Structural and spectral studies of 3-(2-hydroxyphenylimino)-1-phenylbutan-1-one and its diorganotin(IV) complexes

Article abstract of DOI:10.1016/j.jorganchem.2009.03.013

Two diorganotin(IV) complexes of the general formula R₂Sn[Ph(O)C{double bond, long}CH-C(Me){double bond, long}N-C₆H₄(O)] (R = Ph, 1a; R = Me, 1b) have been synthesized from the corresponding diorganotin(IV) dichlorides and

Full text of DOI:10.1016/j.jorganchem.2009.03.013

Journal of Organometallic Chemistry 694 (2009) 2434–2441
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Structural and spectral studies of 3-(2-hydroxyphenylimino)-1-phenylbutan-1-one
and its diorganotin(IV) complexes
b
c
c
d,1
Dilip Kumar Dey a, , Sankar Prasad Dey , Nirmal Kumar Karan , Amitabha Datta , Antonin Lycka
,
*
Georgina M. Rosair e,
*
a Department of Chemistry, Chandidas Mahavidyalaya, Khujutipara 731 215, District – Birbhum, West Bengal, India
b Department of Chemistry, Sri Krishna College, Bagula, District – Nadia, West Bengal, India
c Department of Chemistry, Jadavpur University, Kolkata 700 032, India
d Research Institute for Organic Syntheses, Rybitvi 296, CZ-533 54 Pardubice 20, Czech Republic
e Department of Chemistry, William Perkin Building, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, EH14 4AS Scotland, United Kingdom
a r t i c l e i n f o
a b s t r a c t
Article history:
Two diorganotin(IV) complexes of the general formula R2Sn[Ph(O)C@CH-C(Me)@N–C6H4(O)] (R = Ph, 1a;
R = Me, 1b) have been synthesized from the corresponding diorganotin(IV) dichlorides and the ligand, 3-
(2-hydroxyphenylimino)-1-phenylbutan-1-one (1) in methanol at room temperature in presence of tri-
ethylamine. Both compounds have been characterized by elemental analyses, IR and 1H, 13C, 15N, 119Sn
NMR spectra. The structures of the free ligand and the complexes have been confirmed by single crystal
X-ray diffraction. There are three independent molecules in the crystal structure of the ligand 1 and in all
three the O-bound proton is transferred to the imine nitrogen and makes an intramolecular N–Hꢀ ꢀ ꢀO
hydrogen bond with the carbonyl oxygen. In turn this makes an intermolecular hydrogen bond with
the phenolic H atom. The crystal structure of 1 is trigonal and a new polymorph; triclinic and monoclinic
forms have already been published. In 1a, the central tin atom adopts distorted trigonal–bipyramidal
coordination geometry whereas in dimeric 1b it is distorted octahedral when including the intermolec-
ular Sn–O(phenolic) bond [2.7998(20) Å]. The d (119Sn) values for the complexes 1a and 1b are ꢁ306.6
and ꢁ127.9 ppm, respectively, thus indicating penta-coordinated Sn centres in solution.
Received 15 January 2009
Accepted 11 March 2009
Available online 17 March 2009
Keywords:
Crystal structures of diorganotin(IV)
complexes
13C/119Sn NMR
H,H-COSY
gs-HMQC and gs-HMBC
Ó 2009 Published by Elsevier B.V.
1. Introduction
The ligand, 3-(2-hydroxyphenylimino)-1-phenylbutan-1-one,
used in this study has less conformational flexibility compared to
The coordination chemistry of tridentate amino acid-derived
Schiff bases [1–3] and related tridentate Schiff bases [4–8] with
diorganotin(IV) centres has been discussed widely. Much interest
arises from their pharmacological activity [6] where several
organotin(IV) complexes have shown antitumour and antiviral
activity [8]. Equilibrium and NMR studies on dimethyltin dipeptide
complexes have investigated possible mechanisms for the toxic
and antitumour activity of Sn complexes [9]. The coordination
modes of the ONO donor tridentate N-(2-carboxyphenyl)salicylide-
neimine dianion and N-(2-carboxyphenyl)-50-bromosalicylidenei-
mine dianion towards diorganotin have been reported [10–12]
whilst recently, chiral (salicylaldiminato)tin Schiff base complexes
were reported with non-linear optical properties [12,13].
4-phenyl-2,4-butanedionebenzoylhydrazone(2-) used previously
by us [14] because the former has an extra aromatic ring. We
wanted to observe the change in spectral and structural properties
arising from the this change in flexibility and ascertain the solid
state structure of the ligand and its coordination mode with dior-
ganotin(IV) dichlorides.
This study describes the syntheses and X-ray crystal structures
of the ligand, 3-(2-hydroxyphenylimino)-1-phenylbutan-1-one (1)
and its diorganotin(IV) complexes, Ph2Sn[Ph(O)C@CH-C(Me)@N–
C6H4(O)] (1a) and Me2Sn[Ph(O)C@CH-C(Me)@N–C6H4(O)] (1b).
Both the complexes have been structurally characterized in the so-
lid and solution state by crystallography and NMR spectra.
2. Experimental
* Corresponding authors. Present address: Department of Chemistry, Raja Peary
Mohan College, Uttarpara 712 258, Hooghly, West Bengal, India (D.K. Dey).
E-mail addresses: deydk@yahoo.com (D.K. Dey), g.m.rosair@hw.ac.uk (G.M.
Rosair).
University of Hradec Kralove, Faculty of Education, Rokitanskeho 62, CZ-50003
Hradec Kralove, Czech Republic.
2.1. Materials
All chemicals and reagents were of reagent grade quality.
Diphenyltin dichloride (Aldrich), dimethyltin dichloride (Fluka),
benzoyl acetone (Aldrich), o-aminophenol and trimethylamine
1
0022-328X/$ - see front matter Ó 2009 Published by Elsevier B.V.
doi:10.1016/j.jorganchem.2009.03.013

D.K. Dey et al. / Journal of Organometallic Chemistry 694 (2009) 2434–2441
2435
(S.D. Fine Chemicals, India) were used as received. Methanol
(Ranbaxy, India) was dried over CaO and distilled prior to use.
poor crystal quality probably contributed to this but if face index-
ing was possible this would have improved the absorption correc-
tion. The structures were solved and subsequently refined by full-
2.2. Physical measurements
matrix least-squares procedures on F2
(SHELXTL) [18]. Hydrogen
atom positions were calculated assuming ideal geometry and using
appropriate riding models, but for 1, H1A and H8C were located in
the difference map and though the coordinates were refined the
displacement parameter was treated as riding on the bound O or
N atom, respectively. Further details are given in Table 1.
Infrared spectra were recorded on a Perkin–Elmer 883 infrared
spectrophotometer from 4000 to 200 cmꢁ1 as KBr discs and were
calibrated with respect to the 1601 cmꢁ1 band of polystyrene film.
Tin was estimated gravimetrically as SnO2 after decomposition
with concentrated HNO3. C, H and N analyses were carried out
on a Perkin–Elmer 2400 II elemental analyser. Melting points
(uncorrected) were recorded on an electrical heating-coil
apparatus.
2.4. Synthesis and characterization of the ligand (H2L) (1)
The ligand, 3-(2-hydroxyphenylimino)-1-phenylbutan-1-one
(H2L) has been prepared by refluxing a mixture of benzoyl acetone
(1.23 g, 7.58 mmol) and o-aminophenol (0.827 g, 7.58 mmol) in
methanol (20 ml) for 3 h. Orange crystalline solid appeared on
cooling to room temperature. This was filtered, washed with meth-
anol and dried. Single crystals suitable for X-ray crystallography
were obtained by cooling a dilute methanolic solution of the com-
pound. Yield: 1.54 g (80%); m.p. 169–170 °C. Anal. Calc. for
C16H15NO2 (formula weight 253.29): C, 75.87; H, 5.97; N, 5.53.
Found: C, 75.66; H, 6.02; N, 5.57%. 1H NMR, 400.15 MHz, d6-
DMSO): 9.99 (s, 1H), 7.89 (t, 2H), 4.43–7.49 (m, 3H), 7.24 (t, 1H),
7.03–7.08 (m, 1H), 6.94 (t, 1H), 6.80–6.84 (m 1H), 6.02 (s, 1H),
3.32 (s, 1H), 2.13 (s, 3H); 13C NMR, 100.61 MHz, d6-DMSO):
186.53, 162.57, 150.44, 139.64, 130.86, 128.33, 126.80, 126.48,
125.99, 125.11, 119.13, 115.86, 93.54, 20.08. Probable molecular
structures of the ligand are given in Fig. 1.
1H (400.15 MHz), 13C (100.61 MHz), NMR spectra of ligand 1
were recorded at 300 K in d6-DMSO on a Spect 400 spectrometer.
1H (360.13 MHz), 13C (90.566 MHz), 119Sn (134.3 MHz) and 15N
(36.50 MHz) NMR spectra of the complexes (1a and 1b) were re-
corded at 300 K on a Bruker AMX 360 spectrometer equipped with
5 mm broadband inverse probe and a Silicon Graphics Indy com-
puter. The compounds studied were measured in CDCl3 and 1H
and 13C chemical shifts were referred to the central signal of the
solvent [d = 7.25 (1H) and [d = 77.00 (13C)]. The 15N and 119Sn
chemical shifts were referred to external nitromethane and tetra-
methylstannane, respectively (d = 0.0) placed in a coaxial capillary.
Positive values of the chemical shifts denote downfield shifts with
respect to standards. Two-dimensional H,H-COSY, gs(gradient se-
lected)-HMQC and gs-HMBC techniques were measured using
the standard software provided by Bruker [15].
2.3. X-ray structure analyses of ligand (H2L) (1), and complexes 1a and
1b
2.5. Syntheses and characterization of diorganotin(IV) complexes 1a
and 1b
Single crystals of the ligand, 3-(2-hydroxyphenylimino)-1-phe-
nylbutan-1-one (H2L) (1) was grown from methanol. Crystals of 1a
were obtained from CHCl3/petroleum ether (40–60 °C) mixture
and crystals of Me2Sn[Ph(O)C@CH-C(Me)@N–C6H4(O)] (1b) were
obtained from a methanol solution. Diffraction measurements of
1, 1a [100.0(2) K on a BrukerAXS X8 CCD] [16] and 1b [160(2) K
on a P4 four circle diffractometer] [17] using graphite-monochro-
2.5.1. Ph2Sn[Ph(O)C@CH-C(Me)@N–C6H4(O)] (1a)
To a solution of ligand, 3-(2-hydroxyphenylimino)-1-phenylb-
utan-1-one, (H2L) (0.633 g, 2.50 mmol) in dry methanol (25 ml)
in a 100 ml beaker, triethylamine (0.558 g, 5.52 mmol) was added
and the resulting yellow triethylammonium salt solution of the li-
gand was filtered to remove any insoluble impurities. To this solu-
tion, a solution of Ph2SnCl2 (0.859 g, 2.50 mmol) in 20 ml of dry
methanol was added slowly at room temperature. After 30 min.
shiny yellow crystals of compound 1a appeared. This was filtered,
mated Mo Ka radiation (k = 0.71073 Å) were corrected for absorp-
tion, however, there was a large peak (11 e Åꢁ3) 1 Å from Sn for 1a,
Table 1
Crystal refinement data for the free ligand (H2L) (1), Ph2Sn[Ph(O)C@CH-C(Me)@N–C6H4(O)] (1a) and Me2Sn[Ph(O)C@CH-C(Me)@N–C6H4(O)] (1b).
1
1a
1b
Empirical formula
Formula weight
T (K)
C16H15NO2
253.29
100(2)
C28H23NO2Sn
524.16
100(2)
C18H19NO2Sn
400.03
160(2)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
Trigonal
P32
15.8411(6)
15.8411(6)
14.1075(9)
90
Monoclinic
P21/c
13.8311(17)
15.8066(17)
11.4270(12)
90
Monoclinic
P21/c
10.7540(10)
8.550
18.5040(10)
90
a
(°)
b (°)
90
120
3065.9(3)
9
113.617(5)
90
2289.0(4)
99.800(10)
90
1676.55(18)
4
c
(°)
V (Å3)
Z
4
Dcalc. (g cmꢁ3
)
1.235
1.521
1.585
h range for data collection (°)
Reflections collected
1.48–21.77
31931
2.33–34.35
19442
2.23–25.00
3934
Independent reflections [R(int)
]
4740 [0.0636]
0.9823 and 0.8762
4740/49/525
1.160
7917 [0.0999]
0.796 and 0.582
7917/0/290
1.054
2936 [0.0225]
0.8729 and 0.7083
2936/0/201
1.117
Maximum and minimum transmission
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.1020, wR2 = 0.2635
R1 = 0.1056, wR2 = 0.2662
0.442 and ꢁ0.467
R1 = 0.0874, wR2 = 0.2387
R1 = 0.1139, wR2 = 0.2492
11.44 (near Sn) and ꢁ1.441
R1 = 0.0245, wR2 = 0.0642
R1 = 0.0266, wR2 = 0.0654
0.408 and ꢁ0.521
Largest difference peak and hole (e Aꢁ3
)

2436
D.K. Dey et al. / Journal of Organometallic Chemistry 694 (2009) 2434–2441
OH
OH
N
OH
N
H
H
N
O
O
O
H3C
H3C
H3C
I
III
II
Fig. 1. Structure of ligand (H2L) used in this study.
washed with petroleum ether (40–60 °C) and dried in vacuo. Single
crystals suitable for X-ray crystallography were obtained from
CHCl3/petroleum ether (40–60 °C) mixture. Yield: 1.85 g (84%);
m.p. 186–187 °C. Anal. Calc. for C28H23NO2Sn (formula weight
524.16): C, 64.15; H, 4.42; N, 2.67; Sn, 22.64. Found: C, 64.32; H,
4.36; N, 2.73; Sn, 22.38%.
in solid state. The ligand may exist either in imino-en-ol form (II)
or in amino-en-one form (III) in the solid state (Fig. 1). There is a
singlet signal at d 9.99 ppm in 1H NMR spectra in d6-DMSO indi-
cates the presence of enolic –OH in solution. So the ligand exists
in imino-en-ol form (II) in solution. To ascertain the structure of li-
gand in solid state we performed an X-ray crystallographic study
which indicated that the ligand exists in amino-en-one form (III)
in solid state (vide infra). The most significant difference emerges
from a comparison of vibrational spectra of the ligand (H2L) and
its diorganotin(IV) complexes (1a and 1b) is the disappearance of
2.5.2. Me2Sn[Ph(O)C@CH-C(Me)@N–C6H4(O)] (1b)
To a solution of ligand, 3-(2-hydroxyphenylimino)-1-phenylb-
utan-1-one, (H2L) (0.685 g, 2.704 mmol) in dry methanol (25 ml)
in a 100 ml beaker, triethylamine (0.601 g, 5.95 mmol) was added
and the resulting yellow triethylammonium salt solution of the li-
gand was filtered to remove any insoluble impurities. To this solu-
tion, a solution of Me2SnCl2 (0.593 g, 2.70 mmol) in 20 ml of dry
methanol was added slowly at room temperature. After 30 min.
shiny yellow crystals of compound 1b appeared. This was filtered,
washed with petroleum ether (40–60 °C) and dried in vacuo. Single
crystals suitable for X-ray crystallography were also obtained from
a methanol solution. Yield: 1.32 g (89%); m.p. 135–136 °C. Anal.
Calc. for C18H19NO2Sn (formula weight 400.03): C, 54.04; H, 4.79;
N, 3.50; Sn 29.67. Found: C, 53.91; H, 4.71; N, 3.55; Sn, 29.33%.
Table 2
1H, 13C, 119Sn and 15N NMR chemical shifts and nJ(119Sn,1H) and nJ(119Sn,13C) coupling
constants for 1a and 1b in CDCl3. Coupling constants values (Hz) are given in
parentheses.
H/C no.
Compound 1a
d (1H)
Compound 1b
d (1H)
d (13C)
d (13C)
1
2
3
4
5
6
7
8
–
158.33 (13)
117.85 (12)
127.52
–
158.26 (13.9)
117.41 (7.6)
127.19
7.15
7.15
6.66
7.05
–
6.84
7.06
6.64
7.05
–
115.77
115.44
122.55 (24.1)
132.01 (45.1)
172.52 (10.9)
25.00 (15.6)
98.48 (33.1)
178.63 (22.1)
138.04
126.88
128.57
131.24
122.53 (22.2)
132.06 (42.2)
172.54 (11.8)
24.59 (13.2)
97.73 (31.6)
179.08 (20.8)
138.43
126.88
128.31
130.98
ꢁ1.37 (648.5)
3. Results and discussion
–
–
3.1. Synthesis
2.50
6.06
–
2.44
5.96
–
9
10
11
12
13
14
10
20
30
40
Sn
N
The diorganotin(IV) complexes reported here, have been syn-
thesized from diorganotin(IV) dichlorides (Ph2SnCl2 or Me2SnCl2)
and 3-(2-hydroxyphenylimino)-1-phenylbutan-1-one (H2L) in
methanol at room temperature in presence of triethylamine (Eq.
(1) below) in 1:1:2 ratio with slight excess of Et3N. The complexes
separated out from the reaction mixture
–
8.06
7.53
7.53
–
7.94 (77.2)
7.37
7.37
–
7.82
7.43
7.43
0.73 (77.1)
138.66 (979.0)
136.37 (52.5)
128.63 (84.9)
130.23 (17.3)
ꢁ306.6a
R2SnCl2 þ H2 þ 2Et3N M!eoH R2SnL þ 2Et3N ꢀ HCL ðR ¼ Ph
ꢁ127.9a
ꢁ199.5b
r:t:
–
ꢁ197.7b
: 1a; R ¼ Me : 1bÞ
ð1Þ
d (119Sn).
a
b
d (15N).
Although these two compounds have been prepared in metha-
nol at room temperature, the compounds could also be prepared in
other solvents such as benzene and toluene. Carrying out the reac-
tion at higher temperature and/or using more concentrated solu-
tions could further reduce reaction times. Both 1a and 1b are
stable under atmospheric conditions.
R
O
2
1
R
3
4
Sn
3.2. Spectroscopic studies
6
N
7
O
5
12
In the infrared spectrum of the ligand, 3-(2-hydroxyphenylimi-
11
10
H3C
8
13
14
no)-1-phenylbutan-1-one (H2L) (1) there is one strong band at
9
1608 cmꢁ1 which is assigned to
m
(C@N)/
[19]. IR spectrum also indicates that there is no band correspond-
ing to carbonyl (C@O) vibration. The stretching vibrations for phe-
m(C@C) stretching mode
2' 3'
m
1'
CH3
1'
nolic proton and hydrogen bonded enolic –OH (II)/N–H (III)
protons (Fig. 1) appear as a strong envelope in the range 3496–
2700 cmꢁ1. The O–H bending and C–O stretching vibrations are
found around 1138 cmꢁ1 and 1330 cmꢁ1, respectively [20]. From
infrared spectra, it is very difficult to conclude about its structure
for 1a:
4'
R =
for 1b:
R =
Fig. 2. Constitution of compounds 1a and 1b and numbering scheme for NMR
assignments.

D.K. Dey et al. / Journal of Organometallic Chemistry 694 (2009) 2434–2441
2437
The NMR spectra (1H, 13C, 15N, 119Sn) for the compounds Ph2SnL
(1a) and Me2SnL (1b) were measured and analyzed. Two-dimen-
sional NMR spectra were used to assign proton and carbon chem-
ical shifts unambiguously. H,H-COSY, gs(gradient selected)-HMQC
and gs-HMBC techniques were also applied [21,22]. The 15N NMR
spectra were measured using the gs-HMBC technique (the experi-
ment being optimised for nJ(15N, 1H) = 6 Hz). The 1H, 13C, 15N and
119Sn chemical shifts are given in Table 2. We have been able to
identify all proton and carbon signals separately for both com-
pounds. For each compound the number of 1H, 13C and 15N signals
observed is in good agreement with the numbering shown in Fig. 2.
For the diphenyltin(IV) compound 1a detection of 2J(119Sn,13C)
coupling (22.1 Hz and 10.9 Hz) with C(10) and C(7) carbons, and
3J(119Sn,13C) coupling (33.1 Hz) with C(9) indicates the coordina-
tion of enolic oxygen and nitrogen atoms of the ligand with tin.
The 2J(119Sn,13C) coupling (13 Hz) with C(1) carbon and
3J(119Sn,13C) coupling (12 Hz) with C(2) indicates the coordination
of phenolic oxygen atom of the ligand with tin.
Fig. 3. Perspective view and atom numbering scheme of one of the three
independent molecules of the ligand, 3-(2-hydroxyphenylimino)-1-phenylbutan-
1-one (1) (labelling identical in other molecules apart from the suffix being B or C).
Ellipsoids are drawn at the 50% probability level.
For the dimethyltin(IV) compound 1b the 2J(119Sn,13C) coupling
(20.8 Hz and 11.8 Hz) with C(10) and C(7) and 3J(119Sn,13C) cou-
pling (31.6 Hz) with C(9) indicates the coordination of enolic oxy-
gen and nitrogen atoms of the ligand with tin. The detection of
2J(119Sn,13C) coupling (13.9 Hz) with C(1) and 3J(119Sn,13C) coupling
(7.6 Hz) with C(2) indicates coordination of the phenolic oxygen
atom to tin.
The 1J(119Sn,13C) coupling constant of 979.0 Hz with phenyl car-
bon for 1a is comparable with reported values for phenyltin com-
pounds [23–25] but lower than the value (993.2 Hz) seen in the
hydrazone complex, Ph2Sn[2-OC6H4CH@N-N@C(O)C6H5] [26]. The
corresponding 1J(119Sn,13C) coupling constant, 648.5 Hz with
methyl carbon of 1b is comparable with that seen for Me2Sn[2-
OC6H4CH@N-N@C(O)C6H5] [26].
The C–Sn–C angle in solution can be estimated from
1J(119Sn,13C) coupling constants [24]. Using equation the
/1J(119Sn,13C)/ = (15.91 0.72)h ꢁ (1164 84),
the
Cphenyl–Sn–
Cphenyl angle was found to be 134.72° [cf. 120.1(2)° in the X-ray
study] for compound 1a. For compound 1b, the Cmethyl–Sn–Cmethyl
angle was calculated using the equation /1J(119Sn,13C)/
= 10.7h ꢁ 778 [27] with the 1J(119Sn,13C) value of 649.9 Hz giving
the angle as 133.31o [cf. 141.72° in the X-ray study]. The 2J(Sn–
CH3) value of 77.1 Hz is in agreement with values reported
(77–81 Hz) for the dimethyltin(IV) complexes with ONO donor
tridentate ligands [10,13,26,28,29]. Using Lockhart’s equation
[Me–Sn–Me = 0.0161(/2J(119Sn,1H)/)2 ꢁ1.32(/2J(119Sn,1H)/) + 133.4]
[29], the C–Sn–C angle for 1b is estimated to ca. 129°, yet this is
lower from the value as obtained from X-ray structural study. X-
ray structure of 1b showed that it forms a dimeric structure
through a long range coordination phenolic oxygen atom of second
molecule. There is an expansion of Cmethyl–Sn–Cmethyl (141.72°)
angle to accommodate a sixth coordination site. However, in
solution this dimeric structure dissociates to become a discrete
Fig. 4. View of the crystal packing of 3-(2-hydroxyphenylimino)-1-phenylbutan-1-
one (1) showing intermolecular OHꢀ ꢀ ꢀO hydrogen bonds as dotted lines.
–O–H and N–H band. Strong bands at 1588 cmꢁ1 for both 1a and
1b are assigned to m(C@N–C@C) stretching. This suggests the coor-
dination of imino nitrogen, deprotonated phenolic and enolic oxy-
gen to tin(IV), and therefore the tridentate dibasic nature of the
coordinated ligand. X-ray crystallographic analyses of both com-
plexes indicate that the ligand reacted with R2SnCl2 through its
imino-en-ol form (II) (vide infra).
five-coordinate tin complex. This contributes to the low Cmethyl
Sn–Cmethyl angle as estimated from NMR in solution.
–
The 119Sn NMR spectra were recorded in CDCl3. The d (119Sn)
values for 1a and 1b are ꢁ306.6 and ꢁ127.9 ppm, respectively.
Table 3
Selected bond lengths (Å) for the ligand, 3-(2-hydroxyphenylimino)-1-phenylbutan-1-one (H2L) (1).
O(1A)–C(2A)
O(1A)–H(1A)
C(7A)–N(8A)
N(8A)-C(9A)
N(8A)–H(8A)
C(9A)–C(10A)
C(11A)–O(12A)
1.362(13)
0.89(13)
1.427(13)
1.324(13)
0.88
O(1B)–C(2B)
O(1B)–H(1B)
C(7B)–N(8B)
N(8B)–C(9B)
N(8B)–H(8B)
C(9B)–C(10B)
C(11B)–O(12B)
1.351(12)
0.8400
1.426(12)
1.338(13)
0.88
O(1C)–C(2C)
O(1C)–H(1C)
C(7C)–N(8C)
N(8C)–C(9C)
N(8C)–H(8C)
C(9C)–C(10C)
C(11C)–O(12C)
1.341(11)
0.8400
1.428(15)
1.344(14)
0.84(11)
1.396(15)
1.295(13)
1.348(15)
1.305(12)
1.362(15)
1.308(12)

2438
D.K. Dey et al. / Journal of Organometallic Chemistry 694 (2009) 2434–2441
Table 4
ues depend on the coordination number of the tin centre and the
ligand bite [25]. This difference in d (119Sn) value of 178.7 between
Ph2SnL (1a) and Me2SnL (1b) is comparable with the differences
found for Ph2SnCl2 and Me2SnCl2 [26] and other diorganotin(IV)
complexes having a phenyl or methyl substituent on tin. This indi-
cates that the ligand bite is comparable in both complexes. From
119Sn NMR spectra it is also evident that the five-coordinate solid
state structure for 1a (obtained from X-ray crystallography) is re-
tained in solution. But in case of compound 1b, the dimeric solid
state structure dissociates in solution to form a five-coordinate
tin complex.
Intermolecular hydrogen bonding parameters for the ligand, 3-(2-hydroxyphenyli-
mino)-1-phenylbutan-1-one (H2L) (1) (Å and °).
D–Hꢀ ꢀ ꢀA
d(D–H)
d(Hꢀ ꢀ ꢀA)
1.95
2.32
1.93
1.81
1.97(11)
1.81(13)
d(Dꢀ ꢀ ꢀA)
2.661(12)
2.625(9)
2.648(10)
2.643(10)
2.636(12)
2.640(10)
\(DHA)
N(8A)–H(8A)ꢀ ꢀ ꢀO(12A)
O(1B)–H(1B)ꢀ ꢀ ꢀO(12B)#1
N(8B)–H(8B)ꢀ ꢀ ꢀO(12B)
O(1C)–H(1C)ꢀ ꢀ ꢀO(12C)#2
N(8C)–H(8C)ꢀ ꢀ ꢀO(12C)
O(1A)–H(1A)ꢀ ꢀ ꢀO(12A)#3
0.88
0.84
0.88
0.84
0.84(11)
0.89(13)
136.3
101.9
137.7
171.3
135(10)
153(11)
Symmetry transformations used to generate equivalent atoms: #1 ꢁx + y, ꢁx + 1,
z + 1/3; #2 ꢁy + 1, x ꢁ y, z ꢁ 1/3; #3 ꢁy + 1, x ꢁ y + 2, z ꢁ 1/3.
4. Crystal structures of ligand 1, Ph2Sn[Ph(O)CCH-C(Me) N–
C6H4(O)] (1a) and Me2Sn[Ph(O)CCH-C(Me)N–C6H4(O)] (1b)
These 119Sn chemical shifts are in the range reported (90–310 Hz)
for five-coordinate tin compounds [23,26,27]. These d (119Sn) val-
ues compare well with other diorganotin(IV) complexes containing
ONO donor atoms [10,13,14,26]. It is well known that d (119Sn) val-
To confirm the actual structure of ligand, 3-(2-hydroxyphenyli-
mino)-1-phenylbutan-1-one (H2L) (1), single crystals X-ray struc-
tural study were performed. There are three crystallographically
independent molecules in the asymmetric unit. The molecular
structure of one molecule along with atom numbering scheme
for the ligand is given in Fig. 3, and intermolecular hydrogen bond-
ing and unit cell packing is given in Fig. 4. Selected bond lengths
and angles are listed in Table 3. Intermolecular hydrogen bonding
parameters are listed in Table 4.
Table 5
Selected bond lengths (Å) and angles (o) for 1a and 1b.
Compound 1a
Compound 1b
Sn(1)–O(1)
Sn(1)–O(8)
Sn(1)–C(111)
Sn(1)–C(121)
Sn(1)–N(4)
C(6)–C(7)
C(5)–C(6)
O(1)–C(2)
O(8)–C(7)
N(4)–C(5)
N(4)–C(3)
C(5)–C(13)
2.110(4)
2.115(5)
2.130(6)
2.134(6)
2.140(5)
1.383(9)
1.417(8)
1.339(7)
1.329(7)
1.332(8)
1.421(7)
1.507(8)
1.486(8)
159.31(17)
96.8(2)
Sn(1)–O(1)
Sn(1)–O(2)
Sn(1)–C(20)
Sn(1)–C(21)
Sn(1)–N(1)
C(7)–C(9)
C(9)–C(10)
O(1)–C(1)
O(2)–C(10)
N(1)–C(7)
N(1)–C(6)
C(7)–C(8)
2.1100(19)
2.201(2)
2.100(3)
2.116(3)
2.176(2)
1.405(4)
1.399(4)
1.339(3)
1.282(3)
1.333(4)
1.420(4)
1.516(4)
1.488(4)
156.98(8)
99.76(12)
85.23(11)
98.40(11)
90.94(11)
141.72(14)
76.49(8)
80.75(8)
111.32(12)
105.55(11)
113.60(17)
118.8(3)
122.1(3)
119.0(2)
114.4(2)
124.2(3)
124.2(2)
123.7(2)
110.59(18)
125.88(19)
125.9(3)
121.4(3)
114.4(3)
126.4(3)
123.5(3)
115.6(3)
120.9(3)
2.7998(20)
67.48(8)
112.52(8)
Fig. 5. Perspective view and atom numbering scheme of compound 1a. Ellipsoids
are drawn from 40% probability level.
C(7)–C(14)
C(10)–C(11)
O(1)–Sn(1)–O(8)
O(1)–Sn(1)–C(111)
O(8)–Sn(1)–C(111)
O(1)–Sn(1)–C(121)
O(8)–Sn(1)–C(121)
C(111)–Sn(1)–C(121)
O(1)–Sn(1)–N(4)
O(8)–Sn(1)–N(4)
C(111)–Sn(1)–N(4)
C(121)–Sn(1)–N(4)
C(2)–O(1)–Sn(1)
O(1)–C(2)–C(3)
O(1)–C(2)–C(9)
C(3)–C(2)–C(9)
C(2)–C(3)–N(4)
C(12)–C(3)–N(4)
C(5)–N(4)–C(3)
C(5)–N(4)–Sn(1)
C(3)–N(4)–Sn(1)
C(7)–O(8)–Sn(1)
N(4)–C(5)–C(6)
N(4)–C(5)–C(13)
C(6)–C(5)–C(13)
C(7)–C(6)–C(5)
O(8)–C(7)–C(6)
O(8)–C(7)–C(14)
C(6)–C(7)–C(14)
O(1)–Sn(1)–O(2)
O(1)Sn(1)– C(20)
O(2)–Sn(1)– C(20)
O(1)–Sn(1)–C(21)
O(2)–Sn(1)– C(21)
C(20)–Sn(1)–C(21)
O(1)–Sn(1)–N(1)
O(2)–Sn(1)–N(1)
C(20)–Sn(1)–N(1)
C(21)–Sn(1)–N(1)
C(1)–O(1)–Sn(1)
O(1)–C(1)–C(6)
O(1)–C(1)–C(2)
O(1)–C(1)–C(6)
C(1)–C(6)–N(1)
C(9)–C(7)–N(1)
C(7)–N(1)–C(6)
C(7)–N(1)–Sn(1)
C(6)–N(1)–Sn(1)
C(10)–O(2)–Sn(1)
N(1)–C(6)–C(5)
N(1)–C(7)–C(8)
C(9)–C(7)–C(8)
C(10)–C(9)–C(7)
O(2)–C(10)–C(9)
O(2)–C(10)–C(11)
C(9)–C(10)–C(11)
Sn(1)–O(1A)
94.5(2)
96.5(2)
92.7(2)
120.1(2)
76.85(18)
82.59(18)
116.8(2)
123.1(2)
110.2(4)
118.3(5)
122.6(6)
119.1(6)
114.5(5)
125.0(5)
125.9(5)
123.4(4)
108.8(4)
121.8(4)
122.5(5)
121.4(5)
116.1(5)
126.7(6)
123.6(5)
115.6(5)
120.7(6)
Fig. 6. Perspective view and atom numbering scheme of compound 1b. Ellipsoids
are drawn from 40% probability level. The suffix A denotes the symmetry operation
1 ꢁ x, 1 ꢁ y, ꢁz.
O(1)–Sn(1)–O(1A)
Sn(1)–O(1A)–Sn(1A)

D.K. Dey et al. / Journal of Organometallic Chemistry 694 (2009) 2434–2441
2439
The X-ray structural investigation of ligand confirms that the
enolic proton of imino-en-ol form (II, Fig. 1) is abstracted by the
imine nitrogen and forms a hydrogen bond with a carbonyl oxygen
so the ligand exists in amino-en-one form (III, Fig. 1). In all three
independent molecules (where labels are given the suffix A, B or
C) C11–O12 was chosen as a double bond and C1–O1 a single bond
with O1 treated as a hydroxyl oxygen and O12 as a carbonyl O
atom on the basis of the C–O bond lengths The C(9A)–C(10A) dis-
tance of 1.348(15) Å is very close to C@C distance of 1.34 Å [30],
thereby indicating a double bond. This is only possible if the ligand
exist in amino-en-one form (III Fig. 1). The angles in the range
118.2(9)–125.6(10)° around C(9A) and C(10A) indicate that two
carbons are sp2 hybridised. The –NH–C(Me)@CH–C(@O)– portion
of the ligand is planar in all three independent molecules. These
differ in the relative orientations of the two aromatic rings. These
are tilted in the range 10.5(7)–27.0(7)° with respect to each other,
with molecule A having the largest twist. In comparison with the
planar NH–C(Me)@CH–C(@O) bridge, it is the phenol ring which
is twisted most of that plane [5.9(7)–64.9(7)°] when compared to
the phenyl ring [26.4(7)–42.3(7)°]. In this case the greatest twist
out of the plane containing the bridge is found in molecule C, for
both rings. There is a chain parallel to the c axis propagated by
OHꢀ ꢀ ꢀO hydrogen bonds involving the phenolic proton and the car-
bonyl oxygen atom. Despite the presence of aromatic rings, there is
clinic and monoclinic (P21/n) polymorphs have already been deter-
mined [33]. In contrast to the hydrogen bonded chain in 1, the
triclinic polymorph exists as centrosymmetric hydrogen bonded
dimers, yet it also has more than one molecule in the asymmetric
unit (Z0 = 2). The monoclinic polymorph has only one molecule in
the asymmetric unit but its hydrogen bonding motif is similar to
1, such that it has chains propagated by OHꢀ ꢀ ꢀO hydrogen bonds.
The ethanol solvate of 1 [34] retains the OHꢀ ꢀ ꢀO hydrogen bonded
chain motif but propagation involves ethanol thereby increasing
the chain length.
The molecular structures along with atom numbering schemes
for 1a and 1b are given in Figs. 5 and 6, respectively. Selected bond
lengths and angles for 1a and 1b are listed in Table 5.
The X-ray structural investigations of Ph2Sn[Ph(O)C@CH-
C(Me)@NC6H4(O)] (1a) and Me2Sn[Ph(O)C@CH-C(Me)@NC6H4(O)]
(1b) confirm that the ligand, 3-(2-hydroxyphenylimino)-1-phe-
nylbutan-1-one (H2L) behaves as a tridentate coordinating agent
via imino nitrogen, enolic oxygen and phenolic oxygen atoms.
The ligand forms six- and five-membered chelate rings. The elec-
tron density difference map indicates that no hydrogen is bonded
to the nitrogen atoms and that extensive delocalisation takes place.
The ligand, 3-(2-hydroxyphenylimino)-1-phenylbutan-1-one (H2L)
is not completely planar in either 1a or 1b.
Ph2Sn[Ph(O)C@CH-C(Me)@NC6H4(O)] (1a) crystallises as dis-
crete molecules whereas 1b forms centrosymmetric dimers with
weak Snꢀ ꢀ ꢀO bonding interactions [2.7998(20) Å]. The index of trig-
no sign of p–p stacking in the lattice.
A search of the August 2008 version of the Cambridge Structural
Database [31,32] revealed that this is a new polymorph of 1, tri-
onality, s, for describing the continuum between square-pyramidal
Table 6
Comparison of C–Sn–C, O–Sn–O, C–Sn–N, O–Sn–N, O–Sn–C angles of 1a and 1b with those in some other diphenyltin(IV) and dimethyltin(IV) complexes derived from ONO donor
tridentate Schiff bases.
Complexes
C–Sn–C
O–Sn–O
C–Sn–N
O–Sn–N
O–Sn–C
References
127.09(8)
157.46(6)
121.70(8)
110.79(8)
84.02(7)
73.75(6)
94.54(8)
97.06(8)
94.01(8)
94.31(9)
Unpublished results
OMe
Ph
Ph
O
O
Sn
N
N
Ph
Ph
Ph
Ph
O
O
Sn
121.26(15)
127.74(14)
157.19(10)
157.50(11)
114.36(14)
123.94(13)
112.46(12)
119.33(13)
84.38(11)
73.48(11)
84.16(11)
73.70(11)
97.59(15)
94.56(14)
97.38(14)
94.33(14)
[26]
N
N
Me
Me
O
O
Sn
125.2(4)
122.7(3)
155.83(19)
155.89(19)
121.0(3)
113.2(3)
121.5(3)
115.1(3)
83.7(2)
72.55(19)
83.8(2)
95.9(3)
97.4(3)
94.6(4)
99.2(3)
[26]
N
N
Ph
72.66(19)
Ph
O
Ph
O
Sn
119.9(3)
159.5(2)
156.98(8)
157.7(7)
116.7(3)
123.4(3)
76.7(3)
83.0(3)
96.3(3)
95.2(3)
96.9(3)
91.9(3)
This work
This work
[14]
N
Me
O
Me
O
Sn
141.72(14)
120.81(12)
111.32(12)
105.56(11)
76.49(18)
80.75(8)
99.76(12)
98.40(11)
85.23(11)
90.93(11)
N
Ph
Ph
Ph
Ph
O
Sn
O
121.17(11)
117.79(12)
83.84(10)
74.16(10)
93.63(11)
97.14(14)
95.93(13)
94.97(11)
N
N
Ph
Me
Me
O
Sn
O
125.8(3)
126.9(3)
159.5(2)
158.7(2)
117.0(3)
117.2(3)
123.6(6)
109.2(3)
85.7(3)
73.8(2)
85.6(2)
74.2(2)
92.5(4)
96.9(3)
93.2(4)
96.0(3)
[14]
N
N
Ph

2440
D.K. Dey et al. / Journal of Organometallic Chemistry 694 (2009) 2434–2441
(s
= 0) and trigonal–bipyramidal (
s
= 1), defined by Addison and
larges in the solid state to accommodate a phenoxy oxygen atom,
Reedijk [35] is 0.66 for 1a but 0.25 for 1b (when omitting the inter-
molecular Snꢀ ꢀ ꢀO contact). Distorted trigonal–bipyramidal geome-
try is found in 1a, where the source of the distortion is the
chelating ligand [O(1)–Sn(1)–O(8), 159.31(17)°]. The trigonal an-
gles involving the Ph groups do not differ significantly from 120°
(see Table 5). However, square-pyramidal geometry is dominant
over trigonal–bipyramidal geometry in 1b which is to be expected
with the extension of the tin coordination sphere to include a sixth
atom, O(1A). This gives distorted octahedral coordination geome-
try containing a square plane defined by N(1), O(1), O(2) and
O(1A) from which Sn(1) lies only 0.0609 (10) Å out of this plane to-
wards N(1).
Owing to the geometric restraints of the ligand the coordination
geometry around tin is not regular. The angles subtended at tin(IV)
in 1a by two oxygen atoms are significantly compressed to O(1)–
Sn(1)–O(8), 159.31(17)° yet in dimeric 1b it is compressed slightly
more [O(1)–Sn(1)–O(2), 156.98(8)°]. The bite angles in 1a N(4)–
Sn(1)–O(1), 76.85(18)°, O(8)–Sn(1)–N(4), 82.59(18)° are distorted
from 90° and are comparable with those found in 1b (Table 5)
and similar compounds [1–5,10–14,26,36–39]. These distortions
arise from the rigidity of chelate rings, compounded by the large
tin(IV) covalent radius.
thereby increasing the tin coordination number from five to six.
5. Conclusions
The ligand, 3-(2-hydroxyphenylimino)-1-phenylbutan-1-one,
has reacted with diorganotin(IV) dichlorides to form two stable
compounds 1a and 1b. The discrepancy in the C–Sn–C angle of
1a between the X-ray data and estimation in solution by NMR of
1a may be due to the relieving of some steric strain of the molecule
in solution. The large discrepancy between C–Sn–C angle from X-
ray data and estimation in solution of 1b was due to dissociation
of the dimeric structure to form a monomeric metal complex.
However, 119Sn chemical shift values clearly indicate that the
five-coordinate structure is retained in solution for both
compounds.
6. Supplementary material
CCDC 686749, 634860 and 634861 contain the supplementary
crystallographic data for 1, 1a and 1b. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
The five-membered chelate rings in 1a and 1b are nearly planar
but the six-membered chelate ring in 1a possesses a half chair con-
formation, folded along the Oꢀ ꢀ ꢀN vector by 35.5(3)° and the largest
deviation from the plane defined by the six atoms is ꢁ0.305(5) Å
by O(8) and Sn(1) deviates from the plane by the same magnitude.
In 1b, the six-membered chelate ring is very similar where the fold
is 31.72(12)° and maximum deviation from this plane is 0.272(1) Å
for Sn(1)].
The Sn–O bond lengths [2.110(4), 2.115(5) Å] in 1a and
[2.110(2), 2.201(2) Å] 1b compare well with the reported values
for diorganotin(IV) complexes derived from ONO donor tridentate
Schiff bases [1–5,10,11,14,26] but are shorter than diorganotin(IV)
complexes derived from ONNO donor tetradentate Schiff bases
2.163–2.228 Å [38].
The Sn–N bond lengths of compound 1a [2.140(5) Å] and com-
pound 1b [2.176(2) Å] are very close to Ph2Sn(2-OC10H6CH@NCH2-
COO) [2] and shorter than in Ph2Sn(2-OC6H4CH@NC6H4O) [4],
Me2Sn(2-OC6H4CH@NC6H4O) [5], Me2Sn(2-OC6H4CH@NC6H4COO)
[10], R2Sn[2-OC6H4CH@N-N@C(O)C6H5] (R = Ph, Me) [26] and
much shorter than those found in regular six-coordinate diorgano-
tin(IV) complexes [36–39] e.g. 2.266(2)–2.280(2) Å [36].
The Sn–C bond lengths [2.130(6), 2.134(6) Å] of 1a are within
the range of six-coordinate diorganotin(IV) complexes derived
from ONNO donor tetradentate Schiff bases e.g. 2.126(8)–
2.154(9)Å [37], five-coordinate [1,3,5] and six-coordinated [38]
diorganotin(IV) complexes derived from ONO and ONNO donor
Schiff bases, respectively. The Sn–C(methyl) bond lengths
[2.100(3), 2.116(3) Å] in 1b are comparable with other reported
diorganotin(IV) complexes, [1–5,10–12,26,36–39].
The C–Sn–C and O–Sn–O angles [120.1(2) and 159.31(17)°] for
the diphenyl complex 1a are comparable with the diphenyltin(IV)
complex derived from 4-phenyl-2,4-butanedionebenzoylhydraz-
one(2-) [14]. Although the O–Sn–O angle [156.98(8)°] in 1b is
comparable with dimethyltin(V) complex derived from 4-phenyl-
2,4-butanedionebenzoylhydrazone(2-) [159.5(2); 158.7(2)°] [14]
the C–Sn–C angle in 1b is much higher [141.72(14)° cf. 125.8(3)
and 126.9(3)°]. The C–Sn–C angle is much greater than that ob-
served in 1a as well as the value calculated on the basis of
1J(119Sn,13C) and 2J(119Sn,1H) coupling constant values (vide supra).
A comparison of different angles around tin(IV) of compounds 1a
and 1b with those other similar compounds having ONO donor
atoms have been made in Table 6. It is clear that all angles are
comparable except the C–Sn–C angle [141.72(14)°] in 1b which en-
Acknowledgements
D.K.D. thanks his appreciation to the University Grant Commis-
sion, New Delhi, India [Grant No. F. PSW-004/03-04 (ERO) dated
12.03.2004] for financial assistance. A.L. thanks the Grant Agency
of the Czech Republic for financial support (Grant No. 203/03/
1118). We wish to acknowledge the use of the EPSRC Chemical
Database Service at Daresbury, UK [31,40].
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