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(R9 = R0 = Ar). Importantly, the consistency between absorption
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the basis of the isolobal relationship between neutral tetrahedral
carbon and anionic tetrahedral boron; the electronic spectra of the
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In summary, we have reported the synthesis and structural
characterization of ‘boratatetrazines’, boron complexes of the
formazan ligand. This highlights the potential versatility of
formazans for main group chemistry, and in addition we have
demonstrated a facet of formazan chemistry that is not, to our
knowledge, available to b-diketiminates or other related ligands:
the ability to convert inorganic heterocycles to stable radical
analogues. Current efforts are devoted to further enhancing the
stability of the radical anions via substituent effects and
exploration of other main group element formazan chemistry.
Financial support from the University of Victoria, The Natural
Sciences and Engineering Research Council of Canada, and the
Petroleum Research Fund of the American Chemical Society is
gratefully acknowledged.
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Notes and references
{ Crystal data for 3a: C20H18N4, M = 314.38, monoclinic, P21/c, a =
˚
11.7762(8), b = 13.4272(9), c = 12.0220(8) A, b = 118.5943(12)u, V =
3
1669.08(19) A , Z = 4, T = 193 K, 3429 independent reflections,
˚
R1 = 0.0503, wR2 = 0.1364. Crystal data for 3b: C21H20N4, M = 328.41,
˚
orthorhombic, Pbca, a = 7.830(1), b = 21.154(2), c = 22.289(3) A, V =
3
3691.9(8)A , Z = 8, T = 296 K, 2431 independent reflections, R1 = 0.055,
˚
¯
wR2 = 0.128. Crystal data for 4a: C24H23BN4O4, M = 442.27, triclinic, P1,
˚
a = 10.3612(15), b = 14.925(2), c = 15.608 (2) A, a = 103.098(2), b =
3
97.538(2), c = 95.549(2), V = 2310.5(6) A , Z = 4, T = 193 K, 9430
˚
independent reflections, R1 = 0.0514, wR2 = 0.1460. Crystal data for 4b:
¯
C25H25BN4O4, M = 456.30, triclinic, P1, a = 9.8688(13), b = 10.6690(14),
˚
c = 12.4677(17) A, a = 87.363(2), b = 80.634(2), c = 66.5696(18)u, V =
3
1188.2(3) A , Z = 2, T = 193 K, 4822 independent reflections, R1 = 0.0394,
˚
11 (a) F. A. Neugebauer, Angew. Chem., Int. Ed. Engl., 1973, 12, 455; (b)
B. D. Koivisto and R. G. Hicks, Coord. Chem. Rev., 2005, 249,
2612–2630.
wR2 = 0.1117. CCDC 613050–613053.
1 L. Bourget-Merle, M. F. Lappert and J. R. Severn, Chem. Rev., 2002,
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¨
R. G. Hicks, L. Ohrstro¨m and G. W. Patenaude, Inorg. Chem., 2001, 40,
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128 | Chem. Commun., 2007, 126–128
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