Synthesis and structural characterisation of diorganotin(IV) and diphenyllead(IV) complexes of pyrimidine-2-thionate derivatives

Article abstract of DOI:10.1002/ejic.200600945

The reaction between the ligands 4-(trifluoromethyl)pyrimidine-2-thione (4-CF₃pymSH) and 6-methyl-4-(trifluoromethyl)pyrimidine-2-thione (6-Me-4-CF₃pymSH) and the corresponding diorganotin(IV) dichloride [R₂SnCl₂] (R = Me, (Bu or Ph) or diphenyllead(IV) dichloride in the presence of triethylamine yields the diorganotin(IV) complexes [R₂Sn(4-CF₃pymS)₂] and [R₂Sn(6-Me- 4-CF₃pymS)₂] or diorganolead(IV) complexes [Ph ₂Pb(4-CF₃pymS)₂] and [Ph₂Pb(6-Me-4- CF₃pymS)₂], respectively. The compounds have been characterised by microanalysis, mass spectrometry and by IR and Mossbauer spectroscopy and, in the case of the compound that was sufficiently soluble, by ¹H, ¹³C, ¹¹⁹Sn and ²⁰⁷Pb NMR spectroscopy. The compounds [Me₂Sn(4-CF₃pymS)₂] (1), [Ph₂Sn(4-CF₃pymS)₂] (2), [Ph ₂Sn(6-Me-4-CF₃pymS)₂] (5), [tBu ₂Sn(6-Me-4-CF₃pymS)₂] (6), [Ph ₂Pb(4-CF₃pymS)₂] (7) and [Ph ₂Pb(6-Me-4-CF₃pymS)₂] (8) have also been characterised by X-ray diffraction. The X-ray crystal structures show that the metal centre in all these complexes is in a distorted octahedral environment with bonds to two carbon atoms from the aryl or alkyl substituents and to sulfur and heterocyclic nitrogen atoms from the pyrimidine derivative, which acts a (κ²-N,S) chelating ligand. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.

Full text of DOI:10.1002/ejic.200600945

FULL PAPER
DOI: 10.1002/ejic.200600945
Synthesis and Structural Characterisation of Diorganotin(IV) and
Diphenyllead(IV) Complexes of Pyrimidine-2-thionate Derivatives
Antonio Rodríguez,[a] Antonio Sousa-Pedrares,[a] J. Arturo García-Vázquez,*[a]
Jaime Romero,[a] Antonio Sousa,[a] and Umberto Russo[b]
Keywords: Tin / Lead / N,S ligands / NMR spectroscopy / Moessbauer spectroscopy
The reaction between the ligands 4-(trifluoromethyl)pyrimi-
dine-2-thione (4-CF3pymSH) and 6-methyl-4-(trifluoro-
methyl)pyrimidine-2-thione (6-Me-4-CF3pymSH) and the
corresponding diorganotin(IV) dichloride [R2SnCl2] (R = Me,
tBu or Ph) or diphenyllead(IV) dichloride in the presence of
triethylamine yields the diorganotin(IV) complexes [R2Sn(4-
CF3pymS)2] and [R2Sn(6-Me-4-CF3pymS)2] or diorganolead-
(IV) complexes [Ph2Pb(4-CF3pymS)2] and [Ph2Pb(6-Me-4-
NMR spectroscopy. The compounds [Me2Sn(4-CF3pymS)2]
(1), [Ph2Sn(4-CF3pymS)2] (2), [Ph2Sn(6-Me-4-CF3pymS)2] (5),
[tBu2Sn(6-Me-4-CF3pymS)2] (6), [Ph2Pb(4-CF3pymS)2] (7)
and [Ph2Pb(6-Me-4-CF3pymS)2] (8) have also been charac-
terised by X-ray diffraction. The X-ray crystal structures
show that the metal centre in all these complexes is in a dis-
torted octahedral environment with bonds to two carbon
atoms from the aryl or alkyl substituents and to sulfur and
CF3pymS)2], respectively. The compounds have been charac- heterocyclic nitrogen atoms from the pyrimidine derivative,
terised by microanalysis, mass spectrometry and by IR and
Mössbauer spectroscopy and, in the case of the compound
that was sufficiently soluble, by 1H, 13C, 119Sn and 207Pb
which acts a (κ2-N,S) chelating ligand.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2007)
pers have been dedicated to the design of specific complex-
ing agents.[15,16] In addition, organotin complexes have been
studied more recently in terms of their pharmacological and
antitumour activity.[17–22]
Introduction
The chemistry of metal complexes of heterocyclic thione
ligands is receiving increasing attention, largely because of
the potential relevance of such compounds as models of
active sites in metalloenzymes and also their ability to
adopt geometries of variable nuclearity and great structural
complexity, which is a result of the tendency of thiolate li-
gands to bridge metal centres to yield oligomeric or poly-
meric species.[1–8]
However, in comparison with the coordination chemistry
of transition metals, the chemistry of main group metals
with sulfur ligands remains much less developed.[9–13] In
many cases, the interaction of toxic main group metals with
biological systems frequently involves bonding of the metal
to the sulfhydryl groups present in enzymes. Hence, an in-
sight into the chemistry of main group thiolate compounds
is important in terms of understanding the aforementioned
interaction and for the design of detoxifying agents.[14,15]
This interest has led us to study organotin and organolead
compounds that, in a biological medium, react with thiol
groups in relevant molecules to yield products that are char-
acterised by metal–thiolate interactions, which are of inter-
est in the design of sequestering agents; indeed, several pa-
As a continuation of our studies into the coordination
chemistry of sterically hindered heterocyclic thiones,[23] we
report here the synthesis and characterisation of diorganot-
in(IV) and diphenyllead(IV) complexes with 4-(trifluorome-
thyl)pyrimidine-2-thione and 6-methyl-4-(trifluoromethyl)-
pyrimidine-2-thione ligands, the structures of which are
shown in Scheme 1. These ligands, besides having solubilis-
ing and bulky groups, belong to one of the most versatile
types of sulfur ligand in terms of coordination modes. For
example, they can act (a) as a neutral monodentate ligand
coordinated through the sulfur atom,[24] through one of the
nitrogen atoms,[25] and as a bridging ligand through sul-
fur[26] or as an N,S-chelating ligand,[27,28] or (b) as an an-
ionic ligand, in which case they can be monodentate
through the sulfur atom,[29] an N,S-chelating ligand[30–32] or
[a] Departamento de Química Inorgánica, Universidad de Santi-
ago de Compostela,
15782, Santiago de Compostela, Spain
[b] Dipartartimento di Scienze Chimiche Universiá degli Studi de
Padova,
Padova, Italy
Scheme 1.
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Complexes of Pyrimidine-2-thionates
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a binuclear bridging ligand through nitrogen and sulfur,[33] Molecular Structures of [Me2Sn(4-CF3pymS)2] (1),
or sulfur only,[34] and as a binuclear triply bridging ligand [Ph2Sn(4-CF3pymS)2] (2), [Ph2Sn(6-Me-4-CF3pymS)2] (5)
through sulfur and one of the nitrogen atoms,[31,35] or the and [tBu2Sn(6-Me-4-CF3pymS)2] (6)
two nitrogen and sulfur atoms,[36,37] and as a trinuclear tri-
The molecular structures of 1, 2, 5 and 6 are shown in
ply bridging system.[38]
Figures 1, 2, 3 and 4, respectively, together with the atom
Moreover, these ligands were chosen because they are
labelling scheme adopted. Crystallographic data and a se-
unsymmetrical ambidentate systems and can therefore give
rise to linkage isomerism when they are coordinated in
some of the aforementioned ways.
Results and Discussion
A series of diorganotin(IV) and diphenyllead(IV) com-
plexes of general formulae [R2Sn(RpymS)2] and
[Ph2Pb(RpymS)2] were synthesised in reasonable yields (47–
74%) from the appropriate diorganotin(IV) dichloride
[R2SnCl2] (R = Me, Ph, tBu) or diphenyllead(IV) dichloride
Figure 1. Crystal structure of [Me2Sn(4-CF3pymS)2] (1) (50%
probability displacement ellipsoids).
(Ph2PbCl2) and the corresponding pyrimidine-2-thione de-
rivative in methanol in the presence of triethylamine, ac-
cording to Scheme 2.
The complexes reported here are air-stable as solids and
do not show a tendency to decompose or oxidise. In ad-
dition, they have quite high solubility in the reaction me-
dium, so the resulting solutions were concentrated in order
to obtain the corresponding solids. Crystals of [Ph2Sn(4-
CF3pymS)2] (2), [Ph2Sn(6-Me-4-CF3pymS)2] (5), [Ph2Pb(4-
CF3pymS)2] (7) and [Ph2Pb(6-Me-4-CF3pymS)2] (8) suit-
able for X-ray studies were obtained by slow evaporation of
the mother liquor at room temperature; [Me2Sn(4-
CF3pymS)2] (1) and [tBu2Sn(6-Me-4-CF3pymS)2] (6) were
obtained by recrystallisation of the initial product from eth-
anol.
Figure 2. Crystal structure of [Ph2Sn(4-CF3pymS)2] (2) (50% prob-
ability displacement ellipsoids).
Scheme 2. General synthesis of the diorganotin(IV) and diphenyllead(IV) complexes.
Eur. J. Inorg. Chem. 2007, 1444–1456
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J. A. García-Vázquez et al.
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lection of bond lengths and angles (with the estimated stan- Table 2. Selected bond lengths [Å] and angles [°] for [Ph2Sn(4-
CF3pymS)2] (2).[a]
dard deviations) are given in the Experimental Section and
Tables 1, 2, 3 and 4, respectively.
Sn(1)–C(6)
Sn(1)–N(1)
N(1)–C(4)
N(2)–C(2)
2.121(2)
2.859(2)
1.321(3)
Sn(1)–S(1)
S(1)–C(1)
N(1)–C(1)
N(2)–C(1)
2.4599(7)
1.734(3)
1.337(3)
1.342(3)
1.321(4)
C(6)–Sn(1)–C(6)#1
C(6)#1–Sn(1)–S(1)
C(6)#1–Sn(1)–S(1)#1 112.86(6)
C(6)–Sn(1)–N(1)#1
S(1)–Sn(1)–N(1)#1
C(6)–Sn(1)–N(1)
S(1)–Sn(1)–N(1)
125.67(13)
105.14(6)
C(6)–Sn(1)–S(1)
C(6)–Sn(1)–S(1)#1
S(1)–Sn(1)–S(1)#1
C(6)#1–Sn(1)–N(1)#1
S(1)#1–Sn(1)–N(1)#1
C(6)#1–Sn(1)–N(1)
S(1)#1–Sn(1)–N(1)
C(4)–N(1)–Sn(1)
112.86(6)
105.14(6)
89.31(3)
86.06(7)
58.78(4)
81.82(7)
147.88(5)
154.86(18)
81.82(7)
147.88(5)
86.06(7)
58.78(4)
153.28(8)
N(1)#1–Sn(1)–N(1)
C–H–X interactions[b]
D–H
H···A
D–A
D–H···A
C(7)#1–H(7)#1···S(1)
C(4)#1–H(4)#1···S(1)
C(4)#1–H(4)#1···N(2)
0.930
0.930
0.930
2.772
3.007
2.929
3.573
3.838
3.807
144.79
149.52
157.94
Figure 3. Crystal structure of [Ph2Sn(6-Me-4-CF3pymS)2] (5) (50%
probability displacement ellipsoids).
[a] Symmetry transformations used to generate equivalent atoms:
#1: –x + 2, y, –z + 1/2. [b] Symmetry code #1: x, –1 + y, z.
Table 3. Selected bond lengths [Å] and angles [°] for [Ph2Sn(6-Me-
4-CF3pymS)2] (5).
Sn(1)–C(13)
Sn(1)–S(2)
Sn(1)–N(2)
S(1)–C(1)
N(1)–C(2)
N(2)–C(4)
N(3)–C(8)
N(4)–C(10)
2.126(3)
2.4665(10) Sn(1)–S(1)
2.801(3)
1.753(4)
1.322(5)
1.328(4)
1.309(6)
1.329(5)
Sn(1)–C(19)
2.128(3)
2.4719(10)
2.837(3)
1.750(4)
1.335(4)
1.341(4)
1.338(5)
1.333(5)
Sn(1)–N(4)
S(2)–C(7)
N(1)–C(1)
N(2)–C(1)
N(3)–C(7)
N(4)–C(7)
Figure 4. Crystal structure of [tBu2Sn(6-Me-4-CF3pymS)2] (6)
C(13)–Sn(1)–C(19)
C(19)–Sn(1)–S(2)
C(19)–Sn(1)–S(1)
C(13)–Sn(1)–N(2)
S(2)–Sn(1)–N(2)
C(13)–Sn(1)–N(4)
S(2)–Sn(1)–N(4)
N(2)–Sn(1)–N(4)
126.76(12)
109.24(9)
107.45(9)
84.73(10)
147.22(6)
79.38(10)
59.00(7)
C(13)–Sn(1)–S(2) 107.90(9)
C(13)–Sn(1)–S(1) 110.91(9)
(50% probability displacement ellipsoids).
S(2)–Sn(1)–S(1)
C(19)–Sn(1)–N(2)
S(1)–Sn(1)–N(2)
C(19)–Sn(1)–N(4)
S(1)–Sn(1)–N(4)
C(4)–N(2)–Sn(1)
87.55(3)
84.11(10)
59.70(6)
88.51(10)
146.38(7)
152.1(2)
Table 1. Selected bond lengths [Å] and angles [°] for [Me2Sn(4-
CF3pymS)2] (1).[a]
Sn(1)–C(6)
Sn(1)–N(2)
N(1)–C(2)
N(2)–C(4)
2.108(4)
2.770(3)
1.327(4)
1.315(5)
Sn(1)–S(1)
S(1)–C(1)
N(1)–C(1)
N(2)–C(1)
2.4836(9)
1.744(3)
1.335(4)
153.45(9)
C–H–X interactions[a]
D–H
H···A
D–A
D–H···A
1.345(5)
C(6)–Sn(1)–C(6)#1
C(6)#1–Sn(1)–S(1)#1 107.02(12)
123.0(2)
C(6)–Sn(1)–S(1)#1
C(6)–Sn(1)–S(1)
S(1)#1–Sn(1)–S(1)
C(6)#1–Sn(1)–N(2)
S(1)–Sn(1)–N(2)
C(6)#1–Sn(1)–N(2)#1
S(1)–Sn(1)–N(2)#1
C(4)–N(2)–Sn(1)
113.87(11)
107.02(12)
86.15(4)
82.66(13)
59.70(6)
85.53(13)
145.02(7)
151.8(3)
C(15)#1–H(15)#1···S(1)
C(6)#2–H(6c)#2···S(2)
0.930
0.960
3.056
2.767
3.952
3.677
162.18
158.48
C(6)#1–Sn(1)–S(1)
C(6)–Sn(1)–N(2)
S(1)#1–Sn(1)–N(2)
C(6)–Sn(1)–N(2)#1
S(1)#1–Sn(1)–N(2)#1
N(2)–Sn(1)–N(2)#1
113.87(11)
85.53(13)
145.02(7)
82.66(13)
59.70(6)
[a] Symmetry codes: #1: –x + 2, –y, 1 – z; #2: x + 0.5, –y + 0.5, z
+ 0.5.
Table 4. Selected bond lengths [Å] and angles [°] for [tBu2Sn(6-Me-
4-CF3pymS)2][a] (6).
155.11(12)
C–H–X interactions[b]
D–H
H···A
D–A
D–H···A
Sn(1)–C(7)
Sn(1)–N(2)
N(1)–C(2)
N(2)–C(4)
C(7)–Sn(1)–C(7)#1
C(7)#1–Sn(1)–S(1)
C(7)#1–Sn(1)–S(1)#1
C(7)–Sn(1)–N(2)
S(1)–Sn(1)–N(2)
N(2)–Sn(1)–N(2)#1
2.216(4) Sn(1)–S(1)
2.978(4) S(1)–C(1)
1.336(6) N(1)–C(1)
1.326(6) N(2)–C(1)
2.4886(12)
1.746(5)
1.342(6)
1.345(6)
106.37(13)
C(3)#2–H(3)#2···S(1)
C(6)–H(6b)···S(1)#3
0.930
0.960
2.991
3.036
3.778
3.984
143.34
169.61
[a] Symmetry transformations used to generate equivalent atoms:
#1: –x + 1, y, –z + 3/2. [b] Symmetry codes: #2: 1.5 – x, –0.5 + y,
1.5 – z; #3: x, –y, 0.5 + z.
131.6(2)
C(7)–Sn(1)–S(1)
109.09(13) C(7)–Sn(1)–S(1)#1 109.09(13)
106.37(13) S(1)–Sn(1)–S(1)#1 84.12(5)
87.31(15) C(7)#1–Sn(1)–N(2) 85.26(15)
57.10(8) S(1)#1–Sn(1)–N(2) 141.05(8)
161.82(15) C(4)–N(2)–Sn(1)
The tin atom in 1, 2 and 6 is located on a twofold rota-
tion axis; accordingly, both methyl, phenyl or tert-butyl
groups and both pyrimidine-2-thionate derivatives are sym-
metry equivalent. The molecular structures of 1, 2, 5 and 6
consist of neutral monomeric units with the tin atom
bonded to two carbon atoms from the alkyl or phenyl
groups and two anionic pyrimidinethionate derivatives,
154.6(3)
C–H–X interactions[b]
D–H
H···A
D–A
D–H···A
C(6)#1–H(6c)#1···S(1)
C(6)#1–H(6b)#1···N(1)
0.960
0.960
3.165
2.955 Å
3.733
3.401
119.54
109.70
[a] Symmetry transformations used to generate equivalent atoms:
which act as chelating ligands through the sulfur atom and #1: –x + 1, y, –z + 1/2. [b] Symmetry code: #1: x, –1 + y, z.
1446 Eur. J. Inorg. Chem. 2007, 1444–1456
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Complexes of Pyrimidine-2-thionates
FULL PAPER
one of the nitrogen atoms. Therefore, this pyrimidinethion- elements (2.42 Å). These values are similar to those found
ate derivative is an example of an unsymmetrical ambident- in other hexacoordinate diorganotin(IV) compounds with
ate ligand whose N,S-bidentate coordination to the tin atom anionic heterocyclic thionate N,S-chelate ligands, which
could generate linkage isomerism depending on which ni- have values in the range 2.4476(10)–2.503(2) Å.[22,42–46] Ex-
trogen atom is involved. In the case under discussion, the amples of such complexes include [Me2Sn(pyS)2]
ligand uses the nitrogen atom with less hindrance (i.e., that [2.487(2) Å],[42] [Ph2Sn(4,6-Me2-2-pymS)2] [2.4476(10)],[44]
in position 1), which is the nitrogen atom farthest from the [(cyclo-C6H11)2Sn(pyS)2] [2.503(2) Å][45] and [Ph2Sn(pyS)2]
trifluoromethyl substituent in the pyrimidine ring. This sug- [2.485(1) Å].[46] The Sn–C bond lengths [2.108(4)–
gests that the nitrogen atom involved in the coordination in 2.216(4) Å] are similar to those found in the complexes
1 and 2 is determined by the steric hindrance introduced by [R2Sn(chelate)2] discussed above, which have values in the
the trifluoromethyl group. In the case of the 6-methyl-4- range 2.046(14)–2.25(1) Å. The Sn–N bond lengths
(trifluoromethyl)pyrimidine-2-thionate ligand, the presence [2.770(3)–2.978(4) Å] are shorter than the sum of the van
of the CF3 group in the 4-position produces greater steric der Waals radii of these elements (3.75 Å)[47] but are rather
hindrance than the methyl group in the 6-position and, longer than those found in other complexes containing Sn–
once again, the heterocyclic ligand in [Ph2Sn(6-Me-4- N bonds {e.g., 2.271(9) and 2.256(9) Å in [Cl2Sn(pyS)2]}.[48]
CF3pymS)2] (5) and [tBu2Sn(6-Me-4-CF3pymS)2] (6) However, the values obtained for 1, 2, 5 and 6 are in the
adopts the same coordination mode as the 4-(trifluorome- range found in the aforementioned [R2Sn(chelate)2] com-
thyl)pyrimidine-2-thionate ligand in 1 and 2. Naturally, plexes [2.639(6)–3.083(3) Å].
other factors, such as crystal packing and inter- and/or in-
Both heterocyclic ligands in complexes 1, 2 and 6 are
tramolecular interactions, can also play a role in the coordi- essentially planar, with the sulfur atoms lying practically in
nation mode of the 4-(trifluoromethyl)pyrimidine-2-thion- the plane of the pyrimidine ring to which they are bonded.
ate ligand.
On the other hand, the tin atom lies out of these planes by
These complexes can be considered to be examples of a 0.265(6) Å for 1 and 0.171(8) Å for 6 and practically in the
hexacoordinate bischelate diorganotin(IV) complex in plane of the pyrimidine ring in 2 [0.064(4) Å]. Each of the
which the environment around the tin atom is highly dis- pyrimidine rings in compound 5 is also planar. However,
torted octahedral. The C–Sn–C bond angle [123.0(2)° for 1, whereas the sulfur and tin atoms are in the plane of the
125.67(13)° for 2, 126.76(12)° for 5 and 131.6(2)° for 6] is pyrimidine ring to which they are bound [deviation of
intermediate between the ideal value for the cis isomer (90°) 0.002 Å for S(1) and 0.028 Å for Sn] for one of these li-
and the trans isomer (180°), a similar situation to that found gands, for the other ligand S(2) (0.094 Å) and Sn (0.228 Å)
in the majority of this type of compounds (122–155°), lie out of the plane of the pyrimidine ring. Moreover, the
which suggests that the geometry of 1, 2, 5 and 6 can be interplanar angle between the pyrimidine rings in 2 is only
described as a distorted trapezoidal bipyramid[39] in which 0.23°. Consequently, 2 has an arrangement similar to that
the equatorial plane is formed by the sulfur and nitrogen found in the complex dimethylbis(pyridine-2-thionato)tin-
atoms (the longest vertices of the trapezium consist of the (IV)[42] but is very different to that in the complexes
two nitrogen atoms and the shortest contain the sulfur dichloridobis(pyridine-2-thionato)tin(IV),[48] in which the
atoms) and the axial positions are occupied by the two planes of the two ligand molecules are almost perpendicu-
methyl groups. Another possibility is to consider the com- lar, and in 1, 5 and 6, where the thionate ligands form a
pound as a bicapped tetrahedron[40,41] defined by the car- dihedral angle [20.2(2)°, 6.89° and 9.09°, respectively] inter-
bon and sulfur atoms, with four tetrahedral angles close mediate between those found in the aforementioned com-
to the ideal value [105.14(6)–113.87(11)°] and two C–Sn–C plexes.
[123.0(2)–131.6(2)°] and S–Sn–S [84.12(5)–89.31(3)°] angles
The S–C [1.734(3)–1.753(4) Å] bond lengths in 1, 2, 5
and 6 are intermediate between the values observed in the
distorted by the influence of the capping atoms.
The Sn–S bond lengths [2.4599(7)–2.4886(12) Å] are free ligands 4,6-dimethylpyrimidine-2-thione[28] and 4,6-di-
slightly longer than the sum of the covalent radii of these methyl-1-phenylpyrimidine-2-thione[27]
[1.692(2)
and
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J. A. García-Vázquez et al.
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1.686(4) Å, respectively], which exist in the thione form in Table 5. Selected bond lengths [Å] and angles [°] for [Ph2Pb(4-
CF3pymS)2] (7).
the solid state, and the values of 1.781(2) and 1.782(3) Å
found in bis(pyrimidyl)-2,2Ј-disulfide[49] and bis(4,6-di-
Pb(1)–C(17)
Pb(1)–S(2)
Pb(1)–N(3)
S(1)–C(1)
N(1)–C(4)
N(2)–C(2)
2.189(11) Pb(1)–C(11)
2.196(11)
2.582(3)
methylpyrimidyl)-2,2Ј-disulfide,[50] which possess a simple
C–S bond; this suggests that the ligand is coordinated in a
form that is closer to the pyrimidine-2-thionate than to the
thione form.
2.577(3)
2.824(9)
Pb(1)–S(1)
Pb(1)–N(1)
2.986(10)
1.732(11)
1.346(13)
1.352(13)
1.362(13)
1.336(15)
1.730(11) S(2)–C(6)
1.309(16) N(1)–C(1)
1.309(14) N(2)–C(1)
1.360(16) N(3)–C(6)
1.332(13) N(4)–C(7)
N(3)–C(9)
N(4)–C(6)
C(17)–Pb(1)–C(11)
C(11)–Pb(1)–S(2)
C(11)–Pb(1)–S(1)
C(17)–Pb(1)–N(3)
S(2)–Pb(1)–N(3)
C(17)–Pb(1)–N(1)
S(2)–Pb(1)–N(1)
N(3)–Pb(1)–N(1)
142.8(4)
C(17)–Pb(1)–S(2) 104.0(3)
C(17)–Pb(1)–S(1) 104.1(3)
Molecular Structures of [Ph2Pb(4-CF3pymS)2] (7) and
[Ph2Pb(6-Me-4-CF3pymS)2] (8)
104.6(3)
102.2(3)
89.7(3)
57.86(19)
85.0(3)
S(2)–Pb(1)–S(1)
C(11)–Pb(1)–N(3)
S(1)–Pb(1)–N(3)
C(11)–Pb(1)–N(1)
S(1)–Pb(1)–N(1)
C(4)–N(1)–Pb(1)
83.96(10)
85.7(3)
141.65(19)
88.2(3)
56.38(19)
154.4(9)
The molecular structures of 7 and 8 are shown in Fig-
ure 5 and Figure 6, respectively, together with the atom
labelling scheme adopted. Crystallographic data and se-
lected bond lengths and angles are given in the Experimen-
tal Section and Tables 5 and 6, respectively.
140.23(19)
161.9(2)
C–H–X interactions[a]
D–H
H···A
D–A
D–H···A
C(16)#1–H(16)#1···S(1)
C(22)#1–H(22)#1···S(1)
C(4)#1–H(4)#1···S(1)
C(9)#1–H(9)#1···S(2)
C(4)#1–H(4)#1···N(2)
C(9)#1–H(9)#1···N(4)
0.930
0.930
0.930
0.930
0.930
0.930
2.778
2.785
2.964
3.081
2.711
2.639
3.694
3.704
3.753
3.847
3.598
3.543
168.38°
169.80°
143.65°
140.79°
159.66°
164.16°
[a] Symmetry code: #1: x, y + 1, z.
Table 6. Selected bond lengths [Å] and angles [°] for [Ph2Pb(6-Me-
4-CF3pymS)2] (8).
Pb(1)–C(13)
Pb(1)–S(2)
Pb(1)–N(3)
S(1)–C(1)
2.187(5)
2.5722(1) Pb(1)–S(1)
2.865(5)
1.748(6)
Pb(1)–C(19)
2.190(5)
2.5723(1)
2.909(4)
Pb(1)–N(1)
S(2)–C(7)
1.747(6)
Figure 5. Crystal structure of [Ph2Pb(4-CF3pymS)2] (7) (50% prob-
ability displacement ellipsoids).
N(1)–C(1)
N(2)–C(4)
1.338(6)
1.331(7)
N(1)–C(2)
N(2)–C(1)
1.346(6)
1.343(6)
N(3)–C(8)
1.337(7)
N(3)–C(7)
1.341(6)
N(4)–C(10)
1.333(8)
N(4)–C(7)
1.337(6)
C(13)–Pb(1)–C(19)
C(19)–Pb(1)–S(2)
C(19)–Pb(1)–S(1)
C(13)–Pb(1)–N(3)
S(2)–Pb(1)–N(3)
C(13)–Pb(1)–N(1)
S(2)–Pb(1)–N(1)
N(3)–Pb(1)–N(1)
134.59(19)
105.48(14)
108.76(14)
90.06(15)
57.72(10)
86.88(14)
144.84(10)
156.65(13)
C(13)–Pb(1)–S(2)
C(13)–Pb(1)–S(1)
S(2)–Pb(1)–S(1)
C(19)–Pb(1)–N(3)
S(1)–Pb(1)–N(3)
C(19)–Pb(1)–N(1)
S(1)–Pb(1)–N(1)
C(2)–N(1)–Pb(1)
106.99(13)
103.46(13)
87.66(5)
81.31(16)
145.31(10)
84.43(15)
57.41(10)
151.7(4)
C–H–X interactions[a]
D–H
H···A
D–A
D–H···A
C(23)#1–H(23)#1···S(1)
C(6)#2–H(6c)#2···S(2)
0.930
0.960
2.993
2.914
3.877
3.755
159.47
146.89
[a] Symmetry codes: #1: –x + 2, –y, –z + 2; #2: x + 0.5, –y + 0.5,
z + 0.5.
Figure 6. Crystal structure of [Ph2Pb(6-Me-4-CF3pymS)2] (8) (50%
probability displacement ellipsoids).
The complexes [Ph2Pb(4-CF3pymS)2] (7) and [Ph2Pb(6-
The structures determined for these complexes are, as far Me-4-CF3pymS)2] (8) consist of neutral monomeric mole-
as we know, the first examples of lead(IV) complexes con- cules in which the lead atoms are coordinated by two
taining heterocyclic thione ligands, such as pyridine-2- monoanionic thionate ligands and two phenyl groups. The
thione or pyrimidine-2-thione. The only previously reported thionate ligands are coordinated to the lead through their
structures containing lead and this type of ligand are the sulfur atoms and, more weakly, to one of the nitrogen
mononuclear complex [Pb(3-CF3pyS)2][9] and trinuclear atoms of each ligand, in such a way that each thionate li-
complex [Pb3(3-Me3SipyS)6].[51] In both cases the lead atom gand acts a bidentate chelate system (κ2-N,S). In this way,
is in the oxidation state (II). This situation precludes a di- the coordination number for the lead atom is six and the
rect comparison involving the structural parameters of the environment around this metal atom can be described as
compounds reported here.
being similar to the analogous tin(IV) complexes 2 and 5,
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Complexes of Pyrimidine-2-thionates
FULL PAPER
i.e., a skewed trapezoidal bipyramid or a bicapped tetrahe- to be classified into three groups: (1) interactions that prop-
dron. The C–Pd–C bond angles are 142.8(4) Å for 7 and agate in a direction that gives rise to chains that interact
134.59(19) Å for 8, which are larger than those found in the weakly with one another; (2) bidimensional interactions
diorganotin(IV) complexes previously described. In ad- that give rise to layers that interact weakly with one an-
dition, in 7 and 8 the heterocyclic ligands adopt, for the other; (3) interactions that are similar in intensity in all
same reasons, the same coordination mode as in the tin three dimensions.
complexes mentioned previously.
Compounds with Crystal Packing in Chains
The Pb–S bond lengths, 2.577(3) and 2.582(3) Å for 7
and 2.5722(14) and 2.5723(15) Å for 8, are close to those
found in diorganolead(II) tetracoordinate with thiolate li-
gands; 2.489(6) Å in [Ph3PbSMe][52] or 2.523(5) and
2.580(4) Å in [(Ph3Pb)2(dmit)],[53] where H2dmit is 4,5-di-
mercapto-1,3-dithio-2-thione. However, the values found in
7 and 8 are lower than those found in the hexacoordinate
The crystal packing arrangements in [Ph2Sn(4-
CF3pymS)2] (2), [tBu2Sn(6-Me-4-CF3pymS)2] (6) and
[Ph2Pb(4-CF3pymS)2] (7) can be described as chains paral-
lel to the crystallographic b axis. The pyrimidine rings and
the metal atoms are located approximately in the same
plane throughout each of the chains. This arrangement is
the result of weak C–H···X interactions that propagate
along this direction. In 2 and 7, this arrangement consists
of two C–H···S[58,59] interactions between two C–H groups
from the phenyl rings and the same sulfur atom of one of
the pyrimidine-2-thionate ligands (7; see Figure 7) or with
a sulfur atom of a different pyrimidine-2-thionate ligand
(2). This situation is reflected in the angle between the pla-
nes of the phenyl rings, which is 19.63(80)° for 7 and
58.96(10)° for 2. At the same time, and in the same direc-
tion, C–H···N[60,61] interactions are established between the
uncoordinated nitrogen atom and the symmetry equivalent
C–H para to this nitrogen (see Figure 7).
thiolate
{Ph2Pb[S2P(OCH2Ph)2]2},[54]
2.679(6)
and
2.957(6) Å. The Pb–N bond lengths, 2.824(9) and
2.986(10) Å for 7 and 2.865(5) and 2.909(4) Å for 8, are
much longer than the sum of the corresponding covalent
radii for lead (1.600 Å) and nitrogen (0.700 Å) and also
longer than those found in other hexacoordinate dior-
ganolead(IV) complexes containing a Pb–N bond; for ex-
ample, 2.498(7) and 2.461(7) Å in [Ph2PbCl2(imidazole)
2].[55] The fact that these distances are shorter than the sum
of the van der Waals radii (3.82 Å) suggests that the Pb···N
bonds in complexes 7 and 8 are significantly weaker than a
normal intermolecular Pb–N bond, a situation similar to
that observed in organotin complexes discussed above.
The phenyl and pyrimidine rings are planar [maximum
deviation 0.010(3) Å]. The interplanar angle between the
pyrimidine rings is only 4.75° in 7 and 3.76(3)° in 8 whereas
the rings of the phenyl groups have interplanar angles of
19.63(8)° and 76.04(2)°, respectively. In compound 7, the
sulfur and lead atoms lie approximately in the plane of the
pyrimidine ring to which they are bound. However, in 8 the
sulfur atoms are approximately in the plane of the pyrimi-
dine rings to which they are bound; 0.038(6) Å for S(1) and
0.067(7) Å for S(2). The lead atom is also practically in the
plane of the pyrimidine to which S(1) is bonded [0.055(8) Å]
but is out of the plane of the pyrimidine ring to which S(2)
is attached [0.296(9) Å].
The average length of the S–C bond, 1.731(11) Å, is sim-
ilar to that found in other complexes with pyrimidine-2-
thionate derivatives, a fact that suggests that this ligand is
coordinated in a form that is closer to the thionate than the
thione.
Figure 7. The crystal packing in 7. Dashed lines show the C–H···S
and the C–H···N interactions.
The crystal network of [tBu2Sn(6-Me-4-CF3pymS)2] (6)
contains the same type of chain along the crystallographic
b axis, with weak C–H···N and C–H···S interactions similar
Crystal Packing and Intermolecular Interactions in 1, 2 and
5–8
The crystal packing in compounds 1, 2 and 5–8 is mainly to those in the two previous cases, although in this case the
dictated by C–H···X hydrogen-bonding interactions be- C–H donor is the methyl group para to the uncoordinated
tween different C–H groups and the sulfur and nitrogen nitrogen atom.
atoms of the pyrimidine-2-thionate ligands that are not co-
ordinated, as well as interactions involving the CF3 groups interactions with neighbouring chains in such a way that
(see Tables 1–6).[56,57]
the planes of the pyrimidine rings along the chain are paral-
In all three cases each of the chains is involved in weak
The way in which these C–H···X interactions propagate lel to one another in the resulting crystal packing. These
in space enables the crystal structures of these compounds inter-chain interactions can be classified into two types:
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J. A. García-Vázquez et al.
FULL PAPER
those that involve the phenyl (complexes 2 and 7) or tert-
butyl (complex 6), which are established with other chains
located above and below the plane of the pyrimidine-2-
thionate ligands, and those that involve CF3 groups.[56,57]
These CF3 groups are located near to other trifluoromethyl
groups in all three cases, a situation that is usual for this
type of group.
Compounds with Crystal Packing in Layers
The only compound reported here that shows this type
of packing is [Me2Sn(4-CF3pymS)2] (1). Each pyrimidine-
2-thionate ligand in this compound establishes two C–H···S
interactions between the thionate groups and the C–H
groups para to the sulfur atoms, as shown in Figure 8. The
propagation of these interactions gives rise to layers of
molecules parallel to the crystallographic AB plane. Within
these layers the CF3 groups are located very close to other
CF3 groups in such a way that F···F interactions are also
formed within each layer; these interactions are not shown
in Figure 8.
Figure 9. The crystal packing in 8. Dashed lines show the C–H···S
and the π-π stacking interactions.
3.843 Å from lead. As in the previously discussed com-
plexes, the CF3 groups are located very close to other CF3
groups in such a way that F···F interactions are estab-
lished.[56,57]
Figure 8. The crystal packing in 1. Dashed lines show the C–H···S
interactions.
Spectroscopic Studies
IR Spectroscopy
The layers that are parallel to the AB planes interact
weakly with one another through C–H···S[58,59] interactions
between the methyl groups above and below the layers and
the sulfur atoms of the pyrimidine-2-thionate ligands in
neighbouring layers.
The IR spectra of the complexes (see the Experimental
Section) show that the ν(N–H) bands of the free pyrimi-
dine-2-thione ligands, which appear between 3200–
3050 cm–1, are absent from the thionate complexes. This in-
dicates that deprotonation of the thionate group has oc-
curred and therefore that the pyrimidine-2-thione is coordi-
nated in the thionate form. This conclusion is supported
by the shift to lower wavenumbers (1580–1550 cm–1 in the
complexes) of the strong bands due to ν(C=C) and ν(C=N),
which appear at 1650–1550 cm–1 in the free ligands. The
spectra of the complexes also show bands due to the ring
breathing vibration in the regions 1110–990 cm–1 and 750–
620 cm–1, which are at higher wavenumbers than the corre-
sponding bands in the free ligands. These shifts provide evi-
dence for coordination of the ligands through the nitrogen
atom.[62] The spectra of the methyl and tert-butyl deriva-
tives also show additional medium intensity bands at 3100–
2900 cm–1, which correspond to the vibrations of the methyl
groups.
Compounds with Three-Dimensional Crystal Packing
The compounds [Ph2Sn(6-Me-4-CF3pymS)2] (5) and
[Ph2Pb(6-Me-4-CF3pymS)2] (8) are isomorphous and have
identical crystal packing arrangements as a result of inter-
actions of similar strength in three directions in space. The
interactions responsible for the packing in these compounds
are also C–H···S[58,59] interactions, and each of the thionate
groups in the complex is involved in interactions with dif-
ferent C–H groups of other neighbouring complex mole-
cules, as shown in Figure 9.
The S(1) sulfur atom establishes one of these interactions
with a C–H group of one of the phenyl rings, while the S(2)
sulfur establishes an interaction with a methyl group of a
pyrimidine-2-thionate ligand of a neighbouring complex.
There is another type of interaction in addition to the
C–H···S interactions, which involves π-π stacking between
the phenyl ring not involved in C–H···S interactions and a
NMR Spectra
The main change in the 1H NMR spectra of the thionate
symmetry equivalent centre of the pyrimidine ring con- complexes brought about by complexation is the disappear-
nected to sulfur S(1). This interaction, which is relatively ance of the broad signal due to the N–H proton; this con-
weak, is of the “parallel displaced” type and the centroids firms that the ligand is in the deprotonated thionate form
of the two rings are separated by 3.920 Å from tin and in the complexes.
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Complexes of Pyrimidine-2-thionates
FULL PAPER
The 1H NMR spectra of the complexes show, in addition exhibit signals at δ = –70.3 ppm for 1 and δ = –86.4 ppm
to the signals corresponding to the protons on the heterocy- for 4. These values are within the range reported for other
clic thionate ligand, signals due to the methyl, tert-butyl complexes of diphenyl- or dimethyltin(IV) with pyrimidine
and phenyl groups of the organometallic fragments. The or pyrimidine-2-thionate ligands with the same coordina-
spectra of the dimethyltin(IV) derivatives also contain a sig- tion number.[22,47,65] In the spectra of the tBu2Sn deriva-
nal at high field (δ = 1.1 ppm), which is attributed to the tives, the values of the 119Sn chemical shift are δ =
protons on the methyl groups of the Me2Sn fragment. –32.1 ppm for 3 and δ = –4.8 ppm for 6. These seem to
These signals are accompanied by satellite peaks due to indicate that the complexes have a lower coordination
coupling of the proton with 119Sn and 117Sn nuclei. The number (tetracoordination) in CDCl3 solution than in the
2J1H,119Sn and 2J1H,117Sn coupling constants are 74 and 72 Hz, solid state.[66] This change can be explained in terms of the
respectively, and these values are similar to those found in breakdown of Sn–N interactions in solution, with these
other compounds containing the Me2Sn fragment.[22,63] bonds in 6 (obtained from X-ray crystallography) being
2
These J coupling constant values can be used to estimate longer than the others presented in this work.
the Me–Sn–Me angle.[64] The values calculated for these
The 207Pb NMR spectra of diphenyllead(IV) complexes
angles are 123.9° and 121.8° for 1 and 4, respectively, and were recorded at room temperature in CDCl3 using PbMe4
are very similar to one another and also to that found in as an external standard. The 207Pb chemical shift seems to
the solid state for 1 by X-ray diffraction. This suggests that be particularly sensitive to the electronic environment and
the structures of both compounds in solution are the same is therefore an excellent tool for the study of changes in
as that determined in the solid state for compound 1.
coordination number.[67] The 207Pb spectra contain a single
The 1H NMR spectra of the tBu2Sn derivatives each con- peak at around δ = –199.0 ppm for 7 and δ = –206.7 ppm
tain a singlet at around δ = 1.50 ppm due to the tert-butyl for 8. These values suggest that both complexes of di-
protons. Once more, the corresponding satellite peaks can phenyllead(IV) have the same coordination number in
3
3
be observed. The J1H,119 and J1H,117 coupling constants CDCl3 solution (probably hexacoordinate as in the solid
Sn
Sn
1
in these cases are 52 and 50 Hz, respectively. The H NMR state).
spectra of the Ph2Sn and Ph2Pb derivatives contain peaks
Mass Spectra
attributable to the aromatic protons. Two groups of signals
can be observed. The first is at δ = 7.8 ppm and is due to
The tin and lead complexes were also characterised by
the protons ortho to the Sn atom. The second group ap- mass spectrometry using the positive ion FAB technique in
pears at δ = 7.4 ppm and it is attributable to the other ring 3-nitrobenzyl alcohol (NBA) as matrix. The FAB spectra of
protons. The signals in the first group, in the case of the dimethyl- and di-tert-butyltin with 4-CF3pymS and dimeth-
Ph2Sn derivatives, show satellite signals due to 1H-119Sn yltin with 6-Me-4-CF3pymS show the molecular ion peak
3
coupling. In these cases, the J1H,119 values are close to with the appropriate isotope distribution (m/z 508, 592 and
Sn
75 Hz.
536, respectively). In these cases, peaks were also observed
The 13C NMR spectrum of the free ligand 6-Me-4- due to the fragments produced by the loss of one thionate
CF3pymSH contains twice the expected number of signals ligand (m/z 328, 412 and 342, respectively) or one of these
for C(2), C(6), CF3 and CH3 as the free ligand exists in two ligands and the two alkyl groups. The spectra of the other
tautomeric forms. This doubling in the number of signals is tin complexes do not show the molecular ion peaks but do
not observed in the 13C NMR spectra of the metal com- show peaks associated with loss of one phenyl group [m/z
plexes. This situation provides evidence that the ligand is 555 for PhSn(4-CF3pymS)2 and 582 for PhSn(6-Me-4-
coordinated to the metal only in the thionate form in solu- CF3pymS)2] or one thionate ligand [m/z 453 for Ph2Sn(4-
tion. The 13C NMR spectra of the other complexes that CF3pymS), 467 for Ph2Sn(6-Me-4-CF3pymS) and 427 for
were sufficiently soluble in CDCl3 show, in addition to the tBu2Sn(4-CF3pymS)2].
expected signals for the thionate ligand, signals attributable
The FAB mass spectrum of [Ph2Pb(4-CF3pymS)2] shows
to the methyl group (δ = 6.5–5.5 ppm), phenyl group (δ = the molecular ion peak at m/z = 720. In this compound,
122–140 ppm) and quaternary and primary carbon atoms and also in the other lead compound, peaks corresponding
from the tBu groups (δ = 30–40 ppm) in the organometallic to fragments of the parent ions due to loss of different
fragment.
groups from the compounds are observed. For example,
The 119Sn NMR spectra of these complexes were re- peaks are observed at m/z 540 for 7 and 555 for 8 and these
corded at room temperature in CDCl3 using SnMe4 as an are associated with Ph2Pb(RpymS) formed by loss of one
external standard. The 119Sn chemical shifts seem to depend thionate ligand. Peaks due to the fragments produced by
more on the nature of the alkyl or aryl groups bonded to the loss of two phenyl groups and one thionate ligand (m/z
the tin atom than on the pyrimidine ligand. Indeed, it ap- 386 when R = CF3 and 400 when R = 6-Me-4-CF3) are
pears that these groups do not have a significant effect on also seen.
the shielding or deshielding of the tin nucleus. Whereas the
Mössbauer Spectra
119Sn chemical shift for the diphenyltin(IV) derivatives ap-
pears at δ = –201.0 ppm for 2 and δ = –179.3 ppm for 5,
As expected from their chemical formulae, the Möss-
the compounds containing alkyl groups show less negative bauer spectra of the reported compounds show only a sin-
119Sn chemical shifts. For example, the Me2Sn derivatives gle, slightly asymmetric, quadrupole split doublet (Table 7).
Eur. J. Inorg. Chem. 2007, 1444–1456
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J. A. García-Vázquez et al.
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The linewidths are narrow enough to rule out any doublet dine-2-thione and 6-methyl-4-(trifluoromethyl)pyrimidine-
overlap, which implies the existence of just a single tin site 2-thione in methanol in the presence of triethylamine.
in each complex. The isomer shift values are rather surpris-
The structures of the diorganotin(IV) and diphenyllead-
ing as they are grouped around two values, both of which (IV) compounds have been investigated and the coordina-
are typical for SnR2 derivatives (1.49 and 1.87 mms–1), in tion polyhedron of the metal atom can be described either
an unexpected way. In fact, the inductive effects of the or- as a distorted skew-trapezoid or a bicapped tetrahedron,
ganic groups would lead to increasing values in the order with the heterocyclic thionate acting in a bidentate (κ2-N,S)
Ph ϾϾ Me Ͼ Bu, and so the only explanation must lie in manner. In these arrangements the ligands are unsymmetri-
different geometrical distortions or in varying Sn–N bond cal ambidentate and therefore the N,S-bidentate coordina-
lengths. A closer analysis of Tables 2, 3, 4, and 5 shows that tion to the metallic atom could generate linkage isomerism
the average Sn–N bond length for compounds 1, 2, and 5, through one of the two nitrogen atoms. Only one coordina-
which have the lowest isomer shift values, is tion mode is found in these complexes and this involves the
2.817Ϯ0.039 Å, clearly shorter than that of compound 6 sulfur atom and the less hindered nitrogen atom, which is
[2.978(4) Å]. This value, even though significantly shorter farthest from the group with the highest level of steric hin-
than the sum of the van der Waals radii of these atoms drance in the heterocyclic rings; in both cases this is the
(3.75 Å), indicates that the two Sn–N bonds are rather weak trifluoromethyl group. Furthermore, it is worth noting that
and so the coordination geometry around the tin centre has the R groups (methyl, tert-butyl or phenyl) of the R2M moi-
a considerable fourfold character. This increases the s-elec- ety do not markedly influence the structure of the complex.
tron density at the tin nucleus and so leads to a larger iso-
mer shift. Moreover, the presence of a methyl group in the
Experimental Section
ligand does not affect the electron density on the tin atom,
as expected. The quadrupole splitting values are also very
close to each other and quite low, close to values typical for
cis-SnR2 derivatives (1.7–2.2 mms–1).
General: 4-(Trifluoromethyl)pyrimidine-2-thione, 1,1,1-trifluoro-
2,4-pentanedione, thiourea, triethylamine, dimethyltin(IV) dichlo-
ride, diphenyltin(IV) dichloride, bis(tert-butyl)tin dichloride and di-
phenyllead(IV) dichloride were obtained commercially and used as
supplied.
Table 7. Mössbauer parameters collected at 80 K. The δ values are
quoted relative to SnO2 at room temperature.
Elemental analysis was performed with a Carlo–Erba EA micro-
analyser. IR spectra were recorded as KBr mulls with a Bruker
IFS-66V spectrophotometer. 1H and 13C NMR spectra were re-
corded with a Bruker AMX 300 MHz instrument using CDCl3 or
[D6]DMSO as solvent. Chemical shifts are quoted relative to TMS
as the internal standard. 119Sn and 207Pb NMR spectra were re-
corded with a Bruker AMX500 spectrometer in CHCl3 as solvent
using SnMe4 and PbMe4 as an external standard, respectively. The
Mössbauer spectra were recorded at T = 80 K in a constant acceler-
ation apparatus and are referenced to SnO2. The mass spectra
(FAB) were recorded with a Micromass Autospec spectrometer,
with 3-nitrobenzyl alcohol as the matrix material.
δ
∆EQ
Γ
Γ2/Γ1
[mms–1
]
[mms–1
]
[mms–1
]
[Me2Sn(4-CF3pymS)2] (1)
[Ph2Sn(4-CF3pymS)2] (2)
[tBu2Sn(4-CF3pymS)2] (3)
[Ph2Sn(6-Me-4-CF3pymS)2] (5)
[tBu2Sn(6-Me-4-CF3pymS)2] (6)
1.49
1.49
1.87
1.49
1.87
2.46
2.68
2.74
2.54
2.70
0.87
0.87
0.86
0.85
0.92
0.91
0.97
0.96
1.03
0.93
Point charge calculations performed by ignoring the in-
fluence of the pymS ligand on the electron density around
the tin atoms, but taking into account only the experimental
C–Sn–C bond angles, afforded values that were too high
(2.83–3.14 mms–1) and strongly dependent on the input val-
ues. In fact, the C–Sn–C bond angles [123.0–131.6°] are in-
termediate between the ideal values for the cis (90°) and for
the trans isomer (180°), a situation similar to that found in
the majority of this type of compounds (122–155°). The
coordination geometry for these compounds can, in fact, be
described as a distorted trapezoidal bipyramid[39] in which
the equatorial plane is formed by the sulfur and nitrogen
atoms, or as a bicapped tetrahedron. These results point to
the inability of the point charge method to reproduce the
Mössbauer quadrupole splitting in the case of severely dis-
torted structures.
Synthesis of 6-Me-4-CF3pymSH: This compound was obtained by
direct reaction between thiourea (2.428 g, 32 mmol) and 1,1,1-tri-
fluoro-2,4-pentanedione (5 g, 32 mmol) in ethanol in the presence
of concentrated hydrochloric acid (1 mL) as a catalyst. The mixture
was heated under reflux for 2 h and the resulting dusty yellow solid
was filtered off. C6H5F3N2S: calcd. C 37.11, H 2.60, N 14.43, S
16.51; found C 36.39, H 2.60, N 14.26, S 16.38. IR (KBr): ν =
˜
3100–3200 cm–1 m, br, 1615 vs, 1590 vs, 1440 m, 1350 vs, 1320 w,
1200 s, br, 1130 m, 1100 m, 1030 w, 970 s, 920 m, 860 w, 850 m,
705 w, 660 w, 595 w, 570 w, 530 m, 510 w, 470 m, 450 m, 370 w. 1H
NMR ([D6]DMSO): δ = 14.40 (s, 1 H, NH), 7.19 (s, 1 H, H-5),
2.39 (s, 3 H, CH3) ppm. 13C NMR ([D6]DMSO): δ = 181.00 and
172.13 (s, C-2), 155.86 and 153.72 (q, 2J
(s, C-5), 163.61 (s, C-6), 119.27 and 119.67 (q, J
F = 35 Hz, C-4), 104.89
13C,19
1
13C,19
F
= 275 Hz,
CF3), 23.45 and 18.46 (s, CH3). MS (FAB): m/z (%) 194 (27) [6-
Me-4-CF3pymSH].
Conclusions
Synthesis of [Me2Sn(4-CF3pymS)2] (1): Triethylamine (0.128 mL,
0.700 mmol) was added by syringe to a solution of 4-CF3pymSH
(0.150 g, 0.832 mmol) in methanol (50 mL) and the resulting solu-
tion was stirred for 1 h at room temperature. A solution of dimeth-
yltin dichloride (0.091 g, 0.414 mmol) in methanol (15 mL) was
The work described here involves the synthesis and struc-
tural characterisation of a series of compounds obtained by
the reaction of the appropriate diorganotin(IV) and di-
phenyllead(IV) dichlorides with 4-(trifluoromethyl)pyrimi- then added and the mixture was heated under reflux for about
1452 Eur. J. Inorg. Chem. 2007, 1444–1456
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© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Complexes of Pyrimidine-2-thionates
FULL PAPER
2.5 h. The solution was filtered and slow evaporation of the solvent
gave rise to a cream-coloured solid, which was recrystallised from
1H NMR (CDCl3): δ = 7.14 (s, 1 H, H-5), 2.55 (s, 3 H, H-8), 1.08
(s, 3 H, CH3) ppm. 13C NMR (CDCl3): δ = 176.6 (s, C2), 155 (q,
ethanol to give yellow crystals suitable for X-ray studies. Yield: C4), 110.6 (s, C5), 171 (s, C6), 120 (q, C7) 24.84 (s, C8), 5.79 ppm
0.099 g (47%). C12H10F6N4S2Sn (507.04): calcd. C 28.43, H 1.99, (s, Me). 119Sn NMR (CDCl3): δ = –86.4 ppm. MS (FAB): m/z (%)
N 11.05, S 12.65; found C 28.44, H 1.65, N 11.03, S 12.71. IR
536 (19) [Me2Sn(6-Me-4-CF3pymS)2], 342 (100) [Me2Sn(6-Me-4-
CF3pymS)].
(KBr): ν = 3050 cm–1 w, 1550 s, 1420 m, 1340 vs, 1325 vs, 1200 s,
˜
1160 vs, br, 1110 s, 980 w, 840 sh, 830 s, 780 m, 730 m, 665 m, 555
Synthesis of [Ph2Sn(6-Me-4-CF3pymS)2] (5): A solution containing
diphenyltin dichloride (0.150 g, 0.436 mmol), 6-methyl-4-(trifluoro-
methyl)pyrimidine-2-thione (0.140 g, 0.721 mmol) and triethyl-
amine (0.110 g, 0.400 mmol) in methanol (30 mL) was heated un-
der reflux for 3 h. It was then evaporated to give white, needle-like
crystals that were suitable for X-ray studies. Yield: 0.139 g (52%).
C24H18F6N4S2Sn (659.23): calcd. C 43.73, H 2.75, N 8.50, S 9.73;
w, 520 w, 460 w, 355 w, 320 w. 1H NMR (CDCl3): δ = 8.7 (d, 3JH,H
3
= 4.9 Hz, 1 H, H-6), 7.3 (d, JH,H = 4.9 Hz, 1 H, H-5), 1.1 (s, 3 H,
CH3) ppm. 13C NMR (CDCl3): δ = 175 (s, C2), 160 (s, C6), 150 (q,
C4), 120 (q, C7), 115 (s, C5), 5.4 ppm (s, Me). 119Sn NMR (CDCl3):
δ = –70.29 ppm. MS (FAB): m/z (%) 508 (12) [Me2Sn(4-CF3-
pymS)2], 328 (100) [Me2Sn(4-CF3pymS)].
found C 43.12, H 2.49, N 8.38, S 9.62. IR (KBr): ν = 3080 cm–1 w,
˜
Synthesis of [Ph2Sn(4-CF3pymS)2] (2): The same procedure as for
1 was used for the synthesis of the diphenyltin derivative. A solu-
tion of Ph2SnCl2 (0.142 g, 0.413 mmol), 4-CF3pymSH (0.150 g,
0.832 mmol) and NEt3 (0.128 mL, 0.700 mmol) in methanol
(40 mL) was heated under reflux for 3 h. This solution was concen-
trated to give single crystals suitable for X-ray studies. Yield:
0.193 g (74%). C22H14F6N4S2Sn (631.18): calcd. C 41.86, H 2.24,
N 8.88, S 10.16; found C 42.31, H 2.30, N 8.21, S 10.12. IR (KBr):
1575 s, 1530 s, 1470 w, 1440 w, 1425 m, 1385 s, 1360 m, 1305 vw,
1265 vs, 1250 w, 1220 m, 1190 m, 1170 m, 1135 s, 1110 m, 1070 vw,
995 w, 980 vw, 920 w, 845 s, 730 m, 710 s, 690 m, 545 w, 460 w,
440 m. 1H NMR (CDCl3): δ = 7.85 (m, ortho-phenyl), 7.3 (m,
phenyl) 7.15 (s, 1 H, H-5), 2.5 (s, 3 H, H-8) ppm. 13C NMR
(CDCl3): δ = 173.3 (s, C2), 156.0 (q, C4), 141.5–122.4 (phenyl car-
bons), 112.2 (s, C5), 170.0 (s, C6), 120 (q, C7), 24.13 ppm (s, C8).
119Sn NMR (CDCl3): δ = –179.3 ppm. MS (FAB): m/z (%) 582 (12)
[PhSn(6-Me-4-CF3pymS)2], 467 (52) [Ph2Sn(6-Me-4-CF3pymS)],
312 (15) [Sn(4-Me-6-CF3pymS)].
ν = 3040 cm–1 w, 1550 vs, 1470 m, 1420 s, 1330 vs, br, 1200 s,
˜
1140 m, 1110 m, 1060 w, 1015 w, 990 w, 975 w, 960 vw, 910 w, 830
s, 780 vw, 720 s, 690 m, 665 s, 460 w, 440 m, 355 m, 320 m. 1H
3
Synthesis of [tBu2Sn(6-Me-4-CF3pymS)2] (6): The same procedure
as for 4 was used for the synthesis of the di-tert-butyltin derivative.
A solution of 6-Me-4-CF3pymSH (0.150 g, 0.772 mmol) in meth-
anol (50 mL) was added to a solution containing di-tert-butyltin
dichloride (0.140 g, 0.461 mmol) and NEt3 (0.110 g, 0.700 mmol)
in methanol (15 mL) and the mixture was stirred and heated under
reflux for 4 h. It was then filtered and evaporated to give a white
crystalline solid (0.136 g, 57%). Crystallisation from ethanol gave
single crystals that were suitable for X-ray studies. C20H26F6N4S2Sn
(619.26): calcd. C 38.79, H 4.23, N 9.05, S 10.35; found C 38.76,
NMR (CDCl3): δ = 8.38 (d, JH,H = 5.1 Hz, 1 H, H-6), 7.8 (br,
3
phenyl H) and 7.4 (br, phenyl H), 7.08 (d, JH,H = 5.1 Hz, 1 H, H-
5) ppm. 13C NMR (CDCl3): δ = 129–135 ppm (aromatic carbons).
NO other signals could be detected due to the poor solubility of
this complex. 119Sn NMR (CDCl3): δ = –201 ppm. MS (FAB): m/z
(%) 554.8 (12) [PhSn(4-CF3pymS)2], 452.9, (54) [Ph2Sn(4-
CF3pymS)], 298.8 (7) [Sn(4-CF3pymS)].
Synthesis of [tBu2Sn(4-CF3pymS)2] (3): A solution of tBu2SnCl2
(0.126 g, 0.414 mmol) in methanol was added to a solution of 4-
CF3pymSH (0.150 g, 0.832 mmol) and NEt3 (0.128 mL,
0.421 mmol) in methanol (30 mL) and the reaction mixture was
stirred and heated under reflux for 3 h. The resulting solution was
slowly evaporated at room temperature to give colourless crystals
suitable for X-ray studies. Yield: 0.175 g (74%). C18H22F6N4S2Sn
(591.20): calcd. C 36.57, H 3.75, N 9.48, S 10.85; found C 36.74,
H 4.11, N 8.98, S 10.08. IR (KBr): ν = 3060 cm–1 w, 2980 m, 2940
˜
w, 2840 m, 1570 s, 1530 s, 1450 m, 1430 w, 1390 vs, 1355 w, 1305 m,
1260 vs, br, 1220 m, 1175 m, 1150 vs, br, 1100 w, 1010 w, 970 m,
920 m, 840 s, 800 vw, 780 vw, 655 s, 575 w, 550 m, 480 vw, 450 w.
1H NMR (CDCl3): δ = 7.13 (s, 1 H, H-5), 2.56 (s, 3 H, H-8), 1.49
(s, 9 H, CH3) ppm. 13C NMR (CDCl3): δ = 176 (s, C2), 170.2 (s,
C6), 112.07 (s, C5), 25.02 (s, C8), 46 [s, C(CH3)3], 31.82 ppm [s,
C(CH3)3]. 119Sn NMR (CDCl3): δ = –4.78 ppm. MS (FAB): m/z
(%) 506.9 (13) [Sn(6-Me-4-CF3pymS)2], 427.0 (72) [tBu2Sn(6-Me-
4-CF3pymS)], 312.9 (100) [Sn(6-Me-4-CF3pymS)].
H 3.14, N 9.50, S 10.96. IR (KBr): ν = 3050 cm–1 w, 2980 w, 2940
˜
w, 2840 m, 1550 s, 1460 m, 1450 m, 1425 m, 1340 w, 1330 vs,br,
1205 s, 1190 m, 1150 m, 1140 m, 1110 m, 1080 vw, 1010 w, 975 w,
935 w, 830 m, 730 m, 665 m, 460 vw, 350 w, 315 w. 1H NMR
3
3
(CDCl3): δ = 8.8 (d, JH,H = 4.9 Hz, 1 H, H-6), 7.4 (d, JH,H
=
Synthesis of [Ph2Pb(4-CF3pymS)2] (7): A solution of 4-CF3pymSH
(0.150 g, 0.832 mmol) and NEt3 (0.126 g, 0.700 mmol) in methanol
(50 mL) was added to a stirred suspension of diphenyllead dichlo-
ride (0.179 g, 0.414 mmol) in methanol (15 mL). The reaction mix-
ture was heated under reflux for 4 h and the yellow solid was fil-
tered off, washed with diethyl ether and dried under vacuum. The
mother liquor yielded crystals suitable for X-ray studies (0.112 g,
56%). C22H14F6N4PbS2 (719.68): calcd. C 36.72, H 1.96, N 7.78,
4.9 Hz, 1 H, H-5), 1.50 (s, 9 H, CH3) ppm. 13C NMR (CDCl3): δ
= 170 (s, C2), 160 (s, C6), 155 (q, C4), 120 (q, C7), 95 (s, C5), 29.7,
30.0 and 31.6 ppm (tBu). 119Sn NMR (CDCl3): δ = –32.16 ppm.
MS (FAB): m/z (%) 592 (14) [tBu2Sn(4-CF3pymS)2], 534 (12)
[tBu2Sn(4-CF3pymS)2 – 3F], 412 (76) [tBu2Sn(4-CF3pymS)], 298
(100) [Sn(4-CF3pymS)].
Synthesis of [Me2Sn(6-Me-4-CF3pymS)2] (4):
A solution of
S 8.91; found C 36.70, H 2.03, N 7.78, S 8.90. IR (KBr): ν =
˜
Me2SnCl2 (0.100 g, 0.220 mmol) was added to a solution of (6-Me-
4-CF3pymSH) (0.030 g, 0.157 mmol) and NEt3 (0.073 g,
0.233 mmol) in methanol (40 mL) with constant stirring at room
temperature. This mixture was heated under reflux for 2.5 h. The
solution was the concentrated to give single crystals that were not
suitable for X-ray studies. Yield: 0.132 g (54%). C14H14F6N4S2Sn
(535.09): calcd. C 31.43, H 2.64, N 10.47, S 11.98; found C 31.52,
3040 cm–1 w, 1555 s, 1465 w, 1430 w, 1415 m, 1340 s, 1330 s, 1205
s, 1170 w, 1140 m, 1115 m, 1010 w, 990 m, 975 w, 835 m, 730 m,
720 m, 680 vw, 670 m, 440 m. 1H NMR (CDCl3): δ = 8.54 (d, 3JH,H
3
= 5.0 Hz, 1 H, H-6), 8.14–7.29 (phenyl H), 7.15 ppm (d, JH,H
=
5.0 Hz, 1 H, H-5). 13C NMR (CDCl3): δ = 135–130 ppm (phenyl
C). 207Pb NMR (CDCl3): δ = –199.0 ppm. MS (FAB): m/z (%) 720
(6) [Ph2Pb(4-CF3pymS)2], 540 (100) [Ph2Pb(4-CF3pymS)], 386 (40)
[Pb(4-CF3pymS)], 284 (28) [PhPb].
H 2.52, N 10.51, S 11.72. IR (KBr): ν = 3080 cm–1 w, 3060 w,
˜
1575 m, 1540 s, 1530 vw, 1390 vs, 1365 m, 1310 w, 1265 vs, 1255 m,
1220 w, 1190 w, 1165 w, 1140 m, 1110 m, 1030 w, 990 w, 980 w, Synthesis of [Ph2Pb(6-Me-4-CF3pymS)2] (8): A similar procedure
920 m, 875 w, 855 s, 790 m, br, 710 s, 550 m, 515 w, 480 w, 460 w. to that described above was followed, starting from a suspension
Eur. J. Inorg. Chem. 2007, 1444–1456
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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1453

J. A. García-Vázquez et al.
FULL PAPER
of Ph2PbCl2 (166 mg) in methanol, and a mixture of 6-Me-4-
CF3pymSH (150 mg, mmol) and NEt3 (110 mL, mmol) in meth-
anol (50 mL). Concentration of the mother liquor in air at room
temperature gave crystals of [Ph2Pb(6-Me-4-CF3pymS)2] suitable
for X-ray studies (0.175 g, 61%). C24H18F6N4S2Pb (747.74): calcd.
C 38.55, H 2.43, N 7.49, S 8.58; found C 38.84, H 2.64, N 7.28, S
= 135–130 (phenyl C), 25 ppm (s, C8). 207Pb NMR (CDCl3): δ =
–206.7 ppm. MS (FAB): m/z (%) 555.0 (100) [Ph2Pb(6-Me-4-
CF3pymS)], 400.4 (45) [Pb(6-Me-4-CF3pymS)], 285 (37) [PhPb],
207 (11) [Pb].
Caution: Lead is a highly toxic cumulative poison. Compounds
should be handled carefully.
8.51. IR (KBr): ν = 1570 cm–1 m, 1560 m, 1535 w, 1465 w, 1425 w,
˜
1385 vs, 1360 w, 1305 vw, 1260 vs, br, 1220 m, 1190 w, 1170 w,
Crystal Structure Determinations: X-ray data for compounds 1, 2
1130 m, 1110 w, 1010 w, 990 m, 915 w, 840 m, 720 m, 710 m, 680 and 5–8 were collected on a Bruker Smart CCD 1000 dif-
vw, 540 w, 425 w. 1H NMR (CDCl3): δ = 8.14–7.30 (m, phenyl H),
7.00 (s, 1 H, H-5), 2.32 (s, 3 H, CH3) ppm. 13C NMR (CDCl3): δ
fractometer with graphite-monochromated Mo-Kα radiation (λ =
0.71073 Å). The data were collected at T = 293 K for all structures.
Table 8. Summary of crystal data and structure refinement for ligands and tin and lead compounds.
Compound
[Me2Sn(4-CF3pymS)2] (1)
[Ph2Sn(4-CF3pymS)2] (2)
[Ph2Sn(6-Me-4-CF3 pymS)2] (5)
Empirical formula
Formula weight
Crystal size [mm]
Temperature [K]
Wavelength [Å]
Crystal system
Space group
a [Å]
C12H10F6N4S2Sn
507.05
0.35ϫ0.25ϫ0.20
293(2)
0.71073
monoclinic
C2/c
17.4481(10)
11.8154(7)
11.5926(7)
90
C22H14F6N4S2Sn
631.18
0.40ϫ0.34ϫ0.15
293(2)
0.71073
monoclinic
C2/c
16.7891(6)
6.4499(3)
23.1215(9)
90
C24H18F6N4S2Sn
659.23
0.55ϫ0.20ϫ0.05
293(2)
0.71073
monoclinic
P21/n
13.2553(2)
13.4370(3)
16.4170(3)
90
b [Å]
c [Å]
α [°]
β [°]
129.9330(10)
90.00
1832.55(19)
4
1.838
1.682
91.2600(10)
90.00
2503.18(18)
4
1.675
1.250
108.3050(10)
90
2776.09(9)
4
1.577
1.131
γ [°]
V [Å3]
Z
Calcd. density [Mgm–3]
µ [mm–1]
F(000)
984
6290
1240
8323
1304
19798
No. reflections collected
No. of independent reflections
Data/restraints/parameters
Goodness-of-fit
Final R indices [I Ͼ 2σ(I)]
2272 [R(int) = 0.0382]
2272/0/141
1.024
3096 [R(int) = 0.0334]
3096/0/187
1.018
R1 = 0.0298
wR2 = 0.0646
0.375 and –0.537
6832 [R(int) = 0.0388]
6832/6/390
1.003
R1 = 0.0399
wR2 = 0.0906
0.500 and –0.524
R1 = 0.0394[a]
wR2 = 0.0905[b]
1.252 and –1.886
Largest diff. peak and hole [eÅ–3]
[tBu2Sn(6-Me-4-CF3pymS)2] (6) [Ph2Pb(4-CF3pymS)2] (7)
[Ph2Pb(6-Me-4-CF3pymS)2] (8)
Empirical formula
Formula weight
Crystal size, mm
Temperature [K]
Wavelength [Å]
Crystal system
Space group
a [Å]
C20H26F6N4S2Sn
619.26
0.15ϫ0.08ϫ0.03
293(2)
0.71073
monoclinic
C2/c
15.1671(11)
7.5778(5)
23.3832(17)
90
C22H14F6N4PbS2
719.68
0.22ϫ0.10ϫ0.07
293(2)
0.71073
monoclinic
C2/c
47.497(9)
6.2325(12)
17.665(3)
90
C24H18F6N4PbS2
747.73
0.49ϫ0.19ϫ0.03
293(2)
0.71073
monoclinic
P21/n
12.8826(18)
13.707(2)
16.453(2)
90
b [Å]
c [Å]
α [°]
β [°]
102.7950(10)
90
2620.8(3)
4
1.569
1.192
108.470(3)
90
4959.8(16)
8
1.928
7.035
108.732(2)
90
2751.4(7)
4
1.805
6.344
γ [°]
V [Å3]
Z
Calcd. density [Mgm–3]
µ [mm–1]
F(000)
1240
8267
2736
17872
1432
17498
No. reflections collected
No. of independent reflections
Data / restraints / parameters
Goodness-of-fit
Final R indices [I Ͼ 2σ(I)]
3230 [R(int) = 0.0630]
3230 / 0 / 154
1.001
5039 [R(int) = 0.0697]
5039 / 0 / 316
1.053
R1 = 0.0449
wR2 = 0.1013
1.225 and –1.609
5623 [R(int) = 0.0396]
5623 / 6 / 390
1.043
R1 = 0.0278
wR2 = 0.0506
0.936 and –0.933
R1 = 0.0498[a]
wR2 = 0.0896[b]
0.539 and –1.055
Largest diff. peak and hole [eÅ–3]
[a] R1 = ∑[|Fo| – |Fc|]/∑[|Fo|]. [b] wR2 = [∑(Fo – Fc ) ]/∑(Fo2)2]1/2
.
2
2 2
1454
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© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 1444–1456

Complexes of Pyrimidine-2-thionates
FULL PAPER
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The ω-scan technique was employed to measure intensities for all
crystals. Decomposition of the crystals did not occur during data
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and polarisation effects. Absorption corrections were carried out
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complexes, hydrogen atoms were also included in idealised posi-
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groups of compounds 1, 2, 5 and 8 were found to be disordered
over two positions with occupancies 73:27 and 52:48 for the groups
on C(5) and C(10) in compound 8, 60:40 for the CF3 group in
compound 1, 50:50 for the CF3 group in 2, and 55:45 and 62:38
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Atomic scattering factors and anomalous dispersion corrections for
all atoms were taken from the International Tables for X-ray Crys-
tallography.[70] The crystal data and summary of data collection
and structure refinement for these compounds are given in Table 8.
ORTEP 3 drawings,[71] along with the numbering schemes used, are
provided in the text.
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Acknowledgments
This work was supported by the Xunta de Galicia (Spain) (grant
PGIDT00PXI20305PR) and by the Ministerio de Ciencia y Tecnol-
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Received: October 5, 2006
Published Online: February 23, 2007
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