F. Alan Hart

Low co-ordination numbers in lanthanide and actinide compounds. Part I. The preparation and characterization of tris{bis(trimethylsilyl)-amido}lanthanides

The new three-co-ordinated lanthanide complexes [Ln{N(SiMe3)2}3], where Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Ho, Yb, and Lu, and [Y{N(Sime3)2}3], have been prepared and their 1H n.m.r. and electronic spectra are reported and discussed. The magnetic susceptibility of the Gd complex at 98 and 298 K is reported.

Colour and chemical composition in ancient glass: An examination of some roman and wealden glass by means of ultraviolet-visible-infra-red spectrometry and electron microprobe analysis

Abstract Glass sherds from the Roman town at Colchester and from the post-mediaeval glasshouse site at Knightons near Dunsfold in Surrey have been investigated by ultraviolet-visible-infra-red spectrometry and by electron microprobe analysis. The glass is coloured by visible absorption bands of iron, cobalt and manganese, whose origins are discussed.

An analytical study, using inductively coupled plasma (ICP) spectrometry, of samian and colour-coated wares from the Roman town at Colchester together with related continental samian wares

Abstract Over 200 sherds of samian and colour-coated pottery of late 2nd or early 3rd century date have been analysed by inductively coupled plasma (ICP) emission spectrometry. Most of this material was excavated at Colchester, England; the remainder is related East Gaulish material. Some clay samples were also analysed. The material divides, after multivariate statistical analysis, into 11 clusters. These accord well with known archaeological evidence and suggest assignments of origin where these are uncertain. In particular, the archaeological evidence for a link between Colchester and the Sinzig potters is supported.

Synthesis and structure of lanthanide complexes of a mixed donor macrocyclic ligand

Abstract Complexes of lanthanide nitrates and perchlorates with a hexadentate triamine-triether macrocyclic ligand L have been obtained either by template synthesis for La and Ce or by metal ion transfer for Nd and Sm. IR, NMR, mass spectra, and cyclic voltammograms are discussed. The X-ray crystal structure of [La(NO3)3L] shows 12-coordinated La with LaO (nitrate)= 2.653–2.752 A, LaO (macrocycle) = 2.634–2.781 A, and LaN (macrocycle) = 2.680–2.755 A.

The complex chemistry of scandium. Part 1. Preparation and properties of some scandium(III) complexes of polyamines. X-Ray crystal structures of tri(nitrato-OO′)(2,2′ : 6′,2″-terpyridyl-NN′N″)scandium(III) and [1,2-bis(pyridine-α-carbaldimino)ethane-NN′N″N‴]-di-µ-hydroxo-di(nitrato-OO′)discandium(III) dinitrate bis(acetonitrile)

The complexes Sc(NO3)3(terpy), Sc(NO3)3(terpy)(H2O), ScCl3(tpta), Sc(NO3)3(bpce)(H2O)2, and Sc(NO3)2(OH)(bpce) have been prepared and characterised [terpy = 2,2′ : 6′,2″-terpyridyl, tpta = 2,4,6-tris(α-pyridyl)-1,3,5-triazine, and bpce = 1,2-bis(pyridine-α-carbaldimino)ethane]. Single-crystal X-ray structure determinations show that Sc(NO3)3(terpy) is monomeric, [Sc(NO3)3(terpy)], and nine-co-ordinated, while Sc(NO3)2(OH)(bpce) is dimeric, [Sc2(NO3)2(µ-OH)2(bpca)2][NO3]2, with hydroxo-bridges, each Sc ion being eight-co-ordinated.

Complexes of lanthanide ions with the crown ether 1,4,7,10,13,16-hexaoxacyclo-octadecane

The title crown ether forms three types of compound with lanthanide ions, [M(NO3)3(crown)](M = La—Nd), M4(NO3)12(crown)3(M = La—Gd), and [M(NO3)3(OH2)3]·crown (M =Gd—Lu). Crystal structures of the first and third types have been determined by X-ray diffraction. The complex [La(NO3)3(crown)] is orthorhombic, space group Pbca, with a= 12.249, b= 15.618, c= 21.852 A, and Z= 8. Least-squares refinement using 3 607 observed [I > 1.5σ(I)] intensity data has given R= 0.039 9. The lanthanum co-ordination comprises the six crown oxygens [La–O = 2.627–2.771(3)A] and two oxygens from each of the three bidentate nitrates [La–O = 2.644–2.675(3)A]. The complex [Gd(NO3)3(OH2)3]·crown is also orthorhombic, space group probably Pn21a, with a= 15.259, b= 14.302, c= 11.094 A, and Z= 4. The structure has been refined to R= 0.029 using 2 314 observed data. Here the crown is not co-ordinated to the metal ion but is linked to the [Gd(NO3)3(OH2)3] molecule by O ⋯ HO bonds. The Gd–O bond lengths are 2.41–2.53(1)A for nitrato- and 2.30–2.46(1)A for water oxygens.

Low co-ordination numbers in lanthanoid and actinoid compounds. Part 2. Syntheses, properties, and crystal and molecular structures of triphenylphosphine oxide and peroxo-derivatives of [bis(trimethylsilyl)-amido]lanthanoids

The preparation, properties, and n.m.r. spectra of 1 : 1 triphenylphosphine oxide adducts of [M{N(SiMe3)2}3](M = La Eu, or Lu) and dimeric peroxo-species [M2{N(SiMe3)2}4(O2)(PPh3O)2](M = La, Pr, Sm, Eu, or Lu) are described. The crystal and molecular structures of [La{N(SiMe3)2}3(PPh3O)](1) and [La2{N(SiMe3)2}4(O2)(PPh3O)2](2) have been determined bysingle-crystal X-ray diffraction methods from data measured on a manual diffractometer and refined by least-squares to R 0.116 for 2 770 observed reflections for (1) and to R 0.113 for 2 153 data for (2). Both species crystallise in space group P with cell parameters: (1); a= 19.92, b= 12.64, c= 12.48 A, α= 120.5, β= 87.3, γ= 102.7°, Z= 2; (2); a= 13.55, b= 18.54, c= 12.54 Aα= 90.8, β= 121.7, γ= 115.3°, Z= 1. Complex (1) is monomeric and the lanthanum atom has slightly distorted LaN3O tetrahedral geometry. The La–O–P unit is almost linear, with La–O 2.39(2)A; La–N distances are 2.38(2)–2.41(2)A. Complex (2) is a peroxo-bridged centrosymmetric dimer in which the peroxo-function acts as a symmetrical doubly bidentate bridge linking two La{N(SiMe3)2}2(PPh3O) units. The metal atom can again be considered to have distorted tetrahedral co-ordination if the O2 function is assumed to occupy one co-ordination site. The La–O(O2) distances are both 2.33(3)A, whilst La–O(PPh3O) is 2.42(2) and La–N 2.37(2) and 2.49(3)A. The O–O separation is 1.65(4)A, but this may be artificially lengthened by the effects of crystal decomposition.

12-Co-ordinated crown ether complex of lanthanum; X-ray crystal structure

A single-crystal X-ray study of trinitrato-cis,syn,cis-2,5,8,15,18,21-hexaoxatricyclo[20,4,0, 09,14]hexacosanelanthanum shows the metal ion to be co-ordinated to six polyether oxygen atoms and three bidentate nitrate ions; structural parameters are discussed.

Syntheses, X-ray structures, and properties of complexes of macrocyclic hexaimines with lanthanide nitrates

Complexes [M (NO3)3L1]{M = La or Ce, L1= 2,7,13,18-tetramethyl-3,6,14,17,23,24-hexa-azatricyclo[17.3.1.18,12]tetracosa-1 (23),2,6,8,10,12(24),13,17,19,21-decaene}, [M(NO3)2L1(H2O)]NO3·H2O (M = La, Ce, or Pr), and [{M(NO3)L1(H2O)2}2]NO3[ClO4]3·4H2O (M = Nd, Sm, Eu, Gd, Tb, Dy, Ho, or Er) have been synthesised by a template condensation or by ligand exchange. The X-ray crystal structures of a member of each series, [La(NO3)3L1], [Ce(NO3)2L1(H2O)]NO3·H2O, and [{Nd(NO3)L1(H2O)2}2]NO3[ClO4]3·4H2O have been determined; the complexes contain the hexadentate macrocycle L1 co-ordinated to the lanthanide ion and are respectively 12-, 11-, and 10-co-ordinate. Properties including n.m.r. paramagnetic shifts are described.

Preparation and properties of complexes of lanthanides with a hexadentate nitrogen-donor macrocycle: X-ray crystal structure of the complex [La(NO3)3l]

The template condensation of 2,6-diacetyl-pyridine with ethylenediamine gives complexes [M(NO3)3L](M = La or Ce) of the hexadentate nitrogen donor macrocycle L; the structure of [La(NO3)3L] has been determined by X-ray diffraction, and the complexes, whose 1H n.m.r. spectra are described, are kinetically stable in water with respect to dissociation of the macrocycle.