229491-02-5Relevant academic research and scientific papers
Synthesis and structure of niobium and tantalum derivatives of bis(dicyclohexylphosphino)methane (dcpm)
Riley, Patrick N.,Clark, Janet R.,Fanwick, Phillip E.,Rothwell, Ian P.
, p. 35 - 39 (1999)
The sodium amalgam reduction (2 Na per M) of the Group 5 metal chlorides [M2Cl10] (M=Nb, Ta) in the presence of bis(dicyclohexylphosphino)methane (dcpm) leads to the binuclear compounds [(dcpm)Cl2M(μ2-Cl)2MCl2(dcpm)] (M=Nb, 1; Ta, 2). Solution NMR spectroscopic properties of 1 and 2 indicate that the dcpm ligand does not bridge (binucleate) the di-metal unit but is chelated to a single metal center. A single crystal X-ray diffraction study of 1 confirms this and shows two independent molecules both with an edge shared bis-octahedral geometry with Nb=Nb distances of 2.738(1) and 2.749(1) A. The addition of dcpm to the tantalum trichloride [Ta(OC6H3Pri2-2,6) 2Cl3]2 initially leads to the adduct cis-mer-[Ta(OC6H3Pri2-2,6) 2Cl3(dcpm)] (3). The molecular structure of 3 is found to contain an η1-bound dcpm ligand. In the 31P NMR spectrum of 3 well resolved doublets are present for the coordinated and 'dangling' phosphorus atoms. The sodium amalgam reduction of 3 in hydrocarbon solvents does not lead to any isolable binuclear compounds. Instead the reaction leads to the compound [Ta(OC6H3Pri-η2-CMe=CH 2)Cl(dcpm)] (4). Compound 4 contains an aryloxide ligand chelated to the metal via an η2-interaction with a vinyl group formed by the dehydrogenation of an ortho-isopropyl group. The structural parameters are consistent with a metallacyclopropane bonding description for this interaction.
