Reactivity of cyclo-(PhX)6 (X=As, P) towards [M3L2(CO)10] (M=Ru, L=CO or NCMe; M=Fe, L=CO)

Reaction of [Ru3(CO)10(NCMe)2] with cyclo-(PhX)6 (X=As 1a, P 1b) in toluene at ambient temperature gives [Ru3{μ-cyclo-(PhX)6}(CO)10] (X=As 2a, P 2b), in which the intact six-membered rings adopt chair conformations and bridge metal–metal edges via either two arsine (2a) or two phosphorus (2b) atoms in the 1,5 positions of the respective rings. Conversely, treatment of [Ru3(CO)12] with cyclo-(PhX)6 (X=As 1a, P 1b) in toluene at elevated temperature results in fragmentation of the six-membered rings to afford [Ru4(μ3-AsPh)2(CO)13] (3) and [Ru6(μ4-PPh)3(μ3-PPh)2(CO)12] (4), respectively. Fragmentation of the cyclo-hexaarsane ring in 1a also occurs on reaction with [Fe3(CO)12] in toluene at elevated temperature to furnish [Fe3(μ3-AsPh)2(CO)9] (5) as the sole product. However, treatment of 1b with [Fe3(CO)12] gives [Fe3(μ3-PPh2)2(CO)9] (6), the phosphorus analogue of 5, along with [Fe2{μ-η2-catena-(P4Ph4)}(CO)6] (7) and [Fe2{μ4-(P2Ph2)}(CO)6]2 (8). In addition, the mixed phosphinidene–arsenidene complex [Fe3(μ3-PPh)(μ3-AsPh)(CO)9] (9) can be obtained on treatment of 1 with a 1:1 mixture of 1a and 1b. Single crystal X-ray diffraction studies have been performed on 2a, 3, 4·2CH2Cl2, and 8.