Organoantimony(iii) compounds containing (imino)aryl ligands of the type 2-(RNCH)C6H4 (R = 2′,4′,6′-Me 3C6H2, 2′,6′-iPr 2C6H3): Bromides and chalcogenides

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An international journal of inorganic chemistry

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Volume 42 | Number 4 | 28 January 2013 | Pages 805–1296

ISSN 1477-9226

COVER ARTICLE

Ciprian I. Raţ, Cristian Silvestru, Michael Mehring et al.

Organoantimony(III) compounds containing (imino)aryl ligands of the

type 2-(RN=CH)C₆H₄(R = 2‘,4‘,6‘-Me₃C₆H₂, 2‘,6‘-ⁱPr₂C₆H₃): bromides and

chalcogenides

1477-9226(2013)42:4;1-C

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PAPER

Organoantimony(III) compounds containing (imino)aryl

ligands of the type 2-(RNvCH)C₆H₄(R = 2’,4’,6’-

Me₃C₆H₂, 2’,6’-ⁱPr₂C₆H₃): bromides and chalcogenides†

Cite this: Dalton Trans., 2013, 42, 1144

Ana Maria Preda,^a,bCiprian I. Raţ,*^aCristian Silvestru,*^aHans J. Breunig,^c

Heinrich Lang,^dTobias Rüﬀer^dand Michael Mehring*^b

The reaction of 2-(RNvCH)C₆H₄MgBr [R = 2’,4’,6’-Me₃C₆H₂(R¹), 2’,6’-ⁱPr₂C₆H₃(R²)] [prepared from

2-(R¹NvCH)C₆H₄Br (1) or 2-(R²NvCH)C₆H₄Br (2) and Mg] with SbCl₃in a 2 : 1 and 1 : 1 molar ratio fol-

lowed by treatment with an aqueous KBr solution gave [2-(R¹NvCH)C₆H₄]₂SbBr (3) and [2-(R²NvCH)-

C₆H₄]₂SbBr (4) as well as [2-(R¹NvCH)C₆H₄]SbBr₂(6) and [2-(R²NvCH)C₆H₄]SbBr₂(7). Treatment of 4

with Na₂S·9H₂O provided the dinuclear [{2-(R²NvCH)C₆H₄}₂Sb]₂S (5). Heterocyclic species, i.e. the oxide

cyclo-[{2-(R²NvCH)C₆H₄}SbO]₃(8) and the sulﬁdes cyclo-[{2-(R¹NvCH)C₆H₄}SbS]₂(9) and cyclo-

[{2-(R²NvCH)C₆H₄}SbS]₂(10), were obtained by reacting dibromides 6 and 7 with KOH and Na₂S·9H₂O,

respectively, in a water–toluene solvent mixture. The sulﬁde 10 reacted with [W(CO)₅(thf)] to yield the

heterometallic complex cyclo-[{2-(R²NvCH)C₆H₄}SbS]₂[W(CO)₅] (11). The compounds were characterised by

multinuclear NMR spectroscopy in solution, mass spectrometry and IR spectroscopy in the solid state. The

molecular structures of 4, 5, 6·CHCl₃, 7, 9·CH₂Cl₂, 10 and 11·0.25CH₃OH were established by single-crystal

X-ray diﬀraction. Theoretical calculations using DFT methods were carried out on bromide 7 and the geo-

metrical isomers of its dimer association as well as the geometrical isomers of sulﬁde 10 and its monomer.

Received 19th October 2012,

Accepted 5th November 2012

DOI: 10.1039/c2dt32494f

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“pincer”-type ligands like symmetric 2,6-(Me₂NCH₂)₂C₆H₃

[(N,C,N)-ligand],⁸2,6-(ROCH₂)₂C₆H₃[(O,C,O)-ligand],^8e,9asym-

Introduction

The chemistry of hypervalent organoantimony compounds^1–4metric 2-(Me₂NCH₂)-6-(ROCH₂)C₆H₃[(N,C,O)-ligand],¹⁰or

containing one pendant arm (C,N)-ligand such as 2-[Me₂NCH- E(CH₂C₆H₄)₂(E = RN, O, S) groups,^3,4which all can be con-

(R)]C₆H₄[R

=

H,⁵Me^5h,6

]

or 2-[O(CH₂CH₂)₂NCH₂]C₆H₄,⁷sidered as dianionic (C,E,C)-ligands, aroused in recent years

considerable interest with regard to both fundamental

research and applications. Such ligands can protect the metal

^aDepartamentul de Chimie, Facultatea de Chimie si Inginerie Chimica, Universitatea

Babes-Bolyai, RO-400028 Cluj-Napoca, Romania. E-mail: cristian.silvestru@ubbcluj.ro;

Fax: (+40) 264-590818; Tel: (+40) 264-593833

^bInstitut für Chemie, Technische Universität Chemnitz, Koordinationschemie,

D-09111 Chemnitz, Germany. E-mail: michael.mehring@chemie.tu-chemnitz.de;

Fax: (+49) 371-53121219; Tel: (+49) 371-53135128

centre by increased coordination through intramolecular

E → Sb (E = N, O, S) interactions observed both in the solid

state and in solution, thus providing thermodynamical stabili-

zation and allowing isolation of unusual species, e.g. hetero-

cyclic organoantimony sulfides, (RSbS)₂. Hypervalent [2,6-

(Me₂NCH₂)₂C₆H₃SbE]₂(E = O, S) can be used to trap CO₂or

CS₂; these compounds were found to react reversibly with CO₂

or CS₂in solution.^8f,jAlso their use as reagents or as catalysts

in organic synthesis (e.g. cross-coupling reactions^11,12) was

reported.

^cInstitut für Anorganische und Physikalische Chemie, Universität Bremen, D-28334

Bremen, Germany. E-mail: hbreunig@uni-bremen.de; Fax: (+49) 421-21862809;

Tel: (+49) 421-21863150

^dInstitut für Chemie, Technische Universität Chemnitz, Anorganische Chemie,

D-09111 Chemnitz, Germany. E-mail: heinrich.lang@chemie.tu-chemnitz.de;

Fax: (+49) 371-53121219; Tel: (+49) 371-53121210

†Electronic supplementary information (ESI) available: X-ray crystallographic

data in CIF format for 4, 5, 6·CHCl₃, 7, 9·CH₂Cl₂, 10 and 11·0.25CH₃OH; figures

In contrast to hypervalent organoantimony compounds

containing ligands with an sp³-nitrogen atom in the pendant

representing the optical isomers as well as the supramolecular architectures in

the crystals of these compounds; NMR spectra; representations of calculated vs. arm, related species based on intramolecular N(sp²) → Sb

determined structures of the all-trans dimer association of 7 and of the all-trans

interactions were much less investigated. For example [2-

isomer of 10; selected calculated and experimental bond lengths and angles for

{RNvCH}C₆H₄]₃Sb [R = (R)-MeC₆H₄CH(Me), (R)-HOCH₂CH-

the all-trans dimer of 7 and the all-trans isomer of 10; atomic coordinates for the

(Et)]¹³was obtained by condensation of RNH₂with [2-(OvCH)-

optimized models. CCDC 821266 (4), 821267 (5), 821268 (6·CHCl₃), 821269 (7),

C₆H₄]₃Sb.¹⁴Hypercoordination in tetraarylstibonium salts was

821270 (9·CH₂Cl₂), 821271 (10) and 821272 (11·0.25CH₃OH). For ESI and crystal-

lographic data in CIF or other electronic format see DOI: 10.1039/c2dt32494f

related to the presence of an internal N → Sb interaction in

1144 | Dalton Trans., 2013, 42, 1144–1158

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[RSbR′₃][CuI₂] [R

HOC₆H₂NvCH)C₆H₄(X

MeOC₆H₄NvCH)C₆H₄SbPh₃]₄[Cu₁₄I₁₈].^15b

=

2-(4-MeOC₆H₄NvCH)C₆H₄, 2-(3,5-X₂-4- aqueous solution of KBr the pure bromides R₂SbBr and

=

Cl, Br, Ph)]^15aand [2-(4- RSbBr₂were isolated as yellow solids (yields in the range

A

remarkable 37–53%). Both the organic bromides 1 and 2 and the orga-

achievement was the isolation of an RSb(^I) monomer using the noantimony(^III) bromides [2-(R¹NvCH)C₆H₄]₂SbBr (3) and

pincer (N,C,N)-ligand R = 2,6-[2′,6′-Me₂C₆H₃NvC(Me)]₂C₆H₃.¹⁶[2-(R²NvCH)C₆H₄]₂SbBr (4) as well as dibromides [2-(R¹NvCH)-

Recently, while this work was under progress,¹⁷organoanti- C₆H₄]SbBr₂(6) and [2-(R²NvCH)C₆H₄]SbBr₂(7) are well

mony compounds such as R_nSbCl_3−n(n = 1,2), R₄Sb₂and cyclo- soluble in chlorinated solvents (CH₂Cl₂, CHCl₃). NMR data of

(RSb)₄[R = 2-(2′,6′-iPr₂C₆H₃NvCH)C₆H₄] were reported.¹⁸

1–4, 6 and 7 as well as elemental analytical data are consistent

As part of our interest in organoantimony(III) compounds with the anticipated formulas. The EI mass spectra of the

with pendant arms we report herein the synthesis, spectro- organic bromides 1 and 2 show the corresponding molecular

scopic characterization and crystal structures of species (bro- ions. For the [2-(RNvCH)C₆H₄]_nSbBr_3−n(n = 2, 1) species

mides and chalcogenides) containing (imino)aryl ligands of (compounds 2, 4, 6, 7) the base peaks in the ESI+ mass spectra

the type 2-(RNvCH)C₆H₄(R = 2′,4′,6′-Me₃C₆H₂, 2′,6′-ⁱPr₂C₆H₃). are assigned to [R₂Sb⁺] and [RSbBr⁺] fragments for the

The chemistry of these compounds with rigid and sterically monobromides [2-(RNvCH)C₆H₄]₂SbBr and dibromides

demanding organic groups is compared with that of related [2-(RNvCH)C₆H₄]SbBr₂, respectively.

organoantimony(^III) species containing the 2-(Me₂NCH₂)C₆H₄

ligand.^5g,i,j

The NMR spectra of 1–4, 6 and 7 were recorded in CDCl₃at

room temperature. The assignment of resonances in the ¹H

and ¹³C NMR spectra was based on 2D NMR (HSQC, HMBC

and COSY) correlation spectra, according to the numbering

schemes shown in Scheme 2. The spectra of the dibromides 6

Results and discussion

Synthesis and characterization of organoantimony(III)

bromides

The organic bromides 2-(RNvCH)C₆H₄Br [R = 2′,4′,6′-Me₃C₆H₂

(R¹) (1), 2′,6′-ⁱPr₂C₆H₃(R²) (2)] were obtained as E isomers by

condensation of 2-bromobenzaldehyde with the corresponding

aromatic amine according to a slightly modified literature

method reported for 2 (Scheme 1).¹⁹Both compounds were

isolated as yellow solids after recrystallization from hexane

(85% for 1, 76% for 2). Treatment of the Grignard reagents

RMgBr with SbCl₃in a 2 : 1 and 1 : 1 molar ratio gave mixtures

of chloride/bromide R₂SbX and RSbX₂derivatives, respectively,

due to partial halogen exchange reactions. Following treatment

of the crude organoantimony halides in CH₂Cl₂with an Scheme 2 Numbering scheme for NMR assignments.

Scheme 1 Preparation of compounds 1–11.

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and 7 show one set of resonances for the substituents in ortho 27.77 ppm for C-7′ atoms; Scheme 2b) and for the other substi-

positions as well as for the meta positions of the aromatic R tuent (designated by A) the free rotation of the bulky

group attached to nitrogen, consistent with the presence of 2,6-ⁱPr₂C₆H₃group is blocked. This results in non-equivalence

only one species in solution for which free rotation around the of the two halves of this aromatic moiety (Scheme 2c) as indi-

C–N(vC) single bond is not restricted. The presence of two cated, for example, by the presence of two singlet resonances

doublets for the methyl protons of the ⁱPr groups in 7 indicates at δ 28.00 and 28.48 ppm for C-7′_aand C-7′_b, respectively. The

their diastereotopic nature. No essential changes were diﬀerent behaviour of 3 and 4 in CDCl₃solution at room temp-

observed when the ¹H NMR spectrum of 7 was recorded in erature might be related to the bulkiness of the organic group

CDCl₃at −60 °C.

attached to nitrogen.

Significant diﬀerences should be noted in the solution be-

The IR stretching vibration of the carbon–nitrogen double

haviour of the bromides 3 and 4. For 3 both H and ¹³C NMR bond appears in the 1650–1550 cm⁻¹region as is typical for

spectra exhibit only one set of aromatic resonances and one compounds containing Schiﬀ-base ligands. In the IR spectra

resonance for the imine protons (δ 8.29 ppm). This is consist- of the title organoantimony(^III) bromides the ν_CvNstretching

ent with equivalence of the organic groups attached to anti- vibration was observed at 1624 (for 3), 1634 (for 4), 1617 (for

mony at the NMR time scale, which suggests a fast fluxional 6) and 1621 cm⁻¹(for 7), respectively. This pattern might be

behaviour, i.e. coordination–decoordination of the nitrogen consistent with the presence of intramolecular N → Sb coordi-

atoms. Moreover, the presence of two sharp resonances at δ nation and a delocalization of the π electrons of the –CvN–

1.65 and 2.20 ppm (2 : 1 integral ratio) assigned to methyl bond over the resulting C₃NSb ring.

1

protons indicates that there is no restriction of free rotation of

Single crystals suitable for X-ray diﬀraction studies were

the mesityl groups around the C–N(vC) single bonds. It obtained by slow diﬀusion of n-hexane into CH₂Cl₂(4 and 7)

should be noted that in the case of the related [2-(Me₂NCH₂)- or CHCl₃(6·CHCl₃) solutions. The solid state molecular struc-

C₆H₄]₂SbCl the dynamic process resulting in equivalent tures of these bromides are depicted in Fig. 2–4. Selected

organic ligands is frozen only at −60 °C, while at room temp- interatomic distances and angles are summarized in Tables

erature the ¹H NMR spectrum shows one set of broad resonan- 1 and 2.

ces.^5gBy contrast, the room temperature NMR spectra for 4

As expected, a common feature for the solid state structure

show two sets of resonances indicating that the organic groups of the title compounds is that the imine nitrogen is coordi-

in this molecule are not equivalent as was also observed in the nated intramolecularly to the antimony atom. In related com-

solid state (see subsequent discussion) due to the coordination pounds with pendant arms which contain an sp³-carbon

of nitrogen atoms trans to bromine or to an aromatic carbon atom between the aromatic ring and the donor atom [e.g.

attached to the metal atom, respectively. A similar pattern was 2-[Me₂NCH(R)]C₆H₄, 2-[O(CH₂CH₂)₂NCH₂]C₆H₄, 2,6-(ROCH₂)₂-

also observed at room temperature for the analogous chloride, C₆H₃] a five-membered C₃SbE chelate ring with internal

[2-(2′,6′-ⁱPr₂C₆H₃NvCH)C₆H₄]₂SbCl.¹⁸This is clearly evidenced E → Sb (E = N, O) interaction results. This ring is folded along

by the presence of two sharp singlet resonances in the the Sb⋯C_methyleneaxis and this induces planar chirality.^4,5mIn

aromatic region, assigned to the imine protons of the non- contrast, the presence of the –CvN– bond in the pendant arm

equivalent organic substituents (δ 8.36 and 8.43 ppm, respect- results in a planar C₃SbN unit and thus the title compounds

ively). Moreover, the ¹H (see Fig. 1) and ¹³C NMR (see ESI, do not anymore exhibit planar chirality. However, the intra-

Fig. S3 and S4†) spectra indicate that for one ligand unit molecular N(sp²) → Sb interaction results in “chelate induced-

(designated by B) free rotation around the C–N(vC) single Sb-chiral” compounds.^4,5mThe organic ligands in 4 become

bond is not restricted (e.g. one singlet resonance at δ non-equivalent since the nitrogen atoms are coordinated to

Fig. 1 ¹H NMR spectrum (CDCl₃, 300 MHz) of compound 4, at room temperature.

1146 | Dalton Trans., 2013, 42, 1144–1158

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Table 1 Selected bond distances (Å) and angles (°) for compounds 4 and 5

4

5

Sb(1)–C(1)

Sb(1)–C(20)

Sb(1)–E(1)^a

Sb(1)–N(1)

Sb(1)–N(2)

2.165(5)

2.153(5)

2.6371(11)

2.498(4)

2.996(4)

2.167(2)

2.163(2)

2.4727(6)

2.616(2)

N(1)–C(7)

N(1)–C(8)

N(2)–C(26)

N(2)–C(27)

1.277(6)

1.444(6)

1.252(7)

1.423(6)

1.277(3)

1.432(3)

1.264(3)

1.432(3)

C(1)–Sb(1)–C(20)

E(1)–Sb(1)–C(1)^a

E(1)–Sb(1)–C(20)^a

N(1)–Sb(1)–C(1)

N(1)–Sb(1)–C(20)

N(1)–Sb(1)–E(1)^a

N(1)–Sb(1)–N(2)

N(2)–Sb(1)–C(1)

N(2)–Sb(1)–C(20)

N(2)–Sb(1)–E(1)^a

95.84(19)

93.15(14)

90.88(13)

72.92(17)

86.43(16)

165.43(10)

102.00(13)

163.75(16)

68.20(16)

90.24(9)

101.00(8)

97.01(5)

91.77(5)

71.19(7)

83.66(6)

166.14(3)

Fig. 2 ORTEP representation at 30% probability and atom numbering scheme

for the (C_Sb)-4 isomer.

Sb(1)–E(1)–Sb(1a)^ab

88.57(3)

C(7)–N(1)–C(8)

Sb(1)–N(1)–C(7)

Sb(1)–N(1)–C(8)

117.6(4)

108.2(3)

130.1(3)

119.81(17)

106.2(1)

126.6(1)

C(26)–N(2)–C(27)

Sb(1)–N(2)–C(26)

Sb(1)–N(2)–C(27)

119.9(5)

99.4(4)

140.6(3)

118.68(18)

^aE(1) = Br(1) for 4, and S(1) for 5. ^bSymmetry equivalent atoms (−x, y,

0.5 − z) are given by “a”.

Fig. 3 ORTEP representation at 40% probability and atom numbering scheme

for the dimer association between (C_Sb)- and (A_Sb)-6 isomers in the crystal of

6·CHCl₃(the solvent molecule is not shown) [symmetry equivalent atoms

(2 − x, −y, 1 − z) are given by “prime”].

them. In both diorgano- and monoorganoantimony(^III) deriva-

tives the chirality thus induced at the metal atom can be

described in terms of C_Sband A_Sbisomers²⁰for the square

pyramidal (C,N)₂SbBr (hypervalent 12-Sb-5 species) and pseudo-

trigonal bipyramidal (“see-saw”) (C,N)SbBr₂cores (hypervalent

10-Sb-4 species), respectively.^1,21Indeed, the crystals of the

title bromides contain a 1 : 1 mixture of these isomers.

As expected, in the bromide 4 the length of the internal

N → Sb interactions is diﬀerent, i.e. that one established trans

to the bromine atom [Sb(1)–N(1) 2.498(4) Å; N(1)–Sb(1)–Br(1)

165.43(10)°] being shorter than that one established trans to

the carbon atom [Sb(1)–N(2) 2.996(4) Å; N(2)–Sb(1)–C(1)

163.75(16)°; cf. sums of the corresponding covalent, Σr_cov(Sb,N)

2.11 Å, and van der Waals radii, Σr_vdW(Sb,N) 3.74 Å].²²The

lengths of these N → Sb bonds are similar to those reported

for the analogous chloride [Sb(1)–N(1) 2.416(2) Å; Sb(1)–N(2)

2.952(3) Å]. When compared to the N → Sb interactions in the

related [2-(Me₂NCH₂)C₆H₄]₂SbBr [Sb(1)–N(1) 2.423(3) Å; Sb(1)–

N(2) 3.276(3) Å]^5gthe significant decrease of the interatomic

distance corresponding to the N → Sb interaction trans to the

carbon atom is remarkable. This behaviour is a consequence

of the better donor properties of a N(sp²) atom versus a N(sp³)

Fig. 4 ORTEP representation at 40% probability and atom numbering scheme

for the dimer association between (C_Sb)- and (A_Sb)-7 isomers in the crystal of 7

[symmetry equivalent atoms (1 − x, 1 − y, 1 − z) are given by “prime”].

antimony trans to diﬀerent atoms. Similarly, in 6 and 7 the two atom.

halogen atoms per molecule are not equivalent following the

The antimony–nitrogen distance in the dibromides 6

coordination of the nitrogen in the trans position to one of [Sb(1)–N(1) 2.346(3) Å] and 7 [Sb(1)–N(1) 2.395(3) Å] is shorter

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Table 2 Selected bond distances (Å) and angles (°) for compounds 6·CHCl₃, 7, 9·CH₂Cl₂and 10

6·CHCl₃

7

9·CH₂Cl₂

10

Sb(1)–C(1)

Sb(1)–Br(1)

Sb(1)–Br(2)

Sb(1)–N(1)

2.149(3)

2.8034(5)

2.5749(5)

2.346(3)

2.162(3)

2.7174(7)

2.5426(7)

2.395(3)

Sb(1)–C(1)

Sb(1)–S(1)

Sb(1)–S(1′)

Sb(1)–N(1)

2.161(3)

2.5326(9)

2.4016(9)^c

2.553(2)

2.162(4)

2.5269(9)

2.4167(10)^d

2.558(2)

Sb(1)–Br(1′)

3.2050(5)^a

3.3362(5)^b

N(1)–C(7)

N(1)–C(8)

1.285(5)

1.432(5)

1.283(3)

1.432(4)

N(1)–C(7)

N(1)–C(8)

1.264(4)

1.436(4)

1.261(4)

1.436(4)

C(1)–Sb(1)–Br(1)

C(1)–Sb(1)–Br(2)

Br(1)–Sb(1)–Br(2)

N(1)–Sb(1)–C(1)

N(1)–Sb(1)–Br(1)

N(1)–Sb(1)–Br(2)

Br(1′)–Sb(1)–C(1)

Br(1′)–Sb(1)–Br(1)

Br(1′)–Sb(1)–Br(2)

Br(1′)–Sb(1)–N(1)

90.70(10)

92.42(11)

87.14(1)

75.45(12)

163.60(7)

84.76(7)

80.55(11)

87.53(1)

171.12(1)

98.59(7)

91.86(8)

93.16(8)

89.61(1)

74.84(10)

164.82(5)

83.97(6)

77.61(7)

91.76(1)

170.70(1)

92.44(6)

C(1)–Sb(1)–S(1)

C(1)–Sb(1)–S(1′)

S(1)–Sb(1)–S(1′)

N(1)–Sb(1)–C(1)

N(1)–Sb(1)–S(1)

N(1)–Sb(1)–S(1′)

95.09(8)

100.15(8)

88.69(3)

72.25(10)

161.88(6)

81.12(6)

94.37(8)

99.54(8)

89.08(3)

72.39(11)

161.56(6)

80.82(6)

Sb(1)–Br(1′)–Sb(1′)

92.47(1)

88.24(1)

Sb(1)–S(1′)–Sb(1′)

91.31(3)

90.93(3)

C(7)–N(1)–C(8)

Sb(1)–N(1)–C(7)

Sb(1)–N(1)–C(8)

120.9(3)

111.7(2)

127.0(2)

120.8(3)

111.2(2)

127.99(17)

C(7)–N(1)–C(8)

Sb(1)–N(1)–C(7)

Sb(1)–N(1)–C(8)

120.4(3)

109.00(19)

130.60(18)

119.3(3)

108.9(2)

131.2(2)

^aSymmetry equivalent atoms (2 − x, −y, 1 − z) are given by “prime”. ^bSymmetry equivalent atoms (1 − x, 1 − y, 1 − z) are given by “prime”.

^cSymmetry equivalent atoms (1 − x, −y, −z) are given by “prime”. ^dSymmetry equivalent atoms (−x, −y, 2 − z) are given by “prime”.

than in 4. This is as a result of a combined eﬀect produced by

Intramolecular Br⋯H contacts are established in the mole-

the hybridization nature of the donor atom [N(sp²)] and the cule of 4 [Br(1)⋯H(6)_aryl2.81 Å; Br(1)⋯H(36)_methine2.95 Å]. In

increased Lewis acidity of the metal atom with an increasing addition, a closer look revealed both intra- and intermolecular

number of halogen atoms attached to it [to be compared with C–H⋯π (Ph_centroid) distances consistent with π interactions

i

[2-(Me₂NCH₂)C₆H₄]SbBr₂:^5gSb(1)–N(1) 2.409(3) Å].

between hydrogen atoms of one Pr group and the aromatic

While no intermolecular interactions between heavy atoms rings attached to the metal (i.e. H⋯Ph_centroidcontacts shorter

were observed in the bromide 4, the molecules of the dibro- than 3.1 Å, with an angle γ between the normal to the aromatic

mides are associated into centrosymmetric dimer units built ring and the line defined by the H atom and Ph_centroidsmaller

from C_Sband A_Sbisomers through asymmetric bromine than 30°):²³C(17)–H(17)_methine⋯Ph_centroid{C(20)–C(25)} 2.84 Å,

bridges involving the halogen trans to nitrogen (Fig. 3 and 4). γ = 19.4°, and C(19)–H(19C)_methyl⋯Ph_centroid{C(1a)–C(6a)} 2.76 Å,

As expected, for the molecular unit of the dibromides 6 and 7 γ = 9.7°. The latter one results in the formation of polymeric

the terminal Sb–Br bond is much shorter than that involved in chains of (C_Sb)-4 and (A_Sb)-4 isomers, respectively, without

the bromine Sb–Br⋯Sb bridge, while the Sb–Br bond in 4 is of further contacts between parallel chains (for details, see ESI†).

intermediate length between the values observed for the dibro-

As in the case of the monobromide 4, an intramolecular

mides (see Tables 1 and 2). The overall coordination geometry Br⋯H contact is established in the molecules of 6 or 7

around the metal becomes square pyramidal [(C,N)SbBr₃core] [Br(1)⋯H(6)_aryl2.80 Å]. In addition, further Br⋯H contacts are

in 6 and 7 if the intermolecular antimony–bromine interaction established between the two halves of the centrosymmetric

[Sb(1)–Br(1a) 3.2050(5) Å for 6 and 3.3362(5) Å for 7, respecti- dimer units [Br(1)⋯H(16A′)_methyl3.10

Å

in 6; Br(1)

vely] is taken into account (hypervalent 12-Sb-5 species).^1,21⋯H(14′)_methine2.93 Å in 7]. In the crystal of 6·CHCl₃the dimer

The trans orientation of the Sb–C, terminal Sb–Br and Sb–N units are connected through weak C–H⋯π (Ph_centroid) inter-

bonds of the two molecules in the dimer unit with respect to actions [C(15)–H(15C)_methyl⋯Ph_centroid{C(8′a)–C(13′a)} 2.99 Å,

the central planar Sb₂Br₂ring should be noted (see also the γ = 24.1°] into chain polymers of alternating (C_Sb)- and (A_Sb)-6

Theoretical calculations section). A similar asymmetric dimer isomers. Each chain is further connected to four other parallel

association was described for the related [2-(Me₂NCH₂)C₆H₄]- chains through weak Br⋯H contacts [Br(2)⋯H(7)_imine3.05 Å]

SbBr₂.^5gIn contrast, the crystal of the chloride analogue, [2-(2′- which involve the terminal bromine atoms of the dimer units.

,6′-ⁱPr₂C₆H₃NvCH)C₆H₄]SbCl₂, was reported to contain only By contrast, the crystal of 7 contains layers in which a dimer

discrete molecules, without intermolecular interactions unit is connected to four other dimers through C–H⋯π (Ph_centroid

)

between heavy atoms.¹⁸

[C(3)–H(3)_aryl⋯Ph_centroid{C(8a)–C(13a)} 2.92 Å, γ = 13.4°] and

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Br⋯H [Br(2a) ⋯H(16B)_methyl2.96 Å] contacts (for details, results obtained by single-crystal X-ray diﬀraction (see sub-

see ESI†).

sequent discussion) and the behaviour in solution which

suggests the absence of ring–ring equilibria, it might be con-

cluded that the oligomerization degree observed in the solid

state, i.e. dimer species, is preserved in chloroform solution. A

Synthesis and characterization of organoantimony(^III)

chalcogenides

The synthesis of organoantimony(^III) chalcogenides was based similar situation was reported previously for the related cyclo-

on previously developed mixed-solvent procedures,^5i,ji.e. reac- [{2-(Me₂NCH₂)C₆H₄}SbS]₂.⁵ⁱSeveral isomers can be then con-

tion of 7 with KOH or the bromides 4, 6 or 7 with Na₂S·9H₂O, sidered for sulfides of the type cyclo-[{2-(RNvCH)C₆H₄}SbS]₂

in water–toluene mixtures (Scheme 1). The compounds were with the relative orientation of the Sb–C and Sb–N bonds, i.e.

isolated as colourless (oxide 8) or yellow to orange solids all-trans, trans-Sb–C/cis-Sb–N, cis-Sb–C/trans-Sb–N, and all-cis,

(sulfides 5, 9, 10). Treatment of the heterocyclic sulfide 10 with respectively, with respect to an Sb₂S₂ring (Scheme 3).

[W(CO)₅(thf)] in a 1 : 1 molar ratio gave the metal carbonyl Although the two sets of resonances could not be assigned to a

complex cyclo-[{2-(2′,6′-ⁱPr₂C₆H₃NvCH)C₆H₄}SbS]₂[W(CO)₅] (11) particular isomer, one can assume that the all-trans and all-cis

as an orange-brown solid. The IR bands in the range isomers (see subsequent discussion on compound 11) are

1618–1628 cm⁻¹are assigned to the ν_CvNstretching vibration, most likely to be present in the chloroform solution of the

which is consistent with the presence of the imine ligand in cyclo-[{2-(RNvCH)C₆H₄}SbS]₂derivatives.

the title chalcogenides. The IR spectrum of 11 shows the

The ¹H NMR spectrum of the metal carbonyl complex 11

typical pattern for complexes containing a W(CO)₅fragment. shows one set of broad singlets or poor resolved multiplets, con-

The molecular ion [M⁺] was observed in the EI MS of cyclo-[{2- sistent with equivalent organic ligands attached to the antimony

(2′,4′,6′-Me₃C₆H₂NvCH)C₆H₄}SbS]₂(9). The ESI+ mass spectra atoms and a dynamic process at room temperature. The number

of cyclo-[{2-(R²NvCH)C₆H₄}SbO]₃(8) and cyclo-[{2-(R²NvCH)- of ¹³C resonances assigned to aliphatic carbons and the broad

C₆H₄}SbS]₂(10) (R²= 2′,6′-ⁱPr₂C₆H₃) show the corresponding signal for the C-3′ aromatic carbons suggest that the free rotation

molecular [M⁺+ H] ions, while for [{2-(2′,6′-ⁱPr₂C₆H₃NvCH)- around the C–N(vC) single bond is restricted. The presence of

C₆H₄}₂Sb]₂S (5) the ion [M⁺− H] was observed. For the the W(CO)₅moiety is indicated by a singlet resonance sur-

complex 11 an [M⁺– CO] ion was assigned to the base peak.

rounded by ¹⁸³W satellites, assigned to the equatorial CO groups.

The ¹H and ¹³C NMR spectra, recorded in CDCl₃at room

Single crystals of 5, 9·CH₂Cl₂and 10 were obtained by slow

temperature, provide evidence for some particular behaviour diﬀusion of n-hexane into CH₂Cl₂solutions. Crystals of

in solution for these chalcogenides. The assignment of reson- 11·0.25CH₃OH were similarly grown using a n-hexane–CH₂Cl₂

ances was based on 2D NMR (HSQC, HMBC and COSY) corre- system (3 : 1) (methanol was used as the stabilizing agent for

lation spectra, according to the numbering schemes shown in methylene chloride). The solid state molecular structures of

1

Scheme 2. The H NMR spectrum of the sulfide 5 shows only these sulfides are depicted in Fig. 5–8. Selected interatomic

one set of broad resonances, including that for the imine distances and angles are listed in Tables 1 (for 5), 2 (for

protons (δ 8.34 ppm). This behaviour suggests a quite fast 9·CH₂Cl₂and 10) and 3 (11·0.25CH₃OH).

dynamic process on the NMR time scale to give four equivalent

In contrast to the bromide 4 used as a starting material to

organic groups attached to antimony atoms in this dinuclear prepare 5, the sulfide exhibits only one internal N → Sb inter-

species. A similar solution behaviour was previously described action per metal atom, placed trans to the Sb–S bond [N(1)–

for the related compound [{2-(Me₂NCH₂)C₆H₄}₂Sb]₂S.^5j

Sb(1)–S(1) 166.14(3)°] (Fig. 5). The pendant arm of the second

The H and ¹³C NMR spectra of the oxide 8 show two sets organic ligand attached to the antimony atom is twisted to

of resonances. While the ¹H resonances in the aliphatic region bring the nitrogen atom N(2) as far as possible from the metal.

are not well separated, those in the aromatic region indicate a The antimony–nitrogen distance is intermediate [N(1)–Sb(1)

2 : 1 integral ratio for equivalent protons, e.g. δ 8.35 (2 H) and 2.616(2) Å] between those observed in the molecule of 4

8.36 (1 H) ppm for imine protons. This suggests the presence (Table 1) and considerably shorter than the shortest N → Sb

of a trimer species in solution, with cis and trans organic sub- interaction [2.855(3) Å] in [{2-(Me₂NCH₂)C₆H₄}₂Sb]₂S.^5jThe

stituents with respect to an Sb₃O₃heterocycle. A trimer species result is a pseudo-trigonal bipyramidal coordination environ-

is consistent with the molecular [M⁺+ H] ion observed in the ment for antimony in 5 [(C,N)CSbS core; hypervalent 10-Sb-4

ESI+ mass spectrum of 8. It should be noted that a similar be- species].^1,21This behaviour is clearly due to the steric stress

haviour in solution was reported for the organic groups in produced by the Sb(1)–S(1)–Sb(1′) angle [88.57(3)°] which

cyclo-[{2-(Me₂NCH₂)C₆H₄}SbO]₃, for which the trimeric nature brings the bulky [{2-(2′,6′-ⁱPr₂C₆H₃NvCH)C₆H₄}₂Sb] moieties

1

was also established by single-crystal X-ray structure analysis.⁵ⁱ

in close proximity. It should be noted that the antimony–

For both heterocyclic sulfides 9 and 10 the NMR spectra (in sulfur bond distances are similar in the molecules of 5 [Sb(1)–

CDCl₃, at r.t.) contain two sets of resonance signals both in S(1) 2.4727(6) Å] and the related [{2-(Me₂NCH₂)C₆H₄}₂Sb]₂S

the alkyl and aryl region. The corresponding integral ratio [Sb(1)–S(1) 2.4621(10) Å], but the Sb(1)–S(1)–Sb(1′) angle in the

based on the resonances for the H-6 (for 9) and H-4 (for 10) latter species is much more opened [100.78(5)°]. For

protons (see Scheme 2) is 1.4 : 1 and 1.8 : 1, respectively. No [{2-(Me₂NCH₂)C₆H₄}₂Sb]₂S this allows a square pyramidal

significant changes were observed when the ¹H NMR spectrum (C,N)₂SbS core for both metal atoms to which, in addition, less

of 9 was recorded in CDCl₃at −60 °C. Taking into account the bulky organic ligands are attached.^5j

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Scheme 3 Potential geometric isomers for the heterocyclic sulﬁde 10 with respect to a planar Sb₂S₂ring.

Fig. 5 ORTEP representation at 30% probability and atom numbering scheme

Fig. 6 ORTEP representation at 40% probability and atom numbering scheme

for the (A_Sb,C_Sb’)-9 isomer [symmetry equivalent atoms (1 − x, −y, −z) are given

by “prime”].

for the (C_Sb,C_Sb’)-5 isomer [symmetry equivalent atoms (−x, y, 0.5 − z) are given

by “prime”].

For both heterocyclic sulfides the crystals contain only dis-

for the elongation of the corresponding antimony–sulfur

bonds. As expected for a N(sp²) donor atom, the Sb(1)–N(1)

bond distance [2.553(2) and 2.558(2) Å for 9 and 10, respect-

ively] is shorter than that observed for a N(sp³) donor atom in

cyclo-[{2-(Me₂NCH₂)C₆H₄}SbS]₂[Sb(1)–N(1) 2.634(4) Å].⁵ⁱ

While the reaction of cyclo-[(Me₃Si)₂CHSbS]_n(n = 2, 3) and

[W(CO)₅(thf)] gave the complex cyclo-[(Me₃Si)₂CHSbS]₂-

[W(CO)₅]₂with metal carbonyl units coordinated to the Sb

atoms,²⁴the complex 11 was found to contain a W(CO)₅frag-

ment coordinated to a sulfur atom as in the related cyclo-[{2-

(Me₂NCH₂)C₆H₄}SbS]₂[W(CO)₅].⁵ⁱHowever there is an impor-

tant diﬀerence in the molecular structures of these 1 : 1

adducts. In cyclo-[{2-(Me₂NCH₂)C₆H₄}SbS]₂[W(CO)₅] the metal

crete dinuclear units of the all-trans (A_Sb,C_Sb′)-9 (Fig. 6) and

(C_Sb,A_Sb′)-10 (Fig. 7) isomers with

a crystallographically

imposed inversion symmetry. The overall molecular structures

are very similar to that described for the related cyclo-[{2-

(Me₂NCH₂)C₆H₄}SbS]₂.⁵ⁱThe molecules contain a central,

planar four-membered Sb₂S₂ring, with endocyclic angles at

antimony and sulfur atoms close to 90° (Table 2). In the mole-

cular unit the (N,C)-ligands are placed on opposite sides of the

Sb₂S₂ring. The asymmetry of the ring is reflected in alternat-

ing short [Sb(1)–S(1′) 2.4016(9) and 2.4167(10) Å for 9 and 10,

respectively] and long [Sb(1)–S(1) 2.5326(9) and 2.5269(9) Å for

9 and 10, respectively] antimony–sulfur bonds. The coordi-

nation of a nitrogen atom trans to each sulfur atom accounts

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Table 3 Selected bond distances (Å) and angles (°) for 11·0.25CH₃OH

Sb(1)–C(1)

Sb(1)–S(1)

Sb(1)–S(2)

Sb(1)–N(1)

2.155(3)

2.5523(9)

2.4436(9)

2.529(3)

Sb(2)–C(20)

Sb(2)–S(1)

Sb(2)–S(2)

Sb(2)–N(1)

2.173(3)

2.5594(9)

2.4514(9)

2.470(3)

N(1)–C(7)

N(1)–C(8)

1.280(5)

1.443(4)

N(2)–C(26)

N(2)–C(27)

1.273(5)

1.437(5)

W(1)–S(1)

2.6005(9)

2.036(4)

2.056(4)

2.039(4)

2.051(4)

1.955(4)

W(1)–C(39)

W(1)–C(40)

W(1)–C(41)

W(1)–C(42)

W(1)–C(43)

C(39)–O(1)

C(40)–O(2)

C(41)–O(3)

C(42)–O(4)

C(43)–O(5)

1.148(5)

1.136(5)

1.148(5)

1.141(5)

1.159(5)

C(1)–Sb(1)–S(1)

C(1)–Sb(1)–S(2)

S(1)–Sb(1)–S(2)

N(1)–Sb(1)–C(1)

N(1)–Sb(1)–S(1)

N(1)–Sb(1)–S(2)

94.11(10)

96.00(10)

88.78(3)

73.58(12)

166.13(7)

86.23(6)

C(20)–Sb(2)–S(1)

C(20)–Sb(2)–S(2)

S(1)–Sb(2)–S(2)

N(2)–Sb(2)–C(20)

N(2)–Sb(2)–S(1)

N(2)–Sb(2)–S(2)

92.85(9)

102.25(8)

88.45(3)

73.47(11)

160.64(7)

81.39(7)

Fig. 7 ORTEP representation at 40% probability and atom numbering scheme

for the (C_Sb,A_Sb’)-10 isomer [symmetry equivalent atoms (−x, −y, 2 − z) are given

by “prime”].

Sb(1)–S(1)–Sb(2)

88.64(3)

Sb(1)–S(2)–Sb(2)

93.70(3)

C(7)–N(1)–C(8)

Sb(1)–N(1)–C(7)

Sb(1)–N(1)–C(8)

119.5(3)

107.1(2)

126.3(2)

C(26)–N(2)–C(27)

Sb(2)–N(2)–C(26)

Sb(2)–N(2)–C(27)

120.8(3)

110.1(2)

127.9(2)

Sb(1)–S(1)–W(1)

101.99(3)

Sb(2)–S(1)–W(1)

102.76(3)

S(1)–W(1)–C(39)

S(1)–W(1)–C(40)

S(1)–W(1)–C(41)

92.82(12)

92.84(11)

91.14(11)

S(1)–W(1)–C(42)

S(1)–W(1)–C(43)

91.01(12)

177.63(12)

C(39)–W(1)–C(40)

C(39)–W(1)–C(41)

C(39)–W(1)–C(42)

C(39)–W(1)–C(43)

C(40)–W(1)–C(41)

90.68(14)

175.68(16)

92.22(16)

85.28(16)

90.86(12)

C(40)–W(1)–C(42)

C(40)–W(1)–C(43)

C(41)–W(1)–C(42)

C(41)–W(1)–C(43)

C(42)–W(1)–C(43)

175.06(16)

85.78(14)

85.96(14)

90.81(16)

90.48(15)

and the endocyclic angles at sulfur atoms are significantly

diﬀerent (Table 3).

The all-cis orientation of the Sb–C and Sb–N bonds with

respect to the Sb₂S₂ring is most likely a consequence of the

steric strain due to the bulky substituents on nitrogen. This

also explains the presence of exclusively all-trans and all-cis

isomers in the chloroform solution of 10 (see the above discus-

sion of the NMR spectra).

Fig. 8 ORTEP representation at 40% probability and atom numbering scheme

for the (C_Sb1,A_Sb2)-11 isomer.

carbonyl unit is coordinated to the cis-Sb–C/trans-Sb–N isomer

Intramolecular S⋯H contacts, which involve the hydrogen

of the heterocyclic sulfide.⁵ⁱIn contrast, in the molecule of the atom in the ortho position of the aryl ring bound to antimony,

complex 11 a W(CO)₅fragment is coordinated to the all-cis are established in the molecules of all sulfides described here.

isomer of the sulfide 10 (Fig. 8), occupying a trans position The heterocyclic species 9 and 10 show further intramolecular

relative to the organic ligands with respect to the Sb₂S₂ring. S⋯H_alkylcontacts [S(1)⋯H(14C′)_methyl2.87

Å for 9; S(1)

Both nitrogen atoms are coordinated to antimony atoms trans ⋯H(17′)_methine2.95 Å for 10]. For the molecule of the sulfide 5

to S(1) which is subsequently coordinated to tungsten. One of additional intramolecular C–H⋯π (Ph_centroid) contacts are

the major results is the diﬀerent sequence of Sb–S bonds present [C(5)–H(5)_aryl⋯Ph_centroid{C(27′)–C(32′)} 2.71 Å, γ = 6.4°;

within the Sb₂S₂ring, i.e. alternating short and long bonds in C(17)–H(17)_methine⋯Ph_centroid{C(20′)–C(25′)} 2.85 Å, γ = 16.0°].

cyclo-[{2-(Me₂NCH₂)C₆H₄}SbS]₂[W(CO)₅], while in 11 the S(1)

Although no intermolecular interactions between heavy

atom is involved in longer bonds [Sb(1)–S(1) 2.5523(9) Å; Sb(2)– atoms were found in the crystals of 5, 9·CH₂Cl₂, 10 and

S(1) 2.5594(9) Å] than the S(2) atom [Sb(1)–S(2) 2.4436(9) Å; 11·0.25CH₃OH, a closer inspection revealed supramolecular

Sb(2)–S(2) 2.4514(9) Å]. It should also be noted that the central architectures based on sulfur–hydrogen or C–H⋯π (Ph_centroid

contacts.²³Thus, in the crystal of 5 layers of (C_Sb,C_Sb)- and (A_Sb,

Sb(1)S(2)/S(1)Sb(2)S(2) 6.9, Sb(1)S(1)Sb(2)/Sb(1)S(2)Sb(2) 7.1°] A_Sb)-5 isomers, respectively, are formed through intermolecular C–

)

four-membered Sb₂S₂ring is slightly folded [fold angles: S(1)

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H⋯π (Ph_centroid) interactions [C(11)–H(11)_aryl⋯Ph_centroid{C(27′c)– The calculated relative energy diﬀerences between geometrical

C(32′c)} 2.92 Å, γ = 15.7°], but no further contacts between alter- isomers of the dimer association of 7 and between the isomers

nating parallel layers are established (for details, see ESI†).

of 10, respectively, are very small. The isomers found to have

For the heterocyclic species 9·CH₂Cl₂and 10 diﬀerent the lowest energy by theoretical calculations are diﬀerent from

supramolecular arrangements are established in the crystal. those found in the crystals. This is most likely a result of

Polymer chains of (A_Sb,C_Sb′)-9 isomers are formed based on packing forces in the solid state. The energies of the trans-Sb–

weak sulfur–hydrogen contacts [S(1)⋯H(14Ba)_methyl3.00 Å] C/cis-Sb–N, all-trans, and all-cis isomers of 7 are larger than

with no further contacts between parallel chains. Similarly a the energy of the cis-Sb–C/trans-Sb–N isomer with 1.1, 4, and

chain polymer of (C_Sb,A_Sb′)-10 is formed based on C–H⋯π 8.5 kJ mol⁻¹, respectively. For 10 the theoretical data show the

(Ph_centroid

)

contacts [C(4)–H(4)_aryl⋯Ph_centroid{C(8b)–C(13b)} trans-Sb–C/cis-Sb–N isomer as being the most stable one. The

2.73 Å, γ = 11.2°]. Further contacts of the same type connect energies of the all-trans, cis-Sb–C/trans-Sb–N, and all-cis

parallel chains into layers [C(19)–H(19C)_methyl⋯Ph_centroid

-

isomers of 10 are with 1.8, 4.9, and 6.8 kJ mol⁻¹larger.

{C(8′d)–C(13′d)} 2.81 Å, γ = 3.2°] and parallel layers into a 3D

architecture, respectively [C(15)–H(15A)_methyl⋯Ph_centroid{C(1′e)–

C(6′e)} 2.77 Å, γ = 11.8°] (for details, see ESI†).

Conclusions

Dimer associations are formed in the crystal of

11·0.25CH₃OH through weak sulfur–hydrogen [S(2)⋯H(4′)_arylThe rigidity induced by the presence of the CvN bond in the

3.02 Å] and quite strong C–H⋯π (Ph_centroid) contacts [C(3)–H(3)_arylpendant arm and the sterically demanding group attached to

⋯

Ph_centroid{C(20′)–C(25′)} 2.82 Å, γ = 6.1°]. Further weak O⋯H nitrogen in (imino)aryl ligands of the type 2-(RNvCH)C₆H₄

[O(1)⋯H(12′a)_aryl2.56 Å, O(5)⋯H(26b)_imine2.49 Å] contacts (R = 2′,4′,6′-Me₃C₆H₂, 2′,6′-ⁱPr₂C₆H₃) were expected to influence

and strong C–H⋯π (Ph_centroid) [C(18)–H(18B)_methyl⋯Ph_centroid

-

significantly the solution behaviour and hence the structure

{C(8′a)–C(13′a)} 2.59 Å, γ = 5.3°] connect the dimers into a of the corresponding organoantimony compounds. The chem-

polymer (for details, see ESI†).

istry of the title organoantimony species containing

[2-(RNvCH)C₆H₄]_nSb (n = 1, 2) fragments seems to parallel

generally the results obtained with the wider investigated,

Theoretical calculations

Theoretical calculations using DFT methods (see the Experi- more flexible 2-(Me₂NCH₂)C₆H₄group. However, some impor-

mental section for further details) were carried out in order to tant diﬀerences related to the bulkiness of the organic group

investigate the geometrical isomers of the dimer associations attached to nitrogen were observed: (i) room temperature NMR

of 7 and the geometrical isomers of 10. Comparison of spectra in CDCl₃evidence equivalence of the organic groups at

selected calculated and determined bond lengths and angles antimony for [2-(2′,4′,6′-Me₃C₆H₂NvCH)C₆H₄]₂SbBr (3), while

are provided in ESI, Tables S1 and S2.† A visual comparison of for [2-(2′,6′-ⁱPr₂C₆H₃NvCH)C₆H₄]₂SbBr (4) the NMR data indi-

the calculated and determined structures is shown in ESI, cate not only the non-equivalence of the organic ligands (as

Fig. S26 and S27.†

was also observed in the solid state), but also the restriction of

The calculated geometries reproduced to a great extent the the free rotation of one of the bulky 2,6-ⁱPr₂C₆H₃groups

structures determined by single crystal X-ray diﬀraction analy- around the C–N(vC) single bond; (ii) the steric stress prevents

sis. In the case of the all-trans dimer association of 7 a diﬀer- the intramolecular coordination of both N(sp²) to an antimony

ence larger than 10% was found for the Br(1′)–Sb(1) bond atom in the dinuclear sulfide [{2-(2′,6′-ⁱPr₂C₆H₃NvCH)C₆H₄}₂-

lengths. This suggests that the intermolecular bonds strength Sb]₂S (5); (iii) in the complex cyclo-[{2-(2′,6′-ⁱPr₂C₆H₃NvCH)-

at this level of theory was overestimated. The length of the C₆H₄}SbS]₂[W(CO)₅] (11) the W(CO)₅fragment is coordinated

Sb–N bond was also overestimated by 5.9%, and consequently to the sulfur atom of the all-cis isomer of the sulfide 10, while

the Br–Sb bond trans to N was elongated by the same amount. in the related cyclo-[{2-(Me₂NCH₂)C₆H₄}SbS]₂[W(CO)₅] the

The bonding angles around antimony were slightly better same metal carbonyl unit is coordinated to the cis-Sb–C/trans-

described than the bond lengths. The largest diﬀerence, of Sb–N isomer of the heterocyclic sulfide. Theoretical calcu-

5.9%, was found for the C(1)–Sb(1)–Br(2) bond angle.

lations reveal that in the gas phase the energy diﬀerence

The calculated and determined bond lengths for the all- between the geometrical isomers of the dimer associations of

trans isomer of the sulfide 10 are in better agreement than in 7 and those between the geometrical isomers of 10 are small

the dimer association of the dibromide 7. For the all-trans-10 (<9 kJ mol⁻¹). Most likely, several isomers are present in solu-

isomer the largest diﬀerences, of 3.8 and 3.9%, were found for tion and the packing forces play an important role in the crys-

two of the Sb–S bond lengths. The calculated C–Sb–S angles tallization process.

were 3.9% larger than those determined.

Theoretical calculations reveal that the coordination of the

nitrogen atom to the antimony brings a stabilization of 45.2 kJ

Experimental section

General procedures

mol⁻¹in 7 and of 76.7 kJ mol⁻¹in the monomer of 10. The

dimerization energy of 7, considering the formation of the all-

trans isomer, was found to be 80.1 kJ mol⁻¹. Dissociation of the Multinuclear NMR spectra (¹H, ¹³C) were recorded at room

all-trans isomer of 10 into monomers amounts to 152.4 kJ mol⁻¹

.

temperature on a Bruker Avance 300 (1, 2, 4, 5, 9, 10, 11) and a

1152 | Dalton Trans., 2013, 42, 1144–1158

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Dalton Transactions

Paper

1

3

Bruker Avance III 500 (3, 6, 7, 8) instrument. The H chemical δ 1.21 (12 H, d, H-8′, CH₃, J_HH6.9 Hz), 2.98 (2 H, hept, H-7′,

3

shifts are reported in δ units (ppm) relative to the residual CH, J_HH6.8 Hz), 7.16 (3 H, m, H-3′,4′, C₆H₃), 7.37 (1 H, ddd,

peak of the deuterated solvent (ref. CDCl₃: ¹H 7.26 ppm; H-5, C₆H₄, J_HH= 7.7, J_HH= 1.4 Hz), 7.46 (1 H, dd, H-4, C₆H₄,

3

4

DMSO-d₅: H 2.50 ppm). The ¹³C chemical shifts are reported ³J_HH= 7.5 Hz), 7.65 (1 H, d, H-6, C₆H₄, J_HH= 7.7 Hz), 8.27 (1

1

3

4

in δ units (ppm) relative to the peak of the solvent (ref. CDCl₃: H, dd, H-3, C₆H₄, J_HH= 7.7, J_HH= 1.3 Hz), 8.59 (1 H, s, H-7,

¹³C 77.0 ppm; DMSO-d₆: ¹³C 39.43 ppm). ¹H and ¹³C reso- CHvN). ¹³C NMR (75.5 MHz, CDCl₃): δ 23.55 (s, C-8′, CH₃),

nances were assigned using 2D NMR experiments (COSY, 27.94 (s, C-7′, CH), 123.07 (s, C-3′), 124.39 (s, C-4′), 125.73 (s,

HMQC and HMBC). The NMR spectra were processed using C-1), 127.79 (s, C-4), 128.82 (s, C-3), 132.43 (s, C-5), 133.21 (s,

the MestReC and MestReNova software.²⁵Mass spectra were C-6), 134.57 (s, C-2), 137.59 (s, C-2′), 148.90 (s, C-1′), 161.48 (s, C-7,

recorded with a Finnigan MAT 8200 (EI) and an Applied Bio- CHvN). MS (EI, 70 eV, 200 °C), m/z (%): 343 (100) [M⁺], 328 (85)

systems (Type Mariner) (ESI/APCI-TOF) instrument. Infrared [M⁺− CH₃], 188 (30) [M⁺− C₆H₅Br]. IR: ν(CHvN) 1624 (vs) cm⁻¹

.

spectra were recorded on a BioRad FTS-165 spectrometer,

using ATR-IR. Melting points were measured with an Electro-

Synthesis of [2-(2′,4′,6′-Me₃C₆H₂NvCH)C₆H₄]₂SbBr (3)

thermal 9200 apparatus and are not corrected. Elemental ana- A solution of 1 (2.00 g, 6.62 mmol) in THF (70 mL) was added

lyses were carried out with a Perkin-Elmer 2400 and a dropwise, under stirring, to magnesium filings (0.17 g,

CHN-Analysator Type FlashAE 1112 (Co. Thermo) instrument. 7.08 mmol, 7% excess) activated with 1,2-dibromoethane

All manipulations were carried out under an inert atmosphere (0.5 mL). The addition was completed after 0.5 h and the

of argon using Schlenk techniques. Solvents were dried and brown reaction mixture was stirred for a further 1.5 h under

freshly distilled under argon prior to use. Starting materials reflux. Then it was cooled to room temperature and the

such as 2-(BrCH₂)C₆H₄Br, 2′,4′,6′-Me₃C₆H₂NH₂, 2′,6′-ⁱPr₂C₆- unreacted Mg was separated. The Grignard solution was added

H₃NH₂, SbCl₃, KBr, KOH, Na₂S·9H₂O or W(CO)₆were obtained dropwise to a solution of SbCl₃(0.75 g, 3.30 mmol) in THF

from Aldrich or Merck, and were used as received.

(20 mL) at −78 °C and the reaction mixture was stirred at this

temperature for 1 h, then for 12 h at room temperature. The

solvent was removed under vacuum and the oily residue was

Synthesis of 2-(2′,4′,6′-Me₃C₆H₂NvCH)C₆H₄Br (1)

2-Bromobenzaldehyde (35.00 g, d = 1.585 g cm⁻³, 22.1 mL, washed with diethyl ether and hexane, resulting in a yellow

0.19 mol) and 2,4,6-trimethylaniline (25.50 g, d = 0. 963 g solid which was filtered oﬀ and dried under vacuum (0.80 g,

cm⁻³, 26.5 mL, 0.19 mol) were dissolved in toluene (100 mL) 38%), mp 249–251 °C. Anal. calcd for C₃₂H₃₂BrN₂Sb (646.27):

in a round bottom flask. The reaction mixture was heated at C, 59.47; H, 4.99; N, 4.33; Found: C, 59.13; H, 5.10; N, 4.17%.

reflux for 8 h using a Dean–Stark apparatus to remove the ¹H NMR (500 MHz, CDCl₃): δ 1.65 (12 H, s, H-7′, CH₃), 2.20 (6

water. Then the reaction mixture was cooled to room tempera- H, s, H-8′, CH₃), 6.70 (4 H, s, H-3′, C₆H₃), 7.20 (2 H, ddd, H-4,

ture and the solvent was removed using a rotary evaporator to C₆H₄, ³J_HH= 7.4, ⁴J_HH= 0.9 Hz), 7.35 (2 H, d, H-3, C₆H₄, ³J_HH

=

3

4

give a brown oil which solidified at 0 °C. This solid was recrys- 7.3 Hz), 7.40 (2 H, ddd, H-5, C₆H₄, J_HH= 7.5, J_HH= 0.8 Hz),

3

tallized from hexane to give the title compound as a yellow 7.68 (2 H, d, H-6, C₆H₄, J_HH= 7.4 Hz), 8.29 (2 H, s, H-7,

material (49.0 g, 85%), mp 51–52 °C. Anal. calcd for CHvN). ¹³C NMR (125.8 MHz, CDCl₃): δ 17.75 (s, C-7′, CH₃),

C₁₆H₁₆BrN (302.21): C, 63.59; H, 5.34; N, 4.63; Found: C, 63.26; 20.63 (s, C-8′, CH₃), 127.40 (s, C-2′), 127.65 (s, C-5), 128.24 (s,

1

H, 5.16; N, 4.26%. H NMR (300 MHz, CDCl₃): δ 2.16 (6 H, s, C-3′), 130.70 (s, C-4), 131.53 (s, C-6), 132.49 (s, C-4′), 138.25 (s,

H-7′, CH₃), 2.30 (3 H, s, H-8′, CH₃), 6.92 (2 H, s, H-3′, C₆H₃), C-3), 140.79 (s, C-1), 147.78 (s, C-1′), 148.45 (s, C-2), 164.34 (s,

7.34 (1 H, ddd, H-5, C₆H₄, ³J_HH= 7.4, ⁴J_HH= 1.9 Hz), 7.44 (1 H, C-7, CHvN). MS (ESI+), m/z (%): 565 (100) [R₂Sb⁺] [R =

3

dd, H-4, C₆H₄, J_HH= 7.3 Hz), 7.63 (1 H, dd, H-6, C₆H₄, J_HH

=

2-(2′,4′,6′-Me₃C₆H₂NvCH)C₆H₄]. IR: ν(CHvN) 1624 (vs) cm⁻¹

.

4

3

4

8.0, J_HH= 1.2 Hz), 8.27 (1 H, dd, H-3, C₆H₄, J_HH= 7.7, J_HH

Synthesis of [2-(2′,6′-ⁱPr₂C₆H₃NvCH)C₆H₄]₂SbBr (4)

1.8 Hz), 8.62 (1 H, s, H-7, CHvN). ¹³C NMR (75.5 MHz,

CDCl₃): δ 18.30 (s, C-7′, CH₃), 20.73 (s, C-8′, CH₃), 125.67 (s, A solution of 2 (2.00 g, 5.81 mmol) in THF (70 mL) was added

C-2), 127.01 (s, C-2′), 127.71 (s, C-4), 128.63 (s, C-3), 128.78 (s, dropwise during 0.5 h, under stirring, to magnesium filings

C-3′), 132.32 (s, C-5), 133.12 (s, C-6), 133.33 (s, C-4′), 134.68 (s, (0.15 g, 6.25 mmol, 7.5% excess), activated with 1,2-dibro-

C-1), 148.42 (s, C-1′), 162.16 (s, C-7, CHvN). MS (EI, 70 eV, moethane (0.5 mL). The brown reaction mixture was stirred for

200 °C), m/z (%): 301 (70) [M⁺], 222 (20) [M⁺− Br], 146 (100) an additional 1.5 h under reflux, then cooled to room tempera-

[M⁺− C₆H₅Br]. IR: ν(CHvN) 1628 (vs) cm⁻¹

Synthesis of 2-(2′,6′-ⁱPr₂C₆H₃NvCH)C₆H₄Br (2)

.

ture and the unreacted Mg was separated. The Grignard solu-

tion was added dropwise to a solution of SbCl₃(0.64 g,

2.89 mmol) in THF (20 mL), at −78 °C, and the reaction

Compound 2 was prepared as described above for 1 from mixture was stirred at this temperature for 1 h, then for 12 h at

2-bromobenzaldehyde (27.00 g, d = 1.585 g cm⁻³, 17.0 mL, room temperature. The solvent was removed under vacuum

0.15 mol) and 2,6-diisopropylaniline (25.83 g, d = 0.94 g cm⁻³

,

and the oily residue was washed with hexane and ethanol until

27.5 mL, 0.15 mol), in toluene (100 mL). After removal of the a yellow precipitate deposited. The solid was filtered oﬀ, dried

solvent using a rotary evaporator the remaining brown oil soli- under vacuum, then dissolved in CH₂Cl₂(40 mL) and the solu-

dified at 0 °C. Recrystallization from hexane gave 2 as a yellow tion was treated with an aqueous solution of KBr (0.59 g,

material (39 g, 76%), mp 74–76 °C. ¹H NMR (300 MHz, CDCl₃): 4.96 mmol) at room temperature. The reaction mixture was

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Dalton Transactions

stirred for 12 h. The organic layer was separated, the aqueous 7.28 mmol, 10% excess), activated with 1,2-dibromoethane

layer was washed with CH₂Cl₂(3 × 10 mL) and the unified (0.5 mL). The addition was completed after 0.5 h and the

organic phases were dried over MgSO₄. Evaporation of the brown reaction mixture was stirred for a further 2 h under

solution under vacuum yielded 4 as a yellow solid (0.90 g, reflux. Then it was cooled to room temperature and the

43%), mp 225–226 °C. Anal. calcd for C₃₈H₄₄BrN₂Sb (730.43): unreacted Mg was separated. The Grignard solution was added

C, 62.49; H, 6.07; N, 3.84; Found: C, 62.30; H, 6.07; N, 3.76%. dropwise to a solution of SbCl₃(1.51 g, 6.62 mmol) in THF

¹H NMR (300 MHz, CDCl₃): δ 0.46 [3 H, d, H-8′_a1, CH₃(A), ³J_HH(20 mL), at −78 °C, and the reaction mixture was stirred at this

6.5 Hz], 0.78 [3 H, d, H-8′_a2, CH₃(A), ³J_HH6.5 Hz], 0.95 [6 H, d, temperature for 1 h, then for 12 h at room temperature. The

3

H-8′₁, CH₃(B), J_HH6.5 Hz], 1.06 [12 H, m, H-8′_b1(A) + H-8′_b2solvent was removed under vacuum and the oily residue was

3

(A) + H-8′₂(B), CH₃], 1.81 [1 H, hept, H-7′_a, CH (A), J_HHwashed with hexane and ethanol, when a yellow solid depo-

6.5 Hz], 2.85 [3 H, m, H-7′_b(A) + H-7′ (B), CH], 7.02–7.30 [8 H, sited. The solid was filtered oﬀ, dried under vacuum, then dis-

m, H-5,6, C₆H₄(B) + H-3′_a,3′_b,4′ (A) + H-3′,4′ (B), C₆H₃], 7.45 solved in CH₂Cl₂(40 mL) and the solution was treated with an

3

[1 H, dd, H-4, C₆H₄(B), J_HH= 6.2 Hz], 7.59 [1 H, d, H-3, C₆H₄aqueous solution of KBr (1.89 g, 15.88 mmol) at room temp-

3

(B), ³J_HH= 7.2 Hz], 7.71 [1 H, dd, H-4, C₆H₄(A), J_HH= 7.1 Hz], erature. The reaction mixture was stirred for 12 h. The organic

3

7.80 [1 H, dd, H-5, C₆H₄(A), J_HH= 7.1 Hz], 7.87 [1 H, d, H-3, layer was separated, the aqueous layer was washed with

3

C₆H₄(A), J_HH= 7.0 Hz], 8.36 [1 H, s, H-7, CHvN (B)], 8.43 CH₂Cl₂(3 × 10 mL) and the unified organic phase was dried

3

[1 H, s, H-7, CHvN (A)], 8.99 [1 H, d, H-6, C₆H₄(A), J_HH

=

over MgSO₄. Evaporation of the solution under vacuum yielded

7.0 Hz]. ¹³C NMR (75.5 MHz, CDCl₃): δ 22.09 [s, C-8′_a1, CH₃6 as a yellow solid (1.22 g, 37%), mp 229–230 °C. Anal. calcd

(A)], 23.97 [s, H-8′_b1(A) + H-8′₁(B), CH₃], 24.59 [s, H-8′₂, CH₃for C₁₆H₁₆Br₂NSb (503.87): C, 38.14; H, 3.20; N, 2.78; Found:

1

(B)], 24.80 [s, C-8′_b2, CH₃(A)], 25.08 [s, C-8′_a2, CH₃(A)], 27.77 C, 38.54; H, 3.65; N, 2.49%. H NMR (500 MHz, CDCl₃): δ 2.24

[s, C-7′, CH (B)], 28.00 [s, C-7′_a, CH (A)], 28.48 [s, C-7′_b, CH (A)], (6 H, s, H-7′, CH₃), 2.32 (3 H, s, H-8′, CH₃), 6.96 (2 H, s, H-3′,

3

4

122.89 [s, C-3′ (B)], 123.23 [s, C-3′_a(A)], 123.86 [s, C-3′_b(A)], C₆H₃), 7.68 (1 H, ddd, H-4, C₆H₄, J_HH= 7.5, J_HH= 1.2 Hz),

124.25 [s, C-4′ (B)], 126.89 [s, C-4′ (A)], 129.22 [s, C-4 (A)], 7.80 (1 H, ddd, H-5, C₆H₄, ³J_HH= 7.6, ⁴J_HH= 1.3 Hz), 7.81 (1 H,

3

4

129.51 [s, C-4 (B)], 131.82 [s, C-5 (B)], 132.82 [s, C-3 (A)], 133.19 dd, H-3, C₆H₄, J_HH= 7.5, J_HH= 1.3 Hz), 8.54 (1 H, s, H-7,

3

[s, C-3 (B)], 133.43 [s, C-5 (A)], 135.55 [s, C-6 (B)], 138.53 [s, C-2′ CHvN), 8.84 (1 H, d, H-6, C₆H₄, J_HH= 7.8 Hz). ¹³C NMR

(B)], 139.86 [s, C-2,6 + C-2′_b(A)], 140.42 [s, C-2′_a(A)], 143.64 [s, (125.8 MHz, CDCl₃): δ 18.96 (s, C-7′, CH₃), 20.81 (s, C-8′, CH₃),

C-1′ (A)], 145.59 [s, C-1 (B)], 148.26 [s, C-2, C-1′ (B)], 153.28 [s, 129.33 (s, C-1), 129.56 (s, C-3′, C-2′), 131.14 (s, C-4), 132.69 (s,

C-1 (A)], 164.87 [s, C-7, CHvN (B)], 169.66 [s, C-7, CHvN (A)]. C-3), 134.10 (s, C-5), 136.51 (s, C-6), 136.84 (s, C-4′), 138.69 (s,

+

MS (ESI+), m/z (%): 809 (40) [R₂SbBr₂], 649 (100) [R₂Sb⁺] [R = C-2), 142.14 (s, C-1′), 169.90 (s, C-7, CHvN). MS (ESI+), m/z (%):

2-(2′,6′-ⁱPr₂C₆H₃NvCH)C₆H₄]. IR: ν(CHvN) 1634 (m) cm⁻¹

.

424 (100) [RSbBr⁺] [R = 2-(2′,4′,6′-Me₃C₆H₂NvCH)C₆H₄]. IR:

ν(CHvN) 1617 (s) cm⁻¹

Synthesis of [2-(2′,6′-ⁱPr₂C₆H₃NvCH)C₆H₄]SbBr₂(7)

.

Synthesis of [{2-(2′,6′-ⁱPr₂C₆H₃NvCH)C₆H₄}₂Sb]₂S (5)

A solution of Na₂S·9H₂O (0.04 g, 0.16 mmol, 70% excess) in

water (10 mL) was added to a solution of 4 (0.15 g, 0.21 mmol) A solution of 2 (3.00 g, 8.71 mmol) in THF (70 mL) was added

in toluene (30 mL). The reaction mixture was stirred for 2 days dropwise, under stirring, to magnesium filings (0.25 g,

at room temperature, then the yellow organic phase was separ- 10.04 mmol, 15% excess), activated with 1,2-dibromoethane

ated and the water solution was washed with CH₂Cl₂(2 × (0.5 mL). The addition was completed after 0.5 h, the brown

30 mL). The unified organic phases were dried over anhydrous reaction mixture was stirred for an additional 2 h under reflux,

Na₂SO₄. Removal of the solvent under vacuum gave 5 as a then cooled to room temperature and the unreacted Mg was

yellow solid (0.12 g, 86%), mp 247–249 °C. Anal. calcd for separated. The Grignard solution was added dropwise to a solu-

C₇₆H₈₈N₄SSb₂(1333.12): C, 68.47; H, 6.65; N, 4.20; Found: C, tion of SbCl₃(1.99 g, 8.72 mmol) in THF (20 mL), at −78 °C,

68.92; H, 6.62; N, 4.20%. ¹H NMR (300 MHz, CDCl₃): δ 0.83 (48 and the reaction mixture was stirred at this temperature for

H, s,br, H-8′, CH₃), 2.59 (8 H, s,br, H-7′, CH), 6.73 (4 H, s,br, 1 h, then for 12 h at room temperature. The solvent was

H-4, C₆H₄), 7.06 (12 H, m, H-3′,4′, C₆H₃), 7.24 (8 H, m, H-3,5, removed under vacuum and the oily residue was washed with

3

C₆H₄), 7.62 (4 H, d, H-6, C₆H₄, J_HH= 7.2 Hz), 8.34 (4 H, s,br, hexane, when a yellow precipitate deposited. The solid was fil-

H-7, CHvN). ¹³C NMR (75.5 MHz, CDCl₃): δ 23.72, 24.10 (s, tered oﬀ, dried under vacuum, then dissolved in CH₂Cl₂

C-8′, CH₃), 27.75 (s, C-7′, CH), 122.93 (s, C-3′), 124.45 (s, C-4′), (40 mL) and the solution was treated with an aqueous solution

128.16 (s, C-3,5), 131.22 (s, C-6), 131.49 (s, C-4), 137.33 (s, C-2), of KBr (1.30 g, 10.92 mmol) at room temperature. The reaction

138.65 (s, C-2′), 139.14 (s, C-1), 146.76 (s, C-1′), 164.96 (s, C-7, mixture was stirred for 12 h. The organic layer was separated,

CHvN). MS (ESI+), m/z (%): 1329 (4) [M⁺− H], 649 (100) the aqueous layer was washed with CH₂Cl₂(3 × 10 mL) and the

[R₂Sb⁺] [R = 2-(2′,6′-ⁱPr₂C₆H₃NvCH)C₆H₄]. IR: ν(CHvN) 1626 unified organic phases were dried over MgSO₄. Evaporation of

(m) cm⁻¹

.

the solution under vacuum aﬀorded 7 as a yellow solid (2.50 g,

53%), mp 234–237 °C. Anal. calcd for C₁₉H₄₂₂Br₂NSb (545.95):

Synthesis of [2-(2′,4′,6′-Me₃C₆H₂NvCH)C₆H₄]SbBr₂(6)

A solution of 1 (2.00 g, 6.62 mmol) in THF (90 mL) was added ¹H NMR (500 MHz, CDCl₃): δ 1.16 (6 H, d, H-8′₁, CH₃, J_HH6.8

C, 41.80; H, 4.06; N, 2.57; Found: C, 41.81; H, 3.95; N, 2.50%.

3

dropwise, under stirring, to magnesium filings (0.175 g, Hz), 1.28 (6 H, d, H-8′₂, CH₃, J_HH6.7 Hz), 2.98 (2 H, hept,

1154 | Dalton Trans., 2013, 42, 1144–1158

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Dalton Transactions

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3

H-7′, CH, J_HH6.8 Hz), 7.28 (3 H, m, H-3′,4′, C₆H₃), 7.70 (1 H, H-3′, C₆H₃, 9a + 9b), 7.31 (2 H, dd, H-5, C₆H₄, J_HH= 7.2 Hz,

dd, H-4, C₆H₄, J_HH= 7.5 Hz), 7.81 (2 H, m, H-3,5, C₆H₄), 8.48 9b), 7.41 (2 H, dd, H-4, C₆H₄, ³J_HH= 7.3 Hz, 9b), 7.58 (2 H, dd,

(1 H, s, H-7, CHvN), 8.90 (1 H, d, H-6, C₆H₄, J_HH= 6.7 Hz). H-4, C₆H₄, J_HH= 7.4 Hz, 9a), 7.63 (2 H, d, H-3, C₆H₄, J_HH

3

=

¹³C NMR (125.8 MHz, CDCl₃): δ 23.93 (s, C-8′₂, CH₃), 25.63 (s, 7.4 Hz, 9b), 7.73 (4 H, m, H-3,5, C₆H₄, 9a), 8.346 (2 H, s, H-7,

C-8′₁, CH₃), 28.84 (s, C-7′, CH), 124.19 (s, C-3′), 127.41 (s, C-4′), CHvN, 9b), 8.353 (2 H, s, H-7, CHvN, 9a), 8.54 (2 H, d, H-6,

131.16 (s, C-4), 132.92 (s, C-3), 134.20 (s, C-5), 137.93 (s, C-6), C₆H₄, ³J_HH= 7.2 Hz, 9b), 9.12 (2 H, d, H-6, C₆H₄, ³J_HH= 7.5 Hz,

138.45 (s, C-2), 140.58 (s, C-2′), 141.42 (s, C-1′), 149.38 (s, C-1), 9a); integral ratio 1.4 : 1 for isomers 9a : 9b. ¹³C NMR

169.15 (s, C-7, CHvN). MS (ESI+), m/z (%): 466 (100) [RSbBr⁺] (75.5 MHz, CDCl₃): δ 17.80 (s, C-7′, CH₃, isomer 9a), 18.92 (s,

[R = 2-(2′,6′-ⁱPr₂C₆H₃NvCH)C₆H₄]. IR: ν(CHvN) 1621 (s) cm⁻¹

.

C-7′, CH₃, isomer 9b), 20.74 (s, C-8′, CH₃, isomers 9a + 9b),

128.45 (s, C-4, 9b), 128.49 (s, C-2′, 9b), 128.56 (s, C-3′, 9b),

128.92 (s, C-3′, 9a), 128.99 (s, C-2′, 9a), 129.07 (s, C-4, 9a),

Synthesis of cyclo-[{2-(2′,6′-ⁱPr₂C₆H₃NvCH)C₆H₄}SbO]₃(8)

A solution of KOH (0.022 g, 0.39 mmol, 10% excess) in water 131.12 (s, C-5, 9b), 132.18 (s, C-3, 9b), 132.24, 132.68 (s, C-3/

(10 mL) was added to a solution of 7 (0.10 g, 0.18 mmol) in C-5, 9a), 134.63 (s, C-4′, 9a), 134.70 (s, C-4′, 9b), 136.01 (s, C-6,

toluene (20 mL). The reaction mixture was stirred for 4 days at 9a), 136.46 (s, C-6, 9b), 138.70 (s, C-2, 9b), 138.90 (s, C-2, 9a),

room temperature, then the organic layer was separated and 144.99 (s, C-1′, 9b), 145.32 (s, C-1′, 9a), 152.48 (s, C-1, 9b),

the aqueous phase was washed with toluene (2 × 15 mL). The 153.38 (s, C-1, 9a), 167.01 (s, C-7, CHvN, 9b), 167.32 (s, C-7,

toluene solution was dried over MgSO₄, then filtered and the CHvN, 9a). MS (EI, 70 eV, 200 °C), m/z (%): 752 (70) [M⁺],

solvent was removed under vacuum. The resulting pale yellow 376 (6) [RSbS⁺], 343 (100) [RSb⁺] [R = 2-(2′,4′,6′-Me₃C₆H₂NvCH)

clay was triturated with hexane to aﬀord 8 as a colourless solid C₆H₄]. IR: ν(CHvN) 1622 (vs) cm⁻¹

(0.06 g, 83%), mp 194–195 °C. Anal. calcd for C₅₇H₆₆N₃O₃Sb₃

.

Synthesis of cyclo-[{2-(2′,6′-ⁱPr₂C₆H₃NvCH)C₆H₄}SbS]₂(10)

(1206.42): C, 56.75; H, 5.51; N, 3.48; Found: C, 56.34; H, 5.50;

N, 3.35%. ¹H NMR (500 MHz, CDCl₃): δ 1.09 (36 H, m, H-8′, A solution of Na₂S·9H₂O (0.06 g, 0.26 mmol) in water (10 mL)

CH₃, cis + trans), 3.14 (6 H, m, H-7′, CH, cis + trans), 7.04 (2 H, was added to a solution of 7 (0.10 g, 0.18 mmol) in toluene

3

4

ddd, H-5, C₆H₄, cis, J_HH= 7.4, J_HH= 1.0 Hz), 7.18 (6 H, m, (30 mL). The reaction mixture was stirred for 2 h at room temp-

H-3′,4′, C₆H₃, cis), 7.24 (3 H, m, H-3′,4′, C₆H₃, trans), 7.39 [4 H, erature, then the yellow organic phase was separated and the

m, (H-4, C₆H₄, cis) + (H-4,5, C₆H₄, trans)], 7.57 (1 H, dd, H-3, aqueous phase was washed with toluene (2 × 30 mL). The

3

4

C₆H₄, trans, J_HH= 7.2, J_HH= 1.1 Hz), 7.60 (2 H, d, H-3, C₆H₄, toluene solution was dried over anhydrous Na₂SO₄. Removal of

3

cis, J_HH= 7.2 Hz), 8.18 (2 H, d, H-6, C₆H₄, cis, J_HH= 7.2 Hz), the solvent under vacuum gave 10 as an orange solid (0.06 g,

8.35 (2 H, s, H-7, CHvN, cis), 8.36 (1 H, s, H-7, CHvN, trans), 80%), mp 276–278 °C. Anal. calcd for C₃₈H₄₄N₂S₂Sb₂(836.40):

3

4

8.50 (1 H, dd, H-6, C₆H₄, trans, J_HH= 7.0, J_HH= 1.4 Hz). ¹³C C, 54.57; H, 5.30; N, 3.35; Found: C, 54.89; H, 5.48; N, 3.97%.

NMR (125.8 MHz, CDCl₃): δ 24.33 (s,br, C-8′, CH₃, cis + trans), ¹H NMR (300 MHz, CDCl₃): δ 1.17 (48 H, s,br, H-8′, CH₃,

27.90 (s, C-7′, CH, cis), 28.02 (s, C-7′, CH, trans), 123.25 (s, C-3′, isomers 10a + 10b), 3.06 (8 H, m, H-7′, CH, 10a + 10b), 7.22 (12

cis), 123.43 (s, C-3′, trans), 125.11 (s, C-4′, trans), 125.16 (s, C-4′, H, m, H-3′,4′, C₆H₃, 10a + 10b; 2H, m, H-5, C₆H₄, 10b), 7.42 (2

cis), 128.83 (s, C-4, cis), 128.88 (s, C-4, trans), 131.62 (s, C-5, H, dd, H-4, C₆H₄, ³J_HH= 7.3 Hz, 10b), 7.60 (2 H, dd, H-4, C₆H₄,

cis), 131.82 (s, C-3, cis), 131.96 (s, C-5, trans), 132.08 (s, C-3, ³J_HH= 7.3 Hz, 10a), 7.72 (4 H, m, H-3,5, C₆H₄, 10a; 2 H, m,

trans), 133.85 (s, C-6, cis), 133.96 (s, C-6, trans), 139.36 (s, C-2, H-3, C₆H₄, 10b), 8.35 (4 H, m, H-7, CHvN, 10a + 10b; 2 H, m,

3

trans), 139.50 (s, C-2′, cis), 139.56 (s, C-2′, trans), 139.59 (s, C-2, H-6, C₆H₄, 10b), 9.09 (2 H, d, H-6, C₆H₄, J_HH= 7.2 Hz, 10a);

cis), 146.45 (s, C-1′, cis), 146.98 (s, C-1′, trans), 159.22 (s, C-1, integral ratio 1.8 : 1 for isomers 10a : 10b. ¹³C NMR (75.5 MHz,

trans), 159.97 (s, C-1, cis), 166.24 (s, C-7, CHvN, cis), 166.32 (s, CDCl₃): δ 23.80, 25.30 (s,br, C-8′, CH₃, isomers 10a + 10b),

C-7, CHvN, trans). MS (ESI+), m/z (%): 1206 (50) [M⁺+ H], 28.26 (s, C-7′, CH, 10a), 28.29 (s, C-7′, CH, 10b), 123.58, 123.64,

805 (100) [(RSbO)₂+ H], 402 (48) [RSbO⁺+ H] [R = 2-(2′,6′- 125.89 (s, C-3′,4′, 10a + 10b; C-5, 10b), 128.40 (s, C-4, 10b),

+

ⁱPr₂C₆H₃NvCH)C₆H₄]. IR: ν(CHvN) 1628 (vs) cm⁻¹

.

129.15 (s, C-4, 10a), 132.35 (s, C-3, 10b), 132.48, 132.87 (s,

C-3,5, 10a), 135.96 (s, C-6, 10a), 136.93 (s, C-6, 10b), 138.54 (s,

C-2, 10b), 138.78 (s, C-2, 10a), 139.74 (s, C-1′, 10a + 10b),

Synthesis of cyclo-[{2-(2′,4′,6′-Me₃C₆H₂NvCH)C₆H₄}SbS]₂(9)

A solution of Na₂S·9H₂O (0.06 g, 0.26 mmol) in water (10 mL) 139.99 (s, C-2′, 10a + 10b), 144.71 (s, C-1, 10b), 153.77 (s, C-1,

was added to a solution of 6 (0.13 g, 0.26 mmol) in toluene 10a), 166.45 (s, C-7, CHvN, 10b), 166.74 (s, C-7, CHvN, 10a).

(15 mL). The reaction mixture was stirred for 2 h at room temp- MS (ESI+), m/z (%): 837 (100) [M⁺+ H] [R = 2-(2′,6′-

erature, then the yellow organic phase was separated and the ⁱPr₂C₆H₃NvCH)C₆H₄]. IR: ν(CHvN) 1619 (s) cm⁻¹

.

aqueous phase was washed with toluene (2 × 15 mL). The

toluene solution was dried over anhydrous Na₂SO₄. Evapor-

ation of the solution under vacuum aﬀorded 9 as a yellow

Synthesis of cyclo-[{2-(2′,6′-ⁱPr₂C₆H₃NvCH)C₆H₄}SbS]₂-

[W(CO)₅] (11)

solid (0.07 g, 72%), mp 238–240 °C. Anal. calcd for A solution of [W(CO)₅(thf)] [prepared from W(CO)₆(0.09 g,

C₃₂H₃₂N₂S₂Sb₂(752.24): C, 51.09; H, 4.29; N, 3.72; Found: C, 0.24 mmol) by irradiation with a UV lamp, in THF (200 mL)]

51.17; H, 4.43; N, 3.51%. ¹H NMR (300 MHz, CDCl₃): δ 2.13 (12 was added to 10 (0.20 g, 0.24 mmol) in THF (10 mL) and the

H, s, H-7′, CH₃, isomer 9a), 2.18 (12 H, s, H-7′, CH₃, isomer mixture was stirred for 12 h at room temperature. After

9b), 2.28 (12 H, s, H-8′, CH₃, isomers 9a + 9b), 6.87 (8 H, s, removal of the solvent under vacuum, the remaining yellow-

Dalton Trans., 2013, 42, 1144–1158 | 1155

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Dalton Transactions

brown product was washed with hexane (35 mL) to give 11 as monochromated Mo Kα radiation (λ = 0.71073 Å). The struc-

an orange-brown solid (0.18 g, 65%), mp 279–283 °C. Anal. tures were refined with anisotropic thermal parameters. The

calcd for C₄₃H₄₄N₂O₅S₂Sb₂W (1160.30): C, 44.51; H, 3.82; N, hydrogen atoms were refined with a riding model and a

1

2.41; Found: C, 44.74; H, 3.92; N, 2.28%. H NMR (300 MHz, mutual isotropic thermal parameter. For structure solving and

CDCl₃): δ 1.20 (24 H, m,br, H-8′, CH₃), 2.94 (4 H, s,br, H-7′, refinement the software package SHELX-97 was used.²⁷The

CH), 7.19 (6 H, s,br, H-3′,4′, C₆H₃), 7.49 (4 H, m,br, H-4,5, drawings were created with the Diamond program.²⁸CCDC

C₆H₄), 7.70 (2 H, m,br, H-3, C₆H₄), 8.39 (2 H, s, H-7, CHvN), reference numbers 821266 (4), 821267 (5), 821268 (6·CHCl₃),

8.57 (2 H, m,br, H-6, C₆H₄). ¹³C NMR (75.5 MHz, CDCl₃): δ 821269 (7), 821270 (9·CH₂Cl₂), 821271 (10) and 821272

23.61, 24.07, 25.10, 25.69 (s,br, C-8′, CH₃), 28.26, 28.98 (s,br, (11·0.25CH₃OH).

C-7′, CH), 123.88 (s,br, C-3′), 126.66 (s, C-4′), 129.57 (s, C-4),

132.49, 132.63 (s, C-3,5), 136.58 (s, C-6), 138.46 (s, C-2), 138.94

Computational details

(s, C-2′), 143.68 (s, C-1′), 153.83 (s, C-1), 168.03 (s, C-7, CHvN),

198.41 (s, CO-eq, ¹J_WC= 127.7 Hz), 200.30 (s, CO-ax). MS (ESI+),

Geometry optimizations were carried out with the ORCA 2.8,

rev. 2287 software package using the BP86 functional.²⁹The RI

approximation was used in all the optimizations and

m/z (%): 1134 (100) [M⁺− CO], 1078 (83) [M⁺− 3CO], 748 (28)

[M⁺

−

RSbS], 632 (33) [(RSbS)W(CO)⁺] [R

=

2-(2′,6′-

ⁱPr₂C₆H₃NvCH)C₆H₄]. IR: ν(CO) 2065 (s), 1974 (w), 1914 (vs),

1869 (vs); ν(CHvN) 1618 (m) cm⁻¹

.

Table 5 Crystallographic data for compounds 10 and 11·0.25CH₃OH

10

11·0.25CH₃OH

Crystal structures

Slow diﬀusion of n-hexane into CH₂Cl₂solutions aﬀorded the

isolation of single crystals of 4 (4 : 1 v/v) or 5, 7, 9·CH₂Cl₂and

10 (3 : 1 v/v). Crystals of 11·0.25CH₃OH were similarly grown

using a n-hexane–CH₂Cl₂mixture (3 : 1), which contained

methanol (stabilizer present in the methylene chloride). Slow

diﬀusion of n-hexane at ambient temperature into a CHCl₃

solution (4 : 1 v/v) resulted in crystals of 6·CHCl₃. The details

of the crystal structure determination and refinement are

given in Tables 4 and 5. The crystals were mounted on cryo-

loops (4, 9·CH₂Cl₂) or attached with Krytox™ oil to a glass

fiber (5, 6·CHCl₃, 7, 10, 11·0.25CH₃OH). For 4 and 9·CH₂Cl₂

data were collected at room temperature, while for 5, 6·CHCl₃,

7, 10 and 11·0.25CH₃OH the crystals were cooled under a nitro-

gen stream at low temperature. Data were collected on Bruker

SMART APEX (4, 9·CH₂Cl₂) and Oxford (Type Gemini) (5,

6·CHCl₃, 7, 10, 11·0.25CH₃OH) diﬀractometers, using graphite-

Empirical formula

M

T

Crystal system

Space group

C₃₈H₄₄N₂S₂Sb₂C_43.25H₄₅N₂O_5.25S₂Sb₂W

836.41

110

1168.32

110

Monoclinic

P2₁/n

9.1241(6)

13.9854(9)

14.3083(9)

90.00

92.451(6)

90.00

1824.1(2)

2

Triclinic

P1

ˉ

a/Å

b/Å

c/Å

α/°

β/°

γ/°

12.2021(5)

14.1285(5)

14.3583(5)

82.670(3)

74.980(3)

69.615(3)

2239.14(15)

2

V/Å³

Z

No. of reflections collected 7923

No. of independent

reflections

Absorption correction

μ(Mo Kα)/mm⁻¹

R₁[I > 2σ(I)]

17 692

8584 (R_int= 0.0280)

3567

(R_int= 0.0373)

Multi-scan²⁶

1.624

Multi-scan²⁶

3.898

0.0233

0.0295

wR₂

0.0626

0.872

0.0447

0.918

GOF on F²

Table 4 Crystallographic data for compounds 4, 5, 6·CHCl₃, 7 and 9·CH₂Cl₂

4

5

6·CHCl₃

7

9·CH₂Cl₂

Empirical formula

M

T

Crystal system

Space group

C₃₈H₄₄BrN₂Sb

730.41

Room temperature

Monoclinic

P2₁/c

C₇₆H₈₈N₄SSb₂

1333.09

110

Monoclinic

C2/c

C₁₇H₁₇Br₂Cl₃NSb

623.23

110

Monoclinic

P2₁/c

C₁₉H₂₂Br₂NSb

545.94

110

Orthorhombic

Pbca

C₃₃H₃₂Cl₂N₂S₂Sb₂

835.13

Room temperature

Triclinic

ˉ

P1

a/Å

b/Å

c/Å

α/°

14.302(6)

12.633(6)

20.722(9)

90.00

109.210(7)

90.00

30.5260(15)

10.5847(4)

22.4533(13)

90.00

109.267(6)

90.00

13.5259(4)

16.2912(6)

9.7040(4)

90.00

101.131(4)

90.00

17.248(3)

12.0752(9)

18.737(4)

90.00

8.5344(11)

9.2918(12)

11.0273(14)

98.849(2)

102.661(2)

96.506(2)

833.18(19)

1

β/°

γ/°

V/Å³

3536(3)

4

6848.5(6)

4

2098.08(13)

4

3902.4(11)

8

Z

No. of reflections collected

No. of independent reflections

Absorption correction

μ(Mo Kα)/mm⁻¹

R₁[I > 2σ(I)]

24 116

34 412

9537

11 759

8060

6190 (R_int= 0.0612)

Multi-scan²⁶

1.937

0.0559

0.1160

6689 (R_int= 0.0445)

Multi-scan²⁶

0.863

0.0251

0.0598

4053 (R_int= 0.0299)

Multi-scan²⁶

5.506

0.0266

0.0622

3813 (R_int= 0.0275)

Multi-scan²⁶

5.509

0.0238

0.0525

2922 (R_int= 0.0290)

Multi-scan²⁶

1.932

0.0262

0.0627

wR₂

GOF on F²

1.074

0.929

0.977

0.951

1.099

1156 | Dalton Trans., 2013, 42, 1144–1158

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Dalton Transactions

Paper

relativistic eﬀects were included using the ZORA approxi-

mation. The def2-TZVP basis set was used for the atoms Br, N,

S, Sb, W, and def2-SVP for H and C, both adapted for use in

conjunction with ZORA.³⁰The auxiliary basis sets used were

those generated by ORCA. In all geometry optimizations a Grid

4 was used for integration except for the optimizations of

dimers of 7 and the all-trans isomer of 10 where a Grid 5 was

used and the symmetry detection threshold was increased to

5.0 × 10^–1. In order to have the energy value of the all-trans

isomer of 10 calculated at the same theory level as for the rest

of the isomers, the energy was obtained from a single point

calculation using the integration Grid 4. VeryTightSCF and

TightOpt options were used for all the geometry optimizations

and the final grid generation was suppressed. None of the opti-

mized structures exhibited imaginary frequencies. The energy

of the optimized structures obtained using the BP86 func-

tional was evaluated using the B3LYP functional with the

ORCA 2.9.1 release. In this case the RI approximation was no

longer used. The basis sets used were identical to those used

for the geometry optimizations. VeryTightSCF conditions and

integration Grid 4 were used for all single point calculations.

The energies discussed in the article are those obtained using

the B3LYP functional. In order to evaluate the stabilization

brought by the intramolecular coordination of the nitrogen,

the energy diﬀerence between the optimized structure with the

nitrogen atom coordinated to antimony and the optimized

structure with the nitrogen atom uncoordinated was calculated.

3 K.-y. Akiba, Heteroat. Chem., 2011, 22, 207, and references

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Acknowledgements

Financial support from the National University Research

Council (CNCSIS, Romania; Research Project No. PNII-ID

2052/2009) and National Research Council of Romania (CNCS,

Research Project No. PN-II-ID-PCE-2011-3-0933) is greatly

appreciated. We thank DAAD (Eastern Europe Partnership) for

financial support and Universität Bremen and Technische Uni-

versität Chemnitz for providing research facilities during

research stays of A.M.P. A.M.P. also thanks the European

6 S. Okajima, S. Yasuike, N. Kakusawa, A. Osada,

K. Yamaguchi, H. Seki and J. Kurita, J. Organomet. Chem.,

2002, 656, 234.

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M. Erben, R. Jirásko and L. Dostál, Eur. J. Inorg. Chem.,

Program 2008–2013, POSDRU/6/1.5/S/3). The support provided

by the NATIONAL CENTER FOR X-RAY DIFFRACTION (Babes-

Bolyai University, Cluj-Napoca, Romania) for the solid state

structure determinations is highly acknowledged. Theoretical

calculations were performed using the computational facilities

of Data Centre of National Institute for Research and Develop-

ment of Isotopic and Molecular Technologies – INCDTIM

(Cluj-Napoca).

Notes and references

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2 The Chemistry of Pincer Compounds, ed. D. Morales-Morales

and C. Jensen, Elsevier, Amsterdam, 2007.

Dalton Trans., 2013, 42, 1144–1158 | 1157

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Dalton Transactions

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1158 | Dalton Trans., 2013, 42, 1144–1158

Article Doi

Organoantimony(iii) compounds containing (imino)aryl ligands of the type 2-(RNCH)C6H4 (R = 2′,4′,6′-Me 3C6H2, 2′,6′-iPr 2C6H3): Bromides and chalcogenides

DOI: 10.1039/c2dt32494f

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