Since their discovery in 1967 by Trofimenko, tris(pyrazolyl)hydroborates (Tp) have become one of the most studied ligand systems in coordination chemistry. In general, the weak field hard s-N donor Tp ligands display a marked preference on the formation of half sandwiched metal complexes with a local C3V symmetry. However, various Tp complexes have been reported to differ from the usually found k3-N,N,N-coordination. For instance, the monodentate coordination mode k1-N-Tp and the k2-N,N-Tp coordination mode are now well known in the literature. Additionally, the rarely ko (i.e. uncoordinated counterion) and k5-N,N,N,C,C coordination modes have also been reported recently. With the impressive coordination potential described above, we were surprised on observing that no examples of Tp ligands holding two metal centers simultaneously have been reported so far. In this context, we have foreseen the possibility of constructing heterobimetallic complexes supported by Tp ligands if a controlled k1-N-Tp type-coordination could be achieved. With the premise that NHC-AuX (X = halogen) complexes feature both a linear coordination geometry and the presence of a readily substituted halogen moiety, we report the reaction of NHC-AuCl (NHC = IPr and IMes) precursors with equimolar amounts of KTpR2 (R = Me, H) which generate the heteroleptic complexes of the type NHC-Au-TpR2 in high yields. As the TpR ligand in the latter complexes features a k1-N coordination toward the gold(I) center, the subsequent addition of group 10 metal (Ni, Pt) precursors results in the first examples of heterobimetallic Au/M complexes supported by TpR platforms. Interestingly, if the carbene ligand in the gold complexes is replaced by a mesoionic triazolylidene (MIC), its reaction with KTpMe2 yields an unexpected bis(triazolylidene) gold(I) complex [MIC-Au+-MIC] featuring a large [(TpMe2)2K] anion. The structural diversity in solution and solid state of all new complexes and the preliminary catalytic activities will be discussed.

Reactivity of NHC-gold(I) complexes with tris(pyrazolyl)borate ligands: Preparation of heterobimetallic species and highly protected gold(I) cations

2019 Spring National Meeting

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