Homoleptic Complexes of Cobalt(0) and Nickel(0,I) with 1,1'-Bis(diphenylphosphino)ferrocene (dppf): Synthesis and Characterization
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- 作者：Giuseppe Pilloni ; Antonio Toffoletti ; Giuliano Bandoli ; Bruno Longato
- 刊名：Inorganic Chemistry
- 出版年：2006
- 出版时间：December 11, 2006
- 年：2006
- 卷：45
- 期：25
- 页码：10321 - 10328
- 全文大小：123K
- 年卷期：v.45,no.25(December 11, 2006)
- ISSN：1520-510X
文摘
Reduction of Co(dppf)Cl2 with 2 equiv of sodium naphthalenide in THF, in the presence of dppf, affords the homolepticcomplex Co(dppf)2, 1, isolated in 65% yield as a brick red solid, extremely air sensitive. In solution, under inertatmosphere, 1 slowly decomposes into Co and dppf, following a first-order kinetic law (t1/2 = 21 h at 22 
ages/entities/deg.gif">C).Similarly to the Rh and Ir congeners, 1 undergoes a one-electron reversible reduction to [Co(dppf)2]-. Attempts toobtain this d10 species by chemical as well as electrochemical reduction of 1 lead to the hydride HCo(dppf)2, 2, asthe only product that can be isolated. Reduction of Ni(dppf)Cl2 with sodium in the presence of dppf and catalyticamounts of naphthalene affords Ni(dppf)2, 3, isolated in 60% yield as a yellow air stable solid. The stoichiometricoxidation of 3 with [FeCp2]PF6 forms the d9 complex [Ni(dppf)2]PF6, 4, which represents the second example of astructurally characterized Ni(I) complex stabilized by phosphines. A single-crystal X-ray analysis shows for themetal a distorted tetrahedral environment with a dihedral angle defined by the planes containing the atoms P(1),Ni, P(2) and P(3), Ni, P(4) of 78.2ages/entities/deg.gif"> and remarkably long Ni-P bond distances (2.342(3)-2.394(3) Å). The EPRspectroscopic properties of 1 (at 106 K in THF) and 4 (at 7 K in 2-methyl-THF) have been examined and g tensorvalues measured (1, gx = 2.008, gy = 2.182, gz = 2.326; 4, gx = 2.098, gy = 2.113, gz = 2.332). A lineardependence between the hyperfine constants and the Ni-P bond distances has been evidenced. Finally, the changewith time of the EPR spectrum of 4 indicates that it very slowly releases dppf.