A new p-methoxyphenyl (ML) and p-fluorophenyl (FL) maleanilic acid bidentate ligands were green synthesized by a solvent-free reaction of equimolar amounts of aniline derivatives (4-methoxyaniline or 4-fluoroaniline) with maleic anhydride. Additionally, some mixed ligand organometallic chelates of Cr(0), Mo(0), and W(0) carbonyls were synthesized by the addition of the prepared ligand (L) as a primary ligand to the hexacarbonyl metals, in which carbonyl groups are secondary ligands in a 1:1 molar ratio. The structures of the novel chelates were characterized by elemental analyses, FT-IR, EI-MS, 1 H-NMR spectroscopy, and thermal analyses. FL maleanilic acid free ligand and its chromium complex were screened for antitumor activity in vitro against cell lines of HCT-116 (human colon carcinoma), hepG-2 (human hepatocellular carcinoma), and MCF-7 (human breast carcinoma). The results obtained referred to a high antitumor activity of both FL novel ligand and its chromium organometallic chelates. Keywords p-methoxyphenyl and p-fluorophenyl maleanilic acid ligands; organometallic chelates; spectroscopic and thermal analyses; antitumor screening 2 Journal of Transition Metal Complexes Scheme 1: Synthetic route of maleanilic acid derivatives ML and FL as free ligands and their novel complexes.

A novel p-chlorophenyl maleanilic acid ligand (L) was prepared from condensation reaction of maleic anhydride with p-chloroaniline. New synthesized organometallic chelates of the proposed general formula [M(CO) 4 L], where M = Cr, Mo or W, were prepared by reaction of metal hexa carbonyls condensation with bidentate maleanilic acid ligand in inert nitrogen atmosphere. The prepared novel ligand and its organometallic chelates were characterized by elemental analyses, FT-IR, mass spectra, 1 H-NMR, and thermal analyses. The results obtained refer to an octahedral structure of the prepared organometallic chelates. The free ligand and its chromium chelate were screened for antitumor activity in vitro against cell lines of HCT-116 (human colon carcinoma), hepG-2 (human hepatocellular carcinoma), and MCF-7 (human breast carcinoma). The results obtained referred to a high antitumor activity of both novel ligand and its chromium chelate.