In the book, The Organic Chemistry of Nickel : Organonickel Complexes by PW Jolly, the reaction between sodium hexacarbonyldinickalte(-1) and ammonia produces hydride complex.

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Some possible structures proposed:

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I think the Ni-H bond is formed by the donation of the electron pair in nickel to hydrogen in ammonia molecule to produce sodium amide. So in fact, the hydride complex still obeys 18 electron rule, is it not?

  • 2
    $\begingroup$ You should avoid Google links as it is considered tracking link. See: chemistry.meta.stackexchange.com/a/4832/17368. Instead, write the book name. $\endgroup$ Commented Jun 18 at 11:39
  • $\begingroup$ Can anything be organometallic and inorganic at the same time? $\endgroup$
    – Paul Kolk
    Commented Jun 18 at 12:43

1 Answer 1


All these structures meet the 18-electron rule, but in different ways.

Structures 23 and 24 may each be represented as a superposition of two 18-electron structures, shown below for 23 in which each hydrogen atom is by turns bonded to one or the other nickel atom. Thus the overall structure 23 has three-center binding through the bridging hydrogens, and similarly 24 has three-center bonding through the bridging CO ligands.

enter image description here

Structure 25 is a single 18-electron structure, which is in effect either of the contributing structures in 23 and 24.

  • $\begingroup$ I'd like to confirm the idea that the hydrogens in three structures do not contribute electron to each nickel atoms. Is that true? $\endgroup$
    – Shira
    Commented Jun 18 at 23:09
  • $\begingroup$ No. The hydrogen atoms are covalently bonded to the nickel. The structures shown have each hydrogen atom contributing one electron assuming the nickel is in a neutral state (which then leads to the nickel providing the other electron in the bond). $\endgroup$ Commented Jun 18 at 23:26

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