Topologically unique heterometallic Cu II/Li coordination polymers self-assembled from N, N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid biobuffer: Versatile catalyst precursors for mild hydrocarboxylation of alkanes to carboxylic acids

The facile aqueous medium reactions of copper(II) nitrate with BES biobuffer [(HOCH 2CH 2) 2N(CH 2CH 2SO 3H), hereinafter referred as H 3bes] in the presence of various benzenecarboxylic acids [benzoic (Hba), 3-hydroxybenzoic (Hhba), and 3,5-dihydroxybenzoic (Hdhba) acid] and lithium hydroxide gave rise to the self-assembly generation of three new heterometallic Cu II/Li materials, [Li(H 2O) 4][Cu 4(μ 2- Hbes) 4(μ 2-ba)]•H 2O (1) and [Cu 4(μ 3-Hbes) 4(L){Li(H 2O) 2}] n•3nH 2O {L = μ 2-hba (2) and μ 2-dhba (3)}. They were isolated as air-stable crystalline solids and fully characterized by infrared (IR) and UV-vis spectroscopy and electrospray ionization (ESI)-MS(±), elemental, thermal, and single-crystal X-ray diffraction analyses. The latter revealed that 1-3 have comparable packing patterns and unit cell parameters, being composed of similar [Cu 4(μ-Hbes) 4(μ-carboxylate)] - cores and [Li(H 2O) 4] + cations (in 1) or [μ-Li(H 2O) 2] + groups (in 2 and 3), which are arranged into discrete 0D aggregates in 1 or infinite 3D noninterpenetrating metal-organic networks in 2 and 3. The topological analysis of the coordination polymers 2 and 3 disclosed the trinodal 3,3,4-connected underlying nets with an unprecedented topology defined by the point symbol of (4.6.8) 4(4 2.6) 2(6 2.16 2.18 2), further simplification of which resulted in the binodal 4,4-connected nets with the pts (PtS) topology. Apart from representing very rare examples of coordination compounds derived from H 3bes, 1-3 feature solubility in water and were applied as efficient and versatile catalyst precursors for the mild (60 °C) single-pot hydrocarboxylation, by CO and H 2O, of various gaseous, linear, and cyclic C n (n = 2-9) alkanes into the corresponding C n+1 carboxylic acids, in H 2O/MeCN medium under homogeneous conditions and in the presence of potassium peroxodisulfate. Total yields (based on alkane) of carboxylic acids up to 78% were achieved, which are remarkable in the field of alkane functionalization under mild conditions, especially for a C-C bond formation reaction in aqueous acid-solvent-free medium. © 2012 American Chemical Society.