Treatment of the phosphaalkyne P6-point triple bond; length half of m-dashCAr′ 1 with [W(CO)5(thf)] leads to the complex [W(CO)2{η2-PCAr′)W(CO)5}2] 2 (Ar′=C6H2tBu3-2,4,6) with two side-on coordinated phosphaalkyne moieties. In the presence of equimolar amounts of [W2(OtBu)6], however, the formation of [W(CO)4P(R′)C(Ar′)P{W(CO)5}] 3 (R′=2,4-tBu2-7-Me2-indanyl) is observed. 3 is a product of a ‘head-to-tail' dimerisation of the former phosphaalkynes 1 to give a novel phosphinidene complex containing an indanyl substituent formed via C–H-activation.