An experimental and a DFT study on the synthesis, spectroscopic characterization, and reactivity of the adducts of dimethyl- and diphenyltin(IV) dichlorides with γ-pyrones [4H-pyran-4-one (PYR) and 2,6-dimethyl-4H-pyran-4-one (DMP)]: Crystal structure of Ph2SnCl2(PYR)

Abstract The Sn(IV) R 2 SnCl 2 (γ-pyrone) n [R = Me or Ph; γ-pyrone = 4 H -pyran-4-one (PYR) or 2,6-dimethyl-4 H -pyran-4-one (DMP); n  = 1 or 2] adducts have been synthesized and investigated. The adducts Ph 2 SnCl 2 (PYR) ( 1 ), Me 2 SnCl 2 (PYR) 2 ( 2 ), Ph 2 SnCl 2 (DMP) ( 3 ) and Me 2 SnCl 2 (PYR)(PNO) ( 4 ), (PNO = 4-methylpyridine N -oxide) have been prepared by the addition of the corresponding γ-pyrone to chloroform solution of R 2 SnCl 2 . The new compounds have been characterized by elemental analysis and spectroscopic (IR, 1 H, 13 C NMR and Mossbauer) means. The single-crystal diffraction study of 1 shows the Sn(IV) to be five-coordinate, [Sn–O and Sn–Cl(1), Sn–Cl(2) distances of 2.3190(13) and 2.4312(6), 2.3653(7), respectively], and the Cl–Sn–Cl bond angle to be 91.17°. The reactivity of 2 towards bipy, Ph 3 PO, QNO (Q = quinoline) resulted in complete displacement of PYR and formation of already known compounds whereas, the PNO displaced only one equivalent of PYR, causing the preparation of the new mixed complex 4 , possibly through a S N 1 formation mechanism. DFT/B3LYP molecular orbital calculations were carried out for the 1 – 4 complexes, their precursors, Ph 2 SnCl 2 , ( 5 ) and Me 2 SnCl 2 , ( 6 ) and the ligands, PYR, DMP and PNO in an attempt to explain the structures and reactivity of the complexes. Optimized resulting geometries, vibrational frequencies, and the electron-accepting ability of the complexes and the precursors towards nucleophiles are discussed.