Nickel(II) in an N₄S Donor Environment:  An Unprecedented Alcoholysis Reaction through the Activation of a Carbon−Nitrogen Single Bond

Pentadentate N 4 S ligands based on methyl 2-aminocyclopent-1-ene-1-dithiocarboxylate with flexible pyrazolyl arms (Me 2 pzCH 2 ) 2 NC 2 H 3 RNHC 5 H 6 CSSCH 3 (R = H, Hmmecd and R = CH 3, Hmmpcd ) undergo a nickel(II)-induced alcoholysis reaction through the activation of a saturated C−N bond linkage. The products obtained are square-planar complexes 1 − 4 containing a modified ligand structure possessing an N 3 S donor set and a pendant arm that holds the alkoxy group provided by the solvent. [Ni(N 3 S)-CH 2 OMe]ClO 4 1 crystallizes in the triclinic space group P 1̄ with a = 10.4886(5) Å, b = 10.706(1) Å, c = 11.487(1) Å, α = 108.784(4)°, β = 108.887(6)°, γ = 95.139(6)°, V = 1128.0(4) Å 3, and Z = 2; while [Ni(N 3 S)‘-CH 2 OPr n ]ClO 4 4 has the monoclinic space group P 2 1 / n with a = 8.875(2) Å, b = 18.629(2) Å, c = 15.399(2) Å, β = 91.37(2)°, V = 2545(1) Å 3, and Z = 4 per unit cell. Complexes 1 − 4 with acyclic ligand environments have interesting electrochemical behavior in acetonitrile, involving a reversible Ni(II)/Ni(I) reduction, E 1/2 ca. −1.0 V, and a Ni(II)/Ni(III) irreversible oxidation, E pa ca. 1.0 V vs Ag/AgCl as the reference. The coulometrically reduced solution of 2 displays a rhombic EPR spectrum at 77 K characteristic of nickel(I) with g 1 = 2.217, g 2 = 2.170, and g 3 = 2.054.