Five different types of η⁸-cyclooctatetraenyl-lanthanide half-sandwich complexes from one ligand set, including a “giant neodymium wheel”

Abstract

The lithium-cyclopropylethynylamidinates Li[c-C3H5-C[triple bond, length as m-dash]C-C(NR)2] (1a: R = (i)Pr, 1b: R = cyclohexyl (Cy)) have been used as precursors for the preparation of five new series of half-sandwich complexes. These complexes contain the large flat cyclooctatetraenyl ligand (C8H8(2-), commonly abbreviated as COT), and were isolated as solvated, unsolvated and inverse sandwich complexes. Treatment of the halide precursors [(COT)Pr(μ-Cl)(THF)2]2 with 1b and [(COT)Nd(μ-Cl)(THF)2]2 with 1a and 1b in THF in a 1 : 2 molar ratio, respectively, afforded (COT)Ln[μ-c-C3H5-C[triple bond, length as m-dash]C-C(NR)2]2Li(L) (2: Ln = Pr, R = Cy, L = Et2O; 3: Ln = Nd, R = (i)Pr, L = THF; 4: Ln = Nd, R = Cy, L = THF). Treatment of the dimeric cerium(iii) bis(cyclopropylethynylamidinate) complexes [{c-C3H5-C[triple bond, length as m-dash]C-C(NR)2}2Ce(μ-Cl)(THF)]2 (5: R = (i)Pr; 6: R = Cy) in situ with K2C8H8 in a 1 : 1 molar ratio in THF at room temperature afforded the inverse-sandwich complexes (μ-η(8):η(8)-COT)[Ce{c-C3H5-C[triple bond, length as m-dash]C-C(NR)2}2]2 (7: R = (i)Pr; 8: R = Cy). This reaction represents a new method for encapsulation of a planar (C8H8)(2-) ring in lanthanide complexes containing amidinate ligands in the outer decks. Novel unsolvated dinuclear lanthanide half-sandwich complexes were prepared by using the precursors 1a, 1b and COT(2-). Unlike the complexes 2-4, the reaction of [(COT)Pr(μ-Cl)(THF)2]2 with 1a afforded the unsolvated centrosymmetric complex [(COT)Pr(μ-c-C3H5-C[triple bond, length as m-dash]C-C(N(i)Pr)2)]2 (9). These dimeric structures could be also accessed by reaction of LnCl3 (Ln = Ce or Nd) with 1a or 1b and K2COT in a 1 : 1 : 1 molar ratio as a one-pot reaction to give novel [(COT)Ln(μ-c-C3H5-C[triple bond, length as m-dash]C-C(NR)2)]2 complexes (10: Ln = Ce, R = (i)Pr; 11: Ln = Ce, R = Cy; 12: Ln = Nd, R = (i)Pr). Similar treatment of HoCl3 with 1a or 1b and K2COT as three-component reactions in a 1 : 1 : 1 molar ratio afforded the solvated half-sandwich complexes (COT)Ho(c-C3H5-C[triple bond, length as m-dash]C-C(NR)2)(THF) (13: R = (i)Pr; 14: R = Cy). A unique multidecker sandwich complex [(μ-η(8):η(8)-COT){Nd(c-C3H5-C[triple bond, length as m-dash]C-C(NCy)2)(μ-Cl)}2]4 (15) was prepared by reaction of anhydrous NdCl3 with K2COT and 1b in a one-pot reaction. The solid state structure of 15 revealed the presence of an unprecedented macrocyclic sandwich compound ("giant neodymium wheel") consisting of four COT rings sandwiched between eight Nd(3+) ions, and each Nd(3+) ion is bonded to one amidinate ligand and bridged by two chlorine atoms with the neighbouring Nd(3+) ion.

Synthesis and photophysical properties of rare earth complexes bearing silanediamido ligands Me2Si(NAryl)22− (Aryl = Dipp, Mes)

“…Such ligands with monoatomic bridges (Scheme 1) are extensively implemented in the RE chemistry since they form a four-membered metallacycle and thus the largest bite angles well suitable for RE cations. Amidinates and guanidinates (types A and B, respectively) are the most extensively used, which is reflected in the comprehensive reviews by Edelman [1][2][3][4][5][6] and others. [7][8][9] In addition to these ligands with the NCN backbone, there are several alternatives with a heteroatomic bridge, such as triazenides, iminophosphonamides, or silanediamides (types C-E, respectively), which are much less involved in the RE chemistry.…”

Facile Synthesis, Structural Activity Relationship, Molecular Modeling and In Vitro Biological Evaluation of New Urea Derivatives with Incorporated Isoxazole and Thiazole Moieties as Anticancer Agents

“…Many of drugs containing thiazole moiety in their structure used in wide rang in the pharmaceutical market such as fanetinole, combendazole, niridazole, tiazofuren, bleomycine and sulfathiazole (Figure ). Encouraged by the interesting bioactivity of diarylurea derivatives and in conjunction to our interest in preparation of bioactive molecules, a new series of diarylurea incorporating sulfamethoxazole and thiazole moieties were synthesized and screened for anticancer activity.…”

Crystal structures of two ytterbium(III) complexes comprising alkynylamidinate ligands

“…At 131.1 , the Cp-Yb-Cp angle is close to that observed in [Cp 2 YbCl] 2 (Cp-Yb-Cp 130.0 ; Lamberts et al, 1987;Lueken et al, 1987Lueken et al, , 1989 and compound 1 is therefore a typical bent metallocene complex of trivalent ytterbium. Due to the low formal coordination number of four around the Yb atom, the Yb-N bond lengths of 2.274 (2) and 2.293 (2) Å are short compared to those observed in other late lanthanide amidinates, such as -N 2.342 (3) and 2.349 (3) Å ; Sroor et al, 2016].…”

“…with rising coordination number of the metal and within the lanthanide series from right to left). The C1-N bond lengths of the amidinate ligand are very similar [1: 1.332 (3) and 1.334 (3) Å ; 2: 1.321 (4) and 1.324 (4) Å ], indicating a typical delocalization of the negative charge within the NCN fragment (Sroor et al, 2016).…”