Six derivatives of 2-benzimidazolone, disubstituted in the 4 and 5 positions, have been synthesized, and their structures have been determined in the solid state. Four of these compounds crystallize as molecular tapes. Compounds 1-(CH3)2 , 1-Cl2 , and 1-Br2 form tapes that pack with their long axes parallel; compounds 1-H2 and 2-H2 form tapes that pack with their long axes at an angle to one another. Compounds 1-F2 and 1-I2 crystallize with a three-dimensional network of hydrogen bonds. The packing arrangement of molecular tapes is rationalized on the basis of closest packing and electrostatic interactions between aromatic rings. The occurrence of the network motif rather than the tape motif for 1-F2 and 1-I2 is rationalized on the basis of secondary interactions involving the halogen atoms.

The investigation of transition metal-mediated allyllalkyne coupling reactions has revealed a range of synthetically valuable' or potentially e~p l o i t a b l e~.~ reactivity pattems. Particularly interesting are the q3-allyllalkyne cyclization reactions reported by Rubezhov, assembling the q5-cyclopentadieny13a and 7' ,r4-methanocy~lohexadiene~~ ring systems by incorporation of one or two alkyne equivalents, respectively. In this communication, we report a new reactivity pattem on this energy surface: sevenmembered-ring synthesis via metal-mediated [3 + 2 + 21 cycloaddition, coupling an q3-allyl ligand with two alkynes to yield the q5-cycloheptadienyl ring system (eq 1). Eq. 1Treatment of q3-allyl 2-butyne complex 2a, prepared as previously described or generated in situ from triflate complex 1: with diphenylacetylene leads to the formation of the tetrasubstituted q5-cycloheptadienyl complex 35 in 56% yield, (1) Cyclization or linear coupling of allyl and alkyne ligands. (a) Chuisoli reaction and related Ni "metalla-ene" processes: Chiusoli, G. P.

This paper describes approaches to reduce susceptibility of perfluorosulfonic acid membranes such as Nafion® to degradation through chemical attack by oxygen-based radicals and physical degradation as a result of mechanical stress. These approaches include the incorporation of a continuous reinforcing layer and modification of the polymer to stabilize it against attack by peroxide radicals.

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