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Diorganotin(IV) derivatives of 4‐acyl‐5‐pyrazolones Q2SnR2[HQ = 3‐methyl‐1‐phenyl‐4‐R‐5‐pyrazolone: HQnPe, R = neopentylcarbonyl; HQiPr, R = isopropylcarbonyl; HQtBu, R = tert‐butylcarbonyl; HQCy, R = cyclohexylcarbonyl; HQCp, R = cyclopentylcarbonyl; HQEtCp, R = (ethylcyclopentyl)carbonyl] have been synthesized and characterized spectroscopically (IR, far‐IR, 1H, 13C and 119Sn NMR) and structurally (X‐ray). Steric bulkiness in the acyl fragment of HQtBuinduces partial dissociation in solution of (QtBu)2SnMe2, which exists as an equilibrium mixture of six‐ and five‐coordinate tin species. Single‐crystal X‐ray structure determinations of several representative complexes are presented. Whereas the dialkyltin(IV) complexes are always trans‐octahedral, a diphenyltin(IV) derivative exists in the solid state that has the two phenyl groups in a cisarrangement. DMol3 and CASTEP DFT studies of this unprecedented cis, and the corresponding transconfigurations, show the former to be slightly more stable, in agreement with the diffraction study. Solid‐state 119Sn cross‐polarization magic‐angle spinning NMR spectroscopic data show that the isotropic chemical shifts (δiso,mas) and chemical‐shift anisotropies/spans (Δδ/Ω) that characterize the diphenyl(IV) derivatives are markedly removed from values measured for the corresponding dimethyl and di‐n‐butyl derivatives, thereby adding further evidence for a stable cisconfiguration in the diphenyl(IV) systems. This is supported by GIPAW DFT calculation of the 119Sn isotropic shifts and chemical‐shift anisotropies/spans from fully relaxed structures by using the CASTEP code, which provides a direct link between the cisdiphenyl(IV) arrangement and the reported differences in the 119Sn NMR spectroscopic parameters.

Extension of previous work on the lanthanideIII ion complexes of ptertbutyltetrathiacalix[4]arene has led to a variety of structurally characterised species containing oxo, hydroxo and aqualigands presumably derived from water present in the preparative medium, along with the thiacalixarene in various stages of deprotonation. The overall stoichiometry of some species is remarkably complicated due to the presence of simple anions and multiple solvents. Simplest is the binuclear complex [μH2OLnOdmf22HL·dmf2]·nS dmf = dimethylformamide [1Ln, Ln = Sm nS = 2dmf, Eu nS = 1.5dmf·2MeCN], also the bestdefined of all the arrays studied. The heaviest lanthanides give trinuclear LnOH3·2LnLH·xdmf·yH2O 2Ln, Ln = Yb, Lu, while both oxo and hydroxo species are isolable with Eu: trinuclear Eu3OLLHLH4·13dmf 3 and tetranuclear Eu4OOH2LLH22LH4·12dmf 9, both somewhat atypical species containing uncoordinated thiacalixarene molecules within the lattice. Anion NO3, ClO4 coordination, as in the tri and tetranuclear species, 4–6Ln, 9, 10Ln, 11Ln, 12, seems especially favoured for the lighter lanthanides. In these arrays, the Ln3and Ln4aggregates are triangular or quasisquareplanar, except for Gd4O2LH24·2H2O·2MeOH·2dmf·3.375CH2Cl212, where there is a Zdisposition. Most common is an Ln3O core, which spans the gamut of Ln in three sets of crystal forms with cells of similar dimensions: for Ln = La...Nd, Ln3OHNO34LH22·4.5dmf 5Ln space group C2m, and Sm...Lu, Ln3ONO3LH2·4H2O·2dmso·2MeCN·3py 6Ln space group P21n, conformity with crystallographic symmetryentails disorder of the Ln atoms; in a further form of lowersymmetry Pn, pyHLn3ONO32LH2·2MeCN·xH2O·ydmso·1.5py·MeOH 7Ln, Ln = La, Ce, with no imposed crystallographic symmetry, some disorder persists, but none is found in the crystallographically unrelated form of 8Pr, Pr3ONO3LH2·16H2O·2MeCN·5py. Ln4OHNO33L2·8dmf·2dmso·3H2O 10Ln, Ln = Pr...Gd, previously defined for Nd has a squareplanar Ln4O array sandwiched between a pair of L ligands, with a similar form found for Ln4OClO42L2·xdmf·yH2O 11Ln, Ln = La...Nd.