The structure of triindenylcerium pyridinate

Abstract

457The final atomic parameters and selected interatomic distances are given in Tables 1 and 2 Each Rb ion is coordinated by four Br(2) and five Br(1) ions and the very short Rb-Br(1 ll) bond can be explained by the unsymmetrical nature of this coordination group.

Tris(indenyl)lanthanoid Complexes (Ln = La, Pr, Nd) Containing either (S)-(−)-Nicotine or Two Simpler Pyridine Bases

“…The LnϪC distances involving carbon atoms shared by the C 5 and C 6 units of each indenyl ligand are, as usual, significantly longer than the other LnϪC bonds of each C 5 fragment. The LnϪN distances compare well with that reported for [Ce(C 9 H 7 ) 3 ·Py] [CeϪN 268.4(4) pm], [4] and are also in agreement with those in [Nd(C 5 H 5 ) 3 ·Py] [266. 8(5)] and in [Sm(C 5 H 5 ) 3 ·Py] [265.6(3) pm].…”

“…However, all these preparative attempts remained unsuccessful, as the isolable leek-green, crystalline products turned out to be the starting compound [Pr(Ind) 3 ·THF] (as confirmed by elemental analysis, 1 H NMR spectroscopy, and crystal structure analysis). (4) These results clearly indicate that just one methyl group in the 2-position of a pyridine molecule (i.e. α-picoline) no longer allows the indenyl ligands to adopt orientations that would provide enough space for the coordination of this pyridine derivative.…”

“…This has been suggested for the recently prepared complex [Lu(C 9 H 7 ) 3 ·3THF], in view of its notably higher THF content, [11b] and also for the well-documented crystalline [LuCp 3 ] complex which has an η 1 -coordinated Cp ligand. [12] The failure of α-picoline to enter the coordination sphere of a {Pr(Ind) 3 } fragment indicates that the required change from η 5 to η 1 (or η 3 ) coordination probably needs some auxiliary ''support'' to overcome the higher steric demand of the potential ligands listed in Equation (4).…”

“…Corresponding properties are reported for the cerium homologue [Ce(Ind) 3 ·Py] (7). [4] As the unit cell parameters of 5, 6, and 7 are similar, the three complexes are quasi-isostructural, although their molecular conformations may still Table 3. Distances of the C 6 centers Cti6 (i ϭ 1Ϫ3), and the metal atom Ln, from the best plane spanned by the three C 5 centres, Cti5, of each epimeric or racemic pair of 2؊7 (distances in pm; a negative sign indicates the disposal of Cti6 transoid to Py*) Table 4.…”

“…Whilst the crystal structures of a few 1:1 adducts of a tris(cyclopentadienyl)lanthanoid(III) complex and pyridine (Py), or any pyridine derivative (Py*), have already been reported, [1Ϫ3] only one corresponding indenyl complex [Ce(Ind) 3 ·Py] [4] has so far been characterised, also by X-ray crystallography. Structural studies on adducts containing the chiral pyridine derivative (S)-(Ϫ)-nicotine (Nic) are yet to be reported on, although several [LnCp 3 ·Nic] systems were prepared for early spectroscopic studies.…”