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)I2(thf)3] (Ln = La, 1, Ce, 2, Tb, 3, Ho, 4, Er, 5, Tm, 6); II.N,N'-Bis(2,6-diethylphenyl)formamidinatodiiodidolanthanoid(III) complexes [Ln(EtForm)I2(thf)3]×thf (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)I2(thf)3] (Ln = Ce, 15, Nd, 16, Gd, 17, Tm, 18, Lu 19); IV.N,N¢-bis(phenyl)formamidinatodiiodidolanthanoid complexes [Ln(PhForm)I2(thf)3] (Ln = Nd, 20, Gd, 21, Er, 22). Compound [Ce(XylForm)2I(thf)2] (23) was also synthesized by the same method except the ratio of I2 to XylFormH was 1:4. Divalent N,N¢-bis(2,6-diisopropylphenyl)formamidinato-iodido-lanthanoid(II) complexes [Eu(DippForm)I(thf)4]·thf (24), [Yb(DippForm)I(thf)3]·2DippFormH (25), [Sm(DippForm)I(thf)4]·thf (26) have also been synthesized by direct reactions of the free metals, iodine and DippFormH. Interestingly, [Sm(DippForm)I2(thf)3] (27) was obtained by the oxidation of [Sm(DippForm)I(thf)4]·thf (26) on exposure to air. N,N¢-Bis(2,6-dimethylphenyl)formamidinatoiodidosamarium(II) [Sm(XylForm)I(thf)3]n (28) was also prepared by direct reaction of Sm, iodine and XylFormH (mole ratio of I2: XylFormH = 1:2). All products have been identified by X-ray crystallography and all the trivalent complexes [Ln(Form)nI3-n] (n = 1 or 2) are stable to rearrangement.