Potassium salts of phenolate based polydentate xanthate ligands 4,4′-bis(2-dithiocarbonatobenzylideneamino)diphenyl ether (K2xan1) and 4,4′-bis(2-dithiocarbonatonaphthylmethylideneamino)diphenyl ether (K2xan2) have been synthesized and characterized, prior to use. The reaction of K2xan1 or K2xan2 with M(OAc)2 in Et3N affords access to a rare series of binuclear metallomacrocyclic xanthate complexes of the type [M2-μ2-bis-(κ2S,S-xan1/xan2)] (1–4) which quickly forms [2 : 2] binuclear N,O-bidentate Schiff base macrocyclic complexes of the type [M2-μ2-bis-(κ2N,O-L1/L2)] (L1 = 4,4′-bis(2-hydroxybenzylideneamino)diphenyl ether, L2 = 4,4′-bis(2-hydroxynaphthylmethylidene-amino)diphenyl ether) 5–8via evolution of CS2 in solution. The compounds were characterized by microanalysis, relevant spectroscopy (FT-IR, UV-visible), mass spectrometry (ESI-MS), and powder and single crystal XRD techniques. In vitro anticancer activity of all the compounds was evaluated against HEP 3B (hepatoma) and IMR 32 (neuroblastoma) by the MTT assay. Remarkably, the binuclear copper(II) xanthate complexes were found to be extremely active against both the cell lines (IC50: 8.1 ± 0.8 μM (3), 8.8 ± 1.7 μM (4) against HEP 3B and 1.9 ± 0.3 μM (3) and 7.3 ± 0.6 μM (4) against IMR 32) and this projects them as good candidates for potent antitumor agents and the IC50 values confirm their better potency than the reference drug cisplatin. The flow-cytometric density plot illustrates the induction of apoptosis in HEP 3B and IMR 32 cells after treatment with K2xan1, 1, 3, 6 and 7.