Study On The Si-H Bond Activation And Functionalization By Iron,Cobalt And Nickel Complexes Supported With Trimethylphosphine

In recent decades, the environmental problem has attracted more and more attention. One of the most problems is the pollution of heavy metals used in industry. In comparison with these heavy metals, the iron, cobalt and nickel have been used more and more widely, due to the low toxicity, rich storage and environment friendly. In addition, PMe3 has been employed in the catalyst design and the study of mechanism of organic progress, because of its advantage such as the strong coordination ability, relatively small volume, easy to prepare. It is interesting to synthesize metalsilyl organic complexes which could be obtained by the reactions of iron, cobalt and nickel compounds coordinated with PMe3 via the activation of Si-H bonds.In this thesis, iron, cobalt and nickel complexes coordinated with PMe3 as starting materials were employed in the activation of Si-H bonds. The work includes four parts as below:1. The Si-H bond in the non-auxiliary molecule was activated by iron or cobalt complex coordinated with PMe3. The result pioneered that a η2 complex 1 was obtained by the reaction of Fe(PMe3)4 and (EtO)3SiH. Other silanes such as Et3SiH, Ph3SiH and Me2PhSiH was found no reaction with Fe(PMe3)4, even at higher temperature. The zero valent complex Co(PMe3)4 was found as a good compound in the activation of Si-H bond, as cobalt hydride could be generated by the reaction with the mentioned several silanes, although temperature was needed up to 60 ℃ in toluene. Furthermore, the hydride complex 2 was found that having no ability in the reduction of benzaldehyde.2. The activity of Si-H bond in the pincer complex NSiN(8) has been explored. The Si-H bond in the NSiN ligand was activated by iron, cobalt and nickel complexes coordinated by PMe3. Reaction of Fe(PMe3)4 or Me2Fe(PMe3)4 with NSiN afforded a η2 complex 9 and bis-NSiN product 10. It should be noted that the bis-NSiN product could be obtained in higher yield when extended the reaction time. A zero valent cobalt complex 11 was produced by the reaction of NSiN with Co(PMe3)4 at room temperature. Nevertheless, the cobalt hydride 12 was delivered when reaction temperature was up to 50℃. When treatment NSiN with NiMe2(PMe3)3 in THF for 3 days, the zero valent nickel complex 13 was obtained. Interestingly, the methyl was found transferred from nickel to the silicon atom in the pincer NSiN.3. The synthesis and reactivity of a series of iron, cobalt, and nickel complexes supported by tris(phosphino)silyl ligand 14 have been explored. The iron hydride complex{(Ph2P)C6H4}3SiFeH(PMe3) was generated by combination of ligand with Fe(PMe3)4. The ligand reacted with FeMe2(PMe3)4 delivered five-coordinate paramagnetic Fe (Ⅱ) specie{(Ph2P)C6H4}3SiFe(Me). The Co(Ⅲ) complex {(Ph2P)C6H4}3SiCoH(Cl) was synthesized by oxidative addition of ligand to CoCl(PMe3)3. Treatment of such ligand with Co(PMe3)4 or MeCo(PMe3)4 resulted in the formation of Co(Ⅰ) complex{(Ph2P)C6H4}3SiCo(PMe3) via elimination of H2 or CH4. Tris(phosphino)silyl ligand reacted with Ni(PMe3)4 in THF at room temperature afforded Ni(0) complexη2-(Si-H){(Ph2P)C6H4}2{(Ph2P)C6H4}Ni(PMe3), whereas the oxidative addition product{(Ph2P)C6H4}3SiNiH was obtained by heating Ni(PMe3)4 and tris(phosphino)silyl ligand in toluene at 80℃ for 20 h. The homologues {(Ph2P)C6H4}3SiNiX complexes (X= Cl, Br, I) were synthesized by combination of Cl2MeSiH, EtBr, or CH3I withη2-(Si-H){(Ph2P)C6H4}2{(Ph2P)C6H4}Ni(PMe3). Reaction of ligand with NiMe2(PMe3)3 produced the Ni(Ⅱ) complex {(Ph2P)C6H4}3SiNi(Me).4. A series of iron, cobalt, and nickel complexes supported by bidentate ligand (phosphino)silyl ligand ([PSi] 27) has been obtained. Treatment [PSi] with Fe(PMe3)4 generated the iron hydride complex 28, which showed excellent catalytic ability in the reduction of amides, ketones and aldehydes. Interestingly, a Fe(Ⅲ) hydride 29 was produced by the reaction of FeMe2(PMe3)4 with 27. The three core cobalt complex 30 was obtained by the reaction of 27 with Co(PMe3)4. The cobalt(Ⅲ) (33) and cobalt (Ⅰ) (31) complexes were synthesized by combination of 27 with CoCl(PMe3)3 and MeCo(PMe3)4, respectively. In addition, these two cobalt products 33 and 31 could react with CH3I afforded complex 34 and single electron oxidation product 32.27 reacted with Ni(PMe3)4 delivered the η2-complex 35 when heated in toluene at 80℃ for 20 h. However, when the reaction time was enlonged to 55 h, the bis-nickel complex 36 was produced. When treatment the η2-nickel complex 35 with EtBr, the free ligand and NiBr2(PMe3)3 was generated.