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Bibinou

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Posts posted by Bibinou

  1. Hello everybody,

     

    I have some problems in order to count the electrons in compound using the 18th electrons rule.

     

    In the compound [(BuO)3 Mo Mo (OBu)3] I count 12 electrons (6 e- for Mo, 3 * 1e- for Metal-Metal bound, and 3 * 1e- for OBu). Is it correct?

     

    In the compound W(CO)3(P Pr3)2(H2) I count 18 electrons (6 e- for W, 3 * 2e- for CO and 2*2e- for P Pr3 and 2 for the H). Is it correct?

     

    Moreover, it exist exceptions to the 18-electron rule.

    Why cannot V(CO)6 dimerize?

    What about the compound Mo2(OSiMe3)6 and W(Me6)?

     

    Why are Metallocenes [M (C5H5)2] are only known for M = V to Ni ?

     

    I thank you very much for your help

  2. Hello,

     

    it exists sevaral methods to make the flavone synthesis.

    I see how works the fist step of each method, but don't see how works the mecanism of the other steps in both methods (see enclosed doc.)

     

    I thank you very much for you help.

    flavone.gif

  3. Hello,

     

    Could you find the structure and the geometry of the following compounds ? It will help me to analyse my IR spectrums.

     

    Ni(SCN)2(PPh3)2

    MoO2(C5H7O2)2

    (NH4)2MoS4

    (Pr4N)2[(CN)CuS2MoS2]

    Cu(PPh3)2(NO3)

     

    In fact I mean by "giving the structure" is like what I do in enclosed document for [(Ph3P)2CuS2MoS2Cu(PPh3)]

    (see enclosed document)

     

    Thank you very much for your help

    image.JPG

  4. Good morning,

     

    I have problems in balancing a synthesis reaction. The pathway is given :

    (NH4)6Mo7024.4H2O +28 H2S+8 NH4OH--> 7(NH4)2MoS4 + 36 H20

    NH4)2MoS4 (CuCN/KCN/[Pr4N)Br]) --> (Pr4N)2[(CN)CuS2MoS2]

    (Pr4N)2[(CN)CuS2MoS2] + Cu(PPh3)2(NO3) --> [(Ph3P)2CuS2MoS2Cu(PPh3)]

     

    I don't really see how to equilibrate the 2 last ones and I have also problems to explain really what occurs during this synthesis. How do we explain the fact that we use KCN AND CuCN? Could we also form KBr and NH4CN for the second reaction?

    I found on a contribution from the department of chemistry in Australia. The follwing paragraph explains how works the second reaction :

     

    Synthesis of (n-Pr4N)2[(CN)CuS2MoS2]

     

    a solution of KCN (O.64g 9.8mmol) in H2O (7 cm3) is added to a suspension of NH4CuMoS4 (3g 9.8mmol) in H2O (30 cm3) to produce a deep red solution.

    A solution of (n-Pr4N)Br (5.2g 19.6 mmol) in H20 (10cm3) is added dropwise producing a red precipitate.

    The mixture is stirred 15min before the compound which is washed with H2O, EtOH and ether and dried in air, is isolated. (yield 65% 4.35g)

     

    Ph4As+ et Et4N+ may be prepared in a similar manner. The compounds may also be prepared by combinating equimolar aqueous solution of (NH4)2[MoS4] and [Cu(CN)x ]^(1-x) (produced by combinatingCuSO4.5H20 orCuCN with KCN) followed by the addition of 2-3 equivalents of the quaternary cation.

     

    Thank you very much for your help.

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