Biscarbyne complexes

Further reactions of 5/6 with the sterically less bulky silanes HSiCl3, Ph2SiHCl and Ph2SiH2 give the thermo-labile /x-biscarbyne complex 14, which has been spectroscopically characterized (Table 1). In these cases, formation of the silyl hydrides 11, 13, 15 and 16 as products of an oxidative addition at the 16e -complex generated from 6 (attack at Mn) becomes important. 

EtMe4C5)Mn(CO)3 18 and reaction of the photolytically generated species [(jj5-EtMe4C5)Mn(CO)2 x THF] 19 with (f-Bu)2SiHCl 7 yields the p-biscarbyne complex 20, but also the carbonyl complex 22 with a manganese manganese triple bond (Scheme 3) [12],... 

Reaction of the carbonyl complex 26 with the mercury diazomethane 27 gives the highly reactive 17e intermediate carbyne complex 28 which dimerizes to form the / -biscarbyne complex 30. In this case, the intermediate terminal carbyne complex 28 has been trapped by reaction with the mercury diazomethane 29 to form the cyclic vinylidene complex 31. 31 was also characterized by a single crystal X-ray structure analysis. 

We describe a further reaction channel involving CO-activation by O-attack of the silane (C) and subsequent carbyne-complex formation by electron transfer M—>C and dimerization of the formed 17e intermediate to a stable /i-biscarbyne complex 8 (Chart 1). 

Herrmann has reported the reaction of the mercury diazo compound Hg(CN2C02Et)2 with Mn(CO)sBr to afford the biscarbyne-bridged dimer 90 (128). The intermediacy of a terminal mononuclear carbyne complex 89 is strongly implicated here ... 

The occurrence of discrete oxidation steps for each ferrocenyl substituent in the diferrocene complex indicates that the biscarbyne cobalt core CC03C does not constitute an impassable barrier to electronic interaction between the two redox centers. 

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