Simon A. Parsons

The structures of bis-maltolato-zinc(II) and of bis-3-hydroxy-1,2-dimethyl-4-pyridinonato–zinc(II) and –lead(II)

Abstract The structures of bis-(3-hydroxy-4-pyronato)zinc(II) {bis-maltolato-zinc(II), Zn(malt)2·1.5H2O}, bis-(1,2-dimethyl-3-hydroxy-4-pyridinonato)zinc(II) {Zn(L1)2·7H2O}, and bis-(1,2-dimethyl-3-hydroxy-4-pyridinonato)lead(II) {Pb(L1)2·7H2O}, determined by X-ray diffraction techniques, are reported. The zinc in {Zn(L1)2·7H2O} is five coordinated; in Zn(malt)2·1.5H2O zinc occurs in both five- and six-coordination. Pb(L1)2·7H2O is dimeric; each lead has five oxygens, two of them bridging, in its coordination shell. All three compounds contain water molecules coordinated to the metal; both L1 complexes also contain water of crystallisation in the form of extended chains. All three compounds are extensively hydrogen bonded.

Oxo-tricyano complexes of molybdenum(IV) and tungsten(IV) with bidentate Schiff bases

SummaryThe reaction of [M(CN)4O(OH2)]2− (M = Mo or W) with 2-acetylpyridine and methyl-or butyl-amine in a water-MeOH mixture gave [M(CN)3O(L-L)]- (L-L= Schiff base ligand), isolated as [AsPh4]+ salts. The complexes have been characterized by elemental analysis, and electronic, i.r. and1H-n.m.r. spectroscopy. The Schiff base ligands complex in a bidentate manner through the two nitrogen atoms giving mixed-ligand compounds similarly to 2,2′-bipyridyl or 1,10-phenanthroline.

Structures of bis-ethylmaltolatodichloro-tin(IV) and -titanium(IV) and of trichloro(1-methyl-2-ethyl-3-hydroxy-4H-pyridin-4-onato)aquatin(IV)

Abstract The structures of solvates of the bis-ethylmaltolatodichloro-metal(IV) complexes M(etma)2Cl2, with M=Sn and Ti, and of trichloro(1-methyl-2-ethyl-3-hydroxy-4H-pyridin-4-onato)aquatin(IV), Sn(mepp)Cl3(H2O), have been established by single crystal X-ray diffraction methods. Sn(etma)2Cl2 crystallised with one molecule of dichloromethane, Ti(etma)2Cl2 with one molecule of tetrahydrofuran, and Sn(mepp)Cl3(H2O) with one molecule of acetone, from their respective recrystallisation media. Both ethylmaltol complexes M(etma)2Cl2 are cis-octahedral. The coordination around the tin atom in Sn(mepp)Cl3(H2O) approximates to octahedral, with the three chloride ligands in fac geometry. The tin(IV)–water bond distance in this pyridinone complex is discussed in relation to this distance in other aquatin(IV) complexes. The effects of coordinating tin(IV) on the geometry of the coordinated pyridinone are considered.

Solvent effects on piezochromism of transition metal complexes

We report solvent effects on the piezochromic behaviour of wavelengths of maximum absorption for metal-to-ligand charge-transfer (m.l.c.t.) bands of several molybdenum–diimine–carbonyl and titanium or vanadium–cyclopentadienyl or ethylmaltolate–thiocyanate complexes. These and previously published data are collated in an attempt to establish a pattern for solvent effects on piezochromism of m.l.c.t. bands. Strategies for the design of compounds and complexes for use in establishing a clear pattern for such effects are outlined.

Synthesis and reactivity of bis-4-pyrone and bis-4-pyridinone dichlorotin(IV) compounds

Abstract A number of tin(IV) complexes, Sn(LL) 2 X 2 , have been prepared in which LL is a 4-pyronate or 4-pyridinonate ligand and X is chloride or alkoxide. UV-vis, IR and NMR ( 1 H, 13 C, 119 Sn) spectra are reported for these complexes. Reactivities have been established through kinetic studies of nucleophilic substitution in acetonitrile solution. Ligand effects on spectra and reactivity are discussed and compared with those for similar metal(IV) complexes, especially of titanium.

Kinetics of substitution at bis‐cyclopentadienylvanadium dichloride

Rate constants are reported for substitution at vanadium(IV) in bis-cyclopentadienylvanadium dichloride by a range of anionic and uncharged nucleophiles in acetonitrile solution. Rate constants have been determined for replacement of the first and of the second chloride. The reactivity of V(cp)2Cl2 is compared with that of Ti(cp)2Cl2.

Pyronate and pyridinonate complexes of gadolinium

Abstract The preparation, characterization and properties of gadolinium complexes of 3-hydroxy-2-ethyl-4-pyrone (ethylmaltol) and of 3-hydroxy-1,2-dimethyl-4-pyridinone (L1 or CP20) are reported. The solvation characteristics of complexes of this type, exemplified by solubilities in alcohol-water solvent mixtures, may make them suitable MRI contrast agents for oral administration.

Solvent Effects on the piezochromism of molybdenum(IV) and tungsten(IV) anions [M(CN)3O(diimine)]−

Solvatochromism of the [Mo(CN)3O(phen)]− ion has been studied. Solvent effects on pressure dependence (up to 1.25 kbar) of wavelengths of maximum absorption for charge-transfer bands of several molybdenum(IV) and tungsten(IV) complexes, [M(CN)3O(diimine)]− (M = Mo or W), are described. The effects of applied pressure are larger for less polar unstructured solvents than for highly polar hydrogen-bonded solvents.

Tris-[3-hydroxy-1,2-dimethyl-pyridin-4(1H)-onato]cobalt(III)

The preparation and properties of tris-[3-hydroxy-1,2-dimethyl-pyridin-4(1H)-onato]cobalt(III) are described. The structure of the fac isomer has been established by X-ray diffraction techniques. Solvation characteristics of this complex have been assessed through solubility measurements in methanol–water mixtures. The complex is very inert in neutral solution but undergoes acid-catalysed aquation at lower pHs.