Dimetalated Crown Ether Schiff Base Palladacycles. Influence of the

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Organometallics 2011, 30, 386–395 DOI: 10.1021/om100833w

Dimetalated Crown Ether Schiff Base Palladacycles. Influence of the Carbon Chain Length on the Coordination Mode of Bidentate Phosphines. Crystal and Molecular Structure of the Novel Complex [Pd2{1,4-[C(H)dN{9,10-(C8H16O5)C6H3}]2C6H2-C2,C5}(Cl)2{μ-Ph2P(CH2)5PPh2}2] Alberto Fern andez,*,† Margarita L opez-Torres,† Samuel Castro-Juiz,† Manuel Merino,† † Digna V azquez-Garcı´ a, Jose M. Vila,*,‡ and Jes us J. Fernandez† †

Departamento de Quı´mica Fundamental, Universidade da Coru~ na, E-15071 La Coru~ na, Spain, and Departamento de Quı´mica Inorg anica, Universidad de Santiago de Compostela, E-15782 Santiago de Compostela, Spain

‡

Received August 26, 2010

Reaction of the Schiff base ligand 1,4-[C(H)dN{9,10-(C8H16O5)C6H3}]2C6H4 (a), derived from terephthalaldehyde and 40 -aminobenzo-15-crown-5, with Pd(OAc)2 in chloroform at 50 °C for 96 h, gave the polymeric compound [Pd2{1,4-[C(H)dN{9,10-(C8H16O5)C6H3}]2C6H2-C2,C5,N,N0 }(μ-O2CMe)2]n (1a) after double C-H activation at the C2 and C5 phenyl carbons. The metathesis reaction of 1a with saturated solutions of NtBu4Cl or NtBu4Br gave [Pd2{1,4-[C(H)dN{9,10(C8H16O5)C6H3}]2C6H2-C2,C5,N,N0 }(μ-Cl)2]n (2a) and [Pd2{1,4-[C(H)dN{9,10-(C8H16O5)C6H3}]2C6H2-C2,C5,N,N0 }(μ-Br)2]n (3a), respectively, with exchange of the acetate group by a chloride or bromine ligand, also respectively, which likewise adopt polymeric arrangements. Further reaction of 2a with thallium acetylacetonate gave the dinuclear complex [Pd2{1,4-[C(H)dN{9,10-(C8H16O5)C6H3}]2C6H2-C2,C5,N,N0 }{MeC(O)CH-C(O)Me-O,O0 }2] (4a), whereas treatment of 2a with monophosphines in a 1:1 molar ratio resulted in splitting of the polymer and yielded the dinuclear complexes [Pd2{1,4-[C(H)dN{9,10-(C8H16O5)C6H3}]2C6H2-C2,C5,N,N0 }(Cl)2(L)2] (5a, L = PPh3; 6a, L = P(p-MeOC6H4)3). The reactions of 2a with diphosphines were influenced by the length of the alkyl chain binding the two phosphorus atoms and the relative palladium atom/diphosphine molar ratio. Reaction of 2a with dppm in a 2:1 ratio gave the tetranuclear compound [{Pd 2[1,4{C(H)dN[9,10-(C8H16O5)C6H3]}2C6H2-C2,C5,N,N0 ](Cl)2}2(μ-Ph2PCH2P-Ph2)2] (7a) with the diphosphine in a bridging mode. However, treatment of 2a with dppm or dppe in a 1:1 ratio gave the dinuclear complexes [Pd2{1,4-[C(H)dN{9,10-(C8H16O5)C6H3}]2C6H2-C2,C5,N,N0 }(Ph2PRPh2P,P0 )2][Cl]2 (8a, R = CH2; 9a, R = (CH2)2, respectively) with two chelating phosphines. With the longer chain diphosphines Ph2P(CH2)nPPh2 (n = 4, dppb; n = 5, dpppe; n = 6, dpph) in a 1:1 palladium/diphosphine molar ratio the dinuclear compounds [Pd2{1,4-[C(H)dN{9,10-(C8H16O5)C6H3}]2C6H2-C2,C5}(Cl)2{μ-Ph2P(CH2)nPPh2}2] (10a, n = 4; 11a, n = 5; 12a, n = 6) were obtained, with two diphosphines intramolecularly bridging both palladium atoms. The molecular structures of compounds 5a, and 11a have been determined by X-ray diffraction analysis.

1. Introduction Cyclometalated complexes exhibit a good number of applications, which range from the synthesis of new organic and organometallic compounds to mesogenic species and catalytic materials1 as well as promoting unusual coordination environments.2 On the other hand crown ethers are ubiquitous in supramolecular chemistry as hosts for cations such as alkali and alkaline-earth metal cations. Their coordinating properties depend on many structural characteristics, such as the different cavity size, the conformation of *To whom correspondence should be addressed. E-mail: qiluaafl@ udc.es; [email protected]. pubs.acs.org/Organometallics

Published on Web 01/10/2011

the ether ring, and the solvent; consequently, it is possible to tailor-make different types ligands for specific uses.3 Thus, promising potential applications are being studied, such as the production of sensors, the selective extraction of cations, the ionic transport in membranes, the preparation of photochemically controlled and electrochemically active receptors, and compounds with promising anticancer properties.4 Ryabov5 has reported the first cyclopalladated compound with a crown ether fragment, and, more recently, our laboratory has previously prepared metalloligands derived from cyclometalated complexes whose structure determines the coordination possibilities of the ether crown moieties and, consequently, improves their selectivity toward cations.6 For example palladium(II) cyclometalated acetate-bridged r 2011 American Chemical Society

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complexes bearing a folded structure present a pseudosandwich arrangement capable of coordinating relatively large cations, whereas their derivatives with chlorine bridging ligands, with a planar structure, essentially showed the same reactivity as the stand-alone crown ether ligands. Therefore, by carefully choosing the structural characteristics of a metalloligand it is possible to modulate its reactivity.7 Furthermore, we were also interested in studying not only the coordination possibilities of the attached crown ether rings but likewise their influence in the structure of the metallacycles, in agreement with our past studies related to coordination polymers derived from dicyclometalated Schiff base ligands,8 and we have observed that imine crown ether ligands also give rise to similar 1D polymers. Moreover, we have extensively studied the reactivity of cyclometalated complexes with tertiary diphosphines, and we have found that it mainly depends on two factors: the structure of the parent cyclometalated complex and the relative palladium atom/phosphine molar ratio. While unidentate phosphines usually produce complexes of the same (1) (a) Pfeffer, M.; Sutter, J. P.; Rottevel, M. A.; de Cian, A.; Fischer, J. Tetrahedron 1992, 48, 2427. (b) Ryabov, A. D.; van Eldik, R.; Le Borgne, G.; Pfeffer, M. Organometallics 1993, 12, 1386. (c) Wild, B. S. Coord. Chem. Rev. 1997, 166, 291. (d) Chooi, S. Y. M.; Leung, P. H.; Lim, C. C.; Mok, K. F.; Quek, G. H.; Sim, K. Y.; Tan., M. K. Tetrahedron: Asymmetry 1992, 3, 529. (e) Espinet, P.; Esteruelas, M. A.; Oro, L. A.; Serrano, J. L.; Sola, E. Coord. Chem. Rev. 1992, 17, 215. (f) Navarro-Ranninger, C.; Lopez Solera, I.; Rodríguez, J.; García-Ruano, J. L.; Raithby, P. R.; Masaguer, J. R.; Alonso, C. J. Med. Chem. 1993, 36, 3795. (g) Navarro-Ranninger, C.; L opez-Solera, I.; Gonzalez, V. M.; Perez, J. M.; Alvarez-Valdes, A.; Martin, A.; Raithby, P. R.; Masaguer, J. R.; Alonso, C. Inorg. Chem. 1996, 35, 5181. (h) Bose, A.; Saha, C. H. J. Mol. Catal. 1989, 49, 271. (i) Lopez-Torres, M.; Fernandez, A.; Fernandez, J. J.; Castro-Juiz, S.; Suarez, A.; Vila, J. M.; Pereira, M. T. Organometallics 2001, 20, 1350. (j) Gomez-Quiroga, A.; Navarro-Ranninger, C. Coord. Chem. Rev. 2004, 248, 119. (k) Omae, I. J. Organomet. Chem. 2007, 692, 2608. (l) Ghedini, M.; Aiello, I.; Crispini, A.; Golemme, A.; La Deda, M.; Pucci, D. Coord. Chem. Rev. 2006, 250, 1373. (m) Chase, P. A.; Klein-Gebbink, R. J. M.; van Koten., G. J. Organomet. Chem. 2004, 298, 4016. (2) Vila, J. M.; Pereira, M. T.; Ortigueira, J. M.; Fernandez, J. J.; Fern andez, A.; L opez-Torres, M.; Adams, H. Organometallics 1999, 18, 5484. (3) (a) Izatt, R. M.; Bradshaw, J. S.; Nielsen, S. A.; Lamb, J. D.; Christensen, J. J.; Sen, D. Chem. Rev. 1985, 85, 271. (b) Inoue, Y.; Gokel, G. W., Eds. Cation Binding by Macrocycles; Marcel Dekker: New York, 1990. (c) Lehn, J. M.; Montavon, F. Helv. Chim. Acta 1978, 61, 67. (d) Izatt, R. M.; Christensen, J. J., Eds. Synthetic Multidentate Macrocyclic Compounds; Academic Press: London, 1978. (e) V€ogtle, F.; Weber, E., Eds. Host-/Guest Complex Chemistry: Macrocycles; Springer-Verlag: Berlin, 1985. (f) Izatt, R. M.; Christensen, J. J., Eds. Synthesis of Macrocycles: The Design of Selective Complexing Agents. In Progress in Macrocyclic Chemistry, Vol. 3; Wiley: New York, 1987. (g) Gokel, G. W. Crown Ethers and Cryptands. In Monographs in Supramolecular Chemistry; The Royal Society of Chemistry: Cambridge, 1991. (h) Cooper, S. R., Ed. Crown Compounds: Towards Future Applications; Wiley Interscience: New York, 1992. (i) Yordanov, A. T.; Roundhill, D. M. Coord. Chem. Rev. 1998, 170, 93. (4) (a) Pedersen, C. J. J. Am. Chem. Soc. 1967, 89, 2495. (b) Pedersen, C. J. Science 1988, 241, 536. (c) Steed, J. W. Coord. Chem. Rev. 2001, 215, 171. (d) Xiaotian, Q.; Zaide, Z.; Minggui, X.; Yongchang, Z.; Ying, T. Talanta 1998, 46, 45. (e) Rosa, D. T.; Young, V. G.; Coucouvanis, D. Inorg. Chem. 1998, 37, 5042. (f) Dillon, R. E. A.; Stern, C. L.; Shriver, D. F. Solid State Ionics 2000, 133, 247. (g) Yam, V. W. W.; Tang, R. P. L.; Wong, K. M. C.; Lu, X. X.; Cheung, K. K.; Zhu, N. Chem.;Eur. J. 2002, 8, 4066. (h) Breccia, P.; Van Gool, M.; Perez-Fernandez, R.; Martín-Santamaría, S.; Gago, F.; Prados, P.; de Mendoza, J. J. Am. Chem. Soc. 2003, 125, 8270. (i) Siu, P. K. M.; Lai, S. W.; Lu, W.; Zhu, N.; Che, C. M. Eur. J. Inorg. Chem. 2003, 2749. (j) Ohshita, J.; Uemura, T.; Inoue, T.; Hino, K.; Kunai, A. Organometallics 2006, 25, 2225. (k) Liu, W.; Chen, Y.; Wang, R.; Zhou, X. H.; Zuo, J. L.; You, X. Z. Organometallics 2008, 27, 2990. (l) Perekalin, D. S.; Babak, M. V.; Novikov, V. V.; Petrovskii, P. V.; Lyssenko, K. A.; Corsini, M.; Zanello, P.; Kudinov, A. R. Organometallics 2008, 27, 3654. (m) Kelly, M. E.; Dietrich, A.; Gomez-Ruiz, S.; Kalinowski, B.; Kaluderovic, G. N.; Muller, T.; Paschke, R.; Schmidt, J.; Steinborn, D.; Wagner, C.; Schmidt, H. Organometallics 2008, 27, 4917.

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nuclearity as the parent compound, regardless of the molar ratio,9 the reactivity of diphosphines is more diverse and highly dependent on the number of metal centers at the starting material as well as on the molar ratio used.10 Hence, reaction of the latter with mononuclear palladacycles may give species with bridging or with chelating diphosphines, but with dinuclear complexes the structural possibilities increase enormously, giving di-, tetra-, or polynuclear compounds;3i,8,10,11 also the diphosphines may bridged intraor intermolecularly.12 With these considerations in mind, we reasoned that terdentate [C,N,N,C] crown ether Schiff bases should be adequate to prepare dicyclometalated complexes having a polymeric structure, that is, coordination polymers. Furthermore, we also tested the reactivity of such ligands toward tertiary mono- and diphoshines in order to find new, and hopefully unexpected, results, as has been the case of the unusual structure found for the compound with dpppe, where two diphosphines bridge intramolecularly across the phenyl ring linking the two metal centers.

2. Results and Discussion For the convenience of the reader the compounds and reactions are shown in Schemes 1 and 2. The compounds were characterized by elemental analysis (C, H, N), mass spectrometry, IR, and 1H, 31P{1H}, and (in part) 13C{1H} NMR spectroscopy (data in Experimental Section). 2.1. Synthesis of Cyclometalated Complexes. The Schiff base ligand 1,4-[C(H)dN{9,10-(C8H16O5)C6H3}]2C6H4, a, was prepared by condensation of terephthalaldehyde and 40 aminobenzo-15-crown-5 in chloroform and isolated as an air-stable solid, which was fully characterized (see Experimental Section). We have previously reported that reaction of potentially tetradentate [C,N,C,N] Schiff bases derived from terephthalaldehyde with palladium(II) acetate in acetic acid produces cleavage of one imine CdN double bond to give monocyclometalated complexes with a free formyl group;13 however, (5) Bezsoudnova, E. Y.; Ryabov, A. D. J. Organomet. Chem. 2001, 622, 38. (6) Castro-Juiz, S.; Fernandez, A.; L opez-Torres, M.; VazquezGarcı´ a, D.; Suarez, A.; J. Vila, J. M.; Fernandez, J. J. Organometallics 2009, 28, 6657. (7) Arias, J.; Bardajı, M.; Espinet, P. J. Organomet. Chem. 2006, 691, 4990. (8) (a) L opez Torres, M.; Fernandez, A.; Fernandez, J. J.; Suarez, A.; Castro-Juiz, S.; Pereira, M. T.; Vila, J. M. J. Organomet. Chem. 2002, 655, 127. (b) Fernandez, A.; Pereira, E.; Fernandez, J. J.; Lopez-Torres, M.; Suarez, A.; Mosteiro, R.; Pereira, M. T.; Vila, J. M. New J. Chem. 2002, 26, 895. (9) (a) Vila, J. M.; Alberdi, G.; Pereira, M. T.; Mari~ no, M.; Fernandez, A.; L opez Torres, M.; Ares, R. Polyhedron 2003, 22, 241. (b) Gomez-Blanco, N.; Fernandez, J. J.; Fernandez, A.; Fernandez, J. J.; Vazquez-García, D.; LopezTorres, M.; Rodríguez, A.; Vila, J. M. Polyhedron 2009, 28, 3607. (10) (a) Naya, L.; Vazquez-Garcı´ a, D.; Fernandez, A.; Vila, J. M.; G omez-Blanco, N.; Fernandez, J. J. J. Organomet. Chem. 2008, 693, 685. (b) Fernandez, A.; Vazquez-García, D.; Fernandez, J. J.; Lopez-Torres, M.; Suarez, A.; Castro-Juiz, S.; Vila, J. M. Eur. J. Inorg. Chem. 2002, 2389. (11) Fernandez, A.; Fernandez, J. J.; L opez-Torres, M.; Suarez, A.; Ortigueira, J. M.; Vila, J. M.; Adams, H. J. Organomet. Chem. 2000, 612, 85. (12) L opez-Torres, M.; Juanatey, P.; Fernanez, J. J.; Fernanez, A.; Suarez, A.; Mosterio, R.; Ortigueira, J. M.; Vila, J. M. Organometallics 2002, 21, 3628. (13) (a) Vila, J. M.; Gayoso, M.; Pereira, M. T.; L opez Torres, M.; Alonso, G.; Fernandez, J. J. J. Organomet. Chem. 1993, 445, 287. (b) Vila, J. M.; Gayoso, M.; Pereira, M. T.; Lopez-Torres, M.; Fernandez, J. J.; Fernandez, A. J. Organomet. Chem. 1996, 506, 165.

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Fern andez et al. Scheme 1a

a Conditions: (i) Pd(OAc)2, chloroform; (ii) NtBu4Cl, acetone/water; (iii) NtBu4Br, acetone/water; (iv) Tl(acac), acetone; (v) PPh3 (5a) or P(p-MeOC6H4)3 (6a), dichloromethane (1:1 palladium/phosphine ratio).

double metalation could be achieved when the synthesis was carried out in a nonacidic media.8a Thus, reaction of a with palladium(II) acetate under mild conditions (dry chloroform at 50 °C) gave 1a; a new doubly cyclometalated acetatobridged complex. Unfortunately, the very low solubility of complex 1a precluded its full characterization, and this was achieved by the complete analysis of its derivatives (vide infra). Notwithstanding, the IR spectrum showed strong bands assigned to the νas(COO) and νs(COO) stretching

vibrations at 1574s and 1411s cm-1, respectively, indicating the presence of bridging acetate groups.10b,14 Whether 1a is of dimeric or polymeric nature could not be unambiguously established, contrary to other doubly cyclometalated complexes derived from Schiff base ligands previously reported;15 nevertheless, owing to its low solubility, we (14) Nakamoto, K. IR and Raman Spectra of Inorganic and Coordination Compounds, 5th ed.; Wiley and Sons: New York, 1997.

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Scheme 2a

a Conditions: (i) dppm, acetone (2:1 palladium/dppm ratio); (ii) dppm (8a) or dppe (9a), acetone (1:1 palladium/phosphine ratio); (iii) dppb (10a), dpppe (11a) or dpph (12a), dichloromethane (1:1 palladium/phosphine ratio).

tentatively propose the formulation depicted in Scheme 1, i.e., as a polymeric arrangement. Treatment of 1a with tetrabutylammonium chloride or with tetrabutylammonium bromide produced the chloro- or bromo-bridged complexes 2a and 3a, respectively, after

exchange of the acetate bridging groups by the corresponding halide-bridging ligands. The bulky tetrabutylammonium cation used in the metathesis reaction, as opposed to sodium chloride, was chosen in order to prevent coordination of the cation to the crown ether group.6 Compound 2a was

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insoluble in common organic solvents, but complex 3a was sufficiently soluble in DMSO for characterization by NMR spectroscopy. The 1H NMR spectrum showed a singlet resonance at δ 7.92 assigned to the equivalent H3 and H6 protons, confirming double metalation at C2 and C5. In order to more adequately characterize the complexes, we prepared the very soluble dinuclear species 4a from reaction of 2a with thallium acetylacetonate. The MS-FAB spectra showed the corresponding peaks at m/z 1073 assigned to [M]þ after consideration of the palladium isotopes, in accordance with the proposed structure.16 The 1H NMR spectrum showed the characteristic signals corresponding to the metalated ligand (two singlets at δ 8.18 and 7.60, with a 1:2 relative integration, were assigned to the HCdN and H3/ H6 proton resonances, respectively) as well as the resonances at δ 5.36 and 2.09, 1.89, assigned to the CH proton and to the two inequivalent C-Me groups of each acetylacetonate ligand, respectively. In the 13C{1H} NMR spectrum the most noticeable feature was the high-frequency shift of the CdN, C1/C4, and C2/C5 resonances (ca. δ 15, 13 and 20, respectively), as compared to their value in the spectrum of the free ligand; also assigned were the signals corresponding to the coordinated acac ligands as singlets at δ 188.3 and 185.8 (CO), 100.3 (CH), and 28.1 and 27.5 (C-Me). 2.2. Reactivity with Monophosphines. Reaction of 2a with the tertiary monophosphines PPh3 and P(p-OMeC6H4)3 in a palladium atom/phosphine 1:1 molar ratio gave 5a and 6a, dinuclear species after cleavage of the chloro-bridged bonds and formation of two new Pd-P bonds per compound. The MS-FAB spectra showed among others the peaks corresponding to [M]þ, [M - Cl]þ, and [M - 2Cl]þ, indicating a characteristic fragmentation pattern (see Experimental Section). The 1H NMR spectra showed the resonances assigned to the HCdN and H3/H6 protons as doublets due to coupling to the 31P nucleus [4JPH = 6.4 Hz for HCdN and 5.9 Hz for H3/H6]. The H3/H6 resonances were shifted toward lower frequency by more than 1 ppm, as compared to the parent cyclometalated complexes, due to the shielding effect of the phosphine phenyl groups. The HCdN proton resonance was also high field shifted by ca. 1 ppm; this large shift has not been observed in analogous mononuclear complexes9a,13a and is probably due to the shielding effects of the phosphine phenyl rings, which are close to the HCdN group as a result of double metalation, in accordance with a N-Pd-P trans geometry. The 31P{1H} NMR spectra showed a singlet resonance for the two equivalent phosphorus nuclei; the chemical shift values were also in agreement with a phosphorus trans to nitrogen geometry. In the 13C{1H} NMR spectra the low-field shifts observed for CdN, C1/C4, and C2/C5 were similar to those observed for 4a. The CdN and the C2/C5 and C3/C6 resonances appeared as doublets at ca. δ 174, 149, and 138, respectively, coupled to the phosphorus nucleus. Crystal and Molecular Structure of 5a. Suitable crystals were grown by slowing evaporating a chloroform/hexane solution. The labeling scheme is shown in Figure 1. Crystallographic data and selected interatomic distances and angles (15) (a) C ardenas, D. J.; Echavarren, A. M.; Ramı´ rez de Areyano, M. C. Organometalics 2001, 18, 3337. (b) Chakladar, S.; Paul, P.; Venkatsubramanian, K.; Nag, K. J. Chem. Soc., Dalton Trans. 1991, 2669. (16) (a) Tusek-Bozic, L.; Curic, M.; Traldi, P. Inorg. Chim. Acta 1997, 254, 49. (b) Tusek-Bozic, L.; Komac, M.; Curic, M.; Lycka, A.; Dalpaos, M.; Scarcia, V.; Furlani, A. Polyhedron 2000, 19, 937.

Fern andez et al.

Figure 1. Molecular structure of [Pd2{1,4-[C(H)dN{9,10-(C8H16O5)C6H3}]2C6H2-C2,C5,N,N0 }(Cl)2(PPh3)2] (5a), with labeling scheme. Hydrogen atoms have been omitted for clarity.

are listed in Tables 1 and 2. The structure comprises a halfmolecule of [Pd 2{1,4-[C(H)dN{9,10-(C8 H16O 5 )C6 H3 }]2C6H2-C2,C5,N,N0 }(Cl)2(PPh3)2] (the dinuclear molecule is generated by a crystallographic inversion center located in the middle point of the phenyl ring) and a chloroform solvent molecule per asymmetric unit. The coordination sphere around each palladium atom consists of a nitrogen atom of the imine group, an ortho carbon atom of the phenyl ring, a chlorine atom, and a phosphorus atom of a triphenylphosphine ligand. The sum of angles at palladium is approximately 360°, with the more noticeable distortion in the somewhat reduced ‘‘bite’’ angle C(1)-Pd(1)-N(1) of 81.1(2)° consequent upon chelation. The geometry around the palladium atom is slightly distorted square-planar; the mean deviations from the leastsquares plane [Pd(1), C(1), N(1), P(1), Cl(1); plane 1] is 0.0152 A˚, and this is nearly coplanar with the metallacycle [Pd(1), C(met), C(3), C(4), N(1); plane 2. rms 0.0477 A˚] and with the metalated phenyl ring, rms 0.009 A˚ (plane 3). Angles between planes are as follows: 1/2: 4.9°; 2/3: 5°; 1/3: 8.6°. The palladium-nitrogen bond length, 2.147(5) A˚, is longer than the single bond predicted value of 2.011 A˚ and reflects the trans influence of the phosphorus atom. The palladiumphosphorus bond distance, 2.266(2) A˚, is shorter than the sum of the single-bond radii for palladium and phosphorus, 2.41 A˚, suggesting some partial double bond between both atoms, and is similar to others reported earlier.17 The palladium-chloro and palladium-carbon bond lengths, 2.356(1) and 2.001(6) A˚, respectively, are in agreement with previous findings.8

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Table 1. Crystal and Structure Refinement Data for 5a and 11a

formula Mr temperature (K) wavelength (A˚) cryst syst space group cell dimens a (A˚) b (A˚) c (A˚) R (deg) β (deg) γ (deg) V (A˚3) Z Dcalc (Mg/m3) μ (mm-1) cryst size (mm) 2θmax (deg) indep reflns S R [F, I > 2σ(I)] wR [F2, all data] max F (e A˚3)

5a 3 2CHCl3

11a 3 (C2H5)2O

C74H74Cl8N2O10P2Pd2 1709.69 293(2) 0.71073 monoclinic P21/n

C98H112Cl2N2O11P4Pd2 1901.48 293(2) 0.71073 triclinic P1

14.5712(2) 15.8518(1) 17.1185(2) 90 111.384(1) 90 3681.82(7) 2 1.542 0.881 0.30 0.25 0.20 56.56 9075 (Rint = 0.0541) 1.052 0.0702 0.2059 1.547

13.0434(2) 15.7309(2) 23.6952(1) 88.143(1) 77.156(1) 76.207(1) 4602.46(9) 2 1.372 0.578 0.35 0.25 0.10 56.52 22 500 (Rint = 0.0343) 1.063 0.0438 0.1050 0.831

Short contacts between the solvent CHCl3 hydrogen (H1s) and the O(1) [C(1s)-H(1s), 0.98 A˚; O(1) 3 3 3 H(1s), 2.69 A˚; C(1s)-H(1s) 3 3 3 O(1), 3.47(1) A˚, 137°], O(2) [O(2) 3 3 3 H(1s), 3.17 A˚; C(1s)-H(1s) 3 3 3 O(2), 3.94(2) A˚, 137°], O(3) [C(1s)H(1s),O(3) 3 3 3 H(1s), 3.09 A˚; C(1s)-H(1s) 3 3 3 O(3), 3.70(2) A˚, 121°], and O(5) [O(5) 3 3 3 H(1s), 2.69 A˚; C(1s)-H(1s) 3 3 3 O(1), 3.40(1) A˚, 129°] crown ether oxygen atoms were found. 2.3. Reactions with Diphosphines. Treatment of 2a with bis(diphenylphosphino)methane (dppm) in a 2:1 palladium/ diphosphine molar ratio gave 7a. The phosphorus resonance in the 31P{1H} NMR spectrum, ca. δ 33.7 (s, 4P), was downfield shifted from its value in the free phosphine, suggesting coordination of both phosphorus atoms to the metal center, in a trans to nitrogen arrangement, indicating that the diphosphines were bridging ligands between two cyclometalated fragments. In the 1H NMR spectra a doublet at δ 5.78 was assigned to the H3/H6 protons, coupled to the phosphorus nuclei [4J(PH) = 6.4 Hz]. The FAB mass spectra showed peaks at m/z = 2587 assigned to the [M - 2Cl]þ fragment, which supports a tetranuclear structure in which two doubly cyclometalated ligands are linked by two bridging diphosphines, thus forming a “counterhinged molecular box”, as has been described before for related cyclometalated complexes.3i,8a This was confirmed by the chemical shift shown by the H3/H6 resonances, which appeared at δ 5.78, shielded not only by the phosphine phenyl rings but also by the phenyl rings of the neighboring cyclometalated ligand, cf. H3/H6 δ 7.98, a; and H3/H6 δ 6.3, 5a (vide supra). Treatment of 2a with bis(diphenylphosphino)methane (dppm) or with 1,2-bis(diphenylphosphino)ethane (dppe), in a 1:1 palladium/diphosphine molar ratio, gave dinuclear cyclometalated compounds with two chelated phosphine ligands, 8a and 9a, respectively, as 1:2 electrolytes, as shown by molar conductivity measurements in dry acetonitrile.18 (18) Geary, W. J. Coord. Chem. Rev. 1971, 7, 81. (19) (a) Pregosin, P. S.; Kuntz, R. W. In 31P and 13C NMR of Transition Metal Phosphine Complexes; NMR Basic Principles and Progress, Vol. 16; Diehl, P.; Fluck, E.; Kosfeld, R., Eds.; Springer: Berlin, 1979. (b) K€ uhl, O. Phosphorus-31 NMR Spectroscopy; Springer, Berlin, 2008.

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Table 2. Selected Bond Distances (A˚) and angles (deg) for 5a and 11aa 5a Pd(1)-N(1) Pd(1)-Cmet Pd(1)-P(1) Pd(1)-P(2) Pd(1)-P(3) Pd(1)-Cl(1) Pd(2)-C(4) Pd(2)-P(3) Pd(2)-P(4) Pd(2)-Cl(2) C(met)-Pd(1)-N(1) C(met)-Pd(1)-P(1) N(1)-Pd(1)-Cl(1) P(1)-Pd(1)-Cl(1) C(met)-Pd(1)-P(2) P(2)-Pd(1)-Cl(1) C(met2)-Pd(2)-P(4) P(4)-Pd(2)-Cl(2) C(met2)-Pd(2)-P(3) P(3)-Pd(2)-Cl(2)

2.147(5) 2.001(6) 2.266(2) 2.356(1)

81.1(2) 92.90(17) 92.20(13) 93.79(6)

11a 2.012(3) 2.3407(7) 2.3240(7) 2.4043(7) 2.015(3) 2.3580(8) 2.3274(8) 2.4042(8) 90.25(7) 88.67(7) 88.16(3) 89.02(7) 88.62(3) 89.61(7) 92.77(3)

a Symmetry transformations used to generate equivalent atoms: 5a: #1-x, -yþ1, -z.

The 31P{1H} NMR spectra showed two doublets for the two inequivalent phosphorus nuclei; the resonance at lower frequency was assigned to the phosphorus trans to carbon.19 The 31P chemical shifts were clearly influenced by ring size;20 the four-membered ring in 8a gave a negative ΔR (-36.16),21 while the five-membered ring in 9a gave a positive Δ R (þ16.3). In the 1H NMR spectra the H3/H6 resonances appeared as a doublet of doublets, as a result of coupling to both phosphorus nuclei [4J(Ptrans-CH) = 8.8 Hz, 4J(Ptrans-NH) = 5.4 Hz]. Treatment of 2a with 1,4-bis(diphenylphosphino)butane (dppb), 1,5-bis(diphenylphosphino)pentane (dpppe), or 1,6bis(diphenylphosphino)hexane (dpph) in a 1:1 palladium/ diphosphine molar ratio gave 10a-12a. The conductivity measurements carried out in dry acetonitrile showed the complexes to be nonelectrolytes; this observation precluded their formulation with the diphosphines as chelating ligands. The 31P{1H} NMR spectra showed one singlet at δ 10.2 (10a), 12.3 (11a), and 13.1 (12a), in accordance with four equivalent phosphorus atoms in each case, and, consequently, the diphosphines must be acting as bridging ligands; the low value of the chemical shifts were in agreement with a trans P-Pd-P arrangement in the complexes. In the 1H NMR spectra the HCdN resonance appeared as a singlet at ca. δ9 ppm (cf. δ 8.53 free ligand), evidencing the absence of coupling to the 31P nuclei, in agreement with Pd-N bond cleavage; this would allow free rotation along the Cphenyl-Cimine bond. This assumption was confirmed by the chemical shift of the CdN carbon in the 13C{1H} NMR spectrum of 12a, which appeared at δ 159.2 ppm (cf. δ57.6 free ligand). Therefore, the Schiff base ligand is bonded to the palladium atoms only through the phenyl carbon atoms. The FAB mass spectra showed peaks at m/z = 1763 (10a, [M - Cl]þ), 1827 (11a, [M]þ), and 1855 (12a, [M]þ), indicating a dinuclear formulation for the complexes (Scheme 2). These data suggested a structure in which the two palladium atoms were bridged by two mutually trans diphosphines (20) Garrou, P. E. Chem. Rev. 1981, 81, 229. (21) The difference with respect to an equivalent phosphorus in the nonchelated analogue 5a, with a PPh3 trans to nitrogen δ 42.7.

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Figure 2. Molecular structure of [Pd2{1,4-[C(H)dN{9,10-(C8H16O5)C6H3}]2C6H2-C2,C5}(Cl)2{μ-Ph2P(CH2)5PPh2}2] (11a), with labeling scheme. Hydrogen atoms have been omitted for clarity.

and also by a bidentate [C,C] Schiff base ligand. This structure resembles a “double-A frame” complex that has been studied in some detail containing a bridging halide or hydride, or one of a range of small molecules.22 In the present case, the length between the palladium atoms is greater, due to the presence of the phenyl group, which spans across both metal centers. Crystal Structure of 11a. Suitable crystals were grown by slowing evaporating a chloroform/ether solution. The labeling scheme is shown in Figure 2. Crystallographic data and selected interatomic distances and angles are listed in Tables 1 and 2. The structure comprises a molecule of [Pd2{1,4[C(H)dN{9,10-(C8H16O5)C6H3}]2C6H2-C2,C5}(Cl)2{μ-Ph2P(CH2)5P-Ph2}2] and one diethyl ether solvent molecule. The molecule may be described as a dinuclear complex in which each palladium atom is bonded to a carbon atom of the phenyl ring, one chlorine atom, and two phosphorus atoms from two different diphosphines that bridge across the palladium atoms, which occupy mutually para positions of the dimetalated phenyl ring; the distance between the palladium atoms is 6.88 A˚. The spatial disposition adopted by the CdN groups precluded any interaction with the palladium atoms. The two diphosphine ligands are helicoidally twisted around the Pd-Pd axis, and consequently, the molecule is chiral. However the centrosymmetric nature of the space group P1 indicates that both enantiomers are present in the crystal. The geometry around the palladium atoms is distorted square-planar, with the larger distortion from planarity at Pd(1) (coordination plane rms 0.1113 A˚, plane 1) than at Pd(2) [plane 2; rms 0.0277 A˚]. The angles at palladium are close to the ideal 90°, with the largest distortions, in the absence of the strain due to the chelate ring, corresponding to (22) (a) Clement, S.; Aly, S. M.; Bellows, D.; Fortin, D.; Strohmann, C.; Guyard, L.; Abd-El-Aziz, A. S.; Knorr, M.; Harvey, P. D. Inorg. Chem. 2009, 48, 4118. (b) Evrard, D.; Groison, K.; Decken, A.; Mugnier, Y. P.; Harvey, D. Inorg. Chim. Acta 2006, 359, 2608. (c) Braun, T.; Steffen, A.; Schorlemer, V.; Neumann, B.; Stammler, H. J. Chem. Soc., Dalton Trans. 2005, 3331. (d) Stockland, R. A.; Janka, M.; Hoel, G. R.; Rath, N. P.; Anderson, G. K. Organometallics 2001, 20, 5212. (e) Neve, F.; Ghedini, M.; Tiripicchio, A.; Ugozzoli, F. Organometallics 1992, 11, 795–801. (f) Kubiak, C. P.; Eisenberg, R. J. Am. Chem. Soc. 1977, 99, 6129.

the P(1)-Pd(1)-Cl(1) [93.69(3)°] and P(3)-Pd(2)-Cl(2) [92.77(3)°] bond angles. Consequent upon the spiral arrangement of the dpppe ligands, the dihedral angle between the coordination planes is 48.2°, and these form angles of 67.6° (plane 1) and 65.1° (plane 2) with the metalated phenyl ring. The Pd-C [2.012(3) and 2.015(3) A˚] and Pd-Cl [2.4042(8) and 2.4043(7) A˚] bond distances are within the expected values.23 The Pd-P bond lengths [2.3240(7)-2.3580(8) A˚] are longer than the Pd-P(trans to nitrogen) bond length but similar to the values found in complex 13a (vide infra) and in other related complexes.23,24 The metalated ring is planar (rms 0.0334) (plane 3), but the geometry of the ligand is distorted by the iminic carbon atoms (C7 and C14) above the plane (deviations of 0.284 and 0.278 A˚, respectively). These deviations give the ligand a butterfly wings configuration with the phenyl rings with the crown ethers folded to the phenyl ring 22.7° and 27.9°. Hence, the products resulting from the reaction of 2a with the long-chain diphosphines, dppb, dpppe, and dpph, is strongly influenced by two factors: the length of the alkyl chain between the two phosphorus atoms and the relative palladium atom/diphosphine molar ratio. Thus, three different products may be formulated (see Figure 3): (i) tetranuclear complexes in which two diphosphine ligands are bridging two different dicyclometalated moieties (structure of type A); (ii) dinuclear complexes with chelating diphosphine ligands (structure of type B); (iii) dinuclear compounds in which the phosphine coordinates to two palladium atoms bonded to the same ligand (structure of type C). In order to clarify the influence of these factors on the structural characteristics of the complexes, we carried out the reaction of 2a with the diphosphines in different molar ratios and followed the experiment by 31P{1H} NMR spectroscopy (see Table 3). (23) (a) Granell, J.; Sales, J.; Vilarrasa, J.; Declercq, J. P.; Germain, G.; Miravitlles, C.; Solans, X. J. Chem. Soc., Dalton Trans. 1983, 2441. (b) Takenaka, K.; Minakawa, M.; Uozumi, Y. J. Am. Chem. Soc. 2005, 127, 12273. (c) Albert, J.; Granell, J.; Moragas, R.; Sales, J.; Font-Bardia, M.; Solans, X. J. Organomet. Chem. 1995, 494, 95. (24) Granell, J.; Sainz, D.; Sales, J.; Solans, X.; Font-Altaba, M. J. Chem. Soc., Dalton Trans. 1986, 1785.

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Figure 3. Possible products of the reactions between complex 2a and diphosphines Ph2P(CH2)nPPh2 (n = 1-6). Table 3. Assignment of the 31P{1H} NMR Data for the Products (pure compounds or mixtures) of the Reactions between 2a and Ph2P(CH2)nPPh2 (n = 1-6) palladium/diphosphine molar ratio diphosphine ligand

2:1

Ph2PCH2PPh2 (dppm) Ph2P(CH2)2PPh2 (dppe)

A: 33.7s [Mixture 1 A þ 2 B] A: 63.50s B: 59.00d, 42.20d [Mixture 5 A þ 1 B þ 1 C] A: 35.20s B: 17.81d, -6.95d C: 11.80s [Mixture 1 A þ 1 C] A: 29.27s C: 10.20s C: 12.30s C: 13.10s

Ph2P(CH2)3PPh2 (dppp)

Ph2P(CH2)4PPh2 (dppb) Ph2P(CH2)5PPh2 (dpppe) Ph2P(CH2)6PPh2 (dpph)

Ligand dppm showed a straightforward behavior; thus reaction with 2a in a palladium/diphosphine 2:1 or 1:1 ratio exclusively gave compounds 7a (type A) and 8a (type B), respectively. With dppe a slightly more complicated behavior was found; the reaction in a 2:1 molar ratio afforded a mixture of complexes with the A and B structure; however the reaction in a 1:1 ratio yielded only compound 9a, with a type B structure, which was in accordance with the high stability of five-membered chelate rings. Surprisingly, the reaction between 2a and dppp, regardless of the relative molar ratio used, gave a mixture that contained the three type of complexes: A, B, and C (see Table 3). In the case of dppb, a palladium/dppb 2:1 molar ratio gave rise to complexes with the A and C structure; however when a 1:1 molar ratio was used, only compound 10a (type C structure) was present in the solution. The products of the reaction between 2a and the long-chain diphosphines dpppe and dpph did not depend on the relative molar ratio used, and only complexes with the type C structure (11a and 12a, respectively) were detected in solution. Two conclusions may be drawn from these observations. On one hand, the tendency of diphosphines to act as intermolecularly bridging ligands or as chelating ligands increases and decreases, respectively, with phosphine chain length; very long chain diphosphines display intramolecular coordination. On the other hand, this behavior may be rationalized in terms of the so-called “effective local concentration” and steric factors. The “effective concentration” is a concept used to explain the entropy role in the chelate effect, so once the first phosphorus atom of the phosphine is bonded to the palladium atom, the local concentration of the second phosphorus in the neighborhood of the metal is greater when the carbon chain is short, the coordination of the second phosphorus is more likely, and the equilibrium constant is

1:1 B: 6.54d, -28.60d B: 59.00d, 42.20d [Mixture 1 A þ 2 B þ 1 C] A: 35.20s B: 17.81d, -6.95d C: 11.80s C: 10.20s

greater. The steric factor refers to the unfavorable thermodynamic effect due to the ring strain generated when large chelate rings are formed.

3. Experimental Section 3.1. General Procedures. Solvents were purified by standard methods.25 Chemicals were reagent grade and were purchased from Aldrich and Acros. Microanalyses were carried out using a Carlo Erba elemental analyzer, model 1108. IR spectra were recorded KBr discs on a Perkin-Elmer 1330. NMR spectra were obtained as CDCl3 or CD3SOCD3 solutions and referenced to SiMe4 (1H, 13C{1H}) or 85% H3PO4 31P{1H}) and were recorded on a Bruker AC-200F spectrometer. All chemical shifts were reported downfield from standards. The FAB mass spectra were recorded using a Quatro mass spectrometer with a Cs ion gun; 3-nitrobenzyl alcohol (3-NBA) was used as the matrix. 3.2. Synthesis of the Ligand and Complexes. 1,4-[C(H)dN{9,10-(C8H16O5)C6H3}]2C6H4 (a). 1,4-(COH)2C6H4 (0.30 g, 2.20 mmol) and NH2[9,10-(C8H16O5)]C6H3 (1.28 g, 4.50 mmol) were added to 20 cm3 of dry chloroform. The mixture was heated under reflux in a Dean-Stark apparatus for 12 h. After cooling to room temperature, the solvent was evaporated to give a yellow solid. Yield: 95%. Anal. Found: C, 64.9; H, 6.8; N, 4.2. C36H44N2O10 requires C, 65.0; H, 6.7; N, 4.2. IR: ν(CdN), 1616 m cm-1. 1H NMR (200 MHz, CDCl3, δ ppm, J Hz): 8.53 [s, 2H, Hi]; 7.98 [s, 4H, H2/H3/H5/H6]; 6.92 [d, 2H, H11, 3J(H11H12) = 8.3]; 6.90 [d, 2H, H8, 4J(H8H12) = 2.0]; 6.86 [dd, 2H, H12]. 13 C{1H} NMR (50.28 MHz, CDCl3, δ ppm): 157.6 (CdN); 138.5 (C1, C4); 128.9 (C2, C3, C5, C6); 149.6, 148.1, 145.4 (C7, C9, C10); 114.4, 113.1, 107.9 (C8, C11, C12). FAB-MS: m/z = 663 [M]þ. [Pd2{1,4-[C(H)dN{9,10-(C8H16O5)C6H3}]2C6H2-C2,C5,N, N0 }(μ-O2CMe)2]n (1a). A pressure tube containing 1,4-[C(H)dN{9,10-(C8H16O5)C6H3}]2C6H4 (a) (0.15 g, 0.22 mmol), (25) Armarego, W. L. F.; Chai, C. L. L. Purification of Laboratory Chemicals, 5th ed.; Butterworth-Heinemann: Bodmin, 2003.

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palladium(II) acetate (0.10 g, 0.44 mmol), and 10 cm3 of dry chloroform was sealed under argon. The resulting mixture was heated at 50 °C for 96 h. After cooling to room temperature the solution was filtered through Celite to remove the black palladium formed. The solvent was removed under vacuum, and the precipitate formed was recrystallized from acetone, filtered off, washed with acetone and diethyl ether, and dried under vacuum to give complex 1a as a red solid. Yield: 77%. Anal. Found: C, 50.0; H, 4.9; N, 2.8. C40H48N2O12Pd2 requires: C, 49.9; H, 5.0; N, 2.9. IR: ν(CdN), oc.; νas(COO), 1574s cm-1; νs(COO), 1411s cm-1. [Pd2{1,4-[C(H)dN{9,10-(C8H16O5)C6H3}]2C6H2-C2,C5,N, N0 }(μ-Cl)2]n (2a). A solution of 1a (0.15 g, 0.08 mmol) in acetone (10 cm 3) was treated with a saturated solution of N tBu4Cl in ca. 20 cm 3 of water. The red precipitate formed was filtered off, washed with water, and dried under vacuum. Yield: 92%. Anal. Found: C, 45.4; H, 4.6; N, 3.0. C36H42N2O10Pd2Cl2 requires: C, 45.6; H, 4.4; N, 3.0. IR: ν(CdN), 1599 m cm-1. Compound 3a was synthesized as a dark orange solid following a similar procedure to that for 2a but using NtBu4Br. [Pd2{1,4-[C(H)dN{9,10-(C8H16O5)C6H3}]2C6H2-C2,C5,N, N0 }(μ-Br)2]n (3a). Yield: 85%. Anal. Found: C, 41.5; H, 4.1; N, 2.7. C36H42N2O12Br2Pd2 requires: C, 41.8; H, 4.0; N, 2.7. IR: ν(CdN), 1599 m cm-1. 1H NMR (200 MHz, DMSO-d6, δ ppm, J Hz): 8.38 [s, 2H, Hi]; 7.92 [s, 2H, H3/H6]; 6.90 [m, 6H, H8, H11, H12]. [Pd2{1,4-[C(H)dN{9,10-(C8H16O5)C6H3}]2C6H2-C2,C5,N, (4a). Acetilacetonate N0 }{MeC(O)CHC(O)Me-O,O0 }2] thallium(I) (9.7 mg, 0.032 mmol) was added to a suspension of 2a (30 mg, 0.016 mmol) in acetone (5 cm3). The mixture was stirred for 24 h. The solution was filtered through Celite to eliminate the TlCl precipitate, and then the solvent was removed to give an orange solid, which was recrystallized from dichloromethane/hexane, filtered off, and dried in vacuo. Yield: 75%. Anal. Found: C, 51.5; H, 5.3; N, 2.6. C46H58N2O14Pd2 requires: C, 51.4; H, 5.4; N, 2.6. IR: ν(CdN), 1600sh, m cm-1; ν(C-O), 1577s, 1395s cm-1; ν(C-C), 1509s, 1264s cm-1. 1H NMR (200 MHz, CDCl3, δ ppm, J Hz): 8.18 [s, 2H, Hi]; 7.60 [s, 2H, H3/H6]; 7.16 [d, 2H, H8, 4 J(H8H12) = 2.4]; 6.87 [d, 2H, H11, 3J(H11H12) = 8.8]; 6.95 [dd, 2H, H12]; 5.36 [s, 2H, Hacac]; 2.09 [s, 6H, Meacac]; 1.89 [s, 6H, Meacac]. 13C{1H} NMR (50.28 MHz, CDCl3, δ ppm): 188.3, 185.8 (MeCOCHCOMe); 173.3 (CdN); 151.8 (C1, C4); 148.9 (C2, C5); 148.6, 147.1, 141.9 (C7, C9, C10); 129.5 (C3, C6); 114.4, 113.2, 110.6 (C8, C11, C12); 100.3 (MeCOCHCOMe); 28.1, 27.5 (MeCOCHCOMe). FAB-MS: m/z = 1073 [M]þ; 975 [M - (acac)]þ. [Pd2{1,4-[C(H)dN{9,10-(C8H16O5)C6H3}]2C6H2-C2,C5,N, N0 }(Cl)2(PPh3)2] (5a). PPh3 (8.4 mg, 0.032 mmol) was added to a suspension of 2a (30 mg, 0.016 mmol) in dicloromethane (5 cm3). The mixture was stirred for 24 h, and the orange complex precipitated out by addition of hexane, filtered off, washed with diethyl ether, and dried in vacuo. Yield: 60%. Anal. Found: C, 58.6; H, 4.8; N, 1.7. C72H72N2O10P2Cl2Pd2 requires: C, 58.8; H, 4.9; N, 1.9. IR: ν(CdN), 1589 m cm-1. 1H NMR (200 MHz, CDCl3, δ ppm, J Hz): 7.30 [d, 2H, Hi, 4 J(PHi)= 6.4]; 7.05 [d, 2H, H8, 4J(H8H12) = 2.4]; 6.76 [d, 2H, H11, 3J(H11H12) = 8.8]; 6.65 [dd, 2H, H12]; 6.30 [d, 2H, H3/H6, 4J(PH3)= 5.9]. 13C{1H} NMR (50.28 MHz, CDCl3, δ ppm): 174.0 [d, CdN, 3JPC = 1.4 Hz]; 152.9 (C1, C4); 149.1 (C2, C5); 138.1br (C3, C6); 148.2, 147.9, 143.3 (C7, C9, C10); 115.0, 113.1, 111.7 (C8, C11, C12); P-phenyl: 135.3 [d, Co, 2 JPC0 = 11.4 Hz]; 128.1 [d, Cm, 3JPCm = 10.6]; 130.7 [br, Cp]; 130.9 [d, Ci, 1JPCi = 49.0]. 31P{1H} NMR (80.96 MHz, CDCl3, δ ppm): 42.7s. FAB-MS: m/z = 1470 [M]þ; 1436 [M - Cl]þ; 1400 [M - 2Cl]þ; 1173 [M - Cl - phosphine]þ; 1137 [M - 2Cl - phosphine]þ; 1031 [M - 2Cl - phosphine Pd]þ; 766 [(L - 2H)Pd]þ.

Fern andez et al. Compound 6a was synthesized following a similar procedure to that for 5a as a yellow solid but using P(p-OMeC6H4)3. [Pd2{1,4-[C(H)dN{9,10-(C8H16O5)C6H3}]2C6H2-C2,C5,N, N0 }(Cl)2{P(p-OMe-C6H4)3}2] (6a). Yield: 58%. Anal. Found: C, 56.4; H, 5.5; N, 1.8. C78H90N2O16P2Cl2Pd2 requires: C, 56.5; H, 5.4; N, 1.7. IR: ν(CdN), 1593s cm-1. 1H NMR (200 MHz, CDCl3, δ ppm, J Hz): 7.35 [d, 2H, Hi, 4J(PHi)= 6.4]; 7.06 [d, 2H, H8, 4J(H8H12) = 2.4]; 6.77 [d, 2H, H11, 3J(H11H12) = 8.8]; 6.69 [dd, 2H, H12]; 6.31 [d, 2H, H3/H6, 4 J(PH3) = 5.9]. P-phenyl: δ(p-MeO-C6H4)3P; 7,63 [dd, 1H, Ho, 3J(HoHm) = 8.8, 3J(PHo) = 11,2]; 6.88 [dd, 1H, Hm, 4 J(PHm) = 1.5]; 3.81 [s, 3H, (p-MeO-C6H4)3P]. 13C{1H} NMR (50.28 MHz, CDCl3, δ ppm): 174.5 [d, CdN, 3JPC = 2.1 Hz]; 152.6 (C1, C4); 149.3 [d, C2, C5, 2J(PC2) = 3.5]; 148.4, 148.2, 143.4 (C7, C9, C10); 138.1 [d, C3, C6, 2J(PC3) = 9.9]; 115.3, 113.3, 111.7 (C8, C11, C12); P-phenyl: 136.9 [d, Co, 2JPCo = 12.8 Hz]; 113.6 [d, Cm, 3JPCm = 12.1]; 161.5 [d, Cp, 4JPCp = 2.8]; 122.3 [d, Ci, 1JPCi = 57.5]. 31P{1H} NMR (80.96 MHz, CDCl3, δ ppm): 38.9s. FAB-MS: m/z = 1653 [M]þ; 1615 [M Cl]þ; 1580 [M - 2Cl]þ; 1263 [M - Cl - phosphine]þ; 1227 [M - 2Cl - phosphine]þ; 1121 [M - 2Cl - phosphine - Pd]þ. [{Pd2[1,4-{C(H)dN[9,10-(C8H16O5)C6H3]}2C6H2-C2,C5,N, N0 ](Cl)2}2(μ-Ph2PCH2P-Ph2)2] (7a). PPh2(CH2)PPh2 (6.2 mg, 0.016 mmol) was added to a suspension of 2a (30 mg, 0.016 mmol) in acetone (5 cm3). The mixture was stirred for 12 h, and the orange complex precipitated, was filtered off, and was dried in vacuo. Yield: 93%. Anal. Found: C, 54.9; H, 4.8; N, 1.9. C124H132N4O20P4Cl4Pd4 requires: C, 55.3; H, 4.9; N, 2.1. IR: ν(CdN), 1586 m cm-1. 1H NMR (200 MHz, CDCl3, δ ppm, J Hz): 7.06 [d, 2H, H8, 4J(H8H12) = 2.4]; 6.85 [d, 2H, H11, 3 J(H11H12) = 8.8]; 6.63 [dd, 2H, H12]; 5.78 [d, 2H, H3/H6, 4 J(PH3) = 6.4]; 4.98 [t, 2H, PCH2P, 2J(PH) = 13.2]. 31P{1H} NMR (80.96 MHz, CDCl3, δ ppm): 33.7s. FAB-MS: m/z = 2587 [M - 2Cl]þ; 2064 [M - 3Cl - phosphine - Pd]þ; 1295 [(L-2H)Pd2Cl2phosphine]þ; 1153 [(L-2H)PdClphosphine]þ. [Pd2{1,4-[C(H)dN{9,10-(C8H16O5)C6H3}]2C6H2-C2,C5,N, N0 }(Ph2PCH2Ph2-P,P0 )2][Cl]2 (8a). Ph2PCH2PPh2 (dppm, 24 mg, 0.032 mmol) was added to a suspension of 2a (30 mg, 0.016 mmol) in acetone (5 cm3). The mixture was stirred for 24 h, and the orange solid was precipitated out by addition of water, filtered off, and dried in vacuo. Yield: 86%. Anal. Found: C, 61.1; H, 5.3; N, 1.5. C92H98N2O10P4Cl2Pd2 requires: C, 61.4; H, 5.4; N, 1.6. IR: ν(CdN), 1584sh,w cm-1. 1H NMR (200 MHz, CDCl3, δ ppm, J Hz): 6.46 [d, 2H, H8, 4J(H8H12) = 2.4]; 6.33 [dd, 2H, H3/H6, 4J(PH3) = 8.8, 5.4]; 5.93 [t, 4H, PCH2P, 2J(PH) = 6.3]. 31P{1H} NMR (80.96 MHz, CDCl3, δ ppm): 6.54d, -28.60d, 3J(PP) = 16.94. FAB-MS: m/z = 1643 [M]þ; 1294 [M - phosphine]þ; 1153 [M - Cl - phosphine Pd]þ. Compound 9a was synthesized as a yellow solid following a similar procedure to that for 8a but using Ph2P(CH2)2PPh2 (dppe). [Pd2{1,4-[C(H)dN{9,10-(C8H16O5)C6H3}]2C6H2-C2,C5,N, N0 }{Ph2P(CH2)2PPh2-P,P0 }2][Cl]2 (9a). Yield: 92%. Anal. Found: C, 62.2; H, 5.5; N, 1.7. C90H94N2O10P4Cl2Pd2 requires: C, 62.0; H, 5.4; N, 1.6. IR: ν(CdN), 1586 m cm-1. 1H NMR (200 MHz, CDCl3, δ ppm, J Hz): 6.31 [d, 2H, H11, 3 J(H11H12) = 8.8]; 6.22 [d, 2H, H8, 4J(H8H12) = 2.4]; 6.12 [dd, 2H, H3, H6, 4J(PH3) = 8.8, 5.4]; 2.30 [m, 8H, PCH2]. 31 P{1H} NMR (80.96 MHz, CDCl3, δ ppm): 59.0d, 42.2d, 3 J(PP) = 25.1. FAB-MS: m/z = 1672 [M]þ; 1707 [M][Cl]þ; 1274 [M - phosphine][Cl]þ; 1167 [M - phosphine - Pd]þ; 836 [M]þ2. [Pd2 {1,4-[C(H)dN{9,10-(C8 H16O 5)C6H 3}]2C 6H 2-C2,C5}(Cl)2{μ-Ph2P(CH2)4PPh2}2] (10a). PPh2(CH2)4PPh2 (dppb, 27 mg, 0.064 mmol) was added to a suspension of 2a (30 mg, 0.016 mmol) in dicloromethane (5 cm3). The mixture was stirred for 24 h, and the orange complex was precipitated out by addition of hexane, filtered off, and dried in vacuo. Yield: 40%. Anal. Found: C, 61.1; H, 5.3; N, 1.5.

Article C92H 98N 2O10P4Cl 2Pd2 requires: C, 61.4; H, 5.4; N, 1.6. IR: ν(CdN), 1609 m cm -1. 1H NMR (200 MHz, CDCl3, δ ppm, J Hz): 9.01 [s, 2H, Hi ]. 31P{1H} NMR (80.96 MHz, CDCl3, δ ppm): 10.2s. FAB-MS: m/z = 1763 [M - Cl]þ; 1337 [M - Cl phosphine]þ; 1301 [M - 2Cl - phosphine]þ; 1195 [M - 2Cl phosphine - Pd]þ. Compound 11a was synthesized as a yellow solid, following a similar procedure to that for 10a, but using Ph2P(CH2)5PPh2 (dpppe). [Pd 2{1,4-[C(H)dN{9,10-(C8H 16 O5 )C 6H 3}]2C6 H2 -C2,C5}(Cl)2{μ-Ph2P(CH2)5PPh2}2] (11a). Yield: 69%. Anal. Found: C, 61.5; H, 5.8; N, 1.7. C94H102N2O10P4Cl2Pd2 requires: C, 61.8; H, 5.6; N, 1.5. IR: ν(CdN), 1607w cm-1. 1H NMR (200 MHz, CDCl3, δ ppm, J Hz): 9.17s [s, 2H, Hi]; 7.00 [dd, 2H, H12, 4 J(H8H12) = 2.4]; 6.88 [d, 2H, H11, 3J(H11H12) = 8.8]. 31 P{1H} NMR (80.96 MHz, CDCl3, δ ppm): 12.3s. FAB-MS: m/z = 1827 [M]þ; 1792 [M - Cl]þ; 1350 [M - Cl - phosphine]þ; 1243 [M - Cl - phosphine - Pd]þ; 1209 [M - 2Cl - phosphine Pd]þ. Compound 12a was synthesized as an orange solid, following a similar procedure to that for 10a, but using Ph2P(CH2)6PPh2 (dpph). [Pd 2{1,4-[C(H)dN{9,10-(C8H 16 O5 )C 6H 3}]2C6 H2 -C2,C5}(Cl)2{μ-Ph2P(CH2)6P-Ph2}2] (12a). Yield: 62%. Anal. Found: C, 61.6; H, 5.7; N, 1.4. C96H106N2O10P4Cl2Pd2 requires: C, 62.1; H, 5.7; N, 1.5. IR: ν(CdN), 1608w cm-1. 1H NMR (200 MHz, CDCl3, δ ppm, J Hz): 8.93 [s, 2H, Hi]; 6.90 [dd, 2H, H12, 4 J(H8H12) = 2.4]; 6.83 [d, 2H, H11, 3J(H11H12) = 8.8]. 31 P{1H} NMR (80.96 MHz, CDCl3, δ ppm): 13.1s. 13C{1H} NMR (50.28 MHz, CDCl3, δ ppm): 159.2 (CdN); 149.6 (C1, (26) Sheldrick, G. M. A short history of SHELX. Acta Crystallogr. 2008, A64, 112–122.


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C4); 148.8 (C2, C5); 139.9 [br, C3, C6]; 147.9, 144.2, 143.7 (C7, C9, C10); 114.5, 111.3, 111 (C8, C11, C12). FAB-MS: m/z = 1855 [M]þ; 1820 [M - Cl]þ; 1386 [M - Cl - phosphine]þ; 1257 [M - Cl - phosphine - Pd]þ. 3.3. X-ray Crystallographic Study. Three-dimensional, roomtemperature X-ray data were collected on a Bruker Smart 1k CCD diffractometer using graphite-monochromated Mo KR radiation. All the measured reflections were corrected for Lorentz and polarization effects and for absorption by semiempirical methods based on symmetry-equivalent and repeated reflections. The structures were solved by direct methods and refined by full matrix least-squares on F2. Hydrogen atoms were included in calculated positions and refined in riding mode. In general, the atoms corresponding to the crown ether chain showed less than ideal ellipsoids, indicating a possible disorder problem. C(13), C(14), C(15), C(16), O(2), and O(3) atoms in the crystal of 5a also showed large ellipsoids; however, the models used to take into account of this disorder did not improve appreciably the final results. The structure solution and refinement were carried out using the program package SHELX-97.26

Acknowledgment. We thank the Xunta de Galicia (Project INCITE 10PXIB209226PR; and Grupos Consolidados PGIDIT04PXI10301IF and INCITE07PXI103083ES) for financial support. Supporting Information Available: X-ray crystallographic data and tables giving atomic coordinates, displacement parameters, and bond distances and angles for 5a, 11a, and 13a [CCDC no. 789476 (5a), 789477 (11a)]. This material is available free of charge via the Internet at http://pubs.acs.org.

Dimetalated Crown Ether Schiff Base Palladacycles. Influence of the

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