All-carbon networks

The MejSi protecting groups in 58 a and 59 a could be removed by treatment with sodium tetraborate (borax) in MeOH/THF, yielding 58c and 59 c, respectively, as very unstable compounds [84]. Any attempts to obtain characterizable two-dimensional all-carbon network structures [3,4] by oxidative polymerization of 59 c have failed. 

The link between cyclo[ ]carbons and tetraethynylethene is the occurrence of both structural motifs as repeat units in fascinating two-dimensional all-carbon networks [3,4]. The development of viable preparative approaches toward these elusive acetylenic networks represents one of the true challenges for synthesis at the turn of the millennium. 

But not only organic stannylacetylenes coupled to 62 organometallic stanna-nes also gave rise to the formation of pentametallic complexes 64-67 in fair to good yields, and the cross-shaped complex 64 already is a sizable segment out of the proposed organometallic all-carbon network. It was possible to obtain X-ray... 

Acetylenic Molecular Scaffoldings From Perethynylated Building Blocks to All-Carbon Networks and Carbon-Rich Nanostructures... 

Several two-dimensional all-carbon networks comprise the core of tetraethynylethene (TEE 17) as a monomeric repeat unit11,121 In 1991, we synthesized the hitherto dusive perethynylated ethene 17 on the way to these novel materials.1361 In the... 

High-temperature pyrolysis techniques are now applied with surprising selectivity, leading to all sorts of bowl-shaped molecules, which are substructures of C60 and higher fullerenes. Combinations of saturated and unsaturated, acyclic and cyclic fragments with acetylenic subunits have led to two-dimensional and three-dimensional arrays and all-carbon networks. 

Tetraethynylethene (20) and its differentially protected derivatives are versatile building blocks for two-dimensional all-carbon networks and carbon-rich nanomaterials [1]. In addition, they attract interest for their fully cross-conjugated 7c-electron system [33], The first tetraethynylethene derivative, 21a, was reported in 1969 by Hori and co-workers [34], and the persilylated and peralkylated derivatives 21b-d were prepared in the mid-1970 s by Hauptmann [35]. In 1991, Hopf et al. [36] summarized this early synthetic work (Scheme 13-5) and reported the X-ray crystal structure of 21a the authors also suggested in their paper the potential of substituted tetraethynylethenes as monomers for new polymers. Also In 1991, Rubin et al. [37] reported the first synthesis of the parent compound 20 by a synthetic route, which, after suitable modifications, provided access to tetraethynylethenes with any desired substitution and protection pattern. These transformations are the subject of this Section the application of these compounds as precursors to two-dimensional all-carbon networks tmd carbon-rich nanomaterials will be discussed in the following sections. 

In Section 13-4, it will be shown that tetraethynylethenes are potential monomers for the construction of all-carbon networks [1]. Other perethynylated compounds have been reported, which could also serve as building blocks for infinite two- and three-dimensional carbon nets [46]. They all represent fascinating small molecules of substantial structural and electronic interest [1, 2, 47]. 

Figure 13-1 Planar all-carbon networks 45 and 46 derived from tetraethynylethene.

Scheme 13-10 Preparation of perethynylated dehydroannulene precursors to planar all-carbon networks.

Scheme 28.5 Imaginary all-carbon networks comprising tetraethynylethene as repeat unit 17-19 and retrosyntheti-cally designed monomers 13-16.

For some property predictions of certain all-carbon networks, see (a) Narita, N., Nagai, S., Suzuki, S., and Nakao,... 

For reviews which, at least in part, contain all-carbon networks, see ... 

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