For 10 points, name this coordination number of square pyramidal and trigonal bipyramidal complexes.
Molecules with this coordination number include the intermediate in the counterpart of the Eigen-Wilkins mechanism and the product of the rate-determining step of the SN1cb mechanism. Tren ligands enforce one geometry of this coordination number, which is exemplified by a complex consisting of a metal atom bonded to a scorpionate ligand and dppe. The failure of fluorine-19 NMR to distinguish between (*) axial and equatorial substituents in complexes with this coordination number led to the discovery that they can isomerize through Berry pseudorotation. Associative substitution reactions that go through intermediates of this coordination number experience the trans effect. Intermediates of this coordination number occur in dissociative substitution reactions of octahedral complexes. For 10 points, name this coordination number of square pyramidal and trigonal bipyramidal complexes.
Molecules with this coordination number include the intermediate in the counterpart of the Eigen-Wilkins mechanism and the product of the rate-determining step of the SN1cb mechanism.
five [antiprompt on "square pyramidal" or "trigonal bipyramidal" before mentioned; do not prompt on "trigonal pyramidal" or "pyramidal" alone]