Roman A. Kresinski

Solution and solid-state structures of lanthanide nitrate complexes with [(MeO)2P(O)]2C(OH)R (R=Me, tBu)

Abstract The complexes Ln(NO3)3Laxa02 (La=[(MeO)2P(O)]2C(OH)Me; Ln=La–Er) and Ln(NO3)3Lbxa02 (Lb=[(MeO)2P(O)]2C(OH)tBu); Ln=La–Lu) have been synthesised. The solid-state structures examined by IR spectroscopy, single crystal X-ray diffraction and extended X-ray absorption fine structure show uniformity across the series up to Dy, the metal being ten coordinate. Solution structures have been examined by 31P NMR spectroscopy, conductivity, electrospray mass spectrometry and EXAFS, and results indicate that solution structures fall into two groups, one for the lighter (La–Sm) and one for the heavier (Eu–Lu) lanthanides. This structural change involves the diphosphonate ligands, which appear to be monodenate for the heavier metals, affording these a coordination number of eight.

Complexes of (EtO)2P(O)CH2P(O)(OEt)2 with lanthanide nitrates

The preparation of complexes of (EtO)2P(O)CH2P(O)(OEt)2 n = L, with lanthanide nitrates is described. Stable complexes with composition LnL2(NO3)3 can be isolated for Ln = La–Eu and fully characterised. For Ln = Gd–Lu solid compounds could not be isolated. Conductivity and 31P NMR spectroscopy indicate structural changes in solution between the lighter and heavier lanthanides and, whilst electrospray mass spectrometry confirms a dramatic difference in behaviour with complexes of the heavier lanthanides readily decomposing via loss of EtNO3, other experiments show that this does not occur under the conditions of complex formation. The single crystal X-ray structures for Ln = La and Sm show the nitrates and OEt groups to be in close proximity. The changes in spectroscopic properties correlate well with the difficulties in isolating the complexes of heavier metals, and are possibly due to the formation of dimeric complexes rather than loss of ethyl nitrate.

The preparation, characterisation and in vitro cytotoxicity of potentially chemotherapeutic heterobimetallic complexes containing early and late transition metals

The reactions of phosphine Ph(2)P(CH(2))(2)SO(3)Na with Cp(2)MCl(2) (M=Ti, Zr) in aqueous solution give the metallophosphines, Cp(2)Ti(OSO(2)(CH(2))(2)PPh(2))(2) (Cp=cyclopentadienyl) and CpZr(OH)(OSO(2)(CH(2))(2)PPh(2))(2). These react with CODMCl(2) (M=Pd, Pt) (COD=1,5-cyclooctadiene) in dichloromethane to give heterobimetallic complexes Cp(2)Ti(OSO(2)(CH(2))(2)PPh(2))(2)MCl(2) and CpZr(OH)(OSO(2)(CH(2))(2) PPh(2))(2)MCl(2) respectively. The compounds are characterised by infrared and NMR spectroscopies and elemental analysis. Electrospray mass spectra of the complexes are reported and compared to those of Cp(2)MCl(2) in water and dimethylsulfoxide (DMSO). For zirconocene dichloride and its product heterobimetallic complexes, the addition of ethylenediamine tetraacetic acid disodium salt (Na(2)H(2)EDTA) was found to be an effective ionisation enhancement agent for the electrospray mass spectral studies. Cytotoxicity studies for the previously reported Cl(2)Pt(PPh(2)(CH(2))(2)SO(3)H)(2).3.5H(2)O (Wedgwood et al., Inorg. Chim. Acta 290 (1999) 189), and the compounds Cp(2)Ti(OSO(2)(CH(2))(2) PPh(2))(2).1.5H(2)O and Cp(2)Ti(OSO(2)(CH(2))(2)PPh(2))(2)PtCl(2).4H(2)O reported here, have been evaluated by colony formation assay against cisplatin-sensitive and -resistant cell lines L929 and L929/R to highlight potential chemotherapeutic activity. The compound Cl(2)Pt(PPh(2)(CH(2))(2)SO(3)H)(2).3.5H(2)O overcomes cisplatin resistance.

Synthesis, electrochemistry and spectroelectrochemistry of hydrazido(2-) bridged bimetallic molybdenum species, and the X-ray crystal structure of [Mo{HB(3,5-Me2pz)3}(NO)Cl]2(μ-NHNH) in solid solution

Abstract The species [Mo{HB(3,5-Me2pz)3}(NO)Cl]2(μ-NHNH) (1) (3,5-Me2pz=3,5-dimethylpyrazol-1-yl) and [Mo{HB(3,5-Me2pz)3}(NO)I]2(μ-NHNH) have been synthesised. Electrochemical reduction of 1 results in a species with a near-infrared spectral band which shows no solvent dependence. Reoxidation results in the formation of another species which undergoes reversible reduction resulting in the development of another near-infrared spectral band which also is insensitive to solvent. These observations suggest that, in both cases, the mixed-valence species are class III. Additionally, 1 has been characterised structurally as a component of a solid solution also containing its chlorinated analogues; this determination shows that all components of the solution contain a near-planar Moue5f8NHue5f8NHue5f8Mo array and that Cl replacement is isomorphous.