The interaction of organotin(iv) acceptors with 1,4-bis(5-hydroxy-1-phenyl-3-methyl-1H-pyrazol-4-yl)butane-1,4-dioneCoordination chemistry of bis(pyrazolones): a rational design of nuclearity tailored polynuclear complexes. Part 2.22

Abstract

From the interaction of organotin(IV) halides SnR2Cl2 with 1,4-bis(5-hydroxy-1-phenyl-3-methyl-1H-pyrazol-4-yl)butane-1,4-dione (Q2QH2) in methanol in the presence of base the complexes [SnR2(Q2Q)] (1: R = isobutyl (Bui); 2: R = n-octyl (Ot); 3: R = n-dodecyl (Do)) have been synthesised. The reaction between equimolar quantities of R2SnO and Q2QH2 in toluene yields the dinuclear derivatives [SnR2(Q2Q)]24 (R = Me) and 5 (R = Bun) which have a cis-R2Sn configuration in solution whereas from the reaction of Q2QH2 with SnMe2Cl2 in CH3OH in the presence of KOH, an insoluble probably polynuclear isomeric form of 4 formed. The reaction between Q2QH2 and (R3Sn)2O produces the derivative [(SnR3)2(Q2Q)] (6: R = Bun; 7: R = Ph). 6 reacts with water yielding the aquo complex [(SnBun3)2(Q2Q)(H2O)] 8. The X-ray crystal structures of [SnBun2(Q2Q)]25, [(SnBun3)2(Q2Q)] 6 and [(SnPh3)2(Q2Q)] 7 have been determined. Compound 5 is a binuclear species with the tin atoms in a distorted octahedral Sn-cis-C2O4 environment (skewed trapezoidal bipyramidal) with the C–Sn–C angles ranging from 107.28(14) to 112.4(2)°. The two different carbonyl groups coordinate the metal with different donor abilities (the Sn–O bond lengths range from 2.132(2) to 2.209(2) A). Compounds 6 and 7 contain a dianionic ligand (Q2Q)2− bridged to two triorganotin(IV) fragments with the tin atoms in a strongly distorted trigonal bipyramidal environment. 1H, 13C and 119Sn NMR (rt and −55 °C) data indicate that the diorganotin(IV) derivatives 1–5 are not fluxional in solution whereas 6–8 slowly undergo disproportionation reaction, affording SnR4 and [SnR2(Q2Q)]2.