Antimony as a donor atom in silver coordination chemistry: Synthesis, IR spectra and structure of the silver(I) cyanoximate complexes with triphenylstibine and triphenylphosphine model compounds

Article abstract of DOI:10.1515/znb-1999-0714

Silver(I) cyanoximate complexes Ag{ONC(CN)-R} (R = COPh, {L¹}; COC(CH₃)₃, {L²}; benzothiazol-2-yl, {L³}) with triphenylphosphine and -stibine of compositions Ag(PPh₃)_n{L} (n = 2, 4) and Ag(SbPh₃)_n{L} (n = 3 for {L¹} and {L²}, n = 2 for {L³}) were synthesized by the reaction of the components in acetonitrile solution and characterized by elemental analyses and IR spectroscopy. The crystal structures of Ag(SbPh₃)₃{L} (L = {L¹} (1), {L²} (2), Ag(SbPh₃)₂{L³}·CH₃CN (3) and Ag(PPh₃)₂{L¹}·CH₃CN (4), have been determined by X-ray diffraction. For all the compounds examined the coordination environment of the silver atom has the geometry of a distorted terahedron ([AgP₂NO] (4); [AgSb₃N] (1), (2); [AgSb₂N₂] (3)). The bis adducts Ag(EPh₃)_n{L} adopt molecular structures, in which the organic anions are coordinated in bidentate chelate fashion via the nitroso nitrogen atom and the oxygen (nitrogen for {L³}) atom of the substituent R. In the tris-stibino complexes (Ag-Sb 2.670(4) -2.7748(8) A; Sb-Ag-Sb 108.87(4) - 115.00(2)°) the cyanoximates are unidentate ligands and coordinated via the nitroso nitrogen atoms (Ag-N ca. 2.35(1) A). The different behaviour of N,O and N,N chelating cyanoximes under the same conditions suggests, that the Sb donor triphenylstibine is able to substitute the oxygen atoms in the silver(I) coordination sphere, but not the nitrogen ones. This causes the formation of 1:3 adducts of Ag{L} with SbPh₃ for N,O donors {L¹} and {L²}, and only 1:2 for N,N donor anionic {L³}.

Full text of DOI:10.1515/znb-1999-0714

Antimony as a Donor Atom in Silver Coordination Chemistry: Synthesis,
IR Spectra and Structure of the Silver(I) Cyanoximate Complexes
with Triphenylstibine and Triphenylphosphine Model Compounds
Konstantin V. Domasevitcha, Elena G. Petkovaa, Alexander Yu. Nazarenkob,
Vera V. Ponomareva3, Joachim Sielerc, N. Kent Dalleyb, and Eduard B. Rusanov3
3 Department of Inorganic Chemistry, Kiev University,
Vladimirskaya Street 64, Kiev 252033, Ukraine
b Department of Chemistry and Biochemistry, Brigham Young University,
Provo, Utah 84602, USA
c Institut für Anorganische Chemie, Universität Leipzig,
Linnestraße 3, D-04103 Leipzig, Deutschland
* Reprint requests to Dr. K. V. Domasevitch or Dr. V. V. Ponomareva.
E-mail: vera@anorgchemie.univ.kiev.ua
Z. Naturforsch. 54 b, 904-912 (1999); received December 15, 1998
Silver, Triphenylphosphine, Triphenylstibine, Cyanoximes, X-Ray Data
Silver(I) cyanoximate complexes Ag{ONC(CN)-R} (R = COPh, {L1}; COC(CH3)3, {L2};
benzothiazol-2-yl, {L3}) with triphenylphosphine and -stibine of compositions Ag(PPh3)n{L}
(n = 2, 4) and Ag(SbPh3)n{L} (n = 3 for {L1} and {L2}, n = 2 for {L3}) were synthesized
by the reaction of the components in acetonitrile solution and characterized by elemental
analyses and IR spectroscopy. The crystal structures of Ag(SbPh3)3{L} (L = {L } (1), {L2}
(2), Ag(SbPh3)2{L3} CH3CN (3) and Ag(PPh3)2{L'}CH3CN (4), have been determined by
X-ray diffraction. For all the compounds examined the coordination environment of the silver
atom has the geometry of a distorted terahedron ([AgP2NO] (4); [AgSb3N] (1), (2); [AgSb2N2]
(3)). The bis adducts Ag(EPh3)«{L} adopt molecular structures, in which the organic anions
are coordinated in bidentate chelate fashion via the nitroso nitrogen atom and the oxygen
(nitrogen for {L3}) atom of the substituent R. In the fm-stibino complexes (Ag-Sb 2.670(4) -
2.7748(8) A; Sb-Ag-Sb 108.87(4) - 115.00(2)°) the cyanoximates are unidentate ligands and
coordinated via the nitroso nitrogen atoms (Ag-N ca. 2.35(1) A). The different behaviour of
N,0 and N,N chelating cyanoximes under the same conditions suggests, that the Sb donor
triphenylstibine is able to substitute the oxygen atoms in the silver(I) coordination sphere, but
not the nitrogen ones. This causes the formation of 1:3 adducts of Ag{L} with SbPh3 for N,0
donors {L1} and {L2}, and only 1:2 for N,N donor anionic {L3}.
Introduction
Ag(BiPh3){C104} [4] or [Ag(SbPh3)2{C2B9H12}]2
[5], all prepared from low-basic solvents as diethyl
ether and CH2C12. The factors affecting the forma-
tion and stoichiometry of these complexes are not
always obvious and it is difficult to predict the sta-
bility of inherently weak coordination bonds (c.f
Ag-Sb; Ag-Bi) in the presence of usual N,0 donor
ligands, such as NO?- , (NC)2CNO~, oximes, and
dioximes. In this context it was of special interest to
synthesize the triphenylstibine and -bismuth com-
plexes of silver(I) cyanoximates Ag{ONC(CN)-R}
(R = functional groups such as cyano, carbamoyl,
keto groups, and N-heteroaryls) [6]. In these cases
the donor atom sets available for coordination are
N20 2, N20 3, N3O etc. [7] and it was possible to
Trisubstituted phosphines and arsines represent
are among the most common types of ligands in the
coordination chemistry of copper(I), silver(I) and
gold(I) [1 ], and a large number of triphenylphos-
phine and -arsine complexes M(EPh3)n{X} (M =
Cu, Ag, Au; E = P, As; n = 1 to 4) have
been characterized [1 - 3]. The donor abilities of
triphenylstibine and, especially, triphenylbismuth
are much weaker and their coordination com-
pounds are stable only under special conditions
e. g. because of extremely low nucleophilic prop-
erties of the counter anions in complexes of com-
position [Ag(SbPh3)4]{X} (X = CIO4- , BF4-),
K
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K. V. Domasevitch et al. ■Antimony as a Donor Atom in Silver Coordination Chemistry
905
observed formation of 1:3 adducts with triphenylphos-
phine and the reaction using this stoichiometry yields the
mixture of 1:2 and 1:4 complexes. The silver(I)-triphe-
nylphosphine 1:3 complex, however, was reported for an-
other cyanoxime, dicyanamide ONC(CN)2~, which may
not act as a chelate [3], Thus it may be assumed, that the
Ag(PPh3)3+ core itself is unstable towards the chelating
ligands and tends to dismutate into [Ag(PPh3)2{chelate}]
and [Ag(PPh3)4]+.
establish some regularities for the formation of
Ag-M (M = Sb, Bi) bonds compared to Ag-N and
Ag-O bonds. Earlier, we have reported the crystal
structure of a polymeric silver(I) benzoylcyanox-
imate Ag{0NC(CN)C(0)Ph} and found that the
silver atom is coordinated with both the nitrogen
atomsoof nitroso and cyano groups (Ag-N 2.18,
2.25 A) and oxygen atoms of nitroso and carbonyl
groups [AgNoO}] [8]. The coordination modes of
benzoylcyanoximates in metal complexes and the
Tris(triphenylstibine)benzoylcyanoximatosilver(I)
structure of benzoylcyanoximate compounds have Ag(SbPhih{L1} (1)
been reviewed recently [7],
To a solution of 0.141 g (0.5 mmol) of Ag{L'} in
Following these investigations we were success-
ful in the preparation of 1:2 and 1:3 adducts in the
system silver(I)cyanoximate - triphenylstibine, and
herein we describe the syntheses and results of X-
hot acetonitrile (20 ml) 0.353 g (1 mmol) of SbPh3
was added. The mixture was stirred for 10 min, fil-
tered and allowed to stand at r. t. for a few days.
Then large red-violet crystals of the complex were col-
ray studies of three new Ag(SbPh3) complexes and lected and dried in air. Yield 0.415 g (62%). The com-
pound is soluble in acetonitrile, DMF and decomposes
in water. The syntheses of Ag(SbPh3)3{L2} (2) and
Ag(SbPh3)2{L3}CH 3CN (3) complexes were carried
out in a similar fashion and 1:2 complexes with triph-
enylphosphine (cf Ag(PPh3)3{L'} CH3CN (4)) were pre-
pared analogously starting with PPh3.
the model triphenylphosphine compounds.
Experimental
Preparation ofcoordination compounds
The following oximes, containing functional groups
of different steric and donor properties, were used for the
study:
Tetrakis(triphenylphosphine)silver(I) pivaloyl-
cyanoximate [Ag(PPh^)A]{L2} (1)
To a solution of 0.131 g (0.5 mmol) of Ag{L2} in
hot acetonitrile (20 ml) 0.524 g (2 mmol) of PPh3 was
added. The mixture was stirred for 10 min, filtered and the
transparent yellow solution obtained was evaporated to a
volume of about 10 ml and cooled to r. t. The yellow pris-
matic crystals of the complex deposited were filtered off
and washed with cold acetonitrile. The yield was 0.458 g
(70%). The compound is soluble in hot acetonitrile and
DMF.
H(L‘)
H(L2)
H(L3)
Preparations of benzoylcyanoxime H(L') [9], pival-
oylcyanoxime H(L2) [10], (benzothiazol-2-yl)cyanoxime
H(L3) [11] and their silver salts Ag{L} [7, 8] were as
described previously. Triphenylstibine was prepared by
the standard Grignard procedure.
The silver complexes were synthesized by react-
ing Ag{L} and SbPh3 in acetonitrile solution. All
experiments were carried out in air. For both the
N,0 chelating cyanoximates, {L1}- and {L2}- , even
The analytical data of the complexes are presented in
Table I.
Measurements
IR spectra were recorded on a Carl Zeiss (Jena) UR-
10 spectrometer in KBr pellets (400 - 4000 cm-1). The
characteristic IR absorptions of the silver complexes, al-
kali metal salts and tetraphenylantimony compounds are
presented in Table II.
with
a 1:2 molar ratio of Ag{L} and SbPh3 in
the reaction mixture, the complexes of composition
Ag(SbPh3)3{L'} (1) and Ag(SbPh3)3{L2} (2) were iso-
lated, while (benzothiazol-2-yl)cyanoximate for any mo-
lar ratio Ag{L} / SbPh3 in the solution yielded only the
1:2 adduct Ag(SbPh3)2{L3}CH3CN (3). We were neither
Lattice parameters and the orientation matrix for data
collection were obtained from least squares refinement
successful in the preparation of 1:2 complexes for both of the setting angles of 24 reflections with 12 < 6 <
the anions {L1}- and {L2}- , nor in the synthesis of the
15°. Intensity data were collected at 293(2) K using
ionic 1:4 derivatives [Ag(SbPh3)4]{L}.
graphite-monochromatized MoKct radiation (u;/20 scans,
The interaction in the system Ag{L} - PPh3 differs A = 0.71073 A). Table III lists details of cell parame-
dramatically and leads to coordination compounds of the ters, data acquisition and structure refinement. Correc-
types Ag(PPh3)2{L} and Ag(PPh3)4{L}. We have not tions for Lorentz and polarisation effects were applied.
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906
Table I. Analytical data of the silver(I) cyanoximate complexes.
K. V. Domasevitch et al. ■Antimony as a Donor Atom in Silver Coordination Chemistry
Colour
FW
Compound
Formula
— Found [%] -
— Calcd [%] —
H
C
N
C
H
N
1
2
3
4
5
6
7
Ag(SbPh3)3 {L '}
Ag(SbPh3)3{L /}
red-violet
yellow
Cö3H5oAgN20 2Sb3 1340.2 56.02
2.12
2.13
3.80
4.01
56.46
55.49
53.39
3.76
4.12
3.53
4.52
5.00
2.09
2.12
5.30
4.96
3.57
1320.2 55.11
Cfti Hs4AgN20 2Sb3
Ag(SbPh3)2{L } CH3CN yellow-brown C47H37AgN 4OSSb2 1057.2 52.90 3.30 4.94
Ag(PPh3)2{L } CH3CN
Ag(PPh3)2{L 2}
Ag(PPh3)2{L 3}
Ag(PPh3)4{L 2}
red-violet
pink
yellow-brown
846.6 66.40 4.31 4.61 66.67
785.6 65.92 5.07 3.68 65.74
834.6 65.01 4.13 5.31 64.75 4.11
C47H38AgN302P2
C43H39A gN 20 2P2
C45H34AgN3 0 P2S
C 79H69AgN 20 2P4
5.04
5.54
yellow
2.08
1310.1 71.65
72.42
5.31 2.14
Table II. Vibrational frequences in the infrared spectra
and their assignments, cm- 1.
the same reason the Ag(SbPh3)3{L} complexes (1 ) and
(2) appeared to be actually isostructural (Table III). Reso-
lution of the disorder was possible by introducing a rigid
model for the “A” (43( 1) %) component of the disordered
phenyl group with C-C separations and C-C-C bond an-
gles fixed at 1.39 A and 120°, respectively. No constraints
in bond distances and bond angles were applied for the
major component of the disordered phenyl ring, and the
carbon atoms C(5-9) and C(5a-9a) were refined isotrop-
ically only. The refinement of the disorder model pro-
ceeded satisfactorily, and therefore the hydrogen atoms
were included in the refinement as fixed contributions
with their isotropic U values set invariant at 0.08 A2.
Refinements were terminated with all non-hydrogen
parameter shifts < 0.05 <r; the weighting schemes were
w- 1 = <t2(F2) + (aP)2 + bP, where 3P = (2FC2 + F02)
and a and b are constants adjusted by the program. All
structural calculations were carried out using SHELXS-
86 and SHELXL-93 [12, 13], Convergence was obtained
at the values given in Table III.
Compound
Coordination mode
NC
v(CsN) v(C=0) V(N-O)
Av(N-O)
R
Ag(PPh3)2fL1}-CH3CN
Ag(PPh3)2{L2)
2195
2200
1595
1600
1265 +100
1280
\
/
+30
°
- \ / °
M
AgtPPhjWL3}
Ag(SbPh3)2{L3}- CH3CN
NC
2195
2200
1495 b
1495 6
1290
1295
+75
+80
M
NC
R
Ag(SbPh3)3(L‘}
Ag(SbPh3)3{L2}
2195
2210
1610
1630
1295 +130
\
/
1280
+30
// i
\
O -N
O
M
NC
R
(Q H 5)4Sb{L'} [9]
(C6H5)4Sb{L2) [10]
2210
2210
1628
1662
1130
-35
\
/
1130 -120
O -N
O
/
M
Cs{L‘}
ionic
ionic
ionic
ionic
2205
2205
2205
2200
1620
1635
1630
1510
1165
1250
1225
1215
K{L2}
Ag(PPh3)4{L2)
Cs(L3}
-25
-
Further details of the structure determination, atomic
coordinates, thermal parameters, andbond lengths andan-
gles can be ordered from Fachinformationszentrum Karls-
ruhe, D-76344 Eggenstein-Leopoldshafen (Germany), on
quoting the depository numbers CSD-410268 (1), CSD-
410269 (2), CSD-410270 (3) and CSD-410271 (4).
aWith respect to those for the ionic alkali metal salts;
b-^(C=N) (benzothiazole).
The structures were solved by direct methods and subse-
quent Fourier difference techniques.
The structures of 2 and 3 were refined by full-matrix
least-squares techniques in the anisotropic approxima-
tion. All hydrogen atoms were placed in calculated posi-
tions with their isotropic U values set invariant at 0.08 A2.
In the structure 3 the high thermal motion of atoms of the
nitrile group (for N(3) Ueq = 0.18(2) A2) and the inexact
bond angle C(1)-C(3)=N(3) of 154(4)° indicated possi-
ble disorder, but all attempts to use a split-atom model
with different partial occupancies were not successful.
An examination of residual electron density features
in the structure 1 showed the oximic ligand to be al-
most equally disordered [57(1) and 43(1)%] over two
positions. This may be attributed to the large size of the
Ag(SbPh3)3{L]} molecules and insensitivity of the pack-
ing to the conformations of the coordinated ligand. For
Results and Discussion
The main vibrational frequencies u(C=N), v(C=
O) and is(N-O) for the compound Ag(PPht3)4{L2}
do not differ essentially from those of the potassium
salt (Table II), suggesting thus an ionic nature of the
tetrakis complex. Formation of the bulky tetrahe-
dral cation [Ag(PPh3)4]+ is a characteristic feature
of the Ag+ - triphenylphosphine system [1]. Un-
like this specimen the IR spectra of the compounds
Ag(SbPh3)n{L} (n = 2, 3) and Ag(PPh3)2{L} re-
veal substantially higher values of i'(NO) as com-
pared to those of the ionic alkali metal cyanox-
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K. V. Domasevitch et al. • Antimony as a Donor Atom in Silver Coordination Chemistry
Table III. Experimental data for Ag(SbPh3)3{ L '} (1), Ag(SbPh3)}{L 2} (2), Ag(SbPh3)2{L3}C H 3CN (3),
Ag(PPh3)2{ L 1}C H 3C N (4 ).
1
2
4
3
Formula
C63H5oAgN202Sb3
1340.2
Monoclinic
C47H37AgN 4OSSb.
1057.2
Triclinic
Cfti H54AgN202Sb3
1320.2
Monoclinic
C47H38AgN 30 2P2
846.6
Monoclinic
Formula weight
Crystal system
Space group
P2 |/c
P2 ,/c
Pi
P2 ,
11.08(2)
13.54(1)
15.90(2)
94.2(1)
107.5(1)
101.9(1)
2201(5)
2
9.184(1)
17.107(1)
13.949(1)
90
106.64(1)
90
2099.8(3)
2
1.339
868
14.558(5)
14.226(4)
27.680(9)
90
94.70(3)
90
5713(3)
4
1.558
14.105(3)
14.533(3)
27.480(5)
90
92.46(3)
90
5628(2)
4
1.558
2600
a (A)
b (A)
c (A)
a(°)
PC)
7 O
V (A3)
Z
1.595
1040
Dcalc (g C irT 3)
F(0 0 0 )
2632
//(M oKa) (cm- 1 )
Diffractometer
2#max (°)
Index ranges
17.84
Siemens R3 m/V
40.1
18.10
17.45
5.97
Stoe STADI-4
58.0
h ± 12, k 0-23, / ± 19
7160
CAD -4 Enraf Nonius Siemens R 3m/V
43.9
38.1
h 0-14, k 0-13, / ± 26 h 0-14, k 0-15,1± 28
Ä 0-10,*± 12, / ± 13
3634
Reflections collected 5513
7222
Unique data (Rmt)
Obs. refls (I > 2<r(I)) 4404
5254 (0.031)
6884 (0.023)
4997
3399 (0.030)
2696
6800 (0.0 2 1)
4186
Data used
5231
655
0.040, 0.093
1.069
5227
496
0.031,0.076
1.084
6588
622
0.034, 0.086
1.061
3398
505
0.076, 0.194
1.182
Parameters refined
R(F), w7?(F2) (obs.)
GOF on F2
Largest peak and
hole (e A -3 )
0.57/-0.38
0.81/—0.77
1.75/-1.45
0.64/-0.40
imates, indicating N-coordination of the nitroso - 10 cm-1). This suggests that in Ag(SbPh3)3{L}
group [7, 14]. A similar increase of i'(NO) was de- complexes the carbonyl groups of the ligands take
scribed earlier for cyanoximate complexes of cop- no part in coordination, or that the Ag-0=C bonds
per(II) and nickel(II) [7,9], while O-coordination of (if present) are essentially ionic. The latter possi-
the nitroso group in organoantimony(V) and organ- bility was confirmed earlier for Cu(4-MePy)2{L' } 2
otin(IV) complexes (Table II) effects the shift of (v(C=0) 1600 and 1620 cm-1) [16]. Thus we may
i/(NO) to lower wavenumbers [15]. A certain de- conclude that the organic anions in the bis com-
crease of the v(C=0) frequencies in the spectra of plexes Ag(EPh3)2{L} (E = P, Sb) are coordinated
in a bidentate chelate fashion, in the tris complexes
bis phosphine complexes Ag(PPh3)2{L} (-_\„(oo) =
25 - 35 cm-1) reflects also the formation of Ag- Ag(SbPh3)3{L} they are N-monodentate ligands,
0=C coordination bonds, so that for these com- and in the tetrakis complex Ag(PPh3)4{L2} the an-
pounds the IR data support bidentate chelate coor- ion is not coordinated.
dination of the cyanoximate anion via the nitroso
nitrogen and carbonyl oxygen atoms. Judging by
the values of C=N) (benzothiazole) absorptions
(Table II), the same suggestions may be made for
Ag(PPh3)2{L3} and Ag(SbPh3)2{L3} CH3CN. A
similar coordination mode was observed earlier for
The IR spectroscopic data agree with the results
of the X-ray study. Ag(PPh3)2{L1} CH3CN adopts
a molecular array, the acetonitrile of crystalliza-
tion is not coordinated. The silver atom is coordi-
nated in a distorted tetrahedron by two phosphorus
atoms (Ag-P 2.440(1), 2.441(1) A; P(l)-Ag-P(2)
Cu(H20){L' } 2 (i/(C=0) and u(N-0) at 1600 and 126.60(3)°) and the nitroso nitrogen and the car-
1360 cm-1, respectively) [7]. The decrease of the
u(C=0) frequency in the spectra of tris stibine com-
plexes Ag(SbPh3)3{L} is much lower (Z\„(c=o) = 5
bonyl oxygen atom of the chelating ligand (Fig. 1).
A similar environment of the metal atom was pro-
posed also for Cu(PPh3)2{ONC(CN)C(NH)OCH3}
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K. V. Domasevitch et al. • Antimony as a Donor Atom in Silver Coordination Chemistry
Fig. 1. Perspective view
with 40% probability
thermal ellipsoids of
Ag(PPh3)2{L1 }CH3CN
(4). Hydrogen atoms and
solvate CH3CN are omit-
ted for clarity. Selected
bond lengths and angles
(A,°):
Ag-N(l)
Ag-P(l)
Ag-P(2)
Ag-0(2)
2.341(3)
2.440(1)
2.441(1)
2.515(2)
N(l)-Ag-P(l) 115.0(1)
N(l)-Ag-P(2) 116.1(1)
P(l)-Ag-P(2) 126.60(3)
N(l)-Ag-0(2) 67.49(9)
P(l)-Ag-0(2) 108.87(9)
P(2)-Ag-0(2) 103.74(8)
Table IV. Main geometrical parameters (A,°) of the benzoylcyanoximate {L1} in 1, 4, 2H(L')-(18-crown-6)-4H20
(8) [6], Rb(18-crown-6){H(L')2} (9) [22], Ph4Sb{L‘} (10) [9], T1{L'} (11) [8], AgjL1} (12) [8] and Cu(H20){L' } 2
(13) [7],
l a
4
9
11
12
8
10
13
Configuration
Coordination of ONC
N(l)-0(1)
N(l)-C(l)
C(l)-C(2)
C(2)-0(2)
C(1 )-C(3)
C(3)-N(2)
C(2)-C(4)
cis-anti cis-anti
trans-anti
NOH-—OHt
1.362(2)
1.286(2)
1.489(3)
1.218(2)
1.449(3)
1.141(9)
1.482(2)
114.3(2)
118.6(2)
153.8(2)
trans-anti
NO— H— ON
1.316(4)
trans-anti trans-anti cis-anti cis-anti
N
N
O
H2-0
N,0
1.28(1)
N
1.26(2) 1.259(4)
1.27(1) 1.342(4)
1.48(3) 1.455(5)
1.31(3) 1.227(4)
1.249(4)
1.30(1)
1.32(1)
1.47(1)
1 .22(1 )
1.45(1)
1.15(1)
1.48(1)
113.2(7)
123.7(8)
177.2(8)
1.31(1)
1.33(1)
1.46(1)
1.24(1)
1.44(1)
1.14(1)
1.51(1)
1.34(1) 1.340(5)
1.46(1) 1.442(6)
1.294(5)
1.475(5)
1.210(4)
1.428(6)
1.134(5)
1.487(5)
114.6(3)
119.5(3)
1.253(4)
1.23(1)
1.42(2)
1.16(2)
1.42(1) 1.449(5)
1.443(5)
1.134(5)
1.129(5)
1.468(6)
1.13(1)
1.49(1)
1.61(3) 1.488(5)
0(1)-N(1)-C(1)
N(l)-C(l)-C(2)
N-( 1)-C( 1)-C(2)-0(2)
115.7(8) 117.7(9) 120.7(3)
118.0(3)
117.3(3)
6.9(8)
118(1)
110 (2)
- 1 (2)
118.5(9)
-166(1)
122.7(8)
172(1)
114.8(3)
1.9(9)
-158.1(8)
a Disordering of the ligand effects in accuracy in the bond lengths and angles; the values are given for the major
component.
[3, 17]. The five-membered chelate ring is pla- length is shortened (2.515(2) versus 2.610(8) A) and
nar and the deviation of the silver atom from the is comparable to Ag-N(l). A certain unification of
N(1)C(1)C(2)0(2) mean plane does not exceed the Ag-N and Ag-O separations may be ascribed to
0.050( 1) A. The Ag-N( 1) separations of 2.341 (3) A an effect of the formation of a genuine chelate ring,
are slightly longer than those found in the structure At the same time, the structure of Ag{L' } exhibits a
of Ag{L' } (2.254(8) A) [8], while the Ag-0(2) bond typical collinear N,N coordination at the silver atom
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909
K. V. Domasevitch et al. ■Antimony as a Donor Atom in Silver Coordination Chemistry
C(61)
C(31)
Fig. 2. Molecular structure of AgtSbPh^jL1} (1) with 40% probability thermal ellipsoids. Only the major orientation
of the disordered anion is shown. Selected bond lengths and angles (A,°): Ag-Sb(l) 2.751(1), Ag-Sb(2) 2.712(1), Ag-
Sb(3) 2.721(1), Ag-N(l) 2.349(9), Sb(l)-Ag-Sb(2) 114.84(3), Sb(l)-Ag-Sb(3) 112.08(4), Sb(2)-Ag-Sb(3) 108.87(4),
N(l)-Ag-Sb(l) 87.9(3), N(l)-Ag-Sb(2) 124.6(2), N(l)-Ag-Sb(3) 107.0(3).
via nitroso and nitrilic nitrogen atoms, with an ad- bond angles are almost 120°, while for the O-coor-
ditional weak Ag-O bond [1,8]. The N(l)-Ag-0(2)
angles are the same for both compounds (67.49(9) be proposed, in which the N-O bond lengths are
dinated benzoylcyanoximate another structure may
equal to or exceed the C-N one (Table IV). Unfor-
tunately, the disordering and high thermal motion
in the structures 1 and 2 preclude any discussion of
the anion geometry for these compounds.
and 67.5(3)° respectively).
The geometrical parameters of benzoylcyanox-
imate are accurate and allow a direct compari-
son with the data reported earlier. The C-C, C(3)-
N(2) and C(2)-0(2) bond lengths are insensitive
The molecular structure of the silver-triphenyl-
to the effects of coordination and are actually the stibine complexes and the refined disordering model
same for all the benzoylcyanoximate species (Ta- for coordinated benzoylcyanoximate in 1 are de-
ble IV). At the same time, coordination of the picted in Fig. 2-5. In all the compounds under
nitrogen (oxygen) atoms of the oximic group by consideration the coordination polyhedron of the
the metal centers disturbs the electronic struc- silver atoms is a distorted tetrahedron with ni-
ture of the CNO fragment significantly, as re- troso nitrogen (Ag-N at 2.349(9) and 2.359(5) A)
and three antimony atoms [Ag-Sb separations are
in the range 2.6898(8) - 2.7748(8) A] in 1 and
flected by the differences in the bond lengths for
main types of coordination compounds (Table IV).
The N(l)-0(1) and N(l)-C(l) bond lengths of 2 [AgNSb^], and two nitrogen and two anti-
1.259(4) and 1.342(4) A, respectively, are actually mony atoms [Ag-Sb 2.670(4); 2.682(3) A] in 3
the same like those of Cu(H2 0 ){L' } 2 (1.259(4) and [AgN2Sb2]. In the tris stibine complexes 1 and
1.333(5) A) [7], These separations suggest a nitroso 2 all the Sb-Ag-Sb bond angles lie within the
range of 108.87(4) - 115.00(2)°, the almost per-
character C-N=0 of the oximic group. The CNO
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910
K. V. Domasevitch et al. • Antimony as a Donor Atom in Silver Coordination Chemistry
separations [2.36(2) and 2.43(3) A] are comparable
with those found for 1 and 2. The cyanoxime is ac-
tually planar [within 0.10(2) A] and has a cis-anti
configuration of the CNO group with respect to the
benzothiazole nitrogen atom (torsion angle N(2)-
C(2)-C( 1)-N( 1) is 2( 1)°). The cis orientation of both
nitrogen atoms is stabilized by coordination to the
metal center, while the neutral molecule H(L3) [18]
and both the anionic forms {L3}~ and H(L3)2~ [in
[Cs2(18-crown-6)3]{H(L3)2} 2-2H(L3)-2H20] [19]
possess the more favourable trans-anti configura-
tion. In the five-membered chelate ring the sil-
ver atom deviates by 0.33(1) A from the mean
plane N(1)C(1)C(2)N(2). The geometrical param-
eters of the anion within the values of standard
deviation (±0.03 A) agree with that reported for
[Cs2(18-crown-6)3]{H(L3)2} 2-2H(L3)-2H20 [19]
and Tl( 18-crown-6){H(L3)2} [20].
There are no coordinative bonds of the type Ag-O
with nitroso groups, and long contacts Ag-O (with
the carbonyl group) in structures 1 and 2 are found at
2.81(1), and 2.93(1) and 2.725(6) A (for two orien-
tations of the disordered ligand), respectively. These
distances are essentially longer than the usual val-
ues for silver(I) complexes (ca. 2.20 - 2.50 A [1])
and even slightly exceed the Ag-Sb separations in
the title compounds. Evidently, these long Ag-O
contacts are determined by the structure of the lig-
ands (trans-anti configuration of the nitroso group
with respect to carbonyl) and may be ascribed to
an only weak van der Waals interaction between
the atoms. The same observation for the configura-
tion and coordination mode of benzoylcyanoximate
{L1}" was made for Cu(4-MePy)2{L!} 2 [7, 16].
It should be noted in this context that in coordina-
tion compounds with N,0 donor ligands the silver
Fig. 3. The refined disordering model of the anion in the
structure of 1. The angle between the two orientations
[0(l)-N(l)-0(la)] is ca. 56(2)° (“A” is a minor compo-
nent [43(1)%]). Ag---0(2), Ag---0(2a) are 2.93(1) and
2.81(1) A.
feet values for a tetrahedral environment. The dis-
torted tetrahedral coordination is the most com-
mon for silver(I) complexes with triphenylphos-
phine, -arsine and stibine [Ag(EPh3)2{X}],
[Ag(EPh3)3{X}] and [Ag(EPh3)4]{X} (E = P, As,
Sb) [1].
In Ag(SbPh3)2{L3}CH3CN the angle Sb-Ag- atom tends to demonstrate preferably N coordina-
tion, very often forming two collinear short Ag-N
ter of [Ag(SbPh3)2{C2B9H12}]2 (118.5(1)°) [5] bonds (2.15-2.30 A) [1,8].
Sb of 121.2(2)° agrees well with this parame-
We suppose that weak donor groups such as
and is somewhat smaller than the P-Ag-P an-
gles in Ag(PPh3)2 complexes (126.60(3)° for 4
and 132.83(4)° for dimeric [Ag(PPh3)2{ONC-
(CN)2}]2 [3]). This may be attributed to the longer
Ag-Sb separations as compared with the Ag-P data
(2.67 - 2.71 Ä versus 2.42 A as average of 27 Ag-
PPh3 complexes [2]) and the weaker steric repulsion
of the EPh3 ligands (E = P, Sb) in Ag(SbPh3)2 com-
plexes. The organic anion is coordinated in a biden-
tate chelate manner via the nitrogen atoms of the
nitroso and heteroaryl groups (Fig. 5). Both Ag-N
triphenylstibine may substitute the oxygen atoms
in the silver coordination sphere, but not the ni-
trogen atoms in the AgN2 chelate ring. The large
volume of Sb coordinated triphenylstibine makes
the realization of coordination numbers of the sil-
ver atom higher than four ([AgN2Sb2] or [AgNSb3])
impossible. This is a possible reason for the different
behaviour of triphenylphosphine and -stibine in sil-
ver I) cyanoximates. Thus. PPh3 easily substitutes
even the nitroso nitrogen atoms in the silver co-
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911
K. V. Domasevitch et al. • Antimony as a Donor Atom in Silver Coordination Chemistry
Fig. 4. Molecular structure
ofAg(SbPh3)3{L2}(2),with
40% probability thermal
ellipsoids. Selected, bond
lengths and angles (A,°):
C(35)
Cl36)
2.359(5)
2.6898(8)
2.7748(8)
2.7080(8)
1.265(6)
1.320(8)
1.45(1)
Ag-N(l)
Ag-Sb(l)
Ag-Sb(2)
Ag-Sb(3)
0(1)-N(1)
N(l)-C(l)
C(l)-C(2)
121.7(1)
113.8(1)
115.00(2)
N(l)-Ag-Sb(l)
N(l)-Ag-Sb(3)
Sb(l)-Ag-Sb(2)
Sb(3)-Ag-Sb(2) 109.55(3)
0(1)-N(1)-C(1) 118.6(5)
125.2(4)
C(l)-N(l)-Ag
C(59)
Fig. 5. Molecular structure
ofAg(SbPh3)2{L3}CH 3CN
(3), with 30% probability
thermal ellipsoids. Acetoni-
trile of crystallization omit-
ted. Selected bond lengths
and angles (A,0):
Ag-Sb(l)
Ag-Sb(2)
Ag-N(l)
Ag-N(2)
0( l)-N(l)
N(l)-C(l)
2.670(4)
2.682(3)
2.43(3)
2.36(2)
1.19(2)
1.38(3)
Sb(l)-Ag-Sb(2)
N(l)-Ag-Sb(l)
N(l)-Ag-Sb(2)
N(2)-Ag-Sb(2)
N(l)-Ag-N(2)
121.2(2)
113.4(5)
111.3(4)
113.5(4)
70.5(8)
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912
K. V. Domasevitch et al. • Antimony as a Donor Atom in Silver Coordination Chemistry
ordination sphere with formation of [Ag(PPh3)4]+,
while [Ag(SbPh3)4]+ appears to be unstable to N
donor nucleophiles. The potentially N ,0 chelating
oximate ions (c .f {L 1 }~ , {L2}- orcarbamoylcyan-
oximates {0 NC(CN)C(0 )NR.2} ([6 , 14]) in the co-
ordination compounds of that type may act as N
monodentate groups, and N,N chelating oximates
(c.f. {L3}~ and 2-pyridylcyanoximate [21]) as N,N
bidentate chelating ligands. Therefore, the maxi-
mum ratio SbPh3/Ag+, which may be reached for
these systems even in the presence of an excess of
triphenylstibine in the reaction mixture, is 3:1 for
N ,0 donor and 2:1 for N,N donor chelating cyanox-
imates, as confirmed by the present study.
Acknowledgements
KVD thanks The International Soros Science Educa-
tion Program for a grant (Nr. YSU083019), which has
partially supported this work.
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