ic402342y_si_005.cif (41.48 kB)
Heteroleptic Silver(I) Complexes Prepared from Phenanthroline and Bis-phosphine Ligands
dataset
posted on 2013-12-16, 00:00 authored by Adrien Kaeser, Béatrice Delavaux-Nicot, Carine Duhayon, Yannick Coppel, Jean-François NierengartenThe heteroleptic coordination scenario
of silver(I) with various phenanthroline ligands (NN) and different
bis-phosphine (PP) derivatives has been investigated. In addition
to the X-ray crystal structural characterization of the resulting
mixed ligand Ag(I) complexes, detailed NMR studies have been performed
to disclose the behavior of the prepared silver(I) complexes in solution.
The results obtained with silver(I) have been also systematically
related to the one obtained for copper(I) with the same combination
of PP and NN ligands. Starting from an equimolar mixture of AgBF4, bis[(2-diphenylphosphino)phenyl] ether (POP), and 1,10-phenanthroline
(phen), the mononuclear complex [Ag(POP)(phen)]+ has been
obtained as the tetrafluoroborate salt. By following the same experimental
procedure starting from bis(diphenylphosphino)methane (dppm) or 1,3-bis(diphenylphosphino)propane
(dppp) as the PP ligand, dinuclear complexes with two bridging PP
ligands, i.e., [Ag2(NN)2(μ-dppm)2]2+ and [Ag2(NN)2(μ-dppp)2]2+ with NN = phen or Bphen (bathophenanthroline),
have been isolated as the tetrafluoroborate salts. Surprisingly, by
using an equimolar ratio of AgBF4, phen or Bphen, and 1,2-bis(diphenyl-phosphino)ethane
(dppe), the corresponding monobridged diphosphine dinuclear complexes
[Ag2(NN)2(μ-dppe)]2+ have been
obtained as the tetrafluoroborate salts. These compounds have been
also prepared in excellent yield by using a more appropriate 2:1:2
(phen:dppe:Ag) stoichiometry. These results prompted us to also perform
the reactions with dppm and dppp using a 1:2:2 (PP:NN:Ag) stoichiometry.
Under these conditions, [Ag2(NN)2(μ-dppm)](BF4)2 (NN = phen or Bphen) and [Ag2(NN)2(μ-dppp)](BF4)2 (NN = phen or
Bphen) have been obtained upon crystallization. When compared to their
copper(I) analogues, the complexation scenario becomes more complex
with silver(I) as the system tolerates also coordinatively frustrated
metal ligand assemblies, i.e., with a trigonal coordination geometry.
Depending on the stoichiometry or on the nature of the PP partner,
silver(I) shows an adaptive capability leading to various complexes
with different coordination geometries and composition. However, as
in the case of copper(I), their solution behavior is highly dependent
on the relative thermodynamic stability of the various possible complexes.
In most of the cases, a single Ag(I) complex is observed in solution
and the NMR data are in a perfect agreement with their solid state
structures. The dppp-containing complexes are the only notable exception;
both [Ag2(NN)2(μ-dppp)2](BF4)2 and [Ag2(NN)2(μ-dppp)](BF4)2 are stable in the solid state but a dynamic
mixture is observed as soon as these compounds are dissolved. Finally,
whereas both dppe and dppp are chelating ligands for copper(I), it
is not the case anymore with silver(I) for which a destabilization
of species with chelating dppe and dppp ligands is clearly suggested
by our results.
