Synthesis of novel terdentate N,C,N′-coordinated butyltin(IV) complexes and their redistribution reactions with SnCl4

The Sn(IV) butyl complexes [BunSnCl3 − n(NCN)] (NCN = [C6H3(CH2NMe2)2-2,6]−, n = 1 (1), 2 (2), 3 (3)) were prepared. Spectroscopic analysis of 1–3 by 1H and 119Sn NMR gave evidence for the presence of intramolecular N → Sn interactions in solution. The molecular structure of 1, as determined by a single-crystal X-ray diffraction study, revealed that it contained a six-coordinate Sn(IV) center with intramolecular N → Sn coordination of both ortho-amine substituents. Addition of SnCl4 to 1 resulted in the isolation of the HCl adduct [BuSnCl3(NCN+H)] (6). Reactions of 2 and 3 with SnCl4 each resulted in the HCl salt [SnCl4(NCN+H)] (8) and the corresponding butyltin chloride, Bu2SnCl2 and Bu3SnCl, respectively. The formation of HCl adducts 6 and 8 was ascribed to transfer of the NCN ligand to SnCl4 and the presence of HCl (from partial hydrolysis of the product or SnCl4 during the work up procedure). The molecular structures of 6 and 8 have been determined through single-crystal X-ray diffraction and revealed the presence of a [BuSnCl3(aryl)]− or [SnCl4(aryl)]− stannate anion, respectively, with in each case one coordinated ortho-amine function and one protonated amine moiety involved in N–H⋯Cl–Sn hydrogen bonding in both compounds (2.14 Å for 6 and 2.18 Å for 8).