Versatility and adaptative behaviour of the P^N chelating ligand MeDalphos within gold(i) π complexes.

The hemilabile P^N ligand MeDalphos enables access to a wide range of stable gold(i) π-complexes with unbiased alkenes and alkynes, as well as electron-rich alkenes and for the first time electron-poor ones. All complexes have been characterized by multi-nuclear NMR spectroscopy and whenever possible, by X-ray diffraction analyses. They all adopt a rare tricoordinate environment around gold(i), with chelation of the P^N ligand and side-on coordination of the alkene, including the electron-rich one, 3,4-dihydro-2-pyrane.

π Complexes of P^P and P^N chelated gold(i).

Tricoordinate gold(i) π-complexes containing P-based chelating ligands (P^P and P^N) were prepared. The structure of the gold(i) styrene complexes has been analysed in detail based on NMR and XRD data. The P^N complex is a competent catalyst for indole alkylation.

[2,2'-Bipyridin]-6(1 H)-one, a Truly Cooperating Ligand in the Palladium-Mediated C-H Activation Step: Experimental Evidence in the Direct C-3 Arylation of Pyridine.

The ligand [2,2'-bipyridin]-6(1 H)-one (bipy-6-OH) has a strong accelerating effect on the Pd-catalyzed direct arylation of pyridine or arenes. The isolation of relevant intermediates and the study of their decomposition unequivocally show that the deprotonated coordinated ligand acts as a base and assists the cleavage of the C-H bond. Mechanistic work indicates that the direct arylation of pyridine with this ligand occurs through a Pd(0)/Pd(II) cycle.

Formal Gold-to-Gold Transmetalation of an Alkynyl Group Mediated by Palladium: A Bisalkynyl Gold Complex as a Ligand to Palladium.

The reaction of [Au(C≡C-n-Bu)]n with [Pd(η(3) -allyl)Cl(PPh3 )] results in a ligand and alkynyl rearrangement, and leads to the heterometallic complex [Pd(η(3) -allyl){Au(C≡C-n-Bu)2 }]2 (3) with an unprecedented bridging bisalkynyl-gold ligand coordinated to palladium. This is a formal gold-to-gold transmetalation that occurs through reversible alkynyl transmetalations between gold and palladium.

Detection and reactivity of a palladium alkoxycarbene.

A characterful carbene: The high electrophilicity of a genuine palladium alkoxycarbene, obtained by transmetalation, is evident in its reactivity. Nucleophilic attack on two electrophilic centers (red) is observed. Alkyl abstraction and addition to the carbene carbon by different nucleophiles occur.