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Linking metal centres with 1,4-bis(diphenylphosphino)-2,5-difluorobenzene (dpfb): Syntheses and molecular structures of [{Mo(CO)(4)(mu-dpfb)}(2)] and [{Mo(CO)(4)}(2)(mu-dpfb)(mu-dppa)] (dppa=Ph(2)PC CPPh(2))

Hogarth, G; Norman, T; (1996) Linking metal centres with 1,4-bis(diphenylphosphino)-2,5-difluorobenzene (dpfb): Syntheses and molecular structures of [{Mo(CO)(4)(mu-dpfb)}(2)] and [{Mo(CO)(4)}(2)(mu-dpfb)(mu-dppa)] (dppa=Ph(2)PC CPPh(2)). J CHEM SOC DALTON (6) 1077 - 1085.

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Abstract

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)(mu-dpfb)}(2)] 1, while with equimolar amounts of dpfb and bis(diphenylphosphino)acetylene (dppa) the mixed-ligand complex [{Mo(CO)(4)}(2)(mu-dpfb)(mu-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 pi-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.

Type:Article
Title:Linking metal centres with 1,4-bis(diphenylphosphino)-2,5-difluorobenzene (dpfb): Syntheses and molecular structures of [{Mo(CO)(4)(mu-dpfb)}(2)] and [{Mo(CO)(4)}(2)(mu-dpfb)(mu-dppa)] (dppa=Ph(2)PC CPPh(2))
Keywords:COMPLEXES, DERIVATIVES
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Chemistry

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