Photochemical formation and reversible base-induced cleavage of a phosphagallene.

The reactivity of Cp*Ga (Cp* = C5Me5) towards phosphanylidenephosphoranes of the type ArTerP(PMe3) (ArTer = DipTer 2,6-(2,6-iPr2C6H3)2C6H3), TipTer 2,6-(2,4,6-iPr3C6H2)2C6H3 was investigated. While no thermal reaction was observed (in line with DFT results), irradiation at 405 nm at low temperatures resulted in the formation of phosphagallenes DipTerP = GaCp* (1a) and TipTerP = GaCp* (1b) accompanied by release of PMe3. When warming the reaction mixture to ambient temperatures without irradiation, the clean re-formation of ArTerP(PMe3) and Cp*Ga in a second-order reaction was observed. Upon removal of PMe3, 1a and 1b were isolated and fully characterized. Both derivatives were found to be labile and decomposed to the phosphafluorenes 2a and 2b, indicating generation of the transient phosphinidene ArTerP along with Cp*Ga. First reactivity studies show that CO2 and H2O cleanly reacted with 1a, affording DipTerPCO (3) and DipTerPH2 (4), respectively.

Heavier group 13/15 multiple bond systems: synthesis, structure and chemical bond activation.

Heavier group 13/15 multiple bonds have been under investigation since the late 80s and to date, several examples have been published, which shows the obsoleteness of the so-called double bond rule. Especially in the last few years, more and more group 13/15 multiple bonds became synthetically feasible and their application in terms of small molecule activation has been demonstrated. Our group has recently shown that the combination of the pnictinidene precursor DipTer-Pn(PMe3) (Pn = P, As) in combination with Al(I) synthons afforded the first examples of phospha- and arsaalumenes as isolable and thermally robust compounds. This feature article is intended to show the recent developments in the field, to outline early synthetic approaches and to discuss strategies to unlock the synthetic potential of these elusive chemical bonds.