Abstract:
The synthesis and selected crystal structures of novel (M = Cr or Mo) and known (M =W) [(CO)4(PPh3)
M = C(OEt)R] complexes, M = Cr, R = 2-thienyl (1), 2-furyl (2); M = Mo, R = 2-thienyl (3), 2-furyl (4);
M = W, R = 2-thienyl (5), 2-furyl (6), are presented. Experimental crystal structures and DFT calculations
of selected trans- and cis-triphenylphosphine-substituted Fischer carbene complexes, illustrate that the
minimum energy conformation of triphenylphosphine (PPh3) in octahedral [(CO)4(PPh3)ML]-complexes
generally have distinct features that can be described in terms of the ‘‘plane of nadir energy’’, a plane
linking all points of minimum steric compression between the ligands. The generally observed orientation
of PPh3 involves a correlated feathering of the phenyl groups with the PACipso bond of one phenyl
group orientated near parallel to the nadir plane, and a meta carbon (Cm) of the other two phenyl groups
orientated as near as possible to the nadir plane, orthogonal to the first. Although the orientation of PPh3
in 6-trans, [(CO)4(PPh3)W = C(OEt)2-furyl], deviates from this, DFT correctly calculated the unexpected
and not generally observed PPh3 orientation.
