The interaction of organotin(IV) acceptors with 1,4-bis(5-hydroxy-1-phenyl-3-methyl-1H-pyrazol-4-yl)butane-1,4-dione

A new polydentate ligand, namely 2-[(5-hydroxy-1-phenyl-3-methylpyrazol-4-yl)(5-oxo-1,5-dihydro-4-phenyl-2-methylpyrazol-4-ylidene)methyl]benzoic acid (H(2)QBz), has been prepared and characterized. The structure of the ligand H(2)QBz consists of discrete molecules linked to one another by an extensive H-bonding network. The reactivity of H(2)QBz towards [R3Sn](2)O (R = Ph or Bu-n) and RnSnCl4 - n (R = Me, Bu-n, Bu-t, Ph, n = 2; R = Me, n = 3) has been investigated. Mono- and di-nuclear derivatives have been obtained depending on the nature of the starting acceptor and reaction conditions. [Ph3Sn(HQBz)] 1 contains the HQBz ligand coordinated to Ph3Sn through the deprotonated carboxylic group. In the complex [(H2O)Ph3Sn(HQBz)] 2, obtained by hydration of 1, the coordination sphere of tin is completed by bonding to a water molecule. The compounds [(R3Sn)(2)(QBz)] (R = Me, 3; Bu-n, 4) contain the dianionic ligand bridged to two triorganotin(IV) fragments. In solution the mononuclear triorganotin(IV) aqua complexes [(H2O)R3Sn(HQBz)] (R = Ph, 2; Bu-n, 5) loose the molecule of water and slowly decompose, yielding the free ligand and the R3SnOH species. The diorganotin(IV) derivatives [R2Sn(QBz)](2) (R = Me, 6; Bu-t, 7; Bu-n, 8; Ph, 9) are dinuclear both in the solid state and in solution. In the structure of [Me2Sn(QBz)](2) 6 both acidic H atoms of the ligand are substituted by tin: a dimeric centrosymmetric structure forms, involving two [QBz](2-) ligands acting as bridges between two tin atoms through both pyrazolone and benzoate moieties. Sn centers in the dimer are five-coordinated in a strongly distorted trigonal bypiramidal environment