可以通过Na / Hg还原LCoCl 2或氢解LCoCH 2 SiMe 3来制备形式上为Co(0)的配合物LCo(N 2)(L = 2,6-双(2,6-二甲基苯基亚氨基乙基)吡啶)。在后一反应中,LCOH可以通过与N≡CC反应被截留6 ħ 4 -4-CL,得到LCoN═CHC 6 ħ 4 -4-CL。LCo(N 2)与许多烷基和芳基卤化物RX(包括芳基氯化物)反应,在卤素原子提取机理中得到LCoR和LCoX的混合物。游离烷基和芳基的中间体通过环丙基甲基对巴豆基的开环和2,4,6- t Bu的重排得到证实3 C 6 H 2至3,5- t Bu 2 C 6 H 3 CMe 2 CH 2,然后与Co结合。以这种方式生成的有机钴物质进一步与活化的卤化物R'X(烷基碘;烯丙基和苄基卤化物)反应)以最有可能再次是卤素提取机理的方式产生交叉偶联产物RR'。DFT研究支持为这两个步骤建议的基本途径。MeI与LCoCH
可以通过Na / Hg还原LCoCl 2或氢解LCoCH 2 SiMe 3来制备形式上为Co(0)的配合物LCo(N 2)(L = 2,6-双(2,6-二甲基苯基亚氨基乙基)吡啶)。在后一反应中,LCOH可以通过与N≡CC反应被截留6 ħ 4 -4-CL,得到LCoN═CHC 6 ħ 4 -4-CL。LCo(N 2)与许多烷基和芳基卤化物RX(包括芳基氯化物)反应,在卤素原子提取机理中得到LCoR和LCoX的混合物。游离烷基和芳基的中间体通过环丙基甲基对巴豆基的开环和2,4,6- t Bu的重排得到证实3 C 6 H 2至3,5- t Bu 2 C 6 H 3 CMe 2 CH 2,然后与Co结合。以这种方式生成的有机钴物质进一步与活化的卤化物R'X(烷基碘;烯丙基和苄基卤化物)反应)以最有可能再次是卤素提取机理的方式产生交叉偶联产物RR'。DFT研究支持为这两个步骤建议的基本途径。MeI与LCoCH
The Electronic Structure of (Diiminopyridine)cobalt(
<scp>I</scp>
) Complexes
作者:Quinten Knijnenburg、Dennis Hetterscheid、T. Martijn Kooistra、Peter H. M. Budzelaar
DOI:10.1002/ejic.200300569
日期:2004.3
square-planar (LCoR)-R-I complexes of a diiminopyridine ligand are best regarded as containing low-spin Co-II antiferromagnetically coupled to a ligand radical anion. The lowest triplet state, corresponding to a 3d(z)(2)-->pi* excitation, is calculated to be only a few kcal/mol above the ground state, and is thermally accessible. The anomalous H-1 NMR chemical shifts of the LCoR complexes are suggested to
Reaction of LCoCH2SiMe3(L= 2,6-bis[2,6-dimethyl-phenyliminoethyl]pyridine) with H-2 produces LCo(N-2), presumably via intermediate LCoH. Reaction of LCo(N-2) (prepared in this way or via reaction of LCoCl2 with Na/Hg) with aryl halides ArX (X = Cl, Br, I) produces LCoAr and LCoX in a ratio depending on the nature of Ar and X. For X = Cl, the reaction is slowest but also produces the largest amount of LCoAr. Electron-withdrawing substituents both accelerate the reaction and improve the yield of LCoAr. Computational studies support a radical mechanism for this reaction, involving displacement of N-2 to give LCo(XAr) followed by loss of the Ar radical, which then binds to a second Co(0) moiety.
(Py)<sub>2</sub>Co(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub> As an Easily Accessible Source of “CoR<sub>2</sub>”
作者:Di Zhu、Femke F. B. J. Janssen、Peter H. M. Budzelaar