A new heterotopic Ar-BIAN ligand with a pendant P donor site

The heterotopic ligand 1-[4-(4-diphenylphosphanylphenyl)phenylimino]-2-[3,5-bis(trifluoromethyl)phenylimino]acenaphthene, PN2, was prepared and characterized by NMR spectroscopic and MS methods. Depending on the size and the electronic properties of the metal reagent M, the two binding sites of the new ligand show selective coordination. At 1:1 molar ratio of PN2 and M, the sterically more demanding [Pd(dppe)]2+ and [Pd(dppp)]2+ cations coordinate only to the chelating nitrogen atoms while the less bulky [Pd(dppm)]2+ binds both to the imino and the phosphane donor groups. A 2:1:2 mixture of PN2, [Pd(dppm)(OTf)2] and [Pd(dppe)(OTf)2] results in the formation of a complex in which the [Pd(dppm)]2+ unit selectively coordinates to the terminal P atoms while the more voluminous dppe counterpart resides at the imino nitrogens. On the contrary, the [Pd(dppm)]2+ complex selectively binds to the chelating nitrogen atoms if the Ph2P group is ligated to Au+ center. In the interaction of [Au(PN2)2]PF6 with Ag(OTf), the silver ions do not replace Au+ in the P–Au bonds but occupy the chelating position.

The new Ar-BIAN ligand PN2, with a pendant Ph2P group, demonstrates remarkable selectivity in binding metal complexes of dissimilar steric and electronic properties.Figure optionsDownload as PowerPoint slide