Synthesis and spectroscopy of lanthanide halide and high oxidation state early transition metal complexes with neutral donor ligands

Abstract

The reaction of phosphine oxide ligands (dppmO2, dppeO2 or PPO2) with LnCl3, LnI3 or LnCl3/[NH4][PF6] (Ln = La or Lu) are used to investigate the effect of varying metal ion radius, counter ion and ligand architecture on resulting metal complexes. The phosphine oxide ligand, dppmO2, is coordinated to a range of lanthanide halides in order to further illustrate the effect of the lanthanide contraction on the coordination of this bidentate phosphine oxide.

The first examples of divalent lanthanide halide complexes (SmI2, EuI2, EuBr2 or YbI2) bearing phosphine oxide ligands (OPPh3 or OPMe3) have been isolated and characterised. The species are characterised by elemental analysis, infrared spectroscopy, UV-vis spectroscopy and 31P{1H} NMR spectroscopy. The solid state structures of [EuBr2(OPPh3)4] and [EuI2(OPPh3)4] were obtained. The products are readily oxidised to form [LnX2(OPR3)4]+, with [EuI2(OPPh3)4][I3] being confirmed by crystallographic analysis.

A family of lanthanide (II) halide macrocyclic complexes are synthesised by the controlled addition of the macrocycle ligand to the lanthanide halide (YbI2, EuI2, EuBr2, SmI2). The use of mixed donor macrocyclic ligands allows for the rare coordination of soft thio- or seleno-ether groups to coordinate to hard Ln(II) metal centres.

The coordination chemistry of two series of complexes derived from TaOCl3 and TaSCl3 with neutral N-donor and O-donor ligands is explored. The complexes are synthesised by the addition of O(SiMe3)2 or S(SiMe3)2 to TaCl5 respectively followed by the addition of the relevant neutral ligands. The complexes were characterised by 1H and 31P{1H} NMR spectroscopy, infrared spectroscopy, elemental analysis and single crystal X-ray diffraction where possible. The crystal structures of the distorted octahedral [TaOCl3(1,10-phen)], [TaSCl3(1,10-phen)], [TaOCl3{o-C6H4(P(O)Ph2)2}], [TaSCl3(OPPh3)2], [TaSCl3{Ph2P(O)CH2CH2P(O)Ph2}] and [TaSCl3(MeCN)2] are reported. The complexes are compared to their niobium analogues and appear to be significantly less robust and more readily hydrolysed in solution.

A series of tantalum thio-chloride complexes featuring a range of neutral chalcogenoether ligands of the form, RE{CH2}nER (E = S or Se), are described. Low pressure chemical vapour deposition experiments to establish the suitability of selected candidates, as precursors, to form thin films of TaS2 were explored, but proved unsuccessful.

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ORCID for Gillian Reid: orcid.org/0000-0001-5349-3468

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