The reactivity of various phosphaalkynes versus [W(CO)5thf] has been studied. The reaction with Mes*CP (Mes* = 2,4,6-tBu3C6H2) exclusively leads to the low yield formation of [W(CO)2{(2-PCMes*)W(CO)5}2] (1). The reaction of the less bulky tBuCP with [W(CO)5thf] results in high yields in [W(CO)2{4-(tBuC)2P2W(CO)5}{2-(tBuCP)W(CO)5}] (2) which possesses a 1,3-diphosphete ligand as well as a side-on coordinated tBuCP unit. Experiments employing MesCP (Mes = 2,4,6-Me3C6H2) give the complexes [W(CO)4{4-(MesC)2P2}] (3), [W(CO)2{4-(MesC)2P2}{2-(MesCP)W(CO)5}] (4) and [W(CO)2{4-(MesC)2P2W(CO)5}2-(MesCP)W(CO)5{µ-W(CO)4}] (5) which have a 1,3-diphosphete ligand in their coordination sphere and are partly substituted with an additional side-on coordinated MesCP unit. In 5, two P atoms of the 1,3-diphosphete and the side-on coordinated MesCP are further bridged by a W(CO)4 moiety. Additionally, the unusual product [{W(CO)3}6-1,2,4-(RC)3P3{RCPW(CO)5}2] (R = Mes) (6) resulting from a pentamerization of MesCP initiated by [W(CO)5thf], could be obtained in moderate yield. Comprehensive spectroscopical and structural investigations of all products are presented.