Synthesis and characterisation of a diphosphaalkene, a diphosphaalkyne and the first diphosphavinyl lithium complex

The preparation and characterisation of a diphosphaalkene, (Me3Si)Pdouble bond; length as m-dashC(OSiMe3){C(C2H4)3C}C(OSiMe3)double bond; length as m-dashP(SiMe3), and the second example of a diphosphaalkyne, Ptriple bond; length of mdashC{C(C2H4)3C}Ctriple bond; length of mdashP, are described. In addition, the reaction of another diphosphaalkyne, Ptriple bond; length of mdashC{C(C6H4)3C}Ctriple bond; length of mdashP, with MeLi/LiBr in the presence of tmeda has given the first diphosphavinyl lithium complex, [MePdouble bond; length as m-dashC{Li2Br(tmeda)2}{C(C6H4)3C}C{Li2Br(tmeda)2}double bond; length as m-dashPMe], which is stable at room temperature and has been crystallographically characterised.