Cobalt(II) hydride

Cobalt(II) hydride is an inorganic compound with a chemical formula CoH2. It has dark grey crystals. It oxidizes slowly in air and reacts with water.
Two forms of cobalt(II) hydride exist under high pressure. From 4 to 45 GPa there is a face-centred cubic form with formula CoH. This can be decompressed at low temperatures to form a metastable compound at atmospheric pressure. Over 45 GPa a cobalt(II) hydride CoH2 also crystallises in a face-centred cubic form.
Preparation.
Cobalt(II) hydride can prepared by reacting phenylmagnesium bromide and cobalt(II) chloride in hydrogen gas: