ngsten complexeshave one reversible couple corresponding to the ferrocenyl group and one irreversible oxidation process for the molybdenum ortungsten center. The crystal structures of 3-ferrocenylpyrazole pentacarbonyltungsten (3) and 3-methyl-5-ferrocenylpyrazolepentacarbonyltungsten (6) are determined by X-ray diffraction method, indicating that both 3(5)-ferrocenylpyrazole and3(5)-methyl-5(3)-ferrocenylpyrazole act as a monodentate ligand, and the central metal of W is six-coordinate with a quasi-octahedralcoordination geometry in both complexes. Complex 3 is linked into a one-dimensional chain in solid through intermolecularhydrogen bonds formed by metal carbonyl as hydrogen bond acceptors, while complex 6 forms a dimer by similarintermolecular hydrogen bond interactions. The N-H…O distances in complexes 3 and 6 are 2.932(11) and 2.900 A, respectively. All new compounds have been characterized by elemental analyses, IR, 1H-NMR. 13C-NMR spectra of molybdenum and tungstencomplexes have also been determined.