Hydride-Bridged Pt2M2Pt2 Hexanuclear Metal Strings (M = Pt, Pd

Sep 7, 2012 - Tomoaki Tanase , Kana Yamamoto , Rika Hatano , Kanako Nakamae ... Tomoaki Tanase , Kanako Koike , Miho Uegaki , Satoko Hatada , Kanako ...
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Hydride-Bridged Pt2M2Pt2 Hexanuclear Metal Strings (M = Pt, Pd) Derived from Reductive Coupling of Pt2M Building Blocks Supported by Triphosphine Ligands Eri Goto, Rowshan Ara Begum, Aya Hosokawa, Chie Yamamoto, Bunsho Kure, Takayuki Nakajima, and Tomoaki Tanase* Department of Chemistry, Faculty of Science, Nara Women’s University, Kitauoya-nishi-machi, Nara, 630-8506, Japan S Supporting Information *

ABSTRACT: Linear Pt 2 M 2 Pt 2 hexanuclear clusters [Pt 4 M 2 (μ-H)(μdpmp) 4 (XylNC) 2 ](PF 6 ) 3 (M = Pt (2a), Pd (3a); dpmp = bis(diphenylphosphinomethyl)phenylphosphine) were synthesized by site-selective reductive coupling of trinuclear building blocks, [Pt2M(μ-dpmp)2(XylNC)2](PF6)2 (M = Pt (1a), Pd (1b)), and were revealed as the first example of low-oxidationstate metal strings bridged by a hydride with M−H−M linear structure. The characteristic intense absorption bands around 583 nm (2a) and 674 nm (3a) were assigned to the HOMO−LUMO transition on the basis of a net three-center/twoelectron (3c/2e) bonding interaction within the central M2(μ-H) part. The terminal ligands of 2a were replaced by H−, I−, and CO to afford [Pt6(μH)(H)2(μ-dpmp)4]+ (4), [Pt6(μ-H)I2(μ-dpmp)4](PF6) (5), and [Pt6(μ-H)(μdpmp)4(CO)2](PF6)3 (6). The electronic structures of these hexaplatinum cores, {Pt6(μ-H)(μ-dpmp)4}3+, are varied depending on the σ-donating ability of axial ligands; the characteristic HOMO−LUMO transition bands interestingly red-shifted in the order of CO < XylNC < I− < H−, which was in agreement with calculated HOMO−LUMO gaps derived from DFT optimizations of 2a, 4, 5, and 6. The nature of the axial ligands influences the redox activities of the hexanuclear complexes; 2a, 3a, and 5 were proven to be redox-active by the cyclic voltammograms and underwent two-electron oxidation by potentiostatic electrolysis to afford [Pt4M2(μdpmp)4(XylNC)2](PF6)4 (M = Pt (7a), Pd (8a)). The present results are important in developing bottom-up synthetic methodology to create nanostructured metal strings by utilizing fine-tunable metallic building blocks.

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INTRODUCTION Linearly ordered, high-nuclearity, transition metal clusters are of versatile interest in relation to their unusual electronic, optical, and magnetic properties with respect to metal strings and potential applications for nanoscale molecular devices such as molecular wires, transistors, and sensors.1 In particular, lowoxidation-state, electron-rich “extended metal atom chains” (EMACs) are highly desired as ideal candidates for down-sizing the widely used electronic devices made of metallic materials, and their electron transporting properties in a single string have attracted rapidly growing attention from the viewpoint of quantum conducting phenomena.2 However, successful examples are extremely limited due to difficulties in their syntheses and characterization and predominantly take advantage of the template methodology utilizing linearly well-designed multidonor organic ligands. As the most established system, linear aggregations (M3−M9) mainly including first-row (3d) transition metal MII ions have been established by using oligo-α-pyridylamides as supporting ligands; M3 (M = Ni, Co, Cr, Cu), M5 (M = Cr, Co, Ni), M7 (M = Cr, Ni), and M9 (M = Ni) complexes were systematically synthesized with the corresponding di-, tri-, tetra-, and pentapyridylpolyamide ligands.3 Recently, Peng and his co-workers have successfully © 2012 American Chemical Society

synthesized low-oxidation-state Ni 1 1 metal strings [Ni11(tentra)4X2](PF6)4 (X = Cl, NCS) by using a new tetranaphthyridyltriamine ligand, N2-(2-(1,8-naphthyridin-7ylamino)-1,8-naphthyridine-7-yl)-N7-(1,8-naphthyridin-2-yl)1,8-naphthyridine-2,7-diamine (H3tentra), which contains four low-valent {Ni2}3+ units with class III mixed valency.4 In these systems, the nuclearity of EMACs depends on the number of N donor atoms in the template ligands. In contrast, examples of EMACs with low-valent, second- and third-row (4d and 5d) transition metal centers are further limited. Murahashi and Kurosawa et al. have reported linear palladium complexes (Pd 2 −Pd 5 ) sandwiched by π-conjugated polyenes and perylenes,5 and Harvey et al. reported linear Pt4 and Pd4 complexes supported by bisisocyanides of dmb (1,8-diisocyano-p-menthane).6 While these low-valent metal strings are recognized with formal oxidation states of MI−(M0)n−MI (M = Pt, Pd), the characterized number of metal atoms has been limited to less than five (n ≤ 3 for Pd and n ≤ 2 for Pt). As a second methodology, stepwise expansion of linear metallic modules with metal−metal interactions is one of the Received: July 20, 2012 Published: September 7, 2012 8482

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Scheme 1. Preparations of the Pt2M2Pt2 Hexanuclear Clusters with Isocyanide Terminal Ligands

promising bottom-up approaches to construct functional EMACs; however outstanding examples have also been quite limited because metal−metal bonds are relatively weak and hard to control in comparison with usual C−C bonds by organic chemical techniques. Oro et al. have synthesized the hexanuclear iridium chain [Ir6(μ-Opy)6(I)2(CO)12] (Opy− = 2pyridonate)7 by oxidative coupling of the dinuclear complex [Ir2(μ-Opy)2(CO)4], which involves low-valent Ir centers with a formal oxidation state of +1.33. However, the Ir6 string was barely intact even below 0 °C in the solution state and was likely to be decomposed into Ir4 and Ir2 fragments, which was similar to the fact that linear high-valent octaplatinum complexes bridged by amide ligands were likely to undergo fragmentation into Pt4 and Pt2 units in the solution state.8 These studies implied that the EMACs constructed by connecting dinuclear metal building blocks should be unstable in solution and their expansion as molecules may increase instability with the number of unsupported metal−metal interactions increasing. We have studied linear trinuclear complexes [Pt2M(μdpmp)2(XylNC)2](PF6)2 (M = Pt (1a), Pd (1b); XylNC = 2,6-xylyl isocyanide), with the apparent oxidation state of PtIPt0 MI centers supported by the triphosphine ligand bis(diphenylphosphinomethyl)phenylphosphine (dpmp).9 Complexes 1a and 1b are each of the minimal units for MI−(M0)n− MI type metal strings with an electronically unsaturated linear trinuclear core of 44 CVEs (cluster valence electrons)9a and can be good building blocks for further expanded metal strings because they are very reactive toward small organic molecules and metal species. The axial isocyanide ligands of 1a were exchanged by π-conjugated bisisocyanide ligands to afford rigidrod cluster polymers {[Pt3(μ-dpmp)2(bisNC)]2+}n (bisNC = 2,3,5,6-tetramethylphenyl-1,4-bisisocyanide, 2,2′,6,6′-tetramethyl-4,4′-biphenylene-1,1′-bisisocyanide).10 Recently, complex 1a was shown to react with HgCl2 to yield a planar Pt3Hg3 hexanuclear cluster, [Pt3Hg3Cl4(μ-dpmp)2(XylNC)2]4+; on the other hand, the same reaction of 1b led to intramolecular metal−metal bond rearrangement to afford [Pt2PdHgCl2(μdpmp)2(XylNC)2]2+ through a novel HgI−PdI covalent bond formation.11

In the present study, we have tried to assemble the trimetallic clusters 1a and 1b by generating direct metal−metal bonding interactions and successfully synthesized a series of linear Pt2M2Pt2 clusters, [Pt4M2(μ-H)(μ-dpmp)4(RNC)2]3+ (M = Pt (2), Pd (3); R = Xyl (a), Mes (b), tBu (c)), [Pt6(μ-H)(μdpmp)4(CO)2]3+ (6), and [Pt6(μ-H)X2(μ-dpmp)4]+ (X = H (4), I (5)), where a hydride bridges the central two M atoms (M = Pt, Pd) site-selectively to form an unprecedented Pt2M− H−MPt2 linear structure with 86 CVEs. Furthermore, the hexanuclear strings of 2a and 3a were quite stable even in the solution state and interestingly transformed by two-electron oxidation to linear clusters with 84 CVEs, [Pt4M2(μdpmp)4(XylNC)2](PF6)4 (M = Pt (7a), Pd (8a)). The Pt2M2Pt2 hexanuclear strings were remarkably retained against the apparent hydride dissociation from the central part. These low-valent and redox-active hexanuclear complexes exhibited unique electronic properties concerning the HOMO−LUMO transition and could provide useful information with relevance to developing functional EMACs by stepwise expanding of linear metallic modules and also to the fundamental understanding of the linearly conjugated metal−metal bonds with low-oxidation-state metal centers.12

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RESULTS AND DISCUSSION Synthesis of Hydride-Bridged Linear Pt2M2Pt2 Hexanuclear Clusters (M = Pt, Pd). Reduction of the triplatinum complex [Pt3(μ-dpmp)2(XylNC)2](PF6)2 (1a) with NaBH4 in ethanol afforded a brown precipitate, which was quite unstable and quickly extracted with dichloromethane to remove inorganic salts. When the extract was stirred at room temperature, the color of the solution changed from dark green to dark blue, from which a linear hexaplatinum cluster, [Pt6(μ-H)(μ-dpmp)4(XylNC)2](PF6)3 (2a), was obtained as dark blue cubic crystals in a moderate yield of 44% (Scheme 1). Whereas the same reduction of the heterotrinuclear cluster [Pt2Pd(μ-dpmp)2(XylNC)2](PF6)2 (1b) was not successful due to depositing metal black, reaction of 1b with NaOCH3 in a CH2Cl2/CH3OH mixed solvent yielded a dark green solution of a Pt 4 Pd 2 hexanuclear cluster, [Pt 4 Pd 2 (μ-H)(μdpmp)4(XylNC)2](PF6)3 (3a), which was isolated as dark green cubic crystals in 51% yield (Scheme 1). The linear 8483

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Figure 1. ORTEP views for the cluster cations of (a) 2a and (b) 3a with thermal ellipsoids at the 40% probability level. The C−H hydrogen atoms are omitted for clarity. Pt (yellow), Pd (green), P (pink), N (blue), C (gray), and H (light blue). Selected distances (Å) and angles (deg) for 2a: Pt1−Pt2 = 2.7208(4), Pt2−Pt3 = 2.7365(4), Pt3−Pt4 = 3.3093(4), Pt4−Pt5 = 2.7375(4), Pt5−Pt6 = 2.7103(4), Pt1−C1 =2.002(8), Pt6−C2 = 1.933(9), Pt1−Pt2−Pt3 = 174.939(15), Pt2−Pt3−Pt4 = 178.446(13), Pt3−Pt4−Pt5 = 179.325(13), Pt4−Pt5−Pt6 = 179.511(15), Pt2−Pt1−C1 = 177.0(2), Pt5−Pt6−C2 = 176.7(2). Selected distances (Å) and angles (deg) for 3a: Pt1−Pt2 = 2.7174(3), Pt2−Pd1 = 2.7555(5), Pd1−Pd2 = 3.2514(7), Pd2−Pt3 = 2.7569(6), Pt3−Pt4 = 2.7098(3), Pt1−C1 =1.956(7), Pt4−C2 = 1.949(8), Pt1−Pt2−Pd1 = 174.578(17), Pt2−Pd1−Pd2 = 178.74(2), Pd1−Pd2−Pt3 = 179.77(2), Pd2−Pt3−Pt4 = 179.850(17), Pt2−Pt1−C1 = 177.2(2), Pt3−Pt4−C2 = 177.0(2). ORTEP diagrams for the complex cations of 2a (c) and 3a (d) viewed along the metal axis. The thermal ellipsoids are drawn at the 40% probability level, and the terminal xylyl isocyanide ligands and the hydrogen atoms are omitted for clarity.

hexanuclear clusters 2a and 3a were characterized by IR, UV− vis, 1H and 31P{1H} NMR, and ESI-MS spectroscopic techniques, elemental analyses, and X-ray crystallography. The presence of the central hydride bridge, M(μ-H)M, was unambiguously determined by 1H NMR and ESI-MS, and the detailed structures were determined by X-ray analyses (vide inf ra). Furthermore, treatment of 2a and 3a with an excess of other isocyanides, MesNC or tBuNC, gave a series of isocyanide-capped Pt 4 M 2 clusters, [Pt 4 M 2 (μ-H)(μdpmp)4(RNC)2](PF6)3 (M = Pt, R = Mes (2b), tBu (2c); M = Pd, R = Mes (3b), tBu (3c)), through terminal ligand exchange reactions (Scheme 1). It is noteworthy that the terminal xylyl isocyanide ligands of 2a and 3a were not exchanged by any other sorts of ligands such as CO and phosphines as well as halides and acethylides, and so on. Since

similar reductions by NaBH4 or NaOCH3 for [M2(μdppm)2(XylNC)2](PF6)2 (dppm = bis(diphenylphosphino)methane)13 or a mixture of [M(XylNC)4](PF6)2 and dpmp did not give any linear complexes (M = Pt, Pd), the Pt2M complexes 1a and 1b have proven to be very effective building blocks to construct Pt2M2Pt2 hexanuclear metal strings through reductive coupling of the two fragments. Crystal Structures of [Pt4M2(μ-H)(μ-dpmp)4(XylNC)2](PF6)3 (M = Pt (2a), Pd (3a)). The detailed structures of the xylyl isocyanide-terminated Pt4M2 clusters [Pt4M2(μ-H)(μdpmp)4(XylNC)2](PF6)3 (M = Pt (2a), Pd (3a)) were determined by X-ray crystallography to be isomorphous with each other. ORTEP diagrams for the complex cations of 2a and 3a are shown in Figure 1a and b, with selected bond distances and angles. The asymmetric unit of 2a contains one Pt6 cluster 8484

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Figure 2. 31P{1H} NMR spectra of (a) 2a and (b) 3a in CD2Cl2 at room temperature.

Figure 4. Electronic absorption spectra of 2a (−·−), 3a (···), 1a (−○−), and 1b (−●−) in CH2Cl2 at room temperature.

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Figure 3. H NMR spectra for the hydride peaks of (a) 2a and (b) 3a in CD2Cl2 at room temperature.

significantly longer than those of usual Pt−Pt bonds and strongly suggests the presence of a hydride bridging the two central Pt atoms to form a Pt3−H−Pt4 structure, which is definitively confirmed by 1H NMR and ESI-MS as mentioned in the following part. Although the hydride H was not determined from difference Fourier maps, the hydrogen atom (H1) was calculated at the midpoint of the two central Pt atoms (Pt3, Pt4) in light of the theoretically optimized structure of 2a by DFT calculations (vide inf ra) and was not refined, these procedures preventing a detailed discussion on the Pt−H−Pt structure. The structure of 2a is recognized, in other words, as two trinuclear fragments {Pt 3 (μdpmp)2(XylNC)}2+ being connected by a bridging hydride (H−) to form the Pt3(μ-H)Pt3 hexanuclear chain with 86 CVEs. In the central Pt(μ-H)Pt part, the two platinum atoms are not supported by any organic ligands and the Pt−H−Pt moiety is sterically well protected by phenyl groups of dpmp ligands.

cation and three PF6− anions together with 3.5 dichloromethane and a diethyl ether solvent molecule, indicating that the cluster cations have +3 charge with 86 cluster valence electrons. The cluster cation of 2a consists of six linearly linked platinum atoms with an average Pt−Pt−Pt angle of 178.06°, which is supported by four dpmp ligands and terminated by two XylNC ligands, resulting in a pseudo-C2 symmetrical structure with the axis passing through the midpoint of the Pt3 and Pt4 atoms vertical to the Pt6 string. The average Pt−Pt distances are 2.7156 Å for the outer Pt1−Pt2 and Pt5−Pt6 bonds (dout) and 2.7370 Å for the inner Pt2−Pt3 and Pt4−Pt5 bonds (dinn), and the central Pt3−Pt4 distance is 3.3093(4) Å (dcen). The outer and inner Pt−Pt bond separations are consistent with a formal assignment of Pt−Pt single bonds in comparison with the corresponding values of 1a (av Pt−Pt = 2.72 Å).9a The central Pt−Pt distance of 3.3093(4) Å is 8485

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Scheme 2

Scheme 3

Figure 5. (a) 31P{1H} NMR spectrum of 4 in DMF-d7 at room temperature. (b) 1H NMR spectrum for the hydride peaks of 4 in DMF-d7 at room temperature.

Although the central Pt−Pt length (3.3093(4) Å) is significantly longer than the values usually observed for Pt− Pt distances bridged by bis-hydrides or by a hydride and an organic ligand ( 2σ(I)). bwR2 = [∑w(Fo2 − Fc2)2/∑w(Fo2)2]1/2 (for all reflns). a

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(2) (a) Georgiev, V. P.; McGrady, J. E. J. Am. Chem. Soc. 2011, 133, 12590. (b) Georgiev, V. P.; McGrady, J. E. Inorg. Chem. 2010, 49, 5591. (c) Chae, D. H.; Berry, J. F.; Jung, S.; Cotton, F. A.; Murillo, C. A.; Yao, Z. Nano Lett. 2006, 6, 165. (d) Hsu, L. Y.; Huang, Q. R.; Jin, B.-Y. J. Phys. Chem. C 2008, 112, 10538. (e) Tsai, T. W.; Huang, Q.-R.; Peng, S.-M.; Jin, B.-Y. J. Phys. Chem. C 2010, 114, 3641. (f) Lin, S. Y.; Chen, I. W. P.; Chen, C. H.; Hsieh, M.-H.; Yeh, C. Y.; Lin, T. W.; Chen, Y. H.; Peng, S.-M. J. Phys. Chem. B 2004, 108, 959. (g) Chen, P.; Fu, M.-D.; Tseng, W. H.; You, J.-Y.; Wu, S.-H.; Ku, C.-J.; Chen, C.-H.; Peng, S.-M. Angew. Chem., Int. Ed. 2006, 45, 5814. (h) Shin, K.-N.; Huang, M. J.; Lu, H. G.; Fu, M.-D.; Kuo, C.-K.; Huang, G.-C.; Lee, G.H.; Chen, C.-H.; Peng, S.-M. Chem. Commun. 2010, 46, 1338. (3) (a) Yeh, C.-Y.; Wang, C.-C.; Chen, C.-H.; Peng, S.-M. In Redox Systems under Nano-Space Control; Hirao, T., Ed.; Springer: Berlin, 2006; pp 85−117, and references therein. (b) Berry, J. F. In Multiple Bond between Metal Atoms 3rd ed.; Cotton, F. A.; Murillo, C. A.; Walton, R. A., Eds.; Springer: US, 2005; pp 669−706, and references therein. (c) Liu, I. P.-C.; Wang, W.-Z.; Peng, S.-M. Chem. Commun. 2009, 4323. (d) Chen, C.-H.; Hung, R. D.; Wang, W.-Z.; Peng, S.-M.; Chia, C.-I. ChemPhysChem 2010, 11, 466. (e) Ismailov, R.; Weng, W.Z.; Wang, R.-R.; Huang, Y.-L.; Yeh, C.-Y.; Lee, G.-H.; Peng, S.-M. Eur. J. Inorg. Chem. 2008, 4290. (f) Peng, S.-M.; Wang, C.-C.; Jang, Y.-L.; Chen, Y.-H.; Li, F.-Y.; Mou, C.-Y.; Leung, M.-K. J. Magn. Magn. Mater. 2000, 209, 80. (4) Ismayilov, R. H.; Wang, W.-Z.; Lee, G.-H.; Yeh, C.-Y.; Hua, S.-A.; Song, Y.; Rohmer, M.-M.; Bénard, M.; Peng, S.-M. Angew. Chem., Int. Ed. 2011, 50, 2045. (5) (a) Tatsumi, Y.; Naga, T.; Nakashima, H.; Murahashi, T.; Kurosawa, H. Chem. Commun. 2008, 477. (b) Murahashi, T.; Kato, N.; Uemura, T.; Kurosawa, H. Angew. Chem., Int. Ed. 2007, 46, 3509. (c) Murahashi, T.; Fujimoto, M.; Oka, M.; Hashimoto, Y.; Uemura, T.; Tatsumi, Y.; Nakao, Y.; Ikeda, A.; Sakai, S.; Kurosawa, H. Science 2006, 313, 1104. (d) Tatsumi, Y.; Shirato, K.; Murahashi, T.; Ogoshi, S.; Kurosawa, H. Angew. Chem., Int. Ed. 2006, 45, 5799. (e) Tatsumi, Y.; Murahashi, T.; Okada, M.; Ogoshi, S.; Kurosawa, H. Chem. Commun. 2004, 1430. (f) Murahashi, T.; Uemura, T.; Kurosawa, H. J. Am. Chem. Soc. 2003, 125, 8436. (g) Murahashi, T.; Higuchi, Y.; Katoh, T.; Kurosawa, H. J. Am. Chem. Soc. 2002, 124, 14288. (h) Murahashi, T.; Nagai, T.; Okuno, T.; Matsutani, T.; Kurosawa, H. Chem. Commun. 2000, 1689. (i) Murahashi, T.; Mochizuki, E.; Kai, Y.; Kurosawa, H. J. Am. Chem. Soc. 1999, 121, 10660. (j) Labeguerie, P.; Bénard, M.; Róhmer, M. Inorg. Chem. 2007, 46, 5283. (6) (a) Zhang, T.; Drouin, M.; Harvey, P. D. Inorg. Chem. 1999, 38, 957. (b) Zhang, T.; Drouin, M.; Harvey, P. D. Inorg. Chem. 1999, 38, 1305. (7) (a) Villarroya, B. E.; Tejel, C.; Rohmer, M.-M.; Oro, L. A.; Ciriano, M. A.; Bénard, M. Inorg. Chem. 2005, 44, 6536. (b) Tejel, C.; Ciriano, M. A.; Villarroya, B. E.; López, J. A.; Lahoz, F. J.; Oro, L. A. Angew. Chem., Int. Ed. 2003, 42, 530. (c) Tejel, C.; Ciriano, M. A.; Villarroya, B. E.; Gelpi, R.; López, J. A.; Lahoz, F. J.; Oro, L. A. Angew. Chem., Int. Ed. 2001, 40, 4084. (d) Tejel, C.; Ciriano, M. A.; Oro, L. A. Chem.Eur. J. 1999, 5, 1131. (e) Tejel, C.; Ciriano, M. A.; López, J. A.; Lahoz, F. J.; Oro, L. A. Angew. Chem., Int. Ed. 1998, 37, 1542. (8) (a) Matsumoto, K.; Sakai, K. Adv. Inorg. Chem. 2000, 49, 375. (b) Matsumoto, K.; Ochiai, M. Coord. Chem. Rev. 2002, 231, 229. (c) Ochiai, M.; Lin, Y.-S.; Yamada, J.; Misawa, H.; Arai, S.; Matumoto, K. J. Am. Chem. Soc. 2004, 126, 2536. (d) Lin, Y.-S.; Misawa, H.; Yamada, J.; Matsumoto, K. J. Am. Chem. Soc. 2001, 123, 569. (e) Lin, Y.-S.; Takeda, S.; Matsumoto, K. Organometallics 1999, 18, 4897. (f) Matsumoto, K.; Nagai, Y.; Matsunami, J.; Mizuno, K.; Abe, T.; Somazawa, R.; Kinoshita, J.; Shimura, H. J. Am. Chem. Soc. 1998, 120, 2900. (g) Matsumoto, K.; Matsunami, J.; Mizuno, K.; Uemura, H. J. Am. Chem. Soc. 1996, 118, 8959. (h) Matsumoto, K.; Sakai, K.; Nishio, K.; Tokisue, Y.; Ito, R.; Nishide, T.; Shichi, Y. J. Am. Chem. Soc. 1992, 114, 8110. (i) O’Halloran, T. V.; Mascharak, P. K.; Williams, P. K.; Roberts, M. M.; Lippard, S. J. Inorg. Chem. 1987, 26, 1261. (j) Ginsberg, A. P.; O’Halloran, T. V.; Fanwick, P. E.; Hollis, L. S.; Lippard, S. J. J. Am. Chem. Soc. 1984, 106, 5430. (k) O’Halloran, T. V.; Roberts, M. M.; Lippard, S. J. J. Am. Chem. Soc. 1984, 106, 6427.

(l) Barton, J. K.; Szalda, D. J.; Rabinowitz, H. N.; Waszczak, J. V.; Lippard, S. J. J. Am. Chem. Soc. 1979, 101, 1434. (9) (a) Tanase, T.; Ukaji, H.; Takahata, H.; Toda, H.; Igoshi, T.; Yamamoto, Y. Organometallics 1998, 17, 196. (b) Tanase, T. Bull. Chem. Soc. Jpn. 2002, 75, 1407. (c) Tanase, T.; Hamaguchi, M.; Begum, R. A.; Yano, S.; Yamamoto, Y. Chem. Commun. 1999, 745. (d) Tanase, T.; Ukaji, H.; Igoshi, T.; Yamamoto, Y. Inorg. Chem. 1996, 35, 4114. (e) Tanase, T.; Hamaguchi, M.; Begum, R. A.; Goto, E. Chem. Commun. 2001, 1072. (10) Tanase, T.; Goto, E.; Begum, R. A.; Hamaguchi, M.; Zhan, S.; Iida, M.; Sakai, K. Organometallics 2004, 23, 5975. (11) Hosokawa, A.; Kure, B.; Nakajima, T.; Nakamae, K.; Tanase, T. Organometallics 2011, 30, 6063. (12) (a) Preliminary results with low-grade X-ray crystal structures of 2a and 3a have been reported: Goto, E.; Begum, R. A.; Zhan, S.; Tanase, T.; Tanigaki, K.; Sakai, K. Angew. Chem., Int. Ed. 2004, 43, 5029. (b) In this paper, the crystal structures of 2a and 3a were reassigned by using a high-intensity confocal X-ray beam to obtain more accurate results. (13) Yamamoto, Y.; Yamazaki, H. Organometallics 1993, 12, 933. (14) For example: (a) Minghetti, G.; Banditelli, G.; Bonati, F.; Szostak, R.; Strouse, C. E.; Knobler, C. B.; Kaesz, H. D. Inorg. Chem. 1983, 22, 2332. (b) Knobler, C. B.; Kaesz, H. D.; Minghetti, G.; Bandini, A. L.; Banditelli, G.; Bonati, F. Inorg. Chem. 1983, 22, 2324. (c) Jans, J.; Naegeli, R.; Venanzi, L. M.; Albinati, A. J. Organomet. Chem. 1983, 247, C37. (d) Minghetti, G.; Albinati, A.; Bandini, A. L.; Banditelli, G. Angew. Chem., Int. Ed. Engl. 1985, 24, 120. (e) Siedle, A. R.; Newmark, R. A.; Gleason, W. B. J. Am. Chem. Soc. 1986, 108, 767. (15) (a) Carmona, D.; Thouvenot, R.; Venanzi, L. M.; Bachechi, F.; Zambonelli, L. J. Organomet. Chem. 1983, 250, 589. (b) Bachechi, F.; Mura, P.; Zambonelli, L. Acta Crysallogr. 1993, C49, 2072. (c) Albinati, A.; Bracher, G.; Carmona, D.; Jans, J. H. P.; Klooster, W. T.; Koetzle, T. F.; Macchioni, A.; Ricci, J. S.; Thouvenot, R.; Venanzi, L. M. Inorg. Chim. Acta 1997, 265, 255. (d) Bachechi, F. Acta Crystallogr. 1993, C49, 460. (e) Albinati, A.; Chaloupka, S.; Eckert, J.; Venanzi, L. M.; Wolfer, M. K. Inorg. Chim. Acta 1997, 259, 305. (16) Hill, G. S.; Vittal, J. J.; Puddephatt, R. J. Organometallics 1997, 16, 1209. (17) (a) Tanase, T.; Kawahara, K.; Ukaji, H.; Kobayashi, K.; Yamazaki, H.; Yamamoto, Y. Inorg. Chem. 1993, 32, 3682. (b) Tanase, T.; Ukaji, H.; Yamamoto, Y. J. Chem. Soc., Dalton Trans. 1996, 3059, and references therein. (18) Pyykkö, P.; Atsumi, M. Chem.Eur. J. 2009, 15, 186. (19) (a) Rüffer, T.; Ohashi, M.; Shima, A.; Mizomoto, H.; Kaneda, Y.; Mashima, K. J. Am. Chem. Soc. 2004, 126, 12244. (b) Tanaka, M.; Mashima, K.; Nishino, M.; Takeda, S.; Mori, W.; Tani, K.; Yamaguchi, K.; Nakamura, A. Bull. Chem. Soc. Jpn. 2001, 74, 67. (c) Mashima, K.; Fukumoto, A.; Nakano, H.; Kaneda, Y.; Tani, K.; Nakamura, A. J. Am. Chem. Soc. 1998, 120, 12151. (d) Mashima, K.; Tanaka, M.; Tani, K.; Nakamura, A.; Takeda, S.; Mori, W.; Yamaguchim, K. J. Am. Chem. Soc. 1997, 119, 4307. (e) Mashima, K.; Nakano, H.; Nakamura, A. J. Am. Chem. Soc. 1996, 118, 9083. (f) Mashima, K.; Nakano, H.; Nakamura, A. J. Am. Chem. Soc. 1993, 115, 11632. (20) (a) Kaesz, H. D.; Saillant, R. B. Chem. Rev. 1972, 72, 231. (b) Chatt, J. Chem. Ind. 1962, 318. (c) Chatt, J.; Hayter, R. G. J. Chem. Soc. 1961, 896. (d) Chat, J.; Shaw, B. L. J. Chem. Soc. 1962, 5075. (e) Chatt, J.; Shaw, B. L.; Field, A. E. J. Chem. Soc. 1964, 3466. (f) Vaska, L. J. Am. Chem. Soc. 1961, 83, 756. (g) Vaska, L.; DiLuzio, J. W. J. Am. Chem. Soc. 1961, 83, 1263. (h) Vaska, L.; DiLuzio, J. W. J. Am. Chem. Soc. 1962, 84, 4989. (21) Brown, M. P.; Puddephatt, R. J.; Rashidi, M.; Seddon, K. R. J. Chem. Soc., Dalton Trans. 1978, 516. (22) Bracher, G. B.; Grove, D. M.; Pregosin, P. S.; Venanzi, L. M. Angew. Chem., Int. Ed. Engl. 1979, 18, 155. (23) (a) Reed, A. E.; Curtiss, L. A.; Weinhold, F. Chem. Rev. 1988, 88, 899. (b) Wiberg, K. B. Tetrahedron 1968, 24, 1083. (24) Casida, M. E.; Jamorski, C.; Casida, K. C.; Salahub, D. R. J. Chem. Phys. 1998, 108, 4439. 8496

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(25) Preliminary results for 7a and 8a with low-grade X-ray structures were reported in ref 12a. The details will be reported in our subsequent full report. (26) Cherwinski, W. J.; Johnson, B. F. G.; Lewis, J. J. Chem. Soc., Dalton Trans. 1974, 1405. (27) (a) Sheldrick, G. M. SHELXS-97: Program for the Solution of Crystal Structures; University of Göttingen: Göttingen, Germany, 1996. (b) Sheldrick, G. M. SHELXL-97: Program for the Refinement of Crystal Structures; University of Göttingen: Göttingen, Germany, 1996. (28) Crystal Clear, version 1.3.5; Operating software for the CCD detector system; Rigaku and Molecular Structure Corp.: Tokyo, Japan and The Woodlands, TX, 2003. (29) Jacobson, R. REQAB; Molecular Structure Corporation: The Woodlands, Texas, USA, 1998. (30) Crystal Structure 3.7 and 4.0: Crystal Structure Analysis Package; Rigaku Corporation: Tokyo, Japan, 2000−2010. (31) (a) Becke, A. D. Phys. Rev. A 1988, 38, 3098. (b) Lee, C.; Yang, W.; Parr, R. G. Phys. Rev. B 1988, 37, 785. (32) (a) Adamo, C.; Barone, V. J. Chem. Phys. 1998, 108, 664. (b) Becke, A. D. J. Chem. Phys. 1996, 104, 1040. (33) (a) Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 270. (b) Wadt, W. R.; Hay, P. J. J. Chem. Phys. 1985, 82, 284. (c) Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 299. (34) Frisch, M. J.; et al. Gaussian 03; Gaussian, Inc.: Wallingford, CT, 2004.

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dx.doi.org/10.1021/om300680p | Organometallics 2012, 31, 8482−8497