Premium
Substituent Size Effects in Lewis Base Induced Reductions in Organolanthanide Chemistry
Author(s) -
Bojer Daniel,
Neumann Beate,
Stammler HansGeorg,
Mitzel Norbert W.
Publication year - 2011
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201002707
Subject(s) - chemistry , substituent , steric effects , toluene , medicinal chemistry , dimer , alkyl , divalent , stereochemistry , lewis acids and bases , catalysis , organic chemistry
The reaction of the tripodal 1,3,5‐trialkyl‐1,3,5‐triazacyclohexanes (L= cyclo ‐[N( R )CH 2 ] 3 , R =Et, i Pr, t Bu), with [Sm(AlMe 4 ) 3 ] resulted in the formation of divalent samarium complexes of the constitution [{L n Sm(AlMe 4 ) 2 } m ] ( n , m =1,2) under ethane extrusion. These compounds were characterised by single‐crystal X‐ray diffraction and elemental analyses. Simultaneous occurrence of Lewis base induced reduction and CH‐activation reactions is observed. The ratio of products depends on the bulkiness of the N ‐alkyl substituent R. The reaction of [Sm(AlMe 4 ) 3 ] with 1,3,5‐triisopropyl‐1,3,5‐triazacyclohexane (TiPTAC) in benzene afforded the inversion‐symmetric dimer [{(TiPTAC)(η 3 ‐AlMe 4 )Sm} 2 (μ 2 ‐AlMe 4 ) 2 ], whereas in toluene the pseudo‐samarocene [(TiPTAC) 2 Sm(η 1 ‐AlMe 4 ) 2 ] was obtained. The trisaluminate [(TiPTAC)Sm{(μ 2 ‐Me)(Me 2 Al)} 2 (μ 3 ‐CH 2 ) 2 AlMe 2 )] was found to be the CH‐activation product. In the case of the particular bulky 1,3,5‐tri‐ tert ‐butyl‐1,3,5‐triazacyclohexane (T t BuTAC), the reaction led to the formation of the dimeric [{(T t BuTAC)(η 3 ‐AlMe 4 )Sm} 2 (μ 2 ‐AlMe 4 ) 2 ] even in toluene in comparably high yields. The decrease of the steric demand to ethyl groups in 1,3,5‐triethyl‐1,3,5‐triazacyclohexane (TETAC) afforded the samarocene‐like [(TETAC) 2 Sm(η 1 ‐AlMe 4 ) 2 ] in lower yields. The resulting divalent samarium compounds are found to be stable with respect to reagents like dinitrogen, conjugated olefins and polycyclic aromatic systems.