Chalcogenoether complexes of Nb(v) thio- and seleno-halides as single source precursors for low pressure chemical vapour deposition of NbS and NbSe thin films.

NbSCl was obtained via reaction of NbCl with S(SiMe) in anhydrous CHCl, whilst in MeCN solution the same reaction gives [NbSCl(MeCN)]. [NbSeCl(MeCN)] was obtained similarly from NbCl with Se(SiMe). The chalcogenoether complexes, [NbSCl(ER)] (E = S: R = Me, Bu; E = Se: R = Bu), were obtained from reaction of NbCl, ER and S(SiMe) in CHCl. The structure of the [NbSCl(SMe)] reveals a Cl-bridged dimer with the SMe ligands disposed syn. The Cl bridges are highly asymmetric, with the long Nb-Cl bond trans Nb[double bond, length as m-dash]S. The complexes, [NbSCl(L-L)] (L-L = MeSCHCHSMe, MeS(CH)SMe, PrSCHCHSPr, MeSe(CH)SeMe and BuS(CH)SBu), were obtained from reaction of L-L with preformed [NbSCl(MeCN)]. The structures of the Me-substituted complexes reveal distorted octahedral monomers with the neutral ligands trans to S/Cl. Solution H and Se{H} NMR data showed that the neutral ligands are partially dissociated and undergoing fast exchange at ambient temperatures in CHCl solution, consistent with weak Lewis acidity for NbSCl. The complexes containing Bu-substituted ligands have been used as single source precursors for low pressure chemical vapour deposition (CVD) of 3R-NbS thin films. 2H-NbSe thin films were also obtained via low pressure CVD using [NbSeCl(SeBu)]. The thin films were characterised by grazing incidence and in-plane XRD, pole figure analysis, scanning electron microscopy and energy dispersive X-ray analysis.