Paramagnetic Cluster Ions B6HalnHal'6-n.bul.- (Hal, Hal' = Cl, Br, I). EPR Evidence for Radical Stabilization through Electronic Effects of the Halogen Substituents

, , , and . Inorganic Chemistry, 37 (16): 4011--4014 (1998)
DOI: 10.1021/IC9802698


Monoanionic hexaborate cluster radicals B6HalnHal'6-n.bul.- with mixed halogen substitution were prepd. from oxidizable dianionic precursors and were characterized by vibrational and UV-visible spectroscopy. EPR studies of these and the structurally established homoleptic species B6Hal6.bul.- (Hal = Cl, Br, I) reveal strongly increasing g anisotropy and relaxation rate on replacing Cl by Br and esp. I substituents; the very stable B6I6.bul.- ion (g1 = 2.04, g2 = 1.66, g3 = 1.15) thus exhibits an EPR spectrum only at 4 K. The extent of these effects is attributed to the Jahn-Teller situation in B6X6.bul.- with only partial occupancy of a degenerate MO. Both the absence of B-H bonds and the evidently strong participation of the halogen substituents in the singly occupied MO contribute to the extraordinary stability of these cluster radicals. on SciFinder(R)

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