Chapter Oxidative addition chemistry of Cp*IrOs3(μ-H)2(CO)10 with Group 16 substrates 5.1 Chalcogenide transition metal carbonyl clusters The reaction of group 16 substrates with transition metal carbonyl clusters often resulted in oxidative-addition rather than simple substitution. For example, oxidative addition of PhSeSePh to Os3(CO)10(CH3CN)2 was reported to occur with Se-Se bond cleavage to give Os3(CO)10(SePh)2 (Scheme 5.1) [1]. Os3(CO)10(CH3CN)2 PhSeSePh (CO)4Os Os(CO)3 SePh PhSe -CO isomerisation in refluxing hexane (CO)3 Os (CO)3 Os PhSe Se Se O C Os(CO)3 (CO)4Os Os (CO)2 Os(CO)3 SePh Os (CO)3 Scheme 5.1. Chalcogenide transition metal carbonyl clusters have been attracting attention in recent years both in fundamental research and in technological fields [2]. They are of interest in organometallic chemistry because of the unusual coordination modes and geometries they exhibit [3, 4]. Furthermore, the presence of chalcogenide ligands 171 often appears to be a key factor in cluster growth reactions [5]. The chalcogenide atoms also play a major role in cluster catalysis due to their potential to act as stabilizing ligands, thus preventing cluster fragmentation even under forcing conditions. Some of these clusters also display unique catalytic activity. For example, chalcogenide ruthenium derivatives have shown promising catalytic activity in oxygen reduction reactions in polymer electrolyte fuel cells (PEMFC) [6]. The presence of selenium in these clusters is thought to be responsible for the catalytic activity. One of the effective methods for synthesizing transition metal clusters containing bridging chalcogenido ligands involves the tertiary phosphine chalcogenides R3PE (E = S, Se, Te). This method takes advantage of the frailty of the P=E bond, which leads to its formal oxidative addition to the cluster, resulting in the transfer of the selenium atom to low-valent metal-centres, sometimes followed by release or addition of metal fragments. The product distribution in these reactions is strongly dependent on the reaction conditions and the cluster to phosphine molar ratio. For example, reaction of the tetrahedral mixed-metal clusters, MCo3(μ-H)(CO)12 (M = Ru or Fe), with phosphine selenides afforded new chalcogenido-carbonyl bimetallic clusters. These reactions gave two main types of products: (1) trinuclear selenido clusters of the type MCo2(μ3-Se)(CO)9-n(L)n] (n = 1, with L = monodentate ligand) resulting from selenium transfer, and (2) tetranuclear clusters of the type [MCo3(μ-H)(CO)12-n(L)n] obtained by substitution of carbonyl groups by the deselenized phosphine ligand (Scheme 5.2) [7]. 172 M Co (Ph2RP)Co MCo3(μ-H)(CO)12 + Ph2RP=Se H Co M = Fe or Ru Se not isolated -Co, -H -Se M Se (Ph2RP)Co M Co Co (Ph2RP)Co Co H type type Scheme 5.2. Reactions of homonuclear metal clusters with organosulphur substrates have also been quite extensively studied, and provide an entry into sulphur-containing clusters. Ruthenium, osmium, rhodium and iridium clusters containing sulphide bridges are of special interest since they are known to be good hydrodesulfurization catalysts [8]. Adams has given a detailed report on compounds containing bridging sulfid0 ligand and the transition element osmium [9]. Reactions of aryl or alkyl sulfides with M3(CO)12 (M = Ru, Os) have been reported to afford the clusters Os3(μ-H)(μSR) (μ3,η2-C6H4)(CO)9 (R = Me, iPr) and Ru3(μ-SPh)(μ -η1 η6-C6H5)(CO)8 as a result of aryl-S cleavage (Scheme 5.3) [10]. 173 Ru (CO)2 toluene reflux Ru3(CO)12 + SPh2 Ru (CO)3 (CO)3 Ru SPh Major product Os3(CO)12 + MeSPh nonane reflux Os Os MeS H Os Scheme 5.3. The chemistry of tellurium-containing clusters can be quite different from those of sulphur and selenium analogues. For instance, the difference in reactivity of the trinuclear iron clusters, Fe3(CO)9(μ3-E)2, (E = S, Se, Te), towards Lewis bases has been attributed to the larger size of the Te atom which results in a more strained FeTe-Fe angle in Fe3(CO)9(μ3-Te)2 than in its sulphur and selenium analogues [11]; adduct formation can release the strain by cleavage of the bond between the apical and one of the basal iron atoms (Scheme 5.4). Te E = Te Fe Fe Fe Fe E Fe PPh3 RT E PPh3 Te Fe E = S, Se No reaction Scheme 5.4. 174 Mixed-metal clusters containing chalcogenides are much less common. Some examples are the clusters [Fe2MTe3(CO)11]2⎯ (M = Mo, W) which have been synthesized methanothermally using a mixture of Fe3(CO)12 and M(CO)6 (M = Mo, W) with Na2Te2 in a sealed tube at 80 ºC [12]. Although there are number of reports on the reaction of homonuclear carbonyl clusters with group 16 substrates, relatively little is known on the reactivity of these substrates with mixed-metal clusters. To date there have been no reports on the reactivity of osmium-iridium mixed-metal clusters with chalcogenides. In continuation of our reactivity studies on 3c, we have investigated its reactivity with chalcogenide substrates under mild conditions. The results of these studies are discussed in the following sections. 175 5.2 Reaction of Cp*IrOs3(μ-H)2(CO)10 with thiophenol The reaction of Cp*IrOs3(μ-H)2(CO)10, 3c, with excess thiophenol under chemical activation with TMNO at room temperature afforded the novel cluster Cp*IrOs3(μH)3(CO)9(μ-SPh), 22, as a bright orange crystalline product in ~87% yield (based on consumed 3c). Diffraction-quality crystals were grown by slow diffusion of hexane into a dichloromethane solution. The ORTEP plot is shown in Figure 5.1. Figure 5.1. ORTEP diagram and selected bond parameters for 22. Thermal ellipsoids are drawn at 50% probability level. Organic hydrogens are omitted for clarity. Ir(1)Os(2) = 2.9037(3) Å; Ir(1)-Os(3) = 2.9242(3) Å; Ir(1)-Os(4) = 2.9327(3) Å; Os(2)Os(3) = 2.8387(3) Å; Os(2)-Os(4) = 2.8448(3) Å; Os(3)-S(5) = 2.4343(15) Å; Os(4)S(5) = 2.4257(14) Å; S(5)-Os(3)-Os(2) = 78.00(3)º; S(5)-Os(4)-Os(2) = 78.01(3)º; Os(3)-Os(2)-Ir(1) = 61.213(7)º; Os(4)-Os(2)-Ir(1) = 61.340(7)º. 176 The molecule of 22 contains a wingtip-bridged butterfly cluster core consistent with the total valence electron count of 62. An osmium and iridium atom occupied the hinge of the butterfly while the wingtips were occupied by two osmium atoms. The wingtip osmium atoms were bridged by a benzene thiolato group. Three hydrides were found bridging the three iridium-osmium edges; their presence was further confirmed by 1H NMR spectroscopy. Bridging hydrides tend to elongate metal-metal bond distances and thus the presence of hydride bridges across all the three iridiumosmium bonds led to elongation of the bond distances Ir(1)-Os(2) = 2.9037(3) Å, Ir(1)-Os(3) = 2.9242(3) Å and Ir(1)-Os(4) = 2.9327(3) Å. The Os(3)…Os(4) distance at 3.6970(8) Å was clearly too large to allow any significant direct metal-metal bonding. The open edge of the cluster contained the bridging benzene thiolato group which served formally as a three-electron donor. The Os(3) and Os(4) atoms were asymmetrically bridged by the benzene thiolato moiety [Os(3)-S(5) = 2.4343(15) Å, Os(4)-S(5) = 2.4257(14) Å]. The Os-S distances closely matched the Os-S distances in Os3(μ-H)(μ-SMe)(μ-η2-C6H4)(CO)9 (2.418(4) and 2.433(5) Å, respectively) [13]. The S(5)-Os(4)-Os(2) and Os(4)-S(5)-Os(3) 99.05(5)º, respectively. bond angles were 78.01(3) and The thiolato bridge was oriented perpendicular to the triosmium plane. The carbon-sulphur bond distance [C(4)-S(5)] measuring 1.790(5) Å matched with the S-C bond distance reported in Ru3(μ-SPh)(μ,η1η6-C6H5)(CO)8 [1.796(4) Å] [10]. Rosenberg et.al. and Lewis et al. have investigated the reaction of thiophenol with the triosmium clusters viz., [Os3(CO)10(μ-dppm)] and [Os3(CO)9(μdppm)(MeCN)] [14, 15]. Oxidative addition of an SH bond occurred in both the cases to give the product [Os3(CO)8(μ-S)(μ-dppm)(μ-H)]. However, metal-metal bond cleavage was not observed in these reactions. 177 The formation of 22 from 3c here involves oxidative addition across the S-H bond via cleavage of an Os-Os bond (Scheme 5.5). Ir Os Os H Os Ir H + H TMNO -CO S Os H H H Os Os S Scheme 5.5. 5.3 Reaction of Cp*IrOs3(μ-H)2(CO)10 with triphenylphosphine selenide The reaction of Cp*IrOs3(μ-H)2(CO)10, 3c, with Ph3PSe under TMNO activation proceeded at room temperature in dichloromethane to afford five novel chalcogenbridged osmium-iridium clusters (Scheme 5.6). Se Ir Os H Os Os Ir 2.6 eqTMNO + Ph3PSe Os Os Os Se + Ph3P Os Os H Os + H H H 23 Ir + Os H H PPh3 + Os H Os 24 17a PPh3 Se Ir Os Se Os + H Ir Se PPh3 H Os H H Os 25 Ph3P Os Os 26 Scheme 5.6. 178 The compounds were partially separated by TLC on silica-gel, with hexane/ dichloromethane (4:1, v/v) as eluant. The fastest moving band afforded the novel compound Cp*IrOs3(μ-Η)2(CO)9(μ3-Se), 23, which was completely characterized spectroscopically and analytically, as well as by a single crystal X-ray structural analysis. The ORTEP diagram of 23, together with selected bond parameters, is given in Figure 5.2. Figure 5.2. ORTEP diagram and selected bond parameters for 23. Thermal ellipsoids are drawn at 50% probability level. Organic hydrogens are omitted for clarity. Ir(1)Os(3) = 2.8163(5) Å; Ir(1)-Os(2) = 2.8927(5) Å; Os(2)-Se(5) = 2.5196(9) Å; Os(4)Se(5) = 2.5242(9) Å; Os(2)-Os(4) = 2.8123(5) Å; Os(2)-Os(3) = 2.8477(5) Å; Os(3)Os(4) = 2.9484(5) Å; Ir(1)-Se(5) = 2.4057(9) Å; Ir(1)-Se(5)-Os(4) = 105.81(3)º. 179 Cluster 23 consists of a butterfly Os3Ir core, with two osmium atoms forming the hinge. The butterfly cluster core is the result of cleavage of an iridium-osmium bond in the parent tetrahedral cluster 3c. There is a triply bridging selenium atom along an IrOsOs edge. The selenium atom acts as a four-electron donor, and the cluster has a total valence electron count of 62, consistent with five metal-metal bonds. In butterfly clusters, the Os-Se distances to the wingtip osmium atoms are generally longer than those to the hinge metal atoms. Thus, in 23, the Os-Se distance to the wingtip osmium is longer than to the hinge. The Os-Se bond distances are in agreement to those observed in related clusters, Os3(µ3-Se)(µ-H)2(CO)8(PPh3) [2.5190(8), 2.5061(7) and 2.5065(8) Å] and Os3(µ3-Se) (CO)9(PPh3), [2.5315(7) and 2.5161(6) Å] [16]. The clusters Cp*IrOs3(μ-H)2(CO)9(PPh3), 17a, and Os3(μ-H)2(CO)7(μ3-Se)(PPh3)2, 24, moved together as a single band on the TLC plate. They were crystallized and separated by hand, the former as red crystals and the latter as orange-yellow crystals. Cluster 17a was also obtained from the reaction of 3c with PPh3 and has been described (Chapter 4). Cluster 24 has been characterized by X-ray crystallography; the ORTEP plot is shown in Figure 5.3. It is a triosmium cluster with a capping selenium atom. It is structurally quite similar to the previously reported cluster Os3(CO)9(μ3-Se)(PPh3), except that two of the carbonyls are replaced by a phosphine ligand and two bridging hydrides [16]. 180 5.4 Reaction of Cp*IrOs3(μ-H)2(CO)10 with di-p-tolyl ditelluride The reaction of 3c with di-p-tolyl ditelluride at ambient temperature under chemical activation by TMNO afforded an orange-red solution. Chromatographic separation on silica-gel TLC plates afforded the clusters 27, 28 and 29 in that order of elution, which were isolated as orange (27 and 28) or red (29) crystalline solids. Diffractionquality crystals were obtained by slow diffusion of hexane into dichloromethane (27 and 29) or toluene solutions (28). Single crystal X-ray crystallographic studies carried out on the crystals revealed them to be stereoisomers with the formulation Cp*IrOs3(μ-H)2(μ-Te-p-C6H4CH3)2(CO)8, differing in the arrangements of their ptolyl telluride groups; they also exhibit similar IR spectral profiles. The ORTEP plot for 27 is shown in Figure 5.6. A schematic diagram showing a common atomic numbering scheme for these clusters is shown in Table 5.1 together with selected bond parameters. Figure 5.6. ORTEP diagram for 27. Thermal ellipsoids are drawn at 50% probability level. Organic hydrogens are omitted for clarity. 188 Table 5.1. Common atomic numbering scheme and selected bond parameters for clusters 27-29. Ir(1) Ir(1) Os(4) Os(2) H Os(4) Os(2) Os(3) Te(5) Os(3) Os(2) Te(5) H H Te(5) (1)Ir H H Os (4) H Os(3) Te(6) Te(6) Te(6) (27) (28) (29) Ir(1)-Os(2) 2.7519(5) 2.835(3) 2.9602(5) Ir(1)-Os(4) 2.9299(4) 2.835(3) 2.7842(5) Os(2)-Os(3) 2.9817(4) 2.983(2) 2.9776(5) Os(3)-Os(4) 3.0086(4) 2.983(2) 2.8274(5) Os(2)-Os(4) 2.7803(4) 2.810(4) 2.9188(5) Os(2)-Te(5) 2.6149(7) 2.612(4) 2.7223(7) Os(3)-Te(5) 2.7293(6) 2.699(3) 2.6180(7) Os(3)-Te(6) 2.6927(6) 2.708(3) 2.6385(7) Os(4)-Te(6) 2.6232(6) 2.618(3) 2.6351(6) Te(5)-C(51) 2.129(9) 2.16(2) 2.140(9) Te(6)-C(61) 2.125(9) 2.17(2) 2.136(9) Te(5)-Os(3)-Os(4) 94.966(16) 91.59(8) 101.749(18) Te(6)-Os(3)-Os(2) 92.087(15) 91.69(8) 97.532(18) Te(6)-Os(3)-Te(5) 87.97(2) 80.67(80 154.92(2) Ir(1)-Os(4)-Os(3) 97.644(13) 99.70(8) 105.489(15) Ir(1)-Os(2)-Os(3) 102.377(13) 99.69(8) 97.566(14) Ir(1)-C(11)-O(11) 175.0(9) 151(9) 174.2(9) 189 All the three clusters contain a open butterfly cluster IrOs3 metal core with the iridium at one of the wingtips, and a telluride bridging each of the two Os-Os of the Os3 wing. Besides the Cp*, the iridium also carries a carbonyl group. Clusters 27 and 28 are isomers differing in the relative orientation of the tolyl groups; in 27, one of the tolyl groups is oriented away (exo) from the cluster core and the other inwards (endo), while in 28, both tolyl groups are exo. Cluster 29 differs from 27 and 28 in that (a) one of the tellurium is oriented inwards towards the butterfly rather than away as in the others, (b) the wingtip osmium has only two instead of three carbonyls, this third carbonyl now being located at one of the hinge osmiums, and (c) the positions of the hydrides. The Os-Te bond lengths are comparable to those reported for the related clusters Os3(CO)9(μ-Te)2 [2.6781(8)-2.7351(8) Å], Os3(CO)10(μ-TePh)2 [2.6886(10)2.7274(9) Å] and Os3(CO)10(H)2(μ-TePh)2 [2.7493(4)-2.7348(5) Å] [17]. The 1H NMR spectrum of the crude reaction mixture showed the presence of all three isomers. Thus the products were not formed via decomposition on silica-gel plates. The 1H NMR spectra of 27, 28 and 29 showed two resonances each at high field, indicative of bridging metal hydrides. Two methyl signals were observed for 27 and 29 and one for 28, consistent with their solid-state structures. The aromatic resonances for 28 were also partially assigned through selective decoupling experiment. Solutions of 27 and 28 (d6-benzene) monitored by 1H NMR over a period of time at ambient temperature did not show any interconversion between the isomers; 29 was not sufficiently stable in solution over any appreciable period of time to allow a similar check on isomerization but its separation chromatographically alludes to a slow isomerization process, if any. 190 5.5 Conclusions Cluster 3c was found to be very reactive with Group 16 substrates under chemical activation, all reactions proceeding at ambient temperatures. With thiophenol and diorganoditelluride 3c undergoes oxidative addition reactons. In the latter case stereoisomers are obtained. With phosphine selenide selenium atom transfer seems to be the initial step but the product so obtained is more reactive and quickly reacts further. One unusual structural feature in many of these products is the presence of very short metal-metal bonds, including some which are bridged by hydride. 191 5.6 Experimental 5.6.1 General experimental procedures The general experimental techniques, distillation of solvents, preparation of starting materials and characterization techniques were identical to those described in the experimental section of Chapter 2. Selective decoupling experiments were acquired on a Bruker Avance DRX500 or Bruker AMX500 machine. Di-p-tolyl ditelluride was prepared according to published procedure [18]. All other reagents were from commercial sources and used as supplied. 5.6.2 Reaction of 3c with thiophenol To a 250 ml three necked flask containing 3c (30.0 mg, 0.0254 mmol) in dichloromethane (10 ml) was added thiophenol (4-5 drops). A solution of trimethylamine N-oxide (3.4mg, 0.0304mmol) in dichloromethane (20 ml) was deoxygenated and then introduced dropwise into the solution of 3c via a pressure equalizing dropping funnel over a period of h. The solution was stirred for a further h. Removal of the solvent by rotary evaporation followed by chromatographic separation (6:4, v/v, hexane/dichloromethane) on silica gel TLC plates yielded a broad orange- red band identified as 3c (10 mg, 33%) and a second broad, dark orange band identified as Cp*IrOs3(μ-H)3(CO)9(μ-SPh), 22 (18.7 mg, 58%). IR: νCO (dcm, cm-1) 2072m, 2049vs, 2016s, 1989ms, 1968m, 1936mw, br. H NMR (CDCl3) δ/(ppm) : 7.34-6.90 (m, 5H, C6H5), 2.34(s, 15H, Cp*), -15.58 (s,2H, IrHOs), -16.60 (s, 1H, IrHOs). FAB-MS (m/z): 1261 [M+]. Calculated for C25H23IrO9Os3S : C, 23.79; H, 1.84; S, 2.54% Found: C, 23.73; H, 2.17; S, 2.38%. 192 Diffraction-quality crystals were obtained by slow diffusion of hexane into dichloromethane. Crystal structure and refinement data are given in Table 5.5. 5.6.3 Reaction of 3c with Ph3PSe The reaction of 3c with Ph3PSe was carried out by varying the ratio of 3c, Ph3PSe and TMNO. The ratios of 3c to Ph3PSe, TMNO and the isolated yields of the products are summarized in Table 5.2. IR, NMR, Mass spectroscopic and elemental analysis data for compounds 23-26 are summarized in Table 5.3. Diffraction-quality crystals for compound 23 were obtained from hexane by slow cooling while for compounds 24-26 and 17a were obtained by slow diffusion of hexane into a dichloromethane solution. Crystal structure and refinement data are given in Tables 5.5 and 5.6. 193 Table 5.2. Experimental conditions used for the synthesis of compounds 23-26. Products and isolated yields Amount of Amount of PPh3Se TMNO 23 3c 17a 24 8.6 mg 2.4 mg 1.9 mg 2.6 mg 1.9 mg 0.9 mg 1.0 mg 0.0073 mmol 0.0076 mmol 0.017 mmol 29% 22% 8.7% 9.9% 20.4 mg 5.9 mg 1.9 mg 5.0 mg 12.7 mg - - 0.017 mmol 0.0017 mmol 0.017 mmol 23% 62% 20.4 mg 11.8 mg 1.9 mg 2.7 mg 15.9 mg 5.5 mg 0.2 mg Sl.No Amount of 3c 0.017 mmol 0.035 mmol 0.017 mmol 13% 78% 23% 20.4 mg 17.7 mg 1.9 mg 3.6 mg 16.2 mg 4.1 mg 25 26 - - - - - - 0.4 mg 0.2 mg 1.6% 2sigma(I)] R indices (all data) 2.32 to 30.03° 2.12 to 26.36° 2.06 to 29.61° 41835 89766 30870 11552 [R(int) = 0.0444] 11552 / / 453 8967 [R(int) = 0.1450] 8967 / 57 / 233 9344 [R(int) = 0.0606] 9344 / / 422 1.084 1.114 1.024 R1 = 0.0460, wR2 = 0.0982 R1 = 0.0816, wR2 = 0.1629 R1 = 0.1377, wR2 = 0.1869 2.452 and -1.143 R1 = 0.0439, wR2 = 0.0867 R1 = 0.0669, wR2 = 0.0941 2.186 and -1.130 Largest diff. peak -3 and hole e.Å R1 = 0.0630, wR2 = 0.1058 2.569 and -1.066 201 5.7 References 1. A.J. Arce, P. Arrojo, A.J. Deeming, and Y. De Sanctis, Journal of the Chemical Society, Chemical Communications, 1991, 1491. 2. L.C. Roof, and J.W. Kolis, Chemical Reviews, 1993, 93, 1037. 3. M.L. Steigerwald, T. Siegrist, E.M. Gyorgy, B. Hessen, Y.U. Kwon, and S.M. Tanzler, Inorganic Chemistry, 1994, 33, 3389. 4. P. Braunstein, L.A. Oro, and P.R. Raithby, Metal clusters in chemistry, WileyVCH: Weinheim ; New York, 1999. 5. S.W.A. Fong, and T.S.A. Hor, Journal of the Chemical Society, Dalton Transactions, 1999, 639. 6. J. Mizutani, and K. Matsumoto, Chemistry Letters, 2000, 72. 7. P. Braunstein, C. Graiff, C. Massera, G. Predieri, J. Rose, and A. Tiripicchio, Inorganic Chemistry, 2002, 41, 1372. 8. B.C. Wiegand, and C.M. Friend, Chemical Reviews, 1992, 92, 491. 9. R.D. Adams, Polyhedron, 1985, 4, 2003. 10. W.R. Cullen, S.J. Rettig, and T.C. Zheng, Polyhedron, 1995, 14, 2653. 11. D.A. Lesch, and T.B. Rauchfuss, Organometallics, 1982, 1, 499. 12. B.K. Das, and M.G. Kanatzidis, Inorganic Chemistry, 1995, 34, 1011. 13. R.D. Adams, D.A. Katahira, and L.W. Yang, Organometallics, 1982, 1, 235. 14. K.A. Azam, S.E. Kabir, A. Miah, M.W. Day, K.I. Hardcastle, E. Rosenberg, and A.J. Deeming, Journal of Organometallic Chemistry, 1992, 435, 157. 15. S.R. Hodge, B.F.G. Johnson, J. Lewis, and P.R. Raithby, Journal of the Chemical Society, Dalton Transactions, 1987, 931. 16. W.K. Leong, W.L.J. Leong, and J. Zhang, Journal of the Chemical Society, Dalton Transactions, 2001, 1087. 202 17. J. Zhang, and W.K. Leong, Journal of the Chemical Society, Dalton Transactions, 2000, 1249. 18. N. Petragnani, Tellurium in Organic Synthesis, Academic: London, 1994. 203 [...]... (expt) (calc) (expt) 18 .54 18.70 1.39 1. 45 1231.09 1230.8 - - - - 1371.9 658 1377. 958 51 29 .50 29.70 2.20 2. 25 1464.80 14 65. 35 - - - - 151 4.8414 151 4.84 252 2024vs, 2008m, 2000m, = 3.3 Hz, OsHOs), -16.90 (d, 1H, 2JHH 1989s, 1967w, 1 950 m = 3.3 Hz, IrHOs) 2 057 s, 2038vs, 1991vs, 7 .51 -7.32 (m, 30H, C6H5) -19.21 (dd, 24 1976vs, 1 956 sh, 1923w 1H, 2JPH = 7.4 Hz, 7.4 Hz, OsHOs), 1.22s, -4 .55 s 2 -19.30 (d, 1H, JPH... 2.9232 (5) Å; Os(2)-Os(3) = 2.9 154 (6) Å; Os(2)-Os(4) = 3.0043 (5) Å; Os(3)Os(4) = 2.7423 (5) Å; Ir(1)-Se (5) = 2.4 753 (10) Å; Ir(1)-Se(6) = 2.4967(10) Å; Os(2)Se (5) = 2 .55 3(1) Å; Os(3)-Se (5) = 2.4674(10) Å; Os(3)-Se(6) = 2 .53 46(10) Å; Os(4)Se(6) = 2 .56 13(10) Å; Os(4)-P(7) = 2.337(2) Å; P(7)-Os(4)-Os(2) = 173.39(6)º The molecular structure of 26 consists of a spiked-triangular array of metal atoms The iridium. .. OsHOs) 2063m, 2019vs, 1996m, 7 .56 -7.42 (m, 15H, C6H5), 1 .59 (s, 15H, 5. 05s 25 1974sh, 1948w Cp*), -13. 95 (dd, 1H, 2JP-H = 11 .55 Hz; 2 JHH = 3.3 Hz, OsHOs), -16.87 (d, 1H, 2 JHH = 3.3 Hz, IrHOs) 2060vs, 2005sh, 1991vs, 7.83-7.76 (m, 15H, C6H5), 1.49 (s, 15H, 12.30s 26 1979sh, 1939w, 1910w Cp*), -12.10 (d, 1H, 2 JP-H = 8. 25 Hz, OsHOs), -18.72 (s, 1H, IrHOs) 1 FAB-MS: m/z 1371.9 658 (accurate mass) corresponds... Goodness -of- fit on 2 F Final R indices [I>2sigma(I)] R indices (all data) 2.29 to 30.02° 2.08 to 26.37° 2.12 to 30.01° 144 95 24978 18676 8403 [R(int) = 0.03 45] 8403 / 0 / 357 51 61 [R(int) = 0.0 350 ] 51 61 / 0 / 303 102 65 [R(int) = 0.0 356 ] 102 65 / 1 / 50 5 1.071 1.207 1.036 R1 = 0.0300, wR2 = 0.0641 R1 = 0.0394, wR2 = 0.0668 1.612 and -0.960 R1 = 0.0 358 , wR2 = 0.0723 R1 = 0.0381, wR2 = 0.0733 1 .52 9 and -0.9 95. .. 418 35 89766 30870 1 155 2 [R(int) = 0.0444] 1 155 2 / 0 / 453 8967 [R(int) = 0.1 450 ] 8967 / 57 / 233 9344 [R(int) = 0.0606] 9344 / 0 / 422 1.084 1.114 1.024 R1 = 0.0460, wR2 = 0.0982 R1 = 0.0816, wR2 = 0.1629 R1 = 0.1377, wR2 = 0.1869 2. 452 and -1.143 R1 = 0.0439, wR2 = 0.0867 R1 = 0.0669, wR2 = 0.0941 2.186 and -1.130 3 3 3 Largest diff peak -3 and hole e.Å R1 = 0.0630, wR2 = 0.1 058 2 .56 9 and -1.066 201 5. 7... Ir(1)-Os(4)-Os(3) 97.644(13) 99.70(8) 1 05. 489( 15) Ir(1)-Os(2)-Os(3) 102.377(13) 99.69(8) 97 .56 6(14) Ir(1)-C(11)-O(11) 1 75. 0(9) 151 (9) 174.2(9) 189 All the three clusters contain a open butterfly cluster IrOs3 metal core with the iridium at one of the wingtips, and a telluride bridging each of the two Os-Os of the Os3 wing Besides the Cp*, the iridium also carries a carbonyl group Clusters 27 and 28 are isomers differing... 151 4.84140 (accurate mass) corresponds to C35H29O7PIrSe2188Os190Os192Os (The compound 26 was not stable enough to carry out elemental analysis) 2 1 95 5.6.4 Reaction of 23 with PPh3 To a solution of 23 (5 mg, 0.004 mmol) in dichloromethane (5 ml) was added PPh3 (1.1 mg, 0.004 mmol) and stirred at room temperature for 3 h Formation of 24 (~20%) and 25 (~ 15% ) were verified by 1H NMR spectroscopy 5. 6 .5. .. Lesch, and T.B Rauchfuss, Organometallics, 1982, 1, 499 12 B.K Das, and M.G Kanatzidis, Inorganic Chemistry, 19 95, 34, 1011 13 R.D Adams, D.A Katahira, and L.W Yang, Organometallics, 1982, 1, 2 35 14 K.A Azam, S.E Kabir, A Miah, M.W Day, K.I Hardcastle, E Rosenberg, and A.J Deeming, Journal of Organometallic Chemistry, 1992, 4 35, 157 15 S.R Hodge, B.F.G Johnson, J Lewis, and P.R Raithby, Journal of the... 2.810(4) 2.9188 (5) Os(2)-Te (5) 2.6149(7) 2.612(4) 2.7223(7) Os(3)-Te (5) 2.7293(6) 2.699(3) 2.6180(7) Os(3)-Te(6) 2.6927(6) 2.708(3) 2.63 85( 7) Os(4)-Te(6) 2.6232(6) 2.618(3) 2.6 351 (6) Te (5) -C (51 ) 2.129(9) 2.16(2) 2.140(9) Te(6)-C(61) 2.1 25( 9) 2.17(2) 2.136(9) Te (5) -Os(3)-Os(4) 94.966(16) 91 .59 (8) 101.749(18) Te(6)-Os(3)-Os(2) 92.087( 15) 91.69(8) 97 .53 2(18) Te(6)-Os(3)-Te (5) 87.97(2) 80.67(80 154 .92(2) Ir(1)-Os(4)-Os(3)... Os3(μ3-Se)(CO)9PPh3 [2. 852 8(3), 2.8308(3) and 2.7703 Å] and Os3(μH)2(CO)8(μ3-Se)(PPh3) [non-hydride bridged distance of 2.8 054 (4) Å] are shorter than the value of 2.877 Å in Os3(CO)12 [16] The cluster has both the shortest and the longest Os-Se bond distances [Os(3)-Se (5) = 2.4674(10) Å, Os(4)-Se(6) = 2 .56 13(10) Å] in comparison to clusters 23- 25, in which the Os-Se bond distances range between 2 .55 30(10)-2.4 957 (9) . the reactivity of these substrates with mixed- metal clusters. To date there have been no reports on the reactivity of osmium -iridium mixed- metal clusters with chalcogenides. In continuation of. Os 3 (µ 3 -Se)(µ-H) 2 (CO) 8 (PPh 3 ) [2 .51 90(8), 2 .50 61(7) and 2 .50 65( 8) Å] and Os 3 (µ 3 -Se) (CO) 9 (PPh 3 ), [2 .53 15( 7) and 2 .51 61(6) Å] [16]. The clusters Cp*IrOs 3 (μ-H) 2 (CO) 9 (PPh 3 ), 17a, and Os 3 (μ-H) 2 (CO) 7 (μ 3 -Se)(PPh 3 ) 2 ,. Os(2)-Se (5) = 2 .51 96(9) Å; Os(4)- Se (5) = 2 .52 42(9) Å; Os(2)-Os(4) = 2.8123 (5) Å; Os(2)-Os(3) = 2.8477 (5) Å; Os(3)- Os(4) = 2.9484 (5) Å; Ir(1)-Se (5) = 2.4 057 (9) Å; Ir(1)-Se (5) -Os(4) = 1 05. 81(3)º.