Abstract
The consecutive synthesis of 1,3,5-triferrocenyl-2,4,6-tris(ethynylferrocenyl)benzene (6c) is described using 1,3,5-Cl-3-2,4,6-I-3-C-6 (2) as starting compound. Subsequent Sonogashira C,C cross-coupling of 2 with FcC CH (3) in the molar ratio of 1:4 afforded solely 1,3,5-Cl-3-2,4,6-(FcC C)(3)-C-6 (4c) (Fc = Fe(eta(5)-C5H4)-(eta(5)-C5H5)). However, when 2 is reacted with 3 in a 1: 3 ratio a mixture of 1,3,5-Cl-3-2-(FcC C)-4,6-I-2-C-6 (4a) and 1,3,5-Cl-3-2,4-(FcC C)(2)-6-I-C-6 (4b) is obtained. Negishi C,C cross-coupling of 4c with FcZnCl (5) in the presence of catalytic amounts of [Pd(CH2C(CH3)(2)P((C4H9)-C-t)(2))(mu-Cl)(2) gave 1,3-Cl-2-5-Fc-2,4,6-(FcC C)(3)-C-6 (6a), 1-Cl-3,5-Fc(2)-2,4,6-(FcC C)(3)-C-6 (6b) and 1,3,5-Fc(3)-2,4,6-(FcC C)(3)-C-6 (6c) of which 6b is the main product. Column chromatography allowed the separation of these organometallic species. The structures of 4a,b and 6a in the solid state were determined by single crystal X-ray diffractometry showing a pi-pi interacting dimer (4b) and a complex pi-pi pattern for 6a. The electrochemical properties of 4a-c and 6a-c were studied by cyclic voltammetry (=CV) and square wave voltammetry (=SWV). it was found that the FcC C-substituted benzenes 4a-c show only one reversible redox event, indicating a simultaneous oxidation of all ferrocenyl units, whereby 4c is most difficult to oxidise (4a, E-1 degrees' = 190, Delta E-p = 71; 4b, E-1 degrees' = 195, Delta E-p = 59; 4c, E-1 degrees' = 390, Delta E-p = 59 mV). In case of 4c, the oxidation states 4c(n+) (n = 2, 3) are destabilised by the partial negative charge of the electronegative chlorine atoms, which compensates the repulsive electrostatic Fc(+)-Fc(+) interactions with attractive electrostatic Fc(+)-Cl delta- interactions. When ferrocenyl units are directly attached to the benzene C-6 core, organometallic 6a shows three, 6b five and 6c six separated reversible waves highlighting that the Fc units can separately be oxidised. UV-Vis/NIR spectroscopy allowed to determine IVCT absorptions (=Inter Valence Charge Transfer) for 6c(n+) (n = 1, 2) (n = 1: nu(max) = 7860 cm(-1), epsilon(max) = 405 L mol(-1) cm(-1), Delta nu(1/2) = 7070 cm(-1); n = 2: nu(max) = 9070 cm(-1), epsilon max = 620 L mol(-1) cm(-1), Delta nu(1/2) = 8010 cm(-1)) classifying these mixed-valent species as weakly coupled class II systems according to Robin and Day, while for 6a,b only LMCT transitions (=ligand to metal charge transfer) could be detected.
Original language | English |
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Pages (from-to) | 16310-16321 |
Number of pages | 12 |
Journal | Dalton Transactions |
Volume | 43 |
Issue number | 43 |
DOIs | |
Publication status | Published - 21 Nov 2014 |
Externally published | Yes |
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1,3,5-Triferrocenyl-2,4,6-tris(ethynylferrocenyl)benzene - a new member of the family of multiferrocenyl-functionalized cyclic systems. / Pfaff, Ulrike; Filipczyk, Grzegorz; Hildebrandt, Alexander; Korb, Marcus; Lang, Heinrich.
In: Dalton Transactions, Vol. 43, No. 43, 21.11.2014, p. 16310-16321.Research output: Contribution to journal › Article
TY - JOUR
T1 - 1,3,5-Triferrocenyl-2,4,6-tris(ethynylferrocenyl)benzene - a new member of the family of multiferrocenyl-functionalized cyclic systems
AU - Pfaff, Ulrike
AU - Filipczyk, Grzegorz
AU - Hildebrandt, Alexander
AU - Korb, Marcus
AU - Lang, Heinrich
PY - 2014/11/21
Y1 - 2014/11/21
N2 - The consecutive synthesis of 1,3,5-triferrocenyl-2,4,6-tris(ethynylferrocenyl)benzene (6c) is described using 1,3,5-Cl-3-2,4,6-I-3-C-6 (2) as starting compound. Subsequent Sonogashira C,C cross-coupling of 2 with FcC CH (3) in the molar ratio of 1:4 afforded solely 1,3,5-Cl-3-2,4,6-(FcC C)(3)-C-6 (4c) (Fc = Fe(eta(5)-C5H4)-(eta(5)-C5H5)). However, when 2 is reacted with 3 in a 1: 3 ratio a mixture of 1,3,5-Cl-3-2-(FcC C)-4,6-I-2-C-6 (4a) and 1,3,5-Cl-3-2,4-(FcC C)(2)-6-I-C-6 (4b) is obtained. Negishi C,C cross-coupling of 4c with FcZnCl (5) in the presence of catalytic amounts of [Pd(CH2C(CH3)(2)P((C4H9)-C-t)(2))(mu-Cl)(2) gave 1,3-Cl-2-5-Fc-2,4,6-(FcC C)(3)-C-6 (6a), 1-Cl-3,5-Fc(2)-2,4,6-(FcC C)(3)-C-6 (6b) and 1,3,5-Fc(3)-2,4,6-(FcC C)(3)-C-6 (6c) of which 6b is the main product. Column chromatography allowed the separation of these organometallic species. The structures of 4a,b and 6a in the solid state were determined by single crystal X-ray diffractometry showing a pi-pi interacting dimer (4b) and a complex pi-pi pattern for 6a. The electrochemical properties of 4a-c and 6a-c were studied by cyclic voltammetry (=CV) and square wave voltammetry (=SWV). it was found that the FcC C-substituted benzenes 4a-c show only one reversible redox event, indicating a simultaneous oxidation of all ferrocenyl units, whereby 4c is most difficult to oxidise (4a, E-1 degrees' = 190, Delta E-p = 71; 4b, E-1 degrees' = 195, Delta E-p = 59; 4c, E-1 degrees' = 390, Delta E-p = 59 mV). In case of 4c, the oxidation states 4c(n+) (n = 2, 3) are destabilised by the partial negative charge of the electronegative chlorine atoms, which compensates the repulsive electrostatic Fc(+)-Fc(+) interactions with attractive electrostatic Fc(+)-Cl delta- interactions. When ferrocenyl units are directly attached to the benzene C-6 core, organometallic 6a shows three, 6b five and 6c six separated reversible waves highlighting that the Fc units can separately be oxidised. UV-Vis/NIR spectroscopy allowed to determine IVCT absorptions (=Inter Valence Charge Transfer) for 6c(n+) (n = 1, 2) (n = 1: nu(max) = 7860 cm(-1), epsilon(max) = 405 L mol(-1) cm(-1), Delta nu(1/2) = 7070 cm(-1); n = 2: nu(max) = 9070 cm(-1), epsilon max = 620 L mol(-1) cm(-1), Delta nu(1/2) = 8010 cm(-1)) classifying these mixed-valent species as weakly coupled class II systems according to Robin and Day, while for 6a,b only LMCT transitions (=ligand to metal charge transfer) could be detected.
AB - The consecutive synthesis of 1,3,5-triferrocenyl-2,4,6-tris(ethynylferrocenyl)benzene (6c) is described using 1,3,5-Cl-3-2,4,6-I-3-C-6 (2) as starting compound. Subsequent Sonogashira C,C cross-coupling of 2 with FcC CH (3) in the molar ratio of 1:4 afforded solely 1,3,5-Cl-3-2,4,6-(FcC C)(3)-C-6 (4c) (Fc = Fe(eta(5)-C5H4)-(eta(5)-C5H5)). However, when 2 is reacted with 3 in a 1: 3 ratio a mixture of 1,3,5-Cl-3-2-(FcC C)-4,6-I-2-C-6 (4a) and 1,3,5-Cl-3-2,4-(FcC C)(2)-6-I-C-6 (4b) is obtained. Negishi C,C cross-coupling of 4c with FcZnCl (5) in the presence of catalytic amounts of [Pd(CH2C(CH3)(2)P((C4H9)-C-t)(2))(mu-Cl)(2) gave 1,3-Cl-2-5-Fc-2,4,6-(FcC C)(3)-C-6 (6a), 1-Cl-3,5-Fc(2)-2,4,6-(FcC C)(3)-C-6 (6b) and 1,3,5-Fc(3)-2,4,6-(FcC C)(3)-C-6 (6c) of which 6b is the main product. Column chromatography allowed the separation of these organometallic species. The structures of 4a,b and 6a in the solid state were determined by single crystal X-ray diffractometry showing a pi-pi interacting dimer (4b) and a complex pi-pi pattern for 6a. The electrochemical properties of 4a-c and 6a-c were studied by cyclic voltammetry (=CV) and square wave voltammetry (=SWV). it was found that the FcC C-substituted benzenes 4a-c show only one reversible redox event, indicating a simultaneous oxidation of all ferrocenyl units, whereby 4c is most difficult to oxidise (4a, E-1 degrees' = 190, Delta E-p = 71; 4b, E-1 degrees' = 195, Delta E-p = 59; 4c, E-1 degrees' = 390, Delta E-p = 59 mV). In case of 4c, the oxidation states 4c(n+) (n = 2, 3) are destabilised by the partial negative charge of the electronegative chlorine atoms, which compensates the repulsive electrostatic Fc(+)-Fc(+) interactions with attractive electrostatic Fc(+)-Cl delta- interactions. When ferrocenyl units are directly attached to the benzene C-6 core, organometallic 6a shows three, 6b five and 6c six separated reversible waves highlighting that the Fc units can separately be oxidised. UV-Vis/NIR spectroscopy allowed to determine IVCT absorptions (=Inter Valence Charge Transfer) for 6c(n+) (n = 1, 2) (n = 1: nu(max) = 7860 cm(-1), epsilon(max) = 405 L mol(-1) cm(-1), Delta nu(1/2) = 7070 cm(-1); n = 2: nu(max) = 9070 cm(-1), epsilon max = 620 L mol(-1) cm(-1), Delta nu(1/2) = 8010 cm(-1)) classifying these mixed-valent species as weakly coupled class II systems according to Robin and Day, while for 6a,b only LMCT transitions (=ligand to metal charge transfer) could be detected.
KW - INTRAMOLECULAR ELECTRONIC COMMUNICATION
KW - SOLID-STATE STRUCTURE
KW - MOLECULAR ELECTRONICS
KW - TERMINAL ACETYLENES
KW - NONAQUEOUS SOLVENTS
KW - COMPLEXES
KW - ELECTROCHEMISTRY
KW - CHEMISTRY
KW - OXIDATION
KW - FERROCENE
U2 - 10.1039/c4dt02307b
DO - 10.1039/c4dt02307b
M3 - Article
VL - 43
SP - 16310
EP - 16321
JO - Dalton Transactions: the international journal for inorganic, organometallic and bioinorganic chemistry
JF - Dalton Transactions: the international journal for inorganic, organometallic and bioinorganic chemistry
SN - 1477-9226
IS - 43
ER -