Triorganotin(IV) derivatives of several 4-acyl-5-pyrazolonato ligands: Synthesis, spectroscopic characterization and behavior in solution crystal structure of aquotrimethyl(4-p-methoxybenzoyl-1-phenyl-3-methyl-pyrazolon-5-ato)tin(IV)

Article abstract of DOI:10.1016/0022-328X(96)06170-0

New triorganotin(IV) derivatives [(Q)SnR₃ · x(H₂O)] (x = 0, R = Ph; x = 1, R = Me and ⁿBu) (in general QH = 1-R′-3-methyl-4-R″ (C=O)-pyrazol-5-one; in detail Q′H: R′ = C₆H₅, R″ = C₆H₅; Q_AH: R′ = C₆H₅, R″ = p-CH₃O-C₆H₄; Q_NH: R′ = C₆H₅, R″ = p-NO₂-C₆H₄; Q_BrH: R′ = C₆H₅, R″ = p-Br-C₆H₄; Q″ H: R′ = C₆H₅, R″ = CH₃; Q_ClH: R′ = C₆H₅, R″ = CCl₃; Q_FH: R′ = C₆H₅, R″ = CF₃; Q_MH: R′ = CH₃, R″ = C₆H₅; Q_DH: R′ = CH₃, R″ = CH₃) have been synthesized and characterized by analysis and spectral (IR and ¹H, ¹³C and ¹¹⁹Sn NMR) data. The (Q)SnPh₃ derivatives are five-coordinated in the solid state, with a likely skewed cis-trigonal bipyramidal (cis-TBP) geometry around the tin center and the ligand (Q)^- acting in the bidentate form. In [(Q)SnR₃ · (H₂O)] derivatives (R = ⁿBu or Me) a coordination site is occupied by water, with the ligand (Q)^- coordinating in a monodentate fashion. The crystal structure of [(Q_A)SnMe₃ · (H₂O)] has been determined: the tin atom is found in a distorted TBP environment, with the methyls in the equatorial positions. Two of the Sn-C bond lengths are normal (2.11(1) and 2.08(2) A) whereas the third is longer (2.18(2) A); the ligand binds the metal atom through one carbonyl oxygen in the apical position (Sn-O = 2.10(1) A). The bond length between H₂O and Sn is longer (2.41(2) A), and the O-Sn-O angle is 174.9(5)°. H atoms of water are involved in an intermolecular H-bond network with uncoordinated carbonyl and the pyridinic N atom of the ligand. In chloroform solution the [(Q)SnR₃ · (H₂O)] derivatives (R = Me or ⁿBu) lost the molecule of water and adopt a tetrahedral arrangement. They also give rise to a slow disproportionation, yielding SnR₄ and [(Q)₂SnR₂] derivatives.