SILVER COMPLEXES CONTAINING AN AG4O8 CORE IMPOSED BY MULTI-DENTATE LIGANDS HAVING FIXED GEOMETRY - CRYSTAL-STRUCTURE OF [BIS(1,8-NAPHTHALENEDICARBOXYLATO)][TETRAKIS(TRIPHENYLPHOSPHINE)SILVER(I)]-DIBENZENE

Reactions of (l,8-naphthalenedicarboxylato)disilver(I), (C12H6O4)Ag2, with phosphines yielded the products (C,12H6O4)2(LAg)4, where L = triphenylphosphine or tri-p-tolylphosphine and 2L = bis(diphenylphosphino)methane (dppm) or l,2-bis(di-phenylphosphino)ethane (dppe). An X-ray crystallographic study revealed the molecular structure of [bis(l,8-naphthalenedicarboxylato)][tetrakis(triphenylphosphine)silver(I)]-dibenzene, (C12H6O4)2(Ph3PAg)4.2C6H6: space group P&& with unit cell dimensions a = 11.804 (4) Å, b = 18.390 (4) Å, c = 22.046 (1) Å, α = 103.23 (7)Δ,β = 95.81 (3)Δ,γ = 90.08 (7)Δ, V = 4.633×103 Å3 and Z = 2. The crystal structure was solved for the heavy atoms by direct methods and completed by standard Fourier techniques. Block-diagonal least-squares refinement with 8664 observed diffractometer data converged to RF = 0.055 (Rw = 0.054). The coordination geometry is different for each of the four silver atoms, each of which is bonded to one phosphine and positioned against a core of eight oxygen atoms. The four shortest Ag-Ag distances are in the range of 3.672-3.961 Å while the Ag-P distances amount to 2.378 (5), 2.346 (5), 2.341 (5), and 2.363 (4) Å. The carboxylato groups act as monodentate, chelating, or bridging ligands. The coordination is interpreted in terms of a weak ionic interaction between the oxygen atoms and the Ph3PAg+ ions containing a strong covalent P-Ag bond. Molecular weight determinations together with 31P NMR data show that the tetranuclear structure is retained in solution. The 31P resonances of the four Ph3PAg units are isochronous (J(31P-107Ag) = 650 Hz) pointing to the occurrence of an intramolecular process which renders these groups equivalent. A process involving intermolecular exchange with excess phosphine at low temperature could be excluded. In order to obtain additional information concerning J(Ag-P) in these compounds, the 31P NMR spectra of novel dppm(AgOAc)2 (J(31P-107Ag) = 680 Hz) and dppe(AgOAc)2 (J(31P-107Ag) = 663 Hz) were recorded. © 1979, American Chemical Society. All rights reserved.