Complexation and metallation of the multifunctional [Ph2P(o-C6H4)CHN(CH2)2(o-C5H4N)] ligand on triosmium carbonyl clusters

Abstract

Reaction of the phosphine–imine–pyridine containing ligand Ph₂P(o-C₆H₄)CHN(CH₂)₂(o-C₅H₄N) (abbreviated to PNN) with [Os₃(CO)₁₀(NCMe)₂] at ambient temperature affords {Os₃(CO)₁₀[η²-Ph₂P(o-C₆H₄)CHN(CH₂)₂(o-C₅H₄N)]} 1. Thermolysis of 1 in refluxing toluene leads to CO dissociation to give {Os₃(CO)₉[μ-η³-Ph₂P(o-C₆H₄)CHN(CH₂)₂(o-C₅H₄N)]} 2, and C–H activation of the PNN ligand to give {(μ-H)Os₃(CO)₈[μ₃-η⁴-Ph₂P(o-C₆H₄)CHNCH₂CH(o-C₅H₄N)]} 3 and {(μ-H)Os₃(CO)₈[μ-η⁴-Ph₂P(o-C₆H₄)CN(CH₂)₂(o-C₅H₄N)]} 4. In contrast, co-pyrolysis of [Os₃(CO)₁₂] with PNN in a sealed tube results in 2, 3 and the diosmium phosphido complex {Os₂(CO)₅(μ-PPh₂)[μ-η³-Ph₂P(o-C₆H₄)CN(CH₂)₂(o-C₅H₄N)]} 5. The structures of 1, 3, 4 and 5 have been determined by an X-ray diffraction study. Compounds 3 and 4 are isomers with the methylene and the imine C–H bonds of the PNN ligand being activated by the Os₃ cluster, respectively.