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The synthesis of aryl-alkynyl compounds is usually achieved via Sonogashira catalysis, but this is inefficient for fluorinated aryls. An alternative method reported by Shirakawa and Hiyama, using alkynylstannanes and hemilabile PN ligands, works apparently fine for conventional aryls, but it is also poor for fluorinated aryls. The revision of the unusual literature cycle reveals the existence and nature of unreported byproducts and uncovers coexisting cycles and other aspects that explain the reasons for the conflict. This knowledge provides a full understanding of the real complexity of these aryl/alkynylstannane systems and the deviations of their evolution from that of a classic Stille process, providing the clues to design several very efficient alternatives for the catalytic synthesis of the desired Ar F -alkynyl compounds in almost quantitative yield. The same protocols are also very efficient for the catalytic synthesis of alkynyl-alkynyl' hetero- and homocoupling.

Analysis of the bonding contributions in molecules [M III Cp*(L)XY] (M = Rh, Ir; Cp* = C 5 Me 5 ; L = CO, CN - , CNR) has uncovered a rich variety of types of interaction that seem to have escaped detection so far, in spite of the continuous popularity of cyclopentadienyl transition-metal complexes since the 1970s. At variance with the M-C≡O bond in square-planar systems, which shows typical metal-to-CO π-back-donation, the nonorthogonal arrangement of the Cp* plane and Rh-C≡O fragment and the pseudooctahedral geometry lead to the observation of many direct lateral donations from other ligands that do not involve the metal orbitals, and we name side donations, for instance, Cp* → π*(CO), Cl → π*(CO), and F → π*(CO). Hybrid donations partially involving the metal, M-C aryl → π*(CO), are also observed. The summation of multiple contributions other than back-donation can easily account for about 20% of the electron donation to the π*(C≡O) orbitals.