Metallation of 2-methyl-2-thiazoline at a triosmium cluster: X-ray structure of [(μ-H)Os3(CO)10(μ-η2-CH2C=NCH2CH2S)]

Article abstract of DOI:10.1016/S0277-5387(00)00354-5

The reaction of [Os₃(CO)₁₀(MeCN)₂] with 2-methyl-2-thiazoline at ambient temperature results in the C-H activation of the methyl substituent of the heterocyclic ligand and this gives the new compound [(μ-H)Os₃(CO)₁₀(μ-η²-CH₂C = NCH₂CH₂S] (8) in 55% yield. Compound 8 undergoes decarbonylation and a further C-H bond activation by thermolysis at 98°C or by treatment with trimethylamine-N-oxide to give the dihydrido cluster [(μ-H)₂Os₃(CO)₉(μ-η²-CHC = NCH₂CH₂S] (9) in 45% yield. Both complexes have been characterized by elemental analyses, IR and ¹H NMR spectroscopy, together with X-ray crystallography for 8. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0277-5387(00)00354-5

www.elsevier.nl/locate/poly
Polyhedron 19 (2000) 1081–1084
Metallation of 2-methyl-2-thiazoline at a triosmium cluster:
–
–––––––––
2
o
p
X-ray structure of [(m-H)Os (CO) (m-h -CH C_NCH CH S)]
3
10
2
2
2
a
a
a
a
Kazi A. Azam , Rahima Dilshad , Shariff E. Kabir , M. Abdul Mottalib ,
1,b
b,
Michael B. Hursthouse , K.M. Abdul Malik *
Department of Chemistry, Jahangirnagar University, Savar, Dhaka-1342, Bangladesh
Department of Chemistry, Cardiff University, P.O. Box 912, Park Place, Cardiff CF10 3TB, UK
a
b
Received 28 January 2000; accepted 3 March 2000
Abstract
The reaction of [Os (CO) (MeCN) ] with 2-methyl-2-thiazoline at ambient temperature results in the C–H activation of the methyl
3
10
2
–
––––––––––
2
o
p
substituent of the heterocyclic ligand and this gives the new compound [(m-H)Os (CO) (m-h -CH C_NCH CH S] (8) in 55% yield.
3
10
2
2
2
Compound 8 undergoes decarbonylation and a further C–H bond activation by thermolysis at 988C or by treatment with trimethylamine-N-
––––––––––
–
2
o
p
2
oxide to give the dihydrido cluster [(m-H) Os (CO) (m-h -CHC_NCH CH S] (9) in 45% yield. Both complexes have been characterized
2
3
9
2
1
by elemental analyses, IR and H NMR spectroscopy, together with X-ray crystallography for 8.
q2000 Elsevier Science Ltd All rights
reserved.
Keywords: Osmium; X-ray structures; Metallation
1. Introduction
The study of the reactivity of N and S containing hetero-
cycles with trimetallic clusters of osmium and ruthenium
continues to be the subject of considerable interest; this
is due to their relevance to modelling the industrially im-
portant hydrodenitrogenation (HDN) and hydrodesul-
furization (HDS) processes [1–7]. We have recently
2
reported the thiazolideclusters[(m-H)M (CO) (m-2,3-h -
3
10
–
–––––––––––
o
p
C_NCMe_CHS)] (3, MsOs; 4, MsRu; Scheme 1), with
metallation exclusively at the 2-position, from the reactions
of [M (CO) L ] (1, MsOs, LsMeCN; 2, MsRu,
3
10 2
LsCO) with 4-methyl thiazole [1]. We also found that
the reaction of [Os (CO) (MeCN) ] with thiazole
3
10
2
results in metallation at the 4- and 2-positions, leading
2
to the isomeric compounds [(m-H)Os (CO) (m-2,3-h -
3
10
–
––––––––––
o
p
Scheme 1.
C_NCH_CHS)] (5) and [(m-H)Os (CO) (m-3,4-
h -HC_NC_CHS)] (6) [2]. In contrast, when reacted
3
10
––––––––––
2
o
p
Pyridine and 2-substituted pyridines react with triosmium
and triruthenium clusters by orthometallation to give [(m-
with [Ru (CO) ], thiazole preferentially metallates at
3
12
2
the 2-position yielding [(m-H)Ru (CO) (m-2,3-h -
3
10
–
––––––––––
H)M
3
(CO)10(m-L)] (LsC
5 4 5 3 5
H N, 2-MeC H N, 3-MeC -
o
p
C_NCH_CHS)] (7) [3].
H N, 2-Et-C H N) [8–17]. In comparison to the extensive
3
5
3
orthometallation chemistry of five- and six-membered het-
erocyclic rings, examples of the activation of theirsubstituent
groups are comparatively rare. An example of the ethenyl
group C–H bond activation rather than those at the hetero-
*
Corresponding author. Tel.: q44-29-2087 4950; fax: q44-29-2087
4
030; e-mail: malikka@cardiff.ac.uk
1
Present address: Department of Chemistry, University of Southampton,
Highfield, Southampton SO17 1BJ, UK.
0
277-5387/00/$ - see front matter q2000 Elsevier Science Ltd All rights reserved.
PII S0277-5387(00)00354-5
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K.A. Azam et al. / Polyhedron 19 (2000) 1081–1084
cyclic ring has been observed when [Os (CO) (MeCN) ]
3
10
2
was reacted with 2-ethenyl pyridine leading to the formation
of the open triosmium cluster [HOs (CO) (NC H -
3
10
5
4
C_CH)] [18]. As part of our interest in the reactivity of N
and S containing heterocycles with trimetallic clusters we
have investigated the reaction of [Os (CO) (MeCN) ]
3
10
2
with 2-methyl-2-thiazoline and report herein a rare example
of the C–H activation of the substituent group of the ligand
at ambient temperature.
2. Results and discussion
The lightly stabilized cluster [Os (CO) (MeCN) ]
3
10
2
readily reacts with 2-methyl-2-thiazoline at room temper-
Fig. 1. X-ray structure of 8, showing the atom labelling scheme. The ring
hydrogens are omitted for clarity. Thermal ellipsoids are drawn at 40%
probability level.
2
ature to give the novel cluster [(m-H)Os (CO) (m-h -
3
10
–
––––––––––
o
p
CH C_NCH CH S] (8) in 55% yield (Scheme 2). The
2
2
2
compound 8 has been characterized by microanalysis, IR and
Table 1
1
H NMR spectroscopy as well as X-ray crystallography. The
˚
Selected bond lengths (A) and angles (8) for 8
1
H NMR spectrum of 8 shows four multiplets at d 3.24, 3.37,
3
.89 and 4.18 for the ring protons, which remain intact, and
Os(1)–Os(2)
Os(2)–Os(3)
Os(3)–N(1)
Os(2)–H(23)
S(1)–C(12)
N(1)–C(12)
C(11)–C(12)
C–O
2.9047(8)
2.9414(10) Os(2)–C(11)
Os(1)–Os(3)
2.8858(8)
2.190(11)
two coupled doublets at d 1.81 and 2.40 for the 2-CH group
2
a
2.165(9)
Os–C(CO)
1.923
along with a high field singlet at d y14.20 each integrating
for one hydrogen. The coupling of 20.0 Hz between these
protons and their chemical shifts imply a coordinated CH2
group and metallation at the substituent group. The spectro-
scopic data indicated the activation of the C–H bond of the
methyl substituent of the heterocycle and subsequent coor-
dination of the carbon to the metal. The exact nature of the
bonding of the organic ligand to the cluster was obtained by
a single crystal structure determination for 8.
b
b
1.77
Os(3)–H(23)
S(1)–C(13)
N(1)–C(14)
C(13)–C(14)
1.72
1.747(11)
1.284(14)
1.477(13)
1.778(11)
1.484(12)
1.48(2)
a
1.138
C(3)–Os(1)–C(4)
C(4)–Os(1)–C(1)
C(4)–Os(1)–C(2)
C(5)–Os(2)–C(7)
C(7)–Os(2)–C(6)
C(7)–Os(2)–C(11)
C(11)–Os(2)–Os(1)
C(11)–Os(2)–Os(3)
C(8)–Os(3)–C(9)
C(8)–Os(3)–N(1)
C(9)–Os(3)–N(1)
C(8)–Os(3)–Os(2)
C(12)–S(1)–C(13)
C(12)–N(1)–Os(3)
103.7(4)
90.4(4)
90.4(4)
100.4(5)
92.5(4)
86.1(4)
93.8(3)
84.2(3)
96.1(4)
88.8(4)
93.2(4)
118.9(3)
91.7(6)
126.9(7)
C(3)–Os(1)–C(1)
C(3)–Os(1)–C(2)
C(1)–Os(1)–C(2)
C(5)–Os(2)–C(6)
C(5)–Os(2)–C(11)
C(6)–Os(2)–C(11) 176.3(4)
C(7)–Os(2)–Os(3) 113.2(3)
C(8)–Os(3)–C(10)
C(10)–Os(3)–C(9)
C(10)–Os(3)–N(1) 176.2(4)
N(1)–Os(3)–Os(1)
N(1)–Os(3)–Os(2)
C(12)–N(1)–C(14) 113.2(10)
C(14)–N(1)–Os(3) 119.6(7)
N(1)–C(12)–C(11) 125.6(10)
C(11)–C(12)–S(1) 118.9(8)
94.4(5)
89.4(4)
175.7(5)
92.3(4)
84.7(4)
The structure of a single molecule of 8 is shown in Fig. 1,
and selected bond lengths and angles are given in Table 1.
The molecule consists of a triangular clusterofosmiumatoms
with three distinct metal–metal bonds (Os(1)–Os(2)s
90.7(4)
90.6(4)
91.5(2)
82.9(2)
2
.9047(8), Os(1)–Os(3)s2.8858(8) and Os(2)–Os(3)
˚
s2.9414(10) A). The Os(2)–Os(3) edge which is bridged
simultaneously by the hydride and the heterocyclic ligand
is significantly longer than the two unbridged edges.
C(12)–C(11)–Os(2) 120.1(7)
N(1)–C(12)–S(1)
C(14)–C(13)–S(1)
115.6(8)
107.6(8)
C(13)–C(14)–N(1) 110.9(9)
Os–C–O
b
a
Os(2)–H(23)–Os(3) 115
176.5
a
Average value.
Approximate value.
b
Similar lengthening of the doubly bridged Os–Os edges
2
was also observed in [(m-H)Os (CO) {m-2,3-h -
3
10
–
–––––––––––––
o
p
C_NC(Me)_CHS}] (2.9340(8) versus 2.8590(7),
2
˚
2
.8849(8)
A),
[(m-H)Os (CO) {m-2,3-h -
3
9
–
–––––––––––––
o
p
C_NC(Me)_CHS)}(PPh )]
(2.9674(9)
versus
3
˚
2
.8619(13), 2.8779(9) A) and [(m-H)Os (CO) {m-2,3-
3
8
–
–––––––––––––
2
o
p
h -C_NC(Me)_CHS}(PPh ) ]
(2.9528(6)
versus
3
2
˚
2
.8795(6), 2.9050(6) A) [1]. The bridging hydride is
located close to the plane of the Os triangle, while the
3
heterocyclic ligand is nearly perpendicular to it. The metal
atoms Os(3) and Os(2) each contain three linear terminal
carbonyl ligands while Os(1) is bonded to four. A notable
feature of this structure is that a C–H activation of the methyl
Scheme 2.
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K.A. Azam et al. / Polyhedron 19 (2000) 1081–1084
1083
group of 2-methyl-2-thiazoline occurs during the reaction.
2
The organic ligand is h -coordinated to the longest Os(2)–
Os(3) edge through a metal–carbon s bond from C(11) to
Os(2) and a two-electron donor bond from N(1) to Os(3).
˚
The Os(2)–C(11) bond length of 2.190(11) A and Os(3)–
˚
N(1) bond length of 2.165(9) A are comparable to those
2
of the related compounds [(m-H) Ru (CO) (m -h -
CH(Me)C_NCH CH )}] and [(m-H) Os (CO) (m -h -
CHC_NCH CH CH )] [19]. The C(12)–N(1) bond
length of 1.284(14) A is typical of carbon nitrogen double
2
3
9
3
2
2
p
3
2
3
9
3
–
––––––––––
o
2
2
2
Scheme 3.
˚
bonds in the related triosmium and triruthenium complexes
In conclusion, we have demonstrated herein an unusual C–
H activation of the methyl substituent of 2-methyl-2-thiazo-
line at a triosmium centre to give [(m-H)Os (CO) (m-
[
20–22], while the C(14)–N(1) bond length of 1.484(12)
˚
˚
A is close to that expected for a C–N single bond (1.47 A)
3
10
–
––––––––––
[
1
23]. The S–C distances (1.747(11)–1.778(11), average
2
o
p
h -CH C_NCH CH S)] (8) which undergoes a further
2
2
2
˚
.763 A) are only slightly smaller than the value expected
2
C–H activation to afford [(m-H) Os (CO) (m-h -
2
3
9
˚
–––––––––––
for a S–C single bond (1.81 A) [23]. The Os–C(CO) dis-
tances (1.897(11)–1.954(12), average 1.923 A) and the
o
p
CHC_NCH CH S)] (9). Decarbonylation of 8 using
2
2
˚
Me NO also gives 9 instead of the expected m -imidoyl type
3
3
Os–C–O angles (171.3(10)–179.6(9), average 176.548) are
comparable to the corresponding values in triosmium decar-
bonyl compounds containing a 3, 3, 4 carbonyl ligand distri-
bution and in which the heterocyclic ligand and the hydride
bridge the same Os–Os edge [1,2,20,22].
product, indicating thatC–Hactivationismoreamenablethan
coordination of the double bond of the heterocycle to the rear
metal atom.
3
. Experimental
Thermolysis of 8 in refluxing heptane at 988C gives
2
the
dihydrido
cluster
[(m-H) Os (CO) (m -h -
All reactions were carried out under a dry and oxygen-free
2
3
9
3
–
––––––––––
o
p
atmosphere of N by using standard Schlenk techniques.Rea-
CHC_NCH CH S)] (9) in 45% yield (Scheme 1). The
2
2
2
compound has been characterized on the basis of elemental
gent grade solventswere freshlydistilledfromtheappropriate
1
1
analysis, IR and H NMR spectroscopic data. A direct analog
drying agents. H NMR spectra were recorded on a Varian
of 9 was obtained from the reaction of the m -imidoyl com-
Unity Plus 400 MHz spectrometer. Infrared spectra were
3
–
––––––––––
2
o
p
recorded on a FTIR 8101 spectrophotometer The cluster
pound [(m-H)Os (CO) (m -h -C_NCH CH CH )] (10)
.
3
9
3
2
2
2
with diazomethane (Scheme 3) [19]. The n(CO) frequen-
cies of 9 are very similar to those of 11, indicating that they
have very similar distribution of the carbonyl ligands.
[Os (CO)10(MeCN) ] was prepared according to the
3 2
known procedure [24].
3
.1. Reaction of [Os (CO) (MeCN) ] with 2-methyl-2-
3 10 2
1
The aliphatic region of the H NMR spectrum of 9 contains
thiazoline
a doublet at d 4.24 (Js1.2 Hz) and three multiplets at d
3
3.74, 3.47 and 3.17 in a relative intensity ratio of 1:1:1:2. The
To a dichloromethane solution (40 cm ) of [Os
(CO)10-
3
hydride region shows a doublet at d y14.48 (Js1.6 Hz)
and a doublet of doublets at d y14.61 (Js1.6 and 1.2 Hz)
in a relative intensity of 1:1. The doublet at d 4.24 is due to
the methyne proton and it exhibits coupling to one of the
hydrides which appears as a doublet of doublets at d y14.61.
Irradiation of the methyne proton results in a collapse of the
hydride doublet of doublets at d y14.61 to a doublet. The
hydride chemical shifts, their multiplicity and the long-range
coupling between the methyne proton and one of the hydrides
are almost identical with those reported for 11 (d y14.30
(MeCN) ] (0.188 g, 0.201 mmol) was added 2-methyl-2-
2
thiazoline (0.102 g, 1.0 mmol) and the reaction mixture was
stirred at room temperature for20h. Thesolventwasremoved
in vacuo and the residue was chromatographed by TLC on
silica gel. Elution with hexane/CH
Cl (7:3, v/v) gave one
2
2
2
major band which afforded [(m-H)Os
(CO)10(m-h -
S)] (8) (0.105 g, 55%) as yellow crystals
after recrystallization from hexane/CH Cl at y208C. Anal.
Found: C, 17.82; H, 0.89; N, 1.59. C14 NO10Os S requires:
3
–
––––––––––
o
p
C_NCH CH
2 2
CH
2
2
2
H
7
3
C, 17.66; H, 0.74; N, 1.47%. IR (n(CO), hexane): 2103 m,
(
d, Js1.7 Hz), y14.56 (dd, Js1.7 and 0.8 Hz)) whose
2061 vs, 2050 vs, 2022 vs, 2002 m, 1996 m, 1990 m, 1973
y1
1
structure was established by X-ray diffraction studies [19].
The analytical data and spectroscopic features of 9 are thus
in agreement with the proposed structure.
In order to examine whether the double bond of the het-
erocyclic ligand in 8 would exhibit the ability to coordinate
w cm . H NMR (CDCl ): d 1.81 (d, 1H, Js20.0 Hz),
3
2.40 (d, 1H, Js20.0 Hz), 3.24 (m, 1H), 3.37 (m, 1H), 3.89
(m, 1H), 4.18 (m, 1H), y14.24 (s, 1H).
2
3
.2. Thermolysis of [(m-H)Os (CO) (m-h -
3
10
–
–––––––––––––––
o
p
CH C_NCH CH S)] (8)
2
2
2
to the rare metal atom yielding a m -imidoyl type compound,
3
the compound was treated with Me NO. Contrary to expec-
A solution of 8 (0.070 g, 0.073 mmol) in heptane (20
cm ) was heated to reflux for 22 h. The solvent was removed
under reduced pressure and the residue waschromatographed
3
3
tation, we observed a preferred reaction that involved a fur-
ther C–H activation of the coordinated methylidyne ligand
accompanied by a CO loss.
by TLC on silica gel. Elution with hexane/CH Cl (7:3,
2
2
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K.A. Azam et al. / Polyhedron 19 (2000) 1081–1084
v/v) developed three bands. The fast moving band gave
Os (CO) ] (0.008 g, 12%). The second band gave
tra at the University of Montana, USA. MBH and KMAM
acknowledge the EPSRC support of the national X-Ray Crys-
tallography Service.
[
3
12
a too small amount (;0.002 g) for complete characteriza-
2
tion. The third band gave [(m-H) Os (CO) (m-h -
2
3
9
–
––––––––––
o
p
CHC_NCH CH S)] (9) (0.030 g, 45%) as yellow crystals
2
2
after recrystallization from hexane/CH Cl at y208C. Anal.
2
2
References
Found: C, 17.10; H, 0.82; N, 1.62. C H NO Os requires:
13
7
9
3
C, 16.90; H, 0.76; N, 1.51%. IR (n(CO), CH Cl ): 2103 s,
2
2
[1] K.A. Azam, R. Dilshad, S.E. Kabir, K. Khatoon, L. Nessa, M.M.
Rahman, E. Rosenberg, M.B. Hursthouse, K.M.A. Malik, A.J. Deem-
ing, J. Chem. Soc., Dalton Trans. (1996) 1731.
y1
2
076 vs, 2049 vs, 2019 vs, 2002 s, 1993 m, 1976 m cm
.
1
H NMR (CDCl ): d 3.21 (m, 2H), 3.47 (m, 1H), 3.74 (m,
3
[
2] K.A. Azam, M.B. Hursthouse, S. Hossain, S.E. Kabir, K.M.A. Malik,
M.M. Rahman, E. Rosenberg, J. Organomet. Chem. 559 (1998) 81.
3] K.A. Azam, M.B. Hursthouse, S.E. Kabir, K.M.A. Malik, M. Tesmer,
H. Vahrenkamp, Inorg. Chem. Commun. 1 (1998) 402.
1
H), 4.24 (d, 1H, Js1.2 Hz), y14.48 (d, 1H, Js1.6 Hz),
y14.61 (dd, 1H, Js1.6, 1.2 Hz).
[
3
.3. Reaction of 8 with Me NO
3
[4] A.J. Deeming, K.I. Hardcastle, M. Karim, Inorg. Chem. 31 (1992)
71.
3
3
[
[
[
5] Y.K. Au, K.K. Cheung, W.T. Wong, Inorg. Chim. Acta 228 (1995)
267.
6] A.M. Brodie, H.D. Holden, J. Lewis, M.J. Taylor, J. Chem. Soc.,
Dalton Trans. (1986) 633.
7] Y.K. Au, K.K. Cheung, W.T. Wong, J. Chem. Soc., Dalton Trans.
(1995) 267.
To a dichloromethane solution (20 cm ) of 8 (0.070 g,
3
0
.073 mmol) was added dropwise a CH Cl solution (5 cm )
2
2
of Me NO (0.011 g, 0.146 mmol) over a period of 15 min.
3
The reaction mixture was stirred at room temperature for
20 h. A similar work-up to that above followed by a similar
[
[
8] E.C. Constable, Polyhedron 3 (1984) 1037.
9] M.I. Bruce, M.P. Cifuentes, M.G. Humphrey, Polyhedron 10 (1991)
chromatographic separation of the residue gave 9 (0.024 g,
35%).
2
77.
10] K. Burgess, B.F.G. Johnson, J. Lewis, J. Organomet. Chem. 233
1982) C55.
11] C.C. Yin, A.J. Deeming, J. Chem. Soc., Dalton Trans. (1975) 2091.
[
3.4. X-ray crystallography
(
[
Crystal data for 8: C H NO Os S, Ms951.87, mono-
[12] B.F.G. Johnson, J. Lewis, D.A. Pippard, J. Chem. Soc., Dalton Trans.
(1982) 407.
[13] A.J. Deeming, R. Peters, M.B. Hursthouse, J.D. Backer-Dirks, J.
Chem. Soc., Dalton Trans. (1982) 1205.
1
4
7
10
3
˚
clinic, C2/c, as28.526(6), bs7.758(2), cs17.506(4) A,
3
y3
˚
bs90.08(3)8, Us3873(2) A , Zs8, D s3.265 g cm
,
c
˚
y1
m(Mo Ka)s197.98 cm , ls0.71073 A, Ts150 K, crys-
[14] G.A. Foulds, B.F.G. Johnson, J. Lewis, J. Organomet. Chem. 294
tal size 0.22=0.15=0.12 mm.
(1985) 123.
Intensity data were recorded on a FAST area detector dif-
[15] M.I. Bruce, M.G. Humphrey, M.R. Snow, E.R.T. Tiekink, R.C.
Wallis, J. Organomet. Chem. 314 (1986) 311.
[16] A. Eisenstadt, C.M. Giandomenico, M.F. Frederick, R.M. Laine,
Organometallics 4 (1985) 2033.
fractometer [25], the structure solved by direct methods
2
(
SHELXS-86) [26], and refined on F by full-matrix least-
squares (SHELXL-96) [27] using all 2903 unique data and
[17] K.A. Azam, A.R. Das, M.B. Hursthouse, S.E. Kabir, K.M.A. Malik,
2
2
62 parameters to final wR s0.0645 (on F , all data) and
2
J. Chem. Crystallogr. 28 (1998) 283.
2 2
R s0.0286 (on F, 2484 data with F )2s(F )). The
[18] K. Burgess, H.D. Holden, B.F.G. Johnson, J. Lewis, M.B. Hursthouse,
N.P.C. Walker, A.J. Deeming, P.J. Manning, R. Peters, J. Chem. Soc.,
Dalton Trans. (1985) 85.
1
o
o
bridging hydride was located from a difference map but not
refined.
[19] M. Day, W. Freeman, K.I. Hardcastle, M. Isomaki, S.E. Kabir, T.
McPhillips, E. Rosenberg, L.G. Scott, E. Wolf, Organometallics 11
(
1992) 3376.
Supplementary data
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Acknowledgements
3
We gratefully acknowledge the Jahangirnagar University
for support of this research. We thank Professor Edward
[
26] G.M. Sheldrick, Acta Crystallogr., Sect. A 46 (1990) 467.
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ment, University of G o¨ ttingen, Germany, 1996.
[
1
Rosenberg for help in obtaining the 400 MHz H NMR spec-
Tuesday May 23 10:52 AM
StyleTag -- Journal: POLY (Polyhedron) Article: 3428