om5b00703_si_002.xyz (40.74 kB)
Catalytic Formation of Asymmetric Carbodiimides at Mononuclear Chromium(II/IV) Bis(alkoxide) Complexes
dataset
posted on 2015-10-26, 00:00 authored by Maryam Yousif, Daniel
J. Tjapkes, Richard L. Lord, Stanislav GroysmanHerein
we report the synthesis of Cr imido complexes in bis(alkoxide)
ligand environments and their nitrene transfer reactivity with isocyanides.
The reaction of Cr2(OR)4 (OR = OCtBu2Ph) with bulky aryl or alkyl azide
results in the formation of the trigonal-planar Cr(IV) mono(imido)
complexes Cr(OR)2(NR1), whereas less bulky aryl
azides form the Cr(VI) bis(imido) complexes Cr(OR)2(NR1)2. Cr(IV) mono(imido) complexes undergo facile
reaction with 1 equiv of 2,6-dimethylphenyl isocyanide (CNR2) to form the corresponding carbodiimides R1NCNR2. In contrast, no reaction of Cr(OR)2(NR1)2 complexes with CNR2 is observed. The reaction
of Cr(OR)2(NR1) with excess isocyanide leads
to the isolation of the Cr(II) complex Cr(OR)2(CNR2)4, along with the observation of the anticipated
carbodimide product. Cr(OR)2(CNR2)4, which can also be obtained by treating Cr2(OR)4 with 4 equiv of isocyanide, reacts with azides N3R1 (R1 = adamantyl, mesityl) to produce the respective
carbodiimides. Catalytic formation of carbodiimides R1NCNR2 is observed from the mixtures of azides R1N3 (R1 = mesityl, 2,6-diethylphenyl, 2-isopropylphenyl,
adamantyl) and several different aryl isocyanides CNR2 using
2.5 mol % of Cr2(OR)4.