Alternative η⁵- and η⁶-Bonding Modes for Bis(fluorenyl)lanthanide Complexes by Reactions with AlR₃ and Succesive Addition of THF

Abstract

Reversible and equilibrium isomerization of η 5 -bis(Me 3 Si-fluorenyl)-rare earth metal complexes to η 6 -bis(Me 3 Si-fluorene-AlR 3 )-rare earth metal complexes, which is a novel type of metallotropic tautomerism, was realized by the addition of AlR 3 to the former complexes. Resulting η 6 -complexes also changed to the initial η 5 -complexes reversibly by the addition of excess THF. η 5 -Bis(Me 3 Si-fluorenyl)Sm(THF) 2 (1) was prepared by reaction of Me 3 Sifluorenylpotassium with SmI 2 (THF) 2 , and its structure was analyzed by X-ray diffraction. η 6 -Bis(Me 3 Si-fluorene-AlMe 3 )Sm (2) was synthesized by the reaction of 1 with excess AlMe 3 . The corresponding reaction of excess AlEt 3 with 1 gave η 6 -bis(Me 3 Si-fluorene-AlEt 3 )Sm (3). The structures of 2 and 3 were determined by X-ray analyses. The reaction of bis(Me 3 Sifluorenyl)Yb(THF) 2 ( 4) with an excess amount of AlMe 3 gave η 5 -(Me 3 Si-fluorenyl)-η 6 -(Me 3 -Si-fluorene-AlMe 3 )Yb ( 5), where one equimolar AlMe 3 coordinates to the Yb atom through its two Me groups via an agostic interaction. One of the Me 3 Si-fluorenyl groups assumes η 5 -coordination, while the other Me 3 Si-fluorenyl group shows η 6 -coordination. The addition of excess THF to 5 produced (fluorenyl)Yb(THF) 4 /AlMe 4 (6) in low yield. To understand the primary factor for the alternative η 5 -and η 6 -bonding modes, we have synthesized ( i Prindenyl) 2 Yb(THF) 2 (7) without a Me 3 Si group and with a rather small indenyl ring and examined the reaction with AlR 3 .

Crystallographic report: (η5-Fluorenyl)-tris-pyridine-di-iodo-lanthanum(III) and -neodymium(III)

“…6 Previous attempts to prepare mono-fluorenyl lanthanide complexes by the 1 : 1 reaction of (fluorenyl)Li and LnCl 3 have been unsuccessful. 2,3 Here, we report the X-ray crystal structures of (η 5 -fluorenyl)LnI 2 (py) 3 (Ln = La (1), Nd (2)), which are the first examples of neutral, mono-fluorenyl complexes of the lanthanides.…”

Mononuclear η6‐Arene Complexes of Lanthanides: One‐Step Syntheses, Crystal Structures, and Arene Exchange

“…[6][7][8] One of the simple and most effective synthetic routes to mono(arene)-lanthanide complexes, containing arene ligands that are coordinated to the metal in the η 6 mode, is the reaction of a lanthanide halide with aluminium(III) halides in an arene solution. Employing this method, a series of mononuclear complexes of Sm, [3,[9][10][11] La, [6] Nd, [6,10] Gd, [10] Yb, [10] Y, [16] Pr, [16] Eu, [17] and U [3,15] was prepared. Benzene and its alkylated derivatives have been used as the arene ligands.…”

Synthesis, characterization and catalytic activity of organolanthanide(II) complexes with heterocyclic-functionalized fluorenyl ligands

“…(10)°in compound 4, but smaller than that of 79.26 (18)°found in (C 13 H 9 ) 2 Yb(THF) 2 [10]. This angle is smaller than the O-Yb-O angle of 84.5(3)°and 86.3(3)°found in [g 5 :g 1 -(CH 3 OCH 2 CH 2 C 9 H 5 SiMe 3 )] 2 Yb II [11b], 83.1 (14)°found in [g 5 :g 1 -(C 4 H 7 OCH 2 C 9 H 5 SiMe 3 )] 2 Yb II [11g], also smaller than the N-Yb-N angle of 92.8(5)°, 103.7(2)°found in [g 5 :g 1 -(Me 2 NCH 2 CH 2 -C 9 H 5 SiMe 3 )] 2 Eu II and [g 5 :g 1 -(Me 2 NCH 2 CH 2 C 9 H 6 )] 2 Yb II [11c], but larger than the corresponding angles of 68.05(12)°found in (C 13 H 9 ) (C 5 Me 5 )Yb(DME) [10], and the O-Eu-O angle of 75.15(10)°in compound 4 is smaller than the N-Eu-N angle of 94.49(15)°f ound in compound 6, respectively, suggesting steric and electronic effects.…”

“…(C 13 H 9 ) 2 Sm(THF) 2 [19b], [(C 5 Me 5 )Sm(OAr)] 2 [20], (9-Me 3 Si-C 13 H 8 ) 2 -Sm(THF) 2 , (9-Me 3 Si-C 13 H 8 ) 2 Yb(THF) 2 [21]. Examination of the solvents effects on the catalytic activities of the catalysts 3-6 indicated that the catalytic activities of the catalysts have good activity in toluene and THF.…”

“…The g 5 [10], g 3 [13], g 6 [14] bonding modes of the fluorenyl ligands with the rare-earth metals have been documented. Different kinds of ligands incorporating fluorenyl moiety such as sigle-carbon bridged ansa-metallocenes [15], silylene-bridged ansa-metallocenes [16], and the class of ''constrained geometry" half sandwich complexes have been reported [13].…”