Macrocycle planar pentadentate

A number of similar trinuclear complexes were prepared with Mn(II) using the pentadentate macrocycle maodp as a planar blocking ligand. The reaction between [Mn°(maodp)(H20)2l and [Fe CN)6]" results in the neutral product [Mn maodp)(H20)]2[Fe CN)6] (101). As in the case of the complexes formed with Mn(III) Schiff base building blocks, the H2O molecule coordinated to each peripheral Mn(II) center is arranged trans to the bridging cyanide [Fig. 16(a)]. 

A review of expanded porphyrin hgands can be fonnd. The texaphyrins (8) can be considered as 22-tt-electron benzaimnlene systems with an IS-tt-electron delocahzation path, based on crystal stmctnre data as well as NMR. The cadminm complex of the macrocycle is fonnd to be planar with pentadentate coordination of the macrocycle to cadminm, which becomes seven-coordinate as a resnlt of axial coordination to two pyridine molecnles. The cavity is nearly circular with a center-to-nitrogen distance of 2.39 A. Because of the larger size of this macrocycle, metal ion coordination is generally seen with the larger transition metals and lanthanides. 

Pentadentate macrocyclic ligands with the topology shown in Scheme 18 are flexible enough to wrap around five- or six-coordinated metal centers. However, they often appear in a planar conformation in pentagonal bipyramidal seven-coordinate complexes with a trans conformation. 

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