Cu(I) and Ag(I) complexes of two sterically demanding Xylyl-Substituted phosphine Ligands: Synthesis, Characterization, and structural examination

Two sterically demanding tertiary phosphines, PiPr2Xyl and PtBu2Xyl, (Xyl = 2,6-dimethylphenyl), the latter reported here for the first time, have been used to synthesize a series of dinuclear complexes of the general formula [M(& mu;-X)PR2Xyl]2, (R = iPr, tBu; M = Cu: X = Cl, Br, I, OTf; M = Ag: X = OTf, NTf2). All compounds have been characterized by multinuclear NMR spectroscopy in solution and, with the exception of AgNTf2(PtBu2Xyl), by X-ray diffraction analyses. The doubly halido-bridged compounds [Cu(& mu;-X)PR2Xyl]2 (R = iPr, tBu; X = Cl, Br, I) display Ci, C2-like, or C1 molecular symmetry, depending on the anion and the R group, and enclose planar or disphenoidal [CuX]2 cores with short, bonding Cu-Cu distances in case of X = I. On the other hand, centrosymmetric 8-membered rings with twist-chair conformations are found in the solid state structures of [M(& mu;-OTf) PR2Xyl]2 (R = iPr, tBu; M = Cu, Ag) and [Ag(& mu;-NTf2)PiPr2Xyl]2, with the anions in a & kappa;2-& mu;2 coordination mode. Additionally, the cationic complex [Cu(PR2Xyl)2]+ has been obtained as a triflate or BArF salt (BArF- = B{3,5(CF3)2C6H3}4- ), and shows C2-like symmetry in the solid state, with PCuP angles of ca. 168-169 degrees and synclinal dispositions of the Xyl groups with respect to the P & BULL;& BULL;& BULL;P axis. Comparative discussion of relevant NMR data of Cu (I), Ag(I), and Au(I) adducts of the title phosphines is also provided.

Automated summary

Two sterically demanding tertiary phosphines, PiPr2Xyl and PtBu2Xyl, have been used to synthesize a series of dinuclear complexes. These compounds have been characterized by NMR spectroscopy and X-ray diffraction analyses. Different molecular symmetries and bonding lengths were observed in the halido-bridged compounds, and the cationic complex showed C2-like symmetry.