The manipulation of trinuclear ruthenium clusters [Ru3(CO)9(μ-H)2(μ3-PMes)] (1) with PH2Ph, in refluxing hexane, produces [Ru3(CO)8(PH2Ph)(μ-H)2(μ3-PMes)] (2) where PH2Ph coordinates as a terminal ligand. Cluster 2 gets converted to [Ru3 (CO)9(μ3-PMes)(μ3-PPh)] (3) when heated in a toluene solution in the presence of CO. This study provides the solutions of the X-ray structures for clusters 2 and 3

Kakizawa, Taeko

English

Communications in Inorganic Synthesis

4Commun. Inorg. Synth.                                                                                                                          Kakizawa, T. /Vol. 7, Nº1(2019), 4-6Research ArticleSynthesis and crystal structures of triruthenium clusters containing phosphinidene ligandsTaeko KakizawaCollege of Science and Engineering, Kanto Gakuin University, Mutsuurahigashi, Kanazawa-ku, Yokohama, Kana-gawa 236-8501, Japan. E-mail: kg100683@kanto-gakuin.ac.jpReceived: September 02, 2019; accepted: November 12, 2019Abstract: The manipulation of trinuclear ruthenium clus-ters [Ru3(CO)9(m-H)2(m3-PMes)] (1) with PH2Ph in refluxing hexane produces [Ru3(CO)8(PH2Ph)(m-H)2(m3-PMes)] (2) where PH2Ph coordinates as a terminal ligand. Cluster 2 is converted to [Ru3(CO)9(m3-PMes)(m3-PPh)] (3) when heated in a toluene solution in the presence of CO. This study provi-des the solutions of the X-ray structures for clusters 2 and 3.Keywords: cluster; X-ray crystal structure; ruthenium; phos-phinidene.1. INTRODUCTIONPhosphinidene is a versatile ligand that bridges transition metals in several coordination modes [1,2]. Many transition metal clus-ters with phosphinidene ligands have been reported along with their chemical properties, structures, and preparation methods [3–6]. I previously reported the synthesis of phosphinidene-ca-pped, ruthenium, carbonyl clusters and their expansion reactions using the produced clusters as building blocks containing more ligands or vertices [7,8]. The reactions demonstrated that the phosphinidene ligand is beneficial in preserving the ruthenium cluster core. Cluster expansion reactions are useful for preparing large, complicated molecules. In this study, stepwise formation of triruthenium clusters containing two types of phosphinidene ligands is examined, beginning with the reaction of a phosphini-dene-capped cluster with a terminal phosphine ligand. Clusters produced via these methods were analyzed by X-ray studies.2. EXPERIMENTALAll procedures were performed under a dry nitrogen atmosphe-re using Schlenk techniques. Before usage, toluene and hexane were distilled from sodium benzophenone ketyl. Dichlorome-thane was evaporated over calcium hydride and purified by trap-to-trap distillation, and benzene-d6 was dried over potassium mirrors. 1H and 31P NMR spectra were obtained using a Bruker AVANCE 300 spectrometer and IR spectra were obtained using a HORIBA FT-730 spectrometer. Elemental analyses were per-formed at the Instrumental Analysis Center for Chemistry, To-hoku University. The Ru3 cluster [Ru3(CO)9(m-H)2(m3-PMes)] (1) was prepared as previously reported [7]. All other reagents were purchased and used without further purification.Synthesis of [Ru3(CO)8(PH2Ph)(m-H)2(m3-PMes)] (2).Ru3 cluster 1 (50 mg, 0.071 mmol) and PH2Ph (10 mg, 0.091 mmol) were dissolved in 20 mL of hexane, and the solution was refluxed overnight. The solvent was evaporated at low pressure and the resulting yellow residue was dissolved in tetrahydrofu-ran (THF). The THF solution was adsorbed onto CeliteTM and the solvent was removed under low pressure. The Celite was then placed on a silica gel column (2 cmφ/4 cm) in a hexane/toluene (5/1) mixture under N2 pressure. A yellow fraction with a yield of 57% (32 mg, 0.041 mmol) was collected as cluster 2.1H NMR (300 MHz, CD2Cl2): d −18.80 (brm, 2H, m-H), 2.24 (s, 3H, p-CH3), 2.67 (s, 6H, o-CH3), 5.85 (brd, 2H, JPH = 144.6 Hz, PH), 6.91–7.39 (m, 7H, ArH). 31P{1H} NMR (121.5 CD2Cl2): d−68.9 (d, JPP = 113.6 Hz, PH2Ph), 233.2 (d, JPP = 113.6 Hz, Scheme 1. Synthetic scheme for compounds 2 and 3http://www.cis.latinamres.org                                  	5PMes). IR nCO (KBr, cm−1): 2077 (s), 2043 (s), 2033 (vs), 2008 (m), 1997 (s), 1989 (s), 1968 (s). Anal. Calcd for C23H20O8P2Ru3: C, 34.99; H 2.55. Found: C, 35.05; H, 2.69. Synthesis of [Ru3(CO)9(m3-PMes)(m3-PPh)] (3)Cluster 2 (30 mg, 0.038 mmol) was dissolved in toluene (20 mL) and refluxed overnight under a CO atmosphere. Silica gel chro-matography was performed using the methods discussed above and compound 3 was obtained as a yellow fraction with a 42% yield (13 mg, 0.016 mmol) along with several unidentified pro-ducts. 1H NMR (300 MHz, C6D6): d 1.91 (s, 3H, p-CH3), 2.74 (s, 3H, o-CH3), 2.75 (s, 3H, o-CH3), 6.59–7.55 (m, 7H, ArH). IR nCO (KBr, cm−1): 2056 (s), 2034 (s), 2008 (s), 1996 (s), 1984 (s), 1979 (s).X-ray diffraction data were collected at 150(2) K with a Rigaku R-AXIS RAPID imaging plate using Mo radiation (λ = 0.71069 Å). The structural identification and refinement were performed using the SHELXL-97 software [9]. Two H atoms bridging Ru atoms and two H atoms on the P atom observed in cluster 2 wi-thin a difference-Fourier map were freely refined. All other H atoms were placed at geometrically calculated positions, i.e., C–H = 0.95 or 0.98 A°. Crystallographic data from the structural analyses are available at the Cambridge Crystallographic Data Center, CCDC 1950762 and 1950763.Commun. Inorg. Synth.                                                                                                           Kakizawa, T. /Vol. 7, Nº1(2019), 4-63. RESULTS AND DISCUSSIONThe thermal reaction of [Ru3(CO)9(m-H)2(m3-PMes)] (1) with PH2Ph in a hexane solution formed the complex [Ru3(-CO)8(PH2Ph)(m-H)2(m3-PMes)] (2) (Scheme 1). X-ray analysis suggests that complex 2 is crystallized in the triclinic crystal system with P-1 space group. Complex 2 crystallized with two independent molecules in an asymmetric unit (Figure 1A). The structure of cluster 2 maintains a phosphinidene-capped, triangu-lar, and pyramidal core, in which the PH2Ph moiety coordinates as a terminal phosphine ligand (Figure 1B). The phenyl groups of the two independent molecules, A and B, are inclined in di-fferent directions (Fig. 1B), probably due to intermolecular inte-ractions of aromatic rings (Figure 2). Selected bond lengths and angles for cluster 2 are presented in Table 1. The Ru–Ru bond intervals containing hydrogen bridges, i.e., Ru1–Ru2, Ru1–Ru3, Ru4–Ru5, and Ru4–Ru6, are slightly longer than those without hydrogen bridges, i.e., Ru2–Ru3 and Ru5–Ru6, for molecules A and B, respectively.Heating complex 2 in a toluene solution under CO atmosphe-re produced [Ru3(CO)9(m3-PMes)(m3-PPh)] (3). The crystalline structure of 3 is depicted in Figure 3, with selected bond leng-ths and angles presented in Table 2. The complex 3 is crystalli-zed in the monoclinic crystal system with P 21/c space group. It Figure 1. (A) Packing of [Ru3(CO)8(PH2Ph)(m-H)2(m3-PMes)] (2) along the a axis and (B) the structure of the two independent molecules, A and B, of cluster 2. The thermal ellipsoids are shown at 50% probability.	             Molecule A                                                     Molecule BRu1–Ru2      2.9270(4)              Ru4–Ru5              2.9345(3)Ru1–Ru3      2.9319(3)                   Ru4–Ru6              2.9342(3)Ru2–Ru3      2.8035(3)                   Ru5–Ru6              2.8035(3)Ru1–P1                      2.3243(8)                   Ru4–P3              2.3261(8)Ru2–P1                      2.3178(8)                   Ru5–P3              2.3215(8)Ru3–P1                      2.3218(8)                   Ru6–P3              2.3152(8)Ru1–P2                      2.3622(8)                   Ru4–P4              2.3627(8)Ru2–Ru1–Ru3       57.176(8)                   Ru5–Ru4–Ru6              57.071(8)Ru1–Ru2–Ru3       61.499(8)                   Ru4–Ru5–Ru6              61.459(9)Ru1–Ru3–Ru2       61.325(9)                   Ru4–Ru6–Ru5              61.470(8)Table 1. Selected bond lengths [Å] and angles [°] for molecules A and B of complex 2.Commun. Inorg. Synth.                                                                                                           Kakizawa, T. /Vol. 7, Nº1(2019), 4-6contains a square, pyramidal Ru3P2 core, with a distorted square base comprising two phosphorus atoms, two ruthenium atoms, and a capped Ru(CO)3 moiety. The pyramidal core possesses two different phosphinidene ligands, i.e., m3-PMes and m3-PPh.The creation of Ru3P2 clusters containing two types of phosphi-nidene ligands is possible through several synthetic approaches performed in this study and in the literature. Freytag et al. com-bined asymmetric diphosphene, Mes-P = P-(C6H2-2,4,6-tert-Bu3) and Ru3(CO)12 to produce Ru3(CO)9(μ3-P-Mes)(μ3-PC6H2-2,4,6-tert-Bu3) [10]. Scheer et al. reported [Ru3(CO)9(μ3-PPh){μ3-PC(CO)Ar′}] (Ar′ = (2,4,6-tBu3C6H2)) as a final product of a reaction between [Ru4(CO)13(μ3-PPh)] and phosphalkynes Ar’C ≡ P [11]. Compound 3 produced in this study is also an asymme-tric Ru3P2 cluster formed by stepwise reactions.6	Figure 2. Partial packing of 2. The pale blue dashed lines are C16–C21 (3.384 Å) and C21–C45 (3.364 Å).	Figure 3. The structure of [Ru3(CO)9(m3-PMes)(m3-PPh)] (3). Thermal ellipsoids are shown at 50% probability.In conclusion, the thermal reaction between complex 1 and PH2Ph formed trinuclear ruthenium, complex 2, incorporating PH2Ph as a terminal phosphine ligand. Subsequent thermoly-sis of complex 2, in the presence of CO, produced asymmetric Ru3P2, i.e., cluster 3. X-ray analyses of clusters 2 and 3 revealed that compound 2 crystallized with two independent molecules in an asymmetric unit, while the Ru3P2 cluster 3 combined two different phosphinidene ligands into a molecule.AcknowledgmentsThis study was supported in part by a Waseda University Grant for Special Research Projects (project number 2017K-199). The author thanks Dr. H. Hashimoto and Professor H. Tobita for their useful assistance.4. REFERENCES[1] García, M. E.; García-Vivó, D.; Ramos, A.; and Ruiz, M. A. Coord. Chem. Rev. 2017, 330, 1.[2] Huttner, V. G. and Knoll, K. Angew. Chem. 1987, 99, 765.[3] Field, J. S.; Haines, R. J.; and Smit. D. N. J. of Organomet. Chem. 1986, 304, C17.[4] Sanchez-Nieves, J.; Sterenberg, B. T.; Udachin, K. A. and Carty, A. J. Inorg. Chim. Acta 2003, 350, 486.[5] Bartsch, R.; Blake, A. J.; Johnson, B. F. G.; Jones, P. G.; Ru1–Ru2               2.8700(10)           Ru2–Ru3                 2.8766(10)Ru1–P1                              2.363(2)                          Ru1–P2                 2.315(2)Ru2–P1                              2.391(2)                          Ru2–P2                 2.383(2)Ru3–P1                              2.357(2)                          Ru3–P2                 2.331(2)Ru1–Ru2–Ru3                 82.23(3)                          Ru1–P1–Ru3  106.37(9)P1–Ru2–P3               69.89(8)                          Ru1–P2–Ru3  108.86(9)Table 2. Selected bond lengths [Å] and angles [°] for complex 3.Müller, C.; Nixon, J. F.; Nowotny, M.; Schmutzler, R.; and Shephard, D. S. Phosphorus, Sulfur Silicon Relat. Elem. 1996, 115, 201.[6] Deeming, A. J.; Doherty, S.; and Powell, N. I. Inorg. Chim. Acta 1992, 198–200, 469.[7] Kakizawa, T.; Hashimoto, H.; and Tobita, H. J. Organomet. Chem. 2006, 691, 726.[8] Kakizawa, T.; Hashimoto, H.; and Tobita, H. Inorg. Chim. Acta 2015, 425, 7.[9] Sheldrick, G. M. Acta Cryst. 2008, A64, 112.[10] Freytag, M.; Edelmann, F. T.; Ernst, L.; Jones, P. G.; and Schmutzler, R. Z. Anorg. Allg. Chem. 2004, 630, 377.[11] Scheer, M.; Krug, J.; Kramkowski, P.; and Corrigan J. F. Organometallics 1997, 16, 5917. This  is  an  open  access  article  dis-tributed under  the  Creative  Com-mons  Attribution License,  which permits  unrestricted use, distribu-tion, and reproduction  in any  me-dium, provided the original work is properly cited. Communications in Inorganic Synthesis is sponsored and  supported by: Universidad de Santiago de Chile.

Synthesis and crystal structures of triruthenium clusters containing  phosphinidene ligands

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Synthesis and crystal structures of triruthenium clusters containing phosphinidene ligands

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