Thallous hypophosphite, TlH₂PO₂

Thallous hypophosphite, TlH₂PO₂, is a sparingly soluble salt which crystallises in rhombic bipyramids (a:b:c = 0.786:1:0.806). It melts at 150°, and at higher temperatures decomposes, evolving phosphine and leaving a residue of thallous meta- and pyro-phosphates.