trans-Chelating ligating ability of 1,1'-bis(diphenylselenophosphoryl)ferrocene (dpspf) towards silver(I). Crystal structure of [Ag(dpspf)]ClO4

Article abstract of DOI:10.1016/S0020-1693(99)00439-9

The ligand 1,1'-bis(diphenylselenophosphoryl)ferrocene, Fe[η⁵-C₅H₄P(Se)Ph₂]₂ (dpspf), reacted readily with [Ag(MeCN)₄]C1O₄ in CH₂Cl₂ to quantitatively give the monomeric two-coordinated complex [Ag(dpspf)]ClO₄. The solution behavior of the complex has been probed by variable-concentration and/or -temperature multinuclear NMR spectroscopy (¹H, ¹³C, ³¹P and ⁷⁷Se), which revealed extreme lability. Single-crystal X-ray structural analysis shows that the complex (orthorhombic, Pna2₁, a = 26.34(1), b = 12.363(6), c = 11.209(6) A?, Z = 4) exists as mononuclear species in an almost linear two-coordination environment around the silver atom with an Se(1)-Ag-Se(2) angle of 176.5(1)°. The Ag-Se bond distances (2.456(4) and 2.449(3) A?) and the Ag-Se-P angles (98.1(2) and 102.6(2)°) point towards a substantially sp³ hybridization of the selenium donor atoms. (C) 2000 Elsevier Science S.A.

Full text of DOI:10.1016/S0020-1693(99)00439-9

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Inorganica Chimica Acta 298 (2000) 251–255
Note
trans-Chelating ligating ability of
1,1%-bis(diphenylselenophosphoryl)ferrocene (dpspf) towards
silver(I). Crystal structure of [Ag(dpspf)]ClO4
Giuseppe Pilloni a,*, Bruno Longato a,b, Giuliano Bandoli c
a Dipartimento di Chimica Inorganica, Metallorganica ed Analitica, Uni6ersita` di Pado6a, Via Marzolo 1, I-35131 Padua, Italy
b Centro di Studio sulla Stabilita’ e Reatti6ita’ dei Composti di Coordinazione, CNR, Via Marzolo 1, I-35131 Padua, Italy
c Dipartimento di Scienze Farmaceutiche, Uni6ersita` di Pado6a, Via Marzolo 5, I-35131 Padua, Italy
Received 25 May 1999; accepted 1 September 1999
Abstract
The ligand 1,1%-bis(diphenylselenophosphoryl)ferrocene, Fe[h5-C5H4P(Se)Ph2]2 (dpspf), reacted readily with [Ag(MeCN)4]ClO4
in CH2Cl2 to quantitatively give the monomeric two-coordinated complex [Ag(dpspf)]ClO4. The solution behavior of the complex
has been probed by variable-concentration and/or -temperature multinuclear NMR spectroscopy (1H, 13C, 31P and 77Se), which
revealed extreme lability. Single-crystal X-ray structural analysis shows that the complex (orthorhombic, Pna21, a=26.34(1),
,
b=12.363(6), c=11.209(6) A, Z=4) exists as mononuclear species in an almost linear two-coordination environment around the
,
silver atom with an Se(1)ꢀAgꢀSe(2) angle of 176.5(1)°. The AgꢀSe bond distances (2.456(4) and 2.449(3) A) and the AgꢀSeꢀP
angles (98.1(2) and 102.6(2)°) point towards a substantially sp3 hybridization of the selenium donor atoms. © 2000 Elsevier
Science S.A. All rights reserved.
Keywords: Crystal structures; Silver complexes; Selenide complexes; Ferrocene complexes
documented on the basis of X-ray authenticated ex-
amples of the species [M(dptpf)]+ (M=Cu(I) [2],
Ag(I) and Au(I) [3]). The novel selenium analogue
(dpspf), at variance with the oxygen congener, was
similarly assigned to bind to Cu(I) in the trans-chelate
fashion mainly on the basis of NMR spectroscopy [2].
In fact, owing to the exceeding sensitivity to moisture
and reactivity towards coordinating solvents of solu-
tions of the complex [Cu(dpspf)]BF4 [2], several at-
tempts to obtain suitable crystals for X-ray analysis
failed.
1. Introduction
One of the most interesting features of ferrocene-
based ligands in coordination chemistry is their flexi-
bility, possibly due to the organometallic ‘ball-joint’.
The skeletal flexibility of these metalloligands confers
the ability to stabilize complexes of varied metal ge-
ometry under
a variety of coordinative bonding
modes [1]. In this connection, the unique capability of
1,1%-bis(diphenylthiophosphoryl)ferrocene (dptpf) to
function as a trans-chelating ligand has recently been
However, we were successful in obtaining single
crystals of the more stable and tractable silver deriva-
tive. Herein reported are the synthesis, the solution
multinuclear NMR characterization and the solid-
state X-ray structural characterization of the closely
related complex [Ag(dpspf)]ClO4 (1).
* Corresponding author. Tel.: +39-049-827 5230; fax: +39-049-
827 5161.
E-mail address: pilloni@chim.02.chin.unipd.it (G. Pilloni)
0020-1693/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(99)00439-9

252
G. Pilloni et al. / Inorganica Chimica Acta 298 (2000) 251–255
2. Experimental
(d, JCP=8.8 Hz, Cb), 75.7 (d, JCP=4.4 Hz, Cg), 74.2 (d,
J
CP=87.3 Hz, Ca), cyclopentadienyl resonances.
1
2.1. General procedures and materials
77Se{1H} NMR: l −303 (d, JSeP=598 Hz).
Caution! Perchlorate salts of metal complexes with
organic ligands are potentially explosive.
All reactions and manipulations of solutions were
performed under a dinitrogen atmosphere. 1,1%-bis-
(diphenylselenophosphoryl)ferrocene (dpspf) was pre-
pared as previously reported [2]. Tetrakis(acetonitrile)-
silver(I) perchlorate was obtained by metathesis between
AgNO3 and NaClO4 in acetonitrile. The precipitate of
NaNO3 was filtered and the resulting solution was
concentrated by rotary evaporation until transparent
crystals began to form. Upon cooling in the refrigerator
and addition of Et2O the product precipitated as a white
microcrystalline powder, which was collected by filtra-
tion, rinsed with Et2O and dried under a gentle stream
of nitrogen. All other reagents were of reagent-grade
quality and were used as supplied.
2.4. X-ray crystallography
Complex 1 crystallizes as a CH2Cl2 monosolvate
from dichloromethane–pentane. Single crystals of the
complex were grown in a refrigerator by layering pen-
tane onto the sample solution in dichloromethane. The
experimental X-ray data, collected on
a Nicolet
Siemens R3m/V diffractometer using the ꢀ–2q tech-
nique at a varied scan rate, are summarized in Table 1,
and some selected bond lengths and angles are reported
in Table 2. Further details are provided in Section 4.
Table 1
Crystallographic data for the structure determination and refinement
2.2. Apparatus
Empirical formula
Crystal system
Space group
[C34H28AgFeP2Se2]ClO4·CH2Cl2
The IR spectra were recorded as Nujol mulls on KBr
plates using a Nicolet 5SXC-FTIR spectrometer. 1H, 13C,
31P and 77Se NMR experiments were obtained in CDCl3
solution at 298 K in 5 mm sample tubes on a Jeol 90 MHz
and/or a Bruker AC-200 spectrometer equipped with a
variable temperature apparatus. The 1H and 13C spectra
were referenced by assigning the 1H impurity in the
solvent at l 7.24 and the 13C multiplet at l 77.0. The
external references were H3PO4 (85% w/w) for 31P and
selenophene, adjusted to l 605 from Me2Se [4], for 77Se.
orthorhombic
Pna21 (no. 33)
26.34(1)
12.363(6)
11.209(6)
3650(3)
1.828
,
a (A)
,
b (A)
,
c (A)
3
,
V (A )
Dcalc (g cm−3
)
Z
4
,
u (Mo Ka) (A)
0.71073
32.7
1976
4.5–50.0
293
1394
0.060
0.188
0.947
v (cm−1
F(000)
)
2q Range (°)
T (K)
2.3. Preparation of the complex [Ag(dpspf)]ClO4 (1)
Observed reflections (I]2|(I))
a
R
b
wR2
To a solution of dpspf (1.14 g, 1.60 mmol) in anhy-
drous CH2Cl2 (20 cm3) was added [Ag(MeCN)4]ClO4
(0.595 g, 1.60 mmol) and the mixture was stirred at room
temperature under nitrogen. After 1 h the cloudy solution
was filtered and the filtrate concentrated under vacuum
to a small volume. Addition of Et2O caused the precip-
itation of a brick-red solid which was collected by
filtration, washed with Et2O and dried under vacuum to
constant weight. The yield (1.50 g) was essentially
quantitative. The solid product contained CH2Cl2 of
GOF c
a R=SꢀꢀFoꢀ−ꢀFcꢀꢀ/SꢀFoꢀ.
b wR2=[S(w(ꢀFoꢀ −ꢀFcꢀ ) )/S(w(ꢀFoꢀ ))]1/2
.
2
2 2
2
c GOF=[S(w(ꢀFoꢀ −ꢀFcꢀ ) )/(n−p)]1/2
.
2
2 2
Table 2
,
Selected bond lengths (A) and angles (°) for [Ag(dpspf)]ClO4·CH2Cl2
Bond lengths
AgꢀSe(1)
AgꢀSe(2)
Se(1)ꢀP(1)
Se(2)ꢀP(2)
P(1)ꢀC(1)
P(2)ꢀC(6)
2.456(4)
2.449(3)
2.131(6)
2.133(6)
1.82(2)
P(1)ꢀC(11)
P(2)ꢀC(31)
P(1)ꢀC(21)
P(2)ꢀC(41)
FeꢀCmean
1.85(2)
1.74(2)
1.81(2)
1.81(2)
2.04(1)
1
crystallization as determined by H NMR spectroscopy
and confirmed by elemental analysis. Anal. Found: C,
42.6; H, 2.95; Ag, 11.1. Calc. for C34H28AgClFeO4-
P2Se2·0.7CH2Cl2: C, 42.6; H, 3.00; Ag, 11.0%. IR: 568
cm−1 (PꢁSe) (Dw= −5 cm−1 with respect to uncoordi-
1.79(2)
1
nated dpspf). H NMR (CDCl3, 298 K): l 7.8–7.6 (m,
Bond angles
Se(1)ꢀAgꢀSe(2)
AgꢀSe(1)ꢀP(1)
AgꢀSe(2)ꢀP(2)
Se(1)ꢀP(1)ꢀC(1)
Se(2)ꢀP(2)ꢀC(6)
Se(1)ꢀP(1)ꢀC(11)
176.5(1)
98.1(2)
102.6(2)
112.2(6)
112.2(7)
106.9(7)
Se(2)ꢀP(2)ꢀC(31)
Se(1)ꢀP(1)ꢀC(21)
Se(2)ꢀP(2)ꢀC(41)
FeꢀC(1)ꢀP(1)
115.5(6)
114.8(7)
106.9(7)
129(1)
10H, Ph), 4.70 (q, JHH and JHP:2 Hz, 2H, C5H4), 4.26
(q, JHH and JHP:2 Hz, 2H, C5H4). 31P{1H} NMR
1
(saturated solution): l 33.25 (s with 77Se satellites, JPSe
599 Hz). 13C{1H} NMR: l 133.4 (d, JCP=3.3 Hz, Cd),
131.9 (d, JCP=11.0 Hz, Cb), 129.3 (d, JCP=13.2 Hz, Cg),
129.1 (d, JCP=80.7 Hz, Ca), phenyl resonances; l 76.1
FeꢀC(6)ꢀP(2)
128(1)

G. Pilloni et al. / Inorganica Chimica Acta 298 (2000) 251–255
253
Fig. 1. ORTEP view of the complex. The thermal ellypsoids are drawn at 40% probability.
The final unit-cell parameters were determined from 50
high-angle data (2q\22°). Corrections were applied for
Lorentz, polarization and long-term intensity fluctua-
tions, the latter on the basis of the intensities of two
reflections repeatedly measured during data collection.
Corrections for absorption effects were not applied,
since azimuthal scan data for some reflections at  near
90° proved to be unnecessary. The structure was solved
by heavy-atom methods and refined by full-matrix least-
squares against F2. The nine heavy atoms were assigned
anisotropic displacement parameters and all hydrogen
atoms were constrained to ideal geometries with CꢀH
tions with a symmetrically-related perchlorate oxygen
,
,
(at 3.40 A) (Fig. 2) and the iron atom (at 3.875 A). The
structural features closely parallel those of the parent
complex containing the dptpf ligand [3] and the only
differences in the bond lengths arise from the difference
in the covalent radii of the donor atoms (rSe=1.17;
,
rS=1.04 A) [8]. The AgꢀSe distance (mean value of
,
2.453(3) A) represents the minimum value found among
the 99 observations retrieved in the version 5.16 of
October 1998 of the Cambridge Structural Database [9]
and scattered through a large range (from 2.473 to 3.051
,
,
A), while the SeꢀP distance (mean value of 2.132(6) A)
slightly increases upon coordination, and it is consistent
with the lower PꢁSe stretching frequency observed in the
IR spectrum. In fact, in the uncoordinated ligand this
,
0.96 A and variable isotropic thermal parameters. The
Flack [5] parameter for the absolute configuration was
0.01(3). The thermal parameters for the solvate
molecule were large, indicating possible disorder, a
feature quite common to complexes containing CH2Cl2
solvent. However, the final difference Fourier map was
featureless, the maximum residual density being of 0.6 e
,
length is 2.103(6) A [2] and shows no substantial varia-
,
tion for comparable selenides (2.111(3) A for Me3PSe
,
,
[10]; 2.108(1) A for Cy3PSe [11]; 2.106(1) A for Ph3PSe
,
,
[12]; 2.109(7) A for (m-tolyl)3PSe [13] and 2.116(5) A for
(o-tolyl)3PSe [14]). However, to accommodate the silver
atom the ligand destroys the centrosymmetric arrange-
ment found in the solid state and in the resulting
−3 in the vicinity of the silver atom. The structure was
solved and refined using SHELXTL/PC [6] and SHELXL
,
A
-
93 [7] program packages.
AgꢀSe(1)ꢀP(1)ꢀC(1)ꢀFeꢀC(6)ꢀP(2)ꢀSe(2)
eight-mem-
bered ring the four heavy atoms are virtually coplanar,
while P(1) and C(6) lie below this plane (by 0.63 and
3. Results and discussion
,
0.38 A, respectively) and P(2) and C(1) above (by 0.55
,
and 0.35 A, respectively). In the ferrocene moiety the
Complex 1 can be readily obtained in high yield as a
brick-red solid by ligand-exchange reaction from the
labile precursor [Ag(MeCN)4]ClO4 and equimolar
amounts of dpspf in CH2Cl2 solution at room tempera-
ture. The crystal structure of 1 has been established by
X-ray diffraction. The compound crystallizes as a
CH2Cl2 monosolvate from dichloromethane–pentane
The ORTEP drawing of complex 1·CH2Cl2 is shown in
Fig. 1. The environment about silver is that of the
expected linear two-coordination geometry, with a slight
deviation from the ideal 180° because of the
Se(1)ꢀAgꢀSe(2) angle of 176.5(1)° imposed by the ligand
bite. The metal is only marginally involved in interac-
cyclopentadienyl rings are staggered, forming an angle
of 23.2°, and slightly tilted away from the Fe center with
a dihedral angle of 8.9°. The C(1)ꢀ(5) ring makes
dihedral angles of 84.4 and 58.5° with the phenyl rings
at P(1), while for C(6)ꢀ(10) the values, relative to the
phenyl rings at P(2), are 75.9 and 56.1°.
The solid-state mononuclear structure of 1 appears
not to be maintained in solution, as is evident from the
multinuclear (1H, 13C, 31P and 77Se) NMR spectra in
chlorinated solvents. Thus, the 31P NMR spectrum in
CDCl3 at 25°C (Fig. 3) consists of one major signal, due
to the phosphorus atoms bonded to magnetically

254
G. Pilloni et al. / Inorganica Chimica Acta 298 (2000) 251–255
,
Fig. 2. Packing diagram of the complex showing the intermolecular Ag···O(4) (at x, y, z−1) interaction of 3.40 A.
1:3:3:1 quartets centered at l 4.70 and 4.26 (JHH$2
Hz), the first of which is well resolved and remains
substantially unchanged throughout the concentration
range shown, whereas the quartet at higher field is
poorly resolved and moves slightly to higher frequency
as the solute concentration is increased.
inactive Se nuclei, and of a doublet stemming from the
phosphorus nucleus bonded to 77Se (7.6% natural abun-
dance, I=1/2) with the expected relative intensities. A
splitting pattern arising from coupling to 13C nuclei of
the cyclopentadienyl and phenyl groups is also appar-
ent. It is worth noting, within this set of resonances,
that the doublet attributable to the ortho and meta
carbon atoms of the phenyl substituents shows a sepa-
ration of 12.2 Hz and an intensity almost identical with
that of the 77Se satellites. Remarkably, no coupling of
the phosphorus nuclei to the metal center (107Ag 51.8%,
I=1/2 and 109Ag 48.2%, I=1/2) is observable. More-
over, the chemical shift of the main signal is strongly
effected by the concentration of the solution moving at
higher field by up to 1.077 ppm as the solute concentra-
tion is gradually increased 25 times. Conversely, only
Since the two bond 107/109Agꢀ31P coupling constant is
expected to be approximately 10 Hz [15], it should be
clearly detectable in the presence of kinetically stable
metal–ligand bonds. Hence, these observations point
unambiguously to the occurrence of rapid dissociation
1
minor effects on the JPSe are detectable, with higher
values for more concentrated solutions. For instance, l
(31P) 34.327 (1JPSe 591.2 Hz), 34.024 (592.5 Hz), 33.385
(598.0 Hz) and 33.250 (599.4 Hz) for 8, 41, 170 and 210
mmol dm−3 CDCl3 solutions of 1, respectively. For
comparison, the uncoordinated dpspf ligand in CDCl3
exhibits its 31P resonance at l 30.93 (1JPSe 743 Hz), with
negligible effects on the concentration [2].
A smaller concentration effect is also observed in the
1
corresponding H NMR spectrum, which displays the
usual pair of multiplets typical of two sets of C5H4
protons arranged in a symmetrical environment. The
two sets of equally intense signals occur as apparent
Fig. 3. 31P{1H} NMR spectrum of the complex in CDCl3 (saturated
solution) at 25°C.

G. Pilloni et al. / Inorganica Chimica Acta 298 (2000) 251–255
255
and intermolecular association processes involving the
AgꢀSe bonds. The low-energy exchange process is still
operational at −95°C as is evident from variable temper-
ature 31P NMR studies. Upon cooling a saturated CD2Cl2
solution of 1 from 27 to −95°C, the sharp resonance at
l 33.75 (1JPSe 595.7 Hz) begins moving slowly to higher
field (l 33.14 at −60°C) while retaining the unresolved
fine structure, but still no evidence is found at the lowest
temperature for the expected two doublets in the 31P
resonance. Thus, at −95°C the signal is still a singlet (l
32.43), though quite large (line width Dw1/2)=7.5 Hz),
with sharp pertinent 77Se satellites (1JPSe 598.3 Hz).
The kinetic lability of the AgꢀSe bond in complex 1 is
confirmed by the 77Se NMR spectrum. The sharp doublet
is centered at l −303, slightly shifted upfield with respect
ters, bond lengths, bond angles and thermal parameters
has been deposited at the Cambridge Crystallographic
Data Centre (CCDC no. 137140). Copies of this informa-
tion may be obtained free of charge from: The Director,
CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (fax:
+44-1223-336033; e-mail: deposit@ccdc.cam.ac.uk or
www: http://www.ccdc.cam.ac.uk).
References
[1] K.-S. Gan, T.S.A. Hor, in: A. Togni, T. Hayashi (Eds.), Fer-
rocenes: Homogeneous Catalysis, Organic Synthesis, Materials
Science, VCH, Weinhaim, 1995 (Chapter 1), and references
therein.
[2] G. Pilloni, B. Longato, G. Bandoli, B. Corain, J. Chem. Soc.,
Dalton Trans. (1997) 819.
1
to the uncoordinated ligand (l −297.5, JSeP 743 Hz),
and the separation of the signals is 598 Hz, in good
agreement with the JPSe value already found in the
[3] (a) M.C. Gimeno, P.G. Jones, A. Laguna, C. Sarroca, J. Chem.
Soc., Dalton Trans. (1995) 3563. (b) M.C. Gimeno, P.G. Jones,
A. Laguna, C. Sarroca, J. Chem. Soc., Dalton Trans. (1998)
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[4] H.C.E. McFarlane, W. McFarlane, in: P. Lazlo (Ed.), NMR of
Newly Accessible Nuclei, vol. 2, Academic Press, London,
1983, p. 275.
[5] D. Flack, Acta Crystallogr., Sect. A 39 (1983) 876.
[6] G.M. Sheldrick, SHELXTL/PC, Version 5.03, Siemens Analytical
X-ray Instruments Inc., Madison, WI, 1994.
[7] G.M. Sheldrick, SHELXL-93, Program for the Refinement of
Crystal Structures, University of Go¨ttingen, Germany, 1993.
[8] D.F. Shriver, P.W. Atkins, C.H. Langford, Inorganic Chem-
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[9] F.H. Allen, J.E. Davies, J.J. Galloy, O. Johnson, O. Kennard,
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1261.
[13] T.S. Cameron, K.D. Howlett, K. Miller, Acta Crystallogr.,
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1
corresponding 31P spectrum. Upon cooling the solution to
−65°C, the one observable alteration is a broadening of
the signals without any significant change of the chemical
shift values. Similarly extreme lability has recently been
noted in silver complexes with bis(selenoethers) [16].
The facile fluxionality exhibited by silver complex 1
seems to be in remarkable contrast with the rigidity
claimed for its copper(I) analogue [2]. As a matter of fact,
the kinetic stability of the CuꢀSe bond was merely inferred
by the clear presence in the 31P NMR spectrum of the
complex of a couple of satellites symmetrically flanking
the main resonance (J=12 Hz) in the appropriate :8%
intensity ratio, just as expected for a three-bond
(31PꢀSeꢀCuꢀ77Se) interaction. Now, the similar NMR
features shared by very labile complex 1 are conclusively
rationalized in terms of coupling of 31P nuclei to fortu-
itously overlapping 13Cb and 13Cg of the phenyl sub-
stituents (see Section 2) [17]. Our former statement of
kinetically stable CuꢀSe bonds lacks 77Se NMR support,
and in the light of these additional findings may, conse-
quently, result in an invalid assumption.
[14] T.S. Cameron, B. Dahle`n, J. Chem. Soc., Perkin Trans. II
(1975) 1737.
[15] H. Schmidbaur, J. Adlkofer, W. Buchner, Angew. Chem., Int.
Ed. Engl. 12 (1973) 415.
[16] (a) J.R. Black, N.R. Champness, W. Levason, G. Reid, J.
Chem. Soc., Dalton Trans. (1995) 3439. (b) J.R. Black, N.R.
Champness, W. Levason, G. Reid, Inorg. Chem. 35 (1996)
1820.
4. Supplementary material
A CIF file containing tables of crystal data and
experimental conditions, final atomic positional parame-
[17] B. Longato, G. Pilloni, unpublished results.
.