Chapter Subtitution chemistry of Cp*IrOs3(μ-H)2(CO)10 4.1 Carbonyl substitution in metal carbonyl clusters The ligand substitution chemistry of homometallic clusters have been very well documented but ligand substitution in heterometallic clusters has been the subject of relatively few reports. The varying constituent metals of the heterometallic cluster core afford the possibility of not only metalloselectivity upon ligand substitution but also site selectivity due to a decrease in molecular symmetry. To understand the substitution reactions in heterometallic clusters, it will be useful to have some knowledge on the substitution reactions of homometallic clusters. 4.1.1 Carbonyl substitution in trinuclear metal carbonyl clusters There are two types of CO ligands in M3(CO)12 (M= Ru, Os). Those in the same plane as the M3 triangle are referred to as equatorial and those that are perpendicular to the plane are axial (Figure. 4.1). e e a a M M a a a e e e a a M M a e a a e M M e a e e e a - axial e - equatorial a e Figure 4.1. Substitution positions in trinuclear clusters. 126 When CO is substituted by a phosphine on a cluster, the coordination site adopted is restricted by the steric and electronic requirements of the comparatively bulky phosphine ligand. In trinuclear clusters, the first phosphine is generally found to replace an equatorial ligand. In Os3(CO)12, this preference for equatorial substitution has been accounted for in steric terms, since simple calculations on Os3(CO)12-xLx systems have shown that the equatorial sites in (approximately) anticuboctahedral structures of ligands are less sterically hindered than axial [1-7]. Pomeroy and coworkers have given a detailed discussion on the influence of phosphine substitution on Os3(CO)11PR3 structures [8]. There has also been earlier studies by Bruce and coworkers who determined the structures of 12 different monoand disubstituted phosphine derivatives of Ru3(CO)12 and Os3(CO)12 to investigate the steric and electronic influences of phosphine substitution in these clusters [9, 10]. The following conclusions were obtained from these studies: 1. The group 15 ligand prefers equatorial coordination site in monosubstituted derivatives. In the disubstituted derivatives, the two ligands take up positions that are as far apart as possible; each occupying an equatorial site on adjacent metal atoms. 2. Due to steric interactions between the group 15 ligand and the CO group cis to it on the adjacent metal atom, the M-M bond cis to the phosphine ligand is the longest of the three M-M separations; for the disubstituted derivatives, no such pronounced lengthening of this M-M bond has been observed. 3. Introduction of two group 15 ligands into the M3(CO)12 cluster results in a twisting of the ML4 groups about the M-M axis, distorting the original D3h symmetry of the parent cluster to D3 symmetry. 127 4. In the monosubstituted derivatives, the M-P bond length increases with increasing cone-angle while in the disubstituted derivatives, the M-P bond lengths are almost the same as those in the corresponding monosubstituted derivatives. 5. Axial M-CO bonds are longer than equatorial M-CO bonds. 4.1.2 Carbonyl substitution in heteronuclear tetrahedral clusters Heteronuclear tetrahedral clusters are of interest as species in which to scrutinize metalloselectivity and site selectivity. Basically there are three positions available for substitution in tetrahedral M’M3 clusters, namely axial, equatorial and apical (Figure 4.2). ap ap M' ap eq eq M M ax ax eq M ax ap ap ap M' eq eq eq eq M M ax ax eq eq M ax eq eq eq ax - axial eq - equatorial ap - apical Figure 4.2. Substitution sites in heterometallic tetrahedral clusters. Studies on metalloselectivity of these clusters have revealed that the selectivity could be influenced by factors such as the nature of the metals and the nature of both the existing and incoming ligands. For example, the clusters MCo3(μ-H)(CO)12 (M= Fe, Ru) reacted with secondary and tertiary phosphines to afford monosubstituted derivatives in which the phosphine ligand was always bonded to Co, while Ru3Rh(μH)(CO)12 reacted with phosphines to produce monosubstituted derivatives in which 128 the PR3 ligand was attached to Rh [11-14]. In the disubstituted product, RuCo3(CO)10(μ-H)(PMe2Ph)2, the second PMe2Ph was substituted at Ru, whereas in the case of RuCo3(μ-H)(CO)10(PPh3)2, the phosphines were bonded to one cobalt atom each [15]. Pakkanen and coworkers have recently reported the structures of two isomers of [Ru3Ir(μ-H)3(CO)11(PPh3)] (Figure 4.3) [16]. In one of the isomers, the phosphine ligand was coordinated to an axial position in the Ru3 basal triangle and in the other isomer the phosphine was found coordinated apically to the iridium atom. Ph3P Ir Ir Ph3P Ru H H Ru Ru Ru H H H Ru Ru H Figure 4.3. Isomeric structures of [Ru3Ir(μ-H)3(CO)11(PPh3)]. Table 4.1 summarizes the preferred site of substitution of phosphines for various tetrahedral mixed-metal clusters reported in the literature. It can be noted that axial or apical substitution was always observed for the first phosphine ligand, while the second substitution could be equatorial or axial. For example, the first substitution by PPh3 in FeRu3(μ-H)2(CO)13 occurred at an axial position on one of the basal ruthenium atoms. For tetrahedral mixed metal clusters possessing a Cp or Cp* ligand, the substitution almost always occurred at the basal metal triangle. For example, the reaction of CpRu3Rh(H)2(CO)10 with phosphines afforded mono- and disubstituted phosphine derivatives where the substitution occurred at the ruthenium triangle. This could be attributed to the fact that in these clusters, the bulky Cp ligand was attached to the unique heterometallic vertex. Proton NMR studies of the derivatives have revealed at 129 least three isomers for the monosubstituted derivatives and two isomers for the disubstituted derivatives in solution (Figure 4.4). Table 4.1. Preferred phosphine substitution sites for tetrahedral mixed-metal clusters. Phosphine derivatives Cluster Ref. mono-substituted di-substituted FeRu3(μ-H)2CO)13 axial (Ru) axial, equatorial (Ru, Ru) [17] [IrRu3(μ-H)2(CO)12]⎯ apical (Ru) --- [18] RuRh3(μ-H)(CO)12 axial (Rh) diaxial (Rh, Rh) [15] Os3(μ-H)3IrCO)12 apical (Ir) --- [19] RuCo3(μ-H)(CO)12 axial (Co) diaxial (Co, Co) [18] apical (Ir) --- [20] axial, equatorial (Ru, Ru) [21] IrRu3(μ-H)3(CO)12 axial (Ru) CpRhRu3(μ-H)2(CO)10 axial (Ru) [major] equatorial (Ru) [minor] Cp*RhRu3(μ-H)2(CO)10 equatorial (Ru) [major] axial, equatorial (Ru, Ru) [21] CpNiOs3(μ-H)3(CO)9 --- diaxial (Os, Os) [22] Rh Rh Ru Ru Rh Ru Ru L Ru L Ru Ru1 Ru Ru L (a) (b) (c) L=PPh3 (a) axial (b) equatorial cis to bridging CO (c) equatorial trans to bridging CO (d) axial,equatorial cis to bridging CO (e) axial, equatorial trans to bridging CO Rh Rh Ru Ru L L Ru Ru Ru Ru L (d) L (e) Figure 4.4. Isomeric structures of mono- and disubstitued phosphine derivatives of CpRu3Rh(μ-H)2(CO)10. 130 In contrast, the most stable isomer of the monosubstituted phosphine derivative in the Cp* analogue did not involve phosphine coordination at Ru(1); substitution occurred either at Ru(2) or Ru(3). The reaction of the mixed metal cluster CpNiOs3(μ-H)3(CO)9 with phosphines in the presence of TMNO afforded disubstituted derivatives in which the phosphines were reported to be bound axially to two osmium atoms. Isomers were not observed in solution. In contrast to phosphines, the substitution chemistry with isocyanides is relatively unexplored. Isocyanide ligands generally show a propensity for axial substitution in derivatives of M3(CO)12 (M=Ru, Os). In complexes of the type Os3(μ- H)(H)(CO)10(CNR) (R = Me, Ph), only axial coordination was observed. However, for R = tBu, equatorial substitution occurred, as has been confirmed by X-ray crystallographic analysis of Os3(μ-H)(H)(CO)9(CNBut) [23, 24]. Also, in Os3(CO)11(CNBut), there is NMR evidence for equatorial/axial isomerisation of the t t BuNC ligand [25]. In the related complex, Ru3(CO)11(CNBu ), both axial and equatorial forms existed in solution. However, in the solid state only the axial isomer was observed [26]. Therefore it appears that for CNR ligands, the substituting ligand can occupy an equatorial or axial position depending on the steric requirements of the R group. Although electronic factors favour axial coordination of isocyanide groups, steric constraints may result in equatorial substitution. In addition to the normal η1 terminal bonding mode exhibited, the isocyanides also showed some propensity for μn,η2 C-N bridged bonding modes (Table 4.2). 131 Table 4.2. Bridged bonding modes in isocyanides. Bonding mode cluster Ref. μ2, η2 Νi4(CNBut)7 [27] μ3, η2 Os6(CO)18(CNC6H4Me-4)2 [28] μ4, η2 Ru5(CO)14(CNBut)2 [29] Shawkataly et. al. have reported a triruthenium cluster, Ru3(CO)6(μ3- PPhCH2PPh2)( μ3-CNCy)(CNCy)2Ph, in which one of the isocyanide ligands acted as a four-electron donor [30]. Os3Pt(μ-H)2(CO)9(PCy3)(CNCy) is one of the very few reported tetrahedral heterometallic clusters with isocyanides [31]. The solid state structure was not reported, but 1H and 13C NMR studies have shown that addition of CyNC at 195 K yielded principally only one isomer, Os3Pt(μ- H)2(CO)10(PCy3)(CNCy), which has a butterfly structure with the CyNC bonded to an osmium center. On the other hand, reaction at 273 K produced three isomers which were in dynamic equilibrium. All the three isomers exhibited butterfly geometry for the metal core, with the CyNC ligand bonded to an osmium center. Refluxing a hexane solution of Os3Pt(μ-H)2(CO)10(PCy3)(CNCy) resulted in facile decarbonylation to afford a tetrahedral 58 electron unsaturated cluster Os3Pt(μH)2(CO)9(PCy3)(CNCy) in which the CyNC ligand was bonded to the platinum atom. There was thus a transfer of the CyNC ligand from Os to Pt in the decarbonylation of the butterfly adduct as it closed to form the tetrahedral unsaturated cluster (Scheme 4.1). 132 PCy3 Pt H Os Os Os CNCy H isomer A PCy3 H Cy3P CNCy Os Os 273K H Os H Pt reflux, hexane Os H Os CNCy Cy3P Os Pt H Pt Os Os CNCy Os isomer B H PCy3 H Pt Os Os Os CyNC H isomer C Scheme 4.1. Reaction of CpWIr3(CO)11 with stoichiometric amounts of isocyanides was reported to afford the clusters [CpWIr3(CO)11-n(CNR)n] in 47-63% yields (Scheme 4.2) [32]. The solid state structure of CpWIr3(CO)9(CNXy) [Xy = C6H3Me2-2,6] showed that both the isocyanides were bonded to the same iridium atom. CpWIr3(CO)10(CNR) R = tBu = 58% eq RNC W Ir R = Xy = 60% W Ir eq RNC RNC RNC Ir Ir R = Xy = 47% R = tBu = 58% Ir Ir eq RNC R = Xy = 63% CpWIr3(CO)8(CNR)3 R = tBu = 59% Scheme 4.2. 133 4.2 Substitution type reactions of Cp*IrOs3(μ-H)2(CO)10, 3c It is evident from the foregoing that clusters containing mixed metals are of interest as sites to probe metallo selectivity and site selectivity. Although there has been some reports on the synthesis of Cp- and Cp*- containing osmium-iridium clusters, there have been no reports on the reactivity of these clusters. The following sections present our studies on the substitution reaction of 3c with various group 15 donor substrates like phosphines, phosphites, isocyanides and pyridine. 4.2.1 Reaction of Cp*IrOs3(μ-H)2(CO)10, 3c, with triphenylphosphine Cluster 3c was found to undergo facile substitution in the presence of trimethylamine N-oxide. Reaction of cluster 3c with PPh3 in dichloromethane at ambient temperature in the presence of TMNO (dropwise addition via a dropping funnel) led to gradual deepening of the original orange-red solution to deep red over a period of h. Chromatographic separation of the reaction mixture on silica-gel TLC plates afforded Cp*IrOs3(μ-Η)2(CO)9(PPh3), 17a, and Cp*IrOs3(μ-Η)2(CO)8(PPh3)2, 18a, respectively. Both clusters have been completely characterized, including by single crystal X-ray crystallographic studies. The ORTEP plot of 17a is shown in Figure 4.5. The solid state structure of 17a revealed that the tetrahedral core of the parent cluster was retained; the bridging carbonyl and the two bridging hydrides in the parent cluster were also intact and one of the axial carbonyls attached to the osmium triangle was substituted by a phosphine ligand. The 1H NMR spectrum taken at 300 K in d8 toluene consisted of four resonances; one doublet at δ -19.94 ppm (2JP-H = 9.0 Hz) and three broad singlets. On lowering the temperature to 233 K, the 1H NMR spectrum consisted of well-resolved resonances at δ -16.65d (2JPH = 9.1 Hz), -17.44s, -19.67d (2JPH = 10.7 Hz) and -20.01d (2JPH = 9.1 Hz) ppm (Figure 4.6). 134 Figure 4.5. ORTEP diagram of 17a. Thermal ellipsoids are drawn at 50% probability level. Organic hydrogens are omitted for clarity. Two singlets at δ 2.14 and 2.10 ppm were also observed, assignable to two groups of Cp* methyl protons. Integration of the 1H resonances supported the existence of two isomers in the ratio 1:0.14 (at 233 K) in solution. A 31 P selective decoupling experiment performed on 17a by irradiating at the phosphorous resonances confirmed that the splitting of the hydrides was indeed due to coupling with phosphorous atoms (Figure 4.7). The two doublets observed at δ -16.65 and -19.67 ppm which are of 135 Figure 4.19. ORTEP diagram and selected bond parameters of 20a. Thermal ellipsoids are drawn at 50% probability level. Organic hydrogens are omitted for clarity. Ir(1)-Os(4) = 2.7140(4) Å; Ir(1)-Os(2) = 2.7804(4) Å; Ir(1)-Os(3) = 2.7917(4) Å; Os(2)-Os(4) = 2.8924(4) Å; Os(2)-Os(3) = 2.9578(4) Å; Os(3)-Os(4) = 2.7860(4) Å; Ir(1)-C(11) = 1.899(7) Å; Os(3)-C(11) = 2.249(7) Å; N(23)-C(23)-Os(2) = 178.3(7)º; N(32)-C(32)-Os(3) = 175.0(6)º. In the IR spectrum of 20a, both the NC and CO stretching frequencies appeared to lower frequency compared to 19a (νNC = 2176 cm-1; νCO = 2063-1754 cm-1 in 19a while νNC = 2165 cm-1; νCO = 2036-1745 cm-1 in 20a). These shifts towards lower frequencies can be attributed to the increase in the number of tBuNC ligands. Isocyanides are stronger σ-donors and weaker π-acceptors compared to a carbonyl. 155 4.3.2 Reaction of 3c with pyridine The activation of C-H and N-H bonds of aromatic and aliphatic nitrogen heterocycles by triosmium and triruthenium clusters has been very well studied. These reactions generally required very harsh conditions and orthometallated products were usually obtained. For example the reaction of Os3(CO)12 with pyridine required a temperature of about 128 ºC [40]. The first step in this reaction is believed to be CO dissociation, followed by nitrogen coordination leading to an intermediate, Os3(CO)11(η1-NC5H5). This then eliminated another CO, followed by oxidative addition of the adjacent C-H bond (orthometallation), to give Os3(CO)10(μ-H)(μ-η2-NC5H4). The intermediate, Os3(CO)11(η1-NC5H5), could not be isolated from this reaction but was subsequently isolated from the reaction of Os3(CO)11(CH3CN) with pyridine. Very few examples of mixed metal clusters containing nitrogen heterocycles are known. One example that has been reported is the reaction of RuCo3(μ-H)(CO)12 with amines or trimethylamine N-oxide to yield amine substituted clusters [20]. IR, 1H and 59 Co NMR studies indicated that the substitution of amine ligands took place preferentially at the ruthenium atom whereas substitution by phosphines occurred exclusively at the cobalt atom, thus presenting a good example of metalloselectivity (Scheme 4.4). NMe3 Co Co Co Ru Ru Ru Me3NO Co Co Co PPh3 Co Co PPh3 Co Scheme 4.4 156 Cluster 3c reacted with excess pyridine under TMNO activation. Attempts to purify the crude mixture by recrystallization resulted in decomposition. The 1H NMR spectrum of the crude reaction mixture recorded at room temperature showed two singlets at δ 2.11 and 2.13 ppm assignable to Cp* methyl protons of 3c and the product, respectively and two broad singlets in the hydride region suggesting the presence of bridging hydrides. As the temperature was lowered, the broad resonances resolved into two singlets of equal intensity; this can be seen from the 1H VT NMR spectra recorded between 203 and 300 K (Figure 4.20). Figure 4.20. 1H VT NMR spectrum of 21. 157 The compound was tentatively identified as Cp*IrOs3(μ-H)2(CO)9(py), 21. The other resonances of low intensities observed in the 1H NMR spectrum around δ -14.0, -16.0 and -17.0 ppm could be tentatively assigned to isomers existing in solution. The IR spectrum of 21 recorded in dichloromethane indicated that the bands due to νCO appeared at a lower frequency than that of 3c. Since amines are more electron donating than the carbonyls, substitution of electron donating amines for the carbonyls would result in lowering of the νCO. It is interesting to note that the IR spectrum of 21 in the νCO region was quite different from those of the PR3 as well as the RNC substituted clusters. This suggested that the site for the substitution of pyridine in cluster 3c is different. A FAB-MS spectrum of the crude reaction mixture showed a very strong molecular ion peak at m/z = 1231.1 and fragment clusters of peaks corresponding to successive loss of up to nine carbonyls. The molecular ion peak further confirmed the formulation. Two possible structures proposed for 21 are shown in Figure 4.21. Ir Os Ir Os H Os H Os H Os Os Py H Py (A) (B) Figure 4.21. Possible structures of 21. 158 4.4 Conclusions Cluster 3c underwent substitution reactions at room temperature in the presence of TMNO with various group 15 substrates to give the monosubstituted and disubstituted derivatives, Cp*IrOs3(μ-H)2(CO)9(L) (where L = PPh3, 17a; P(OMe)3, 17b; tBuNC, 19a; CyNC, 19b; and py, 21) and Cp*IrOs3(μ-H)2(CO)8(L)2 (where L = PPh3, 18a; P(OMe)3, 18b; and tBuNC, 20a) in good yields. In the absence of TMNO, the reactions did not proceed. For the monosubstituted derivatives, the substitution site was exclusively at an osmium atom in a pseudo-axial position for L = phosphine or phosphite. Spectroscopic evidence suggested the presence of isomers in solution for the PPh3 derivative. In contrast, for L = cyanide or isocyanide, the ligand occupied a pseudo-equatorial site. In the disubstituted derivatives, the group 15 ligands were coordinated to two osmium atoms at pseudo-axial and equatorial sites. 159 4.5 Experimental 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, spin saturation transfer and 2D spectra (EXSY, NOESY) were acquired on a Bruker Avance DRX500 or Bruker AMX500 machine. All ligands were from commercial sources and used as supplied. 4.5.1 Reaction of 3c with triphenylphosphine To a 250 ml three necked flask containing Cp*IrOs3(H)2(CO)10, 3c (60 mg, 0.051 mmol) in dichloromethane (10 ml) was added PPh3 (20 mg, 0.076 mmol). A solution of trimethylamine N-oxide (6.7 mg, 0.07 mmol) 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/dcm) on silica gel TLC plates yielded a red band of Cp*IrOs3(μ-H)2(CO)9(PPh3), 17a, (50 mg, 69%) and another red band of Cp*IrOs3(μH)2(CO)8(PPh3)2, 18a, (12 mg, 14%). A series of derivatives of 3c were prepared by a similar procedure as summarized in Table 4.4. The spectroscopic and elemental analysis data for the products are given in Tables 4.5 - 4.7. Crystal structure and refinement data are given in Tables 4.8 and 4.9. 160 Table 4.4. Summary of the substitution reactions of 3c. Mass of 3c used Ligand 60 mg PPh3 0.05 mmol 30 mg 0.025 mmol 30 mg 0.025 mmol 30 mg 0.025 mmol 30 mg 0.025 mmol Amount of ligand P(OMe)3 t BuNC CyNC C5H5N product Rf yield 20 mg 17a 0.30 50 mg, 69% 0.07 mmol 18a 0.15 12 mg, 14% 0.003 ml 17b 0.29 20 mg, 63% 0.04 mmol 18b 0.07 5.3 mg, 15% 0.006 ml 19a 0.19 22 mg, 70% 0.05 mmol 20a 0.11 mg, 17% 19b 0.25 24 mg, 75% 21 - - 0.004 ml 0.03 mmol excess Table 4.5. Infrared spectroscopic data for the derivatives of 3c. Cluster IR νCO cm-1 (dcm) 2062s, 2039sh, 2024vs, 2012sh, 1982s, 1956ms, 1767w, br, 1720w, br 17a (KBr) 2059s, 2023vs, 2011sh, 1984sh, 1975vs, 1961s, 1951sh, 1935ms, 1768ms, 1727w 17b 2064s, 2041sh, 2025vs, 1986m, 1965ms, 1720w, br 18a 2037vs, 2004s, 1987m, 1962vs, 1946m, 1713ms 18b 2040vs, 2015s, 1995m, 1965vs, 1718m 19a 2063s, 2038sh, 2027vs, 2013sh, 1981s, 1962sh, 1754w,br, νCN 2176m,br 19b 2065s, 2040sh, 2028vs, 2014sh, 1982s, 1756w, br, νCN 2184m,br 20a 2034s, 2003vs, 1989sh, 1962s, 1947sh, 1736w, br, νCN 2160ms,br 21 2063m, 2039s, 2021sh, 1997vs, 1967sh, 1937mw, 1727w, br 161 Table 4.6. NMR spectroscopic data for the derivatives of 3c. Cluster 31 H NMR C NMR [ δ/(ppm)] (C6D6) [δ/(ppm)] (d8-toluene) 17a (Major isomer) 300 K 13 P NMR (CDCl3) 7.51-7.32 (m, 15H, C6H5), 2.14 (s, 15H, Cp*), -16.66 (br, 1H, OsHOs) - (CDCl3) 0.15s 19.54 (br, 1H, OsHOs) [δ/(ppm)] (d8-toluene) 134.52 (s, Ph), 130.69 (s, Ph), 130.38 (s, Ph), 128.77 (s, Ph), 97.97 (s, Cp* ring carbons), 10.93 (s, Cp* 233 K methyl carbons) (CDCl3) 7.51-7.32 (m, 15H, C6H5), 2.12 (s, 15H, Cp*), -16.65 (d, 1H, OsHOs, JPH = - - (CDCl3) 16.26s 134.41 (s, Ph), 130.67 (s, Ph), 9.1 Hz), -19.67 (d, 1H, OsHOs, 2JPH = 9.1 Hz) 17a (Minor isomer) 300 K (CDCl3) 7.51-7.32 (m, 15H, C6H5), 2.10 (s, 15H, Cp*), -19.94 (d, 1H, OsHOs, 2JPH = 7.4 Hz) 233 K 130.35 (s, Ph), 128.41 (s, Ph), 97.50 (s, Cp* ring carbons), 10.77 (s, Cp* (CDCl3) 7.51-7.32 (m, 15H, C6H5), 2.07 (s, 15H, Cp*), -17.44 (s, 1H, OsHOs,), methyl carbons) -20.01 (d, 1H, OsHOs, JPH = 9.1 Hz) 17b 300 K 3.19 (d, 9H, OMe, 3JPH = 12.4 Hz), 1.90 (s, 15H, Cp*) 233 K 3.08 (d, 9H, OMe, JPH = 12.4 Hz), 1.83 (s, 15H, Cp*), -17.64 (d, 1H, OsHOs, JPH = 97.36s - - - -11.02s, - 9.9 Hz), -20.33 (d, 1H, OsHOs, JPH = 9.9 Hz) 18a 300 K (C6D6) 7.48-6.98 (m,30H, C6H5), 2.08 (s, 15H, Cp*), -15.71(d, 1H, OsHOs, 2JPH = 14.0 Hz), -18.18 (dd, 1H, OsHOs, JPH = 8.3 Hz, 8.3 Hz) 18b 300 K -14.94s (C6D6) 3.48 (d, 9H, OMe, 2JPH = 11.6 Hz) 3.27 (d, 9H, OMe, 2JPH = 11.5 Hz), 2.05 (s, 118.0s, 96.6s - 15H, Cp*), -17.08 (d, 1H, OsHOs, JP-H = 10.7 Hz), -20.41 (dd, 1H, OsHOs, JPH = 10.7 Hz, 9.9 Hz) 162 19a 300 K 19a (Major isomer) 1.88 (s, 15H, Cp*), 0.90 (br, tBu), -20.25 (br, 1H, OsHOs) t 1.84 (s, 15H, Cp*), 0.96 (s, 9H, Bu), -18.08 (s, 1H, OsHOs), -20.02 (s, 1H, OsHOs) - - - - - - - - - - - - - - - - 253 K 19a (Minor isomer) 1.81(s, 15H, Cp*), 0.86 (s, 9H, tBu), -17.24 (s, 1H, OsHOs) -20.42 (s, 1H, OsHOs) 253 K 19b (Major isomer) 298 K 3.1 (broad cyclohexyl), 1.89 (s, 15H, Cp*), 1.32 (broad, cyclohexyl), 0.98 (broad, cyclohexyl) 253 K 1.83 (s, 15H, Cp*), 1.29, 0.96 (broad, cyclohexyl), -17.28 (s, 1H, OsHOs) -20.45 (s, 1H, OsHOs) 19b (Minor isomer) 253 K 1.85 (s, 15H, Cp*), -17.99 (s, 1H, OsHOs), -20.02 (s, 1H, OsHOs) 20a (Major isomer) 298 K 2.02 (s, 15H, Cp*), -17.90 (s, 1H, OsHOs) -20.03 (s, 1H, OsHOs) 1.98 (s, 15H, Cp*), 1.02 (s, 9H, tBu), 0.81 (s, 9H, tBu), 253 K -17.92 (s, 1H, OsHOs) -19.27 (s, 1H, OsHOs) 20a (Minor isomer) 253 K 2.00 (s, 15H, Cp*), 1.08(s, 9H, tBu), 0.86 (s, 9H, tBu), -17.80 (s,1H, OsHOs), -19.99 (s,1H, OsHOs) 21 203K 300K (CDCl3) 2.11 (s, 15H, Cp*), -14.29 (br, 2H, OsHOs) 1.85 (s, 15H, Cp*), -17.15(s, 1H, OsHOs), -18.12 (s, 1H, OsHOs) 163 Table 4.7. Elemental analysis data for derivatives of 3c Compound C(calc) C(expt) H(calc) H(expt) N(calc) N(expt) MS m/z calculated 17a 31.42 31.33 2.28 1.98 - - 1415.8 1414.4 17b 20.70 20.87 2.05 2.30 - - 1276.3 1276.2 18a 39.34 39.73 2.87 3.03 - - 1648.1 1648.7 18b 21.00 21.29 2.57 2.62 - - 1373.6 1372.3 19a 23.33 23.78 2.12 2.06 1.13 0.84 1236.8 1235.4 19b 24.76 24.92 2.24 2.36 1.11 0.97 1261.2 1261.3 20a 26.06 26.48 2.73 2.59 2.17 1.97 1290.4 1290.4 21 - - - - - - 1231.1 1232.0 164 Table 4.8. Crystal and structure refinement data for 17a, 17b and 18a. Compound 17a 17b 18a Empirical formula C37H32IrO9Os3P C22H26IrO12Os3P C54H47IrO8Os3P2 Formula weight 1414.40 1276.20 1648.66 Temperature K 223(2) 223(2) 223(2) Wavelength Å 0.71073 0.71073 0.71073 Crystal system Triclinic Monoclinic Triclinic Space group P⎯1 P21/c P⎯1 Unit cell a = 10.0041(3) Å a = 18.4173(18) Å a = 13.0331(9) Å dimensions b = 13.7645(5) Å b = 9.7730(9) Å b = 13.0913(9) Å c = 14.5798(5) Å c = 18.6227(18) Å c = 17.4377(12) Å α= 78.676(1)° α= 90° α= 105.049(2)° β= 86.286(1)° β= 117.830(2)° β= 92.577(2)° γ = 70.749(1)° γ = 90° γ = 110.219(2)° Volume Å 1858.50(11) 2964.2(5) 2666.2(3) Z ρ(calculated) Mg/m 2.527 2.860 2.054 Absorption -1 coefficient mm F(000) 13.887 17.403 9.724 1292 2296 1540 Crystal size mm 0.12 x 0.06 x 0.06 0.36 x 0.20 x 0.06 0.16 x 0.08 x 0.03 Theta range for data 2.16 to 29.43° 2.19 to 26.37° 2.13 to 26.37° 25504 26985 35856 9246 [R(int) = 0.0338] 9246 / / 473 6057 [R(int) = 0.0658] 6057 / / 360 10904 [R(int) = 0.0671] 10904 / 11 / 618 0.994 1.058 1.106 R1 = 0.0289, wR2 = 0.0640 R1 = 0.0407, wR2 = 0.0672 1.962 and -0.794 R1 = 0.0488, wR2 = 0.1152 R1 = 0.0580, wR2 = 0.1207 3.695 and -2.654 R1 = 0.0600, wR2 = 0.1386 R1 = 0.0754, wR2 = 0.1469 5.755 and -1.686 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 165 Table 4.9. Crystal and structure refinement data for 18b, 19b and 20a. Comound 18b 19b 20a Empirical formula C24H35IrO14Os3P2 C26H28IrNO9Os3 C28H35IrN2O8Os3 Formula weight 1372.26 1261.29 1290.38 Temperature K 223(2) 223(2) 223(2) Wavelength Å 0.71073 0.71073 0.71073 Crystal system Monoclinic Monoclinic Triclinic Space group P21/c P21 P⎯1 Unit cell a = 17.9642(7) Å a = 9.8674(6) Å a = 9.9572(6) Å dimensions b = 9.4765(3) Å b = 10.9098(6) Å b = 11.2613(6) Å c = 20.2004(7) Å c = 14.3200(8) Å c = 16.3334(9) Å α= 90° α= 90° α= 76.2690(10)° β= 95.172(1)° β= 102.908(1)° β= 83.7040(10)° γ = 90° γ = 90° γ = 73.6600(10)° Volume Å 3424.9(2) 1502.61(15) 1705.47(17) Z ρ(calculated) Mg/m 2.661 2.788 2.513 Absorption 15.121 17.107 15.074 2504 1136 1172 Crystal size mm 0.18 x 0.13 x 0.05 0.33 x 0.15 x 0.07 0.15 x 0.09 x 0.08 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) 2.02 to 30.02° 2.29 to 30.01° 2.07 to 26.37° 49890 13889 23064 9439 [R(int) = 0.0542] 9439 / / 421 8297 [R(int) = 0.0400] 8297 / / 366 6972 [R(int) = 0.0331] 6972 / 21 / 403 1.096 1.005 1.030 R1 = 0.0384, wR2 = 0.0732 R1 = 0.0499, wR2 = 0.0771 1.854 and -0.966 R1 = 0.0376, wR2 = 0.0779 R1 = 0.0416, wR2 = 0.0798 2.221 and -1.522 R1 = 0.0301, wR2 = 0.0636 R1 = 0.0409, wR2 = 0.0671 1.456 and -0.762 coefficient mm -1 F(000) Largest diff. peak -3 and hole e.Å 166 4.6 References 1. 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Pippard, Journal of the Chemical Society, Dalton Transactions, 1981, 407. 170 [...]... mg, 69%) and another red band of Cp*IrOs3(μH)2(CO)8(PPh3)2, 18a, (12 mg, 14% ) A series of derivatives of 3c were prepared by a similar procedure as summarized in Table 4. 4 The spectroscopic and elemental analysis data for the products are given in Tables 4. 5 - 4. 7 Crystal structure and refinement data are given in Tables 4. 8 and 4. 9 160 Table 4. 4 Summary of the substitution reactions of 3c Mass of 3c... ligands attached to the osmium triangle in 3c is substituted by the CyNC ligand and it is oriented cis to the Os (4) -Os(3) bond The CyNC ligand is slightly bent ( . containing mixed metals are of interest as sites to probe metallo selectivity and site selectivity. Although there has been some reports on the synthesis of Cp- and Cp*- containing osmium -iridium clusters, . Chapter 4 Subtitution chemistry of Cp*IrOs 3 (μ-H) 2 (CO) 10 4. 1 Carbonyl substitution in metal carbonyl clusters The ligand substitution chemistry of homometallic clusters have been. of osmium -iridium atoms. Two phosphine ligands, P(5) and P(6) were coordinated to two adjacent osmium atoms in an axial and equatorial fashion, respectively. Figure 4. 12. IR spectrum of