To shed light on the interaction in molecule-based magnetic materials, the decamethyl metallocenium hexafluorophosphates, [(C5Me5)(2)M](+) [PF6](-) with M = Cr, Mn, Fe, Co, and Ni, as well as the tetracyanoethenides, [(C5Me5)(2)M](+) [TCNE]- with M = Cr, Mn, Fe, and Co, have been investigated in the solid state by using H-1, C-13, F-19, and P-31 NMR spectroscopy under magic angle spinning (MAS). The isotropic C-13 and H-1 NMR signals cover ranges of about 1300 and 500 ppm, respectively. From the shift anisotropies of the ring carbon signal of the [(C5Me5)(2)M](+) Cations, the total unpaired electron spin density in the ligand pi orbitals has been calculated; it amounts up to 36% (M = Ni) and is negative for M = Cr, Mn, and Fe. The radical anion of [(C5Me5)(2)M](+) [TCNE](-) shifts the C-13 NMR signals of all [(C5Me5)(2)M](+) cations to high frequency, which establishes transfer of positive spin density from the anions to the cations. The F-19 and P-31 NMR signals of the paramagnetic salts [(C5Me5)(2)M](+) [PF6](-) are shifted up to 13.5 ppm relative to diamagnetic [(C5Me5)(2)Co](+) [PF6](-). The signs of these shifts are the same as those of the pi, spin density in [(C5Me5)(2)M](+). After consideration of interionic ligand- and metal-centered dipolar shifts, this establishes cation-anion spin delocalization. The mixed crystals [(C5Me5)(2)MxCo1-x](+) [PF6](-) have been prepared for M = Cr and Ni. They are isostructural with [(C5Me5)(2)Co](+) [PF6](-) whose single-crystal structure has been determined by X-ray diffraction. The C-13, F-19, and P-31 MAS NMR spectra of the mixed crystals show that the respective two closest paramagnetic ions in the lattice delocalize spin density to [(C5Me5)(2)Co](+), [(C5Me5)(2)Ni](+), and [PF6](-). In [(C5Me5)(2)M](+), about 10(-4) au per carbon atom are transferred.