American Chemical Society
ic5019357_si_002.cif (172.12 kB)

Isomer Dependence in the Assembly and Lability of Silver(I) Trifluoromethanesulfonate Complexes of the Heteroditopic Ligands, 2‑, 3‑, and 4‑[Di(1H‑pyrazolyl)methyl]phenyl(di‑p‑tolyl)phosphine

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posted on 2014-11-17, 00:00 authored by James R. Gardinier, Jeewantha S. Hewage, Sergey V. Lindeman
Three isomers of a new heteroditopic ligand that contains a di­(1H-pyrazolyl)­methyl (−CHpz2) moiety connected to a di­(p-tolyl)­phosphine group via a para-, meta-, or ortho-phenylene spacer (pL, mL, and oL, respectively) have been synthesized by using a palladium(0)-catalyzed coupling reaction between HP­(p-tolyl)2 and the appropriate isomer of (IC6H4)­CHpz2. The 1:1 complexes of silver­(I) trifluoromethanesulfonate, Ag­(OTf), were prepared to examine the nature of ligand coordination and the type of supramolecular isomer (monomeric, cyclic oligomeric, or polymeric) that would be obtained. The single crystal X-ray diffraction studies showed that [Ag­(pL)]­(OTf), 1, and [Ag­(mL)]­(OTf), 2, possessed cyclic dimeric dications, whereas [Ag­(oL)]­(OTf), 3, was a coordination polymer. The polymeric chain in 3 could be disrupted by reaction with triphenylphosphine, and the resulting complex, [Ag­(oL)­(PPh3)]­(OTf), 4, possessed a monometallic cation where the ligand was bound to silver in a chelating κ2P,N- coordination mode. The solution structures of 14 were probed via a combination of IR, variable-temperature multinuclear (1H, 13C, 31P) NMR spectroscopy, as well as by electron spray ionization (ESI)­(+) mass spectrometry. A related complex [Ag­(m-IC6H4CHpz2)2]­(OTf), 5, was also prepared, and its solid-state and solution spectroscopic properties were studied for comparison purposes. These studies suggest that the cyclic structures of 1 and 2 are likely preserved but are dynamic in solution at room temperature. Moreover, both 3 and 4 have dynamic solution structures where 3 is likely extensively dissociated in CH3CN or acetone rather than being polymeric as in the solid state.