An Organometallic Methodology Affording Dinuclear Copper(I) Complexes

Full text of DOI:10.1021/ic960072k

4526
Inorg. Chem. 1996, 35, 4526-4528
Scheme 1
An Organometallic Methodology Affording
Dinuclear Copper(I) Complexes
Euro Solari, Mario Latronico,† Philippe Blech, and
Carlo Floriani*
Institut de Chimie Mine´rale et Analytique, BCH, Universite´
de Lausanne, CH-1015 Lausanne, Switzerland
Angiola Chiesi-Villa and Corrado Rizzoli
Dipartimento di Chimica, Universita` di Parma,
I-43100 Parma, Italy
ReceiVed January 24, 1996
Introduction
cylaldimine)], and o-phthalic acid, leading to a variety of
dinuclear copper(I) complexes.
Synthetic access to the very important class of copper(I)
coordination compounds is based on the metathesis reaction
between copper halides and the salt of the corresponding
ligand.1-3 Such reactions must be carried out in coordinating
polar solvents, which is usually why copper(I) disproportionates
to copper(II) and copper metal. An additional problem, mainly
when we are dealing with a polynucleating polyprotic ligand,
can be the difficulty in obtaining the ligand as the alkali metal
salt and in managing the nuclearity of the resulting compound.
Thus we felt the necessity for a different metalating methodology
in the case of copper(I) complexes, which should avoid the use
of any salt and halide derivative, that is, the direct reaction of
a copper(I) source with the protic form of the ligand in an
innocent solvent. This method employing [Cu5Mes5]4 [Mes )
2,4,6-Me3C6H2] as starting material has been efficiently used
in organometallic chemistry by van Koten and co-workers.5 We
wish to illustrate the effectiveness of such a method in the
synthesis of dinuclear copper(I) complexes,6,7 which are par-
ticularly attractive, and, among others, in the field of dioxygen
activation.6,7 In order to emphasize the relevance of this
synthetic approach, we used molecules which are usually
mononucleating ligands but are potential binucleating ligands,
such as the tetradentate Schiff bases, which can force two
copper(I) ions into an interesting close geometrical proximity.
These ligands, used under conventional conditions, induce the
disproportionation of copper(I).2 We report here the reaction
of the homoleptic copper(I)-aryl [Cu5Mes5] compound, which
is available on a large scale,4 with acacenH2 [N,N′-ethylenebis-
(acetylacetone imine)], salophenH2 [N,N′-o-phenylenebis(sali-
Results and Discussion
The metalation of tetradentate Schiff bases, such as acacenH2
[N,N′-ethylenebis(acetylacetone imine)] and salophenH2 [N,N′-
o-phenylenebis(salicylaldimine)], in their protic forms was
carried out by mixing either toluene or THF solutions of [Cu5-
Mes5], 1 (Mes ) 2,4,6-Me3C6H2), and the ligand in the presence
of a copper(I)-stabilizing agent such as CO, PPh3, RNC.2 The
metalation of acacenH2 and salophenH2 is reported in Scheme
1.
The trans arrangement of the halves of such ligands, which
normally act as tetradentate binders for a single metal ion, is
based on the X-ray-determined solid state structure of 4. We
should comment, however, that we are referring to the solid
state, while in solution the cis arrangement may also be possible
and the two metal centers may be accessible in the appropriate
disposition for dinuclear reactivity. In the case of complex 2,
the reaction was also carried out in a carbon monoxide
atmosphere. Although CO loss from the solid is facile, it rebinds
under such conditions. The CO stretching vibration for 2 is
very high (2071 cm-1),8 in agreement with the electrophilic
nature of the d10 metal which is unable to π-back-donate.
Compound 3 shows the same spectroscopic characteristics as
2, with a very high stretching vibration of the CtNR group at
2166 cm-1, though in the latter case there is no reversibile
binding of ButNC, as in the case of carbon monoxide.8 On the
(7) Wei, N.; Lee, D. H.; Murthy, N. N.; Tyeklar, Z.; Karlin, K. D.; Kaderli,
S.; Jung, B.; Zuberbuehler, A. D. Inorg. Chem. 1994, 33, 4625. Karlin,
K. D.; Nasir, M. S.; Cohen, B. I.; Cruse, R. W.; Kaderli, S.;
Zuberbuehler, A. D. J. Am. Chem. Soc. 1994, 116, 1324. Wei, N.;
Murthy, N. N.; Tyeklar, Z.; Karlin, K. D. Inorg. Chem. 1994, 33,
1177. Sanyal, I.; Karlin, K. D.; Strange, R. W.; Blackburn, N. J. J.
Am. Chem. Soc. 1993, 115, 11259. Karlin, K. D.; Tyeklar, Z.; Farooq,
A.; Haka, M. S.; Ghosh, P.; Cruse, R. W.; Gultneh, Y.; Hayes, J. C.;
Toscano, P. J.; Zubieta, J. Inorg. Chem. 1992, 31, 1436. Sanyal, I.;
Mahroof-Tahir, M.; Nasir, M. S.; Ghosh, P.; Cohen, B. I.; Gultneh,
Y.; Cruse, R. W.; Farooq, A.; Karlin, K. D.; Liu, S.; Zubieta, J. Inorg.
Chem. 1992, 31, 4322. Mahroof, T. M.; Karlin, K. D. J. Am. Chem.
Soc. 1992, 114, 7599. Paul, P. P.; Tyeklar, Z.; Jacobson, R. R.; Karlin,
K. D. J. Am. Chem. Soc. 1991, 113, 5322. Sanyal, I.; Strange, R. W.;
Blackburn, N. J.; Karlin, K. D. J. Am. Chem. Soc. 1991, 113, 4692.
Tyeklar, Z.; Paul, P. P.; Jacobson, R. R.; Farooq, A.; Karlin, K. D.;
Zubieta, J. J. Am. Chem. Soc. 1989, 111, 388. Karlin, K. D.; Haka,
M. S.; Cruse, R. W.; Meyer, G. J.; Farooq, A.; Gultneh, Y.; Hayes, J.
C.; Zubieta, J. J. Am. Chem. Soc. 1988, 110, 1196. Karlin, K. D.;
Cruse, R. W.; Gultneh, Y.; Farooq, A.; Hayes, J. C.; Zubieta, J. J.
Am. Chem. Soc. 1987, 109, 2668.
† Present address: D.I.F.A., Universita` della Basilicata, I-85100 Potenza,
Italy.
(1) (a) Copper Coordination Chemistry: Biochemistry and Inorganic
PerspectiVes; Karlin, K. D., Zubieta, J., Eds.; Adenine: Guilderland,
NY, 1983. (b) Biological and Inorganic Copper Chemistry; Karlin,
K. D., Zubieta, J., Eds.; Adenine: Guilderland, NY, 1986.
(2) Hataway, B. In ComprehensiVe Coordination Chemistry; Wilkinson,
G., Gillard, R. D., McCleverty, J. A., Eds.; Pergamon: Oxford, U.K.,
1987; Vol. 5, p 533.
(3) Jardine, F. H. AdV. Inorg. Chem. Radiochem. 1975, 17, 115.
(4) Meyer, E. M.; Gambarotta, S.; Floriani, C.; Chiesi-Villa, A.; Guastini,
C. Organometallics 1989, 8, 1067.
(5) (a) Aalten, H. L.; van Koten, G.; Goubitz, K.; Stam, C. H. J. Chem.
Soc., Chem. Commun. 1985, 1252-1253. (b) Aalten, H. L.; van Koten,
G.; Riethorst, E.; Stam, C. H. Inorg. Chem. 1989, 28, 4140-4146.
(c) Aalten, H. L.; van Koten, G.; Goubitz, K.; Stam, C. H. Organo-
metallics 1989, 8, 2293-2299. (d) van Koten, G.; Stuart, L. J.;
Jastrzebski, J. T. B. H. In ComprehensiVe Organometallic Chemistry
II; Abel, E. W., Stone, F. G., Wilkinson, G., Eds.; Pergamon: Oxford,
U.K., 1995; Vol. 3, Chapter 2.
(6) Kitajima, K.; Moro-oka, Y. Chem. ReV. 1994, 94, 737 and references
(8) Pasquali, M.; Floriani, C. Copper(I)-Carbon Monoxide Chemistry:
Recent Advances and Perspectives. In Ref 1a, pp 311-330.
therein.
S0020-1669(96)00072-9 CCC: $12.00 © 1996 American Chemical Society

Notes
Inorganic Chemistry, Vol. 35, No. 15, 1996 4527
Figure 1. SCHAKAL drawing of complex 4. Prime indicates a
transformation of 1 - x, -y, -z.
Figure 2. SCHAKAL drawing of complex 8.
Scheme 2
Table 1. Selected Bond Distances (Å) and Angles (deg) for
Complex 4
Cu-P1
Cu-P2
Cu-O1
Cu-N1
O1-C2
N1-C4
2.258(1)
2.277(1)
2.038(4)
2.019(4)
1.275(6)
1.301(6)
N1-C6
C1-C2
C2-C3
C3-C4
C4-C5
C6-C6′
1.467(7)
1.517(8)
1.368(8)
1.422(8)
1.510(9)
1.518(8)
O1-Cu-N1
P2-Cu-N1
P2-Cu-O1
P1-Cu-N1
P1-Cu-O1
94.2(2)
108.1(1)
101.3(1)
119.8(1)
103.1(1)
P1-Cu-P2
Cu-O1-C2
Cu-N1-C6
Cu-N1-C4
123.5(1)
122.0(4)
117.2(3)
123.2(4)
other hand, the kinetic lability of CO makes 2 particularly
appropriate for reactivity studies. In case of PPh3, we have an
overstabilization of copper(I), achieving tetracoordination in both
4 and 5. The major difference between the two stays in the
approximately juxtaposition of the two copper(I) centers in the
possible cisoid arrangement. The centrosymmetric structure of
complex 4 is shown in Figure 1, and a selection of bond
distances and angles is given in Table 1. The structural
parameters are in the usual range for both the coordination
sphere1 and the ligand acacen,9 are quite close to what we found
in dinuclear copper(I)-CO and copper(I)-CNR complexes
containing the N,N′-ethylenebis(benzaldimine) ligand,10 and are
not affected by the trans arrangement of the halves of the ligand.
The reactions in Scheme 1 should lead to the disproportion-
ation of copper(I). This is not observed for two reasons: the
nature of the solvent (i.e. toluene) and the auxiliary ligands (i.e.
CO, PPh3, and ButNC).1 Such ligands function to stabilize
copper(I) and greatly enhance the solubility of the resulting
complexes. Even in the absence of such ligands, in non-
strongly-coordinating solvents we obtained dinuclear copper(I)
complexes which, however, disproportionate in protic solvents,
such as methanol. An unprotected copper(I) dinuclear complex
has been isolated and used in further synthesis (see Scheme 2).
The copper carboxylate 6 made by this method is stable even
in the absence of a stabilizing agent, which can be added in a
subsequent step.11 This methodology has been previously
successfully applied to the synthesis of monocarboxylato copper-
(I) derivatives by van Koten.5 The polymeric form 6, which is
quite insoluble, dissolves in the presence of auxiliary ligands;
thus 6 can be a source of an appropriate dinuclear skeleton.
Copper(I) becomes three-coordinate in 7 and tetracoordinate in
8, as in Scheme 1. We should mention that carboxylate ligands
are among the most interesting starting materials in copper(I)
chemistry and oligomeric stable forms derived from monocar-
boxylic acids are well-known.5,11 The proposed dinuclear
skeleton shown for 6-8 is based on the X-ray analysis of 8,
shown in Figure 2. In complex 8, the bidentate bonding mode
of the carbocylato anions is nonsymmetric with significant
differences between Cu1-O1 (oxy) and Cu1-O2 and between
Cu2-O3 and Cu2-O4 (see Table 2). There is an additional
difference in the Cu-O environment between Cu1 and Cu2.
All these parameters are in agreement with those found in a
series of copper(I) carboxylato derivatives.5,11 The Cu1‚‚‚Cu2
distance [6.241(2) Å] may be appropriate for the interaction of
the dinuclear unit with a single substrate.
Experimental Section
All operations were carried out under an atmosphere of purified
nitrogen. All solvents were purified by standard methods and freshly
distilled prior to use. The NMR spectra were recorded on a 200-AC
instrument.
Preparation of 2. Solid 1 (1.28 g, 7.03 mmol) was added to a THF
(100 mL) solution of acacenH2 (0.79 g, 3.52 mmol) cooled to -20 °C.
(11) (a) Pasquali, M.; Leoni, P.; Floriani, C.; Gaetani-Manfredotti, A. Inorg.
Chem. 1982, 21, 4324. (b) Toth, A.; Floriani, C.; Chiesi-Villa, A.;
Guastini, C. Inorg. Chem. 1987, 26, 236. (c) Lockhart, T. P.; Haito,
D. A. Polyhedron 1985, 4, 1745. (d) Lijima, K.; Itoh, T.; Shibata, S.
J. Chem. Soc., Dalton Trans. 1985, 2555. (e) Rodesiler, P. F.; Amma,
E. L. J. Chem. Soc., Chem. Commun. 1974, 599. (f) Mounts, R. D.;
Ogura, T.; Fernando, Q. Inorg. Chem. 1974, 13, 802. (g) Drew, M.
G. B.; Edwards, D. A.; Richards, R. J. Chem. Soc., Dalton Trans.
1977, 299. (h) Drew, M. G. B.; Edwards, D. A.; Richards, R. J. Chem.
Soc., Chem. Commun. 1973, 124. (i) Edwards, D. A.; Richards, R. J.
Chem. Soc., Dalton Trans. 1973, 2463.
(9) Mazzanti, M.; Rosset, J.-M.; Floriani, C.; Chiesi-Villa, A.; Guastini,
C. J. Chem. Soc., Dalton Trans. 1989, 953. Corazza, F.; Solari, E.;
Floriani, C.; Chiesi-Villa, A.; Guastini, C. J. Chem. Soc., Dalton Trans.
1990, 1335. Solari, E.; Corazza, F.; Floriani, C.; Chiesi-Villa, A.;
Guastini, C. J. Chem. Soc., Dalton Trans. 1990, 1345. Rosset, J.-M.;
Floriani, C.; Mazzanti, M.; Chiesi-Villa, A.; Guastini, C. Inorg. Chem.
1990, 29, 3991. Gallo, E.; Solari, E.; Floriani, C.; Chiesi-Villa, A.;
Rizzoli, C. Organometallics 1995, 14, 2156.
(10) Toth, A.; Pasquali, M.; Floriani, C.; Gaetani-Manfredotti, A.; Chiesi-
Villa, A.; Guastini, C. Inorg. Chem. 1985, 24, 648.

4528 Inorganic Chemistry, Vol. 35, No. 15, 1996
Notes
Table 2. Selected Bond Distances (Å) and Angles (deg) for
Complex 8
Table 3. Experimental Data for the X-ray Diffraction Studies of
Complexes 4 and 8a
Cu1-P1
Cu1-P2
Cu1-O1
Cu1-O2
O1-C7
O2-C7
C1-C7
2.236(4)
2.248(4)
2.268(9)
2.140(9)
1.258(18)
1.246(17)
1.504(16)
Cu2-P3
Cu2-P4
Cu2-O3
Cu2-O4
O3-C8
O4-C8
C2-C8
2.229(4)
2.246(4)
2.350(10)
2.092(9)
1.245(18)
1.256(18)
1.503(16)
4
8
empirical formula
Mr
cryst syst
C84H78Cu2N2O2P4‚C7H8 C80H64Cu2O4P4‚C7H8
1490.7
monoclinic
P21/n
1432.5
monoclinic
P21/n
space group
cell params at 295 Kb
a, Å
b, Å
c, Å
18.612(2)
14.341(1)
14.840(1)
99.05(1)
3911.7(6)
2
12.253(1)
22.403(2)
26.696(2)
98.68(1)
7244.2(11)
4
O2-Cu1-C7
O1-Cu1-C7
O1-Cu1-O2
P2-Cu1-C7
P2-Cu1-O2
P2-Cu1-O1
P1-Cu1-C7
P1-Cu1-O2
P1-Cu1-O1
P1-Cu1-P2
Cu1-O1-C7
Cu1-O2-C7
29.5(4)
29.8(4)
59.3(3)
O4-Cu2-C8
O3-Cu2-C8
O3-Cu2-O4
P4-Cu2-C8
P4-Cu2-O4
P4-Cu2-O3
P3-Cu2-C8
P3-Cu2-O4
P3-Cu2-O3
P3-Cu2-P4
Cu2-O3-C8
Cu2-O4-C8
29.5(4)
29.1(4)
58.5(4)
â, deg
V, Å3
Z
112.4(3)
111.8(3)
108.9(3)
122.5(3)
117.6(3)
116.2(3)
124.9(2)
86.6(8)
109.4(4)
108.4(3)
108.2(3)
123.0(4)
121.4(3)
112.8(3)
126.7(2)
84.0(9)
D
calcd, g cm-3
1.266
1560
1.313
2976
7.25
F(000)
linear abs coeff, cm-1 6.73
cryst dimens, mm
2θ range, deg
no. of unique total data 5508
no. of unique obsd data 3452
0.37 × 0.64 × 0.67
0.32 × 0.51 × 0.55
6-46
6-46
9225
3248
0.060
92.8(8)
95.6(8)
R ) ∑|∆F|/∑|Fo|
R ) ∑w1/2|∆F|/
∑w1/2|Fo|
0.048
0.052
After complete dissolution of the solid, the solution was saturated with
CO while being stirred and a progressive darkening of the yellow color
observed. The solution was then cooled to -30 °C and kept at this
temperature for 5 days. Colorless thin needles formed, which, after
filtration, became yellowish. After 30 min of drying (oil pump), the
product was completely yellow but became colorless again when
exposed to a CO atmosphere (44%). Anal. Calcd for C14H18-
Cu2N2O4: C, 41.48; H, 4.48; N, 6.91. Found: C, 41.36; H, 4.50; N,
6.95. 1H NMR (200 MHz, CD2Cl2, 298 K, ppm): δ 4.93 (s, 2 H),
3.76 (s, 2 H), 3.76 (s, 4 H), 1.94 (m, 12 H). IR (Nujol): ν(CO) 2071
2
GOF ) ∑w|∆F| /
0.85
(NO - NV)]1/2
a Details pertaining to both complexes: Philips PW 1100 diffrac-
tomter; ω/2θ scan type; monochromated Mo KR radiation (λ ) 0.710 69
Å); criterion for observation I > 2σ(I). b Unit cell parameters were
obtained by least-squares analysis of the setting angles of 25 carefully
centered reflections chosen from diverse regions of reciprocal space.
resulting yellow suspension was stirred for 12 h, after which ButNC
(0,50 mL, 4.42 mmol) was added Via syringe. The suspended solid
dissolved, and after 5 min, a white microcrystalline solid precipitated,
which was filtered off and dried (85%). IR (Nujol): ν(CtN) 2168
cm-1
.
Preparation of 3. Solid 1 (1.42 g, 1.42 mmol) was added to a THF
(100 mL) solution of acacenH2 (0.87 g, 3.28 mmol) cooled to -20 °C.
After complete dissolution of the solid, ButNC was added Via syringe.
Thin white needles formed suddenly, which were filtered off and dried
(55%). Anal. Calcd for C22H36Cu2N4O2: C, 51.25; H, 7.04; N, 10.86.
cm-1 1H NMR (200 MHz, CD2Cl2, 298 K, ppm): δ 7.60 (m, 2 H),
.
7.30 (m, 2 H), 1.41 (s, 18 H).
Preparation of 8. Addition of 6 (0.25 g, 0.86 mmol) to a stirred
solution of PPh3 (0.91 g, 3.47 mmol) in toluene (100 mL) resulted in
a solution, which was then left at -30 °C for 10 days. Translucent
crystals were collected (66%). Anal. Calcd for C80H64Cu2O4P4: C,
71.69; H, 4.81; P, 9.24. Found: C, 73.35; H, 5.17; P, 8.22. 1H NMR
(200 MHz, CD2Cl2, 298 K, ppm): δ 7.25 (m, 64 H).
X-ray Diffraction Study of 4 and 8. Crystal data and details
associated with data collection and refinement are given in Table 3.
The crystal quality was tested by ψ scans showing that crystal
absorption effects could be neglected. The structures were solved by
the heavy-atom method (Patterson and Fourier techniques). For
complex 4, refinement was done first isotropically and then anisotro-
pically for all the non-hydrogen atoms except for those of the toluene
solvent molecule, which was found to be disordered about a center of
symmetry. For complex 8, all atoms except the phosphine phenyl
carbons and the toluene solvent carbons were allowed to vary
anisotropically. For both structures, all the Ph rings were constrained
to be regular hexagons (C-C ) 1.395 Å). All H atoms were put in
calculated positions and introduced in refinement as fixed contributors
with isotropic U values fixed at 0.08 Å2.
Found: C, 51.40; H, 6.98; N, 10.84. IR (Nujol): ν(CtN) 2166 cm-1
.
Preparation of 4. Addition of a solution of acacenH2 (0.57 g, 2.56
mmol) and PPh3 (2.69 g, 10.25 mmol) in toluene (100 mL) to a toluene
(100 mL) solution of 1 (0.94 g, 5.12 mmol) resulted in a bright-yellow
solution which under stirring turned to opalescent-white. Standing for
24 h at room temperature gave translucent crystals, which were filtered
off. The mother liquor was concentrated and cooled to +4 °C. After
1 week, more crystals formed (38%). Anal. Calcd for C84H78-
Cu2N2O2P: C, 72.14; H, 5.62; N, 2.00; P, 8.86. Found: C, 72.36; H,
5.74; N, 1.88; P, 8.64. 1H NMR (200 MHz, CD2Cl2, room temperature,
ppm): δ 7.35 (m, 30 H), 4.68 (s, 2 H), 3.41 (s, 4 H), 1.93 (s, 6 H),
1.41 (s, 6 H).
Preparation of 5. Addition of a solution of salophenH2 (0.70 g,
2.22 mmol) and PPh3 (2.33 g, 8.88 mmol) in toluene (100 mL) to a
toluene (100 mL) solution of 1 (0.81 g, 4.44 mmol) resulted in a yellow
solution which turned bright-orange as the reaction proceeded. After
some minutes of stirring, an orange microcrystalline solid formed, which
was filtered off and dried for 2 h in Vacuo (68%). The product was
air stable. Anal. Calcd for C92H74Cu2N2O2P4: C, 74.13; H, 5.00; N,
1.88; P, 8.31. Found: C, 74.10; H, 4.86; N, 6.98; P, 8.19. 1H NMR
(200 MHz, CD2Cl2, 298 K, ppm): δ 7.30 (m, 72 H), 7.60 (m, 2 H).
Preparation of 6. To a solution of 1 (0.74 g, 4.05 mmol) in toluene
(100 mL) was added o-phthalic acid (0.34 g, 2.05 mmol). The reaction
was slow, due to the low solubility of the o-phthalic acid in the reaction
solvent. After 12 h of stirring, an amorphous light-yellow solid was
collected and dried for 2 h in Vacuo (65%). Anal. Calcd for C8H4-
Cu2O4: C, 33.00; H, 1.38. Found: C, 33.01; H, 1.52.
Acknowledgment. We thank the Fonds National Suisse de
la Recherche Scientifique (Grant No. 20-40268.94) for financial
support.
Supporting Information Available: Tables of fractional atomic
coordinates, thermal parameters, and complete interatomic distances
and angles for 4 and 8 (11 pages). Ordering information is given on
any current masthead page.
Preparation of 7. To a stirred toluene (100 mL) solution of 1 (0.74
g, 4.23 mmol) was added o-phthalic acid (0.35 g, 2.11 mmol), and the
IC960072K