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.

Synthesis of bi- and tetradentate poly-Lewis acids by hydroalumination of poly-alkynyl-anthracene derivatives.

Photo-dimers of 1,5-diethynylanthracene and 1,5-bis[(trimethylsilyl)ethynyl]anthracene, obtained by UV radiation of the monomers, were treated with the bulky aluminium hydride [(SiMe)HC]AlH in hydroalumination reactions. Hydroalumination of the tetraethynyl-substituted anthracene photo-dimers ( and ) led to fourfold aluminium-functionalized Janus-like products with two aluminium functions on each side oriented towards the same direction. The reactions of the monomeric anthracene derivatives with [(SiMe)HC]AlH afforded semi-flexible bidentate Lewis acids, which are interesting building blocks for molecular chains bearing multiple Lewis-acidic functions.

Carbon dioxide reduction by an Al-O-P frustrated Lewis pair.

The reaction of BuP(O)H with BisAlH (Bis = CH(SiMe)) afforded the adduct BuP(H)-O-Al(H)Bis (3). It slowly releases H to form the first oxygen-bridged geminal Al/P frustrated Lewis pair BuP-O-AlBis. It is capable of reversibly binding molecular hydrogen to afford 3, shown by NMR and H/D scrambling experiments, and forms a 1,2-adduct with CO.

Bidentate Lewis Acids Derived from o-Diethynylbenzene with Group 13 and 14 Functions.

Starting from 1,2-diethynylbenzene, a series of bidentate Lewis acids was prepared by means of hydrometalations, in particular hydrosilylation, hydroboration, hydroalumination and terminal metalation based on group 13 and 14 elements. In the case of terminal alkyne metalation, the Lewis-acidic gallium function was introduced using triethylgallium under alkane elimination. A total of six different Lewis acids based on a semiflexible organic scaffold were prepared, bearing -SiClMe , -SiCl Me, -SiCl , -B(C F ) , -AlBis (Bis=bis(trimethylsilyl)methyl) and -GaEt as the corresponding functional units.

A P-H functionalized Al/P-based frustrated Lewis pair - hydrophosphination of nitriles, ring opening with cyclopropenones and evidence of P[double bond, length as m-dash]C double bond formation.

Hydroalumination of R-P(H)-C[triple bond, length as m-dash]C-tBu with bulky H-Al[CH(SiMe3)2]2 afforded the new P-H functionalized Al/P-based frustrated Lewis pair R-P(H)-C[[double bond, length as m-dash]C(H)-tBu]-AlR2 [R = CH(SiMe3)2; FLP 7]. A weak adduct of 7 with benzonitrile (8) was detected by NMR spectroscopy, but could not be isolated. tert-Butyl isocyanide afforded a similar, but isolable adduct (9), in which the isocyanide C atom was coordinated to aluminium.