Tin(IV) and organotin(IV) derivatives of novel β-diketones. III1 Diorgano- and dihalotin(IV) complexes of 1,3-dimethyl-4-R(C=O)-pyrazol-5-one (R=CH3, C6H5) and the crystal structure of trans-dicyclohexylbis(1,3-dimethyl-4-acetylpyrazolon-5-ato)tin(IV)

Article abstract of DOI:10.1016/S0022-328X(97)00680-3

Several diorgano- and dihalotin(IV) derivatives of new β-diketonate donors, 1,3-dimethyl-4-R(C=O)pyrazol-5-ones (R=Me, Q_DH; R=Ph, Q_MH) have been synthesized and characterized with analytical and spectroscopic methods. They are stable monomeric species, very soluble not only in aromatic and chlorohydrocarbon solvents, but also in alcohols and hydroalcoholic solutions. In the solid state, the diorganotin(IV) derivatives adopt a skewed trapezoidal bipyramidal geometry. The X-ray structure of bis(1,3-dimethyl-4-acetylpyrazolon-5-ato)dicyclohexyltin(IV) shows marked distortion of the organometallic C-Sn-C angle (155°) and two different sets of Sn-O distances. The factors affecting the distortion of this type of complex are discussed. The dihalotin(IV) derivatives (Q)₂SnX₂ (X=F, Cl, Br and I) are likely cis octahedral in the solid state, whereas in solution they exist as a mixture of cis and trans isomers. ¹¹⁹Sn-NMR solution data are discussed and related to electronic and steric properties of the β-diketonate donor, and also to the nature of the halo and organic groups bound to tin.

Full text of DOI:10.1016/S0022-328X(97)00680-3

Journal of Organometallic Chemistry 557 (1998) 187–205
Tin(IV) and organotin(IV) derivatives of novel i-diketones. III1
Diorgano- and dihalotin(IV) complexes of
1,3-dimethyl-4-R(CꢀO)-pyrazol-5-one (R=CH3, C6H5) and the crystal
structure of
trans-dicyclohexylbis(1,3-dimethyl-4-acetylpyrazolon-5-ato)tin(IV)
C. Pettinari a,*, F. Marchetti a, A. Cingolani a, D. Leonesi a, E. Mundorff b, M. Rossi b,
F. Caruso c
a Dipartimento di Scienze Chimiche, Uni6ersita` degli Studi, 6ia S. Agostino 1, 62032 Camerino, Macerata, Italy
b Vassar College, Department of Chemistry, Poughkeepsie, NY 12604-0484, USA
c Istituto di Strutturistica Chimica ‘G. Giacomello’, CNR, CP 10, 00016, Monterotondo Stazione, Roma, Italy
Received 18 July 1997; received in revised form 6 October 1997
Abstract
Several diorgano- and dihalotin(IV) derivatives of new i-diketonate donors, 1,3-dimethyl-4-R(CꢀO)pyrazol-5-ones (R=Me,
QDH; R=Ph, QMH) have been synthesized and characterized with analytical and spectroscopic methods. They are stable
monomeric species, very soluble not only in aromatic and chlorohydrocarbon solvents, but also in alcohols and hydroalcoholic
solutions. In the solid state, the diorganotin(IV) derivatives adopt a skewed trapezoidal bipyramidal geometry. The X-ray
structure of bis(1,3-dimethyl-4-acetylpyrazolon-5-ato)dicyclohexyltin(IV) shows marked distortion of the organometallic C–Sn–C
angle (155°) and two different sets of Sn–O distances. The factors affecting the distortion of this type of complex are discussed.
The dihalotin(IV) derivatives (Q)2SnX2 (X=F, Cl, Br and I) are likely cis octahedral in the solid state, whereas in solution they
exist as a mixture of cis and trans isomers. 119Sn-NMR solution data are discussed and related to electronic and steric properties
of the i-diketonate donor, and also to the nature of the halo and organic groups bound to tin. © 1998 Elsevier Science S.A. All
rights reserved.
Keywords: Tin(IV) complexes; 4-Acyl-5-pyrazolones; Crystal structure; IR; NMR
1. Introduction
interesting coordination behavior with several metal
ions [4].
With several of these asymmetric donors we have
obtained (Q)2SnR2 derivatives having structural and
chemical properties clearly different from the analogous
acetylacetonato–tin(IV) complexes [5]. Several of these
complexes show X-ray crystal structures with strongly
distorted octahedral geometries around tin and two
different sets of Sn–O distances and a C–Sn–C angle
smaller than 180° [6]. Also these structures always show
a short C–H· · ·O contact between the carbonyl (5
position) oxygen of the pyrazole ring and the ortho
C–H in the R1 phenyl (Fig. 2).
A few years ago we initiated the investigation on the
interaction between organotin(IV) acceptors and a class
of i-diketonate ligands [1], 4-acyl-5-pyrazolones (QH),
which possess the chelating moiety fused with a pyra-
zole ring (Fig. 1).
These molecules are currently used as metal extrac-
tants [2] and dyes [3], and they have recently shown
* Corresponding author.
1 Part II is ref. ([6]e)
0022-328X/98/$19.00 © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(97)00680-3

188
C. Pettinari et al. / Journal of Organometallic Chemistry 557 (1998) 187–205
As predicted by Kepert in his theoretical model [7],
an increase in octahedral distortion is accompained by
a reduction of the ligand bite angle Os–Sn–Op (where
Os/Op stands for oxygen atoms associated to secondary/
primary Sn–O bonds). This feature can be ascribed to
two factors: the type of organic groups bonded to tin
and the type of substituents R1, R2 and R3 in the
ligand. So far we have investigated the modification in
the 4-acyl moiety (R3), because of easier synthetic
routes and, in fact, the literature reports only ligands
having different R3 groups, with R1=Ph and R2=Me
[8].
In this report we describe the synthesis of two novel
ligands, QDH (R1=R2=R3=Me) and QMH (R1=
R2=Me and R3=Ph) (see Fig. 1). For R1=Me the
previously mentioned C–H· · ·O contact is eliminated
and so one factor that can potentially contribute to the
octahedral distortion is avoided.
The ligand QDH can be regarded as the simplest in
the family of 4-acyl-5-pyrazolones and the most similar
to acetylacetone or 2,4-pentanedione (acacH). It is in-
teresting to note that acacH (the first ligand to be used
as a complexing agent) is the prototype of i-diketonate
donors, whereas QDH has now been synthesized by us,
about 30 years after 1-phenyl-3-methyl-4-benzoyl-5-
pyrazolone (Q%H) (Fig. 1), which can be regarded as the
prototype of acylpyrazolones [9].
Fig. 2. The intramolecular O· · ·H interaction.
exert their antitumor action is not known. Two factors
concur to make their formulation as drugs difficult: the
high cytotoxicity and insolubility in physiological media
[11].
The synthesis of several (Q)2SnR2 derivatives (R=
Me, Et, Bun, But, Cy, Bz, Ph, F, Cl, Br and I), together
with a study of their analytical, spectroscopic and struc-
tural features in the solid state and in solution are
reported. The X-ray crystal structure of a dicyclohexyl-
tin(IV) derivative provides additional information
about the particular mode of action of these donors.
We also report here the synthesis and characteriza-
tion of novel dihalotin(IV) derivatives (Q)2SnX2 (Q=
Q% and Q¦; X=F, Cl, Br and I).
The ligand QMH is a structural isomer of the previ-
ously employed 1-phenyl-3-methyl-4-acetyl-5-pyra-
zolone (Q¦H) (Fig. 1) ([1,6]c) from which it differs only
by the inversion of one Me with a Ph group in R1 and
R3 positions.
These donors are markedly different with respect to
the previously employed 4-acyl-5-pyrazolones. They
show good solubility not only in several organic sol-
vents, as did previous ligands, but also in alcohols and
water: a very important property in view of the possible
biological applications of their R2Sn(IV) and X2Sn(IV)
derivatives. In fact, several related tin(IV) compounds
are known to possess in vitro antitumoral activity,
comparable to that of Cisplatin [10]. It is believed that
the ligand behaves as a carrier of the R2Sn2+ moiety
through cell membranes to allow interaction with the
target cell. The mechanism by which these compounds
2. Results and discussion
Derivatives 1, 3–8, 10–15, 17, 20 and 25 have been
synthesized as reported in Eq. (1):
MeOH
2QH+2KOH+RnSnX4−n “ (Q)2RnSnX2−n+2KX
+2H2O(QH=QMH, QDH, Q¦H; R
=Me, Et, But, Cy, Bz, Ph, Cl, Br; n=0, 1, 2)
(1)
Derivatives 2 and 9 have been obtained in the following
way:
2QH+Bun2SnOBenzene, D
“
(Q)2SnBun2+H2O
×(QH=QMH, QDH)
(2)
Derivatives 16, 19, 22 and 24 have been obtained in the
following way:
CHCl , D(Q)2SnF2+2HF
3
2QH+SnF4
“
×(QH=QMH, QDH, Q¦H, Q%H)
(3)
Derivatives 18, 21, 23 and 26 have been obtained by
halogen exchange of the corresponding dichlorotin(IV)
complexes treated with a large excess of sodium iodide:
Fig. 1. 4-Acyl-5-pyrazolone proligands.

C. Pettinari et al. / Journal of Organometallic Chemistry 557 (1998) 187–205
189
(Q)2SnCl2+2NaITH“F, D(Q)2SnI2+2NaCl
×(QH=QMH, QDH, Q¦H, Q%H)
therefore there is more diketonic form in QDH than in
QMH.
(4)
The shift towards lower frequencies of the w(CꢀO)
indicates strong coordination of the ligand in the
monoanionic form through both the carbonylic oxy-
gens. In the region 470–390 cm−1 we have observed
two or more strong absorptions, which have been as-
signed to w(Sn–O) stretching [13]. The appearance of
several Sn-O bands is likely due to the presence of
different Sn–O bond distances (see diffraction study
below). These absorptions also appear at higher fre-
quencies (about 10–20 cm−1) with respect to those of
the previously synthesized (Q)2SnR2 compounds [1,6],
thus indicating a stronger donor–acceptor interaction.
In the region below 650 cm−1 we assign other
bands to w(Sn–C) stretching modes [14]. In the case of
Me, Et, Bun, Bz and Ph groups bonded to tin, well-
distinguished strong or medium absorptions are found,
but in the case of derivatives containing Cy and But
groups the assignements are not certain, due to the
presence of Sn–O and donor bands in the same area.
The absorptions due to Sn–X (X=F, Cl, Br, I) are
observed at very different frequencies (Fig. 3).
In the spectra of 16, 19, 22 and 24, the w(Sn–F) are
found at 580–560 cm−1 as one or two medium ab-
sorptions ([14]b). For the cis isomer, both symmetric
and asymmetric Sn–F stretching modes are IR active.
Also in the spectra of 15, and of the other (Q)2SnCl2
derivatives (where Q=QM, Q% and Q¦) [1,6] the w(Sn–
Cl) fall at 350–330 cm−1 as two broad and intense
peaks, indicating the presence of cis isomers in the
solid state. Whereas in the spectra of 17, 20, 25 and
(Q’)2SnBr2 [12], the w(Sn–Br) fall at 250–200 cm−1
and, in these cases, there are two or more strong
bands. Finally, also diiodotin(IV) derivatives 18, 21,
23 and 26 show two or more strong absorbances due
to w(Sn–I) at about 200–220 cm−1. Therefore, for
dibromo- and diiodotin(IV) compounds we cannot ex-
clude the presence of both cis and trans isomers in the
solid state.
Dibromo and diiodotin(IV) derivatives (Q)2SnX2 (X=
Br or I) can be obtained also by oxidative addition of
X2 to (Q)2Sn(II) [12]:
CH Cl , h6/D(Q)2SnX2
(5)
2
2
(Q)2Sn(II)+X2
“
Analytical data are reported in Table 1.
Because (QM)− and (QD)− derivatives have high or
medium solubility in most common solvents, it is more
difficult to isolate and purify their complexes with
respect to previously synthesized (Q)2SnR2 which have
more hindered (Q)− donors. In fact, this type of com-
pound is generally insoluble in polar protic solvents
and precipitates from the alcoholic reaction solution,
whereas compounds 1–20 show high solubility in alco-
hol and also in hydroalcoholic solutions. The latter
are colloidal type solutions.
This particular physical property can be attributed
to the ligands (QM)− and (QD)−. In fact, the proli-
gands QMH and QDH possess good solubility in water,
probably due to H-interactions among H2O molecules
and the carbonylic O atoms and/or the N(2) atom (see
later Fig. 8). This interaction seems not possible when
the N(1) environment involves hindered or lipophilic
groups such as a phenyl and so the solubility in protic
solvents decreases.
2.1. Conducti6ity and molecular weight data
Derivatives
1–26
are
non-electrolytes
in
dichloromethane. Moreover, the osmometric molecular
weight determinations (Table 1), carried out in chloro-
form for several compounds, indicate a stable covalent
mononuclear species in solution, thus excluding any
dissociative equilibrium.
2.2. Infrared data
In addition, the w(Sn–O) also are influenced by the
type of halogens bonded to tin. In fact, these occur at
higher frequencies in the presence of fluorine atoms,
whereas they occur at lower frequencies in diiodo-
tin(IV) derivatives. The ꢀ10 cm−1 increase in fre-
quency of these bands on going from (Q)2SnI2 to
(Q)2SnF2 can be interpreted in terms of the inductive
effect of the increasing electron withdrawing power of
the corresponding halogens, which strengthens the
Sn–O bonds. Another explanation could be based on
the variation in mass of the SnX2 group to which the
oxygens are linked in the series (Q)2SnX2.
IR and far-IR data reported in Table 2 provide
information about the nature of the donor–acceptor
interaction. Assignments have been made on the basis
of the literature available for dihalotin(IV) and
diorganobis(i-diketonate)tin(IV) derivatives.
Comparing the spectra of the neutral proligands QH
and those of compounds 1–26 the disappearance of
the broad band between 3200 and 2700 cm−1 can be
noted. This is due to the loss of the enolic proton
upon complexation and so, an absence of the O–
H· · ·O intramolecular interaction.
It is known that i-diketones generally exist as a
mixture of diketonic and keto-enolic tautomers. The
neutral QDH ligand shows the first carbonyl band at
This effect provides further support to our assign-
ment of the 450 cm−1 bands to Sn–O stretching
modes.
1680 cm−1, whereas for QMH the value is 1630 cm−1
,

190
C. Pettinari et al. / Journal of Organometallic Chemistry 557 (1998) 187–205
Table 1
Analytical data of compounds 1–26
Compound (empirical formula)
No.
M.p. (°C)
Yield (%)
Elemental analysesa
F.W.
M.W.b Conc.c
rd
C
H
N
(QM)2SnEt2
1
2
167–170
83–85
58
85
55.3
(55.4)
57.7
5.5
(5.3)
6.3
9.3
(9.2)
8.4
607
663
476
508
519
608
570
1.0×10−2 0.78
2.0×10−2 0.84
1.1×10−2 0.78
2.2×10−2 0.92
0.6×10−2 0.86
C28H32N4O4Sn
(QM)2SnBun2
C32H40N4O4Sn
(57.9)
(6.1)
(8.4)
(QM)2SnBut2
C32H40N4O4Sn
(QM)2SnCy2
C36H44N4O4Sn
(QM)2SnBz2
C38H36N4O4Sn
(QM)2SnPh2
C36H32N4O4Sn
(QD)2SnMe2
C16H24N4O4Sn
(QD)2SnEt2
3
4
242–244
137–140
65–69
71
66
44
78
74
70
64
68
76
58
80
54
75
54
63
55
84
74
68
74
58
83
75
42
57.7
(57.9)
60.1
(60.4)
62.2
(62.4)
62.3
(61.5)
42.5
(42.3)
45.0
(44.8)
48.7
(49.0)
48.1
(49.0)
55.6
(55.4)
55.0
(55.4)
54.1
(53.9)
38.1
(37.9)
34.1
(33.9)
36.6
(36.3)
28.5
(28.7)
24.5
(24.8)
49.3
(49.1)
40.5
(40.7)
35.8
(35.9)
57.2
(57.4)
44.1
(44.0)
49.0
(49.1)
40.7
(40.7)
35.7
6.0
(6.1)
6.4
(6.2)
4.8
(4.9)
4.5
(4.6)
5.5
(5.3)
6.3
(5.8)
6.8
(6.7)
6.9
(6.7)
5.5
(5.3)
5.5
(5.3)
5.0
(4.9)
4.5
(4.4)
3.9
(3.7)
4.0
(3.9)
3.2
(3.1)
2.8
(2.7)
3.9
(3.8)
3.1
(3.1)
2.9
(2.8)
3.8
(3.7)
2.9
(2.8)
3.9
(3.8)
3.2
(3.1)
2.0
8.3
(8.4)
7.7
(7.8)
7.5
(7.7)
7.9
(8.0)
12.0
(12.3)
11.2
(11.6)
10.2
(10.4)
10.2
(10.4)
9.3
(9.2)
8.9
(9.2)
9.4
(9.6)
11.5
(11.9)
11.1
(11.3)
12.0
(12.1)
9.4
(9.6)
8.2
(8.2)
9.5
(9.5)
8.0
(7.9)
7.1
5
731
455
636
649
0.9×10−3 0.87
1.8×10−2 0.89
6
104–108
220–221
178–181
76–77
7
476
455
1.8×10−2 1.05
1.0×10−2 1.00
8
C18H28N4O4Sn
(QD)2SnBun2
9
C22H36N4O4Sn
(QD)2SnBut2
C22H36N4O4Sn
(QD)2SnCy2
C26H40N4O4Sn
(QD)2SnBz2
C28H32N4O4Sn
(QD)2SnPh2
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
191–192
145–147
177–179
205–208
209–211
102–105
195–200
234–239
280dec
539
591
607
579
556
1.0×10−2 1.03
537
498
509
500
556
493
1.0×10−2 0.91
1.8×10−2 0.84
0.9×10−2 0.84
0.9×10−2 0.82
1.1×10−2 0.96
1.8×10−2 0.85
C26H28N4O4Sn
(QD)2SnMeCl
C15H21ClN4O4Sn
(QD)2SnCl2
C14H18Cl2N4O4Sn
(QD)2SnF2
C14H18F2N4O4Sn
(QD)2SnBr2
C14H18Br2N4O4Sn
(QD)2SnI2
C14H18I2N4O4Sn
(QM)2SnF2
C24H22F2N4O4Sn
(QM)2SnBr2
C24H22Br2N4O4Sn
(QM)2SnI2
C24H22I2N4O4Sn
(Q%)2SnF2
C34H26F2N4O4Sn
(Q%)2SnI2
C34H26I2N4O4Sn
(Q¦)2SnF2
C24H22F2N4O4Sn
(Q¦)2SnBr2
C24H22Br2N4O4Sn
(Q¦)2SnI2
C24H22I2N4O4Sn
128–131
140dec
240dec
(7.0)
7.8
(7.9)
6.1
(6.0)
9.3
(9.5)
7.8
252–254
222–225
265–268
240–242
227–228
(7.9)
7.0
(7.0)
(35.9)
(2.8)
a Values calculated in parentheses.
b Molecular weight determined osmometrically in chloroform solution at 40°C.
c Concentrations are in mol per 1000 g of solvent.
d r=M.W./F.W.

C. Pettinari et al. / Journal of Organometallic Chemistry 557 (1998) 187–205
191
Table 2
IR data (nujol mull) of compounds 1–26
No.
Compound
QM
1700–1500 cm−1
Sn–O
Sn–C
Sn–Xa
B650 cm−1
H
1632sbr,1620s
1613sbr,1573s
1566s,1559s
1536s,1513m
1503m
615s,580s,553w
520m,458w,426s
408m,378s,338m
285s,270m,189s
1
2
(QM)2SnEt2
(QM)2SnBun2
1600s,1593sh
1574m,1557sh
1523s,1498s
1600sh,1592s
1570s,1556sh
1527m,1497s
460m
408s
392s
461m
404m
390vs
550m
535s
637w,627w,605s
533s,362m,302m
275w,256w,212m
647w,630w,605vs
580w,368m,302m
286w,266w,255m
209s,181s
3
4
5
6
(QM)2SnBut2
(QM)2SnCy2
(QM)2SnBz2
(QM)2SnPh2
QDH
1598vs,1589s
1574s,1558m
1539sh,1532s
1527sh,1505m
1595sh,1584s
1565vs,1557sh
1522s,1496m
462m
400m
393s
380s
551w,540sh,531s
369s,294s,280sh
260m,229m,169s
153m
643m,628m,602vs
371m,338m,317m
300m,279w,265m
216m
640m,629m,601s
554w,418m,368m
303s,280w,268w
248m,226m
642w,630w,605s
537s,443s,426s
368m,307m,219w
206w,191w,165m
620s,598m,575s
552w,454w,425s
397m,329s,280w
243m,251s,203w
195m
461m
401m
390vs
535m
528m
1597sh,1585vs
1573s,1568s
1557m,1537m
1524br,1504s
1602s,1586s
1574s,1557sh
1525sh,1520s
1504s
455vs
408s
395sh
532s
460s
409m
233m
266s
245m
1686s,1628sbr
1584s,1520s
1506sh
7
(QD)2SnMe2
1601sbr,1575s
1557m,1526s
1505s
456s
419m
398m
586s
551s
639s,615m,598s
552w,374m,368m
353w,326w,303m
280s,253m,247s
222m,202s,177s
151s
642m,625w,606s
499w,351w,291s
268w,220m,165sbr
631s,495w,368m
351w,289m,262w
247w,201m
8
9
(QD)2SnEt2
(QD)2SnBun2
1598sbr,1557sh
1527s,1501m
370m
1605sh,1592vs
1557sh,1530m
1487m
457s
421m
458s
412s
406s
603sbr
510w
393m
10
11
(QD)2SnBut2
(QD)2SnCy2
1592sbr,1575s
1557sh,1531m
1505m
457sbr
406m
392s
376m
633s,605s,551w
495w,351w,292s
263m,225w,201m
170sbr
631s,606s,552w
374m,352w,341w
326m,291w,280m
267m,252w,224m
187vs,169sh,151s
631s,604s,501w
489w,340m,327m
289s,268s,225w
179sbr,155w
1595sbr,1577s
1558s,1526s
1506s
459m
408sbr
501w
490w
12
13
(QD)2SnBz2
(QD)2SnPh2
1599vs,1583s
1575s,1557s
1538s,1531sh
1504s
1598s,1587s
1556s,1539m
1528s,1502m
458s
415sbr
554m
464sbr
435sbr
277s
244s
643m,623w,605m
553m,373s,291m
205w,179m

192
C. Pettinari et al. / Journal of Organometallic Chemistry 557 (1998) 187–205
Table 2 (continued)
No.
Compound
1700–1500 cm−1
Sn–O
Sn–C
541s
Sn–Xa
303sbr
B650 cm−1
14
(QD)2SnMeCl
(QD)2SnCl2
(QD)2SnF2
1597sbr,1574s
1532s,1505s
447s
1602s,1574sbr
1534m,1508s
302m
1601s,1582s
1574s,1537s
1514s
1598s,1578vs
1533m,1506sh
458s
471s
454sh
643m,619m,603s
371s,274s,217m
203m,187s
15
16
17
463vsbr
330vs
338sh
619m,604vs,553w
374s,269m,203sh
197s,169m,159m
620sh,605s,555sh
377m,342w,298w
267w,228mbr,178sh
615m,604s,552m
542sh,419w,398w
376m,354w,324w
302w,290w,280m
265w,203w,171m
151s
473vsbr
440sh
588s
576s
(QD)2SnBr2
471sh
463s
234m
253m
246vs
228m
18
19
(QD)2SnI2
(QM)2SnF2
1593vsbr, 1575sh
15232m, 1504m
470sh
454s
221sbr
204sh
618sh,603s,552w
372m,296m,268m
138m
641w,629m,604s
551s,510w,373m
311m,267sh,239sbr
188sh
1597s,1583s
1568s,1512vs
468sbr
588mbr
20
(QM)2SnBr2
1590sbr,1580sh
1573s,1567vs
1558s,1523s
464sh
455s
247vs
235sh
640w,628m,603s
549s,370w,334sh
315m,152m
1510sh,1504s
21
22
(QM)2SnI2
1591s,1578s
1558m,1525m
1505m
1599s,1558s
1537s,1504s
450m
467m
452s
222s
202s
640w,629m,603s
544s,370w,314m
260m
645w,622m,618w
554s,506m,398w
355m,335m,289w
280w,245m,227s
202w,151m
(Q%)2SnF2
475s
468s
592s
588sh
23
24
(Q%)2SnI2
1594s,1581s
1560vs,1540s
1525s
452s
443sh
432m
234sh
225vs
206s
643w,622s,611m
555s,515m,502m
468w,406w,382w
352m,337m,324m
300w,249m,187w
646w,622m,612m
563m,512m,394m
358w,333m,303w
279w,267w,252s
227w,214m,181w
151m
199sh
(Q¦)2SnF2
1601s,1592s
1574s,1538s
1504m
489s
410m
595m
582vs
25
26
(Q¦)2SnBr2
(Q¦)2SnI2
1595sbr,1554s
1514sbr
485s
403m
234vsbr
644w,625s,612s
582w,552w,511s
390sh,353w,329w,
308m,277m,202w
171m,151w
642w,620s,611s
582w,553w,509s
391m,354w,328m
303m,276m,245w
183w,151w
1597s,1556s
1538s,1503s
472sh
460s
404m
223s
217sh
208s
a X=F, Cl, Br or I.
1
2.3. NMR data
In the H-NMR spectra of the complexes (Q)2SnR2
and (Q)2SnX2 an upfield shift of the hydrogens in the
R1, R2 and R3 groups is generally observed. In the
13C-NMR spectra two trends are observed, in agree-
ment with those previously reported for analogues
The NMR data of the ligands and of compounds
1–26 are reported in Table 3 (1H), Table 4 (13C) and
Table 5 (119Sn).

C. Pettinari et al. / Journal of Organometallic Chemistry 557 (1998) 187–205
193
Fig. 3. Far-IR spectra of (QM)2SnX2.
plexes in 1,1,2,2-tetrachloroethane-d2 in the range 0–
130°C (Fig. 4). The solvent was chosen because of its
long liquid range and its homologous relationship with
deuterated chloroform and dichloromethane. 1,1,2,2-
Tetrachloroethane has a single sharp resonance at 2.17
ppm, which does not overlap with any of the derivative
absorptions.
The methyl region between 2.20 and 3.60 ppm shows,
at room temperature (r.t.), three main groups of bands,
one for each methyl of the donor (QD) (N(1)–Me,
C(3)–Me and (CꢀO)–Me). Each group is composed of
two or four signals, with additional broadening and
side bands caused by long-range (1H–19F) coupling in
the spectrum of (QD)2SnF2. The increase of the temper-
ature causes a progressive broadening and coalescence
of the resonances. As expected, at 130°C only three
distinct signals are present in the spectrum of
(QD)2SnF2, thus indicating a fluxionality between the
possible configurations on the NMR time-scale. In-
stead, for (QD)2SnCl2 at 135°C the coalescence is not
complete, thus indicating a higher activation energy for
the rearrangement in solution of the latter compound.
(Q)2SnR2 derivatives. Carbon atoms C(3), C(4), C(5)
and those of the R2 and R3 groups are deshielded and
resonate upfield, whereas those of R1 and of the chain
carbonyl are downfield shifted upon coordination.
When at least one halogen is bonded to tin, several
isomers are present in solution.
n
The J(Sn–H) coupling constants are typical of trans
1
six-coordinate tin compounds [15]. The J(Sn–C) of di-n-
butyltin(IV) derivatives 2 and 9 and of diethyltin(IV)
and dicyclohexyltin(IV) derivatives 1, 4 and 11 can be
used, in the empirical equations of Holecek [16] and of
Lockhart [17] respectively, to derive C–Sn–C values
(155 for 1, 161 for 2, 149 for 4, 163 for 9 and 149° for
11) which indicate distorted trans octahedral
configurations.
The proton and carbon spectra of all the dihalo-
tin(IV) derivatives always show two, three or four sets
of resonances, due to the presence of isomers in
solution.
1
We have carried out variable temperature H-NMR
experiments for the (QD)2SnF2 and (QD)2SnCl2 com-

194
C. Pettinari et al. / Journal of Organometallic Chemistry 557 (1998) 187–205
Table 3
1H-NMR data (in CDCl3) of compounds 1–26
No.
Compound
QM
R2
R1
R3
Sn–R
Other dataa
H
2.02s
1.78s
1.75s
3.66s
3.60s
3.58s
7.40–7.63m
7.45–7.52m
7.40–7.52m
9.20–9.60sbr
(O–H· · ·O)
1
2
(QM)2SnEt2
(QM)2SnBun2
1.18t
1.60q
0.77t
2J=96.0,90.8
3J=160.4,153.1
1.25m
1.55m
1.20s
1.12m
1.45m
1.97m
2.93s
6.95m
7.50m
7.70m
8.12dd
3
4
(QM)2SnBut2
(QM)2SnCy2
1.75s
1.75s
3.60s
3.55s
7.38–7.60m
7.40–7.52m
3J=134.8,126.1
2J=124.3,119.7
5
6
(QM)2SnBz2
1.75s
3.48s
7.30–7.55m
7.30–7.45m
(QM)2SnPh2
1.76sbr
3.52sbr
QDH
(QD)2SnMe2
(QD)2SnEt2
2.38s
2.36s
2.38s
3.57s
3.50s
3.51s
2.41s
2.34s
2.36s
7
8
0.74s
1.08t
1.42q
0.78t
2J=103.1,98.9
2J=95.8,91.7
3J=158.3,150.0
9
(QD)2SnBun2
2.38s
3.49s
2.35s
1.26m
1.42m
1.11s
1.15m
1.50m
1.85m
2.73s
7.35m
7.58d
7.62d
0.92s
0.96s
1.04s
10
11
(QD)2SnBut2
(QD)2SnCy2
2.38s
2.38s
3.50s
3.48s
3.51s
2.36s
2.36s
2.42s
3J=132.7,126.9
12
13
(QD)2SnBz2
(QD)2SnPh2
2.22s
2.32s
3.38s
3.40sbr
2.17s
2.28sbr
2J=125.2,121.2
1J=86.9
14
15
16
(QD)2SnMeCl
(QD)2SnCl2
(QD)2SnF2
2.26s
2.32s
3.50s
3.55s
2.33s
2.50s
2.52s
2.44s
2.46s
2.60s
2.46s
2.48s
2.59s
2.62s
2.47s
2.50s
2.45s
2.47s
2.58s
2.62s
3.40s
8.06dbr
2J=128.6,125.3
123.3,120.0
2.40s
2.41s
3.45s
3.60s
2.40sb
2.42sc
3.48sd
3.60se
17
18
(QD)2SnBr2
(QD)2SnI2
2.42s
2.44s
2.38s
2.40s
2.42s
3.43s
3.61s
3.40s
3.42s
3.58s
19
20
21
(QM)2SnF2
(QM)2SnBr2
(QM)2SnI2
1.75s
3.50s
3.52s
3.62s
3.67s
7.40–7.70mbr
1.80s
1.87s
2.08s
2.12s
3.70s
7.40–7.70mbr
1.78s
1.87s
1.90s
2.04s
3.45s
3.48s
3.58s
3.62s
3.64s
3.68s
7.38–7.66mbr
1.78s
1.86s
2.44s
2.46s

C. Pettinari et al. / Journal of Organometallic Chemistry 557 (1998) 187–205
195
Table 3 (continued)
No.
Compound
R2
R1
R3
Sn–R
Other dataa
1.88s
2.62s
1.92s
1.80s
1.82s
1.90s
2.00s
1.68s
1.78s
1.90s
2.67s
22
(Q%)2SnFf2
(Q%)2SnIf2
(Q¦)2SnFg2
(Q¦)2SnBrg2
(Q¦)2SnIg2
7.20–7.40m
7.42–7.60m
7.62–7.75m
7.95d
7.15–7.40m
7.45–7.70m
7.95dd
7.20–7.40m
7.42–7.60m
7.62–7.75m
7.95d
23
7.15–7.40m
7.45–7.70m
7.95dd
2.02s
24
2.17s, 2.48s
2.51s, 2.53s
2.56s, 2.65s
2.68s, 2.70s
2.35s, 2.43s
2.47s, 2.51s
2.53s, 2.60s
2.67s
2.30s, 2.42s
2.44s, 2.50s
2.53s, 2.55s
2.58s, 2.65s
7.25–7.50m
7.67t, 7.89dd
25
7.15–7.40m
7.48t, 7.67dd
7.92dd
26
7.16–7.42m
7.50t, 7.64d
7.95dd
a J in Hz.
b J(H–F)=2.2 Hz.
c J(H–F)=4.0 Hz.
d J(H–F)=7.7 Hz.
e J(H–F)=5.5 Hz.
f Signals of R1 and R3 are indistinguishable.
g Signals of R1 and R2 are indistinguishable.
In the same solvent comparable coalescence tempera-
tures and two bands were shown by analogous acety-
lacetonate derivatives; these exist in solution as two cis
isomers ([14]b). Instead, our derivatives are likely to
exist in solution as a mixture of cis and trans isomers,
as indicated by the presence of more than two sets of
signals.
There are reports in the literature on possible mecha-
nisms for configurational rearrangements of dihalo-
bis(i-diketonate)tin(IV) complexes ([14]b)[18]. These
include:
(Q)2SnX2 v[(Q)SnX2]+ +Q−
(Q)2SnX2 v[(Q)2SnX]+ +X−
Although we cannot indicate which of the intramolecu-
lar mechanisms (3) or (4) could be operating in the
present study, difficulty in obtaining crystals useful for
diffraction study of bis(i-diketonate)dihalotin(IV)
derivatives may be ascribed to a mixture of isomers and
fluxionality.
19F-NMR spectra also have been carried out for
(Q)2SnF2 derivatives (Table 5). They show one or two
absorptions in the range between +160 and +186
ppm relative to the external CFCl3 standard. They are
deshielded with respect to (acac)2SnF2 (+153 ppm)
([14]b), thus indicating that fluorine atoms behave more
as donating ligands in our derivatives. Moreover, the
deshielding increases on going from (QD)2SnF2 (+160
ppm) to (Q%)2SnF2 (+186 ppm), in accord with a
decrease of the (Q)− donor power, caused by a pro-
gressive substitution of one and two Me with Ph groups
in R1 and R3 positions of the acylpyrazolonates. This
trend can be explained in terms of the Pauling Elec-
troneutrality Principle: the more electron donating are
the i-diketonate ligands, the less electron donating are
the fluorine atoms, and vice versa.
1. complete dissociation of one i-diketonate donor, to
give a four- coordinate intermediate;
2. dissociation of a halide ion, to give a five-coordinate
intermediate;
3. breaking of one M–O bond also to give, in this
case,
a
five-coordinate intermediate, with
a
monodentate i-diketonate donor;
4. twisting mechanisms and consequent rearrangement
without any metal–ligand bond breaking.
Intermolecular mechanisms (1) and (2) are improba-
ble based on evidence from acetylacetonatetin(IV)
derivatives ([14]b), and our complexes. In fact, it is
possible from the lack of conductivity in
dichloromethane solution, to exclude both the follow-
ing dissociative equilibria:

196
C. Pettinari et al. / Journal of Organometallic Chemistry 557 (1998) 187–205
Table 4
13C-NMR data (in CDCl3) of compounds 1–15, 23, 25 and 26
No.
Compound
R2
R1
R3
CO
C(5)
C(3)
C(4)
R–Sn
Other dataa
QM
H
15.5
16.3
16.8
32.5
31.8
32.2
127.7,128.3
130.0,138.4
127.4,128.2
130.8,139.8
127.9,128.8
131.3,140.4
193.0
160.4
191.4
162.7
191.8
163.2
147.0
102.3
148.1
103.5
148.5
104.0
1
2
(QM)2SnEt2
(QM)2SnBun2
9.4
21.7
14.1,26.4
27.5,29.1
1J=891.7,851.9
1J=860.5,822.7
2J=44.4
3J=129.5
3
4
(QM)2SnBut2
(QM)2SnCy2
16.4
16.8
31.6
32.2
127.4,128.2
130.7,140.1
127.8,128.8
131.1,140.7
n.o.
n.o.
192.0
163.3
147.7
n.o.
148.5
104.3
29.2
50.3
27.4,29.0
29.3,30.0
30.3,47.6
36.8,124.6
127.8,129.5
139.8
1J=819.1,785.7
2J=20.5
3J=94.7
5
6
(QM)2SnBz2
(QM)2SnPh2
16.5
15.8
32.2
32.1
127.6,128.6
131.5,138.6
n.o.
148.4
104.2
3J=51.2
4J=32.6
127.9,128.7
131.2,138.5
190.3br
163.9br
148.0
103.8
128.3,128.7
135.2, n.o.
2J=58.8
3J=86.9
4J=19.7
QDH
15.3
17.1
17.1
17.6
32.3
31.7
31.6
32.1
27.2
27.7
27.6
28.1
195.0
159.4
192.2
161.8
192.7
161.8
193.1
162.2
146.6
103.0
147.7
103.6
147.5
103.7
147.9
104.1
7
8
9
(QD)2SnMe2
(QD)2SnEt2
(QD)2SnBun2
8.2
9.3
21.2
14.1,26.4
27.3,28.5
1J=880.0,841.4
2J=43.5
3J=129.6
10
11
(QD)2SnBut2
(QD)2SnCy2
17.1
17.2
31.4
31.5
27.8
27.6
193.3
n.o.
192.7
161.9
147.2
104.7
147.1
104.0
29.1
49.5
26.5,26.8
28.5,28.8
29.6,30.0
36.4,124.5
127.8,129.5
140.1
1J=820.0,800.0
2J=23.1
3J=90.4
12
13
14
(QD)2SnBz2
(QD)2SnPh2
(QD)2SnMeCl
17.4
17.5
31.9
32.1
27.6
27.5
193.1
n.o.
148.0
104.2
3J=50.5
4J=30.5
n.o.
n.o.
148.9
n.o.
128.5,129.1
135.6,148.4
2J=59.6,56.0
3J=93.0,89.2
4J=19.0
16.8
17.0
31.8
32.1
26.6
26.6
26.8
26.5
21.8
21.9
22.0
22.5
192.0
192.6
162.4
148.4
104.1
104.3
9.9
10.2
11.7
15
23
(QD)2SnCl2
17.1
17.2
27.4
27.6
188.5
188.8
189.2
159.0
159.2
190.0
190.1
190.4
162.1
162.3
162.4
144.6
144.6
99.8
100.1
(Q%)2SnIb2
16.2
16.3
16.4
16.5
120.9,121.2,121.6
121.7,126.7,126.9
127.1,127.2,128.3
128.4,128.5,128.6
128.7,128.8,128.9
129.0,129.1,132.3
132.5,132.7,136.7
136.8,136.9
121.0
121.6
121.7
126.9
127.0
150.0
150.1
150.3
n.o.
25
(Q¦)2SnBr2
16.9
17.0
17.1
17.2
27.0
27.1
27.2
27.3
193.9
194.2
194.7
161.2
161.9
162.0
149.9
150.0
150.3
105.2
105.4
105.5
127.1
127.2

C. Pettinari et al. / Journal of Organometallic Chemistry 557 (1998) 187–205
197
Table 4 (continued)
No.
Compound
R2
R1
R3
CO
C(5)
C(3)
C(4)
R–Sn
Other dataa
128.5
128.9
129.0
129.1
136.7
136.8
136.9
120.9
121.5
121.6
126.8
126.9
127.0
128.7
128.9
129.0
129.1
136.7
136.9
26
(Q¦)2SnI2
16.9
17.0
17.1
26.9
27.1
27.3
192.9
193.4
194.2
161.5
161.8
150.0
150.3
104.8
105.0
a J in Hz.
b Signals of R1 and R3 are indistinguishable.
The 119Sn-NMR data support our previous conclu-
sions. In the spectra of 1–13 there is only one reso-
nance. The values of l(119Sn) observed are in agreement
with the trends reported in the literature [15]. They are
a function of the nature of R groups linked to tin and
decrease in the following order:
Hz) ([14]b), and in accord with the previously discussed
stronger Sn–F linkage in our derivatives.
The (Q)2SnCl2 resonances fall between −620 and
−650 ppm, those of (Q)2SnBr2 between −850 and
−880 ppm and finally the (Q)2SnI2 derivatives absorb
from −1300– −1470 ppm. The latter are the most
119Sn shielded bis(acylpyrazolonate)tin(IV) derivatives
synthesized. However in the literature, other SnO4I2
complexes are known to absorb at more negative fields,
for example bis(tetraphenylimidodiphosphinato) di-
iodotin(IV) shows a signal at −1759 ppm [19]. In Fig.
7 the trend of 119Sn chemical shifts as a function of the
type of halogens bonded to tin is reported: on going
from F to I the absorptions describe a 2nd order poly-
nomial function, similar to those reported in the case of
RnSnCl4−n [20].
MeBBunBEtBCyBButBBzBPh
The effect caused by the substitution of each Me
group by a chlorine atom is roughly additive. In Fig. 5
the trend of (QD)− derivatives 7, 14 and 15 is compared
with that of the (QM)− analogues previously synthe-
sized ([6]a). It seems that the ligand (QD)− behaves as
a better donor than (QM)−, due to the presence of three
electron releasing methyls in R1, R2 and R3 positions,
which increase the ‘|’ donor character.
In Fig. 6 the effect of increasing substitution in R
groups bonded to tin on the 119Sn chemical shift can be
seen. As expected, such an increase leads to a higher
donor character of the alkyl groups (MeBEtBCyB
But) and is the reason for the electron density increase
on the tin atom.
This feature can be explained by the electron with-
drawing inductive effect of the halogens and, also, by a
possible additional y contribution to the Sn–X bonds
[20,21], in the case of Cl, Br and I, which would shield
the tin nucleus to a greater extent. This trans-inductive
effect can be schematically indicated:
’
This is the first 119Sn-NMR report for derivatives
having a SnO4X2 core, where X stands for the complete
series of the halogens F, Cl, Br and I. In the literature,
some reports ([14]b)([18]a) dealing with IR and 1H-
NMR trends for dihalotin(IV)(O2-donor)2 exist.
The (Q)2SnF2 derivatives absorb in the range from
−740– −770 ppm relative to SnMe4, giving rise to two
main groups of signals stemming from (119Sn–19F) cou-
pling. These are of the order of 2050/2250 Hz, relatively
higher than those observed in (acac)2SnF2, (1850/1950
O−Sn−X (where X=Cl, Br and I)
It is probable that in the case of difluorotin(IV) deriva-
tives, whose resonances fall in the range between those
of (Q)2SnCl2 and (Q)2SnBr2, the reverse effect is
operating.
“
O−Sn− F
This is due to the higher electronegativity of fluorine
compared to oxygen and the lack of y contribution to
the Sn–F bond.

198
C. Pettinari et al. / Journal of Organometallic Chemistry 557 (1998) 187–205
2.4. Diffraction study of (QD)2SnCy2 (12)
Selected bond distances and angles are given in Table 7
and an ORTEP view of the molecule, with H atoms
omitted for clarity, is shown in Fig. 8.
The crystal structure of the title compound,
(QD)2SnCy2, is composed of well separated and discrete
molecules as there are no intermolecular contacts
shorter than the van der Waals radii of the atoms.
Atomic coordinates for non-H atoms are given in Table
6; those for H atoms are in the supplementary material.
The molecular structure of the title compound shows
the tin having coordination number six and the metal
octahedral geometry strongly distorted as shown in
previous related complexes. The coordination polyhe-
dron is formed by four O atoms, from two chelating
pyrazolonates, and two C atoms, from the cyclohexyl
groups. The four O atoms lie in the equatorial plane
and the four O–Sn–O cis bond angles equal 360°.
The organic groups are trans to each other although
a strong distortion from 180° is found and the angle is
154.6(5)°. Another common feature in these complexes
is two different sets of Sn–O distances. Thus, for one
Table 5
119Sn and 19F-NMR dataa (CDCl3) of derivatives 1–26
Compound No. l(119Sn)
Other data
l(19F)
(QM)2SnEt2
(QM)2SnBun2
(QM)2SnBut2
(QM)2SnCy2
(QM)2SnBz2
(QM)2SnPh2
(QD)2SnMe2
(QD)2SnEt2
(QD)2SnBun2
1
2
3
4
5
6
7
8
9
−349.9
−345.5
−448.5
−421.3
−449.0
−485.1
−312.9
−351.6
−347.2
˚
˚
ligand there is a short bond length Sn–O1=2.094(9) A
(primary bond) and a longer one, Sn–O2=2.42(1) A
(secondary bond). For the other ligand the correspond-
˚
ing values are Sn–O51=2.132(9) A and Sn–O52=
˚
2.405(8) A. This asymmetry in bond length is a result of
(QD)2SnBut2 10 −448.5
(QD)2SnCy2 11 −427.7
(QD)2SnBz2 12 −449.9
(QD)2SnPh2 13 −490.3
(QD)2SnMeCl 14 −492.6,−493.0
−495.4,−499.4
asymmetric nature of the ligand.
In contrast, a symmetric ligand (acacH) stabilizes the
perfect octahedral complex (acac)2Sn(CH3)2 ([5]a) with
the metal on an inversion center and the same coordi-
nation environment as the title compound. In addition,
the equatorial plane made by the four O atoms has the
oxygen atoms associated with the primary bonds, O1
and O51, closer to each other than those associated
with the secondary bonds, O2 and O52, as shown by
the corresponding angles O1–Sn–O51=77.8(3)° and
O2–Sn–O52=121.2(3)°.
(QD)2SnCl2 15 −629.4,−632.9
−637.0
(QD)2SnF2
16 −751.1
−770.4
1J(Sn–F)=n.o.
1J(Sn–F)=n.o.
+160.2
(QD)2SnBr2 17 −849.4,−861.4
−872.8
(QD)2SnI2
18 −1318.2,
The location of the cyclohexyl groups relative to the
equatorial plane is such that they are folded towards
the side of the secondary bonds. This feature decreases
the repulsion among the corresponding atoms in the
coordination sphere. The cyclohexyl groups show C10
and C16 displayed symmetrically above and below the
equatorial plane (the angle between the bond Sn–C10
and the equatorial plane is 77° and that between the
bond Sn–C16 and the equatorial plane is 78°). The title
compound structure has approximate Cs symmetry.
In previous related structures [1,6,22], a phenyl group
is the substituent on N1. This Ph group is coplanar
with the attached pyrazole ring and has an intramolecu-
lar separation between an ortho-H atom and O1 of
−1371.9
−1441.4,
−1477.3
19 −743.7
(QM)2SnF2
1J(119Sn–19F)=2234.0 +185.1
1J(117Sn–19F)=2188.1
1J(119Sn–19F)=2297.9
1J(117Sn–19F)=2160.6
−752.5
(QM)2SnBr2 20 −731.4,−735.6
−739.9,−744.4
−848.0,−858.5
−867.2,−868.9
21 −1318.2,
(QM)2SnI2
−1371.9
22 −749.4
(Q%)2SnF2
1J(119Sn–19F)=2200.4 +184.7
1J(117Sn–19F)=2131.7 +186.4
1J(119Sn–19F)=2237.0
−758.0
1J(117Sn–19F)=2179.1
about 2.2 A; such a distance is shorter than the corre-
˚
˚
(Q%)2SnI2
(Q¦)2SnF2
23 n.o.b
24 −745.7
sponding sum of the van der Waals parameters (1.20 A
1J(119Sn–19F)=2255.3 +176.5
1J(117Sn–19F)=2074.6
1J(119Sn–19F)=2215.6
1J(117Sn–19F)=2179.1
˚
˚
(H)+1.40 A (O)=2.60 A [23]). Instead, the title com-
pound has a methyl group (C6) rather than a Ph group.
This methyl has a H at a longer distance from O1,
−755.6
˚
(Q¦)2SnBr2
(Q¦)2SnI2
25 −859.3,−869.6
−879.2
greater than 2.48 A according to a model scheme (see
Section 3). This implies that the C–O· · ·H interactions
are certainly weaker in this complex than those found
in previous structures. Nevertheless, the distortion in
this complex is of the same order as found for the other
26 n.o.b
a In ppm from external standard Sn(CH3)4 and CFCl3, respectively.
b Probably due to low solubility of compound in CDCl3.

C. Pettinari et al. / Journal of Organometallic Chemistry 557 (1998) 187–205
199
Fig. 4. 1H-NMR variable temperature experiments of (QD)2SnF2 (a) and of (QD)2SnCl2 (b).
dialkyltins pyrazolonates (range 150–162°), thus the
characteristic distortion (skewed trapezoidal bipyrami-
dal, STB) of this family of complexes cannot be as-
cribed solely to the C–O· · ·H interaction.
Selected structural parameters for related species are
shown in Table 8 and, for comparison purposes, this
Table includes (acac)2Sn(CH3)2 as well. Some parame-
ters in Table 8 show clear trends. Thus, increasing the
C–Sn–C angle is associated with:
1. a smaller difference in bond length between primary
and secondary bonds (Sn–O1 and Sn–O2);
2. a smaller difference between Os–Sn–Os and Op–
Sn–Op (Os/Op=oxygen atom associated to sec-
ondary/primary bond);

200
C. Pettinari et al. / Journal of Organometallic Chemistry 557 (1998) 187–205
Fig. 5. Substituent effect on the 119Sn chemical shift of (Q)2MenSnCl2−n (Q=QD and QM, average value for n=0 and n=1).
3. an increasing bite angle O1–Sn–O2 (and O51–Sn–
O52 in the other ligand);
4. less deformation of the octahedron.
Therefore, the structural behavior of the title com-
pound appears to corroborate previous results. This
comparison does not take into account the differences
among ligands (Q% and QD) and such an assumption
appears reasonable as shown below.
With respect to the second modification, substitution
on C8, it is apparent that this change implies less
structural variation on the whole complex than that
obtained by substitution on the metal. However, there
are not yet sufficient complexes studied to elucidate the
rules governing such structural variations. The same
applies for substitution on N1. We will further investi-
gate this point.
The bite angle is considered a principal reason for the
octahedral deformation by Kepert [7] who calculated
the repulsion among the atoms forming the coordina-
tion sphere and defined the distorted system as STB.
From results of energy calculations on STB complexes
containing symmetric ligands, Kepert concluded that
the smaller the bite angle, the stronger the distortion.
Table 8 shows that the same conclusion holds for
asymmetric ligands.
The structural behavior of these complexes can be
explained on the basis of the chemical modifications:
1. the organic groups attached to the metal;
2. the ligand substituent on C8;
3. Experimental section
3. the ligand substituent on N1.
In the first case, as shown ([6]c) previously, the phenyl
groups attached to the tin atom stabilize the largest
C–Sn–C bond angle (173.0°). The electronic nature
(withdrawing effect) of this group is considered respon-
sible for this value ([6]c). On the contrary, alkyl groups
attached to the metal (better electron donors than
phenyl groups) show much smaller C–Sn–C angles
(about 150–162°). It is observed that the distortion
induced by the cyclohexyl group, which is a tertiary
alkyl group, in the title compound is of the same order
as that found for alkyl groups. Moreover, a comparison
of the effect of a primary methyl group in (Q%)2Sn(Me)2
(C–Sn–C=153.3(3)°) ([6]a), that of a secondary n-
butyl group in (Q%)2Sn(Bun)2 (C–Sn–C=154.7(8)°)
([22]a) and that of a quaternary t-butyl group in
(Q%)2Sn(But)2 (C–Sn–C=150.0(5)°) [1] shows even
more similarity in the octahedral distortion with the
title compound which has a C–Sn–C of 154.6(5)°.
3.1. General comments
The tin(IV) and organotin(IV) halides were pur-
chased from Alfa (Karlsruhe) and Aldrich (Milwaukee)
and used as received, except for dibenzyltin dichloride
which was synthesized according to a reported proce-
dure [24].
The samples for microanalysis were dried in vacuo to
constant weight (20°C, ca. 0.1 Torr). Elemental analy-
ses (C, H, N) were performed in house with Fisons
Instruments 1108 CHNS-O Elemental analyzer. Molec-
ular weight determinations were performed with a
Knauer membrane osmometer. IR spectra were
recorded from 4000–100 cm−1 with a Perkin-Elmer
System 2000 FT-IR instrument. H, 13C, 19F and 119Sn-
NMR spectra were recorded on a VXR-300 Varian
spectrometer operating at r.t. (300 MHz for 1H, 75
MHz for 13C, 282.2 MHz for 19F and 111.9 MHz for
1

C. Pettinari et al. / Journal of Organometallic Chemistry 557 (1998) 187–205
201
Fig. 6. The effect of increasing substitution of R on the 119Sn chemical shift of (QD)2SnR2 (R=Me, Et, Cy, But).
119Sn). Melting points were taken on an IA 8100 Elec-
trothermal instrument. The electrical conductance of
the dichloromethane solutions was measured with a
Crison CDTM 522 conductimeter at r.t.
poured into HCl 2 N (200 ml) to decompose the
calcium complex. The resulting clear solution was
heated to reduce the volume to one half, then
dichloromethane (100 ml) was added and two phases
formed. The organic phase, separated from the aqueous
phase, was evaporated under reduced pressure to give a
light brown solid, which was recrystallized from diethyl
ether and dried to constant weight (4.6 g, 29.4 mmol,
55% yield).
3.2. Synthesis of the donors
The precursor 1,3-dimethyl-5-pyrazolone was synthe-
sized by a reported procedure [25].
3.2.1. Synthesis of QMH
3.3. Synthesis of the complexes
1,3-Dimethyl-5-pyrazolone (6.0 g, 53.5 mmol) was
placed in a flask equipped with a stirrer, separating
funnel and a reflux condenser and dissolved in dry
dioxane (60 ml) by warming. Calcium hydroxide (10.0
g, 135 mmol) and then benzoyl chloride (6.5 ml, 7.9 g,
56.0 mmol) were added, the latter dropwise for 10 min.
The mixture was heated to reflux overnight and then
poured into HCl 2 N (200 ml) to decompose the
calcium complex. The resulting clear solution was
heated to reduce the volume to one half, then ice was
added and a precipitate formed. It was filtered and
recrystallized from methanol–water and dried to con-
stant weight (8.2 g, 38.2 mmol, 71% yield).
3.3.1. Diethyltin(IV)bis(1,3-dimethyl-4-benzoylpyrazo-
lon-5-ato) (QM)2SnEt2 (1)
Diethyltin dichloride (0.248 g, 1 mmol) was added to
a methanolic solution (30 ml) of the ligand QMH (0.432
g, 2 mmol) and KOH (0.112 g, 2 mmol). The clear
solution was stirred overnight at r.t., then water was
added (15 ml). Immediately a precipitate formed, which
was filtered, recrystallized from a mixture of chloro-
form and light petroleum and dried to constant weight.
The
complexes
(QD)2SnMe2,
(QD)2SnEt2
and
(QD)2SnMeCl were synthesized by the same procedure.
3.3.2. Di-n-butyltin(IV)bis(1,3-dimethyl-4-benzoylpyra-
zolon-5-ato) (QM)2SnBun2 (2)
3.2.2. Synthesis of QDH
1,3-Dimethyl-5-pyrazolone (6.0 g, 53.5 mmol) was
placed in a flask equipped with a stirrer, separating
funnel and a reflux condenser and dissolved in dry
dioxane (60 ml) by warming. Calcium hydroxide (10.0
g, 135 mmol) and then acetyl chloride (3.8 ml, 4.2 g,
54.0 mmol) were added, the latter dropwise for 10 min.
The mixture was heated to reflux overnight and then
A benzene solution (20 ml) of di-n-butyltin oxide
(0.248 g, 1 mmol) was added to a benzene solution (20
ml) of the ligand QMH (0.432 g, 2 mmol), and the
reaction mixture was refluxed for about 6 h. After
removing the solvent under reduced pressure on a
rotary evaporator, a thick oil was obtained. This was
dissolved in diethyl ether (40 ml) and the solution left

202
C. Pettinari et al. / Journal of Organometallic Chemistry 557 (1998) 187–205
Fig. 7. Halogen effect on 119Sn chemical shift of (QD)2SnX2 (X=F, Cl, Br and I).
to evaporate until a yellow precipitate formed. This was
filtered, recrystallized from methanol/diethyl ether and
dried to constant weight. The complex (QD)2SnBun2 was
obtained using the same procedure.
diethyl ether and dried to constant weight. The com-
plexes (QD)2SnCy2, (QD)2SnCl2, (QD)2SnBr2 and
(QM)2SnBr2 were synthesized using the same procedure.
3.3.5. Dibenzyltin(IV)bis(1,3-dimethyl-4-benzoylpyrazo-
lon-5-ato) (QM)2SnBz2 (5)
3.3.3. Di-t-butyltin(IV)bis(1,3-dimethyl-4-benzoylpyra-
zolon-5-ato) (QM)2SnBut2 (3)
Dibenzyltin dichloride (0.372 g, 1 mmol) was added to
a methanolic solution (30 ml) of the ligand QMH (0.432
g, 2 mmol) and KOH (0.112 g, 2 mmol). The clear
solution was stirred overnight at r.t., then evaporated to
dryness under reduced pressure on a rotary evaporator.
The residue was treated with dichloromethane (20 ml)
and methanol was added (40 ml) to the filtered solution.
A precipitate formed, which was filtered, recrystallized
from ethyl acetate and dried to constant weight. The
complexes (QM)2SnPh2, (QD)2SnBz2 and (QD)2SnPh2
were synthesized using the same procedure.
Di-t-butyltin dichloride (0.304 g, 1 mmol) was added
to a methanolic solution (30 ml) of the ligand QMH
(0.432 g, 2 mmol) and KOH (0.112 g, 2 mmol). The clear
solution was stirred overnight at room temperature,
then evaporated to dryness under reduced pressure on a
rotary evaporator. The residue was treated with chloro-
form (20 ml) and to the filtered solution diethyl ether
was added (40 ml): a yellow precipitate formed, which
was filtered, recrystallized from diethyl ether and dried
to constant weight. The complex (QD)2SnBut2 was ob-
tained using the same procedure but light petroleum was
used instead of diethyl ether.
3.3.6.
Difluorotin(IV)bis(1,3-dimethyl-4-acetylpyrazo-
lon-5-ato) (QD)2SnF2 (16)
3.3.4. Dicyclohexyltin(IV)bis(1,3-dimethyl-4-benzoylpyr
azolon-5-ato) (QM)2SnCy2 (4)
Tin tetrafluoride (0.195 g, 1 mmol) was added to a
dichloromethane solution (40 ml) of the ligand QDH
(0.312 g, 2 mmol). The resulting suspension was left
to reflux with stirring for 2 days, then unreacted SnF4
was removed by filtration of the hot solution and the
filtrate was evaporated to dryness under reduced pres-
sure on a rotary evaporator. The residue was extracted
using hot diethyl ether (30 ml) from which a yellow
precipitate slowly formed on cooling. The complexes
(QM)2SnF2, (Q%)2SnF2 and (Q¦)2SnF2 were obtained in a
similar way by using choloroform instead of di-
choloromethane.
Dicyclohexyltin dibromide (0.445 g, 1 mmol) was
added to a methanolic solution (30 ml) of the ligand
QMH (0.432 g, 2 mmol) and KOH (0.112 g, 2 mmol).
The clear solution was stirred overnight at r.t., then
evaporated to dryness under reduced pressure on a
rotary evaporator. The residue was treated with chloro-
form (20 ml) and to the filtered solution diethyl ether
was added (40 ml). From the solution, left to evaporate
overnight at r.t., a light brown precipitate formed, which
was filtered, recrystallized from a mixture of methanol/

C. Pettinari et al. / Journal of Organometallic Chemistry 557 (1998) 187–205
203
Table 7
3.3.7. Diiodotin(i6)bis(1,3-dimethyl-4-acetyllpyrazolon-
5-ato) (QD)2SnI2 (16)
Selected bond distances and angles
To a THF solution (40 ml) of the derivative
(QD)2SnCl2, (0.607 g, 1 mmol) was added an excess of
NaI (0.600 g, 4 mmol) and the resulting suspension was
left to reflux with stirring for 3 days. Then it was
filtered to separate the excess NaI and the NaCl formed
by the Cl/I exchange, and the filtrate was evaporated to
dryness under reduced pressure on a rotary evaporator.
The residue was recrystallized with methanol/diethyl
ether. The complexes (QM)2SnI2, (Q%)2SnI2 and
(Q¦)2SnI2 were synthesized in the same way.
Distances
Sn1–O1
Sn1–O2
Sn1–O51
Sn1–O52
Sn1–C10
Sn1–C16
O1–C5
2.094(9)
2.42(1)
2.132(9)
2.405(8)
2.17(1)
2.14(1)
1.29(1)
1.27(2)
1.30(2)
1.25(2)
O2–C8
O51–C55
O52–C58
Angles
C(16)–Sn(1)–C(10)
O(2)–Sn(1)–O(1)
O(52)–Sn(1)–O(51)
O(51)–Sn(1)–O(1)
O(52)–Sn(1)–O(2)
O(51)–Sn(1)–O(2)
O(52)–Sn(1)–O(1)
C(10)–Sn(1)–O(1)
C(10)–Sn(1)–O(2)
C(10)–Sn(1)–O(51)
C(10)–Sn(1)–O(52)
C(16)–Sn(1) - O(1)
C(16)–Sn(1)–O(2)
C(16)–Sn(1)–O(51)
C(16)–Sn(1)–O(52)
154.6(5)
80.4(3)
80.5(3)
77.8(3)
121.2(3)
158.2(3)
158.3(4)
101.6(4)
85.3(4)
98.4(4)
81.8(4)
100.2(4)
85.6(4)
98.8(4)
82.7(4)
3.4. X-ray diffraction
A preliminary study was performed using a Weis-
senberg Camera to determine cell parameters and space
group. A P21 Syntex diffractometer was used for the
measurements of the cell constants and for the data
collection. A summary of crystal data together with
Table 6
Atomic coordinates and isotropic displacement parameters
Sn
O1
O2
O51
O52
N1
0.12540(2)
0.1350(3)
0.0699(3)
0.1780(2)
0.1364(3)
0.1319(3)
0.1115(4)
0.2248(3)
0.2389(4)
0.0839(4)
0.0862(4)
0.1177(4)
0.1650(5)
0.0578(5)
0.0638(4)
0.0287(4)
0.1513(4)
0.1608(4)
0.1808(4)
0.1556(5)
0.1466(4)
0.1265(5)
0.0844(4)
0.0535(4)
0.0281(5)
0.0084(6)
0.0391(6)
0.0656(5)
0.2161(5)
0.1863(4)
0.1942(4)
0.2445(4)
0.2251(6)
0.1568(4)
0.1494(6)
0.27023(4)
0.1674(5)
0.2045(5)
0.2880(4)
0.3972(5)
0.0434(6)
−0.0182(6)
0.3518(7)
0.4237(8)
0.0074(7)
0.0853(6)
0.1062(6)
0.0366(9)
−0.0483(8)
0.1358(7)
0.114(1)
0.2555(6)
0.1752(6)
0.1693(7)
0.2046(9)
0.2844(7)
0.2914(7)
0.3155(8)
0.3654(9)
0.400(1)
0.3089(1)
0.408(1)
0.183(1)
0.4552(9)
0.257(1)
0.437(1)
0.381(1)
0.599(1)
0.626(1)
0.278(2)
0.265(1)
0.371(1)
0.551(2)
0.192(2)
0.177(1)
0.067(2)
0.110(1)
0.081(1)
−0.056(1)
−0.186(2)
−0.156(1)
−0.020(1)
0.439(2)
0.352(2)
0.461(2)
0.543(2)
0.627(2)
0.523(2)
0.536(2)
0.447(2)
0.493(1)
0.679(2)
0.542(2)
0.330(2)
0.295(2)
2.79(2)
3.7(2)
4.0(2)
3.3(2)
3.8(2)
4.0(3)
4.7(4)
4.4(3)
5.0(4)
3.8(4)
2.8(3)
3.1(3)
5.0(5)
4.9(4)
3.3(3)
5.8(5)
2.9(3)
3.1(3)
3.9(4)
4.9(4)
4.1(4)
4.3(4)
3.8(4)
5.2(5)
6.9(6)
7.4(7)
7.2(7)
5.8(5)
5.0(5)
4.5(4)
3.8(4)
4.9(4)
7.6(7)
4.0(4)
6.2(6)
details of data collection and computer resolution is
given in Table 9. Monitoring of the standard reflections
[0,4,0], [0,−4,0] and [1,1,−1], taken every 100 reflec-
tions, indicated no decay. A c-scan showed no absorp-
tion anisotropy. Data were corrected for Lorentz and
polarization effects. The molecular structure was solved
using the heavy atom method with CAOS [26]. Subse-
quent calculations were performed as follows: refine-
ment based on the minimization of the function
ꢀw(ꢁFoꢁ−ꢁFcꢁ)2 with the weighting scheme w=1/(a+
Fo+cF2o), where a and c are of the order of 2Fo(min)
and 2/Fo(max) [27], respectively; H atoms were intro-
duced at fixed positions according to C–H distance=
N2
N51
N52
C3
C4
C5
C6
C7
C8
C9
C10
C11
C12
C13
C14
C15
C16
C17
C18
C19
C20
C21
C53
C54
C55
C56
C57
C58
C59
˚
0.96 A. Anisotropic displacement parameters were
allowed for non-H atoms and H isotropic displacement
parameters were kept fixed during refinement. The final
refinement showed no residual peaks. Atomic scattering
factors and anomalous dispersion terms were taken
from the literature [28].
0.342(1)
0.291(1)
0.258(1)
0.4648(8)
0.4257(8)
0.3510(8)
0.2905(8)
0.547(1)
4. Supplementary material
Hydrogen coordinates, full list of bond distances and
angles and anisotropic displacement parameters. Fo/Fc
listing is available from F. Caruso (e-mail:
caruso@isc.mlib.cnr.it).
0.4444(7)
0.5237(8)

204
C. Pettinari et al. / Journal of Organometallic Chemistry 557 (1998) 187–205
Fig. 8. ORTEP view of the compound (QD)2SnCy2.
Table 8
Selected geometrical data in the coordination sphere for diorganotinbis(i-diketonate) compounds
Compounda
Sn–Obp
(a)
Sn–Ocs
(b)
(b)–(a) Sn–C
2.14(2)
Op–Sn–Op Os–Sn–Os
94(1)
Op–Sn–Os C–Sn–C Geometry
(bite)
Ref.
Me2Sn(acac)2
2.18(1)
2.20(2)
86(1)
180
Octahedral ([5]a)
Ph2Sn(QBr 2
)
2.143(7) 2.223(8) 0.08
2.12(1) 2.26(1) 0.14
2.105(6) 2.359(7) 0.254
2.109(7) 2.329(7) 0.220
2.123(4) 2.288(4) 0.165
2.105(5) 2.321(4) 0.216
2.11(1)
2.11(2)
2.12(1)
2.15(1)
2.101(8) 82.7(1)
2.118(7)
2.07(2)
2.09(2)
2.07(2)
2.12(2)
2.17(1)
2.14(1)
2.097(8) 75.5(2)
2.099(8)
2.095(8) 77.2(1)
2.090(8)
2.20(1)
2.20(2)
91.9(3)
84.1(3)
98.6(3)
84.5(4)
85.1(3)
83.5(2)
85.0(3)
82.9(2)
83.2(1)
81.8(4)
83.7(4)
82.0(4)
80.3(4)
80.4(3)
80.5(3)
78.5(2)
79.5(2)
80.9(1)
80.7(1)
79.3(2)
79.8(2)
173.0(7)
164.5(4)
162.1(3)
157.0(8)
154.7(8)
154.6(5)
154.5(3)
153.3(3)
150.0(5)
STB
STB
STB
STB
STB
STB
STB
STB
STB
([6]c)
Bz2Sn(QOMe
)
107.4(2)
111.5(2)
112.7(4)
118.7(4)
121.2(3)
126.7(2)
121.6(1)
127.4(2)
([6]e)
2
Me2Sn(Q¦)2
([22]b)
([6]d)
([22]a)
This work
([6]b)
([6]a)
Me2Sn(Q2O-i-Pr) 2.10(1)
2.09(1)
2.39(1)
2.39(1)
2.35(2)
2.38(2)
0.29
0.30
0.23
0.27
0.326
82.0(4)
79.2(5)
77.8(3)
Bun2Sn(Q%)2
2.12(2)
2.11(2)
Cy2Sn(QD)2
2.094(9) 2.42(1)
2.132(9) 2.405(8) 0.273
2.104(4) 2.385(5) 0.281
2.099(4) 2.436(5) 0.337
2.104(3) 2.337(4) 0.233
2.103(4) 2.412(4) 0.309
2.145(5) 2.381(7) 0.236
2.135(6) 2.461(6) 0.326
Me2Sn(QBr 2
)
Me2Sn(Q%)2
But2Sn(Q%)2
74.1(2)
[1]
a acac=pentane-2,4-dionato; Q%=1-phenyl-3-methyl-4-benzoylpyrazolon-5-ato; Q¦=1-phenyl-3-methyl-4-acetylpyrazolon-5-ato; QBr=1-phenyl-
3-methyl-4-p-bromobenzoylpyrazolon-5-ato;
O-i-Pr=1-phenyl-3-methyl-4-isopropoxycarbonylpyrazolon-5-ato; OMe=1-phenyl-3-methyl-4-
Q
Q
methoxycarbonyl pyrazolon-5-ato; QD=1,3-dimethyl-4-acetylpyrazolon-5-ato.
b Op, primary bond.
c Os, secondary bond.

C. Pettinari et al. / Journal of Organometallic Chemistry 557 (1998) 187–205
205
Table 9
Summary of crystal data
golani, J. Tanski, M. Rossi, F. Caruso, Inorg. Chim. Acta 257
(1997) 37. (e) C. Pettinari, F. Marchetti, A. Cingolani, A.
Lorenzotti, E. Mundorff, M. Rossi, F. Caruso, Inorg. Chim.
Acta 262 (1997) 33.
Formula
C24H40N4O4Sn
567.30
Formula weight
[7] D.L. Kepert, Prog. Inorg. Chem. 23 (1977) 1.
[8] E.C. Okafor, B.A. Uzoukwu, Synth. React. Inorg. Met. Org.
Chem. 23 and references reported therein.
[9] B.S. Jensen, Acta Chem. Scand. 13 (1959) 1347, 1668, 1890.
[10] D. Searle, P.J. Smith, N.A. Bell, L.A. March, I.W. Nowell, J.D.
Donaldson, Inorg. Chim. Acta 162 (1989) 143.
[11] (a) A.J. Crowe, P.J. Smith, Chem. Ind. (1980) 200. (b) A.J.
Crowe, P.J. Smith, G. Atassi, Chem. Biol. Interact. 32 (1980)
171. (c) M. Gielen (Ed.), Tin-based Antitumor Drugs, NATO
ASI Ser. H. Cell Biology, vol. 37, Brussels, 1989.
˚
a (A)
34.398(10)
18.242(7)
9.248(3)
97.81(3)
5749(3)
C2/c
8
0.35×0.20×0.20
˚
b (A)
˚
c (A)
i (°)
Volume (A3)
Space group
Z
Crystal dimensions
(mm)
Density calc. (g cm− 1.311
3)
[12] C. Pettinari, F. Marchetti, A. Cingolani, C. Marciante, R.
Spagna, M. Colapietro, Polyhedron 13 (1994) 939.
Temperature
298 K
2352
9.296
[13] K. Nakamoto, Infrared and Raman Spectra of Inorganic and
Coordination Compounds, 4th ed., Wiley Interscience, New
York, 1986, chap. III, pp. 259–267.
F(000)
v (cm−1
)
Radiation
Mo–Kh
ꢀ
[14] (a) M. McGrady, R.S. Tobias, Inorg. Chem. 3 (1964) 1157. (b)
R.W. Jonas, R.C. Fay, Inorg. Chem. 12 (1973) 2599. (c) I.
Wharf, D.F. Shiver, Inorg. Chem. 8 (1969) 914. (d) J.R. May,
W.R. McWhinnie, R.C. Poller, Spectrochim. Acta 27A (1971)
969. (e) A.L. Smith, Spectrochim. Acta 24A (1967) 695. (f) M.S.
Dance, W.R. McWhinnie, R.C. Poller, J. Chem. Soc. Dalton
Trans. (1976) 2349. (g) G.K. Sandhu, N.S. Boparoy, J.
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G. Ruisi, R. Barbieri, Appl. Organomet. Chem. 7 (1993) 243.
[15] B. Wrackmeyer, Annu. Rep. NMR Spectrosc. 16 (1985) 73.
[16] J. Holecec, A. Lycka, Inorg. Chim. Acta 118 (1986) L15.
[17] T.P. Lockhart, W.F. Manders, Inorg. Chem. 25 (1986) 892.
[18] (a) J.A.S. Smith, E.J. Wilkins, J. Chem. Soc. A (1966) 1749. (b)
R. Ueeda, Y. Kawasaki, T. Tanaka, R. Okawara, J. Organomet.
Chem. 5 (1966) 194. (c) V. Doron, C. Fischer, Inorg. Chem. 6
(1967) 1917. (d) J.W. Faller, A. Davison, Inorg. Chem. 6 (1967)
182. (e) G.E. Glass, R.S. Tobias, J. Organomet. Chem. 15 (1968)
481.
Data collection mode
Scan speed (° min−1
Scan range (°)
Background counts
2q range (°)
)
2
0.6
1/4 of scan time at the end of scan range
3–56
2886
316
Reflections refined
Final no. variables
Rf, Rw
0.059, 0.080
Acknowledgements
Financial support by Universita` degli Studi di
Camerino, Consiglio Nazionale delle Ricerche C.N.R.-
Rome, Research Committee and URSI program at
Vassar College.
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Puddephatt, W. Ramsay, W. McFarlane, J. Chem. Soc. C (1969)
1136.
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