Synthese von Phosphaalkenclustern durch reduktive Phosphinidenfragmentierung zweizähniger Halogenphosphane RXP— CH2 — PXR mit Fe2(CO)9 / Synthesis of Phosphaalkene Clusters by Reductive Phosphinidene Fragmentation of Bidentate Halogenphosphines RXP—CH2—PXR with Fe2(CO)9

Reaction of halogen functional methylenebisphosphines 1 XRP–CH2–PRX (X = Cl, Br) with excess Fe2(CO)9 affords μ3-phosphinidene clusters (5) containing phosphaalkene ligands R–P=CH2. The fragmentation of the P–C–P skeletons in 1 proceeds stepwise, phosphide complexes 2 and novel Fe3 clusters 3 with RP–CH2–PR bridging units being formed as intermediates of the oxidative addition reductive elimination process. The X-ray structural analysis for 5b (R = NEt2) reveals an Fe3(CO)9PR butterfly core to which the phosphaalkene ligand R–P=CH2 (P=C bond length 1.766(4) A) is coordinated in a μ3,η2-manner. In case of methylenebisphosphines 1 with bulky substituents (R = 2,4,6-iPr3C6H2) the phosphinidene fragmentation of the P–C–P skeleton is accompanied by the formation of 2,3-dihydrobenzo[b]-phosphole ligands.