A new organic ligand of pyrene-containing tetracarboxylic acid and its first metal−organic framework UTSA-72 was designed and synthesized. The MOF has the two-dimensional (4,4) framework topology. The activated UTSA-72a exhibits permanent porosity and moderately high selectivities for CO 2 /N 2 , C 2 H 2 /CH 4 , and CO 2 /CH 4 gas separations at room temperature because of the small pores within the framework.

The cobalt­(I) pincer complex, [Co­(N2)­(CyPNP)] (CyPNP = anion of 2,5-bis­((dicyclohexylphosphino)­methyl)­pyrrole), reacts with aromatic, vinylic, and aliphatic aldehydes to produce the corresponding hydrocarbon products and [Co­(CO)­(CyPNP)]. The pathway for aldehyde decarbonylation is found to involve initial coordination of the aldehyde to Co­(I), followed by oxidative addition of the C–H bond to produce a cobalt­(III) acyl hydride. The acyl hydride species then undergoes CO deinsertion, followed by reductive elimination to afford the decarbonylated product and [Co­(CO)­(CyPNP)]. Reactions of [Co­(N2)­(CyPNP)] with other carbonyl containing groups such as carboxylic acids and amides also proceed via oxidative addition to give Co­(III) intermediates arising from activation of the X–H (X = O or NH) bond. In these cases, however, the Co­(III) species extrude molecular hydrogen to produce Co­(II) species of the form [Co­(X­{O}­CR)­(CyPNP)] (X = O or NH). The ability of [Co­(N2)­(CyPNP)] to undergo facile oxidative addition is discussed in the context of potential bond activation processes mediated by well-defined Co species.

The Co(I) complex, [Co(N 2 )( Cy PNP)] ( Cy PNP = anion of 2,5-bis-(dicyclohexylphosphinomethyl)pyrrole), is active toward the catalytic hydrogenation of terminal alkenes and the semi-hydrogenation of internal alkynes under 2 bar of H 2 (g) at room temperature. The products of alkyne semi-hydrogenation are a mixture of E-and Z-alkenes. By contrast, use of the related cobalt(I) precatalyst, [Co(PMe 3 )-( Cy PNP)], results in formation of exclusively Z-alkenes. A semi-stable Co(II) species, [CoH( Cy PNP)], can also be generated by treatment of degassed solutions of [Co(N 2 )( Cy PNP)] with H 2 . The Co II -hydride displays activity toward both alkene hydrogenation and isomerization, but its instability hampers implementation as a catalyst. Several species relevant to potential catalytic intermediates have been isolated and detected in solution. These compounds include alkene and alkyne adducts of Co(I) as well as a Co(III) dihydride species. Catalytic results with the compounds examined are most consistent with a process involving shuttling between Co(I) and Co(III) states. However, generation of small quantities of Co(II) during catalytic turnover appears to be responsible for the isomerization observed for alkyne semi-hydrogenation. The interplay of cobalt oxidation states within the same catalyst system is discussed in the context of mechanistic scenarios for catalytic hydrogenation.

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