Cyclooligomerization reactions of different phosphaalkynes in the presenceof [W(CO)(5)thf] - A route to tungsten-stabilised phosphorus heterocycles

The reactivity of various phosphaalkynes Versus [W(CO)(5)thf] has been stud ied. The reaction with Mes*C=P (Mes* = 2,4,6-tBu(3)C(6)H(2)) exclusively le ads to the low yield formation of [W(Co)(2)(eta(2)-PCMes *)W(CO)(5))(2)] (1 ). The reaction of the less bulky tBuC-P with [W(CO)(5)thf] results in high yields in [W(Co)(2)(eta(4)-(tBUC)(2)P2W(CO)(5))(eta(2)-(tBuCP)W(CO)(5))] ( 2) which possesses a 1,3-diphosphete ligand as well as a side-on coordinate d tBuCP unit. Experiments employing MesC=P (Mes = 2,4,6-Me3C2H2) give the c omplexes [W(CO)(4)(eta(4)-(MesC)(2)P-2)] (3), [W(CO)(2)(eta(4)-(MesC)(2)P-2 )(eta(2)-(MesCP)W-(CO)(5))] (4) and [W(CO)(2)(eta(4)-(MesC)(2)P2W(CO)(5))(e ta(2)-(MesCP)W(CO)(5)(mu-W(CO)(4)))] (5) which have a 1,3-diphosphete ligan d in their coordination sphere and are partly substituted with an additiona l side-on coordinated MesC=P unit. In 5, two P atoms of the 1,3-diphosphete and the side-on coordinated MesC=P are further bridged by a W(CO), moiety. Additionally, the unusual product [(W(CO)(3))(eta(6)-1,2,4-(RC)(3)P-3(RCP- ->W(CO)(5))(2))] (R = Mes) (6) resulting from a pentamerization of MesC=P i nitiated by [W(CO)(5)thf], could be obtained in moderate yield. Comprehensi ve spectroscopical and structural investigations of all products are presen ted.