Synthesis and spectroscopic and X-ray structural characterization of R 2SnIV-oxydiacetate and -iminodiacetate complexes

Article abstract of DOI:10.1021/ic048240t

Seven novel R₂Sn^IV-oxydiacetate (oda) and -iminodiacetate (ida) compounds of the form [R₂Sn(oda)(H ₂O)]₂ (R = Me, ⁿBu, and Ph) (1-3), [(R ₂SnCl)₂(oda)(H₂O)₂]_n (R = Et, ⁱBu, and ^tBu) (4-6), and [Me₂Sn(ida)(MeOH) ]₂ (7) have been synthesized and characterized by IR, ¹H, ¹³C, and ¹¹⁹Sn NMR (solution), solid-state ¹¹⁹Sn CPMAS NMR, and ^119mSn Moessbauer spectroscopy. The crystal structure of [Me₂Sn(oda)(H₂O)]₂, 1, shows it to be dinuclear (centrosymmetric), with two seven-coordinated tin atoms, bridged by one arm of the carboxylate group from each oda. By contrast, the crystal structure of [(Et₂SnCl)₂(oda)(H ₂O)₂]_n, 4, comprises a zigzag polymeric assembly containing a pair of different alternating subunits, {Et ₂SnCl(H₂O)} and {Et₂SnCl(H₂O)(oda)}, which are connected by way of bridging oda carboxylates, thus giving seven-coordinate tin centers in both components. Finally, the structure of [Me₂Sn(ida)(MeOH)]₂, 7, also centrosymmetric dinuclear, is comprised of a pair of mononuclear units with seven-coordinate tin. The ¹¹⁹Sn solid-state CPMAS NMR and ^119mSn Moessbauer suggest the presence of seven-coordinate Sn metal atoms in some derivatives and the existence of two different tin sites in the [(R₂SnCl) ₂(oda)(H₂O)₂]_n compounds.

Full text of DOI:10.1021/ic048240t

Inorg. Chem. 2005, 44, 3094−3102
Synthesis and Spectroscopic and X-ray Structural Characterization of
R2SnIV
Oxydiacetate and Iminodiacetate Complexes
−
−
Corrado Di Nicola,† Agustin Galindo,‡ John V. Hanna,§ Fabio Marchetti,† Claudio Pettinari,*,†
Riccardo Pettinari,† Eleonora Rivarola,| Brian W. Skelton, and Allan H. White
Dipartimento di Scienze Chimiche, UniVersita` degli Studi di Camerino, Via S. Agostino 1,
62032 Camerino, Italy, ANSTO NMR Facility, Materials & Engineering Science, Lucas Heights
Research Laboratories, PriVate Mail Bag 1, Menai, NSW 2234, Australia, Chemistry M313,
The UniVersity of Western Australia, Crawley, Western Australia 6009, Australia, Dipartimento di
Chimica Inorganica e Analitica Stanislao Cannizzaro, UniVersita` di Palermo, Italy, and
Departamento de Qu´ımica Inorga´nica, UniVersidad de SeVilla, Aptdo. 553, 41071 SeVilla, Spain
Received December 15, 2004
Seven novel R2SnIV
Me, nBu, and Ph) (1
−
−
oxydiacetate (oda) and
−
iminodiacetate (ida) compounds of the form [R2Sn(oda)(H2O)]2 (R
)
i
t
3), [(R2SnCl)2(oda)(H2O)2]n (R
)
Et, Bu, and Bu) (4−6), and [Me2Sn(ida)(MeOH)]2 (7) have
been synthesized and characterized by IR, H, 13C, and 119Sn NMR (solution), solid-state 119Sn CPMAS NMR, and
119mSn Mo¨ssbauer spectroscopy. The crystal structure of [Me2Sn(oda)(H2O)]2, 1, shows it to be dinuclear
(centrosymmetric), with two seven-coordinated tin atoms, bridged by one arm of the carboxylate group from each
oda. By contrast, the crystal structure of [(Et2SnCl)2(oda)(H2O)2]n, 4, comprises a zigzag polymeric assembly containing
1
a pair of different alternating subunits, {Et2SnCl(H2O)} and {Et2SnCl(H2O)(oda)}, which are connected by way of
bridging oda carboxylates, thus giving seven-coordinate tin centers in both components. Finally, the structure of
[Me2Sn(ida)(MeOH)]2, 7, also centrosymmetric dinuclear, is comprised of a pair of mononuclear units with seven-
coordinate tin. The 119Sn solid-state CPMAS NMR and 119mSn Mo¨ssbauer suggest the presence of seven-coordinate
Sn metal atoms in some derivatives and the existence of two different tin sites in the [(R2SnCl)2(oda)(H2O)2]n
compounds.
Introduction
The oxydiacetate anion [oda ) O(CH2COO)22-] is a
versatile ligand having five potential oxygen-donor atoms
from two carboxylate groups and from an ethereal function
(Figure 1).1 It has been widely explored as a multidentate
bridging and chelating unit toward several metal acceptors,2-5
Figure 1. Acids odaH2 and idaH2.
mainly d-6-15 and f-16-22 block metals. Spectral and structural
studies on a number of metal complexes have shown that
the oda ligand may bind in mono-, bi-, tri-, and multidentate
fashion but can also exist as an anionic noncoordinated
species.23 The more usual chelating mode is tridentate,
* Author to whom correspondence should be addressed. E-mail:
claudio.pettinari@unicam.it. Tel.: +39 0737 402234. Fax: +39 0737
637345.
† University of Camerino.
‡ Universidad de Sevilla.
§ ANSTO NMR Facility.
(6) Bonomo, R. P.; Rizzarelli, E.; Bresciani-Pahor, N.; Nardin, G. Inorg.
Chim. Acta 1981, 54, L17-L19.
| University of Palermo.
University of Western Australia.
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M. J.; Clegg, W. J. Chem. Soc., Dalton Trans. 1992, 203-207.
(8) Grirrane, A.; Pastor, A.; Alvarez, E.; Mealli, C.; Ienco, A.; Rosa, P.;
Montilla, F.; Galindo, A. Eur. J. Inorg. Chem. 2004, 707-717.
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C. Inorg. Chem. Commun. 2000, 3, 32-34.
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2236.
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1811.
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3094 Inorganic Chemistry, Vol. 44, No. 9, 2005
10.1021/ic048240t CCC: $30.25
© 2005 American Chemical Society
Published on Web 03/29/2005

Oxy- and Iminodiacetate Organotin(IV) Complexes
whereby two isomers may be possible, where oda is
planar9,10,24-28 or puckered.6,27,29 Moreover, in several cases
oda can act further as a connecting donor in various homo-
and heterometallic extended solids, generally structured as
two-dimensional sheets with oda ligands connecting the metal
centers through the carboxylate groups.30,31 Despite the
possibility of different coordination modes, only a few
organometallic compounds, limited to some cyclopenta-
dienyltitanium and -zirconium derivatives,25 have been
isolated hitherto.
There has been some interest in incorporating tin(IV)
carboxylate groups into polymers because of their potential
as slow-release antifouling coatings on ships.32 Dialkyltin
dicarboxylates, mainly dibutyltin laurate, are used as catalysts
in silicone vulcanization processes that involve the cross-
linking of silicone chains with a tetraalkoxysilane.33 As an
extension of our previous work on R2SnIV with several types
of O-donors, such as â-diketonate,34 acylpyrazolonate,35 and
pyrazolonecarboxylate donors,36 we have initiated a study
of the interaction of odaH2 with R2SnIV moieties in the
presence of strong bases. There appear to be only two
relevant reports in the literature, on thermodynamic and NMR
studies of a dimethyltin(IV) oda complex in aqueous solu-
tion;37,38 to our knowledge, X-ray structural characterizations
of oxydiacetate p-block complexes have only been reported
for lead.4,5 We now report the synthesis and spectroscopic
characterization of six new compounds and the crystal
structures of two of them, the dinuclear [Me2Sn(oda)(H2O)]2,
1, and the polynuclear [(Et2SnCl)2(oda)(H2O)2]n, 4. We also
report a dialkyltin derivative, 7, with the “isoelectronic”
iminodiacetate anion [ida ) HN(CH2COO)22-] (Figure 1),
a donor similar to oda, which was prepared and characterized
for comparative purposes.
Experimental Section
Materials and Measurements. All reagents and solvents were
obtained from commercial sources and were used without further
purification. Samples for microanalysis were dried in a vacuum to
constant weight (20 °C, about 0.1 Torr). Elemental analyses (C,
H, N) were performed with a Fisons Instruments 1108 CHNS-O
elemental analyzer. IR spectra were recorded from 4000 to 200
cm-1 with a Perkin-Elmer System 2000 FT-IR instrument. 1H, 13C,
and 119Sn NMR spectra were recorded on a VXR-300 Varian
1
spectrometer operating at room temperature (300 MHz for H, 75
(12) Albertsson, J.; Grenthe, I.; Herbertsson, H. Acta Crystallogr., Sect. B
1973, 29, 1855-1860.
MHz for 13C, and 117.9 MHz for 119Sn). Proton and carbon chemical
shifts are reported in parts per million vs Me4Si, while tin chemical
shifts are reported in parts per million vs neat Me4Sn. Melting points
were determined using an IA 8100 electrothermal instrument. The
electrical conductances of the CH3OH and DMSO solutions were
measured with a Crison CDTM 522 conductimeter at room
temperature.
(13) Albertsson, J.; Grenthe, I.; Herbertsson, H. Acta Crystallogr., Sect. B
1973, 29, 2839-2844.
(14) Albertsson, J.; Grenthe, I. Acta Crystallogr., Sect. B 1973, 29, 2751-
2760.
(15) Del Rio, D.; Galindo, A.; Vicente, R.; Mealli, C.; Ienco, A.; Masi, D.
J. Chem. Soc., Dalton Trans. 2003, 1813-1820.
(16) Vannerberg, N.-G.; Albertsson, J. Acta Chem. Scand. 1965, 19, 1760-
1761.
119mSn Mo1ssbauer Measurements. 119mSn Mo¨ssbauer spectra
were recorded on solid samples at liquid-nitrogen temperature using
a conventional constant-acceleration spectrometer, coupled with a
multichannel analyzer (Aen, Ponteranica (BG), Italy) equipped with
a cryostat Cryo (Rial, Parma, Italy). The solid sample placed into
the cryostat was dried with a flow of helium and then dried under
vacuum. A Ca119SnO3 Mo¨ssbauer source, 10 mCi (Ritverc, St.
Petersburg, Russia), moving at room temperature with constant
acceleration in a triangular waveform was used. The velocity
calibration was made using a 57Co Mo¨ssbauer source, 10 mCi, and
an iron foil as absorber (from Ritverc, St Petersburg, Russia).
119Sn Solid-State NMR. High-resolution solid-state 119Sn magic-
angle-spinning (MAS) NMR spectra were acquired at ambient
temperatures using a Bruker MSL-400 NMR spectrometer (Bo )
9.4 T) operating at the 119Sn frequency of 149.20 MHz. These
experiments were conducted using a Bruker 4 mm double-air-
bearing MAS probe from which rotational frequencies of ∼3-12
kHz were implemented. All experimental data were acquired under
1H-119Sn cross-polarization conditions which used recycle delays
of 5-20 s, Hartmann-Hahn contact periods of 2 ms, and an initial
1H π/2 pulse width of 3.5 µs. A nominal 1H decoupling field
strength of ∼80 kHz was employed during acquisition. Each
spectrum was externally referenced to Me4Sn via a secondary
external reference of Cy4Sn that is located upfield from Me4Sn at
-97.35 ppm;39 this sample of Cy4Sn was also used to establish the
Hartmann-Hahn contact condition required for cross-polarization
(17) Albertsson, J. Acta Chem. Scand. 1968, 22, 1563-1578.
(18) Albertsson, J. Acta Chem. Scand. 1970, 24, 3527-3541.
(19) Albertsson, J.; Elding, I. Acta Crystallogr., Sect. B 1976, 32, 3066-
77.
(20) Fronczek, F. R.; Banerjee, A. K.; Watkins, S. F.; Schwartz, R. W.
Inorg. Chem. 1981, 20, 2745-2746.
(21) Albin, M.; Whittle, R. R.; De Horrocks, W. Inorg. Chem. 1985, 24,
4591-4594.
(22) Rao, L.; Garnov, A. Y.; Jiang, J.; Di Bernardo, P.; Zanonato, P.;
Bismondo, A. Inorg. Chem. 2003, 42, 3685-3692.
(23) Baggio, R.; Garland, M. T.; Perec, M. Inorg. Chim. Acta 1998, 281,
18-24.
(24) Bresciani-Pahor, N.; Nardin, G.; Bonomo, R. P.; Rizzarelli, E. J. Chem.
Soc., Dalton Trans. 1983, 1797-1799.
(25) Thewalt, U.; Guthner, T. J. Organomet. Chem. 1989, 379, 59-65.
(26) Powell, A. K.; Charnock, J. M.; Flood, A. C.; Garner, C. D.; Ware,
M. J.; Clegg, W. J. Chem. Soc., Dalton Trans. 1992, 203-207.
(27) Baggio, R.; Garland, M. T.; Perec, M. Inorg. Chim. Acta 2000, 310,
103-109.
(28) Grirrane, A.; Pastor, A.; Ienco, A.; Mealli, C.; Galindo, A. J. Chem.
Soc., Dalton Trans. 2002, 3771-3777.
(29) Whitlow, S. H.; Davey, G. J. Chem. Soc., Dalton Trans. 1975, 1228-
1232.
(30) Mao, J.-G.; Song, L.; Huang, X.-Y.; Huang, J.-S. Polyhedron 1997,
16, 963-966.
(31) Baggio, R.; Garland, M. T.; Moreno, Y.; Pena, O.; Perec, M.; Sposine,
E. J. Chem. Soc., Dalton Trans. 2000, 2061-2066.
(32) Organotin Carboxylates and Other Oxyesters. In Organotin Chemistry;
Davies, A. G., Ed.; VCH: Weinheim, Germany, 1997; Chapter 11, p
159.
(33) Evans, C. J.; Karpel, S. Organotin Compounds in Modern Technology;
Elsevier: Amsterdam, 1985.
(34) Pettinari, C.; Marchetti, F.; Pettinari, R.; Gindulyte, A.; Massa, L.;
Rossi, M.; Caruso, F. Eur. J. Inorg. Chem. 2002, 1447-1455 and
references therein.
(35) Pettinari, C.; Marchetti, F.; Cingolani, A.; Gindulyte, A.; Massa, L.;
Rossi, M.; Caruso, F. Eur. J. Inorg. Chem. 2001, 2171-2180 and
references therein.
(36) Pettinari, C.; Marchetti, F.; Pettinari, R.; Martini, D.; Drozdov, A.;
Troyanov, S. J. Chem. Soc., Dalton Trans. 2001, 1790-1797 and
references therein.
(37) Cucinotta, V.; Gianguzza, A.; Maccarone, G.; Pellerito, L.; Purrello,
R.; Rizzarelli, E. J. Chem. Soc., Dalton Trans. 1992, 2299-2304.
(38) Pellerito, L.; Dia, G.; Gianguzza, A.; Girasolo, M. A.; Rizzarelli, E.;
Purrello, R. Polyhedron 1987, 6, 1639-1645.
(39) Ku¨mmerlen, J.; Sebald, A.; Reuter, H. J. Organometallic Chem. 1992,
427, 309-323.
Inorganic Chemistry, Vol. 44, No. 9, 2005 3095

Di Nicola et al.
spectral acquisition. The 119Sn CPMAS spectrum of each complex
was acquired at three different MAS frequencies to allow an
unambiguous assignment of the isotropic chemical shift (δiso), and
to clearly identify the chemical shift tensor elements δ11, δ22, and
δ33, particularly where multiple Sn sites were present. The MAS
NMR spectra acquired at ∼3 kHz were more selectively utilized
to identify δ11, δ22, and δ33 since increased MAS rates invoked the
appearance of biasing the downfield tensorial positions to lower
ppm values and the upfield tensorial positions to higher ppm values.
Parameters defining the chemical shift interaction were calculated
from these measured chemical shift tensorial elements δ11, δ22, and
δ33 according to IUPAC-recommended conventions as discussed
by Mason40 and Mackenzie et al.;41 here δ11 > δ22 > δ33 with the
isotropic chemical shift δiso ) (δ11 + δ22 + δ33)/3, span Ω ) δ11
- δ33, and skew κ ) 3(δ22 - δiso)/(δ11 - δ33), where 1 g κ g -1.
Additional representations of chemical shift interaction param-
eters such as the anisotropy (∆δ) and asymmetry (η) can be
calculated if an alternate frequency convention |δ33 - δiso| g
|δ11 - δiso| g |δ22 - δiso| is invoked; in this case the anisotropy
∆δ ) δ33 - (δ11 + δ22)/2 ) 3(δ33 - δiso)/2 and asymmetry η )
(δ22 - δ11)/(δ33 - δiso), where η is restricted within the range 1 g
η g 0.
X-ray Structure Determinations. Full spheres of “low-tem-
perature” CCD area-detector data were measured (Bruker AXS
instrument, ω-scans, monochromatic Mo KR radiation, λ ) 0.710 73
Å; T ca. 153 K) yielding Nt(otal) reflections. These were merged to
N unique after “empirical”/multiscan absorption correction (pro-
prietary software), No with F > 4σ(F) being considered “observed”
and used in the full-matrix least-squares refinements, refining
anisotropic displacement parameter forms for the non-hydrogen
atoms and with (x, y, z, Uiso)H constrained at estimated values
(exception: the water molecule hydrogen atoms in 2 which could
not be confidently located in difference maps). Conventional
residuals R and Rw (weights: (σ2(F) + 0.000nwF2)-1) are quoted
on |F| at convergence. Neutral atom complex scattering factors were
employed within the context of the Xtal 3.7 program system.42
Pertinent results are given below and in the tables and figures, the
latter showing non-hydrogen atoms with 50% probability amplitude
displacement ellipsoids, hydrogen atoms having arbitrary radii of
0.1 Å.
C, 37.63; H, 6.98. IR (Nujol, cm-1): 3276 br ν(H2O), 1633 s, 1579
s νasym(CdO), 1434 m νsym(CdO), 1124 s νsym(OCO), 592 m ν(Sn-
1
C), 460 s, 349 s ν(Sn-O). H NMR (CD3OD, 20 °C): δ 1.02 (t),
1.40-1.65 (m) (18H, SnnBu), 4.35 (s, 2H, H2O), 4.99 (s, 4H, CH2
of oda).
[Ph2Sn(oda)(H2O)]2 (3). Compound 3 has been synthesized
using a procedure similar to that reported for 1. Yield: 51%. Mp:
327-330 °C. Anal. Calcd for C16H16O6Sn: C, 45.43; H, 3.81.
Found: C, 45.51; H, 4.26. IR (Nujol, cm-1): 3366 br ν(H2O), 3052
m ν(C-Harom), 1653 s, 1635 s, 1582 s νsym(CdO), 1427 m
1
ν
asym(CdO), 261 m, 226 m ν(Sn-C), 461 vs, 301 s ν(Sn-O). H
NMR (DMSO-d6, 20 °C): δ 3.32 (s, 2H, H2O), 3.75 (s, 4H, CH2
of oda), 7.20-7.40 (m) 7.67 (d br) (10H, Sn-Ph).
[(Et2SnCl)2(oda)(H2O)2]n (4). Compound 4 has been obtained
using a procedure similar to that reported for 1. Yield: 41%. Mp:
156-159 °C. Anal. Calcd for C12H26O6Cl2Sn2: C, 25.08; H, 4.56.
Found: C, 25.85; H, 4.66. IR (Nujol, cm-1): 3250 br ν(H2O), 1651
m δ(H2O), 1592 s, 1574 s νsym(CdO), 1440 m νasym(CdO), 1125
s νsym(OCO), 548 m ν(Sn-C), 448 w, 375 m ν(Sn-O), 295 s, 287
1
s, 280 s ν(Sn-Cl). H NMR (CD3OD, 20 °C): δ 1.17 (t, 12H,
3J(119Sn-1H) ) 179.5 Hz, 3J(117Sn-1H) ) 171.4 Hz, SnCH2CH3),
1.58 (q, 8H, 2J(119Sn-1H) ) 105.5 Hz, 2J(117Sn-1H) ) 100.7 Hz,
SnCH2CH3), 4.24 (s, 2H, H2O), 4.98 (s, 8H, CH2 of oda). 13C NMR
(CD3OD, 20 °C): δ 10.2 (s, 2J(119/117Sn-13C) ) 52 Hz, SnCH2CH3),
25.4 (s, 1J(119Sn-13C) ) 796 Hz, 1J(117Sn-13C) ) 744 Hz,
SnCH2CH3), 68.8 (s, CH2COO of oda), 175.0 (s, CH2COO of oda).
[(iBu2SnCl)2(oda)(H2O)2]n (5). Compound 5 has been prepared
using a procedure similar to that reported for 1. Yield: 62%. Mp:
146-149 °C. Anal. Calcd for C20H44O7Cl2Sn2: C, 32.98; H, 6.92.
Found: C, 33.16; H, 6.73. IR (Nujol, cm-1): 3234 br ν(H2O), 1648
m δ(H2O), 1632 s, 1596 s br νsym(CdO), 1442 m νasym(CdO), 1115
s νsym(OCO), 596 m ν(Sn-C), 454 w, 394 m ν(Sn-O), 301 s, 290
1
s, 283 s ν(Sn-Cl). H NMR (CD3OD, 20 °C): δ 0.91 (t), 1.28-
1.60 (m) (18H, SniBu), 4.23 (s, 4H, H2O), 4.86 (s, 4H, CH2 of
oda).
[(tBu2SnCl)2(oda)(H2O)2]n (6). Compound 6 has been prepared
using a procedure similar to that reported for 1. Yield: 68%. Mp:
141-148 °C. Anal. Calcd for C20H44O7Cl2Sn2: C, 32.98; H, 6.92.
Found: C, 32.95; H, 6.58. IR (Nujol, cm-1): 3443 br ν(H2O), 1644
m δ(H2O), 1620 m, 1596 s νsym(CdO), 1443m νasym(CdO), 1142
s νsym(OCO), 592 m ν(Sn-C), 440 w, 348 m ν(Sn-O), 283 s, 230
s br ν(Sn-Cl). 1H NMR (CD3OD, 20 °C): δ 1.54 (s, 18H,
2J(119Sn-1H) ) 112.6 Hz, 2J(117Sn-1H) ) 107.4 Hz, SntBu), 4.55
(s, 8H, H2O), 4.98 (s, 4H, CH2 of oda).
Syntheses of Complexes. [Me2Sn(oda)(H2O)]2 (1). Oxydiacetic
acid (odaH2) (0.134 g, 1.0 mmol) and KOH (0.112 g, 2.0 mmol)
were added to a MeOH solution (50 mL) containing Me2SnCl2
(0.219 g, 1.0 mmol). The reaction mixture was stirred at 60 °C for
48 h and then filtered off. Colorless crystals of 1 were obtained
upon slow evaporation of the methanol filtrate. Yield: 52%. Mp:
>350 °C (dec). Anal. Calcd for C6H12O6Sn: C, 24.11; H, 4.05.
Found: C, 24.08; H, 4.26. IR (Nujol, cm-1): 3461 br ν(H2O), 1675
m δ(H2O), 1646 s, 1598 s νsym(CdO), 1428 m νasym(CdO), 1147
[Me2Sn(ida)(MeOH)]2 (7). Compound 7 has been obtained by
using a procedure similar to that reported for 1 but using idaH2
instead of odaH2. Yield: 57%. Mp: 293-296 °C. Anal. Calcd for
C7H15O5NSn: C, 26.96; H, 4.85; N, 4.49. Found: C, 27.15; H,
4.96; N, 4.26. IR (Nujol, cm-1): 3366 br ν(O-H), 3169 m ν(N-
H), 1680 s, 1654 s, 1631 sh νsym(CdO), 1441 sh νasym(CdO), 572
1
s νsym(OCO), 562 s ν(Sn-C), 440 m, 372 s, 356 sh ν(Sn-O). H
2
NMR (D2O, 20 °C): δ 0.88 (s, 12H, J(119Sn-1H) - 110.6 Hz,
1
m ν(Sn-C), 399 s, 344 s ν(Sn-O), 263 s ν(Sn-N). H NMR
2J(117Sn-1H) ) 105.5 Hz, SnCH3), 4.23 (s, 4H, H2O), 4.77 (s, 8H,
CH2 of oda). 13C NMR (D2O, 20 °C): δ 12.9 (s, SnCH3), 67.5 (s,
CH2), 175.2 (s, COO). 119Sn NMR (D2O, 22 °C): δ -365.
(CD3OD, 20 °C): δ 1.54 (s, 6H, 2J(119Sn-1H) ) 68.7 Hz, 2J(117Sn-
1H) ) 65.7 Hz, SnMe), 4.55 (s, 3H, CH3OH), 4.87 (s, 4H, CH2 of
ida). 13C NMR (DMSO-d6, 20 °C): δ 6.5 (s br, SnCH3), 50.7 (s,
CH2), 170.6 (s, COO). 119Sn NMR (DMSO-d6, 22 °C): δ -222.
[Me2Sn(ida)]2 (8). Compound 8 has been obtained by maintain-
ing compound 7 at 70 °C under vacuum for 6 h. Mp: 293-296
°C. Anal. Calcd for C6H11O4NSn: C, 25.75; H, 3.96; N, 5.00.
Found: C, 25.56; H, 4.03; N, 5.08. IR (Nujol, cm-1): 3096 br
ν(N-H), 1643 s, 1590 s, 1558, 1494 sh νsym(CdO), 1407 s
[nBu2Sn(oda)(H2O)]2 (2). Compound 2 has been obtained using
a procedure similar to that reported for 1, in 64% yield. Mp: 202-
205 °C. Anal. Calcd for C12H24O6Sn: C, 37.63; H, 6.32. Found:
(40) Mason, J. Solid State Nucl. Magn. Reson. 1993, 2, 285-288.
(41) Mackenzie, K. J. D.; Smith, M. E. Multinuclear Solid-State NMR of
Inorganic Materials; Pergamon: Oxford, U.K., 2002.
(42) Hall, S. R.; du Boulay, D. J.; Olthof-Hazekamp, R.; Eds. The Xtal
3.7 System; University of Western Australia: Crawley, Australia,
2001.
ν
asym(CdO), 589 m, 551 m, 523 w ν(Sn-C), 491 s, 415 w, 398 m,
1
350 m, ν(Sn-O), 279 ν(Sn-N). H NMR (DMSO-d6, 20 °C): δ
0.66 (s, 6H, J(119Sn-1H) ) 93.4, Hz, J(117Sn-1H) ) 90.1 Hz,
2
2
3096 Inorganic Chemistry, Vol. 44, No. 9, 2005

Oxy- and Iminodiacetate Organotin(IV) Complexes
Scheme 1
SnMe), 3.34 (dq, 4H, CH2 of ida), 6.6 (m, 1H, NH). 13C NMR
(DMSO-d6, 20 °C): δ 6.5 (s br, SnCH3), 50.7 (s, CH2), 170.6 (s,
COO). 119Sn NMR (DMSO-d6, 22 °C): δ -222.
Single-Crystal X-ray Studies. The results of the “low-
temperature” single-crystal X-ray structure determinations
for 1, 4, and 7 are consistent with the above formulations,
all solvent residues being coordinated. For 1 and 4, oda
ligands may be viewed as oda2-, all being quasi-planar in
respect of their non-hydrogen components and behaving as
tridentates toward closely associated tin atoms; the peripheral
oxygen atoms of both types, coordinated and not to the
central tin, interact diversely with other tin atoms, leading
in the case of 1 to a binuclear complex and in the case of 4
to a quasi-one-dimensional polymer. Interactions of the latter
type and the stacking of planar ligand motifs may be viewed
as determinants of the interesting lattice array; hydrogen-
bonding interactions may also be postulated from the limited
proportion of water molecules in the array, approximately
half of these seemingly internal to the molecular units. About
all tin(IV) atoms, the pairs of alkyl groups are trans, quasi-
linear, the axial component of a stereochemistry which, in
all cases, may be viewed as seven-coordinate pentagonal
bipyramidal, although the equatorial interactions are diverse
in their strengths.
Results and Discussion
The interaction of oxydiacetic acid (odaH2) with an
n
equimolar amount of R2SnCl2 (R ) Me, Bu, Ph) in the
presence of 2 equiv of KOH in methanol afforded the
dinuclear derivatives 1-3, [R2Sn(oda)(H2O)]2 (R ) Me, nBu,
Ph), in high yield (Scheme 1).
By contrast under the same conditions, the reaction of
i
t
odaH2 with R2SnCl2 (R ) Et, Bu, Bu) yielded the poly-
nuclear derivatives [(R2SnCl)2(oda)(H2O)2]n, 4-6 (Scheme
1), in which a different ligand-to-metal ratio has been found,
only one chloride group being substituted in the tin coordina-
tion sphere by a carboxylate group. Compounds 4-6 were
also formed when an excess of KOH and odaH2 ligand was
employed or when the reaction was carried out under forcing
conditions as, for example, refluxing solvents and long
reaction times. This could be ascribed to a progressive
increase in steric hindrance about the tin center on going
Compound 1 is binuclear (Figure 2), the two halves of
the dimer being related by a crystallographic center of
symmetry, with half comprising the asymmetric unit; the
complement of coordinating atoms in the equatorial plane
about each tin atom comprises the tridentate oda, the water
molecule oxygen atom, and O(11) bridging from the oda
ligand of the other tin. The carboxylate oxygen O(21) is more
strongly bound to tin than the ethereal O(1) atom, the latter
i
t
from Et2Sn to Bu2Sn and Bu2Sn moieties, which, presum-
ably, inhibits complete substitution of the chlorides by oda.
Finally, the interaction of iminodiacetic acid (idaH2) with
an equimolar amount of Me2SnCl2 in the presence of KOH
in methanol afforded the dinuclear complex [Me2Sn(oda)-
(MeOH)]2, 7, in high yield. When compound 7 was stored
under vacuum at 60 °C for 6 h, the anhydrous amorphous
form [Me2Sn(oda)] was obtained.
Greater yields have been obtained when the reactions
described above were carried out in methanol rather than
water or DMSO as solvent, crystalline deposits generally
forming on slow evaporation (many days) of the cooled
solutions.
All derivatives 1-6 show limited solubility in DMSO but
are insoluble in chlorinated solvents, diethyl ether, aromatics,
and aliphatic hydrocarbons. Compound 1 is also soluble in
D2O, whereas derivatives 2-6 are quite soluble in MeOH.
Derivatives 7 and 8 are only slightly soluble in MeOH. All
are nonelectrolytes in DMSO solution, the Λm values being
always less than 4.5 Ω-1 cm2 mol-1.
Figure 2. Single centrosymmetric dimer of 1: Sn-C(01,02),O(03,1,11,
21,11′), 2.103(2), 2.104(2), 2.218(1), 2.357(2), 2.498(2), 2.200(2), 2.505(2)
Å; O(11)‚‚‚O(11′), 2.771(2); Sn‚‚‚Sn′, 4.1653(4) Å; C(01)-Sn-C(02),
171.59(7)°.
Inorganic Chemistry, Vol. 44, No. 9, 2005 3097

Di Nicola et al.
Figure 3. Single strand of the “polymer” of 4 (c lies horizontal in the page): Sn(1)-C(011,021),Cl(1),O(01, 1, 11, 21), 2.114(7), 2.103(9), 2.505(2),
2.281(6), 2.525(5), 2.450(5), 2.333(5) Å; C(011)-Sn(1)-C(021), 167.9(3)°; Sn(2)-C(031,041),Cl(2),O(02,11,22′,12), 2.132(7), 2.103(7), 2.446(2), 2.272(5),
2.953(5), 2.797(5), 2.278(5) Å; C(031)-Sn-C(041), 155.9(3)°; Sn(1)‚‚‚Sn(2),Sn(2)(x - 1/2, 1/2 - y, z + 1/2), 5.2707(8), 6.1402(8) Å.
in turn being more strongly bound than the bridging O(11)
atom, with the two Sn-O(11) distances, tridentate and
bridging, identical.
Sn(2) are much more diverse (2.272(5)-2.953(3) Å); Sn(2)-
O(11),O(22)(x - 1/2, 1/2 - y, 1/2 + z) are long (2.953(5),
2.797(5) Å) with Sn(2)-Cl(2) now shortened to 2.446(2) Å
and Sn(2)-O(02,12) < 2.28 Å. The coordination sphere is
now quite unsymmetrical, with the “axial” C-Sn-C angle
closing away from Cl(2) to 155.9(3)°. Although water
molecule hydrogen atoms were not located, they may be
tentatively inferred as reinforcing the polymeric linkage:
The different natures of the two carboxylate groups are
reflected in the variations in their associated geometrical
parameters C(n2)-O(n1,2) and, more sensitively, in the
associated angular parameters which differ appreciably on
either side of the ligand, even about the central O(1). This
type of coordination mode is not common, and it has been
defined only in the cadmium-oda derivative [Cd(oda)-
(H2O)3]2.43 Although quasi-planar (Figure 2), the chelate rings
of the tridentate are somewhat puckered. One of the water
molecules hydrogen bonds to the other half of the dimer
(O(3),H(03b)‚‚‚O(12)(1/2 - x, 1/2 - y, 1 - z) ) 2.592(3),
1.80 Å (estimate)), and the other to an adjacent dimer
(O((3),H(03a)‚‚‚O(21)(1 - x, y, 3/2 - z) ) 2.744(2), 1.86
Å (estimate)).
In 4, although the asymmetric unit of the structure contains
a pair of tin atoms, their roles are quite different; the complex
may be considered as an aggregate: [Et2SnCl(H2O)]+[Et2SnCl-
(H2O)(oda)]- with bridging peripheral carboxylate oxygens
from a pair of anions making up the (otherwise rather sparse)
coordination sphere of each of the cation metal atoms (Figure
3). Interestingly, whereas the bridging interaction in 1 arose
from one of the “endo” peripheral oxygen atoms, i.e., an
O(1) of the tridentate, here that interaction is weak, perhaps
only consequent on the now strong interaction of O(12), one
of a pair arising from both O(n2)’s (that involving O(22)
much weaker) which link anions and cations alternately into
a one-dimensional polymeric string. Although in consequence
of the use of less congenial material the precision of this
determination is inferior to that of 1, it suffices to define
similarly diverse differences in geometries between the two
halves of the tridentate, both within 4 and relative to 1.
Whereas the distances within the equatorial plane about
(anionic) Sn(1) in 4 are similar (Sn-O, Sn-Cl ranging
between 2.281(6) and 2.525(5) Å), those about (cationic)
1
O(01)‚‚‚O(22)(x - /2, 1/2 - y, 1/2 + z), O(02)‚‚‚O(21)
(x - 1/2, 1/2 - y, 1/2 + z) ) 2.685(7), 2.679(7) Å. The
bridging coordination mode of the oda ligand in 4 is
uncommon and has only been defined in a cadmium complex
Cd(oda):H2O (2:7).44
The structure of 7 is closely related to the known binuclear
[Me2Sn(ida)(H2O)]2 complex45 but with water replacing the
methanol ligand. Compound 7 is also analogous to 1
(compare the unit cells, Table 1), the asymmetric unit again
containing one tin atom with associated ligands; the equato-
rial aqua ligand of 1 is replaced by a methanol molecule,
somewhat disordered and, interestingly, pivoting about the
hydroxyl hydrogen, which is hydrogen-bonded to O(11) of
the inversion-related ligand (Figure 4). The O(11)-Sn-
O(21) angle is much smaller in 7 than in 1 (144.85(8)°; cf.
158.40(5)°), presumably a consequence of replacing the
quasi-planar O(1) by a quasi-tetrahedral N(1). The distance
to the latter is the shorter (Sn-N(1) ) 2.282(2); cf. Sn-
O(1) )2.357(2) Å), with the range of angles between axial
and equatorial donors in 1 (86.15(5)-94.89(7)°) less diverse
than that in 7 (80.7(1)-97.2(3)° or 72.4(3)-100.4(1)° if the
minor component O(03′) is considered). The overall outcome
of the aggregate of the above effects is a more compact
tridentate, with more closely bound central atom (and,
presumably, concomitant trans effect) and weaker methanol
compared to H2O donor. Additionally, the dimer formation,
with the centrosymmetrically related second monomer, is
(44) Boman, C.-E. Acta Crystallogr. 1977, B33, 838.
(45) Lee, F. L.; Gabe, E. J.; Khoo, L. E.; Leong, W. H.; Eng, G.; Smith,
F. E. Inorg. Chim. Acta 1989, 166, 257.
(43) Boman, C.-E. Acta Crystallogr. 1977, B33, 1529.
3098 Inorganic Chemistry, Vol. 44, No. 9, 2005

Oxy- and Iminodiacetate Organotin(IV) Complexes
and bridging coordination of oda.46 However, in some cases
some additional bands are present in the 1700-1600 cm-1
region which could be indicative of a different coordination
mode for the ligands in the same complexes. Thus, e.g., the
spectrum of 6 exhibits, for νas, two different absorptions,
the first similar to that reported for compound 4 and the
second similar to that reported for derivative 1 and indicative
of a free CdO group. Also, in accordance with the 119Sn
CPMAS and 119Sn Mo¨ssbauer data, some structural differ-
ences between compounds 4 and 6 are likely.
Table 1. Crystal/Refinement Details
param
formula
Mr/Da
cryst system
space group
a/Å
1
4a
7b
C12H24O12Sn2
597.7
C12H28Cl2O7Sn2
592.7
C7H15NO5Sn
311.9
monoclinic
C2/c (No. 15)
22.608(2)
6.6669(7)
15.527(7)
125.015(2)
1917
monoclinic
P21/n (No. 14)
8.137(1)
17.648(3)
14.085(2)
98.296(4)
2002
1.967
4
2.8
monoclinic
P21/c (No. 14)
10.6103(7)
6.7816(5)
15.501(1)
107.231(1)
1085
b/Å
c/Å
â/deg
V/Å3
Dc/g cm-3
Z/f.u.
2.071
4
2.7
1.944
4
2.4
It has been recently proposed,28 and theoretically sup-
ported,15 that the IR band corresponding to the antisymmetric
COC stretching at the ethereal oxygen can be discriminative
of the coordination mode adopted by the oxydiacetate ligand.
Thus, a planar oxydiacetate is characterized by a sharp and
strong band in the region 1120-1150 cm-1, while this IR
band falls in the region around 1100 cm-1 when the
arrangement is puckered. For all oda complexes, 1-6, this
absorption appears within the range 1115-1147 cm-1, i.e.,
at higher values than a limit of 1100 cm-1, so that the planar
disposition of oda may be invariably presumed, consistent
with the X-ray structural determinations of 1 and 4.
Only one ν(Sn-C) stretching vibration is found, at ca.
560 cm-1 in the spectra of derivatives 1 and 4, as expected
for an axial trans-R2Sn configuration, also supported by the
X-ray data (see below). Analogous absorptions have been
found in the spectra of derivatives 2, 3, 5, and 6 at ca. 590,
260, 596, and 490 cm-1, respectively. Strong absorptions in
the region 450-350 cm-1 may be ascribed, on the basis of
literature data, to ν(Sn-O) stretching vibrations.47 Finally,
Sn-Cl vibration modes are assigned below 300 cm-1 in the
spectra of 4-6.48
µ
Mo/mm-1
specimen/mm 0.40 × 0.35 × 0.32 0.32 × 0.18 × 0.10 cuboid, 0.10
Tmin/max
2θmax/deg
Nt
0.77
75
19 338
5001 (0.028)
4646
0.62
55
40 395
4613 (0.068)
3905
0.89
70
21 952
4562 (0.032)
3887
N(Rint
No
)
Rc
0.024
0.043(1)
0.058
0.090(5)
0.034
R
w (nw)c
0.047(0.7)
a Sample quality presented difficulty, being badly twinned. b The metha-
nol ligand was modeled in terms of a pair of H3CO components disposed
over a pair of sites, occupancies 0.81(1) and complement, pivoted about a
2
common hydroxyl hydrogen. c R ) Σ∆/Σ|Fo|; Rw ) (Σw∆2/wFo )1/2
.
Figure 4. Centrosymmetric mutual approach of the pair of molecules of
7. Note the disordered minor component of the methanol molecule. Sn-
C(01,2),O(3,03′,11,21),N(1): 2.107(4), 2.109(4), 2.391(4), 2.35(1), 2.346(2),
2.156(2), 2.282(2) Å. C(01)-Sn-C(02): 159.5(1)°.
NMR Solution Studies. The 1H NMR spectrum of 1 was
recorded in D2O whereas the spectra of 2-7 were recorded
in DMSO-d6 or CD3OD, the choice depending on the
much more tenuous with the Sn‚‚‚O(11)(2 - x, 1 - y, 1 -
z) approach now very long (2.953(2) Å).
2
solubility of the species. The J(119/117Sn-1H) values of 1
and 4 are typical of trans six-coordinated tin centers.
The same trans disposition is likely for 4 and 6, their
3J(119/117Sn-1H) values being harmonious with those reported
in the literature for analogous compounds.49 The CH2
chemical shifts of (oda)2- and (ida)2- in the spectra of 1-7
are always to lower field with respect to the corresponding
resonances in the spectra of free odaH2 and idaH2, and water
(in 1-6) or methanol (in 7) have been detected as narrow
signals, thus indicating that they are coordinated to tin also
in solution. The poor solubility in almost all solvents has
precluded the measurement of 13C and 119Sn NMR of almost
Spectroscopy. IR Spectroscopy. It has been previously
reported46 that bands due to carboxylate groups can be used
to distinguish between the various -COO- group coordina-
tion modes. Upon coordination to tin centers, the strong IR
absorptions due to νas(COO) in the free odaH2 (νas(COO):
1734 cm-1) and idaH2 (νas(COO): 1733 cm-1) are generally
displaced to lower frequencies (from 1680 to 1570 cm-1),
whereas a negligible shift to higher frequencies (ranging from
1450 to 1430 cm-1) has been detected for the νs(COO) which
appear in the free ligands at ca. 1420 cm-1. Here the highest
values of νas have been found for species 1 and 7 for which
dimeric structures containing uncoordinated CdO groups
have been established on the basis of X-ray studies. By
contrast, lower values have been found in the derivative 4
for which a polynuclear structure containing chelating and
bridging carboxylate groups has been found. The ∆ values
1
all the derivatives 2-7, apart from 4. The J(119Sn-13C) in
4 is 796 Hz. This application of the linear relationship
previously proposed for R2SnIV 49,50 derivatives indicates a
θ(C-Sn-C) angle of 157.4°; cf. the value of 155.9(3)° found
-
-
(47) Szorcsik, A.; Nagy, L.; Sletten, J.; Szalontai, G.; Kamu, E.; Fiore, T.;
Pellerito, L.; Ka´lma´n, E. J. Organomet. Chem. 2004, 689, 1145-1154.
(48) Nakamoto, K. Infrared and Raman Spectra of Inorganic and Coor-
dination Compounds, 5th ed.; Wiley-Interscience: New York, 1997,
Part B, Sect. III, pp 57-68, and Sect. IV, pp 257-276.
(49) Lockhart, T. P.; Manders, W. F. Inorg. Chem. 1986, 25, 892-895.
(50) Howard, W. F., Jr.; Crecely, R. W.; Nelson, W. H. Inorg. Chem. 1985,
24, 2204-2208.
()[νasym(CO2 ) - νsym(CO2 )]) for compounds 1 and 7 are
218 and 239 cm-1, respectively which support unidentate
carboxylate coordination. In the case of 4-6, the ∆ range
from 152 (4) to 180 (6) cm-1 in accordance with chelating
(46) Deacon, G. B.; Phillips, R. J. Coord. Chem. ReV. 1980, 33, 227-250.
Inorganic Chemistry, Vol. 44, No. 9, 2005 3099

Di Nicola et al.
trans, quasi-linear (or axial) coordination of the aliphatic or
aromatic substituents. Although no formal axis of rotation
perpendicular to this planar oxo environment exists, there
must be sufficient uniformity in the deshielding character-
istics of this present arrangement to invoke axial character
in the 119Sn chemical shift tensor. Given the diversity of the
Sn(IV)-O interactions within this oxo environment, with
each Sn site within the asymmetric unit being more
dominantly influenced by tridendate coordination from
bridging O(11) atoms and the O(21) carboxylate oxygen and
with weaker contributions exerted by the ethereal O(1) and
the water molecule oxygen O(03), some degree of fortuitous
symmetry in bond strengths and bond angles is manifested.
For complexes 1-3 the skew κ ) 1 with δ11 and δ22
represents the most deshielded components, which thus
corresponds to a prolate representation of the 119Sn shift
tensor.40,41,52 Although the crystal structures of complexes 2
and 3 have not been obtained, from these 119Sn CPMAS
NMR observations it can be inferred that they are isostruc-
tural with complex 1.
The measured isotropic chemical shifts δiso,mas of com-
plexes 1-3 increase monotonically from -403.8 ppm
(methyl) to -442.0 ppm (n-butyl) and -587.9 ppm (phenyl),
reflecting the increasing electron withdrawal (or deshielding)
capability of the trans-organic substituents. Similar isotropic
chemical shifts and behavioral trends with changing substit-
uents have been observed with seven-coordinate tris-
(tropolonato) systems which feature nonplanar six-coordinate
oxo coordination, with δiso,mas values of -532 and -585 ppm
being reported for BuSn(trop)3 and PhSn(trop)3, respec-
tively.53 The spans reported for complexes 1-3 of up to
∼1230 ppm (see Table 2) represent the largest Ω values for
Sn(IV) systems with direct oxo coordination,52-55 but these
Ω magnitudes are still much smaller than those reported for
monomeric, two-coordinate Sn(II) systems such as [Sn(X)-
C6H3-2,6-Trip2],56 where Ω values can exceed 4000 ppm.
The X-ray crystal structure determination of complex 4
defines a very different binuclear Sn(IV) system with a quasi-
one-dimensional polymeric linkage being created essentially
by an adjacent [Et2SnCl(H2O)]+[Et2SnCl(H2O)(oda)]- ion
pair connected by bridging peripheral carboxylate oxygens.
This gives rise to two very distinct Sn(IV) sites, both of
which are seven-coordinate and very different from the
pentagonal bipyramidal environments described in 1-3.
Although X-ray data for compounds 5 and 6 are unavailable,
it is concluded from the IR analyses given above that they
Figure 5. The 119Sn CPMAS NMR spectra of (a) [Me2Sn(oda)(H2O)]2
(1), (b) [nBu2Sn(oda)(H2O)]2 (2), and (c) [Ph2Sn(oda)(H2O)]2 (3) acquired
at MAS frequencies of 3, 7, and 11 kHz.
for the {Et2SnCl(H2O)(oda)} subunit in the crystal structure
of 4 (see below) and 167.0(2)° observed in the other
{Et2SnCl(H2O)} subunit. The 119Sn chemical shift of 1 in
D2O is -365 ppm consistent with a six-coordinate tin
coordination environment which suggests dissociation of the
dimeric species in solution.51
119Sn Solid-State CPMAS NMR Discussion. The 119Sn
CPMAS NMR spectra of complexes 1-3 are shown in
Figure 5; each spectrum has been acquired at MAS frequen-
cies of 3, 7, and 11 kHz, allowing accurate identification of
δiso,mas, δ11, δ22, and δ33. The isotropic chemical shifts (δiso,mas
and δiso,calc), the chemical shift tensorial values (δ11, δ22, and
δ33) and the calculated parameters defining the chemical shift
interaction (span Ω, skew κ, anisotropy ∆δ, asymmetry η)
are summarized in Table 2. From Table 2 it can be observed
that excellent agreement exists between the measured
isotropic shift (δiso,mas) and the calculated isotropic shift
(δiso,calc) (calculated from the tensorial values δ11, δ22, and
δ33), suggesting that nominated positions of δ11, δ22, and δ33
from each 119Sn CPMAS spectrum have been determined
accurately. The 119Sn chemical shift tensor of each dimeric
complex 1-3 appears to exhibit strict axial symmetry,
possessing spans which range from ∼828 ppm (3, phenyl)
to ∼1230 ppm (2, n-butyl) (Table 2). These Sn(IV) com-
plexes represent a deviation from the conventional notion
of tensor axial symmetry of metals in coordination environ-
ments. Usually, axial symmetry in a chemical shift tensor is
identified with coordination environments possessing strict
tetrahedral or octahedral symmetry (i.e. where proper n-fold
(n g 3) axes of symmetry exist). The X-ray crystal structure
analysis of 1 defines overall pentagonal bipyramidal coor-
dination about each Sn(IV) site, comprised of a quasi-planar,
equatorial five-coordinate oxo environment coupled with
(51) Pettinari, C. Heteronuclear NMR Applications (Ge, Sn, Pb). In
Encyclopedia of Spectroscopy and Spectrometry; Lindon, J. C., Ed.;
Academic Press: London, 1999; pp 704-717.
(52) Sebald, A. Advanced Applications of NMR to Organometallic
Chemistry. In Solid State NMR Applications in Organotin and
Organolead Chemistry; John Wiley & Sons: Chichester, U.K., 1996;
Chapter 5, pp 123-155.
(53) Camacho-Camacho, C.; Contreras, R.; Noth, H.; Bechmann, M.;
Sebald, A.; Milius, W.; Wrackmeyer, B. Magn. Reson. Chem. 2002.
40, 31-40.
(54) Harris, R. K.; Sebald, A. J. Organometallic Chem. 1987, 331, C9-
C12.
(55) Ng, S. W.; Hook, J. M.; Gielen, M. Appl. Organomet. Chem. 2000,
14, 1-7.
(56) Eichler, B. E.; Phillips, B. L.; Power, P. P.; Augustine, M. P. Inorg.
Chem. 2000, 39, 5450-5453.
3100 Inorganic Chemistry, Vol. 44, No. 9, 2005

Oxy- and Iminodiacetate Organotin(IV) Complexes
Table 2. 119Sn Isotropic Chemical Shifts and Chemical Shift Tensorial Parameters Measured from the 119Sn CPMAS NMR Spectra of Figures 5 and 6a
δiso,mas
δ22
δiso,calc
Ω
∆δ
complex
((2 ppm)
δ11
1.2
-39.8
-324.7
((30 ppm)
δ33
((30 ppm)
(ppm)
κ
(ppm)
η
[Me2Sn(oda)(H2O)]2 (1)
[nBu2Sn(oda)(H2O)]2 (2)
[Ph2Sn(oda)(H2O)]2 (3)
[(tBu2SnCl)2(oda)(H2O)2]n (5)
site 1
-403.8
-442.0
-587.9
1.2
-39.8
-324.7
-1146. 0
-1269. 7
-1152. 5
-381. 2
-449. 8
-600. 6
1133. 2
1229. 9
827.8
1
1
1
-1133 .2
-1229 .9
-827. 8
0
0
0
-229.3
N/D
134.8
∼125
-68.4
∼125
-731.1
N/D
-221. 6
N/D
865.9
N/D
0.53
∼1
-764. 2
N/D
0.40
∼0
site 2
[(iBu2SnCl)2(oda)(H2O)2]n (6)
site 1
-391.6
∼-445
-4.3
∼246
-4.3
∼-115
-1147.1
N/D
-385. 1
N/D
1142. 8
N/D
1
-1142 .8
N/D
0
site 2
N/D
N/D
a Parameters defining the chemical shift interaction are calculated from the measured chemical shift tensorial elements δ11, δ22, and δ33 according to the
(IUPAC recommended) conventions: δ11 > δ22 > δ33, isotropic chemical shift δiso ) (δ11 + δ22 + δ33)/3, span Ω ) (δ11 - δ33), skew κ ) 3(δ22 - δiso)/(δ11
- δ33), where 1 g κ g -1. Additional representations: |δ33 - δiso| g |δ11 - δiso| g |δ22 - δiso|, isotropic chemical shift δiso ) (δ11 + δ22 + δ33)/3,
anisotropy ∆δ ) δ33 - (δ11 + δ22)/2 ) 3(δ33 - δiso)/2, asymmetry η ) (δ22 - δ11)/(δ33 - δiso), where 1 g η g 0. N/D ≡ not determined.
The residual 1J(119Sn,35/37Cl) coupling scheme obtained after
MAS is Bo-field dependent and is complicated by the
influence of many parameters.59,61,62 Previous 119Sn CPMAS
studies of organotin halides of the form R3SnX (R ) alkyl,
aryl; X ) Cl, Br) have demonstrated that residual
1J(119Sn,35/37Cl) couplings are not always observable, and this
has been attributed to fast relaxation of the halogen which
thus introduces efficient self-decoupling.52,60 It is assumed
that this halogen relaxation phenomenon is influencing the
more intense Sn sites in the polymeric structures of 5 and 6,
1
facilitating a partial or total collapse of J(119Sn,35/37Cl)
1
coupling fine structure. Furthermore, differing H-119Sn
1
cross-polarization efficiencies and H T1’s may also hinder
the achievement of true quantitation for the site 1 and site 2
sites in each complex.
From Table 2, the more easily observed (self-decoupled)
Sn sites of complexes 5 and 6 are denoted as “site 1” in
each case, and they afford reliable measurement of all the
chemical shift parameters (the labels “site 1” and “site 2” in
Table 2 are not to be confused with labels “Sn(1)” and
Figure 6. 119Sn CPMAS NMR spectra of (a) [(tBu2SnCl)2(oda)(H2O)2]n
(5) and (b) [(iBu2SnCl)2(oda)(H2O)2]n (6) acquired at MAS frequencies of
3, 7, and 11 kHz. The expansions of the MAS spectra acquired at 7 kHz
(for 5) and 11 kHz (for 6) show the existence of a second Sn(IV) site which
“Sn(2)” generated by the X-ray crystal structure determina-
tion, and no direct correlation with them is inferred as there
is no basis on which to attempt a formal assignment of these
sites). This is verified by the excellent agreement observed
between δiso,mas and δiso,calc for these Sn sites in each
polymeric complex. It is of interest to note that the span
and the skew for these sites are markedly different; for 6, Ω
is considerably larger (∼1143 ppm as compared to ∼866
ppm) and κ is 1, suggesting far greater axial symmetry. These
differences inply that 5 and 6 may not be strictly isostructural,
as suggested by the IR analysis that alludes to possible
coordination differences among complexes 4-6. However,
this analysis is not conclusive since only incomplete data
describing the chemical shift interactions of the 1J(119Sn,35/37Cl)
coupled sites in 5 and 6 are accessible. A poor signal/noise
ratio obtained for the spans of these sites makes the low-
field (δ11) and high-field (δ33) edges of the chemical shift
tensor difficult to locate with accuracy, and δiso,mas is not
discernible due to the severe spectral overlap with the more
intense span of the self-decoupled site.
1
is influenced by J(119Sn,35/ 37Cl) coupling.
should have a form similar to 4 even though some different
coordination modes may prevail. This conclusion is further
corroborated by the 119Sn CPMAS spectra of Figure 6a,b
from which it is observed that one Sn site appears more
dominant in intensity; an expansion of Figure 6a,b for
complexes 5 and 6 shows that 1J(119Sn,35/37Cl) fine structure
is observed to influence the spinning sideband manifold
defining the spans of only one of the two observed 119Sn
1
tensors. For the less intense site J(119Sn,35/37Cl) coupling
observed between these I ) 1/2 119Sn nuclei and the I ) 3/2
35/37Cl nuclei constitutes an example of quadrupolar perturbed
combined dipolar (direct)/scalar (indirect) coupling. This
phenomenon has been treated by many authors57-62 with
particular emphasis being directed toward the Sn-Cl case.57-60
(57) Harris, R. K. J. Magn. Reson. 1988, 78, 389-393.
(58) Apperley, D. C.; Haiping, B.; Harris, R. K. Mol. Phys. 1989, 68, 1277-
1286.
(59) Harris, R. K.; Olivieri, A. C. Prog. Nucl. Magn. Reson. Spectrosc.
1992, 24, 435-456.
119mSn Mo1ssbauer Study. Compounds 1-4 and 7 were
examined by 119mSn Mo¨ssbauer spectroscopy, and the results
are reported in Table 3. Complex 1 shows a well-resolved
(60) Harris, R. K.; Sebald, A.; Furlani, D.; Tagliavini, G. Organometallics
1988, 7, 388-394.
(61) Menger, E. M.; Veeman, W. S. J. Magn. Reson. 1982, 46, 257-268.
(62) Olivieri, A. C. J. Am. Chem. Soc. 1992, 114, 5758-5763.
Inorganic Chemistry, Vol. 44, No. 9, 2005 3101

Di Nicola et al.
Table 3. 119mSn Mo¨ssbauer Data
b
δa,b
∆
Γ(b,c
A
complex
(mm s-1
1.43
)
(mm s-1
4.56
)
(mm s-1
)
(%)d
[Me2Sn(oda)(H2O)]2 (1)
[nBu2Sn(oda)(H2O)]2 (2)
first doublet
0.95
100
1.49
1.30
4.63
3.52
0.83
0.95
50
50
second doublet
[Ph2Sn(oda)(H2O)]2 (3)
first doublet
second doublet
1.04
1.43
4.18
4.22
0.80
0.80
50
50
[(Et2SnCl)2(oda)(H2O)2]n (4)
first doublet
second doublet
1.57
1.61
0.93
4.68
4.50
2.46
0.90
0.90
0.81
50
50
100
[Me2Sn(ida)(MeOH)]2 (7)
a With respect to room temperature spectrum of CaSnO3. b (0.01 mm
s-1 c Full width at half-maximum. d Percentage area.
.
doublet with a Γ( value of 0.95 mm/s that indicates a similar
environment in the two tin sites of the dinuclear complex.
The quadrupole splitting ∆, 4.56 mm/s, confirms the trans-
Me2 arrangement; the large value is consistent with a seven-
coordination of the Sn(IV) atoms, and it is comparable to
that of heptacoordinated [nBu2Sn{O2CC6H3-2,6(OH)2}2].63
Compound 4 shows a slightly asymmetrical doublet with
different Γ values; Γ1, 1.03 mm/s, and Γ2, 0.91 mm/s. The
spectrum was deconvoluted with two doublets with similar
δ, ∆, and Γ parameter values (see Table 3), the ∆ values
being consistent with seven-coordinate tin atoms. The larger
∆ value, 4.68 mm/s, can be assigned to the cationic subunit
that shows a distorted pentagonal bipyramidal geometry with
Sn-O and Sn-Cl bond distances varying in a wide range;
cf. the anionic subunit.
The spectrum of 7 shows a single doublet, and the Γ(
value of 0.81 mm/s is characteristic of a single Sn(IV) site.
The ∆ parameter value is lower than those generally found
in trans-Me2 six- and seven-coordinated complexes. The
discrepancy between Mo¨ssbauer and X-ray results can arise
from loss of methanol-coordinated molecule which yields
compound 8 and also from the possible dissociation of the
dimeric complex followed by a subsequent rearrangement
around the tin atom. The ∆ value, in fact, agrees with TBP
or with octahedral distorted geometries.64
The spectra of the dinuclear complexes 2 and 3 have been
recorded to obtain further information on the structure in
the solid state in the absence of X-ray data. These spectra
are similar, but the contribution of two doublets is more
evident in 2 (Figure 7), indicating the presence of two
different tin sites. One doublet (δ1 and ∆1 values 1.49 and
4.63 mm/s, respectively) can be associated with a hepta-
coordinated tin atom, as in 1; the parameters of the second
doublet (δ2 and ∆2 values 1.30 and 3.52 mm/s, respectively)
address a six-coordinated, trans-nBu2Sn moiety. In 3 the two
doublets have similar parameters, and they can be assigned
to two slightly different seven-coordinated trans-Ph2SnIV sites
although a six-coordinated arrangement cannot be excluded.64
Figure 7. Mo¨ssbauer spectrum of [nBu2Sn(oda)(H2O)]2 (2).
Conclusions
In this work we have prepared and characterized, through
a variety of techniques, an array of new oxydiacetate
derivatives of tin(IV) and, for comparison, an iminodiacetate
compound of the same metal. The results reported expand
our knowledge of oxydiacetate compounds of p-block metals,
a field hitherto poorly developed, particularly from a
structural perspective, in contrast to the abundant structural
information available for transition metal oxydiacetate
complexes. It is of interest that different kinds of compounds
may be obtained depending on the nature of the R group
bonded to tin(IV), no [(R2SnCl)2(oda)(H2O)2]n resulting when
R ) Me, Ph, or nBu (1-3) or [R2Sn(oda)(H2O)]2 when R )
i
t
Et, Bu, or Bu (4-6) respectively, presumably due to a
combination of different factors such as the electronic and
steric properties of R and crystal packing forces.
Detailed study by way of a number of spectroscopic
techniques such as 119mSn Mossbauer, 119Sn CPMAS NMR,
and 119Sn NMR (solution) are useful in the assignment of
structures to tin(IV) species when single-crystal X-ray studies
are not accessible: 119mSn Mo¨ssbauer data confirm seven-
coordinated tin sites in the complexes 1, 3, and 4, while in
complex 2 two different trans-R2SnIV geometries are sug-
gested, one with a seven-coordinated tin atom, as in 1, and
the other with an octahedral trans-nBu2Sn moiety. The
Mo¨ssbauer results of compound 7 are indicative of a six- or
five-coordinated distorted geometry arising by the loss of
the methanol-coordinated molecule, the ∆ parameters value
suggesting a remarkable deviation of the C-Sn-C bond
from the linearity.
Acknowledgment. We thank the University of Camerino,
Palermo, Italy, Cooperlink (MIUR), and the CARIMA
Foundation for financial help.
(63) Gielen, M.; Bouhdid, A.; Kayser, F.; Biesemans, M.; de Vos, D.;
Mahieu, B.; Willem, R. Appl. Organomet. Chem. 1995, 9, 251.
(64) Barbieri, R.; Huber, F.; Pellerito, L.; Ruisi, G.; Silvestri, A. 119Sn
Mo¨ssbauer Studies on Tin Compounds. In Chemistry of Tin; Smith,
P. J., Ed.; Blackie Academic Press & Professional: London, 1998;
pp 496-540.
Supporting Information Available: An X-ray crystallographic
file in CIF format. This material is available free of charge via the
Internet at http://pubs.acs.org.
IC048240T
3102 Inorganic Chemistry, Vol. 44, No. 9, 2005