Stuart P.W. Hill

LANTHANIDE METAL COMPLEXES OF N, N'-ETHYLENEBIS( (PYRIDIN-2-ONE); FROM CHELATES TO METALLACYCLIC FRAMEWORKS

Abstract The ligand N,N′ -ethylenebis(pyridin-2-one) (EBP) forms a range of lanthanide (Ln) complexes of types Ln(EBP) 2 (NO 3 ) 3 (Ln = La-Gd), Ln 2 (EBP) 3 (NO 3 ) 6 ·2MeOH (Ln=GdYb and also Y), Ln 2 (EBP) 3 (NO 3 ) 6 · n MeCN (Ln=TbYb), representative members of which have been studied by single crystal X-ray diffraction. Crystals of Eu(EBP) 2 (NO 3 ) 3 are monocline, space group C 2/ c , a =20.583(3). b = 9.453(2), c = 17.006(2) A , β = 120.58(2)°, Z = 4 . The compound is mononuclear with each Eu centre having a coordination environment comprising three chelating nitrates and two nine-membered chelate rings formed by the EBP ligands. Crystals of Tb 2 (EBP) 3 (NO 3 ) 6 ·5MeCN are triclinic, space group P Ī, a = 10.504(5), b = 10.854(4), c = 17.145(6) A , α = 84.23(2), β = 72.68(2), γ = 72.79(2)°, Z = 2 . The EBP ligands bridge the Tb centres forming sheets of contiguous 54-membered rings. The MeCN molecules of solvation are occluded within the lattice, some lying within the metallamacrocyclic rings and some between the sheets. Crystals of &{[Ho(EBP) 2 (MeOH)(NO 3 ) 3 ]0.5(EBP)&} 0 are triclinic, space group P Ī, a = 8.316(2), b = 10.138(2), c = 15.441(3) A , α = 92.82(2), β = 92.29(2), γ = 102.99(2)°, Z = 2 . Each Ho atom is coordinated to three chelating nitrate groups, two bridging EBP ligands and one methanol molecule leading to the formation of polymeric chains [Ho(EBP) 2 (MeOH)(NO 3 ) 3 ] 0 . The remaining EBP molecules are non-coordinated but form hydrogen bonds to the methanol ligands and thereby link adjacent chains to form sheets of contiguous 78-membered rings.

Framework coordination chemistry; generalised entry into a new class of supramolecular compounds exemplified by the structures of [Mn2(ebpy)3(NO3)4]n[where ebpy =N,N′-ethylenebis(2-pyridone)] and [Er2(ebpyrr)3(NO3)6]n[where ebpyrr =N,N′-ethyienebis(2-pyrrolidone)]

The ethylene-bridged bis(2-pyridone) ligand N,N′-ethylenebis(2-pyridone) and its bis(2-pyrrolidone) analogue react with manganese(II) nitrate and erbium(III) nitrate to form polymers containing 36-membered or 54-membered metallomacrocyclic rings, respectively; the 36-membered rings are linked to form a chain polymer and the 54-membered form contiguous two-dimensional sheets.

Synthesis and X-ray characterisation of some heterometallic Hg–M complexes with 2-oxazolidone

Mercury(II) acetate reacts with 2-oxazolidone (1,3-oxazolidin-2-one, C3H5NO2) in methanol to produce [HgL2](L = C3H4NO2, the anion of 2-oxazolidone). An X-ray diffraction study has shown that the Hg atom binds to the ring nitrogen atom with a near linear N–Hg–N geometry. There are two HgL2 groups in the asymmetric unit which are orthogonal to one another and linked via pairs of Hg ⋯ O interactions to form dimers. These bind to neighbouring units via weaker Hg–O interactions to form a one-dimensional chain polymer. When yttrium or lanthanide(III) nitrates are added to the reaction an isostructural series of compounds of formula [{Hg2L4M(NO3)3}n], where MLa–Yb or Y, is obtained. A representative member of this group, [{Hg2L4Gd(NO3)3}n], was studied by single-crystal X-ray diffraction methods. This forms a two-dimensional polymeric array comprising two sizes of metallamacrocyclic rings (16- and 48-membered) fused together, with the gadolinium(III) ion surrounded by nine oxygen atoms in a trigonal tricapped-prismatic arrangement. The IR, UV/VIS reflectance, EPR and solid-state NMR spectroscopic properties of these complexes and, where appropriate, those of [Hg3L6Co(NO3)2] and [Hg2L4Zn(NO3)1.33(OMe)0.67] are reported.

Crystal structures of [AgHgL2(NO3)]n, where LH=2-oxazolidone and β-propiolactam ; formation of helical chains and new 12-membered Ag/Hg metallamacrocyclic rings in the propiolactam complex

Abstract Reaction of 2-oxazolidone (C3H5NO2) or β-propiolactam (C3H5NO) with mercury(II) acetate and silver(I) nitrate in methanol leads to the formation of the polymeric heterometallic complexes [AgHg(C3H4NO2)2(NO3)]n (1) and [AgHg(C3H4NO)2(NO3)]n (2), respectively; the structures of which have been determined by X-ray diffraction methods. In each case, the deprotonated organic ligands bind to the mercury via nitrogen with nearly linear NHgN bonding and to the silver atom via oxygen. Despite the similar nature of the ligands, totally different three-dimensional assemblies are produced. Complex 1 is dimeric with a folded Ag2O2 ring in which the bridging oxygen atoms are provided by the exocyclic oxygen atoms of the 2-oxazolidone anions. These dimers are further linked in pairs to produce a “stepped” Ag4O4 species. Each silver atom is six-coordinate. Weak electrostatic, anion-mediated interact ions bridge these tetrameric units so as to produce loosely linked polymeric sheets. In compound 2 the silver atoms are linked by twisted Hg(β-propiolactam)2 bridges to form a helical chain. Each turn of the helix is bridged by a nitrate anion linking between adjacent silver atoms forming a 12-membered metallamacrocycle. Here the silver atoms are tetrahedrally coordinated.

X-ray structure of a mercury(II) complex of 4-methyl-2-(1H)-quinolone, [Hg(C10H8NO)2]; an example of a mercury(II)-π-aryl stacked sandwich compound

Abstract Reaction of 4-methyl-2-(1H)-quinolone (C10H9NO) with mercury(II) acetate in methanol yields the compound Hg(C10H8NO)2 (1), which has been structurally characterized by X-ray crystallography. The deprotonated 4-methyl-2-(1H)- quinolone ligands bind to the mercury via nitrogen with essentially linear NHgN bonding and with a nearly co-planar and anti disposition of the rings. In the solid state the HgL2 molecules form an unusual stacked structure, in which each mercury atom is sandwiched between the planes of the phenyl rings of adjacent HgL2 units at distances of 3.24 and 3.32 A. Solid-state 13C NMR spectra were recorded to investigate the Hg-phenyl ring interactions.

Fused-ring metallamacrocyclic mercury/lanthanide complexes formed by fused-ring lactams

Abstract Mercury(II) acetates reacts with the fused-ring lactams (I) and lanthanide(III) nitrates, Ln = La-Gd (Pm not studied), to give [LnHg2L4(NO3)3]n and with Y and Ln = Tb-Yb to yield [Y2Hg3L6(NO3)6]n and [Ln2Hg3L6(NO3)6]n, respectively. Each set of compounds forms an isostructural series. For the ligand Ic representative members of each series (Ln = Nd and Er, respectively) have been characterized by single-crystal X-ray diffraction methods. Both compounds form two-dimensional polymeric metallamacrocyclic arrays. They differ in the sense that the erbium complex comprises sheets of contiguous 48-membered rings, whereas in the neodymium compound two sizes of metallamacrocyclic coexist—one 48-membered and one 16-membered, which are fused together. The erbium ion is nine-coordinate and the neodymium atom 10-coordinate. The nitrate anions are involved in weak intra- and intermolecular interactions within the macrocycles.

Synthesis, X-ray characterisation and spectroscopic studies of metal complexes of N,N′-1,2-xylene-α,α′-diylbis(pyridin-2-one)

The co-ordination modes adopted by N,N′-1,2-xylene-α,α′-diylbis(pyridin-2-one)(o-xbp) with Sc, Y, lanthanides, ThIV, MnII, FeIII, CoII and ZnII have been studied. Five representative complexes have been structurally characterised by single-crystal X-ray diffraction. In the monomeric ten-co-ordinate complex [Ce(o-xbp)2(NO3)3]·MeOH both o-xbp ligands form eleven-membered chelate rings. In the dinuclear complex [Y2(o-xbp)3(NO3)6]·3MeCN pairs of nine-co-ordinate Y atoms are linked by an o-xbp bridge, whilst the other o-xbp ligands form chelate rings. The dinuclear complex [{Zn(o-xbp)Cl2}2] forms individual 22-membered rings in which pairs of tetrahedrally co-ordinated Zn atoms are linked by o-xbp bridges. In the iron(III) complex [Fe(o-xbp)2Cl2][FeCl4]·MeOH the Fe atom in the cation has cis-octahedral co-ordination geometry with the o-xbp ligands forming eleven-membered chelate rings; the anion is tetrahedral. In the cobalt(II) complex [Co(o-xbp)2(MeOH)2]I2·2MeOH the o-xbp ligands also chelate but the Co atom has a trans-octahedral geometry in which the two axial ligands are methanol molecules. A distinctive pattern of ligand conformations is observed in this series of compounds. Relevant spectroscopic results are also given.

Formation of a novel “bedspring”-like framework structure by a neodymium nitrate complex with N,N′-butylenebis(2-pyridone)

Abstract Reaction of N,N′-butylenebis(2-pyridone) (BBP) with hydrated M(NO3)3 salts (M = Y or a lanthanide ion) affords the complexes M2(BBP)3(NO3)6. Thorium(IV) nitrate and dioxouranium(VI) nitrate give Th2(BBP)3(NO3)8·0.5Me2CO and UO2(BBP)(NO3)2, respectively. X-ray diffraction studies on the Nd complex show it to contain arrays of contiguous 66-membered macrocyclic rings arranged so as to form as unusual “bedspring”-like network structure.

Ligand-induced formation of a triple helical bridge involving O-donor ligands in dimeric lanthanide complexes

The complexes [M2(p-XBP)3(NO3)6][M Pr, Nd.Sm, Er; p-XBP N,N′-xylene-1,4-diylbis(pyridin-2-one)] are shown by X-ray diffraction methods to contain the first example of an O-bonded triple helical bridge.