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Interactions of Remote Alkyl Groups with Lanthanide Metal Centers: Synthesis, Characterization and Ligand Redistribution Reactions of Heterobimetallic Species Containing Trialkylaluminum Fragments
Author(s) -
Giesbrecht Garth R.,
Gordon John C.,
Brady John T.,
Clark David L.,
Keogh D. Webster,
Michalczyk Ryszard,
Scott Brian L.,
Watkin John G.
Publication year - 2002
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/1099-0682(200203)2002:3<723::aid-ejic723>3.0.co;2-2
Subject(s) - chemistry , agostic interaction , methylene , crystal structure , lanthanide , adduct , alkyl , crystallography , stereochemistry , ligand (biochemistry) , samarium , ethylene , medicinal chemistry , metal , inorganic chemistry , organic chemistry , ion , biochemistry , receptor , catalysis
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; R 1 = 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 center and the methylene carbons of the triethylaluminum groups. The room temperature 13 C NMR spectrum of 4 exhibits a 1 J C‐H coupling constant of 102 Hz; additionally, the fluxional process that exchanges methyl groups in 1 and 2 is slow enough on the NMR time scale to allow distinct methylene groups in 4 to be observed. Crystal data for 4 : a = 19.318(1) Å; b = 20.150(1) Å; c = 26.280(1) Å; α = 90°; β = 90°; γ = 90°; V = 10229.8(9) Å 3 ; Z = 8; R 1 = 3.53%. Thermolysis of 1 − 4 results in ligand redistribution to form [R 2 Al(OAr)] 2 [R = Me, Et ( 5 )] and other unidentified species. Crystal data for 5 : a = 9.496(4) Å; b = 10.183(4) Å; c = 18.794(7) Å; α = 90.06(1)°; β = 92.394(7)°; γ = 114.976(6)°; V = 1645.6(11) Å 3 ; Z = 2; R 1 = 10.13%.