Formation of manganese enediyne complexes from manganese alkynylcarbene complexes

Article abstract of DOI:10.1016/S0020-1693(02)01273-2

Dimerization of the alkynylcarbene complex (C₅H₄Me)(CO)₂Mn=C(Tol)C≡CTol (10) occurred at 65°C to give a mixture of E- and Z-enediyne complexes [(C₅H₄Me)(OC)₂Mn]₂[η ²,η²-TolC≡C(Tol)C=C(Tol)C≡CTol] (13). Thermolysis of alkynye complexes 10 at higher (100°C) temperature led to the formation of manganese-free E- and Z-enediynes TolC≡C(Tol)C=C(Tol)C≡CTol (14-E and 14-Z). Attempted synthesis of the tethered bis-(alkynylcarbene) complex Cp(OC)₂Mn=C(Ph)C≡CCH₂CH₂CH ₂C≡CC(Ph)=Mn(CO)₂Cp led instead to the cyclic enediyne complex [Cp(OC)₂Mn]₂[η²,η²- PhC≡CC(CH₂CH₂CH₂)=CC≡CPh] (19), from which the metal-free enediyne 1,2-bis(phenylethynyl)cyclopentene (20) was released by thermolysis at 90°C.

Full text of DOI:10.1016/S0020-1693(02)01273-2

Inorganica Chimica Acta 345 (2003) 320ꢂ326
/
www.elsevier.com/locate/ica
Formation of manganese enediyne complexes from
manganese alkynylcarbene complexes
Charles P. Casey *, Trevor L. Dzwiniel, Stefan Kraft, Michael A. Kozee,
Douglas R. Powell
Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706-1322, USA
Received 20 June 2002; accepted 16 August 2002
Dedicated to Professor Richard Schrock on the occasion of his 60th Birthday and in recognition of his pioneering contributions
to the chemistry of metal carbene complexes
Abstract
Dimerization of the alkynylcarbene complex (C5H4Me)(CO)2MnÄ
and Z-enediyne complexes [(C5H4Me)(OC)2Mn]2[h2,h2-TolCÅ
C(Tol)CÄ
10 at higher (100 8C) temperature led to the formation of manganese-free E- and Z-enediynes TolCÅ
E and 14-Z). Attempted synthesis of the tethered bis-(alkynylcarbene) complex Cp(OC)2MnÄC(Ph)CÅ
Mn(CO)2Cp led instead to the cyclic enediyne complex [Cp(OC)2Mn]2[h2,h2-PhCÅ
CC(CH2CH2CH2)Ä
/
C(Tol)CÅ
/
CTol (10) occurred at 65 8C to give a mixture of E-
CTol] (13). Thermolysis of alkynye complexes
C(Tol)CÄC(Tol)CÅCTol (14-
CCH2CH2CH2CÅCC(Ph)Ä
CCÅCPh] (19), from which
/
/
C(Tol)CÅ
/
/
/
/
/
/
/
/
/
/
/
the metal-free enediyne 1,2-bis(phenylethynyl)cyclopentene (20) was released by thermolysis at 90 8C.
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Manganese alkynylcarbene complexes; Enediyne; Manganese alkyne complexes
1. Introduction
[Cp(OC)2Re]2[h2,h2-TolCÅ
/
C(Me)CÄ
/
C(Me)CÅ
/
CTol]
(5) as a 1.2:1 mixture of E- and Z-alkene isomers
(Scheme 2), demonstrating that the coupling mechanism
has no intrinsic bias toward E-enediyne complexes. The
overall regioselectivity stands in contrast to the reported
ability of Fischer carbene complexes to couple the
carbene carbons and form alkenes [5]. Sierra has
reported a selective ‘head-to-head’ coupling in the Pd-
Heteroatom substituted alkynylcarbene complexes
such as (OC)5MÄ
/
C(OR)CÅCR? are highly reactive,
/
easily accessible, and useful in a plethora of high-
yielding transformations [1]. Despite the large number
of these Fischer carbene complexes [2], only recently
have [1,3] metal shifts been documented, as in the case of
Cp(OC)2ReÄ
/
C(Tol)CÅ
/
CPh (1) (Cpꢀ
/
h5-C5H5, Tolꢀ
C(Ph)CÅCTol (2)
/
4-
catalyzed dimerization of (OC)5CrÄ
(E,Z)-PhCÅC(OEt)CÄC(OEt)CÅCPh, with no evidence
/
C(OEt)CÅ
/
CPh to
MeC6H4) rearranging to Cp(OC)2ReÄ
/
/
/
/
/
upon thermolysis at 120 8C (Scheme 1) [3]. However,
the major product in this reaction was the dimeric E-
of ‘tail-to-tail’ or ‘head-to-tail’ coupling products [6].
We have recently shown that the tethered bis-(alky-
enediyne complex [Cp(OC)2Re]2[h2,h2-TolCÅ
/
C(Ph)CÄ
/
nylcarbene) rhenium complex, Cp(OC)2ReÄ
CCH2CH2CH2CÅCC(Tol)ÄRe(CO)2Cp (6) readily re-
/
C(Tol)CÅ
/
C(Ph)CÅ/CTol] (3) formed by the regioselective coupling
/
/
of the remote alkynyl carbons in a kinetically 2nd order
process [4].
The closely related dimerization of Cp(OC)2ReÄ
/
C(Tol)CÅCMe (4) at 100 8C in toluene provided
/
* Corresponding author. Tel.: ꢁ
4534.
E-mail address: casey@chem.wisc.edu (C.P. Casey).
/
1-608-262 0584; fax: ꢁ1-608-265
/
Scheme 1.
0020-1693/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 0 - 1 6 9 3 ( 0 2 ) 0 1 2 7 3 - 2

C.P. Casey et al. / Inorganica Chimica Acta 345 (2003) 320ꢂ
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326
321
Scheme 2.
arranges to the cyclic enediyne complex [Cp(OC)2-
Re]2[h2,h2-TolCÅ
CC(CH2CH2CH2)ÄCCÅCTol] (7) be-
/
/
/
low room temperature by the coupling of the remote
alkynyl carbons (Scheme 3) [4b]. This straightforward
route to enediynes under mild conditions has potential
value in organic synthesis. However, this reaction is
hampered by the difficulty of releasing the tightly bound
alkynes from rhenium as well as by the high expense of
stoichiometric rhenium reactions. Here we report the
synthesis of the more economical manganese alkynyl-
carbene complexes and their conversion to manganese
enediyne complexes and to free enediynes.
Scheme 3.
Scheme 4.
2. Results and discussion
2.1. Synthesis of manganese alkynylcarbene complexes
Simple manganese alkynylcarbene complexes have
been prepared by us [7] and by Lugan [8]. Addition of
acetylide anions to manganese carbyne complexes leads
to good yields of manganese alkynylcarbene complexes
as dark brown to black materials (Scheme 4). The Cp
compounds are generally highly crystalline while the
C5H4Me complexes are often oily. In a representative
procedure, the deep yellow thermally sensitive manga-
nese carbyne complex [Cp(OC)2MnÅ
[9] was dissolved in methylene chloride at ꢃ
When an equivalent amount of PhCÅCZnBr in THF,
prepared from PhCÅCLi and ZnBr2, was added to
carbyne complex 8, the solution turned deep redꢂ
brown. After slow warming to room temperature,
Cp(OC)2MnÄC(Tol)CÅCPh (9) was isolated in 44%
yield after preparative thin layer chromatography as a
redꢂbrown solid. The reaction yield depends strongly on
/
CTol]ꢁBCl4 (8)
ꢃ
/
35 8C.
Fig. 1. X-Ray crystal structure of Cp(OC)2MnÄ
/
C(Tol)CÅ
/
CPh (9).
/
˚
Selected bond lengths (A) and angles (8): MnÄ
C(2), 1.423(2); C(2)ÅC(3), 1.201(3); C(1)ÃC(11), 1.487 (2); MnÃ
1.792(2); MnÃC(1)ÃC(2), 117.6 (1); MnÃC(1)ÃC(11), 129.9(1); C(2)Ã
C(1)ÃC(11), 112.4(2); C(1)ÃC(2)ÃC(3), 178.1(2); C(2)ÃC(3)ÃC(18),
175.1(2); C(1)ÃMnÃC(4), 95.4(1); C(1)ÃMnÃC(5), 90.8(1); C(4)ÃMnÃ
C(5), 87.9(1).
/
C(1), 1.892(2); C(1)Ã
/
/
/
/
/
C(4),
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
shows two metal carbonyl peaks at 1975 and 1915
cmꢃ1. X-ray quality crystals were obtained by slow
evaporation of a methylene chloride/pentane solution.
X-ray crystallography confirmed the structure of 9 (Fig.
1) [10].
the purity of carbyne complex 8; higher yields were
obtained using freshly prepared 8. The related manga-
nese alkynylcarbene complexes (h5-C5H4Me)(CO)2MnÄ
/
/
C(Tol)CÅ
CTol (11), and (h5-C5H4Me)(CO)2MnÄ
(12) were prepared by similar procedures.
/
CTol (10), (h5-C5H4Me)(CO)2MnÄ
C(Tol)CÅ
/
C(Ph)CÅ
/
/CPh
The spectroscopic properties of the manganese alky-
nylcarbene complexes are similar to those of their
rhenium analogues. The 13C NMR spectrum of 9
contains two characteristic peaks, one at d 234.3
assigned to the CO ligands and the other at d 301.1
assigned to the carbene carbon. Infrared spectroscopy
2.2. Dimerization of manganese alkynylcarbene
complexes to enediyne complexes
We have found that mild heating converts the
manganese alkynylcarbene complexes to a mixture of
E- and Z-enediyne manganese complexes. Thermolysis

322
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/
of
a
0.8
CTol (10) in toluene at 65 8C for 8 h provided
the bright red enediyne complex [(h5-C5H4Me)-
CTol] (13-
M
solution of (h5-C5H4Me)(CO)2MnÄ
/
C(Tol)CÅ
/
CTol (14-E and 14-Z) and small amounts of
(h5-C5H4Me)Mn(CO)3 (Scheme 5). The presence of a
peak at m/z 816.2 in the mass spectrum of 14 clearly
indicated the formation of dimers. Thermolysis of the
isolated manganese enediyne complex 13 at 100 8C for
several hours resulted in decomplexation and formation
of free E- and Z-enediynes 14-E and 14-Z [11]. In
contrast, rhenium enediyne complexes 3 and 5 are stable
at 120 8C.
C(Tol)CÅ
/
(OC)2Mn]2[h2,h2-TolCÅ
/
C(Tol)CÄ
/
C(Tol)CÅ
/
E and 13-Z) in 30% yield after column chromatography
(Scheme 5). Infrared spectroscopy showed only two
peaks for 13 at 1978 and 1915 cmꢃ1. However, the H
1
NMR spectrum exhibited at least six separate methyl
resonances, consistent with the presence of E- and Z-
enediyne isomers with three methyl resonances each.
Note that, unlike the dimerization of rhenium alkynyl-
carbene complex 2 which gave only E-enediyne complex
3, similar amounts of manganese E- and Z-enediyne
complexes13-E and 13-Z were obtained.
Thermolysis of the regioisomeric manganese alkynyl-
carbene complexes 11 and 12 at 100 8C for 8ꢂ12 h
produced free enediynes directly, as determined by mass
spectrometry (Scheme 6). There are six possible en-
/
ediyne isomers: E- and Z-PhCÅ
CPh (15-E and 15-Z) from ‘tail-to-tail’ dimerization of
11, E- and Z-PhCÅC(Tol)CÄC(Ph)CÅCTol (16-E and
16-Z) from ‘tail-to-tail’ cross-dimerization of 11 and 12,
and E- and Z-TolCÅC(Ph)CÄC(Ph)CÅCTol (17-E and
17-Z) from ‘tail-to-tail’ dimerization of 12. The sym-
metric dimers 15 and 17 have one kind of methyl group
each, while the cross dimers 16 have two different
methyl groups each, giving a total of eight different
methyl groups.
The 1H NMR spectra of the mixtures of enediyne
dimers from thermolysis of both 11 and 12 showed the
same eight methyl resonances between d 2.5 and 2.25
but in different ratios, suggesting some regioselectivity
in the dimerization. If no isomerization of the starting
alkynylcarbene complex 11 occurred, regioselective ‘tail-
to-tail’ dimerization would produce only 15-E and 15-Z
and only two methyl resonances should have been seen.
If isomerization of alkynylcarbene complexes 11 and 12
were much faster than dimerization, the same ratio of
eight methyl resonances would be expected from either
complex. Our observations require competitive rates of
isomerization and dimerization and regioselectivity in
the dimerization process.
/
C(Tol)CÄ
/
C(Tol)CÅ
/
Some dimerization of (h5-C5H4Me)(CO)2MnÄ
C(Ph)CÅCTol (11) occurred when it was stored as an
/
/
/
/
/
oil over 7 days at room temperature. The high concen-
tration of 11 in the oil speeds up the kinetically 2nd
order dimerization and allows dimerization to occur at
room temperature. In contrast, dilute solutions of 11
require heating in toluene for dimerization. The mixture
of dimers was difficult to separate from alkynylcarbene
complex 11 due to their similar polarity; however, a
small amount of the mixture of dimers was isolated by
preparative TLC.
The 1H NMR spectrum of this mixture of dimers
showed at least eight overlapping methyl resonances,
suggesting a mixture of several isomeric manganese
enediyne complexes. Two methyl resonances each would
be expected for the E- and Z-enediyne isomers from
‘tail-to-tail’ and from ‘head-to-head’ coupling; and four
methyl resonances each would be expected for the E-
and Z-enediyne isomers from ‘head-to-tail’ coupling.
/
/
/
2.3. Thermal release of enediynes from manganese
enediyne complexes
Tentative but self-consistent assignments of the meth-
yl resonances of the enediyne dimers to specific isomers
were made by assuming that: (1) the major product in
each reaction was an E-enediyne resulting from ‘tail-to-
tail’ coupling of the starting alkynylcarbene complex, as
Manganese enediyne complexes are much more
thermally labile than their rhenium counterparts. Ther-
molysis of (h5-C5H4Me)(CO)2MnÄ
/
C(Tol)CÅ
in toluene at 100 8C generated a 1:1 mixture of the
metal-free E- and Z-enediynes TolCÅCC(Tol)Ä
/
CTol (10)
/
/
Scheme 5.

C.P. Casey et al. / Inorganica Chimica Acta 345 (2003) 320ꢂ
/
326
323
Scheme 6.
seen for the related dimerization of rhenium complex 2;
and (2) cross-dimerization products 16-E and 16-Z give
rise to two equal-intensity peaks in the products from
either 11 or 12. The chemical shift assignments for the
complexes were: 15-E (d 2.429), 15-Z (2.314), 16-E
(2.423 and 2.304), 16-Z (2.360 and 2.337), 17-E (2.330),
and 17-Z (2.366). Using these assignments, the ratio of
15:16:17 from the thermolysis of 0.75 M 11 was
0.54:0.36:0.10. Thermolysis of a more dilute solution
(0.3 M) of the regioisomeric alkynylcarbene complex 12
gave a 0.20:0.35:0.45 ratio of 15:16:17. The lower initial
concentration in 12 allows the 1st order isomerization to
more effectively compete with the 2nd order dimeriza-
tion, resulting in a less selective dimerization.
dimerization. In contrast, the similar rates of isomeriza-
tion to dimerization of manganese alkynylcarbene com-
plexes results in low regioselectivity of dimerization.
2.4. Formation of cyclic enediyne manganese complexes
Intramolecular dimerization of tethered bis-(alkynyl-
carbene) complexes occurs well below room temperature
in both rhenium [4b] and manganese systems. The
reaction of
a
slight excess of [Cp(OC)2Mnꢀ
CPh]ꢁBCl4 (18) with the bis-alkynylzinc compound
BrZnCÅCCH2CH2CH2CÅCZnBr in CH2Cl2ꢂTHF at
78 8C initially produced a dark red solution, consis-
/
ꢃ
/
/
/
ꢃ
/
tent with formation of a manganese bis-(alkynylcar-
bene) complex (Scheme 7). However, all attempts to
isolate this complex failed because of rapid isomeriza-
The ratio of products formed in both dimerizations
could be simulated using the different initial concentra-
tions and the same relative rates of isomerization to
tion to the light redꢂ
plex
[Cp(OC)2Mn]2[h2,h2-PhCÅ
CCÅCPh] (19). When a sample taken from the
78 8C reaction mixture was analyzed immediately
/orange manganese enediyne com-
dimerization of k2(dimer)/k1(isom)ꢀ
/
2.3 Mꢃ1. The
/
CC(CH2CH2CH2)Ä
/
(observed, calculated) product ratios for dimerization
of 0.75 M 11 were: 15 (0.54, 0.60): 16 (0.36, 0.31): 17
(0.10, 0.09); and for dimerization of 0.30 M 12 were: 15
(0.20, 0.14): 16 (0.35, 0.39): 17 (0.45, 0.47). The close
agreement between the observed and calculated ratios
supports our NMR assignments and rate assumptions.
It is remarkable that our ‘house of cards’ is surprisingly
robust.
Substantial variation in Z/E ratios was observed: for
example, although the ratio of 17-E:17-Z remained
relatively constant at approximately 3:1, the 15-E:15-Z
ratio varied from 2:1 to 4:1, and the 16-E:16-Z ratio
changed from 1.8:1 to 1:1.6 in the thermolyses of 11 and
12. We do not know whether the observed Z/E ratios
are kinetically controlled or whether some isomerization
has occurred. In the case of rhenium enediyne complex
5-Z, exposure to air resulted in isomerization of 5-Z to
5-E [4b].
/
ꢃ
/
by thin layer chromatography, only the bright red
coupled product 19 was seen; there was no evidence
for a dark red faster moving manganese carbene
complex. The enediyne complex 19 was isolated by
column chromatography in 71% yield (based on 1,6-
heptadiyne). Infrared spectroscopy of 19 showed the
expected two carbonyl bands at 1982 and 1916 cmꢃ1
.
The 1H NMR spectrum of 19 was broadened by
paramagnetic impurities, and could not be readily
assigned.
The enediyne complex 19 was also thermally labile
and released the enediyne upon mild heating in toluene
at 90 8C over 16 h. Preparative TLC provided 1,2-
bis(phenylethynyl)cyclopentene (20) as an off-white
solid in 70% yield.
The rates of dimerization of manganese alkynylcar-
bene complexes are faster than those of the correspond-
ing rhenium complexes, allowing dimerization at lower
temperature (65 8C for Mn, 120 8C for Re). There is an
even greater difference between the rates of isomeriza-
tion of manganese and rhenium alkynylcarbene com-
plexes. The ratio of isomerization to dimerization is
small for rhenium and results in high regioselectivity of
2.5. Summary
We have shown that the dimerization of manganese
alkynylcarbene complexes occurs at temperatures lower
than those required for the corresponding rhenium
complexes. Unlike the thermally stable rhenium en-
ediyne complexes, manganese enediyne complexes re-
lease the free enediyne upon moderate heating. The

324
C.P. Casey et al. / Inorganica Chimica Acta 345 (2003) 320ꢂ326
/
Scheme 7.
reactions of manganese alkynylcarbene complexes pro-
vide a facile synthesis of the Z-enediyne skeleton.
3.3. (h5-C5H4Me)(CO)2MnÄ
/
C(Tol)CÅ
/
CTol (10)
1H NMR (500 MHz, CDCl3, all signals broad): d 7.95
(2H, Tol), 7.43 (2H, Tol), 7.20 (4H, Tol), 5.08 (2H, Cp?),
4.97 (2H, Cp?), 2.36 (Me), 2.33 (Me), 1.95 (Me).
13C{1H} NMR (125 MHz, CDCl3): d 152.68, 139.87,
139.35, 134.16, 130.92, 129.53, 128.85, 126.02 (aro-
3. Experimental
3.1. General
matic); 122.06 (MeC of Cp?); 107.58, 105.08, (CÅ
/
C);
94.73, 93.36, (Cp); 21.72, 21.47, 13.53 (Me). IR (C6H14,
cmꢃ1): 1974, 1918.
All air sensitive materials were manipulated under
nitrogen in a glovebox or by standard high-vacuum and
Schlenk-techniques. Hexane and THF were distilled
from Na and benzophenone. Dichloromethane was
distilled from CaH2. Phenylacetylene, 4-ethynyltoluene,
1,6-heptadiyne, BuLi (1.6 M, hexanes), and ZnBr2 were
3.4. (h5-C5H4Me)(CO)2MnÄ
1H NMR (250 MHz, CDCl3): d 7.95 (d, Jꢀ
/
C(Ph)CÅ
/
CTol (11)
/
8.0 Hz,
2H, Tol), 7.46ꢂ7.36 (m, 5H, Ph), 7.22 (d, Jꢀ8.0 Hz,
2H, Tol), 5.11ꢂ5.09 (m, 2H, Cp?), 5.00ꢂ4.98 (m, 2H,
Cp?), 2.38 (s, TolCH3), 1.97 (s, 3H, CpCH3). 13C{1H}
Mn); 233.90
/
/
purchased from Aldrich. [Cp(CO)2MnÅ
/CPh]BCl4,
/
/
[Cp(CO)2MnÅCTol]BCl4, and their methylcyclopenta-
/
dienyl analogues were synthesized according to modified
literature procedures [9].
NMR (62.9 MHz, CDCl3) d 300.91 (CÄ
/
(CO); 155.62, 139.49, 135.00, 130.98, 129.55, 128.97,
128.07, 125.26 (aromatic); 122.01 (MeC of Cp?); 107.69
1H and 13C NMR spectra were obtained on a Bruker
AC 250 or AC 300 or Varian Unity 500 spectrometer.
IR spectra were recorded on a Mattson Polaris FT IR
spectrometer. Mass spectra were obtained on a Kratos
MS-80 or Micromass AutoSpec spectrometer.
(Cp?); 105.65, 94.81 (CÅ
/
C); 94.53, 93.44 (Cp?); 21.72,
13.51 (Me). IR (C6H14, cmꢃ1): 1978, 1920.
3.5. (h5-C5H4Me)(CO)2MnÄ
1H NMR (250 MHz, CDCl3): d 7.98 (d, Jꢀ
/
C(Tol)CÅ
/
CPh (12)
/
7.3 Hz,
3.2. Cp(CO)2MnÄ
/
C(Tol)(CÅ
/
CPh) (9)
2H, Tol), 7.6ꢂ7.3 (m, 5H, Ph), 7.22 (d, Jꢀ7.7 Hz, 2H,
/
/
Tol), 5.10 (br s, 2H, Cp?), 4.99 (br s, 2H, Cp?), 2.34 (s,
TolCH3), 1.97 (s, CpCH3). 13C{1H} NMR (62.9 MHz,
CDCl3): d quaternary carbons not found above noise.
130.79, 128.89, 128.80, 128.72, 126.0 (aromatic); 94.80,
93.46 (Cp?); 21.48, 13.53 (Me). IR (C6H14, cmꢃ1): 1975,
1915.
Addition of BrZnCÅ
0.20 mmol) and ZnBr2 (45 mg, 0.20 mmol) in 0.5 ml
THF] to an orange solution of [Cp(CO)2MnÅCTol]BCl4
in 1 ml THF at ꢃ35 8C produced a redꢂbrown
solution which was directly placed on a preparative
thin layer chromatography plate. A redꢂbrown band
(silica, C6H14, Rfꢀ0.3) was isolated. The brownꢂred
solid was redissolved in a little CH2Cl2 in a vial and
layered with C5H12. Redꢂbrown crystals of 9 (32 mg,
/
CPh [from LiCÅ
/
CPh (22 mg,
/
/
/
/
/
/
3.6. Thermolysis of (h5-C5H4Me)(CO)2MnÄ
CÅCTol (10) at 65 8C
/
C(Tol)-
/
/
44%) suitable for an X-ray crystal structure analysis
were obtained. Presumably due to paramagnetic impu-
A solution of 10 (253 mg, 0.619 mmol) in 1.0 ml
C6H5CH3 was heated at 65 8C for 19 h. TLC analysis
1
rities, lines in the H NMR spectrum were too broad to
analyze (v1/2
MHz): d 21.54 (CH3), 87.56 (CÅ
105.27 (CÅC), 126.28 (aromatic), 129.14 (aromatic),
:
/
1000 Hz). 13C{1H} NMR (CD2Cl2, 500
revealed one red spot (10% ether/hexanes, Rfꢀ0.6) and
/
/C), 94.05 (C5H5),
extensive baseline decomposition. Column chromato-
/
graphy (silica gel, 10% ether/hexanes) gave [(h5-
129.25 (aromatic), 129.40 (aromatic), 131.29 (aromatic),
134.19 (aromatic), 140.69 (aromatic), 153.21 (aromatic),
C5H4Me)(OC)2Mn]2[h2,h2-TolCÅ
/
CC(Tol)Ä
CTol] (13) as a sticky red solid (75 mg, 30%). H NMR
(300 MHz, CDCl3): d 7.87 (d, Jꢀ7.8 Hz, Htol), 7.4ꢂ6.8
(series of overlapping d’s, Htol), 4.8ꢂ4.0 (series of
/
C(Tol)CÅ
/
1
234.30 (CO), 301.11 (MnÄ/C). A Cp impurity was seen at
/
/
d 85.58.
All other manganese alkynyl carbene complexes were
prepared in a similar way.
/
overlapping m, Cp?), 2.426, 2.389, 2.371, 2.340, 2.333,
2.311, 2.295, 2.247, 2.232 (overlapping Me of tolyl and

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326
325
Cp? groups). IR (C6H14, cmꢃ1): 1976, 1915. MS (ESI)
m/z calc. for C50H42 55Mn2O4 [Mꢁ]: 816.1844. Found:
816.1837.
TLC gave a mixture of enediynes 15, 16, and 17 (15 mg,
26%) as a yellow solid. Partial Data: 1H NMR (500
MHz, CDCl3): d 8.0ꢂ
/
7.9 (m), 7.6ꢂ7.0 (series of m,
/
aromatic), 2.429 (0.110H, 15-E), 2.423 (0.067H, 16-E),
2.366 (0.117H, 17-Z), 2.360 (0.108H, 16-Z), 2.337
(0.108H, 16-Z), 2.330 (0.332H, 17-E), 2.314 (0.037 H,
15-Z), 2.304 (0.067 H, 16-E) (Me’s).
3.7. Thermolysis of (h5-C5H4Me)(CO)2MnÄ
CÅCTol (10) at 100 8C
/C(Tol)-
/
A solution of 10 (67 mg, 0.164 mmol) in 0.27 ml
C6H5CH3 was heated at 100 8C for 8 h. A Â1:1
CTol (14)
/
3.10. [Cp(OC)2Mn]2[h2,h2-PhCÅ
CCÅCPh] (19)
/
CC(CH2CH2CH2)Ä
/
mixture of Z-:E-TolCÅ
/
CC(Tol)Ä
/
C(Tol)CÅ
/
/
(15 mg, 42%) was isolated as a yellow solid by
1
preparative TLC (5% EtOAc/hexanes). H NMR (250
BuLi (1.6 M, hexanes, 0.47 ml, 0.752 mmol) was
added to a solution of 1,6-heptadiyne (0.043 ml, 0.376
MHz, CDCl3): d 7.89 (d, Jꢀ
Jꢀ8.5 Hz, 2H, Htol), 7.22 (d, Jꢀ
(d, Jꢀ8.5 Hz, 2H, Htol), 7.10 (d, Jꢀ
7.02 (d, Jꢀ 8.0 Hz, 2H, Htol), 2.429 (s, 3H, Me), 2.368
/
8.5 Hz, 2H, Htol), 7.44 (d,
7.8 Hz, 6H, Htol), 7.13
8.3 Hz, 2H, Htol),
/
/
mmol) at ꢃ78 8C followed by slow warming to room
/
/
/
temperature to give a fine suspension of dilithiohepta-
diyne. After 10 min, ZnBr2 (0.1743 g, 0.774 mmol) was
/
(s, 3H, Me), 2.343 (s, 3H, Me), 2.316 (s, 3H, Me).
13C{1H} NMR (125 MHz, CDCl3): d 138.49, 137.95,
137.51, 136.42, 134.85, 131.53 (CH), 131.26 (CH),
129.60 (CH), 129.15 (CH), 129.09 (CH), 129.04 (CH),
128.73 (CH), 128.42 (CH), 127.57, 120.44, (CTol), 98.36,
added to give a thick white suspension of BrZnCÅ
CCH2CH2CH2CÅCZnBr. The suspension was then
cannula transferred into a solution of [Cp(CO)2MnÅ
CPh]BCl4 (18) (348.5 mg, 0.834 mmol) in 70 ml
CH2Cl2 at ꢃ78 8C. The color of the carbyne solution
changed from yellow to red. After 20 min at ꢃ78 8C, a
/
/
/
/
96.57, 91.60, 90.75, (CÅ/C) 21.53 (2 CH3), 21.39 (CH3),
/
21.27 (CH3). Not all quaternary carbons were identified.
MS (EI) m/z calc. for C34H28 [Mꢁ]: 436.2191. Found:
436.2185.
TLC sample was taken. The deep red solution visibly
lightened in the capillary tube and TLC analysis showed
only the enediyne complex 19. Evaporation of solvent
followed by flash chromatography (silica, 20% ether/
hexanes) gave 19 (165 mg, 71%) as a bright red solid.
NMR analysis was complicated by facile decomposition
3.8. Thermolysis of (h5-C5H4Me)(CO)2MnÄ
CTol (11) at 100 8C
/
C(Ph)CÅ
/
1
of the sample, leading to broad lines. H NMR (500
A solution of 11 (292 mg, 0.74 mmol) in 1.0 ml
C6H5CH3 was heated at 90 8C for 30 min. TLC analysis
MHz, 5 8C, CDCl3): d 7.3ꢂ7.0 (m, Ph), 4.710 (s, Cp),
/
3.2ꢂ
/
2.8 (m, CH2). 2.3ꢂ2.2 (m, CH2). IR (C6H14): 1982,
/
showed complete disappearance of 11 (deep red, Rfꢀ
0.33, 5% EtOAc/hexanes) and appearance of a new light
red spot, presumably enediyne complex (light red, Rfꢀ
0.28). After 6 h at 90 8C, TLC showed a new yellow
spot at Rfꢀ0.35. Flash chromatography (5% EtOAc/
/
55
1916 cmꢃ1. MS (ESI) m/z calc. for C35H Mn2O4
26
[Mꢁ]: 620.0592. Found: 620.0565.
/
/
3.11. 1,2-Bis(phenylethynyl)cyclopentene (20)
hexanes) followed by preparative TLC gave a mixture of
enediynes 15, 16, and 17 (60 mg, 40%) as a yellow wax.
A solution of 19 (60 mg, 0.097 mmol) in 0.98 ml
C6H5CH3 was heated at 90 8C for 14 h. Preparative
thin layer (5% EtOAc/hexanes) gave 20 (24 mg, 85%
pure by NMR, 70% yield) as a slightly yellow solid.
1
Partial Data: H NMR (500 MHz, CDCl3): d 7.99 (t,
Jꢀ
/
8 Hz, Tol), 7.92 (d, Jꢀ
/
8 Hz, Tol), 7.6ꢂ7.0 (m, Ph),
/
2.429 (0.360 H,15-E), 2.423 (0.166 H, 16-E), 2.366
(0.026 H, 17-Z), 2.360 (0.065 H, 16-Z), 2.337 (0.065
H, 16-Z), 2.330 (0.077 H, 17-E), 2.314 (0.174 H, 15-Z),
2.304 (0.116 H, 16-E) (Me’s). 13C{1H} NMR (125 MHz,
CDCl3): d 138.64, 138.12, 137.66, 136.24, 134.65 (Ar,
Complex 20 was contaminated with Â15% CpMn(CO)3
/
[1H NMR: d 4.759 (s); 13C{1H} NMR: d 82.78].
CpMn(CO)3 did not interfere with the spectroscopic
identification of 20 by comparison with the literature
1
quat), 131ꢂ
/
127 (overlapping peaks, aromatic), 98.19,
C); 21.547, 21.399 (2C),
21.275 (Me). HRMS m/z calc. for C32H24: 408.1878.
data [12]. H NMR (500 MHz, CD2Cl2): d 7.56ꢂ
/
7.46
7.5 Hz,
7.5 Hz, 2H,
CH2CH2CH2). 13C NMR (125 MHz, CD2Cl2): d
96.38, 92.06, 91.21, 90.55 (CÅ
/
(m, 2H, Ph), 7.40ꢂ
/
7.30 (m, 3H, Ph), 2.70 (t, Jꢀ
/
4H, CH2CH2CH2), 2.03 (pentet, Jꢀ
/
Found: 408.1894.
1
3
131.88 (dt, JCH
ꢀ
/
163 Hz, JCH
ꢀ
/
7 Hz, CPh), 130.69
3.9. Thermolysis of (h5-C5H4Me)(CO)2MnÄ
CÅCPh (12) at 100 8C
/C(Tol)-
(m, CÄ
/
C), 128.78 (dt, 1JCH
ꢀ
/
163 Hz, 1JCH
ꢀ
/
6 Hz, CPh),
1
128.76 (d, JCH
3
/
ꢀ
/
162 Hz, CPh), 123.76 (t, JCH
5 Hz, CÅCPh), 86.62 (s, CÅ
132 Hz, CH2CH2CH2), 23.52 (t, 1JCH
ꢀ
/
7 Hz,
CPh), 96.80 (t, 3JCH
37.41 (t, 1JCH
ꢀ
/
/
/CPh),
A solution of 12 (113 mg, 0.29 mmol) in 1.0 ml
C6H5CH3 was heated at 90 8C for 6 h. Flash chroma-
tography (5% EtOAc/hexanes) followed by preparative
ꢀ
/
ꢀ
/
131 Hz, CH2CH2CH2). HRMS m/z calc. for C21H16:
268.1252. Found: 268.1247.

326
C.P. Casey et al. / Inorganica Chimica Acta 345 (2003) 320ꢂ326
/
(b) C.P. Casey, T.J. Burkhardt, C.A. Bunnell, J.C. Calabrese, J.
Am. Chem. Soc. 99 (1977) 2127;
4. Supplementary material
(c) C.P. Casey, S.W. Polichnowski, J. Am. Chem. Soc. 99 (1977)
6097;
Crystallographic data (excluding structure factors)
have been deposited with the Cambridge Crystallo-
graphic Data Centre, CCDC No. 186957 for com-
pound 9. Copies of the data may be obtained free of
charge from The Director, CCDC, 12 Union Road,
(d) H. Fischer, J. Schmid, J. Mol. Catal. 46 (1988) 277;
(e) H. Fischer, S. Zeuner, K. Ackermann, J. Schmid, Chem. Ber.
119 (1986) 1546;
(f) S. Fischer, K. Ackermann, Chem. Commun. (1984) 684;
(g) F. Hohmann, S. Siemoneit, M. Nieger, S. Kotila, K.H. Dotz,
Chem. Eur. J. 3 (1997) 853.
Cambridge CB2 1EZ, UK (fax: ꢁ44-1223-336-033; e-
/
mail: deposit@ccdc.cam.ac.edu or www: http://
www.ccdc.cam.ac.uk).
[6] M.A. Sierra, J.C. del Amo, M.J. Mancheno, M. Go´mez-Gallego,
˜
J. Am. Chem. Soc. 123 (2001) 851.
[7] S. Kraft, Ph.D. Thesis, University of Wisconsin-Madison, Madi-
son, 2001.
[8] Y. Ortin, Y. Coppel, N. Lugan, R. Mathieu, M.J. McGlinchey,
Chem. Commun. (2001) 1690.
[9] E.O. Fischer, E.W. Meineke, F.R. Kreißl, Chem. Ber. 110 (1977)
References
[1] For reviews of heteroatom substituted alkynylcarbene complexes,
see: (a) R. Aumann, H. Nienaber, Adv. Organomet. Chem. 41
(1997) 163;
1140.
˚
7.7162(6) A,
¯
[10] X-ray crystal data for C23H17MnO2: triclinic, P1; aꢀ
/
˚
˚
bꢀ
102.651(3)8, xꢀ
133(2) K, Dcalc
pendent reflections (2.615
/
8.2328(8) A, cꢀ
104.937(2)8, Vꢀ
1.400 mg mꢃ3, R(F)ꢀ
u 528.278). All non-hydrogen atoms
/
15.3872(12) A, aꢀ
/
97.730(2)8, bꢀ
/
(b) W.D. Wulff, in: E.W. Abel, F.G.A. Stone, G. Wilkinson
(Eds.), Comprehensive Organometallic Chemistry II, Pergamon
Press, Oxford, 1995; vol. 12, chapter 5.3;
3
˚
/
/
902.42(13) A , Zꢀ
/
2, Tꢀ
/
ꢀ/
/
0.0352 for 3735 inde-
/
/
(c) J.W. Herndon, Coord. Chem. Rev. 181 (1999) 177;
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(f) J.W. Herndon, Coord. Chem. Rev. 206/207 (2000) 237;
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J.A. Ramsden, A.M. Arif, J.A. Gladysz, J. Am. Chem. Soc. 115
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were refined with anisotropic displacement coefficients. All
hydrogen atoms were included in the structure as idealized
contributors. All software and sources of the scattering factors
are contained in the SHELXTL (version 5.1) program library (G.
Sheldrick, Bruker Analytical X-ray Systems, Madison, WI).
Further details are available from Supporting Information.
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(b) W. Weng, A.M. Arif, J.A. Gladysz, Angew. Chem., Int. Ed.
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See also (f) O.I. Yurchenko, N.V. Komarov, T.N. Dybova, J.
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[5] (a) C.P. Casey, R.L. Anderson, J. Chem. Soc., Chem. Commun.
(1975) 895;