Studies of the Activation of Carbon-Gold and Carbon-Hydrogen Bonds by the Pentaruthenium Carbonyl Cluster Ru5(μ5-C)(CO)15

The current practical uses of hydrocarbons by industry are discussed in Chapter 1. Carbon-hydrogen (C-H) bond activation and selective functionalization by transition metal complexes is presented as a possible alternative for the upgrading of hydrocarbons. The comparison of carbon-gold (C-Au) bond activation to C-H bond activation based on isolobal principles by transition metal complexes is presented. The high nuclearity ruthenium cluster complexes Ru6C and Ru5C are presented and their early chemistry is discussed. The reactions of high nuclearity carbido cluster complexes, Ru6C(CO)17 and Ru5C(CO)15, with PhAuNHC are presented in Chapter 2. The reaction of Ru6C(CO)17 with PhAuNHC yields the π-arene complex Ru6C(CO)14[η6-PhAu(NHC)], 2.3 that does not involve activation of the Au-C bond. The oxidative addition of the Au-C bond of PhAuNHC to Ru5C(CO)15 yielded two new cluster complexes: Ru5C(CO)14(Ph)[μ- Au(NHC)], 2.4 and Ru5C(CO)13(μ–η2-Ph)[μ-Au(NHC)], 2.5. Both 2.4 and 2.5 react with CO to yield the complex Ru5C(CO)14(μ–η2-O=CPh)[μ-Au(NHC)], 2.6, that contains a bridging benzoyl formed from the insertion of CO into the Ru-Ph bond. The reaction of Ru5C(CO)15 with CH3AuPPh3 is reported in Chapter 3. Three hetero-bimetallic Ru5CAu cluster complexes containing methyl ligands were isolated: Ru5(μ5-C)(CO)14(μ-η2-O=CMe)[μ-Au(PPh3)], 3.5; Ru5(μ5-C)(CO)13(μ-η2- O=CMe)(Me)[μ-Au2(PPh3)2], 3.6; Ru5(μ5-C)(CO)14(μ-η2-O=CMe)(η1-O=CMe)[μ-Au2(PPh3)2], 3.7. The PPh3 substituted complex Ru5(μ5-C)(CO)13(PPh3)(μ-η2-O=CMe)[μ- Au(PPh3)], 3.8, was also isolated. Two nonmethyl complexes: Ru5(μ5-C)(CO)11(μ-CO)3[μ- Au(PPh3)]2, 3.9, and Ru5(μ5-C)(CO)11(μ-CO)2[μ-Au(PPh3)]4, 3.10 were also isolated. The synthesis, structures and interrelationships of these new complexes are described. The products formed from the cluster opening reaction of Ru5C(CO)15 with benzoic acid are presented in Chapter 4. Two new isomeric Ru5C open square pyramidal complexes: Ru5(C)(CO)14(η2-O2CC6H5)(μ-H), 4.2 and Ru5(C)(CO)14(μ–η2-O2CC6H5)(μ- H), 4.3 were isolated that possess a benzoate ligand in η2-chelating and μ–η2-bridging coordination modes, respectively. An equilibrium between the isomerization of the two benzoate isomers was established. The studies of aldehydic C-H activation by Ru5C(CO)15 are introduced in Chapter 5. The reaction of Ru5C(CO)15 with benzaldehyde yielded two new complexes: Ru5(μ5- C)(CO)14(η2-O=CH(C6H4))(H), 5.2, and Ru5(μ5-C)(CO)14(μ-η2-O=CPh)(μ-H), 5.3. 5.2 possesses a η2-chelating benzoyl ligand formed by C-H activation at the ortho position of the phenyl ring and 5.3 contains μ-η2-bridging benzoyl ligand formed from activation of the aldehydic C-H bond. Comparison studies of the reaction of Ru5(μ5-C)(CO)15 with cinnamaldehyde produced two analogous complexes: Ru5(μ5-C)(CO)14(η2- O=CHCH=CPh)(μ-H), 5.4 and Ru5(μ5-C)(CO)14[μ-η2-O=C(CH=CHPh)](μ-H), 5.5. Compounds 5.4 and 5.5 show similar differences in the site of C-H activation of cinnamaldehyde. The decomposition reactions of the coordinated acyl ligands in the product complexes are also presented. The activation of formyl C-H bonds of aldehydes presented in chapter 5 is expanded on in Chapter 6 and looks at the activation of the formyl C-H bond of N,N dimethylformamide (DMF). The reaction of Ru5C(CO)15 with DMF yields two new Ru5C complexes that contain μ-η2-bridging formamido ligands: Ru5(μ5-C)(CO)14(μ-η2- O=CNMe2)(μ-H), 6.2nand Ru5(μ5-C)(CO)13)(HN(Me2)(μ-η2-O=CNMe2)(μ-H), 6.3. The reaction of 6.3 with C2H2 yields the hydrocarbamoylation product Ru5(μ5-C)(CO)13[μ-η3- O=CN(CH3)2CHCH](μ-H), 6.4, from coupling of the μ-η2-bridging formamido ligand with C2H2 to form a μ-η3-bridging acrylamido ligand. Placing complex 6.4 under an atmosphere of CO yields the CO addition product Ru5(μ5-C)(CO)14[η2- O=CN(CH3)2CH=CH](μ-H), 6.6. Under more forcing conditions of CO, reductive elimination of the η2-chelating acrylamido ligand and the bridging hydride to yield N,Ndimethylacrylamide, effectively forming a catalytic cycle. The investigations of olefinic C-H activation of substituted olefins with Ru5C(CO)15 are discussed in Chapter 7. The reaction of Ru5C(CO)15 with methyl acrylate yielded the new chelating acryloyl complex: Ru5(μ5-C)(CO)14[η2-O=CO(CH3)CH=CH](μ- H), 7.2. The reaction of Ru5C(CO)15 with vinyl acetate yielded the new complex Ru5(μ5- C)(CO)14[C(=CH2)(O2CMe)](μ-H), 7.3. The two C-H activated olefin complexes differ by the location of the C-H activation. Compound 7.2 is activated at the β-carbon of the olefin while 7.3 is activated at the α-carbon of the olefin. The work in Chapter 8 is a continuation of the chemistry presented in Chapter 7. The functionalization of the activated olefinic C-H bonds of methyl acrylate, dimethylacrylamide, and vinyl acetate through the tail-to-tail coupling of a second equivalent of the olefin to the activated ligand in the complex was investigated. The reaction of the activated methyl acrylate 8.2 with Me3NO and excess methyl acrylate yielded five new Ru5C complexes of methyl acrylate: Ru5(μ5-C)(CO)13[μ-η3- O=CO(Me)CHCH](μ-H), 8.6, Ru5(μ5-C)(CO)13[η3-anti,anti-(Me)OC=O-C3H3-η1- O=CO(Me)CH2](μ-H), 8.7, Ru5(μ5-C)(CO)13[η3-anti,syn-(MeO2C)CH2C3H3-CH2-η1- O=C(OMe)](μ-H), 8.8, Ru5(μ5-C)(CO)12[μ-η3-O=C(OMe)CH=CH][η2- CH=CHCO2Me](μ-H), 8.9, and Ru5(μ5-C)(CO)13[η3-syn,anti-(MeO2C)C3H3-η1- O=C(OMe)CH2](μ-H), 8.10 where complexes 8.7, 8.8, and 8.10 show carbon-carbon formation between methyl acrylate units. Reaction of the activated dimethylacrylamide ligand in 8.3 with additional dimethylacrylamide yielded two new coupled dimethylacrylamide complexes: Ru5(μ5-C)(CO)13[η3-syn,anti-Me2NC=O-C3H3-η1- O=CNMe2CH2](μ-H), 8.11 and Ru5(μ5-C)(CO)13[η3-anti,syn-Me2NC=O-C3H3-CH2-η1- O=CNMe2](μ-H), 8.12. Two new hetero-coupled substituted olefin complexes, Ru5(μ5- C)(CO)12[μ-η3-O=C(NMe2)]CH=CH][η2-CH=CHCO2Me](μ-H), 8.13 and Ru5(μ5- C)(CO)13[η3-anti,syn-MeO2CCH2-C3H3-η1-O=C(NMe2)](μ-H), 8.14, were obtained from the reaction of 8.3 with methyl acrylate. Reaction of activated vinyl acetate ligand in 8.5 with an additional equivalent of vinyl acetate in the presence of Me3NO yielded a new uncoupled bis-vinyl acetate complex: Ru5(μ5-C)(CO)12[μ-η2-(MeO2C)CH=CH](η3- CH2=CHOC(=O)Me)(μ-H), 8.15