In search of the [PhB(mu-N(t)Bu)2]2As. radical: experimental and computational investigations of the redox chemistry of group 15 bis-boraamidinates.
DFT calculations for the group 15 radicals [PhB(mu-N(t)Bu)2]2M. (M = P, As, Sb, Bi) predict a pnictogen-centered SOMO with smaller contributions to the unpaired spin density arising from the nitrogen and boron atoms. The reactions of Li 2[PhB(mu-NR)2] (R = (t)Bu, Dipp) with PCl 3 afforded the unsolvated complex LiP[PhB(mu-N(t)Bu)2] 2 ( 1a) in low yield and ClP[PhB(mu-NDipp)2] (2), both of which were structurally characterized. Efforts to produce the arsenic-centered neutral radical, [PhB(mu-N (t) Bu) 2] 2As., via oxidation of LiAs[PhB(mu-N(t)Bu)2]2 with one-half equivalent of SO 2Cl 2, yielded the Zwitterionic compound [PhB(mu-N (t) Bu) 2As(mu-N(t)Bu)2B(Cl)Ph] (3) containing one four-coordinate boron center with a B-Cl bond. The reaction of 3 with GaCl3 produced the ion-separated salt, [PhB(mu-N(t)Bu)2] 2As (+)GaCl 4 (-) ( 4), which was characterized by X-ray crystallography. The reduction of 3 with sodium naphthalenide occurred by a two-electron process to give the corresponding anion [{PhB(mu-N(t)Bu)2} 2As] (-) as the sodium salt. Voltammetric investigations of 4 and LiAs[PhB(mu-N (t) Bu) 2] 2 ( 1b) revealed irreversible processes. Attempts to generate the neutral radical [PhB(mu-N(t)Bu)2] 2As. from these ionic complexes via in situ electrolysis did not produce an EPR-active species.
Konu
Jari
J
Department of Chemistry, University of Calgary, Calgary, Alberta, Canada.
Tuononen
Heikki M
HM
Chivers
Tristram
T
Corrente
Andrea M
AM
Boeré
René T
RT
Roemmele
Tracey L
TL