Cyclopentadienyl Behavior of Pyrrolyl Anions within the meso-Octaethylporphyrinogen-Binding Lanthanides: Carbon-Hydrogen and Metal-Carbon Bond Rearrangements.
The complexation of Ln(III) ions by the meso-octaethylporphyrinogen [Et(8)N(4)H(4)], 1, has been achieved by reacting the sodium derivative [Et(8)N(4)Na(4).THF(3)], 2, with [LnCl(3).THF(2)]. Depending on the reaction or crystallization solvent, a variety of structural categories of Ln-porphyrinogen complexes have been isolated and structurally characterized. When the reaction was carried out in THF and the final complex recrystallized from THF, [{(eta(5):eta(1):eta(5):eta(1)-Et(8)N(4))Ln(THF)}-eta(3)-Na(THF)(2)] complexes [Ln = Pr (3), Nd (4), Sm (5), Eu (6), Gd (7), Yb (8)] were obtained in a monomeric form. When their recrystallization was performed in dioxane, a dimerization occurred thanks to dioxane bridging the sodium cations of the monomeric units [{(eta(5):eta(1):eta(5):eta(1)-Et(8)N(4))Ln(DME)}-eta(3)-Na](dioxane)(1.5)] [Ln = Nd, 14; Ln = Sm, 15]. In a third category we isolated complexes where two monomeric monoanions [(eta(5):eta(1):eta(5):eta(1)-Et(8)N(4))Ln](-) are eta(2):eta(3) sandwiching two sodium cations, which are exclusively solvated by the pyrrolyl anions [{(eta(5):eta(1):eta(5):eta(1)-Et(8)N(4))Ln}(2)-eta(2):eta(3)-Na(2)] [Ln = Pr, 16; Ln = Sm, 17]. The three classes of compounds mentioned above, all of them containing the monomeric unit [Ln-porphyrinogen-Na], are characterized by the following structural parameters: Ln-eta(5)(pyrrole)(av), 2.490(7) Å for 7, 2.556(2) Å for 14, 2.543(2) Å for 16; Ln-eta(1)(pyrrole)(av), 2.43(1) Å for 7, 2.494(4) Å for 14, 2.485(4) Å for 16; centroid-Ln-centroid, 174.6(3) degrees for 7, 168.1(1) degrees for 14, 169.7(2) degrees for 16; Na-eta(3)(pyrrole), 2.50(1) Å for 7, 2.515(3) Å for 14. The recrystallization of complexes 3-8 from DME led to dimeric organometallic complexes, where the dimerization has been via the desolvation of the Ln ion and the formation of a Ln-C sigma bond with the beta-carbon of a pyrrole of an adjacent Ln-porphyrinogen unit. Such dimers occur in the ion-separated form [(eta(5):eta(1):eta(5):eta(1)-Et(8)N(4))(2)Ln(2)][NaS(n)()](2) [Ln = Pr (9), Nd (10), Sm (11), Gd (12), Eu (13)]. Their recrystallization from THF led to the ion-pair derivatives in which two sodium cations are eta(2)-bonded to the eta(1)-pyrrolyl anions of the dimer [{(eta(5):eta(1):eta(5):eta(1)-Et(8)N(4))(2)Ln(2)}-eta(2)(NaS(n)())(2)] [Ln = Pr (18), Nd (19), Sm (20), Gd (21); S = DME, THF; n = 2]. When the crystallization of 9-13 was carried out from THF/dioxane, polymeric structures were isolated, where cations are bridged by dioxane molecules [{(eta(5):eta(1):eta(5):eta(1)-Et(8)N(4))(2)Ln}(2)-eta(2){Na(THF)}(2)(&mgr;-dioxane)][Ln = Nd, 22; Ln = Gd, 23]. In the three classes made up from the dimeric building block, the structural leit-motiv is constant and two structural parameters are very close [Ln-eta(5)(pyrrole)(av), 2.538(3) Å for 11, 2.578(1) Å for 18; centroid-Ln-centroid, 172.3(2) degrees for 11, 170.4(1) degrees for 18; Ln-C, 2.471(7) Å for 11, 2.512(2) Å for 18].
Campazzi
Elisa
E
Institut de Chimie Minérale et Analytique, BCH, Université de Lausanne, CH-1015 Lausanne, Switzerland.
Solari
Euro
E
Scopelliti
Rosario
R
Floriani
Carlo
C