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Adducts of Ferrocenylboranes and Pyridine Bases: Generation of Charge‐Transfer Complexes and Reversible Coordination Polymers
Author(s) -
Fontani Marco,
Peters Frank,
Scherer Wolfgang,
Wachter Wolfgang,
Wagner Matthias,
Zanello Piero
Publication year - 1998
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/(sici)1099-0682(199810)1998:10<1453::aid-ejic1453>3.0.co;2-x
Subject(s) - chemistry , pyridine , substituent , moiety , ferrocene , ligand (biochemistry) , medicinal chemistry , electron donor , polymerization , comproportionation , pyridinium , bipyridine , crystallography , photochemistry , stereochemistry , polymer , electrochemistry , crystal structure , organic chemistry , biochemistry , receptor , electrode , catalysis
Compared to parent ferrocene, the redox potential of the Fe II /Fe III transition is shifted to much more cathodic values in B–N adducts 1 ·Do and 2 ·(Do) 2 of borylated ferrocenes FcBMe 2 ( 1 ) and 1,1′‐fc(BMe 2 ) 2 ( 2 ) with pyridine bases Do [Fc: (C 5 H 5 )Fe(C 5 H 4 ); fc: (C 5 H 4 )Fe(C 5 H 4 ); Do: γ‐picoline, 4‐(dimethylamino)pyridine, N ‐( n ‐propyl)‐4‐(4′‐pyridyl)pyridinium hexafluorophosphate]. Electron donation by one single BMe 2 ·Do substituent at the cyclopentadienyl ligand is approximately equal to the positive inductive effect of the five methyl groups in a C 5 Me 5 (cp*) moiety. Using the bidentate nitrogen ligand 4,4′‐bipyridine (bipy), the dark‐purple dimetallic complex 1 ·bipy· 1 is obtained upon reaction with 2 equiv. of 1 . 1 ·bipy· 1 has been structurally characterized by X‐ray crystallography. The compound tolerates loss of two electrons at the ferrocene groups, as well as two one‐electron reductions at the bipy linker. Dark purple coloured coordination polymers [ 2 ·bipy] n are accessible from bipy and 1 equiv. of the diborylated derivative 2 . The intense colours of 1 ·bipy· 1 and [ 2 ·bipy] n are indicative of charge‐transfer interactions between the electron‐rich ferrocene fragments and the viologen‐like R 3 B–bipy–BR 3 acceptor. Neat, solid [ 2 ·bipy] n is thermally stable up to 240 °C, but in the presence of toluene, polymerization is fully reversible at about 85 °C.