Direct Reaction - One Step Route to Synthesize Lanthanoid-iodide Formamidinates

This paper describes a novel and simple method direct reaction of lanthanoid metals with equimolar amounts of iodine and a formamidine under ultrasonication as an effective, metal-based route to lanthanoid(III) diiodide formamidinates, namely I. N,N'-Bis(2,6-diisopropylphenyl)formamidinatodiiodidolanthanoid(III) complexes [Ln(DippForm)I-2(thf)(3)] (Ln= La, 1, Ce, 2, Tb, 3, Ho, 4, Er, 5, Tm, 6); II. N,N'-Bis(2,6diethylphenyl)formamidinatodiiodidolanthanoid(III) complexes [Ln(EtForm)I-2(thf)(3)] (Ln= Ce, 7, Nd, 8, Gd, 9, Tb, 10, Dy, 11, Ho, 12, Er, 13, Lu, 14). III. N,N'-bis(2,6-dimethylphenyl)formamidinatodiiodidolanthanoid(III) complexes [Ln(XylForm)I-2(thf)(3)] (Ln= Ce, 15, Nd, 16, Gd, 17, Tm, 18, Lu 19); IV. N,N'-bis(phenyl)formamidinatodiiodidolanthanoid complexes [Ln(PhForm)I-2(thf)(3)] (Ln= Nd, 20, Gd, 21, Er, 22). Compound [Ce(XylForm)(2)I(thf)(2)] (23) was also synthesized by the same method except the ratio of I-2 to XylFormH was 1: 4. Divalent N,N'-bis(2,6-diisopropylphenyl)formamidinato-iodido-lanthanoid(II) complexes [Eu(DippForm)I(thf)(4)] center dot thf (24), [Yb(DippForm)I(thf)(3)] center dot 2DippFormH (25), [Sm(DippForm)I(thf)(4)] center dot thf (26) have also been synthesized by direct reactions of the free metals, iodine and DippFormH. Interestingly, [Sm(DippForm)I-2(thf)(3)] (27) was obtained by the oxidation of [Sm(DippForm)I(thf)(4)] center dot thf (26) on exposure to air. N,N'-Bis(2,6dimethylphenyl)formamidinatoiodidosamarium(II) [Sm(XylForm)I(thf)(3)](n) (28) was also prepared by direct reaction of Sm, iodine and XylFormH (mole ratio of I-2: XylFormH= 1: 2). All products have been identified by X-ray crystallography and all the trivalent complexes [Ln(Form)(n)I-3-(n)] (n= 1 or 2) are stable to rearrangement.

Automated summary

This paper describes a novel and simple method to synthesize lanthanoid(III) diiodide formamidinates through direct reaction of lanthanoid metals with equimolar amounts of iodine and a formamidine under ultrasonication. The products were identified by X-ray crystallography and all the trivalent complexes were found to be stable to rearrangement.