Two new tin(iv)-containing phosphate fluorides with two types of Sn(iv)–P–O–F frameworks and short cutoff edges†
Two new tin(IV)-containing phosphate fluorides, K2SnPO4F3 and K6Sn(P2O7)2F2, have been obtained in a sealed system. Interestingly, K2SnPO4F3 and K6Sn(P2O7)2F2 are the first tin(IV)-containing phosphate fluorides in the K–Sn(IV)–P–O–F system. Both of them crystallize in the monoclinic space group P21/c; however, the 2D [SnPO4F3]∞ layer and isolated [Sn(P2O7)2F2] units can be found in K2SnPO4F3 and K6Sn(P2O7)2F2, respectively. A structural comparison indicates that K6Sn(P2O7)2F2 is the first inorganic tin(IV)-containing phosphate with an isolated Sn(IV)–P–O framework. Meanwhile, the structural evolution from KSnOPO4 to K2SnPO4F3 is discussed in detail. And the optical properties, including UV-Vis-NIR diffuse reflectance spectra and infrared spectra, are also reported. In addition, first-principle theoretical studies help us understand the electron structures of the title compounds.