Fe(η5-C5H5)+ initiated construction of hexaruthenium-polypyridine complexes

Article abstract of DOI:10.1039/a700386b

Aromatic stars containing hexa-pyridine, -bipyridine and -terpyridine branches are synthesised with or without the central Fe(η⁵-C₅H₅)⁺ group and coordinated to ruthenium(II) polypyridine moities to construct he

Full text of DOI:10.1039/a700386b

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Fe(h5-C5H5)+ initiated construction of hexaruthenium–polypyridine complexes
Vale´rie Marvaud and Didier Astruc
Laboratoire de Chimie Organique et Organome´tallique, URA CNRS No 35, Universite´ Bordeaux I, 33405 Talence Ce´dex, France
Aromatic stars containing hexa-pyridine, -bipyridine and
-terpyridine branches are synthesised with or without the
central Fe(h5-C5H5)+ group and coordinated to ru-
thenium(II) polypyridine moities to construct hexa- and
hepta-nuclear hexa-bipyiridine and -terpyridine com-
plexes.
and metallo-dendrimers6 containing photoactive redox sites.1,4,7
In this context, and given our interest in redox-active metal-
lodendrimers for molecular recognition and electronics and
polyelectronic redox catalysis,8 we have synthesized
‘inorganometallic’ hexaruthenium(ii) bipyridine and terpyr-
idine complexes which we are now reporting for the first
time.
Oligopyridines have recently fascinated the supramolecular
chemistry community1 as powerful building blocks for the
construction of inorganic helicates,2,3 antennas,4 metallo-stars5
Our standard route which involves the hexa-alkylation of
5
6
[FeII(h -C5H5)(h -C6Me6)]PF6 using iodoalkyl derivatives
under basic conditions is very successful, for instance to
OH
HO
OH
i, ii, iii
a
b
= nothing
= Fe(η5-C5H5)+
HO
OH
HO
1
iv
vi
v
N
N
N
N
N
N
N
N
N
N
N
N
N
N
O
O
N
O
N
N
O
O
N
N
O
O
O
O
O
O
O
N
O
O
O
N
N
N
N
N
N
N
N
O
N
O
O
N
N
N
N
N
N
N
2
3
4
vii
viii
n +
n +
N
N
N
N
N
N
Ru
Ru
N
N
N
N
N
N
N
N
N
N
N
N
N
N
Ru
Ru
N
N
N
N
N
N
N
N
N
N
Ru
N
Ru
N
O
N
O
N
N
N
O
O
O
O
O
O
N
N
O
O
N
N
N
N
N
N
N
N
Ru
N
Ru
N
N
N
Ru
N
N
Ru
N
N
N
O
N
O
N
N
N
N
N
N
N
N
N
N
N
N
Ru
N
Ru
N
N
N
5a n = 12
b n = 13
6a n = 12
b n = 13
Scheme 1 Synthesis of the hexaruthenium and heptametallic complexes; Reagents and conditions: i, ButOK, allylbromide, thf; ii, if decomplexation is
required: hnvis, PPh3, MeCN; iii, BH3·thf, methylbut-2-ene, thf; then H2O2, OH2; iv, KOH, Me2SO, 4-bromopyridine, 30 °C; v, KOH, Me2SO, 4-chloro-
2,2A-bipyridine, 30 °C; vi, KOH, Me2SO, 4A-chloro-2,2A:6A2B-terpyridine, 30 °C; vii, [Ru(bipy)2Cl2], ethanol, 80 °C, NH4PF6; viii, [Ru(terpy)Cl3],
N-ethylmorpholine, methanol, 80 °C, NH4PF6
Chem. Commun., 1997
773

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(t, 1 H, CHterpyext 4A), 7.86 (m, 4 H, CHterpy 4), 7.73 and 7.60 (d, 4 H,
CHterpy 6), 7.18 (br. s, 4 H, CHterpy 5), 4.85 (br. t, 2 H, CH2O), 3.18 (br.
s, 2 H, CH2Ar), 2.44 (br. s, 2 H, CH2CH2O), 2.16 (br s, 2 H, CHCH2Ar); 13
synthesize hexaferrocene stars.9 However, all attempts to obtain
5
the hexapyridine compound by direct alkylation of [FeII(h -
C
6
C5H5)2(h -C6Me6)]PF6 with 4-iodoalkyl-4A-methyl-2,2A-bipyr-
NMR [250 MHz, (CD3)2CO], d 167.00 (CqterpyO), 159.34 and 156.84 (Cq
terpy 2 and 2A), 153.57 and 153.26 (CHterpy 6), 138.77 and 137.71
(CHterpy 4 and 4A), 137.71 (Cq Ar), 128.55 (CHterpy 5), 125.5 and 125.24
(CHterpy 3), 124.72 (CHterpyext 3A), 112.18 (CHterpyint 3A), 71.36 (CH2O),
30.68, 30.25, 29.01 (CH2); MS (MALDI-TOF): m/z 5499.1 (M 2 PF6),
C210H174F72N36O6P12Ru6 requires m/z 5643.92, (2PF6) m/z 5498.9.
6b: 1H NMR [250 MHz, (CD3)2CO], d 8.95 (br. d, 12 H, CHterpyext 3A),
8.68 (br m, 24 H, CHterpy 3), 8.61 (br s, 12 H, CHterpyint 3A), 8.47 (br t, 6
H, CHterpyext 4A), 7.88 (br m, 24 H, CHterpy 4), 7.72 and 7.58 (d, 24 H,
CHterpy 6) 7.17 (br s, 24 H, CHterpy 5), 4.93 (br s, 5 H, C5H5), 4.82 (br. t,
12 H, CH2O), 3.43 (br s, 12 H, CH2Ar), 2.37 (br s, 12 H, CH2CH2O), 2.07
(br s, 12 H, CH2CH2Ar); 13C NMR [250 MHz, (CD3)2CO], d 166.98
(CqterpyO), 158.32 and 155.63 (Cqterpy 2 and 2A), 152.56 and 152.07
(CHterpy 6), 138.68 and 137.75 (CHterpyext 4 and 4A), 127.56 (CHterpy 5),
124.48 and 124.18 (CHterpy 3), 123.71 (CHterpyext 3A), 111.21 (CHterpyint
3A), 102.55 (Cq Ar), 78.32 (C5H5), 69.38 (CH2O), 29.57, 28.86, 26.48
(CH2). MS (ES): m/z 1333.8 (M4+), 1037.6 (M5+), 840.2 (M6+), correspond-
ing to a measured mass of 5911.92 (M+), C215H179FeF78N36O6P13Ru6
requires m/z 5912.37.
idine in the presence of KOH and dimethoxyethane (dme)
failed, apparently due to dehydrohalogenation or/and partial
5
6
decomplexation of the [Fe(h -C5H5)(h -C6Me6)]+ complex in
the presence of 2,2A-bipyridine. A new synthetic strategy was
therefore required, the principle of which consisted of synthe-
sizing the hexol before coupling the 4-chloro-2,2A-bipyridine
derivative by alkoxy dehalogenation.10 Using this approach, we
also synthesized the hexapyridine and hexaterpyridine com-
pounds which were successfully hexaruthenated.
Perallylation of [FeII(h -C5H5)(h -C6Me6)]PF6 eventually
followed by visible photolysis, regiospecific hydroboration and
oxidation using H2O2 under basic conditions yields the hexol 1a
and the corresponding iron complex 1b, as already known,9b
Scheme 1. The reaction of these two products, 1a and 1b, with
bromo- or chloro-pyridyl compounds (4-bromopyridine,
4-chloro-2,2A-bipyridine and 4A-chloro-2,2A:6A,2B-terpyridine)
in Me2SO in the presence of KOH gave the associated
hexasubstituted products, soluble in organic solvents and fully
characterised by NMR (1H, 13C, COSY spectroscopy) and mass
spectra (FAB+). The analytical and spectroscopic data for
hexapyridine 2a, hexabipyridine 3a, hexaterpyridine 5a,
5
6
References
1 J.-M. Lehn, Supramolecular Chemistry, VCH, Weinheim, 1995;
V. Balzani and F. Scandola, Supramolecular Photochemistry, Ellis
Horwood, New York, 1991. V. Balzani, Supramolecular Photo-
chemistry, Reidel, Dordrecht, 1987, p. 35; F. Vo¨gtle, Supramolecular
Chemistry, 2nd edn., Wiley, Chichester.
2 K. Wa¨rnmark, O. Heyke, J. A. Thomas and J.-M. Lehn, Chem.
Commun., 1996, 2603; C. Fouquey, J.-M. Lehn and A.-M. Levelut, Adv.
Mater., 1990, 2, 254; T. Gulik-Krzywicki, C. Fouquey and J.-M. Lehn,
Proc. Natl. Acad. Sci. USA, 1993, 90, 163; R. Kra¨mer, J.-M. Lehn and
A. Marquis-Rigault, Proc. Natl. Acad. Sci. USA, 1993, 90, 53934.
3 E. C. Constable, in Comprehensive Supramolecular Chemistry, ed. J.-P.
Sauvage and M.-W. Hosseini, Pergamon, Oxford, 1996, vol. 9, ch. 6,
pp. 213–252; C. Piguet, G. Hopfgartner, B. Bocquet, O. Schaad and
A. F. Williams, J. Am. Chem. Soc., 1994, 116, 9092; C. Piguet,
J. C. G. Bunzli, G. Bernardinelli, G. Hopfgartner and A. F. Williams,
J. Chem. Soc., Chem. Commun., 1995, 491; U. Velten and M. Rehahn,
Chem. Commun., 1996, 2639.
5
5
[Fe(h -C5H5)(hexapyridine)]PF6 2b and [Fe(h -C5H5)(hex-
aterpyridine)]PF6 5b† show the expected structures. The
reaction of 1b with 4-chloro-2,2A-bipyridine was disappointing,
5
the expected Fe(h -C5H5) complex of the hexabipyridine 3b
was never cleanly obtained. This is probably due to a partial
decomplexation of the [Fe(h -C5H5)(h -C6Me6)]+ complex, as
mentioned above. Interestingly, this decomplexation is limited
with the terpyridine derivatives, the difference with the
bipyridine case being explained by steric effects. The ruthen-
ation of 3a, 4a and 4b was carried out using standard procedures
with [Ru(bipy)2Cl2] and [Ru(terpy)Cl3] as starting materials.
The products 5a and 6a were then obtained and fully
characterized by NMR (1H, 13C, COSY spectroscopy) and mass
spectra (MALDI-TOF and electrospray, ES).
5
6
4 S. Serroni, G. Denti, S. Campagna, A. Juris, M. Ciano and V. Balzani,
Angew. Chem., 1992, 104, 1540; Angew. Chem., Int. Ed. Engl., 1992,
31, 1493; S. Denti, S. Campagna, S. Serroni, M. Ciano and V. Balzani,
J. Am. Chem. Soc., 1992, 114, 2944; S. Campagna, G. Denti, S. Serroni,
M. Ciano, A. Juris and V. Balzani, Inorg. Chem., 1992, 31, 2982;
V. Balzani, A. Credi and F. Scandola, in Transition Metals in
Supramolecular Chemistry, ed. L. Fabbrizzi and A. Poggi, Kluwer,
Dordrecht, 1994, p. 1.
5 G. R. Newkome, F. Cardullo, E. C. Constable, C. N. Moorefield and
A. M. W. Cargill Thomson, J. Chem. Soc., Chem. Commun., 1993, 925;
E. C. Constable and P. Harverson, Chem. Commun., 1996, 33;
E. C. Constable, P. Harverson and M. Oberholzer, Chem. Commun.,
1996, 1821.
6 C. Moucheron, A. Kirsch-De Mesmaeker, A. Dupont-Gervais, E. Leize
and A. Van Dorsselaer, J. Am. Chem. Soc., 1996, 118, 12834.
7 V. Balzani, A. Juris, M. Venturi, S. Campagna and S. Serroni, Chem.
Rev., 1996, 96, 759; J.-P. Sauvage, S. Guillerez, C. Coudret, V. Balzani,
F. Barigeletti, L. De Cola and L. Flamigni, Chem. Rev., 1994, 94, 993;
A. Juris, V. Balzani, F. Barigeletti, S. Campagna, P. Belser and A. Von
Zelewski, Coord. Chem. Rev., 1988, 84, 85; P. J. Steel, Coord. Chem.
Rev., 1990, 106, 227.
The MALDI-TOF spectra show peaks at m/z 5510.7 and
5499.1 which are assigned to (5a 2 PF6) and (6a 2 PF6); these
results were confirmed by the ES spectra. Further evidence for
the presence of the terminal [Ru(bipy)3]2+ moieties is given by
electrochemical measurements where the set of RuII–RuIII
redox systems gives a single and reversible anodic wave at
+0.82 and +0.79 V (vs. Fc–Fc+) respectively. For compound 6b,
partial decomplexation of the iron core is indicated by the ES
data.
We have shown that a new synthetic route for metallo-stars is
open via a combination of organometallic, organic and
inorganic chemistry. We are currently carrying out further
studies on the construction of higher generations of function-
alised dendrimers containing ruthenium polypyridine com-
plexes at the periphery.
We thank J. Guittard, J.-C. Blais, E. Leize and A. Van
Dorsselaer for the mass spectroscopic studies.
Footnotes
8 D. Astruc, Electron Transfer and Radical Processes in Transition-Metal
Chemistry, VCH, New York, 1995, ch. 2; D. Astruc, in Mechanisms and
Processes in Molecular Chemistry, ed. D. Astruc, Gauthier-Villard,
Paris; New J. Chem., 1992, 16, 305.
9 (a) J.-L. Fillaut, J. Linares and D. Astruc, Angew. Chem., 1994, 106,
2540; Angew. Chem., Int. Ed. Engl., 1994, 33, 2460; (b) F. Moulines and
D. Astruc, Angew. Chem., 1988, 100, 1394; Angew. Chem., Int. Ed.
Engl., 1988, 27, 1347.
10 C. A. Fyfe, in The Chemistry of the Hydroxyl group, Part 1, ed. S. Patai,
Wiley, New York, 1971, pp. 83–124.
11 (a) R. A. Jones, B. d. Roney, W. H. F. Sasse and K. O. Wade, J. Chem.
Soc. B, 1967, 106; (b) B. P. Sullivan, J. M. Calvert and T. Meter, Inorg.
Chem., 1980, 19, 1404.
† Preparations of 4-chloro-2,2A-bipyridine11a and [Ru(terpy)Cl3]11b were
performed by the literature method.
5a (89% yield): 1H NMR [250 MHz, (CD3)2CO], d 8.73 (d, 5 H, CHbipy
3A), 8.20 (s 1 H, CHbipyint 3), 8.13 (d, 5 H, CHbipy 4A), 7.99 (d, 5 H, CHbipy
6A), 7.66 (d, 1 H, CHbipyint 6), 7.52 (m, 5 H, CHbipy 5A), 7.03 (m, 1 H,
CHbipyint 5), 4.28 (br. s, 2 H, CH2O), 2.67 (br. s, 2 H, CH2Ar), 1.89 (br. s,
2 H, CH2CH2O), 1.65 (br. s, 2 H, CH2CH2Ar); 13C NMR [250 MHz,
(CD3)2CO], d 167.64 (CqO), 158.92 and 158.08 (Cq bipy), 152.96 and
152.56 (CHbipy 6 and 6A), 138.72 (CHbipy 4A), 137.40 (Cq Ar), 128.72
(CHbipy 5A), 125.22 (CHbipy 3A), 115.57 (CHbipy 5), 111.71 (CHbipy 3),
66.14 (CH2O), 29.35, 29.05 and 25.82 (CH2); MS (MALDI-TOF): m/z
5510.7 (M 2 PF6), C210H186F72N36O6P12Ru6 requires m/z 5655.97, 2PF6
m/z 25510.9.
6a (88% yield): 1H NMR [250 MHz, (CD3)2CO], d 8.97 (d, 2 H,
CHterpyext 3A), 8.71 (m, 4 H, CHterpy 3), 8.61 (s, 2 H CHterpyint 3A), 8.47
Received, 16th January 1997; Com. 7/00386B
774
Chem. Commun., 1997