The synthesis and structures of rare earth 2-fluorophenyl- and 2,3,4,5-tetrafluorophenyl-N,N′-bis(aryl)formamidinate complexes

Redox transmetallation/protolysis (RTP) reactions between free rare-earth metals (La, Nd, or Yb), Hg(C6F5)2, and FFormH (FFormH = N,N′-bis(2-fluorophenyl)formamidine) in thf afforded four rare-earth complexes: trivalent [La(FForm)3(thf)2]·thf, [Nd(FForm)3(thf)x], [Yb(FForm)3(thf)] (when a slight excess of Yb was used), and divalent [Yb(FForm)2(thf)2] (when a large excess of Yb was used). With the exception of [Yb(FForm)3(thf)], the complexes did not readily crystallise from thf. However, crystallisation from either dme (La, Yb) or diglyme (Nd), produced single crystals of [La(FForm)3(dme)], [Yb(FForm)2(dme)2], and [Nd(FForm)3(diglyme)], respectively. A Nd complex of N,N′-bis(2,3,4,5-tetrafluorophenyl)formamidine (TFFormH): [Nd(TFForm)3(dme)], was also prepared by a similar RTP reaction, and was crystallised from dme. Heating the previously reported divalent TFForm complex: [Yb(TFForm)2(thf)3], in either PhMe or diglyme, separated out trace amounts of the trivalent complex [Yb(TFForm)3(thf)2] from PhMe, or the mixed oxidation state, solvent separated ion pair (SSIP) [Yb(TFForm)(diglyme)2][Yb(TFForm)4] from diglyme. The SSIP complex is the first crystallographically characterised trivalent ytterbium complex coordinating four discrete amidinate ligands.

A range of rare earth complexes involving fluorinated formamidinato complexes have been synthesised. Crystallisation from either dme or diglyme produced single crystals of all compounds and their X-ray crystal structures were determined.Figure optionsDownload as PowerPoint slide