Synthesis and characterization of the lithium organoargentate salts [Li(THF)4][Ag(Triph)2]·THF and [Li(THF)4][Ag(C6H3-2,6-Mes2) 2]·1/8OEt2 (Triph=-C6H2-2,4,6-Ph3; Mes=C6H2-2,4,6-Me3)

Article abstract of DOI:10.1016/S0022-328X(99)00412-X

The synthesis and structural characterization of the new metal-terphenyl derivatives [Li(THF)₄][Ag(Triph)₂]·THF (1, Triph=C₆H₂-2,4,6-Ph₃) and [Li(THF)₄][Ag(C₆H₃-2,6-Mes₂) ₂]·1/8 Et₂O (2, Mes=C₆H₂-2,4,6-Me₃) are described. Both compounds crystallize as solvent separated ion pairs that are composed of THF solvated Li⁺ cations and argentate anions. The Li⁺ cations are approximately tetrahedrally coordinated by four THFs in both structures. The silvers are essentially linearly coordinated by ipso-carbons of the aryl ligands with Ag-C distances in the range 2.048(15) to 2.112(10) A with an average distance near 2.10 A. These bond lengths clearly demonstrate that silver terphenyl complexes have a metal carbon distance that is ca. 0.2 A longer than those in related copper complexes. Crystal data at 130 K with Cu-K_α (λ=1.54178 A) radiation: 1, a=14.440(3), b=18.670(4), c=21.550(4) A, β=104.25(3)°, Z=4, monoclinic, space group P2₁/n, R₁=0.0741 for 4589 (I>2(σ)I) data, 2, a=22.395(5), b=16.262(3), c=33.877(7) A, β=104.79(3)°, Z=8, monoclinic, space group P2₁/n, R₁=0.1288 for 7553 (I>2(σ)) data.

Full text of DOI:10.1016/S0022-328X(99)00412-X

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 589 (1999) 234–238
Synthesis and characterization of the lithium organoargentate salts
[Li(THF)4][Ag(Triph)2]·THF and
[Li(THF)4][Ag(C6H3-2,6-Mes2)2]·1/8OEt2
(Triph= –C6H2-2,4,6-Ph3; Mes=C6H2-2,4,6-Me3)
Cheong-Soo Hwang, Philip P. Power *
Department of Chemistry, Uni6ersity of California, Da6is, CA 95616, USA
Received 7 April 1999
Abstract
The synthesis and structural characterization of the new metal–terphenyl derivatives [Li(THF)4][Ag(Triph)2]·THF (1, Triph=
C6H2-2,4,6-Ph3) and [Li(THF)4][Ag(C6H3-2,6-Mes2)2]·1/8 Et2O (2, Mes=C6H2-2,4,6-Me3) are described. Both compounds crystal-
lize as solvent separated ion pairs that are composed of THF solvated Li+ cations and argentate anions. The Li+ cations are
approximately tetrahedrally coordinated by four THFs in both structures. The silvers are essentially linearly coordinated by
,
,
ipso-carbons of the aryl ligands with Ag–C distances in the range 2.048(15) to 2.112(10) A with an average distance near 2.10 A.
,
These bond lengths clearly demonstrate that silver terphenyl complexes have a metal carbon distance that is ca. 0.2 A longer than
,
those in related copper complexes. Crystal data at 130 K with Cu–Ka (u=1.54178 A) radiation: 1, a=14.440(3), b=18.670(4),
c=21.550(4) A, i=104.25(3)°, Z=4, monoclinic, space group P21/n, R1=0.0741 for 4589 (I\2(|)I) data, 2, a=22.395(5),
b=16.262(3), c=33.877(7) A, i=104.79(3)°, Z=8, monoclinic, space group P21/n, R1=0.1288 for 7553 (I\2(|)) data. © 1999
,
,
Elsevier Science S.A. All rights reserved.
Keywords: Argentate; Silver; Cyanate; Terphenyl
however [3]. In addition, experimental work on related
solvated, e.g. 2,4,6-Ph3H2C6Cu(m-C6H2-2,4,6-Ph3)-
Cu(SMe2)2, [4] and unsolvated, e.g. (CuC6H3-2,6-Ph2)3,
[5] copper species bearing identical or almost identically
sized substituents indicated that association of the puta-
tive monomers could indeed occur to give species with
previously unobserved structures. Another unusual fea-
ture of the original report on the MC6H2-2,4,6-Ph3
(M=Cu or Ag) species was that the reported M–C
distances were almost identical, in spite of the fact that
1. Introduction
Organometallic derivatives of silver(I) have received
considerably less attention than their organocopper(I)
counterparts [1]. This is probably a consequence of
their less-widespread employment as synthetic reagents
in comparison with the ubiquitous organocuprates. In
addition, the greater cost of the silver derivatives has
probably played a role in restricting their use. The
terphenyl and related ligand derivatives of copper have
proven to be a particularly interesting and unusual class
of organocopper species. The controversial compound
CuC6H2-2,4,6-Ph3 and its silver analogue AgC6H2-
2,4,6-Ph3 [2] were said to possess the first examples of
one-coordinate metals in the solid state. Subsequent
reinterpretation of their structural and spectroscopic
data cast considerable doubt on their formulation,
the effective ionic radius of two-coordinate Ag+ is ca.
+
,
0.2 A larger than two-coordinate Cu [6]. The struc-
tures of terphenyl complexes of silver are therefore of
significance in establishing whether or not there are any
unique features associated with the M–C distances in
these derivatives. In this paper the structures of two
new organo silver(I) derivatives of terphenyl ligands are
reported. Their Ag–C distances, which average ca. 2.10
,
,
A in length, are ca. 0.2 A longer than those in related
copper complexes.
* Corresponding author.
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00412-X

C.-S. Hwang, P.P. Power / Journal of Organometallic Chemistry 589 (1999) 234–238
235
2. Experimental
posed to a black powder at 150–152°C. 1H-NMR
(THF-d8, 25°C) l 6.59 (t, J=7.2 Hz, p-C6H3); 6.54 (s,
m-Mes); 6.32 (d, J=7.2 Hz, m-C6H3); 3.58 (br, THF-
d8); 2.13 (br, s, o-CH3 (Mes)); 1.74 (br, THF-d8); 1.59
(br, s, p-CH3(Mes)). Small peaks at 3.34 (q) and 1.08 (t)
ppm were assigned to Et2O (solvant) which, upon inte-
gration, afforded an intensity ratio of 0.13:1 with re-
spect to the cation and anion peaks. 13C{1H}-NMR
(THF-d8, 25°C) l 180.89 (br, i-C6H3); 152.09 (i-Mes);
148.93 (o-C6H3); 136.36 (o-Mes); 132.27 (p-Mes);
128.75 (p-C6H3); 127.50 (m-Mes); 121.91 (m-C6H3);
67.41 (quintet, THF-d8); 25.32 (quintet, THF-D8); 21.89
(o-CH3(Mes)); 21.51 (p-CH3(Mes)) very small peaks at
59.21 and 15.65 ppm were assigned to be Et2O (sol-
vent). 7Li-NMR (THF-d8, 25°C: LiCl–D2O was used as
reference) l −0.62 ppm (br, s).
2.1. General procedures
All experiments were performed under a nitrogen
atmosphere either by using modified Schlenk techniques
or in a Vacuum Atmospheres HE43-2 drybox. Solvents
were freshly distilled from a sodium–potassium alloy
and degassed twice prior to use. The 13C-, 1H- and
7Li-NMR spectra were recorded in C6D6 or THF-D8
solutions by using a General Electric QE-300 NMR
spectrometer. The compounds (Et2O)2LiTriph [7] and
(LiC6H3-2,6-Mes2)2 [8] were synthesized by literature
procedures. Silver cyanate was obtained commercially
and used as received.
2.2. [Li(THF)4][Ag(Triph2)]·THF
2.4. X-ray data collection, the solution and refinement
(Et2O)2LiTriph (2.30 g, 5.0 mmol) was dissolved in
Et2O (30 ml) and the solution was added dropwise to a
rapidly stirred suspension of AgOCN (0.37 g, 2.50
mmol) in a 3:1 Et2O–THF mixture (20 ml) and cooled
to ca. −78°C. During the reaction, light was excluded
by wrapping the Schlenk tube with aluminum foil.
After 2 h stirring at ca. −78°C, the mixture was
allowed to warm to ca. 0°C over 3 h. The gray precipi-
tate was then removed by filtration. The resultant pale-
green filtrate was stored in a ca. −20°C freezer for 3
days to afford the product as colorless crystals: yield
of the structures
The crystals were coated with a layer of hydrocarbon
oil upon removal from the Schlenk tube. Suitable crys-
tals were selected, attached to a glass fiber, and immedi-
ately placed in the low-temperature N2 stream [9]. Both
X-ray data sets were collected with Cu–Ka (u=1.54178
,
A) radiation by using a Siemens P4RA diffractometer
equipped with a rotating anode X-ray source, nickel
filter and a locally modified LT apparatus. Calculations
were carried out on a Micro Vax 3200 computer using
1
0.94 g (35%); m.p.: 122–124°C dec. H-NMR (C6D6,
the SHELXTL-PLUS [10] program system. The structures
25°C) l 7.79, (br, s); 7.72 (d, J=6.0 Hz); 7.65 (d,
J=6.0 Hz); 7.56 (br, s); 7.32 (d, J=6.0 Hz); 7.17ꢀ
6.96 (m) [aromatic H’s]; 7.15 (C6D6); 2.99 (br, s, THF);
0.93 (br, s, THF). 13C{1H}-NMR (C6D6, 25°C) l
192.23 (i-C6H2); 153.76 (o-C6H2); 153.04 (p-C6H2);
144.59 (i-(o-Ph)); 143.76 (i-(p-Ph)); 142.85 (o-(p-Ph));
141.52 (p-(p-Ph)); 137.68 (m-(p-Ph)); 129.10 (m-C6H2);
128.00 (t, C6D6); 125.52 (p-(o-Ph)); 125.04 (o-(o-Ph));
121.89 (m-(o-Ph)); 68.18 (THF); 25.24 (THF). 7Li-
NMR (C6D6, 25°C: LiCl in D2O was used as a refer-
ence) l 1.49 ppm (br, s).
were solved by direct methods. The data were subse-
quently refined by full-matrix least-squares procedures.
Hydrogen atoms were included by the use of a riding
,
model with C–H distance of 0.96 A and fixed isotropic
2
,
thermal parameters with UH(iso)=0.06 A . For the
absorption correction, an empirical method, XABS2,
was applied [11]. Although the data for 1 generally
refined satisfactorily, there were residual electron den-
−3
,
sity values of 1.79 and 1.44 e A
that were 1.226 and
,
1.339 A distant from the silver. These probably resulted
from absorption problems associated with use of cop-
per radiation. For 2, the higher than usual R value is
probably due to disorder problems in the Li(THF)4 and
OEt2 (solvent) groups. The atoms in these groups were
located from successive difference maps. But poor con-
vergence during refinement was observed, probably as a
result of their large thermal motion. For several of
these atoms, more reasonable geometries were obtained
from the difference map positions than from those
obtained after anisotropic refinement. Consequently,
the original positions were retained and their isotropic
2.3. [Li(THF)4][Ag(C6H3-2,6-Mes2)2]·1/8 Et2O
(LiC6H3-2,6-Mes2)2 (1.6 g, 5.0 mmol) was dissolved
in Et2O (30 ml) and added dropwise to a stirred suspen-
sion of AgOCN (0.37 g, 2.50 mmol) in a 3:1 Et2O–
THF mixture (20 ml) and cooled to ca. −78°C. Light
was excluded by wrapping the Schlenk with aluminum
foil during the reaction. After 2 h stirring at ca.
−78°C, the mixture was allowed to warm to ca. 0°C,
whereupon the gray residue was filtered off. The yel-
low–green supernatant liquid was placed in a −20°C
freezer for 1 day, which afforded the product 2 as
colorless crystals: yield: 1.97 g (37.9%); m.p.: the white
crystalline became light-brown at 134°C and decom-
thermal parameters were simply fixed at a relatively
2
,
high value of 0.15 A by use of the SHELXTL AFIX
1
feature during the final cycle of the refinement. Both
Li(2) and C(117) were successfully modeled with two
split positions; Li(2A) and Li(2B) (50:50) and C(117)

236
C.-S. Hwang, P.P. Power / Journal of Organometallic Chemistry 589 (1999) 234–238
Table 1
some important structural details are provided in Ta-
bles 1 and 2, respectively.
Selected data collection parameters for 1 and 2 a
Compound
[Li(THF)4]-
[Ag(Triph2)]
·THF
[Li(THF)4]-
[Ag(C6H3-2,6-Mes)2]·1/8
OEt2
3. Discussion
The compounds 1 and 2 were synthesized by the
reaction of the respective lithium reagents with silver
cyanate, AgOCN. This reagent was chosen for its
greater solubility than the silver halides. In addition it
had already been shown that AgOCN was a suitable
precursor for the synthesis of silver amides (AgNR2)4
[12]. Attempts to use silver chloride in the synthesis of
1 and 2 eventually led to decomposition and the isola-
tion of the respective arenes and a gray solid which
contained elemental silver.
The ion-pair argentate structures of 1 and 2 were
suggested by 1H, 13C and 7Li solution NMR spec-
troscopy. The 13C{1H}-NMR spectra each revealed a
peak at low field (i.e. at l 192.23 (1) and 180.89 (2))
attributable to the ipso-C atom of the central aromatic
ring. These shifts are comparable to those previously
described for cuprates [13].
C68H74AgLiO5
1086.08
Colorless/block
0.36×0.10×0.04
C64.50H83.25AgLiO4.13
1039.37
Colorless/block
0.22×0.20×0.14
Formula weight
Crystal color/habit
Crystal size (mm)
Unit cell dimensions
,
a (A)
14.440(3)
18.670(4)
21.550(4)
104.25(3)
5631.0(19)
4
Monoclinic
P21/n
1.281
22.395(5)
16.262(3)
33.877(7)
104.79(3)
11929(4)
8
Monoclinic
P21/n
1.257
,
b (A)
,
c (A)
i (°)
3
,
V (A )
Z
Crystal system
Space group
Dcalc. (g cm−3
Absorption
coefficient (mm−1
Trans. coefficient
2q range (°)
Number of unique
data
)
3.260
3.039
)
0.88–0.39
0–113
14 855
0.68–0.55
0–113
15 452
The ionic structures of 1 and 2 were confirmed by
single-crystal X-ray diffraction studies. Both structures
were marred by disordering coupled with relatively high
thermal motion, both in the cation and in the solvent
molecules of crystallization. Such disorder is a common
feature of this general structure type. There were also
minor absorption problems owing to the use of copper
radiation in conjunction with crystals containing silver
atoms. Nonetheless, these problems do not affect the
overall interpretation of the structure in any significant
way.
The structures of 1 (Fig. 1) and 2 (Fig. 2) consist of
well-separated cations and anions. In 1 the THF
molecule of crystallization (see Fig. 1) shows no inter-
action with either the Li+ or Ag+ ions. The Li+, which
is bound to four THF donors, has distorted tetrahedral
coordination with O–Li–O angles in the range 103.6(7)
to 114.9(7)°. The Li–O distances, which average 1.92(1)
Observed
reflections
4589
7553
(I\2 |(I))
R2, wR2
0.0741, 0.1549
0.1288, 0.3116
a R1=SꢀꢀFoꢀ−ꢀFcꢀꢀ/SꢀFoꢀ, wR2=SꢀꢀFoꢀ−ꢀFcꢀꢀ,
w
1/2/SꢀFoꢀ, w−1
=
|2(F2o)+(0.0663P)2+4.49P (P=(Fo2+2F2c)/3). Data were collected at
,
130 K using Cu–Ka radiation (u=1.54178 A), Siemens P4RA.
and C11A (50:50), respectively. Finally, the solvent
(diethyl ether) molecules were most suitably refined
with quarter occupancy. The crystal data for this com-
pound was also recollected with Siemens R3 m/V dif-
fractometer with Mo–Ka (u=0.71069 A) radiation.
However, no improvement in the data was obtained.
An abbreviated list of data collection parameters and
,
Table 2
,
Some important bond distances (A) and bond angles (°) for 1 and 2
[Li(THF)4][Ag(Triph2)]·THF
[Li(THF)4][Ag(C6H3-2,6-Mes)2]·1/8 OEt2
(1)
(2)
Ag–C(ipso)
Ag(1)–C(1)
2.091(9)
Ag(1)–C(25)
2.103(9)
Ag(1)–C(1)
2.107(18)
Ag(1)–C(25)
2.112(19)
(avg=2.097(9))
Ag(2)–C(49)
2.048(15)
Ag(2)–C(73)
2.098(13)
(avg=2.09(3))
Li–O (avg)
C–Ag–C
1.921(6)
1.92(18)
C(1)–Ag(1)–C(25)
176.7(4)
C(1)–Ag(1)–C(25)
177.4(6)
C(49)–Ag(2)–C(73)
176.0(7)

C.-S. Hwang, P.P. Power / Journal of Organometallic Chemistry 589 (1999) 234–238
237
attached to silver is 56.5° for 1 and has an average
value of 83.4° for 2.
The structures of 1 and 2 may also be compared
with related organocuprate species, for instance the
compound LiCu{C6H3-2,6-Ph2}2 [5] which has a con-
tact ion-pair structure composed of a [Cu{C6H3-2,6-
Ph2}2]− and a Li+ cation. The latter associates with
the anion through an h6–p interaction with one of the
ortho-Ph substituents. The Cu–C distances in the an-
,
ion are 1.922(5) and 1.957(5) A, which are slightly
longer than the values seen in the related copper ter-
,
phenyls; 1.906(4) A in [Li(THF)2{Cu(CN)C6H3-2,6-
,
Trip2}2]2 [19] (Trip= –C6H2-2,4,6-i-Pr3) or 1.894(6) A
in the neutral monomer (Me2S)CuC6H3-2,6-Trip2 [20].
The consistency and relatively narrow range of the
Cu–C distances in this group of compounds show that
Cu–C distances in terphenyl and related copper com-
Fig. 1. Computer-generated drawing of 1. H atoms are not shown for
clarity.
,
pounds are roughly 0.2 A shorter than those in the
corresponding silver species reported here. This is,
of course, in harmony with the different covalent and
ionic radii of copper and silver which differ
by a similar amount. The structure of 2, although not
as accurate as that of 1, validates the important struc-
tural parameters at silver; i.e. almost linear co-
ordination of the Ag+ ion and very similar Ag–C
distances.
,
A, are similar to those previously observed for this
type of cation [14]. The [Ag(Triph)2]− and [Ag(C6H3-
2,6-Mes2)2]− anions consist of silver bound to two aryl
groups through their ipso-carbon atoms. The silver
coordinations are almost linear with C–Ag–C angles
of 176.7(4) and 176.8(8)°. The Ag–C distances, which
,
average 2.097(9) and 2.09(3) A, are shorter than
the 2.162(7) and 2.198(7)
In summary, the data for the argentate ions in 1
and 2 are in agreement with each other and confirm
that the Ag–C bonds in these terphenyl derivatives are
,
A
in [Li(THF)4]-
[Ag{C(SiMe3)3}2] [15] or the average Ag–C distances
seen in the anions [Li2Ag3Ph6]− [16] (2.13 A) and
,
,
0.2 A longer than the Cu–C bonds in closely related
¸¹¹¹¹¹¹¹º
,
copper species. Thus, these results do not support the
[Ag{CS(O)2(CH2)3S(O)2}2] [17] (2.14 A). However,
they are comparable to the two Ag–C bond lengths
,
almost equal Cu–C=1.890(6) A and Ag–C=1.902(5)
,
A distances reported for MC6H2-2,4,6-Ph3 [2] and lend
,
(2.191(7)
and
2.015(35)
A)
reported
for
[Ag{CF(CF3)2}2]− [18]. It appears, therefore, that the
further support to the reassessment of Haaland and
co-workers, which suggested that each of these com-
pounds mostly consisted of the starting material
BrC6H2-2,4,6-Ph3 [3].
,
Ag–C bond lengths 2.091(9) and 2.103(9)A in 1 are at
the low end of the currently known range of Ag–C
distances in diorgano argentates [1,15–18]. The differ-
ence in size between the Triph and –C6H3-2,6-Mes2
substituents in the structures of 1 and 2 is reflected in
the fact that the torsion angles between the aryl rings
4. Supplementary material
The X-ray data have been deposited with the Cam-
bridge Crystallographic Data Center as supplementary
publication nos. CCDC-121767 and CCDC-121768.
Copies of the data can be obtained on application to
CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK
(fax: +44-1223-336-033; e-mail: deposit@ccdc.cam.-
ac.uk).
Acknowledgements
The authors are grateful to the National Science
Foundation and the Donors of the Petroleum Re-
search fund administered by the American Chemical
Society for financial support.
Fig. 2. Computer-generated drawing of 2. Molecule 2 in the asymmet-
ric unit is omitted and H atoms are not shown for clarity.

238
C.-S. Hwang, P.P. Power / Journal of Organometallic Chemistry 589 (1999) 234–238
Characterization, ACS Symp. Ser. 357, American Chemical Soci-
ety, Washington, DC, 1987, p. 257.
[10] G.M. Sheldrick, SHELXTL PLUS, A program package for refine-
ment of Crystal Structures, University of Go¨ttingen, 1989.
[11] XABS2: an empirical absorption program. S. Parkin, B. Moezzi,
H. Hope, J. Appl. Cryst. 28 (1995) 53.
[12] P.B. Hitchcock, M.F. Lappert, L.J.-M. Pierssens, Chem. Com-
mun. (Cambridge) (1996) 1189.
[13] S.H. Bertz, J. Am. Chem. Soc. 113 (1991) 5470.
[14] W.N. Setzer, P.v.R. Schleyer, Adv. Organomet. Chem. 24 (1985)
35.
References
-
[1] (a) J.G. Noltes, G. van Koten, Comprehensive Organometallic
Chemistry, vol. 2, Pergamon, Oxford, 1982, p. 709. (b) J.G. Noltes,
G. van Koten, Comprehensive Organometallic Chemistry, vol. 3,
Elsevier, Amsterdam, 1995, p. 57.
[2] R. Lingnau, J. Stra¨hle, Angew. Chem. Int. Ed. Engl. 27 (1988) 436.
[3] A. Haaland, K. Rypdal, H.P. Verne, W. Scherer, W.R. Thiel,
Angew. Chem. Int. Ed. Engl. 33 (1994) 2443.
[4] X. He, M.M. Olmstead, P.P. Power, J. Am. Chem. Soc. 114 (1992)
9668.
[15] C. Eaborn, P.B. Hitchcock, J.D. Smith, A.C. Sullivan, J. Chem.
Soc. Chem. Commun. (1984) 870.
[16] M.Y. Chiang, E. Bo¨hlen, R. Bau, J. Am. Chem. Soc. 107 (1985)
1679.
[17] J.R. DeMember, H.F. Evans, F.A. Wallace, P.A. Tariverdian, J.
Am. Chem. Soc. 105 (1983) 5647.
[18] R.R. Burch, J.C. Calabrese, J. Am. Chem. Soc. 108 (1986) 5359.
[19] C.-S. Hwang, P.P. Power, J. Am. Chem. Soc. 120 (1998) 6409.
[20] B. Schiemenz, P.P. Power, Organometallics 15 (1996) 958.
[5] M. Niemeyer, Organometallics 17 (1998) 4649.
[6] R.D. Shannon, Acta. Crystallogr. Sect. A 32 (1976) 752.
[7] (a) M.M. Olmstead, P.P. Power, J. Organomet. Chem. 408 (1991)
1. (b) G.S. Girolami, M.E. Riehl, K.S. Suslick, S.R. Wilson,
Organometallics 11 (1992) 3907.
[8] K. Ruhlandt-Senge, J.J. Ellison, R.J. Wehmschulte, F. Pauer, P.P.
Power, J. Am. Chem. Soc. 115 (1993) 11353.
[9] H. Hope, in: A.L. Wayda, M.Y. Darensbourg (Eds.), Experimen-
tal Organometallic Chemistry: A practicum in Synthesis and
.