investigating the mechanism of hydrolysis and the nature of the
intermediate complexes.
G. S. H. thanks the NSERC of Canada and l’Universite´ de
Montre´al for financial support. E. A. M. thanks the
Commonwealth Foundation for graduate support.
Notes and references
{ Crystal data for [CuL1]2(PF6)2, C58H36Br2Cu2F12N14P2: data were
collected on a Bruker APEX at 220(2) K using Cu-Ka radiation (l =
2
1.54178 A). Full-matrix, least squares refinements on F using all 77402
˚
data; M = 1505.85, monoclinic, space group P21/c, a = 17.2216(15), b =
˚
3
˚
27.920(2), c = 13.7457(12) A, b = 98.733(4)u, U = 6532.7(10) A , Z = 4, R1
[I . 2s(I)] = 0.1034, wR2 (all data) = 0.3117.
Crystal data for [CuL2]2(PF6)2?EtOH?MeCN, C50H40Cu2F12N12O5P2:
data were collected on a Bruker APEX at 100(2) K using Cu-Ka radiation
˚
(l = 1.54178 A). Full-matrix, least squares refinements on F2 using all
¯
35310 data; M =1305.96, triclinic, space group P1, a = 11.4580(12), b =
Fig. 5 Solid-state structure of [CuL2]22+ with ligands differentiated (left,
black and gray) and the hydrolyzed ligand L2 coordinated to the Cu(II)
centres (right).
˚
11.8380(12), c = 21.346(2) A, a = 96.286(4), b = 103.165(4), c = 110.023(4)u,
3
U = 2592.6(4) A , Z = 2, R1 [I . 2s(I)] = 0.0543, wR2 (all data) = 0.1458.
˚
CCDC 642096 and 642097. For crystallographic data in CIF or other
electronic format see DOI: 10.1039/b711765e
reversible behaviour of [CuL1]22+ at 25 mV s21 is supported by the
solid-state structure in that minimal structural rearrangement is
required to satisfy Cu(II) ion in a pseudo square-pyramidal
geometry. However, at 5 V s21 the second Cu(I) oxidation is
irreversible, indicating that a greater structural rearrangement is
required for a reversible process to occur.
1 (a) J.-P. Collin, V. Heitz and J.-P. Sauvage, Top. Curr. Chem., 2005, 262,
29; (b) J.-P. Sauvage, Acc. Chem. Res., 1998, 31, 611; (c) S. Bonnet,
J.-P. Collin, M. Koizumi, P. Mobian and J.-P. Sauvage, Adv. Mater.,
2006, 18, 1239–1250.
2 (a) S. J. Loeb, Chem. Soc. Rev., 2007, 36, 226–235; (b) S. J. Loeb, Chem.
Commun., 2005, 1511; (c) L. Fabbrizzi, M. Licchelli and P. Pallavicini,
Acc. Chem. Res., 1999, 32, 846.
2+
Efforts to chemically oxidise [CuL1]2 to a single new species
3 M. D. Ward, Chem. Soc. Rev., 1995, 24, 121.
were unsuccessful employing NOBF4 as an oxidising agent. The
oxidation process was followed by electronic absorption spectro-
scopy, which indicated that several species were produced by
chemical oxidation. Crystallisation of an acetonitrile–ethanol
4 A. M. Brouwer, C. Frochot, F. G. Gatti, D. A. Leigh, L. Mottier,
F. Paolucci, S. Roffia and G. W. H. Wurpel, Science, 2001, 291, 2124.
5 J. P. Collin, C. Dietrich-Buchecker, P. Gavina, M. C. Jimenez-Molero
and J.-P. Sauvage, Acc. Chem. Res., 2001, 34, 477.
6 V. Amendola, L. Fabbrizzi and P. Pallavicini, Coord. Chem. Rev., 2001,
216–217, 435.
2+
solution of [CuL1]2 left open to air resulted in the isolation of
green crystals suitable for analysis by X-ray diffraction (Fig. 5).{
The Cu(I) slowly oxidised to Cu(II) to form a dinuclear, dihelical
structure in which both ligands were hydrolysed to the
bis(2,29-dipyridyl-6-carbonyl)imidate ligand L2. The hydrolysis of
7 M. Barley, E. C. Constable, S. A. Corr, R. C. S. McQueen, J. C. Nutkins,
M. D. Ward and M. G. B. Drew, J. Chem. Soc., Dalton Trans., 1988,
2655.
8 K. T. Potts, M. Keshavarz-K, F. S. Tham, H. D. Abruna and
C. R. Arana, Inorg. Chem., 1993, 32, 4422.
a
related tridentate ligand, 2,4,6-tris(29-pyridyl)-1,3,5-triazine
9 E. A. Medlycott, I. Theobald and G. S. Hanan, Eur. J. Inorg. Chem.,
2005, 1223.
10 C. Dietrich-Buchecker, G. Rapenne, J.-P. Sauvage, A. De Cian and
J. Fischer, Chem.–Eur. J., 1999, 5, 1432.
11 E. C. Constable, M. J. Hannon and D. A. Tocher, J. Chem. Soc., Dalton
Trans., 1993, 1883.
12 PM3 energy minimized structure, Chem 3D.
13 K. T. Potts, M. Keshavarz-K, F. S. Tham, H. D. Abruna and C. Arana,
Inorg. Chem., 1993, 32, 4450.
14 N. Armaroli, Chem. Soc. Rev., 2001, 30, 113.
(tptz), was previously observed in the synthesis of its Cu(II)
complexes15 and hydrolysis of tptz has since been observed with a
number of metal ions.16
The Cu(II) ion is in a pseudo-square-pyramidal geometry with
each Cu(II) coordinated to two bpy motifs from both ligands and
the N(imido) occupying the fifth coordination site (Fig. 5).
˚
Elongated Cu–N (imido) distances (2.698(4) and 2.7038(4) A)
15 E. I. Lerner and S. J. Lippard, J. Am. Chem. Soc., 1976, 98, 5397.
16 (a) X. Chen, F. J. Femia, J. W. Babich and J. A. Zubieta, Inorg. Chem.,
2001, 40, 2769; (b) T. Kajiwara, R. Sensui, T. Noguchi, A. Kamiyama
and T. Ito, Inorg. Chim. Acta, 2002, 337, 299; (c) J. M. Rowland,
M. M. Olmstead and P. K. Mascharak, Inorg. Chem., 2002, 41, 2754; (d)
P. Paul, B. Tyagi, A. K. Bilakhiya, M. M. Bhadbhade, E. Suresh and
G. Ramachandraiah, Inorg. Chem., 1998, 37, 5733; (e) P. Paul, B. Tyagi,
M. M. Bhadbhade and E. Suresh, J. Chem. Soc., Dalton Trans., 1997,
2273; (f) P. Paul, B. Tyagi, A. K. Bilakhiya, P. Dastidar and E. Suresh,
Inorg. Chem., 2000, 39, 14.
are observed to the imido group on the second ligand. Short intra-
molecular, face-to-face, p-stacking interactions are observed
between the pyridyl rings adjacent to the imido group on each
˚
ligand (centroid–centroid distances of 3.37 and 3.62 A).
We expect that the hydrolysis of L1 to L2 occurs after the
2+
oxidation of Cu(I) in [CuL1]2 to Cu(II) and that several
intermediate complexes play a role as suggested by electronic
absorption spectroscopy of the oxidation process. We are currently
4886 | Chem. Commun., 2007, 4884–4886
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