Potassium diplatinum(II) tetrakispyrophosphite (abbreviated as [Pt<sub>2</sub>(pop)<sub>4</sub>]4−) is the inorganic compound with the formula K4[Pt<sub>2</sub>(HO<sub>2</sub>POPO<sub>2</sub>H)<sub>4</sub>]. It is a water-soluble yellow salt. The compound has a long-lived, strongly luminescent excited state, with an emission maximum at ~510 nm and a lifetime near 10 μs.[1]
The complex is prepared by heating a mixture of potassium tetrachloroplatinate and phosphorous acid:[2]
2K2PtCl4 + 8H3PO3 → K4[Pt<sub>2</sub>(HO<sub>2</sub>POPO<sub>2</sub>H)<sub>4</sub>] + 8HCl + 4H2OSeveral quat salt derivatives are known.[3] [4]
The anion reacts with boron trifluoride to give the BF2-capped complex [Pt<sub>2</sub>(P<sub>2</sub>PO<sub>5</sub>)<sub>4</sub>(BF<sub>2</sub>)<sub>8</sub>]4-.[5]
The compound reacts with halogens to give Pt(III) dimers:
K4[Pt<sub>2</sub>(HO<sub>2</sub>POPO<sub>2</sub>H)<sub>4</sub> + Cl<sub>2</sub> → K<sub>4</sub>[Pt<sub>2</sub>(HO<sub>2</sub>POPO<sub>2</sub>H)<sub>4</sub>Cl<sub>2</sub>]
With substoichiometric halogen, linear chain compounds result.
The pair of square-planar platinum(II) centers are bridged by four pyrophosphito (HO(O)POP(O)OH2-) ligands. The ligands interact via hydrogen bonds between the POH and P=O group. The Pt---Pt separation is 293 pm for the dihydrate. In the Pt(III) dichloride, the Pt-Pt distance is 270 pm, indicating Pt-Pt bonding.[1]