The Mossbauer spectra of the imidazole, pyridine, and piperidine adducts of a"8, , -tetraphenylporphyriniron(II) and protoporphyriniron(II) and the imidazole and pyridine adducts of the corresponding porphyriniron(III) chlorides have been measured. Only the heme compound could be obtained with piperidine because piperidine causes spontaneous reduction of iron(III) to iron(II) in porphyrin complexes. For the iron(II) cases, the imidazole and pyridine adducts show similar isomer shifts, while the piperidine adducts have slightly larger isomer shifts. Imidazole gives the smallest quadrupole splitting; piperidine gives the largest. For the iron(III) cases, imidazole gives a somewhat larger isomer shift than pyridine and causes a much greater quadrupole splitting than pyridine, in contrast to the iron(II) cases. These results are discussed in terms of differences in x-bcmding characteristics between the added ligand and the iron atom. Pyridine appears to have a greater affinity for heme than does piperidine.

In most general chemistry textbooks the discussion of Lewis structures is unnecessarily complicated by the misuse made of the octet rule. (For textbooks consulted see ref.1.) Several pages are devoted to apparent "exceptions" to this rule, mainly involving boron compounds such as BF3 or BCI3 (which is shown with an "incomplete octet" of six electrons around the boron) and oxygen-containing compounds of the nonmetals (oxides, oxoacids, oxoanions such as S03, H3S04, C10,r, with a multitude of mesomeric and resonance forms involving anywhere from eight to 16 electrons around the central atom). Many of these discussions are misleading and some are incorrect. It is the purpose of this paper to consider evidence for multiple bonding in boron compounds. A subsequent paper will consider oxygen bonds to other nonmetals. DiscussionMuch of the confusion regarding the supposed exceptions to the octet rule can be circumvented by considering it to apply only to compounds of the 2p elements B, C, N, O, and F, and then very strictly. That is, there are (almost) always eight electrons around the B, C, N, O, and F atoms in their compounds, never more than eight, and less than eight only in cases where eight is mathematically impossible, i.e., when there is an odd number of valence electrons, as in NO and N02, or when there are not enough valence electrons, as in boron hydrides, or compounds like (CH3)3B. (Consideration of hyperconjugation is inappropriate in a general chemistry context.) In this view, the octet rule takes precedence over electronegativity and formal charge concepts (2) for these elements but does not apply to compounds of the 3p, 4p, and 5p nonmetals. This modified interpretation implies the maximum amount of it-bonding Literature Cited

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Several new iron(IV) complexes of , -disubstituted dithiocarbamates have been prepared by reaction of tris(dithiocarbamato)iron(III) complexes with boron trifluoride in the presence of air. These have been characterized as tris(N,N-disubstituted dithiocarbamato)iron(IV) tetrafluoroborates by a number of physical methods. The isomer shifts of these compounds (0.46 ± 0.02 mm/sec) are significantly lower than those of iron(III) dithiocarbamates (0.64 ± 0.03 mm/sec). The quadrupole splittings are 2 mm/sec or greater.