Synthesis, characterization and chemistry of some long chain alkoxycarbonyl manganese pentacarbonyl complexes [Mn(CO)5{C(O)OR}] (where R=n-C7H15 to n-C10H21, n-C12H25, n-C14

Article abstract of DOI:10.1016/S0022-328X(98)00644-5

The long chain alkoxycarbonyl complexes, [Mn(CO)₅{C(O)OR}], where R=CH₂R′, and R=n-C₇H₁₅ to n-C₁₀H₂₁, n-C₁₂H₂₅ and n-C₁₆H₃₃, have been synthesize

Full text of DOI:10.1016/S0022-328X(98)00644-5

Journal of Organometallic Chemistry 564 (1998) 267–276
Synthesis, characterization and chemistry of some long chain
alkoxycarbonyl manganese pentacarbonyl complexes
[
Mn(CO) {C(O)OR}] (where R=n-C H to n-C H , n-C H ,
5
7
15
10 21
12 25
n-C H , and n-C H )
14
29
16 33
1
Xiaolong Yin *, Jo-Ann M. Andersen , Alan Cotton, John R. Moss
Department of Chemistry, Uni6ersity of Cape Town, Rondebosch 7701, South Africa
Accepted 27 April 1998
Abstract
The long chain alkoxycarbonyl complexes, [Mn(CO) {C(O)OR}], where R=CH R%, and R=n-C H to n-C H , n-C H
12 25
5
2
7
15
10 21
and n-C H , have been synthesized by the reactions of the acyl complexes [Mn(CO) {C(O)R%}], where R%=n-C H to n-C H ,
16
33
5
6
13
9
19
n-C H and n-C H , with synthesis gas in hexane. In addition, the complexes [Mn(CO) {C(O)OR}] (R=n-C H and
11
23
15 31
5
9
19
n-C H ) have been synthesized by the reactions of the alkyl complexes [Mn(CO) R%%], where R%%=n-C H and n-C H , with
14
29
5
8
17
13 27
synthesis gas in hexane. These new alkoxycarbonyl complexes have been fully characterized by elemental analysis, melting point,
1
13
IR, H-NMR, C-NMR and mass spectroscopy. The thermal behaviour of these complexes has been investigated by differential
scanning calorimetry and thermal gravimetry analysis. The reaction of the acyl complex [Mn(CO) {C(O)C H }] with synthesis
5
11 23
gas in THF gave [Mn (CO) ] (95%) and the alcohol n-C H OH (92%). The reaction of the alkoxycarbonyl complex
2
10
12 25
[
Mn(CO) {C(O)OC H }] with synthesis gas in hexane at 85°C gave the formate HCO C H (66%), the alcohol n-C H OH
5 12 25 2 12 25 12 25
(
33%) and [Mn (CO) ] (96%). The same reaction as above in THF yielded the formate HCO C H (12%), the alcohol
2 10 2 12 25
n-C H OH (46%) and the ester CH (CH ) CO C H (43%) as well as [Mn (CO) ] (63%). These studies show that the reactions
12
25
3
2 3
2
12 25
2
10
of the acyl complexes [Mn(CO) {C(O)R%}], the alkyl complexes [Mn(CO) R%%] and the alkoxycarbonyl complexes
5
5
[
Mn(CO) {C(O)OR}] with synthesis gas are both solvent and temperature dependent. © 1998 Elsevier Science S.A. All rights
5
reserved.
Keywords: Manganese; Alkoxycarbonyl; Acyl; Alkyl; Alcohol
1
. Introduction
such as hydroformylation and hydrocarboxylation of
olefins [1–5], carbonylation of alcohols and alkyl
halides [1,6–10], Fischer–Tropsch synthesis [2], synthe-
sis of alkyl carbonates and of oxalate esters [8].
The study of transition metal alkoxycarbonyl com-
plexes [L M{C(O)OR}] is of general interest, because
n
Investigations of the synthesis and chemistry of the
these complexes have been recognized as intermediates
and/or products in a number of important heteroge-
neous and homogeneous catalytic processes [1–10],
alkyl complexes [Mn(CO) R%%] and acyl complexes
5
[
Mn(CO) {C(O)R%}] have been extensively carried out
5
in this laboratory [11–14]. During our studies on the
reactions of such alkyl and acyl complexes with synthe-
*
Corresponding author. Department of Chemistry, University of
sis gas (syngas, CO/H ), we found that the reaction
2
Louisville, Louisville, KY 40292, USA. Fax: +1 502 8528149; e-
mail: x0yin001@homer.louisville.edu
products are largely solvent dependent. Long chain
1
alkoxycarbonyl complexes [Mn(CO) {C(O)OR}] or al-
Current address: School of Chemistry, University of St Andrews,
5
St Andrews, Fife, KY16 9ST, UK.
cohols can be selectively obtained from the reaction of
0022-328X/98/$19.00 © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(98)00644-5

268
X. Yin et al. / Journal of Organometallic Chemistry 564 (1998) 267–276
[
Mn(CO) R%%] (or [Mn(CO) {C(O)R%}]) with CO/H ,
5 5 2
when the solvent is hexane or THF. Some short chain
alkoxycarbonyl complexes [Mn(CO) {C(O)OR}] (R=
5
C H , n-C H ) have been previously reported in the
2
5
6
13
literature [15–17].
We now report our studies (1) on the synthesis of
long chain alkoxycarbonyl complexes [Mn(CO) {C(O)-
5
OR}] (R=CH R%) by the reaction of the acyl com-
2
plexes [Mn(CO) {C(O)R%}] (R%=n-C H to n-C H ,
5
6
13
9
19
n-C H , and n-C H ) with syngas, or by the reaction
1
1
23
15 31
of the alkyl complexes [Mn(CO) R%%] (R%%=n-C H
5
8
17
Scheme 2.
and n-C H ) with syngas in hexane; (2) on some
1
3
27
reactions of the alkoxycarbonyl complexes [Mn(CO)5-
synthesized by the reaction of the alkyl complexes
{C(O)OR}].
[
Mn(CO) R%%] (R%%=n-C H and n-C H ) with syngas
5 8 17 13 27
in hexane. This is to be expected since compounds of
the type [Mn(CO) R%%] are known to react with CO to
5
2. Results and discussion
give [Mn(CO) {C(O)R%%}] under mild conditions [11,14]
5
(
Scheme 2).
2
.1. Synthesis and characterization of alkoxycarbonyl
The new complexes 1–7 were obtained as low-melt-
complexes [Mn(CO) {C(O)OR}]
5
ing white or off-white crystalline solids. These com-
plexes have been fully characterized by melting point,
2
.1.1. Synthesis
The acyl complexes [Mn(CO) {C(O)R%}] (where R%=
1
elemental analysis (Table 1), IR (Table 2), H-NMR
5
13
(
Table 3), and C-NMR (Table 4), and mass spec-
n-C H to n-C H , n-C H , and n-C H ) and the
alkyl complexes [Mn(CO) R%%] (R%%=n-C H and n-
6
13
9
19
11 23
15 31
troscopy (Tables 1 and 5).
5
8
17
C H ) were synthesized according to the methods
reported by Andersen and Moss [11]. The long chain
1
3
27
2
.1.2. Characterization
The IR spectral data of the complexes 1–7 are in
alkoxycarbonyl complexes [Mn(CO) {C(O)OR}] (R=
5
good agreement with the values reported for other
related [Mn(CO) {C(O)OR}] complexes [15–17] and
show peaks (Table 2) in hexane solution at ca. 2124w,
n-C H , 1; n-C H , 2; n-C H , 3; n-C H , 4; n-
7
15
8
17
9
19
10 21
5
C H , 5; and n-C H , 7) were synthesized by the
1
2
25
16 33
reaction of the corresponding acyl complexes
-1
(
A ); 2031s, (E); 2007s cm , (A ); for w(CO) terminal
1
1
[
Mn(CO) {C(O)R%}] with syngas in hexane as shown in
−1
5
carbonyls; and at about 1652m and 1021m cm
for
Scheme 1. This method is similar to that reported by
Orchin and co-workers [16,17] for the preparation of
w(CꢀO) acyl and w(C–O–C), respectively. There is no
significant variation in the w(CO) upon changing the
length of the alkyl chain.
[
Mn(CO) {C(O)OR}] (R=C H and n-C H ).
5 2 5 6 13
Alternatively, the alkoxycarbonyl complexes [Mn-
1
The H-NMR data for the complexes 1–7 reported
(
CO) {C(O)OR}] (R=n-C H , 3, n-C H , 6) can be
5
9
19
14 29
in Table 3 are in good agreement with the data reported
for complexes of the type [Mn(CO) {C(O)OR}] [15–
5
1
1
7]. From the H-NMR data, it can be seen that
separate resonances are observed for the h [h to C(O)O,
etc.] and i protons and the methyl protons of the alkyl
chain. These resonances are not affected by the alkyl
chain length. Thus integration is the only way to distin-
1
guish these complexes by H-NMR spectroscopy. The
resonances of the h and i protons of the alkyl chain in
these alkoxycarbonyl complexes shift downfield com-
pared with the h and i protons in the starting acyl
complexes [11], due to the deshielding effect of the
electron-withdrawing C(O)O group.
13
No C-NMR data have been previously reported for
the alkoxycarbonyl complexes [Mn(CO) {C(O)OR}]
5
13
[
15–17]. We have recorded the C-NMR spectra for
these complexes (except 6) and the data are presented in
Table 4, with suggested assignments. The assignments
were made by comparison with the related acyl com-
Scheme 1.

X. Yin et al. / Journal of Organometallic Chemistry 564 (1998) 267–276
269
Table 1
Data for the alkoxycarbonyl complexes [Mn(CO) {C(O)OR}]
5
Compound no.
n-R
Ma calc.
M+b observed
Yield (%)
M.p. (°C)
Elemental analysis (%)
C found (calc.)
H found (calc.)
1
2
3
4
5
6
C H
338
352
366
380
408
436
464
338
352
366
380
408
436
464
40
44
47
45
87
32
44
51-53
52-54
49-51
48-51
54-55
35-37
49-52
46.25 (46.15)
47.31 (47.73)
48.86 (49.18)
50.23 (50.53)
53.69 (52.95)
c
4.46 (4.44)
4.78 (4.83)
5.06 (5.19)
5.60 (5.53)
6.42 (6.17)
c
7
15
17
19
C H
8
C H
9
C10H21
C12H25
C14H29
C16H33
7c
c
a
b
c
M is the calculated molecular mass.
+
M
is the molecular ion observed in the mass spectrum of the compound.
No satisfactory data were obtained.
plexes [Mn(CO) {C(O)R%}] [11] and by means of a
observed for all the compounds under discussion, but
are of low intensity. The intensities of the major
organometallic peaks of the complexes 5 and 7 are
reported in Table 5 with suggested assignments.
All the complexes show similar fragmentation path-
ways. The fragmentation pathways for the complex 5
are shown in Scheme 3. The predominant fragmenta-
tion pathway is sequential loss of carbonyl groups from
the molecular ion, followed by the loss of the OR
5
heteronuclear correlation (HETCOR) experiment. For
all the complexes, the spectra show the terminal car-
bonyl resonance at l 208 ppm and the alkoxycarbonyl
carbon (CꢀO) resonance at l 200 ppm in CDCl solu-
3
tion. In C D solution, the resonances of the terminal
6
6
carbonyl and the alkoxycarbonyl carbon atoms are
found at l 208 and 198 ppm, respectively. These do not
show any variation in chemical shifts with increase in
the length of the alkyl chain. The resonances due to the
central methylene carbon atoms were not completely
resolved and could not be assigned unambiguously, as
was observed for the long chain acyl complexes [11].
The low resolution electron impact mass spectra for
the complexes 1–7 were recorded. Molecular ions are
group. The spectra of these complexes exhibit peaks
+
corresponding to the ions [Mn(CO) ]
(m/z 223),
(m/z 167),
6
+
+
[
[
[
Mn(CO)5]
(m/z 195), [Mn(CO)4]
+
+
Mn(CO)3]
(m/z 139), [Mn(CO)2]
(m/z 111),
+
+
+
Mn(CO)] (m/z 83), [Mn] (m/z 55), [CO2] (m/z 44)
+
and [CO] (m/z 28).
Table 2
2
.1.3. Thermal properties of the alkoxycarbonyl
IR spectroscopic data for the alkoxycarbonyl complexes
[
Mn(CO) {C(O)OR}] in hexane
complexes [Mn(CO) {C(O)OR}]
5
5
The thermal behaviour of the complexes 1–4 and 7
was studied by DSC. The results are summarized in
Table 6. A sharp endothermic peak is seen for each
complex in the temperature range which corresponds to
the melting range measured by conventional means
Compound n-R
no.
IR (cm−1)
wꢁ(CO)
w(CꢀO)
w(C–O–C)
1022m
1022m
1020m
1022m
1021m
1022m
1024m
1
2
3
4
5
6
7
C H
2124w, 2031s, 1652m
007s
2124w, 2031s, 1652m
007s
2124w, 2031s, 1651m
008s
C10H21 2124w, 2031s, 1652m
007s
C12H25 2126w, 2033s, 1654m
010s
C14H29 2126w, 2029s, 1657m
010s
C16H33 2125w, 2031s, 1654m
008s
7
15
17
19
2
(
Kofler hot-stage microscope). A slight increase of the
C H
8
melting point (Tmax) with the increase of alkyl chain
length from n=8 to 10 was observed. Another broad
endothermic peak is observed in the DSC traces in the
temperature range 103–140°C, all with a maximum at
2
C H
9
2
2
1
21–123°C, which corresponds to the decomposition of
the complexes. This is supported by the observation of
a significant mass loss in the TGA traces of these
complexes over the temperature range 80–140°C. The
mass remaining after heating these complexes to 200°C
corresponds to the degradation of the alkoxycarbonyl
complexes to MnO2.
2
2
2
W, weak; s, strong; m, medium.

270
X. Yin et al. / Journal of Organometallic Chemistry 564 (1998) 267–276
Table 3
1
H-NMR data for the alkoxycarbonyl complexes [Mn(CO) {C(O)OR}] (400 MHz, CDCl )
5
3
Compound no.
n-R
C(O)OCH
J(HH)
C(O)OCH CH
J(HH)
C(O)OCH CH (CH )
CH
3
J(HH)
2
2
2
2
2
2 n
3
3
3
1
2
C H
4.03, 2H, br
4.05, 2H, t, 6.4 Hz
4.04, 2H, br
4.04, 2H, br
4.03, 2H, br
1.59, 2H, br
1.59, 2H, qn, 6.1 Hz
1.59, 2H, br
1.58, 2H, br
1.58, 2H, br
1.27, 8H, br
1.27, 10H, br
1.26, 12H, br
1.26, 14H, br
1.25, 18H, br
1.26, 22H, br
1.25, 26H, br
0.87, 3H, br
0.87, 3H, t, 6.6 Hz
0.87, 3H, br
0.87, 3H, br
0.87, 3H, br
7
15
17
19
a
C H
8
3
4
5
6
7
C H
9
C10H21
C12H25
C14H29
C16H33
4.04, 2H, t, 6.4 Hz
4.04, 2H, br
1.58, 2H, br
1.58, 2H, br
0.87, 3H, t, 6.8 Hz
0.87, 3H, br
Br, broad; t, triplet; qn, quintet.
a
The 1H-NMR spectrum for this compound was recorded at 200 MHz in CDCl3.
2
.2. Reacti6ity of acyl complexes [Mn(CO) {C(O)R%}],
[HMn(CO) ] could be formed under the reaction condi-
5
5
alkyl complexes [Mn(CO) R%%] and alkoxycarbonyl
tions, and this hydride might be able to protonate the
acyl complex to give a hydroxycarbene species, which
5
complexes [Mn(CO) {C(O)OR}]
5
can then undergo reaction with H , as shown in step (a)
2
2
.2.1. Reactions of the acyl complex
of Scheme 6. The formation of hydroxycarbene species
by protonolysis of acyl complexes has been demon-
strated [21,22] and the crystal structure of a cationic
hydroxycarbene (shown below)
[Mn(CO) {C(O)C H }] and the alkyl complex
5
11 23
[Mn(CO) (C H )] with syngas in THF: synthesis of
5 9 19
alcohols
We have shown that the reactions of alkyl complexes
+
−
[
CH3 CꢀMn(CO) (DPPP)] CF SO
–
3
3
3
[
Mn(CO) R%%] or acyl complexes [Mn(CO) {C(O)R%}]
5
5
(
DPPP=bis(diphenylphosphino)propane)
with syngas in hexane give the alkoxycarbonyl com-
plexes [Mn(CO) {C(O)OR}] (R=CH R% or CH R%%) as
5
2
2
has been determined [22]. (2) In non-polar solvents,
such as in hexane, the reaction might take place via
another route, as shown in step (b) of the Scheme 6, to
produce the alkoxycarbonyl species. The ruthenium
complex (see below) containing a four-membered
metallacycle similar to that of the key intermediate A in
Scheme 6 has recently been reported [23].
the sole products. Similar results have also been ob-
tained by Orchin and co-workers [16,17]. However, the
reactions of the acyl complexes [Mn(CO) {C(O)R%}]
5
with syngas in the highly polar solvent sulfane were
reported to give exclusively aldehydes [17,18].
We have carried out the reactions of the acyl com-
plex [Mn(CO) {C(O)C H }] and the alkyl complex
5
11 23
[
Mn(CO) (C H )], respectively, with syngas in THF
5 9 19
and found that these reactions give exclusively alcohols
and [Mn (CO) ] (Schemes 4 and 5). These products
2
10
were isolated by chromatography on a short silica gel
column and identified by their melting points, IR,
1
13
H-NMR, C-NMR and mass spectroscopy. No alde-
Orchin and co-workers have proposed another mech-
hyde, formate, or the alkoxycarbonyl complex was
detected for these reactions.
The formation of alcohol from the reaction of
anism for the formation of [Mn(CO) {C(O)OR}], and
5
suggested that the insertion of CO into the Mn–OR
bond of intermediates [Mn(CO) (OR)] might be the key
5
[
Mn(CO) {C(O)C H }] with syngas in THF has pro-
5 11 23
step for the formation of [Mn(CO) {C(O)OR}] [16,17].
5
vided further evidence for the previous proposal that
the acyl complexes [Mn(CO) {C(O)R%}] (R%=R%%) are
the most probable intermediates in the reactions of
5
2
.2.2. Reacti6ity of the alkoxycarbonyl complexes
[Mn(CO) {C(O)OR}]
5
[
[
[
Mn(CO) R%%] with syngas [14,20], since the reaction of
5
The reaction of the short chain complex
Mn(CO) R%%] with CO is known to give
5
[Mn(CO) {C(O)OC H }] with acids was reported to
give cationic carbonyls [Mn(CO) ] (and C H OH as
6 2 5
the organic product) [24,25]. It was also reported [26]
that the reactions of [Mn(CO) {C(O)OC H }] with
5 2 5
Mn(CO) {C(O)R%}] (R%=R%%) [11,14,21].
+
5
Since different products were obtained by the reac-
tions of acyl complexes [Mn(CO) {C(O)R%}] with syn-
5
5
2
5
gas in different solvents, this suggests that the solvents
play a crucial role in these reactions. The effect of the
solvents could be rationalized as follows: (1) in the
polar, coordinating solvents, such as in THF,
[HCo(CO) ] or [HMn(CO) ] give ethyl formate and
4 5
[MnCo(CO) ], or ethyl formate and [Mn (CO) ], re-
9
2
10
spectively.
The
reactivity
of
long
chain
[Mn(CO) {C(O)OR}] complexes, especially the reactiv-
5

X. Yin et al. / Journal of Organometallic Chemistry 564 (1998) 267–276
271
Table 4
1
3C-NMR chemical shift (l ppm) data for the alkoxycarbonyl complexes [Mn(CO)5{C(O)OR}] (100 MHz, CDCl3)
a
2
b
2 n
Compound no. n-R
CO
C(O)O
OCH2 OCH CH
OCH CH (CH )
CH CH CH CH CH CH3
2
2
2
2
2
3
2
3
1
2
3
3
4
5
7
C H
207.84
207.90
207.83
208.45
200.30
200.31
200.31
197.81
e
64.54
64.54
64.55
64.70
64.56
64.57
64.57
31.75
31.75
31.85
29.58
31.88
31.92
31.92
29.08, 28.88
29.18, 29.09
29.50, 29.20, 29.09
26.07
26.11
26.11
26.45
26.12
26.13
26.13
22.54
22.61
22.65
23.06
22.66
22.69
22.68
14.03
14.01
14.07
14.31
14.08
14.11
14.10
7
15
17
19
19
c
C H
8
C H
9
d
C H
32.23, 29.91
9
C10H21 207.97
C12H25 207.82
C16H33 207.86
29.50, 29.29, 29.23, 29.09
29.64, 29.56, 29.35, 29.25, 29.10
29.68, 29.56, 29.35, 29.25, 29.10
200.32
200.33
a
b
c
The resonance for this carbon atom was assigned tentatively.
Peaks for these carbon atoms were not completely resolved or assigned.
13
The C-NMR spectrum for this compound was measured at 50 MHz.
d
e
C D , the assignments were confirmed by a HETCOR experiment.
6
6
This peak was not observed.
1
13
ity of these complexes under conditions similar to hy-
droformylation conditions, is unknown. We now report
organic products was made by IR, H and C-NMR,
and mass spectroscopy (Scheme 7).
the reactions of [Mn(CO) {C(O)OR}] complexes with
The formation of the formate HCO C H25 by the
2 12
5
syngas in hexane and in THF.
reaction of the alkoxycarbonyl complex 5 with syngas
under hydroformylation conditions is not unexpected.
In fact, formates have been reported as by-products in
the Fischer–Tropsch synthesis [2,27], and alkoxycar-
bonyl complexes have been suggested as intermediates
for the formate formation [1]. Hence, the manganese
complexes may serve as model complexes for intermedi-
ates involved in the Fischer–Tropsch synthesis. The
2
.2.2.1. Reaction of [Mn(CO) {C(O)OC H }], 5 with
5
12 25
syngas in hexane. The reaction of 5 with CO/H (48
2
bar) in hexane was carried out at 85°C for 11 h, and
gave [Mn (CO) ] quantitatively. The organic products
2
10
isolated by chromatography were dodecyl formate
HCO C H in 33% yield, and dodecyl alcohol n-
2
12 25
C H OH in 66% yield. The identification of these
production of methyl formate by the reaction of CO ,
2
1
2
25
H and MeOH might also involve alkoxycarbonyl inter-
2
mediates [28].
Table 5
Mass spectral data for [Mn(CO) {C(O)OR}]
5
Iona
Relative intensitiesb (%)
R=n-C12H25, 5
R=n-C16H33, 7
M
M–CO
0.3
3
0.4
2
M–4CO
M–5CO
0
2
0.2
1
M–6CO
M–R
100
0.5
1
0.3
0.4
0.4
0.5
21
6
4
4
5
7
100
0.7
0.2
0.3
0.4
0.9
1
20
7
3
4
6
10
27
M–R–CO
M–R–2CO
M–R–3CO
M–R–4CO
M–R–5CO
M–OR
M–OR–CO
M–OR–2CO
M–OR–3CO
M–OR–4CO
M–OR–5CO
M–OR–6CO (ꢀMn)
26
a
M=[Mn(CO) {C(O)OR}]; all ions have a single positive charge;
5
ion refers to probable assignment.
b
Peak intensities are relative to [M–6CO], i.e. [MnOR].
Scheme 3.

272
X. Yin et al. / Journal of Organometallic Chemistry 564 (1998) 267–276
Table 6
Thermal analysis data for the complexes [Mn(CO) {C(O)OR}]
5
M.p. (°C)a
T (°C)b
Tmax (°C)c
DHendo (kJ mol
−1 d
)
Compound no.
n-R
i
1
2
3
4
7
C H
51–53
52–54
49–51
48–51
49–52
54.8
52.7
53.2
53.5
54.1
56.4
54.5
55.5
58.0
56.6
24.46
21.72
28.77
27.46
32.75
7
15
17
19
C H
8
C H
9
C10H21
C16H33
a
Determined on a Kofler hot-stage microscope.
Temperature corresponding to the onset of a peak.
b
c
Temperature corresponding to the peak maximum.
d
Calculated by Perkin Elmer PC Series DSC7 machine (J g−1).
2
.2.2.2. Reaction of [Mn(CO) {C(O)OC H }], 5 with
coordinating ligand THF, the solvent might be coordi-
nated to the manganese centre yielding the THF-coordi-
5
12 25
syngas in THF. Since solvents play a crucial role in
product formation, we have also investigated the reac-
tion of 5 with syngas in THF. The reaction was carried
out at 60°C for 23 h under a pressure of 48 bar of
nated
intermediate
[Mn(CO) (THF){C(O)OR}].
4
Solvents-coordinated acyl complexes [Mn(CO) (S)-
4
{C(O)R}] (S=DMSO and DMF) have been previously
CO/H2.
Chromatographic
separation
yielded
reported [19], and the THF-coordinated species
+
[
Mn (CO) ] in 63% yield. The hydride [HMn(CO) ] was
[Mn(CO) (THF)] has been proposed [14]. Direct evi-
2
10
5
5
detected by IR spectroscopy but this complex was not
isolated owing to its instability. The organic products
obtained by column chromatography were the alcohol
n-C H OH in 46% yield and the formate HCO C H
dence for the formation of the intermediate
[Mn(CO) (THF){C(O)OR}] complex, however, has not
4
been obtained.
1
2
25
2
12 25
in 12% yield. Similar products were obtained for the
reaction in hexane. In addition, another product was
obtained in 43% yield. This product was identified as the
ester CH (CH ) CO (CH ) CH , on the basis of its
mass spectrum ([M] , 271), IR, H and C-NMR.
The isolation of the ester product from the reaction of
3. Conclusion
A series of new long chain alkoxycarbonyl manganese
pentacarbonyl complexes [Mn(CO) {C(O)OR}] has
3
2 3
2
+
2 11
3
1
13
5
been synthesized and fully characterized. The results of
the reactions of manganese pentacarbonyl alkyl, acyl
and alkoxycarbonyl complexes with syngas in hexane
and THF show solvent effects. These reactions are
relevant to catalytic reactions such as hydroformylation
and the Fischer–Tropsch synthesis, where metal alkyl,
acyl and alkoxycarbonyl species have been proposed as
key intermediates.
5
with syngas in THF strongly implied that the solvent
THF reacted with 5 under these conditions. Our results
show that the solvent indeed plays a crucial role in
determining the nature of the products obtained from
the reaction of alkoxycarbonyl complexes with syngas.
We propose the following mechanism, as shown in
Scheme 8, to account for the products obtained in
hexane and in THF. The routes (a) and (b) in Scheme
8
apply to the reaction in the non-polar solvent—hex-
ane, whereas the routes (a), (b) and (c) for the reaction
in the polar, coordinating solvent—THF (Scheme 9).
The CO dissociation from the alkoxycarbonyl com-
4. Experimental
All reactions were carried out under an atmosphere of
high purity nitrogen using standard Schlenk tube tech-
niques unless otherwise stated. Tetrahydrofuran (THF)
and hexane were dried by distilling over sodium/bene-
zophonone. [Mn (CO) ] was obtained from Strem
plex [Mn(CO) {C(O)OR}] may form the 16-electron
5
intermediate [Mn(CO) {C(O)OR}], which has been ob-
4
served in the mass spectra of the alkoxycarbonyl com-
plexes. The intermediate [Mn(CO) {C(O)OR}] may
4
2
10
undergo: (a) alkoxy group migration to form the alkoxy
Chemical Inc. and the compounds Cl(CO)(CH ) CH
2 n 3
complex [Mn(CO) (OR)], which can then be proto-
nated; (b) proton coordination followed by elimination
to yield the formate; and (c) in the presence of the
were obtained from Aldrich, and were used without
further purification. Alumina (BDH, active neutral,
Brockman grade I) was deactivated before use.
5
Scheme 4.
Scheme 5.

X. Yin et al. / Journal of Organometallic Chemistry 564 (1998) 267–276
273
Scheme 6.
Melting points were recorded on a Kofler hot-stage
microscope (Reichert-Thermovar) and are uncorrected.
Differential scanning calorimetry (DSC) and thermal
gravimetry analysis (TGA) were performed on a
Perkin-Elmer PC Series 7 instrument under a nitrogen
solvent signals were used as references and the chemical
shifts adjusted accordingly. Low resolution mass spec-
tra were recorded with a VG Micromass 16F spectrom-
eter operated at 70 eV ionizing voltage and using an
accelerating voltage of 4 kV. All high pressure reactions
were carried out in a 250 ml Berghoff autoclave.
−
1
atmosphere with a heating rate of 10 or 20°C min
.
Microanalyses were performed by the University of
Cape Town Microanalytical Laboratory. Infrared spec-
tra were recorded on either a Perkin-Elmer 983 or a
Paragon 1000 FT-IR spectrophotometer in solution
cells with NaCl windows.
The acyl complexes [Mn(CO)
13 to n-C
alkyl complexes [Mn(CO)
27) were prepared according to the literature meth-
5
{C(O)R%}] (R%=n-
31) and the
R%%] (R%%=n-C H17 and n-
8
C
H
H19, n-C11H23, and n-C15H
9
6
5
C H
13
ods [11].
1
H-NMR spectra were recorded on a Varian XR 200
(
4
at 200 MHz) spectrometer or a Varian Unity 400 (at
4.1. Synthesis of [Mn(CO) {C(O)OR}] (R=CH R%)
5 2
13
00 MHz) spectrometer.
C-NMR spectra were
recorded on the Varian XR 200 (at 50 MHz) spectrom-
eter or the Varian Unity 400 (at 100 MHz) spectrome-
ter. The chemical shifts are relative to TMS (0 ppm) in
The complexes [Mn(CO)
1–4 and 7) were synthesized by the reactions of the acyl
{C(O)OR}] (R=CH R%,
5 2
complexes [Mn(CO)
{C(O)R%}] (R%=n-C H13 to n-
6
5
1
13
the H and C-NMR spectra, where the deuterated
Scheme 7.
Scheme 8.

274
X. Yin et al. / Journal of Organometallic Chemistry 564 (1998) 267–276
Scheme 9.
C H , n-C H and n-C H ) with syngas (CO/H )
4.2. Reacti6ity of alkyl complexes [Mn(CO) R%%], acyl
9
19
11 23
15 31
2
5
in hexane according to the following general proce-
dure.
complexes [Mn(CO) {C(O)R%}] and alkoxycarbonyl
5
complexes [Mn(CO) {C(O)OR}]
5
In a typical reaction, the autoclave was charged
with the acyl complex [Mn(CO) {C(O)R%}] (ca. 200
4.2.1. Reaction of the acyl complex
5
mg) in hexane (10 ml) with a stirrer bar in a flask
[Mn(CO) {C(O)C H }] with syngas in THF: synthesis
5
11 23
and was sealed. The autoclave was filled with CO/H2
of alcohol
(
20 bar) and the gas vented. This procedure was re-
The reaction was carried out in an autoclave which
was charged with [Mn(CO) {C(O)C H }] (0.20 g, 0.53
peated two more times and then the autoclave was
5
11 23
pressurized with CO/H until a total pressure of 40
mmol) and THF (15 ml). The autoclave was sealed and
filled with syngas to 20 bar and the gas vented. This
procedure was repeated two more times. The autoclave
was then pressurized with syngas to 48 bar. The solu-
tion was then heated at 60°C for 8 h with stirring. The
autoclave was allowed to cool to room temperature and
the gases vented. A yellow solution was obtained,
which, after removing the solvent under vacuum, gave a
yellow solid. The IR spectrum of the solvent that was
removed showed two w(CO) bands at 2020s, 1995s
2
bar was reached. The reaction mixture was then
heated to ca. 60°C for 3 h. The autoclave was cooled
to room temperature and the gases vented. The sol-
vent was removed, leaving a yellow residue. This was
then dissolved in a minimum amount of petroleum
ether (b.p. 40–60°C) and the solution cooled to −
7
8°C to crystallize the product. The product was re-
crystallized again to give the alkoxycarbonyl complex
Mn(CO) {C(O)OR}] (R=CH R%) as an off-white mi-
[
5
2
−
1
crocrystalline solid.
cm , suggesting that the solvent contained a small
The complex [Mn(CO) {C(O)OC H }], 5 was simi-
amount (B5%) of [HMn(CO) ] [29]. The yellow solid
5
12 25
5
larly prepared by the reaction of [Mn(CO)5-
C(O)C H }] (2.50 g, 6.3 mmol) with CO/H (45 bar)
was dissolved in a minimum amount of CH Cl /pen-
tane (25%) and chromatographed on a short silica gel
2
2
{
1
1
23
2
o
in hexane (20 ml) at 60 C, with a longer reaction time
15 h). Recrystallization from pentane twice at −78°C
column (7 cm x 2 cm). Elution with 5% CH Cl /pen-
2
2
(
tane separated a yellow band, which, on evaporation of
the solvent and drying under vacuum, yielded a yellow
solid identified as [Mn (CO) ] (0.097 g, 95%), on the
gave 5 (2.35 g, 87%) as a white microcrystalline solid.
The complexes [Mn(CO) {C(O)OR}] (R=n-C H ,
5
9
19
2
10
3
and n-C H , 6) were also synthesized by the reaction
basis of its IR spectrum (w(CO) in Nujol mull, 2045s,
1
4
29
−
1
of the alkyl complexes [Mn(CO) R%%}] (R%%=n-C H
and n-C H ) with syngas in hexane using a similar
2013vs, 1983m cm , these data are the same as the IR
spectrum of authentic [Mn (CO) ]). Elution with
5
8
17
1
3
27
2
10
procedure as described above.
CH Cl separated a second band which was colourless.
2 2

X. Yin et al. / Journal of Organometallic Chemistry 564 (1998) 267–276
275
After removing the solvent and drying under vacuum,
this gave an off-white solid (m.p. 24–27°C) which was
identified as n-C H OH (0.090 g, 92%; literature m.p.
vented. The reaction had gone to completion and a
yellow solution was obtained. After removing the sol-
vent under vacuum, a mixture of white and yellow
solids was obtained. The IR spectrum of the removing
solution showed two w(CO) bands at 2019s, 1993s
1
2
25
1
[
30]: 26°C), on the basis of its IR, MS, H-NMR and
1
3
+
C-NMR data. Low-resolution MS: 179 (M–OH) ;
−
1
−1
IR w/cm
(neat): 3343m, br (wOH), 2925s, 2854s
cm , suggesting that the solution contained [HM-
1
[
w(CH +CH )], 1466m, 1378w, 1056m, 720w; H-
n(CO) ] [29]. The solid mixture was dissolved in a
2
3
5
NMR (CDCl ) l (ppm): 3.88 (2H, b, CH O), 2.46 (1H,
minimum amount of CH Cl /pentane (5%) and chro-
2 2
3
2
b, OH), 1.53 (2H, m, CH CH O), 1.25 (18H, b, 9×
matographed on a short silica gel column (7 cm×2
cm). Four fractions were obtained. The first fraction,
2
3
2
1
CH ), 0.86(3H, b, CH ); C-NMR (CDCl ) l (ppm):
2
3
3
6
2
3.44 (CH OH), 32.94, 31.92, 29.62, 29.46, 29.35, 25.80,
eluted with 5% CH
Evaporation of the solvent and drying under vacuum
gave yellow solid, which was identified as
[Mn (CO)10] (0.06 g, 63%), on the basis of its IR
spectrum. The other fractions were eluted with CH Cl .
2 2
Cl /pentane, was a yellow band.
2
2.68, 14.09 (CH ). These data are in good agreement
3
1
13
with the reported IR [31], H-NMR [32] and C-NMR
33] data.
a
[
2
2
2
4
.2.2. Reaction of [Mn(CO) {C(O)OC H }] with
The second band gave a white solid product and was
identified as n-C12 25OH (0.04 g, 46%), on the basis of
its IR spectrum and H-NMR. The next product was
identified as an ester CH (CH CO (CH (0.06
g, 43%), on the basis of its mass spectrum, IR, H and
5
12 25
syngas in hexane at 85°C
H
1
A solution of [Mn(CO) {C(O)OC H }] (0.13 g, 0.32
5
12 25
mmol) in hexane (10 ml) in a flask was placed in an
autoclave. The autoclave was sealed and filled with
syngas to 20 bar and the gas vented. This procedure
was repeated two more times. The autoclave was pres-
surized with syngas to 48 bar, then heated at 85°C for
3
2
)
3
2
)11CH
2 3
1
13
C-NMR. The last product was identified as
HCO C H (ca. 0.015 g, 12%), on the basis of its IR
2
12 25
1
and H-NMR.
11 h with stirring. The autoclave was allowed to cool to
room temperature and the gases vented. A yellow solu-
tion was obtained, which, after removing the solvent
under reduced pressure, gave a mixture of white and
yellow solids. This mixture was dissolved in a minimum
amount of CH Cl /hexane (5%) and chromatographed
Acknowledgements
We thank the University of Cape Town, SASOL and
FRD for support.
2
2
on a short silica gel column (7×2 cm). Three fractions
were obtained. Elution with 5% CH Cl /hexane sepa-
2
2
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