184701-35-7Relevant academic research and scientific papers
Synthesis of bis(methoxycarbene) and bis(alkylidene) ligands bridging two iron centers in the Cp*Fe(L1)(L2) series. X-ray crystal structure of the iron alkylidene [Cp*Fe(dppe)(=C(H)Me)][PF6]
Mahias, Virginie,Cron, Stéphane,Toupet, Loic,Lapinte, Claude
, p. 5399 - 5408 (1996)
The carbene [Cp*Fe(dppe)(=C(OMe)Me)][CF3SO3] [2b, Cp* = η5-C5Me5, dppe = ethyl-enebis(diphenylphosphine)] was prepared in 97% yield from [Cp*Fe(CO)2(=C(OMe)Me)][CF3-SO3] upon photochemical displacement of the carbonyl ligands, and the iron methoxycarbene [Cp*Fe(CO)(PMe3)(=C(OMe)Me)][CF3SO3] (2c) was obtained (80%) upon alkylation of the acyl derivative Cp*Fe(PMe3)(CO)(COCH3) (4). The iron-methylidene [Cp*Fe(dppe)(=C(H)-Me)][PF6] (6) was synthesized (95%) by treatment of Cp*Fe(dppe)(CH(OMe)Me) (5) with an aqueous solution of hexafluorophosphate acid. The ethylidene 6 is very stable in solution as in the solid state, and no decomposition reaction was observed by NMR spectroscopy at 50 °C. The X-ray crystal structure of 6 was solved and refined. The Fe-C(37) bond distance (1.787 A?) reveals the double-bond character of the metal-carbon bond. Reaction of the iron carbene complexes 2a-c and 6 with 2 equiv of potassium tert-butoxide in THF gave the corresponding vinyl derivatives 7a-d in high yield (80-90%). CV analyses of the vinyl complexes 7a-d display at 20 °C an oxidation wave at a platinum electrode with the (ipa/ipc) current ratio less than unity. CV and ESR measurements established the stability of the 17-electron vinyl radical in CH2Cl2 at -80 °C. Warming to 20 °C of the 17-electron iron(III) complexes [7a-d]?+[PF6-] in solid state allows the vinyl-vinyl coupling providing the new binuclear bis(carbene) complexes 8a-d in 60-95% yield. The complex 8a was isolated as a pure diastereoisomer, whereas 8b was a mixture of the meso 8b(RS,SR) and dl 8b(BR,SS) isomers in the 2/1 ratio. The diastereoisomers were separated by CH2Cl2 extraction which only solubilizes the dl pair.
