Carbyne, reactive preparation

Yasuda, A. Kawase, N. Matsui, T. Shimidzu, T. Yamaguchi, C. Matsui, H. Carbyne electrochemical preparation and nanotube formation. Reactive Funct. Polymers 1999, 41. 13-19. 

The octahedral Ru(II) and Os(II) carbyne complexes are isoelectronic with the Group 6 compounds R—0=M(CO)4X prepared by Fischer and co-workers. Many of the Fischer compounds, particularly the cationic complexes, are susceptible to nucleophilic attack at the carbyne carbon (see Section II,B,2), and similar reactivity might be anticipated for the Group 8 carbynes. 

The first synthesis of a complex containing a metal-carbon triple bond was reported in 1973 [1]. Since then, numerous carbyne complexes have been prepared. In recent years, the study of the reactivity of these complexes has attracted considerable interest [2]. E.g. carbyne complexes have extensively been used as building blocks in the synthesis of transition metal clusters [3]. The coupling of carbyne ligands with CO or isocyanide ligands has also been studied in detail [4]. However, the number of reports on the use of carbyne complexes in synthetic organic chemistry is rather limit in contrast to carbene complexes which have found many applications in the synthesis of carbo- and heterocycles [5]. 

The preparation and study of metallacycles has been a subject of active investigation for organometallic chemists. We have just seen one example where metallacycle formation is a key step in a catalytic process and there are several others most notably, olefin metathesis. The metal acts as a geometrical and electronic template in these reactions. For unsaturated metallacycles there are interesting questions concerning delocalization [29]. Certain metal carbynes can react with acetylene to give metallacyclobutadienes as intermediates [30]. One such example of an insoluble molecule is the tungstenacyclobutadiene complex, 18.36 [31]. The compound is quite stable and not very reactive (in contrast to cyclobutadienes... 

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