Linking metal centres with 1,4-bis(diphenylphosphino)-2,5-difluorobenzene (dpfb): Syntheses and molecular structures of [{Mo(CO)4(μ-dpfb)}2] and [{Mo(CO)4}2(μ-dpfb)(μ-dppa)] (dppa = Ph2PC≡CPPh2)

DOI: 10.1039/DT9960001077

Source and publish data:

Journal of the Chemical Society, Dalton Transactions p. 1077 - 1085 (1996)

Update date:2022-08-03

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Authors:

Hogarth, Graeme

Norman, Tim

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Article abstract of DOI:10.1039/DT9960001077

The rigid diphosphine 1,4-bis(diphenylphosphino)-2,5-difluorobenzene (dpfb) has been prepared via addition of 2 equivalents of lithium diphenylphosphide to 1,2,4,5-tetrafluorobenzene and characterised by multinuclear NMR spectroscopy. Reaction with cis-[Mo(CO)₄(pip)₂] (pip = piperidine) afforded doubly bridged [{Mo(CO)₄(μ-dpfb)}₂] 1, while with equimolar amounts of dpfb and bis(diphenylphosphino)acetylene (dppa) the mixed-ligand complex [{Mo(CO)₄}₂(μ-dpfb)(μ-dppa)] 2 was isolated. Both 1 and 2 have been characterised crystallographically. The dfpb ligand always adopts a syn-type configuration. Complex 1 shows a weak π-stacking interaction between the bridging aryl rings, while in 2 the dppa ligand adopts an anti conformation. Variable-temperature multinuclear NMR experiments revealed that 1 undergoes two fluxional processes in solution; twisting of the central core of the molecule and a low-energy process involving the flipping up and down of molybdenum tetracarbonyl units which interconverts the anti and syn conformations of the diphosphines.