Conjugated Organometallic Polymers Containing Vollhardt's Cyclobutadiene Complex: Aggregation and Morphologies

Abstract

Organometallic polymers were prepared by acyclic diyne metathesis (ADIMET) or by Pd-catalyzed coupling of 1,3-diethynylcyclobutadiene(cyclopentadienyl)cobalt with a suitably substituted diiodobenzene. The polymers obtained by Heck coupling show a degree of polymerization (Pn) of 20-60. The monomers for ADIMET were made by the Pd-catalyzed coupling of [1,3-bis(trimethylsilylethynyl)-2,4-bis(trimethylsilyl)cyclobutadiene](cyclopentadienyl)cobalt to 1-bromo-2,5-dialkyl-4-propynylbenzenes in the presence of KOH in yields of 40-48%. The monomers carry hexyl, ethylhexyl, and (S)-3,7-dimethyloctyl side chains. Polymerization of the propynylated monomers furnishes organometallic polymers with a Pn of up to 230 arylene-ethynylene units. The polymers were fully characterized by polarizing microscopy, transmission electron microscopy, circular dichroism, differential scanning calorimetry, and X-ray diffraction (XRD). They show nematic, lyotropic liquid crystalline phases as well as chiroptical properties from which aggregation in poor solvents and in the solid state can be concluded. Lamellar or irregular honeycomb-shaped morphologies in these organometallic polymers can be detected by electron microscopy.

Metallochain Cluster Complexes and Metallomacrocyclic Triangles Based on Coordination Bonds between Palladium or Platinum and Diphosphinoacetylene Ligands

“…As a cluster component, we investigated the tetrahedral, redox-active acetylene-dicobaltcarbonyl unit, accessible by reaction of [Co 2 (CO) 8 ] with alkynes. [30] Reaction of 5 with two equivalents of [Co 2 (CO) 8 ] affords the cluster model compound 7 in good yield (82 %; Scheme 2).…”

“…[30] Reaction of 5 with two equivalents of [Co 2 (CO) 8 ] affords the cluster model compound 7 in good yield (82 %; Scheme 2). The reaction was performed in CH 2 Cl 2 at room temperature and was easily monitored by the evolution of CO.…”

“…Species 8 is accessible in a similar reaction by treatment of 6 with two equivalents of [Co 2 (-CO) 8 ]. The 31 P NMR resonance of d 37.9 ppm (J(Pt,P) 3695 Hz) is again shifted downfield from the starting material 6 (d À 11.8 ppm; J(Pt,P) 3475 Hz), due to the ring-contribution of the five-membered ring system.…”

“…[1±4] For example, the presence of transition metal centers has been shown to permit redox control of the size and shape of a macroscopic object [5] and the ™wiring∫ of enzymes to electrodes, [6] selective binding and sensing, [7] and the generation of liquid crystallinity [8] and magnetic nanoparticle composites, [9,10] etch resistance to plasmas, [11,12] as well as other desirable physical and chemical characteristics. [13] The use of covalent bonds to create main-chain metallopolymers is now relatively well-developed as illustrated by the cases of extensively studied systems such as polyferrocenes and polymetallaynes.…”

Polymer science with transition metals and main group elements: Towards functional, supramolecular inorganic polymeric materials

“…For example, novel rigid-rod organocobalt polymers have been prepared via metalcatalyzed acyclic diyne metathesis and have been shown to form lyotropic liquid-crystalline phases in solution and lamellar and irregular honeycomb-shaped morphologies in the solid state. 73 In addition, weak metal-metal interactions involving the heavy late-transition elements Cu, Ag, and Au have been recently used to guide the self-assembly of metallacyclic building blocks into luminescent, superhelical fibers. 74 Clearly, the structural diversity and immense range of properties and molecular interactions made possible by the presence of inorganic elements coupled with the reality of a growing number of critically needed synthetic breakthroughs is expected to make the study of the supramolecular science of inorganic polymers an exciting and expanding area of future research.…”