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Reversible Fixation of Carbon Dioxide at Nickel( 0 ) Centers: A Route for Large Organometallic Rings, Dimers, and Tetramers
Author(s) -
Walther Dirk,
Fugger Christine,
Schreer Heike,
Kilian Rainer,
Görls Helmar
Publication year - 2001
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 - 10.1002/1521-3765(20011203)7:23<5214::aid-chem5214>3.0.co;2-j
Subject(s) - chemistry , dimer , nickel , isomerization , benzene , monomer , benzaldehyde , crystallography , stereochemistry , medicinal chemistry , catalysis , organic chemistry , polymer
The reaction between bis(cycloocta‐1,5‐diene)nickel( 0 ), carbon dioxide and benzaldehyde‐ N ‐furfurylideneimine ( A ) in 1,4‐dioxane or THF results in the formation of the 24‐membered organometallic macrocycles of the type [( A )Ni(‐CH(R 1 )‐N(R 2 )‐COO‐)] 6 (solv) n (R 1 : phenyl, R 2 : furfurylidene, solv: 1,4‐dioxane in 1 a , THF in 1 b ). According to the X‐ray analyses, six monomeric nickelacyclic units are connected through six Ni‐ μ 2 ‐OCO‐Ni bridges in these macrocycles. The cavities of the metallomacrocycles (diameter: 9.410(1) Å in 1 a , 9.250(1) Å in 1 b ) each contain one solvent molecule. Reaction of 1 b with Me 3 P results in the displacement of the peripheral ligands A by the phosphine to form the 24‐membered organometallic macrocycle 1 c . Both 1 a and 1 b isomerize in benzene to form the dimeric complex [( A )Ni(‐CH(R 1 )‐N(R 2 )‐COO‐)] 2 (solv) n ( 2 ). The X‐ray crystal structure reveals that 2 consists of the same monomeric units as found in 1 a and 1 b . However two Ni‐ μ 2 ‐O‐Ni bonds link the carboxylato groups. The solvent‐dependent isomerization of 1 b yielding 2 is a reversible reaction. Furthermore, the macrocycle 1 b partially eliminates carbon dioxide above 20 °C, followed by elimination of half of the monodentately coordinated Schiff base ligands to form the planar tetrameric complex 6 . This is also a reversible process.