Synthesis and reactivity studies of cyclopentadienyl derivatives of ruthenium iridium and osmium iridium mixed metal clusters 3

Chapter Reactivity of Cp*- containing ruthenium-iridium and osmium-iridium mixed metal clusters towards alkynes 3.1 Introduction Mixed-metal alkyne clusters have generated much interest in recent years largely due to their catalytic potential in hydrogenation reactions [1]. They have been proven to serve as models for the carbon-carbon triple bond activation on metal surfaces and also for chemisorption of small molecules on metal surfaces [2-7]. Braunstein and coworkers have recently found that silica-tethered alkyne mixed metal clusters obtained by the sol-gel method have the potential to function as precursors to bimetallic nano particles (Scheme 3.1) [8]. Scheme 3.1. 71 The reaction of tetrahedral clusters with internal and terminal alkynes often results in cluster opening to give butterfly structures [9]. The butterfly clusters are quite interesting because they represent an intermediate arrangement between the tetrahedral clusters and the planar clusters. The relationship between tetrahedral, butterfly and “spiked” triangular clusters is depicted in Scheme 3.2. M M M M M M M Tetrahedron 60-e M M M M M Butterfly "Spiked" triangle 62-e 64-e Scheme 3.2. Sappa and coworkers have classified butterfly clusters into 13 classes (A-M). Tetrahedral clusters are known to react with alkynes to give class B butterfly clusters where the M3M’ skeleton takes the form of a butterfly and the alkyne C2 unit bonds to the metal framework in a μ4,η2 fashion to form a quasi-octahedral M3M’C2 skeleton (Figure 3.1) [10-12]. The acetylenic C≡C bond is disposed parallel to the “hinge” metal–metal bond of the butterfly, and the alkyne interacts with all four metal atoms. Wing tip metal atoms C π π M π C σ σ M' M π M Hinge metal atoms Figure 3.1. M3M’C2 butterfly cluster core. 72 The alkyne is coordinated to the two “hinge” metal atoms via σ bonds and to the two “wing-tip” metal atoms via its π bonds. The total electron count for these clusters depends on the method used for counting. Considering the alkyne as a four-electron donor, as is conventional in the EAN formalism, these clusters are 60-electron systems. This gives an implication that they are electron deficient, since a M3M’ butterfly cluster consistent with the noble gas rule would require 62 electrons. However, according to Wade’s system, they are considered as octahedral M3M’C2 clusters, with each CR unit donating three electrons to the skeletal bonding. The clusters are therefore 62-electron “electron precise” butterflies or 14-electron closo octahedra [13]. The acetylenic C-C bond lengths in the coordinated “alkyne” in these clusters show considerable variations, ranging from 1.34 to 1.56 Å, indicating considerable bond lengthening and possible deactivation. Following a criterion used by Muetterties, the elongation of the alkyne C≡C bond after coordination to more than one metal centre is taken as a parameter of activation upon coordination and used for comparison with the behaviour of these molecules on surfaces [14]. According to his hypothesis, the stronger the interaction of the alkyne with the cluster, either for σ−bound or for σ-πbound alkynes, the greater is the probability of finding long C-C bond distances, sometimes close to C-C single bond. The nature of the metal is also thought to play a role in the activation process with the longest C-C bonds observed in the complexes of the heaviest metals [9, 15, 16]. The dihedral angle between the two M’MM planes usually lies in very narrow range between 112º and 118º, because of the restrictions imposed on the metal framework by the coordinated alkyne. Various isomers are possible for the M3M’C2 skeleton and for the coordinated alkynes. It can be seen that in Figure 3.2 (a) and (c) the alkyne is disposed parallel to a 73 heterometallic MM’ bond (MM’) whereas in (b) the alkyne is disposed parallel to a homometallic MM bond (MM) and thus they are related as hinge-apex isomers; (c) differs from both (a) and (b) in the orientation of the alkyne and thus they are related as alkyne isomers. R' R' R R C C C M C M M M M M' M M' (a) (b) R R' C C M M M M' (c) Figure 3.2. (a), (b) Metal hinge-apex isomers (c) alkyne isomer. Table 3.1 summarises some of the reactions of tetrahedral mixed metal clusters with alkynes. It can be seen that most heterometallic tetrahedral clusters reacted with alkynes to afford butterfly clusters. Most of these reactions afforded products exhibiting either hinge-apex or alkyne, or both types of isomerisms. In some cases the reactions were found to be highly stereoselective. For example, the reaction of [CpMRu3(CO)12]⎯ (M=W, Mo), IrRu3(μ-H)(CO)13 and [Ru3Ir(CO)13]⎯ towards internal alkynes afforded M-Ru (M = W, Mo and Ir ) clusters with alkyne insertion into the Ru-Ru bond as the only product. However, the reaction of [CpMRu3(CO)12]⎯ (M=W, Mo) clusters with phenyl acetylene afforded M-Ru cis and trans isomers. 74 Table 3.1. Reactions of tetrahedral mixed-metal clusters with alkynes. Cluster CpRhRu3(μ-H)4(CO)9 Cp*RhRu3(μ-H)4(CO)9 Alkyne Substrate PhC≡CPh Isomerism observed Conditions hinge apex 25 ºC THF 2-4 d EtC≡CEt 50 ºC THF 2h PhC≡CPh - PhC≡CPh hinge apex MeC≡CMe hinge apex PhC≡CMe [MoRu3Cp(CO)12][PPh4] MeC≡CMe PhC≡CH hinge apex, alkyne alkyne [WRu3Cp(CO)12][PPh4] MeC≡CMe PhC≡CH alkyne [RuCo3(CO)12]⎯ PhC≡CPh PhC≡CH alkyne IrRu3(μ-H )(CO)13 PhC≡CPh MeC≡CMe - Hex, 80 ºC, h Hex, 85 ºC, h [Ru3Ir(CO)13]⎯ PhC≡CPh EtC≡CEt - Hex, 90 ºC, h FeRu3(μ-H)2(CO)13 Hexane reflux 15 THF reflux, h THF reflux, h THF reflux, h Product Major isomer Ru-Ru Minor isomer Ru-Rh Ref. [17] Ru-Ru Ru-Rh Ru-Ru - Fe-Ru, 48% Ru-Ru, 17% Ru-Ru, 25% Ru-Ru, 41% Fe-Ru, 5% Fe-Ru, (Ph cis to Fe) 31% Fe-Ru, (Ph trans to Fe) 10% Mo-Ru, 65% Mo-Ru (Ph cis to Mo) 50% Mo-Ru (Ph trans to Mo) W-Ru, 70% W-Ru (Ph cis to W) 45% W-Ru (Ph trans to W) Co-Ru, 75% Co-Ru (Ph cis to Co) 73% Co-Ru (Ph trans to Co) Ru-Ir, 11% Ru-Ir, 3% Ru-Ir, 85% Ru-Ir, 75% Ru-Ir, 80% [17] [18] - [19] } - [19] } - [8] } - [20] - [21] 75 The reaction of FeRu3(μ-H)2(CO)13 with alkynes is quite interesting as it afforded hinge-apex as well as alkyne isomers (Figure 3.3). R' R' R C C C Fe C R Ru Ru Ru Ru Fe Ru ia: R = R' = Ph iia: R = R' = Me iiia: R = Ph; R' = Me Ru ib: iib: iiib: iiic: R = R' = Ph R = R' = Me R = Me R' = Ph R = Ph; R' = Me Figure 3.3. Hinge-apex and alkyne isomerism in FeRu3(CO)12(RCCR’) clusters. In the reaction of both CpRhRu3(μ-H)4(CO)9 and FeRu3(μ-H)2(CO)13 towards alkynes, hinge-apex isomerism was observed and the isomer with the heterometal atom at the hinge (Rh-Ru or Fe-Ru) was obtained as the major isomer from the reaction. However, this isomer readily isomerised to the Ru-Ru isomer with the heterometal at the wingtip in both cases. In the case of CpRhRu3(μ-H)4(CO)9, the isomerisation was observed on purification of the product on TLC plates while in the case of FeRu3(μ-H)2(CO)13, isomerisation occurred upon heating. The reverse isomerisation was not facile in these systems. This suggested that for these two systems, the isomer with the heterometal atom in the hinge was the kinetically favored product and that with the heterometal atom in the wingtip was the thermodynamically stable product. The reactions of the neutral cluster IrRu3(μ-H)(CO)13, and the anionic cluster [Ru3Ir(CO)13]⎯, towards alkynes were found to afford clusters exhibiting μ3,η2 76 coordination mode of the alkynes on a face of a tetrahedral metal framework, in addition to the μ4,η2 coordination mode (Scheme 3.3). IrRu3(μ-H)(CO)13 was found to be an excellent catalyst for the hydrogenation of diphenylacetylene to stilbene and the alkyne substituted clusters were found to represent side-channels of the catalytic cycle. R R H Ru C C Ru H RCCR' Ru Ru Ru -2CO Ir Ir + RCCR Ru + RCCR - CO - 3CO R R C C Ru Ru Ru R = Ph or Me Ir H C C R Scheme 3.3. Thus it can be observed from these reactions that both the nature of the metals and the alkynes played an important role in determining the products and the isomers obtained; the isomer with the heterometal atom in the hinge was the kinetically favoured product in most of the cases. 77 3.2 Reaction of Cp*IrRu3(μ-H)2(CO)10, 3a, with internal alkynes 3.2.1 Reaction of 3a with RCCR (R = Ph, Et) The thermal reaction of 3a with RCCR (R = Ph, Et) in hexane afforded a dark red solution which after separation by TLC on silica-gel plates afforded three bands. In both the reactions the fastest moving band afforded red crystals which were characterized by IR and H NMR spectroscopy, microanalyses and further characterized by single X-ray crystallographic studies; the compounds were identified as the novel clusters, Cp*Ru3Ir(CO)9(RCCR) [R = Ph = 10a; R = Et = 10b]. The IR spectrum of 10b recorded in hexane is shown in Figure 3.4 and the ORTEP diagram of 10a is shown in Figure 3.5. Figure 3.4. IR spectrum of 10b in hexane. 78 Figure 3.5. ORTEP diagram of Cp*Ru3Ir(CO)9(PhCCPh),10a. Thermal ellipsoids are drawn at the 50% probability level. The phenyl hydrogens are omitted for clarity. The molecular structure of 10a consisted of a butterfly skeleton; the butterfly backbone consisted of ruthenium and iridium atoms which were bonded to two wingtip ruthenium atoms. Each of the three ruthenium atoms were bonded to carbonyls and the iridium atom was bonded to a Cp* ring. All carbonyls were terminal. The PhCCPh ligand was coordinated to the Ru3Ir metal core in a μ4,η2 fashion. One of the carbon atoms (C50) was σ−bonded to Ir(1), and the second one (C60) was σ−bonded to Ru(3). Both carbon atoms were π-bonded to the two wingtip ruthenium atoms. The 79 C-C bond of the alkyne was disposed almost parallel to the hinge [(Ru(3)–Ir(1)] of the butterfly. The other two products from the reactions were the previously reported clusters, Ru3(CO)8(C4R4) [R = Ph = 12a, R = Et = 12b], which were identified by their IR and H NMR spectroscopic data [22], and the novel trinuclear clusters Cp*IrRu2(CO)7C2R2 [R = Ph = 11a, R = Et = 11b]. The latter were characterized by IR and 1H NMR spectroscopy, FAB-MS, microanalyses and single crystal X-ray crystallographic studies. The IR spectrum of 11b recorded in hexane is shown in Figure 3.6 and the ORTEP diagram of 11a is shown in Figure 3.7. Selected bond lengths and bond angles for 11a and 11b are presented in Table 3.2. Figure 3.6. IR spectrum of 11b in hexane. 80 Table 3.7. IR and 1H NMR spectroscopic data for 10a-11b. IR [ν(CO) (cm-1)] (hex) H NMR [δ/(ppm)] 10a 2067m, 2046vs, 2023s, 1994s, 1973m (CDCl3) 7.13–6.85 (m, 10H, C6H5), 2.07 (s, 15H, Cp*), 10b 2062m, 2038vs, 2018s, 1988s, 1971m (C6D6) 2.85 (q, 3JHH =7.4 Hz, 2H, CH3CH2CCCH2CH3), 2.61 (q, 3JHH = 7.4 Hz, 2H, CH3CH2CCCH2CH3), 1.76 (s, 15H, Cp*), 1.21 (t, 3JHH = 7.4 Hz, 3H, CH3CH2CCCH2CH3), 0.97 (t, 3JHH =7.4 Hz, 3H, CH3CH2CCCH2CH3) 10c 2060m, 2037vs, 2027(sh), 2015s, 1986s, 1968m (CDCl3) 2.73 (s, 3H, CH3), 2.08 (s, 15H, Cp*), 1.45 (s, 9H, tBu) 10d 2064m, 2041vs, 2016s, 1991s, 1973m (CDCl3) 10.53 (s, 1H), 2.07 (s, 15H, Cp*), 0.25 (s, 9H, SiMe3) 10e 2062m, 2039vs, 2015s, 1989s, 1972m (C6D6) 10.51 (s, 1H), 1.72 (s, 15H, Cp*), 1.09 (q, 6H, CH2), 0.92 (t, 9H, CH3) 10f1 2070m, 2048vs, 2024vs, 1996s, 1960w (C6D6) 10.58 (s, 1H, PhCCH), 7.00-7.77 (m, 5H, C6H5), 1.82 (s, 15H, Cp*) 10f2 2069vs, 2048vs, 2036s, 2024s, 2016m,1995s (C6D6) 11.37 (s, 1H, PhCCH), 7.00-7.77 (m, 5H, C6H5), 1.87 (s, 15H, Cp*) 10f3 2071vs, 2048vw, 2031vs, 2019vs, 2001m, (C6D6) 9.44 (s, 1H, PhCCH), 7.75-6.60 (m, 5H, C6H5), 1.16 (s, 15H, Cp*) 1991m, 1981w, 1973mw, 1960m, 1950w 10g 2064m, 2042vs, 2028(sh), 2019s, 1991s, 1974m low yield 11a 2065s, 2032vs, 1992m, 1963m, 1846br (CDCl3) 7.12–6.88 (m, 10H. C6H5), 1.87 (s, 15H, Cp*) 11b 2060s, 2027vs, 1989vs, 1962m, 1834br (C6D6) 2.65 (dq, 3JHaHc = 3JHbHc = 7.4 Hz, 2H, CH3cCHaHbCCCHa’ Hb’CH3c’), 2.47 (dq, CH3cCHaHbCCCHa’ Hb’CH3c’, 3JHa’Hc’ = 7.4 Hz, 1H), 2.27 (dq, 3JHb’Hc’ =7.4 Hz, 1H, CH3cCHaHbCCCHa’ Hb’CH3c’), 1.67 (s, 15H, Cp*), 1.24 (t, 3JHH =7.4 Hz, 3H, CH3cCHaHbCCCHa’ Hb’CH3c’), 1.15 (t, 3JHH =7.4 Hz, 3H, CH3cCHaHbCCCHa’Hb’CH3c’) 110 3.8.2 Thermolysis of 10a and 10b Cluster 10a (6.7 mg, 0.006 mmol) in hexane (20 ml) was placed in a Carius tube fitted with a Teflon valve, the reaction mixture degassed by three freeze-pump-thaw cycles, and then heated to 90 ºC for h. Chromatographic separation of the mixture on silica-gel TLC plates using hexane as eluant afforded three bands. Band was identified as unreacted 10a (2.01 mg, 30%) from its IR spectrum. Band was identified as 11a (2.5 mg, 40%) and band was identified as 3a (0.5 mg, 8%) from its IR spectrum. Heating 10b (8.4 mg, 0.008 mmol) under the same conditions followed by a similar work-up afforded 10b (3.3 mg, 40%), by 11b (2.4 mg 35%) and 3a (0.6 mg, 7%). 3.8.3 Photolysis of 10a and 10b A hexane solution of 10a (6 mg, 0.006 mmol) was photolysed in a quartz vessel under UV light for h. Chromatographic separation of the mixture on silica-gel TLC plates using hexane as eluent afforded three bands identified as 10a (2.3 mg, 40%), 11a (2 mg, 30%) and 3a (0.4 mg, 6%), respectively. Irradiation of 10b (8.5 mg, 0.009 mmol) under the same conditions, followed by a similar work-up, afforded 10b (3.4 mg, 40%), 11b (2.5 mg, 38%) and 3a (0.5 mg, 6%). 3.8.4 Reaction of 4b with alkynes To a Schlenk flask containing cluster 4b in hexane, was added the alkyne. Triethyl amine was then added to the solution and stirred at ambient temperature. The reaction was monitored by solution IR spectroscopy till completion. The solvent was removed under reduced pressure and the residue obtained was redissolved in the minimum volume of dichloromethane and chromatographed on silica-gel TLC plates with 111 hexane as eluent. The reaction conditions and yields are summarized in Table 3.8. The spectroscopic data are tabulated in Tables 3.9 and 3.10. Diffraction-quality crystals for X-ray studies were grown from hexane by slow cooling. The crystal structure and data refinement for the compounds 15a1 to 16 are presented in Tables 3.14 and 3.15. Table 3.8. Summary of the reactions of 4b with alkynes. Amount of 4b 10.0 mg 0.009 mmol 10.0 mg 0.009 mmol 10.0 mg 0.009 mmol Alkyne Amount of alkyne Conditions PhC≡CPh 1.5 mg 0.008 mmol hexane 2.5 h/ 25 ºC 1.5 ml Et3N EtC≡CEt 0. 05 ml PhC≡CH 0.05 ml Product Yield 15a1 red crystals 3.5 mg 26% 15a2 red crystals 15b1 red crystals 1.6 mg 14% 0.2 mg 1.7% 15b2 red crystals 15c1 red crystals 2.1 mg 18% 0.5 mg 5% 15c2 red crystals - 16 orange crystals 1.2 mg 10% hexane h/ 25 ºC 1.5 ml Et3N Hexane 2.5 h/25 ºC 1.5 ml Et3N Table 3.9. Elemental analysis and mass spectroscopic data for compounds 15a1-16 Compound C(calc) C(expt) H(calc) H(expt) 15a1 29.84 15b1 30.20 1.90 2.00 low yield 15c1 MS m/z calculated 1330.1 1328.3 1232.7 1232.3 1252.2 1252.2 15a2 29.84 30.18 1.90 1.87 1330.3 1328.3 15b2 24.37 23.88 2.04 1.81 1231.9 1232.3 1252.2 1252.2 1354.6 1354.4 low yield 15c2 16 31.04 31.04 2.01 1.87 112 Table 3.10. Spectroscopic data for the alkyne substituted compounds 15a1-16 IR[ν(CO) (cm-1)] (hexane) H NMR [δ/(ppm)] (C6D6) 15a1 2071m, 2050vs, 2027s, 1993s, 1972mw, 1952w 7.42–6.70 (m, 10H, C6H5), 1.85 (s, 15H, Cp*) 15b1 2066m, 2042vs, 2022s, 1985s, 1967ms, 1955w low yield 15c1 2071m, 2050vs, 2025s, 1993s, 1972m, 1954w 15a2 2077s, 2050w, 2036s, 2023vs, 2005mw, 1987w, 11.32 (s, 1H), 7.42-6.73 (m, 5H, C6H5), 1.89 (s, 15H, Cp*) 6.84–6.73 (m, 10H, C6H5), 1.19 (s, 15H, Cp*) 1979w, 1967w, 1954mw 15b2 2072s, 2032s, 2019vs, 1996mw, 1981m, 1976sh, 1963w,1949ms 3.16 (dq, 2JHaHb = 16 Hz, 3JHcHa = 7.4 Hz, 2H, CH3cCHaHbCCCHa HbCH3c ) 2.48 (dq, 2JHaHb = 16 Hz, 3JHcHb = 7.4 Hz, 2H, CH3cCHaHbCCCHaHbCH3,), 1.28 (s, 15H, Cp*), 1.01 (dd, 3JHcHa/Hb = 7.4 Hz, 6H, CH3cCHaHbCCCHaHbCH3c) 15c2 2076s, 2048w, 2035s, 2021vs, 2003m, 1986mw, low yield 1972w, 1953w, 1948sh 16 (dcm) 2072m, 2046vs, 2029m, 1994ms, 1973br, 7.56-7.03 (m, 10H, C6H5), 6.89 (s, 1H), 6.31 (s, 1H), 1.89 (s, 15H, Cp*) 1960sh 113 3.8.5 Reaction of 4b with alkynes in the presence of TMNO To a Schlenk flask containing 4b (20.6 mg, 0.018 mmol) and PhCCPh (1.5 mg, 0.008 mmol) in dichloromethane was added TMNO (3.9 mg, 0.054 mmol) dissolved in dichloromethane (15 ml) through a dropping funnel and the reaction mixture stirred for 2.5 h. The solvent was removed under reduced pressure and the residue redissolved in the minimum volume of hexane and subjected to TLC on silica-gel plates. Elution with hexane afforded 15a1 and 15a2 in 3% and 5% yields respectively. 3.8.6 Reaction of 4b with triethylamine To a Schlenk flask containing 4b (10 mg, 0.009 mmol) in hexane (5 ml) was added triethylamine (1.5 ml, 10.8 mmol) and the reaction mixture stirred for h at room temperature. The IR spectrum of the proposed intermediate species, Cp*IrOs3(μH)2(CO)9(Et3N), in the crude reaction mixture showed peaks at 2066m, 2040vs, 1996s, 1967sh, 1942sh and 1701br cm-1 and the 1H NMR spectrum showed resonances at δ 1.92 (s, 15H, Cp*) which was assigned to Cp* protons an -18.85 (s, 2H. OsHOs). Removal of the solvent under reduced pressure followed by TLC on silica-gel plates afforded two bands. The fast moving band was identified as 3c (1.1 mg, 13%) from its IR spectrum. The second band was identified as (Cp*IrOs3(μH)2(CO)9(Et3N). However, there was an additional weak peak at 2079 cm-1 in the IR spectrum. Band Yield = 2.5 mg, IR: νCO cm-1: 2079w, 2065s, 2040vs, 1996vs, 1966s, 1941w, 1701br H NMR (δ ppm) (C6D6): 1.92 (s, 15H, Cp*), -18.86 (s, 1H, OsHOs), -17.36 (s, 1H, OsHOs). 114 3.8.7 Reaction of 4b with PPh3 To a Schlenk flask containing 4b (8 mg, 0.007 mmol) in dichloromethane was added triethylamine (1.5 ml, 10.8 mmol) and the reaction mixture stirred for h at ambient temperature. The solvent and excess triethylamine were removed under reduced pressure. The residue was redissolved in dichloromethane (10 ml) and triphenyl phosphine (1.8 mg, 0.007 mmol) was added. The reaction mixture was stirred for h followed by TLC separation on silica-gel plates with 100% hexane. The major band was identified as Cp*IrOs3(μ-H)2(CO)9(PPh3), 17a, from its IR spectrum. Yield = mg, 51%. (Note: This compound was also obtained from the reaction of 3c with PPh3 in the presence of TMNO and has been characterized spectroscopically and also by single crystal X-ray crystallographic studies. A detailed discussion of the spectral characteristics and the molecular structure of 17a is given in section 4.2.1). 3.8.8 Reaction of 3c with alkynes To a Schlenk flask containing 3c (10 mg, 0.008 mmol) and PhCCPh (1.5 mg, 0.008 mmol) in hexane was added triethylamine (1.5 ml) and TMNO (0.8 mg, 0.008 mmol). The reaction mixture was stirred at ambient temperature for 20 min. The solvent was removed under reduced pressure and the residue obtained was subjected to TLC separation on silica-gel plates with hexane as eluant. The fast moving band was identified as 15a1 (1.2 mg, 10%) and the slow moving band was identified as 15a2 (2.8 mg, 24%) from their IR spectra. 3.8.9 Reaction of 3a with 1-hexene Cluster 3a, (5 mg, 0.005 mmol) and 1-hexene (0.01 ml, 0.08 mmol) in deuterated toluene (0.5 ml) were stirred in an NMR tube and the reaction monitored by 1H NMR over a period of h. Signals due to a mixture of and 3-hexene were observed in the 115 H NMR spectrum suggesting isomerisation of the alkene. The infrared spectrum of the reaction mixture showed that cluster 3a remained mainly unchanged. 3.8.10 Reaction of 3c with PhCCPh To a Parr bomb of 60 ml capacity fitted with a glass-lining were added 3c (5 mg, 0.004 mmol) and PhCCPh (37.7 mg, 0.21 mmol). The solids were dissolved in octane (2 ml) and the solution was purged with nitrogen for min. The bomb was then fitted with a gauge, flushed three times with H2 and then pressurized to 40 psi. The contents were then heated at 120 ºC for h. The reaction mixture was then cooled and the solvent was removed under reduced pressure. The residue obtained was redissolved in hexane and subjected to TLC with 100% hexane as eluant. The colourless, fast moving, broad band was identified as a mixture of cis stilbene, trans-stilbene and bibenzyl by GC analysis. The identities of these compounds were further confirmed by 1H NMR spectroscopy. Band was identified as 3c (3.5 mg) from its IR spectrum. 116 Table 3.11. Crystal and data refinement for 10a-10c. Compound 10a 10b 10c Empirical formula C33H25IrO9Ru3 C25H25IrO9Ru3 C26H27IrO9Ru3 Formula weight Temperature Wavelength Crystal system Space group Unit cell dimensions Å 1060.94 223(2) K 0.71073 Å Monoclinic P21/c a = 14.0776(5) Å b = 9.6907(3) Å c = 23.9906(9) Å α= 90° β= 92.603(2)° γ = 90° 3269.5(2) 2.155 5.470 964.86 223(2) K 0.71073 Å Monoclinic P21/n a = 9.6671(4) Å b = 15.1800(7) Å c = 19.4979(9) Å α= 90° β= 99.630 (1)° γ = 90° 2820.9(2) 2.272 6.326 978.89 223(2) K 0.71073 Å Monoclinic P21/n a = 10.7358(3) Å b = 14.8779(4) Å c = 18.1779(5) Å α= 90° β= 92.275 (1)° γ = 90° 2901.20(14) 2.241 6.153 2016 0.22 x 0.16 x 0.10 2.18 to 26.37° 1824 0.32 x 0.24 x 0.20 2.12 to 26.37° 1856 0.34 x 0.26 x 0.14 2.17 to 30.01° 25711 41944 24638 6683 [R(int) = 0.0444] 6683 / / 420 5761 [R(int) = 0.0303] 5761 / / 350 8188 [R(int) = 0.0277] 8188 / / 361 1.107 1.090 1.050 R1 = 0.0399, wR2 = 0.0842 R1 = 0.0460, wR2 = 0.0867 1.836 and -0.755 R1 = 0.0213, wR2 = 0.0520 R1 = 0.0231, wR2 = 0.0528 1.141 and -0.575 R1 = 0.0277, wR2 = 0.0621 R1 = 0.0318, wR2 = 0.0637 1.570 and -0.847 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) Largest diff. peak -3 and hole e.Å 117 Table 3.12. Crystal and data refinement for 10d, 10e and 10f2. Compound 10d 10e 10f2 Empirical formula C24H25IrO9Ru3Si C27H31IrO9Ru3Si C27H21IrO9Ru3 Formula weight Temperature Wavelength Crystal system Space group Unit cell dimensions 980.94 223(2) K 0.71073 Å Monoclinic P21/c a = 9.3772(4) Å b = 15.5636(7) Å c = 20.0285(9) Å α= 90°. β= 93.409(1)° γ = 90° 2917.8(2) 2.233 6.157 1023.02 223(2) K 0.71073 Å Orthorhombic Pbca a = 16.5440(7) Å b = 17.7258(8) Å c = 21.6281(9) Å α= 90° β= 90° γ = 90° 6342.6(5) 2.143 5.670 984.85 223(2) K 0.71073 Å Monoclinic P21/c a = 16.2320(8) Å b = 13.0498(7) Å c = 13.5375(7) Å α= 90° β= 90.843(2)° γ = 90° 2867.3(3) 2.281 6.227 1856 0.30 x 0.22 x 0.08 2.04 to 29.55° 3904 0.12 x 0.04 x 0.01 2.25 to 26.37° 1856 0.13 x 0.12 x 0.02 2.00 to 26.37° 22671 49894 36509 7440 [R(int) = 0.0326] 7440 / / 355 6478 [R(int) = 0.1287] 6478 / / 381 5864 [R(int) = 0.0848] 5864 / / 370 1.036 1.034 1.386 R1 = 0.0307, wR2 = 0.0645 R1 = 0.0363, wR2 = 0.0666 1.127 and -0.796 R1 = 0.0504, wR2 = 0.0870 R1 = 0.0898, wR2 = 0.0996 1.276 and -0.871 R1 = 0.0733, wR2 = 0.1350 R1 = 0.0826, wR2 = 0.1383 2.152 and -2.267 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) Largest diff. peak -3 and hole e.Å 118 Table 3.13. Crystal and data refinement for 10f3, 11a and 11b. Compound 10f3 11a 11b Empirical formula C27H21IrO9Ru3 C31H25IrO7Ru2 C23H25IrO7Ru2 Formula weight Temperature Wavelength Crystal system Space group Unit cell dimensions 984.85 223(2) K 0.71073 Å Monoclinic Cc a = 19.9566(11) Å b = 9.9529(4) Å c = 16.6241(7) Å α= 90° β= 119.6740(10)° γ = 90° 2868.9(2) 2.280 6.223 903.85 223(2) K 0.71073 Å Monoclinic P21/n a = 10.0663(3) Å b = 19.1058(6) Å c = 15.2570(6) Å α= 90° β= 97.0130(10)° γ = 90° 2912.34(17) 2.061 5.628 807.77 223(2) K 0.71073 Å Orthorhombic Pbca a = 9.9869(3) Å b = 16.0665(4) Å c = 30.8922(8) Å α= 90° β= 90° γ = 90° 4956.8(2) 2.165 6.599 1856 0.20 x 0.08 x 0.06 2.35 to 28.28° 1728 0.22 x 0.10 x 0.08 2.13 to 24.71° 3072 0.18 x 0.16 x 0.02 2.49 to 26.37° 42704 23408 40378 3553 [R(int) = 0.0777] 3553 / / 369 4960 [R(int) = 0.0449] 4960 / / 375 5060 [R(int) = 0.0593] 5060 / / 305 0.929 1.064 1.195 R1 = 0.0297, wR2 = 0.0810 R1 = 0.0302, wR2 = 0.0817 1.623 and -1.490 R1 = 0.0333, wR2 = 0.0746 R1 = 0.0374, wR2 = 0.0765 2.138 and -0.488 R1 = 0.0405, wR2 = 0.0776 R1 = 0.0487, wR2 = 0.0803 1.214 and -1.151 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) Largest diff. peak -3 and hole e.Å 119 Table 3.14. Crystal and data refinement for 15a1, 15a2 and 15b2. Compound 15a1 15a2 15b2 Empirical formula C33H25IrO9Os3 C33H25IrO9Os3 C25H25IrO9Os3 Formula weight Temperature Wavelength Crystal system Space group Unit cell dimensions 1328.33 223(2) K 0.71073 Å Monoclinic P21/c a = 14.0473(11) Å b = 9.6988(8) Å c = 24.0120(19) Å α= 90° β= 92.335(2)° γ = 90° 3268.7(5) 2.699 15.736 1328.33 223(2) K 0.71073 Å Monoclinic P21/c a = 10.461(2) Å b = 16.140(3) Å c = 20.075(4) Å α= 90° β= 104.498(6)° γ = 90° 3281.6(11) 2.689 15.674 1232.25 223(2) K 0.71073 Å Orthorhombic Pna21 a = 20.7574(5) Å b = 8.6815(2) Å c = 15.3589(4) Å α= 90° β= 90° γ = 90° 2767.76(12) 2.957 18.570 2400 0.18 x 0.06 x 0.04 2.19 to 26.37°. 2400 0.14 x 0.06 x 0.02 2.10 to 26.37°. 2208 0.20 x 0.16 x 0.10 2.37 to 29.64°. 45562 21242 23601 6666 [R(int) = 0.0771] 6666 / / 255 6686 [R(int) = 0.1244] 6686 / 54 / 243 3801 [R(int) = 0.0449] 3801 / / 350 1.245 1.206 1.017 R1 = 0.0953, wR2 = 0.2297 R1 = 0.1035, wR2 = 0.2331 6.610 and -3.538 R1 = 0.1186, wR2 = 0.2206 R1 = 0.1532, wR2 = 0.2364 6.247 and -3.605 R1 = 0.0256, wR2 = 0.0551 R1 = 0.0280, wR2 = 0.0559 1.858 and -1.115 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 F2 Final R indices [I>2sigma(I)] R indices (all data) Largest diff. peak -3 and hole e.Å 120 Table 3.15. Crystal and data refinement for 15c1 and 16. Compound 15c1 16 Empirical formula C27H21IrO9Os3 C35H27IrO9Os3 Formula weight Temperature Wavelength Crystal system Space group Unit cell dimensions 1252.24 223(2) K 0.71073 Å Monoclinic P21/n a = 10.6110(3) Å b = 19.1640(5) Å c = 28.3928(8) Å α= 90° β= 93.7540(1)° γ = 90° 5761.3(3) 2.887 17.846 1354.37 223(2) K 0.71073 Å Monoclinic P21/c a = 10.3772(6) Å b = 18.6177(10) Å c = 18.5247(10) Å α= 90° β= 100.849(1)° γ = 90° 3515.0(3) 2.559 14.636 4480 0.14 x 0.09 x 0.04 2.01 to 26.37° 2456 0.30 x 0.22 x 0.20 2.00 to 26.37° 78947 32453 11788 [R(int) = 0.0873] 11788 / 15 / 719 7179 [R(int) = 0.0502] 7179 / / 444 1.110 1.035 R1 = 0.0497, wR2 = 0.1005 R1 = 0.0705, wR2 = 0.1080 4.693 and -1.723 R1 = 0.0348, wR2 = 0.0727 R1 = 0.0482, wR2 = 0.0777 1.442 and -0.853 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) Largest diff. peak -3 and hole e.Å 121 3.9 References 1. 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Ir(1)-C(51) 2.17 (3) 2.156(9) Ir(1)-C(2) 2.147(10) Ir(1)-C(61) 2.15 (3) 2.152(9) Ru (3) -C(1) 2.2 03( 9) Os(2)-C(51) 2.19 (3) 2.170(11) Ru (3) -C(2) 2. 237 (10) Os (3) -C(61) 2.15 (3) 2.218(10) Ru(4)-C(1) 2.148(9) Os(4)-C(51) 2.22 (3) 2.264(9) Ru(2)-C(2) 2.1 63( 10) Os(4)-C(61) 2.28 (3) 2.249(9) C(1)-C(2) 1.477( 13) C(51)-C(61) 1.56 (3) 1.458(15) 1 03 3.6 Comparison of the reactivity of Cp*IrRu3(μ-H)2(CO)10, 3a, and Cp*IrRu3(μ-H)4(CO)9,... 2.6947(4) 2.7 132 (5) 2.6987(11) 2.7071( 13) Os (3) -Os(4) 2.7 233 (17) 2.7 538 (7) Ir(1)-C(50) 2.059(6) 2.057 (3) 2.0 53( 3) 2.0 23( 4) 2.026(9) 2.047(11) Ir(1)-C(50) 2.15(2) 2.069(12) Ru(2)-C(50) 2.258(6) 2.270 (3) 2.246 (3) 2.202(4) 2.197(9) 2. 236 (11) Os(2)-C(50) 2 .30 (2) 2.195( 13) Ru(2)-C(60) 2. 230 (5) 2.260 (3) 2 .31 2 (3) 2.241(4) 2.257(9) 2.220(12) Os(2)-C(60) 2.26 (3) 2.274(11) Ru(4)-C(50) 2.261(6) 2.242 (3) 2.286 (3) 2.186(4)... are omitted for clarity 3. 2 .3 Reaction of 3a with R3SiCCSiR3 (R = Me, Et) The thermal reaction of 3a with R3SiCCSiR3 (R = Me, Et) in hexane afforded two products (Scheme 3. 5) One of them were the known triruthenium clusters Ru3(CO)9(μ-H)(C2SiR3) (R = Me , 13; R = Et , 14), obtained in ~ 30 % yields as yellow crystalline solids, identified by their IR and 1H NMR spectroscopic data [30 ] A second red, crystalline... [29, 34 , 37 -39 ] 3 The Ir-C bond lengths are shorter than the sum of the covalent radii of iridium and carbon while the Ru-C and Os-C bond lengths are longer The covalent radii of ruthenium and osmium are almost identical and this is reflected in the similar ranges observed for the corresponding Ru-C and Os-C bond lengths The covalent radius of iridium is extremely large compared to that for ruthenium and. .. 2.6542 (3) 2.6699 (3) 2.6 734 (4) 2.6 836 (8) 2.6545(10) Ir(1)-Os(2) 2.6886(16) 2.6759(7) Ir(1)-Ru (3) 2.7997(5) 2.8019 (3) 2.8078 (3) 2.7964 (3) 2.7864(8) 2.7865(11) Ir(1)-Os (3) 2.8048(16) 2.7940(7) Ir(1)-Ru(4) 2.6 435 (5) 2.6594 (3) 2.6456 (3) 2.6840(4) 2.6845(8) 2.6980(10) Ir(1)-Os(4) 2.6510(16) 2.6561(7) Ru(2)-Ru (3) 2.7011(7) 2.6979(4) 2.69 03( 4) 2.7054(4) 2.7 033 (10) 2.7266(14) Os(2)-Os (3) 2. 732 4(16) 2.7504(7) Ru (3) -Ru(4)... during chromatographic work-up Vahrenkamp and coworkers have also reported desilylation in the reaction of RuCo2(CO)11 with Me3SiC≡CMe The initial product, RuCo2(CO)9( 3- Me3SiC≡CMe), formed in the reaction underwent subsequent desilylation to give RuCo2(CO)9( 3- HC≡CMe) [33 ] 3. 3 Reaction of 3a with terminal alkynes 3. 3.1 Reaction of 3a with PhCCH Reaction of cluster 3a with phenyl acetylene afforded three... R Ru (3) Ir(1) C (61) (2) Os Ru(4) Os (3) 10f3 Os(4) 15 10f3 15a2) R = R' = Ph 15b2) R = R' = Et 15a2 15b2 Ir(1)-Ru(2) 2. 736 0(8) Ir(1)-Os(2) 2.6968(17) 2.7119(5) Ir(1)-Ru(4) 2.7 136 (7) Ir(1)-Os (3) 2. 731 4(17) 2.72 63( 5) Ru(2)-Ru (3) 2. 738 (1) Os(2)-Os (3) 2. 835 6 (18) 2. 835 7(5) Ru (3) -Ru(4) 2.7571(9) Os(2)-Os(4) 2.7672(17) 2.7617(5) Ru(2)-Ru(4) 2.7890(9) Os (3) -Os(4) 2.7440(18) 2.7 535 (5) Ir(1)-C(1) 2.1 03( 8)... trans-stilbene and bibenzyl Cluster 3c mainly remained unreacted and was isolated by chromatographic separation However, further experiments were not carried out to separate and isolate the products 99 3. 5 Solid state structures of Cp*IrRu3(RCCR’) clusters and Cp*IrOs3(RCCR’) clusters The general structural features of the Cp*IrRu3(RCCR’) clusters 10a-e, 10f2, 15a1 and 15c1, obtained from the reaction of 3a and. .. carried out to isolate and quantify the products (d) (c) (b) (a) Figure 3. 12 1H NMR spectrum (δ 4.0 - 6.0 ppm region) of (a) 1-hexene (b) immediately after mixing (c) after 3 h (d) 2-hexene 93 3.4 Reaction of Cp*IrOs3(μ-H)2(CO)10, 3c and Cp*IrOs3(μ-H)4(CO)9, 4b, towards alkynes The mixed metal clusters, Cp*IrOs3(μ-H)2(CO)10, 3c, and Cp*IrOs3(μ-H)4(CO)9, 4b, did not react with excess alkyne even at 120 ºC... 2.261(6) 2.242 (3) 2.286 (3) 2.186(4) 2.2 03( 9) 2.240(11) Os(4)-C(50) 2. 23 (3) 2.177( 13) Ru(4)-C(60) 2.265(6) 2.254 (3) 2.296 (3) 2.259(4) 2.255(9) 2.214(11) Os(4)-C(60) 2. 23( 3) 2.224(12) Ru (3) -C(60) 2.170(6) 2.184 (3) 2.224 (3) 2.178(4) 2.2 03( 9) 2. 139 (12) Os (3) -C(60) 2.18 (3) 2.140(12) C(50)-C(60) 1.470(8) 1.458(5) 1.457(5) 1.454(5) 1.444(2) 1.477(16) C(50)-C(60) 1. 43( 4) 1.446(16) 101 The Ir-C bond lengths . Chapter 3 Reactivity of Cp*- containing ruthenium- iridium and osmium -iridium mixed metal clusters towards alkynes 3. 1 Introduction Mixed- metal alkyne clusters have generated. for clarity. 3. 2 .3 Reaction of 3a with R 3 SiCCSiR 3 (R = Me, Et) The thermal reaction of 3a with R 3 SiCCSiR 3 (R = Me, Et) in hexane afforded two products (Scheme 3. 5). One of them were. desilylation to give RuCo 2 (CO) 9 (μ 3 -HC≡CMe) [33 ]. 3. 3 Reaction of 3a with terminal alkynes 3. 3.1 Reaction of 3a with PhCCH Reaction of cluster 3a with phenyl acetylene afforded three red