Novel Bidentate [N,S] Palladacycle Metalloligands. 1H–15N HMBC as a Decisive NMR Technique for the Structural Characterization of Palladium–Rhodium and Palladium–Palladium Bimetallic Complexes

Cyclometallated Platinum(II) Complexes with Small Crown Ether Rings: Appropriate Choice of the Bridging Diphosphane to Coordinate Potassium Cations

This account reports the synthesis and structural characterization of the first cyclometallated platinum(II) complex that coordinates a potassium cation in a sandwich arrangement via two 15-crown-5 ether rings within the same molecule. The cooperation of the two small crown ether moieties allows the entrapment of the non-ideal potassium ion. The reaction of the parent thiosemicarbazone ligand 3,4-(C₈H₁₆O₅)C₆H₃C(Me)=NN-(H)C(=S)NHMe, 1, containing the crown ether ring, with K₂[PtCl₄], or alternatively with PtCl₂(DMSO)₂, and subsequent treatment with the diphosphanes Ph₂PCH₂PPh₂ (dppm) and Ph₂PC(=CH₂)PPh₂ (vdpp) produced the double nuclear platinacycles 3a, 3b, and 4, probably via formation of the 2a and 2b intermediates. Complex 3a with the K⁺ cation in a sandwich coordination was slightly mixed with 3b lacking any K⁺. Alternatively, reaction of 1 with K₂[PtCl₄] or with PtCl₂(DMSO)₂ followed by the diphosphane Ph₂PC(=CH₂)PPh₂ (vdpp) only gave the dinuclear phosphane-bridged compound 4; this highlights the importance of choosing the right diphosphane ligand. Density functional theory calculations (B3LYP-D3/LANL2DZ-ECP-6.311++G**) revealed similar affinities for both dppm and vdpp derivatives to coordinate potassium cations. Crystal structure analysis was performed for compounds 3a and 4.

One-Pot Cross-Coupling/C-H Functionalization Reactions: Quinoline as a Substrate and Ligand through N-Pd Interaction

Herein, we report a one-pot process that marries mechanistically distinct, traditional cross-coupling reactions with C-H functionalization using the same precatalyst. The reactions proceed in yields of up to 95%, in air, and require no extraneous ligand. The reactions are thought to be facilitated by harnessing the substrate quinoline as an N-ligand, and evidence of the palladium-quinoline interaction is provided by ¹H-¹⁵N HMBC NMR spectroscopy and X-ray crystallographic structures. Application of the methodology is demonstrated by the quick formation of fluorescent, π-extended frameworks.

From Chemical Serendipity to Translational Chemistry: New Findings in the Reactivity of Palladacycles

In the world of science, in particular the section concerning the field of chemistry, when the results encountered during the experiment do not meet our expectations, our shrewdness may play an important role to open up new unexplored fields that could be much more interesting than what we were seeking. In those cases, our research undergoes an unforeseen shift, delivering novel and challenging results that may altogether alter our point of view and our future work. We have then struck serendipity. Specifically, in our investigation linked to palladacycles we have found that the new trends in their reactivity, as well as in their structure, have been, in many cases, related to this experience, broadening our research scope within this field. Herein, we describe our most relevant findings, which have shed new light upon the reactivity of palladacycles, thus opening new routes that lead to novel unexpected structures.

Palladium iminophosphorane complexes: the pre-cursors to the missing link in triphenylphosphane chalcogenide metallacycles

A dinuclear iminophosphorane palladacycle produces the missing link in the triphenylphosphane chalcogenide series of metallacycles.

Palladacycle catalysis: an innovation to the Suzuki–Miyaura cross-coupling reaction

A new approach to the Suzuki cross-coupling reaction based on the catalysis of a thiosemicarbazone palladacycle is presented.