Three mononuclear metal complexes [M^II(L-N₃O₂)(MeCN)₂][BPh₄]₂ (M = Fe, 1; Co, 2; Ni, 3) were isolated and structurally characterized. Magnetic studies revealed uniaxial magnetic anisotropy for 1 (D = −17.1 cm⁻¹) and 3 (D = −14.3 cm⁻¹) and easy-plane magnetic anisotropy for 2 (D = +36.9 cm⁻¹). Slow magnetic relaxation was observed for complexes 1 and 2 under an applied magnetic field, both of which are dominated by a Raman process.