An Intermolecular Double [2+2] Cyclodimerization of a Tetraalkyne

Abstract

Double take: An intermolecular double [2+2] cyclodimerization of vinylidene bisalkynes gives an air‐stable organometallic complex with an extraordinary ligand motif (see scheme). The central six‐membered ring has all sp2‐hybridized carbon atoms and two exocyclic double bonds, and is a stable de‐aromatized analogue of p‐xylene.

Overcoming a Tight Coil To Give a Random “Co” Polymer Derived from a Mixed Sandwich Cobaltocene

“…71,72 CpCoCb also has the important advantage of the facile preparation of a wide variety of derivatives using well-established cyclodimerization chemistry from substituted alkynes, to install a functionalized cyclobutadiene (Cb) ring, which again opens doors for novel, onward chemistry, or in imposing additional chemical functionality to the sandwich complex. 73,74 Our group has previously reported the first polymer derived from polymerization of such a mixed sandwich cobaltoarenocene-containing monomer (3). In this study, the polymer-ization reaction time was lengthy (days), and despite up to 90% monomer conversion, only low molecular weight polymers were produced.…”

“…Cobaltoarenocene featuring η 5 -cyclopentadienylcobalt-η 4 -cyclobutadiene (CpCoCb) is a neutral, 18-electron species, isoelectronic with ferrocene (Fc) and cobaltocenium ion ([Cp 2 Co] + ) with physical and chemical properties more closely aligned with Fc, such as excellent solubility in a wide range of common organic solvents. , CpCoCb also has the important advantage of the facile preparation of a wide variety of derivatives using well-established cyclodimerization chemistry from substituted alkynes, to install a functionalized cyclobutadiene (Cb) ring, which again opens doors for novel, onward chemistry, or in imposing additional chemical functionality to the sandwich complex. , …”

The Development of Boronic Acids as Sensors and Separation Tools

“…in a study of the reactions of the boronic acid fragment;[19] this concept was applied in the sensing arena by Xu et al., where the rate of a palladium catalyzed cross‐coupling reaction that delivered a probe molecule was modulated by the presence of sugars, thus acting as an indirect, but very effective, probe for saccharides. [18b] The application of polyalkynes, which are in themselves versatile building blocks in organometallic chemistry[20] and have the potential to be developed into bespoke, selective, and complex click‐fluor sensors, was elegantly demonstrated by Shao and Zhao. [18c]…”

Organometallic chemistry of bi- and poly-metallic complexes

“…95 The cobalt complex (22) has been synthesised from an intermolecular double [2+2] cyclodimerization of a tetraalkyne instead of the expected intramolecular double [2+2] cyclodimerization. 96 A DFT study into the level of unsaturation in binuclear (cyclobutadiene)cobalt carbonyls with axial and perpendicular structures has been carried out and a comparison made with the isoelectronic binuclear cyclopentadienyliron carbonyls. 97 The bimetallic complexes [Fe 2 (CO) 5 (m-Pn*)] and [Co 2 (CO) 4 (m-Pn*)] (Pn* = synpermethylpentalene) have been studied theoretically and found not to contain metal-metal bonds despite the close proximity of the metal atoms revealed by Xray crystallography.…”