Mono-aryltin(IV) and mono-benzyltin(IV) complexes with pyridine-2-carboxylic acid and 8-hydroxyquinoline. X-ray structure of p-chloro-phenyl-tris(8-quinolinato)tin(IV)-2CHCl3

Article abstract of DOI:10.1016/S0022-328X(99)00103-5

Complexes RSn(O₂CPy)₃·2H₂O and RSn(Ox)₃, (PyCOOH = pyridine-2-carboxylic acid, HOx = 8-hydroxyquinoline, R = o- and p-Tolyl, o- and p-ClC₆H₄ = o- and p-ClPh, o-ClC₆H₄CH₂ = o-ClBenzyl; besides, R = Ph in RSn(Ox)₃) have been synthesized and characterized by elemental analysis and determination of molecular weights in CHCl₃ solutions. The structure of p-ClPh-Sn(Ox)₃·2CHCl₃ has been determined by X-ray diffractometry. The 7-coordinated tin atom of the monomeric compound is in the center of a pentagonal bipyramid formed by (p-ClPh)C and O and N atoms of the chelating Ox^- ligands. The latter type of structure would hold for all complexes according to ¹¹⁹Sn Moessbauer (including the determination of the dynamics of ¹¹⁹Sn nuclei) and IR spectroscopy in the solid state; the ligand ^-O₂CPy appears to chelate Sn through one oxygen atom of the -COO^- group and the N atom, although the occurrence of one chelating and two monodentate PyCO^-₂ ligands (through -COO^-), and coordination by the H₂O molecules to Sn cannot be excluded. In CDCl₃ and CHCl₃ solutions, the persistence of the pentagonal bipyramidal species is assumed, in line with ¹H-, ¹³C-, ¹¹⁹Sn-NMR and UV-vis spectroscopic studies.

Full text of DOI:10.1016/S0022-328X(99)00103-5

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 584 (1999) 103–117
Mono-aryltin(IV) and mono-benzyltin(IV) complexes with
pyridine-2-carboxylic acid and 8-hydroxyquinoline. X-ray structure
of p-chloro-phenyl-tris(8-quinolinato)tin(IV)·2CHCl3
Markus Schu¨rmann a, Ralf Schmiedgen a, Friedo Huber a,*, Arturo Silvestri b,
Giuseppe Ruisi b, Adriana Barbieri Paulsen c, Renato Barbieri b
a Fachbereich Chemie, Uni6ersita¨t Dortmund, Otto-Hahn Str. 6, D-44221 Dortmund, Germany
b Dipartimento di Chimica Inorganica, Uni6ersita` di Palermo, 6iale delle Scienze, I-90128 Palermo, Italy
c Institut fu¨r Physik, Medizinische Uni6ersita¨t Lu¨beck, Ratzeburger Allee 160, D-23538 Lu¨beck, Germany
Received 30 October 1998; received in revised form 17 December 1998
Abstract
Complexes RSn(O2CPy)3·2H2O and RSn(Ox)3, (PyCOOH=pyridine-2-carboxylic acid, HOx=8-hydroxyquinoline, R=o- and
p-Tolyl, o- and p-ClC6H4=o- and p-ClPh, o-ClC6H4CH2=o-ClBenzyl; besides, R=Ph in RSn(Ox)3) have been synthesized and
characterized by elemental analysis and determination of molecular weights in CHCl3 solutions. The structure of p-ClPh-
Sn(Ox)3·2CHCl3 has been determined by X-ray diffractometry. The 7-coordinated tin atom of the monomeric compound is in the
center of a pentagonal bipyramid formed by (p-ClPh)C and O and N atoms of the chelating Ox− ligands. The latter type of
structure would hold for all complexes according to 119Sn Mo¨ssbauer (including the determination of the dynamics of 119Sn nuclei)
and IR spectroscopy in the solid state; the ligand −O2CPy appears to chelate Sn through one oxygen atom of the ꢀCOO− group
and the N atom, although the occurrence of one chelating and two monodentate PyCO2− ligands (through ꢀCOO−), and
coordination by the H2O molecules to Sn cannot be excluded. In CDCl3 and CHCl3 solutions, the persistence of the pentagonal
bipyramidal species is assumed, in line with 1H-, 13C-, 119Sn-NMR and UV–vis spectroscopic studies. © 1999 Elsevier Science S.A.
All rights reserved.
Keywords: Tin; Pyridyl-2-carboxylic acid; 8-Hydroxyquinoline; X-ray structure
Among the RSn(SPy)3 species investigated, organo-
tin(IV) moieties RSnIV with R=o-Tolyl, p-Tolyl, o-
ClPh, p-ClPh, Benzyl and o-ClBenzyl have been taken
into account [1], whose coordination chemistry has
rarely been studied [2].
Continuing our work in the field, we report here on
complex formation of RSn moieties with the ligands
pyridine-2-carboxylate (−O2CPy) and 8-hydroxy-
quinolinate (Ox−), Fig. 1; complexes RSn(O2CPy)3 and
RSnOx3 have been synthesized, and structurally
characterized.
1. Introduction
In a preceding paper, we reported the synthesis and
characterization of mono-organotin(IV) complexes
RSnCl2(L), RSnCl(L)2 and RSn(L)3 (HL=2-mercapto-
pyridine=HSPy,
and
2-mercapto-pyrimidine=
HSPym, R=Alkyl, Ph) by IR and 119Sn Mo¨ssbauer
spectroscopy in the solid state, and 1H-, 13C- and
119Sn-NMR spectroscopy in solution phases [1]. X-ray
diffractometry revealed that in complexes RSn(SPy)3
(R=Me, Ph) bidentate SPy− ligands and (R)C form a
pentagonal bipyramidal polyhedron around tin [1].
−O2CPy (potentially tridentate [3,4]) may act as
bidentate ligand, coordinating to metal centers by hete-
rocyclic nitrogen and one oxygen atom of the car-
boxylic group, and forming chelate rings analogous to
those in 8-hydroxyquinolinate complexes; it follows
that related compounds are mutually comparable [5].
Besides, bonding and structure in −O2CPy and Ox−
* Corresponding author. Tel.: +49-231-7553801; fax: +49-231-
7553797.
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00103-5

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M. Schu¨rmann et al. / Journal of Organometallic Chemistry 584 (1999) 103–117
2.2. Syntheses
These were generally effected in dry solvents, under
stirring, in dry nitrogen atmosphere. Mono-organotin
trichlorides were prepared by the Kozeschkow reaction
[60] from R4Sn and SnCl4 [61]; tetraorganotin(IV)
derivatives, R=o- and p-Tolyl, o- and p-chlorophenyl,
Benzyl and o-chloro-Benzyl, were obtained by standard
procedures [61].
Fig. 1. Ligand molecules, and labelling employed in Tables 8 and 9,
NMR data. (A) pyridine-2-carboxylic acid; (B) 8-hydroxyquinoline;
(C) organic radicals (benzyl and tolyl) bound to Sn.
The complexes RSn(O2CPy)3·2H2O, 1–5 in Table 1,
were obtained by reaction of NaO2CPy, in methanol
solution, with RSnCl3 in chloroform, by the same pro-
cedure employed for the syntheses of −SPy and
−SPym complexes [1]. The p-TolylSnIV derivative, 1 in
Table 1, was also obtained from p-TolylSn(OOH)
[19](a), according to previously reported procedures [1].
Compound 5% in Table 4, BzSn(O2CPy)3, was prepared
by reaction of a mixture of BzHgCl and BzSnCl3 with
NaO2CPy, again following the procedure reported for
−SPy, −SPym complexes [1]; in the present context,
attempts to separate the products BzHg(O2CPy) and
BzSn(O2CPy)3 were unsuccessful.
complexes may be discussed in connection with the
corresponding SPy− derivatives [6].
The coordination of −O2CPy to organotin(IV) ac-
ceptors, mainly R2SnIV and R3SnIV, has been previously
investigated by X-ray diffractometry [3,4,7,8] as well as
by IR, NMR and 119Sn Mo¨ssbauer spectroscopies [4–
6,9–14]. It has been established that the ligand may act
as mono-, bi- and tridentate, in the latter case yielding
polymeric species through bridging by the carboxylate
group [3–14].
Complexes of RnSnIV (n=1–3) with 8-hydroxy-
quinoline and related ligands have been widely investi-
gated by X-ray diffractometry [2,15–19], 119Sn Mo¨ss-
bauer spectroscopy [6,20–34], IR, NMR, UV–vis and
other techniques [6,9,13,19–21,26,33–57]. UV spectra
and syntheses have been reported as early as in 1950–
1961 [58]. The ligand Ox− behaves essentially as biden-
tate in solid state complexes, possibly as monodentate
in R3SnOx in ethanol (aqueous) solution [36,37]; it
chelates Sn in R3SnOx in anhydrous cyclohexane, diox-
ane and CCl4 solutions [39,53]. In R2SnOx2, the R
radicals and the two chelating Ox− ligands may lie in
cis-position, both in the solid state [2,15,18] and in
solution phases [41], as well as in trans-configuration
[16]. Ox− proved to be bidentate in R2SnCl(Ox) in
alcohol and benzene solution [42]. Mono-organotin(IV)
complexes nBuSnOx3 [21,25,28,43], and EtSnOx3 [30]
(Ox=5,7-dichloro-; 5,7-dibromo; 5-nitro-8-oxy-quino-
linate [30]), have been determined to consist of pentago-
nal bipyramidal type species, with 7-coordinated Sn, by
119Sn Mo¨ssbauer spectroscopy [21,25,28,30], and IR,
NMR,UV spectroscopies [43].
2.2.1. Complexes RSnOx3 were prepared as follows
(a) Numbers 6–10, Table 1: RSnCl3 (6 mmol) and 1
ml of concentrated NH3 were added to a solution of
HOx (24 mmol) in 60 ml MeOH. The mixture was
refluxed for 3 h. The obtained solid product was filtered
off, washed with MeOH and dried under vacuum in the
presence of P2O5.
(b) Number 11, Table 1: HOx (21 mmol) was treated
with NaOMe (21 mmol, 42 ml of a 0.5 M solution); the
obtained solution was added dropwise, within 1 h, to a
solution of o-ClBzSnCl3 (6 mmol) in 40 ml of absolute
MeOH. After stirring (24 h) at r.t., the solvent was
removed in a rotary evaporator; the residue was dis-
solved in 50 ml CHCl3, and NaCl was filtered off. The
volume of the solution was reduced to about 20 ml, and
petroleum ether (b.p. 30–60°C) was added in small
portions till the solution attained a yellowish color. The
crystallization of the complex was obtained at −30°C;
the product was filtered off and dried under vacuum.
2.3. Characterization of the complexes
2. Experimental
Decomposition temperatures (uncorrected; Table 1)
were determined by DTA/TG measurements with a
Mettler Vacuum thermoanalyzer T1 (Reference: Al2O3,
25°C; N2, 6°C min−1; Pt/PtRh thermoelement). Molec-
ular weights (Table 1) were measured with a Knauer
vapor pressure osmometer on CHCl3 solutions. C, H,
N analyses (Table 1) were effected with an Elemental
Analyzer 1106, Carlo Erba, or determined at the Dipar-
timento di Chimica Inorganica, Organometallica ed
Analitica, University of Padova (Italy).
2.1. Materials
Pyridine-2-carboxylic acid, 8-hydroxyquinoline and
Ph4Sn were products from E. Merck, Darmstadt, and
SnCl4 from Th. Goldschmidt A.G., Essen. Other
reagents and solvents were commercial products, which
were purified and dried according to standard proce-
dures [59].

M. Schu¨rmann et al. / Journal of Organometallic Chemistry 584 (1999) 103–117
105
Table 1
Analytical data for mono-aryltin(IV) and mono-benzyltin(IV) complexes with pyridine-2-carboxylic acid (HO2CPy) and 8-hydroxyquinoline
(HOx)
a
Number Compound
Yield (%)
M.P. (°C)
Mol. wt. found (calc.) b
Analytical data: found (calcd.)%
C
H
N
1
2
3
4
5
p-TolSn(O2CPy)3·2H2O
71
68
70
65
70
256(dec)
245(dec)
267(dec.)
265(dec)
240(dec)
607 (612.2)
585 (612.2)
638 (632.6)
633 (632.6)
647 (646.6)
49.1 (49.1)
48.9 (49.1)
45.2 (45.6)
45.5 (45.6)
46.3 (46.4)
3.1 (3.8)
3.4 (3.8)
2.9 (3.2)
3.0 (3.2)
3.5 (3.4)
6.9 (6.9)
7.0 (6.9)
6.5 (6.6)
6.6 (6.6)
6.5 (6.5)
o-TolSn(O2CPy)3·2H2O
p-ClPhSn(O2CPy)3·2H2O
o-ClPhSn(O2CPy)3·2H2O
o-ClBzSn(O2CPy)3·2H2O
6
7
8
9
10
11
PhSn(Ox)3
p-TolSn(Ox)3
o-TolSn(Ox)3
p-ClPhSn(Ox)3
o-ClPhSn(Ox)3
o-ClBzSn(Ox)3·CHCl3
82
79
78
84
80
74
316(dec)
249(dec)
270(dec.)
245(dec)
273(dec)
151(dec)
—(628.2)
—(642.3)
—(642.3)
—(662.7)
—(662.7)
655(676.7) c
62.8 (63.1)
63.6 (63.6)
63.4 (63.6)
59.3 (59.8)
59.6 (59.8)
52.7 (52.8)
3.7 (3.7)
3.9 (3.9)
4.0 (3.9)
3.4 (3.4)
3.5 (3.4)
3.3 (3.2)
6.7 (6.7)
6.5 (6.5)
6.5 (6.5)
6.3 (6.4)
6.5 (6.4)
4.9 (5.3)
a Abbreviations: Tol=Tolyl; Ph=Phenyl; Bz=Benzyl; o=ortho; p=para.
b In CHCl3 solutions. The calculated MW values for Numbers 1–5 include 2H2O per mole. Numbers 6–10: MW not determined owing to
insufficient solubility.
c Molecular mass calculated for o-ClBzSn(Ox)3.
The UV–vis absorption spectra were obtained with a
Perkin–Elmer Lambda 15 instrument.
Single crystals of p-ClPhSnOx3·2CHCl3 were ob-
tained by crystallization from CHCl3, analogously to
the procedure in a previous study [1]. Intensity data for
the yellow crystals were collected with ꢀ/2r scans on a
Nicolet R3m/V diffractometer with graphite-monochro-
mated Mo–Ka radiation at 170(1)K. The lattice
parameters were determined from a symmetry-con-
strained least-squares fit of the angular settings for 49
reflections with 2qmax=30.4°. Six standard reflections
were recorded every 300 reflections and anisotropic
intensity loss up to 2.3% was detected during X-ray
exposure. The data were corrected for Lorentz-polarisa-
tion decay and for absorption effects. The structure was
solved by direct methods using SHELXS86 [62] and
successive difference Fourier syntheses. Refinement ap-
plied full-matrix least-squares methods (SHELXL93 [63]).
The H atoms were placed in geometrically calculated
3. Results and discussion
The results of the elemental analyses reported in
Table 1 indicate for all complexes here investigated the
stoichiometry to correspond to the formula RSnL3.
Molecular weights in CHCl3 indicate the occurrence of
monomeric species (Numbers 1–5, 11, Table 1).
positions and refined with a common isotropic tempera-
2
,
,
ture factor (Haryl CꢀH 0.95 A, Uiso 0.049(4) A ). Disor-
dered Cl atoms were found for one solvent molecule
CHCl3 at Cl(5A), Cl(5B), Cl(6A) and Cl(6B) (s.o.f. 0.5)
(Table 3). Atomic scattering factors for neutral atoms
and real and imaginary dispersion terms were taken
from International Tables for X–ray Crystallography
[64]. Figs. 2 and 3 were created by SHELXTL-Plus [65].
Crystallographic data are given in Table 2, selected
bond distances and angles in Table 3.
The 119Sn Mo¨ssbauer spectra (Tables 4 and 6) were
obtained by the instrumentation and procedure previ-
ously reported [66,67]. Infrared spectra (KBr pellets)
(Table 7) were determined on a Bruker FTIR spectrom-
eter IFS 113V; NMR spectra (Tables 8–10) were mea-
sured on a Bruker AM 300 spectrometer (T=37°C).
Fig. 2. General view (SHELXTL-Plus) of a molecular unit of p-ClPh-
Sn(Ox)3 (9a) showing 50% probability displacement ellipsoids and the
atom numbering.

106
M. Schu¨rmann et al. / Journal of Organometallic Chemistry 584 (1999) 103–117
solution
in
CHCl3;
single
crystals
p-ClPh-
Sn(Ox)3·2CHCl3 (9a) separated from a saturated solu-
tion of 9 in CHCl3 on standing at 4°C; the latter were
submitted to X-ray diffractometry (Tables 2 and 3);
CHCl3 could not be removed from complex 11 even
at 50°C under vacuum.
3.1. Structures in the solid state
3.1.1. X-ray diffractometry
No X-ray structure of species RSn(Ox)3 has so far
been reported in the literature. X-ray diffractometry
of single crystals of p-ClPhSn(Ox)3·2CHCl3, 9a, Ta-
bles 2 and 3 and Figs. 2 and 3, showed the complex
9a to be monomeric, Fig. 2; four CHCl3 molecules are
present in the unit cell, Fig. 3, two Cl atoms in two
CHCl3 molecules being disordered (Table 3). The Ox
ligands are bidentate, coordinating Sn through N, O
atoms; two N and three O atoms yield a pentagonal
plane centered on Sn, two Ox ligands lying in the
equatorial plane, while the third Ox is perpendicular
to the plane, with axial N and equatorial O in the
axially distorted pentagonal bipyramid (Fig. 2 and
Table 3).
Fig. 3. View (SHELXTL-Plus) of p-ClPhSn(Ox)3 (9a) showing the unit
cell with four CHCl3 molecules.
Comments on the syntheses of the complexes
RSn(O2CPy)3·2H2O, listed in Table 1, correspond to
reports for species RSnL3 (L=SPy, SPym [1]); a pe-
culiarity of the −O2CPy derivatives is their content of
H2O molecules (as detected, inter alia, by differential
thermal analysis); also the failure to separate
BzHg(O2CPy) from BzSn(O2CPy)3 is remarkable (see
Section 2, this work).
Table 2
Crystallographic data for p-ClPhSn(Ox)3·2CHCl3 (9a)
Formula
C33H22N3O3ClSn·2CHCl3 (9a)
Formula weight
Crystal system
Crystal size, mm
Space group
901.41
Triclinic
0.40×0.34×0.32
P1
,
a (A)
9.484(3)
11.968(3)
17.164(7)
88.94(3)
88.46(3)
66.75(2)
1789.3(9)
2
The compounds RSn(Ox)3, 6–10 in Table 1, were
obtained by the reaction:
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
RSnCl3+4 HOxNH /MeOH
“
RSn(Ox)3+NH4(Ox)
3
+3 NH4Cl
(1)
3
,
V (A )
Z
[See Section 2.2.1, method (a)]; complex 11 (Table 1)
could not be obtained by Eq. (1), but metathesis ac-
cording to Eq. (2) was successful:
zcalcd (Mg m−3
)
1.673
1.278
896
v (mm−1
F(000)
)
Absorp. corr., type
max./Tmin.
Empirical, C scan
0.954/0.871
1.85 to 25.05
−115h52
−145k513
−205l519
5690
5460/0.0250
462
4675
T
3 NaOx+o-ClBzSnCl3“o-ClBzSn(Ox)3+3 NaCl
q range, (°)
Index ranges
(2)
[Section 2.2.1, method (b)]. Attempts to separate NaCl
from the dried reaction mixture with H2O yielded a
hydrolyzed product; however, the separation of o-
ClBzSn(Ox)3 from NaCl could be effected by dissolv-
ing the oxinate complex with CHCl3. This procedure
could not be employed for other RSn(Ox)3 species due
to their insufficient solubility in CHCl3. Crystals
which include one mole CHCl3 per mole of complex
(11, Table 1), were obtained at −30°C after addition
of petroleum ether (b.p. 30–60°C) to a concentrated
Reflect. Collect.
Indep. Reflect./Rint
Ref. Parameters
Reflect. Obs. with (I\2|(I))
GooF (F2)
R1 (F) (I\2|(I))
wR2 (F2) (all Data)
0.1143 (F2)
1.025
0.0435 (F)
(D/|)max.
Largest diff. peak/hole (e A
0.001
1.071/−0.979
−3
,
)

M. Schu¨rmann et al. / Journal of Organometallic Chemistry 584 (1999) 103–117
107
Table 3
,
Selected bond distances (A) and bond angles (°) in p-ClPhSn(Ox)3·2CHCl3 (9a)
Bond distances
Sn(1)ꢀC(1)
Sn(1)ꢀO(1)
Sn(1)ꢀO(2)
Sn(1)ꢀO(3)
Sn(1)ꢀN(11)
O(1)ꢀC(18)
N(11)ꢀC(11)
N(11)ꢀC(19)
C(11)ꢀC(12)
C(12)ꢀC(13)
C(13)ꢀC(14)
C(14)ꢀC(15)
C(14)ꢀC(19)
C(15)ꢀC(16)
C(16)ꢀC(17)
C(17)ꢀC(18)
C(18)ꢀC(19)
C(41)ꢀCl(2)
C(41)ꢀCl(3)
C(41)ꢀCl(4)
2.136(4)
2.120(3)
2.099(3)
2.114(3)
2.205(4)
1.308(5)
1.311(6)
1.354(6)
1.425(7)
1.368(8)
1.415(8)
1.415(8)
1.423(6)
1.357(9)
1.405(8)
1.385(7)
1.464(7)
1.757(6)
1.781(7)
1.759(6)
Sn(1)ꢀN(21)
Sn(1)ꢀN(31)
Cl(1)ꢀC(4)
C(1)ꢀC(6)
C(1)ꢀC(2)
2.491(4)
2.472(4)
1.743(5)
1.395(6)
1.396(6)
1.338(6)
1.295(6)
1.363(6)
1.397(7)
1.360(7)
1.409(7)
1.419(7)
1.422(6)
1.388(7)
1.398(7)
1.390(6)
1.425(6)
1.749(9)
1.652(13)
1.804(9)
C(2)ꢀC(3)
C(3)ꢀC(4)
C(4)ꢀC(5)
C(5)ꢀC(6)
1.386(7)
1.395(7)
1.367(7)
1.408(7)
O(2)ꢀC(28)
N(21)ꢀC(21)
N(21)ꢀC(29)
C(21)ꢀC(22)
C(22)ꢀC(23)
C(23)ꢀC(24)
C(24)ꢀC(25)
C(24)ꢀC(29)
C(25)ꢀC(26)
C(26)ꢀC(27)
C(27)ꢀC(28)
C(28)ꢀC(29)
C(51)ꢀCl(5A) a
C(51)ꢀCl(6A) a
C(51)ꢀCl(5B) a
O(3)ꢀC(38)
1.335(6)
1.331(6)
1.354(6)
1.403(7)
1.345(8)
1.414(7)
1.406(8)
1.422(7)
1.366(8)
1.430(7)
1.352(7)
1.432(7)
1.85(2)
N(31)ꢀC(31)
N(31)ꢀC(39)
C(31)ꢀC(32)
C(32)ꢀC(33)
C(33)ꢀC(34)
C(34)ꢀC(35)
C(34)ꢀC(39)
C(35)ꢀC(36)
C(36)ꢀC(37)
C(37)ꢀC(38)
C(38)ꢀC(39)
C(51)ꢀCl(6B) a
C(51)ꢀCl(7)
1.747(6)
Bond angles
O(2)ꢀSn(1)ꢀO(3)
O(2)ꢀSn(1)ꢀO(1)
O(3)ꢀSn(1)ꢀO(1)
O(2)ꢀSn(1)ꢀC(1)
O(3)ꢀSn(1)ꢀC(1)
O(1)ꢀSn(1)ꢀC(1)
O(2)ꢀSn(1)ꢀN(11)
O(3)ꢀSn(1)ꢀN(11)
O(1)ꢀSn(1)ꢀN(11)
C(1)ꢀSn(1)ꢀN(11)
O(2)ꢀSn(1)ꢀN(31)
O(3)ꢀSn(1)ꢀN(31)
O(1)ꢀSn(1)ꢀN(31)
C(1)ꢀSn(1)ꢀN(31)
N(11)ꢀSn(1)ꢀN(31)
O(2)ꢀSn(1)ꢀN(21)
O(3)ꢀSn(1)ꢀN(21)
O(1)ꢀSn(1)ꢀN(21)
C(1)ꢀSn(1)ꢀN(21)
N(11)ꢀSn(1)ꢀN(21)
N(31)ꢀSn(1)ꢀN(21)
C(6)ꢀC(1)ꢀSn(1)
C(2)ꢀC(1)ꢀSn(1)
74.14(12)
139.76(12)
138.69(12)
100.73(14)
100.57(14)
94.97(14)
86.51(13)
86.85(13)
75.80(13)
170.77(14)
144.76(13)
70.63(13)
72.42(13)
86.53(14)
90.83(14)
70.65(12)
144.43(12)
72.33(12)
90.79(14)
86.19(13)
144.26(12)
121.5(3)
C(5)ꢀC(4)ꢀCl(1)
C(3)ꢀC(4)ꢀCl(1)
C(18)ꢀO(1)ꢀSn(1)
119.4(4)
118.7(4)
117.6(3)
126.0(3)
113.2(3)
123.3(3)
129.9(3)
110.8(3)
122.5(3)
129.7(3)
111.0(3)
110.4(4)
108.2(3)
109.4(3)
112.9(6)
82.8(7)
C(11)ꢀN(11)ꢀSn(1)
C(19)ꢀN(11)ꢀSn(1)
C(28)ꢀO(2)ꢀSn(1)
C(21)ꢀN(21)ꢀSn(1)
C(29)ꢀN(21)ꢀSn(1)
C(38)ꢀO(3)ꢀSn(1)
C(31)ꢀN(31)ꢀSn(1)
C(39)ꢀN(31)ꢀSn(1)
Cl(2)ꢀC(41)ꢀCl(4)
Cl(2)ꢀC(41)ꢀCl(3)
Cl(4)ꢀC(41)ꢀCl(3)
Cl(6A) aꢀC(51)ꢀCl(7)
Cl(6A) aꢀC(51)ꢀCl(5A) a
Cl(7)ꢀC(51)ꢀCl(5A) a
Cl(6A) aꢀC(51)ꢀCl(5B) a
Cl(7)ꢀC(51)ꢀCl(5B) a
Cl(7)ꢀC(51)ꢀCl(6B) a
Cl(5A) aꢀC(51)ꢀCl(6B) a
Cl(5B) aꢀC(51)ꢀCl(6B) a
110.9(4)
117.9(7)
106.0(4)
103.9(6)
99.4(6)
134.7(6)
119.6(3)
a Site occupancy factor 0.5.
3.1.2. 119Sn Mo¨ssbauer spectroscopy: structure and dy-
namics
ture, corresponding to that of the other derivatives in
the Table.
High quality 119Sn Mo¨ssbauer spectra, measured for
the complexes listed in Table 4, were obtained, as
shown in Fig. 4. The latter is quite surprising and
unexpected for BzSn(O2CPy)3, considering the failure
to separate a pure compound (see Section 2.2). In fact,
the sample submitted to Mo¨ssbauer spectroscopy
(Table 4) showed the following analytical data, found
(Anal. Calc.)%: C, 45.12 (49.05); H, 2.85 (3.79); N, 5.27
(6.86); the parameters in Table 4 clearly indicate that
the species BzSn(O2CPy)3, as part of the reaction mix-
ture obtained, is a complex with a fully regular struc-
The Mo¨ssbauer parameters listed in Table 4 are
typical for mono-organotin derivatives [68]. In particu-
lar, data insert quite well into l and DE values reported
for aryltin(IV) derivatives characterized by three tin–
oxygen bonds [69]. Substantial differences are detected
with respect to ArSn(S,N)3 complexes [1], where larger
isomer shift values occur, owing to S“Sn charge trans-
fer [1]; besides, a wider interval for nuclear quadrupole
splitting data has been interpreted to be due to the
occurrence of a series of structures [1].
On the contrary, the parameters inherent to the

108
M. Schu¨rmann et al. / Journal of Organometallic Chemistry 584 (1999) 103–117
Table 4
119Sn Mo¨ssbauer parameters of mono-organotin(IV) complexes with pyridine-2-carboxylic acid and 8-hydroxyquinoline
a
b,c
b,d
b,e
Number
Compound
l
(mm s−1
)
DE
(mm s−1
)
G1; G2
(mm s−1
)
1
2
3
4
5
5%
6
p-TolSn(O2CPy)3·2H2O
o-TolSn(O2CPy)3·2H2O
p-ClPhSn(O2CPy)3·2H2O
o-ClPhSn(O2CPy)3·2H2O
o-ClBzSn(O2CPy)3·2H2O
BzSn(O2CPy)3
PhSn(Ox)3
p-TolSn(Ox)3
0.61
1.82
0.81
0.62 (0.61190.003)
0.61 (0.60990.004)
0.55
0.69 (0.68690.003)
0.74
1.87 (1.84290.009)
1.82 (1.84090.012)
1.62
1.82 (1.81690.004)
1.83
0.85 (0.81990.008)
0.90 (0.89090.027)
0.92
0.84 (0.84690.009)
0.84
f
0.59 (0.58490.005)
0.60
2.02 (2.01590.004)
1.82
0.80 (0.78390.011)
0.86
7
8
9
10
11
o-TolSn(Ox)3
0.60 (0.59390.007)
0.56
0.52 (0.51190.012)
0.63
1.68 (1.68190.009)
1.71
1.57 (1.55890.008)
1.57
0.79 (0.79490.016)
0.82
0.86 (0.84490.011)
0.90
p-ClPhSn(Ox)3
o-ClPhSn(Ox)3
o-ClBzSn(Ox)3·CHCl3
a See Table 1 for abbreviations.
b Determined at 77.3 K on finely powdered solid absorber samples. Data in parentheses: average values in the T ranges reported in Table 6,
with standard error.
c Isomer shift with respect to r.t. Ca119SnO3.
d Nuclear quadrupole splitting.
e Full width at half height. The spectra were fitted as symmetrical doublets with NORMOS program.
f Mixture with the solid complex of BzHgII, see Sections 2 and 2.2.
−O2CPy and Ox− complexes here investigated (Table
4) are generally corresponding; besides, in some in-
stances l and DE for couples of derivatives with a given
Ar are almost identical (Table 4). One is then tempted
to conclude that the same structure of tin environments
occurs for all complexes listed in Table 4.
[71,72] were applied to pentagonal bipyramidal configu-
rations [73,74]. Anyhow, no pqs data for (Ox)O− and
(Py)COO− in trigonal bipyramidal structures, to be
For proving this assumption, the starting point could
be the crystal and molecular structure of p-ClPhSnOx3,
Tables 2 and 3 and Figs. 2 and 3, which is the only one
reported in the literature for RSn(L)3 complexes, L=
−O2CPy and Ox−; this structure type is also sketched
in Table 5 (I), bond angles being idealized according to
a regular structure. The same could be assumed for all
RSn(Ox)3 derivatives here investigated: in fact, X-ray
diffractometry of a series of complexes R2Sn(Ox)2
2,15,16,19b, R2SnClOx [17] and RSnCl(Ox)2 [18] all
show the occurrence of N, O chelation of tin by the
ligand. In the case of −O2CPy complexes of organo-
tin(IV) acceptors, single crystal X-ray diffractometry
reveals a series of possible coordination situations, from
Me2SnCl(O2CPy) where the ligand behaves as triden-
tate through N, O, O yielding a polymeric species with
6-coordinated tin [3], to Me2Sn(O2CPy)2 with 7-coordi-
nated tin, into a polymeric species, due to one bridging
(tridentate) ligand [4], to Me3Sn(O2CPy) · H2O [7], and
Ph3SnCl(O2CPy(H)) [8] with monodentate ꢀCOO− and
trigonal bipyramidal tin environment; −O2CPy then
acts as mono-, bi- and tridentate. Anyhow, the maxi-
mum tin coordination number detected is seven.
On these grounds, structural assignments by the
point-charge model formalism [70–72] through calcula-
tion of DE parameters have been attempted for the
complexes in Table 4. Partial nuclear quadrupole split-
tings, pqs, inherent to five-coordinated tin structures
Fig. 4. The quality of variable temperature 119Sn Mo¨ssbauer spectra
measured in the present study: data for o-TolylSn(Ox)3 (Number 8,
Tables 4 and 6).

M. Schu¨rmann et al. / Journal of Organometallic Chemistry 584 (1999) 103–117
109
Table 5
Point-charge model (Refs. [70–72]) estimates of the partial nuclear quadrupole splitting, pqs, {(Ox)O}pbe, inherent to the oxygen atom of
8-hydroxyquinoline bound to Sn in pentagonal bipyramidal RSn(Ox)3 complexes (equatorial position), and the determination of its reliability from
calculations of the nuclear quadrupole splittings, DE, for RSn(Ox)3 and R3Sn(Ox) complexes a
Number Compound
DEexp (mm s−1
)
Refs.
Structure
{(Ox)O}pbe (mm s−1
)
(A) Calculations of {(Ox)O}pbe
1.
2.
p-ClPhSn(Ox)3
1.71
This work (Table 4)
28
(I)
(I)
−0.312 b
−0.182
nBuSn(Ox)3
(+)1.82 c (p=0.2) d
e
(B)
Calculations of DE
Compound or class of compounds
ArylSn(Ox)3
DEexp or range (mms−1
1.57–2.02
)
Refs.
Structure
(I)
(I)
(II)
(II)
DEcalcd (mms−1
)
3.
4.
5.
6.
7.
8.
This work (Table 4)
21, 25, 28, 30
28
6, 21, 30, 32
30
6
(+)1.84; p d=0.99
(+)1.93; p d=0.94
f
AlkylSn(Ox)3
1.67–2.18
Ph3Sn(Ox) g
Ph3Sn(Ox) g
Ph3Sn(Ox) h
Me3Sn(Ox)
(−)1.75 c (p=0.7) d
1.69−2.36
(−)2.02; p d=0.46
(−)2.24; p d=0.68
1.53 i; 2.57 i
2.27
(II)
(II)
a Abbreviations: Me=methyl; Et=ethyl; Bu=butyl; Ph=phenyl; Bz=benzyl; HOx=8–hydroxyquinoline and derivatives (see notes). Partial
nuclear quadrupole splitting values, mms−1, employed in the calculations (Refs. [71,74]): {Alk}tba=−0.94; {Alk}tbe=−1.13; {Aryl}tba
{Bz}tba=−0.89; {Aryl}tbe=−0.98; {Nhet tba=−0.035; {Nhet tbe=+0.147; see also footnote (e). tba=trigonal bipyramidal axial, tbe=trigonal
=
}
}
bipyramidal equatorial. These values are assumed to hold also for pentagonal bipyramidal structures (see Ref. [73]; equatorial, pbe; axial, pba).
b DEcalcd with this pqs value shows a negative sign. The employment of the crystallographic angles (Table 3) does not consistently vary the
calculated parameters.
c Sign of DE obtained from the Mo¨ssbauer–Zeeman spectrum (Ref. [28]).
d Asymmetry parameter p=Vxx−Vyy/Vzz (Refs. [70–72]).
e Employing the values {(Ox)O}pbe=−0.182 mm s−1, and {(Ox)O}pba,tba=−0.282 mm s−1; the latter is obtained from {(Ox)O}pbe=−0.182
mm s−1, assumed to hold also for trigonal bipyramidal structures, employing the relationship [3{L}the−4{L}tba]=0.58 mm s−1 (Ref. [71]). Other
pqs values: see footnote (a).
f Alkyl=Bu, HOx=8-hydroxyquinoline; Alkyl=Et, HOx=(5,7-dichloro)-; (5,7-dibromo)-; (5-nitro)-; -8-hydroxyquinoline.
g HOx=8-hydroxyquinoline [6,21];=(5,7-dichloro)–; (5,7-dibromo)–; (5-COCH3)–; (5-COC6H5)–; (5-NꢁNꢀC6H5)ꢀ; -8-hydroxyquinoline
[30,32].
h HOx=(2-CH3)ꢀ; (5,7-diiodo)–; -8-hydroxyquinoline.
i Out of correlation ꢀDEexp−DEcalcdꢀ=0.4 mms−1: M.G. Clark, A.G. Maddock, R.H. Platt, J. Chem. Soc. Dalton Trans. (1972) 281. In
structures
(I)
and
(II),
x, y, z
are
the
principal
axes
of
the
electric
field
gradient
tensor
(Refs
[70–72]).
employed in complexes of ArSnIV with 8-hydroxy-
quinoline and pyridine-2-carboxylic acid, respectively,
have been insofar reported: for 8-hydroxyquinoline,
data related to Ox/2 are quoted [71,72], and existing
values for ꢀCOO− concern carboxylate groups from
aliphatic acids [71,72] and amino acids [75], which
cannot be reliably employed in the present context. We
then proceed to argue as follows: (i) we assume an
idealized regular pentagonal bipyramidal structure for
p-ClPhSnOx3, (I) in Table 5, corresponding to the
determined crystal and molecular structure, Figs. 2 and
3; (ii) employing the experimental value DE=1.71
mms-1, Table 4, as well as the pqs values listed in Table
5, the pqs {(Ox)O}pbe is calculated (Table 5, [68,70–
73]); (iii) the value thus obtained is adjusted in order to
yield a positive sign for DEcalcd, according to the Mo¨ss-
n
bauer–Zeeman spectrum of BuSnOx3 (Table 5) [28];
(iv) the reliability of the latter pqs value is checked by

110
M. Schu¨rmann et al. / Journal of Organometallic Chemistry 584 (1999) 103–117
interactions (including H-bonds by H2O molecules, and
bridging by ꢀCOO groups, in RSn(O2CPy) · 2H2O com-
plexes), possibly corresponding to the structure deter-
mined for p-ClPhSn(Ox)3, Fig. 2, and assumed for
RSn(Ox)3 in Table 5. The nature of the R radicals in
RSn(L)3, as well as the occurrence of o- and p- sub-
stituent in R, would then show no structural influence
in the complexes. It would then be inferred that all
species in Table 1 show analogous structures, possibly
of pentagonal bipyramidal type.
It seems worth to note that complexes RSn(SPy)3,
where SPy− is the bidentate N, S ligand anion from
2-mercaptopyridine, belong to the class of RSn(Ox)3
and RSn(O2CPy)3 species, three members of the series
(R=Me, Ph, p-Tolyl) showing a pentagonal bipyrami-
dal X-ray structure [1,79], and exhibit dynamical data
[74,80] quite similar to those for Ox− and −O2CPy
complexes reported here (Table 6). These circumstances
further support the assumption of ‘monomeric’ struc-
tures for all members of the class of RSnL3 species
commented above.
point-charge model estimates of DE for pentagonal
bipyramidal RSnOx3 and trigonal bipyramidal
R3SnOx complexes whose DE data are quoted in the
literature (Table 5).
From the data in Table 5, it is concluded that the
pqs values {(Ox)O−}pbe= −0.182 mm s−1, and the
related {(Ox)O−}pba,tba= −0.282 mm s−1, are highly
reliable, and that all ArSnOx3 complexes in Table 4
show the same structure, of type (I) in Table 5. As
far as the ArSn(O2CPy)3 complexes are concerned, for
which no crystal and molecular structures are avail-
able, we are inclined to assume that the pqs for
{(Py)COO−}pbe corresponds to the value for
{(Ox)O−}pbe, the structure being then corresponding
to that for ArSnOx3 in Figs. 2 and 3, and in Table 5,
with seven coordinated Sn. In fact, H2O molecules in
the −O2CPy complexes (Table 1) could be hydrogen
bonded to carboxyl oxygens although possibly bound
to the metal [7]. Further work is obviously needed on
the latter argument.
Structural information may be extracted also from
variable temperature 119Sn Mo¨ssbauer spectroscopy
data and functions. From the data l, DE and Y in
Table 4, measured in the T ranges reported in Table
6, inherent to the representative complexes
2, 3, 5, 6, 8, 10, the following is inferred:
1. The invariability of l and DE parameters indicate
the lack of phase transitions [76], as well as of l’s
second-order Doppler shifts [77];
2. The areas under the two resonant peaks, e.g. Fig. 4,
are symmetric, which excludes anisotropy for the
recoil-free fractions fa [78];
3. The narrowness of Y indicates the persistence of
single tin coordination sites in the related T ranges.
Molecular dynamics data and functions (as e.g.
defined and treated in a recent review [68]) in Table
6 and Figs. 5 and 6, suggest the following:
4. The linearity of functions ln A(T), frael,abs(T) and
Žx2(T) further implies the general absence of phase
transitions;
5. Parameters and functions extracted from slopes
d ln A/dT (‘relative’) [68] and from the recoil free
fraction of the source (‘absolute’) [68] are practically
coincident, which implies the nature of Debye solids
[68] for the complexes here investigated;
6. Parameters and functions for the complexes
2, 3, 5, 6, 8, 10 are mutually corresponding, which
suggests the occurrence of strict structural analogies.
In particular, by fingerprint criteria [68], rD values
are typical for monomeric species, while slopes
d ln A/dT, functions Žx2(T) and parameters MrD2
lie in monomer polymer border zones [68].
Fig. 5. Examples for the temperature dependence of the normalized
total Lorentzian areas, A, under the 119Sn Mo¨ssbauer peaks. 2
PhSnOx3 (6), ꢀ o-Cl-BzSn(O2CPy)3 (5). Lines are the least squares
fits of the linear functions to the experimental data points, the related
equations being: 2 ln(AT/A77.3)=0.980–1.355×10−2 T; ꢀ ln(AT/
A77.3)=0.961–1.242·10−2 T.
It is concluded that the complexes listed in Table 6
show structures which imply the lack of intermolecular

Table 6
Variable temperature 119Sn Mo¨ssbauer spectroscopy measurements: experimental data sets, and molecular dynamics data functions
a
2
d
2
2
e,f,h
f,h
g,h
102(d ln A/dT) b fa(T) c,d
Žx (T) (A ×10 ) rD
(K)
w˜D
(cm−1
)
Mr2D
(amu×
)
,
Number Compound
Tmax in the T range
investigated 77.3}Tmax (K) (K−1
)
K2×10−6
2
o-TolSn(O2CPy)3·2H2O
170.0
−1.397 (0.999)
−1.392 (0.994)
−1.242 (0.999)
−1.355 (0.998)
−1.421 (0.999)
−1.461 (0.999)
0.340 } 0.093
(0.489 } 0.121) (0.490 } 1.445)
0.341 } 0.082 0.737 } 1.716
(0.462 } 0.091) (0.528 } 1.642)
0.383 } 0.121 0.658 } 1.446
(0.467 } 0.137) (0.521 } 1.362)
0.351 } 0.100 0.717 } 1.577
(0.413 } 0.103) (0.605 } 1.557)
0.333 } 0.071 0.752 } 1.812
(0.372 } 0.071) (0.678 } 1.809)
0.323 } 0.083 0.773 } 1.701
(0.383 } 0.089) (0.657 } 1.658)
0.739 } 1.626
49.9 (55.792.5) 34.7 (38.791.7) 1.524
49.2 (52.192.7) 34.2 (36.291.9) 1.531
52.8 (55.291.1) 36.7 (38.390.8) 1.714
50.0 (51.191.1) 34.7 (35.590.8) 1.571
48.3 (49.290.8) 33.5 (34.290.5) 1.498
46.9 (48.591.0) 36.2 (33.790.7) 1.458
3
p-ClPhSn(O2CPy)3·2H2O 180.0
/
5
o-ClBzSn(O2CPy)3·2H2O
PhSn(Ox)3
170.0
170.0
186.25
170.0
6
8
o-TolSn(Ox)3
10
o-ClPhSn(Ox)3
a Abbreviations: see Fig. 1 and note (a) to Table 1. The molecular weights (including 2H2O for compounds 2, 3, 5) have been employed as the effective vibrating mass, EVM, in the calculations.
b A=(y/2)mY, mm s−1, is the total Lorentzian area under the resonant peaks at the temperature T (K). m=percent resonant effect; Y=full width at half height of the resonant peaks. Slopes
of functions: total area under the resonant peaks versus temperature (see Fig. 4).
c The recoil-free fraction (Debye–Waller–Mo¨ssbauer factor).
d The mean square displacement of 119Sn atoms. Values in the first line are ‘relative’ data obtained from slopes d ln A/dT, at 77.3 K and Tmax, respectively; values in parentheses are the
584
‘absolute’ data at 77.3 K and Tmax
.
e Debye temperature.
(
f Debye cut-off frequency. First line, ‘relative’ data; values in parentheses, ‘absolute’ data, with standard error, calculated from faabs
.
g Parameter of intermolecular force constant, calculated for M=molecular mass (including 2H2O for Numbers 2, 3, 5) and rD=‘relative’ Debye temperature.
h For complexes 2, 3 and 5, data essentially corresponding to the tabulated values have been obtained by employing EVM=MW without 2H2O.
103
1

112
M. Schu¨rmann et al. / Journal of Organometallic Chemistry 584 (1999) 103–117
Fig. 6. Recoil-free fractions of the absorber 119Sn nuclei, fa, and mean-square displacements of 119Sn, Žx2, as a function of temperature, for
representative RSnL3 complexes. Lines are plots of frael, and the related Žx2 functions, as extracted from the slopes d ln At/dT, while data points
are ‘absolute’ data, faabs, and corresponding Žx2. o-TolylSn(Ox)3 (8), ꢁ and – – - ; p-ClPhSn(O2CPy)3 (3), 2 and · · · ·.
essentially correspond to data reported in the literature
for the complexes: RSn(Ox)3 (R=nBu [19b,21], Et [45],
Me [19b]); RSnCl(Ox)2 (R=nBu [19b,21], Ph [19b,21],
Me [19b,39]); R2Sn(Ox)2 (R=Alk [19b,21,35],
3.1.3. Vibrational spectroscopy
The structural assumptions reported in the preceding
were checked by studying the vibrational data reported
in Table 7. In compounds 1–5, RSn(O2CPy)3·2H2O,
the carboxylate group would coordinate Sn in a
monodentate fashion; in fact, was(OCO) around 1680
cm−1 suggest the occurrence of free CꢁO, while
ws(OCO) in the range 1331–1408 cm−1 is typical of a
coordinated carboxyl oxygen (Table 7). These data and
assumptions correspond to findings reported for a se-
ries of SnIV and RnSnIV (n=2, 3) pyridyl carboxylate
complexes. In fact, inter alia, the occurrence of
monodentate carboxyl bound to Sn has been assumed
to occur for: Snhal(O2CPy)3 [5]; Snhal2(O2CPy)2 [5]
(hal=Cl, Br); R2Sn(O2CPy)2 [5,11]; R2Snꢀ(O2CPy)2,
MeOCOCH2CH2
[34]);
R2SnCl(Ox)
(R=Alk
[19b,21,39], MeOCOCH2CH2 [34]); R3SnOx (R=Me
[39], Et [45], tBu [19b], Cy [19b], Ph 19b,45) (Ox=8-hy-
droxyquinoline [19b,21,34,35,39], and = halogeno-
and nitro-substituted 8-hydroxyquinoline [45]). In all
complexes, Ox− ligands are assumed to chelate tin
through coordination by O, N atoms.
In conclusion, taking also into account the corre-
spondence of the spectra of the complexes 6–11, Table
7, the vibrational data suggest the occurrence of a
general pentagonal bipyramidal structure for RSn(Ox)3,
analogous to that determined for p-ClPhSn(Ox)3, Fig. 2
and Table 3.
t
ꢀ(Py-3-CO2)2 and ꢀ(Py-4-CO2)2 [12]; Bu2Sn(O2CPy)2
[14]; nBu3Snꢀ(O2CPy), ꢀ(Py-3-CO2) and ꢀ(Py-4-CO2)
[10].
No information on the possible occurrence of N“Sn
bonds in RSn(O2CPy)3·2H2O can be extracted from
modes was,s(CꢁC/NꢁC) listed in Table 7; in fact, inter
alia, the related vibrational data of Me3Sb-
(PyꢀCH2ꢀCO2)2 [81] and Me2Sn(O2CPy)2 [12], practi-
cally coincide, though these compounds are character-
ized by the absence [81] and the occurrence [12],
respectively, of N“metal coordination. In addition the
vibrational spectra of RSn(O2CPy)3·2H2O contain no
information on the occurrence of tin coordination by
the two H2O molecules.
It is concluded that, according to the IR data, com-
plexes RSn(O2CPy)3·2H2O, Table 7, Numbers 1–5,
consist of monomeric species, in line with the results
obtained from variable temperature 119Sn Mo¨ssbauer
spectroscopy studies (vide supra).
3.2. Structures in solution
1
3.2.1. H-, 13C-, 119Sn-NMR spectroscopy
The complexes RSn(O2CPy)3 and RSn(Ox)3 have
been investigated in CDCl3 solutions by H-, 13C- and
1
119Sn-NMR spectroscopy, and the results obtained are
compiled in Tables 8–10.
Chemical shifts l (1H) and l (13C) inherent to ligand
atoms in RSn(O2CPy)3 have been assigned by compari-
son with the spectra of the free ligand, pyridine-2-car-
boxylic acid [82,83] as well as of the complex
tBu2Sn(O2CPy)2, where the ligand chelates Sn through
ꢀCOO− (monodentate) and the N atom [14]. Shifts l
(1H) and l (13C) related to the organic radicals bound
to Sn have been assigned on the basis of the related
data for R4Sn compounds [19,84]. Signal integrations
indicate the stoichiometry RSn(O2CPy)3.
As far as complexes RSn(Ox)3, Numbers 6–11, are
concerned, the vibrational frequencies listed in Table 7

M. Schu¨rmann et al. / Journal of Organometallic Chemistry 584 (1999) 103–117
113
Complexes 1–5% in Table 8 (I) generally show a
broad signal for H-6 (which is the nearest one to N,
Fig. 1), shifted to low field with respect to the value for
tBu2Sn(O2CPy)2 [14], which could be interpreted in
terms of weak N“Sn interactions, possibly not due to
all three −O2CPy ligands. Shifts are larger for the
o-substituted ArSnIV acceptors, 2 and 4 in Table 8, with
respect to the corresponding p-substituted species, 1
and 3, which is attributed to the decrease in the extent
of N“Sn coordination owing to steric effects due to
the o-substituents in the organic radicals bound to tin.
Analogous effects have been detected to occur in RSn(-
SPy)3 complexes [1].
The H atoms in the ꢀCH2ꢀ groups bound to tin in
the benzyl derivatives are strongly deshielded due to tin
bonding by the carboxylic group of the ligand, as
shown by the magnitude of the coupling constants
2J(119Sn1H) for complexes 5 and 5% (Table 8, footnotes
e, f) with respect to data for the corresponding R4Sn
derivatives [19,84]; these data would be in agreement
with the decrease of the s-character of the C(Bz)ꢀSn
bonds on going from 4- to 7-coordination, the latter
assumed for the RSn(O2CPy)3 complexes (6ide supra).
In the 13C-NMR spectra [Table 9 (I)] parameters l
(13C) for ligand atoms LC-2 to LC-6, as well as LC=O
(Fig. 1), correspond to data reported for
tBu2Sn(O2CPy)2 [14]; moreover, broad signals occur for
LC-2, LC-4 and LC-6 atoms in the complexes, due to
the similarity of the respective chemical shifts, in a
special way for LC-2 and LC-6 (the latter according to
free ligand shifts [83]).
The broad signals l (13C) for LC-2 and LC-6 further
suggest the occurrence of both bi- and mono-dentate
−O2CPy species (vide supra). In the organic radicals
bound to tin, nuclei C-1 and C-8 (Fig. 1(C)) are
deshielded going from R4Sn [19a,84] to RSn(O2CPy)3,
clearly owing to the increase of the acid character of Sn
due to coordination by the carboxylic group.
Signals l (1H) and l (13C) for ligand atoms in
RSn(Ox)3, Table 8(II) and Table 9(II), have been at-
tributed by comparison with spectral data reported for
the free ligand 8-quinolinol, HOx, as well as Ox− and
H2Ox+ [19b,34,44,55]; besides, with data for complexes
nBuSn(Ox)3 [19b,43]. Signals concerning H and C atoms
in the organic radicals bound to Sn were attributed
according to data for R4Sn [19a,84]. The ratios of
integrated signals generally indicate the occurrence of
species with stoichiometry RSn(Ox)3, Numbers 6–11, in
CDCl3 solutions.
Chemical shifts inherent to ligand atoms H-2, H-4,
LC-2 and LC-8, Table 8(II) and Table 9(II), in the
complexes RSn(Ox)3 here investigated are essentially in
ranges reported for R3Sn(Ox), R2Sn(Ox)2, R2Sn(X)(Ox)
and RSnhal(Ox)2, all species being characterized by
chelating Ox− [34,44,54–56]; strong N“Sn interac-
tions shift downfield the H-2 resonance of Ox− [44]
Table 7
Infrared spectral data for mono-organotin(IV) derivatives of pyridine-2-carboxylic acid and 8-hydroxyquinoline
a
Num Compound
ber
was(OCO) (cm−1
)
ws(OCO) (cm−1
)
Dw
was,s(CꢁC/NꢁC) (cm−1
)
(I)
RSn(O2CPy)3·2H2O
1
p-TolSn(O2CPy)3·2H2O
o-TolSn(O2CPy)3·2H2O
p-ClPhSn(O2CPy)3·2H2O
o-ClPhSn(O2CPy)3·2H2O
o-ClBzSn(O2Cpy)3·2H2O
1687 vs,1670 vs
1680 vs
1336 vs,1408 vs
1340 vs
351, 262
340
1605 s; 1560 s; 1555 s;
1478 s; 1442 m
1602 s; 1600 s; 1569 s;
1471 s; 1445 m
1605 s; 1565 s; 1473 s;
1444 m
1602 s; 1569 s; 1472 s;
1445 m
2
3
4
5
1698 vs, 1680 vs
1680 vs
1331 vs, 1400 s
1332 vs
357, 280
348
1681 vs
1338 vs
343
1602 s; 1569 s; 1471 s;
1441 m; 1439 m
(II)
RSn(Ox)3
w(CꢀN) (cm−1
)
w(CꢀO) (cm−1
)
w(SnꢀC) (cm−1
)
w(SnꢀO) (cm−1
)
w(SnꢀN) (cm−1
)
6
7
8
9
10
11
PhSn(Ox)3
p-TolSn(Ox)3
o-TolSn(Ox)3
p-ClPhSn(Ox)3
o-ClPhSn(Ox)3
o-ClBzSn(Ox)3·CHCl3
1570 s
1570 s
1570 s
1570 s
1570 s
1570 s
1105 s
565 w
565 w, 575 w
570 w
565 w
565 vw
570 vw
510 s
510 s
510 s
515 s
515 s
525 s
395 m
400 m, 390 w
400 m
400 m, 390 w
395 m
400 m
1115 m, 1105 s
1115 m, 1105 s
1115 m, 1105 s
1110 s
1110 s
a See Table 1 and Fig. 1. Abbreviations: s=strong; m=medium; w=weak; v=very. Solid compounds in KBr pellets. Numbers 1–5: a large
band around 3400 cm−1 is attributed to H2O vibrations.

114
M. Schu¨rmann et al. / Journal of Organometallic Chemistry 584 (1999) 103–117
Table 8
1H-NMR spectral data [l (ppm) with respect to TMS] for mono-organotin(IV) derivatives of pyridine-2-carboxylic acid and 8- hydroxyquinoline
in CDCl3 solutions
a
c
Number
(I)
Compound
H-3 b
H-4 b
H-5 b
H-6 b
R
HO2CPy and RSn(O2CPy)3·2H2O
HO2CPy d
8.17
8.08
7.70
8.81
–
1
2
3
4
p-TolSn(O2CPy)3·2H2O
o-TolSn(O2CPy)3·2H2O
p-ClPhSn(O2CPy)3·2H2O
o-ClPhSn(O2CPy)3·2H2O
8.40 d
8.33 d
8.42 d
8.38 d
8.11 t
8.08 t
8.12 t
8.14 t
7.69 t
7.69 t
7.71 t
7.72 t
8.87 b
9.10 b
8.89 b
9.06 b
7.62 d; 7.16 d; 2.29 s
7.23–6.93 m; 2.61 s
7.69 d; 7.32 d
7.93–7.72 m; 7.22–
7.00 m
5
o-ClBzSn(O2Cpy)3·2H2O
8.28 d
8.29 d
8.05 t
8.08 t
7.64 t
7.68 t
8.99 b
8.92 b
7.08–7.00 m; 6.96–
6.68 m; 3.29 s e
7.26–7.05 m; 6.95–
6.65 m; 3.15 s f
g
5%
BzSn(O2CPy)3
(II)
HOx and RSn(Ox)3
H-2 b
H-4 b
R c
HOx h
8.79 d
8.12 d
–
6
7
8
PhSn(Ox)3
p-TolSn(Ox)3
o-TolSn(Ox)3
9.03 d; 8.79 d
9.01 d; 8.78 d
9.12 d; 8.78 d
8.17 d; 8.06 d
8.16 d; 8.04 d
8.16 d; 7.79 d
7.52–7.11 m
7.51–7.11 m; 2.14 s
7.51–7.05 m; 2.76 s
(12 Hz)
9
10
11
p-ClPhSn(Ox)3
o-ClPhSn(Ox)3
o-ClBzSn(Ox)3·CHCl3
9.01 d; 8.76 d
8.79 d
8.99 d; 8.76 d
8.14 d; 8.02 d
8.17 d
8.13 d; 7.97 d
7.48–7.06 m
7.48–7.22 m
7.48–7.14 m; 3.11 s
a See Table 1. Abbreviations: s=singlet; d=doublet; t=triplet; m=multiplet; b=broad.
b Numbering of protons in the ligand, see Fig. 1A and B.
c l of protons in the organic group bound to Sn; see Fig. 1C.
d Ref. [82].
e Coupling constants 2J(119Sn1H): 167 Hz.
f Coupling constants 2J(119Sn1H): 160 Hz.
g Mixture with the complex of BzHgII, see Sections 2 and 2.2.
h Ref. [19b].
and the resonance of ligand H-4 goes gradually
downfield with increasing N“Sn interaction [44].
Downfield shifts of ligand l (1H) then generally indicate
a greater extent of Ox−ꢀSn chelation [34]. Analogous
criteria have been reported for LC-2 and LC-8 [55]. For
example, l (H-2) shifts upfield, and l (H-4) downfield,
in nBuSn(Ox)3, (p-Tolyl)2Sn(Ox)2 and (C6F5)2Sn(Ox)2
with respect to HOx [19b,43] which is attributed to
N“Sn coordination with the consequent deshielding of
H-2; in fact, H-2 in HOx appears to be shielded by the
lone electron pair of the N atom [44,50,54].
In the RSn(Ox)3 complexes Numbers 6–9 and 11,
Table 8(II), two sets of l (1H) signals have been de-
tected, which is interpreted in terms of the occurrence
of two different types of Ox− coordination to RSnIV.
The latter is in line with the crystal and molecular
structure of p-ClPhSn(Ox)3, where two different sets of
N–Sn bond lenghts (one shorter and two longer bonds)
have been detected (vide supra: Table 3 and Fig. 2).
The same holds for the CDCl3 solutions, as extracted
from the integration of the l (H-2) and l (H-4) signals;
in fact, for p-ClPhSn(Ox)3 the ratio 2:1 has been de-
tected for the (‘weak’) coordination at 9.01 and 8.02
ppm with respect to the (‘strong’) coordination at 8.76
and 8.14 ppm (Table 8(II)), the same occurring also for
complexes 7, 8, 11, R being p-Tolyl, o-Tolyl and o-
ClBz. Instead, the ratio is reversed in PhSn(Ox)3, Num-
ber 6; moreover, in o-ClPhSn(Ox)3, Number 10, a
single set of l (1H) signals is detected, which would
indicate the occurrence of three equivalent Ox− ligands
with ‘strong’ tin coordination, according to findings for
nBuSn(Ox)3 [43].
In the 13C-NMR spectra of the complexes RSn(Ox)3,
on the other hand, single signals are detected for l (13C)
of the ligand atoms C-2 (adjacent to N) and C-8
(bound to O), Fig. 1 and Table 9(II), which would
suggest the bonding equivalence of the three Ox−
coordinated to Sn. Limited l (13C) shifts are detected,
analogous to literature reports for a series of RnSnIV
(n=2, 3) coordinated by Ox− [50].
The order of magnitude of l (119Sn) chemical shifts
for complexes 1–5% and 7–11 in Table 10 indicates the
occurrence of 7-coordinated tin centers, in line with
parameters reported for a series of organotin(IV) com-

M. Schu¨rmann et al. / Journal of Organometallic Chemistry 584 (1999) 103–117
115
Table 9
13C-NMR spectral data [l (ppm) with respect to TMS] for mono-organotin(IV) derivatives of pyridine-2-carboxylic acid and 8-hydroxyquinoline
in CDCl3 solutions
a
Number
(I)
Compound
LC-2 b
LC-3 b
LC-4 b
LC-5 b
LC-6 b
LC=0 b C-1 c
C-7 c; C-8 c
HO2CPy and RSn(O2CPy)3·2H2O
d
HO2CPy
148.4
124.8
125.2
124.9
125.5
124.7
124.9
125.0
137.6
140.9
141.6
141.1
141.6
141.4
141.2
127.2
127.2
127.9
128.0
127.6
127.7
127.8
149.5
146.4
146.7
146.7
146.9
146.6
146.9
166.2
165.2
163.9
165.2
163.7
164.1
164.2
–
–
1
2
3
4
5
5%
p-TolSn(O2CPy)3·2H2O
o-TolSn(O2CPy)3·2H2O
p-ClPhSn(O2CPy)3·2H2O
o-ClPhSn(O2CPy)3·2H2O
o-ClBzSn(O2CPy)3·2H2O
146.4
146.7
146.6
146.9
146.6
146.9
146.1
146.2
146.2
146.2
146.2
146.2
21.0
24.0
–
–
33.8
35.8
e
BzSn(O2CPy)3
(II)
HOx and RSn(Ox)3
LC-2 b
LC-8 b
C-1 c
C-7; C-8 c
HOx g
147.4
145.6
145.7
145.6
145.8
145.9
152.6
157.4
156.9
–
–
7
8
9
10
11
p-TolSn(Ox)3
o-TolSn(Ox)3
p-ClPhSn(Ox)3
o-ClPhSn(Ox)3
o-ClBzSn(Ox)3·CHCl3
147.8
147.8
146.8
147.8
147.8
21.3
23.8
–
–
34.3
157.0
f
157.3
a See Table 1.
b Carbon atoms in the ligand. See Fig. 1.
c Carbon atoms in the radicals bound to Sn. See Fig. 1.
d Data from Ref. [83], DMSO solutions.
e Mixture with the complex of BzHgII, see Section 2.2.
f Complex 6, PhSn(Ox)3, and LC-8 for complex 10: data not measured owing to insufficient solubility.
g Data from Ref. [19b].
plexes [48]. For compounds RSn(O2CPy)3 · 2H2O, seven
coordination of Sn could be assumed to be due to
bonding by the three carboxylate groups (monoden-
tate), one ligand nitrogen, and the two H2O molecules;
the latter in line with the magnitude of ligand l (1H)
parameters for H-6, Table 8(I), discussed here in the
preceding. As far as complexes RSn(Ox)3 are con-
cerned, seven coordination is also suggested by the
value l (119Sn)= −561 ppm (vs. TMT) reported for
nBuSn(Ox)3 [48,57].
6–11 in CHCl3 solutions show umax=380}382 nm,
which indicates tin chelation by the three Ox− ligands,
n
analogously to BuSn(Ox)3 in benzene.
5. Conclusions
In the solid state, complexes RSn(O2CPy)3·2H2O and
RSn(Ox)3 exhibit a common pentagonal bipyramidal
configuration, with 7-coordinated Sn, as extracted from
Table 10
119Sn-NMR chemical shifts [l (ppm) with respect to TMT] of mono-
aryltin(IV) and mono-benzyltin(IV) complexes with pyridine-2-car-
boxylic acid and 8-hydroxyquinoline in CDCl3 solutions
4. UV–vis spectroscopy
The occurrence of metal chelation by N, O donor
atoms in 8-hydroxyquinoline complexes has been suc-
cesfully inferred by electronic spectroscopy in solution
phases since the early fifties [58], and the method has
been widely employed for the study of solutions of
organotin(IV) oxinates [33–39,43,45,50]: the occurrence
of absorption bands with maxima in the range 360–400
nm corresponds to metal chelation, while bands around
315 nm (as the data for the free ligand) indicate oxy-
gen–metal coordination only. In particular, nBuSn(Ox)3
in dry benzene shows a maximum at 385 nm with
m=2.5×m(Me3Sn(Ox)) [43], which has been interpreted
in terms of tin chelation by all three oxinate ligands,
yielding a pentagonal bipyramidal tin coordination en-
vironment [43]. The spectra for RSn(Ox)3 complexes
a
Number
Compound
l (ppm)
1
2
3
4
5
5%
7
8
9
p-TolSn(O2CPy)3·2H2O
o-TolSn(O2CPy)3·2H2O
p-ClPhSn(O2CPy)3·2H2O
o-ClPhSn(O2CPy)3·2H2O
o-ClBzSn(O2CPy)3·2H2O
BzSn(O2CPy)3
p-TolSn(Ox)3
o-TolSn(Ox)3
−620
−671
−626
−679
−644
−642
−611
−618
−615
−616
−593
b
p-ClPhSn(Ox)3
o-ClPhSn(Ox)3
o-ClBzSn(Ox)3·CHCl3
10
11
a See Table 1. Complex 6, PhSn(Ox)3: data not measured owing to
insufficient solubility.
b Mixture with the complex of BzHgII, see Section 2.2.

116
M. Schu¨rmann et al. / Journal of Organometallic Chemistry 584 (1999) 103–117
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