Synthesis and characterisation of tin(IV) and organotin(IV) derivatives 2-{[(2-hydroxyphenyl)imino]methyl}phenol

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Inorganica Chimica Acta 325 (2001) 103–114

Synthesis and characterisation of tin(IV) and organotin(IV)

derivatives 2-{[(2-hydroxyphenyl)imino]methyl}phenol

Claudio Pettinari ^a,*, Fabio Marchetti ^a, Riccardo Pettinari ^a, Domenico Martini ^a,

Andrei Drozdov ^b, Sergei Troyanov ^b

^aDipartimento di Scienze Chimiche, Uni6ersita` degli Studi, 6ia S. Agostino 1, 62032 Camerino, Italy

^bDepartment of Chemistry, Moscow State Uni6ersity, Vorobje6y Gory, 119899 Moscow, Russia

Received 2 May 2001; accepted 27 August 2001

Abstract

From the interaction of 2-{[(2-hydroxyphenyl)imino]methyl}phenol(salopH₂) with tin and organotin(IV) acceptors, the deriva-

tives [SnR₃(salopH)] (R=Me or Buⁿ), [SnR₂(salop)] (R=Me, Buⁿ, Bu^t, Vin or Ph), [SnRX(salop)(solvent)] (R=Me, Buⁿ, Ph or

X; X=Cl, Br or I; solvent=CH₃OH or H₂O), [Sn(salop)₂], [R₂SnCl₂(salopH₂)] (R=Me or Buⁿ) have been obtained and

characterised. The chelates, containing the Schiff base in mono or dianionic form, are generally stable both in the solid state and

in solution, whereas the [SnR₂Cl₂(salopH₂)] adducts slowly decompose in acetone or DMSO yielding [SnR₂(salop)] and releasing

HCl. All the [SnR₂(salop)] and [SnRX(salop)(solvent)] complexes are ﬂuxional in solution. The ¹¹⁹Sn NMR chemical shift is a

function of the number of R groups. The X-ray single crystal diffraction study of [SnVin₂(salop)] shows the metal to be

,

ﬁve-coordinate in a distorted square pyramidal environment, SnꢀC distances being 2.112(2) and 2.113(2) A, SnꢀO 2.117(2) and

,

2.125(2) A and SnꢀN 2.227(2) A. The whole structure consists of molecular units connected by weak intermolecular SnꢀO

interactions. In the complexes [SnX₂(salop)(CH₃OH)]·CH₃OH complexes (X=Cl or Br), the tin atom is found in a strongly

,

distorted octahedral environment with the SnꢀO bond ranging from 1.995(3) to 2.055(2) A. The SnꢀN bond is 2.116(4) A in the

,

Keywords: Tin(IV) compounds; Organotin (IV) complexes; X-ray crystal structures; Schiff base

tentially ONO tridentate Schiff base ligand forming

1. Introduction

stable complexes with many transition and post-transi-

tion metal ions [5]. Its coordination chemistry is less

developed with respect to that of tetradentate Schiff

bases as N,N%-ethylenbis(salicylaldimine) (salenH₂) [6].

Literature on metal–salopH₂complexes of the

Group IV elements is rather sparse [7], only three

tin(IV) complexes structurally characterised being re-

ported, i.e [SnMe₂(Salop)] [8], [SnPh₂(salop)] [9] and

[Sn(salop)]₂[10]. In addition, the organotin(IV) deriva-

tives reported have not been fully spectroscopically

characterised. As a part of our project dealing with the

study of the interaction of tin(IV) and organotin(IV)

species with O-donor and N-donor ligands, we report

here synthesis and full characterisation of 15 new

derivatives containing the schiff base in mono- (sa-

lopH)⁻, di-anionic(salop)²⁻or neutral form (salopH₂).

We described here also a new route for the synthesis

Schiff bases still play an important role as ligands in

metal coordination chemistry even after almost a cen-

tury since their discovery [1]. Recently, this class of

molecules has been employed as models for biological

systems [2] and in the control of the stereochemistry in

six-coordinate [(Schiff base)MCl₂] complexes (M=Ti

or Zr) which are potential catalysts for alkene poly-

merisation [3]. Increasing attention has also been

devoted to Schiff base complexes of organotin(IV) moi-

eties in view of their potential applications in medicinal

chemistry and biotechnology [4]. 2-{[(2-Hydrox-

yphenyl)imino]methyl}phenol(salopH₂) is a typical po-

* Corresponding author. Tel.: +39-0737-402 217; fax: +39-0737-

637 345.

E-mail addresses: pettinar@camserv.unicam.it (C. Pettinari), droz-

dov@inorg.chem.msu.ru (A. Drozdov).

PII: S0020-1693(01)00654-5

104

C. Pettinari et al. / Inorganica Chimica Acta 325 (2001) 103–114

and not-reported spectroscopic features of [SnMe₂-

(salop)] [8], [SnPh₂(salop)] [9] and [Sn(salop)₂] [10], as

well as the X-ray crystal structure of [SnVin₂(salop)],

surements (\_M, reported as V⁻¹cm²mol⁻¹) of

dichloromethane solutions of complexes 1–18 were

taken with a Crison CDTM 522 conductimeter at r.t.

[SnCl₂(salop)(CH₃OH)]·CH₃OH,

OH)]·CH₃OH.

[SnBr₂(salop)(CH₃-

2.3. Synthesis of the donor salopH₂

The 2-{[(2-hydroxyphenyl)imino]methyl}phenol (Fig.

1) has been synthesised by stirring at 60–80 °C a 1:1

molar ratio mixture of salicylaldehyde and 2-hydrox-

yaniline in reﬂuxing methanol following a reported

method [11]. M.p. 187–189 °C. IR (Nujol, cm⁻¹):

2300br, 1800br (OH), 1631s, 1612s, 1593s, 1530s, 1506w

2. Experimental

2.1. Materials

All chemicals and reagents were reagent grade qual-

ity and were used as received without further puriﬁca-

tion. Solvent evaporations were always carried out

under vacuum by using a rotavaporator. The samples

for microanalysis were dried in vacuo to constant

weight (20 °C, ca. 0.1 Torr). All syntheses were carried

out under a nitrogen atmosphere. Hydrocarbon sol-

vents were dried by distillation from sodium–potas-

sium; dichloromethane was distilled from calcium

hydride; benzene and light petroleum (40–60 °C) were

dried by reﬂuxing over freshly cut sodium; methanol

was dried over CaO. All solvents were degassed with

dry nitrogen prior to use.

1

(C···C, C···N). H NMR (CDCl₃, 293 K): l, 5.84, 12.28

(s br, OH) 6.93–7.46 (m, 8H, H_aromatic), 8.66 (m, 1H,

1

CH). H NMR (acetone-d₆, 293 K): l, 6.88–7.56 (m,

1

8H, H_aromatic), 8.56 (s br, OH), 8.92 (m, 1H, CH). H

NMR (DMSO-d₆, 293 K): l, 6.82–7.62 (m, 8H,

H

_aromatic), 8.95 (m, 1H, CH), 11.10 (s br, OH). ¹³C

NMR (CDCl₃, 293 K): l, 117.3, 128.7, 119.5, 121.0,

135.9, 119.3, 115.9, 133.7, 118.3, 132.6 (s, C_aromatic),

149.9, 160.6 (s, CO), 163.9 (s, CN). ¹³C NMR (acetone-

d₆, 293 K): l, 118.8, 130.0, 121.8, 122.2, 138.1, 120.9,

118.5, 134.9, 120.8, 134.6 (s, C_aromatic), 152.9, 163.2 (s,

CO), 165.0 (s, CN). ¹³C NMR (DMSO-d₆, 293 K): l,

116.7, 128.1, 119.6, 119.5, 134.9, 119.5, 116.5, 132.9,

119.6, 132.3 (s, C_aromatic), 151.1, 160.7 (s, CO), 161.7 (s,

CN). UV (CHCl₃, u_max, nm): 243, 270, 354.

2.2. Physical measurements

2.4. Synthesis of complexes

Elemental analyses (C, H, N) were performed in-

house with a Fison’s instruments 1108 CHNS-O ele-

mental analyser. IR spectra were recorded from 4000 to

100 cm⁻¹with a Perkin–Elmer system 2000 FT-IR

instrument. ¹H, ¹³C and ¹¹⁹Sn NMR spectra were

recorded on a VXR-300 Varian instrument and on a

Bruker AC 200 spectrometers operating at room tem-

2.4.1. [SnMe₂(salop)] (1)

To a hot methanol solution (30 ml) of the Schiff base

salopH₂(0.42 g, 2.0 mmol), sodium methoxide was

added (0.21 g, 4.0 mmol). When the colour of the

solution changed from orange to red, SnMe₂Cl₂(0.42 g,

2.0 mmol) was added. After 3 h stirring, the solvent was

removed and the residue was treated with chloroform

(15 ml). The solution formed was ﬁltered off to remove

the sodium salt and then evaporated to dryness. The

red powder was re-crystallised from diethyl ether and

shown to be compound 1. Yield 54%. M.p. 169−

170 °C. Anal. Calc. for C₁₅H₁₅NO₂Sn: C, 50.05; H,

4.20; N, 3.89. Found: C, 49.88; H, 4.30; N, 3.76%. IR

(Nujol, cm⁻¹): 3059w (CH), 1606s, 1585s, 1567sh,

1530s, 1514m (C···C, C···N), 528s, 520m (SnꢀO), 573m,

1

perature (r.t.) (at 300 and 200 MHz for H; 75 and 50

MHz for ¹³C; and 111.9 MHz for ¹¹⁹Sn). The chemical

shifts (l) are reported in parts per million (ppm) from

SiMe₄(¹H and ¹³C calibration by internal deuterium

solvent lock) and SnMe₄(external). The spectral width

is 900 ppm (from +200 to −700 ppm). Peak multi-

plicities are abbreviated: singlet, s; doublet, d; triplet, t;

multiplet, m. UV spectra were recorded on a HP-8453

spectrometer. Melting points are uncorrected and were

taken on an SMP3 Stuart scientiﬁc instrument and on a

capillary apparatus. The electrical conductivity mea-

1

545w (SnꢀC), 321s (SnꢀN). H NMR (CDCl₃, 293 K):

2

l, 0.8 (s, 6H, J(¹¹⁹Snꢀ¹H): 78.1 Hz, J(¹¹⁷Snꢀ¹H): 74.8

Hz, SnꢀCH₃) 6.6–6.8 (m), 7.1–7.5 (m) (8H, H_aromatic),

8.7 (s, 1H, ³J(^119/117Snꢀ¹H): 50.6 Hz, CH_salop). ¹³C

NMR (CDCl₃, 293 K): l, 0.99 (s, J(¹¹⁹Snꢀ¹³C): 660

1

Hz, SnꢀCH₃), 114.66, 116.59, 117.26, 117.79, 118.47,

122.56, 130.24, 135.22, 136.84, 137.12 (s, C_aromatic),

158.84, 168.85 (s, CO), 161.98 (s, CN). ¹¹⁹Sn NMR

(CDCl₃, 293 K): l, −146.4. UV (CHCl₃, u_max, nm):

249, 316, 455. \_M(DMSO, c (mol l⁻¹)=1.0×

10⁻³)=1.3 V⁻¹cm²mol⁻¹. \_M(CH₂Cl₂, c (mol

Fig. 1. Structure of the Schiff base salopH₂.

l .

⁻¹)=0.9×10⁻³)=0.1 V⁻¹cm²mol⁻¹

C. Pettinari et al. / Inorganica Chimica Acta 325 (2001) 103–114

105

2.4.2. [SnBuⁿ₂(salop)] (2)

\

(DMSO, c (mol l⁻¹)=0.9×10⁻³, V⁻¹cm²

M

Complex 2 (orange) was prepared as 1. Yield 44%.

M.p. 131 °C dec. Anal. Calc. for C₂₁H₂₇NO₂Sn: C,

56.79; H, 6.13; N, 3.15. Found: C, 56.63; H, 5.97; N,

3.26%. IR (Nujol, cm⁻¹): 3053w (CH), 1607s, 1589sh,

1538m, 1509w (C···C, C···N), 504vs, 475s (SnꢀO), 578s,

mol⁻¹)=0.5.

\

(CH₂Cl₂, c (mol l

⁻¹)=1.1×

M

10⁻³)=0.2 V⁻¹cm²mol⁻¹

.

2.4.5. [SnPh₂(salop)] (5)

To a hot ethanol solution (30 ml) of salopH₂(2.0

mmol), NaOMe was added (4.0 mmol). After the

colour of the solution changed from orange to red.

After a few minutes Ph₂SnCl₂(2.0 mmol) was added

and a red precipitate immediately formed. After 3 h

stirring, the solid was ﬁltered off, washed with ethanol,

dried under reduced pressure to constant weight and

shown to be compound 5. Yield 70%. M.p. 200–

201 °C. Anal. Calc. for C₂₅H₁₉NO₂Sn: C, 62.02; H,

3.96; N, 2.89. Found: C, 62.25; H, 4.06; N, 3.02%. IR

(Nujol, cm⁻¹): 3047w (CH), 1605s, 1590s, 1567sh,

1539s, 1506w (C···C, C···N), 605s, 536vs (SnꢀO), 262m,

243m (SnꢀC), 334 (SnꢀN). ¹H NMR (CDCl₃, 293 K): l,

6.7–7.5 (m, 8H, H_aromaticof salop), 7.9–8.0 (m, 10H,

1

534m (SnꢀC), 324m (SnꢀN). H NMR (CDCl₃, 293 K):

l, 0.9–1.1 (m), 1.7–1.8 (m) (18H, SnꢀBuⁿ), 6.7–7.4 (m,

8H, H_aromatic), 8.6 (s, 1H, ³J(^119/117Snꢀ¹H): 44.8 Hz,

CH_salop

)

¹³C NMR (CDCl₃, 293 K): l, 13.49 (s,

SnꢀBuⁿ), 26.37, 26.47, 26.58 (s, SnꢀBuⁿ), 116.69,

118.02, 118.32, 119.39, 121.18, 129.10, 133.00, 134.56,

136.30, 149.87 (s, C_aromatic) 159.43, 162.11 (s, CO),

163.35 (s, CN). ¹¹⁹Sn NMR (CDCl₃, 293 K): l, −

186.4. UV (CHCl₃, u_max, nm): 249, 318, 454. \_M

(CH₂Cl₂, c (mol l⁻¹)=1.0×10⁻³)=0.1 V⁻¹cm²

mol⁻¹

.

2.4.3. [SnBu^t₂(salop)] (3)

3

Complex 3 was prepared as 1 by using 2.0 mmol of

salopH₂, 4.0 mmol of NaOMe and 2.0 mmol of

SnBu^t₂Cl₂. Yield 45%. M.p. 127–129 °C. Anal. Calc.

for C₂₁H₂₇NO₂Sn: C, 56.79; H, 6.13; N, 3.15. Found:

C, 56.55; H, 6.22; N, 3.03%. IR (Nujol, cm⁻¹): 3050w

(CH), 1605s, 1584s, 1559sh, 1533s (C···C, C···N), 525s

³J(^119/117Snꢀ¹H): 92.0 Hz, SnꢀC₆H₅), 8.7 (s, 1H, J(^119/

117Snꢀ¹H): 59.6 Hz, CH_salop). ¹³C NMR (CDCl₃, 293

K): l, 114.63, 116.86, 117.50, 119.04, 122.81, 125.05,

125.25, 127.84, 128.67, 129.50, 129.72, 130.12, 130.29,

131.13, 131.83, 135.09, 135.38, 136.04, 136.59, 137.00,

137.14, 139.70 (s, C_salop+SnꢀC₆H₅). 158.96, 169.47 (s,

CO), 161.57 (s, CN). ¹¹⁹Sn NMR (CDCl₃, 293 K): l,

−328.35. UV (CHCl₃, u_max, nm): 246, 318, 454. \_M

(DMSO, c (mol l⁻¹)=1.0×10⁻³, V⁻¹cm²mol⁻¹)=

0.2. \_M(CH₂Cl₂, c (mol l⁻¹)=1.1×10⁻³)=0.1 V⁻¹

1

(SnꢀO), 488m, 441w (SnꢀC), 318m (SnꢀN). H NMR

(CDCl₃, 293 K): l, 1.30 (s, 18H, SnꢀBu^t, J(¹¹⁹Snꢀ¹H):

3

108.4 Hz, ³J(¹¹⁷Snꢀ¹H): 104.3 Hz), 6.6–7.4 (m, 8H,

H_aromatic), 8.7 (s, 1H, ³J(^119/117Snꢀ¹H): 41.9 Hz, CH_salop).

¹³C NMR (CDCl₃, 293 K): l, 29.85 (s, SnꢀC(CH₃)₃),

40.68 (s, SnꢀC(CH₃)₃), 114.67, 115.84, 116.44, 118.49,

122.57, 129.81, 132.23, 135.00, 136.47, 160.36 (s,

C_aromatic), 161.34 (s, CN), 160.36, 170.66 (s, CO). ¹¹⁹Sn

cm²mol⁻¹

.

2.4.6. [SnCl₂(Salop)(H₂O)] (6)

Complex 6 was prepared in methanol as 5 by using

2.0 mmol of salopH₂, 4.0 mmol of NaOMe and 2.0

mmol of SnCl₄·5H₂O. Yield 74%. M.p. 290 °C dec.

Anal. Calc. for C₁₃H₁₁Cl₂NO₃Sn: C, 37.28; H, 2.65; N,

3.34. Found: C, 37.20; H, 2.73; N, 3.46%. IR (Nujol,

cm⁻¹): 3000–3400 (H₂O), 1608s, 1590w, 1557w,

1544m, 1508w (C···C, C···N), 502s, 490s (SnꢀO), 377sh,

NMR (CDCl₃, 293 K): l, −279.2. UV (CHCl₃, u_max

,

nm): 248, 465. \_M(CH₂Cl₂, c (mol l⁻¹)=1.0×

10⁻³)=0.3 V⁻¹cm²mol⁻¹

.

2.4.4. [SnVin₂(salop)] (4)

Complex 4 was prepared as 2 by using 2.0 mmol of

salopH₂, 4.0 mmol of NaOMe and 2.0 mmol of

SnVin₂Cl₂. Yield 31%. M.p. 133–134 °C. Anal. Calc.

for C₁₇H₁₅NO₂Sn: C, 53.17; H, 3.94; N, 3.65. Found:

C, 53.04; H, 4.02; N, 3.76%. IR (Nujol, cm⁻¹): 3050w

(CH), 1605s, 1584s, 1567sh, 1535s (C···C, C···N), 519vs,

489m (SnꢀO), 557s, 539m (SnꢀC), 328m (SnꢀN). ¹H

NMR (CDCl₃, 293 K): l, 6.14 (dd) 6.22 (dd) 6.30 (dd)

1

366s, 348sh (SnꢀCl). H NMR (acetone-d₆, 293 K): l,

6.8–7.0 (m) 7.2–7.3 (m) 7.4–7.9 (m) (8H, H_aromatic), 8.9

(br, 2H, H₂O), 9.2 (s, 1H, CH_salop, ³J(^119/117Snꢀ¹H): 86.7

Hz). ¹¹⁹Sn NMR (CDCl₃, 293 K): l, −563.37. UV

(CHCl₃, u_max, nm): 246, 315, 426. \_M(DMSO, c (mol

l

⁻¹)=1.1×10⁻³)=4.6 V⁻¹cm²mol⁻¹. \_M(CH₂Cl₂,

c (mol l⁻¹)=1.0×10⁻³)=0.3 V⁻¹cm²mol⁻¹

.

(6H, J(¹Hꢀ¹H)_gem

:

3.6 Hz, J(¹Hꢀ¹H)_cis: 11.8 Hz,

J(¹Hꢀ¹H)_trans: 19.9 Hz, SnꢀCHꢁCH₂), 6.7–7.0 (m) 7.2–

2.4.7. [SnCl₂(salop)(CH₃OH)]·CH₃OH (7)

7.5 (m) (8H, H_aromatic), 8.6 (s, 1H, J(^119/117Snꢀ¹H): 55.8

Complex 7 was obtained from the mother liquor of

complex 6. M.p. 300 °C dec. Anal. Calc. for

C₁₅H₁₇Cl₂NO₄Sn: C, 38.75; H, 3.69; N, 3.01. Found: C,

38.64; H, 3.46; N, 3.18%. IR (Nujol, cm⁻¹): 3000–3400

(OH), 1607s, 1591w, 1559w, 1543m, 1507w (C···C,

C···N), 501s, 482s (SnꢀO), 367m, 353s, 335s (SnꢀCl). ¹H

NMR (acetone-d₆, 295 K): l, 3.3 (s, 3H, CH₃OH),

6.8–7.0 (m) 7.2–7.3 (m) 7.4–7.9 (m) (8H, H_aromatic), 8.9

3

Hz, CH_salop). ¹³C NMR (CDCl₃, 293 K): l, 114.67,

116.84, 117.46, 118.75, 122.61, 130.29, 131.10, 136.96,

138.50, (s, C_aromatic), 135.30 (s, ²J(^117/119Snꢀ¹³C): 442

Hz, SnꢀCHꢁCH₂), 136.77 (s, ¹J(¹¹⁹Snꢀ¹³C): 975 Hz,

¹J(¹¹⁷Snꢀ¹³C): 930 Hz, SnꢀCHꢁCH₂), 161.59 (s, CN),

169.28, 158.84 (s, CO). ¹¹⁹Sn NMR (CDCl₃, 293 K): l,

−320.69. UV (CHCl₃, u_max, nm): 248, 291, 317, 454.

106

C. Pettinari et al. / Inorganica Chimica Acta 325 (2001) 103–114

(br, 1H, CH₃OH), 9.2 (s, 1H, CH_salop³J(^119/117Snꢀ¹H):

84.2 Hz). ¹¹⁹Sn NMR (CDCl₃, 295 K): l, −542.74,

−558.10. ¹¹⁹Sn NMR (acetone-d₆, 295 K): l, −545br,

−562br. \_M(DMSO, c (mol l⁻¹)=1.0×10⁻³)=4.0

V⁻¹cm²mol⁻¹. \_M(CH₂Cl₂, c (mol l⁻¹)=1.1×

316, 436. Complex 10 can also be obtained by interac-

tion of 2.0 mmol of salopH₂with 2.0 mmol of SnI₄in

reﬂuxing toluene without base. \_M(DMSO, c (mol

l

⁻¹)=1.0×10⁻³)=44.8 V⁻¹cm²mol⁻¹

.

\

M

(CH₂Cl₂, c (mol l⁻¹)=1.0×10⁻³)=0.5 V⁻¹cm²

mol⁻¹

10⁻³)=0.2 V⁻¹cm²mol⁻¹

.

2.4.8. [SnBr₂(salop)(H₂O)] (8)

2.4.11. [SnMeCl(salop)(H₂O)] (11)

Complex 8 was prepared as 6 by using 2.0 mmol of

salopH₂, 4.0 mmol of NaOMe and 2.0 mmol of SnBr₄.

Yield 76%. M.p. 218 °C dec. Anal. Calc. for

C₁₃H₁₁Br₂NO₃Sn: C, 30.75; H, 2.18; N, 2.76. Found: C,

30.54; H, 2.22; N, 2.84%. IR (Nujol, cm⁻¹): 3000–3400

(H₂O), 1605s, 1589sh, 1557w, 1543s, 1519w, 1503w

(C···C, C···N), 501s, 485s (SnꢀO), 234s, 200vs (SnꢀBr).

¹H NMR (CDCl₃, 294 K): l, 3.45 (s br, 2H, H₂O),

6.8–7.1 (m) 7.2–7.5 (m) (8H, H_aromatic), 8.57 (s, 1H,

CH_salop³J(^119/117Snꢀ¹H): 76.6 Hz). ¹¹⁹Sn NMR (ace-

tone-d₆, 293 K): l, −755.1. UV (CHCl₃, u_max, nm):

245, 315, 429. \_M(DMSO, c (mol l⁻¹)=1.1×

10⁻³)=21.5 V⁻¹cm²mol⁻¹. \_M(CH₂Cl₂, c (mol

Complex 11 was obtained as 2 by using 2.0 mmol of

salopH₂, 4.0 mmol of NaOMe and 2.0 mmol of

SnMeCl₃. Yield 32%. M.p. \350 °C. Anal. Calc. for

C₁₄H₁₄ClNO₃Sn: C, 42.11; H, 3.54; N, 3.51. Found: C,

42.46; H, 3.48; N, 3.23%. IR (Nujol, cm⁻¹): 3000–

3400br (H₂O), 1606s, 1586s, 1539s (C···C, C···N), 579w

1

(SnꢀC), 497m, 487s (SnꢀO), 269vs (SnꢀCl). H NMR

(acetone-d₆, 293 K): l, 0.95 (s, 3H, SnꢀCH₃,

2

²J(¹¹⁹Snꢀ¹H): 122.1 Hz, J(¹¹⁷Snꢀ¹H): 111.0 Hz), 3.47

(s, 3H, CH₃OH), 6.7–7.8 (m, 8H, H_aromatic), 9.03 (s, 1H,

³J(^119/117Snꢀ¹H): 91.7 Hz, CH_salop). ¹³C NMR (acetone-

d₆, 293 K): l, 115.80, 117.30, 117.88, 119.06, 121.25,

123.14, 126.76, 130.21, 132.99, 136.06, 137.69 (s,

C_aromatic), 157.34, 168.69, 173.73, (s, CO), 159.76 (s,

CN), resonance of SnꢀCH₃not observed. ¹³C NMR

(CDCl₃, 293 K): l, 115.8, 117.29, 117.88, 119.06,

119.31, 121.24, 123.14, 126.76, 130.21, 130.73, 132.99,

136.06, 136. (s, C_aromatic), 168.69, 157.34 (s, CO), 159.76

(s, CN). ¹¹⁹Sn NMR (DMSO-d₆, 293 K): l, −436.44,

−442.54. UV (CHCl₃, u_max, nm): 252, 286, 312, 430.

l

⁻¹)=1.1×10⁻³)=0.1 V⁻¹cm²mol⁻¹

.

2.4.9. [SnBr₂(salop)(CH₃OH)]·CH₃OH (9)

Complex 9 was obtained from the mother liquor of

complex 8. M.p. 230 °C dec. Anal. Calc. for

C₁₄H₁₃Br₂NO₃Sn: C, 32.53; H, 3.09; N, 2.51. Found: C,

32.44; H, 3.12; N, 2.72%. IR (Nujol, cm⁻¹): 3000–3400

(OH), 1605s, 1590sh, 1558w, 1544s, 121w, 1504w

(C···C, C···N), 502s, 497w, 483s (SnꢀO), 226s, 203vs

\

(DMSO, c (mol l⁻¹)=1.1×10⁻³)=2.2 V⁻¹cm²

M

mol⁻¹. \_M(CH₂Cl₂, c (mol l⁻¹)=1.0×10⁻³)=0.4

1

(SnꢀBr). H NMR (acetone-d₆, 293 K): l, 3.36 (s, 3H,

V⁻¹cm²mol⁻¹

.

CH₃OH), 6.8–7.0 (m) 7.2–7.3 (m) 7.4–7.9 (m) (8H,

H_aromatic), 9.22 (s, 1H, CH_salop

,

³J(^119/117Snꢀ¹H): 75.5

2.4.12. [SnBuⁿCl(salop)(CH₃OH)] (12)

Hz). ¹¹⁹Sn NMR (CDCl₃, 293 K): l, −756.58. \_M

(DMSO, c (mol l⁻¹)=1.0×10⁻³)=21.9 V⁻¹cm²

mol⁻¹. \_M(CH₂Cl₂, c (mol l⁻¹)=1.2×10⁻³)=0.1

To a hot methanol solution (30 ml) of salopH₂(0.21

g, 1.0 mmol), SnBuⁿCl₃(0.56 g, 2.0 mmol) was added

and a yellow precipitate immediately formed. After 8 h

stirring, the solid was ﬁltered off, washed with

methanol and shown to be compound 12. Yield 96%.

M.p. 233–235 °C. Anal. Calc. for C₁₈H₂₂ClNO₃Sn: C,

47.57; H, 4.88; N, 3.08. Found: C, 47.74; H, 4.68; N,

3.20%. IR (Nujol, cm⁻¹): 3000–3400br (OH), 1605s,

1588s, 1568sh, 1539s (C···C, C···N), 584w (SnꢀC),

494m, 481s (SnꢀO), 283s, 275s (SnꢀCl). ¹H NMR

(CDCl₃, 293 K): l, 0.96, 1.00, 0.9–1.1 (t, 3H, SnꢀBuⁿ),

1.4–1.6 (m) 1.9–2.1 (m) (6H, Sn–Buⁿ), 3.49 (s, 3H,

CH₃OH), 6.7–7.4 (m, 8H, H_aromatic), 8.41 (s, 1H,

V⁻¹cm²mol⁻¹

.

2.4.10. [SnI₂(salop)(CH₃OH)] (10)

Complex 10 was prepared as 6, by using 2.0 mmol of

salopH₂, 4.0 mmol of NaOMe and 2.0 mmol of SnI₄.

Yield 85%. M.p. \350 °C. Anal. Calc. for

C₁₄H₁₃I₂NO₃Sn: C, 27.31; H, 2.13; N, 2.28. Found: C,

27.56; H, 2.20; N, 2.40%. IR (Nujol, cm⁻¹): 3000–3400

(CH₃OH), 1602s, 1588s, 1543s (C···C, C···N), 508m,

1

481s (SnꢀO), 178s, 143m (SnꢀI). H NMR (CDCl₃, 293

3

K): l, 3.51 (s, 3H, CH₃OH), 6.8–7.8 (m, 8H, H_aromatic),

CH_salop³J(¹¹⁹Snꢀ¹H): 85.1 Hz, J(¹¹⁷Snꢀ¹H): 81.4 Hz).

3

8.50 (br, 1H, CH₃OH), 8.93 (s, 1H, J(¹¹⁹Snꢀ¹H): 86.7

¹³C NMR (DMSO-d₆, 293 K): l, 13.56 (s, SnꢀBuⁿ),

26.02 (s, SnꢀBuⁿ), 27.41 (s, SnꢀBu^{n 2}J(^119/117Snꢀ¹³C):

Hz; ³J(¹¹⁷Snꢀ¹H): 82.0 Hz, CH_salop). ¹³C NMR

(DMSO-d₆, 293 K): l, 48.59 (s, CH₃OH) 116.00,

116.28, 117.63, 117.99, 118.52, 119.03, 119.19, 119.46,

119.84, 121.93, 128.77, 129.27, 130.57, 130.68, 136.78,

137.16, 153.56, 154.02, 154.16, 154.49 (s, C_aromatic),

166.40, 165.85, 165.17, 164.42 (s, CO), 162.84, 162.34

(s, CN). ¹¹⁹Sn NMR (DMSO-d₆): l, −620.9, −622.6,

−813.94, −814.99. UV (CHCl₃, u_max, nm): 245, 286,

1

59.7 Hz), 29.64 (s, SnꢀBuⁿ, J(¹¹⁹Snꢀ¹³C): 1138.2 Hz,

¹J(¹¹⁷Snꢀ¹³C): 1070.9 Hz), 50.87 (s, CH₃OH), 113.88,

118.48, 119.34, 120.00, 123.01, 130.38, 134.17, 135.93 (s,

C

_aromatic), 154.97, 164.58 (s, CO), 159.03 (s, CN). ¹¹⁹Sn

NMR (DMSO-d₆, 293 K): l, −452.32. UV (CHCl₃,

u_max, nm): 246, 313, 431. \_M(DMSO, c (mol l⁻¹)=

1.0×10⁻³)=1.1 V⁻¹cm²mol⁻¹. \_M(CH₂Cl₂, c (mol

C. Pettinari et al. / Inorganica Chimica Acta 325 (2001) 103–114

107

l

⁻¹)=0.9×10⁻³)=0.2 V⁻¹cm²mol⁻¹. Compound

C₁₆H₁₉NO₂Sn: C, 51.25; H, 4.84; N, 3.73. Found: C,

51.38; H, 4.92; N, 3.85%. IR (Nujol, cm⁻¹): 3061w

(CꢀH), 1606s, 1586s, 1565sh, 1530s, 1512w (C···C,

C···N), 571s, 528s, 520s (SnꢀC), 486s, 458s br (SnꢀO).

¹H NMR (CDCl₃, 293 K): l, 0.56 (s, 9H, SnꢀCH₃,

12 has been obtained also from the reaction of

SnBuⁿCl₃with salopH₂in reﬂuxing toluene, in absence

of base.

2

2.4.13. [SnPhCl(salop)(CH₃OH)] (13)

²J(¹¹⁹Snꢀ¹H): 57.2 Hz, J(¹¹⁷Snꢀ¹H): 55.0 Hz), 6.6–7.3

Complex 13 was prepared as 2 by using 2.0 mmol of

salopH₂, 4.0 mmol of NaOMe and 2.0 mmol of

SnPhCl₃. Yield 93%. M.p. \350 °C. Anal. Calc. for

C₂₀H₁₈ClNO₃Sn: C, 50.63; H, 3.82; N, 2.95. Found: C,

50.38; H, 3.88; N, 3.06%. IR (Nujol, cm⁻¹): 3000–

3400br (OH), 1606s, 1586s, 1538s (C···C, C···N), 485sbr

(m, 8H, H_aromatic), 8.67 (s, 1H, CH_Salop), 6.05, 12.14,

14.02 (s br, 1H, OH+NH). ¹³C NMR (CDCl₃, 293 K):

1

l, −2.70(s, J(^119/117Snꢀ¹³C): 400 Hz, SnꢀCH₃), 114.8,

119.52, 120.28, 128.1, 131.30, 131.97, 132.69, 133.77,

136.88 (s, C_aromatic), 163.67, 161.49 (s, CO), 162.03 (s,

CN). ¹¹⁹Sn NMR (CDCl₃, 293 K): l, +50.8. \_M

(CH₂Cl₂, c (mol l⁻¹)=1.0×10⁻³)=0.05 V⁻¹cm²

mol⁻¹. UV (CHCl₃, u_max, nm): 244, 323, 335, 361, 453.

1

(SnꢀO), 278vs (SnꢀCl), 243s (SnꢀC). H NMR (CDCl₃,

293 K): l, 3.48 (s, 3H, CH₃OH), 6.7–7.6 (m, 13H,

CH_salop+SnꢀPh), 8.91 (s, 1H, CH_salop, J(^119/117Snꢀ¹H):

3

1

88.0 Hz). H NMR (DMSO-d₆, 293 K): l, 3.41 (s, 3H,

2.4.16. [SnBuⁿ₃(salopH)] (16)

CH₃OH), 6.6–8.0 (m, 13H, CH_salop+SnꢀPh), 8.97,

9.07 (br, 1H, CH_salop). ¹³C NMR (DMSO-d₆, 293 K): l,

48.61 (s, CH₃OH), 115.67, 115.83, 116.04, 116.26,

116.88, 117.58, 117.82, 118.21, 118.46, 121.92, 122.21,

127.40, 128.48, 129.11, 129.33, 129.60, 130.40, 134.74,

134.87, 135.12, 135.51, 135.68, 136.02, 146.22 (s,

Complex 16 was prepared as 1 by using 2.0 mmol of

salopH₂, 2.0 mmol of NaOMe and 2.0 mmol of

SnBuⁿ₃Cl. Yield 72%. M.p. 128–130 °C. Anal. Calc. for

C₂₅H₃₇NO₂Sn: C, 59.78; H, 7.43; N, 2.79. Found: C,

59.53; H, 7.56; N, 2.64%. IR (Nujol, cm⁻¹): 3058w

w(CH), 1617s, 1589s, 1565sh, 1531m (C···C, C···N),

1

C

_salop+SnꢀPh), 150.01, 154.82, 156.38, 165.75, 167.42

569m, 526br w(SnꢀC), 472s, 457s w(SnꢀO). H NMR

(s, CO), 157.21, 158.53 (s, CN). ¹¹⁹Sn NMR (DMSO-d₆,

293 K): l, −497.40, −508.04, −571.96. UV (CHCl₃,

u_max, nm): 247, 286, 315, 431. \_M(DMSO, c (mol

(CDCl₃, 293 K): l, 0.8–1.0 (m, 9H, SnꢀBuⁿ), 1.1–1.8

(m, 18H, SnꢀBuⁿ), 6.6–7.4 (m, 8H, H_aromatic), 8.66, 8.84

(s, 1H, CH_salop), 5.90, 12.15, 14.05, (s br, 1H, OH_salopH

and/or NH_salopH). ¹³C NMR (CDCl₃, 293 K): l, 13.06

(s, SnꢀBuⁿ), 16.40 (s, SnꢀBuⁿ), 27.10 (s, ²J(^119/

117Snꢀ¹³C): 45.8 Hz, SnꢀBuⁿ), 27.73 (s, SnꢀBuⁿ),

114.83, 116.06, 116.33, 116.94, 117.34, 117.61, 117.93,

118.97, 119.64, 119.87, 120.79, 121.42, 122.50, 127.65,

130.09, 131.73, 132.43, 133.52, 133.76, 135.23, 136.73,

137.03, 139.18 (s, C_aromatic), 155.68, 159.53, 161.86,

166.46, 196.63 (s, CO), 162.22, 169.51 (s, CN). ¹¹⁹Sn

NMR (CDCl₃, 293 K): l, +123.3. \_M(CH₂Cl₂, c (mol

l

⁻¹)=1.1×10⁻³)=1.9 V⁻¹cm²mol⁻¹. \_M(CH₂Cl₂,

c (mol l⁻¹)=1.0×10⁻³)=0.2 V⁻¹cm²mol⁻¹. Com-

pound 13 has been also obtained by the reaction of

SnPhCl₃with salopH₂in methanol, in the absence of

base.

2.4.14. [Sn(salop)₂] (14)

Complex 14 was prepared as 2 by using 2.0 mmol of

SalopH₂, 4.0 mmol of NaOMe and 1.0 mmol of SnBr₄,

or by using 2.0 mmol of SalopH₂, 4.0 mmol of NaOMe

and 1.0 mmol of SnCl₄·H₂O or by using 2.0 mmol of

SalopH₂, 4.0 mmol of NaOMe and 2.0 mmol of

Vin₂SnCl₂. Yield 74%. M.p. \350 °C. Anal. Calc. for

C₂₆H₁₈N₂O₄Sn: C, 57.71; H, 3.35; N, 5.18. Found: C,

57.53; H, 3.41; N, 5.30%. IR (Nujol, cm⁻¹): 1605s,

1586s, 1538s, 1506w (C···C, C···N), 495m, 485s (SnꢀO).

¹H NMR (CDCl₃, 293 K): l, 6.8–7.0 (m), 7.2–7.6 (m)

l

⁻¹)=1.0×10⁻³)=0.05 V⁻¹cm²mol⁻¹

.

2.4.17. SnMe₂Cl₂(salopH₂)] (17)

To a diethyl ether solution (30 ml) of salopH₂(0.21

g, 1.0 mmol), SnMe₂Cl₂(1.75 g, 8.0 mmol) was added,

and a yellow precipitate immediately formed. After 8 h

stirring, the solid was ﬁltered off, washed with diethyl

ether and shown to be compound 17. Yield 88%. M.p.

174–177 °C. Anal. Calc. for C₁₅H₁₇Cl₂NO₂Sn: C,

42.90; H, 4.50; N, 3.13. Found: C, 42.74; H, 4.54; N,

3.24%. IR (Nujol, cm⁻¹): 1633sbr, 1595s, 1528w, 1505s

(C···C, C···N), 576s, 567s (SnꢀC), 496sbr, 478s (SnꢀO),

3

(16H, H_aromatic), 8.90 (s, 2H, J(^119/117Snꢀ¹H): 86.7 Hz,

CH_salop). ¹³C NMR (CDCl₃, 293 K): l, 114.55, 118.40,

119.01, 110.50, 123.59, 135.99, 137.25 (s, C_salop); the CN

and CO resonance were not observed. \_M(DMSO, c

(mol l⁻¹)=1.0×10⁻³)=1.3 V⁻¹cm²mol⁻¹. \_M

(CH₂Cl₂, c (mol l⁻¹)=1.1×10⁻³)=0.2 V⁻¹cm²

1

299br (SnꢀCl). H NMR (DMSO-d₆, 293 K): l, 1.02 (s,

6H, ²J(¹¹⁹Snꢀ¹H): 114.7 Hz, ²J(¹¹⁷Snꢀ¹H): 109.9 Hz,

mol⁻¹

.

¹¹⁹Sn NMR (CDCl₃, 293 K): l, −567.94. UV

CH₃), 6.8ꢀ7.5 (m, 8H, H_aromatic), 9.13 (s, 1H, CH_salopH),

2

(CHCl₃, u_max, nm): 247, 319, 436.

10.24, 10.74 (s br, OH_salopHand/or NH_salopH). ¹³C

2

1

NMR (DMSO-d₆, 293 K): l, 23.88 (s, J(^119/117Snꢀ¹H):

931.0 Hz, SnꢀCH₃), 136.46, 134.62, 133.31, 132.16,

129.12, 124.23, 122.32, 119.17, 118.32, 116.72, (s,

C_arom), 150.82, 161.07, 161.72, 191.65 (s, CO and CN).

¹¹⁹Sn NMR (DMSO-d₆, 293 K): l, −241.55. \_M

2.4.15. [SnMe₃(salopH)] (15)

Derivative 15 was prepared as 2 by using 2.0 mmol of

salopH₂, 2.0 mmol of NaOMe and 2.0 mmol of

SnMe₃Cl. Yield 65%. M.p. 141–144 °C. Anal. Calc. for

108

C. Pettinari et al. / Inorganica Chimica Acta 325 (2001) 103–114

Table 1

Crystallographic data, details of data collection and reﬁnement for complexes 4, 7 and 9

Compound

[SnVI₂(salop)] (4)

[SnCI₂(salop)(CH₃OH)]·CH₃OH (7)

[SnBr₂(salop)(CH₃OH)]·CH₃OH (9)

Molecular formula

M

C₁₇H₁₅NO₂Sn

383.99

C₁₅H₁₇C1₂NO₄Sn

464.87

C₁₅H₁₇Br₂NO₄Sn

553.79

Crystal system

Space group

triclinic

(

P1

,

a (A)

7.597(2)

10.203(2)

10.378(2)

103.40(3)

94.56(3)

103.16(2)

754.5(3)

2

7.642(2)

9.162(2)

12.897(3)

92.42(3)

95.99(3)

106.11(3)

860.4(4)

2

7.638(2)

9.330(3)

13.080(4)

93.91(4)

96.05(4)

105.15(4)

890.2(5)

2

,

b (A)

,

c (A)

h (°)

i (°)

k (°)

3

,

V (A )

Z

D_calc(Mg m⁻³

)

1.690

16.96

1.794

18.13

2.066

59.41

v (cm⁻¹

)

Temperature (K)

q (max) (°)

180(2)

26.8

180(2)

26.8

180(2)

27.0

Number of reﬂections collected

Numberof unique reﬂections

Reﬂections with I\2|(I)

Reﬂections/parameters in reﬁnement

wR₂(all)

5751

2902

2751

2875/250

0.0572

0.0223

4869

3267

2574

2776/218

0.0623

0.0235

7491

3450

2745

3016/236

0.0688

0.0282

R₁(I\2|(I))

(DMSO, c (mol l⁻¹)=1.0×10⁻³)=0.05 V⁻¹cm²

mol⁻¹. UV (CHCl₃, u_max, nm): 243, 270, 354.

graphite monochromated Mo Ka radiation. Numerical

absorption correction was only applied for structure 9

due to the higher absorption coefﬁcient. The structures

were solved by direct methods (^SHELXS-86) [12] and

reﬁned anisotropically for all non-hydrogen atoms us-

ing crystallographic program package ^SHELXL-93 [13].

Hydrogen atoms of vinyl groups in 4 and that of OH

group in methanol molecules in both 7 and 9 were

located from the difference Fourier maps and reﬁned

isotropically. All other H atoms were included in the

calculated positions and reﬁned in a riding mode. In the

structure 9, the bridging N and C(7) atoms of the salop

ligand were found to be disordered between two posi-

tions with occupancy ratio 80:20, which corresponds to

the disorder of the whole salop ligand. The compara-

2.4.18. [SnBuⁿ₂Cl₂(salopH₂)] (18)

Complex 18 was prepared as 17 by using 1.0 mmol of

salopH₂and 5.0 mmol of SnBuⁿ₂Cl₂. Yield 76%. M.p.

192–194 °C. Anal. Calc. for C₂₁H₂₉Cl₂NO₂Sn: C,

48.78; H, 5.65; N, 2.71. Found: C, 48.43; H, 5.58; N,

2.55%. IR (Nujol, cm⁻¹): 3193br (H₂O), 1626s, 1590s,

1508s (C···C, C···N), 577s, 533m (SnꢀC), 502sbr, 475s

1

(SnꢀO), 285br (SnꢀCl). H NMR (DMSO-d₆, 293 K):

l, 0.84 (t, 6H, SnꢀCH₂CH₂CH₂CH₃), 1.2–1.3 (m, 8H,

SnꢀBuⁿ), 1.5–1.6 (m, 4H, SnꢀBuⁿ), 6.8–7.7 (m, 8H,

H_aromatic), 9.16 (s, 1H, CH_salopH), 10.2, 10.8 (s br,

2

OH_salopHand/or NH_salopH). ¹³C NMR (DMSO-d₆, 293

2

K): l, 13.82 (s, SnꢀBuⁿ),²17.04 (s, SnꢀBuⁿ), 25.66 (s,

SnꢀBuⁿ), 27.73 (s, SnꢀBuⁿ), 116.24, 116.63, 116.86,

117.31, 118.19, 118.89, 119.31, 119.44, 119.60, 119.71,

122.32, 124.22, 128.99, 129.34, 131.90, 133.44, 134.74,

136.40 (s, C_aromatic), 150.79, 155.89, 157.28, 159.65,

160.79, 161.04, 161.70, 167.24, 191.68 (s, CO and CN).

¹¹⁹Sn NMR (DMSO-d₆, 293 K), l −211.1. \_M

(DMSO, c (mol l⁻¹)=1.1×10⁻³)=0.05 V⁻¹cm²

mol⁻¹. UV (CHCl₃, u_max, nm): 243, 270, 355.

tively high residual electron density (about 1 e A⁻³),

,

however, without chemical meaning was found for

,

structures 4 and 9 at the distance ꢀ1 A from the tin

atoms.

Crystallographic data and some details of data col-

lection and structures reﬁnement are given in Table 1.

The most relevant bond distances and angles in the

structures of 4, 7 and 9 are listed in Table 2. From the

recrystallisation of compound 15 we have obtained

good-quality crystals of 1 for which a single crystal

X-ray study has been previously reported [8]. Our data

compare well with those in literature [8] and are in-

serted in Table 2.

2.5. X-ray crystallography

The data for the complexes 4, 7 and 9 were collected

on an Image-Plate diffractometer (IPDS, Stoe) using

C. Pettinari et al. / Inorganica Chimica Acta 325 (2001) 103–114

109

Table 2

Selected bond distances and angles of complexes 1, 4, 7 and 9

a

Distances/angles [SnMe₂(Salop)](1)

[SnVi₂(Salop)] (4)

[SnCl₂(Salop)(CH₃OH)]·CH₃OH (7)

[SnBr₂(Salop)(CH₃OH)] (9)

SnꢀO(1)

SnꢀO(2)

SnꢀN

SnꢀC(14)

SnꢀC(16)

SnꢀX(1)

SnꢀX(2)

SnꢀO(3)

2.117(2)

2.139(3)

2.221(3)

2.112(3)

2.117(4)

2.117(2)

2.125(2)

2.227(2)

2.112(2)

2.113(2)

2.009(2)

2.055(2)

2.171(3)

2.005(2)

2.056(2)

2.178(5) ^b

2.348(1)

2.400(1)

2.182(2)

2.506(1)

2.553(1)

2.194(3)

C(14)ꢀSnꢀC(16) 140.1(1)

X(1)ꢀSnꢀX(2)

138.3(1)

96.18(4)

162.6(1)

90.0(1)

77.55(9)

83.69(9)

82.83(9)

83.76(9)

96.72(3)

161.5(1)

90.1(1)

76.6(1)

83.3(1)

82.3(1)

82.9(1)

O(1)ꢀSnꢀO(2)

O(1)ꢀSnꢀN

O(2)ꢀSnꢀN

158.7(1)

75.4(1)

83.5(1)

158.88(8)

75.79(7)

83.34(7)

O(1)ꢀSnꢀO(3)

O(2)ꢀSnꢀO(3)

NꢀSnꢀO(3)

C(14)ꢀSnꢀO(1)

C(16)ꢀSnꢀO(1)

C(14)ꢀSnꢀO(2)

C(16)ꢀSnꢀO(2)

C(14)ꢀSnꢀN

C(16)ꢀSnꢀN

X(1)ꢀSnꢀO(1)

X(1)ꢀSnꢀO(2)

X(2)ꢀSnꢀO(1)

X(2)ꢀSnꢀO(2)

X(1)ꢀSnꢀN

97.8(1)

99.3(1)

87.4(1)

89.6(1)

112.3(1)

106.9(1)

98.60(8)

95.91(8)

91.00(9)

89.12(8)

108.57(9)

112.81(8)

97.15(7)

93.43(7)

96.00(7)

96.60(7)

168.55(7)

91.91(7)

88.16(6)

175.66(6)

97.41(9)

93.72(8)

96.07(9)

97.30(9)

167.5(1)

92.3(1)

X(2)ꢀSnꢀN

X(1)ꢀSnꢀO(3)

X(2)ꢀSnꢀO(3)

88.09(7)

175.19(6)

^aFor [SnMe₂(Salop)], C(15) in the atom list corresponds to C(16) in this table. The data for this compound derived from our determination,

more reﬁned with respect to that reported in Ref. [8].

^bThe geometrical parameters are given for the main (80%) component of the disordered Salop ligand.

3. Results and discussion

With the triorganotin(IV) derivatives SnR₃Cl, the

complexes [SnR₃(salopH)] (R=Me or Buⁿ) 15 and 16,

containing the monoanionic Schiff base likely coordi-

nate in bidentate fashion, have been prepared.

3.1. Synthesis

From the reaction of SnR₂Cl₂acceptors with an

equimolar amount of 2-{[(2-hydroxyphenyl)imino]-

methyl}phenol(salopH₂) in methanol in the presence of

bases (KOH, MeONa or NEt₃), the complexes

[SnR₂(Salop)] 1–5 (R=Me, Ph, Vi, Buⁿ, Bu^t), contain-

ing the donor in the dianionic tridentate form, have

been obtained (Fig. 2). When SnRX₃or SnX₄acceptors

were employed in the same reaction conditions, the

complexes [SnX₂(salop)(S)] 6–13 (X=Cl, Br, I or R;

R=Me, Ph or Buⁿ; S=H₂O or MeOH) (Fig. 3) can be

easily obtained. Although these reactions seem to be

instantaneous when all reactants are mixed, reﬂuxing

for approximately 24 h was carried out to ensure

complete reaction.

On the other hand the reaction of SnX₄with 2 mol of

SalopH₂and 4 mol of base affords the compound

[Sn(salop)₂] 14 in which all halides groups have been

substituted by two dianionic tridentate Schiff bases.

Fig. 2. Structure proposed for the diorganotin(IV) salop derivatives.

110

C. Pettinari et al. / Inorganica Chimica Acta 325 (2001) 103–114

protonation of the ligand and involvement of both

phenolate oxygens in bonding to tin. In the triorganotin

complexes 15 and 16, the presence of a broad absorp-

tion between 2600 and 2300 cm⁻¹indicates that only

one phenolic group is deprotonated, that is in accor-

dance with a bidentate O,N-coordination of the ligand.

In the 3500–2300 cm⁻¹region the spectra of 17 and 18

are similar to that of the free ligand, indicating coordi-

nation of salopH₂in neutral form. In the spectra of

di-(6–10) and mono-halo (11–13) complexes, new

broad absorptions at ca. 3400–3000 cm⁻¹, due to

w(OꢀH) of MeOH or H₂O bonded to tin, were detected

according to the formulations proposed.

In derivatives 1–16 the w(CꢁN) band, occurring be-

tween 1617 and 1567 cm⁻¹, is considerably shifted

towards lower frequencies with respect to that of the

free Schiff base (1631–1593 cm⁻¹), conﬁrming the

coordination of the azomethine nitrogen to the

diorganotin(IV) moiety. The stretching frequency is

lowered owing to the displacement of electron density

from N to Sn atom, thus resulting in the weakening of

the CꢁN bond as reported in the literature [16]. The

major shift of CꢁN is observable in the IR spectrum of

the halide derivatives 6–13 as compared with that in

the triorganotin species 14 and 15, indicating a strong

participation of N atoms of the former in the coordina-

tion to the Sn atom. On the other hand, the w(CꢁN)

remains unchanged in the spectra of adducts 17 and 18

with respect to the free base, whereas a band assignable

to w(CꢀO) stretching vibration at approximately 1290

cm⁻¹in the ligand is shifted to 1250 cm⁻¹upon

adduct formation. Coordination through the phenolic

oxygen is conﬁrmed by l(OꢀH) absorption deforma-

tion, which falls at approximately 1290 cm⁻¹in the

spectra of 17 and 18.

In the spectra of 1–16 we have assigned some bands

in the region 460–500 cm⁻¹to w(SnꢀO) which in our

series seems to be little inﬂuenced by the type of

halogen bonded to tin, but strongly inﬂuenced by the

number and type of organic groups. The 20 cm⁻¹

increase on going from Me and Buⁿto Ph can be

interpreted in terms of the inductive effect of the in-

creasing electron withdrawing power of the correspond-

ing organic groups, which strengthens the SnꢀO bonds.

The absorptions at approximately 262 and 243 cm⁻¹

(5), 577 and 533 cm⁻¹(2) and ﬁnally 573 and 545

cm⁻¹(1) are due to w(SnꢀPh), w(SnꢀBuⁿ) and

w(SnꢀMe), respectively [17]. In the case of 3 and 4

(SnꢀBu^t₂and SnꢀVin₂derivatives) the assignment of

w(SnꢀC) is not certain, due to the overlapping with

SnꢀO and Whiffen-notation bands. The presence of

three absorptions due to SnꢀC in the spectra of tri-

organotin(IV) derivatives 15–16 is in accordance with a

ﬁve-coordinate tbp fac-SnR₃structure, with two other

positions likely occupied by two donor atom from

Salop [18].

Fig. 3. Structure proposed for the mono- and dihalotin(IV) salop

derivatives.

Finally, if the reaction between salopH₂and SnR₂Cl₂

was carried out in diethyl ether or CHCl₃in the absence

of a base, the adducts [SnR₂Cl₂(salopH₂)] 17 and 18

were formed.

Compounds 1–13 can be also prepared by reﬂuxing a

mixture of the proligand salopH₂with the tin(IV) ac-

ceptors in toluene with azeotropical removal of water.

Under our conditions no derivative was obtained

when SnCy₃Cl or SnPh₃Cl were employed.

In some cases, from the reaction of salopH₂with di

and tri organotin(IV) acceptors, the mono-organ-

otin(IV) complexes were obtained due to dissociation of

the starting acceptors according to the reaction of

Kocheskov [14].

In the presence of moisture the [SnR₂(salop)] and

[SnR₃(salopH)] complexes slowly hydrolyse even in

CHCl₃solution, yielding the R₂SnO and (R₃Sn)₂O ox-

ides or the hydroxides R₃SnOH [15]. The hydrolysis is

faster when R=Buⁿ. The adducts 17 and 18 are not

stable in solution yielding, in quantitative yields after

48 h, complexes 1 and 2, respectively.

Compounds 1–16 are stable under atmospheric con-

ditions and are thermally stable up to their m.p. They

all have intense colours (red, orange or yellow) and are

soluble in acetone, DMSO and chlorinate solvents in

which they are non-electrolytes, thus ruling out ionic

structure or displacement of the ligand salop by solvent

molecules, with the exception of compounds 8–10 for

which in DMSO a conductivity value has been found in

accordance with the partial ionic dissociation (Eq. (1)).

[SnX₂(salop)(CH₃OH)]+xDMSO

X[SnX_2−n(salop)(DMSO)_x]⁺+nX⁻+CH₃OH (1)

(n=1 or 2, X=Br or I)

3.2. Spectroscopy

3.2.1. IR

Selected IR data for all complexes are reported in

Section 2.

The strong broad band due to w(OꢀH), centred in the

free donor at approximately 2300 cm⁻¹, disappears in

the complexes 1–14, in accordance with complete de-

C. Pettinari et al. / Inorganica Chimica Acta 325 (2001) 103–114

111

3

In the far-IR region of 6–10 two w(SnꢀO) and two or

more w(SnꢀCl), w(SnꢀBr) and w(SnꢀI) bands were de-

tected, indicating halogen atoms being in cis position in

accordance with crystal structures (see above). For

SnꢀX stretching absorptions, the following trend, typi-

cal of dihalide complexes, has been found: w(SnCl)\

w(SnBr)\w(SnI) [19].

is possible to observe the J(SnꢀH) coupling involving

the azomethine proton, thus indicating direct SnꢀN

3

bonding. The magnitude of J(SnꢀH) can be employed

to evaluate the strenght of SnꢀN interaction. It has

3

been found that the values of J(SnꢀH) in mono and

di-halotin(IV) derivatives are greater than in the tri-

organotin(IV) complexes 15 and 16. The ¹H NMR

spectrum of the adducts 17 and 18 shows the azome-

thine proton unchanged with respect to the free ligand

indicating the absence of coordination of the imine N

atom to tin atom.

3.2.2. UV spectra

Details of the electronic spectra (in all cases recorded

in CHCl₃) are also given in the experimental section.

The spectra of 1–14 remain unchanged after a few

days, conﬁrming the stability of the complexes and

remain unaffected by dilution. The spectra of 1–16

contain a characteristic band in the region 240–267 nm

and two or more intense broad bands in the region

280–456 nm. The band in the region 240–270 nm can

be considered a p–p* benzenoid band, in view of the

assignments made by Chatterijee and Douglas [20]. In

the UV–Vis spectra of 1–5, all three bands, due to

conjugate systems of the coordinated ligand, reveal a

red shift with respect to analogue absorptions in the

spectrum of free salopH₂. In particular, the absorption

at 354 nm, due to CꢁN system between phenyl rings in

salopH₂, undergoes a shift to approximately 454–465

nm.

In the ¹H NMR spectra of 1–9 and 11–13 the HCꢁN

proton is observed as one sharp singlet due to absence

of isomers or ﬂuxionality in solution. In the H NMR

1

spectrum of the diiodo complex 10 three different sig-

nals have been found for the HCꢁN groups. This

multiplicity, also found in the ¹³C and ¹¹⁹Sn spectra, is

in accordance with the occurrence of equilibrium 1.

The J(¹¹⁹Snꢀ¹H) of dimethyltin derivative 1 has a

2

value of 78.1 Hz, typical of ﬁve-coordinated tin species.

On the basis of Lockarts’s Eq. (2):

[Me−Sn−Me]=0.0161×

(²J(¹¹⁹Sn−¹H))2−1.32×²J(¹¹⁹Snꢀ¹H)+133.4 (2)

the MeꢀSnꢀMe angle is estimated to approximately

128° [22]. The discrepancy between the CꢀSnꢀC angle

from X-ray data (see below) and the empirical estima-

tion in solution suggests a change of the structure with

the long SnꢀO bond interaction being likely broken

upon dissolution.

The replacement of methyl or butyl groups by the

more electronegative chloride results in pronounced

blue shifts of the long wavelength absorption band of

the coordinated dinegative anion, a behaviour previ-

ously reported for other tin(IV) derivatives containing

schiff bases [21].

The spectra of the adducts 17 and 18 are similar to

that of the free ligand, suggesting that in chloroform

solution they completely dissociate into starting

reagents, as also indicated by NMR data (see below).

The ¹³C NMR spectra show a signiﬁcant downﬁeld

shift of all carbon resonances. The shift is a conse-

quence of an electron density transfer from the ligand

n

to the acceptor. The J(¹¹⁹Snꢀ¹³C) coupling constants

were detected in the case of sufﬁciently soluble deriva-

tives. In derivatives 1–5, the order of magnitude of the

coupling constants is the same as those previously

reported for analogous ﬁve-coordinate derivatives [23],

whereas in the case of derivatives 11–13 the

ⁿJ(¹¹⁹Snꢀ¹³C) are close to those found for six-coordi-

nate skewed trapezoidal organotin(IV) complexes

[19,23]. By using the simple linear relationship between

¹J(¹¹⁹Snꢀ¹³C) and the CꢀSnꢀC bond angles derived by

Lockart [22] and Howard [24] for dimethyltin species a

value has been found for compound 1 in the range

130–134° which well agrees with the angle of 138°

found in the crystal structure [8].

3.2.3. NMR spectra

The ¹H NMR data for the ligand and its tin(IV)

complexes have been reported in Section 2. The choice

of the solvent was dictated by the solubility, the order

of preference being CDCl₃, acetone-d₆and DMSO-d₆.

The absence of the OH proton signals in the complexes

1–14 further supports the binding of the tin centre to

both ligand oxygen atoms through the replacement of

both phenolic hydrogens. Whereas the OH resonance is

present in the spectra of the triorganotin(IV) complexes

15 and 16, in accordance with a partial deprotonation

of the ligand, as also in the adducts 17 and 18, in which

the ligand is in the neutral form. The chemical shift

values of the ligand protons in 1–16 are as expected: a

downﬁeld shift in the l value of azomethine (HCꢁN)

proton resonance upon coordination, supports the liga-

tion of azomethine nitrogen to tin. The SnꢀN bond

found in the solid state (see below) is retained also in

solution. In fact, in the proton NMR spectra of 1–16 it

The ¹¹⁹Sn NMR spectra of 1–5 show only one sharp

resonance in the range −140 to −330 ppm, typical of

ﬁve-coordinated diorganotin compounds [23]. As previ-

ously reported the ¹¹⁹Sn chemical shift increases with

the following order:

Me:BuⁿBBu^tBVinBPh

112

C. Pettinari et al. / Inorganica Chimica Acta 325 (2001) 103–114

The ¹¹⁹Sn NMR chemical shift of 6–13 is typical of

oxygen atoms (SnꢀO: 2.117(2) and 2.125(2) A) are in

axial positions, with a OꢀSnꢀO angle of 158.88 (8)°.

The vinyl groups, directed above and below the plane

deﬁned by Sn, N and both O atoms, adopt a conforma-

tion with the terminal C atom bent toward the O2 of

salop, the CꢀSnꢀC angle being 138.3(1)°. Each molecu-

lar units weakly interact with another one through the

O1 atom of salop, which is involved in an interaction

with the metal of the second complex molecule

,

six-coordinate tin(IV) [19,23] and increases also when

the R groups are replaced by more electronegative

groups such as halides. As previously reported in the

case of acylpyrazolonates the trend of chemical shift

can be related to the electron-withdrawing inductive

effect of the halogens and also to the possibility of

additional p-contribution to the SnX bonds which

would shield the nucleus to a greater extent. In the

¹¹⁹Sn spectrum of 10 four resonances have been de-

tected, two at approximately −621 ppm likely due to

[Sn(salop)(DMSO)₂(CH₃OH)]²⁺[I₂]²⁻and two at ap-

proximately −814 ppm—due to [SnI(salop)(DMSO)-

(CH₃OH)]⁺[I]⁻species in accordance with equilibrium

1 proposed on the basis of the conductivity measure-

ments which indicate the existence in solution of 1:1

electrolytes.

,

(Sn···O:2.748(2)A). The structure is very similar to that

of derivatives 1 and 5, reported previously [8,9], how-

ever, in 5 no Sn···O interactions between the complex

molecules were found, and the CꢀSnꢀC angle was less

(121.4°) than in 1 and 4.

The equatorial angles in the structure of 4 are close

to that reported for [SnMe₂(salop)] [8], whereas they

differ from those reported for diphenyltin derivative [9].

The SnꢀO distances are in the range typical for the

Sn(IV) derivatives of salop, but are slightly shorter with

respect to those reported for [SnBuⁿ₂(Vanophen)] [6 h].

The monomeric [SnVin₂(salop)] units are linked into

dimers by weak intermolecular interactions with SnꢀO

distance being 2.748(2). This is similar to [SnMe₂-

(salop)] complex [8], in which the value of additional

1

The H and ¹¹⁹Sn NMR spectra of the adducts 17

and 18 are typical of completely dissociated species, all

signals being analogous to that of the free ligand and of

the solvated organotin species.

3.3. X-ray diffraction study

,

The single-crystal X-ray diffraction (XRD) study of

derivative 4 shows the tin center coordinated by ﬁve

donor atoms, two O and one N from the salop ligand

and two C of the vinyl groups, in a distorted trigonal

pyramidal geometry (Fig. 4). The distortion is mainly

due to the rigidity of chelate rings, together with the

large covalent radius of tin(IV). The nitrogen (SnꢀN:

SnꢀO bonding is 2.881(8) A, but differs from

[SnPh₂(salop)] [9], in which this interaction is absent

likely due to steric factors. The comparison of three

structures with R=Me, Vin, Ph shows the [SnVin₂-

(salop)] derivative being much more similar to methyl-

one. On the contrary to 4, the divinyltin(IV) derivative

of N-(2-hydroxyacetophenone)glycinate reported re-

cently contains a water molecule coordinated to tin

[25]. The coordination of water in this case can be

,

2.227(2) A) and the carbon atoms (SnꢀC: 2.112(2) and

,

2.113(2) A) occupy the equatorial plane, whereas the

Fig. 4. The molecular structure of 4.

C. Pettinari et al. / Inorganica Chimica Acta 325 (2001) 103–114

113

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Article Doi

Synthesis and characterisation of tin(IV) and organotin(IV) derivatives 2-{[(2-hydroxyphenyl)imino]methyl}phenol

DOI: 10.1016/S0020-1693(01)00654-5

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