Synthesis and properties of mixed-metal phosphido and phosphinidene clusters derived from reaction between Ru 3(CO) 10(μ-H)(μ-PPh 2) and Cp ★ Mo(CO) 3H

Abstract

The tetranuclear phosphido cluster Cp ★ MoRu 3(CO) 10(μ-H) 2(μ-PPh 2) ( 5) and the phosphinidene cluster Cp ★ MoRu 3(CO) 10(μ 3-H) (μ 3-PPh) ( 6) have been synthesized by reaction of Ru 3(CO) 10(μ-H)(μ-PPh 2) with excess molybdenum hydride Cp ★ Mo(CO) 3H in refluxing toluene solution. Crystals of 5 are monoclinic, space group P 2 1 with a = 10.708(2), b = 10.848(4), c = 14.885(2) Å, β = 97.63(2)°, Z = 2, R = 0.021, R w = 0.019 for 3025 observed reflections. The cluster has a tetrahedral array of metal atoms with one edge-bridging and one face-bridging hydride, and a phosphido ligand bridged across a basal Ru-Ru edge. Thermolysis of 5 under similar conditions produced the phosphinidene cluster 6 in high yield via elimination of a benzene molecule, indicating that 5 is an intermediate in the formation of 6. Subsequent treatment of 6 with CO caused fragmentation of the cluster affording a trinuclear phosphinidene cluster Cp ★ MoRu 2(CO) 8(μ-H)(μ 3-PPh) ( 7). Dimerization of 7 occurred upon thermolysis to afford hexanuclear Cp 2 ★ Mo 2Ru 4(CO) 12(μ-PPh) 2 ( 8), which has also been characterized by X-ray diffraction. Crystal data of 8: space group C 2/c; a = 45.333(7), b = 10.185(2), c = 21.915(8) Å, β = 93.82(3)°, Z = 8. The structure was solved by direct method and refined to R and R w of 0.035 and 0.030 for 6135 observed reflections with I > 2σ-( I). The molecule adopts a square pyramidal MoRu 4 skeleton with a tentacle Mo atom bridging a Ru-Ru edge, on which the novel μ 4-η 2-CO ligand is associated with the butterfly Mo 2Ru 2 array; one μ 4-PPh ligand occupies a MoRu 3 square face and a second μ 3-PPh ligand caps a MoRu 2 face.