Interactions of Remote Alkyl Groups with Lanthanide Metal Centers: Synthesis, Characterization and Ligand Redistribution Reactions of Heterobimetallic Species Containing Trialkylaluminum Fragments

Abstract

The reaction of [Ln(OAr) 3 ] 2 with four equivalents of trialkylaluminum leads to the formation of the bis-trialkylaluminum adducts (ArO)Ln[(µ-OAr)(µ-R)AlR 2 ] 2 [Ln = La, R = Me (1); Ln = La, R = Et (3); Ln = Sm, R = Et (4)]. The X-ray crystal structure of 1 reveals short La−C(bridging) distances of 2.800(5) and 2.759(5) Å . A reduced 1 J C-H coupling constant of 110 Hz and a low energy ν(C−H) stretch in the solution and solid state IR spectra are consistent with a strong agostic La···H−C interaction in solution. Crystal data for 1: a = 11.708(2) Å ; b = 18.416(4) Å ; c = 20.949(4) Å ; α = 90°; β = 90°; γ = 90°; V = 4516.8(15) Å 3 ; Z = 4; R1 = 4.69%. The solid-state structure of the samarium ethyl derivative 4 reveals close contacts of 2.627(4) and 2.649(4) Å between the samarium

The First Example of a μ2-Imido Functionality Bound to a Lanthanide Metal Center: X-ray Crystal Structure and DFT Study of [(μ-ArN)Sm(μ-NHAr)(μ-Me)AlMe2]2 (Ar = 2,6-iPr2C6H3)1

“…Compound 2 also maintains a short Sm−C distance (i.e. aluminum-bound methyl group) of 2.649(14) Å, which is similar to the Sm−C(alkyl group) distances previously determined for (ArO)Sm[μ-OAr)(μ-R)AlR 2 ] 2 (R = Me, 2.620(5) and 2.632(5) Å; R = Et, 2.627(4) and 2.649(4) Å) . This distance is slightly shorter than typical Ln−C distances found in complexes containing bridging methyl groups − and suggests the presence of an agostic interaction between the aluminum methyl group(s) and the metal center.…”

“…At this point, we suspected that the residual aluminum complex was being generated in solution as a result of the decomposition of 2 . We have recently observed similar redistribution reactions in related 4f-element complexes supported by phenoxide ligation . However, thermolysis experiments did not indicate any significant decomposition, suggesting that difficulties in obtaining pure samples of 2 are due to the similar solubility properties of [Me 2 Al(NHAr)] 2 and [(μ-ArN)Sm(μ-NHAr)(μ-Me)AlMe 2 ] 2 ( 2 )…”

Crystal structure of bis(μ2-methanolato-κO:κO)hexamethylbis(μ2-triphenylacetato-κO:κO′)bis(μ2-triphenylacetato-κ2 O,O′:κO)dialuminiumdilanthanum toluene tetrasolvate

“…There is only one related compound having the La-[(Alkyl/ Aryl) 3 Al(OAlkyl/OAryl)] motif (CSD refcode MIMPED; Giesbrecht et al, 2002) , 2.367 (3) Å ] and Al-C [2.040 (5), 2.053 (6) Å ] bond lengths within the LaAl 2 (-Me) 2 (-OAryl) 2 fragment are similar to those found in the LaAl(-Me)(-OMe) fragment of the complex reported herein. However, the La1-C2 distance in the title compound (Table 1) is considerably longer (by 0.24-0.28 Å ) than the corresponding La-C distances in MIMPED [2.800 (5), 2.759 (5) Å ], presumably due to steric reasons.…”

“…Cg1, Cg2, Cg3 and Cg4 are the centroids of the C33-C38, C39-C44, C52-C57 and C19-C24 rings, respectively. Occhipinti et al, 2011;GEQMOF, GEQMUL, Fischbach et al, 2006b) Biagini et al, 1994;WAPYIV, WAPYOB, Evans et al, 1993a;WEHHAS, Evans et al, 1993b) Fischbach et al, 2003;MIMPED, Giesbrecht et al, 2002;MOQYOG, Gordon et al, 2002;PETMUX, Fischbach et al, 2006c) Giesbrecht et al, 2002;ROCHOH, Sommerfeldt et al, 2008) Evans et al, 1998). MIMPED is the only La structure among them.…”

Samarium versus aluminium Lewis acidity in a mixed alkyl carboxylate complex related to alkylaluminium activation in diene polymerization catalysis

“…8,9 Yellow [(C 5 Me This emphasizes the delicate balance that allows 2 to be isolated. Although there are several examples of adduct formation between lanthanide alkoxides and trialkyl aluminium, [12][13][14] to our knowledge there is only one other example of a structurally characterized adduct of a lanthanide carboxylate with trialkyl aluminium, {Me 2 Al(O 2 CC 6 H 2 i Pr 3 -2,4,6) 2 } 2 Nd(AlMe 4 ). 15 Complex 2 not only is a model for the intermediate in alkylaluminium activation of a lanthanide carboxylate, but it also has an unusual structure that bears on the relative Lewis acidities of aluminium samarium.…”