Coordination Chemistry of Bidentate Difluorophosphines

• Main Author: Gallup, Darrell Lynn
• Format: Others
• Published: DigitalCommons@USU 1978
• Subjects: coordination; chemistry; bidentate difluorophosphines; Chemistry
• Online Access: https://digitalcommons.usu.edu/etd/6681; https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=7874&context=etd

The reactions of 1, 2–bis(difluorophosphino)cyclohexane, PF2C6H10PF2, with hexacarbonyls of Cr(O), Mo(O), and W(O) have been extensively investigated. The hexacarbonyls react, either under photolytic or thermolytic conditions, to produce carbon monoxide and oily mixtures of products of the general formulations, [M(CO)4(PF2C6H10PF2C)]x, where x varies apparently from 1 – 4. The higher values of x, corresponding to species involving bridging ligands, are more common to the photolysis rather than the thermolysis reactions. Photolysis reactions of Mo(Co)6 with increasing amounts of the ligand does not result in the higher substitution products, Mo(Co)2(PF2C6H10PF2)2 and Mo(PF2C6H10PF2)3. The reactions of PF2C6H10PF2 with the norbornadiene tetracarbonyl complexes of Cr(O), Mo(O), and W(O) produce relatively air-stable chelates of the general formulation, M(Co)4(PF2C6H10PF2). Mo(CO)4(PF2C6H10PF2) will react with more PF2C6H10PF2 to give [Mo(CO)2(PF2C6H10PF2)2]2. A slight excess of PF2C6H10PF2 also reacts readily with ditoluenemolybdenum (O) displacing toluene to give Mo(PF2C6H10PF2)3, and air-stable monomer. Analysis of the infrared spectra of these chelates indicates that the ligand fits into a sequence of π–acceptor strength as: PF3>PCI3~ PF2C6H10PF2>RN(PF2)2>>Ph2PC2H4PPh2. NMR spectral parameters for the chelates verify the very strong coordination of the bidentate ligand to the metals. 1, 2-bis(difluorophosphino)cyclohexane has also been found to react with pentacarbonyliron(O), Fe(Co)5 and with pentacarbonylmanganese(I) bromide, Mn(CO)5Br, in hexane, displacing two moles of carbon monoxide per mole of ligand. The products resulting, (PF2C6H10PF2)Fe(Co)3, (PF2C6H10PF2)2Fe(CO), (PF2C6H10PF2)Mn(CO)3Br, and (PF2C6H10PF2)2Mn(CO)Br, are all air-stable solid monomers indicating that the ligand is an effective chelating agent. Analysis of their and nmr spectral data supports the conclusion that PF2C6H10PF2 functions as a strong π–acceptor and assists in assigning structures. The reactions of PF2C6H10PF2 in solution with Co2(CO)8 and the chlorides of Ni(II), Pd(II), and Pt(II) have been investigated. The resultant complexes are not well defined. The characterization of the complexes has given ambiguous results, although the nickel group metal complexes appear to be dimeric. The ligand, 1,2-bis(difluorophosphino)ethane, PF2C2H4PF2, reacts with tetracarbonylnickel(O), Ni(Co)4, in the gas phase and in solution, to produce carbon monoxide and the polymer, [Ni(PF2C2H4PF2)2]x. PF2C2H4PF2 displaces norbornadiene from (C7H8)Mo(Co)4 to yield the relatively air-stable complex, Mo(CO)4(PF2C2H4PF2). Analysis of the infrared spectrum of the monomeric complex indicates that the ligand exhibits π–acceptor strength equal to PF2C6H10PF2.