Cyclopropylcarbyne complexes

The synthesis of cyclopropyl carbyne complexes follows the general Fischer synthesis of carbyne complexes from alkoxycarbene complexes typical of transition metals of group 6 (Cr, Mo, W). Thus, addition of cyclopropyllithium to chromium and tungsten hexacar-bonyl followed by alkylation of the acylmetallate intermediate with triethyloxonium fluo-roborate gave cyclopropyl ethoxycarbene complexes which, upon subsequent reaction with boron tribromide at -25 °C, afforded the corresponding /ra 5 -bromotetracarbonyl cyclopropylcarbyne complexes (equation 91). However, whereas the monotungsten... 

Irradiation of 69 in chlorinated solvents in the presence of tri-methylphosphine gives rise to the oxidized products 70. The reaction was postulated to proceed via short-lived 17-electron carbyne complex intermediates. Electrochemical evidence for the existence of 17-electron species was reported. In the absence of trimethylphosphine no products could be characterized for the molybdenum phenylcarbyne complex. In the absence of trimethylphosphine the tungsten cyclopropylcarbyne complex affords W( / -C5H5)Cl3(CO)[P(OMe)3] and cyclopentenone [Eq. (59)] (99). 

Similarly, the ketenyl complex 187 forms after addition of trimethylphos-phine to the cyclopropylcarbyne complex 186 at — 15°C (Eq. (151)] (168). 

---