Herein we report a Suzuki-Miyaura type cross-coupling between an aryl halide and a functionalized boronic acid palladacycle in the absence of an external catalyst. This reaction is an unprecedented case of catalysis in palladium metallacycle chemistry.
Palladacycles of the type [Pd(PhPCHPPh-P,P)(C,N:C,N)] (C,N:C,N = bis(N-2,3,4-trimethoxybenzylidene)-4,4'-sulfonyldianiline or -4,4'-oxydianiline) can undergo a spontaneous slow chelate-to-bridging diphosphane coordination shift in solution. Following this strategy a tailor-made synthetic procedure was devised that culminates in isolation of double A-frame tetranuclear palladium complexes.
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.
The Cover Feature shows four structures depicting (clockwise from the top‐left corner) a beautiful tetranuclear layered compound, a bis‐pseudopentacoordinated palladium moiety, the only known trinuclear thiosemicarbazone palladacycle, and the sandwiched coordination of the potassium cation by small crown ether rings attached to the metallated phenyl enclosures of a dinuclear diphosphine‐bridged palladium complex. All of these unexpected findings put forward the presence of serendipity in the reactivity of palladacycles and highlight the relevance of such an experience in their chemistry. More information can be found in the Review by A. Fernández‐Figueiras et al. on page 754 in Issue 10, 2018 (DOI: https://doi.org/10.1002/open.201800036).
Thiosemicarbazones are used as ligands forming many examples of compounds. Chemistry of these molecules with palladium often includes cyclopalladated but in some cases coordination compounds were reported. Structure of these complexes has not been widely described; different studies show wide structures variety. The treatment of these ligands with palladium salts lead the formation of these kind of complexes which structure and reactivity is more similar to organometallic cyclopalladated compounds than expected.
This paper presents the preparation, characterization and structural study of novel tridentate [C,N,S] biscyclopalladated complexes with ligands derived from the condensation of a primary amine −2-(methylthio)aniline− with the corresponding aromatic dialdehyde −terephthalaldehyde−. The compounds are also interesting due to their close-to-planarity arrangement and to the presence of seven fused rings in their structure.
Palladacycles are an important class of organometallic compounds. They are interesting for their stability and for their important applications as catalysts in cross-coupling reactions. The work described herein relates to the synthesis of a dicyclometallated compound stemming from a diamine ligand, with a doubly metallated aromatic ring. Its reactivity towards a variety of tertiary diphosphines is also considered. The latter ligands show diverse coordination modes, opening the possibility of synthesizing quite different complex structures bearing transition metal atoms in close proximity to each other.
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