Supramolecular Organoplatinum (IV) Chemistry: Sequential

May 27, 2009 - Muhieddine A. Safa , Anwar Abo-Amer , Aneta Borecki , Benjamin F. T. Cooper , and Richard J. Puddephatt. Organometallics 2012 31 (7), ...
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Organometallics 2009, 28, 3754–3762 DOI: 10.1021/om900272w

Supramolecular Organoplatinum(IV) Chemistry: Sequential Introduction of Amide Hydrogen Bonding Groups Richard H. W. Au, Michael C. Jennings, and Richard J. Puddephatt* Department of Chemistry, University of Western Ontario, London, Ontario, Canada N6A 5B7 Received April 9, 2009

The self-assembly of organoplatinum(IV) complexes to give supramolecular polymers and network materials is described, using the ligand ethyl 50 -[(ethoxycarbonyl)amino]-2,20 -bipyridine5-carboxylate (1), which contains the EtOC(dO)NH- hydrogen bonding donor group. Ligand 1 reacts with [Pt2Me4(μ-SMe2)2] to give [PtMe2(1)] (2), which forms a supramolecular polymer in the solid state through formation of intermolecular NH 3 3 3 OdC hydrogen bonds with further selfassembly to a sheet structure through π-stacking. Oxidative addition of bromomethyl compounds RCH2Br to complex 2 gave the corresponding organoplatinum(IV) complexes [PtBrMe2(CH2R)(1)], in which the group R could contain a further hydrogen bonding carboxamide group, and the organoplatinum(IV) complexes with two hydrogen-bond donor groups could form either supramolecular polymers or sheet structures through hydrogen bonding. As well as the anticipated NH 3 3 3 OdC hydrogen bonds, some complexes formed hydrogen bonds to solvent molecules NH 3 3 3 O (solvent) or to coordinated bromide NH 3 3 3 BrPt or a combination of π-stacking with CH 3 3 3 Br hydrogen bonding. New forms of self-assembly in organometallic compounds were identified, one involving polymerization through intermolecular NH 3 3 3 Br 3 3 3 HN supramolecular chelation and one involving a combination of NH 3 3 3 OdC and CH 3 3 3 Br hydrogen bonding along with π-stacking to form a network composed of multiply intercalated sheets.

Introduction The crystal engineering of organometallic compounds has developed more slowly than with either organic or coordination compounds.1,2 This is natural, because many metalcarbon bonds are reactive toward the types of functional groups, such as the protic groups used as hydrogen bond donors, which are commonly used in self-assembly and crystal engineering.1 For example, self-assembly of platinum(II) and palladium(II) coordination complexes has been studied extensively, but there are fewer papers on *To whom correspondence should be addressed. E-mail: pudd@ uwo.ca. (1) (a) Haiduc, I.; Edelmann, F. T. Supramolecular Organometallic Chemistry; Wiley-VCH: Weinheim, Germany, 1999. (b) Natale, D.; Mareque Rivas, J. C. Chem. Commun. 2008, 425. (c) Laguna, A. Ed. Modern Supramolecular Gold Chemistry; Wiley-VCH: Weinheim, Germany, 2008.(d) Braga, D.; Giaffreda, S. L.; Grepioni, F.; Pettersen, A.; Maini, L.; Curzi, M.; Polito, M. Dalton Trans. 2006, 1249. (2) (a) Desiraju, G. R. Crystal Engineering-The Design of Organic Solids; Elsevier: Amsterdam, 1989. (b) Etter, M. C. Acc. Chem. Res. 1990, 23, 120. (c) Atwood, J. L.; Steed, J. W. Encyclopedia of Supramolecular Chemistry; Marcel Dekker: New York, 2004. (d) Kitagawa, S.; Uemura, K. Chem. Soc. Rev. 2005, 34, 109. (e) Tiekink, E. R. T.; Vittal, J. J. Frontiers of Crystal Engineering; Wiley: Chichester, U.K., 2006. (f) Beatty, A. M. Coord. Chem. Rev. 2003, 248, 131. (g) Brammer, L. Chem. Soc. Rev. 2004, 33, 476. (3) (a) Smith, M. B.; Dale, S. H.; Coles, S. J.; Gelbrich, T.; Hursthouse, M. B.; Light, M. E.; Horton, P. N. CrystEngComm 2007, 9, 165. (b) Zhao, C. Q.; Jennings, M. C.; Puddephatt, R. J. Inorg. Chim. Acta 2008, 361, 3301. (c) Fisher, M. G.; Gale, P. A.; Light, M. E.; Quesada, R. CrystEngComm 2008, 10, 1180. (d) Kieltyka, R.; Englebienne, P.; Fakhoury, J.; Autexier, C.; Moitessier, N.; Sleiman, H. F. J. Am. Chem. Soc. 2008, 130, 10040. pubs.acs.org/Organometallics

self-assembly of the corresponding organometallic complexes.1-4 However, alkylplatinum(IV) groups are typically inert toward protonolysis or oxidation, and so organoplatinum(IV) complexes can provide a paradigm for the selfassembly of complex structures from alkyl derivatives of transition metals, and the chemistry is no more difficult than with platinum(IV) coordination complexes.5-9 For example, (4) (a) Zheng, Y. R.; Yang, H. B.; Northrop, B. H.; Ghosh, K.; Stang, P. J. Inorg. Chem. 2008, 47, 4706. (b) Mehendale, N. C.; Lutz, M.; Spek, A. L.; Klein Gebbink, R. J. M.; van Koten, G. J. Organomet. Chem. 2008, 693, 2971. (c) Addicott, C.; Das, N.; Stang, P. J. Inorg. Chem. 2004, 43, 5335. (d) Gianneschi, N. C.; Tiekink, E. R. T.; Rendina, L. M. J. Am. Chem. Soc. 2000, 122, 8474. (e) Crisp, M. G.; Rendina, L. M. Can. J. Chem. 2009, 87, 212. (5) (a) Hoseini, S. J.; Mohamadikish, M.; Kamali, K.; Heinemann, F. W.; Rashidi, M. Dalton Trans. 2007, 1697. (b) Zhang, F.; Jennings, M. C.; Puddephatt, R. J. Chem. Commun. 2007, 1496. (c) Vetter, C.; Wagner, C.; Kaluderovic, G. N.; Paschke, R.; Steinborn, D. Inorg. Chim. Acta 2009, 362, 189. (6) (a) Fraser, C. S. A.; Jenkins, H. A.; Jennings, M. C.; Puddephatt, R. J. Organometallics 2000, 19, 1635. (b) Fraser, C. S. A.; Jennings, M. C.; Puddephatt, R. J. Chem. Commun. 2001, 1310. (c) Fraser, C. S. A.; Jennings, M. C.; Puddephatt, R. J. Chem. Commun. 2002, 1224. (d) Fraser, C. S. A.; Eisler, D. J.; Puddephatt, R. J. Polyhedron 2005, 25, 266. (7) (a) Au, R. H. W.; Jennings, M. C.; Puddephatt, R. J. Dalton Trans. 2009, 3519. (b) Au, R. H. W.; Jennings, M. C.; Puddephatt, R. J. Eur. J. Inorg. Chem. 2009, 1526. (c) Au, R. H. W.; Fraser, C. S. A.; Eisler, D. J.; Jennings, M. C.; Puddephatt, R. J. Organometallics 2009, 28, 1719. (8) Mishur, R. J.; Zheng, C.; Gilbert, T. M.; Bose, R. N. Inorg. Chem. 2008, 47, 7972. (9) (a) Canty, A. J., Ed. Comprehensive Organometallic Chemistry III; Elsevier: Amsterdam, 2007; Vol. 8. (b) Rashidi, M.; Momemi, B. J. Organomet. Chem. 1999, 574, 286. (c) Hill, R. H.; Puddephatt, R. J. J. Am. Chem. Soc. 1985, 107, 1218. (d) Zhang, F.; Jennings, M. C.; Puddephatt, R. J. Chem. Commun. 2007, 1498.

Published on Web 05/27/2009

r 2009 American Chemical Society

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Scheme 1. Organoplatinum(IV) Complexes with Amide Substituents and Their Supramolecular Structures

amide groups have been incorporated into organoplatimum (IV) complexes by oxidative addition of the carbon-bromine bonds of compounds containing amide units to the complex [PtMe2(bu2bipy)] (bu2bipy = 4,40 -di-tert-butyl2,20 -bipyridine), as shown by the example using t-BuC(dO)NHC6H4CH2Br in Scheme 1.7 The amide groups then take part in self-assembly by either NH 3 3 3 OdC or NH 3 3 3 BrPt hydrogen bonding to give supramolecular polymers A and B, respectively (Scheme 1).7 This paper describes a new approach to the incorporation of amide groups into organoplatinum(IV) complexes by introducing the amide group into the 2,20 -bipyridine ligand. Several such derivatives have been reported for use in compounds as diverse as ruthenium(II) complexes for use as photosensitizers to palladium(II) complexes for use as anion sensors.1-3,10 They have obvious promise for application in organoplatinum(IV) chemistry because it is well-known that complexes of the type [PtMe2(LL)], where LL is a derivative of 2,20 -bipyridine, are very reactive in oxidative addition (e.g., Scheme 1) and give robust organoplatinum(IV) complexes.11 Bipyridine derivatives with two amide groups can give insoluble complexes; therefore, the unsymmetrical monoamide derivative ethyl 50 -[(ethoxycarbonyl)amino]-2,20 -bipyridine-5-carboxylate, 5-EtO2C-2,20 -C5H3N-C5H3N-50 -NHCO2Et (1), was chosen for study.12 (10) (a) Kaes, C.; Katz, A.; Hosseini, M. W. Chem. Rev. 2000, 100, 3553. (b) Albrecht, M. Chem. Rev. 2001, 101, 3456. (c) Newkome, G. R.; Patri, A. K.; Holder, E.; Schubert, U. S. Eur. J. Org. Chem. 2004, 235. (d) Benniston, A. C.; Harriman, A. Coord. Chem. Rev. 2008, 252, 2528. (11) (a) Rendina, L. M.; Puddephatt, R. J. Chem. Rev. 1997, 97, 1735. (b) Monaghan, P. K.; Puddephatt, R. J. J. Chem. Soc., Dalton Trans. 1988, 595. (12) (a) Newkome, G. R.; Gross, J.; Patri, A. K. J. Org. Chem. 1997, :: 62, 3013. (b) Janiak, C.; Deblon, S.; Wu, H. P.; Kolm, M. J.; Klufers, P.; Piotrowski, H.; Mayer, P. Eur. J. Inorg. Chem. 1999, 1507. (c) Ishida, H.; Kyakuno, M.; Oishi, S. Biopolymers (Pept. Sci.) 2004, 76, 69. (d) Abdolmaleki, A. Polym. Degrad. Stab. 2007, 92, 292.

Results and Discussion The Dimethylplatinum(II) Complex [PtMe2(5-EtO2C-2,20 C5H3N-C5H3N-50 -NHCO2Et)] (2). The reaction of ligand 1 with the complex [Pt2Me4(μ-SMe2)2]13 gave the dimethylplatinum(II) derivative [PtMe2(1)] (2), according to Scheme 2. Complex 2 was isolated as a red solid that was soluble in acetone or dichloromethane, and so it was suitable for further functionalization. Because the ligand 1 is unsymmetrical, the 1H NMR spectrum of complex 2 contained two equal-intensity methylplatinum resonances at δ 1.12 (2J(PtH) = 84 Hz) and 1.19 (2J(PtH) = 86 Hz). The structure of complex 2 is shown in Figure 1 and is typical of square-planar complexes of formula [PtMe2(NN)], with NN = 2,20 -bipyridine derivative.14 The intermolecular NH 3 3 3 OdC interaction between the carbamate NH group (H-bond donor) and ester carbonyl group (H-bond acceptor) of complex 2 gives a zigzag polymer in the solid state, as shown in Figure 1a. The hydrogen bond (N 3 3 3 O) distance of 2.887(9) A˚ is typical of amide hydrogen bonds.1-7,15 There is also π-stacking of the almost planar molecules of 2, as shown in Figure 1b. The interplanar distance is about 3.3 A˚, but the closest Pt 3 3 3 Pt distance (indicated by a dashed line in Figure 1b) is 4.0 A˚, which is too long for direct metallophilic bonding. The parallel anti arrangement of nearest neighbors is well precedented in stacked square-planar complexes.14 The combination of hydrogen bonding and π-stacking gives (13) (a) Scott, J. D.; Puddephatt, R. J. Organometallics 1983, 2, 1643. (b) Hill, G. S.; Irwin, M. J.; Levy, C. J.; Rendina, L. M.; Puddephatt, R. J. Inorg. Synth. 1997, 32, 149. (c) Achar, S.; Scott, J. D.; Vittal, J. J.; Puddephatt, R. J. Organometallics 1993, 12, 4592. (d) Hill, G. S.; Manojlovic-Muir, L.; Muir, K. W.; Puddephatt, R. J. Organometallics 1997, 16, 525. (14) Achar, S.; Catalano, V. J. Polyhedron 1997, 16, 1555. (15) (a) Desiraju, G. R.; Steiner, T. The Weak Hydrogen Bond: Oxford Science: Oxford, U.K., 1999. (b) Jeffrey, G. A. An Introduction to Hydrogen Bonding; Oxford University Press: Oxford, U.K., 1997. (c) Qin, Z.; Jennings, M. C.; Puddephatt, R. J. Inorg. Chem. 2001, 40, 6220.

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Figure 2. Molecular and partial supramolecular structure of complex 3. Selected bond distances (A˚): Pt-C(1) = 2.06(1), Pt-C(2) = 2.06(1), Pt-C(41) = 1.95(3), Pt-N(11) = 2.16(1), Pt-N(22) = 2.19(1), Pt-Br = 2.526(2). The distance between bipy planes is 3.3 A˚, and the shortest Br 3 3 3 HC contact is BrA 3 3 3 C18 = 3.70 (1) A˚. The symmetry for the neighboring molecule is -x, -y, -z + 2. Scheme 3. Synthesis of the Platinum(IV) Complex 3

Figure 1. Structure of complex 3: (a) hydrogen bonding to give a supramolecular polymer, with the hydrogen bond distance N(21A) 3 3 3 O(32) = 2.887(9) A˚; (b) π-stacking which gives a polymer with planes separated by ca. 3.3 A˚; (c) space-filling model of part of the sheet structure, propagated through H-bonding and π-stacking in the vertical and horizontal directions, respectively. Selected bond distances (A˚): Pt-C(13) = 2.038(9), Pt-C(14) = 2.032(9), Pt-N(1) = 2.094(6), Pt-N(2) = 2.094(8). Scheme 2. Synthesis of Complex 2

rise to a supramolecular corrugated sheet structure, as illustrated in Figure 1c. Model Organoplatinum(IV) Complexes with a Bulky Benzyl Group. When additional amide groups were added by oxidative addition to complex 2, difficulties were encountered in several cases because the products were sparingly soluble. To overcome this problem, bulky tert-butyl groups were used, due to the ability of these groups to solubilize rigid polymers by disrupting the packing forces in the solid state through the motion of twisting and rotation.16 As a model (16) (a) Heo, R. W.; Park, J.-S.; Goodson, J. T.; Claudio, G. C.; Takenaga, M.; Albright, T. A.; Lee, T. R. Tetrahedron 2004, 60, 7225. (b) MacIness, D. Jr.; Funt, B. L. Synth. Met. 1988, 25, 235.

to study the effects of incorporating tert-butyl groups, complex 3 was synthesized (Scheme 3). Complex 3 was formed in high yield, and it was easily soluble in organic solvents such as acetone, tetrahydrofuran, dichloromethane, and chloroform. The 1H NMR spectrum of complex 3 showed that reaction occurred by trans oxidative addition. Thus, there were two methyl platinum resonances at δ 1.47 and 1.55, each with coupling constant 2J(PtH) = 70 Hz, typical of methylplatinum(IV) groups trans to a bipyridine ligand.6,7,9,11 Because the ligand 1 is unsymmetrical, the benzylic PtCH2 protons in complex 3 are diastereotopic and they appeared as an “AB” multiplet with δ 2.83 and 2.87, each with coupling constant 2J(PtH) = 88 Hz. No resonances attributable to the product of cis oxidative addition were present.9 In other benzyl complexes studied below, the “AB” protons were sometimes close to being degenerate and so the coupling constant 2J(HH) = 9 Hz in 3 was not resolved. The structure of complex 3 is shown in Figure 2. The platinum(IV) center is octahedral, and the benzyl group π-stacks with one of the pyridyl groups in a typical way.6,7 The molecules form weakly bonded supramolecular dimers (Figure 2) by a combination of π-stacking of the ligands 1 (the distance between bipy planes is 3.3 A˚) and weak CH 3 3 3 Br hydrogen bonding (BrA 3 3 3 C18 = 3.70(1), BrA 3 3 3 C15 = 3.89(1) A˚). In addition, the self-assembly

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through hydrogen bonding gives a supramolecular polymer through intermolecular NH 3 3 3 OdC bonding, as shown in Figure 3. The hydrogen bond distance in complex 3, N 3 3 3 O = 3.06(1) A˚, is longer than in 2 but is in the accepted range for NH 3 3 3 O hydrogen bonds of 2.5-3.2 A˚.15 The overall effect is to form a double-stranded supramolecular polymer. It should be noted that the X-ray structure indicates disorder of the positions of the benzyl and bromo groups with about 80:20 occupation. The propagation of the polymer units will naturally be disrupted by this disorder. The binuclear platinum(IV) complexes 4a,b were prepared by displacement of the bromo ligand from complex 3 by reaction with Ag[PF6] followed by addition of pyrazine or 4,40 -bipyridine, as shown in Scheme 4. The complexes 4a,b

Figure 3. Hydrogen bonding in complex 3. Hydrogen bond distance (A˚): N(28A) 3 3 3 O(24) = 3.06(1). Symmetry-equivalent molecule: x, y - 1, z.

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were characterized spectroscopically (see the Experimental Section), and complex 4b was structurally characterized (Figure 4). It was not possible to prepare similar derivatives of the platinum(IV) complexes with the amide-substituted benzyl groups described below because of low solubility. Each platinum(IV) center in 4b retains its octahedral stereochemistry, with the benzyl group trans to the 4,40 bipyridine bridging ligand. There is an inversion center at the center of the 4,40 -bipyridine unit which connects the two platinum(IV) centers. Each NH group forms a hydrogen bond to a THF solvent molecule (Figure 4), and there are no other hydrogen bond donors present; therefore, no longrange supramolecular structure is formed through hydrogen bonding. However, π-stacking of the ligands 1 is present, and this leads to formation of a supramolecular polymer, as shown in Figure 5. The interplanar distance between ligands 1 is about 3.4 A˚. Platinum(IV) Complexes with Additional Amide Groups. The benzyl bromide derivatives BrCH2-4-C6H4-R, in which the substituent group R contained an amide group, reacted with complex 2 to give only the products of trans oxidative addition 5-9 (Scheme 5). These platinum(IV) complexes were less soluble than the model complex 3, but they were sufficiently soluble that the stereochemistry could be determined from the 1H NMR spectra, and the structures

Scheme 4. Synthesis of Binuclear Platinum(IV) Complexes 4a,b

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Figure 4. Molecular structure of complex 4b (THF solvate). The [PF6]- ions and nonparticipating THF solvent molecules are omitted for clarity. Selected bond distances (A˚): Pt-C(1) = 2.061(9), Pt-C(2) = 2.072(8), Pt-C(51) = 2.089(8), Pt-N(11) = 2.147(7), Pt-N(22) = 2.165(6), Pt-N(41) = 2.184(6), N(28) 3 3 3 O(201) = 2.79(2). Symmetry-equivalent molecule: -x, 1 - y, 2 - z.

Figure 6. Molecular structure of complex 5 (top) and hydrogen bonding to a neighboring molecule (bottom). Selected bond distances (A˚): Pt-C(1) = 2.040(4), Pt-C(2) = 2.046(4), Pt-C (41) = 2.078(4), Pt-N(11) = 2.157(4), Pt-N(22) = 2.172(3), Pt-Br = 2.6061(5). Hydrogen-bonding parameters: N (28) 3 3 3 Br(A) = 3.498(4) A˚; N(50) 3 3 3 Br(A) = 3.737(4) A˚. Symmetry-equivalent neighbors: 1 - x, 1/2 + y, -1/2 - z; 1 - x, -1/2 + y, -1/2 - z. Scheme 5. Synthesis of Platinum(IV) Complexes 5-9

Figure 5. Supramolecular polymeric structure of complex formed by π-stacking between ligands 1 in complex 4b. The tert-butyl and ethyl groups are omitted for clarity. Symmetry for neighboring molecules: x - 1, y, z; x + 1, y, z.

of complexes 5 and 9 were confirmed by structure determinations. The structure of complex 5, which is formed by trans oxidative addition, is shown in Figure 6. The complex adopts a conformation in which the NH group of the ligand 1 and the NH group of the benzyl group are oriented roughly parallel to each other, and both form a NH 3 3 3 BrPt hydrogen bond to the PtBr group of a neighboring molecule (Figure 6: N(28) 3 3 3 Br(A) = 3.498(4) A˚; N(50) 3 3 3 Br(A) = 3.737(4) A˚). This type of hydrogen bonding in which a bromide is “chelated” by two NH groups has been found previously in ionic bromide salts, such as in the compound [PPh4]2[m-C6H4(CONHPh)2Br][Br] 3 CH2Cl2, which shows

1:1 complexation of a bromide anion via two NH 3 3 3 Brhydrogen bonds with N 3 3 3 Br = 3.44 and 3.64 A˚, but apparently not in covalent bromo complexes.17 The NH 3 3 3 Br- hydrogen -bonding interaction is thought to be largely electrostatic in nature; thus, it is not surprising that (17) Grapperhaus, C. A.; Li, M.; Gibson, E. R.; Mashuta, M. S. J. Chem. Crystallogr. 2004, 34, 5.

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the distances are somewhat longer for the NH 3 3 3 BrPt interaction, because it involves a covalent PtBr group.

Figure 7. Molecular structure of complex 9. Selected bond distances (A˚): Pt-C(2) = 2.040(10), Pt-C(1) = 2.045(9), PtC(41) = 2.111(8), Pt-N(11) = 2.159(7), Pt-N(22) = 2.172(7), Pt-Br = 2.565(1).

Figure 8. Sheet structure in complex 9 formed through NH 3 3 3 OdC hydrogen bonding. Hydrogen bond distances (A˚): N (28) 3 3 3 O(50)0 = 2.74(1), N(51) 3 3 3 O(24)0 = 2.84(1). The central molecule (red) interacts with four adjacent molecules A-D related by symmetry operations: (A) 3/2 - x, 1/2 + y, 1/2 - z; (B) 1 + x, y, z; (C) 3/2 - x, -1/2 + y, 1/2 - z; (D) -1 + x, y, z.

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Propagation of the hydrogen-bonding interaction leads to formation of a supramolecular polymer. Neither NH 3 3 3 OdC hydrogen bonding nor π-stacking of the bipy groups is observed for complex 5. The molecular structure of complex 9 (Figure 7) is similar to those of complexes 3 and 5 (Figures 2 and 6), but there is a longer substituent on the benzyl group, which is π-stacked with one of the pyridyl rings of ligand 1. The extra methylene groups in 9 compared to 5 allow greater flexibility of the benzyl-amide group, and its NH group is less sterically blocked than in 5. This complex has a particularly interesting and complex supramolecular structure, illustrated in Figures 8 and 9. The hydrogen bonding involving the two NH groups is illustrated in Figure 8. Each molecule provides two NH hydrogen bond donors and two carbonyl group hydrogen bond acceptors, and each molecule forms hydrogen bonds to four others through these interactions, as shown in Figure 8. The NH group of the ligand 1 forms an NH 3 3 3 OdC hydrogen bond to the benzyl-amide carbonyl group of an adjacent molecule B (N(28) 3 3 3 O(50B) = 2.74(1) A˚), and the NH group of the benzyl-amide group forms an NH 3 3 3 OdC hydrogen bond with the carbonyl substituent of the CO2Et group in ligand 1

Figure 9. (left) π-Stacking and CH 3 3 3 Br interactions which connect the sheet structures in Figure 8 to form a three-dimensional supramolecular network structure. Symmetry-equivalent molecule: 2 - x, -y, -z. (right) Space-filling view of a face of a single sheet, showing the edge-on ligands 1 and associated bromide atoms (brown) into which the complementary sheet intercalates by the interactions shown at left.

Table 1. Crystallographic Data for 2, 3, 4b, 5, and 9 2 formula fw temp (K) cryst syst space group a (A˚) b (A˚) c (A˚) R (deg) β (deg) γ (deg) V (A˚3) Z dcalcd (Mg/m3) abs coeff (mm-1) F(000) R1, wR2

C18H23N3O4Pt 540.48 150(2) orthorhombic Pbca 18.5936(7) 7.8441(3) 24.628(1) 90 90 90 3592.1(3) 8 1.999 7.842 2096 0.0401, 0.0741

3 C30H41.4BrN3O4Pt 783.06 150(2) triclinic P1 11.073(1) 12.092(2) 12.318(2) 81.087(6) 86.929(6) 80.804(7) 1607.8(3) 2 1.618 5.642 775 0.0799, 0.2023

4b 3 4THF

5

9

C92H132F12N8O12P2Pt2 2222.18 150(2) triclinic P1 11.4642(8) 15.153(2) 16.140(2) 68.503(4) 87.713(6) 70.740(5) 2452.2(4) 1 1.505 2.966 1130 0.0572, 0.1228

C30H39BrN4O5Pt 810.65 150(2) orthorhombic Pbca 19.5742(9) 11.7078(6) 26.404(1) 90 90 90 6051.0(5) 8 1.780 6.004 3200 0.0358, 0.0662

C38H47BrN4O5Pt 914.80 150(2) monoclinic P21/n 7.5405(2) 27.6582(6) 18.4131(4) 90 99.126(1) 90 3791.6(2) 4 1.603 4.801 1824 0.0529, 0.1449

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of another molecule A (N(51) 3 3 3 O(24A) = 2.84(1) A˚). There are then the complementary hydrogen bonds O (24) 3 3 3 N(51C) to molecule C and O(50) 3 3 3 N(28D) to molecule D (Figure 8). Propagation of these NH 3 3 3 OdC hydrogen-bonding interactions gives rise to a supramolecular corrugated sheet structure. The relatively short N 3 3 3 O distances in complex 9 indicate strong intermolecular association.1-3 The strongly bound sheet units in complex 9 are held together by weaker π-stacking and CH 3 3 3 Br interactions (Figure 9, left), which are similar to those observed for complex 3 (Figure 2). The planes of the ligands 1 in complex 9 are separated by about 3.4 A˚ and the shortest CH 3 3 3 Br interaction Br 3 3 3 C(15A) = 3.62(1) A˚. The way in which the sheets intercalate can be envisaged from the space-filling diagram of the face of a single sheet (Figure 9, right) into which the complementary adjacent sheet (related by an inversion center) intercalates by sliding the ligands 1 into the π-stacking positions.

Conclusions It is shown that an unsymmetrical 5,50 -disubstituted 2,20 bipyridine derivative, 1, containing an amide functional group for hydrogen bonding, forms the stable platinum(II) complex [PtMe2(1)] (2), which reacts with alkyl bromides RBr to give the stable organoplatinum(IV) complexes [PtBrMe2R(1)] by trans oxidative addition. The reaction tolerates alkyl groups R which can contain an amide functionality, and so the corresponding product complexes [PtBrMe2R(1)] contain at least two hydrogen bond donor NH groups. The nature of the self-assembly of these complexes in the solid state has been explored and can involve several types of secondary bonding. These involve not only the predicted NH 3 3 3 OdC or NH 3 3 3 BrPt hydrogen bonds but also π-stacking forces between ligands 1 on adjacent molecules and weak CH 3 3 3 BrPt hydrogen bonding. The parent complex [PtMe2(1)] has only one NH group, and it forms a supramolecular polymer by hydrogen bonding of the type NH 3 3 3 OdC. The square-planar complex is well suited to π-stacking of ligand groups 1, and this leads to an increase in dimensionality, with formation of a sheet structure (Figure 1). The complex [PtBrMe2(CH2R)(1)] (3; R = 3,5-t-Bu2C6H3) also contains only one NH group, but it also contains a PtBr unit which can act as a hydrogen bond acceptor. The hydrogen bonding still involves NH 3 3 3 OdC units to give a supramolecular polymer, but pairs of polymer chains are held together by complementary π-stacking and CH 3 3 3 BrPt hydrogen-bonding interactions. Overall, this gives a double-stranded polymer (Figures 2 and 3). Two complexes having two NH groups of the formula [PtBrMe2(CH2R)(1)] (5, R = 4-t-BuNHC(dO)C6H4; 9, R = 4-t-BuC6H4CH2NHC(dO)CH2-4-C6H4) were structurally characterized. In complex 5, both NH groups form NH 3 3 3 Br hydrogen bonds to the same BrPt acceptor group of a neighboring molecule; thus, only a supramolecular polymer is formed. This structure appears to be favored by the proximity of the two NH groups, which allows an unusual kind of supramolecular chelation. In complex 9 the NH groups are further apart and the main self-assembly occurs through NH 3 3 3 OdC hydrogen bonding. Each molecule provides two NH donors and two OdC acceptors interacting with four neighbors, to give a supramolecular sheet structure. These sheets are then further self-assembled

Au et al.

into a three-dimensional network by multiple interaction of the ligands 1 in neighboring sheets through the same kind of complementary π-stacking and CH 3 3 3 BrPt hydrogen bonding interactions that had been identified in complex 3. The introduction of an amide group into both the bipyridine ligand and one of the alkyl groups has given rise to two new forms of self-assembly in complexes 5 and 9, one involving polymerization through intermolecular NH 3 3 3 Br 3 3 3 HN supramolecular chelation and one involving a combination of NH 3 3 3 OdC and CH 3 3 3 Br hydrogen bonding along with π-stacking. The prediction of preferred hydrogen bonding patterns for crystal engineering is still challenging in these organometallic complexes, but it is clear that organoplatinum(IV) complexes have considerable potential as building blocks in the development of supramolecular organometallic chemistry.

Experimental Section The ligand ethyl 50 -[(ethoxycarbonyl)amino]-2,20 -bipyridine5-carboxylate (1),12 bromoalkyl reagents BrCH2R,7 and [Pt2Me4(μ-SMe2)2]13 were synthesized by the literature methods. 1H NMR spectra were recorded using a Varian Mercury 400 NMR or a Varian Inova 400 NMR, and assignments were confirmed by recording the 1H-1H correlated COSY spectra. Since the bipyridine supporting ligand is unsymmetrical, the resonances associated with the carbamate functional group are represented by the note “carbamate” and the peaks related to the ester are designated as “carboxylate”. [PtMe2(1)] (2). Ligand 1 (190 mg, 0.60 mmol) in 1:2 benzene/ acetone solution (45 mL) was added to [Pt2Me4(μ-SMe2)2] (180 mg, 0.30 mmol) in acetone (10 mL). The reaction mixture had an instant color change from colorless to dark red and was stirred for 1 h. A dark red solid precipitated out from the solution and was collected by vacuum filtration, washed with pentane, and dried in vacuo. Yield: 62% (200 mg). 1H NMR (CDCl3): δ(1H) 1.12 (s, 3H, 2JPt,H = 86 Hz, PtMe), 1.19 (s, 3H, 2JPt,H = 86 Hz, PtMe), 1.35 (t, 3H, 3JH,H=7 Hz, Me(carbamate)), 1.44 (t, 3H, 3 JH,H=7 Hz, Me(carboxylate)), 4.30 (q, 2H, 3JH,H=7 Hz, CH2(carbamate)), 4.47 (q, 2H, 3JH,H = 7 Hz, CH2(carboxylate)), 7.05 (s, broad, 1H, NH), 7.96 (d, 1H, 3JH,H =0 8 Hz, bipy-H3(carbamate)), 8.00 (d, 1H, 3JH,H = 8 Hz, bipy-H3 (carboxylate)), 8.64 (d, 1H, 3JH,H =0 8 Hz, bipy-H4(carbamate)), 8.66 (d, 1H, 3JH,H = 8 Hz, bipy-H4 (carboxylate)), 9.03 (s, 1H, 3JPt,H = 23 Hz, bipy-H60 (carbamate)), 9.77 (s, 1H, 3JPt,H = 22 Hz, bipy-H6 (carboxylate)). Anal. Calcd for C18H23N3O4Pt: C, 40.00; H, 4.29; N, 7.77. Found: C, 40.24; H, 3.99; N, 7.60. [PtBrMe2{CH2-3,5-C6H3-t-Bu2}(1)] (3). A mixture of complex 2 (25.0 mg, 0.05 mmol) and BrCH2-3,5-C6H3(t-Bu)2 (13.0 mg, 0.05 mmol) in acetone (15 mL) was stirred at room temperature for 8 h. The color changed from red to pale yellow. The volume of solvent was reduced, and the product was precipitated by addition of ether (10 mL). Yield: 90% (37.0 mg). 1H NMR (CD2Cl2): δ(1H) 0.99 (s, 18H, t-Bu), 1.33 (t, 3H, 3JH,H = 7 Hz, Me(carbamate)), 1.43 (t, 3H, 3JH,H = 7 Hz, Me(carboxylate)), 1.47 (s, 3H, 2JPt,H = 70 Hz, PtMe), 1.55 (s, 3H, 2JPt,H = 70 Hz, PtMe), 2.83 (AB, 1H, 2JAB = 9 Hz, 2 JPt,H = 88 Hz, PtCH2), 2.87 (AB, 1H, 2JAB = 9 Hz, 2JPt,H = 88 Hz, PtCH2), 4.26 (q, 2H, 3JH,H = 7 Hz, CH2(carbamate)), 4.42 (q, 2H, 3JH,H = 7 Hz, CH2(carboxylate)), 6.23 (s, 2H, Ph(H2, H6)), 6.77 (d, 1H, 3JH,H = 8 Hz, Ph(H4)), 7.94 (d, 1H, 3JH,H = 8 Hz, bipy-H3(carbamate)), 7.97 (d, 1H, 3JH,H = 8 Hz, bipy0 H3 (carboxylate)), 8.18 (d, 1H, 3JH,H = 8 0Hz, bipy-H4(carbamate)), 8.44 (d, 1H, 3JH,H = 8 Hz, bipy-H4 (carboxylate)), 8.90 6 (s, 1H, 3JPt,H = 16 Hz, bipy-H (carbamate)), 9.11 (s, 1H, 3 60 JPt,H = 16 Hz, bipy-H (carboxylate)). Anal. Calcd for C33H46BrN3O4Pt: C, 48.12; H, 5.63; N, 5.10. Found: C, 47.79; H, 5.29; N, 4.99.

Article [PtBrMe2(CH2-4-C6H4CONH-t-Bu)(1)] (5). This was prepared similarly from complex 2 (25.0 mg, 0.046 mmol) and BrCH2-4-C6H4CONH-t-Bu (12.5 mg, 0.046 mmol) in acetone (20 mL). Yield: 94% (35.0 mg). 1H NMR (CD2Cl2): δ(1H) 1.30 (t, 6H, 3JH,H = 7 Hz, Me(carbamate + carboxylate)), 1.35 (s, 9H, t-Bu), 1.46 (s, 3H, 2JPt,H = 70 Hz, PtMe), 1.51 (s, 3H, 2 JPt,H = 70 Hz, PtMe), 2.83 (AB, 1H, 2JAB = 9 Hz, 2JPt,H=96 Hz, PtCH2), 2.85 (AB, 1H, 2JAB=9 Hz, 2JPt,H = 96 Hz, PtCH2), 4.18 (q, 2H, 3JH,H =7 Hz, CH2(carbamate)), 4.50 (q, 2H, 3JH,H = 7 Hz, CH2(carboxylate)), 6.36 (d, 2H, 3JH,H = 8 Hz, 4JPt,H = 19 Hz, Ph(H2, H6)), 6.92 (d, 2H, 3JH,H = 8 Hz, Ph(H3, H5)), 7.87 (d, 1H, 3JH,H = 8 Hz, bipy-H4(carbamate)), 7.95 (d, 1H, 3JH,H = 08 Hz, bipy-H3(carbamate)), 7.99 (d, 1H, 3JH,H = 80 Hz, bipy-H3 (carboxylate)), 8.47 (d, 1H, 3JH,H = 8 Hz, bipy-H4 (carboxylate)), 8.72 (s, 1H, 3JPt,H = 140 Hz, bipy-H6(carbamate)), 9.03 (s, 1H, 3 JPt,H = 14 Hz, bipy-H6 (carboxylate)]. Anal. Calcd for C30H39BrN4O5Pt: C, 44.45; H, 4.85; N, 6.91. Found: C, 44.70; H, 4.92; N, 6.52. [PtBrMe2(CH2-4-C6H4CONH-4-C6H4-t-Bu)(1)] (6). This was prepared similarly from complex 2 (25.0 mg, 0.046 mmol) and BrCH2-4-C6H4CONH-4-C6H4-t-Bu (16.0 mg, 0.046 mmol) in acetone (20 mL). Yield: 90% (37.0 mg). 1H NMR (CD2Cl2): δ(1H) 1.27 (t, 3H, 3JH,H =7 Hz, Me(carbamate)), 1.30 (s, 9H, t-Bu), 1.38 (t, 3H, 3JH,H = 7 Hz, Me(carboxylate)), 1.47 (s, 3H, 2 JPt,H = 70 Hz, PtMe), 1.48 (s, 3H, 2JPt,H = 70 Hz, PtMe), 2.76, 2.77 (m, 2H, 2JPt,H = 95 Hz, PtCH2), 4.21 (q, 2H, 3JH,H = 7 Hz, CH2(carbamate)), 4.40 (q, 2H, 3JH,H = 7 Hz, CH2(carboxylate)), 6.51 (d, 2H, 3JH,H = 8 Hz, 4JPt,H = 19 Hz, Ph1(H2, H6)), 7.31 (d, 2H, 3JH,H = 8 Hz, Ph1(H3, H5)), 7.36 (d, 2H, 3JH,H = 9 Hz, Ph2(H2, H6)), 7.69 (d, 2H, 3JH,H = 9 Hz, Ph2(H3, H5)), 8.38 (d, 1H, 3JH,H = 9 Hz, bipy-H4(carbamate)), 8.47 (d, 1H, 3 JH,H =0 9 Hz, bipy-H3(carbamate)), 8.52 (d, 1H, 3JH,H = 9 Hz, 3 bipy-H (carboxylate)), 8.54 (d, 1H, 3JH,H = 9 Hz, bipy0 H4 (carboxylate)), 8.97 (s, 1H, 3JPt,H = 12 Hz, bipy-H6(carbamate)), 8.98 (s, 1H, NH), 8.99 (s, 1H, 3JPt,H = 12 Hz, bipy0 H6 (carboxylate)), 9.53 (s, broad, 1H, NH). Anal. Calcd for C36H43BrN4O5Pt: C, 48.76; H, 4.89; N, 6.32. Found: C, 48.46; H, 5.11; N, 5.94. [PtBrMe 2(CH2 -4-C 6H 4CONHCH 2-4-C6H 4-t-Bu)(1)] (7). This was prepared similarly from complex 2 (25.0 mg, 0.046 mmol) and BrCH2-4-C6H4CONHCH2-4-C6H4-t-Bu (16.5 mg, 0.046 mmol) in acetone (20 mL). Yield: 91% (37.7 mg). 1H NMR (CD2Cl2): δ(1H) 1.26 (t, 3H, 3JH,H = 7 Hz, Me(carbamate)), 1.30 (s, 9H, t-Bu), 1.43 (t, 3H, 3JH,H = 7 Hz, Me (carboxylate)), 1.48 (s, 3H, 2JPt,H = 70 Hz, PtMe), 1.52 (s, 3H, 2 JPt,H = 70 Hz, PtMe), 2.85, 2.86 (m, 2H, 2JPt,H = 95 Hz, PtCH2), 4.17 (q, 2H, 3JH,H = 7 Hz, CH2(carbamate)), 4.41 (q, 2H, 3JH,H = 7 Hz, CH2(carboxylate)), 4.58 (d, 2H, 3JH,H = 6 Hz, NCH2), 6.36 (d, 2H, 3JH,H = 8 Hz, Ph1(H2, H6)), 6.99 (d, 2H, 3JH,H = 8 Hz, Ph1(H3, H5)), 7.20 (d, 2H, 3JH,H = 8 Hz, Ph2(H2, H6)), 7.37 (d, 2H, 3JH,H = 8 Hz, Ph2(H3, H5)), 7.47 (d, 1H, 3JH,H = 80 Hz, bipy-H3(carbamate)), 7.77 (d, 1H, 3JH,H = 8 Hz, bipy-H3 (carboxylate)), 7.94 (s, 1H, 3JPt,H = 16 Hz, bipy-H6(carbamate)), 7.97 (d, 1H, 3JH,H = 8 Hz, bipy-H4(car3 40 bipy-H (carboxylate)), bamate)), 8.45 (d, 1H, JH,H = 8 Hz, 0 9.07 (s, 1H, 3JPt,H = 16 Hz, bipy-H6 (carboxylate)). Anal. Calcd for C37H45BrN4O5Pt: C, 49.34; H, 5.04; N, 6.22. Found: C, 49.07; H, 5.33; N, 6.03. [PtBrMe2(CH2-4-C6H4CH2CONH-4-C6H4-t-Bu)(1)] (8). This was prepared similarly from complex 2 (50.0 mg, 0.092 mmol) and BrCH2-4-C6H4CH2CONH-4-C6H4-t-Bu (33.5 mg, 0.092 mmol) in acetone (40 mL). Yield: 89% (74.0 mg). 1H NMR (acetone-d6): δ(1H) 1.29 (t, 3H, 3JH,H = 7 Hz, Me(carbamate)), 1.31 (s, 9H, t-Bu), 1.41 (t, 3H, 3JH,H = 7 Hz, Me (carboxylate)), 1.43 (s, 3H, 2JPt,H = 70 Hz, PtMe), 1.47 (s, 3H, 2 JPt,H = 70 Hz, PtMe), 2.75, 2.77 (m, 2H, 2JPt,H = 91 Hz, PtCH2), 3.24 (s, 2H, OdCCH2), 4.24 (q, 2H, 3JH,H = 7 Hz, CH2(carbamate)), 4.41 (q, 2H, 3JH,H = 7 Hz, CH2(carboxylate)), 6.25 (d, 2H, 3 JH,H=8 Hz, 4JPt,H=19 Hz, Ph1(H2, H6)), 6.55 (d, 2H, 3JH,H = 8 Hz, Ph1(H3, H5)), 7.34 (d, 2H, 3JH,H = 9 Hz, Ph2(H2, H6)), 7.59 (d, 2H,

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JH,H = 9 Hz, Ph2(H3, H5)), 8.21 (d, 1H, 3JH,H = 9 Hz, bipy0 H3(carbamate)), 8.28 (d, 1H, 3JH,H = 9 Hz, bipy-H3 (carboxylate)), 0 8.29 (s, 1H, NH), 8.35 (d, 1H, 3JH,H =0 9 Hz, bipy-H4 (carbamate)), 3 4 9.01 (d, 1H, JH,H = 9 Hz, bipy-H (carboxylate)), 9.06 (s, 1H, 3 JPt,H =0 16 Hz, bipy-H6(carbamate)), 9.08 (s, 1H, 3JPt,H = 16 Hz, bipy-H6 (carboxylate)). Anal. Calcd for C37H45BrN4O5Pt: C, 49.34; H, 5.04; N, 6.22. Found: C, 49.77; H, 5.33; N, 6.53. [PtBrMe2(CH2-4-C6H4CH2CONHCH2-4-C6H4-t-Bu)(1)] (9). This was prepared similarly from complex 2 (50.0 mg, 0.092 mmol) and BrCH2-4-C6H4CH2CONHCH2-4-C6H4-tBu (34.5 mg, 0.092 mmol) in acetone (40 mL). Yield: 87% (73.0 mg). 1H NMR (acetone-d6): δ(1H) 1.28 (s, 9H, t-Bu), 1.31 (t, 3H, 3JH,H = 7 Hz, Me(carboxylate)), δ 1.43 (t, 3H, 3JH,H = 7 Hz, Me(carbamate)), 1.44 (s, 1H, 2JPt,H = 70 Hz, PtMe), 1.46 (s, 1H, 2JPt,H = 70 Hz, PtMe), 2.74, 2.75 (m, 2H, 2JPt,H = 91 Hz, PtCH2), 3.13 (s, 2H, OdCCH2), 4.26 (q, 2H, 3JH,H = 7 Hz, CH2(carbamate)), 4.33 (d, 2H, 3JH,H = 3 Hz NCH2), 4.46 (q, 2H, 3JH,H = 7 Hz, CH2(carboxylate)), 6.24 (d, 2H, 3 JH,H = 8 Hz, 4JPt,H = 19 Hz, Ph1(H2, H6)), 6.52 (d, 2H, 3JH,H = 8 Hz, Ph1(H3, H5)), 7.20 (d, 2H, 3JH,H = 8 Hz, Ph2(H2, H6)), 7.35 (d, 2H, 3J0 H,H = 8 Hz, Ph2(H3, H5)), 8.24 (d, 2H, 3JH,H = 8 Hz, bipy-H3,3 (carbamate + carboxylate)), 8.29 (s, 1H, NH), 8.46 0 (d, 2H, 3JH,H = 8 Hz, bipy-H4,4 (carbamate + carboxylate)), 9.03 (s, 1H, 3JPt,H =0 15 Hz, bipy-H6(carbamate)), 9.04 (s, 1H, 3JPt, 6 H = 15 Hz, bipy-H (carboxylate)). Anal. Calcd for C38H47BrN4O5Pt: C, 49.89; H, 5.18; N, 6.12. Found: C, 50.09; H, 5.32; N, 6.28. [{PtMe2(CH2-3,5-C6H3-t-Bu2)(1)}2(μ-pyz)][PF6]2 (4a). A solution of AgPF6 (9.22 mg, 0.0365 mmol) in THF (5 mL) was added dropwise to a solution of complex 3 (31.0 mg, 0.0365 mmol) in THF (15 mL), and the mixture was stirred for 1 h. AgBr began to precipitate, and the mixture was filtered through Celite into a solution of pyrazine (1.46 mg, 0.0182 mmol). After 12 h of stirring at room temperature, the solvent was evaporated and the product was washed with pentane to give a white solid. Yield: 85% (28.7 mg). 1H NMR (CD2Cl2): δ(1H) 1.00 (s, 36H, t-Bu), 1.32 (s, 6H, 2JPt,H = 72 Hz, PtMe), 1.42 (t, 6H, 3JH,H = 7 Hz, Me(carbamate)), 1.43 (t, 6H, 3 JH,H = 7 Hz, Me(carboxylate)), 3.01, 3.05 (m, 4H, 2JPt,H = 90 Hz, PtCH2), 4.26 (q, 4H, 3JH,H = 7 Hz, CH2(carbamate)), 4.42 (q, 4H, 3JH,H = 7 Hz, CH2(carboxylate)), 6.21 (d, 4H, 4 JH,H = 2 Hz, 4JPt,H = 10 Hz, Ph(H2, H6)), 6.86 (d, 2H, 3JH,H = 2 Hz, Ph(H4)), 7.72 (s, 2H, NH), 7.72 (s, 4H, pyz(H2, H3, H5, H6)), 8.00 (d, 2H, 3JH,H = 8 Hz, bipy-H4(carbamate)), 8.12 0 (d, 4H, 3JH,H = 8 Hz, bipy-H3,3 (carbamate + carboxylate)), 0 8.50 (d, 2H, 3JH,H = 8 Hz, bipy-H4 (carboxylate)), 8.66 (s, 2H, 3 JPt,H =0 13 Hz, bipy-H6(carbamate)), 9.05 (s, 2H, 3JPt,H = 13 Hz, bipy-H6 (carboxylate)). Anal. Calcd for C70H96F12N8O8P2Pt2: C, 45.26; H, 5.21; N, 6.03. Found: C, 44.95; H, 5.10; N, 5.99. [{PtMe2(CH2-3,5-C6H3-t-Bu2)(1)}2(μ-4,40 -bipy)][PF6]2 (4b). This was prepared by the same method as for complex 4a from complex 3 (16.3 mg, 0.0194 mmol), AgPF6 (4.91 mg, 0.0194 mmol), and 4,40 -bipyridyl (1.52 mg, 0.00972 mmol). A white solid was produced. Yield: 93% (17.5 mg). 1H NMR (CD2Cl2): δ(1H) 1.02 (s, 36H, t-Bu), 1.32 (t, 6H, 3JH,H = 7 Hz, Me (carbamate)), 1.35 (t, 6H, 3JH,H = 7 Hz, Me(carboxylate)), 1.35 (s, 6H, 2JPt,H = 72 Hz, PtMe), 1.42 (s, 6H, 2JPt,H = 72 Hz, PtMe), 3.01, 3.03 (m, 4H, 2JPt,H = 88 Hz, PtCH2), 4.30 (q, 4H, 3 JH,H = 7 Hz, CH2(carbamate)), 4.46 (q, 4H, 3JH,H = 7 Hz, CH2(carboxylate)), 6.26 (s, 4H, 4JPt,H = 9 Hz, Ph(H2, H6)),0 6.85 3 (s, 02H, Ph(H4)), 7.39 (d, 4H, 3JH,H = 6 Hz, μ-bipy(H , H3 , H0 5, 5 3 2 20 H )), 7.55 (d, 4H, JH,H = 6 Hz, μ-bipy(H , H , H6, H6 )), 7.72 (s, 2H, NH), 7.99 (d, 2H, 3JH,H = 8 Hz, bipy-H4(carbamate)), 8.06 (d, 2H, 3JH,H = 8 Hz, bipy-H3(carbamate)), 8.08 3 30 (d, 2H, JH,H = 8 Hz,0 bipy-H (carboxylate)), 8.52 (d, 2H, 3 JH,H = 8 Hz, bipy-H4 (carboxylate)), 9.06 (s, 2H, 3JPt,H = 13 Hz, 0bipy-H6(carbamate)), 9.12 (s, 2H, 3JPt,H = 13 Hz, bipy-H6 (carboxylate)). Anal. Calcd for C76H100F12N8O8P2Pt2: C, 47.20; H, 5.21; N, 5.79. Found: C, 47.00; H, 5.20; N, 5.51. X-ray Structure Determinations. Data were collected with a Nonius-Kappa CCD diffractometer using COLLECT (Nonius

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BVm 1997-2002) software. The unit cell parameters were calculated and refined from the full data set. Crystal cell refinement and data reduction was carried out using HKL2000 DENZO-SMN (Otwinowski and Minor, 1997). The absorption correction was applied using HKL2000 DENZO-SMN (SCALEPACK). The SHELXTL/PC V6.14 for Windows NT (G. M. Sheldrick, 2001) program package was used to solve the structures by direct methods. Subsequent difference Fourier syntheses allowed the remaining atoms to be located. All non-hydrogen atoms were refined with anisotropic thermal parameters. The hydrogen atom positions were calculated geometrically and were included as riding on their respective heavy atoms. Details of the data collection and refinement are given in Table 1. Brief comments on unusual features are given below. [PtMe2(1)] (2). Crystals were grown by slowly diffusing a solution of ligand 1 in acetone into an acetone solution of [Pt2Me4(μ-SMe2)2]. [PtBrMe2{CH2-3,5-C6H3-t-Bu2}(1)] (3). Crystals were grown by slow evaporation of a solution of complex 3 in CCl4/MeOH/ hexane. There was disorder of one of the ethyl groups, and it was modeled isotropically in a ratio of 0.35/0.65. There was evidence for disorder of the positions of the Br and CH2R groups: Br was modeled as an 80:20 ratio, but the presumed minor CH2R group could not be refined and so was not considered. Platon indicated a significant void where this unit should be located, but no atoms

Au et al. were clearly defined. NMR of the crystals indicated the presence of pure 3. [{PtMe2(CH2-3,5-C6H3-t-Bu2)(1)}2(μ-bipy)][PF6]2 (4b). Crystals of 4b 3 4THF were grown by slow evaporation of a concentrated THF solution. The molecule was located on a symmetry element. There was disorder of one of the ethyl groups and one of the THF molecules of solvation. These were both modeled isotropically at a ratio of 58/42. There were close HH contacts associated with the disorder fragments. [PtBrMe2(CH2-4-C6H4CONH-t-Bu)(1)] (5). Crystals were grown from a concentrated acetone/methanol solution by slow evaporation. [PtBrMe2(CH2-4-C6H4CH2CONHCH2-4-C6H4-t-Bu)(1)] (9). Crystals were grown from a concentrated toluene/methanol solution by slow evaporation.

Acknowledgment. We thank the NSERC of Canada for financial support of this work. Supporting Information Available: CIF files giving tables of crystal and structure refinement data, atomic coordinates, bond lengths and angles, anisotropic displacement parameters, and hydrogen coordinates for 2, 3, 4b, 5, and 9. This material is available free of charge via the Internet at http://pubs.acs.org.