MERCURY(II) DIPHOSPHATE, HG2P2O7

Mercury(II) diphosphate, Hg2P2O7, belongs to the M2X2O7 family of comp ounds with dichromate-type crystal structures and is isotypic with Cd2 P2O7. The structure consists of alternating layers built from P2O7 gro ups and highly distorted HgO6 polyhedra with bond distances in the ran ges 2.120(6) less than or equal to d(Hg1O(6)) less than or equal to 2. 793 (7) Angstrom and 2.208 (6) less than or equal to d(Hg2O(6)) less t han or equal to 2.509(6) Angstrom. The diphosphate anion has a P-O-P b ridging angle of 133.4(4)degrees. The average P-O bond length is 1.604 Angstrom for bridging and 1.524 Angstrom for terminal bonds. [Hg1(2)O (10)] and [Hg2(2)O(10)] form chains running along [110] through edge-s haring dimers. These chains link to form layers parallel to ((1) over bar 10) via common vertices.