Synthesis, spectroscopic, and structural characterization of new functionalized gem-bisphosphonate complexes of tin(IV) chloride

Abstract Bisphosphonates of the types X(P(O)(OEt) 2 ) 2 (X = CH 2 = C ( 1a ), CNCH 2 CH ( 1b ) and PhCH 2 NCH 2 CH ( 1c )) react with SnCl 4 in anhydrous dichloromethane to produce the new tin(IV) adducts [SnCl 4 ( 1a )] ( 2a ), [SnCl 4 ( 1b )] ( 2b ) and [SnCl 4 ( 1c )] ( 2c ) in 72–80% yields. These complexes were characterized using IR, multinuclear ( 1 H, 13 C, 31 P, 119 Sn) NMR spectroscopy, elemental analysis, and in one case by single crystal X-ray diffraction. The NMR data show that the bisphosphonate ligands are coordinated to the tin center in a bidentate fashion forming cis octahedral tin complexes. Furthermore, the X-ray structure of complex 2b reveals that the bisphosphonate ligand is coordinated in a bidentate manner to the metal center in a distorted octahedral arrangement with Sn-O-P bond angles in the range 135.95(16)–137.99(18)°. The P = O and Sn-O bond lengths of 1.495(3)-1.497(3) and 2.134(3)-2.146(2) A, respectively are in the order expected for phosphonate tin(IV) complexes. The results are discussed and compared with closely related analogues.