Ambireactive (R 3 P) 2 BH 2 Groups Facilitating Temperature-Switchable Bond Activation by an Iron Complex.

An iron pincer complex containing a hemi-labile (R3P)(2)BH2 group exhibits temperature-switchable reactivity patterns: a reversible B-H activation concomitant with a P-B bond cleavage is observed at room temperature. Below 4 degrees C, intra- and intermolecular C-H activation pathways are becoming faster and more dominant. Mechanistic investigations reveal that the lability of the (R3P)(2)BH2 group in combination with the exothermic formation of sigma-bonded complexes are responsible for the switchable bond activation. Finally, a protocol for an iron-catalyzed H/D-exchange of organic solvents in the absence of oxidants has been developed.