Seven tin(IV) amidinates were prepared and isolated from the reactions of tin(II) bisamidinate [Cy-NC(nBu)N-Cy]2Sn with a series of various 1,2-diones ((4 + 1) oxidative cycloaddition mechanism) and chlorine/oxygen molecules, respectively. The ligand substitution effect of (non)symmetric 1,3-diones to starting stannylene as well as intermolecular CO2 activation via prepared dimeric stannoxane is also reported. All the prepared tin containing compounds as well as ligand substitution reactions were investigated by the multinuclear NMR (1H, 13C, and 119Sn) spectroscopic techniques. Molecular structures of one tin(II) and seven tin(IV) amidinates investigated were determined by X-ray diffractions and also evaluated by DFT methods. The UV-vis absorption spectra of all desired colored tin(IV) diolates and its diketo precursors were recorded and simulated by TD-DFT methods.