Synthesis and crystallographic characterization of thiazoIe-2-dithiocarboxylate methyl ester complexes of chromium

Article abstract of DOI:10.1039/b004251j

Co-ordination of 4-methylthiazole-2-dithiocarboxylate methyl ester, I, or benzothiazole-2-dithiocarboxylate methyl ester, II, to [Cr(CO)₅(THF)]. [W(CO)5(THF)] or [Fe(CO)4(THF)] afforded the new complexes [lI(CO)₄{S=C(SCH₃)C=yC(CH₃)=CHS}] (M = Cr 1 or W 2), [Cr(CO)₄{S=C(SCH})C=ffC₆H4a-o}] 3, [Fe(CO)₃{S=C(SCH₃)C=yC(CH₃)=CHS}] 4 and [Fe(CO)a{S=C(SCH3)0=ISC₆H₄S-o}] 5. Single crystal X-ray structure determinations of 1 and 5 revealed co-ordination of the bidentate ligands through the exocyclic thione sulfur and endocyclic imine nitrogen atoms by five-membered chelate ring formation. Compound 5 has a unique trigonal bipyramidal configuration. The Royal Society of Chemistry 2000.

Full text of DOI:10.1039/b004251j

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Synthesis and crystallographic characterization of thiazole-2-dithio-
carboxylate methyl ester complexes of chromium, tungsten and
iron carbonyls†
Helgard G. Raubenheimer,*a Eugene K. Marais,b Stephanie Cronje,a Catharine Esterhuysen
(neé Thompson)a and Gert J. Krugerb
a Department of Chemistry, University of Stellenbosch, Private Bag X1, Matieland,
Stellenbosch, 7602, South Africa. E-mail: hgr@maties.sun.ac.za
b Department of Chemistry, Rand Afrikaans University, P.O. Box 524, Auckland Park, 2006,
Johannesburg, South Africa
Received 30th May 2000, Accepted 19th July 2000
Published on the Web 14th August 2000
Co-ordination of 4-methylthiazole-2-dithiocarboxylate methyl ester, I, or benzothiazole-2-dithiocarboxylate
methyl ester, II, to [Cr(CO)5(THF)], [W(CO)5(THF)] or [Fe(CO)4(THF)] afforded the new complexes
[M(CO) {S᎐C(SCH )C᎐NC(CH )᎐CHS}] (M = Cr 1 or W 2), [Cr(CO) {S᎐C(SCH )C᎐NC H S-o}] 3,
᎐
᎐
᎐
᎐
᎐
4
3
3
4
3
6
4
[Fe(CO) {S᎐C(SCH )C᎐NC(CH )᎐CHS}] 4 and [Fe(CO) {S᎐C(SCH )C᎐NC H S-o}] 5. Single crystal
᎐
᎐
᎐
᎐
᎐
3
3
3
3
3
6
4
X-ray structure determinations of 1 and 5 revealed co-ordination of the bidentate ligands through the
exocyclic thione sulfur and endocyclic imine nitrogen atoms by five-membered chelate ring formation.
Compound 5 has a unique trigonal bipyramidal configuration.
plexes co-ordinated through the C᎐S group and the azomethine
Introduction
᎐
nitrogen.12
Pseudoaromatic azolyl compounds are important both from
a biological1,2 and an industrial3 viewpoint and their co-
ordination chemistry merits further investigation. The rich
organic chemistry of azoles4 provides a myriad of ligands for
complexation to transition metals. Our investigation involves
the co-ordination of thiazolyldithiocarboxyl esters, derived
from the same type of heterocycle that occurs in vitamin B1,
to Group 6 transition metal and iron carbonyl complexes. The
presence of a N atom in the pseudoaromatic ring provides an
alternative co-ordination possibility to the usual η1-S or η2-S,S
co-ordination of the dithiocarboxyl ester ligand.
We report here the synthesis of thiazolyldithiocarboxyl esters
and the co-ordination of these esters to iron, chromium and
tungsten carbonyls as well as the first crystal and molecular
structures of bidentate thiazolyldithiocarboxyl ester iron and
chromium carbonyl complexes.
Results and discussion
Preparation and characterization of the ligands
Thiazole derived esters S᎐C(SCH )C᎐NC(CH )᎐CHS I and
᎐
᎐
᎐
3
3
Ligands containing exocyclic S- and endocyclic N- and
S-donor atoms and their co-ordination possibilities have
been explored for different metals and in different media.5,6
Although iron() and iron() complexes containing 2-quino-
linedithiocarboxylate ligands are known,7 X-ray crystallo-
graphic data for these complexes, or any other iron(0) or Group
6 transition metal complexes containing ligands with an imine
group and a dithiocarboxylate group or dithiocarboxyl ester,
have not been reported.
S᎐C(SCH )C᎐NC H S-o II. We achieved C–C bond formation
᎐
᎐
3
6
4
readily by treating thiazol-2-yllithium with CS2 followed by
conversion of the dithiocarboxylate into the ester with CF3-
SO3CH3 (Scheme 1). Purification by column chromatography
and crystallization produced red, air stable S᎐C(SCH )-
᎐
3
C᎐NC(CH )᎐CHS I or S᎐C(SCH )C᎐NC H S-o II, soluble
᎐
᎐
᎐
᎐
3
3
6
4
in the polar organic solvents, diethyl ether and CH2Cl2. The
ligands were characterized by elemental analysis (Table 1), mass
spectra (that showed all molecular ions) and 1H and 13C NMR
spectra (see Experimental section).
Despite the similarity between Group 6 transition metal
and iron complexes containing deprotonated 1,1-dithioacid
ligands and metalloenzymes as well as their ability to form
complexes with high co-ordination numbers and different
oxidation states,8,9 few examples of complexes of Group 6
transition metals and iron with dithiocarboxyl ester derivatives
are known.
Preparation and structural characterization of Group 6 transition
metal compounds
Disubstituted carbonyl complexes [M(CO) {S᎐C(SCH )-
᎐
4
3
C᎐NC(CH )᎐CHS}] (M ؍ Cr 1 or W 2) and [Cr(CO) {S᎐C-
The η1-S, η2-S,C and unusual η3-S,C,S co-ordination modes
of S᎐C(R)SCH (R = CH3 or C6H5) and other S–P ligands
᎐
᎐
᎐
3
4
(SCH )C᎐NC H S-o}] 3. Addition of compound I or II to
᎐
3
6
4
᎐
3
to Group 6 metal and iron carbonyl fragments have been
[M(CO)5(THF)] (M = Cr or W) in THF not only substitutes
THF but also a CO group to yield the tetracarbonyl complexes
described.10,11 Reaction of the thio-Schiff base R(R1)C᎐NNHC-
᎐
(S)SCH3 [R = C6H5, C4H3O or o-C4H4(OH) and R1 = H or CH3]
with M(CO)6 (M = Cr or Mo) yields tetracarbonyl com-
[M(CO) {S᎐C(SCH )C᎐NC(CH )᎐CHS}] (M = Cr 1 or W 2)
᎐
᎐
᎐
3
4
3
and [Cr(CO) {S᎐C(SCH )C᎐NC H S-o}] 3 (Scheme 1), which
᎐
᎐
4
3
6
4
were purified by column chromatography at Ϫ20 ЊC and
recrystallization. Crystals of 1, 2 and 3 are stable in the absence
† Dedicated to Professor Herbert Schumann of the Technical Uni-
versity of Berlin on the occasion of his 65th birthday.
3016
J. Chem. Soc., Dalton Trans., 2000, 3016–3021
This journal is © The Royal Society of Chemistry 2000
DOI: 10.1039/b004251j

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Table 1 Analytical, physical and infrared data for compounds I, II and 1–5
Analysisa (%)
Yield
(%)
Compound
mp/ЊC
Colour
ν(CO)/cmϪ1
C
H
N
I S᎐C(SCH3)C᎐NC(CH3)᎐᎐CHS
93–94
Red
72b
67b
31d
27d
29d
26d
27d
38.3
(38.1)
48.3
(48.0)
34.4
(34.0)
24.9
(24.8)
39.7
(40.1)
32.9
(32.8)
39.7
3.7
(3.7)
3.3
(3.1)
2.2
(2.0)
1.6
(1.5)
1.9
(1.8)
2.3
(2.1)
2.0
7.2
(7.4)
6.0
(6.2)
4.0
(4.0)
2.8
(2.9)
3.5
(3.6)
4.5
(4.3)
3.6
᎐
᎐
II S᎐C(SCH3)C᎐NC6H4S-o
175–176
Red
᎐
᎐
1 [Cr(CO)4{S᎐C(SCH3)C᎐NC(CH3)᎐᎐CHS}] 94c
Blue-green
Dark blue
Dark green
Blue-purple
Blue
A(11)
B1 ϩ A(21)
B2
᎐
᎐
2014m
1949s (br)
B1 ϩ A(21)
1939s (br)
B1 ϩ A(21)
1944s (br)
AЉ
1899me
B2
126c
95c
A(11)
2 [W(CO)4{S᎐C(SCH3)C᎐NC(CH3)᎐᎐CHS}]
᎐
᎐
2020m
A(11)
2015m
2AЈ
2039s
2AЈ
2045s
1899me
B2
3 [Cr(CO)4{S᎐C(SCH3)C᎐NC6H4S-o}]
᎐
᎐
1877mf
4 [Fe(CO)3{S᎐C(SCH3)C᎐NC(CH3)᎐᎐CHS}] 82c
᎐
᎐
1972 (br)e
AЉ
5 [Fe(CO)3{S᎐C(SCH3)C᎐NC6H4S-o}]
87c
᎐
᎐
1982 (br)e
(39.5)
(1.9)
(3.8)
a Required values are given in parentheses. b Based on thiazole. c With decomposition. d Based on metal carbonyl. e In hexane. f In CH2Cl2.
their mass spectra. Peaks in the infrared spectra were assigned
(Table 1) for cis-tetracarbonyl complexes with octahedral co-
ordination.13 The broad band at ca. 1945 cmϪ1 represents the
B1 and A(12) vibrations which overlap in certain solvents14 or
when the carbonyl ligands are bent away from the sterically
demanding bidentate ligand [C(1)–Cr–S(1) 177.02(1), C(2)–
Cr–N 169.96(13), C(3)–Cr–C(4) 171.21(14)Њ].15
A small but significant downfield shift is observed in the
1H NMR spectra of complexes 1–3 for all the protons in the
ligands as can be expected with negative charge donation to the
metal centre upon co-ordination of the ligand. Although it is
generally accepted that 13C NMR spectra give a better indi-
cation of electron density redistribution,16 it has, nevertheless,
been shown that 13C chemical shifts do not always represent
electron charge densities17 and that the paramagnetic compo-
nent of the 13C chemical shift cannot always be ignored as for
1H chemical shifts when correlating chemical shifts and charge
densities. Keeping these facts in mind it seems that the 13C
chemical shift changes from the “free” to the co-ordinated
ligand, ∆δ Ϫ2.5 to 5 ppm for thiazole ring carbons and 15.4 to
17.2 for the CS2 carbon, can be interpreted as the result of two
opposing effects, viz. a downfield shift caused by donation of
electron density to the metal opposed by an upfield shift caused
by π-back donation into the d orbitals of the S atoms of the CS2
carbon and thus a π-electron redistribution along the S᎐CCSC
᎐
backbone of the bidentate ligand.
The single signal observed for the CO ligands in complex
2 and no signals for 1 and 3 in the 13C NMR spectra at
room temperature (in CDCl3) indicate that the molecules
are fluxional18,19 and involved in intramolecular carbonyl
scrambling at room temperature. Spectra recorded in d8-THF
at Ϫ90, Ϫ45 and 45 ЊC confirmed this impression. At Ϫ90 ЊC
the configurations in 2 become distinguishable. Three signals,
viz. two at δ 216.1 and 211.1 for the two trans-carbonyl ligands
and one at δ 194.8 for the two cis-carbonyl ligands, are assigned.
At Ϫ45 ЊC these disappear and collapse into one signal, a broad
based singlet at δ 204.2 (204.6 is the weighted average of the
CO signals at Ϫ90 ЊC),20 at room temperature and 45 ЊC.
Similar results were obtained for the CO ligands of complex
1 (δ 234.9, 229.5 for COtrans and 210.4 for COcis) and 3 (δ 237.6,
229.3 for COtrans and 211.4 for COcis). Efforts to locate the
single collapsed signal at higher temperatures (expected at δ 221
for 1 and 222 for 3) were unsuccessful because the complexes
decompose at 45 ЊC. Diimine chelates of Group 6 transition
metals previously yielded analogous results.15 The distorted
angle (<180Њ) between the cis-carbonyl groups, identified in the
infrared spectra of 1, 2 and 3 and the molecular structure of 1
(see below), implies that the distorted octahedral co-ordination
has a tendency towards a trigonal prismatic arrangement of
Scheme 1
of air and moisture, soluble in polar solvents, e.g. diethyl ether
and CH2Cl2, only slightly soluble in the less polar solvents
hexane and pentane, and slowly decompose in solution.
Characterization data of complexes 1, 2 and 3 are shown
in Table 1. The mass and infrared spectra confirm the presence
of four carbonyl ligands and bidentate co-ordination for the
thiazolyldithiocarboxyl ester. Molecular ions were observed in
J. Chem. Soc., Dalton Trans., 2000, 3016–3021
3017

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Table 2 Selected bond lengths (Å) and angles (Њ) of complex 1
In agreement with bond distances observed for the trans-CO
ligands in A and B, the Cr–COtrans bond lengths in complex 1
[Cr–C(1) 1.845(4) and Cr–C(2) 1.830(4) Å] are shorter than the
Cr–COcis bond lengths [Cr–C(3) 1.895(5) and Cr–C(4) 1.902(4)
Å] with the difference between the average Cr–COcis and Cr–
COtrans bond distances being 0.06 Å, similar to the value for A
(0.06 Å). The C(3)–Cr–C(4) bond angle is 171.21(14)Њ with the
two cis-CO ligands bent away from the bidentate ligand. The
same effect was observed in A [176.9(3)Њ] and B [169.2(10)Њ].
As expected the N–Cr–S(1) angle is smaller for the five-
membered chelate ring in complex 1 [80.45(8)Њ] than for the six
membered chelate ring in A [84.9(1)Њ] and the seven membered
chelate ring in B [91.7(4)Њ]. The Cr–S(1) bond distance of
2.3474(11) Å is shorter than the corresponding bonds in A
[2.392(2) Å] and B [2.433(5) Å]. The Cr–N bond length
[2.137(3) Å] is similar to the corresponding bond in B [2.133(15)
Å] but longer than that in A [2.095(5) Å].
Cr–S(1)
2.3474(11)
1.652(4)
1.421(5)
1.845(4)
1.895(5)
1.725(3)
1.377(4)
1.353(5)
1.694(4)
Cr–N
N–C(5)
2.137(3)
1.333(4)
S(1)–C(9)
C(5)–C(9)
Cr–C(1)
Cr–C(3)
S(3)–C(9)
N–C(7)
Cr–C(2)
Cr–C(4)
S(3)–C(10)
C(7)–C(8)
1.830(4)
1.902(4)
1.770(5)
1.487(5)
C(6)–C(7)
S(2)–C(6)
S(2)–C(5)
1.716(3)
C(2)–Cr–S(1)
N–Cr–S(1)
C(2)–Cr–N
89.95(11)
80.45(8)
169.96(13)
117.5(2)
122.3(3)
110.8(3)
113.9(3)
112.0(3)
127.0(2)
C(1)–Cr–N
102.19(13)
177.02(11)
171.21(14)
102.85(13)
116.9(2)
89.44(17)
113.9(3)
C(1)–Cr–S(1)
C(3)–Cr–C(4)
C(9)–S(1)–Cr
C(5)–C(9)–S(1)
C(6)–S(2)–C(5)
C(6)–C(7)–N
C(6)–C(7)–C(8)
C(9)–S(3)–C(10)
C(5)–N–Cr
N–C(5)–C(9)
C(5)–N–C(7)
N–C(5)–S(2)
C(7)–C(6)–S(2)
S(1)–C(9)–S(3)
124.59(4)
103.5(2)
The single and double CS bonds are normal. Bond lengths
and angles in the thiazole unit of the ligand in complex 1 are
essentially the same as those of the thiazole unit in the penta-
carbonyl complex [Cr(CO) {N᎐C(SCH )SC(H)᎐C(CH )}]24
᎐
᎐
5
3
3
and agree with average values obtained from microwave
spectra.25
Preparation and structural characterization of the iron
compounds
[Fe(CO) {S᎐C(SCH )C᎐NC(CH )᎐CHS}] 4 and [Fe(CO) {S᎐
᎐
᎐
᎐
᎐
3
3
3
3
C(SCH )C᎐NC H S-o}] 5. These were prepared by the addition
᎐
3
6
4
of a solution of compound I or II in THF to a red solution of
[Fe2(CO)9] in THF (the dissociation of [Fe2(CO)9] in THF
yields Fe(CO)5 and [Fe(CO)4(THF)] which is responsible for the
red colour of the solution26). The THF and a CO ligand in
[Fe(CO)4(THF)] are substituted by the bidentate thiazole-2-
dithiocarboxylate methyl esters to generate the tricarbonyl iron
complexes 4 and 5 (Scheme 1). The compounds were purified
by column chromatography at Ϫ20 ЊC and crystallization at
Ϫ25 ЊC.
Table 1 contains the physical and infrared data for complexes
4 and 5. Further evidence for the formation of iron tricarbonyl
complexes was obtained from the infrared spectra. Two
carbonyl vibrations at ≈2041 (two AЈ vibrational modes)
and ≈1979 cmϪ1 (the AЉ vibrational mode) were observed
as expected for [Fe(CO)3(L–L)] compounds with a local Cs
symmetry.13 Overlap of the two AЈ bands and the broadening
of the AЉ band can be ascribed to a deviation from Cs symmetry
as verified in the solid state by the crystal structure determin-
ation of 5 showing essentialy trigonal bipyramidal configur-
ation instead of the usual square pyramidal configuration
observed for other [Fe(CO)3(L–L)] compounds.27–29
Fig. 1 An ORTEP21 drawing of [Cr(CO)4{S᎐C(SCH3)-
᎐
C᎐NC(CH3)᎐᎐CHS}] 1 at 50% probability level.
᎐
the ligands, which would facilitate a turnstile or umbrella-like
Berry pseudorotation of the four carbonyl ligands, although
a Bailar twist favoured by a small bidentate ligand bite angle
should also remain an option. A second mechanism described
for racemization of octahedral complexes, the Rây-Dutt twist,
could, however, also be considered.19
1
The downfield shift of the signals in the H NMR spectra
of complexes 1–3 when compared to the signals for I or II is
also observed in the signals for 4 and 5 but to a lesser extent,
indicating less negative charge transfer from the ligand to the
metal centre in the case of the iron tricarbonyl complexes than
for the Group 6 tetracarbonyl complexes. Like the results for 1,
2 and 3, an upfield shift of the 13C NMR signals upon co-
ordination is observed for 4 and 5 but the values for the CS2
carbon ∆δ >50 ppm and the NCS carbon ∆δ ≈19 ppm are
much larger than for the Group 6 complexes.
Structure of [Cr(CO) {S᎐C(SCH )C᎐NC(CH )᎐CHS}] 1.
᎐
᎐
᎐
3
4
3
The crystal structure of 1 is shown in Fig. 1, and selected bond
lengths and bond angles are in Table 2. The chromium
atom is octahedrally surrounded by four carbonyl ligands and
a bidentate 4-methylthiazole-2-dithiocarboxylate methyl ester.
The N- and S-donor atoms of the bidentate ligand are co-
ordinated to the metal cis to each other. Deviations from the
idealized 90 and 180Њ angles around the Cr atom [C(2)–Cr–S(1)
89.95(11), N–Cr–S(1) 80.45(8), C(3)–Cr–C(4) 171.21(14) and
C(1)–Cr–N 102.19(13)Њ] accommodate the five membered ring
formed by the bidentate ligand and the Cr atom. Similar devi-
Comparing 13C NMR spectra30 and the molecular struc-
tures31 of [Fe(CO) (X᎐CHCH᎐Y)] compounds (X = NR, CHR
᎐
᎐
3
or O and Y = NR or CHR) Leibfritz and Dieck30 postulated
that an upfield shift of 50 ppm in the 13C signals of the CH
carbons with respect to the “free” ligand serves as an indication
for π-type donor interaction whereas a small upfield shift of
20 ppm indicates such interaction to be of the σ-type utilizing
the heteroatoms. In the 13C NMR data of both 4 and 5 the
signal for the carbon connected to the S-donor atom is shifted
ations have been observed in the structures of [Cr(CO) {NH᎐
᎐
4
C(OCH CH )C(OCH CH )᎐CS(CH ) S}]22 A and [Cr(CO)4-
᎐
2
3
2
3
2 3
{N(CH )᎐C(OCH CH )C(OCH CH )᎐CHCHS(CH ) S]23 B.
᎐
᎐
3
2
3
2
3
2 3
With the exception of C(10) which is displaced 0.187(7) Å from
the plane, the thiazoledithiocarboxyl ester ligand is planar and
coplanar with the trans-CO ligands within 0.085(3) Å.
3018
J. Chem. Soc., Dalton Trans., 2000, 3016–3021

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Table 3 Selected bond lengths (Å) and angles (Њ) of complex 5
upfield by 53.9 ppm and the one bonded to the N-donor atom
by only ≈19 ppm. This would then suggest a σ-type interaction
Fe–S(1)
2.191(1)
1.678(5)
1.389(6)
1.820(2)
1.750(2)
1.738(4)
1.402(6)
1.392(6)
1.398(8)
1.391(5)
1.732(5)
Fe–N
N–C(4)
1.958(4)
1.337(5)
for N᎐C in the N᎐CC᎐S chelate ring and a π-type interaction
᎐
᎐
᎐
S(1)–C(11)
C(11)–C(4)
Fe–C(1)
Fe–C(3)
S(3)–C(11)
N–C(6)
C(6)–C(7)
C(8)–C(9)
C(5)–C(10)
S(2)–C(5)
for the C᎐S donor section.
᎐
It followed from the structure determination of complex 5
(see below) that co-ordination occurs only through the hetero-
atoms. The upfield shift of 53.9 ppm of the carbon connected
to the S-donor is best explained by somewhat better π-back
donation into the available d orbitals of S whereas the N-donor
atom with no available d orbitals has little or no possibility for
π acceptance and thus the carbon connected to the N atom is
only shifted upfield by ≈19 ppm. S-donor systems have not been
included in previous studies.
The remaining singlets at δ 213.3 for 4 and 212.7 for 5 in
the 13C NMR spectra were assigned to the three CO ligands.
It is difficult to reconcile three identical CO ligands when the
non-C2v-symmetric thiazoledithiocarboxyl ester ligands in 4 and
5 are considered. The 13C NMR spectra recorded at Ϫ90 ЊC
do not differ from those recorded at room temperature and
we conclude that a rapid Berry pseudorotation or turnstile
rotation, as proposed for Fe(α-diimine)(CO)3 complexes19,32
Fe–C(2)
1.759(8)
S(3)–C(12)
C(5)–C(6)
C(7)–C(8)
C(9)–C(10)
1.747(6)
1.390(6)
1.366(5)
1.378(7)
S(2)–C(4)
1.726(5)
N–Fe–S(1)
C(3)–Fe–S(1)
C(2)–Fe–N
84.2(1)
128.5(8)
167.1(9)
119.0(3)
119.9(4)
115.5(3)
110.7(3)
111.4(2)
124.9(2)
C(1)–Fe–S(1)
C(3)–Fe–C(1)
130.7(7)
100.8(3)
C(4)–N–Fe
C(11)–S(1)–Fe
C(4)–C(11)–S(1)
C(4)–S(2)–C(5)
C(5)–C(6)–N
101.9(2)
114.9(3)
89.08(18)
113.3(3)
N–C(4)–C(11)
N–C(4)–S(2)
C(4)–N–C(6)
C(6)–C(5)–S(2)
S(1)–C(11)–S(3)
C(11)–S(3)–C(12)
102.5(3)
and for complexes of the formula [Fe(CO) (X᎐CHCH᎐Y)]
᎐
᎐
3
(X = NR, CHR or O; Y = NR or CHR),30 is responsible for the
chemical equivalence of the CO ligands.
Structure of [Fe(CO) {S᎐C(SCH )C᎐NC H S-o}] 5. The
᎐
᎐
3
3
6
4
molecular structure of complex 5 shown in Fig. 2 reveals a
five-co-ordinate iron atom. Viewed as a trigonal bipyramid, the
S(1) atom of the bidentate benzothiazole-2-dithiocarboxylate
methyl ester ligand and the carbonyl ligands, C(1)–O(1) and
C(3)–O(3) are in the equatorial positions and the N atom
and carbonyl ligand C(2)–O(2) axially positioned. This unique
configuration for iron tricarbonyl compounds with bidentate
ligands, which usually have a square pyramidal configuration,
e.g. in [Fe(CO)3{N(2,6-iPr2C6H3)CHCHN(2,6-iPr2C6H3)}]28 and
[Fe(CO) {N(CH )᎐NN᎐N(CH )}],29 is probably a consequence
᎐
᎐
3
3
3
of the rigid and sterically demanding phenyl ring contained
in the benzothiazoledithiocarboxyl ester ligand.
The Fe–S(1)–C(1)–C(3) plane [Fe has a maximum deviation
from the plane of 0.028(1) Å], with an approximate Cs sym-
metry about the Fe–S(1) bond, has a distorted trigonal planar
geometry with C(1)–Fe–S(1) 130.7(7), C(3)–Fe–S(1) 128.5(8)
and C(3)–Fe–C(1) 100.8(3)Њ (Table 3) but the angles in the plane
add up to 360Њ confirming planarity. Accommodation of the
bidentate ligand in the structure necessitates a significant dis-
tortion of the C(2)–Fe–N bond angle [167.1(9)Њ] from linearity.
Only the C(12) atom of the SCH3 group in the bidentate ligand
is displaced more than 0.080(4) Å from the plane formed by the
benzothiazole-2-dithiocarboxylate methyl ester ligand and this
plane is arranged at an angle of 89.1(1)Њ with the trigonal
Fe–S(1)–C(1)–C(3) plane. The N–Fe–S(1) bond angle in the
five membered chelate ring is 84.2(1)Њ similar to the N–Fe–N
bond angle [80.1(10)Њ] in the disubstituted carbonyl complex
[Fe(CO)3N(2,6-iPr2C6H3)CHCHN(2,6-iPr2C6H3)}].28 Although
the Fe–N bond length 1.958(4) Å (Table 3) is slightly longer
than that of 1.928 Å in the latter compound and the Fe–S(1)
bond distance [2.191(1) Å] is at the short end of the range of
reported Fe–S bond distances (2.18–2.35 Å),33 the Fe ؒ ؒ ؒ C(11)
[3.022(4) Å] and the Fe ؒ ؒ ؒ C(4) separations [2.856(5) Å] dispel
any possibility of major π-type interaction that typically
leads to Fe–C distances of 2.03–2.07 Å, e.g. 2.06 0.03 Å
Fig. 2 An ORTEP21 drawing of [Fe(CO)3{S᎐C(SCH3)C᎐NC6H4S-o}]
᎐
᎐
5 at 50% probability level.
same as those of the thiazole unit in [Fe(η5-C5H5)(CNHC6H4S-
o)(C᎐NC H S-o)(dppe)].35
᎐
6
4
The average Fe–CO bond distance (1.776 Å) is in agreement
with the corresponding bond lengths in the square pyramidal
complexes [Fe(CO)3{N(2,6-iPr2C6H3)CHCHN(2,6-iPr2C6H3)}]
(Fe–COaverage 1.792 Å)28 and [Fe(CO) {N(CH )᎐NN᎐N(CH )}]
᎐
᎐
3
3
3
(Fe–COaverage 1.760 Å),29 and the trigonal bipyramidal
complexes trans-[Fe(CO)3(PPh3)2] (1.770 Å)36 and trans-
[Fe(CO)3(Ph2Ppy)2]ؒ¹C6H6 (1.783 Å).37
¯
²
Experimental
General procedures
All reactions and manipulations were performed under a
nitrogen atmosphere with the use of standard vacuum-line and
Schlenk techniques. Melting points were determined on a Büchi
535 apparatus and are uncorrected. Mass spectra (electron
impact at 70 eV) were recorded on a Finnigan Mat 8200
instrument, infrared on a Perkin-Elmer 841 spectrometer
and NMR spectra (1H at 300.1 MHz and 13C at 75.5 MHz in
d8-THF, referenced to the internal standard TMS at 20 ЊC) on
a Gemini 2000 spectrometer. Elemental analyses were carried
in [Fe(CO)3(CH2CHCHCH2)] and 2.067(4) and 2.031(5) Å in
[Fe(CO)3{C6H5CHCHC(O)H}],31 at least in the solid state.
Once again (compare 1 above) the S(1)–C(11) [1.678(5) Å]
and S(3)–C(11) [1.738(4) Å] bond distances do not differ
significantly from the reported average values for C᎐S (1.67 Å)
᎐
and C–S (1.71 Å)34 bond distances. Bond lengths and angles in
the thiazole unit of the ligand in complex 5 are essentially the
J. Chem. Soc., Dalton Trans., 2000, 3016–3021
3019

View Article Online
out by the Division of Materials Science Technology, Council
for Scientific and Industrial Research, Pretoria.
CH S, 78), 99 [HC᎐NC(CH )᎐CHS, 15], 72 [SCH᎐C(CH ),
᎐
᎐
᎐
3
3
3
54], 71 (SCH᎐C᎐CH , 60), 52 (Cr, 74) and 45 (HCS, 71). δ 7.95
᎐ ᎐
2
H
(1H, s, SCH), 3.09 (3H, s, SCH3) and 2.80 (3H, s, NCCH3).
δC (Ϫ90 ЊC) 234.9 (s, trans-CO), 229.5 (s, trans-CO), 210.4 (s,
cis-CO), 203.3 (s,CS2CH3), 167.5 (s, NCS), 159.1 (s, NCCH3),
122.5 (s, SCH), 20.1 (s, SCH3) and 19.5 (s, NCCH3).
Materials
Benzothiazole, 4-methylthiazole, methyl trifluoromethane-
sulfonate, [Cr(CO)6], [Fe2(CO)9] (Aldrich), CS2, silica gel 60 and
n-butyllithium (Merck) were used without further purification.
Tetrahydrofuran and diethyl ether were distilled under N2
from sodium diphenylketyl, pentane and hexane from sodium
wire and CH2Cl2 from CaH2.
[W(CO) {S᎐C(SCH )C᎐NC(CH )᎐CHS}] 2. Compound 2
᎐
᎐
᎐
3
4
3
was prepared by employing the same method as used for 1 with
[W(CO)6] (1.06 g, 3.0 mmol) and I (0.57 g, 3.0 mmol). The
purple-black reaction mixture was reduced to dryness in vacuo
after stirring for two hours and the residue purified by column
chromatography at Ϫ20 ЊC on silica with diethyl ether–hexane
(1:4) as eluent. The blue fraction containing the product was
evaporated to dryness in vacuo. Dark blue crystals of 2 were
obtained at Ϫ25 ЊC by layering a saturated solution of 2
in diethyl ether with hexane. Yield 0.40 g. MS: m/z 485 (Mϩ,
28%), 457 (M Ϫ CO, 21), 429 (M Ϫ 2CO, 27), 401 (M Ϫ 3CO,
33), 373 (M Ϫ 4CO, 90), 143 (M Ϫ 4CO Ϫ W Ϫ CH2S, 17),
Preparations
S᎐C(SCH )C᎐NC(CH )᎐CHS I. Treatment of 4-methyl-
᎐
᎐
᎐
3
3
thiazol-2-yllithium in THF (60 cm3), prepared from 4-methyl-
thiazole (0.46 cm3, 5.0 mmol) and 1.6 mol dmϪ3 n-butyllithium in
hexane (3.1 cm3, 5.0 mmol) at Ϫ78 ЊC and stirring for 30 min,38
with an excess of CS2 (1.2 cm3, 12.5 mmol) at Ϫ78 ЊC yielded
a yellow reaction mixture. After gradually increasing the
temperature to Ϫ50 ЊC the reaction mixture was stirred for 30
min at this temperature and a change from yellow to dark red
was observed. The reaction mixture was alkylated with CF3-
SO3CH3 (0.57 cm3, 5.0 mmol) at Ϫ50 ЊC with stirring and
allowed to reach room temperature after one hour. The mixture
was reduced to dryness in vacuo. The residue was extracted
with the minimum amount of CH2Cl2, the extract filtered
through silica and reduced to dryness. The crude product was
purified by column chromatography on silica with CH2Cl2–
hexane (2:3) as eluent. Red microcrystalline I was obtained
at Ϫ25 ЊC after layering of a saturated CH2Cl2 solution of 1
with hexane. Yield 0.68 g. MS: m/z 189 (Mϩ, 76%), 143 (M Ϫ
142 (M Ϫ 4CO Ϫ W Ϫ CH S, 25), 72 [SCH᎐C(CH ), 31], 71
᎐
3
3
(SCH᎐C᎐CH , 51) and 45 (HCS, 100). δ 8.04 (1H, s, SCH),
᎐ ᎐
2
H
3.01 (3H, s, SCH3) and 2.81 (3H, s, NCCH3). δC (Ϫ90 ЊC) 216.1
(s, trans-CO), 211.1 (s, trans-CO), 203.7 (s,CS2CH3), 194.8
(s, cis-CO), 171.7 (s, NCS), 159.2 (s, NCCH3), 124.0 (s, SCH),
21.2 (s, SCH3) and 19.5 (s, NCCH3).
[Cr(CO) {S᎐C(SCH )C᎐NC H S-o}] 3. The method used for
᎐
᎐
4
3
6
4
compound 1 was employed to prepare 3 from [Cr(CO)6] (0.66 g,
3.0 mmol) in THF (100 cm3) and II (0.68 g, 3.0 mmol) in THF
(30 cm3). The dark green reaction mixture was purified in a
similar fashion as that of 2. Dark green, needle like crystals
of 3 were obtained at Ϫ25 ЊC by layering a saturated CH2Cl2
solution of 3 with hexane. Yield 0.34 g. MS: m/z 389 (Mϩ, 28%),
305 (M Ϫ 3CO, 30), 277 (M Ϫ 4CO, 11), 225 (M Ϫ 4CO Ϫ Cr,
16), 179 (M Ϫ 4CO Ϫ Cr Ϫ CH2S, 21), 178 (M Ϫ 4CO Ϫ Cr Ϫ
CH S, 63), 142 (M Ϫ CH S, 100), 99 [HC᎐NC(CH )᎐CHS, 4],
᎐
᎐
3
2
3
72 [SCH᎐C(CH ), 13], 71 (S᎐CHC᎐CH , 15) and 45 (HCS, 23).
᎐
᎐
᎐
3
2
δH 7.44 (1H, s, SCH), 2.72 (3H, s, SCH3) and 2.46 (3H,
s, NCCH3). δC 217.2 (s, CS2CH3), 171.5 (s, NCS), 156.7
(s, NCCH3), 123.9 (s, SCH), 19.2 (s, SCH3) and 17.2 (s,
NCCH3).
CH S, 25), 135 (HC᎐NC H S-o, 10), 108 (C H S, 69), 91
᎐
3
6
4
6
4
(C6H4NH, 11), 52 (Cr, 100) and 45 (HCS, 20). δH 8.96 [1H, m,
NCCH(CH)3CS], 8.19 [1H, m, NC(CH)3CHCS], 7.78 [2H,
m, NCCH(CH)2CHCS] and 3.18 (3H, s, SCH3). δC (Ϫ90 ЊC)
237.6 (s, trans-CO), 229.3 (s, trans-CO), 211.4 (s, cis-CO),
203.1 (s, CS2CH3), 166.8 (s, NCS), 154.1 [s, NC(CH)4S], 136.0
[s, NC(CH)4CS], 130.9 [s, NCCHCH(CH)2CS], 129.3 [s, NC-
(CH)2CHCHCS], 125.1 [s, NCCH(CH)3CS] 123.4 [s, NC(CH)3-
CHCS] and 20.3 (s, SCH3).
S᎐C(SCH )C᎐NC H S-o II. This compound was prepared
᎐
᎐
3
6
4
in the same way as I from benzothiazole (0.55 cm3, 5.0 mmol),
1.6 M n-butyllithium in hexane (3.1 cm3, 5.0 mmol) (yellow
after addition), CS2 (1.2 cm3, 12.5 mmol) (dark green after
addition) and CF3SO3CH3 (0.57 cm3, 5.0 mmol) (red
after addition). Yield 0.75 g. MS: m/z 225 (Mϩ, 69%), 179
(M Ϫ CH S, 86), 178 (M Ϫ CH S, 100), 135 (HC᎐NC H S-o,
᎐
2
3
6
4
13), 108 (C6H4S, 12), 91 (C6H4NH, 27) and 45 (HCS, 20).
δH 8.15 [1H, m, NCCH(CH)3CS], 8.02 [1H, m, NC(CH)3-
CHCS], 7.53 [2H, m, NCCH(CH)2CHCS] and 2.80 (3H,
s, SCH3). δC 218.5 (s, CS2CH3), 171.4 (s, NCS), 155.2 [s,
NC(CH)4S], 139.4 [s, NC(CH)4CS], 128.2 [s, NCCHCH(CH)2-
CS], 128.1 [s, NC(CH)2CHCHCS], 126.5 [s, NCCH(CH)3CS],
122.8 [s, NC(CH)3CHCS] and 19.6 (s, SCH3).
[Fe(CO) {S᎐C(SCH )C᎐NC(CH )᎐CHS}] 4. A solution of
᎐
᎐
᎐
3
3
3
compound I (0.42 g, 2.2 mmol) in THF (80 cm3) was slowly
added with stirring to [Fe2(CO)9] (0.80 g, 2.2 mmol). The dark
blue solution was stirred for two hours, evaporated to dryness
in vacuo and the residue purified by column chromatography at
Ϫ20 ЊC on silica and eluted with diethyl ether–hexane (1:4).
The intensely coloured purple-blue fraction yielded micro-
crystalline 4 upon evaporation to dryness in vacuo. Yield 0.19 g.
MS: m/z 329 (Mϩ, 10%), 301 (M Ϫ CO, 12), 273 (M Ϫ 2CO,
40), 245 (M Ϫ 3CO, 50), 189 (M Ϫ 3CO Ϫ Fe, 57), 143
(M Ϫ 3CO Ϫ Fe Ϫ CH2S, 58), 142 (M Ϫ 3CO Ϫ Fe Ϫ CH3S,
[Cr(CO) {S᎐C(SCH )C᎐NC(CH )᎐CHS}] 1. A solution of
᎐
᎐
᎐
3
4
3
compound I (0.57 g, 3.0 mmol) in THF (25 cm3) was added
slowly to a solution of [Cr(CO)5(THF)], prepared from
[Cr(CO)6] (0.66 g, 3.0 mmol) in THF (100 cm3).39 The dark
green reaction mixture was stirred for 2 hours at room tem-
perature and evaporated to dryness in vacuo. The residue was
purified by column chromatography in silica at Ϫ20 ЊC and
eluted with diethyl ether–hexane (1:3). The blue green fraction
containing the product was evaporated to dryness in vacuo.
Blue-green needle like crystals suitable for a crystal structure
determination were obtained by layering a saturated solution of
the residue in diethyl ether with hexane and cooling to Ϫ25 ЊC.
Yield 0.33 g. MS: m/z 353 (Mϩ, 13%), 297 (M Ϫ 2CO, 6), 269
(M Ϫ 3CO, 35), 241 (M Ϫ 4CO, 100), 189 (M Ϫ 4CO Ϫ Cr,
32), 143 (M Ϫ 4CO Ϫ Cr Ϫ CH2S, 37), 142 (M Ϫ 4CO Ϫ Cr Ϫ
100), 99 [HC᎐NC(CH )᎐CHS, 5], 72 [SCH᎐C(CH ), 23], 71
᎐
᎐
᎐
3
3
(SCH᎐C᎐CH , 28), 56 (Fe, 9) and 45 (HCS, 33). δH 7.45 (1H, s,
᎐ ᎐
2
SCH), 2.90 (3H, s, SCH3) and 2.77 (3H, s, NCCH3). δC (Ϫ90 ЊC)
213.3 (s, 3CO), 165.1 (s, CS2CH3), 155.4 (s, NCCH3), 152.6
(s, NCS), 115.8 (s, SCH), 19.4 (s, SCH3) and 18.7 (s, NCCH3).
[Fe(CO) {S᎐C(SCH )C᎐NC H S-o}] 5. Compound 5 was
᎐
᎐
3
3
6
4
prepared and purified in the same way as 4 from II (0.59 g,
2.6 mmol) in THF (100 cm3) and [Fe2(CO)9] (0.95 g, 2.6 mmol).
The dark blue reaction mixture yielded blue crystals of 5
3020
J. Chem. Soc., Dalton Trans., 2000, 3016–3021

View Article Online
after purification. Yield 0.26 g. MS: m/z 365 (Mϩ, 5%), 337
(M Ϫ CO, 10), 309 (M Ϫ 2CO, 24), 281 (M Ϫ 3CO, 100), 225
(M Ϫ 3CO Ϫ Fe, 10), 179 (M Ϫ 3CO Ϫ Fe Ϫ CH2S, 15), 178
(M Ϫ 3CO Ϫ Fe Ϫ CH3S, 28), 108 (C6H4S, 5), 56 (Fe, 11) and
45 (HCS, 5). δH 8.79 [1H, m, NCCH(CH)3CS], 7.98 [1H,
m, NC(CH)3CHCS], 7.60 [2H, m, NCCH(CH)2CHCS] and
2.77 (3H, s, SCH3). δC (Ϫ90 ЊC) 212.7 (s, 3CO), 163.6 (s,
CS2CH3), 154.0 [s, NC(CH)4S], 152.2 (s, NCS), 132.1 [s,
NC(CH)4CS], 128.7 [s, NCCHCH(CH)2CS], 127.6 [s, NC-
(CH)2CHCHCS], 125.4 [s, NCCH(CH)3CS], 121.3 [s, NC-
(CH)3CHCS] and 19.0 (s, SCH3).
11 A. Galindo, C. Mealli, J. Cuyás, D. Miguel, V. Riera, J. A. Pérez-
Martínez, C. Bois and Y. Jeannin, Organometallics, 1996, 15, 2735;
D. Miguel, V. Riera, J. A. Miguel, M. Gómez and X. Solans,
Organometallics, 1991, 10, 1683; A. Galindo, E. Gutiérrez-Puebla,
A. Monge, A. Pastor, A. Pizzano, C. Ruiz, L. Sánchez and
E. Carmona, Inorg. Chem., 1993, 32, 5569.
12 O. P. Pandey, S. K. Sengupta and S. C. Tripathi, Synth. React. Inorg.
Metal-Org. Chem., 1984, 14, 827.
13 P. S. Braterman, Struct. Bonding (Berlin), 1976, 26, 1; L. M. Haines
and M. H. B. Stiddard, Adv. Inorg. Chem. Radiochem., 1969, 12, 53.
14 L. E. Orgel, Inorg. Chem., 1962, 1, 25; F. A. Cotton and C. S.
Kraihanzel, J. Am. Chem. Soc., 1962, 84, 4432; B. E. Douglas,
D. H. McDaniel and J. J. Alexander, Concepts and Models of
Inorganic Chemistry, John Wiley & Sons, Inc., New York, 3rd edn.,
1994, p. 601.
15 W. Majunke, D. Leibfritz, T. Mack and H. Tom Dieck, Chem. Ber.,
1975, 108, 3025.
16 J. B. Stothers, Carbon-13 NMR Spectroscopy, Academic Press,
New York, 1972.
17 R. F. Fenske, in Organometallic Compounds: Synthesis, Structure
and Theory, ed. B. L. Shapiro, Texas A & M University Press, Texas,
1983, p. 305.
18 E. L. Muetterties, Inorg. Chem., 1965, 4, 769; J. R. Shapley and
J. R. Osborn, Acc. Chem. Res., 1973, 6, 305; W. von E. Doering
and W. R. Roth, Angew. Chem., Int. Ed. Engl., 1963, 2, 115.
19 B. E. Douglas, D. H. McDaniel and J. J. Alexander, Concepts and
Models of Inorganic Chemistry, John Wiley & Sons, Inc., New York,
1994, p. 433.
Crystal data
[Cr(CO) {S᎐C(SCH )C᎐NC(CH )᎐CHS}] 1. C H CrNO
-
᎐
᎐
᎐
4
3
3
10
7
4
S3, M = 353.35, monoclinic, space group P21/n, a = 8.948(2),
b = 16.647(3), c = 9.4732(18) Å, β = 97.854(19)Њ, U = 1397.9(5)
Å3, T = 293(2) K, Z = 4, µ(Mo-Kα) = 1.27 mmϪ1, 2535 reflec-
tions, 1941 unique [Rint = 0.016], R1 = 0.050 and wR2 = 0.093
(all data).
[Fe(CO) {S᎐C(SCH )C᎐NC H S-o}] 5. C H FeNO S , M =
᎐
᎐
3
3
6
4
12
7
3 3
365.23, monoclinic, space group P21, a = 9.312(2), b = 7.317(3),
c = 10.741(4) Å, β = 94.38(2)Њ, U = 729.6(4) Å3, T = 293(2) K,
Z = 4, µ(Mo-Kα) = 1.448 mmϪ1, 2752 reflections, 1845 unique
[Rint = 0.033], R1 = 0.034 and wR2 = 0.031 [I > 2σ(I)].
CCDC reference number 186/2093.
20 W. Kemp, NMR in Chemistry:
A Multinuclear Introduction,
Macmillan Education Ltd., London, 1986, p. 165.
21 L. J. Farrugia, J. Appl. Crystallogr., 1997, 565.
22 G. J. Kruger, G. Gafner, J. P. R. de Villiers, H. G. Raubenheimer and
H. Swanepoel, J. Organomet. Chem., 1980, 187, 333.
23 H. G. Raubenheimer, G. J. Kruger and H. W. Viljoen, J. Organomet.
Chem., 1987, 319, 361.
See http://www.rsc.org/suppdata/dt/b0/b004251j/ for crystal-
lographic files in .cif format.
24 S. Cronje, H. G. Raubenheimer, C. Esterhuysen and G. J. Kruger,
unpublished results.
25 A. R. Katritzky, Handbook of Heterocyclic Chemistry, Pergamon
Press, Oxford, 1st edn., 1985, p. 95.
26 F. A. Cotton, D. L. Hunter and J. M. Troup, Inorg. Chem., 1976, 15,
63; G. Natile and G. Bor, J. Organomet. Chem., 1972, 35, 185.
27 H. Tom Dieck and A. Orlopp, Angew. Chem., 1975, 87, 246;
N. Feiken, P. Schreuder, R. Siebenlist, H.-W. Frühauf and K. Vrieze,
Organometallics, 1996, 15, 2148.
28 M. W. Kokkes, D. J. Stufkens and A. Oskam, J. Chem. Soc., Dalton
Trans., 1983, 439.
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