Preparation and structural studies on diorganotin(IV) complexes of N-nitroso-N-phenylhydroxylaminates

Article abstract of DOI:10.1016/j.jorganchem.2007.04.003

Diorganotin(IV)-complexes of the N-nitroso-N-phenylhydroxylaminates (hereinafter cupf), Et₂Sn(cupf)₂ (1), Bu₂Sn(cupf)₂ (2), {[Bu₂Sn(cupf)]₂O}₂ (3), t-Bu₂Sn(cupf)₂ (4) and Oc₂Sn(cupf)₂ (5, 6) were prepared and characterised by FT-IR and M?ssbauer spectroscopic measurements. The binding modes of the ligand were identified by FT-IR spectroscopy, and it was found that the ligand is coordinated in chelating or bridging mode to the organotin(IV) center. The ¹¹⁹Sn M?ssbauer and FT-IR studies support the formation of trans-O_h (1-6) structures. The X-ray diffraction analysis of 4 revealed that the tin centre is in a skew-trapezoidal geometry defined by four donors derived from the cupferronato ligands and two carbon atoms from the tin-bound ^tbutyl substituents. The ¹¹⁹Sn NMR investigations indicate that in solution 4 retains its hexacoordinated nature.

Full text of DOI:10.1016/j.jorganchem.2007.04.003

Journal of Organometallic Chemistry 692 (2007) 3409–3414
www.elsevier.com/locate/jorganchem
Preparation and structural studies on diorganotin(IV) complexes
of N-nitroso-N-phenylhydroxylaminates
a
b,
b
c
d
*
´
´
´
´
´
Attila Szorcsik , Laszlo Nagy , Istvan Ko¨keny , Andrea Deak , Michelangelo Scopelliti ,
d
d
Tiziana Fiore , Lorenzo Pellerito
a
Bioinorganic Chemistry Research Group of the Hungarian, Academy of Sciences, P.O. Box 440, 6701 Szeged, Hungary
b
SZTE, Department of Inorganic and Analytical Chemistry, P.O. Box. 440, 6701 Szeged, Hungary
Institute of Structural Chemistry, Chemical Research Center, Hungarian Academy of Sciences, P.O. Box 17, 1525 Budapest, Hungary
c
d
Universita´ di Palermo, Dipartimento di Chimica Inorganica e Analitica, Viale delle Scienze, Parco d’Orleans, 90128 Palermo, Italy
Received 20 September 2006; received in revised form 2 April 2007; accepted 10 April 2007
Available online 14 April 2007
Abstract
Diorganotin(IV)-complexes of the N-nitroso-N-phenylhydroxylaminates (hereinafter cupf), Et2Sn(cupf)2 (1), Bu2Sn(cupf)2 (2),
{[Bu2Sn(cupf)]2O}2 (3), t-Bu2Sn(cupf)2 (4) and Oc2Sn(cupf)2 (5, 6) were prepared and characterised by FT-IR and Mo¨ssbauer spectro-
scopic measurements. The binding modes of the ligand were identified by FT-IR spectroscopy, and it was found that the ligand is coor-
dinated in chelating or bridging mode to the organotin(IV) center. The 119Sn Mo¨ssbauer and FT-IR studies support the formation of
trans-Oh (1–6) structures. The X-ray diffraction analysis of 4 revealed that the tin centre is in a skew-trapezoidal geometry defined by
four donors derived from the cupferronato ligands and two carbon atoms from the tin-bound tbutyl substituents. The 119Sn NMR inves-
tigations indicate that in solution 4 retains its hexacoordinated nature.
ꢀ 2007 Published by Elsevier B.V.
Keywords: Diorganotin(IV); FT-IR; Mo¨ssbauer; 1H; 13C and 119Sn NMR spectroscopy; Cupferron; X-ray diffraction
1. Introduction
nism of activation of NO-receptor enzyme guanylate
cyclase [2].
The ammonium salt of N-nitroso-N-phenylhydroxyl-
amine, NH4[PhN(O)NO], cupferron (hereinafter cupf)
(Scheme 1), is a well known analytical reagent and it was
very popular especially during the classical period of ana-
lytical chemistry [1]. This ligand is known to form com-
plexes with many metals but few of them have been
structurally characterised. The biological activity of cupf
has also been investigated: carcinogenic, mutagenic, geno-
toxic and DNA-damaging effects were noted [2]. The
knowledge of the coordination chemistry of cupferron
could provide useful information about the interaction
modes of NO with metal centres of biologically important
species, and it may also contribute to elucidate the mecha-
The organotin(IV) complexes of cupf may be interesting
to study, since many organotin compounds are known to
display antitumour activity and the ligand itself has some
biological activity [3]. Some diaryltin(IV)-cupferronates,
Ar2Sn(cupf) (Ar = Ph, o-Tol, m-Tol, p-Tol), were prepared
and characterized by IR spectroscopy [4].
Recently, one of us reported the synthesis and structural
characterisation of organotin(IV) cupferronato complexes,
such as [Me3Sn(cupf)]4 [5], Ph2Sn(cupf)2 [6], [Me2Sn
(cupf)2]2 [3]. It was found that, depending on the number
(2, 3) and the nature (Me, Ph) of the organic substituents
at the tin(IV) atom, the cupferronato anion displays vari-
ous coordination patters in these molecules, chelating
(Scheme 2a), bridging (Scheme 2b), and bridging chelating
(Scheme 2c). As a consequence, the central tin(IV) atom
*
Corresponding author. Tel.: +36 62 544335; fax: +36 62 420505.
assumes
a penta-, hexa- or hepta-coordinate state,
E-mail address: laci@chem.u-szeged.hu (L. Nagy).
0022-328X/$ - see front matter ꢀ 2007 Published by Elsevier B.V.
doi:10.1016/j.jorganchem.2007.04.003

3410
A. Szorcsik et al. / Journal of Organometallic Chemistry 692 (2007) 3409–3414
2.2. Syntheses
The complexes 1, 2, 4 and 5 were prepared as already
N
N
O
O
described in [8]. The appropriate amount of cupf (2 mmol)
and diorganotin(IV)dichloride compounds (1 mmol) were
dissolved in dry methanol. After stirring and refluxing, or
only stirring, the resulting solution was kept in refrigerator.
The precipitated NH4Cl was filtered off, and the solution
was taken for crystallisation. Compounds 3 and 6 were pre-
pared by refluxing appropriate quantity of cupf (2 mmol)
and Bu2SnO or Oc2SnO in methanol for 3 h. Reaction of
ligand and diorganotin(IV) oxides yielded NH3 which
was removed by reflux. Compounds 3 and 6 were crystal-
lised out after slow evaporation of the solvent at room tem-
perature, then washed with methanol. All products were
recrystallised from hexane or methanol.
NH4
Scheme 1.
N
N
N
N
N
N
O
O
O
O
O
O
M
M
M
M
M
Scheme 2.
2.3. Analytical and spectroscopic (FT-IR, Mo¨ssbauer and
multinuclear NMR) measurements
respectively, and the resulting complexes display different
coordination geometries at the central tin(IV) atom [5–7].
Bridging chelating coordination of the cupferronato ligand
to Me2Sn(IV)2+ cation gives the dimeric species (Scheme
2c) [6], whereas a bridging coordination to Me3Sn(IV)+
affords the tetrameric complex (Scheme 2b) [5].
In order to demonstrate the influence of longer (Et, Bu,
Oc) alkyl chains and larger (t-Bu) organic substituents on
the structure of diorganotin(IV)-cupferronates we prepared
the Et2Sn(cupf)2 (1), Bu2Sn(cupf)2 (2), {[Bu2Sn(cupf)]2O}2
(3), t-Bu2Sn(cupf)2 (4) and Oc2Sn(cupf)2 (5, 6) complexes.
They were characterised by analytical and spectroscopic
(FT-IR, Mo¨ssbauer) methods. To accumulate precise
structural data concerning the binding mode of the cupfer-
ronato anion, the X-ray diffraction analysis of 4 was also
performed.
Microanalyses were performed at the Department of
Organic Chemistry, University of Szeged. The Sn contents
were measured by Inductively Coupled Plasma Atomic
Emission Spectrometry (ICP-AES) [8] and found to corre-
spond to the theoretically calculated values. The analytical
data on the compounds are presented in Table 1, together
with other characteristic physical constants.
FT-IR spectra of the ligand and of the complexes were
recorded in Vibrational Laboratory of Szeged University
on a BIORAD FTS-65A FT-IR spectrometer in KBr pel-
lets in the range 4000–400 cmꢀ1
.
Mo¨ssbauer spectroscopic measurements were performed
as described previously [8]. In order to determine the steric
arrangement of the coordination sphere, the experimental
quadrupole splitting values (jDexpj) were compared with
those calculated Dcalc for different tetra-, penta- and hexa-
coordinated symmetries of the tin(IV) centres on the basis
of point charge model formalism (partial quadrupole split-
ting, pqs) [9]. On the basis of these calculations, the most
probable stereochemistry of a given complex can be sug-
gested. The pqs values of the different functional groups
in question were taken in part from the relevant literature
[10,11].
2. Experimental
2.1. Materials
Et2SnCl2 was purchased from Alfa Aesar, Bu2SnCl2,
Bu2SnO and cupferron were purchased from Fluka. All
other compounds were Sigma–Aldrich products. All the
starting reagents were of A.R. grade and were used without
further purification.
Solution NMR data were recorded on Bruker Avance
500 spectrometer in CDCl3, using TMS as internal
Table 1
Physical and analytic data (calculated % values in parentheses) of diorganotin(IV) cupferronato 1–6 complexes
Complex/starting diorganotin(IV) compounds Analysis (%)
C
Colour
Yield (%) M.p. (ꢁC)
H
N
Sn
Et2Sn(cupf)2 (1)/Et2SnCl2
Bu2Sn(cupf)2 (2)/Bu2SnCl2
{[Bu2Sn(cupf)]2O}2 (3)/Bu2SnO
t-Bu2Sn(cupf)2 (4)/t-Bu2SnCl2
Oc2Sn(cupf)2 (5)/Oc2SnCl2
Oc2Sn(cupf)2 (6)/Oc2SnO
42.60 (42.94) 4.44 (4.48) 12.42 (12.56) 26.34 (26.47) White
47.36 (47.93) 5.53 (5.58) 11.05 (11.12) 23.43 (23.68) Yellowish-white 68
44.48 (43.93) 6.09 (5.85) 7.41 (7.18) 31.43 (31.29) Yellowish-white 56
47.36 (47.48) 5.53 (5.55) 11.05 (11.08) 23.43 (23.50) Yellow
85
80–83
50–52
90–93
107–110
>300
74
64
71
54.31 (53.97) 7.11 (7.03)
54.31 (54.44) 7.11 (7.25)
9.05 (9.26)
9.05 (9.14)
19.19 (18.94) Colourless
19.19 (19.33) Colourless
>300

A. Szorcsik et al. / Journal of Organometallic Chemistry 692 (2007) 3409–3414
3411
1
standard for H and 13C, and SnEt4 for 119Sn as external
Table 2
˚
Selected interatomic bond distances (A) and bond angles (ꢁ) for complex 4
reference.
Sn(1)–O(1)
Sn(1)–O(2)
Sn(1)–C(1)
O(1)–N(1)
O(2)–N(2)
N(1)–N(2)
N(1)–C(5)
C(1)–Sn(1)–C(1)i
O(2)–Sn(1)–O(1)
O(1)–Sn(1)–C(1)
O(2)–Sn(1)–C(1)
2.347(2)
2.172(2)
2.199(2)
1.301(2)
1.305(2)
1.285(3)
1.445(3)
151.3(2)
68.76(5)
86.4(1)
2.4. X-ray crystallography
Crystal data for t-Bu2Sn(cupf)2 (4): C20H28N4O4Sn,
Mr = 507.15, monoclinic, space group C2/c (No. 15), with
˚
˚
˚
a = 23.636(3) A, b = 6.123(1) A, c = 16.235(2) A, b =
3
˚
111.487(9)ꢁ, V = 2186.3(5) A , Z = 4, qcalc = 1.541 Mg/
3
˚
m , F(000) = 1032, k = 0.71073 A, T = 295(2) K, l (Mo
Ka) = 1.201 mmꢀ1
, crystal size 0.15 · 0.25 · 0.35 mm.
101.5(1)
Intensity data of 8205 reflections were measured
(2.65 6 h 6 31.92ꢁ) on an Enraf-Nonius CAD-4 diffrac-
tometer (x ꢀ 2h scans) of which 3770 were independent
(Rint = 0.020). The intensities of the standard reflections
indicated a crystal decay of 2%, which was corrected. A
semi-empirical (psi-scan) absorption correction was also
applied (min/max transmission: 0.6785/0.8404). The struc-
ture was solved by direct methods (SHELXS-97) and refined
by full-matrix least-squares (SHELXL-97) [12]. 3770 reflec-
tions were employed in the structure refinement (135
Equivalent atom generated by (i) ꢀx, y, 1/2 ꢀ z.
geometry, as they exhibit an intermediate skew-trapezoidal
geometry, where the C–Sn–C angle varies from 135 to 155ꢁ
[13]. In complex 4, this C–Sn–C angle is 151.3(2)ꢁ. The
SnO2N2 chelate ring is planar, with an r.m.s. deviation of
˚
fitted atoms of 0.0065 A; the O(1)–N(1)–N(2)–O(2) torsion
angle is 1.7(3)ꢁ. The chelating cupferronato ligand exhibits
different Sn–O bond lengths, thus the Sn(1)–O(1) bond is
˚
parameters,
0
restraints). The final
R
values were
longer (by 0.175 A) than the Sn(1)–O(2) bond. The N(1)–
˚
R1 = 0.0297 (I > 2r(I)) and wR2 = 0.0758 (all data); the
goodness of fit was S = 1.01; min/max residual electron
N(2) bond length of 1.285(3) A is intermediate to that of
˚
the corresponding single (1.45 A) and double bond
density ꢀ0.89/0.81 e Aꢀ3. All non-hydrogen atoms were
(1.21 A) lengths. The average N–O bond length of
˚
˚
˚
˚
refined anisotropically. Hydrogen atomic positions were
generated from assumed geometries. A riding model refine-
ment was applied for the hydrogen atoms.
1.303(2) A is between that of a single (1.40 A) and double
˚
bond (1.21 A). These structural features suggest significant
electron delocalisation along the N(O)NO moiety, which is
typical for organotin(IV) cupferronates [5–7]. The plane
defined by the cupferronato O(1)–N(1)–N(2)–O(2) atoms
forms an angle of 18.7(1)ꢁ with the plane of the phenyl
group. In the crystal, C–Hꢁ ꢁ ꢁp and p–p interactions play
a major role in the molecular self-assembly.
3. Results and discussion
3.1. X-ray structural study
The molecular structure of 4 is shown in Fig. 1. Selected
bond lengths and angles are listed in Table 2. The X-ray
analysis established that the cupferronato anions in 4 are
coordinated to the tin centre in a bidentate chelating fash-
ion leading to five-membered SnO2N2 chelate rings with an
O(1)–Sn(1)–O(2) bite angle of 68.76(5)ꢁ. The tin centre is in
a skew-trapezoidal geometry defined by four donors
derived from the cupferronato ligands and two carbon
atoms from the t-butyl substituents. Several dialkyltin(IV)
complexes are neither in regular cis nor in regular trans
3.2. FT-IR spectroscopic characterisation
The coordination sites of the ligand were determined by
means of FT-IR spectroscopy. For comparison, the FT-IR
spectra of the starting diorganotin(IV) compounds and
their cupferronato complexes were recorded. The assign-
ment of the characteristic bands of the ligand is based
mainly on data published in [14]. On the ligand spectrum,
the most important bands from coordination chemistry
point of view are following: m(NH4+) 3160 cmꢀ1; m(@CH)Ph
3050–2852 cmꢀ1; m(C@C)Ph 1483 and 1460 cmꢀ1; m(N–N)
1331 and 1314 cmꢀ1; m(N@O) 1264 and 1221 cmꢀ1
;
d(ONNO) 907 cmꢀ1; c(CH)Ph 755 and 689 cmꢀ1 d(NNO)
581 cmꢀ1. The characteristic FT-IR bands, which are
observed for the 1–6 complexes together with vibrational
assignments, are detailed in Table 3.
A comparison of IR spectra of the investigated com-
plexes 1–6 with that of cupferron reveals significant
changes in the position of the above-mentioned bands
due to electron delocalisation over the coordinated ONNO
unit. The stretching vibration (3160 cmꢀ1) related to the
ammonium salt of the ligand is absent from the spectra
of the complexes, indicating formation of the Sn–O bonds.
Fig. 1. ORTEP diagram of the molecular structure of complex 4, with
atom labelling scheme. Non-hydrogen atoms are shown as 50% proba-
bility ellipsoids and hydrogen atoms are shown as open cycles.

3412
A. Szorcsik et al. / Journal of Organometallic Chemistry 692 (2007) 3409–3414
Table 3
Characteristic vibration bands for 1–6 complexes
Assignment
1
2
3
4
5 and 6
m(CHx) (x = 1–3)
m(N–N)
d(ONNO)
c(CH)Ph
m(Sn–O–Sn)
dÆ(O–Sn–O)
ma(Sn–C)
2975 w – 2687 w
1338 m, 1293 vs
918 s
754 s, 692 s
–
2960 m – 2858 m
1334 m, 1288 vs
921 s
750 m, 692 s
–
2955 vs – 2855 m
1341 s, 1300 s
925 vs
758 vs, 693 s
591 s
2975 w – 2846 m
1342 vs, 1303 s
917 s
755 s, 691 s
–
2955 – 2853 m
1345 m, 1291 vs
928 m
757 s, 693 m
–
681 s
541 m
682 s
544 m
–
684 m
595 m
685 m
592 m
556 s
ms(Sn–C)
489 w
488 w
489 w
526 w
494 w
m(Sn–O)
399 m
400 m
389 s
388 s
400 m
Abbreviations: s = strong; m = medium; w = weak; vs = very strong, sh = shoulder.
The m(N–N) and d(ONNO) modes are shifted to higher/
lower by 3–15/14–26 and to higher by 10–26 cmꢀ1, respec-
tively (see Table 3). In the case of complexes 1, 2 and 4–6,
the wave numbers of the bands appeared in the 1350–
400 cmꢀ1 spectral region do not differ as much, indicating
the formation of similar structures for the mentioned
complexes.
The sharp and strong bands characteristic of the differ-
ent dialkyltin(IV) cations (mCH3 and mCH2) in the interval
2900–2700 cmꢀ1 were not significantly affected by the coor-
dination. The presence of two (asymmetric and symmetric)
Sn–C absorption bands between 600 and 480 cmꢀ1 in the
spectra of all compounds strongly suggests that the C–
Sn–C bond angle is less than 180ꢁ. This is in accord with
the 119Sn Mo¨ssbauer spectroscopic and X-ray diffraction
results.
3.3. Mo¨ssbauer spectroscopic characterisation
In order to gain further structural information on the
solid complexes, the Mo¨ssbauer spectra of the compounds
were recorded and analysed. The spectra of compounds 1,
2 and 4–6 comprised only one, well developed doublet (the
narrowness of the full width at half the maximum of the
observed of the resonance line being average), which sug-
gests the presence of completely equivalent Sn environ-
ments in these compounds. An unsymmetric doublet with
the line width greater than 1.0 was observed in the spec-
trum of compound 3, indicating the presence of Sn in
two different coordination environments. This doublet
was decomposed into two doublets. The 119Sn Mo¨ssbauer
spectroscopic parameters are listed in Table 4, together
with the suggested configurations according to the pqs con-
cept. The magnitudes of the isomer shift (d) indicate an oxi-
dation state of Sn(IV) for all the complexes. For Sn(IV)
complexes containing the R2Sn(IV) moiety, the quadrupole
splitting is dominated by highly covalent Sn–C bonds and
if the contributions of the other donor atoms are ignored, it
can be shown that D is given by
The wave number of the Sn–O stretching is one of the
most important data relating to the bonding mode of the
ligand. It was observed that, if the cupferronato anion is
coordinated to the tin centre in common bidentate chelat-
ing mode, the m(Sn–O) a band appears at 399–406 cmꢀ1
,
while, for the bridging coordination pattern, the m(Sn–O)
band is centered around 389 cmꢀ1 [14]. In our compounds,
this band can be assigned in 399–403 cmꢀ1 spectral region,
except for complexes 3 and 4. In the case of 3, the analyt-
ical data suggest 1:1 metal to ligand molar ratio. A strong
band, characteristic of the tetraorganodistannoxanes and
attributed to the (Sn–O)2 ring vibration, is present in the
spectrum of 3 at 591 cmꢀ1. It is very interesting that, in
the case of dioctyltin(IV)-compounds, the FT-IR spectra
of the two Oc2Sn(IV)complexes (5 and 6) are quite similar.
This, and the absence of the characteristic m(Sn–O–Sn)
band suggested that, in this case, the distannoxane ring for-
mation did not take place. This observation is in good
agreement with the results of Mo¨ssbauer spectroscopic
investigations.
1=2
D ¼ ꢀ4½Rꢂ½1 ꢀ ð3=4Þ sin2 hꢂ
;
where [R] denotes the pqs value of group R, and h is the C–
Sn–C bond angle [15]. This equation has been satisfactory
applied to penta- and hexacoordinated Sn(IV) compounds,
with the use of appropriate values of [R] for each coordina-
tion number [11,16–19]. The model assumes that quadru-
pole splitting (D) arises from point-charge hydrocarbon
groups separated by a C–Sn–C angle of (180 ꢀ 2h)ꢁ, with
contributions from other coordinated ligands being ig-
nored. The quadrupole splitting has been used to estimate
the C–Sn–C angle, and they are listed in Table 4.
The full width at half maximum of the peaks (C) and the
asymmetrical shape of the Mo¨ssbauer spectrum of 3 indi-
cate more than one tin coordination environment. Resolu-
tion of the spectrum results in adjacent quadrupole
splitting values of 3.18 and 3.93 mm sꢀ1, which indicate
mer-Tbp and trans-Oh tin(IV) coordination environments
(Fig. 2). In contrast with this, the spectrum of analogous
The molecular geometry of compound 4 was investi-
gated by X-ray diffraction analysis. These results showed
that, in this complex, the anion is coordinated to the tin
centre in a bidentate chelating mode. Therefore, we could
not explain why the Sn–O stretching appears 12 cmꢀ1
lower than we expected.

A. Szorcsik et al. / Journal of Organometallic Chemistry 692 (2007) 3409–3414
3413
Table 4
Experimental and calculated Mo¨ssbauer parameters and the proposed structures for complexes 1–6
Complex
dm1/m2
jDm1/m2
j
Dcalc1/calc2
C1/2
Ia
h
Geometry
1
2
3
1.40
1.41
1.23
1.27
1.56
4.12
4.18
2.99
3.87
3.49
4.23
4.23
3.18
3.93
3.58
0.86
0.86
0.87
0.87
0.91
0.95
0.82
0.87
–
–
1:1
180
168
122
154
138
(151)
165
162
trans-Oh
trans-Oh
mer-Tbp
trans-Oh
trans-Oh
4
–
5
6
1.41
1.46
4.21
3.99
4.23
3.93
–
–
trans-Oh
trans-Oh
m, experimental; calc, calculated; Tbp, trigonal bipyramidal; Oh, octahedral; h is C–Sn–C bond angle, given in ꢁ, value in parentheses was obtained from
X-ray diffraction measurement.
values normally expected and can be found at the end of
this chapter with some of the detectable couplings.
Within a given set of related diorganotin(IV) complexes,
N
N
the chemical shift of the 119Sn nuclei has been shown to
reflect the coordination number, the size of the chelate ring,
and the nature of the donor atom directly bonded to the
central tin(IV) atom: higher coordination numbers, larger
ring sizes, and lower electronegativities of the donor atoms
shift the 119Sn resonance to lower frequencies [20]. The
119Sn chemical shift values for the complexes studied, in
general follow the expected trends. Thus in 4, the observed
ꢀ222 ppm, falls in the range typical of hexacoordinated
organotin(IV) complexes in chloroform solution. In case
of 1 and 2, the magnitude of the dSn values (ꢀ356 and
ꢀ376 ppm) reflects also the existence of the distorted octa-
hedral geometry in solution, but it can not be ruled out that
in these compounds the central Sn(IV) atoms are in hepta-
coordinated surroundings, adopting one more ligand which
can be one methanol or one water molecule. The measured
two dSn values for 3 are in accordance with the Mo¨ssbauer
spectroscopy results for this complex (two quadrupole
splitting values of 3.18 and 3.93 mm sꢀ1). The magnitude
of dSn values (ꢀ140 and ꢀ68 ppm) indicate trans-Oh and
mer-Tbp tin(IV) coordination environments as obtained
in the solid state. These data suggesting that the coordina-
tion geometry of this complex remains unaffected by
dissolution.
O
N
O
N
O
O
Bu
Sn
R
Bu
O
Bu
Bu
Bu
Bu
Bu
O
O
Sn
O
N
O
Bu
Sn
N
N
N
N
Sn
R
Sn
O
O
O
N
O
O
N
N
Fig. 2. Proposed solid-state structures for R2Sn(cupf)2 [R = Et (1), Bu (2),
t-Bu (4) and Oc (5, 6)] and {[Bu2Sn(cupf)]2O}2 (3) complexes.
complexes 1, 2 and 4–6 exhibit only a symmetrical doublet.
In these complexes, the experimental d and jDj values fall in
the range of those noted for the trans-Oh complexes [16],
with the four O donor atoms in equatorial position
(Fig. 2). In case of 1, 2 and 5, the Dexp values are much
higher than 4.00 mm sꢀ1, as observed for the earlier studied
Bu2Sn(IV)-complexes of pyridine mono- and dicarboxylic
acids [8]. Therefore, it can not be ruled out that in these
compounds the central Sn(IV) atoms are in heptacoordi-
nated surroundings, adopting one more ligand which can
be one solvent or one water molecule as obtained for the
numerous diorganotin(IV) cupferronato complexes [7]. In
compound 4 the bulkiness of the t-butyl-groups prevents
the formation of trans-Pbp coordination environment.
Et2Sn(cupf)2 (1): 1H NMR (CDCl3, 500.13 MHz, 25 ꢁC)
d = 8.0 (m, Ph-H2, -H6), 7.37 (m, Ph-H3, -H4, -H5), 1.38
(m, 2H, Sn(CH2CH3)), 1.38 (m, 3H, Sn(CH2CH3)). 13C
NMR (CDCl3, 125.76 MHz, 25 ꢁC) d = 140.5 (s, Ph-C1),
130.63 (s, Ph-C4), 129.22 (s, Ph-C3, -C5), 118.4 (s, Ph-
C2, -C6), 18.2 (s, Et-C1[1J(119Sn–13C) = 812]), 13.2 (s, Et-
C2 [2J(119Sn–13C = 27.3) 119Sn NMR (CDCl3, 186.36
MHz, 25 ꢁC) d = ꢀ356.
3.4. Structure determination by NMR spectroscopy in
solution
1H, 13C and 119Sn NMR spectra were recorded (in
CDCl3) to gain some insight into the solution structure
of the complexes. For proton-containing groups directly
attached to the Sn atom (Et, Bu, t-Bu, Oc and Ph), proton
spectra exhibited 119Sn (and 117Sn) satellite signals due to
Bu2Sn(cupf)2 (2): 1H NMR (CDCl3, 500.13 MHz,
25 ꢁC) d = 7.97 (d, 2H, Ph-H2, -H6) 7.46 (s, 3H, Ph-H3,
-H4, -H5) 1.69 (m, 8H, Sn(CH2)2CH2CH3) 1.35 (m, 4H
Sn(CH2)2CH2CH3) 0.89 (t, 6H, Sn(CH2)3CH3). 13C
NMR (CDCl3, 125.76 MHz, 25 ꢁC) d = 135 (s, Ph-C1
[1J(119Sn–13C) = 808]), 130.1, 129.5 (s, Ph-C4), 129.1,
128.8 (s, Ph-C3, -C5), 120.24, 119.5 (s, Ph-C2, -C6),
29.69, 29.13 (s, C1, [1J(119Sn–13C) = 1028.8]), 28.4, 27.7
2J(119Sn–1H) or J(119Sn–1H) couplings. In a similar fash-
3
ion, resonance due to the carbon atoms in groups attached
to tin exhibited 119Sn (and 117Sn) satellites arising from
one-bond and multiple-bond J(119Sn–13C) spin–spin cou-
n
plings. All the H, 13C and 119Sn chemical shifts have the
1

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A. Szorcsik et al. / Journal of Organometallic Chemistry 692 (2007) 3409–3414
(s, C2, [2J(119Sn–13C) = 24.2]) 27.05, 26.5 (s, C3,
[3J(119Sn–13C) = 105.6]) 13.7 (s, C4). 119Sn NMR (CDCl3,
186.36 MHz, 25 ꢁC) d = ꢀ376.
the Ministero dell’Istruzione, dell’Universita e della Ric-
`
`
erca (M.I.U.R, CIP 2004059078_003) and the Universita
di Palermo (ORPA 41443), Italy.
{[Bu2Sn(cupf)]2O}2 (3): 1H NMR (CDCl3, 500.13 MHz,
25 ꢁC) d = 7.69 (dd, 2H Ph-H2, -H6) 7.45 (m, 3H, Ph-H3,
-H4, -H5) 4.72 (s, (CH2)3CH3). 13C NMR (CDCl3,
125.76 MHz, 25 ꢁC) d = 144 (s, Ph-C1,), 130.9 (s, Ph-C4),
130.8 (s, Ph-C3, -C5), 121 (s, Ph-C2, -C6) 29.9 (d, C1,
[1J(119Sn–13C) = 919]), 27.3 (d, C2, [2J(119Sn–13C) = 25.6])
24 (d, C3, [3J(119Sn–13C) = 114.3]), 13.3 (d, C4). 119Sn
NMR (CDCl3, 186.36 MHz, 25 ꢁC) d = ꢀ140, ꢀ68.
t-Bu2Sn(cupf)2 (4): 1H NMR (CDCl3, 500.13 MHz,
25 ꢁC) d = 7.97 (m, 2H, Ph-H2, -H6) 7.46 (m,
[J(119Sn–1H) = 99] 3H, Ph-H3, -H4, -H5), 1.4 (m, 8H,
t-Bu2Sn), 1.27 (m, 4H, [J(119Sn–1H) = 183, t-Bu2Sn) 1.17
(m, 6H, t-Bu2Sn). 13C NMR (CDCl3, 125.76 MHz, 25 ꢁC)
d = 140.2 (s, Ph-C1 [3J(119Sn–13C) = 1001]), 129.9 (s, Ph-
C4), 129.1 (s, Ph-C3, -C5), 119.6 (s, Ph-C2, -C6), 25.3
(s, C1 [1J(119Sn–13C) = 1017]), 30.0 (s, C2 [2J(119Sn–13C)
= NO]). 119Sn NMR (CDCl3, 186.36 MHz, 25 ꢁC) d = ꢀ222.
Oc2Sn(cupf)2 (5): 1H NMR (CDCl3, 500.13 MHz,
25 ꢁC) d = 8.29 (d, Oc-H1), 8.14 (d, Ph-H2, -H6), 7.61 (t,
Oc-H2), 7.55 (q, Oc-H3), 7.49 (t, Ph-H3, -H4, -H5), 7.41
(t, Oc-H4), 7.33 (d, Oc-H5), 3.31 (m, Oc-H6), 1.28 (t, Oc-
H7), 0.81 (d, Oc-H8). 13C NMR (CDCl3, 125.76 MHz,
25 ꢁC) d = 142.8 (s, Ph-C1), 130.1 (s, Ph-C4), 129.8 (s,
Ph-C3, -C5), 115.6 (s, Ph-C2, -C6), 33.3 (s, C1,
[1J(119Sn–13C) = 737]), 31.9 (s, C2, [2J(119Sn–13C) =
31.4]), 29.7 (s, C3, [3J(119Sn–13C) = 119.1]), 29.2 (s, C4),
25.9 (s, C5), 24.1 (s, C6), 22.0 (s, C7), 14.2 (s, C8). 119Sn
NMR (CDCl3, 186.36 MHz, 25 ꢁC) d = ꢀ156.
Appendix A. Supplementary material
CCDC 614144 contains the supplementary crystallo-
graphic data for this paper. These data can be obtained free
of charge via http://www.ccdc.cam.ac.uk/conts/retriev-
ing.html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax:
(+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.jorganchem.
2007.04.003.
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Acknowledgements
This work was supported by the Hungarian Scientific
Research Funds (OTKA) T 043551 and F 60496 Projects,