The use of weakb ases and mild conditions is currently the most sustainable and attractive synthetica pproach for the preparation of late-transition metal complexes, some of which are widely used in catalysis, medicinal chemistry and materials science.H erein, the use of cuprate, aurate or palladate speciesf or ac ontinuous flow preparation of Cu I ,A u I and Pd II-NHC complexes is reported. All reactions examined proceed under extremely mild conditions and make use of technicalg rade acetonea s solvent. The scalability of the process was exemplified in a multigram-scale synthesis of [Cu(IPr)Cl]. N-Heterocyclic carbenes (NHCs) have become am ost popular ligand family for the synthesis of organometallic compounds with uses in catalysis. [1] The surprising stabilityo ft he metal-NHC bond has also permitted the study and use of transition metal-NHC complexes in medicinal chemistry [2] and mostr ecently in materials science. [3] The nowadays ubiquitousu se of this fascinating class of ligandsh as been ad riving force encouraging the development of sustainable, efficient and userfriendly routes leadingt otheir syntheses. [4] Although not quite sustainable, the most commonly used synthetic strategy,b ased on the seminal work of Arduengo, [5] involves the generation of free NHC by deprotonation of the corresponding azolium salt with as trong base (e.g. NaH, KOtBu)a nd subsequent coordination to am etal. The most significant drawbacks of the free carbene route lies in the need for strictly anhydrous conditions. Additionally,t his route is not suitable for complexes requiring the use of metal precursors sensitivet ostrong bases.

The first continuous flow syntheses of amido and thiolato families are reported. Our studies focused on [M(NHC)(Cbz)] (Cbz=carbazolyl) and [M(NHC)(SPh)] (NHC=N‐heterocyclic carbene) as general proof‐of‐concepts and has led to a simple protocol with unprecedented short reaction times and high product yields. The scope of supporting ligands and substrates permits to assess the versatility of the process and a one‐pot synthesis starting from the imidazolium salt, metal source and carbazole substrate highlights the simplicity and sustainability of this operating design. The process was made possible through a detailed mechanistic understanding of the underlying reaction chemistry.

The use of weak and inexpensive bases has recently opened promising perspectives towards the simpler and more sustainable synthesis of Au(I)-aryl complexes with valuable applications in catalysis, medicinal chemistry, and materials science. In recent years, continuous manufacturing has shown to be a reliable partner in establishing sustainable and controlled process scalability. Herein, the first continuous flow synthesis of a range of Au(I)-aryl starting from widely available boronic acids and various [Au(NHC)Cl] (NHC = N-heterocyclic carbene) complexes in unprecedentedly short reaction times and high yields is reported. Successful synthesis of previously non-or poorly accessible complexes exposed fascinating reactivity patterns. Via a gram-scale synthesis, convenient process scalability of the developed protocol was showcased.

The first continuous flow syntheses of sulfur‐ and selenium−NHC (NHC=N‐heterocyclic carbene) adducts in unprecedented short reaction times and high yields are reported. The importance of these species in coordination chemistry or as efficient tools for determining the π‐acceptor character of NHC ligands make any improvement in their synthesis a worthy goal. Thiourea derivatives bearing both saturated and unsaturated NHCs were obtained using NEt3 as a weak base (homogeneous setup) in conjunction with a bed of elemental sulfur (S8). The synthetic route proving optimal for selenoureas involves the use of a simple Se/K2CO3 heterogeneous microreactor design.

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