We do know that the Grignard Reagent is $\ce{RMgX}$ where R is some alkyl group & X is any halogen group. So, my question is that, whether $\ce{HMgX}$ is also a Grignard Reagent like $\ce{RMgX}$?


1 Answer 1


According to Ashby and Goel [1,2] $\ce{HMgX}$ compounds are a thing. You can't make them with magnesium +$\ce{HX}$, of course (what actually happens?), but you can get them from magnesium halide salts plus an "active" form of magnesium hydride in THF. They act as hydride ion sources for reaction with $\ce{AlH3}$ and $\ce{BH3}$ (forming mixed tetrahydridoaluminate and tetrahydridoborate salts, respectively), and reference [2] also indicates some substrates such as benzophenone are also reduced through accepting hydride ions from the hydromagnesium complex. Such a hydride transfer would be analogous to conventional Grignard reagents transferring their alkyl or aryl anion moieties.


  1. E. C. Ashby and A. B. Goel (1977). "Preparation of HMgX compounds and their reactions with alane and borane in tetrahydrofuran". Inorg. Chem. 16, 11, 2941–2944. https://doi.org/10.1021/ic50177a055

  2. E. C. Ashby and A. B. Goel (1977). "The preparation of HMgX compounds". J. Am. Chem. Soc. 99, 1, 310–311. https://doi.org/10.1021/ja00443a085

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    $\begingroup$ But it is probably better not to call them a Grignard reagent as they will have far more in common with metal hydrides. $\endgroup$
    – matt_black
    Commented Dec 8, 2018 at 15:39
  • $\begingroup$ Do we call them "Grignard reagents"? Do we call Pluto or Ceres a "planet"? That's ultimately not so much a law of nature as our nature. $\endgroup$ Commented Dec 9, 2018 at 22:48

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