Unusual modification methods for the ureido ligand of lanthanocene derivatives

Isocyanate diinsertion into the N-H bond of the 2-pyridylamino ligand of organolanthanides

[Cp2LnNHPy]2 (Py = 2-pyridyl) (1a-e) react with phenyl isocyanate to form the N-H diinsertion products Cp2Ln[eta2:eta1-PyNCON(Ph)CONHPh](THF) (Ln = Yb (3a), Er (3b), Y (3c), Dy (3d), Gd (3e)). It has been proven that nPr2NH can abstract one PhNCO unit from 3c to form Cp2Y[eta3-OC(NHPh)NPy] (2c) and nPr2NHCONHPh (4), representing a rare example of selective release of a functional group of ligands in organolanthanide chemistry. Hydrolysis of 2c gives the organic nitrogen-containing product PyNHCONHPh (5). Moreover, 3c can also be obtained by the reaction of 2c with PhNCO. These results demonstrate that the diinsertion of PhN=C=O into the N-H bond of coordinated amino ligands might proceed in a stepwise manner. All the compounds were characterized by elemental analysis and spectroscopic properties. The structures of compounds 3a-e and 4 are also determined through X-ray single-crystal diffraction analysis.

Selective Reaction Based on the Linked Diamido Ligands of Dinuclear Lanthanide Complexes

The dinuclear ytterbium pyridyl diamido complexes [Cp(2)Yb(THF)](2)[mu-eta(1):eta(2)-(NH)(2)(C(5)H(3)N-2,6)] (1a) and [Cp(2)Yb(THF)](2)[mu-eta(1):eta(2)-(NH)(2)(C(5)H(3)N-2,3)] (1b) are easily prepared by protonolysis of Cp(3)Yb with 0.5 equiv of the corresponding diaminopyridine in accepted yields, respectively. Treatment of 1a with 2 equiv of dicyclohexylcarbodiimide (CyN=C=NCy) in THF at low temperature leads to the isolation of the formal double N-H addition product (Cp(2)Yb)(2)[mu-eta(2):eta(2)-(CyN(CyNH)CN)(2)(C(5)H(3)N-2,6)] (2) in 42% yield. Compound 2 is unstable to heat and slowly isomerized to the mixed neutral/dianionic diguanidinate complex (Cp(2)Yb)(2)[mu-eta(2):eta(2)-(CyNH)(2)CN(C(5)H(3)N-2,6)NC(NCy)(2)](THF) (3) at room temperature. Similarly, treatment of 1b with 2 equiv of CyN=C=NCy gives the addition/ isomerization product (Cp(2)Yb)(2)[mu-eta(2):eta(2):eta(1)-(CyNH)(2)CN(C(5)H(3)N-2,3)NC(NCy)(2)] (4). Moreover, the reaction of various ytterbium aryl diamido complexes (prepared in situ from [Cp(2)YbMe](2) and aryldiamine, respectively) with CyN=C=NCy affords the corresponding addition products (Cp(2)Yb)(2)[mu-eta(2):eta(2)-{CyN(CyNH)CN}(2)(C(6)H(4)-1,4)] (5), (Cp(2)Yb)(2)[mu-eta(2):eta(2)-{CyN(CyNH)CN}(2)(C(6)H(4)-1,3)](6), and (Cp(2)Yb)(2)[mu-eta(2):eta(2)-{CyN(CyNH)CN}(2)(C(13)H(8)-2,7)] (7), respectively. In contrast to pyridyl-bridged bis(guanidinate monoanion) complexes, aryl-bridged bis(guanidinate monoanion) complexes 5-7 are stable even with prolonged heating at 110 degrees C. All the results not only demonstrate that the presence of the pyridyl bridge can impart the diamido complexes with a unique reactivity and initiate the unexpected reaction sequence but also indicate evidently that the number and distribution of negative charges of the diguanidinate ligand is tunable from double monoanionic units to mixed neutral/dianionic isomers. All the complexes are characterized by elemental analysis and IR spectroscopies. The structures of complexes 1a, 3, 5, 6, and 7 are also determined through X-ray single-crystal diffraction analysis.

Facile construction of novel organolanthanide square-planar macrocycles through addition of carbodiimide to an amino group

The reactivity of lanthanocene derivatives containing the p-aminothiophenolate ligand towards carbodiimide was examined. Reaction of Cp2Ln(p-SC6H4NH2)(THF) with RN=C=NR in THF at room temperature gave four novel organolanthanide guanidinate complexes [Cp2Ln(p-SC6H4N(H)C(NHR)=NR)]4 (R = iPr, Ln = Yb (1a), Er (2a); R = Cy, Ln = Yb (2a), Er (2b)), formed by the addition of the C[double bond, length as m-dash]N double bonds of the carbodiimide molecule to the para-position amino group. Their unique square-planar macrocycle structures have been determined through X-ray single-crystal diffraction analysis. This result provides a potential method for the construction of organolanthanide macrocycles.

Facile Construction of Lanthanide Metallomacrocycles with the Bridging Imidazolate and Triazolate Ligands and Their Ring Expansions

Four novel tri- or tetranuclear organolanthanide metallomacrocycles [Cp2Ln(mu-Im)(THF)3 (Cp = C5H5, Ln = Yb (1), Er (2)], [Cp2Dy(mu-Im)]4(THF)]3 x 2THF (3), and [Cp'2Yb(mu-eta1:eta2-Tz)]4 x 2THF (Cp' = CH3C5H4) (4) have been synthesized through protolysis of Cp3Ln or Cp'3Yb with imidazole or triazole, indicating that both the bridge-ligand size and the lanthanide-ion radii can be applied in the modulation of the metallomacrocycles. Further investigations on the reactivity of complexes 1, 3, and 4 toward phenyl isocyanate reveal that PhNCO inserts readily into the simple bridge Ln-N bonds of 1 and 3 to yield the corresponding insertion products [Cp2Ln(mu-eta1:eta2-OC(Im)NPh)]3 (Ln = Yb (5), Dy (6)) but cannot insert into the Ln-N bond with a mu-eta1:eta2-bonding mode in 4. The novel bridge ligand [OC(Im)NPh] can expand the numbers of the ring members from 12 to 18 in 5 or 16 to 18 in 6. The number of metal atoms in the metallacycles with the ligand [OC(Im)NPh] is independent of the lanthanide-ion size; both trinuclear lanthanide macrocycles are observed in 5 and 6. All of these new complexes have been characterized by elemental analysis and spectroscopic properties, and their structures have also been determined through X-ray single-crystal diffraction analysis.