A novel compound containing tetraphenylphosphonium and nickel dicarbollyl, [[P(C₆H₅)₄][Ni(B₉C₂H₁₁)₂] · CCl₄ (I) was synthesized and studied by X-ray diffraction and EPR methods. The crystals are monoclinic: C₂₉H₄₂B₁₈PCl₄Ni (M = 816.69), space group P2/c, the unit cell parameters a = 13.3964(5), b = 7.0556(2), c = 20.6610(8) Å, β = 94.9070(13)°, V = 1945.7(2) ų, Z = 2, ρ(calcd.) = 1.394 g/cm³, T = 100 K, F(000) = 834, μ = 0.081 mm⁻¹. The structure was solved by the direct and Fourier methods and refined by the full-matrix least-squares method in the anisotropic (isotropic for the hydrogen atoms) approximation (R ₁ = 0.032 for 4027 I _hkl ≥ 2σ(I), 19886 measured and 5379 independent I _hkl ; X8 APEX Bruker difractometer, λMoK _α, graphite monochromator, ϕ/ω scan mode). At 100 K, the crystal contains the intermolecular hydrogen bonds B–H…Cl that favor the formation of infinite chains of the alternating anions and solvate molecules along the z axis of the unit cell. The single-crystal EPR study of complex I showed that the temperature changes of the cell parameters induce changes in the parameter of the g-factor g ₁ directed along Cb-Ni-Cb. The cell parameters are increased and the g ₁ value is gradually decreased with the increasing temperature. The temperature study of the EPR spectra of the powdered compound I revealed also jumpwise changes in g ₂ and g ₃ with hysteresis at 183–203 K depending on the direction of the temperature changes. The differences observed in the EPR spectra of the powders and single crystal of compound I in both the g-factor and the temperature dependence of its components are supposed to be caused by the CCl₄ vacancies formed in the crystal structure of a complex as a result of the partial removal of the solvate CCl₄ molecules when grinding the sample and by the change in the lability of the solvate molecules of a solvent with temperature.