Dramatic influence of an anionic donor on the oxygen-atom transfer reactivity of a Mn(V) -oxo complex.

Addition of an anionic donor to an Mn(V) (O) porphyrinoid complex causes a dramatic increase in 2-electron oxygen-atom-transfer (OAT) chemistry. The 6-coordinate [Mn(V) (O)(TBP8 Cz)(CN)](-) was generated from addition of Bu4 N(+) CN(-) to the 5-coordinate Mn(V) (O) precursor. The cyanide-ligated complex was characterized for the first time by Mn K-edge X-ray absorption spectroscopy (XAS) and gives MnO=1.53 Å, MnCN=2.21 Å. In combination with computational studies these distances were shown to correlate with a singlet ground state. Reaction of the CN(-) complex with thioethers results in OAT to give the corresponding sulfoxide and a 2e(-) -reduced Mn(III) (CN)(-) complex. Kinetic measurements reveal a dramatic rate enhancement for OAT of approximately 24 000-fold versus the same reaction for the parent 5-coordinate complex. An Eyring analysis gives ΔH(≠) =14 kcal mol(-1) , ΔS(≠) =-10 cal mol(-1) K(-1) . Computational studies fully support the structures, spin states, and relative reactivity of the 5- and 6-coordinate Mn(V) (O) complexes.

4-Bromo-2-(5-bromo-thio-phen-2-yl)-1-[(5-bromo-thio-phen-2-yl)meth-yl]-5,6-dimethyl-1H-benzimidazole.

The title compound, C18H13Br3N2S2, was obtained via the reaction of N-bromo-succinamide with 5,6-dimethyl-2-(thio-phen-2-yl)-1-[(thio-phen-2-yl)meth-yl]-1H-benzimidazole. The compound exhibits rotational disorder of the 5-bromo-thio-phen-2-yl substituent with a refined major:minor occupancy ratio of 0.876 (7):0.124 (7). The 5-bromo-thio-phen-2-yl mean plane is canted to the benzimidazole plane by 20.0 (4) and 21 (4)° in the major and minor components, respectively. In the crystal, weak C-H⋯N inter-actions link the mol-ecules into infinite C(7) chains along the 21 axes.

2-Amino-5-nitro-N-[(E)-thio-phen-2-yl-methyl-idene]aniline.

In the title mol-ecule, C(11)H(9)N(3)O(2)S, the thio-phene and benzene rings form a dihedral angle of 17.68 (9)°. The thio-phene S atom and the imine N atom are syn with respect to each other. In the crystal, N-H⋯O and N-H⋯N hydrogen bonds connect mol-ecules, forming a two-dimensional network parallel to (10-1).