Synthesis and coordination chemistry of cyclic seleno- and telluroureas

Abstract

<jats:title>Abstract</jats:title> <jats:p>Chalcogenated derivatives of N-heterocyclic carbene ligands have received increasing attention due to their diverse chemical reactivity and potential applications in fields such as medicine and materials chemistry. This chapter summarizes the synthetic methods for the preparation of cyclic heavy chalcogenoureas featuring heterocyclic cores and explores their diverse coordination chemistry with p- and d-block metals.</jats:p>

A Mechanistically and Operationally Simple Route to Metal–N‐Heterocyclic Carbene (NHC) Complexes

“…The importance of these has been addressed in recent reviews and reports on their use as Sa nd Se synthons in materials science. [20] Ad etailed mechanistic and synthetics cope of the use of other weak bases in these and relatedt ransformations is presently being finalized in our laboratories and will be communicated shortly.…”

Straightforward access to chalcogenoureas derived from N-heterocyclic carbenes and their coordination chemistry

“…7,8 In addition to revealing the π-accepting ability of the parent NHC, [9][10][11][12] selenoureas have themselves found applications in coordination chemistry with several transition metals. [13][14][15] Other chalcogen-based derivatives, such as thio-and telluroureas, have also made an impact in this field, [13][14][15][16][17] although the tellurium analogues are far less common. 14 NHC-based seleno-and thioureas can typically be synthesised either by deprotonating the corresponding imidazolium salts using a strong base (e.g.…”

“…[13][14][15] Other chalcogen-based derivatives, such as thio-and telluroureas, have also made an impact in this field, [13][14][15][16][17] although the tellurium analogues are far less common. 14 NHC-based seleno-and thioureas can typically be synthesised either by deprotonating the corresponding imidazolium salts using a strong base (e.g. KO t Bu, NaH), or by adding elemental selenium or sulfur to a free NHC species.…”

“…KO t Bu, NaH), or by adding elemental selenium or sulfur to a free NHC species. 14,15 Some reports have used K2CO3 in methanol yielding lower yields, as it generates the strong base KOMe in situ. 18 It should be noted that in all approaches, a significant excess of elemental chalcogen is needed.…”

“…NHC-derived telluroureas, on the other hand, are more scarcely reported, owing to the lower reactivity of elemental tellurium and its more metallic character when compared to selenium and sulfur. [14][15][16] We have recently developed a systematic approach to the synthesis of NHC-based compounds by means of weak bases such as K2CO3 and NEt3. In a recent report, we accessed [S(IPr)] and [Se(IPr)] compounds (IPr = N,N'-bis [2,6-(di-isopropyl)phenyl]imidazol-2-ylidene) using NEt3 as the base.…”