Syntheses and electrochemistry of imidochromium(V) compounds. Crystal structure of [PPh4][Cr(NBut)Cl4(OH2)]
摘要:
Reactions of [Cr(NBu(t))Cl3(dme)] (dme = 1,2-dimethoxyethane) or [PPh4][Cr(NBu(t))Cl4] with Tl(C5H5) and NaL' {L' = (eta-C5H5)Co[PO(OEt)2]3} gave respective paramagnetic (mu(eff) ca. 1.7 mu(B)) half-sandwich imidochromium(v) compounds [CrL(NBu(t))Cl2] (L = eta-C5H5 1 or L' 2). The structure of [PPh4][Cr-(NBu(t))Cl4(OH2)] has been established by X-ray crystallography. The [Cr(NBu(t))Cl4(OH2)]- anion has an octahedral geometry with Cr-N (imido) 1.619(3) angstrom. Treatment of [Cr(NBu(t))(L)Cl] [H2L = N,N'-bis(salicylidene)ethane-1,2-diamine or its 3,5-Bu(t)2 derivative] with AgBF4 afforded cationic imidochromium(v) Schiff-base compounds [Cr(NBu(t))L]BF4. Reactions of the imidochromium(v) compounds with PPh3 at reflux or on irradiation with UV light gave Ph3P=NBu(t) and Cr(III). Cyclic voltammetry of the imidochromium(v) compounds showed in most cases irreversible oxidation and reduction waves, which are attributed to oxidation and reduction of Cr(v).