Finally, Clark and Barnes 11 mentioned using SnCl4 to obtain stannosilicates (23A/23B). The possibility for an irreversible exchange of Cl -between different tin(IV) species appeared highly questionable to us. Our calculations show that although the condensation reaction is still spontaneous in this case, it is hardly irreversible with ΔG 298.15 of at most -16 and as little as -7 kJ mol -1 . A facile ligand exchange with SnMe3Cl, leading to a mixture of SnMe2Cl2 and SnMeCl3 is also a possibility.