An experimental and a DFT study on the synthesis, spectroscopic characterization, and reactivity of the adducts of dimethyl- and diphenyltin(IV) dichlorides with γ-pyrones [4H-pyran-4-one (PYR) and 2,6-dimethyl-4H-pyran-4-one (DMP)]: Crystal structure of Ph2SnCl2(PYR)

Article abstract of DOI:10.1016/j.jorganchem.2008.01.014

The Sn(IV) R₂SnCl₂(γ-pyrone)_n [R = Me or Ph; γ-pyrone = 4H-pyran-4-one (PYR) or 2,6-dimethyl-4H-pyran-4-one (DMP); n = 1 or 2] adducts have been synthesized and investigated. The adducts Ph₂SnCl₂(PYR) (1), Me₂SnCl₂(PYR)₂ (2), Ph₂SnCl₂(DMP) (3) and Me₂SnCl₂(PYR)(PNO) (4), (PNO = 4-methylpyridine N-oxide) have been prepared by the addition of the corresponding γ-pyrone to chloroform solution of R₂SnCl₂. The new compounds have been characterized by elemental analysis and spectroscopic (IR, ¹H, ¹³C NMR and Mo?ssbauer) means. The single-crystal diffraction study of 1 shows the Sn(IV) to be five-coordinate, [Sn-O and Sn-Cl(1), Sn-Cl(2) distances of 2.3190(13) and 2.4312(6), 2.3653(7), respectively], and the Cl-Sn-Cl bond angle to be 91.17°. The reactivity of 2 towards bipy, Ph₃PO, QNO (Q = quinoline) resulted in complete displacement of PYR and formation of already known compounds whereas, the PNO displaced only one equivalent of PYR, causing the preparation of the new mixed complex 4, possibly through a S_N¹ formation mechanism. DFT/B3LYP molecular orbital calculations were carried out for the 1-4 complexes, their precursors, Ph₂SnCl₂, (5) and Me₂SnCl₂, (6) and the ligands, PYR, DMP and PNO in an attempt to explain the structures and reactivity of the complexes. Optimized resulting geometries, vibrational frequencies, and the electron-accepting ability of the complexes and the precursors towards nucleophiles are discussed.

Full text of DOI:10.1016/j.jorganchem.2008.01.014

Available online at www.sciencedirect.com
Journal of Organometallic Chemistry 693 (2008) 1203–1214
www.elsevier.com/locate/jorganchem
An experimental and a DFT study on the synthesis,
spectroscopic characterization, and reactivity of the adducts
of dimethyl- and diphenyltin(IV) dichlorides with c-pyrones
[4H-pyran-4-one (PYR) and 2,6-dimethyl-4H-pyran-4-one
(DMP)]: Crystal structure of Ph2SnCl2(PYR)
a
a,
b,
c
*
Hariklia Papadaki , Aristides Christofides , Evangelos G. Bakalbassis *, John C. Jeffery
a Department of Chemistry, Section of General and Inorganic Chemistry, Aristotle University of Thessaloniki, P.O. Box 135, 54 124 Thessaloniki, Greece
b Department of Chemistry, Laboratory of Applied Quantum Chemistry, Aristotle University of Thessaloniki, P.O. Box 135, 54 124 Thessaloniki, Greece
c School of Chemistry, Section of Inorganic Chemistry, The University of Bristol, Bristol BS8 ITS, England, United Kingdom
Received 7 November 2007; received in revised form 9 January 2008; accepted 9 January 2008
Available online 16 January 2008
Abstract
The Sn(IV) R2SnCl2(c-pyrone)n [R = Me or Ph; c-pyrone = 4H-pyran-4-one (PYR) or 2,6-dimethyl-4H-pyran-4-one (DMP); n = 1 or
2] adducts have been synthesized and investigated. The adducts Ph2SnCl2(PYR) (1), Me2SnCl2(PYR)2 (2), Ph2SnCl2(DMP) (3) and
Me2SnCl2(PYR)(PNO) (4), (PNO = 4-methylpyridine N-oxide) have been prepared by the addition of the corresponding c-pyrone to
1
chloroform solution of R2SnCl2. The new compounds have been characterized by elemental analysis and spectroscopic (IR, H, 13C
NMR and Mo¨ssbauer) means. The single-crystal diffraction study of 1 shows the Sn(IV) to be five-coordinate, [Sn–O and Sn–Cl(1),
Sn–Cl(2) distances of 2.3190(13) and 2.4312(6), 2.3653(7), respectively], and the Cl–Sn–Cl bond angle to be 91.17°. The reactivity of
2 towards bipy, Ph3PO, QNO (Q = quinoline) resulted in complete displacement of PYR and formation of already known compounds
1
whereas, the PNO displaced only one equivalent of PYR, causing the preparation of the new mixed complex 4, possibly through a SN
formation mechanism. DFT/B3LYP molecular orbital calculations were carried out for the 1–4 complexes, their precursors, Ph2SnCl2,
(5) and Me2SnCl2, (6) and the ligands, PYR, DMP and PNO in an attempt to explain the structures and reactivity of the complexes.
Optimized resulting geometries, vibrational frequencies, and the electron-accepting ability of the complexes and the precursors towards
nucleophiles are discussed.
Ó 2008 Elsevier B.V. All rights reserved.
Keywords: Adducts of tin(IV); Carbonyl ligands; 4H-Pyran-4-one; 2,6-Dimethyl-4H-pyran-4-one; Density functional calculations
1. Introduction
and (HgX2)3(DMP)2 (X = Cl or Br) have been prepared
[3], the incorporated DMP being weakly bound to the
metal. Twelve years ago tin adducts of the types
Sn(DMP)2Cl2 and Sn(DMP)2Cl4 were prepared by Freg-
ona et al. [4]. So far we have been reviewing the coordina-
tion chemistry of DMP, and one might think that there
have been no reports on organometallic compounds of
the ligand in question. However, the survey of the literature
reveals only one paper [5], dealing with the synthesis of the
organotin complexes PhSn(DMP)Cl3, Ph2Sn(DMP)Cl2,
The complexes of 2,6-dimethyl-4H-pyran-4-one (DMP)
with various metal salts have long been known [1]. Later
on the lanthanide complexes of the same c-pyrone, gener-
ally having octahedral symmetry, have been isolated [2].
Mercury(II) compounds of the formulae [Hg(DMP)X2]n
*
Corresponding authors. Tel.: +30 2310 997695; fax: +30 2310 997837.
E-mail address: bakalbas@chem.auth.gr (E.G. Bakalbassis).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.01.014

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H. Papadaki et al. / Journal of Organometallic Chemistry 693 (2008) 1203–1214
Ph3Sn(DMP)Cl, Me2Sn(DMP)X2 (X = Cl or Br) and
Me2Sn(DMP)2Cl2. Although no X-ray data is appeared
in that paper, it is reported that in all the above compounds
the DMP ligand is coordinated to the metal via the car-
bonyl oxygen, causing a low energy shift of m(C@O) as
expected.
It should be stressed out here that, despite our numerous
attempts, we failed to grow single-crystals proper for a
X-ray structural study for all but one (1) complexes.
2.2. X-ray structural analysis of Ph2SnCl2(PYR) (1)
Continuing our work on organotin adducts with oxygen
donor ligands [6], herein we report on the synthesis and the
spectroscopic characterization of four complexes. Three of
them incorporate 4H-pyran-4-one (PYR), for which, as far
as we know there have been no reports on tin organometal-
lic complexes, whereas the other one includes DMP. The
X-ray, single-crystal diffraction study of the adduct
Ph2SnCl2(PYR) is also reported, along with the reactivity
of Me2SnCl2(PYR)2 towards some ligands. To the best of
our knowledge, this is the first X-ray structure ever
reported on the Sn(IV) organometallic complexes incorpo-
rating the pyrone ligand (4H-pyran-4-one), which, from the
two known coordination modes – (i) via the carbonyl oxy-
gen [7,8], or (ii) through both the carbonyl oxygen and the
ortho carbon atom of its ring [9] – prefers the first one.
Lack of X-ray structural data for most of the complexes
under examination, led to theoretical B3LYP/LANL2DZ
studies on the structure and reactivity of all complexes
under study, their precursors and their ligands.
The molecular structure of the adduct 1, is shown in
Fig. 1 together with the atomic numbering scheme. Selected
bond lengths and angles are listed in Table 1.
An examination of the packing diagram reveals no unu-
sual intermolecular contacts. Thus, there is a discrete penta-
coordinated molecule of trigonal-bipyramidal geometry in
which the two C atoms of two phenyl groups and one chlo-
rine atom are located at equatorial positions; the other Cl
atom and the carbonyl O atom of the PYR ligand occupy
the axial positions. The two phenyl rings are mutually
twisted with respect to the equatorial plane [defined by
Cl(2), C(11) and C(21)] probably to avoid steric congestion.
It is worth mentioning here that, the anticancer profile of
many diorganotin compounds, R2SnX2, in combination
with the nature of the R groups and of the X ligands has
been investigated [10]. In relation with the above, we hope
that our reactions may help in understanding how tin(IV)
tetracoordinate species may bind to DNA by acquiring
penta- or hexacoordinate structures [11]. On the other hand,
it is known that some dialkyl organotin compounds exhibit
catalytic activity in the production of polyurethane foam
and in the vulcanization of silicones [12]. This is another
field in which our compounds might find some application.
Fig. 1. Molecular structure of 1 with the atom-labeling scheme.
Table 1
˚
Selected bond lengths (A) and angles (°) for 1
2. Results and discussion
Sn–C(21)
Sn–C(11)
Sn–O(30)
Sn–Cl(2)
Sn–Cl(1)
C(11)–C(12)
C(11)–C(16)
C(21)–C(22)
2.121 (2)
2.133 (2)
2.3190 (13)
2.3653 (7)
2.4312 (6)
1.395 (3)
1.400 (3)
1.387 (3)
2.1. Synthesis
Treatment of a chloroform solution of Me2SnCl2 with
PYR in 1:2 molar ratio, affords the adduct 2 (Eq. (1)).
The reaction of a chloroform solution of adduct 2 with
4-methylpyridine N-oxide (PNO) in 1:1 molar ratio results
in displacement of one equivalent of PYR and the forma-
tion of the mixed complex 4 (Eq. (2)). The adducts 1 and
3 are formed by the reaction of the Lewis acid Ph2SnCl2
with PYR and DMP, respectively, in 1:1 molar ratio in
the above solvent (Eq. (3)).
C(21)–Sn–C(11)
C(21)–Sn–O(30)
C(11)–Sn–O(30)
C(21)–Sn–Cl (2)
C(11)–Sn–Cl (2)
O(30)–Sn–Cl (2)
C(21)–Sn–Cl (1)
C(11)–Sn–Cl (1)
O(30)–Sn–Cl (1)
Cl(2)–Sn–Cl(1)
127.29 (7)
85.59 (6)
85.59 (6)
114.25 (5)
115.84 (5)
82.46 (4)
96.19 (5)
98.15 (5)
173.56 (4)
91.17 (2)
133.63 (12)
120.2 (2)
125.1(2)
Me2SnCl2 þ 2PYR ! Me2SnCl2ðPYRÞ2 ð2Þ
Me2SnCl2ðPYRÞ þ PNO
ð1Þ
ð2Þ
ð3Þ
! Me2SnCl2ð2PYRÞðPNOÞ ð4Þ þ PYR
Ph2SnCl2 þ L ! Ph2SnCl2L
C(31)–O(30)–Sn
O(30)–C(31)–C(32)
O(30)–C(31)–C(36)
C(32)–C(31)–C(36)
114.7 (2)
½1 ðL ¼ PYRÞ or 3 ðL ¼ DMPÞꢀ

H. Papadaki et al. / Journal of Organometallic Chemistry 693 (2008) 1203–1214
1205
The dihedral angles between the rings defined by C(11),
C(16) and C(21), C(26) and the trigonal plane are 106°
and 43°, respectively. The pyrone ring is not positioned
between the two phenyl groups when viewed along the api-
cal O–Sn–Cl axis, thereby avoiding steric encumbrance,
whereas in Ph2SnCl2 (2,6-Me2C5H3NO) [13], the pyridine
ring for the same reasons lies directly below the Cl atom
of the trigonal plane. The Sn atom does not lie exactly in
the equatorial trigonal plane, but is displaced towards the
1609 cmꢁ1 symmetric assignable to m(C@O) and m(C@C),
respectively [19,20], whereas the free DMP shows the corre-
sponding frequencies [19] at 1609 and 1670 cmꢁ1. In the
complexes of PYR the m(C@O) occurs at the 1580–
1560 cmꢁ1 range and is shifted to lower energy by ca
92 cmꢁ1, as compared to that of the free ligand. The
m(C@C) of the same complexes occurs at ca. 1638 cmꢁ1
,
probably the asymmetric one, and seems to be insensitive
to complexation. The DMP adduct (3) shows two strong
absorptions at 1651 and 1539 cmꢁ1, assignable to m(C@C)
and m(C@O), respectively, the former being shifted to lower
energy by 18 cmꢁ1, whereas the latter by 70 cmꢁ1. The IR
data for the adduct 3 is almost identical with that for the
same compound [5]. These main absorptions of the used
ligands appear a change in ordering upon complexation,
as it has been observed by others [21] in the case of Al and
Ga complexes with several 3-hydroxyl-4-pyrones.
The single Sn–Me stretching frequencies at 582 and
567 cmꢁ1 for six coordinate adducts 2 and 4, respectively,
are indicative of trans-methyl configuration [18]. However,
we cannot be sure for the chlorine atoms of the same
adducts (pointing to a trans configuration), because the
apparently single bands around 266 cmꢁ1 are not well
resolved. The 1 and 3 adducts appear absorptions at ca.
337 and 270 cmꢁ1 assignable to m(Sn–Cl), which indicate
different orientations for the two chlorine atoms. In fact,
the X-ray structure determination of 1 showed one Cl at
the equatorial position, whereas the other occupies an axial
one in a trigonal-bipyramidal environment. Moreover, the
above bands appear in the same range with those occurring
in other adducts bearing monodentate O-donors and hav-
ing similar structure [5]. The infrared spectrum of 4 shows
a strong intensity band at 390 cmꢁ1, probably belonging to
m(Sn–O).
˚
Cl atom by ca 0.15 A. The Cl–Sn–O angle is 173.56(4)°,
and the sum of the equatorial angles in the trigonal girdle
subtended at tin by the two ipso carbons and the Cl(2) is
357.38°. The Sn–O–C angle is 133.63(12)° and is larger than
the corresponding Sn–O–N in Ph2SnCl2 (2,6-Me2C5H3NO)
˚
[13] [125.7(2)°]. The tin oxygen distance here is 2.3190(13) A
and is longer than the corresponding lengths of Me2-
˚
Sn-Cl2(QNO)2 [2.220(2) A] [14], Me2SnCl2(PyNO)2
˚
˚
[2.251(16) A] [15] and Me2SnCl2(4-PhPyNO)2 [2.227(2) A]
[6], indicating perhaps better coordination for aromatic N-
oxides. The same distance is shorter than the corresponding
lengths in the hexacoordinated adducts of dimethyl tin(IV)
dichloride with cyclopropenone [2.380(2)] [16] and salicylal-
dehyde 2.680(12)] [17].
2.3. Reactivity
The behaviour of Me2SnCl2(PYR)2, 2 towards some
ligands has been examined (Scheme 1).
The reactions of adduct 2 with bipy or QNO and Ph3PO
in 1:1 and 1:2 molar ratios, respectively, result in displace-
ment of PYR and formation of the corresponding previ-
ously reported compounds [14,18]. As expected, the same
product was received by the reaction of QNO with adduct
2 in 2:1 molar ratio. Addition of 1 mol of 4-methylpyridine
N-oxide (PNO) to complex 2 leads to novel mixed complex
4, whilst reactions with 4-dimethylaminopyridine (4-
Me2NPy) and 4-cyanopyridine N-oxide (4-CNPyNO) do
not give clear cut results. This seems to indicate that the
coordination capacity of PYR towards Sn(IV) is almost
equal to that of PNO and lower than those of the ligands
which displace it completely.
2.5. NMR spectra
The 1H NMR spectra af PYR adducts show doublets at
ca 6.41 and 7.79 ppm, assignable to Ha and Hb hydrogens
of the pyrone ring, respectively, being almost insensitive to
complexation, only for 2 both signals are observed slightly
down field with respect to those of the free ligand. The
3J(1Ha–1Hb) values of 2 and 4, and 1 are slightly increased
and decreased, respectively, as compared to that of the free
PYR, the larger decrease (0.92 Hz) was observed for
2.4. IR spectra
The infrared spectrum of the employed free PYR ligand
appears strong absorptions at 1658 and 1640 asymmetric,
1
adduct 1. In the H NMR spectrum of 3 the single peak
Me2SnCl2(4H-pyran-4-one)(4-MePyNO)
4-MePyNO
QNO
bipy
Me2SnCl2(QNO)2
Me2SnCl2(4H-Pyran-4-one)2
Ph3PO
Me2SnCl2(bipy)
Me2SnCl2(Ph3PO)2
Scheme 1.

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H. Papadaki et al. / Journal of Organometallic Chemistry 693 (2008) 1203–1214
assignable to Ha of the DMP, do not exhibit any apprecia-
ble difference in chemical shift from that of the free DMP.
The reason for these slight shifts for all the studied adducts
may be, the partial dissociation of the ligands (PYR or
DMP) in chloroform solutions. The above explanation
was provided by others for analogous dimethyltin adducts,
displaying the same behaviour [5]. The methyl hydrogens
resonances (ca. 1.19 ppm) for 2 and 4 are close to those
observed for the parent Lewis acid (1.22 ppm) in CDCl3
the two employed pyrones, the DMP possesses better coordi-
nation ability, since the IR spectra have indicated the
opposite.
2.6. 119Sn Mo¨ssbauer data
The 119Sn Mo¨ssbauer data for complexes 1–4 are listed
in Table 2. The q values (q = QS/IS) obtained for all com-
plexes indicate higher than four coordination number [25].
Inspection of the quadrupole splitting (QS) of the hexa-
coordinated complexes 2 and 4 show essential trans-
[SnMe2] arrangement for 4, whereas for 2 its Mo¨ssbauer
spectrum displaying two doubles indicated a mixture of
56% trans- and 44% cis-isomer. The parameters of the spec-
solution. The J (119Sn–1H) and J (117Sn–1H) values are
ca 83.3 and 79.8 Hz, respectively, being similar to those
observed for hexacoordinate adducts of Me2SnCl2 with
monodentate aromatic N-oxides [6]. Moreover, adduct 4
exhibits all the resonances due to 4-MePyNO.
2
2
In the 13C NMR spectra of the investigated adducts the
peaks due to all carbons of the pyrone rings can be seen,
the majority of them show smaller slight shifts relative to
those of the free ligands (PYR or DMP). In particular, the
C(2) carbons of adducts 2 and 3 are shifted downfield by
0.9 and 1.8 ppm, respectively. The carbonyl carbons of the
same adducts show more or less similar also behaviour,
the effect being larger for 3 (d ppm, 1.0). The cause for the
above small or slight shift can be again the ligand dissocia-
tion, as in the case of the 1H NMR spectra. The methyl car-
bons of dimethyl tin adducts (2, 4) resonate at ca 10.9 ppm
and are shifted downfield as compared to the analogous
peak of Me2SnCl2 (6.6 ppm) in the same solvent (CDCl3).
The reason for this expected shift, which is not observed
for the methyl hydrogen in the respective 1H NMR spectra,
has been explained elsewhere [6,22]. The 2J (119Sn–1H) and
1J (119Sn–13C) values of the adducts 2 and 4 are ca. 83.4
and 644.8 Hz, respectively, being remarkably increased rel-
ative to those of Me2SnCl2 (68.7 and 478 Hz) [6] in chloro-
form solutions. However, the same values are not as high
as they could be expected for hexacoordinate adducts of
the same Lewis acid with monodentate O-donors. For com-
parison, the 2J (119Sn–1H) values for Me2SnCl22L (L =
PyNO, 4-ClPyNO, PNO) are ca 92.8 Hz in CDCl3 [23],
trum are consistent with trans- (IS 1.42, QS 4.20 mm sꢁ1
)
and cis- (IS 1.54, QS 3.63 mm sꢁ1), the assignment being
made on the base that the trans- isomer possesses the larger
QS value [26]. The existence of the cis-isomer in the solid
state for complex 2 is further substantiated by the shape
of the Sn–Cl stretching band at 270 cmꢁ1 in the far-infra-
red region [27]. However, it must be pointed out that both
compounds were assigned a trans-stereochemistry on the
1
evidence of just one methyl resonance in their H NMR
spectra as measured in solution [25,26]. That brings about
for 2 the unlike possibility of a trans- to cis-process, taken
place to a certain degree on crystallization. In addition, its
1H NMR spectrum do not support a fluxional behaviour
which would make chemically equivalent the methyl
groups. Based on the above arguments we cannot provide
a clear answer for the behaviour of adduct 2. The diphenyl-
tin(IV) adducts 1 and 3 having trigonal-bipyramidal geom-
etry, as showed the X-ray structure determination of 1,
appear a substantial difference in their quadrupole splitting
values, the one of 1 being larger than that of 3. This differ-
ence may be interpreted in terms of better coordination
ability of PYR towards Sn(IV) than that of DMP [28], sup-
ported by the observation that between the two pentacoor-
dinated adducts (1, 3) the larger negative shift of m(C–O) is
obtained for 1.
1
whereas the magnitude of J(119Sn–13C), attributed to the
formation of Me2SnCl2 ꢂ 2DMSO in DMSO solution of
Me2SnCl2, is 1014.4 Hz [24]. Moreover, the coupling con-
stants in question of adducts 2 and 4 are even lower than
those of the analogous octahedral dimethyl tin compounds
with monodentate N-oxides, reported in our earlier work [6]
and for which significant complex dissociation in solution
was confirmed by other data. The above situation indicates
that the adducts 2 and 4 are largely dissociated in solution.
The examination of the 13C NMR spectra of the substi-
tuted phenyl tin(IV) adducts 1 and 3 shows that the ipso
carbon atoms of the phenyl rings exhibit small downfield
shifts, relative to the corresponding of the free Lewis acid
(136.8 ppm) [24], upon increase in coordination number of
the tin atom from four to five, in CDCl3 solutions. The
1J(119Sn–13C) values are ca 908.2 Hz, being increased as
compared to that of the Ph2SnCl2 (786 Hz). The above cou-
pling constant of 3 is larger than that of 1 by 34.1 Hz; we
think that the difference is too small to suggest that between
2.7. Evaluation of the proper computational level
It was shown above that there is only one X-ray crystal
structure study for the one out of four complexes studied.
In order to verify the actual relationships between the spec-
troscopic and structural features, as well as the electronic
Table 2
119Sn Mo¨ssbauer Data for 1–4
Compound ISa
(mm sꢁ1
QSa
(mm sꢁ1
C/2a
q
T
)
)
(mm sꢁ1
)
(QS/IS) (K)
1
2
1.36
1.42
1.54
1.20
1.34
3.81
4.20
3.63
2.71
3.96
0.79
0.41
2.80
56% 2.96
44% 2.36
2.26
80
80
3
4
0.41
0.37
80
85
2.96
a
Error 0.02 mm sꢁ1
.

H. Papadaki et al. / Journal of Organometallic Chemistry 693 (2008) 1203–1214
1207
structure and reactivity of the complexes, an investigation
was undertaken at the density functional theory (DFT)
[29] level on all complexes, precursors and ligands involved
in the present study. With the aim of evaluating a proper
computational set-up, owing to the lack of structural
experimental studies in the gas-phase for the same com-
pounds, calculations have been carried out with different
functionals and basis sets (BS’s), on the only experimental
structural data available, being the solid-state X-ray crys-
tallographic study of 1. In particular, both B3LYP [30]
and BP86 [30b,31] functionals were used with the 6-
311+G(d,p), 6-31+G(d), LanL2DZ, and SDD (vide infra)
BS’s for the organic framework, and two different BS’s
with relativistic effective core potentials for the metal ion
[LanL2DZ [32], and Stuttgart RSC, [33] (SDD)]. Examina-
tion of the results of the above calculations (Table 3) allows
one to deduce that: (a) the two BS’s [6-311+G(d,p), 6-
31+G(d)] used for the C, Cl, O and H yield very similar
results, (b) the B3LYP functional with the same BS’s
(LanL2DZ) used for both the light atoms and the central
metal ion, yields slightly overestimated bond distances
and angles, compared to the solid-state experimental val-
ues; still, this level yields the best simulation for the Sn–
O coordination bond than any other level tested, (c) the
Stuttgard BS gives the poorest estimates, corresponding
to the highest bond distances and angles, and (d) the
BP86 functional with the same BS’s used (LanL2DZ) for
both the light atoms and the metal, yields larger values
than the corresponding B3LYP functional calculation,
for all coordination bond lengths, and this is also the case
with the BP86/6-31+G(d) calculation.
the gas and the solid state is not allowed, and owing to
the lack of structural experimental studies in the gas phase
for the same compounds, the gas-phase computed data is
only compared in the figures.
Fig. 2 shows the computer plots and selected geometri-
cal parameters of the B3LYP/LanL2DZ-optimized struc-
tures for the model compounds 1 and 3. It is easily seen
that in both cases, there is a pentacoordinate molecule of
1
3
Bond Lengths (Å)
Sn–O
2.330
2.486
2.457
2.126
2.132
–
2.287
2.495
2.459
2.129
2.134
1.496
1.289
Sn–Clax
Sn–Cleq
Sn–C(1)
Sn–C(2)
C(6)–C(7)
C(3)–O
1.284
Bond Angles (º)
Clax–Sn–O
173.2
92.5
173.1
91.8
Based on the above results obtained for 1, DFT calcula-
tions with the B3LYP functional, using the same BS’s
(LanL2DZ) for both the light atoms and the central metal
ion were performed on all complexes under examination.
Clax–Sn–Cleq
C(1)–Sn–C(2)
C(1)–Sn–Cleq
C(2)–Sn–Cleq
Sn–O–C(3)
126.9
116.3
113.6
138.5
126.2
114.3
117.1
138.7
2.8. Equilibrium geometries
All tables with the structural data for all complexes,
their precursors, and the ligands PYR, PNO and DMP,
under examination are given as Supplementary material.
Selected geometrical parameters of the B3LYP/LanL2DZ
optimized model compounds 1–4 and their precursors are
given in Figs. 2–4. Since comparison between results in
Dihedral Angles (º)
Cleq–Sn–C(1)–C(5)
68
86.3
95.3
Cleq–Sn–C(2)–C(4)
112.1
Fig. 2. Computer plots and selected geometrical parameters of the
B3LYP/LanL2DZ-optimized structures for the model compounds
1
and 3.
Table 3
Selected optimized bond lengths (A) and angles (°) calculated at the DFT level with different hybrid functionals and basis sets [BS’s] on the model complex 1
˚
Functional
B3LYP
C,Cl,O,H BS
Sn BS
Sn–Ca
Sn–C
Sn–Clbax
Sn–Clceq
Sn–O
C–Sn–C
Cl–Sn–Cl
LanL2DZ
6-311+G(d,p)
6-31+G(d)
SDD
LanL2DZ
6-31+G(d)
LanL2DZ
LanL2DZ
LanL2DZ
SDD
LanL2DZ
LanL2DZ
2.132
2.137
2.138
2.148
2.148
2.154
2.126
2.131
2.134
2.145
2.142
2.150
2.486
2.425
2.427
2.500
2.496
2.441
2.457
2.381
2.389
2.473
2.472
2.406
2.330
2.478
2.474
2.472
2.360
2.470
126.9
126.1
125.8
127.3
126.9
125.9
92.5
95.9
94.2
93.9
92.7
94.0
BP86
a
˚
Experimental values: Sn–C = 2.121, Sn–C = 2.133, Sn–Clax = 2.431, Sn–Cleq = 2.365, Sn–O = 2.319 A, C–Sn–C = 127.3°, Cl–Sn–Cl = 91.2°.
Sn–Clax stands for the Sn–Cl axial bond lengths.
Sn–Cleq stands for the Sn–Cl equatorial bond lengths.
b
c

1208
H. Papadaki et al. / Journal of Organometallic Chemistry 693 (2008) 1203–1214
C
trigonal-bipyramidal geometry, in close agreement with the
X-ray crystal data of 1. Two carbon atoms of the two dif-
ferent phenyl groups and one chlorine atom are located in
the equatorial plane, the second Cl and the carbonyl O
atom of the PYR ligand lie at the axial positions. The most
significant change in the coordination sphere, between the
Cl
Cl
Sn
O
N
O
O
C
˚
two structures is the shortening (ca. 0.04 A) of the Sn–O
bond length, on passing from 1 to 3. This is further sub-
stantiated by the corresponding Sn–O overlap population
values, being 0.0274 and 0.0323 e for 1 and 3, respectively,
and the m(Sn–O) vibrational frequency values (vide infra).
Moreover, the two phenyl rings are mutually twisted with
respect to the equatorial plane, to avoid steric congestion.
The dihedral angles between the rings, defined by C(1)–
C(5) and C(2)–C(4) and the trigonal plane, are 113.9°
and 86.2°, and 95.6° and 69.8° for 1 and 3, respectively,
showing a stronger steric effect in the latter complex, in line
with the closer proximity to Sn ion of the DMP and its dif-
ferent orientation opposite the two phenyl rings, compared
to the PYR ligand. The sum of the equatorial angles in the
trigonal girdle subtended at Sn by the two ipso carbons and
the Cl are almost identical (357.7° and 357.6°, for 1 and 3,
respectively). The pyrone rings in 1 and 3, are not posi-
tioned between the two phenyl groups, when viewing along
the apical O–Sn–Cl axis, in close agreement with the anal-
ogous X-ray crystal data of 1.
2
4
Bond Lengths (Å)
Sn–OPYR
2.392
–
2.429
2.305
2.548
2.566
2.120
1.278
1.370
2.464
2.495
Sn–OPNO
'
2.547
–
Sn–ClPYR
'
Sn–ClPNO
2.119
1.278
–
Sn–C
C=OPYR
N=OPNO
H…ClPYR
H…ClPNO
2.467
–
Bond Angles (º)
ClPYR'–Sn–O
90.4
–
90.9
89.0
99.5
166.3
80.7
'
ClPNO –Sn–O
99.2
165.2
80.0
Cl–Sn–Cl
C–Sn–C
O–Sn–O
Fig. 3. Computer plots and selected geometrical parameters of the
B3LYP/LanL2DZ-optimized structures for the model compounds 2 and
4. (Primes denote trans-configuration, with respect to the corresponding
group).
Fig. 3 exhibits the computer plots and selected geomet-
rical parameters of the B3LYP/LanL2DZ-optimized struc-
tures for the model compounds 2 and 4. It is easily seen
that, contrary to the model complexes 1 and 3, in the pres-
ent case there is a hexacoordinated molecule of distorted
compressed octahedral geometry. The two carbon atoms
of two different methyl groups, lying trans- to each other,
occupy the axial positions, and the two chlorine atoms
(located cis- to each other), along with the two carbonyl
O atoms of two different PYR and/or the PYR and PNO
ligands, form the equatorial plane. All the four equatorial
atoms lie on the same plane (dihedral angles of ꢁ0.3°
and 3.5° for 2 and 4, respectively). The most salient feature
of these structures is the formation of two Clꢂ ꢂ ꢂH linkages
˚
˚
(=2.467 A for the PYR ligands and 2.495 A for the PNO
one) between the equatorial Cl atoms and the H of the
ortho- carbon atoms, strengthening further, the whole
structures. As a consequence (i) the two PYR molecules
lie on the same equatorial plane of 2 with the two Cl atoms
and the Sn ion, however (ii) in 4, the PYR and PNO ligand
planes form 26.2° and ꢁ125.2° dihedral angles, respec-
tively, with the equatorial plane, probably to avoid steric
encumbrance. Hence, there is a stronger steric effect in 4,
in line with the closer proximity to Sn metal ion of the
PNO ligand. The Sn–OPYR bond length is longer by ca.
5
6
Bond Lengths (Å)
Sn–Cl
2.411
2.108
2.414
2.116
Sn–C
Bond Angles (º)
Cl(1)–Sn–C(1)
110.8
105.8
105.2
117.7
106.8
106.8
107.1
121.6
Cl(2)–Sn–C(1)
Cl(1)–Sn–Cl(2)
C(1)–Sn–C(2)
˚
0.04 A in 4, compared to that in 2, all of the rest mutual
structural parameters remain almost unchanged. It should
be stressed out here that, upon the PYR and/or PNO
ligands coordination, there is a medium Cl–Sn–Cl angle
closing (by ca. 7–8°), followed by a concomitant significant
C–Sn–C angle opening (by ca. 44°), compared to the
Fig. 4. Computer plots and selected geometrical parameters of the
B3LYP/LanL2DZ-optimized structures for the precursor model com-
pounds 5 and 6.

H. Papadaki et al. / Journal of Organometallic Chemistry 693 (2008) 1203–1214
1209
precursor Me2SnCl2 complex (vide infra). This is probably
due to the approaching point of the two PYR and/or the
PYR and PNO ligands, lying in-between the two Me
groups of the Me2SnCl2 precursor. Hence, the steric effect
of the two PYR and/or the PYR and PNO coordination
would be stronger on the two Me groups, resulting to a sig-
nificant C–Sn–C angle opening, and weaker on the Cl–Sn–
Cl one. The Sn–OPYR bond length is longer than the corre-
sponding lengths of the pentacoordinate complexes 1 and
compared to the experimental values. Therefore, it is usual
to scale frequencies predicted at the B3LYP model of DFT
theory by an empirical factor of 0.9610 [34]. The harmonic
oscillator approach, which is used for calculated frequen-
cies, usually produces higher values than the fundamental
ones.
From all frequency values of the complexes only a few
have been properly scaled and their values are given in Table
4. Those were chosen based upon the importance of the
bond and the intensity of the corresponding absorption.
PYR and DMP ligands, for instance, are mostly charac-
terized by the C@C and C@O stretching bands, while PNO
by the N–O one. Table 4 includes the scaled calculated fre-
quency values for the above bands, along with the vibrat-
ing atoms. The frequencies given in Table 4, are well
characterized as stretch bands, since both their atom’s ori-
entation and eigenvector orientation lie on a single plane.
The first band examined corresponds to the pyrone
C@O stretching frequency, appearing at 1657.2 and
1652.7 cmꢁ1, for PYR and DMP, respectively. These
values are in very good agreement with the only existing
vapor-phase C@O stretching frequency value of six
2-cyclohexane-1 ones, occurring in the region of 1710–
1691 cmꢁ1 [35]. For the two C@C scaled calculated stretch-
ing frequencies of the same ligands, as well as for the N–O
one of the PNO there are not vapor-phase values to com-
pare with. Nevertheless, both PYR and DMP ligands exhi-
bit very similar corresponding C@O and C@C scaled
calculated stretching frequencies.
˚
3, (by ca. 0.06–0.1 A, respectively), while the Sn–OPNO is
shorter than the Sn–OPYR one in 1. This could be due to
the weaker coordination of the PYR ligands and the
stronger one of the PNO, in close agreement with both
(i) the corresponding Sn–O overlap population values of
0.0239 e and 0.0257 e (0.0636 e for the Sn–OPNO), and (ii)
the m(Sn–O) vibrational frequency values (vide infra). The
sum of the equatorial angles in the tetragonal girdle
subtended at Sn by the two PYR and/or the PYR and
PNO carbonyl O atoms and the two Cl ones is 360°.
In Fig. 4 the computer plot and selected geometrical
parameters of the B3LYP/LanL2DZ-optimized structures
for the two model precursors 5 and 6 are given. Both com-
plexes present a distorted tetrahedral geometry, as a result
of different corresponding Sn–Cl and Sn–C bond lengths
and angles. Two carbon atoms of two different methyl or
phenyl groups, and two chlorine atoms occupy the four
apices. It is interesting to note that despite the almost iden-
tical corresponding bond lengths, their corresponding bond
angles are different. As a matter of fact, the Cl–Sn–Cl and
C–Sn–C angles are larger in 6 by ca. 2° and 4°, respectively,
compared to those of 5, possibly due to the weaker steric
effect of the two Me groups, to that of the phenyls.
Frequency information from infrared and Raman spec-
tra in the gas-phase is not available for any of the com-
plexes under study. Table 4 shows that contrary to 2,
exhibiting two m(C@O) stretching bands, 1, 3 and 4, show
only one, and this is also the case with the m(Sn–O) stretch-
ing bands. As expected, the corresponding m(C@O) stretch-
ing frequencies of all complexes are lowered, upon
complexation, by ca. 145 cmꢁ1, compared to those of the
2.9. Vibrational frequencies
Frequency values calculated at the B3LYP level contain
known systematic errors that produce an overestimation
Table 4
Selected scaled, B3LYP/LanL2DZ-calculated, harmonic frequencies [cmꢁ1] of the model complexes 1, 2, 3 and 4, and the PYR, DMP and PNO Ligands
Ligand/ m(C@C)sym m(C@C)asym m(C@O)asym m(C@O)asym D m(C–O)b m(Sn–C)sym m(Sn–C)asym m(Sn–O)sym m(Sn–O)asym m(Sn–Cl)eq m(Sn–Cl)ax
complex
PYR
DMP
PNO
1
2
3
4
1604.6
1622.5
1540.9
1580.6
1657.2
1652.7
1261.6
1510.4
1618.2
1507.7
1518.8
(1141.7)g
1607.1
1610.4
1632.3
1613.2
1520.7
1527.9
1566.4
1527.8
147
135
145
138
(120)
640.9c
646.5c
550.9
646.4c
546.0c
507.1
506.0
509.5
500.6
d
300.6
253.4e
298.1
251.8e
278.7
248.5f
274.2
244.0f
d
1519.7
502.2
641.1c
d
a
PYR and DMP ligands, and complexes 1 and 3 exhibit only one m(C@O) vibrational frequency, and this is also the case with the m(Sn–O) one of
complexes 1 and 3; PNO ligand exhibits only one m(N–O) vibrational frequency, while complex 4 one m(N–O) and one m(C@O) vibrational frequencies.
b
Dm(C–O) = [m(C–O)lig ꢁ m(C–O)compl].
c
Frequency vibrations exhibiting low IR intensities.
d
Not determined.
m(Sn–Cl) asymmetric vibration.
m(Sn–Cl) symmetric vibration.
Numbers in parentheses correspond to the PNO ligand vibrational frequency values of 4.
e
f
g

1210
H. Papadaki et al. / Journal of Organometallic Chemistry 693 (2008) 1203–1214
ligands; the same holds also true for the m(N–O) stretching
frequency of 4, the corresponding lowering upon complex-
ation amounting to ca. 120 cmꢁ1. Moreover, for the same
reason, the m(C@C) stretching bands of the complexes,
are lowered by ca. 13–20 cmꢁ1 [m(C@C)asym] or increased
by ca. 2.5–10 cmꢁ1 [m(C@C)sym]. The m(Sn–O) stretching-
bands trend (4 < 2 < 1 < 3) is in excellent agreement with
that (2 > 1 > 3 > 4) expected on the basis of the corre-
sponding Sn–O bond lengths. Finally, it is well known
[35] that formation of a hydrogen bond, leads to a stretch-
ing frequency shift towards a lower value the neighbouring
bonds. This is also, in excellent agreement with the lower-
ing (by ca. 35–49 cmꢁ1) of both m(Sn–Cl) stretching bands
in 2 and 4, (in which two Hꢂ ꢂ ꢂCl bonds are formed) com-
pared to those in 1 and 3.
bonyl O atom. The nature of the two HOMO’s, along with
the high frontier density values, Pr(HOMO) [36] for the car-
bonyl O atom, (0.37 and 0.37, respectively) and their high,
calculated, negative charges, (qr = ꢁ0.58 e and ꢁ0.60 e,
respectively), strongly suggest that (i) the latter atom should
be the nucleophilic center for Sn(IV) attack of either ligand,
and (ii) both ligands show identical nucleophilic ability.
Fig. 5 also presents the LUMO and LUMO + 1 of the
two precursor complexes 5 and 6, respectively. It is easily
seen that in both cases, the LUMO’s are located mainly
on the central Sn ion. In particular, in the LUMO of 5 there
is only one vacant lobe directed trans- to one of the Cl
atoms. Hence, the LUMO–HOMO interaction between
the 6 and the PYR ligand should yield complex 1, in excel-
lent agreement with the X-ray experimental structural data
of the latter complex. However, in the case of 6, possibly due
to the weaker than in 5 steric repulsions, two vacant lobes
appear in its LUMO + 1, directed trans- to its two Cl atoms.
Hence, a (LUMO + 1)–HOMO interaction, like above,
should yield complex 2, in excellent agreement with the the-
oretical structural data of the latter complex. Moreover, due
to the positive charge on the Sn(IV) ion (ca. 1.00 e), in both 5
and 6, the nucleophilic attack described above, should be
both a charge- and frontier-orbital-controlled one.
Finally, the possible mechanism of formation of the 4
adduct (the monoexchange from 2), was also investigated
with the aid of additional calculations, described below.
The nature of the FMO’s of the PNO ligand and its
nucleophilic ability was investigated first. The p-type
HOMO of PNO, mostly centered on the O atom of the
N–O group, is also shown in Fig. 5. Moreover, its
HOMO ꢁ 1 is quite analogous to the HOMO’s of PYR
and DMP. The nature of the two FMO’s of PNO, along
with the rather lower than the PYR frontier density value,
Pr(HOMO) of its carbonyl O atom, (0.28 compared to
0.37), and its, almost equal to the PYR, calculated negative
charge, (qr = ꢁ0.55 e compared to ꢁ0.58 e), could suggest
that (a) its carbonyl O atom should also be the nucleophilic
center for Sn(IV) attack, and (b) PNO shows an inferior
than the PYR nucleophilic ability.
2.10. Reactivity of the complexes
Prompted by the above experimental reactivity findings,
we initiated a systematic quantum-chemical investigation
in an attempt to understand the reactivity of both the
PYR and DMP ligands towards the Sn ions. In particular,
B3LYP/6-311+G(d,p) calculations, with a natural bond
analysis, were carried out on both ligands, which were
combined with the calculations described above for the
precursor complexes 5 and 6.
The most salient features of the ground-state electronic
structure of PYR and DMP, are their HOMO’s, which are
schematically depicted in Fig. 5. In particular, the two
HOMO’s are almost identical, mostly centered on the car-
Next, an additional B3LYP/LanL2DZ calculation was
performed, in the search of a sevencoordinate transition
state (TS), involving the adduct 2 and a PNO ligand, lying
at the equatorial plane of 2, in between its two PYR
ligands, namely:
Me
PYR
Cl
PNO
PYR
Sn
Cl
Me
The latter TS, if any, should correspond to a SN2 mecha-
nistic scheme for the formation of the 4 adduct. However,
calculations failed to afford a TS stationary point of that
kind. This is in close agreement with the inferior nucleophilic
Fig. 5. The LUMO and LUMO + 1 of the precursor model compounds 5
and 6, respectively, and the HOMO’s of the PYR, DMP and PNO ligands.

H. Papadaki et al. / Journal of Organometallic Chemistry 693 (2008) 1203–1214
1211
ability of the PNO ligand compared to that of PYR. Hence, a
SN mechanism could be excluded for the corresponding
ing points were determined in open tubes. IR spectra were
recorded on a Perkin Elmer FT 16500 spectrometer and
samples prepared as KBr disks. The far-IR spectra were
taken on Bruker FT IR IFS 113v spectrometer (resolution
2
mechanism of formation. Moreover, additional calculations
have shown that the dissociation of 2 to the monosubstituted
Sn complex and the PYR ligand (Eq. (4) below) requires an
energy of only 9.7 kcal/mol, showing that this dissociation
could easily occur at room temperature in solution. This is
in close agreement with the large dissociation observed
experimentally in solution for the adduct 2, (vide supra).
1
2 cmꢁ1, 64 scans) as polyethylene disks. H and 13C NMR
spectra were measured on a Brucker 300 spectrometer.
119Sn Mo¨ssbauer spectra of powder samples were obtained
at 85 K in an exchange gas cryostat, using a constant accel-
eration spectrometer and a 10 mCi calcium stannate source
kept at room temperature. Spectrometer calibration was
effected using a metallic iron foil. Isomer shifts were
reported relative to CaSnO3, assuming that they are the
same as those of the BaSnO3. The chloroform solutions
of all the new adducts do not show appreciable electrical
conductivity.
1
2
Hence, a SN formation mechanism rather than a SN one
seems most probable for 4, namely:
Me
Sn
Me
Sn
PYR
PYR
PYR
Cl
Cl
Cl
Cl
PYR
+
Me
Me
4.2. Synthesis of Ph2SnCl2(PYR) (1)
2
ð4Þ
PNO
+
PYR (0.048 g, 0.5 mmol) was added to a solution of
Ph2SnCl2 (0.172 g, 0.5 mmol) in CHCl3 (15 mL), under
constant stirring. The reaction mixture was stirred for 1 h
and left to concentrate slowly in air, affording crystals of
the product. The off white crystals were collected by suc-
tional filtration and were recrystallized from CHCl3, dried
in vacuo. X-ray quality crystals of 1 were grown from
CHCl3. Yield (0.079 g, 36%).
Me
Sn
PYR
PNO
Cl
Cl
Me
3. Conclusion
1
Mp 100–101 °C. H NMR (300 MHz, CDCl3): d = 7.8
3
3
The adducts Ph2SnCl2(PYR) (1), Me2SnCl2(PYR)2 (2),
Ph2SnCl2(DMP) (3) and Me2SnCl2(PYR)(PNO) (4), have
been prepared by the addition of the corresponding c-pyr-
one (PYR or DMP) to chloroform solution of R2SnCl2,
and characterized analytically and spectroscopically.
Moreover, the single-crystal X-ray diffraction study of 1
shows the Sn(IV) to be five-coordinated, and the PYR
ligand is attached to the metal via its carbonyl O. The reac-
tivity of 2 towards bipy, Ph3PO, QNO (Q = quinoline)
resulted in complete displacement of PYR, whereas, the
PNO displaced only one equivalent of PYR, causing the
preparation of the new mixed complex 4, possibly via a
SN1 formation mechanism. DFT/B3LYP molecular orbital
calculations carried out for the 1–4 complexes, their pre-
cursors, Ph2SnCl2, (5) and Me2SnCl2, (6) and the ligands,
PYR and DMP explained the structures, vibrational fre-
quencies, and the electron-accepting ability of the com-
plexes, and the reactivity of their precursors towards
nucleophiles.
(d, J Hb, Ha = 5.4 Hz, 2H, 2,6 of PYR), 6.4 (d, J Ha,
Hb = 5.4 Hz, 2H, 3,5 of PYR), 7.9–7.7 (m, 10H, Sn–Ph2)
ppm. 13C NMR (75 MHz, CDCl3): d = 155.4 (2C, 2,6
PYR), 118.4 (2C, 3,5 of PYR), 178.5 (1C, C@O), d =
139.7 (1J C, 119Sn = 891.1 Hz, 2C, ipso Sn–Ph2, 1J C,
117Sn = 849.6 Hz, 2 C, ipso Sn–Ph2), 135.2 (2J C, 119Sn =
69.5 Hz, 2C, ortho Sn–Ph2), 129.2 (3J C, 119Sn = 90.3 Hz,
2C, meta Sn–Ph2) 131.02 (4J C, 119Sn = 17.1 Hz, 2C, para
Sn–Ph2) ppm. IR (KBr pellets, cmꢁ1): m = 1688 (vw), 1673
(vw), 1639 (vs, broad), 1566 (sh), 1560 (vs), 1533 (sh),
1479 (w), 1446 (w), 1430 (m), 1394 (vw), 1324 (s), 1225
(vw), 1198 (m), 997 (w), 937 (sh), 930 (s), 863 (w), 856 (m),
850 (w), 846 (w), 835 (w, broad), 695 (vs, broad), 669 (vw),
526 (m), 520 (m), 481 (m), 476 (m), 469 (s, broad), 458 (s,
broad) 444 (m), 340 (w), 292 (m), 277 (m), 285 (m) cmꢁ1
.
Anal. Calc. for C17H14O2Cl2Sn (439.91): C, 46.42; H, 3.34.
Found: C, 46.28; H, 3.34%.
4.3. Synthesis of Me2SnCl2(PYR)2 (2)
PYR (0.096 g, 1 mmol) was added to a solution of
Me2SnCl2 (0.109 g, 0.5 mmol) in CHCl3 (10 mL). The solu-
tion was stirred for 1 h and became slightly turbit. Then, it
was filtrated and to the clear pale yellow filtrate petroleum
ether (bp 40–60 °C) was added (5 mL) and left aside to
crystallize slowly. The mother liquid was discarded and
the precipitated crystals were dried in air. The product
was dissolved in a mixture of CH2Cl2 and petroleum ether
and was left in the freezer affording big pale yellow crystals,
which were dried in vacuo. Yield (0.105 g, 51%).
4. Experimental
4.1. General procedures
All the reactions were performed in air at room temper-
ature. Me2SnCl2, was purchased from Alfa Products Ven-
tron, whereas Ph2SnCl2, DMP and PYR from Aldrich.
C, H and N analyses were carried out in our microanalyt-
ical laboratory with a Perkin Elmer 240 instrument. Melt-

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H. Papadaki et al. / Journal of Organometallic Chemistry 693 (2008) 1203–1214
1
Mp 82–84 °C. H NMR (300 MHz, CDCl3): d = 7.9 (d,
ether (2 mL) was added and left to crystallize slowly in
air, affording off yellow crystals of the new product
Me2SnCl2(PYR)(PNO) (4). Yield (0.059 g, 70%).
3J Hb, Ha = 6.6 Hz, 2H, 2,6 of PYR), 6.5 (d, J Ha, Hb =
3
6.6 Hz, 2H, 3,5 of PYR), and 1.3 (s, J 119Sn, H = 79.4
2
Hz, J 117Sn, H = 76.3 Hz, 6H, SnMe2) ppm. 13C NMR
Mp 165–167 °C. H NMR (300 MHz, CDCl3): d = 7.8
2
1
3
3
(75 MHz, CDCl3): d = 178.5 (1C, C@O), 156.3 (2C, 2,6
(d, J Hb, Ha = 5.7 Hz, 2H, 2,6 of PYR), 6.4 (d, J, Ha,
of PYR), 118.1 (2C, 3,5 of PYR), and 10.3 (1J C, 119Sn =
Hb = 5.7 Hz, 2H, 3,5 of PYR), 1.1 (s, J H, 119Sn = 87.2
2
595.7 Hz, J C, 117Sn = 571.3 Hz, SnMe2) ppm. IR (KBr
Hz, 2J H, 117Sn = 83.4 Hz, 6H, SnMe2), 7.4 (br, 2H,
MeC5H4NO), 8.3 (br, 2H, MeC5H4NO) and 2.5 (s, 3H,
MeC5H4NO) ppm. 13C NMR (75 MHz, CDCl3, 25 °C):
d = 155.5 (2C, 2,6 PYR), 118.1 (2C, 3,5 of PYR), 177.9
(1C, C@O), 20.8 (s, 1C, MeC5H4NO) and 11.4 (1J C,
119Sn = 693.9 Hz, 2C, SnMe2) ppm. IR (KBr pellets,
cmꢁ1): m = 1637 (s), 1624 (w), 1560 (w), 1498 (s), 1482 (s),
1459 (s, broad), 1322 (w), 1243 (vw), 1201 (vs), 1184 (s),
1171 (s), 1121 (vw), 1108 (w), 1040 (w), 975 (vw), 956
(w), 930 (w), 854 (s), 842 (sh), 837 (s), 698 (vs), 669 (w),
662 (m), 567 (s), 530 (m), 482 (vs), 464 (vs), 390 (s), 321
(vw), 262 (vw), 231 (w), 151 (m). Anal. Calc. for
C13H17O3Cl2NSn (424.89): C, 36.75; H, 4.03; N, 3.29.
Found: C, 36.82; H, 4.05; N, 3.46%.
1
pellets, cmꢁ1): m = 1675 (m), 1639 (s), 1579 (s), 1536 (m),
1435 (m), 1321 (s), 1376 (w), 1321 (s), 1229 (w), 1199 (m),
1036 (w), 1016 (w), 926 (s), 857 (s), 799 (w), 540 (w), 516
(w), 470 (w, broad), 461 (w, broad), 267 (w, broad), 261
(w, broad). Anal. Calc. for C12H14O4Cl2Sn (411.86): C,
34.99; H, 3.43. Found: C, 34.97; H, 3.75%.
4.4. Synthesis of Ph2SnCl2(DMP) (3)
The DMP (0.050g, 0.4 mmol) was added to a solution of
Ph2SnCl2 (0.136 g, 0,4 mmol) in CHCl3 (10 mL) contained
in a small flask. The DMP was added under constant stir-
ring which was kept for 3 h. Then petroleum ether (bp 40–
60 °C) was added (ꢃ2 mL) and left aside to crystallize
slowly in air affording big white crystals, which were dried
in vacuo. Yield (0.120 g, 64%).
4.6. X-ray crystal structure determination for 1
Mp 145–146 °C. 1H NMR (300 MHz, CDCl3): d = 6.2 (s,
2H, 3,5 of DMP), 2.3 (s, 6H, Me of DMP), and 7.9–7.5 (m,
10H, Sn–Ph2) ppm. 13C NMR (75 MHz, CDCl3):
d = 167.2 (2C, 2,6 DMP), 113.7 (2C, 3,5 of DMP), 180.9
The crystal was mounted on a glass fibre and data were
collected at 173 K on a Brucker SMART CCD area detec-
tor 3-circle diffractometer (Mo Ka X-radiation, graphite
˚
monochromator (k = 0.71073 A)). It was confirmed that
(1C, C@O), 140.27 (1J C, 119Sn = 925.9 Hz, J C, 117Sn =
crystal decay had not taken place during the course of the
data collection. Narrow ‘‘frames” were collected for 0.3°
increments in W for three settings of U. In each of these
three cases a total of 1271 frames of data were collected
affording rather more than a hemisphere of data. The sub-
stantial redundancy in data allows empirical absorption
corrections (SADABS) [37] to be applied using multiple mea-
surements of equivalent reflections. The data frames were
integrated using SAINT [38]. The structure was solved by con-
ventional direct methods and refined by full matrix least
squares on all F2 data using SHELXTL ver. 5.03 [39]. All
non hydrogen atoms were refined with anisotropic thermal
parameters. All hydrogen atoms were included in calculated
positions with isotropic thermal parameter ca. 1.2 ꢄ (aro-
matic CH) the equivalent isotropic thermal parameters of
their parent carbon atoms. Details of the crystal data and
intensity collection are summarized in Table 5. All calcula-
tions were carried out on Silicon Graphics Iris Indigo or
Indy computers.
1
882.1 Hz, 2C, ipso Sn–Ph2), 135.3 (2J C, 119Sn = 64.2 Hz,
2J C, 117Sn = 61.0 Hz, 2C, ortho Sn–Ph2), 129.2 (3J C,
3
119Sn = 92.6 Hz, J C, 117Sn = 88.4 Hz, 2C, meta Sn–Ph2)
and 130.9 (4J C, 119Sn = 17.8 Hz, 2C, para Sn–Ph2) ppm.
IR (KBr pellets, cmꢁ1): m = 1651 (vs), 1599 (sh), 1576 (m),
1539 (vs), 1478 (m), 1447 (w), 1428 (m), 1417 (w), 1337
(m), 1199 (s), 1171 (w), 1063 (w), 1039 (w), 998 (w), 954
(w), 906 (m), 877 (m), 847 (w), 748 (m), 734 (s), 695 (s), 621
(m), 543 (m), 524 (w), 454 (m), 445 (w), 369 (vw), 333 (m),
270 (m) 243 (m), 202 (w). Anal. Calc. for C19H18O2Cl2Sn
(467.97): C, 48.45; H, 3.81. Found: C, 48.77; H, 3.88%.
4.5. Reactivity of Me2SnCl2(PYR)2 (2)
(I) Addition of QNO (0.27 mmol) or bipy (0.2 mmol) to
equimolar chloroform solutions of 2, led to the complete
displacement of PYR. After stirring for 1 h and addition
of petroleum ether, the mixtures were left in air to concen-
trate slowly affording crystals of the known adducts
Me2SnCl2(QNO)2 [8] or Me2SnCl2(bipy) [18]. The reaction
of QNO and the starting adduct 2 in 2:1 molar ratio and
work up as above gave again the same product. (II) Addi-
tion of solid OPPh3 (0.4 mmol) to a chloroform (0.2 mmol)
solution of 2, resulted in complete displacement of the PYR
from the starting adduct. Work up as above gave the
known solid Me2SnCl2(OPPh3)2 [18]. (III) The ligand
PNO (0.092 g, 0.2 mmol) was added to a chloroform solu-
tion (10 mL) of 2 (0.082 g, 0.2 mmol), contained in a small
beaker. The mixture was stirred for 1 h, then petroleum
4.7. Quantum-chemical calculations
For the reasons explained in another section of this
study, the geometries of all minimum energy structures
for all complexes and their corresponding precursors were
fully optimized at the B3LYP/LanL2DZ level of theory;
the PYR, DMP and PNO ligands at the B3LYP/
6-311+G(d,p) level. C1 point group symmetry for each
species was assumed as the initial geometry of the
optimization procedure. All calculations investigating the

H. Papadaki et al. / Journal of Organometallic Chemistry 693 (2008) 1203–1214
1213
Table 5
with this article can be found, in the online version, at
doi:10.1016/j.jorganchem.2008.01.014.
Crystal data and structure refinement for 1
Formula
C17H14Cl12O2Sn
Fw
T (K)
439.87
173(2)
References
Crystal system
Space group
Monoclinic
P21/c
0.71073
[1] E.M. Brigs, A.E. Hill, J. Chem. Soc. A (1969) 1835 and references
therein.
[2] S. Sitran, D. Fregona, G. Faraglia, J. Coord. Chem. 20 (1989) 193,
and references therein.
[3] G. Faraglia, Z. Guo, S. Sitran, Polyhedron 10 (1991) 351.
[4] D. Fregona, G. Faraglia, S. Sitran, J. Coord. Chem. 30 (1993) 221.
[5] D. Fregona, Z.J. Guo, G. Faraglia, S. Sitran, J. Coord. Chem. 28
(1993) 73.
[6] H. Papadaki, A. Christofides, J.C. Jeffery, T. Bakas, J. Coord. Chem.
47 (1999) 559.
[7] I. Saura-Liamas, D.M. Dalton, A.M. Artif, J.A. Gladysz, Organo-
metallics 11 (1992) 683.
[8] D. Fregona, Z.J. Guo, G. Faraglia, S. Sitran, Transition Met. Chem.
17 (1992) 242.
[9] Q. Lin, W.K. Leong, Organometallics 22 (2003) 3639.
[10] M. Gielen, Appl. Organomet. Chem. 16 (2002) 481.
[11] V. Valla, M. Bakola-Christianopoulou, Synth. React. Inorg. Met.-
Org. Nano-Met. Chem. 37 (2007) 507.
[12] G. Wilkinson, F.G.A. Stone, E.W. Abel, Comprehensive Organome-
tallic Chemistry, vol. 2, Pergamon Press, Oxford, 1982, p. 616
(chapter II) and references therein.
[13] A.L. Rheingold, S.W. Ng, J.J. Zuckerman, Organometallics 3 (1984)
233.
[14] S.W. Ng, V.G. Kumar Das, Z. Kristallogr. 209 (1993) 744.
[15] E.A. Blom, B.R. Penfold, N.T. Robinson, J. Chem. Soc. A (1969)
913.
[16] S.W. Ng, J.J. Zuckerman, J. Chem. Soc., Chem. Commun. (1982)
475.
[17] D. Cunningham, J. Douek, M.J. Fraser, M. Mc Partlin, J. Organo-
met. Chem. C23 (1975) 90.
[18] J.P. Clark, C.I. Wilkins, J. Chem. Soc. A (1966) 871.
[19] A.R. Katritzky, R.A. Jones, Spectrochim. Acta 17 (1961) 64.
[20] J.H. Looker, W.W. Hanneman, J. Org. Chem. 27 (1962) 381.
[21] M.M. Finnegan, T.G. Lutz, W.O. Nelson, A. Smith, C. Orvig, Inorg.
Chem. 26 (1987) 2171.
˚
k (A)
˚
a (A)
8.452(2)
˚
b (A)
9.3752(13)
21.405(4)
92.76(2)
1694.1(6)
4
1.725
1.826
864
0.50 ꢄ 0.20 ꢄ 0.15
1.90–27.50
ꢁ10 6 h 6 10,
ꢁ12 6 k 6 12,
ꢁ27 6 l 6 27
16,895
˚
c (A)
b (°)
3
˚
V (A )
Z
Dcalc (g/cm3)
l (mmꢁ1
F(000)
)
Crystal size (mm)
h Range for data collection (°)
Index ranges
Reflections collected
Independent reflections (Rint
Absorption correction
Maximum and minimum
transmission
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
R1, wR2, (I > 2r(I))
R1, wR2 (all data)
)
3865 (0.0243)
SADABS
0.646824 and 0.509887
Full-matrix least-squares on F2
3865/0/199
1.057
0.0193, 0.0459
0.0232, 0.0469
Weighting scheme
Calc w = 1/[s2(F2o) + (0.0244P)2
+ 0.0000P] where P = (F2o + 2Fc2)/3
0.255/ꢁ0.615
Largest differenceꢁi3n
˚
peak/hole (e A
)
structural parameters of the molecules addressed here are
based on final frequency calculations that provide energy
minima with certainty. For each molecule full optimization
calculations were performed in an attempt to determine the
closest structure to the global minimum. The non-appear-
ance of negative frequencies was assumed to be evidence
for a global potential energy minimum of each calculated
structure. Although the use of all-electron basis sets pro-
vides better accuracy, pseudopotential techniques are use-
ful when relativistic effects have to be taken into account.
Thus, the LanL2DZ BS’s with relativistic effective core
potentials were tested for all complexes of‘ this study.
The GAUSSIAN-03W software package [40] was used.
[22] W.F. Howard Jr., R.W. Crecely, W.H. Nelson, Inorg. Chem. 24
(1985) 2204.
[23] W. Kitching, V.G. Kumar Das, Aust. J. Chem. 21 (1968) 2401.
[24] T.A.K. Al-allaf, J. Organomet. Chem. 306 (1986) 337.
[25] V.G. Kumar Das, Y. Chee-Keong, P.J. Smith, J. Organomet. Chem.
327 (1987) 311.
[26] B.W. Fitzsimmons, N.J. Sealey, A.W. Smith, J. Chem. Soc. A (1969)
143.
[27] T.N. Srivastava, P.C. Srivastava, J.S. Gaur, Indian J. Chem. A 17
(1979) 142.
[28] R.W.J. Wedd, J.R. Sams, Can. J. Chem. 48 (1970) 71.
[29] (a) E.S. Kryachko, E.V. Ludena, Energy Density Functional Theory
of Many Electron Systems, Kluwer Academic Publisher, Dordrecht,
1990;
(b) W. Koch, M.C. Holthausen, A Chemist’s Guide to Density
Functional Theory, 2nd ed., Wiley-VCH, Stuttgart, 2002.
[30] (a) A.D. Becke, J. Chem. Phys. 98 (1993) 5648;
(b) A.D. Becke, Phys. Rev. A 38 (1988) 3098;
(c) C. Lee, W. Wang, R.G. Parr, Phys. Rev. B 37 (1988) 785.
[31] J.P. Perdew, Phys. Rev. B 33 (1986) 8822.
[32] J.V. Ortiz, P.J. Hay, R.L. Martin, J. Am. Chem. Soc. 114 (1992) 2736.
[33] (a) P. Fuentealba, H. Preuss, H. Stoll, L.V. Szentpaly, Chem. Phys.
Lett. 89 (1982) 418;
Appendix A. Supplementary material
CCDC 657306 contains the supplementary crystallo-
graphic data for 1. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif. Cartesian coor-
dinates for the B3LYP/LanL2DZ optimized 1, 2, 3, 4, 5
and 6 and the B3LYP/6-311+G(d,p) optimized PYR,
DMP and PNO structures. Supplementary data associated
(b) A. Bergner, M. Dolg, W. Kuechle, H. Stoll, H. Preuss, Mol.
Phys. 80 (1993) 1431;
(c) P. Fuentealba, L.V. Szentpaly, H. Preuss, H. Stoll, J. Phys. B 18
(1985) 1287;

1214
H. Papadaki et al. / Journal of Organometallic Chemistry 693 (2008) 1203–1214
(d) G. Igel-Mann, H. Stoll, H. Preuss, Mol. Phys. 65 (1988) 1321;
(e) M. Dolg, U. Wedig, H. Stoll, H. Preuss, J. Chem. Phys. 86 (1987)
866;
(f) M. Dolg, H. Stoll, H. Preuss, R.M. Pitzer, J. Phys. Chem. 97
(1993) 5852.
[40] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb,
J.R. Cheeseman, J.A. Montgomery Jr, T. Vreven, K.N. Kudin, J.C.
Burant, J.M. Millam, S.S. Iyengar, J. Tomasi, V. Barone, B.
Mennucci, M. Cossi, G. Scalmani, N. Rega, G.A. Petersson, H.
Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa,
M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X.
Li, J.E. Knox, H.P. Hratchian, J.B. Cross, C. Adamo, J. Jaramillo, R.
Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C.
Pomelli, J.W. Ochterski, P.Y. Ayala, K. Morokuma, G.A. Voth, P.
Salvador, J.J. Dannenberg, V.G. Zakrzewski, S. Dapprich, A.D.
Daniels, M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck, K.
Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui, A.G. Baboul, S.
Clifford, J. Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko,
P. Piskorz, I. Komaromi, R.L. Martin, D.J. Fox, T. Keith, M.A.
Al-Laham, C.Y. Peng, A. Nanayakkara, M. Challacombe, P.M.W.
Gill, B. Johnson, W. Chen, M.W. Wong, C. Gonzalez, J.A. Pople,
GAUSSIAN 03, Revision B.03, Gaussian, Inc., Pittsburgh, PA, 2003.
[34] A.P. Scott, L. Radom, J. Phys. Chem. 100 (1996) 16502.
[35] D. Lin-Vien, N.B. Coltharp, W.G. Fateley, J.G. Grasselli, The
Handbook of Infrared and Raman Characteristic Frequencies of
Organic Molecules, Academic Press, San Diego, 1991.
[36] K. Fukui, H. Fujimoto, Tetrahedron Lett. (1965) 4303.
[37] G.M. Sheldrick, SADABS,
A Program for Absorption Correc-
tion with the Siemens SMART System, University of Go¨ttingen,
1996.
[38] SAINT Integration Software, Siemens Analytical X-ray Instruments
Inc., Madison, WI, 1994.
[39] SHELXTL 5.03 Program System, Siemens Analytical X-ray Instruments,
Madison, WI, 1995.