Chemical Properties Of Nickel Hydride And Cobalt Hydrides With Assistance Of Organophosphorus

Organometallic hydrides are widely used as catalysts in the field of alkene and alkyne oligomerization and polymerization, also they exhibit their applications in the field of organic synthesis. Particular attention has always been paid to these metal-hydrides in academe and industry, therefore, the study of reactive characters of M-H bond has been focused on for a long time. Nickel hydrides and cobalt hydrides show their attraction owing to the low prices and environment friendly. In this doctoral dissertation, reaction activities of M-H bond in nickel hydride and cobalt hydride with assistance of organophosphorus are studied. The main contents are described as follows:Reactions of alkynes with Ni-H bond in nickel hydride containing a [P,S]-chelated ligand When terminal alkynes with different substituted group reacting in situ with Ni-H bond in nickel hydride containing a [P,S]-chelated ligand and supported by trimethylphosphine, two types of reactions are found according to the different temperature. At room temperature a kind of novel branched σ-vinyl nickel(II) complexes are synthesized by insertion of alkynes into Ni-H bonds in accord with Markovnikov rule.The influence factors of this high regio-selectivity are analyzed. The determinant factor is the inherent structure of nickel hydride instead of electronic and steric effects of substituted group of alkynes. The insertion products are tetracoordinate vinyl nickel(II) complexes with square-planar geometry confirmed by X-ray diffraction techniques. There is definite relationship between the substituted group of alkyne and the structure of branched-vinyl nickel(II) complex. Large steric group such as trimethylsilyl and t-butyl group afford distorted square-planar geometry.Reaction activities of insertion products are studied in order to develop the potential application of nickel hydride. These stable products are diffcult to carring out oxidative addition or substituted reaction. When the products react with CO, σ-vinyl ligands dissociate from the Ni(II) complexes. On the condition of low temperature, terminal alkynes with different substituted group reacting in situ with Ni-H bond in nickel hydride tend to afford substituted products-σ-alkynyl Ni(II) complexes.Reactions of (2-diphenylphosphanyl)thiophenol with acyl(hydrido)cobalt(III) complexes Four kinds of products are isolated from the reaction of acyl(hydrido)cobalt(III) complexes with (2-diphenylphosphanyl)thiophenol. It generated two types of chelate cobalt(III) complexes, one chelate cobalt(I) complex and one chelate cobalt(II) complex. Complex bearing a soft/soft [P, S]-chelate ligand and a soft low-valent cobalt(I) central atom was obtained in the highest yield of about 30-40%, while the expected products with a soft/soft [P, S]-chelate ligand and a hard high-valent cobalt(III) central atom show low yields (less than 10%). The by-products with a hard/hard [O, O]-chelating ligand and a hard cobalt(III) center are very stable. Cobalt(II) complex could be separated as a result of a disproportionation reaction of cobalt(I) complex. Regarding all information obtained from this complicated reaction system a mechanism is proposed. In combination with the earlier work, the influence of chelating ligands containing hard/soft donor atoms on the relative stabilities of cobalt complexes can be described. Coordination of chelating ligands at Co(III) decreases as [N, O] > [P, O] > [P, S], while at Co(I) this order is reversed, which is in accord with the HSAB rule.Reactions of acyl(hydrido)cobalt(III) complex with 2-propyn-1-ol Acyl(hydrido)cobalt(III) complexes react with 2-propyn-1-ol and generate branched σ-vinyl Co(III) complexes products owing to the insertion of alkyne bond into Co-H bond in accord with Markovnikov rule. X-ray diffraction analysis of products indicate that they are bis-chelating vinyl-cobalt(III) complexes in which the vinyl ligands form novel four-membered cycles which contribute stability to the complexes. The unusual stability of complexes is a crucial factor for the unsuccess of the reaction with carbon monoxide. On the contrary, the vinyl chelating ligand and acylenolato ligand are prone to be dissociated being substituted by HCl to generate more stable chloro- or trichloro-cobalt(III) complexes according to the ratio of HCl. Reations of conjugated dialkyne with nickel hydride and cobalt hydride Terminal alkynes with different substituted group reacting with nickel hydride and cobalt hydrides afford vinyl metal complexes. When single alkynes are replaced by conjugated dialkynes, dinuclear complexes with conjugated bridges are expected. Non-substituted terminal conjugated dialkynes react with nickel hydride containing a [P,S]-cheIated ligand or acyl(hydrido)cobalt(III) complexes generate homo-dinuclear nickel(II) complex and cobalt(III) complex with branched σ,σ-vinyl conjugated bridges which have potential applications on the studies of molecular-scale electronic devices, such as molecular wires and molecular switches. This reaction opens a new facile route to synthesize bimetallic nickel and cobalt complexes. Single insertion products can not be obtained by controling the ratio of reactants.Substituted terminal conjugated dialkynes react with nickel hydride or cobalt hydrides undergo single insertion reaction. When the substituted group is trimethylsilyl group, the product has E- and Z- two isomers which have different ³¹P NMR spectrum characters-E-isomer has larger ²J_PP value and the ratio of Z- to E- is 4:1.Hetero-dimetallic complexes are facile to form un-central-symmetry crystal. Generally, they exhibit more excellent properties such as magnetic, optical and electronic properties under the external magnetic field. The synthsis of hetero- dimetallic cobalt-nickel complex is also attempted. When the related nickel and cobalt hydrides react with non-substituted terminal conjugated dialkynes simultaneously, the expected Ni-Co complex through competitive reaction between the two hydrides was not obtained. Instead, two hydrides react mutually to undergo redox and ligand exchange affording two stable produdts- [P,S]-chelating Co(I) complex and 2-acylenolato Ni(II) complex.Reactions of imine with nickel(II) and nickel(O)Activation of C-H bond is an effective method to synthesis metal hydrides and it isusually a key step in many catalytic processes. It is one of the most attractive field oforganometallic study. Few examples of C-H activation related to nickel complex arepublished. C-H bonds of imine group and σ-position phenyl ketimine are selected to beaim bonds.Through the reaction of imine with trimethylphosphine and triphenylphosphine nickel(II) and nickel(O) complexes, a cyclometalation reaction is expected to generated nickel hydride. Under the experimental conditions, a C=N bond Ï€-coordinated Ni(0) complex is obtained when NiMe₂(PMe₃)₃ and NiMe₂(PMe₃)₂ were employed. As to Ni(0) complexes, Ni(PPh₃)₃ can also attain a C=N bond Ï€-coordinated Ni(0) complex with low yield while Ni(PMe₃)₄ does not carry out any reaction.All of the new complexes are characterized by IR, ¹H, ¹³C and ³¹P NMR. Structures of some single crystals have been confirmed by X-ray diffraction techniques.