Synthesis and structural systematics of mixed triphenylphosphine/imidazole base adducts of silver(I) oxyanion salts

Article abstract of DOI:10.1039/a906624a

From the interaction between imidazole-type ligands B and [Ag(PPh₃)₄]X (X = NO₃, BF₄, ClO₄ or CF₃CO₂), [Ag(PCy₃)₂(NO₃)] and [Ag(PPh₃)X)] (X = NO₂ or CH₃SO₃), new ionic mononuclear [Ag(PR₃)_4-n(B)_n]⁺[X]^- (R = Ph or Cy) and neutral mono- ([Ag(PR₃)_3-n(B)_n(X)]) and di-nuclear ([{Ag(PPh₃)(B)(μ-X)}₂]) complexes have been obtained which have been characterized through elemental analysis, IR and far-IR, conductivity, ¹H NMR and in some cases also by vaporimetric molecular weight measurements and ³¹P NMR. Stoichiometries and molecular structures are dependent on the nature of the azole (steric hindrance and basicity), of the counter ion, and on the number of the P-donor ligands in the starting reactants. Solution data are consistent with a partial dissociation of complexes, occurring through breaking of both Ag-N and Ag-P bonds. The majority of the possible Ph₃P/imidazole base combinations have been characterized structurally by room-temperature single crystal X-ray studies, thus: [Ag(PPh₃)₃(4-Ph-im)]NO₃ (4-Ph-im = 4-phenylimidazole), [Ag(PPh₃)₂B₂]NO₃ for B = imidazole (Him) or 2-methylimidazole (2-Me-im), [Ag(PPh₃)(2-Me-im)₃][CF₃CO₂], [Ag(PPh₃)₂(2-Me-im)(O₂NO)], [{Ag(PPh₃)(1-Me-im)(μ-OSOCH₃O)}₂] and [{Ag(PPh₃)(Him)(μ-ONO)}₂]; the latter is a mixture of isomers in which one or both oxygen atoms of the anions interact with silver atoms. In the methanesulfonate complex the interactions of the anions with the silver may be regarded as a perturbation on a proto-linear P-Ag-N array (Ag-P,N 2.3662(6), 2.189(1) A P-Ag-N 144.28(6)°). The Royal Society of Chemistry 1999.

Full text of DOI:10.1039/a906624a

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Synthesis and structural systematics of mixed triphenylphosphine/
imidazole base adducts of silver(I) oxyanion salts†
Augusto Cingolani,a Effendy,b,c Fabio Marchetti,a Claudio Pettinari,*a Brian W. Skeltonb
and Allan H. Whiteb
a Dipartimento di Scienze Chimiche, via S. Agostino 1, Università degli Studi,
62032 Camerino (MC), Italy
b Department of Chemistry, University of Western Australia, Nedlands, WA, 6907, Australia
c Jurusan Pendidikan Kimia, FPMIPA IKIP Malang, Jalan Surabaya 6, Malang 65145,
Indonesia
Received 16th August 1999, Accepted 28th September 1999
From the interaction between imidazole-type ligands B and [Ag(PPh3)4]X (X = NO3, BF4, ClO4 or CF3CO2),
[Ag(PCy3)2(NO3)] and [Ag(PPh3)X)] (X = NO2 or CH3SO3), new ionic mononuclear [Ag(PR3)4Ϫn(B)n]ϩ[X]Ϫ (R = Ph or
Cy) and neutral mono- ([Ag(PR3)3Ϫn(B)n(X)]) and di-nuclear ([{Ag(PPh3)(B)(µ-X)}2]) complexes have been obtained
which have been characterized through elemental analysis, IR and far-IR, conductivity, 1H NMR and in some cases
also by vaporimetric molecular weight measurements and 31P NMR. Stoichiometries and molecular structures are
dependent on the nature of the azole (steric hindrance and basicity), of the counter ion, and on the number of the
P-donor ligands in the starting reactants. Solution data are consistent with a partial dissociation of complexes,
occurring through breaking of both Ag–N and Ag–P bonds. The majority of the possible Ph3P/imidazole base
combinations have been characterized structurally by room-temperature single crystal X-ray studies, thus:
[Ag(PPh3)3(4-Ph-im)]NO3 (4-Ph-im = 4-phenylimidazole), [Ag(PPh3)2B2]NO3 for B = imidazole (Him) or 2-methyl-
imidazole (2-Me-im), [Ag(PPh3)(2-Me-im)3][CF3CO2], [Ag(PPh3)2(2-Me-im)(O2NO)], [{Ag(PPh3)(1-Me-im)(µ-
OSOCH3O)}2] and [{Ag(PPh3)(Him)(µ-ONO)}2]; the latter is a mixture of isomers in which one or both oxygen atoms
of the anions interact with silver atoms. In the methanesulfonate complex the interactions of the anions with the
silver may be regarded as a perturbation on a proto-linear P–Ag–N array (Ag–P,N 2.3662(6), 2.189(1) Å; P–Ag–N
144.28(6)Њ).
During our studies of the co-ordination chemistry of pyrazole,
imidazole and their derivatives, several zinc,1 cadmium,1
mercury,2 tin(),3–5 and organotin(IV)3–5 complexes were syn-
thesized and characterized. It has been found that these
compounds display a diversity of stable structural types in
which the azole ring can be N- or C-bonded depending on the
relationship between the steric and electronic preferences of the
metal ions and the co-ordinating properties of the ligand. In
fact, the Group 12 and 14 metal ions, having no stereoelectronic
geometric preferences associated with partially filled d shells,
permit more extensive examination of the possible co-
ordination modes of a ligand in the absence of metal-directed
requirements. In particular, from 1980, several papers have
appeared reporting the synthesis and characterization of a
number of copper complexes relevant for their structural
features,6 useful in organic synthesis and in catalysis7 and for
investigation of the role of copper centres at the active sites of
a number of proteins.8
plexes exhibit antimicrobial and anticancer activity,13 while
macrocyclic silver() compounds have widely been investigated
because they undergo very slow acid-dependent decomplex-
ation and therefore may be useful for 111Ag-based radio-
immunotherapy.14
As a part of our studies into the structural and spectro-
scopic properties of mixed phosphine/N-donor derivatives of
silver()15 we were interested in extending the available literature
data to include complexes incorporating azole and phos-
phine ligands with different steric and electronic profile. To
this end we have synthesized some new silver() complexes
containing azole-type ligands (Him = imidazole, 1-Me-im =
1-methylimidazole, 2-Me-im = 2-methylimidazole, 4-Me-im =
4-methylimidazole, 2-Et-im = 2-ethylimidazole, 4-Ph-im = 4-
phenylimidazole, Bz-im = benzoimidazole), characterizing a
representative array by X-ray diffraction studies and spectro-
scopic and analytical measurements.
Despite the large number of known copper()–azole com-
plexes,9 only a few papers have been published dealing with
analogous silver() systems,10 although the first silver() azolides
were obtained as early as 198311 with interest in this class of
compounds continuing thereafter, with potential applications
in photography or silver plating by electrochemical processes.12
Furthermore, it has been reported that these silver() com-
Results and discussion
Syntheses
By the interaction of [Ag(PPh3)4]NO3 with an excess of 4-Ph-im
in diethyl ether the ionic compound [Ag(PPh3)3(4-Ph-im)]NO3 1
has been obtained upon displacement of one Ph3P ligand from
the co-ordination centre. The donors Him, 2-Me-im, 4-Me-im
and 2-Et-im react immediately with [Ag(PPh3)4]NO3 displacing
two molecules of Ph3P and yielding the ionic 1:2:2 complexes
[Ag(PPh3)2B2]NO3ؒxH2O (B = Him, x = 0 2; B = 2-Me-im, x = 0
3; B = 4-Me-im, x = 1 4; B = 2-Et-im, x = 0 5). Different
Ag(NO3)/PPh3/imidazole base combinations may be obtained
depending on the imidazole substituents: 1-Me-im forms the
† Supplementary data available: rotatable 3-D crystal structure diagram
in CHIME format. See http://www.rsc.org/suppdata/dt/1999/4047/.
Also available: synthesis and characterisation data. For direct electronic
access see http://www.rsc.org/suppdata/dt/1999/4047/, otherwise avail-
able from BLDSC (No. SUP 57652, 9 pp.) or the RSC Library. See
Instructions for Authors, 1999, Issue 1 (http://www.rsc.org/dalton).
J. Chem. Soc., Dalton Trans., 1999, 4047–4055
This journal is © The Royal Society of Chemistry 1999
4047

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1:1:3 derivative [Ag(PPh3)(1-Me-im)3]NO3 6 whereas Bz-im
gives 1:1:2 [Ag(PPh3)(Bz-im)2(ONO2)]ؒ2H2O 7, always with
the displacement of three Ph3P groups. The donor 2-Me-im
also forms the 1:2:1 adduct [Ag(PPh3)2(2-Me-im)(ONO2)] 8
when its reaction with [Ag(PPh3)4]NO3 is carried out in a strict-
ly equimolar ratio.
The weak interactions between the silver() cation and the
nitrate group in 8 are reflected in the small magnitude of the
splitting of the asymmetric N–O stretching modes.17
In the IR spectra of derivatives 11–13 the difference ∆
between νasym(CO2) and νsym(CO2) falls in the range 230–260
cmϪ1, consistent with the presence of ionic trifluoroacetato
groups.18 Although derivatives 14–19 also are ionic in the solid
state, the ν3 modes of BF4 and ClO4 always show a splitting into
three and two components respectively, typical of a lowering
in symmetry from Td to C3v, consistent with the involvement
of BF4 and ClO4 in a hydrogen-bonding network with N–H of
azoles,19 ν(N–H) also being considerably broadened.
Variation of the type of P-donor ligand in the starting
reactants has been found to change the reactivity and also the
stoichiometry of the species: no product has been obtained
from the reaction of [Ag(PCy3)2(O2NO)] with Him, 1-Me-im,
4-Me-im or 4-Ph-im, whereas 2-Me-im and Bz-im form the
derivatives [Ag(PCy3)(2-Me-im)2(ONO2)] 9 and [Ag(PCy3)2(Bz-
im)2]NO3ؒH2O 10 respectively. Only the donors 2-Me-im, 4-Me-
im and Bz-im were found to interact with [Ag(PPh3)4][CF3CO2],
yielding the ionic derivatives [Ag(PPh3)(2-Me-im)3][CF3CO2]
11, [Ag(PPh3)2(4-Me-im)2][CF3CO2] 12, and [Ag(PPh3)2(Bz-
im)2][CF3CO2] 13 upon displacement of 3 or 2 Ph3P ligands
respectively. The reaction between [Ag(PPh3)4]ClO4 and [Ag-
(PPh3)4]BF4 is often very difficult to interpret, intractable
material being in most cases recovered. Upon continued
crystallization of the reagent mixture, the derivatives
[Ag(PPh3)2(1-Me-im)2]ClO4 14, [Ag(PPh3)2(Bz-im)2]ClO4ؒ
Bz-im 15, [Ag(PPh3)3(2-Me-im)]BF4ؒ2(2-Me-im) 16, [Ag-
(PPh3)3(1-Me-im)]BF4 17, [Ag(PPh3)3(Bz-im)]BF4 18, and
[Ag(PPh3)3(4-Ph-im)]BF4 19 have been obtained. In the case of
derivatives 15 and 16 for which silver:phosphine:imidazole
base ratios 1:2:3 and 1:3:3 have been found respectively, the
presence of ligand molecules clathrated or hydrogen bonded to
ClO4 and BF4 groups is likely, as has been previously observed
in other Group 11–azole derivatives.16 Finally, when the mono
triphenylphosphine complexes [Ag(PPh3)(O3SCH3)] and [Ag-
(PPh3)(O2N)] interact with our imidazole bases B, the dinuclear
complexes [{Ag(PPh3)(1-Me-im)(OSOCH3O)}2] 20, [{Ag-
(PPh3)(Him)(ONO)}2] 21, [{Ag(PPh3)(1-Me-im)(ONO)}2] 22,
[{Ag(PPh3)(4-Ph-im)(ONO)}2] 23 and [{Ag(PPh3)(Bz-im)-
(ONO)}2] 24 have been obtained. Although derivatives 1–24
generally absorb water from atmospheric moisture, they are
generally very stable when stored, at room temperature, in a
desiccator under reduced pressure. They are soluble in chlor-
inated solvents, acetonitrile, acetone and DMSO, but insoluble
in Et2O, alcohols, and aromatic and aliphatic hydrocarbons.
The conductance values of dichloromethane solutions of
derivatives 2, 3, 5, 6, 10, 15 and 23 have been found to fall in the
range 14–24 ΩϪ1 cm2 molϪ1, typical of 1:1 electrolytes or of
complexes partially ionized in solution. The remainder of the
compounds are apparently un-ionized, having ΛM values lower
than 11 ΩϪ1 cm2 molϪ1. This behaviour, however, may be due to
the formation in solution of solvated ion pairs or, alternatively,
to dissociation of P- or N-donor ligands from silver with con-
comitant re-association of the counter ion.
In the far-IR spectra of methanesulfonate (20) and nitrito
(21–24) derivatives some absorptions typical of Ag–O stretch-
ing are consistently found in the 300–400 cmϪ1 region. The
presence of co-ordinated nitrite and methanesulfonate groups
has been confirmed also by the presence in the 1500–1000 and
1100–1000 cmϪ1 regions of bands typical of bridging bidentate
ONO20 and OؒSOCH3ؒO groups.21 In particular, for the nitrito
complexes 21–24, an examination of the literature data20 sug-
gests that two absorptions peaking at ca. 1400 and 1060 cmϪ1
Ϫ
may be attributed to the stretching frequencies of the NO2
group: these values are consistent with a µ-1,1 bridging mode.
The 1H and 31P NMR spectra have been measured in CDCl3,
in which these derivatives show good solubility. The solutions
are generally stable enough, and only after some days decom-
1
position can be detected, silver metal being formed. In the H
NMR spectra of 1–24 the signals due to azoles are always
deshielded with respect to those in the spectra of the free
donors: the higher the ∆ (∆ = δadduct Ϫ δazole), the higher is the
donation of electron density from the donor to the metal, and
the stronger the corresponding Ag–N interaction. The ∆ values
further confirm the existence, at least partial, of complexation
in solution.
The solution 31P NMR spectrum for each triphenylphosphine
complex (1–8, 11–24) at room temperature consists of a broad
singlet, presumed to be consequent on the presence of rapid
exchange equilibria. A unique absorption is generally detected,
always at lower fields than that of the free phosphine. The
chemical shift values move upfield towards the values of free
Ph3P with increasing co-ordination number, with very little
difference being generally observed between the tris(tri-
phenylphosphine)silver() derivatives 1 and 16–19 and the
starting tetrakis(triphenylphosphine)silver() reagent. The ∆
(∆ = δadduct Ϫ δphosphine) values vary from 7 to 18 ppm and for
analogous complexes are not strongly dependent on the par-
ticular imidazole base employed. Lability of the phosphorus
ligands was evident in the temperature dependence of the 31P
NMR spectra of some derivatives: for example for 1 δ 9.55 at
room temperature and 6.16 at 223 K. The 31P NMR chemical
shifts of 1–10 may be compared with those of the analogous
copper() compounds,9 the substitution of silver for copper
The vaporimetric molecular weight measurements strongly
suggest that mixed triphenylphosphine/imidazole base
adducts of silver() oxyanion salts may be partially dissociated
in chloroform solution, the dissociation being generally
dependent on the concentration. For example the ratio of
experimental M to formula weight for derivative 1, which is
not an electrolyte in solution, is 0.62:1 at c = 1 × 10Ϫ2 m and
0.53 at c = 0.7 × 10Ϫ2 m.
producing a small but significantly deshielding effect on the 31
P
nuclei. The trifluoroacetate derivatives 11–13 show extensive
disproportionation, even at very low temperature: for example,
in the 31P NMR spectrum (203 K) of 11, three signals, presum-
ably corresponding to [Ag(PPh3)]X (δ 11.6), [Ag(PPh3)2]X (4.4),
and [Ag(PPh3)3]X (2.8) species, have been observed.
The spectra at 218 K of most of these complexes normally
show splittings due to J(Ag–31P), but the separate splitting
1
Spectroscopy
arising from the different 107Ag and 109Ag nuclei is usually
observed only at 208 K. The phosphorus ligand exchange
rates are sensibly lower in the tricyclohexylphosphine com-
plexes 9 and 10 where the splitting due to 107Ag and 109Ag
nuclei is also observed at room temperature. The observation
of 1J(107,109Ag–31P) at room temperature has been reported
previously for complexes containing chelating or strongly
sterically hindered phosphine ligands, as is also the case in
In the spectra of derivatives 1–6 and 10 the ν2, ν3 and ν4 modes
of vibration of ionic NO3Ϫ groups (D3h symmetry) and a unique
ν1 ϩ ν4 combination band in the overtones region 1700–1800
cmϪ1 have been detected throughout in accordance with their
ionic structure.17 In the spectra of complexes 7 and 8 the separ-
ation between ν1 and ν4 is ca. 60 cmϪ1, in accordance with a
bidentate nitrato group.17 However, in the spectrum of 9 three
combination ν1 ϩ ν4 bands with a separation of ca. 20 cmϪ1
were found, in accordance with a unidentate nitrato ligand.17
1
this work.22 The J(107,109Ag–31P) coupling constants for 9 and
10 are significantly greater than those for analogous Ph3P
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compounds, presumably in consequence of the high base
strength of Cy3P.
being devoid of crystallographic symmetry, the cation
approximates closely to 2 symmetry. This determination is of
modest precision and a study of its 2-Me-im counterpart, which
offered better quality material, was undertaken.
The 1J(107,109Ag–31P) coupling constant values observed in
this study generally correlate well with the relationship between
this parameter and the molecular structure (Ag–P distances),
as has previously been found for other silver/phosphine
systems.23,24 They provide a useful guide to the hybridization of
the silver atom and hence to its solution co-ordination number:
for example the 1J(Ag–31P) coupling constant value of 6 is 642
Hz correspond to sp silver hybridization in association with
[Ag(PPh3)2(2-Me-im)2]NO3 3. One half of the formula unit
now comprises the asymmetric unit, achieved via the dis-
position of the silver atom on a crystallographic 2 axis which
relates pairs of each of the ligands, and the nitrate as disordered
about an inversion centre. Perhaps because of packing con-
straints introduced with the imidazole methyl substituents, the
geometries of the cations of 2 and 3 differ appreciably, in a
manner clearly perceptible in Fig. 1 and Table 1. While the P–
Ag–P and N–Ag–N angles differ little between the two com-
plexes, considerable disparities are found in N–Ag–P, range
104.3(4)–115.1(4)Њ in 2, 98.15(5) and 119.33(5)Њ in 3, reflecting a
twist in the relative disposition of the AgN2 and AgP2 planes
about the (putative) 2 axis, these being almost normal in 2, and
considerably skewed in 3; remarkably, both (〈)Ag–P(〉) and
(〈)Ag–N(〉) are longer in 3. Again, close imidazole H(3) ؒ ؒ ؒ O
(anion) interactions are evident, in 2 for ligand a only
(O(1) ؒ ؒ ؒ H(3a) (1 Ϫ x, 1 Ϫ y, 1 Ϫ z) 1.86 Å) and in 3 bifur-
cating (H(3) ؒ ؒ ؒ O(1) (1 Ϫ x, y, ¹ Ϫ z), O(3) (x Ϫ ¹, ¹ Ϫ y, z Ϫ ¹)
1
a co-ordination number of 2, whereas J(Ag–31P) of 1 is 297
Hz, corresponding to sp2 hybridization and co-ordination
number 3.
Surprisingly, two different signals have been found in the low
temperature 31P NMR spectrum of complex 20, suggesting
disproportionation or the existence of two isomers. The last
hypothesis is consistent with the results of the crystallographic
studies (see below).
Crystallographic studies
The present array of single crystal structure determinations
defines the nature of a variety of complexes encompassing the
majority of accessible stoichiometries of mixed triphenyl-
phosphine/imidazole base arrays about a silver() central atom,
the oxyanion counter ions being less competitive in respect of
co-ordinating capacity vis-à-vis the unidentate pnictide bases.
In the present work, no attempt has been made to introduce
control of stoichiometry or stereochemistry by systematic
variation of pnictide base steric or electronic parameters
beyond that of the parent base, such substituents as are found
in the present imidazole bases being introduced for the purpose
of accessing a spectrum of complexes readily amenable to con-
genial crystallization, within the desired range of types. We note
at the outset for the purposes of comparison that the prevailing
co-ordination number of the silver atoms throughout the
present array is (at least) four; the baseline [Ag(PPh3)4]ϩ array is
well defined25 and of putative 32 (T ) symmetry, perhaps
perturbed by distortions suggestive of overcrowding among the
phenyl rings, Ag–P being 3 × 2.668(2) Å plus 2.650(2) Å in, e.g.,
the perchlorate, the mean value (2.66 Å), perhaps slightly exces-
sively long vis-à-vis that expected for an unstrained system, but
with the difference here in the silver complex greatly diminished
relative to that in the isomorphous copper() counterpart
(2.524(6), 2.605(11) Å)26 suggesting that associated residual
strain in the former may not be large. We now discuss the com-
pounds individually, the silver atom environments and other
significant/relevant geometries being recorded in Table 1.
¯
²
¯ ¯
² ²
¯
²
1.95, 1.89 Å). All co-ordinated bond distances are shorter
here than in 1, Ag–P very appreciably (with concomitant
enlargement of P–Ag–P), and Ag–N marginally so. The other
possible Ag/P/N stoichiometry within the bound of a four-
co-ordinate metal environment, PAgN3, is represented by com-
plex 11.
[Ag(PPh3)(2-Me-im)3][CF3CO2] 11. One formula unit,
devoid of crystallographic symmetry, comprises the asymmetric
unit of the structure. Here, relative to [Ag(PPh3)4]ϩ, 1, 2 and 3,
Ag–P is further shortened, almost linearly, with 〈Ag–N〉 little
changed; indeed 〈N–Ag–N〉 also is little changed down the
array. The molecule, in projection down its axis, exhibits quasi-3
symmetry broken primarily by the dispositions of the methyl
substituents, two of which might be considered ‘endo’ and one
‘exo’, vis-à-vis the silver, the variation seemingly having little
effect on other molecular parameters, and suggesting that,
at least in this array, their steric effect, if any, is of little
consequence. The bonding parameters may be compared with
those in [(py)3Ag(Ph2P(CH2)2PPh2)Ag(py)3][ClO4]2,28 wherein
Ag–P 2.375(1) Å is closely comparable with the present, Ag–N
(range 2.304(3)–2.444(4), average 2.38 Å) being rather longer,
and more variable, as are the ‘equivalent’ P–Ag–N angles
(110.6(1)–134.46(9)Њ), perhaps in response to the asymmetry in
the substitution about the phosphorus.
In the above, the role of the oxyanion counter ion is
co-ordinatively passive. With reduction in the metal: total
unidentate Group 15 base stoichiometry, (implicitly four-)
co-ordination saturation is maintained by entry of the oxy-
anion into the co-ordination sphere. For total metal: base
stoichiometry of 1:3, two arrays P2NAg and PN2Ag (oxyanion)
are available. The first of these has been found structurally
accessible in complex 8.
[Ag(PPh3)3(4-Ph-im)]NO3 1. This complex crystallizes with
one formula unit devoid of crystallographic symmetry com-
prising the asymmetric unit of the structure. 〈Ag–P〉, 2.54 Å, is
diminished relative to the value found in [Ag(PPh3)4]ϩ (see
above) but comparable with numerous values established
in other [Ag(PPh3)3X] arrays,27 as also is the array of angles
about the silver atom. There appear to be no other [Ag-
(PPh3)3(unidentate N-base)] arrays structurally characterized
which might offer counterpart comparators in that dimension.
The silver atom lies well out of the imidazole plane, with an
associated asymmetry in the two Ag–N–C angles, possibly
electronic in origin, because of the persistence of such asym-
metry throughout most of the present array of structures,
also suggestive of the possibility of steric crowding or lattice
forces, in particular here the hydrogen contact H(3a) ؒ ؒ ؒ O(1)
(1.87 Å). The major component of the disordered phenyl ring is
quasi-coplanar with the parent imidazole ring (dihedral angle
9.5(3)Њ).
[Ag(PPh3)2(2-Me-im)(O2NO)] 8. Unlike the above, which are
all ionic, in this complex a neutral molecular array, one mol-
ecule devoid of crystallographic symmetry, comprises the
asymmetric unit of the structure. The nitrate interacts with the
silver as an essentially symmetrical chelate of small ‘bite’,
essentially coplanar with the silver despite Ag–O being long.
Despite the latter, the oxygen interactions clearly impact on
the silver environment, the P2AgN array being well removed
from planarity, although the quasi-right angles among the
O–Ag–P,N angles strongly suggest the approach to constitute a
perturbation on a proto-planar P2AgN array. Ag–N (im) is now
the shortest such distance observed, while Ag–P are lengthened
to values comparable to those found in the other AgP2 arrays
above, with a correspondingly large P–Ag–P angle.
[Ag(PPh3)2(Him)2]NO3 2. This complex crystallizes with one
formula unit as the asymmetric unit of the structure. Despite
J. Chem. Soc., Dalton Trans., 1999, 4047–4055
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Fig. 1 Molecular projections of the structurally characterized species; 20% thermal ellipsoids are shown for the non-hydrogen atoms, hydrogen
atoms having arbitrary radii of 0.1 Å. For 21 the upper figure shows major solid and minor core components superimposed; in the lower figure the
minor component has been isolated.
As yet we do not have a structurally characterized represent-
ative of Ag (oxyanion):P:N2 stoichiometry. Further reduc-
tion in metal salt:base stoichiometry leads to 1:1:1 Ag
oxyanion:PPh3 :im-base arrays, with an implication of more
intimate oxyanion involvement with the silver atom if co-
ordination saturation is to be maintained, achievable by
increase in anion denticity or by bridging. The two examples
structurally characterized are binuclear, involving centro-
symmetric arrays with diversely bridging oxyanions; one O,OЈ
bridging, entailing eight-membered central ring formation, 20,
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J. Chem. Soc., Dalton Trans., 1999, 4047–4055

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Table 1 Silver atom environments. r/Å is the silver–ligand atom distance, the other entries in the matrices being the angles (Њ) subtended at the silver
by the relevant atoms at the head of the row and end column
(a) [Ag(PPh3)3(4-Ph-im)]NO3 1
(d) [Ag(PPh3)(2-Me-im)3][CF3CO2] 11
Atom
r
P(2)
P(3)
N(1a)
Atom
r
N(1a)
N(1b)
N(1c)
P(1)
P(2)
P(3)
N(1a)
2.521(1)
2.554(1)
2.555(2)
2.369(4)
112.11(5)
113.78(5)
114.96(4)
111.2(1)
106.9(1)
96.6(1)
P(1)
2.376(2)
2.330(9)
2.321(5)
2.336(5)
115.9(2)
123.5(1)
92.7(2)
120.6(2)
105.0(2)
93.9(2)
N(1a)
N(1b)
N(1c)
In the anion, N–O (1–3) are 1.231(6), 1.222(7), 1.222(7) Å, with
opposite angles of 123.4(5), 116.8(5), 119.8(5)Њ. Ag–N(1a)–C(2,5a) are
135.6(3), 119.0(3), Ag–P–C range from 110.9(1) to 117.5(2), with C–P–
C 101.6(2)–104.7(2)Њ. The silver atom lies 0.301(9) Å out of the C3N2
plane of the Him ligand, H(3a) contacting O(1) of the anion at 1.87 Å.
Anion geometries are imprecise in consequence of high “thermal
motion”. Ag–N(1a–c)–C(2a–c) are 136.6(5), 126.2(5), 131.1(6)Њ and
Ag–N(1a–c)–C(5a–c) 119.4(6), 127.4(5), 122.3(5)Њ, with Ag 0.14(2),
0.49(1), 0.09(2) Å out of the C3N2 planes of the three ligands. Ag–P–C
range between 113.2(2) and 116.3(2)Њ and C–P–C 103.5(4)–104.1(3)Њ.
(e) [{Ag(PPh3)(1-Me-im)(OSOCH3O)}2] 20; * denotes a centrosym-
metrically related atom here and for 21 in (f)
(b) [Ag(PPh3)2B2]NO3 (B = Him 2 or 2-Me-im); values for the 2-Me-im
adduct are given italicized below those for the Him counterpart
Atom
r
N(1a)
O(1)
O(2*)
Atom
r
P(2)
N(1a)
N(1b)
P(1)
N(1a)
O(1)
2.3362(6)
2.189(1)
2.480(2)
2.666(2)
144.28(6)
118.55(4)
85.88(6)
96.08(4)
103.28(5)
103.50(6)
P(1)
2.428(4)
2.4704(6)
2.458(5)
(2.4704(6))
2.26(2)
2.348(2)
2.34(2)
(2.348(2))
125.1(1)
125.96(3)
115.1(4)
98.15(5)
104.3(4)
119.33(5)
106.7(3)
(119.33(5))
106.7(4)
(98.15(5))
94.4(6)
P(2)
O(2*)
N(1a)
N(1b)
S–O(1,2,3),C are 1.463(2), 1.457(2), 1.448(1), 1.762(2) Å; C–S–O(1–3)
are 105.6(1), 106.16(9), 107.49(9)Њ, O–S–O ranging from 111.62(9) to
113.1(1)Њ. Ag–O(1,2*)–S(*) are 121.48(8), 131.71(9)Њ. Ag–N(1a)–
C(2,5a) are 127.5(1), 125.6(1)Њ. Ag–P(1)–C(111–113) are 110.14(5),
121.89(7), 112.36(6)Њ, with C–P–C 103.24(9)–103.8(1)Њ. The silver atom
lies 0.370(3) Å out of the imidazole plane.
91.94(7)
Anion geometries are relatively imprecise/disordered. Ag–N(1a,b)–
C(2a,b) are 132(1), 137(1)Њ with Ag–N(1a,b)–C(5a,b) 123(1), 118(2)Њ
for complex 2, Ag–N(1a)–C(2,5a) being 129.2(2), 119.2(2)Њ for 3;
Ag lies 0.70(4), 0.33(4) Å out of the C3N2 planes in 2 and 0.875(4) Å
in that of 3. In the phosphine ligands of 2, Ag–P–C range between
108.1(5) and 116.3(6)Њ and C–P–C between 102.9(8) and 107.6(7)Њ;
in 3 the counterpart ranges are 111.60(7)–116.49(8) and 103.4(1)–
104.6(1)Њ.
(f) [{Ag(PPh3)(Him)(O2N)}2] 21; values for [{Ag(PPh3)(Him)(ONO)}2]
are given italicized below those of the major component
Atom
r
N(1a)
O(1)
O(1*)
O(2)
P(1)
2.369(1)
2.369(4)
2.223(3)
2.365(7)
2.412(4)
2.739(6)
2.571(5)
2.082(8)
129.41(9)
122.6(3)
124.0(1)
111.3(2)
105.7(1)
92.6(2)
106.8(1)
128.8(3)
94.9(1)
107.1(2)
73.2(1)
113.39(9)
—
93.6(1)
—
46.0(1)
—
118.5(1)
—
(c) [Ag(PPh3)2(2-Me-im)(O2NO)] 8
N(1a)
O(1)
Atom
r
P(2)
N(1a)
O(1)
O(2)
80.8(3)
125.4(3)
96.7(3)
42.4(4)
75.6(2)
P(1)
P(2)
N(1a)
O(1)
O(2)
2.447(3)
2.461(3)
2.311(7)
2.75(1)
129.48(9)
113.6(3)
105.6(3)
122.2(3)
88.9(3)
87.8(4)
O(1*)
O(2)
2.692(3)
Ag ؒ ؒ ؒ AgЈ is 0.733(6)
2.86(1)
Ag(1) lies 0.02(2) Å out of the NO2 (as chelate) plane; that plane has a
dihedral angle of 48.1(2)Њ to the central (obligate) Ag2O(1)2 plane.
Ag(1,1Ј) lie 0.169(7)–0.08(1) Å out of the C3N2 ligand plane. Ag,AgЈ–
N(1a)–C(2a) are 124.6(3), 113.3(3)Њ; Ag,AgЈ–P–C range between
108.8(1) and 116.2(1), 100.2(2) and 123.5(2)Њ, C–P–C between 104.8(2)
and 105.2(1)Њ.
N–O(1,2,3) are 1.14(2), 1.22(2), 1.23(1) Å with opposite angles 116(1),
126(1), 119(1)Њ, Ag lying 0.13(2) Å out of the NO3 plane, 0.04(2) Å out
of the ligand plane, with Ag–N(1a)–C(2,5a) being 128.1(8), 124.8(7)Њ.
Ag–P–C range between 109.2(4) and 119.0(4), C–P–C between 101.9(5)
and 105.9(5)Њ.
and the other O bridging, entailing a four-membered obligate
planar system, 21.
ordination is observed, Ag–N,P both short and subtending a
large P–N–Ag angle; indeed the interactions of the sulfonate
ligands may be regarded as perturbations on the novel linear
P–Ag–N archetype.
[{Ag(PPh3)(1-Me-im)(OSOCH3O)}2] 20. One half of the
binuclear array (= one AgX:PPh3 :im base (1:1:1) formula
unit) comprises the asymmetric unit of the structure, the dimer
being disposed about a crystallographic inversion centre, the
central eight-membered ring presumably associated with a
lower degree of strain than that of the four-membered Ag-
(µ-O)2Ag array described below for 21, with O–Ag–O being
103.50(6)Њ, a considerably larger effective ‘bite’ than that of the
compact bidentate ligand imposed by that four-membered ring
or the four-membered ring in 8 above; Ag–O are shorter than
the values found in the monomer 8, but not the dimer 21, with
which they are comparable. With two Group 15 base donors
only now in the co-ordination sphere, these being stronger bases
than the oxyanions, a pronounced tendency toward two-co-
[{Ag(PPh3)(Him)(ONO)}2] 21. One half of the dimeric array,
also a 1:1:1 formula unit, comprises the asymmetric unit of the
structure. Disorder is observed, deconvolutable into major and
minor binuclear isomeric components in approximately 10:1
ratio. In both isomers O(1) of the nitrate group bridges the two
silver atoms; in the major isomer, O(2) together with O(1) of
the same anion chelates the silver atom, the NO2/Ag(µ-O)2Ag
interplanar-dihedral angle being 48.1(2)Њ. The other, minor,
dimeric isomer is obtained in association with resolvable
disordered components of Ag and O(2), AgЈ and O(2Ј), con-
strained to the same site occupancy after trial refinement,
wherein the nitrite has swivelled about O(1)–N so that O(2Ј)
J. Chem. Soc., Dalton Trans., 1999, 4047–4055
4051

View Article Online
now lies away from the previously chelated silver. (Presumably
other components of the structure also move in concert with
this change, but to a smaller extent, so that their components
are not resolvable.) The two isomers are thus presumed to be of
the form below with, possibly, a third in which mixtures of the
two nitrite types are incorporated in the one dimer. The geom-
etries of the two centrosymmetric forms are given in Table 1;
O(2Ј) appears to be unfavourably situated to act as a chelating
component to the alternative centrosymmetrically related AgЈ
component, O(2Ј) ؒ ؒ ؒ Ag (1 Ϫ x, 1 Ϫ y, 1 Ϫ z) being 2.98(3) Å.
(br), 467m (Cy). Calc. for C36H99AgNO3P2: C, 59.2; H, 9.1; N,
1.9. Found: C, 59.6; H, 9.5; N, 2.1%.
[Ag(PPh3)4][CF3CO2]ؒH2O. This compound was obtained
similarly to [Ag(PPh3)4]NO3 by using Ph3P (10.492 g, 40 mmol)
and AgCF3CO2 (2.2 g, 10 mmol) (88% yield), mp 214–217 ЊC.
1H NMR (CDCl3, 293 K): δ 7.3 (m br, 60 H, C6H5). 31P NMR
(CDCl3): (293 K) δ 3.4 (br), (223 K) δ 5.6 (d) (1J(Ag,31P) = 239
Hz). IR (Nujol, cmϪ1): 3300 (br) (H2O), 1645m (H2O), 1684s,
1435m (CF3COO), 511s, 495s (br), 432m (Ph). Calc. for
C74H62AgF3O3P4: C, 69.0; H, 4.9. Found: C, 68.9; H, 5.2%.
[Ag(PPh3)4]ClO4. This compound, previously described,27,30
was obtained similarly to [Ag(PPh3)4]NO3 by using Ph3P (5.246
g, 20 mmol) and AgClO4 (1.035 g, 5 mmol) (84% yield), mp
266–270 ЊC. 1H NMR (CDCl3, 293 K): δ 7.3 (m br, 60 H, C6H5).
31P NMR (CDCl3): (293 K) δ 4.0s (br), (223 K) δ 5.7 (d)
(1J(Ag,31P) = 238 Hz). IR (Nujol, cmϪ1): 1088s (br), 1024m,
998m (ClO4), 514s, 498s, 437m, 427m (Ph). Calc. for
C72H60AgClO4P4: C, 68.8; H, 4.8. Found: C, 68.4; H, 5.1%.
[Ag(PPh3)4]BF4. This compound was obtained similarly to
[Ag(PPh3)4]NO3 by using PPh3 (10.48 g, 40 mmol) and AgBF4
(1.94 g, 10 mmol) (92% yield), mp 294–297 ЊC. 1H NMR
(CDCl3, 293 K): δ 7.3–7.5 (m br, 60 H, C6H5). 31P NMR
(CDCl3): (293 K) δ 7.3 (br), (223 K) δ 5.6 (dd) (1J(Ag,31P) = 238
Hz). IR (Nujol, cmϪ1): 1053s, 541m (BF4), 512s, 499s, 437m,
426m (Ph). Calc. for C72H60AgBF4P4: C, 69.5; H, 4.9. Found:
C, 69.2; H, 5.2%.
Experimental
General procedures
All reactions were carried out under an atmosphere of dry
oxygen-free dinitrogen, using standard Schlenk techniques.
Solvents were freshly distilled over an appropriate drying agent
and further degassed before use where necessary. In some cases
the reactions were protected from light by covering reaction
vessels with aluminium foil. Concentration was always carried
out in vacuo (water aspirator). The samples for microanalysis
were dried in vacuo to constant weight (20 ЊC, ca. 0.1 Torr).
Elemental analyses (C,H,N) were performed in house with a
Carlo-Erba model 1106 instrument. The IR spectra were
recorded from 4000 to 100 cmϪ1 with a Perkin-Elmer System
2000 FT-IR instrument, 1H, 13C and 31P spectra on a VXR-300
Varian spectrometer operating at room temperature (300 MHz
for 1H, 75 MHz for 13C and 121.4 MHz for 31P). The electrical
resistance of acetone solutions was measured with a Crison
CDTM 522 conductimeter at room temperature. The osmo-
metric measurements were carried out at 40 ЊC over a range of
concentrations with a Knauer KNA0280 vapour pressure
osmometer calibrated with benzil. The solvent was Baker
Analyzed Spectrophotometric grade chloroform. The results
were reproducible to 2%.
[Ag(PPh3)(O2N)]. Silver() nitrite (1.54 g, 10 mmol) was
added to a warm ethanol solution (100 ml) of Ph3P (2.62 g, 10
mmol). After 24 h the warm clear solution was allowed to cool
slowly in the dark to give well formed crystals of [Ag-
1
(PPh3)(O2N)] (2.08 g, 50% yield), mp 156–157 ЊC. H NMR
(CDCl3, 293 K): δ 7.26–7.50 (m br, 15 H, C6H5). 31P NMR
(CDCl3): (293 K)
δ 12.2s (br), (203 K) δ 15.8 (dd)
1
(1J(109Ag,31P) = 768, J(107Ag,31P) = 666 Hz). IR (Nujol, cmϪ1):
3060w (CH), 1308m, 1204m, 838m (NO3), 522s, 500s, 488s,
436m (Ph). Calc. for C18H15AgNO2P: C, 51.9; H, 3.6; N, 3.4.
Found: C, 52.0; H, 3.8; N, 3.4%.
[Ag(PPh3)(SO3CH3)]ؒH2O. Silver() methanesulfonate (2.02
g, 10 mmol) was added to a warm ethanol solution (100 ml) of
Ph3P (2.62 g, 10 mmol). After 24 h the warm clear solution was
allowed to cool slowly in the dark to give well formed crystals
of [Ag(PPh3)(OS3CH3)]ؒH2O (4.35 g, 90% yield), mp 199–
1
203 ЊC. H NMR (CDCl3, 293 K): δ 1.3 (br, 2 H, H2O), 2.87
(s, 3 H, CH3), 7.25–7.55 (m br, 15 H, C6H5). 31P NMR (CDCl3):
(293 K) δ 14.9 (br), (218 K) δ 15.3 (dd, br) (1J(Ag,31P) = 718
Hz). IR (Nujol, cmϪ1): 3155w, 3125w (CH), 2650–2350 (br)
(OH), 1198m, 1168m, 1149m (SO3), 515s, 501s, 440 (sh), 432m,
436m (Ph). Calc. for C19H20AgO4PS: C, 47.2; H, 4.2; S, 6.6.
Found: C, 47.3; H, 4.4; N, 6.8%.
Synthesis of complexes
[Ag(PPh3)4]NO3. This compound, well described in the liter-
ature,24 can be prepared also by the following procedure:
silver() nitrate (1.698 g, 10 mmol) was added to a warm ethanol
solution (100 ml) of Ph3P (10.492 g, 40 mmol). After 2 h the
warm clear solution was allowed to cool slowly in the dark to
give well formed crystals of [Ag(PPh3)4]NO3 (10.12 g, 83%
[Ag(PPh3)3(4-Ph-im)]NO3 1. 4-Phenylimidazole (0.144 g, 1.0
mmol) was added to a diethyl ether suspension (100 ml) of
[Ag(PPh3)4]NO3 (1.219 g, 1.0 mmol). After 72 h stirring, the
solid was filtered off and washed with diethyl ether, affording
compound 1, which was recrystallized from CHCl3–Et2O (3:1)
(50% yield), mp 170–173 ЊC (decomp.) 1H NMR (CDCl3,
293 K): δ 3.5 (br, 1 H, NH), 7.2–7.5 (m br, 49 H, C6H5 and
5-CH), 7.7 (d, 2 H, C6H5) and 7.8 (s, 1 H, 2-CH). 31P NMR
(CDCl3): (293 K) δ 6.12, (223 K) δ 6.16 (1J(Ag,31P) = 297 Hz).
IR (Nujol, cmϪ1): 3400–3100 (br) (NH), 1960 (br), 1900 (br),
1830 (br), 1740w, 1434s, 833s, 694s (NO3), 1585w, 1560m
1
yield), mp 218–220 ЊC. H NMR (CDCl3, 293 K): δ 7.20–7.5
(m br, 60 H, C6H5). 31P NMR (CDCl3): (293 K) δ 4.0s (br),
(223 K) δ 5.7 d (1J(Ag,31P) = 238 Hz). IR (Nujol, cmϪ1): 3046w
(CH), 1970m, 1891m, 1814m, 1774m, 1340 (sh), 830m (NO3),
512s, 499s, 437m, 428w (Ph). Calc. for C72H60AgNO3P4: C, 70.9;
H, 5.0; N, 1.1. Found: C, 70.4; H, 5.1; N, 1.1%.
[Ag(PCy3)2(O2NO)]. This compound, previously described,29
was obtained similarly to [Ag(PPh3)4]NO3 by using Cy3P (5.0 g,
17.8 mmol) and AgNO3 (0.76 g, 4.6 mmol) (93% yield),
1
ؒ ؒ ؒ
ؒ ؒ ؒ
mp 234–235 ЊC. H NMR (CDCl3, 293 K): δ 1.2–1.8 (m br,
(C C and C N), 515s, 503s, 491s, 441m, 429m, 419m (Ph).
᎐᎐ ᎐᎐
66 H, C6H11). 31P NMR (CDCl3, 293 K): δ 32.4 (dd)
Calc. for C63H53AgN3O3P3: C, 68.7; H, 4.8; N, 3.8. Found: C,
68.2; H, 5.0; N, 3.6%. Λm (CH2Cl2, c = 0.9 M) 0.2 ΩϪ1 mol2
cmϪ1. M (CHCl3) (c = 1 × 10Ϫ2 m) 682, (c = 0.7 × 10Ϫ2 m) 583.
(1J(109Ag,31P) = 527, J(107Ag,31P) = 456 Hz). IR (Nujol, cmϪ1):
1
1749w, 1738w, 1734w, 1294s (br), 752m, 734m, 704w (NO3), 512
4052
J. Chem. Soc., Dalton Trans., 1999, 4047–4055

View Article Online
[Ag(PPh3)2(Him)2]NO3 2. Imidazole (Him) (0.0136 g, 2.0
mmol) was added to a diethyl ether suspension (100 ml) of
[Ag(PPh3)4]NO3 (1.219 g, 1 mmol). After 48 h stirring the solid
was filtered off and washed with diethyl ether, affording com-
pound 2 (0.774 g, 93% yield), which was recrystallized from
CHCl3–Et2O (4:1), mp 178–182 ЊC. 1H NMR (CDCl3, 293 K):
δ 4.4 (br, 2 H, NH), 6.90 (br, 4 H, 4- and 5-CH), 7.3–7.5 (m br,
32 H, C6H5 and 2-CH). 31P NMR (CDCl3): (293 K) δ 9.55,
(223 K) δ 6.03 (dd) (1J(Ag,31P) = 339 Hz). IR (Nujol, cmϪ1):
3455 (br) (NH), 1774w, 1437m, 841m, 694s (NO3), 1580 (br),
[{Ag(PPh3)(1-Me-im)(O2SOCH3)}2] 20. Derivative 20 was
obtained similarly to 1 by using 1 mmol of [Ag(PPh3)-
(O2SOCH3)] and 1 mmol of 1-Me-im, and recrystallized from
1
CHCl3–Et2O (3:2) (73% yield), mp 121–124 ЊC (decomp.). H
NMR (CDCl3, 293 K): δ 2.62 (s, 3 H, SO3CH3), 3.74 (s, 3 H,
1-CH3), 6.92, 7.07 (2s, 2 H, 4- and 5-CH), 7.41 (s, 1 H, 2-CH),
7.4–7.6 (m, 15 H, C6H5). 31P NMR (CDCl3): (293 K) δ 12.1 (br),
(223 K) δ 14.05 (dd) (1J(109Ag,31P) = 740, 1J(107Ag,31P) = 641
Hz). IR (Nujol, cmϪ1): 3120w (CH), 1188s, 1170s (SO3), 520s,
498s, 437w (Ph). Calc. for C23H24AgN2O3PS: C, 48.9; H, 4.6; N,
5.0; S, 5.7. Found: C, 48.9; H, 4.5; N, 5.3; S, 5.9%. Λm (CH2Cl2,
ؒ ؒ ؒ
ؒ ؒ ؒ
1550w (C C and C N), 515m, 505m, 492s, 442m, 421m (Ph),
᎐᎐ ᎐᎐
280w, 247w, 226w and 205w. Calc. for C42H38AgN5O3P2: C,
60.7; H, 4.6; N, 8.4%. Found: C, 60.9; H, 5.0; N, 8.2%. Λm
(CH2Cl2, c = 1.2 M) 14.8 ΩϪ1 mol2 cmϪ1. M (CHCl3) (c =
1 × 10Ϫ2 m) 471, (c = 0.7 × 10Ϫ2 m) 383.
c = 1.0 M) 3.4 ΩϪ1 mol2 cmϪ1
.
[{Ag(PPh3)(Him)(ꢀ-O2N)}2] 21. Derivative 21 was obtained
similarly to 1 by using 1 mmol of [{Ag(PPh3)(O2N)}2] and 1
mmol of Him, and recrystallized from CHCl3–Et2O (3:2) (75%
1
yield), mp 138–141 ЊC (decomp.). H NMR (CDCl3, 293 K):
[Ag(PPh3)2(2-Me-im)2]NO3 3. Derivative 3 was obtained
similarly to 2 and recrystallized from CHCl3–Et2O (2:1) (90%
δ 6.99 (s, 1 H, 4- and 5-CH), 7.62 (s, 2 H, 2-CH), 9.0 (s br, 1 H,
NH), 7.3–7.5 (m, 15 H, C6H5), 31P NMR (CDCl3): (293 K)
δ 12.9 (br), (201 K) δ 9.0 (dd) (1J(109Ag,31P) = 480, 1J(107Ag,31P) =
416) and 12.6 (dd) (1J(109Ag,31P) = 692, 1J(107Ag,31P) = 599 Hz).
IR (Nujol, cmϪ1): 3100 (br) (NH), 1331m, 1305m, 1199w, 823m
(NO2), 516s, 494s, 433s (Ph). Calc. for C21H19AgN3O2P: C, 51.8;
H, 4.1; N, 9.0. Found: C, 52.1; H, 3.9; N, 8.7%. Λm (CH2Cl2,
1
yield), mp 167–174 ЊC (decomp.). H NMR (CDCl3, 293 K):
δ 2.35 (s, 6 H, 2-CH3), 4.5 (br, 2 H, NH), 6.92 (br, 4 H, 4- and
5-CH), 7.3–7.5 (m br, 30 H, C6H5). 31P NMR (CDCl3, 293 K):
δ 9.83. IR (Nujol, cmϪ1): 3160 (br) (NH), 1962 (br), 1890 (br),
1831 (br), 1812w, 1770w, 1433 (sh), 848m, 692s (NO3), 1585w,
ؒ ؒ ؒ
ؒ ؒ ؒ
1565m (C C and C N), 512 (sh), 508s, 490s, 428m, 419m
᎐᎐ ᎐᎐
c = 1.0 M) 0.2 ΩϪ1 mol2 cmϪ1
.
(Ph). Calc. for C44H42AgN5O3P2: C, 61.6; H, 4.9; N, 8.2. Found:
C, 61.4; H, 5.0; N, 7.8%. Λm (CH2Cl2, c = 1.1 M) 15.0 ΩϪ1 mol2
cmϪ1. M (CHCl3) (c = 1.1 × 10Ϫ2 m) 511, (c = 0.7 × 10Ϫ2 m)
480.
The synthesis and spectroscopic characterization of com-
pounds 4–7, 9, 10, 12–19, and 22–24 are available as SUP
57652.
Structure determinations (general procedure, with individual
variations noted)
[Ag(PPh3)(1-Me-im)3]NO3 6. Derivative 6 was obtained
similarly to 2 and recrystallized from CHCl3–Et2O (3:1) (89%
yield), mp 88–90 ЊC (decomp.). 1H NMR (CDCl3, 293 K): δ 3.74
(s, 9 H, 1-CH3), 6.94 (s, 3 H, 4- or 5-CH), 7.08 (s, 3 H, 4- or
Unique room-temperature four-circle/single counter dif-
fractometer data sets were measured (2θ–θ scan mode, 2θmax as
specified; monochromatic Mo-Kα radiation, λ = 0.71073 Å;
T ca. 295 K) on fibre mounted specimens, yielding N independ-
ent reflections, No with I > 3σ(I) being considered ‘observed’
and used in the full matrix least squares refinement after gaus-
sian absorption correction. Anisotropic thermal parameters
were refined for the non-hydrogen atoms, (x, y, z, Uiso)H being
constrained at estimated values; the unco-ordinated nitrogen
atoms of the unsubstituted imidazole ligands were assigned
from refinement behaviour and geometrical considerations.
Conventional R, RЈ(statistical weights) at convergence are
quoted. Neutral atom complex scattering factors were used,
within the XTAL 3.4 program system.31
5-CH), 7.3–7.5 (m br, 15 H, C6H5) and 7.74 (s, 3 H, 2-CH). 31
P
NMR (CDCl3): (293 K) δ 13.2, (218 K) δ 12.6 (d br)
(1J(Ag,31P) = 642 Hz). IR (Nujol, cmϪ1): 3117w (CH), 1870 (br),
1836 (br), 1812w, 1770w, 1744w 1436m, 828m, 697s (NO3),
ؒ ؒ ؒ
ؒ ؒ ؒ
1521m, 1510w (C C and C N), 511m, 504m, 442m, 431m
᎐᎐ ᎐᎐
(Ph). Calc. for C30H31AgN7O3P: C, 53.3; H, 4.6; N, 14.5. Found:
C, 53.6; H, 4.8; N, 14.3%. Λm (CH2Cl2, c = 1.0 M) 16.1 ΩϪ1 mol2
cmϪ1
.
[Ag(PPh3)2(2-Me-im)(ONO2)] 8. Derivative 8 was obtained
similarly to 3 by using 1 mol of [Ag(PPh3)4]NO3 (1.219 g) and
1 mol of 2-Me-im. After 36 h stirring the solid was filtered off
and washed with diethyl ether, affording compound 8, which
was recrystallized from CHCl3–Et2O (2:1) (85% yield), mp
Crystal/refinement data. [Ag(PPh3)3(4-Ph-im)]NO3 1.
1
1
>200 ЊC (decomp.). H NMR (CDCl3, 293 K): δ 2.15 (s, 3 H,
¯
C63H53AgN3O3P3, M = 1101.0, triclinic, space group P1 (Ci ,
2-CH3), 6.77 (s, 4 H, 4- and 5-CH), 7.1–7.4 (m br, 30 H, C6H5).
31P NMR (CDCl3): (293 K) δ 7.98, (218 K) δ 6.51 (d, br)
(1J(Ag,31P) = 361 Hz) and 6.69 s (br). IR (Nujol, cmϪ1): 3000–
2700 (br) (NH), 1433 (sh), 1340s, 1278s, 850m, 825s, 692s
no. 2), a = 15.805(4), b = 13.353(3), c = 13.251(2) Å, α =
83.32(2), β = 83.92(2), γ = 87.91(2)Њ, V = 2761 Å3, Dc (Z = 2) =
1.324 g cmϪ3, F(000) = 1136, µMo = 5.0 cmϪ1, specimen 0.12 ×
0.42 × 0.34 mm, A*min,max = 1.06, 1.18, 2θmax = 50Њ, N = 9673,
No = 6504, R = 0.048, RЈ = 0.046, nν = 676, |∆ρmax| = 0.53 e ÅϪ3
.
ؒ ؒ ؒ
ؒ ؒ ؒ
(NO ), 1584w, 1565m (C C and C N), 512 (sh), 505s, 490s,
᎐᎐ ᎐᎐
3
436m, 428m, 419m (Ph), 367m, 277m. Calc. for C40H36-
AgN3O3P2: C, 61.9; H, 4.7; N, 5.4. Found: C, 62.1; H, 4.7; N,
The imidazole phenyl substituent was modelled as disordered
over two sets of sites, for which occupancies were set at 0.75,
0.25 after trial refinement (see Fig. 1).
5.2%. Λm (CH2Cl2, c = 1.0 M) 0.6 ΩϪ1 mol2 cmϪ1
.
[Ag(PPh3)(2-Me-im)3][CF3CO2] 11. Derivative 11 was
obtained similarly to 2 by treating 1 mmol of [Ag(PPh3)4]-
[CF3CO2] with 2 mmol of 2-Me-im, and recrystallized from
CHCl3–Et2O (2:1) (88% yield), mp 145–148 ЊC. 1H NMR
(CDCl3, 293 K): δ 2.31 (s, 9 H, 2-CH3), 6.86 (s, 6 H, 4- and
5-CH), 7.3–7.5 (m br, 15 H, C6H5) and 10.0 (br, 3 H, NH).
31P NMR (CDCl3): (293 K) δ 11.3 (br), (203 K) δ 4.4
(dd) (1J(109Ag,31P) = 391, 1J(107Ag,31P) = 342) and 11.6 (dd)
[Ag(PPh3)2(Him)2]NO3 2. C42H38AgN5O3P2, M = 830.6,
monoclinic, space group P21/c (C52h, no. 14), a = 12.947(7),
b = 15.034(2), c = 20.551(2) Å, β = 99.43(3)Њ, V = 3946 Å3,
Dc (Z = 4) = 1.398 g cmϪ3, F(000) = 1704, µMo = 6.4 cmϪ1
,
=
specimen 0.31 × 0.20 × 0.18 mm, Am* in,max = 1.11, 1.13, 2θmax
46Њ, N = 5482, No = 2281, R = 0.069, RЈ = 0.068, nν = 478,
|∆ρmax| = 0.95 e ÅϪ3
.
1
(1J(109Ag,31P) = 629, J(107Ag,31P) = 545 Hz). IR (Nujol, cmϪ1):
[Ag(PPh3)2(2-Me-im)2]NO3 3. C44H42AgN5O3P2, M = 858.7,
monoclinic, space group C2/c (C62h, no. 15), a = 21.888(4),
b = 9.895(3), c = 19.241(4) Å, β = 92.09(1)Њ, V = 4146 Å3, Dc
(Z = 4) = 1.369 g cmϪ3, F(000) = 1768, µMo = 6.1 cmϪ1, specimen
0.40 × 0.50 × 0.68 mm, A*min,max = 1.21, 1.28, 2θmax = 60Њ,
3300–3150 (br) (NH), 1679s, 1440s (CF3CO2), 520s, 502s, 494s,
434m, 422m (Ph), 272m, 180m and 172m. Calc. for C32H33-
AgF3N6O2P: C, 52.7; H, 4.6; N, 11.5. Found: C, 52.6; H, 4.2; N,
10.9%. Λm (CH2Cl2, c = 1.2 M) 5.3 ΩϪ1 mol2 cmϪ1
.
J. Chem. Soc., Dalton Trans., 1999, 4047–4055
4053

View Article Online
3 C. Pettinari, F. Marchetti, A. Cingolani and S. Bartolini,
N = 5932, No = 4981, R = 0.041, RЈ = 0.043, nν = 266, |∆ρmax| =
0.72 e ÅϪ3
The criterion for No was I > 2σ(I ). The nitrate ion was
modelled as disposed with the nitrogen located on a crystallo-
graphic inversion centre with an O3 array, occupancy 0.5,
disordered about it.
Polyhedron, 1996, 15, 1263; C. Pettinari, F. Marchetti, M. Pellei,
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C. Santini and M. Miliani, Polyhedron, 1998, 17, 561.
.
4 C. Pettinari, A. Lorenzotti, G. Sclavi, A. Cingolani, E. Rivarola,
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5 G. Gioia Lobbia, P. Cecchi, R. Spagna, M. Colapietro, A. Pifferi
and C. Pettinari, J. Organomet. Chem., 1995, 485, 53.
6 G. A. Ardizzoia, M. A. Angaroni, G. La Monica, F. Cariati,
M. Moret and N. Masciocchi, J. Chem. Soc., Chem. Commun., 1990,
1021; M. K. Ehlert, S. J. Rettig, A. Storr, R. C. Thompson and
J. Trotter, Can. J. Chem., 1990, 68, 1444; R. G. Raptis, H. H. Murray
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25; N. Masciocchi, M. Moret, P. Cariati, A. Sironi, G. A. Ardizzoia
and G. La Monica, J. Am. Chem. Soc., 1994, 116, 7668.
[Ag(PPh3)2(2-Me-im)(ONO2)] 8. C40H36AgN3O3P2, M =
776.6, monoclinic, space group P21/c, a = 13.684(1), b =
12.965(2), c = 23.464(3) Å, β = 116.461(8)Њ, V = 3727 Å3, Dc
(Z = 4) = 1.384 g cmϪ3, F(000) = 1592, µMo = 6.7 cmϪ1, specimen
0.04 × 0.52 × 0.34 mm, A*min,max = 1.03, 1.28, 2θmax = 50Њ, N =
6309, No = 2695, R = 0.052, RЈ = 0.048; nν = 443, |∆ρmax| = 0.52 e
ÅϪ3
.
[Ag(PPh3)(2-Me-im)3][CF3CO2] 11. C32H33AgF3N6O2P, M =
¯
729.5, triclinic, space group P1, a = 14.516(5), b = 14.219(5),
c = 10.022(4) Å, α = 89.71(3), β = 71.83(3), γ = 62.54(3)Њ, V =
1720 Å3, Dc (Z = 2) = 1.408 g cmϪ3, F(000) = 744, µMo = 6.9
cmϪ1, specimen 0.20 × 0.24 × 0.38 mm, Am*in,max = 1.11, 1.21,
2θmax = 50Њ, N = 6076, No = 3537, R = 0.047, RЈ = 0.043,
7 M. R. Malachowski, J. Carden, M. G. Davidson, W. L. Driessen
and J. Reedijk, Inorg. Chim. Acta, 1997, 257, 59; M. Hvastijova,
J. Kohout, J. Kozisek, L. Jager and I. Svoboda, Monogr. Ser. Int.
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J. Mathew, Indian J. Chem. A: Inorg. Bio-inorg., Phys. Theor. Anal.
Chem., 1997, 36, 303.
8 K. D. Karlin and J. Zubieta (Editors), Biological and Inorganic
Copper Chemistry, Adenine Press, New York, 1986; H. B. Gray
and E. I. Solomon, in Copper Proteins, ed. T. G. Spiro, Wiley
Interscience, New York, 1981, ch. 1; Metal Ions in Biological
Systems, ed. H. Siegel, Marcel Dekker, New York, 1973, vol. 13.
9 See for example: C. Pettinari, F. Marchetti, R. Polimante,
A. Cingolani, G. Portalone and M. Colapietro, Inorg. Chim. Acta,
1996, 249, 215 and refs. therein; C. Pettinari, G. Gioia Lobbia, G.
Sclavi, D. Leonesi, M. Colapietro and G. Portalone, Polyhedron,
1995, 14, 1709 and refs. therein.
nν = 539, |∆ρmax| = 0.53 e ÅϪ3
.
(x, y, z, Uiso)H were refined.
[{Ag(PPh3)(1-Me-im)(OSOCH3O)}2] 20. C46H48Ag2N4-
O6P2S2, M = 1094.7, monoclinic, space group C2/c, a =
29.421(3), b = 9.270(1), c = 19.122(2) Å, β = 117.888(1)Њ, V =
4609 Å3, Dc (Z = 4 dimers) = 1.577 g cmϪ3, F(000) = 2224,
µMo 10.6 cmϪ1, specimen 0.35 × 0.25 × 0.08 mm, Tmin,max
=
0.77, 0.93, 2θmax = 58Њ, N = 5800, No = 5800, nν = 377, |∆ρmax| =
0.66 e ÅϪ3
.
10 H. Schmidbaur, A. Mair, G. Muller, J. Lachmann and S. Gamper,
Z. Naturforsch., 1991, 465, 912; K. Nomiya, K. Tsuda, Y. Tanabe
and H. Nagano, J. Inorg. Biochem., 1998, 69, 9; K. Nomiya,
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W. McFarlane, P. D. Akrivos, P. Aslanidis, P. Karagiannidis,
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1992, 70, 943; D. Reinoso Lopez, J. Inorg. Biochem., 1994, 54, 21;
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A full sphere of area-detector data was measured at ca. 153 K
using a Bruker CCD instrument. 26676 Total reflections were
merged after ‘empirical’ absorption correction (proprietary
software: SAINT, SADABS, etc.) to 5209 independent
(Rint = 0.020). The ‘observed’ refinement criterion was
F > 4σ(F ); (x, y, z, Uiso)H were refined.
[{Ag(PPh3)(Him)(O2N)}2] 21. C42H38Ag2N6O4P2, M = 968.5,
monoclinic, space group P21/c, a = 11.972(5), b = 10.496(6),
c = 17.98(2) Å, β = 111.24(6)Њ, V = 2105 Å3, Dc (Z = 4) = 1.527
g cmϪ3, F(000) = 976, µMo = 10.5 cmϪ1, specimen 0.85 × 0.60 ×
1.10 mm, Am*in,max = 1.78, 2.41, 2θmax = 50Њ, N = 3700, No = 3105;
R = 0.037, RЈ = 0.054, nν = 263, |∆ρmax| = 0.78 e ÅϪ3
.
The criterion for No was I > 2σ(I ). A sphere of data was
measured (10291 reflections; Rint = 0.058). Disorder was evi-
dent, most notably and clearly resolved in one nitrite oxygen
and the silver atoms, the former bonding in two modes, with
O(2) disordered over two sites, seemingly concerted with Ag
occupancies constrained to equivalence and refining to
0.911(2) and complement, after independent trial refinement
to eliminate the possibility of admixture of any small nitrate
component.
11 E. Buchner and M. Fritsch, Ber. Bunseges. Phys. Chem., 1893, 20,
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12 S. Maki and Y. Takaya, Pat. Jpn. Kokai Tokkyo Koho, 1994, JP
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15 C. Santini, G. Gioia Lobbia, C. Pettinari, M. Pellei, G. Valle and
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CCDC reference number 186/1666.
See http://www.rsc.org/suppdata/dt/1999/4047/ for crystallo-
graphic files in .cif format.
Acknowledgements
We gratefully acknowledge support of this work by University
of Camerino and by grants from the Australian Research
Council and Fondazione “CARIMA”.
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