Dianionic Platinadiphospholene Complexes

1,2,3,4-Tetraphenyl-1,2-dihydrodiphosphetene 1 reacts with lithium or sodium naphthalenide to afford the corresponding
dianionic salts 2 and 3. An X-ray crystal structure analysis shows that dianion 3 of general formula [(1)2-2Na3(DME)2,
Na(DME)3] is a polymeric structure consisting of [(1)2-2Na3(DME)2] units which are connected together through
one sodium atom. Reaction of the dianionic lithium salt 2 with [Pt(COD)Cl2] affords the 4[Li(2.2.1)]2 complex, after
the addition of 2 equiv of (2.2.1) cryptate. The overall geometry around platinum in 4[Li(2.2.1)]2 can be described
as distorted square planar, and only the diastereomer (1-R, 2-S, 3-R, 4-S) is formed. X-ray data indicate that no
delocalization takes place within each platinadiphospholene unit and that complex 4[Li(2.2.1)]2 must be regarded
as the coordination of two molecules of dianion 2 onto a Pt2+ center. Reaction of the dianionic sodium salt 3 with
1 equiv of [Pt(COD)Cl2] produces the 4[Na(DME,Et2O)]2 complex which adopts a pseudotetrahedral geometry
around platinum (θ between interplane angles = 35°), the two cationic units [Na(DME, Et2O)] being located along
a C2 axis. Four weak interactions exist between the sodium cations and the phosphorus atoms. Only the (1-S, 2-S,
3-S, 4-S) diastereomer is formed. Bond distances in the diphospholene units of 4[Na(DME,Et2O)]2 are close to that
of dianion 3 indicating that, like in 4[Li(2.2.1)]2, the complex can be described as a platinum (+2) dianionic species.