A calix [4]arene-based biarylphosphine has been synthesised and catalytically converted into two diastereomeric, calixarene-fused phospholes. arene has been prepared and its coordinative properties investigated. When heated in the presence of palladium, the new biarylphosphine undergoes conversion into two diasteromeric, calixarene-fused phospholes. In both, the P lone pair adopts a fixed orientation with respect to the calixarene core. The more hindered phosphole (8), i.e. the one with the endo-oriented lone pair (cone angle 150°-175°), forms complexes having their metal centre positioned very near the calixarene unit but outside the cavity, this inducing an unusual chemical shift of one of the methylenic ArCH 2 Ar protons owing to interactions with the metal centre. As expected for dibenzophospholes, the complex [Rh(acac)(CO)•8], when combined with one equivalent of free 8, efficiently catalyses the hydroformylation of styrene, the catalytic system displaying high regioselectivity in favour of the branched aldehyde (b/l ratio up to 30). The optical and redox properties of the derivatives have also been investigated.
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