Reactivity of Cycloplatinated Amine Complexes: Intramolecular C鈥揅 Bond Formation, C鈥揌 Activation, and PPh2 Migration in Coordinated Alkynylphosphines
文摘
The monomeric ortho-platinated complexes [Pt{R1CH(1-C6H4)NMe2-C,N}{Ph2PC鈮R2}Cl] (R1 = Me, Et; R2 = Me, Ph) with trans-N,P geometries were obtained regiospecifically from the reaction between the dimeric [Pt2(渭-Cl)2{R1CH(1-C6H4)NMe2-C,N}2] and the corresponding alkynylphosphines in high yields. The phosphine complexes are highly stable in the solid state and in solution. However, in the presence of additional Pt(II) ions, an intramolecular coupling reaction occurred in which a new carbon鈥揷arbon bond was formed between the aromatic 纬-carbon of the ortho-platinated chiral phenylamine and the 伪-carbon of the (Ph2P)鈥揅伪鈮尾鈥?R2) ligand. The (Ph2P) moiety migrated to the neighboring 尾-carbon during the coupling reaction. By the judicious selection of the substituents on the alkynylphoshine along with deliberate introduction of selected chirality on the ortho-platinated phenylamine, the coupling reaction and the (Ph2P) migration were found to proceed via an associative intramolecular mechanism that involves a Pt-vinylidene intermediate.