<atl>Reactions of bulky alkyl lithium reagents with a phosphaalkyne (P&z.tbnd6;CBut): synthesis and structural characterisation of a mixed valent phosphorus cage compound, PIII{μ-C(H)(But)}2{μ-C(H)(SiMe3)Si(Me)2C(H)2}PV&z.dbnd6;C(SiMe3)2, and a phosphaalkenyl-substituted η3-azaallyl-lithium complex, [Li(tmeda){C(SiMe3)(2-NC5H3Me-6)[P&z.dbnd6;C(But)(SiMe3)]}]

The reactions of the phosphaalkyne, P&z.tbnd6;CBut, with the bulky alkyl lithium reagents, [LiCH3−n(SiMe3)n] n=1–3 and [LiC(SiMe3)2(2-NC5H3Me-6)], have been investigated. These have led to unexpected results which include the formation of the mixed valent phosphorus cage compound, PIII{μ-C(H)(But)}2{μ-C(H)(SiMe3)Si(Me)2C(H)2}PV&z.dbnd6;C(SiMe3)2, and the phosphaalkenyl-substituted η3-azaallyl-lithium complex, [Li(tmeda){C(SiMe3)(2-NC5H3Me-6)[P&z.dbnd6;C(But)(SiMe3)]}], both of which have been crystallographically characterised. A mechanism for the formation of each complex has been discussed. [Copyright &y& Elsevier]