Tetrapyrroles With N-Substituents

These derivatives (Type B) are at least formally prepared by the insertion of a fragment into a M-N bond to yield a new M-X-N unit. Such species have been suggested as possible intermediates in the insertion of an oxygen atom into a G-H bond by cytochrome P-450. Several of these derivatives have formally had a carbene fragment inserted into a M-N bond. Such derivatives include a Ni derivative and a cobalt(III) species that has undergone two such insertion reactions. Other species represent the formal reaction of a vinylidene with iron(III) (two different crystalline forms). This iron derivative has an intermediate-spin state. Other complexes result from the insertion of a nitrene or an oxene This last derivative can also be considered to be a porphyrin N-oxide derivative and the structure of a free base species of a porphyrin N-oxide has also been reported . Appropriate stereochemical parameters for the members of this class are found in Table IX. 

A related substance, another sitting-atop model, is a bischloromercury(II) complex of N-tosylaminooctaethylporphyrin. The two Hg ions are on opposite sides of the porphyrin plane and are in quite different coordination environments. One Hg ion is coordinated to the tosylamino nitrogen and a chloride ion in a linear fashion. The second Hg ion is coordinated to the three other porphyrin nitrogen atoms and one chloride ion. (See structure F). 

A most remarkable compound with N-substituents has been obtained by reaction of iodonium ylides with an Fe porphyrinate. The product is a bis(metallocycle) of type D. The iron(II) ion is high spin. The structure has an in-plane iron(II) with Fe-N(alkyl) = 2.242(5) A and Fe-N = 2.082(5) A. The latter bond distance is slightly larger than that of other six-coordinate high-spin iron(II) species. 

Balch and coworkers have reported that triruthenium dodecacarbonyl reacts with a N,N -vinyl bridged porphyrin to yield structure E. Ru-N bond distances range from 2.068 to 2.257 A. 

The structures of two crystalline forms of monoprotonated octaethylporphyrin (monocation) have now been reported in detail. One pyrrole ring is tipped out of the plane of the other three in order to allow the simultaneous positioning of three hydrogen atoms at the center of the ring. 

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