroleptic O-centered cuprate anion [(MesCuI)4 (μ4-O)]2 linked via four trans-oriented σ-mesityl bridges to two flanking binuclear CuI-pyrazolates [(L1 L6)CuI 2]þ. Thus, 1 and 2 can also be viewed as capping binuclear CuI-complex units that are concealed by two ancillary PMe3 and tBuNC ligands, respectively. The exemplary reaction of 4 with an excess of dimethyl acetylenedicarboxylate (DMDAC) supports the observed cuprate features of 3 8, since after hydrolysis the corresponding (syn-)addition product MesC(CO2Me)dC(CO2Me)H (9) and the free ligand L2H are found as major products. peerReviewed