THE THERMAL-DECOMPOSITION OF (BU2P)-BU-T- P=P(ME)BU-T(2)

The thermal decomposition of (Bu2P)-Bu-t-P=P(Me)Bu-t(2) 2 in C6H6 at 2 0 degrees C is detectable after 10 h; (Bu2PMe)-Bu-t, ((Bu2P)-Bu-t)(2)P H and small amounts of the cyclotetraphosphanes P-4((PBu2)-Bu-t)(4) an d P-4((PBu2)-Bu-t)(2) are formed. At 70 degrees C (14 h) 83% of 2 are decomposed, and even 96% after 74 h. The main products are (Bu2PMe)-Bu -t (68%) and P-4((PBu2)-Bu-t)(4) (20%). With 2,3-dimethyl-1,3-butadien e as a trapping reagent (Bu2PMe)-Bu-t (62%) is still the main product, however, P-4((PBu2)-Bu-t)(4) is no longer found, but phosphino)-4,5-d imethyl-1,2-diphosphacyclohexene-4 (22%) is formed instead. Also with cyclohexene (Bu2PMe)-Bu-t (78%) remains the major product besides P-4( (PBu2)-Bu-t)(4) (9%) and small amounts of the trapping product ert-but ylphosphino-7-phosphabicyclo[4.1.0]heptane. Thus, the thermal decompos ition of 2 at 70 degrees C proceeds very similar to that of (Bu2P)-Bu- t-P=P(Br)Bu-t(2) at -30 degrees C and starts yielding and the phosphin ophosphinidene (Bu2P)-Bu-t-P. In CH2Cl2 the decomposition of 2 include s the chlorination of the ylidic molecule.