Access to 1,2,3-triphospholide ligands by reduction of di- tert -butyldiphosphatetrahedrane.

Di- tert -butyldiphosphatetrahedrane ( t BuCP) 2 (A) is a reactive tetrahedral molecule which may serve as a source of new phosphaorganic molecules and ligands. However, the redox chemistry of this compound has not yet been investigated. Here, we show that the reduction of A with alkali metals (AM = Li, Na, K, Rb and Cs) affords 1,2,3-triphospholides [AM(crown ether)][1,2,3-P 3 C 2 t Bu 2 ] (1-5, [AM(crown ether)] = [Li([12]crown-4) 2 ] + , [Na([15]crown-5) 2 ] + , [K([18]crown-6)] + , [Rb([18]crown-6)] + , and Cs + ) with 1,3-diphospholides [AM(crown ether)][1,3-P 2 C 3 t Bu 3 ] (6-10) formed as by-products. The potassium salt 3 was isolated on a preparative scale, allowing for reactivity studies. Transmetalation with iron(II) and ruthenium(II) chlorides yielded the sandwich complexes [Cp*M(η 5 -1,2,3-P 3 C 2 t Bu 2 )] (11, M = Fe; 12, M = Ru, Cp* = C 5 Me 5 ) featuring η 5 -coordinated triphospholide ligands. Treatment of 3 with [Cp 2 Fe][BAr 4 F ] or [H(Et 2 O) 2 BAr 4 F ] (BAr 4 F = B{C 6 H 3 (CF 3 ) 2 } 4 ) afforded the polyphosphorus compound t Bu 4 C 4 P 6 (13), which presumably results from the dimerisation of a 1,2,3-triphospholyl radical intermediate (1,2,3-P 3 C 2 t Bu 2 )˙ (3˙). Tetracyclic 13 is closely structurally related to an isomer of the hydrocarbon hypostrophene (C 10 H 10 ).