Organometallic clusters as precursors of metallic nanoparticles 3

Chapter Deposition of osmium clusters onto inorganic oxide surfaces Over the past two decades or so there has been sustained interest in the synthesis, characterization and chemistry of transition metal clusters, which provide an opportunity to examine the evolution of properties associated with the bulk state Metal clusters have found many important applications in homo and heterogeneous catalysis One example is their use as precursors for the deposition of particularly small and well-defined homonuclear or heteronuclear metal particles on oxide supports In addition, clusters can act as valuable models for the structure and reactivity of reagents and fragments that are bound to metal surfaces during reactions Direct interaction of carbonyl clusters with high-surface-area oxides can give rise to chemisorbed derivatives, and in most cases anchoring of osmium clusters to inorganic oxides can been studied by comparison of their IR spectra with known osmium clusters Most often, cluster attachment has been effected by simple ligand association and ligand exchange Attachment of osmium clusters with inorganic oxide surfaces proceeds through reactions with the groups on the surfaces The surface species Os3(CO)10(μ-H)(μ-OSi≡) (where Si≡ represents surface) from the reaction between Os3(CO)12 Os3(CO)10(NCCH3)2, or Os3(CO)10(μ-H)2 with silica support has been confirmed by many characterization methods, such as IR, Raman, XPS, EXAFS, UV-visible spectroscopies and TEM Oxidative fragmentation of the clusters Os3(CO)12 adsorbed on MgO powder was investigated by X-ray absorption spectroscopy and scanning transmission electron microscopy (STEM) Exposure of the clusters to air leads to their fragmentation, oxidation of the osmium, and formation of ensembles consisting of three Os atoms [Os5C(CO)14]2- was synthesized on the surface of MgO by reductive carbonylation of adsorbed Os3(CO)12 at 548 K The 27 supported species were characterized by IR, 13C NMR, and EXAFS spectroscopies The attachment of osmium clusters on functionalized silica support (ligand used = Ph2PCH2CH2Si(OEt)3-x(OSi≡), between HS(CH2)3Si(OMe)3-x(OSi≡))or the interaction Os3(CO)10(μ-H)[μ-S(CH2)3Si(OMe)3] with silica gel have been well studied using IR spectroscopy Bimetallic catalysts of gold-osmium supported on silica have also been studied 10 Some of these supported osmium clusters with well-defined structures are listed in Table 2.1 Table 2.1 Supported osmium clusters with well-defined structures on functionalized silica surface Metal framework Support Surface structures Characterization method Os3 Ph2P-Si≡ H2Os3(CO)9(Ph2P-Si≡) IR Os3 Ph2P(CH2)2-Si≡ Os3(CO)9(μ-Cl)PPh2(CH2)-Si≡ IR AuOs3 Ph2P(CH2)2-Si≡ HAuOs3(CO)10Ph2P(CH2)-Si≡ IR Ph2P(CH2)2-Si≡ ClAuOs3(CO)10Ph2P(CH2)-Si≡ Os3 HS-Si≡ HOs3(CO)10S(CH2)3-Si≡ IR Os3 SiO2 HOs3(CO)10-O-Si≡ IR, Raman, TEM, XPS, composition EXAFS, UV-visble In this chapter, the synthesis of osmium and ruthenium clusters with bifunctional ligands and their deposition onto inorganic oxides will be described 2.1 Synthesis of osmium and ruthenium clusters with ligands containing two functional groups The triosmium clusters Os3(CO)10(μ-H)(μ-OH), or Os3(CO)10(NCCH3)2, have been reported to react with various alcohols to form hydridoalkoxy and dialkoxy-derivatives with the general formulae Os3(CO)10(μ-H)(μ-OR) and 28 Os3(CO)10(μ-OR)2, respectively; 11 and with thiols and carboxylic acids to form hydridothiolato or hydridocarboxylato derivatives, respectively 12 The reaction between Os3(CO)10(NCCH3)2 and dicarboxylic acids afforded linked clusters with the general formula [{Os3(CO)10(μ-H)}2(μ-L’)] 13 With HSCH2CH2SH or diols, only clusters with one triosmium moiety, viz., Os3(CO)10(μ-H)(μ-SCH2CH2SH) or Os3(CO)10(μ-H)[μ-O(CH2)nOH], were obtained respectively However, the reaction of Ru3(CO)12 with HSCH2COOH gave only Ru3(CO)10(μ-H)(μ-SCH2COOH) 14 We have found that the reaction of in refluxing toluene, or at ambient temperature in dichloromethane, with bifunctional ligands afforded two types of clusters (Scheme 2.1 and 2.2, respectively) The major product is of the general formula Os3(CO)10(μ-H)(μ-L ͡ L’H)(type ‘a’) In some cases, a minor product of the general formula Os3(CO)10(μ-H)(μ-L ͡ L’)Os3(CO)10(μ-H) (type ‘b’) was also obtained The reaction of with 2,5-dimercapto-1,3,4-thiadiazol afforded a complex with a more complex bonding mode, viz Os3(CO)10(μ-H)(μ-SC=NNCSS-μ3, η2) Os3(CO)9(μ-H), 29 OH Os H + HL L'H Os Os L L'H Os Os or H Os L Os Os Os Os type 'b' 4a (58 %) HS Os H H Os type 'a' HS(CH2)3SH L' 5a (63 %) SH CH2SH HSCH2 5b (3 %) 6a (37 %) HS(CH2)8SH 7a (61 %) HSCH2CH2OH 9a (95 %) HSCH2CH2CH2OH 10a (53 %) HS 7b (13 %) 11a (32 %) CH2OH HS(CH2)11OH 12a (10 %), 12a' (8 %)* HSCH2COOH 13a (77 %) HS(CH2)10COOH 17a (44 %) 17b (4 %) HS(CH2)15COOH 18a (46 %) 18b (3 %) HO(CH2)12OH 21a (48 %) 21b (3 %) 12b (1 %) * for 12a’, L = O, L’ = S Scheme 2.1 H3C Os N Os Os + HL N L L'H Os L'H CH3 Os Os H or type 'a' HS(CH2)2COOH HS HS COOH COOH L Os Os Os L' Os H H Os Os type 'b' 14a (64 %) 15a (73 %) 15b (3 %) 16a (68 %) HOOC(CH2)10OH 19a (73 %) HO(CH2)4OH 20a (52 %) Scheme 2.2 30 With the exception of 8, 15b, 17b and 18b, the products show similar patterns in the carbonyl region of their IR spectra, which are comparable to those of other triosmium clusters of the type Os3(CO)10(μ-H)(μ-SR), indicating that the metal core of these products are structurally similar; that for 17a is shown in Figure 2.1 The similar patterns of the IR spectra suggest that the anchoring of the organic fragments has little structural effect on the triosmium framework In the case of products containing two triosmium moieties bridging by thiolato-carboxylato ligands, more complicated patterns are observed Their IR spectra can be regarded as the overlap of that due to a thiolato-bridged Os3(CO)10(μ-H) moiety, which has the highest energy band at 2108-2110 cm-1, and a carboxylato-bridged Os3(CO)10(μ-H) moiety, which has the highest energy band at 2113-2114 cm-1 In the 1H NMR spectra, the thiolato bridged osmium clusters exhibit a hydride resonance at about -17 ppm For carboxylato bridged clusters, this appears at about -10 ppm, and for alkoxy bridged clusters at about -12 ppm There is also an upfield shift in the hydride resonances of osmium clusters containing an aromatic ring compared to the alkyl analogues about 0.3-0.7 ppm for thiolato bridged clusters, and about 0.3 ppm for carboxylato bridged clusters The resonances for organic fragments nearer to the clusters are also shifted upfield compared to the free ligands This suggests that the clusters exert some electronic effect on the organic substrates 100 %T 2067.23 20 2160 2140 2120 os3s10cooh in hex 2100 2080 2060 2040 1989.59 1998.75 2019.00 40 2024.79 2058.55 60 1982.84 2109.18 80 2020 2000 1990 1980 1970 1960 1/cm Figure 2.1 Solution IR spectrum of 17a in the carbonyl region 31 Whether products containing one or two triosmium moieties (type ‘a’) are formed depend on the nature of the ligand The methylene chain length of the ligands has a strong influence A longer methylene chain favors a product containing two triosmium moieties while a shorter chain favors the formation of a product containing one triosmium moiety An aromatic ring spacer also favors the formation of a product containing two triosmium moieties Furthermore, propensity of the functionalities to bond to osmium follows the order SH > COOH > OH Ru + HS COOH Ru Ru S COOH Ru Ru Ru H type 'a' 14a(Ru) (31 %) HS(CH2)2COOH 15a(Ru) (61 %) HS COOH COOH 16a(Ru) (27 %) HS(CH2)10COOH 17a(Ru) (43 %) HS(CH2)15COOH 18a(Ru) (80 %) HS Scheme 2.3 In the reactions with Ru3(CO)12, 3, only products of type ‘a’ moiety were formed (Scheme 2.3) This showed that the metal has an important influence on the product formed The IR spectra of the products also showed patterns in the metal carbonyl region that are similar to the type ‘a’ osmium clusters, and the metal hydride resonances are at ~ -15 ppm, which indicated that it is the SH which has reacted with 32 the triruthenium core.14 Os (1) S(1) Os (3) C(1) Os (2) Table 2.2 Selected bond lengths (Å) and bond angles (o) for 5a, 5b, 9a, 13a, 14a and 15a Selected Bond 5a 5b 9a 13a 14a 15a Os(1)-Os(2) 2.8628(2) 2.8571(4) 2.8841(4) 2.8546(4) 2.8518(6) 2.8694(4) Os(2)-Os(3) 2.8628(2) 2.8565(4) 2.8347(4) 2.8563(4) 2.8574(6) 2.8418(4) Os(3)-Os(1) 2.8462(2) 2.8658(5) 2.8349(4) 2.8483(4) 2.8436(7) 2.8544(4) Os(1)-S(1) 2.4171(10) 2.4185(18) 2.4102(16) 2.4059(18) 2.399(3) 2.4119(16) Os(2)-S(1) 2.4171(10) 2.4153(18) 2.4124(16) 2.4063(19) 2.418(3) 2.4123(16) S(1)-C(1) 1.793(4) 1.779(8) 1.828(6) 1.836(8) 1.833(11) 1.788(6) 72.63(3) 72.47(5) 73.46(4) 72.77(5) 72.60(8) 73.00(5) Lengths Bond angles (o) Os(1)-S(1)-Os(2) Five clusters of type ‘a’ (5a, 5b, 9a, 13a, 14a, and 15a) and two of type ‘b’ (5b and 15b), together with 8, were characterized crystallographically The molecular structures of 5a and 5b are shown in Figures 2.2 and 2.3 respectively The overall structure of 5b is very similar to that of the methanedithiolate osmium analog of [Os3(CO)10(μ-H)]2(μ-η2-SCH2S) and propanedithiolato osmium/ruthenium analogs of [M3(CO)10(μ-H)]2(μ-η2-SCH2CH2CH2S) (M = Os, Ru).13b, 13e Structurally, 5b is equivalent to two moieties of 5a and hence it is discussed together with the other type ‘a’ clusters Selected bond parameters and a common atomic number scheme for 5a, 33 5b, 9a, 13a, 14a, and 15a are shown in Table 2.2 In all these structures, the Os-S distances [2.399(3)-2.4185 Å] is similar to reported values The Os-Os distances [2.8347(4)-2.8694(4) Å] are also similar to reported values for μ-S bridging clusters However, it is interesting to note that the latter does not show any trend with respect to the other Os-Os bond lengths Figure 2.2 ORTEP diagram for 5a; thermal ellipsoids were drawn at the 50% probability level and aromatic hydrogens have been omitted Figure 2.3 ORTEP diagram for 5b; thermal ellipsoids were drawn at the 50% probability level 34 Compound 15b is a type ‘b’ cluster in which L ≠ L’ The molecular structure of compound 15b and selected bond parameters are given in Figure 2.4 The Os-Os bond length for osmium clusters which are bridging by the carboxylate is longer compared to the others in the same unit [2.9244(10), 2.8659(7), 2.8758(8) Å] This effect is well-known and is sensitive to the other donor atoms coordinated to the osmium atoms.13d The Os-O distances [2.131(7)-2.150(7) Å] and metal carbonyl distance are similar to reported values So are the Os-Os and Os-S distances for the thiolato-bridged moiety 15 Figure 2.4 ORTEP diagram for 15b, with thermal ellipsoids drawn at the 50% probability level Selected bond lengths (Å) and bond angles (o) for 15: Os(1)-Os(2) 2.8708(7), Os(2)-Os(3) 2.8746(8), Os(3)-Os(1) 2.8450(7), Os(4)-Os(5) 2.9244(10), Os(5)-Os(6) 2.8659(7), Os(6)-Os(4) 2.8758(8), Os(1)-S(1) 2.418(3), Os(2)-S(1) 2.426(3), Os(4)-O(71) 2.131(7), Os(5)-O(72) 2.150(7), S(1)-C(1) 1.807(10), Os(1)-S(1)-Os(2) 72.69(8) The structure of is shown below (Figure 2.5) It is structurally similar to 5b, except that an additional nitrogen atom has also coordinated to one of the triosmium 35 moiety in place of a carbonyl The Os(1)-Os(2) distance [2.8067 Å] in this particular unit is shorter compared to the others in the same cluster [2.8413(9)-2.8503(10) Å], and the thiolato-bridged Os-Os bond length is similar to those of structurally similar clusters such as Os3(CO)9(μ-H)(μ-pyS) [2.874(1) Å] and [{Os3(CO)9(μ-H)}(μ-SC5H3NCO2){Os3(CO)10(μ-H)}] [2.853(1) Å] 16,15b Figure 2.5 ORTEP diagram and selected bond lengths (Å) and angles (o) for (thermal ellipsoids were drawn at the 50% probability level): Os(1)-Os(2) 2.8067(10), Os(2)-Os(3) 2.8318(10), Os(3)-Os(1) 2.8083(10), Os(4)-Os(5) 2.8464(9), Os(5)-Os(6) 2.8413(9), Os(6)-Os(4) 2.8503(10), Os(1)-S(1) 2.426(5), Os(2)-S(1) 2.453(4), Os(4)-S(2) 2.413(4), Os(5)-S(2) 2.417(2), S(1)-C(1) 1.733(17), S(2)-C(2) 1.791(17), Os(1)-S(1)-Os(2) 70.23(12), Os(4)-S(2)-Os(5) 72.11(11) 36 2.6.1.2 Synthesis of osmium and ruthenium clusters with a ligand containing a bifunctional group In a typical experiment, to a solution of (30 mg, 0.035 mmol) in toluene (20 ml) was added the ligand in excess and HBF4/ether (1 drop) and the resulting mixture refluxed for h The reaction was monitored by NMR spectroscopy With cluster (80 mg, 0.085 mmol), the mixture with excess ligand in dichloromethane (30 ml) was allowed to stir at ambient temperature overnight After the reaction, the solvents were removed in vacuo and the products purified by column chromatography using hexane/DCM as the eluant With cluster (30 mg), the mixture with a stoichiometric amount of ligand in toluene (10 ml) was heated at 60 oC for h After the reaction, the solvents were removed in vacuo and the products purified by column chromatography using pure dichloromethane as the eluant Tables 2.4-2.6 list the products obtained from the various ligands, and their yields Tables 2.7-2.9 contains the characterization data of the products Table 2.4 Reaction of with bifunctionalized ligands Ligand used Amount Products Colour Yield (%) of ligand 1,3-propanedithiol 0.1 ml 4a yellow 58 1,3-benzenedithiol 0.1 ml 5a yellow 63 5b yellow 1, 4-benzenedimethyldithiol 0.1 ml 6a yellow 37 1,8-octanedithiol 0.1 ml 7a yellow oil 61 7b yellow oil 14 2, 5-dimercapto-1, 3, 4-thiadiazol mg red 2-mercaptoethanol 0.1 ml 9a yellow 95 3-mercaptopropanol 0.1 ml 10a yellow 53 57 2-mercaptobenzyl alcohol mg 11a yellow 32 11-mercapto-1-undecanol mg 12a yellow oil 10 12a’ yellow oil 12b yellow oil mercaptoacetic acid 0.1 ml 13a yellow 77 11-mercaptoundecanoic acid mg 17a yellow oil 44 17b yellow oil 18a yellow oil 46 18b yellow oil 21a yellow oil 48 21b yellow oil Products Colour Yield (%) 16-mercaptohexadecanoic acid 11 mg 1, 12-dodecadiol mg Table 2.5 Reaction of with bifunctionalized ligands Ligand used Amount of ligand 2-mercaptobenzyl alcohol 12 mg 11a yellow 70 3-mercaptopropanoic acid 0.1 ml 14a yellow 64 3-mercaptobenzoic acid 16 mg 15a yellow 73 15b yellow 4-mercaptobenzoic acid 16 mg 16a yellow 68 11-hydroxyundecanoic acid 22 mg 19a yellow oil 73 1,4-butanediol 0.1 ml 20a yellow 52 Table 2.6 Reaction of with bifunctionalized ligands Ligand used Products Colour Yield (%) 3-mercaptopropanoic acid 14a(Ru) Red solid 31 3-mercaptobenzoic acid 15a(Ru) red oil 61 4-mercaptobenzoic acid 16a(Ru) red solid 27 11-mercaptoundecanoic acid 17a(Ru) red oil 43 16-mercaptohexadecanoic acid 18a(Ru) red oil 80 58 Table 2.7 Characterization data of osmium clusters IR (hexane) vCO (cm-1) 4a FAB (m/z) [M+]: Calcd (Found) 2109w, 2067vs, 2058s, 2021vs, 2110w, 2071s, 2059m, 2023s, 993 (994) H δ (ppm in CDCl3) Calcd (Found) 2.62 (q, 2H, CH2SH), 2.47 (t, 2H, SCH2), 1.94 (quintet, 2H, C,16.28 (16.75); H, 0.84 (0.85); SCH2CH2), 1.39 (t, SH), -17.40 (s, 1H, OsHOs) 959 (960) 1996m, 1987w 5a Elemental analysis (%) S, 6.69 (6.98) 7.23-7.01 (m, 4H, Ph), 3.47 (s, 1H, SH), -17.05 (s, 1H, OsHOs) C, 19.35 (19.80);H, 0.61 (0.63); S, 6.46 (6.13) 2000m, 1998w** 6a 2109w, 2067s, 2058m, 2022s, 1021 (1020) (t,1H, SH), -17.38 (s, 1H, OsHOs) 1997w, 1981w** 7a 2109m, 2067vs, 2058s, 2026vs, 7.27 (d, 4H, Ph), 3.71 (d, 2H, CH2SH), 3.58 (s, 2H, SCH2), 1.73 1029 (1028) C, 21.01 (21.28); H, 1.76 CH2CH2SH, 2019s, 1999m, 1989m, 1983w 2.50 (q, 2H, CH2SH), 2.35 (t, 2H, SCH2), 1.63 (m, 5H, SCH2CH2, (2.03); S, 6.23 (6.04) SH), 1.30-1.47 (m, 8H, SCH2- CH2(CH2)4CH2CH2SH), -17.40 (s, 1H, OsHOs) 2114w, 2088m, 2075vs, 2067s, -16.93 (s, H, OsHOs), -11.70 (s, 1H, OsHOs) 2030vs, 2003s, 1958w 9a 2109w, 2068s, 2059m, 2025s, 929 (930) 10a 2108w, 2067vs, 2057m, 2021s, 11a 2110w, 2069vs, 2057vs, 2024s, 991 (992) 1999m, 1967w 12a 2109w, 2069vs, 2058m, 2020s, 1998w, 1980w 1054 (1055) 3.77 (q, 2H, CH2OH), 2.49 (t, 2H, SCH2), 1.87 (quintet, 2H, C, 16.56 (16.44); H, 0.86 (0.89); S, 3.57 (3.40) 7.32-7.40 (m, 3H, Ph ), 6.82 (d, 1H, Ph), 5.09 (s, 2H, CH2) -16.92 C, 20.60 (20.32); H, 0.81 (s, 1H, OsHOs) 1995w, 1980w (0.79); S, 3.45 (3.01) SCH2CH2), 1.34 (t, 1H, OH), -17.38 (s, 1H, OsHOs) 945 (944) C, 15.52 (15.51); H, 0.65 -17.36 (s, 1H, OsHOs) 2020sh, 2001w, 1990w, 1984w 3.85 (t, 2H, CH2OH), 2.62 (t, 2H, SCH2) , 1.74 (t, 1H, OH), (0.78); S, 3.24 (2.91) 3.63 (t, 2H, CH2OH), 2.35 (t, 2H, SCH2), 1.54 (m, 4H, SCH2CH2, C, 23.90 (24.32); H, 2.29 CH2CH2OH), 1.27 (m, 14H, SCH2CH2(CH2)7CH2CH2OH)), (2.14); S, 3.04 (2.84) -17.40 (s, 1H, OsHOs) 59 12a’ 2108w, 2066vs, 2057m, 2021s, 1054 (1057) 3.52 (t, 2H, CH2O), 2.67 (t, 2H, HSCH2), 1.54 (m, 4H, SCH2CH2, CH2CH2OH), 1.27 (m, 14H, SCH2CH2(CH2)7CH2CH2OH), 1997w, 1983w -12.53 (s, 1H, OsHOs) 13a 2111w, 2070s, 2060m, 2023s, 942 (941) 3.21 (s, 2H, CH2), -17.36 (s, 1H, OsHOs) C, 15.29 (15.63); H, 0.43 (0.78); S, 3.40 (3.29) 1999 w** 14a 2112w, 2071s, 2061m, 2026vs, 957 (958) 2.74-2.87 (m, 4H, CH2CH2), -17.30 (s, 1H, OsHOs) C, 16.32 (16.54); H, 0.63 (0.62); S, 3.35 (3.49) 2021 m (sh), 2001m, 1989w, 1984w 15a 2110w, 2069s, 2060m, 2024vs, 1005 (1005) 16a 2110w, 2070s, 2060m, 2024vs, C, 20.32 (20.18); H, 0.60 Ph), -16.98 (s, 1H, OsHOs) 2001m, 1982w 8.0 (s, 1H, Ph), 7.96 (d, 1H, Ph), 7.56 (d, 1H, Ph), 7.41 (t, 1H, (0.65); S, 3.19 (3.12) 1005 (1006) 8.04 (d, 2H, Ph), 7.39 (d, 2H, Ph), -7.06 (s, 1H, OsHOs) 1070 (1072) 2.35 (m, 4H, SCH2, CH2COOH), 1.65 (m, 4H, SCH2CH2, C, 23.59 (23.56); H, 2.07 CH2CH2COOH), 1.27 (m, 12H, SCH2CH2(CH2)6), -17.41 (s, 1H, (1.70); S, 3.00 (3.07) 2001m, 1982w** 17a 2108w, 2066vs, 2057m, 2024s, 2020s, 1996m, 1989w, 1982w OsHOs) 18a 2108w, 2066vs, 2057m, 2021vs, 1996w, 1982w** 3.63 (t, 2H, SCH2), 2.35 (t, 2H, CH2COOH), 1.54 (m, 4H, C, 27.41 (27.40); H, 2.83 SCH2CH2, CH2CH2COOH), 1.24 (m, 22H, SCH2CH2(CH2)11), 1139 (1140) (2.25); S, 2.81 (2.87) -17.41 (s, 1H, OsHOs) 19a 2113w, 2074vs, 2062s, 2024vs, 1067 (1068) 3.63 (t, 2H, CH2OH), 2.18 (t, 2H, CH2COO), 1.54 (m, 4H, HOCH2CH2, 2014s, 1981w OOCCH2CH2), 1.22 (m, C, 24.76 (25.22); H, 2.27 (2.49) 14H, HOCH2CH2(CH2)7CH2CH2COOH), -10.51 (s, 1H, OsHOs) 20a 2109w, 2067vs, 2058s, 2025vs, 941 (942) 3.57 (m, 4H, CH2(CH2)2CH2), 1.53 (m, 4H, CH2(CH2)2CH2) C, 17.87 (18.26); H, 1.07 (1.14) 1988w 60 21a 2109w, 2069vs, 2058s, 2020vs, 3.63 (t, 2H, CH2OH), 3.51 (t, 2H, OCH2) 1.45 (m, 4H, 1053 (1054) C, 25.09 (24.67); H, 2.49 (2.53) HOCH2CH2, OCH2CH2), 1.23 (m, 16H, HOCH2CH2(CH2)8), 1997m, 1977w -12.53 (s, 1H, OsHOs) ** IR was recorded in dichloromethane Table 2.8 Characterization data of osmium clusters IR (CH2Cl2) FAB (m/z) [M+]: vCO (cm-1) Calcd(Found) H δ (ppm in CDCl3) 5b 2109w, 2071s, 2061m, 2027vs, 2021sh, 2004w 1844 (1843) 7.42 (s, 1H, Ph), 7.32 (t, 1H, Ph), 7.03 (d, 2H, Ph), -17.05 (s, 1H, OsHOs) 7b 2108w, 2066vs, 2057m, 2020vs, 1998m 2056 (2056) 2.67 (t, 2H, CH2S), 2.35 (t, 2H, SCH2), 1.66 (quintet, 4H, SCH2CH2), 1.32 (m, 8H, SCH2CH2(CH2)4CH2CH2SH), -17.40 (s, 1H, OsHOs) 12b 2108w, 2068vs, 2058m, 2020s, 1996w, 1982w 1906 (1905) 3.52 (t, 2H, CH2O), 2.35 (t, 2H, SCH2), 1.54 (m, 4H, SCH2CH2, CH2CH2OH), 1.27 (m, 14H, SCH2CH2(CH2)7CH2CH2OH), -12.53 (s, 1H, OsHOs), -17.40 (s, 1H, OsHOs) 15b 2114w, 2110w, 2076m, 2070s, 2066m, 2061m, 1856 (1857) 2027vs, 2017m, 2003w, 1991w, 1986w 17b 2112w, 2109w, 2072s, 2067vs, 2063s, 2058m, OsHOs), -17.08 (s, 1H, OsHOs) 1919 (1920) 2029vs, 2023vs, 2014s, 2000m, 1989m, 1985w 18b 2113w, 2109w, 2075s, 2067vs, 2063s, 2058m, 2109w, 2069vs, 2059m, 2021s, 1997w 2.35 (t, 2H, SCH2), 2.18 (t, 2H, CH2COOH), 1.61 (m, 4H, SCH2CH2, CH2CH2COOH), 1.24 (m, 22H, SCH2CH2(CH2)11), -10.51 (s, 1H, OsHOs), -17.41 (s, 1H, OsHOs) 1990 (1990) 2028vs, 2024vs, 2014s, 1999m, 1989m, 1984w 21b 7.58 (d, 1H, Ph), 7.56 (s, 1H, Ph), 7.47 (d, 1H, Ph), 7.21 (m, 1H, Ph), -10.28 (s, 1H, 2.35 (t, 2H, SCH2), 2.18 (t, 2H, CH2COOH), 1.54 (m, 4H, SCH2CH2, CH2CH2COOH), 1.24 (m, 22H, SCH2CH2(CH2)11), -10.51 (s, 1H, OsHOs), -17.41 (s, 1H, OsHOs) 1904 (1902) 3.51 (t, 4H, CH2O), 1.47 (m, 4H, HOCH2CH2), 1.22 (m, 16H, HOCH2CH2(CH2)8), -12.53 (s, 1H, OsHOs) 61 Table 2.9 Characterization data of ruthenium clusters IR (CH2Cl2) vCO (cm-1) 14a(Ru) FAB (m/z) [M+]: Calcd (Found) 2105w, 2066s, 2057m, Elemental analysis (%) H δ (ppm in CDCl3) 689 (685) 3.13 (t, 2H, CH2), 2.95 (t, 2H, CH2), -15.42 (s, 1H, RuHRu) 738 (737) Calcd (Found) 8.0 (s, 1H, Ph), 7.94 (d, 1H, Ph), 7.59 (d, 1H, Ph), 7.35 (t, 1H, Ph), -14.96 (s, 2024s, 2010w, 1992w 15a(Ru) 2107w, 2068s, 2058m, 1H, RuHRu) 2022vs, 1962w 16a(Ru) 2106w, 2067s, 2057m, 738 (663) 8.08 (d, 2H, Ph), 7.47 (d, 2H, Ph), -15.08 (s, 1H, RuHRu) 802 (799) 2.34 (t, 2H, CH2COOH), 2.14 (t, 2H, SCH2), 1.62 (m, 4H, SCH2CH2, C, 31.46 (31.84); CH2CH2COOH), 1.28 (m, H, 2.77 (3.19); 2024s, 2015w 17a(Ru) 2104w, 2064vs, 2053m, 2022s, 2005w 12H, SCH2CH2(CH2)6CH2CH2COOH), -15.36 (s, 1H, RuHRu) 18a(Ru) 2104w, 2063vs, 2055m, 2021s, 2006w, 1988w 872 (873) S, 4.00 (4.29) 2.34 (t, 2H, CH2COOH), 2.14 (t, 2H, SCH2), 1.64 (m, 4H, SCH2CH2, C, 35.82 (36.07); CH2CH2COOH), 1.25 (m, H, 3.70 (3.57); 1H, RuHRu) 22H, SCH2CH2(CH2)11CH2CH2COOH), -15.36 (s, S, 3.68 (3.57) 62 Table 2.10 Crystal data for 5a, 5b, and 9a Compound 5a 5b 9a Formula Fw Temperature (K) Crystal system Space group Unit cell dimensions a (Å) b (Å) c (Å) α (o) β (o) γ (o) Volume (Å3) Z ρc (mg m-3) μ(Mo Kα) (mm-1) F(000) Crystal size (mm3) θ range (o) Index ranges C16 H6 O10 Os3 S2 992.93 223(2) Triclinic P⎯1 C26 H6 O20 Os6 S2 1843.63 223(2) Monoclinic C2/c C21 H2 N2 O19 Os6 S3 1823.63 223(2) Orthorhombic P212121 C12 H6 O11 Os3 S 928.83 223(2) Monoclinic P21/n 9.1515(3) 9.3399(3) 14.6987(5) 80.5880(10) 86.0230(10) 63.6290(10) 1110.46(6) 2.970 17.358 884 0.32 x 0.20 x 0.06 2.46 to 30.50 -12