Studies Relevant to the Functional Model of Mo-Cu CODH: In Situ Reactions of Cu(I)-L Complexes with Mo(VI) and Synthesis of Stable Structurally Characterized Heterotetranuclear MoCu Complex.

In this study, we report the synthesis, characterization, and reactions of Cu(I) complexes of the general form Cu(L)(LigH) (LigH = xanthene-based heterodinucleating ligand (E)-3-(((5-(bis(pyridin-2-ylmethyl)amino)-2,7-di-tert-butyl-9,9-dimethyl-9H-xanthen-4-yl)imino)methyl)benzene-1,2-diol); L = PMe, PPh, CN(2,6-MeCH)). New complexes [Cu(PMe)(LigH)] and [CuCN(2,6-MeCH)(LigH)] were synthesized by treating Cu(LigH) with trimethylphosphine and 2,6-dimethylphenyl isocyanide, respectively. These complexes were characterized by multinuclear NMR spectroscopy, IR spectroscopy, high-resolution mass spectrometry (HRMS), and X-ray crystallography. In contrast, attempted reactions of Cu(LigH) with cyanide or styrene failed to produce isolable crystalline products. Next, the reactivity of these and previously synthesized Cu(I) phosphine and isocyanide complexes with molybdate was interrogated. IR (for isocyanide) and P NMR (for PPh/PMe) spectroscopy demonstrates the lack of oxidation reactivity. We also describe herein the first example of a structurally characterized multinuclear complex combining both Mo(VI) and Cu(I) metal ions within the same system. The heterobimetallic tetranuclear complex [CuMoO(μ-O)(Lig)]·HOSiPh was obtained by the reaction of the silylated Mo(VI) precursor (EtN)(MoO(OSiPh)) with LigH, followed by the addition of Cu(NCMe). This complex was characterized by NMR spectroscopy, high-resolution mass spectrometry, and X-ray crystallography.