Synthesis, characterisation and complexation of phosphino disilenes

The treatment of disilenide Tip2SiSi(Tip)Li (1, Tip = 2,4,6-iPr3C6H2) with P-chloro phosphines affords the phosphino disilenes (2a-d; a: R = Ph, b: R = iPr, c: R = Cy, d: R = tBu), which were characterised by multinuclear NMR spectroscopy for 2a-d and a single crystal X-ray diffraction study in case of 2c. As an alternate synthetic method, the diphenyl derivative 2a could also be prepared by reaction of LiPPh2 with the thermally unstable iododisilene, Tip2SiSi(Tip)I (3), which in turn was obtained by oxidation of 1 with stoichiometric amounts of iodine. Providing the first example for a SiSi bond with an iodo functionality, disilene 3 was fully characterised by multinuclear NMR and X-ray diffraction. The thermal rearrangement of phosphine disilene 2avia a C–H insertion reaction yields the diastereomeric mixture of a 1-phospha-2,3-disilaindane 4. The structure of the cis-diastereomer of 4 was determined by X-ray diffraction. Finally, the synthesis of first transition metal complex of 2a and 2b by their coordination to the [Pd(PCy3)] fragment is reported. The solid state structure of complex 5a reveals η2-coordination of the SiSi bond of the phosphino disilene 2a with an intermediate bonding mode between π-complex and metallacyclopropane rather than coordination of the phosphino group.