Indenols, indenones and (arylcyclohexadienyl)Mn(CO)3 π-complexes from the thermally promoted reactions of alkynes with ortho-Mn(CO)4 aryl ketone, amide, ester and aldehyde derivatives

Article abstract of DOI:10.1016/j.jorganchem.2005.04.050

Thermally promoted reactions of a range of alkynes with the orthomanganated acetophenone (η²-2-acetylphenyl)Mn(CO)₄ generally give 1H-inden-1-ols in good yield; effects of substituents and solvent on these reactions are reported, along with the crystal structure of 1-methyl-2,3- diphenyl-1H-inden-1-ol. The corresponding orthomanganated benzophenone similarly gives the indenol with diphenylacetylene but by exception, orthomanganated 3-acetylthiophene with phenylacetylene reacts via triple alkyne insertion and cyclisation, shown by crystal structure determination of the π-complex product [(1,2,3,4,5-η)-2-(3-acetylthien-2-yl)-1,3,5- triphenylcyclohexadienyl]tricarbonylmanganese. Corresponding orthomanganated derivatives of N,N-dimethylbenzamide, methyl 3,4,5-trimethoxybenzoate and 4-dimethylaminobenzaldehyde all give indenones with diphenylacetylene, but with (excess) acetylene only the aldehyde gives an indenone, the amide and ester giving instead [(1,2,3,4,5-η)-6-arylcyclohexadienyl]Mn(CO)₃ complexes. ¹H NMR analysis of these complexes shows H at C6 to be on the same face of the cyclohexadienyl ring as Mn(CO)₃ (endo-6-H; exo 6-aryl) as expected from three successive syn additions of alkyne at metallated carbon followed by intramolecular syn addition of alkene in the final cyclisation stage.

Full text of DOI:10.1016/j.jorganchem.2005.04.050

Journal of Organometallic Chemistry 690 (2005) 3827–3837
www.elsevier.com/locate/jorganchem
Indenols, indenones and (arylcyclohexadienyl)Mn(CO)3
p-complexes from the thermally promoted reactions of alkynes with
ortho-Mn(CO)4 aryl ketone, amide, ester and aldehyde derivatives
*
Nicholas P. Robinson, Gary J. Depree, Rene W. de Wit, Lyndsay Main ,
*
Brian K. Nicholson
Department of Chemistry, School of Science and Technology, University of Waikato, Private Bag 3105, Hamilton, New Zealand
Received 24 February 2005; accepted 15 April 2005
Available online 22 June 2005
Dedicated to colleague and mentor Professor Ken Mackay on the occasion of his 70th birthday
Abstract
Thermally promoted reactions of a range of alkynes with the orthomanganated acetophenone (g2-2-acetylphenyl)Mn(CO)4 gen-
erally give 1H-inden-1-ols in good yield; effects of substituents and solvent on these reactions are reported, along with the crystal
structure of 1-methyl-2,3-diphenyl-1H-inden-1-ol. The corresponding orthomanganated benzophenone similarly gives the indenol
with diphenylacetylene but by exception, orthomanganated 3-acetylthiophene with phenylacetylene reacts via triple alkyne insertion
and cyclisation, shown by crystal structure determination of the p-complex product [(1,2,3,4,5-g)-2-(3-acetylthien-2-yl)-1,3,5-triphe-
nylcyclohexadienyl]tricarbonylmanganese. Corresponding orthomanganated derivatives of N,N-dimethylbenzamide, methyl 3,4,5-
trimethoxybenzoate and 4-dimethylaminobenzaldehyde all give indenones with diphenylacetylene, but with (excess) acetylene only
1
the aldehyde gives an indenone, the amide and ester giving instead [(1,2,3,4,5-g)-6-arylcyclohexadienyl]Mn(CO)3 complexes. H
NMR analysis of these complexes shows H at C6 to be on the same face of the cyclohexadienyl ring as Mn(CO)3 (endo-6-H; exo
6-aryl) as expected from three successive syn additions of alkyne at metallated carbon followed by intramolecular syn addition
of alkene in the final cyclisation stage.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Manganese; Metallocycle; Alkyne coupling; Indenol; Cyclohexadienyl complex; Crystal structure
1. Introduction
communication in a review, reporting thermal activation
to be applicable also to the formation of indenones from
cyclomanganated aryl amides, esters and some alde-
hydes [3]. The cyclopentannulation method has been ap-
plied to preparation of ring C aromatic steroidal
analogues from orthomanganated ketone derivatives
of the natural product podocarpic acid [4] and to the
formation of 1-indenylhydrazines through alkyne-cou-
pling reactions of cyclomanganated N,N-diphenylhyd-
razones of acetophenone and benzaldehyde [5]. We
now report more fully on factors influencing the out-
come of the thermally promoted reactions, including
Cyclomanganated aryl ketones were first shown to
couple with alkynes at the metalated ortho-carbon to
form 1H-inden-1-ols (2; Scheme 1) via activation at
the metal center by oxidative decarbonylation with tri-
methylamine oxide in acetonitrile [1] or by thermal acti-
vation in benzene [2]. We expanded the latter
*
Corresponding authors. Tel.: +64 7 8562889; fax: +64 7 8384219.
E-mail addresses: l.main@waikato.ac.nz (L. Main), b.nicholson@
waikato.ac.nz (B.K. Nicholson).
0022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.04.050

3828
N.P. Robinson et al. / Journal of Organometallic Chemistry 690 (2005) 3827–3837
OH
Mn(CO)
4
3
R
2
R
2
O
R
2
R
O
R
R
1
3
5
1
2
3
2
3
1
R
1
2
R
2
Mn(CO)
1
R
4
CO
2'
6
3
1
R
2
1
R
7
6
1
7
CR
R C
1
2
1
R
2
R
3'
4'
4
6
1'
6'
4
6
4
5
1
5
5
3
2
4
5'
Scheme 1. Alternative products from alkyne-coupling reactions.
the competing formation in some cases of p-cyclohexa-
dienyltricarbonylmanganese complexes, products of tri-
ple alkyne insertion not so far reported from the
oxidative activation method, and the X-ray crystal
structural determination of one such complex.
on the metal prior to syn-addition (step (i)). The pro-
posed route to cyclohexadienyl complexes 3 involves a
sequence of successive syn additions (steps (i), (iii) (vi)
which would lead as shown to R1 at C6 being on the
same face of the cyclohexadienyl complex as the Mn
moiety (endo position).
2. Results and discussion
2.1. 1H-inden-1-ol formation
Products and yields under a range of conditions are
summarized in the Table 1. Likely routes to products,
in the case of 2 as suggested earlier [1,2], are indicated
in Scheme 2, which for space excludes the presumed ini-
tial coordination of alkyne to a vacant coordination site
Results indicate a useful general route to indenols,
which is not significantly sterically limited if the 85% yield
of 1,2,3-triphenylindenol (2j; entry 20: Table 1) is any
guide. The ready availability of substituted acetophe-
nones, and the range of alkynes that could be used, means
Table 1
Products from alkyne-coupling reactions
Entry
Reactant
Alkyne R1, R2 (mol/mol reactant)
Solvent (reflux period/h)
Yield/% (Producta)
1
2
1a (R = Me)
Ph, Ph (1.1)
(1.5)
(1.5)
C6H6 (8)
98 (2a)
90
Pet. sp.b (7)
MeCN (3)
CCl4 (3)
3
78
57
51c
4
(1.5)
5
(1.1)
MeOH (18)
C6H6 (18)
C6H6 (18)
C6H6 (64)
C6H6 (4.5)
Pet. sp.b (24)
MeCN (1)
CCl4 (3)
6
H, H (satd)d
Pr, Pr (1.1)
SiMe3, SiMe3 (1.1)
CO2Me, CO2Me (1.5)
(1.5)
64 (2b)
51 (2c)
7
8
9 (2d)
67 (2e)
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
a
54
91
(1.5)
(1.5)
87
H, Ph (1.1)
(3.0)
C6H6 (3)
C6H6 (3.5)
C6H6 (2)
43 (2f) + 3 (3a)e
84 (2f) + 14 (3a)e
82 (2g)
H, SiMe3 (3.5)
Me, Pr (0.7)
(0.7)
C6H6 (22)
MeCN (3.5)
CCl4 (7)
Pet. sp.b (5)
C6H6 (18)
C6H6 (1)
51f(ca. 2:1 2h:2i)g
38f (ca. 2:1 2h:2i)g
36f (ca. 2:1 2h:2i)g
60 (ca. 3:1 2h:2i)g
85 (2j)
(0.7)
(1.8)
1b: R = Ph
1c: R = NMe2
Ph, Ph (1.1)
Ph, Ph (1.1)
H, H (satdd)
Ph, Ph (1.1)
H, H (satdd)
Ph, Ph (1.1)
H, H (satdd)
Ph, H
56 (4a)
55 (3b)
C6H6 (2)
C6H6 (1)
1d: R = OMe; 4,5,6-(OMe)3
1e: R = H; 5-NMe2
100 (4b; 4,5,6-(OMe)3)
36 (3c; 40,50,60-(OMe)3)
46 (4c; 5-NMe2)
20 (4d; 5-NMe2)
(6)
C6H6 (7)
C6H6 (9)
C6H6 (3.5)
C6H6 (8)
3-Ac-2-thienyl-Mn(CO)4 (5)
Product R, R1, R2 groups as for reactants; other substituents as indicated.
Petroleum spirit; b.p. 60–80 ꢁC.
Demetallated reactant (acetophenone) also formed (22%).
b
c
d
e
f
Acetylene-saturated reaction solution by continuous bubbling of acetylene gas.
Indefinite structural assignment; see discussion section p-Cyclohexadienyl complexes.
Based on alkyne as limiting reagent.
2h (R, R1 = Me, R2 = Pr) and 2i (R, R2 = Me, R1 = Pr) are chromatographically inseparable; ratio by 1H NMR.
g

N.P. Robinson et al. / Journal of Organometallic Chemistry 690 (2005) 3827–3837
3829
O[Mn]
[Mn]
R2
R1
R2
R
R
R
O
O
2
2
2
1
6
Mn(CO)4
R1C
R1C
CR2
CR2
3
3
3
1
1
R1
(i)
(ii)
4
4
4
6
6
5
5
5
2
1
-[Mn]R
[H+]
(iii)
(iv)
R2
(v)
OH
R2
O
R2
R1
R
R
R1
CO
R1
R1
[Mn]
R2
R2
R1
4
2
(vi)
R2 [Mn]
Mn(CO)3
R1
R1
R2
R2
R1
5
4
R
R1
R2
3
R2
CO
R
(vii)
CO
2'
6
R1
1
2
R2
3'
4'
1'
6'
3
5'
Scheme 2. Routes to alternative products. Metal ligands are omitted at intermediate stages: symbol [Mn].
that this reaction can generate specifically substituted
1-methylinden-1-ols, from which, for example, benzoful-
venes can easily be obtained by elimination of water un-
der acidic conditions. There is current interest in
potential applications of a novel thermoreversible solid-
state non-radical polymerisation of a benzofulvene [6].
Other factors for consideration from the current
study are as follows.
carbon in the parent ketone, possibly reflecting a steric
bias in the orientation of alkyne coordination to metal
(not shown Scheme 2) prior to insertion. Similar regio-
specificity was observed for mono-substituted acetylenes
when the coordination site is freed by CO oxidation with
trimethylamine oxide rather than thermally [1], except in
the case of 1-hexyne (12% of the 3-butylindenol isomer),
though alkynes of the form RC2CO2Et inserted with the
ester group adjacent to the aromatic ring, irrespective of
the size of the other acetylene substituent (R = Me, Et,
cyclohexyl), suggesting a possible electronic effect.
2.1.1. Solvent
These thermally promoted reactions proceed in good
or reasonable yield in most solvents studied (products
2a, 2e, 2h/i: entries 1–5, 9–12, 16–19) though protic sol-
vents may promote unwanted demetallation of the par-
ent manganated ketone (2a; entry 5 for MeOH).
Reactions proceeded fastest in acetonitrile where tested
(products 2a, 2e, 2h/i; entries 3, 11 and 17) but not to
an extent that this would normally be an issue in synthe-
sis; if this is a polarity effect it is not a strong one as,
where determined, rates in CCl4 (c.f entries 3,4; 11,12;
17,18) and petroleum spirit (17 and 19) are not a lot
slower.
2.1.3. Triple-insertion-cyclisation sequences
Formation of [(1,2,3,4,5-g)-6-arylcyclohexadienyl]-
Mn(CO)3 products (3; see Scheme 2) is the only detected
reaction for acetylene in some cases (entries 22 and 24)
but is not observed at all in others (entries 6 or 26).
Triple insertion competes weakly with indenol forma-
tion for phenylacetylene (entries 13 and 14) and is not
observed at all for disubstituted acetylenes. Steric limita-
tion on successive insertion (steps iii; Scheme 1) or
cyclisation (step vi) may be responsible for the latter.
There is further discussion in the section Cyclohexadie-
nyl complexes below.
In the case of 2-hexyne, which is unsymmetrical but
with similarly sized groups on the triple bond, there is
no marked solvent effect on regioselectivity (2h:2i:
entries 16–19).
2.2. Indenone formation
2.1.2. Alkyne substituent groups
This has been tested for in the current exploratory
study only with diphenylacetylene but formation of inde-
nones (4a, 4b and 4c) with the orthomanganated second-
ary amide (1c), ester (1d), and aldehyde (1e; entries 21,
23, 25 and 26) indicates useful general routes to
The smaller alkyne substituent is attached either
exclusively (H in a number of cases) or preferentially
(Me vs. n-Pr in the 2h/i case; entries 16–19) at the 3-po-
sition in the indenol next to what was the metalated aryl

3830
N.P. Robinson et al. / Journal of Organometallic Chemistry 690 (2005) 3827–3837
indenones. The reaction presumably occurs from the ini-
tial mono-insertion product either stepwise through the
carbonyl addition intermediate as shown in Scheme 2
(steps [ii] and [v]), or directly, the carbonyl substituent
(amide, alkoxide or hydride) being eliminated with Mn.
No solvent or substituent effects have been studied. For
acetylene itself in excess (saturation), the orthomanga-
nated aldehyde (1e) gives indenone, though in poor yield
(entry 26), and none of the indenol expected by analogy
with the ketone (1a; entry 6), while the ester and amide
substrates (1c and 1d) give cyclohexadienyl complexes
(entries 22 and 24), not indenones. This raises the ques-
tion of whether the addition step to form the indenone
precursor (step [ii], Scheme 2) is slowed in the case of
amide or ester carbonyl relative to the more electrophilic
aldehyde (or ketone) carbonyl group, limiting competi-
tion with successive insertion (steps [iii]). However con-
tinuous replenishment of acetylene to saturation level
may also work in favour of multiple insertion.
ence of other isomers or decomposition, and further
attempts at purification were unsuccessful. The primary
product is suggested to be 3a (3; R1 = H; R2 = Ph),
assuming successive syn additions of coordinated
alkyne (steps [i] and [iii]; Scheme 2) and alkene (step
[vi]). Diagnostic NMR assignments became possible
when cyclohexadienyl complexes were obtained in
quantity as the only products: 3b obtained pure from
acetylene and the o-manganated benzamide (entry
22), and 3c from the benzoate ester complex (entry
24). Their NMR data may be compared with those
of complexes such as 8a,b (obtained from nucleophilic
carbonyl addition by (4-substituted-phenyl)MgBr to
the oxo group of [(1,2,3,4,5-g)-6-oxocyclohexadienyl]-
Mn(CO)3, followed by oxyanion acetylation with acetic
anhydride [13]) and [(1,2,3,4,5-g)-6-phenylcyclohexa-
dienyl]Mn(CO)3 complexes such as 9a which were
obtained using Stille and related Pd-promoted synthetic
methodology on [(1,2,3,4,5-g)-1-chlorocyclohexadienyl]-
Mn(CO)3 complexes [14].
Since the initial reports [1,2] of indenol and indenone
formation from alkynes and o-manganated aryl ketones,
the first analogous reaction reported for another ortho-
metalated arylcarbonyl system was that for orthopalla-
diated acetophenone and benzaldehyde derivatives,
which included the formation of indenone 4b [7]. Later
an analogous catalytic (palladium acetate) route to
1H-inden-1-ols (including 2a and 2c) directly from al-
kyne and o-bromoacetophenone was reported [8] for
conditions very similar to those reported much earlier
[9] for Pd(OAc)2-catalysed indenone synthesis from
ortho-iodobenzaldehyde and diaryl ketones. More
recently, high-yield cobalt-catalysed formation of
1H-inden-1-ols (including 2a and 2c) has been reported
[10] for alkynes with o-iodoacetophenone using
Co(Ph2PCH2CH2PPh2)I2 and zinc in acetonitrile at
80 ꢁC; unsymmetrical alkynes gave similar regiochem-
istry patterns to those reported here.
MuraiÕs closely related Ru-catalysed alkyne coupling
ortho to arylketone groups [11], which could provide a
better catalysed pathway to indenols by a similar
sequence of steps to those for the formation of 2 in
Scheme 2, gives instead routine alkenylation without
cyclisation, though, as a single exception, 1-methyl-3-
phenyl-2-trimethylsilyl-1H-benz[e]inden-1-ol wasreported
as a byproduct from the reaction of 1-acetylnaphthalene
and 1-phenyl-2-trimethylsilylacetylene in the presence of
RuH2(CO)(PPh3)3 as catalyst [12].
According to the implicit syn-syn-syn-syn-addition
sequence of formation of cyclohexadienyl complex (3;
Scheme 2), the C–H bond at C6 (C-R1 in Scheme 2)
should be in the same direction on the face of the p-
complex as the Mn(CO)3 moiety (endo-H orientation).
To confirm this stereochemistry for 3b (entry 22) and
3c (entry 24), the chemical shifts for H6 (3.91 and
4.41 ppm) and coupling constants (with H5: J = 5.9
and 5.4 Hz) can be considered. They are consistent
with signals of the endo-H in complexes 8a
(4.54 ppm; J = 6.6 Hz) and 8b (4.40 ppm; J = 6.2 Hz)
and other acetoxy-substituted complexes [13], as well
as of the endo-H in 9a (4.47; J = 6 Hz) [14b]. However,
for definitive assignment of H6 as endo, data for 6-
unsubstituted cyclohexadienyl complexes (e.g. 9b
[13b]) need to be considered. Chemical shift does not
allow a definite distinction between endo vs. exo H as
although the latter are often at least 0.5 ppm higher
field (e.g. 3.19 for endo-H vs. 2.48 for exo-H in 9b) this
is not always so [14b]. However, the coupling constant
of endo-H6 to H5 is routinely about 5–6 Hz (6 Hz in
the case of 9b) while that for exo-H6 to H5 is not re-
ported so is presumably quite small: the signal for
the exo-H is reported as a simple doublet (geminal cou-
pling to endo-H of about 15 Hz). A much less favour-
able torsion angle for coupling of exo-H6 to H5 than
applies for endo-H6 is borne out by the solid state
structure of the related cyclohexadienyl complex 6
(see below). In 6, the substituent bond at C5 is C–Ph
rather than C–H, but for an indicative torsion angle
between this bond and the C6-exo-H and C6-endo-H
bonds in these complexes generally, it is an adequate
model. As noted in the caption to its crystal structure
diagram (Fig. 2; note the different atom numbering
scheme), the torsion angle between C(5)–Ph and the
exo C–H is 87.5ꢁ, while for the endo C–H it is 33.1ꢁ.
2.3. Cyclohexadienyl complexes
A
(cyclohexadienyl)Mn(CO)3 complex was first
detected as a very minor product (3%) for the reaction
of 1a with phenyacetylene in a 1.1 molar excess (entry
13; Table 1). Raising the alkyne excess to 3 molar
provided sufficient product (14%; entry 14) for NMR
spectroscopy, but multiple signals indicated the pres-

N.P. Robinson et al. / Journal of Organometallic Chemistry 690 (2005) 3827–3837
3831
Me
The first is close to 90ꢁ and so correlates well according
Me
O
CO
2'
Mn(CO)
to the Karplus equation with the coupling constant of
near-zero between H5 and exo-H6 as inferred in the
above discussion on 9b. The second (33ꢁ) is likewise
consistent with a coupling constant of 5–6 Hz. Torsion
angles of C6-H and C5-H will of course vary with sub-
stituent on C5 or C6 but the crystal structure data
when linked to the concordant coupling constants
across the compounds 3b, 3c, 8a, 8b, 9a and 9b pro-
vides strong support for the assignment of the single
H6 in 3b and 3c as endo rather than exo and thereby
for the successive syn addition sequence proposed in
Scheme 2.
3
Ph
Mn(CO)
H
4
3
4
Ph
1'
2
Ph
5
S
S
1
6
H
6
5
H
Mn(CO)
4
3
H
Ph
6
5
Me
3
Ph
CO H
2
1
2
H
Ph
1
7
S
Mn(CO)
Mn(CO)
4
3
3
H
5
H
4
H
6
R4
5
3
H
3
H
H
H
6
2.4. X-ray crystallography
1
2
H
1
2
H
OAc
R1
R6
1
4
6
9a; R = N(CH CH ) O; R = OMe; R = Ph
8a; R = CF
2
2
2
2.4.1. Structure of 1-methyl-2,3-diphenyl-1H-inden-1-ol
(2a; Fig. 1)
3
1
4
6
9b; R = N(CH CH ) O; R = R = H
R
8b; R = OMe
2
2
2
Molecules of 2a pack in the crystal as tetrameric aggre-
gates, linked by a slightly puckered square arrangement
of four ꢀ ꢀ ꢀO–Hꢀ ꢀ ꢀO hydrogen bonds about the crystallo-
graphic 42 axis. The indene skeleton is planar, with the
two peripheral phenyl rings twisted from this plane to
form dihedral angles of 53ꢁ in each case (Fig. 1). This pre-
cludes extended delocalisation so the C–C bonds fall into
normal ranges, with C(2)–C(3) an unperturbed double
Only cyclohexadienyl product was obtained from the
reaction of phenylacetylene with orthomanganated 3-
acetylthiophene (5; entry 27), possibly because cyclisa-
tion to form the indenol equivalent (cf. step [ii] in
Scheme 2) may be limited by the requirement to fuse
two five-membered rings; this may also be the reason
that diphenylacetylene unexpectedly gave an intractable
product and no indenol with 5 (not shown in Table 1).
However, the crude product from phenylacetylene
showed complex line-broadened NMR spectra indicat-
ing decomposition. A crystalline product was fortu-
itously obtained after two successive silica plate
chromatograms, followed by crystallization from hex-
ane. The compound was unstable when dissolved in
chloroform and NMR data could not be obtained for
line broadening effects. However, the compound was
pure in the crystalline state and its X-ray crystal struc-
ture was determined as the complex 6. Most likely, 7 is
initially formed, as for 3 in Scheme 2, but undergoes
prototropic rearrangement to 6 while the reaction solu-
tion is still under reflux or with heat on solvent re-
moval: isomerisation through thermally promoted
Mn-mediated endo-H migration in similar (cyclohexa-
dienyl)Mn(CO)3 complexes has been reported by Pau-
son [15] and this supports the endo-6H isomer 7,
stereochemically analogous to 3a and 3b, as the likely
primary cyclisation product and precursor of isolated
6. Although 6 may be considered to be more stable
than 7 on the grounds that all four aryl groups are con-
jugated to the delocalised p-system of the cyclohexadie-
nyl ring, the solid state structure of 6 (see below) shows
that all the aryl rings are at large dihedral angles to the
planar g5-coordinated part of the cyclohexadienyl ring
so that the level of stabilization by increased conjuga-
tion in solution is questionable.
˚
˚
bond (1.347(4) A). The C(1)–O(1) bond [1.453(4) A] is
˚
longer than usual (range 1.388–1.454 A, average
˚
1.427 A, for the 25 related examples in the CCDC data-
base) and the C(10)–C(1)–O(1) angle is small [105.9(3)ꢁ]
compared with the database range of 106–109ꢁ [16], pre-
sumably to accommodate the hydrogen bonding.
There are only three previous examples of
structurally characterised 1H-inden-1-ol derivatives:
C(23)
C(21)
C(22)
C(4)
C(5)
C(8)
C(16)
C(3)
C(2)
C(6)
C(9)
C(11)
C(1)
C(7)
C(12)
C(10)
O(1)
Fig. 1. Molecular structure of 1-methyl-2,3-diphenyl-1H-inden-1-ol
˚
(2a). Selected bond lengths (A): C(1)–O(1) 1.453(4), C(1)–C(10)
1.530(4), C(1)–C(2) 1.548(4), C(2)–C(3) 1.347(4), C(3)–C(8) 1.488(4).

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N.P. Robinson et al. / Journal of Organometallic Chemistry 690 (2005) 3827–3837
1-phenyl-2-p-tosyl [17], 1-methyl-2-carboethoxy-3-p-
tolyl [18], and the benzoindenol 1-methyl-3-phenyl-
2-trimethylsilyl-1H-benz[e]inden-1-ol [12].
of analytical grade. Other commercial reagents were
used without purification. Dimethyl acetylenedicarb-
oxylate is abbreviated as DMAD in the text. P.l.c. re-
fers to preparative layer chromatography on silica
(Merck Kieselgel 60PF254: 200 · 200 · 2 mm) and
t.l.c. to thin layer chromatography on foil-backed silica
(Merck Kieselgel 60PF254). Infrared spectra (chloro-
form solvent) were recorded on a Digilab FTS-45
FTIR instrument and NMR spectra (CDCl3) on a Bru-
ker AC300 instrument. Number labels used on struc-
tures for assigning NMR signals of H or C atoms
are not necessarily associated with systematic number-
ing, nor are those in the X-ray crystal structure
diagrams.
2.4.2. Structure of [(1,2,3,4,5-g)-2-(3-acetylthien-2-yl)-
1,3,5-triphenylcyclohexadienyl]tricarbonylmanganese
(6; Fig. 2)
The structure determination of 6 showed all four aryl
groups to be bonded to unsaturated carbons in the g5-
coordinated cyclohexadienyl ring. The phenyl rings
attached to C(2), C(4) and C(6) (Fig. 2 numbering) are
orientated at dihedral angles to the g5-ring of 61ꢁ, 40ꢁ
and 66ꢁ, respectively, and for the thiophene ring at
C(1) the angle is 70ꢁ. The five metal-coordinated cyclo-
hexadienyl carbon atoms, C(1)–C(4) and C(6) (Fig. 2
Benzylpentacarbonylmanganese was prepared by the
standard method of Closson et al. [19]. It had m.p. 36–
37 ꢁC (lit. 37.5–38.5 ꢁC [19]); IR (CHC13): m(CO) 2108
˚
numbering), are coplanar to within 0.03 A, with the
˚
manganese atom 1.709 A from this plane and individual
Mn–C distances in the range 2.136–2.289 A. These are
(m), 2012 (vs, br), 1993 (s) cmꢁ1
.
˚
towards the longer end of the range observed for other
g5-cyclohexadienyl manganese molecules for which
structures are available, presumably reflecting the
crowded nature of the ring in 6. The methylene carbon,
C(5), is tilted out of the ring and does not interact at all
with the manganese, as expected.
3.2. Preparation of orthomanganated complexes
Orthomanganated acetophenone (1a) was synthe-
sized by the standard method previously reported [20]
as were the corresponding complexes of benzophenone
(1b) [21], N,N-dimethylbenzamide (1c) [22] and 4-dim-
ethylaminobenzaldehyde (1e) [22]. The same method
with minor variations was applied as follows to the syn-
thesis of g2-(2-methoxycarbonyl-4,5,6-trimethoxyphe-
nyl)tetracarbonylmanganese (1d).
3. Experimental
3.1. General
Methyl 3,4,5-trimethoxybenzoate (0.162 g, 0.717
mmol) and benzylpentacarbonylmanganese (0.246 g,
0.860 mmol) were dissolved in freshly distilled heptane
Petroleum spirit (b.p. 60–80 ꢁC) and all other sol-
vents in preparative and chromatographic work were
C(16)
O(1)
C(63)
C(15)
C(62)
C(13)
C(12)
C(5)
C(46)
C(6)
C(11)
C(1)
C(2)
C(14)
C(4)
C(3)
C(41)
S(1)
C(21)
C(42)
O(8)
C(26)
Mn(1)
C(25)
O(7)
O(9)
Fig. 2. Molecular structure of [(1,2,3,4,5-g)-2-(3-acetylthien-2-yl)-1,3,5-triphenylcyclohexadienyl]tricarbonylmanganese (6). Selected bond lengths
˚
(A): Mn(1)–C(1) 2.191(2), Mn(1)–C(2) 2.154(2), Mn–C(3) 2.136(2), Mn(1)–C(4) 2.289(2), Mn(1)–C(6) 2.239(2), C(1)–C(2) 1.434(3), C(1)–C(6)
1.415(3), C(2)–C(3) 1.425(3), C(3)–C(4) 1.403(3), C(4)–C(5) 1.515(3), C(5)–C(6) 1.518(3). Selected torsion angles: C(41)–C(4)–C(5)–H(5-exo)-87.5ꢁ;
C(41)–C(4)–C(5)–H(5-endo) 33.1ꢁ.

N.P. Robinson et al. / Journal of Organometallic Chemistry 690 (2005) 3827–3837
3833
(30 mL) and the solution degassed and flushed with
nitrogen several times. After refluxing under nitrogen
for 2 h, heptane was removed under vacuum, and
the yellow solid dissolved in dichloromethane (5 mL).
Deactivated neutral alumina (3 g, activity IV) was
added and the mixture shaken vigorously while the
solvent was evaporated under vacuum. The absorbed
product was transferred onto a column of neutral alu-
mina (2 · 15 cm; activity IV). Elution with hexane
removed a trace of unreacted benzylpentacarbonyl-
manganese and as the polarity of the eluent was grad-
ually increased with dichloromethane, a bright yellow
fraction was collected. It yielded g2-(2-methoxycar-
bonyl-4,5,6-trimethoxyphenyl)tetracarbonylmanganese
(1d; 0.247 g, 73%). M.p. 121–125 ꢁC. IR m(CO)
(CH2C12) 2082 (m), 1991 (vs, br), 1940 (s). 1H
NMR: d 7.16 (s, 1H, s, H 3), 4.01 (s, 3H), 3.95 (s,
3H), 3.87 (s, 3H), 3.85 (s, 3H). 13C NMR: (CDC13)
d 220.5 (s, br), 213.8 (s, br), 211.7 (s), 179.6 (s),
166.3 (s), 160.5 (s), 151.6 (s), 148.5 (s), 128.2 (s),
109.1 (d), 60.7 (q), 60.0 (q), 56.1 (q), 54.2 (q). MS:
m/e 392 (10.7), 308 (19.0), 280 (100.0), 250 (47.1),
223 (30.6), 195 (8.3), 192 (8.3), 162 (6.2), 140 (11.8),
55 (12.5).
also passed through the reaction solution for air
exclusion).
3.4. Reactions of g2-(2-acetylphenyl)tetracarbonyl-
manganese (1a)
3.4.1. With diphenylacetylene to form 1-methyl-2,3-
diphenylinden-1-ol (2a)
Following the general procedure above, 1a (0.104 g,
0.364 mmol)
and
diphenylacetylene
(0.067 g,
0.376 mmol) under reflux in benzene for 8 h followed
by p.l.c. (2:3 dichloromethane/petroleum spirit) gave
Mn2(CO)10 (0.026 g) and 1-methyl-2,3-diphenylinden-
1-ol (2a; 0.107 g, 98%], which crystallised from
CH2C12/petroleum spirit as white crystals, m.p. 145–
146 ꢁC (lit. [1] 143 ꢁC).
Corresponding yields of 2a in other solvents for the
reflux period stated (1.5 mol excess of PhC2Ph):
petroleum spirit (7 h) 90%; MeCN (3 h) 78%;
CCl4 (3 h) 57%; MeOH (18 h) 51% (plus 22%
acetophenone).
3.4.2. With acetylene to form 1-methylinden-1-ol
(2b)
1a (0.103 g, 0.360 mmol) and acetylene (continuous
saturation) under reflux in benzene over 18 h gave
Mn2(CO)10 (0.010 g, 18%) and 2b (0.034 g, 64%) as
thin white needles, m.p. 93–96 ꢁC (lit. [24] 96–98 ꢁC.
Anal. Calc. for C10H10O: C, 82.16; H, 6.89. Found:
3.3. General procedure for thermally promoted coupling
reactions of alkynes with orthomanganated compounds
The orthomanganated compound (ca. 100 mg) and
alkyne (1.1–1.5 mol equivalent) were dissolved in sol-
vent (20 mL; analytical grade), and the solution was de-
gassed and flushed with nitrogen several times. The
mixture was heated under reflux under nitrogen, the ex-
tent of reaction being monitored by thin layer chroma-
tography and/or IR spectroscopy. At completion,
solvent was removed under vacuum and the residue sub-
jected to p.l.c. on a silica-layered plate (200 · 200 ·
2 mm) or a rotating silica plate by use of a Chromato-
tron, with ethyl acetate/petroleum spirit or dichloro-
methane/petroleum spirit as eluent.
In the cases of reactions with acetylene the same pro-
cedure was used except that acetylene was continuously
replenished by bubbling it through the reaction solution
for the duration of the reaction. The concentration of
acetylene at saturation is unknown as the only literature
data on acetylene solubility we can trace is at equilibra-
tion with 1 atmosphere acetylene gas at 4 ꢁC [23] at
which temperature benzene dissolves about 0.55 mmol/
mL of acetylene, and cyclohexane (the best available
hydrocarbon match for petroleum spirit in the reported
study) about 0.35 mmol/mL acetylene. In relation to the
amount of manganated complex used here (<0.05 mmol/
mL solvent) these concentrations represent large ex-
cesses of acetylene, but the solubility of acetylene will
be significantly lower at the b.p. of benzene or petroleum
spirit and also at less than 1 atmosphere (nitrogen was
1
C, 81.44; H, 7.10%. MS (m/z): 146 (M+). H NMR: d
7.41 (m, 4H, H4-7), 6.65 (d, J = 5.6 Hz, 1H, H2),
6.32 (d, J = 5.6 Hz, 1H, H3), 2.10 (br s, 1H, OH),
1.61 (s, 3H, CH3). 13C NMR: d 149.4 (C7a), 143.0
(C2), 141.2 (C3a), 130.1(C3), 128.4, 126.4 (C6,7),
121.6, 121.5 (C4,5), 82.3 (C1), 23.7 (CH3). The only
previous preparation of 1a that we are aware of in-
volved the reaction of 1-methylinden-1-yllithium with
oxygen [24].
3.4.3. With 4-octyne to form 1-methyl-2,3-dipropylinden-
1-ol (2c)
1a (0.111 g, 0.388 mmol) and 4-octyne (60 lL,
0.409 mmol) under reflux in benzene over 18 h gave
Mn2(CO)10 (0.009 g, 15%) and 2c (0.046 g, 51%) as col-
ourless square plates, m.p. 79.5–81 ꢁC (lit. [11,12]: no
m.p. reported). Anal. Calc. for C16H22O: C, 83.43; H,
9.63. Found: C, 83.31; H, 9.61%. MS (m/z): 230
(M+). 1H NMR: d 7.18 (m, 4H, H4-7), 2.42 (t,
J = 6.4 Hz, 2H, H10 or 100), 2.33 (t, J = 7.3 Hz, 2H,
H10 or 100), 1.58 (m, 4H, H20, 200), 1.54 (s, 3H, 1-
CH3), 1.00 (t, J = 7.3 Hz, 3H, 30 or 300-CH3), 0.98 (t,
J = 7.3 Hz, 3H, 30 or 300-CH3). 13C NMR: d 149.6
(C7a), 148.0 (C2), 143.0 (C3a), 136.5 (C3), 128.0,
125.1 (C6,7), 121.2, 118.8 (C4,5), 82.5 (C1), 27.4, 27.2
(C10,100), 23.6 (1-CH3), 22.8, 21.7 (C20,200), 14.7, 14.3
(C30,300).

3834
N.P. Robinson et al. / Journal of Organometallic Chemistry 690 (2005) 3827–3837
3.4.4. With bis(trimethylsilyl)acetylene to form
1-methyl-2,3-bis(trimethylsilyl)inden-1-ol (2d)
82%) as colourless square plates, m.p. 104.5–105 ꢁC
(1it. [1] 103–105 ꢁC). Anal. Calc. for C13H18OSi: C,
71.50; H, 8.31. Found: C, 71.50; H, 8.44%. MS (m/z):
218 (M+). 1H NMR: d 7.08 (m, 4H, H4-7), 6.71 (s,
1H, H3), 1.47 (s, 3H, 1-CH3), 0.17 (s, 9H, Si–CH3).
13C NMR: d 157.2 (C2), 152.9 (C7a), 141.6 (C3a),
139.9 (C3), 128.3, 126.4 (C6,7), 121.6, 121.1(C4,5),
86.9 (C1), 25.0 (1-CH3), ꢁ0.44 (Si–CH3).
1a (0.108 g, 0.378 mmol) and bis(trimethylsilyl)acety-
lene (0.068 g, 0.399 mmol) under reflux in benzene over
64 h gave Mn2(CO)10 and some unreacted 1a as an
inseparable mixture (0.030 g) and 1-methyl-2,3-bis(trim-
ethylsilyl)inden-1-ol (2d; 0.008 g, 9%) as white granules,
m.p. 125–128 ꢁC, identified by spectra only: MS (m/z):
290 (M+). 1H NMR: d 7.35 (m, 4H, H4-7), 2.61 (s,
1H, OH), 1.60 (s, 3H, 1-CH3), 0.41 (s, 9H, Si–CH3),
0.38 (s, 9H, Si–CH3).
3.4.8. With 2-hexyne to form 1,3-dimethyl-2-propylinden-
1-ol (2h) and 1,2-dimethyl-3-propylinden-1-ol (2i)
1a (111 mg, 0.387 mmol] and 2-hexyne (0.031 mL,
0.276 mmol) under reflux in benzene for 22 h gave
after p.l.c. (1:1 CH2C12/petroleum spirit) an insepara-
ble mixture of 1,3-dimethyl-2-propylinden-l-ol (2h)
and 1,2-dimethyl-3-propylinden-l-ol (2i) as a white so-
lid (28 mg; 51%). Integration of the proton methyl
singlets showed the ratio 2h:2i to be approximately
2:1. Assignments were made by nOe of aryl 4-H
(d 7.10) by irradiation of 3-CH3 (d 1.88) in 2h and
of 1-CH3 (d 1.47) by irradiation of 2-CH3 (d 1.89)
in 2i.
3.4.5. With dimethyl acetylenedicarboxylate to form
dimethyl 1-hydroxy-1-methylindene-2,3-dicarboxylate
(2e)
1a (0.105 g, 0.368 mmol) and dimethyl acetylenedi-
carboxylate (DMAD) (0.097 g, 0.684 mmol) under re-
flux in benzene for 4.5 h gave after p.l.c. (1:3 ethyl
acetate/petroleum spirit) dimethyl 1-hydroxy-l-methyl-
indene-2,3-dicarboxylate (2e; 64 mg, 67%) as a colour-
less oil, identified by spectra only. HRMS: Anal. Calc.
for C14H14O5: M, 262.0841. Found: M+, 262.0840. H
1
NMR: d 7.48–7.26 (m, 4H, Ar–H), 3.92 (s, 3H,
OCH3), 3.84 (s, 3H, OCH3), 3.92 (s, br, 1H, 1-OH),
1.69 (s, 3H, 1-CH3). 13C NMR: d 165.0 (s, C@O),
164.9 (s, C@O), 149.3 (s), 141.4 (s), 140.3 (s), 136.3
(s), 129.6 (d), 129.1 (d), 123.1 (d), 122.6 (d), 82.0 (s,
C-1), 52.5 (q, OCH3), 52.2 (q, OCH3), 24.8 (q, 1-
CH3).
Yields in other solvents for the reflux period stated
(1.5 mol excess of DMAD): petroleum spirit (24 h)
54% 2e and 11% unreacted 1a; MeCN (1 h) 91% 2e;
CCl4 (3 h) 87% 2e.
1
2h: H NMR: d 7.37 (d, 1H, J = 7.6 Hz, Ar–H), 7.26
(m, 1H, Ar–H), 7.14 (m, 2H, Ar–H), 2.34 (m, 2H,
CH2CH2CH3), 1.98 (s, 3H, 3-CH3), 1.59 (m, 2H,
CH2CH2CH3), 1.51 (s, 3H, 1-CH3), 1.00 (t, 3H,
J = 7.4 Hz, CH2CH2CH3). 13C NMR: d 149.2 (s),
147.8 (s), 143.8 (s), 132.3 (s), 128.3 (d, Ar-C), 125.4 (d,
Ar-C), 121.1 (d, Ar-C), 118.4 (d, ArC), 82.6 (s, C-1),
27.0 (t, 2-CH2CH2CH3), 23.4 (q, 1-CH3), 22.8 (t, 2
CH2CH2CH3), 14.7 (q, 2-CH2CH2CH3), 10.4 (q, 3-
CH3). GCMS: m/z 202 (M+).
1
2i: H NMR: d 7.40 (d, 1H, J = 7.5 Hz, Ar–H), 7.25
(m, 1H, Ar–H), 7.14 (m, 2H, Ar–H), 2.34 (m, 2H, 3-
CH2CH2CH3), 1.89 (s, 3H, 2-CH3), 1.59 (m, 2H,
CH2CH2CH3), 1.47 (s, 3H, 1-CH3), 0.94 (t, 3H,
J = 7.4 Hz, 3-CH2CH2CH3). 13C NMR: d 149.5 (s),
144.4 (s), 143.2 (s), 135.3 (s), 128.2 (d, Ar-C), 125.1 (d,
Ar-C), 121.4 (d, Ar-C), 118.7 (d, Ar-C), 81.9 (s, C1),
27.0 (t, CH2CH2CH3), 23.1 (q, 1-CH3), 21.6 (t, 3-
CH2CH2CH3), 14.1 (q, 3-CH2CH2CH3), 9.0 (q, 2-
CH3). GC–MS: m/z 202 (M+).
Yields in other solvents for the reflux period stated
(1.3 mol excess of 1a over 2-hexyne as above): MeCN
(3.5 h) 38%; CCl4 (7 h) 36% (ca. 2:1 ratio 2h:2i as in ben-
zene for both solvents). In petroleum spirit (using 1.7
molar excess of 2-hexyne over 1a) (5 h) 60%; with ca.
3:1 ratio 2h:2i.
3.4.6. With phenylacetylene to form 1-methyl-2-
phenylinden-1-ol (2f) and cyclohexadienyl complex 3a
1a (0.090 g, 0.315 mmol) and phenylacetylene
(0.104 mL, 0.947 mmol) under reflux in benzene over
3.5 h gave 1-methyl-2-phenylinden-l-o1 (2f; 0.059 g,
84%) as a white solid, m.p. 123–125 ꢁC (lit. [1] 123–
125 ꢁC). Anal. Calc. for C16H14O: C, 86.45; H, 6.35.
Found: C, 86.49; H, 6.24%. MS (m/z): 222 (M+). A
separate fraction yielded a yellow brown oil (0.027 g)
tentatively identified as a cyclohexadienyltricarbonyl-
manganese complex by IR (2015(s), 1939 (br, s) cmꢁ1
)
and by MS (m/z 564; c.f M+ for 3a). NMR gave multiple
signals indicative of 3a and isomerisation or decomposi-
tion product (c.f preparation of 6 in section (f) below)
and no attempts to further purify this minor product
were successful.
3.5. Reaction of g2-(2-benzoylphenyl)tetracarbonyl-
manganese (1b) with diphenylacetylene to form
1,2,3-triphenylinden-1-ol (2j)
3.4.7. With (trimethylsilyl)acetylene to form
1-methyl-2-(trimethylsilyl)inden-1-ol (2g)
1a (0.110 g, 0.386 mmol) and (trimethylsilyl)acetylene
(200 lL, 1.415 mmol) under reflux in benzene over 2 h
gave 1-methyl-2-(trimethylsilyl)inden-l-ol (2g; 0.069 g,
1b (0.122 g, 0.350 mmol) and diphenylacetylene
(0.065 g, 0.365 mmol) in benzene under reflux over

N.P. Robinson et al. / Journal of Organometallic Chemistry 690 (2005) 3827–3837
3835
18 h gave Mn2(CO)10 (0.010 g, 18%) and 2j (0.107 g,
85%) as a colourless oi1, pure by NMR, identified by
130.9 (C100), 129.8, 128.9 (C10), 128.4, 127.8
(C20,30,50,60,200,300,500,600), 127.2 (C4,40), 126.2 (C2),
105.0 (C7), 61.0 (4,5-OCH3), 56.5 (6-OCH3).
1
NMR only [8]. H NMR: d 7.90 (m, 19H). 13C NMR:
d 150.9 (C7a), 147.6 (C2), 142.7 (C3a), 141.7 (C10),
140.5 (C3), 134.8 (C100), 133.9 (C1000), 129.5, 129.2,
128.7, 128.4, 127.8, 127.2, 127.0 (C20–60,200–600,2000–6000),
125.1 (C6,7), 123.2, 121.0 (C4,5), 87.0 (C1).
3.7.2. With acetylene to form [(1,2,3,4,5-g)-6-
(2-methoxycarbonyl-4,5,6-trimethoxy phenyl)cyclohexa-
dienyl]tricarbonylmanganese (3c)
1d (0.110 g, 0.280 mmol) and acetylene under reflux
in benzene over 7 h gave Mn2(CO)10 (0.004 g, 9%) and
a yellow oi1 (0.045 g) assigned by spectra only as the
6-endo-H isomer 3c (36%). MS (m/z) 386:
3.6. Reactions of g2-(2-N,N-dimethylamidophenyl)
tetracarbonylmanganese (1c)
1
3.6.1. With diphenylacetylene to form
2,3-diphenylindenone (4a)
(M+ ꢁ 2CO). H NMR: d 6.70 (s, 1H, H20), 5.74 (t,
J = 4.7 Hz, 1H, H3), 4.87 (t, J = 6.1 Hz, 2H, H2,4),
4.44 (t, J = 5.6 Hz, 1H, H6), 4.07 (t, J = 7.9 Hz, 2H,
H1,5), 3.91 (OCH3), 3.82 (OCH3), 3.53 (OCH3). 13C
NMR: d 222.1 (CO), 169.6 (C@O), 152.6 (C50), 151.8
(C60), 144.6 (C40), 131.6 (C20), 126.2 (C10), 107.8
(C30), 96.7 (C2,4), 79.2 (C3), 60.6 (OCH3), 60.5
(OCH3), 58.7 (C1,5), 55.9 (OCH3), 52.2 (CO2CH3),
34.9 (C6).
1c (0.108 g, 0.343 mmol) and diphenylacetylene
(0.062 g, 0.348 mmol) under reflux in benzene over 1 h
gave Mn2(CO)10 (0.012 g, 22%) and 4a (0.054 g, 56%)
as red needles, m.p. 152–156 ꢁC (lit. 152–153 ꢁC [25].
Anal. Calc. for C21H14O: C, 89.33; H, 5.00. Found: C,
89.61; H, 5.01%. MS (m/z) 282 (M+).
3.6.2. With acetylene to form [(1,2,3,4,5-g)-6-
(2-dimethylamidophenyl)cyclohexadienyl]tricarbonyl-
manganese (3b)
3.8. Reactions of g2-(2-formyl-5-dimethylaminophenyl)
tetracarbonylmanganese (1e)
1c (0.110 g, 0.349 mmol) and acetylene (continuous
saturation) under reflux in benzene over 2 h gave the
endo-6H isomer of 3b (0.070 g, 55%), as yellow needles,
m.p. 61–65 ꢁC (dec.). Anal. Calc. for C18H16MnNO4: C,
59.19; H, 4.42; N, 3.83. Found: C, 58.90; H, 4.36; N,
3.80%. MS (m/z): 309 (M+ ꢁ 2CO). IR: 2017(s),
3.8.1. With diphenylacetylene to form 2,3-diphenyl-5-
dimethylaminoindenone (4c)
1e (0.181 g, 0.574 mmol) and diphenylacetylene
(0.103 g, 0.578 mmol) under reflux in benzene over 9 h
gave Mn2(CO)10 (0.032 g, 36%) and 4c (0.086 g, 46%)
as a maroon solid, m.p. 213–218 ꢁC. Anal. Calc. for
C23H19NO: C, 84.89; H, 5.88; N, 4.30. Found: C,
84.99; H, 5.58; N, 4.38%. MS (m/z): 325 (M+). 1H
NMR: d 7.39 (s, 5H, ArH), 7.26 (s, 5H, ArH), 6.45 (br
d, J = 12 Hz, 1H, H6), 3.04 (s, 6H, NCH3). 13C NMR:
d 194.7 (C@O), 154.3 (C5), 152.0 (C3), 148.2 (C3a),
134.3, 133.3 (C10,100), 131.4 (C2), 130.0, 128.7, 127.8,
127.4 (C20–60,200–600), 125.2 (C7), 117.9 (C7a), 108.2
(C6), 106.5 (C4), 40.4 (NCH3).
1
1930(s), 1640(m) cmꢁ1. H NMR: d 7.27 (td, J = 7.6
and 1.4 Hz, 1H, H40 or 50), 7.18 (td, J = 7.5 and
1.3 Hz, 1H, H40 or 50), 7.08 (dd, J = 7.8 and 1.2 Hz,
1H, H30 or 60), 7.05 (dd, J = 7.5 and 1.4 Hz, 1H, H30
or 60), 5.75 (tt, J = 5.3 and 1.3 Hz, 1H, H3), 4.97 (br t,
J = 5.5 Hz, 2H, H2,4), 3.91 (t, J = 5.9 Hz, 1H, H6),
3.38 (br t, J = 6.3 Hz, 2H, H1,5), 3.18 (s, 3H, NCH3),
2.80 (s, 3H, NCH3). 13C NMR: d 222.6 (CO), 171.1
(C@O), 142.9 (C20), 133.7 (C10), 128.8, 126.9, 126.6,
125.6 (C30–60), 96.5 (C2,4), 79.2 (C3), 57.1 (C1,5), 38.7
(NCH3), 36.5 (C6), 34.5 (NCH3).
3.8.2. With acetylene to form 5-dimethylaminoindenone
(4d)
3.7. Reactions of g2-(2-methoxycarbonyl-4,5,6-
trimethoxyphenyl)tetracarbonylmanganese (1d)
1e (0.138 g, 0.438 mmol) and acetylene (continuous
saturation) under reflux in benzene (40 mL) over 3.5 h
gave Mn2(CO)10 (0.004 g, 6%) and 4d (0.015 g, 20%) as
a red oil, assigned only by 1H NMR: d 7.73 (d,
J = 8.9 Hz, 1H, H7), 7.34 (d, J = 5.7 Hz, 1H, H2), 6.43
(d, J = 2.3 Hz, 1H, H4), 6.26 (dd, J = 8.8 and 2.9 Hz,
1H, H6), 5.84 (d, J = 5.8 Hz, 1H, H3), 3.06 (s, 6H, NCH3).
3.7.1. With diphenylacetylene to form 2,3-diphenyl-4,5,6-
trimethoxyindenone (4b)
1d (0.098 g, 0.250 mmol) and diphenylacetylene
(0.048 g, 0.269 mmol) under reflux in benzene over 1 h
gave Mn2(CO)10 (0.002 g, 5%) and 4b (0.098 g, 100%)
as a maroon solid, m.p. 124–126 ꢁC (lit. [7b] 121–
122 ꢁC). Anal. Calc. for C24H20O4: C, 77.40; H, 5.41.
Found: C, 77.39; H, 5.57%. MS (m/z) 372 (M+). 1H
NMR: d 7.34 (s, 5H, ArH), 7.16 (s, 5H, ArH), 7.08 (s,
1H, H7), 3.89 (s, 6H, 4,5-OCH3), 3.29 (s, 3H, 6-
OCH3). 13C NMR: d 195.3 (C@O), 156.2 (C5), 154.3
(C3), 149.3, 147.7 (C4,6), 134.6 (C7a), 132.3 (C3a),
3.9. Reaction of g2-(3-acetylthien-2-yl)tetracarbonyl-
manganese (5) with phenylacetylene to form [g5-2-
(3-acetylthien-2-yl)-1,3,5-triphenylcyclohexadienyl]
tricarbonylmanganese (6)
g2-(3-Acetylthien-2-yl)tetracarbonylmanganese
0.136 g, 0.47 mmol) and phenylacetylene (0.240 g,
(5;

3836
N.P. Robinson et al. / Journal of Organometallic Chemistry 690 (2005) 3827–3837
2.3 mmol) were heated under reflux in benzene for 8 h.
Rotary evaporation gave a dark oil which by p.l.c.
(1:10 diethyl ether/petroleum spirit) gave a broad band
yielding an orange oil. Further p.l.c. (1:10 ethyl ace-
tate/petroleum spirit) gave one major band
(Rf = 0.34) which was extracted with dichloromethane.
Solvent removal gave an orange crystalline solid
(168 mg) which was unstable in solution preventing
NMR characterization, but which by crystallisation
from hexane under refrigeration provided a sample
of [g5-2-(3-acetylthien-2-yl)-1,3,5-triphenylcyclohexa-
dienyl]tricarbonylmanganese (6) as pure orange crys-
tals, stable in the solid state and characterized by
X-ray crystal structure analysis.
Cambridge CB2 1EZ, UK (fax: +44 1223 336 033;
e-mail: deposit@ccdc.cam.ac.uk or www:http//www.
ccdc.cam.ac.uk).
Acknowledgement
We thank Professor Ward Robinson, University of
Canterbury, for collection of X-ray intensity data.
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space group P42/n, a = 11.900(2), c = 24.250(8)
3
A, V = 3434.0(5) A , Dcalc = 1.154 g cmꢁ3, Z = 8, l
(Mo Ka) = 0.069 mmꢁ1, size 0.64 · 0.34 · 0.10 mm3,
F(000) = 1264, T = 173 K. Total data 2448, unique data
2204 (Rint = 0.0455), 4ꢁ < 2h < 45ꢁ, R1 (I > 2r(I)) =
˚
˚
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Orange crystals were obtained from hexane. Crystal
data: C33H23MnO4S, Mr 570.51, monoclinic, space
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3
˚
˚
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4ꢁ < 2h < 52ꢁ, R1 (I > 2r(I)) = 0.0380, wR2 (all
data) = 0.0934, GoF = 1.037, residual De +0.36/ꢁ0.35
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˚
e A
.
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Full details of the structure determinations have been
deposited with the Cambridge Crystallographic Data
Centre as CCDC 263454 (2a) and CCDC 263453 (6).
Copies of this information may be obtained free of
charge from The Director, CCDC, 12 Union Road,
See also: M.I. Bruce, M.J. Liddell, G.N. Pain, Inorg. Synth. 26
(1989) 172.

N.P. Robinson et al. / Journal of Organometallic Chemistry 690 (2005) 3827–3837
3837
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5426.
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