Four half-sandwich ruthenium(II) complexes were prepared by reacting dichloro(p-cymene)ruthenium(II) dimer or dichloro(benzene)ruthenium(II) dimer with 3,5-dimethylpyrazole (L1), bis(3,5-dimethylpyrazolyl)methane (L2), tris(3,5-dimethylpyrazolyl)methane (L3) and potassium tris(3,5-dimethylpyrazolyl)borate (L4) under air free conditions in good yields. All of the complexes were duly characterized by molar conductivity measurement, IR, UV, NMR spectroscopy, and elemental analysis. Solid state molecular structures of the complexes C2 and C4 were determined by single crystal X-ray crystallographic studies. Profound influence of the steric factors of the ligand substituents on the coordination chemistry and molecular structure of the complexes was profiled and compared with the related complexes in literature. An interesting solvent induced geometrical change was documented in the case of complex C4, bearing κ2-tris(3,5-dimethylpyrazolyl)borate and η6-p-cymene ligands. DFT calculations were used to understand the energetics and electronic structures of the polymorphic structures C4 and C4´. © 2021 Elsevier B.V.