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

Pentadentate N4S ligands based on methyl 2-aminocyclopent-1-ene-1-dithiocarboxylate with flexible pyrazolyl arms (Me2pzCH2)2NC2H3RNHC5H6CSSCH3 (R = H, Hmmecd and R = CH3, 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 N3S donor set and a pendant arm that holds the alkoxy group provided by the solvent. [Ni(N3S)-CH2OMe]ClO4 1 crystallizes in the triclinic space group P1̄ 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) Å3, and Z = 2; while [Ni(N3S)‘-CH2 OPrn]ClO4 4 has the monoclinic space group P21/n with a = 8.875(2) Å, b = 18.629(2) Å, c = 15.399(2) Å, β = 91.37(2)°, V = 2545(1) Å3, 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, E1/2 ca. −1.0 V, and a Ni(II)/Ni(III) irreversible oxidation, Epa 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 g1 = 2.217, g2 = 2.170, and g3 = 2.054.