The reaction of 3 (5)-methylthio-5 (3)-phenylpyrazole with dibromomethane under phase-transfer catalytic conditions onlyaffords a new ligand, bis (3-phenyl-5-methylthiopyrazol-1-yl) methane. However, the reaction of 3 (5)-methylthio-5 (3)-pmethoxyphenylpyrazoleor 3 (5)-methylthio-5 (3)-tert-butylpyrazole with dibromomethane under the same conditions yields threeisomers, respectively, indicating that the substituents significantly affect the steric and electronic properties of pyrazole ring duringthe formation of ligands. Treatment of these potential polydentate ligands with M (CO) 6 (M=Cr, MoorW) under UV irradiationat room temperature affords (NN) M (CO) 4 derivatives, in which some complexes contain asymmetric substituted bis (pyrazol-1-yl) methane ligands. The X-ray crystal structure analyses indicate that the sulfur atoms in these complexes do not take part in thecoordination to the metal centers, and S-rich bis (pyrazol-1-yl) methanes actually act as bidentate chelating ligands by two nitrogenatoms. It is also interesting that in order to reduce the repulsion of methyl groups with carbonyls, the methyl groups in thesecomplexes are oriented away from the metal centers.