Diphosphinite AgI and PdII dinuclear complexes as adaptable anion receptors: An unprecedented bridging mode for the PF 6- ion

Article abstract of DOI:10.1002/anie.200801850

(Figure Presented) The special guest: In the host-guest chemistry of dinuclear complexes that contain the 9H-fluorene-9,9′- dimethanediphenylphosphinite ligand the synergy between the phenyl groups and the axial fluorene moiety leads to the formation of m

Full text of DOI:10.1002/anie.200801850

Communications
DOI: 10.1002/anie.200801850
Host–Guest Chemistry
Diphosphinite AgI and PdII Dinuclear Complexes as Adaptable Anion
À
Receptors: An Unprecedented Bridging Mode for the PF6 Ion **
Changxiu Li, Roberto Pattacini, Roland Graff, and Pierre Braunstein*
The coordination chemistry of anions has attracted much
attention, as the supramolecular host–guest chemistry involv-
ing their binding is relevant to ion-pairing effects,[1] which play
an important role in the reactivity and catalytic properties of
metal complexes.[2] Herein we describe host–guest interac-
tions between transition-metal complexes bearing the new
diphosphinite ligand 1 (Scheme 1) and weakly coordinating
Ligand 1 was reacted with [PdCl2(NCPh)2] to give the
mononuclear, chelated complex [PdCl2(1)] (2). Chloride
abstraction by AgBF4 or AgPF6 afforded the dinuclear,
chloro-bridged complexes [Pd(m-Cl)(1)]2[BF4]2 (3) and [Pd(m-
Cl)(1)]2[PF6]2 (4), respectively, in which 1 remains chelated to
the metal centers (Scheme 1, for experimental details see the
Supporting Information). Their molecular structure was
determined by single-crystal X-ray diffraction (Figure 1 and
Figure 2).[4]
À
anions such as PF6 and BF4À, which exert a remarkable
structural effect on the conformation of the cationic complex
owing to specific metal–anion interactions.
The anions of complexes 3 and 4 occupy cavities above
and below the metal coordination planes. The nature of these
pockets depends on the size of the accommodated anion. In 3,
one BF4À ion occupies a cavity below the Pd2Cl2 core which is
À
delimited by four phenyl groups (Scheme 2). The second BF4
Scheme 1.
[*] C. Li,[+] Dr. R. Pattacini, Dr. P. Braunstein
Laboratoire de Chimie de Coordination
Institut de Chimie (UMR 7177 CNRS)
UniversitØ Louis Pasteur
4 rue Blaise Pascal, 67070 Strasbourg (France)
Fax: (+33)3-9024-1322
E-mail: braunstein@chimie.u-strasbg.fr
Dr. R. Graff
Service de RMN, Institut de Chimie (UMR 7177 CNRS)
UniversitØ Louis Pasteur
1 rue Blaise Pascal, 67070 Strasbourg (France)
[+] Permanent address:
Beijing Research Institute of Chemical Industry
SINOPEC, Beijing, 100013 (China)
Figure 1. ORTEP plots of complex 3 in 3·3CH2Cl2 (top) and 4 in
centrosymmetric 4·2CH2Cl2·C5H12 (bottom). Selected distances [Š] and
angles [8] for 3: Pd1–P1 2.2480(1), Pd1–P2 2.2422(9), Pd2–P3
2.2660(9), Pd2–P4 2.234(1), Pd1–Cl1 2.3922(9), Pd1–Cl2 2.3893(9),
Pd2–Cl1 2.3944(9), Pd2–Cl2 2.3866(8); P2-Pd1-P1 90.71(3), P4-Pd2-P3
91.19(3); For 4: Pd1–P1 2.236(2), Pd1–P2 2.244(2), Pd1–Cl1 2.400(2),
Pd1–Cl1’ 2.4140(16); P1-Pd1-P2 91.53(7).
[**] This work was supported by the CNRS, the Minist›re de
l’Enseignement SupØrieur et de la Recherche, and the Agence
Nationale de la Recherche (ANR-06-BLAN-410). We are grateful to
SINOPEC for supporting C.L.
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.200801850.
6856
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2008, 47, 6856 –6859

Angewandte
Chemie
Supporting Information). These contacts are retained in
solution, as demonstrated by 19F, 1HHOESY (heteronuclear
Overhauser enhancement spectroscopy) NMR spectroscopy
(Figure 2, see details in the Supporting Information).[3]
The strongest signal in the HOESY spectrum of 3
consistently corresponds to the interactions between the
À
fluorine atoms of the BF4 ion and the ortho protons of the
phenyl groups. Other couplings with the fluorine atoms
involve both the methylene groups, the meta protons of the
phenyl groups, and the fluorene hydrogen atoms that point
towards the anion (Scheme 2). The absence of couplings with,
for example, the para protons of the phenyl groups indicates
that the HOESY signals do not originate from the formation
of extended aggregates in solution. Further evidence for the
existence of discrete anion–cation couples is provided by the
19F{1H} NMR spectrum at 193 K, which shows two resonances
À
for the BF4 ion, at d = À143.7 and À151.6 ppm (Figure 3).
Figure 2. 19F,1HHOESY NMR spectrum of complex 3 in CD2Cl2.
T=298 K, d1=3 s, mixing time=250 ms, 2 Kꢀ256 real data points.
Figure 3. 19F NMR spectrum of complex 3 in CD2Cl2 at 298 and 193 K.
These resonances coalesce to form a singlet at room temper-
ature (d = À149.2 ppm). The peak at À151.6 ppm corresponds
to free BF4À, the signal at À143.7 ppm should correspond to
the anion involved in the host–guest couple. Indeed, addition
of [NEt4]BF4 to a solution of 3 resulted in a shift of the peak at
À149.2 ppm towards the usual value for free tetrafluorobo-
rate.
The reaction of 1 with AgPF6 afforded in good yields the
complex [Ag(1)(PF6)]2 (5), which was characterized by X-ray
crystallography (Figure 4). The metal centers of 5·2CH2Cl2
are bridged by two molecules of 1, leading to a 16-membered
dimetallocycle. Their coordination geometry can be described
as distorted tetrahedral, and the metal centers are further
À
À
bridged by a fluorine atom of each of the PF6 ions [Ag F1
[5]
Scheme 2.
À
2.639(3), Ag F2 2.638(1) Š]. To the best of our knowledge,
this type of M···F···M (M = transition metal) interaction
involving the PF6À ion is unprecedented. Although complexes
featuring terminally coordinated PF6À are not rare,[6] the few
ion lies in the upper pocket generated by four phenyl and the
two fluorene groups, the latter being almost orthogonal with
respect to the P1-Pd-P2 plane. In contrast, the larger PF6À ions
in 4 occupy two centrosymmetric pockets that are formed by
one fluorene and four phenyl moieties. The anion thus exerts
a remarkable effect on the conformation of the dipalladium
complex (Scheme 2).
examples of intramolecular[7] or intermolecular[8] bridging
À
À À
PF6 ions reported are of the type M···F P F···M, and
generally display rather long mean F···M distances (mini-
mum = 2.804(4) Š).[8d] In one case, a very short Cu F
À
interaction (2.345(2) Š) was observed.[8c]
The metal–anion interactions are probably rather weak
and no evidence for Ag···F contacts could be found in solution
by multinuclear 1D NMR spectroscopy. A fast dynamic
In each case, the structural data indicate that the cation–
anion couple is stabilized by multiple H···F contacts (see the
Angew. Chem. Int. Ed. 2008, 47, 6856 –6859
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
6857

Communications
conformational changes (compounds 3 and 4) and 2) give rise
to unprecedented bonding modes for the guest, including
À
commonly used anions (compound 5). The fact that the PF6
ion was found to be less coordinatively “innocent” than
previously assumed may have broader implications in the
field of coordination chemistry.
Received: April 21, 2008
Published online: July 25, 2008
Keywords: anion effect · bridging ligands · coordination modes ·
.
host–guest systems · structure elucidation
Figure 4. ORTEP plot of centrosymmetric complex 5 in 5·2CH2Cl2.
Phenyl groups are omitted for clarity. Selected distances [Š] and angles
[8]: Ag1–P1 2.419(1), Ag1–P2 2.413(1), Ag1–F1 2.639(3), Ag1–F2
2.638(1); P1-Ag1-P2’ 140.62(4), F1-Ag1-F1’ 62.18(9).
[1] a) P. D. Beer, P. A. Gale, Angew. Chem. 2001, 113, 502 – 532;
Angew. Chem. Int. Ed. 2001, 40, 486 – 516; b) I. E. D. Vega, P. A.
Gale, M. E. Light, S. J. Loeb, Chem. Commun. 2005, 4913 – 4915;
c) S. O. Kang, R. A. Begum, K. Bowman-James, Angew. Chem.
2006, 118, 8048 – 8061; Angew. Chem. Int. Ed. 2006, 45, 7882 –
7894; d) R. Frantz, C. S. Grange, N. K. Al-Rasbi, M. D. Ward, J.
Lacour, Chem. Commun. 2007, 1459 – 1461; e) C. A. Black, L. R.
Hanton, M. D. Spicer, Chem. Commun. 2007, 3171 – 3173; f) P.
Gamez, T. J. Mooibroek, S. J. Teat, J. Reedijk, Acc. Chem. Res.
2007, 40, 435 – 444; g) C. Olivier, Z. Grote, E. Solari, R. Scopelliti,
K. Severin, Chem. Commun. 2007, 4000 – 4002; h) P. A. Gale,
S. E. Garcia-Garrido, J. Garric, Chem. Soc. Rev. 2008, 37, 151 –
190.
process is likely to take place in solution, resulting in the
equivalence of the fluorine atoms on the NMR timescale.
A comparison between the unprecedented metal–anion
interaction in 5 and the related situations in 3 and 4 very
clearly illustrates the mutual influence of the metal cation and
the anion on such host–guest features. The aryl groups
synergistically cooperate in 5 to form hemispherical cavities
situated on opposite sides of the Ag2P4 moiety (Scheme 3).
The steric complementarity and resulting affinity between
the anion and the cationic complex is emphasized in the
space-filling model shown in Figure 5.
We have shown herein that the synergy between axial
planar groups and phenyl groups in the coordination com-
plexes of functional ligands can induce the formation of
cavities with dimensions of supramolecular relevance, which
can 1) be modified by the size of the anion, resulting in major
[2] A. Macchioni, Chem. Rev. 2005, 105, 2039 – 2073.
[3] For recent examples see e.g.: a) G. Ciancaleoni, G. Bellachioma,
G. Cardaci, G. Ricci, R. Ruzziconi, D. Zuccaccia, A. Macchioni, J.
Organomet. Chem. 2006, 691, 165 – 173; b) D. Zuccaccia, G.
Bellachioma, G. Cardaci, G. Ciancaleoni, C. Zuccaccia, E. Clot,
A. Macchioni, Organometallics 2007, 26, 3930 – 3946; c) D. Nama,
P. Butti, P. S. Pregosin, Organometallics 2007, 26, 4942 – 4954;
d) D. Nama, P. S. Pregosin, A. Albinati, S. Rizzato, Organo-
metallics 2007, 26, 2111 – 2121; e) B. Binotti, G. Bellachioma, G.
Cardaci, C. Carfagna, C. Zuccaccia, A. Macchioni, Chem. Eur. J.
2007, 13, 1570 – 1582.
[4] X-ray diffraction data: 3·3CH2Cl2: C81H70B2Cl8F8O4P4Pd2, T=
¯
173 K, M = 1901.27, triclinic P1, a = 13.7361(4), b = 16.0504(4),
c = 20.0595(4) Š, a = 103.023(1), b = 106.833(1), g = 98.008(1)8,
V= 4023.69(17) Š3, Z = 2, 1calcd = 1.569 gcmÀ3
,
m(MoKa) =
8.61 mmÀ1, F(000) = 1916, 2qmax = 538, R1 = 0.0477, wR2 = 0.1252,
R(int) = 0.0544 parameters = 1018, observed reflections = 12085
(16670 measured); 4·2CH2Cl2·C5H12: C85H78Cl8F12O4P6Pd2, T=
¯
173 K, M = 2073.69, triclinic P1, a = 11.3740(13), b =
14.1500(17), c = 15.905(2) Š, a = 114.812(5), b = 99.373(7), g =
97.914(8)8, V= 2231.0(5) Š3, Z = 1, 1calcd=1.543 gcmÀ3
,
m-
(MoKa) = 8.24 mmÀ1
, F(000) = 1046, 2qmax = 528, R1 = 0.0755,
Scheme 3.
wR2 = 0.1444, R(int) = 0.0879 parameters = 525, observed reflec-
tions = 3839 (8475 measured); 5·2CH2Cl2: C80H68Ag2Cl4F12O4P6,
T= 173 K, M = 1864.70, triclinic P21/c, a = 14.1605(5), b =
13.6956(5), c = 23.8959(8) Š, b = 123.245(2), V= 3875.8(2) Š3,
Z = 2, 1calcd = 1.598 gcmÀ3, m(MoKa) = 8.46 mmÀ1, F(000) = 1880,
2qmax = 558, R1 = 0.0500, wR2 = 0.1003, R(int) = 0.0674 parame-
ters = 523, observed reflections = 4663 (8856 measured).
CCDC 685553 (3), 685554 (4), and 685555 (5) contain the
supplementary crystallographic data for this paper. These data
can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif
[5] CCDC database, November 2006 update.
[6] For a recent example see: N. Muresan, K. Chlopek, T. Weyher-
mueller, F. Neese, K. Wieghardt, Inorg. Chem. 2007, 46, 5327 –
5337.
Figure 5. Orthogonal views of space-filling diagrams of the molecular
structure of 5 in 5·2CH2Cl2. Color code: aryl groups: gray, PF6: white.
[7] a) L. Carlucci, G. Ciani, D. M. Proserpio, A. Sironi, Inorg. Chem.
1997, 36, 1736 – 1737; b) A. Knoepfler-Muhlecker, B. Scheffter, H.
6858
www.angewandte.org
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2008, 47, 6856 –6859

Angewandte
Chemie
Kopacka, K. Wurst, P. Peringer, J. Chem. Soc. Dalton Trans. 1999,
2525 – 2528; c) Y. Suenaga, T. Kuroda-Sowa, M. Maekawa, M.
Munakata, J. Chem. Soc. Dalton Trans. 2000, 3620 – 3623; d) P.
Gentschev, N. Moller, B. Krebs, Inorg. Chim. Acta 2000, 300, 442 –
452; e) J. Liu, H.-K. Liu, X.-L. Feng, H.-X. Zhang, Z.-Y. Zhou,
A. S. C. Chan, B.-S. Kang, Inorg. Chem. Commun. 2001, 4, 674 –
677; f) H.-K. Liu, J. Hu, T.-W. Wang, X.-L. Yu, J. Liu, B. Kang, J.
Chem. Soc. Dalton Trans. 2001, 3534 – 3540.
[8] a) D. A. McMorran, P. J. Steel, Angew. Chem. 1998, 110, 3495 –
3497; Angew. Chem. Int. Ed. 1998, 37, 3295 – 3297; b) B.-K. Koo,
L. Bewley, V. Golub, R. S. Rarig, E. Burkholder, C. J. OꢀConnor,
J. Zubieta, Inorg. Chim. Acta 2003, 351, 167 – 176; c) K. I.
Nꢁttinen, P. E. N. de Bairos, P. J. Seppala, K. T. Rissanen, Eur. J.
Inorg. Chem. 2005, 2819 – 2825; d) C. Jocher, T. Pape, W. W.
Seidel, P. Gamez, J. Reedijk, F. E. Hahn, Eur. J. Inorg. Chem.
2005, 4914 – 4923.
Angew. Chem. Int. Ed. 2008, 47, 6856 –6859
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org 6859