059 VSSe(SR) IC - 3030 I norg. Chem. 1987, 26, 3 030-3034 i...

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3030 Inorg. Chem. 1987, 26, 3030-3034 inspection of Table VI reveals that AEQ values increase steadily as the precentage of S = 3/2 character increases. We have noted previously the correlation of large with small spin-orbit coupling ({) and small hyperfine field (pK/g~&).~" The results suggest that the carborane ligand is a stronger field ligand than hexafluoroantimonate since they analyze for 92 and 98% S = 3/2, respectively. This is interesting because viewing their structures solely in the context of spin state would lead to the opposite conclusion. The Fe-N bond lengths and the Fe out-of-plane displacements1' are smaller for the carborane than for the hex- afluoroantimonate, as expected for a lower S = 5/2 contribution. An explanation lies in the interplay of field strengths and binding strength and reminds us that these factors are not synonymous nor necessarily correlated. The pr donor capability of the fluoride donor apparently makes SbF, a weaker field ligand than BIICH,< despite the stronger binding indicated in the structural comparison. The carborane is not capable of pr donation. If the two anions were hypothetically assumed to have equal u-donor interactions, then the SbF6- coordination parameters would be expected to be the same as or smaller than B11CH12-. That they are larger indicates that the a-donor interaction of SbF,- is considerably greater than that of Bl,CHl,-. This further supports the hy- pothesis" that BIICHIZ- is the lesser coordinating of these two anions. In summary, a combination of susceptibility and Mossbauer studies and a knowledge of structure lead to a good quantitative description of the magnetic properties of intermediate-spin iron- (111) porphyrins. Previously unrecognized intermolecular anti- ferromagnetic coupling of moderate magnitude seems to be the rule rather than the exception in five-coordinate complexes, particularly when association into dimers occurs in the crystal lattice. The question of spin coupling among six-coordinate porphyrin complexes remains open since coupling involving more than a pair of lattice sites does not provide an easily identified signature in the Mossbauer spectrum. Acknowledgment. We thank the National Institutes of Health for support of this work under Grants HL-16860 (G.L.) and GM-38401 (W.R.S.) and the National Science Foundation for the support under Grant CHE85-19913 (C.A.R.). Registry No. [Fe(TPP)(B, ,CH,,)]C,H~, 102 149-5 1-9; Fe(TPP)Br, 25482-27-3. Supplementary Material Available: For [Fe(TPP)(Bl,CH12)]C7H,, Table IS (magnetic measurements), Tables IIS and IIIS (fixed atomic coordinates), and Table IVS (anisotropic temperature factors) (5 pages); a listing of observed and calculated structure amplitudes (XlO) (25 pages). Ordering information is given on any current masthead page. Contribution from the Department of Chemistry and the Molecular Structure Center, Indiana University, Bloomington, Indiana 47405 Direct Synthesis of VE2+ (E = S, Se) Complexes Using Elemental Chalcogens.
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This note was uploaded on 01/20/2012 for the course CHM 2210 taught by Professor Reynolds during the Fall '01 term at University of Florida.

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059 VSSe(SR) IC - 3030 I norg. Chem. 1987, 26, 3 030-3034 i...

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