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Single crystal X-ray structural characterisations are reported for adducts of the form [(L- O)Eu(O , O ′-dpm)3] obtained by the crystallisation of tris(dipivaloylmethanato)europium(iii) (dpm = [HC(C(tBu).CO)2]−) from an array of dipolar aprotic oxygen-donor solvents L (L = N -methylpyrrolidinone (nmp), trimethylphosphate, (MeO)3PO, (tmp), hexamethylphosphoramide (hmpa), dimethylacetamide (dma), dimethyl sulfoxide (dmso), and the bidentate octamethylpyrophosphoramide (ompa). In all adducts, the resulting arrays contain seven-coordinate metal atoms, which adopt two different isomeric forms of the mono-capped trigonal prismatic stereochemistry, the L = dma and dmso adducts corresponding to one type, nmp and tmp the other. The adduct formed with ompa behaves as a pair of discrete metal environments bridged by the O -ompa- O ′ ligand, thus; [(dpm- O , O ′)3Eu(O -ompa- O ′)Eu(O , O ′-dpm)3], and is found in two forms, one in which both Eu environments is of the tmp type, the other of the dmso/dma type. In the hmpa adduct, the asymmetric unit of the structure is a disordered composite of both types. In none of the adducts is there any further solvation beyond coordination of a single L. Structural studies of crystalline adducts of [Eu(dipivaloylmethanato)3] with dmso, dma, tmp, hmpa, and ompa have shown all to contain seven-coordinate EuIII. This low coordination number appears to be a consequence of partial coordination sphere interpenetration in the solid state. [ABSTRACT FROM AUTHOR]

Adducts of the form Ln(pic)3(tmp)3 (Ln = lanthanide(iii); pic = picrate = 2,4,6-trinitrophenoxide; tmp = trimethylphosphate, (MeO)3PO) have been prepared for extremal Ln = La, Lu and some intermediate members, also Y, and characterised by single crystal X-ray structure determinations as unsolvated, mononuclear, molecular species. The lanthanide atom has nine-coordinate, tri-capped trigonal prismatic stereochemistry in all cases, the picrate components behaving as O , O ′-bidentate ligands chelating through the phenoxy- and an adjacent O -nitro oxygen atom, thus: [Ln(tmp- O)3(pic- O , O ′)3]. Two isomeric forms are found, one mer in which the three unidentate tmp- O ligands coordinate in cis -sites spanning the upper and lower triangles and a capping site of the coordination sphere, and fac , in which all three unidentate ligands occupy the mutually cis -sites of one triangular face. The mer isomer has been described as an isomorphous series in a monoclinic P 21/ c , Z 4, form, for Ln = La, Ce, Pr, Nd, Sm, Gd, Lu, and Y, presumptively accessible for the full gamut of Ln. The fac -isomer also crystallises in a monoclinic P 21/ c form, Z 8, two independent molecules of similar stereochemistry here comprising the asymmetric unit and described for Ln = Eu, Lu(isomorphous); it has also been described in a triclinic P CH19176_IE1.gif , Z 2 form for Ln = La. Trimethylphosphate (tmp) is the first of a series of related O-donor solvates of lanthanide(III) picrates to give isomeric mer- and fac- [Ln(pic)3(tmp)3] complexes. [ABSTRACT FROM AUTHOR]

Addition of various oxygen-donor ligands (L, all dipolar, aprotic solvents), to a solution of hydrated scandium picrate in weakly coordinating solvents (S), has yielded several crystalline adducts of the form Sc(pic)3(L) m (· n S) in which all ligands L are coordinated, subsequently characterised by a series of single crystal X-ray studies. For L = dmso, m = 3 and the picrate anions are all bound as phenoxide-O donor units, while for nmp, dma, tmp, and hmpa, m = 2 and one of the bound picrates becomes bidentate through phenoxide- and nitro-O donation. For L = ompa, m = 2 and two picrate ligands are bound through phenoxide-O while one is displaced from the primary coordination sphere. All complexes contain six-coordinate ScIII, confirming that this coordination number is a consequence of ligand bulk. Six-coordination of ScIII is observed throughout in crystalline adducts of scandium picrate with dmso, dma, nmp, tmp, hmpa, and ompa, although with variations in the adduct stoichiometry and the coordination mode of picrate. [ABSTRACT FROM AUTHOR]

Single crystal X-ray structure determinations have previously been described for picrate salts of a variety of nitrogen bases. Herein, these have been extended to encompass monoprotonated mono- and oligo-dentate cyclic nitrogen-donor ligand systems derived from pyridine, some via saturation (piperidine and morpholine) and others via lateral extension of the aromatic system (2,2'-bipyridine, 1,10-phenanthroline, 2,9-dimethyl-1,10-phenanthroline, bis(2-pyridyl)amine, 2,2':6',2"-terpyridine, and 8-hydroxyquinoline). Hydrogen-bonding interactions are dominant determinants of the structures, complemented by or in competition with parallel stacking of anion and (aromatic) base planes. Furthermore, nitro⋯nitro, nitro⋯7i and phenoxy-0⋯7i inter-species contacts play a significant role in the crystal packing. It also appears that cation...anion interactions arising from CH(adjacent to NH)⋯O(o-nitro) interactions are more important than the available secondary bifurcating component associated with any NH⋯O(o-nitro) approach, resulting, in many cases, in a bidentate NH⋯HC base approach to an (ON)O⋯O⋯O(NO) triadic array. The nature of the anion-cation interactions and their importance are explored using the Hirshfeld surface method. The precision of the structure determinations establishes the quinonoid form of the picrate to be a widespread contributor. Theoretical calculations on picric acid and the parent pyridinium-picrate ion-pair confirm the energetic favourability of the base-triad approach and the dominance of the quinonoid resonance form. [ABSTRACT FROM AUTHOR]