Nuclear spectroscopic quantities under influences of covalency

On the basis of Mössbauer isomer shift data, nuclear quadrupole interactions and NMR¹J(¹³C?¹¹⁹Sn) spin-spin coupling constants, the problem of the nonadditivity of the isomer shifts and unexpected quadrupole interactions in tin organic compounds SnX_4?nR_n (X-halide, R-org. lig.) with the degree of substitution n has been treated by means of pseudopotential HF SCF calculations supplemented by efficient methods for comprehending core reorganizations and nucleus near electronic charge distributions. The nonadditivity of the isomer shifts and the progression of the nuclear quadrupole interactions has been explained by the evident momentum separated electronic reorganization. The clearly proved relation between s electron densities and higher orbital imbalances brings the isomer shift in relation to the valence part of the electric field gradient (EFG). An interrelation between isomer shifts and NMR spin-spin coupling constants has been deduced.