Reactivity of Oxygen-Bridged Geminal Al/P and Si/P Frustrated Lewis Pairs towards Heterocumulenes.

The two oxygen-bridged geminal frustrated Lewis pairs (FLP) tBu P-O-AlBis (Bis=CH(SiMe ) ; 1) and tBu P-O-Si(C F ) (2) were reacted with the heterocumulenes PhNCO, PhOCN, PhNCS, CS and PhNSO as well as SO . With isocyanate and cyanate, both 1 and 2, form addition products under formation of five-membered rings. With CS , isothiocyanate and sulfinylaniline, only 1 forms stable adducts, whereas 2 shows reactivity towards sulfinylaniline, but the product decomposed after a few minutes. The reaction of 1 with SO led to partial cleavage of the P-O-Al and Al-C units, as confirmed by X-ray diffraction studies of a complex aggregate. The reaction of 2 with SO affords the 1,2-addition product. All adducts were characterized by means of multinuclear NMR spectroscopy, X-ray crystallography and CHN analyses.