Abstract:
Reactions of Fischer alkoxycarbene complexes
[W(CO)5{C(OEt)Ar}], Ar = thienyl (1) or furyl (2), with ethylene
diamine lead to the formation of two different reaction products:
an aminolysis product (5 or 6) where the ethoxy substituent of the
carbene ligand is replaced by the ethylene diamine moiety, as well
as a chelated product where aminolysis and substitution of one
carbonyl ligand had taken place, yielding 7 or 8. Aminolysis of 1
and 2 with cyclohexyl amine (CHA) produced the aminocarbene
complexes 3 (Ar = thienyl) and 4 (Ar = furyl). Complexes 1-8 are
electrochemically investigated by means of cyclic voltammetry.
The relative shifts in the oxidation and reduction potentials are
discussed and related to density functional theory (DFT) calculated
energies. DFT calculations further show that the oxidation
center is located on the metal and the carbonyl groups, while the
reduction center is localized on the carbene moiety and is strongly
influenced by the electronic properties of its substituents. Crystal
structures of 1-4, 6 and 8 are reported.
