New (Q)(2)SnR2 derivatives (HQ in general; in detail: HQ(CHPh2) = 4-diphenylacetyl-3-methyl-1-phenyl-5-pyrazolone; HQ(Bn) = 3-methyl-1-phenyl-4-phenylacetyl-5-pyrazolone; HQ(naph) = 3-methyl-4-naphthoyl-1-phenyl-5-pyrazolone; R = CH3, C2H5, C6H11, n- and t-C4H9, C6H5,) have been synthesised and characterised by analytical and spectral techniques. Variable temperature NMR studies of (Q(CHPh2))(2)SnR2 derivatives (R = CH3 and C2H5) in chlorohydrocarbon solvents indicate a fluxional behaviour, with rapid interconversion between six- and five-coordinate species, the latter containing a bidentate acylpyrazolonate and a monodentate one. The X-ray crystal structures of the diorganotin(IV) derivatives (Q(CHPh2))(2)SnMe2, (Q(CHPh2))(2)SnEt2, (Q(Bn))(2)SnMe2 and (Q(naph))(2)SnBu2n, inclusive of a representative of each Q(x) family, show the metal centres in a skewed trans octahedral configuration. The 4-acyl moiety of the beta-diketonate donor exerts a steric effect which is correlated to structural behaviour in the solid and solution state. A solid state Sn-119 CPMAS NMR study of the (Q(Bn))(2)SnR2 (R = CH3, C2H5, t-C4H9 and C6H5) complexes shows a marked deshielding effect and upfield movement of the 119Sn isotropic chemical shift (delta(iso)) through this series. The Sn-119 chemical shift spans (Omega) are the largest reported for directly oxo-coordinated Sn(IV) systems, although the markedly reduced Omega value for the (Q(Bn))(2)SnPh2 complex may be indicative of a cis octahedral coordination, in contrast to the trans octahedral coordination characterising the other complexes of this suite. (C) 2010 Elsevier B.V. All rights reserved.