Craig M. Grant

Studies of a Nickel-Based Single-Molecule Magnet

A cyclic complex [Ni12(chp)12(O2CMe)12(thf)6(H2O)6] (1) has been synthesised and studied (chp=6-chloro-2-pyridonate). Complex 1 exhibits ferromagnetic exchange between the S=1 centres, giving an S=12 spin ground state. Detailed studies demonstrate that it is a single-molecule magnet with an energy barrier of approximately 10 K for reorientation of magnetisation. Resonant quantum tunnelling is also observed. The field between resonances allows accurate measurement of D, which is 0.067 K. Inelastic neutron scattering studies have allowed exchange parameters to be derived accurately, which was impossible from susceptibility data alone. Three exchange interactions are required: two ferromagnetic nearest neighbour interactions of approximately 11 and 2 cm−1 and an anti-ferromagnetic next nearest neighbour interaction of −0.9 cm−1.

Discovery and evaluation of highly active imidotitanium ethylene polymerisation catalysts using high throughput catalyst screening

A family of ca. 50 imidotitanium precatalysts [Ti(NR)(Me(3)[9]aneN(3))Cl(2)](R = alkyl or aryl; Me(3)[9]aneN(3)= 1,4,7-trimethyltriazacyclononane) were prepared in good yields using semi-automated procedures; high-throughput screening techniques identified seven highly active ethylene polymerisation precatalysts with activities in the range ca. 3 400 to 10 000 kg(PE) mol(-1) h(-1) bar(-1).

Synthesis, crystal structures and thermal decomposition studies of a series of copper–lanthanoid complexes of 6-methyl-2-pyridone

A series of mixed copper-Ianthanoid complexes have been synthesised and structurally characterised. All the compounds were made from the reaction of [Cu6Na(mhp)12]NO3(mhp is the anion of 6-methyl-2-pyridone) with hydrated lanthanoid nitrates in methanol. In each case X-ray crystallographic analysis revealed a central Cu2O2 ring bridged to peripheral lanthanoid (Ln) atoms by mhp ligands. For early lanthanoids (La, Ce and Nd) the complex has a stoichiometry [Ln2Cu2(OMe)2(mhp)4(NO3)4(Hmhp)2-(MeOH)4], in which the Ln atoms are nine-co-ordinate, with approximate tricapped-trigonal prismatic, geometry. For later lanthanoids (Gd, Dy and Yb) the stoichiometry is [Ln2Cu2(OMe)2(mhp)4(NO3)4-(Hmhp)2(MeOH)2] and the Ln atoms are eight-co-ordinate, with a geometry that can be related to a dodecahedron. For Ln = Sm a disordered co-ordination sphere results, presumably caused by the intermediate ionic radius of Sm leading to very similar stabilities for the eight- and nine-co-ordinate structures. Thermal decomposition studies of these complexes have also been carried out which indicate that decomposition occurs initially to monometallic oxides or oxide carbonates, followed by production of the mixed-oxide phase Ln2CuO4(for Ln = La, Nd, Gd or Dy) or Ln2Cu2O5(for Ln = Er or Yb). In most cases CuO is also found. All oxide and oxide-carbonate phases have been characterised by X-ray powder diffraction.

Diiron(III) and polymeric iron(III)–sodium complexes with bridging and terminal pyridonate ligands: structures and magnetic properties

The reaction of anhydrous iron(III) chloride or [NEt4]2[Fe2Cl6O] with equimolar quantities of 6-chloro-2-pyridone (Hchp) and NaOMe in MeOH afforded, after recrystallisation from tetrahydrofuran (thf), the one-dimensional polymer [{Fe(µ-chp)6Na3(µ-MeOH)6·2thf}n]1. When the reaction of FeCl3 with NaOMe and Hchp was performed in the presence of 4,4′-dimethyl-2,2′-bipyridine (dmbipy) or 1,10-phenanthroline (phen) the dinuclear complexes [Fe2(µ-OMe)2(chp)4(dmbipy)2]·2MeOH 2 or [Fe2(µ-OMe)2(chp)4(phen)2]·2MeOH 3 resulted. The molecular structures at 150 K and magnetic properties between 1.8 and 280 K of 1–3 have been investigated. Complex 1 displays magnetic behaviour consistent with a paramagnet while 2 and 3 exhibit antiferromagnetic exchange interactions between the spins of the iron(III) ions through OMe bridges (J=–26.8 to –28.6 cm–1).

The synthesis, structure and magnetic properties of a cyclic dodecanuclear nickel complex

The synthesis and characterisation of the dodecanuclear nickel complex, [Ni12(O2CMe)12(chp)12(H2O)6(THF)6](where chp = the anion of 6-chloro-2-pyridone) is described; structure determination shows formation of a metallocycle, while magnetic studies indicate ferromagnetic coupling between the nickel(II) ions within the complex leading to a high spin multiplicity in the ground state.

Bis(β-diketonate) ligands for the synthesis of bimetalliccomplexes of TiIII, VIII, MnIII andFeIII with a triple-helix structure

Addition of the bis(β-diketone) ligand L [L = 1,3-bis(3-phenyl-3-oxopropanoyl)benzene] to a suitable source of M III ions (M = Ti, V, Mn, Fe) in a L:M = 3:2 ratio gives the dinuclear products [M 2 L 3 ], which have a triple-helical structure.

Single-molecule magnets: out-of-phase ac susceptibility signals from tetranuclear vanadium(III) complexes with an S = 3 ground state

The salts of the tetranuclear vanadium(III) ions [V4O2(O2- CEt)7(L–L)2]z (L–L = bpy, z = +1; L–L = pic–, z = –1) with a V4 butterfly topology and a S = 3 ground state have been found to exhibit out-of-phase ac susceptibility signals, a signature of single-molecule magnets.

Dalton communications. Syntheses, structures and magnetic studies of homometallic manganese and heterometallic iron–sodium one-dimensional polymers

Two one-dimensional polymers involving pyridone ligands, [{Mn2(chp)2(O2CMe)2(MeOH)2}n] and [{Fe(chp)6Na3(MeOH)6}n](Hchp = 6-chloro-2-pyridone), have been synthesised and structurally characterised, and their magnetic properties investigated.

New polynuclear nickel complexes with a variety of pyridonate and carboxylate ligands

A general synthetic strategy for making, and structures and some properties of, several new polynuclear nickel complexes of pyridonate ligands are reported: these complexes include a linear trinuclear complex [Ni3(ChP)4(O2CMe)2(MeOH)6], a tetranuclear cubane [Ni4(OMe)4(η-ChP)(ChP)3(MeOH)7] and two undecanuclear complexes [Ni11(µ-OH)6(O2CMe)6(mhp)9(H2O)3]2[CO3] and [Ni11(µ3-OH)6(O2CMe)7(mhp)9(Hmhp)2](Hchp and Hmhp = 6-chloro- and 6-methyl-2-pyridone respectively).

Use of a hexanuclear copper complex as a ligand transfer agent : crystal structures of hexakis(6-methyl-2-pyridone)iron(III) nitrate and tetrakis(6-methyl-2-pyridone)bis(nitrato)cobalt(II)

Abstract The hexanuclear copper complex [Cu6Na(MeL)12][NO3](1) (where MeL = C6H6NO, the anion of 2-hydroxy-6-methylpyridine) undergoes ligand transfer reactions with solid hydrated transition metal nitrates. With iron(III) nitrate the salt [Fe(MeLH)6][NO3]3 (2) results, while with cobalt(II) nitrate the complex [Co (MeLH)4(NO3)2] (3) is formed. Both compounds have been characterized by X-ray crystallography, which reveals that in both cases the metals have regular octahedral coordination geometries, and that the protonated ligands are involved in either inter- or intra-molecular hydrogen bonding.