Silver complexes containing an Ag4O8 core imposed by multidentate ligands having fixed geometry. Crystal structure of**[bis(1,8-naphthalenedicarboxylato)] [tetrakis(triphenylphosphine)silver(I)] dibenzene

Abstract

Reactions of (1,8-naphthaIenedicarbxylato)disilver(I), (c&@4)Ag~, with phosphines yielded the products (C&O&(LAg),, where L = triphenylphosphine or tri-p-tolylphosphine and 2L = bis(dipheny1phosphino)methane (dppm) or 1,2-bis(dipheny1phosphino) ethane (dppe). An X-ray crystallographic study revealed the molecular structure of [bis( 1,8-naphthalenedicarboxylato)][ tetrakis(triphenylphosphine)silver(I)]-dibenzene, (C12H604)2(Ph3PAg),.2csp6aHc6e :g roup Pi with unit cell dimensions a = 11.804 (4) A, b = 18.390 (4) A, c = 22.046 (1) A, 01 = 103.23 (7)O, p = 95.81 (3)O, y = 90.08 (7)O, V = 4.633 X lo3 A3, 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 (R, = 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 A while the Ag-P distances amount to 2.378 (5), 2.346 (5), 2.341 (5): and 2.363 (4) A. 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 ,IP resonances of the four Ph3PAg units are isochronous (J(3'P-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 ,'P NMR spectra of novel dppm(AgOAc)2 (J(,IP-'07Ag) = 680 Hz) and dppe(AgOAc)2 (J(31P-'07Ag) = 663 Hz) were recorded.