Sequential Reactions of Alkynes on an Iridium(III) Single Site

Abstract

Sequential insertion of terminal alkynes on Ir cyclometalated complexes allow the formation of novel metallapolycycles in a controlled and efficient manner. ortho-Methylarylethynyl derivatives led to an unprecedented cascade combination of three fundamental processes (C-C bond formation, C(sp )-H activation, and reductive coupling) on a single Ir center, in a process compatible with functionalized biomolecules and photoactive substrates. The reaction with tert-butylacetylene led to a [6,5,4]-polycycle that incorporates an iridacyclobutenylidene in its structure. The sequence is a multicomponent reaction in which the metal not only promotes the different steps but also determines their stereoselectivity. This is an elegant example of the synergy between a metal-promoting reaction and a symmetry-defined stereochemistry.

Osmium-Promoted σ-Bond Activation Reactions on Nucleosides

“…5 The postfunctionalization of these complexes using alkyne insertion reactions results in methodologies to selectively incorporate fluorescent or redox labels in their structures 6 and to design novel tandem processes (Scheme 1). 7 The use of osmium polyhydrides 8 to study new ways of interaction and structural modification of biomolecules by transition metals is an emerging research field. Thus, the hexahydride complex OsH 6 (P i Pr 3 ) 2 and the dihydride derivative OsH 2 Cl 2 (P i Pr 3 ) 2 selectively activate N−H, O−H, and N−C bonds of pyrimidine nucleobases, leading to a new class of mono-and dinuclear Os(IV) polyhydride nucleosides.…”

Unravelling Molecular Aspects of the Migratory Insertion Step in Cp*CoIII Metallacyclic Systems

“…However, other types of products could be potentially formed whether the corresponding electrophile inserts into the Co–C bond multiple times or insertion occurs in a 1,1-fashion (Figure ). We have targeted these terminal alkynes and alkenes for our reactivity study because different literature reports have shown these nontraditional insertion modes with analogous Cp*Ir III - and Cp*Rh III -based systems …”

“…Despite our contributions , and the recent observation of analogous insertion products, ,, there are still important fundamental questions regarding the insertion step, fundamental in different Cp*Co-catalyzed C–H functionalization reactions (Scheme ), that need to be addressed. In sharp contrast to analogous iridium- and rhodium-based systems, to date, there is a dearth of fundamental information on the reactivity and regioselectivity of the insertion of alkynes or alkenes into Co–C bonds of Cp*Co III cyclometalated complexes.…”

Synthesis, Structure, and Photophysical Properties of Platinum(II) (N,C,N′) Pincer Complexes Derived from Purine Nucleobases

“…Our research group is a pioneer in the development of methodologies to prepare cyclometalated transition metal complexes [M = Ir­(III), Rh­(III), Os­(IV)] derived from nucleobases, nucleosides, and nucleotides. − In these studies, purine derivatives were excellent substrates to carry out cyclometalation reactions, and we reasoned that they could be interesting scaffolds to build cyclometalated platinum­(II) (pincer) complexes. The idea was challenging, as purine nucleobase derivatives are highly functionalized systems with many positions prone to interact with the metal.…”