Abstract:
Homo- and heteronuclear bimetallic carbene complexes of group VII
transition metals (Mn and Re), with cymantrene or cyclopentadienyl
rhenium tricarbonyl as the starting synthon, have been synthesized
according to classic Fischer methodology. Crystal structures of the carbene
complexes with general formula [RC5
H4
M'(CO)2
{C(OEt)(C5
H4
M(CO)3
)}], where
M = M′ = Mn, R = H (1), R = Me (2); M = Mn, M′ = Re, R = H (3); M = M′ = Re,
R = H (4); and M = Re, M′ = Mn, R = H (5), are reported. A density functional
theory (DFT) study was undertaken to determine natural bonding orbitals
(NBOs) and conformational as well as isomeric aspects of the binuclear
complexes. Application of second-order perturbation theory (SOPT) of
the NBO method revealed stabilizing interactions between the methylene
C–H bonds and the carbonyl ligands of the carbene metal moiety. Energy
calculations in the gas phase of the cis and trans conformations of the Cp
rings relative to one another are comparable, with the trans conformation
slightly lower in energy. The theoretical findings have also been confirmed
with single-crystal X-ray diffraction, and all solid-state structures are found
in the trans geometry.
