SYNTHESIS AND OXIDATION OF CATIONIC HETEROBINUCLEAR CYANIDE-BRIDGED COMPLEXES OF MANGANESE AND IRON

Several heterobinuclear cyanide-bridged cationic complexes of the type [LnM1-CN-M2Ln]+, where LnM1 and LnM2 are the fragments Fe(C5H5)(dppe) or cis- or trans-Mn(CO)2(L-L)L [L-L = dppm, dppe; L = P(OPh)3, PEt3; dppe = Ph2P(CH2CH2)PPh2; dppm = Ph2P(CH2)PPh2], have been prepared as hexafluorophosphate salts by reacting the appropriate mononuclear complexes LnM1-CN and X-M2Ln (X = Br, I) in the presence of TlPF6 or (NH4)PF6 as halogen abstractors. The oxidation of these compounds have been studied electrochemically by cyclic voltammetry and chemically by infrared spectroscopy. The results indicated that the first oxidation of the cations affects the Fe or Mn fragment depending on its position relative to the cyanide bridge and the stereochemistry (cis or trans) of the dicarbonyl fragments. When the oxidation affects a cis-Mn(CO)2(L-L)L moiety, a very rapid isomerization to the trans form is observed and, in the case of the cis-dicarbonyl complexes [(C5H5)(dppe)Fe-CN-Mn(CO)2(L-L)L]+, the first oxidation takes place at Fe but is followed by electron transfer to Mn with concomitant isomerization to the trans-dicarbonyl form.