Synthesis and reactivity studies of cyclopentadienyl derivatives of ruthenium iridium and osmium iridium mixed metal clusters 2

Chapter Synthesis of Cp- and Cp*- containing ruthenium-iridium and osmium- iridium mixed metal clusters 2.1 Introduction Although the chemistry of mixed metal platinum group metals have been extensively studied, a greater proportion of these studies have involved clusters of Ru, Pd and Pt mixed metal framework. Tetrahedral clusters containing Rh, Os, Ir or Ru mixed metal framework have been less extensively studied. Very few clusters containing a Ru3Ir or Os3Ir mixed metal frame work have been reported in the literature. Recently SussFink and coworkers have reported a very high yield synthesis of the carbonyl cluster anions [Ru3Ir(CO)13]- and [Os3Ir(CO)13]- by a redox condensation reaction [1, 2]. The reaction sequences are shown in Schemes 2.1 and 2.2, respectively. Os3(CO)12 + [Ir(CO)4]-3CO Ir Ir Os +H+ Os Os H Os Os Os +H2 +H2 -CO -CO - Ir Os H Ir Os Os +H- Os H H H Os Os H Scheme 2.1. 27 Ru3(CO)12 + [Ir(CO)4]-3CO Ir Ru Ir +H+ Ru Ru Ru Ru H Ru +H2 -CO +H2 -CO - H Ru Ru H Ir Ru +H- Ru +H- Ir H H Ru Ru H salt elimination Scheme 2.2. Another interesting synthesis reported involves between Ir((CO)Cl(PPh3)2 and Na[Ru3H(CO)11] in THF at room temperature to yield several Ru-Ir mixed metal clusters (Scheme 2.3) [3, 4]. [Ru3(CO)12] Ru2IrH2(CO)10(PPh3)2 Ru4H4(CO)11(PPh3) V Ru3IrH3(CO)10(PPh3)2 IV [Ir(CO)Cl(PPh3)2] + Na[Ru3H(CO)11] Ru2IrH3(CO)11(PPh3) I Ru4H2(CO)12(PPh3) Ru2IrH3(CO)11(PPh3) III Ru3IrH(CO)12(PPh3) II Scheme 2.3. 28 The low temperature 1H NMR of cluster III suggested the presence of two isomers IIIa and IIIb in solution. In Cluster IIIa, (structurally characterized in the solid state) two of the bridging hydrides were found to be equivalent but different from the third, whereas in cluster IIIb, all three hydrides were found to be nonequivalent. The structures of the two isomers are shown Figure 2.1. IIIa IIIb Figure 2.1. Two different isomeric forms of Ru3Ir(CO)11PPh3 in solution. Among the very few literature reports available on tetranuclear clusters containing the Ru3Ir and Os3Ir mixed metal framework, only a handful are on clusters containing a Cp or Cp* ligand. Table 2.1 summarizes the known tetranuclear Ru3Ir and Ru3Rh, as well as Os3Ir and Os3Rh clusters possessing either a Cp or Cp* ligand, along with the isolated yields and 1H NMR chemical shifts. 29 Table 2.1. Known Cp and Cp* containing Ru3Ir and Ru3Rh tetranuclear clusters. Cluster and yield reported Cp*IrRu3(μ-H)4(CO)9 (Crystal structure not reported) 5% Shape & total electron count Tetrahedral 60 H NMR δ ppm Cp*/Cp M-H-M Ref. 2.20 -18.71 [5] 1.94 -17.95 -18.64 [5] Butterfly 62 2.07 -20.29 [5] Tetrahedral 60 1.71 -15.93 [6] CO Ir B H H (OC)3 Ru Open butterfly or spike triangle 64 Ru(CO)3 Ru (CO)3 H (Two isomers reported) 15% H H Rh B Ru(CO)3 Ru(CO) (OC) Ru H (Proposed structure) 40% H Rh Ru Ru H H Ru H 20% 30 Rh Ru Ru H Tetrahedral 60 5.16 -17.2 [6] H Ru 45% Rh Ru Ru H (Isomers reported) 15% (Cp*)2Rh2Ru2(CO)7 (Crystal structure not reported) 30% -13.0, -17.0 -20.3 [6] - 1.64 [6] Planar 62 2.03 [7] CO Os Os 1.63, 1.54 H Ru Ir Tetrahedral 60 Os Ir Os Os H Os Tetrahedral 60 5.8 -18.95, -21.80 [8] Tetrahedral 60 -1.89 -16.53, -20.08 [9] H 21% Rh Os Os H Os H 12% 31 Rh H Os OC H Os Tetrahedral 60 1.94, 1.92 -14.57, -18.80 [9] Rh 7.2% OC Rh Os CO Os Tetrahedral 60 1.70 [9] Rh 40% H Rh Os Os H H Os Tetrahedral 60 1.94 -15.17, -19.68 [9] H 36% OC Rh CO Os Os Tetrahedral 60 2.19 Tetrahedral 60 1.57 [10] Os 20% H Rh CO Os Os -14.06 [10] Os Cl 25% 32 Tetranuclear clusters containing Os3Ir and Ru3Ir mixed metal framework possessing a Cp or Cp* ligand seems to be unexplored. The next section of the thesis describes the attempts made to synthesize Ru3Ir amd Os3Ir clusters containing a Cp or Cp* ligand. 2.2 Reactions of cyclopentadienyl iridium dicarbonyls with Ru3(CO)12 Attempts were made to synthesize Cp*IrRu3 clusters by reacting various Cp*Iridium complexes with triruthenium clusters. The reaction of Ru3(CO)12 with acetonitrile in the presence of TMNO led to the formation of the bis acetonitrile derivative of ruthenium, Ru3(CO)10(CH3CN)2., which was subsequently reacted with Cp*Ir(CO)2 at ambient temperature and also under photolytic conditions. IR monitoring of the reactions did not suggest the formation of any new product. Decomposition of Ru3(CO)10(CH3CN)2 was observed during the reaction and the IR spectrum showed strong peaks due to unreacted Cp*Ir(CO)2. Ionic coupling between Cp*Ir(CH3COCH3)3]2+ or [Cp*Ir(CH3CN)3]2+ with [Ru3(CO)11]2- afforded an unidentified brown solid. An attempt at chromatographic separation of the product mixture yielded several bands in low yields which have not been identified. Attempted purification by solvent extraction also afforded a mixture. The reaction of Cp*Rh(CO)2 with Ru3(CO)12 in the presence of hydrogen has been reported by Knobler and coworkers to yield Cp*RhRu3(μ-H)2(CO)10 [6]. Attempts to synthesize the iridium analogue by reacting Cp*Ir(CO)2 and CpIr(CO)2 with Ru3(CO)12 in the presence of molecular hydrogen afforded new ruthenium-iridium mixed metal clusters in moderate yields. The synthetic procedures, yields and characterization of the new clusters will be discussed in the following sections. 33 2.2.1 Reaction of Cp*Ir(CO)2 with Ru3(CO)12 and H2 The mixed–metal clusters Cp*IrRu3(μ-H)2(CO)10, 3a, and Cp*IrRu3(μ-H)4(CO)9, 4a, are formed in 40% and 13% yields, respectively, when H2 is bubbled through solutions of Ru3(CO)12 and Cp*Ir(CO)2 at 70-90 ºC (Scheme 2.4). Ir H Ir Ru3(CO)12 + Cp*Ir(CO)2 H2 atm 70 °C Ru H 2a H Ru Ru + Ru H 3a H Ru Ru H 4a Scheme 2.4. Cluster 3a is stable in air in the solid state for a few days. It is sparingly soluble in hexane and completely soluble in dichloromethane. The IR spectrum of 3a in hexane solution exhibited a peak at 1788 cm-1, showing the presence of bridging carbonyl. The IR pattern was similar to that of the related cluster Cp*RhRu3(H)2(CO)10 [6]. A FAB-MS spectrum showed a very strong molecular ion peak at m/z = 911.8 and fragment clusters of peaks corresponding to successive loss of up to 10 carbonyls. Diffraction-quality crystals were obtained from hexane by slow cooling. The molecular structure of 3a is shown in Figure.2.2. In the solid state structure, one of the two hydrides is found bridging an edge of the Ru3 triangle and the second hydride is found bridging a ruthenium-iridium edge. The molecule is asymmetric and the two hydrides are inequivalent. However, the ambient temperature proton NMR spectrum shows a single sharp hydride signal at δ -18.21 ppm. A VT 1H NMR experiment showed broadening of the hydride resonance on cooling, but no decoalescence was observed even down to 190 K. 34 Figure 2.2. ORTEP diagram of Cp*IrRu3(μ-H)2(CO)10, 3a. Thermal ellipsoids are drawn at 50% probability level. Organic hydrogens are omitted for clarity. The cluster 4a is stable in air for a short period of time. Slow decomposition to an insoluble black solid was observed after a few hours. This cluster was previously reported as a by product from the reaction of [Cp*IrCl2]2 and [(NPPh3)2][Ru3(CO)9(B2H5)] by Galsworthy et.al. [5]; it was characterized by 1H NMR, IR and MS. However, the solid state structure of the compound was not reported. We have determined the molecular structure of 4a by an X-ray crystallographic analysis. The ORTEP plot of 4a is shown in Figure 2.3. 35 Figure 2.3. ORTEP diagram of Cp*IrRu3(μ-H)4(CO)9, 4a. Thermal ellipsoids are drawn at 50% probability level. Organic hydrogens are omitted for clarity. The solution IR spectrum recorded in hexane shows bands only in the terminal carbonyl region, consistent with the solid-state structure. At room temperature, the proton NMR spectrum in deuterated toluene showed a singlet at δ 1.79 ppm which could be assigned to the Cp* ligand and another sharp singlet at δ -18.59 ppm assignable to rapidly exchanging hydrides; on cooling the solution, the hydride signal broadens, but no decoalescence was observed down to 200 K. A FAB-MS spectrum of the crystals showed a very strong molecular peak at m/z = 887. 36 bonds are significantly longer than the remaining Os-Os bonds and the values correspond well with those in the above related clusters (Table 2.5). The non-bridged iridium-osmium bonds [Ir(1)-Os(3) = 2.7644(4) Å; Ir(1)-Os(4) = 2.7326(3) Å] are significantly shorter than the sum of the covalent radii (ca. 2.828 Å), but they are close to the bond lengths reported in CpIrOs3(μ-H)2(CO)10. Although the non-bridged Os(2)-Os(4) bond length of 2.7801(3) Å is 0.0969 Å shorter than the mean value of 2.877(3) Å in the triangular species, Os3(CO)12, it is comparable to the unbridged distances in the related neutral tetrahedral cluster complexes CpMOs3(μ-H)2(CO)10 (M = Ir, Rh, Co) and Cp*RhOs3(μ-H)2(CO)10 [8, 9, 19, 22] (Table 2.5). Table 2.4. CO bridged and unbridged M-Os bond distances in 3c and related clusters. Carbonyl bridged Cluster M-Os Non-bridged M-Os bond lengths bond lengths (Å) (Å) Cp*IrOs3(μ-H)2(CO)10 (3c) 2.7789(4) 2.7644(4), 2.7326(3) Cp*RhOs3(μ-H)2(CO)10 2.769(1) 2.769(1), 2.734(1) CpIrOs3(μ-H)2(CO)10 2.798(1) 2.749(1), 2.740(1) CpRhOs3(μ-H)2(CO)10 2.736(2) 2.730(1), 2.729(1) CpCoOs3(μ-H)2(CO)10 2.645(1) 2.672(1), 2.680(1) Table 2.5. Hydride bridged and unbridged Os-Os bond distances in 3c and related clusters. Hydride Cluster bridged Non-bridged Os-Os Os-Os bond lengths bond lengths (Å) (Å) Cp*IrOs3(μ-H)2(CO)10 (3c) 2.8855(4), 2.9656(4) 2.7801(3) Cp*RhOs3(μ-H)2(CO)10 2.876(1), 2.952(1) 2.787(1) CpIrOs3(μ-H)2(CO)10 2.889(1), 2.944(1) 2.763(1) CpRhOs3(μ-H)2(CO)10 2.867(1), 2.950(1) 2.782(1) CpCoOs3(μ-H)2(CO)10 2.870(1), 2.940(1) 2.778(1) 55 In 4b, one of the hydrides bridges an osmium-osmium edge, while the other three hydrides span iridium-osmium edges. Interestingly, the disposition of the bridging hydrides in the solid state structure is different from those observed in its rhodium analogue, Cp*RhOs3(μ-H)4(CO)9 as well as other related Cp*MOs3 clusters, in which two Os-Os edges and two Ir-Os edges are bridged [9, 26]. However, the solid state structure is similar to that of Cp*IrRu3(μ-H)4(CO)9, 4a. The hydride bridged Os-Os bond [Os(3)-Os(3A) = 2.9799(5) Å] is longer than those observed for Cp*RhOs3(μH)4(CO)9 [Os-Os = 2.844(1) Å], CpWOs3(μ -H)(CO)12 [Os-Os = 2.932(2) Å] and CpWOs3(μ-H)3(CO)11 [Os-Os = 2.941(2) Å] but is close to the values observed for Os4(CO)11(μ-H)4(NCMe) [Os-Os = 2.956(1)-2.971(1) Å] [20, 27, 28]. 2.5 Comparison of Ru3Ir and Os3Ir clusters A comparison of the Cp*Ru3Ir clusters and Cp*IrOs3 clusters shows the following aspects: The Cp*- containing ruthenium–iridium clusters as well as the Cp*- containing osmium-iridium clusters have been synthesized from the reaction of Cp*Ir(CO)2 with Ru3(CO)12 and Os3(CO)12, respectively, in the presence of H2. We believe that in both the cases, the reactions involve the hydrido species, Os3(μ-H)2(CO)10 or Ru3(μH)2(CO)10. The reaction of Ru3(CO)12 with hydrogen generates Ru3(μ-H)2(CO)10 as an intermediate which can quickly convert to Ru4(μ-H)4(CO)12. This competing reaction accounts for the low yields of Cp*- containing iridium-ruthenium clusters; Ru4(μH)4(CO)12 mixed with unreacted Ru3(CO)12 is obtained as the major product. Attempts to synthesize Ru3(μ-H)2(CO)10 under photolytic conditions by literature method first and then subsequently reacting it with Cp*Ir(CO)2 did not lead to any 56 reaction [29]. On the other hand, the reaction of Os3(μ-H)2(CO)10 with Cp*Ir(CO)2 affords the Cp* iridium-osmium clusters in about 70-90% yields. Both the clusters Cp*IrRu3(μ-H)2(CO)10, 3a, and Cp*IrOs3(μ-H)2(CO)10, 3c, tend to adopt structures with a carbonyl bridging a ruthenium-iridium, or osmium-iridium, edge. Two bridging hydrides are found in both the structures. However, the position of the bridging hydrides is different in the solid state. The fluxional processes are faster for Cp*- containing ruthenium-iridium clusters than for Cp*- containing osmium-iridium clusters. The slow exchange limit or even decoalescence was not observed in the 1H NMR spectra for the Cp*- containing Ru3Ir clusters even down to 190 K. Cluster 3b is indefinitely stable in the solid form but 3a is stable only for a few days after which slow decomposition to an insoluble black solid is observed. Cluster 3a is sparingly soluble in hexane and completely soluble in toluene while 3b is sparingly soluble in both hexane and toluene. Both are highly soluble in dichloromethane but the solutions are stable only for short periods of time. If left to stand in CDCl3, signals due to Cp*Ir(CO)2 and Cp*Ir(CO)Cl2 were observed in the 1H NMR and the IR spectra. Both 3a and 3b react with hydrogen to give the tetrahydrido clusters Cp*IrRu3(μH)4(CO)9, 4a and Cp*IrOs3(μ-H)4(CO)9, 4b, respectively; the carbonyls are all terminal in the solid-state structures of these. In the case of 4b, the reverse reaction occurs when hydrogen is displaced by CO to yield 3c. For 4a, the reverse reaction in the presence of CO results in breakdown of the cluster skeleton to yield Ru3(CO)12 and Cp*Ir(CO)2. 57 2.6 Experimental 2.6.1 General techniques All reactions were carried out using standard Schlenk techniques under an atmosphere of nitrogen [30]. Solvents used in reactions were of AR grade, and were dried, distilled and kept under argon in flasks fitted with Teflon valves prior to use. Hexane, toluene and heptane were dried over potassium/ benzophenone and dichloromethane over dried calcium hydride [31]. High pressure reactions were carried out in a Parr screw-cap bomb of 60 ml capacity. The products were generally separated by column chromatography on silica gel 60 (230-430 mesh ASTM) or by thin-layer chromatography (TLC), using plates coated with silica gel 60 F254 of 0.25 mm or 0.5 mm thickness and extracted with hexane or dichloromethane. Infrared spectra were recorded on a Bio-Rad FTS 165 FTIR spectrometer at a resolution of 1cm-1 using a solution cell with NaCl windows of path length 0.1 mm. Routine NMR spectra were acquired on a Bruker ACF 300 MHz, while 2D NMR spectra were recorded on a Bruker AMX 500 MHz NMR spectrometer. 1H chemical shifts reported are referenced against the residual proton signals of the solvents, and 31 P with respect to 85% aqueous H3PO4 (external standard). Mass spectra were collected using the Fast Atom Bombardment (FAB) technique and were carried out on a Finnigan MAT95XL-T mass spectrometer normally with 3nitrobenzyl alcohol and occasionally with 3-mercapto-1,2-propane diol matrix at the National University of Singapore mass spectrometry laboratory. Microanalyses were carried out by the microanalytical laboratory at the National University of Singapore. Single crystal X-ray crystallographic studies were carried out by A/P Leong Weng Kee. Diffraction-quality crystals were grown by slow cooling of solutions of the 58 compounds in the appropriate solvent and the crystals selected were mounted on quartz fibers, or in glass capillaries. X-ray data were collected on a Bruker AXS APEX system, using Mo Kα radiation with the SMART suite of programs [32]. Data were corrected for Lorentz and polarization effects with the SAINT suite of programs, and for absorption effects with SADABS [33, 34]. Structural solution and refinement were carried out with the SHELXTL suite of programs [35]. The structures were solved by a combination of direct methods, or Patterson maps, to locate the heavy atoms followed by difference maps for the light atoms. The organic hydrogens were placed in calculated positions. Metal hydride positions were either located by low angle difference maps or placed in calculated positions using the XHYDEX program [36]. All non-hydrogen atoms were given anisotropic displacement parameters in the final refinement. The iridium compounds, Cp*Ir(CO)2, 2a and CpIr(CO)2, 2b and the osmium clusters Os3(μ-H)2(CO)10, and Os3(CO)10(CH3CN)2, were prepared according to literature methods [37-40]. All other reagents were from commercial sources and used as supplied. 2.6.2 Reaction of Cp*Ir(CO)2, 2a with Ru3(CO)12, A steady stream of dihydrogen was bubbled through a solution of Ru3(CO)12, 1, (114.7 mg; 0.18 mmol) and Cp*Ir(CO)2, 2a, (68.9 mg; 0.18 mmol) in heptane (60 ml) at 70 °C for 1.25 h. The solution turned dark red during this period. After cooling to room temperature, chromatographic separation of the reaction mixture on silica gel with hexane as eluant gave a broad orange yellow band consisting of unreacted Ru3(CO)12 and Ru4(μ-H)4(CO)12 (60 mg) Continuing with hexane gave an orange band identified as Cp*IrRu3(μ-H)4(CO)9, 4a. Further elution gave a deep red band identified 59 as Cp*IrRu3(μ-H)2(CO)10, 3a. Both 3a and 4a were recrystallized from hexane at –30 °C. Air-stable diffraction-quality crystals were obtained by slow cooling from hexane. 3a. Yield = 48.4 mg, 30%. IR: νCO (hex, cm-1): 2081m, 2061s, 2051m, 2041vs, 2003s, 1966w, 1788m H NMR (d8-toluene): δ 1.78 (s, 15H, Cp*), -18.20 (s, 2H, MHM) FAB-MS (m/z) calculated: 912.75; observed: 911.8 (M+) Calculated for C20H17IrO10Ru3 : C, 26.31; H, 1.87% Found: C, 26.58; H, 1.48% 4a. Yield = 15.4 mg, 9.7% IR: νCO (hex, cm-1): 2080s, 2066s, 2048vs, 2025s, 2008m(sh), 1988m, 1954w H NMR (d8-toluene, δ, ppm): 1.79 (s, 15H, Cp*), -18.59 (s, 4H, MHM) FAB-MS (m/z) calculated: 886.75; observed: 887.6 (M+) Calculated for C19H19IrO9Ru3.1/4 toluene : C, 27.28; H, 2.32% Found: C, 26.90; H, 1.92% Crystal and structure refinement data for 3a and 4a are given in Table 2.6. 2.6.3 Reaction of CpIr(CO)2, 2b, with Ru3(CO)12, A steady stream of dihydrogen was bubbled through a solution of Ru3(CO)12, 1, (114.8 mg; 0.18 mmol) and excess CpIr(CO)2, 2b, in hexane (60 ml) for h. The yellow orange solution turned dark brown during this period. After cooling to room temperature chromatographic separation of the reaction mixture on a silica gel column afforded a yellow band which consisted of unreacted Ru3(CO)12 mixed with Ru4(μH)4(CO)12 (55 mg). Further elution with hexane gave a deep red band, which on evaporation yielded CpIrRu3(μ-H)2(CO)10, 3b. Air-stable, diffraction-quality, dark red crystals were obtained by slow evaporation from CH2Cl2/hexane solutions at –30 °C. 60 3b. Yield = 45.8 mg, 30%. IR: νCO (hex, cm-1): 2088m, 2067vs, 2047vs, 2020m, 2009s, 2002sh, 1976w, 1820w. H NMR (CDCl3): 4.84 (s, 5H, Cp), -17.84 (s, 2H, MHM). FAB-MS (m/z) calculated: 842.62; observed: 842.4 (M+). Crystal and structure refinement data for compounds 3b is given in Table 2.6. 2.6.4 Reaction of Cp*Ir(CO)2, 2a with (μ-H)2Os3(CO)10, Both (μ-H)2Os3(CO)10, 5, (250.3 mg, 0.29 mmol), and Cp*Ir(CO)2, 2a, (112.5 mg, 0.29 mmol), were placed in a Carius tube fitted with a Teflon valve. Toluene (20 ml) was added, the solution was degassed with three freeze-pump-thaw cycles and then heated at 120 ºC for d. During this period the CO generated was pumped away once every 24 h. At the end of the reaction, the volatile compounds were removed under reduced pressure and the residue redissolved in the minimum amount of hexanetoluene mixture and subjected to column chromatography. Elution with hexane yielded an orange-red band identified to be Cp*IrOs3(μ-H)2(CO)10, 3c. Continuing with (1:4) hexane /dichloromethane yielded a pink band in trace amounts identified as Cp*IrOs4(μ-H)2(CO)13 , 7. Air-stable, diffraction-quality, dark red crystals for 3c were obtained by slow cooling from hexane while crystals for were obtained by slow diffusion of hexane into dichloromethane at –30 °C. 3c. Yield = 245 mg, 71%. IR: νCO (hexane, cm-1): 2085m, 2065s, 2040vs, 2006m, 2000vs, 1967w, 1959mw, 1782br. H NMR (d8-toluene, 233 K, δ, ppm): 1.60 (s, Cp*), -17.65 (s, OsHOs), -20.66 (s, OsHOs) FAB-MS (m/z) calculated: 1180.14; observed: 1180.8 (M-) 61 Calculated for C20H15IrO10Os3 : C, 20.33; H, 1.44% Found: C, 20.54; H, 1.55% 7. Yield = mg (< 1%). IR: νCO (dcm, cm-1): 2081m, 2067s, 2050s, 2030m, 1955w H NMR (CDCl3, δ, ppm): 1.85 (s, Cp*), -19.74 (s, OsHOs) FAB-MS (m/z) calculated: 1454.37; observed: 1370.4 (M--3CO) Crystal and structure refinement data for 3c and are given in Table 2.7. 2.6.5 Reaction of 3c with H2 A hexane solution (6 ml) of cluster 3c (59.9 mg, 0.05 mmol), was placed in a Parr bomb, pressurized with H2 (100 psi) and heated to 120 ºC for 24 h. The colour of the solution changed from red to bright orange. TLC separation of the mixture with 100% hexane yielded the cluster Cp*IrOs3(μ-H)4(CO)9, 4b. Air-stable, diffraction-quality, dark red crystals for 4b were obtained by slow cooling from hexane at –30 °C. 4b. Yield = 53 mg, 91%. IR: νCO (hex, cm-1) 2084s, 2053vs, 2047vs, 2025w, 2005vs, 1992m, 1983vs, 1947w. H NMR (d8-toluene, 300 K, δ, ppm): 1.57 (s, Cp*), -19.27 (s, 4H, MHM) FAB-MS (m/z) calculated: 1154.14; observed: 1154.8 (M-). Calculated for C19H19IrO9Os3 : C, 19.76; H, 1.64% Found: C, 20.09; H, 1.59% Crystal and structure refinement data for 4b is given in Table 2.8. 2.6.6 Reaction of 2a with A solution of Os3(CO)10(CH3CN)2, (80 mg, 0.085 mmol) in CH2Cl2 (10 ml) was cannula transferred into a solution of Cp*Ir(CO)2, 2a (32.8 mg, 0.085 mmol) in CH2Cl2 (10 ml). A colour change from yellow to red occurred immediately. After 62 stirring at room temperature for h, the solvent was removed on the vacuum line and the residue so obtained was redissolved in the minimum volume of dichloromethane and chromatographed on silica-gel TLC plates. Elution with hexane/dichloromethane (9/1, v/v) gave one major band and two minor bands. Band gave orange crystals of Cp*IrOs2(CO)9, 8, (trace amount) identified by comparison with the X-ray, IR, 1H NMR and MS data reported [25]. Band gave unreacted Cp*Ir(CO)2, identified by its IR spectrum. Band gave brown crystals of Cp*IrOs3(CO)11, 9. Diffraction-quality crystals for were obtained by slow diffusion of hexane into dcm at –30 °C. 9. Yield: (21 mg, 20%). IR: νCO (dichloromethane, cm-1): 2072s, 2033vs, 2025s, 1996w, 1980m, 1837m H NMR (CDCl3, δ, ppm): 2.07 (s, Cp*) FAB-MS (m/z) calculated: 1206.13; observed: 1208 [M+], 1179 [M-CO]+, 1150 [M2CO]+, 1122 [M-3CO]+, 1094 [M-4CO]+, 1066 [M-5CO]+, 1038 [M-6CO]+. Calculated for C21H15IrO11Os3 : C, 21.27; H, 1.54% Found: C, 20.89; H, 1.24% Crystal and structure refinement data for compound is given in Table 2.8. 2.6.7 Reaction of 4a with CO A hexane solution of 4a (5 mg) was stirred in ml of hexane under CO (1 atm) at ambient temperature. IR spectrum of the reaction mixture showed quantitative conversion to and 2a within h. 2.6.8 Reaction of 4b with CO A hexane solution (6 ml) of 4b (10 mg) was placed in a Parr bomb, pressurized with CO (100 psi) and heated at 120 ºC for h. TLC separation of the mixture with 100% 63 hexane afforded two bands identified as unreacted 4b (2 mg, 20%) and 3c (7 mg, 68%). 2.7 Conclusions The mixed metal clusters Cp*IrRu3(μ-H)2(CO)10, 3a, Cp*IrRu3(μ-H)4(CO)9, 4a, and CpIrRu3(μ-H)2(CO)10, 3b, were obtained in low to moderate yields when hydrogen was bubbled through solutions of Ru3(CO)12 and Cp*Ir(CO)2 or CpIr(CO)2 at 70-90 ºC. The osmium analogue Cp*IrOs3(μ-H)2(CO)10, 3c, was obtainable in 71% yield from the reaction of Os3(μ-H)2(CO)10 with Cp*Ir(CO)2 at elevated temperatures, together with a trace amount of the pentanuclear cluster Cp*IrOs4(μ-H)2(CO)13, 7. Hydrogenation of 3c (100 psi, 120 ºC, 24 h) afforded Cp*IrOs3(μ-H)4(CO)9, 4b, in 91% yield. The reaction of Cp*Ir(CO)2 with Os3(CO)10(CH3CN)2 afforded the known trinuclear cluster Cp*IrOs2(CO)9, 8, and the novel cluster Cp*IrOs3(CO)11, 9. Clusters 3c and 4b were readily interconvertible. However, 3c and were not interconvertible with 9. 64 Table 2.6. Crystal and structure refinement data for 3a, 3b and 4a. Compound 3a 3b 4a Empirical formula C20H17IrO10Ru3 C15H7IrO10Ru3 C19H19IrO9Ru3 Formula weight Temperature Wavelength Crystal system Space group Unit cell dimensions 912.75 223(2) K 0.71073 Å Monoclinic P21/n a = 8.7203(4) Å b = 14.4647(7) Å c = 19.7560(9) Å α= 90° β= 97.229(2)° 842.62 223(2) K 0.71073 Å Orthorhombic Pbca a = 14.8001(9) Å b = 15.1152(9) Å c = 17.618 (1) Å α= 90° β= 90° 886.75 223(2) K 0.71073 Å Monoclinic P21/m a = 8.4923(5) Å b = 15.7031(8) Å c = 9.8804(5) Å α= 90° β= 110.129(3)° γ = 90° 3941.2(4) 2.840 9.037 γ = 90° 1237.13(11) 2.380 7.201 3088 0.30 x 0.26 x 0.08 2.25 to 30.04° 828 0.12 x 0.06 x 0.05 2.55 to 30.01° γ = 90° Volume Å 2472.1(2) Z ρ (calc) Mg/m 2.452 Absorption coefficient 7.214 -1 mm F(000) 1704 Crystal size mm 0.16 x 0.14 x 0.01 Theta range for data 2.08 to 24.71° collection Reflections collected 17513 Independent 4213 [R(int) = reflections 0.0463] Data / restraints / 4213 / / 287 parameters Goodness-of-fit on F 1.226 Final R indices R1 = 0.0617, wR2 = [I>2sigma(I)] 0.1288 R indices (all data) R1 = 0.0699, wR2 = 0.1320 Largest diff. peak and 4.486 and -2.806 -3 60014 5760 [R(int) 0.0290] 5760 / / 290 10789 = 3427 [R(int) 0.0310] 3427 / / 165 1.116 R1 = 0.0176, wR2 = 0.0435 R1 = 0.0197, wR2 = 0.0441 0.595 and -1.097 = 1.057 R1 = 0.0327, wR2 = 0.0696 R1 = 0.0364, wR2 = 0.0711 1.783 and -0.760 hole e.Å 65 Table 2.7. Crystal and structure refinement data for 3c and 7. Compound 3c Empirical formula C20H17IrO10Os3 C23H17IrO13Os4 Formula weight Temperature Wavelength Crystal system Space group Unit cell dimensions 1180.14 223(2) K 0.71073 Å Triclinic P⎯1 a = 9.5705(11) Å b = 10.4175(12) Å c = 12.4073(15) Å α= 84.465(2)° β= 88.361(2)° 1454.37 223(2) K 0.71073 Å Orthorhombic Pnma a = 18.0156(3) Å b = 13.8807(3) Å c = 11.5849(2) Å α= 90° β= 90° γ = 76.665(2)° 1198.0(2) Å 3.271 21.446 γ = 90° 2897.03(9) Å 3.334 22.119 1044 0.26 x 0.10 x 0.04 2.02 to 30.06° 2560 0.14 x 0.12 x 0.08 2.09 to 26.37° Volume Z ρ (calc) Mg/m Absorption -1 coefficient mm F(000) Crystal size mm Theta range for data collection Reflections collected Independent reflections Data / restraints / parameters Goodness-of-fit on F Final R indices [I>2sigma(I)] R indices (all data) 18224 6813 [R(int) 0.0342] 6813 / / 320 30673 = 3098 [R(int) 0.0342] 3098 / / 208 1.017 R1 = 0.0265, wR2 = 0.0635 R1 = 0.0315, wR2 = 0.0654 Largest diff. peak 2.433 and -1.556 -3 and hole e.Å = 1.109 R1 = 0.0211, wR2 = 0.0485 R1 = 0.0237, wR2 = 0.0496 1.057 and -0.822 66 Table 2.8. Crystal and structure refinement data for 4b and 9. Compound 4b Empirical formula C19H19IrO9Os3 C21H15IrO11Os3 Formula weight Temperature Wavelength Crystal system Space group Unit cell dimensions 1154.14 223(2) K 0.71073 Å Monoclinic P21/m a = 8.4877(2) Å b = 15.7727(4) Å c = 9.8993(3) Å α= 90° β= 110.381(1)° 1206.13 223(2) K 0.71073 Å Orthorhombic Pnma a = 17.6000(17) Å b = 13.9732(13) Å c = 10.004(1) Å α= 90° β= 90° γ = 90° 1242.29(6) 3.085 20.675 γ = 90° 2460.3(4) 3.256 20.893 1020 0.22 x 0.10 x 0.04 2.19 to 28.28° 2136 0.16 x 0.06 x 0.03 2.31 to 26.37° Volume Å Z ρ (calc) Mg/m Absorption -1 coefficient mm F(000) Crystal size mm Theta range for data collection Reflections collected Independent reflections Data / restraints / parameters Goodness-of-fit on F Final R indices [I>2sigma(I)] R indices (all data) 10624 3177 [R(int) 0.0357] 3177 / / 163 19877 = 2618 [R(int) 0.0632] 2618 / / 175 1.046 R1 = 0.0277, wR2 = 0.0644 R1 = 0.0329, wR2 = 0.0661 Largest diff. peak 2.428 and -1.575 -3 and hole e.Å = 1.155 R1 = 0.0374, wR2 = 0.0692 R1 = 0.0457, wR2 = 0.0715 1.561 and -1.784 67 2.8 References 1. 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Shipley, Organometallics, 1991, 10, 3629. 26. S.G. Shore, W.L. Hsu, C.R. Weisenberger, M.L. Caste, M.R. Churchill, and C. Bueno, Organometallics, 1982, 1, 1405. 27. M.R. Churchill, and F.J. Hollander, Inorganic Chemistry, 1979, 18, 161. 28. M.R. Churchill, and F.J. Hollander, Inorganic Chemistry, 1980, 19, 306. 29. N.E. Leadbeater, Journal of Organometallic Chemistry, 1999, 573, 211. 30. D.F. Shriver, and M.A. Drezdzon, The manipulation of air-sensitive compounds, 2nd Edition: Wiley: New York, 1986. 31. J.A. Riddick, W.B. Bunger, T. Sakano, and A. Weissberger, Organic solvents : physical properties and methods of purification, 4th Edition: Wiley: New York, 1986. 32. SMART, version 5.628, Bruker AXS Inc.,: Madison, Wisconsin, USA, 2001. 33. SAINT, version 6.22a, Bruker AXS inc.,: Madison, Wisconsin, USA, 2001. 34. G.M. Sheldrick, SADABS, University of Göttingen, 1996. 35. SHELXTL, version 5.03, Siemens Energy & Automation Inc: Madision, Wisconsin, USA, 1995. 36. A.G. Orpen, XHYDEX: A Program for locating Hydrides in Metal Complexes, School of Chemistry, University of Bristol, 1997. 37. R.G. Ball, W.A.G. Graham, D.M. Heinekey, J.K. Hoyano, A.D. McMaster, B.M. Mattson, and S.T. Michel, Inorganic Chemistry, 1990, 29, 2023. 38. E. Otto Fischer, and K.S. Brenner, Zeitschrift fuer Naturforschung, 1962, 17b, 774. 39. H.D. Kaesz, Inorganic Syntheses, 1990, 28, 238. 40. J.N. Nicholls, and M.D. Vargas, Inorganic Syntheses, 1990, 28, 232. 70 [...]... 3b 2. 727 6 (2) Ir(1)-Ru(3) 2. 7695( 12) 2. 9061(4) Ir(1)-Ru(4)/(3A) 2. 7659( 12) Ru (2) -Ru(3) H C( 12) Os (2) Os(3) H Ir(1) H H (2) Os H Os(3) Os (3A) H Ir(1)-Os (2) 3c 2. 7789(4) 4b 2. 9513(4) 2. 7788 (2) Ir(1)- Os(3) 2. 7644(4) 2. 9148(3) 2. 9061(4) 2. 7077 (2) Ir(1)- Os(4)/(3A) 2. 7 326 (3) 2. 9148(3) 2. 78 62( 16) 2. 76 52( 6) 2. 924 6(3) Os (2) - Os(3) 2. 9656(4) 2. 8013(4) Ru (2) -Ru(4)/(3A) 2. 8990(17) 2. 76 52( 6) 2. 8765(3) Os (2) -... lengths bond lengths (Å) (Å) Cp*IrOs3(μ-H )2( CO)10 (3c) 2. 7789(4) 2. 7644(4), 2. 7 326 (3) Cp*RhOs3(μ-H )2( CO)10 2. 769(1) 2. 769(1), 2. 734(1) CpIrOs3(μ-H )2( CO)10 2. 798(1) 2. 749(1), 2. 740(1) CpRhOs3(μ-H )2( CO)10 2. 736 (2) 2. 730(1), 2. 729 (1) CpCoOs3(μ-H )2( CO)10 2. 645(1) 2. 6 72( 1), 2. 680(1) Table 2. 5 Hydride bridged and unbridged Os-Os bond distances in 3c and related clusters Hydride Cluster bridged Non-bridged... Cp*IrOs3(μ-H )2( CO)10 (3c) 2. 8855(4), 2. 9656(4) 2. 7801(3) Cp*RhOs3(μ-H )2( CO)10 2. 876(1), 2. 9 52( 1) 2. 787(1) CpIrOs3(μ-H )2( CO)10 2. 889(1), 2. 944(1) 2. 763(1) CpRhOs3(μ-H )2( CO)10 2. 867(1), 2. 950(1) 2. 7 82( 1) CpCoOs3(μ-H )2( CO)10 2. 870(1), 2. 940(1) 2. 778(1) 55 In 4b, one of the hydrides bridges an osmium- osmium edge, while the other three hydrides span iridium- osmium edges Interestingly, the disposition of the bridging... (hex, cm-1): 20 88m, 20 67vs, 20 47vs, 20 20m, 20 09s, 20 02sh, 1976w, 1 820 w 1 H NMR (CDCl3): 4.84 (s, 5H, Cp), -17.84 (s, 2H, MHM) FAB-MS (m/z) calculated: 8 42. 62; observed: 8 42. 4 (M+) Crystal and structure refinement data for compounds 3b is given in Table 2. 6 2. 6.4 Reaction of Cp*Ir(CO )2, 2a with (μ-H)2Os3(CO)10, 5 Both (μ-H)2Os3(CO)10, 5, (25 0.3 mg, 0 .29 mmol), and Cp*Ir(CO )2, 2a, (1 12. 5 mg, 0 .29 mmol),... [Os-Os = 2. 956(1) -2. 971(1) Å] [20 , 27 , 28 ] 2. 5 Comparison of Ru3Ir and Os3Ir clusters A comparison of the Cp*Ru3Ir clusters and Cp*IrOs3 clusters shows the following aspects: The Cp*- containing ruthenium iridium clusters as well as the Cp*- containing osmium -iridium clusters have been synthesized from the reaction of Cp*Ir(CO )2 with Ru3(CO) 12 and Os3(CO) 12, respectively, in the presence of H2 We believe... 20 91m, 20 70m, 20 44vs, 20 04vs, 1992m(sh), 1974m, 1965m, 1 824 w CpRhOs3(μ-H )2( CO)10 20 83m, 20 63vs, 20 42vs, 20 10vs, 20 00s(sh), 1982m, 1972m, 1819m Cp*RhOs3(μ-H )2( CO)10 20 84m, 20 64s, 20 41s, 20 02s, 1969w, 1962w, 1792m 41 Figure 2. 6 ORTEP diagram of Cp*IrOs3(μ-H )2( CO)10, 3c Thermal ellipsoids are drawn at 50% probability level Organic hydrogens are omitted for clarity The proton NMR spectrum of 3c at room... 2. 8765(3) Os (2) - Os(4)/(3A) 2. 7801(3) 2. 8013(4) Ru(3)-Ru(4)/(3A) 2. 76 12( 18) 2. 9400(7) 2. 7433(3) Os(3)- Os(4)/(3A) 2. 8855(4) 2. 9799(5) Ir(1)-C(34) 1.983(19) - 1.888(3) Ir(1)-C( 12) 1.910(5) - Ru(3)-C(34) 2. 145(15) - 2. 325 (3) Os (2) -C( 12) 2. 239(5) - O(34)-C(34)-Ir(1) 141.3(15) - 149.8 (2) O( 12) -C( 12) -Ir(1) 145.6(5) - O(34)-C(34)-Ru(3) 134.4(15) - 128 .3 (2) O( 12) -C( 12) -Os (2) 130.7(4) - 53 In 3a and 3b, an asymmetric... HRu3Ir(CO)13 [2] The carbonyl bridged iridium -ruthenium bond in 3b [Ir(1)-Ru (2) = 2. 7788 (2) Å] is longer than the unbridged bonds [Ir(1)-Ru(3) = 2. 727 6 (2) Å, Ir(1)-Ru(4) = 2. 7077 (2) Å] Elongation of metal- metal bond distances upon bridging by CO has been observed for analogous clusters [6, 8] In 3c, an asymmetric bridging carbonyl spans the Ir(1)-Os (2) bond with metal carbon distances of Os (2) -C( 12) = 2. 239(5)... Calculated for C19H19IrO9Ru3.1/4 toluene : C, 27 .28 ; H, 2. 32% Found: C, 26 .90; H, 1. 92% Crystal and structure refinement data for 3a and 4a are given in Table 2. 6 2. 6.3 Reaction of CpIr(CO )2, 2b, with Ru3(CO) 12, 1 A steady stream of dihydrogen was bubbled through a solution of Ru3(CO) 12, 1, (114.8 mg; 0.18 mmol) and excess CpIr(CO )2, 2b, in hexane (60 ml) for 2 h The yellow orange solution turned dark... 4a and 4b and to a Cp ring in cluster 3b Selected bond lengths and bond angles are listed in Table 2. 3 together with the cluster numbering scheme 52 Table 2. 3 Selected bond lengths (Å) and bond angles (º) for clusters 3a-c, 4a and 4b O(34) O(34) Ir(1) (4) Ru H H C(34) Ru(3) Ru (2) (3) Ru H H Ir(1) H Ir(1) H Ru (2) Ru (3A) (3) Ru H H O( 12) C(34) Ir(1) Ru (2) (4)Os Ru (2) Ir(1)-Ru (2) 3a 2. 90 82( 12) 4a 2. 9480(5) . cm -1 CpIrOs 3 (μ-H) 2 (CO) 10 20 91m, 20 70m, 20 44vs, 20 04vs, 1992m(sh), 1974m, 1965m, 1 824 w CpRhOs 3 (μ-H) 2 (CO) 10 20 83m, 20 63vs, 20 42vs, 20 10vs, 20 00s(sh), 1982m, 1972m, 1819m Cp*RhOs 3 (μ-H) 2 (CO) 10 20 84m,. Chapter 2 Synthesis of Cp- and Cp*- containing ruthenium- iridium and osmium- iridium mixed metal clusters 2. 1 Introduction Although the chemistry of mixed metal platinum group metals have. the new clusters will be discussed in the following sections. 33 2. 2.1 Reaction of Cp*Ir(CO) 2 with Ru 3 (CO) 12 and H 2 3a, and Cp*IrRuThe mixed metal clusters Cp*IrRu 3 (μ-H) 2 (CO) 10,