Alkoxy-substituted group 6 allenylidene complexes - Synthesis and properties

Article abstract of DOI:10.1016/j.ica.2005.08.010

Bis(alkoxy)allenylidene complexes, [(CO)₅MCCC(OR′)OR], as well as mono(alkoxy)allenylidene complexes, [(CO)₅MCCC(OR′)Ph], of chromium and tungsten are accessible from propynones [HCCC(O)Ph] or propynoic acid esters [HCCC(O)OR; R = Et, (-)-menthyl, endo-bornyl] by the following reaction sequence: (a) deprotonation of the alkynes, (b) reaction with [(CO)₅M-THF] (M = Cr, W), and (c) alkylation of the resulting alkynyl metallate, [(CO)₅MCCC(O)R], with Meerwein salts. Vinylidene complexes, [(CO)₅MCC(R′)C(O)OR], are formed as a by-product by C_β-alkylation of the alkynyl metallate. Dimethylamine displaces one alkoxy substituent of the bis(alkoxy)allenylidene complexes to give dimethylamino(alkoxy)allenylidene complexes, [(CO)₅MCCC(OR)NMe ₂]. The analogous reaction of dimethylamine with a mono(alkoxy)-substituted allenylidene complex affords the aminoallenylidene complex [(CO)₅CrCCC(NMe₂)Ph]. When the amine is used in large excess, the α,β-unsaturated aminocarbene complex [(CO) ₅CrC(NMe₂)C(H)C(NMe₂)Ph] is additionally formed by addition of the amine across the C_αC_β-bond of the allenylidene ligand. The reaction of [(CO)₅MCCC(OEt) ₂] with dimethyl ethylenediamine offers access to bis(amino)allenylidene complexes, in which C_γ is part of a five-membered heterocycle. Photolysis of bis(alkoxy)allenylidene complexes in the presence of triphenylphosphine yields tetracarbonyl- and tricarbonyl{bis(phosphine)}allenylidene complexes. Diethylaminopropyne inserts into the C_βC_γ bond of [(CO) ₅MCCC(OEt)OMethyl] to give alkenylallenylidene complexes. Subsequent acid-catalyzed intramolecular cyclization affords a pyranylidene complex.

Full text of DOI:10.1016/j.ica.2005.08.010

Inorganica Chimica Acta 359 (2006) 617–632
www.elsevier.com/locate/ica
Alkoxy-substituted group 6 allenylidene complexes –
Synthesis and properties
*
Normen Szesni, Bernhard Weibert, Helmut Fischer
Fachbereich Chemie, Universita¨t Konstanz, Fach M727, D-78457 Konstanz, Germany
Received 14 July 2005; accepted 14 August 2005
Available online 19 September 2005
Abstract
Bis(alkoxy)allenylidene complexes, [(CO)5M@C@C@C(OR0)OR], as well as mono(alkoxy)allenylidene complexes, [(CO)5M@C@
C@C(OR0)Ph], of chromium and tungsten are accessible from propynones [HAC„CAC(@O)Ph] or propynoic acid esters [HAC„
CAC(@O)OR; R = Et, (ꢀ)-menthyl, endo-bornyl] by the following reaction sequence: (a) deprotonation of the alkynes, (b) reaction with
[(CO)5M-THF] (M = Cr, W), and (c) alkylation of the resulting alkynyl metallate, [(CO)5MAC„CAC(@O)R], with Meerwein salts.
Vinylidene complexes, [(CO)5M@C@C(R0)C(@O)OR], are formed as a by-product by Cb-alkylation of the alkynyl metallate. Dimeth-
ylamine displaces one alkoxy substituent of the bis(alkoxy)allenylidene complexes to give dimethylamino(alkoxy)allenylidene complexes,
[(CO)5M@C@C@C(OR)NMe2]. The analogous reaction of dimethylamine with a mono(alkoxy)-substituted allenylidene complex affords
the aminoallenylidene complex [(CO)5Cr@C@C@C(NMe2)Ph]. When the amine is used in large excess, the a,b-unsaturated aminocar-
bene complex [(CO)5Cr@C(NMe2)AC(H)@C(NMe2)Ph] is additionally formed by addition of the amine across the CaACb-bond of the
allenylidene ligand. The reaction of [(CO)5M@C@C@C(OEt)2] with dimethyl ethylenediamine offers access to bis(amino)allenylidene
complexes, in which Cc is part of a five-membered heterocycle. Photolysis of bis(alkoxy)allenylidene complexes in the presence of triphe-
nylphosphine yields tetracarbonyl- and tricarbonyl{bis(phosphine)}allenylidene complexes. Diethylaminopropyne inserts into the
Cb@Cc bond of [(CO)5M@C@C@C(OEt)OMethyl] to give alkenylallenylidene complexes. Subsequent acid-catalyzed intramolecular
cyclization affords a pyranylidene complex.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Allenylidene complexes; Chromium; Tungsten; Carbene complexes; Substitution
1. Introduction
increasingly attracted interest [4–13]. Experimental and
theoretical studies confirm their great potential as building
blocks for stoichiometric syntheses and as pre-catalysts
[14,15]. In addition, allenylidene complexes exhibit interest-
ing physico-chemical properties that make them potentially
useful as one-dimensional wires [16] and for opto-electronic
devices [17].
Analogously to carbene complexes, the substitution pat-
tern at the terminal carbon atom (Cc) of the allenylidene li-
gand [4h,4k] and the steric and electronic requirements of
the metal–ligand moiety [4g,4f] exert considerable influence
on the electronic structure and determines to some extent
the reactivity of these complexes. Most studies on the reac-
tivity of allenylidene complexes carried out until now were
performed with non-heteroatom substituted complexes like
In 1964 Fischer and Maasbo¨l reported on the synthesis
and characterization of the first transition metal carbene,
[(CO)5M@C(Ph)OMe] [1,2]. Since then, a large number
of carbene complexes have been prepared and their proper-
ties and reactivity have been studied in detail. Carbene
complexes have found broad application in synthesis and
catalysis and have been evolved into one of the most pow-
erful tools in organic and organometallic chemistry [3].
In recent years unsaturated carbene complexes like
allenylidene complexes, [LnM@C@C@C(R1)R2], have
*
Corresponding author. Tel.: +49 7531 882783; fax: +49 7531 883136.
E-mail address: helmut.fischer@uni-konstanz.de (H. Fischer).
0020-1693/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2005.08.010

618
N. Szesni et al. / Inorganica Chimica Acta 359 (2006) 617–632
diarylallenylidene complexes. These compounds are readily
available for a broad range of transition metals by Sele-
gueÕs protocol [18] starting from 1,1-disubstituted propar-
gylic alcohols. Although two of the very first allenylidene
complexes to be prepared [19,20] were mono(amino)-
substituted complexes, general methods for the synthesis
of a broad variety of p-donor-substituted allenylidene com-
plexes were lacking until recently. Some p-donor/methyl-
substituted ruthenium allenylidene complexes [21,22] were
prepared by addition of protic nucleophiles such as amines,
thiols or selenoles to the Ca@Cb bond of highly reactive
butatrienylidene ruthenium intermediates. Winter et al.
studied the influence of the substitution pattern on the elec-
tronic properties of these allenylidene ruthenium com-
plexes [4h,21]. This butatrienylidene route is restricted to
the synthesis of mono-heteroatom-substituted ruthenium
allenylidene complexes and does not allow to prepare alk-
oxy-substituted allenylidene complexes, since butatrienyli-
dene intermediates do not add alcohols. However, addition
of alcohols to pentatetraenylidene complexes affords alke-
nyl(alkoxy)allenylidene complexes [23].
Previously, we described a new route to N-stabilized
allenylidene complexes of chromium and tungsten using
propynoic acid amides, C-ethinylimines or 2-ethinylpyri-
dine as precursors. Deprotonation of the alkynes, subse-
quent reaction with [(CO)5M-THF] (M = Cr, W) and
alkylation of the alkynyl metallate afforded NR2/OR-,
NR2/R-, NR2/SR- or pyridyl-substituted allenylidene com-
plexes [4k,24]. We now report on the synthesis of alkoxy-
substituted allenylidene complexes (OR/OR; OR/R) of
chromium and tungsten and on their reaction with nucleo-
philes such as dimethylamine, triphenylphosphine, and
diethylaminopropyne.
2.2. Reaction of in situ generated bis(alkoxy)-substituted
allenylidene complexes 1a and 1b with dimethylamine or
N,N0-dimethyl ethylene diamine
2.2.1. Preparation of solutions containing 1a and 1b
Method (a). At ꢀ78 ꢁC a solution of 3.1 ml of BuLi
(5 mmol, 1.6 M in hexane) was added dropwise to a solu-
tion of 0.51 ml (5 mmol) of ethyl propiolate in 50 ml of
dry THF. The solution was stirred for 20 min at this tem-
perature and then 50 ml of a solution of [(CO5)M(THF)]
(M = Cr, W; 0.1 M in THF) was added. The cooling bath
was removed and the brown solution was stirred for 30 min
at ambient temperature. The solvent was removed in va-
cuo. The remaining oily residue was dissolved in 50 ml of
CH2Cl2 and treated at 0 ꢁC with 5 mmol of [Et3O]BF4.
Stirring was continued for another 20 min at this
temperature.
Method (b). At ꢀ78 ꢁC a solution of 3.1 ml of BuLi
(5 mmol, 1.6 M in hexane) was added dropwise to a solu-
tion of 0.86 g (5 mmol) of 1,1,1-tris(ethoxy)propyne in
50 ml of dry THF. The solution was stirred at ꢀ78 ꢁC for
20 min. Then 50 ml of a solution of [(CO5)M(THF)]
(M = Cr, W; 0.1 M in THF) was added. The cooling bath
was removed and the brown solution was stirred for 60 min
at ambient temperature. The solvent was removed in va-
cuo. The remaining oily residue was dissolved in 50 ml of
CH2Cl2. The solution was treated with 5 g of silica gel at
ambient temperature and stirred for further 60 min. The
complexes can be identified by their IR spectra.
2.2.1.1. Pentacarbonyl(3,3-bisethoxy-1,2-propadienylidene)
chromium (1a). IR (CH2Cl2, cmꢀ1): m(CO) = 2083 vw,
1943 vs, 1921 sh; m(CCC) = 1978 m.
2. Experimental
2.2.1.2. Pentacarbonyl(3,3-bisethoxy-1,2-propadienylidene)
tungsten (1b). IR (CH2Cl2, cmꢀ1): m(CO) = 2088 vw, 1938
vs; m(CCC) = 1976 m.
2.1. General
All operations were performed in an inert gas atmo-
sphere using standard Schlenk techniques. Solvents were
dried by distillation from CaH2 (CH2Cl2), LiAlH4 (pen-
tane) and sodium (THF, Et2O). The silica gel used for
chromatography (Baker, silica for flash chromatography)
was argon-saturated. The yields refer to analytically pure
compounds and were not optimized. Instrumentation:
1H, 13C and 31P NMR spectra were recorded with Jeol
JNX 400, Varian Inova 400 and Bruker AC 250 spec-
trometers at ambient temperature. Chemical shifts are
relative to the residual solvent or tetramethyl silane
peaks (1H, 13C) or 100% H3PO4 (31P). IR: Biorad FTS
60. MS: Finnigan MAT 312. Elemental analysis: Heraeus
CHN-O-Rapid. 1,1,1-Tris(ethoxy)propyne [25], (ꢀ)-men-
thyl propiolate [26], endo-bornyl propiolate [26], phenyl-
propynone [27], and 1-N,N-diethylamino propyne [28]
were prepared according to the literature procedures.
All other chemicals were used as supplied by commercial
suppliers.
2.2.2. Reaction of in situ prepared 1a and 1b with
dimethylamine
At ambient temperature, 2 ml of dimethylamine was
added to a freshly prepared solution of 1a or 1 b in 50 ml
of CH2Cl2. After 2 min, the excess of dimethylamine and
the solvent were evaporated. The remaining residue was
chromatographed on silica gel at ꢀ20 ꢁC using a mixture
of pentane/CH2Cl2 as the eluent.
2.2.2.1. Pentacarbonyl(3-ethoxy-3-dimethylamine-1,2-propa-
dienylidene)chromium (2a). Yield: 0.32 g (20%; method a);
0.16 g (10%; method b). Identification through comparison
of its spectroscopic data with those published [24].
2.2.2.2. Pentacarbonyl(3-ethoxy-3-dimethylamine-1,2-propa-
dienylidene)tungsten (2b). Yield: 0.45 g (21%; method a);
0.15 g (7%; method b). Identification through comparison
of its spectroscopic data with those published [24].

N. Szesni et al. / Inorganica Chimica Acta 359 (2006) 617–632
619
2.2.3. Reaction of in situ prepared 1a and 1b with N,N0-
dimethyl ethylenediamine
following green band contained the vinylidene complexes
7a,b–9a,b (pentane/CH2Cl2, 2:1).
At ambient temperature, 1 ml of N,N0-dimethyl ethylene
diamine was added to a freshly prepared solution of 1a or
1b in 50 ml of CH2Cl2. After 10 min at this temperature,
the solvent was evaporated and the remaining residue
was chromatographed on silica gel at ꢀ20 ꢁC using THF
as the eluent.
The carbon and hydrogen atoms of the terpene substit-
uents of the compounds are numbered as follows:
7
(-)-menthyl:
endo-bornyl:
2
10
7
3
1
O
2
1
O
4
8
6
9
6
3
5
2.2.3.1. Pentacarbonyl(N,N0-dimethyl-4,7-diaza-cyclo[03,7]-
hepta-1,2-dien-1-ylidene)chromium (3a). Yellow solid.
Yield: 0.31 g (20%; method a); m.p. 143 ꢁC. IR (THF,
cmꢀ1): m(CO) = 2087 vw, 1929 vs, 1904 m; m(CCC) = 2021
m. 1H NMR (400 MHz, [d6]-acetone): d = 3.15 (s, 6H,
NCH3), 3.85 (s, 4H, NCH2). 13C NMR (100 MHz, [d6]-ace-
tone): d = 34.1 (NCH3), 49.0 (NCH2), 96.9 (Cb), 147.9 (Cc),
185.1 (Ca), 219.0 (cis-CO), 222.3 (trans-CO). MS (FAB), m/
z (%): 314 (26) [M+], 300 (41) [(M ꢀ CH2)+], 272 (13)
[(M ꢀ CH2M ꢀ CO)+], 244 (48) [(M ꢀ CH2 ꢀ 2CO)+],
216 (100) [(M ꢀ CH2 ꢀ 3CO)+]. UV–Vis (kmax, nm (log e)
[CH2Cl2]): 380 (4.103). Anal. Calc. for C12H10CrN2O5
(314.22): C, 45.87; H, 3.21; N, 8.92. Found: C, 45.17; H,
3.46; N, 8.52%.
5
9
8
4
10
2.3.1. Pentacarbonyl(3-(ꢀ)-menthyloxy-3-methoxy-1,2-propa
dienylidene)chromium (4a)
Orange oil. Yield: 0.23 g (11%). IR (THF, cmꢀ1):
1
m(CO) = 2083 vw, 1944 vs, 1926 sh; m(CCC) = 1981 m. H
NMR (400 MHz, [d6]-acetone): d = 0.79 (d, 3JHH = 6.6 Hz,
3H, H7), 0.82 (m, 1H, H3), 0.86 (d, 3JHH = 7.0 Hz, 3H, H9),
3
0.89 (d, JHH = 6.7 Hz, 3H, H10), 1.09 (m, 2H, H5), 1.53
(m, 2H, H4), 1.68 (m, 2H, H2), 1.82 (m, 1H, H8), 2.21
(m, 1H, H6), 4.18 (s, 3H, OCH3), 5.11 (td, 3JHH = 10.9 Hz,
2JHH = 4.2 Hz, 1H, H1). 13C NMR (100 MHz, [d6]-ace-
tone): d = 16.3 (C7), 20.5 (C9), 21.7 (C10), 23.2 (C5), 26.2
(C8), 31.5 (C3), 33.7 (C4), 40.2 (C2), 46.8 (C6), 60.3
(OCH3), 88.2 (C1), 107.4 (Cb), 149.1 (Cc), 216.2 (cis-CO),
221.0 (trans-CO), 240.9 (Ca). MS (EI), m/z (%): 414 (18)
[M+], 358 (10) [(M ꢀ 2CO)+], 330 (10) [(M ꢀ 3CO)+], 302
(39) [(M ꢀ 4CO)+], 276 (100) [(M ꢀ C10H18)+], 274 (37)
[(M ꢀ 5CO)+]. UV–Vis (kmax, nm (log e) [CH2Cl2]): 442
(4.269). Anal. Calc. for C19H22CrO7 (414.38): C, 55.07;
H, 5.35. Found: C, 55.14; H, 5.52%.
2.2.3.2. Pentacarbonyl(N,N0-dimethyl-4,7-diaza-cyclo[03,7]-
hepta-1,2-dien-1-ylidene)tungsten (3b). Yellow solid. Yield:
0.29 g (13%; method a); m.p. 123 ꢁC. IR (THF, cmꢀ1):
1
m(CO) = 2090 vw, 1924 vs, 1898 m; m(CCC) = 2024 m. H
NMR (400 MHz, [d6]-acetone): d = 3.15 (s, 6H, NCH3),
3.87 (s, 4H, NCH2). 13C NMR (100 MHz, [d6]-acetone):
d = 34.5 (NCH3), 49.4 (NCH2), 95.9 (Cb), 148.4 (Cc),
167.3 (Ca), 198.6 (cis-CO), 203.9 (trans-CO). MS (FAB),
m/z (%): 446 (11) [M+], 306 (100) [(M ꢀ 5CO)+]. UV–Vis
(kmax, nm (log e) [CH2Cl2]): 377 (4.042). Anal. Calc. for
C12H10N2O5W (446.07): C, 32.31; H, 2.26; N, 6.28. Found:
C, 31.96; H, 2.36; N, 6.37%.
2.3.2. Pentacarbonyl(3-(ꢀ)-menthyloxy-3-methoxy-1,2-
propadienylidene)tungsten (4b)
Orange oil. Yield: 0.16 g (6%). IR (THF, cmꢀ1
)
m(CO) = 2088 vw, 1938 vs, 1921 sh; m(CCC) = 1980 m.
3
1H NMR (400 MHz, CDCl3): d = 0.71 (d, JHH = 6.9 Hz,
3
2.3. General procedure for the preparation of bis(alkoxy)-
substituted allenylidene complexes 4a,b–6a,b and vinylidene
complexes 7a,b–9a,b
3H, H7), 0.74 (m, 1H, H3), 0.85 (d, JHH = 7.2 Hz, 3H,
H9), 0.90 (d, JHH = 6.9 Hz, 3H, H10), 1.06 (m, 2H, H5),
3
1.49 (m, 2H, H4), 1.65 (m, 2H, H2), 1.79 (m, 1H, H8),
2.17 (m, 1H, H6), 4.17 (s, 3H, OCH3), 5.08 (td,
3JHH = 10.9 Hz, JHH = 4.2 Hz, 1H, H1). 13C NMR
2
At ꢀ78 ꢁC, a solution of 3.1 ml of BuLi (5 mmol, 1.6 M
in hexane) was added dropwise to a solution of 5 mmol of
the appropriate propiolate in 50 ml of dry THF. The solu-
tion was stirred for 20 min at ꢀ78 ꢁC. Then 50 ml of a solu-
tion of [(CO5)M(THF)] (M = Cr, W; 0.1 M in THF) was
added. The cooling bath was removed and the brown solu-
tion was stirred for 30 min at ambient temperature. The
solvent was removed in vacuo. The remaining oily residue
was dissolved in 50 ml of CH2Cl2 and treated with 5 mmol
of [R3O]BF4 (R = Me, Et) at 0 ꢁC. The solution was then
stirred for another 60 min at 0 ꢁC. The solvent was again
removed in vacuo and the crude reaction mixture chro-
matographed on silica using mixtures of pentane/CH2Cl2
as the eluent. The first red fraction contained the allenylid-
ene complexes 4a,b–6a,b (pentane/CH2Cl2, 7:1) and the
(100 MHz, CDCl3): d = 16.4 (C7), 20.4 (C9), 21.7 (C10),
23.2 (C5), 26.2 (C8), 31.5 (C3), 33.6 (C4), 40.2 (C2), 46.8
(C6), 60.5 (OCH3), 88.6 (C1), 106.1 (Cb, JWC = 26.7 Hz),
152.2 (Cc), 195.9 (cis-CO, JWC = 125.0 Hz), 201.1 (trans-
CO, JWC = 126.9 Hz), 214.8 (Ca, JWC = 109.6 Hz). MS
(EI), m/z (%): 546 (12) [M+], 406 (100) [(M ꢀ 5CO)+].
UV–Vis (kmax, nm (log e) [CH2Cl2]): 437 (4.336). Anal.
Calc. for C19H22O7W (546.23): C, 41.78; H, 4.06. Found:
C, 41.70; H, 4.28%.
2
1
1
1
2.3.3. Pentacarbonyl(3-ethoxy-3-(ꢀ)-menthyloxy-1,2-
propadienylidene)chromium (5a)
Orange oil. Yield: 1.05 g (49%). IR (THF, cmꢀ1):
1
m(CO) = 2084 vw, 1944 vs, 1926 sh; m(CCC) = 1983 m. H

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N. Szesni et al. / Inorganica Chimica Acta 359 (2006) 617–632
NMR (400 MHz, CDCl3): d = 0.78 (d, 3JHH = 7.1 Hz, 3H,
nm (log e) [CH2Cl2]): 440 (4.249). Anal. Calc. for
C20H22CrO7 (426.39): C, 56.34; H, 5.20. Found: C, 56.30;
H, 5.26%.
3
H7), 0.82 (m, 1H, H3), 0.86 (d, JHH = 7.1 Hz, 3H, H9),
3
0.89 (d, JHH = 6.7 Hz, 3H, H10), 1.08 (m, 2H, H5), 1.40
3
(t, JHH = 8.0 Hz, 3H, OCH2CH3), 1.45 (m, 2H, H4),
1.67 (m, 2H, H2), 1.78 (m, 1H, H8), 2.20 (m, 1H, H6),
2.3.6. Pentacarbonyl(3-endo-bornyloxy-3-ethoxy-1,2-
propadienylidene)tungsten (6b)
3
4.61 (q, JHH = 7.1 Hz, 2H, OCH2CH3), 5.11 (td,
2
3JHH = 10.9 Hz, JHH = 4.3 Hz, 1H, H1). 13C NMR
Orange-red oil. Yield: 1.43 g (51%). IR (THF, cmꢀ1):
1
(100 MHz, CDCl3): d = 14.0 (OCH2CH3), 16.3 (C7), 20.5
(C9), 21.7 (C10), 23.3 (C5), 26.2 (C8), 31.5 (C3), 33.7 (C4),
40.3 (C2), 46.9 (C6), 70.9 (OCH2CH3), 87.8 (C1), 107.1
(Cb), 148.8 (Cc), 216.3 (cis-CO), 221.0 (trans-CO), 238.2
(Ca). MS (EI), m/z (%): 428 (32) [M+], 372 (17)
[(M ꢀ 2CO)+], 344 (13) [(M ꢀ 3CO)+], 316 (82)
[(M ꢀ 4CO)+], 290 (100) [(M ꢀ C10H18)+], 288 (70)
[(M ꢀ 5CO)+]. UV–Vis (kmax, nm (log e) [CH2Cl2]): 439
(4.243). Anal. Calc. for C20H24CrO7 (428.37): C, 56.07;
H, 5.65. Found: C, 55.63; H, 5.42%.
m(CO) = 2087 vw, 1938 vs, 1924 sh; m(CCC) = 1980 m. H
NMR (400 MHz, [d6]-acetone): d = 0.79 (m, 1H, H4),
0.86 (s, 3H, H7), 0.89 (s, 3H, H10), 0.91 (s, 3H, H9), 1.25
3
(m, 2H, H5), 1.40 (t, JHH = 7.2 Hz, 3H, OCH2CH3),
1.73–1.85 (m, 3H, H2/H3), 2.56 (m, 1H, H4), 4.70 (q,
3
3JHH = 7.4 Hz, 2H, OCH2CH3), 5.37 (dt, JHH = 10.2 Hz,
2JHH = 4.2 Hz, 1H, H1). 13C NMR (100 MHz, [d6]-ace-
tone): d = 13.7 (OCH2CH3), 14.2 (C7), 18.9 (C9), 19.8
(C10), 27.6 (C4), 28.1 (C5), 36.7 (C2), 45.4 (C3), 48.9 (C8),
50.4 (C6), 72.7 (OCH2CH3), 94.0 (C1), 106.3 (Cb,
1
2JWC = 29.7 Hz), 154.6 (Cc), 196.8 (cis-CO, JWC
=
1
2.3.4. Pentacarbonyl(3-ethoxy-3-(ꢀ)-menthyloxy-1,2-
propadienylidene)tungsten (5b)
124.0 Hz), 201.6 (trans-CO, JWC = 125.9 Hz), 204.3 (Ca,
1JWC = 96.1 Hz). MS (EI), m/z (%): 558 (13) [M+], 418
(100) [(M ꢀ 5CO)+]. UV–Vis (kmax, nm (log e) [CH2Cl2]):
436 (4.266). Anal. Calc. for C20H22O7W (558.24): C,
43.03; H, 3.97. Found: C, 43.09; H, 3.92%.
Orange oil. Yield: 1.29 g (46%). IR (THF, cmꢀ1):
1
m(CO) = 2088 vw, 1939 vs, 1924 sh; m(CCC) = 1982 m. H
3
NMR (400 MHz, CDCl3): d = 0.78 (d, JHH = 6.8 Hz,
3
3H, H7), 0.80 (m, 1H, H3), 0.87 (d, JHH = 7.0 Hz, 3H,
3
H9), 0.89 (d, JHH = 6.9 Hz, 3H, H10), 1.03 (m, 2H, H5),
2.3.7. Pentacarbonyl(2-(ꢀ)-menthyloxycarbonyl-2-methyl-
1-ethenylidene)chromium (7a)
3
1.40 (t, JHH = 7.0 Hz, 3H, OCH2CH3), 1.49 (m, 2H,
H4), 1.65 (m, 2H, H2), 1.76 (m, 1H, H8), 2.18 (m, 1H,
Green oil. Yield: 0.43 g (21%). IR (THF, cmꢀ1):
3
H6), 4.60 (q, JHH = 7.0 Hz, 3H, OCH2CH3), 5.08 (td,
m(CO) = 2095 m, 2035 w, 1999 sh, 1981vs. 1H NMR
2
3
3JHH = 10.9 Hz, JHH = 4.2 Hz, 1H, H1). 13C NMR
(250 MHz, [d6]-acetone): d = 0.77 (d, JHH = 6.8 Hz, 3H,
3
3
(100 MHz, CDCl3): d = 14.1 (OCH2CH3), 16.4 (C7), 20.5
(C9), 21.7 (C10), 23.2 (C5), 26.2 (C8), 31.5 (C3), 33.7 (C4),
40.3 (C2), 46.9 (C6), 71.2 (OCH2CH3), 88.2 (C1), 105.9
(Cb, 2JWC = 26.9 Hz), 151.8 (Cc), 195.9 (cis-CO,
H7), 0.86 (d, JHH = 7.0 Hz, 3H, H9), 0.91 (d, JHH =
7.0 Hz, 3H, H10), 1.03 (m, 2H, H5), 1.37 (m, 1H, H3),
1.50 (m, 1H, H8), 1.68 (m, 2H, H2), 1.79 (s, 3H, CbCH3),
3
1.93–2.11 (m, 3H, H6 + H4), 4.80 (td, JHH = 10.8 Hz,
1
1JWC = 125.0 Hz), 201.1 (trans-CO, JWC = 125.0 Hz),
2JHH = 4.0 Hz, 1H, H1). 13C NMR (62.5 MHz, [d6]-ace-
tone): d = 8.9 (CbCH3), 17.0 (C7), 21.7 (C9), 23.0 (C10),
24.5 (C5), 27.4 (C8), 32.9 (C3), 35.7 (C4), 42.6 (C2), 48.7
(C6), 75.2 (C1), 120.1 (Cb), 170.9 (COOR), 213.4 (cis-
CO), 220.4 (trans-CO), 397.5 (Ca). MS (FAB), m/z (%):
414 (11) [M+], 358 (11) [(M ꢀ 2CO)+], 330 (17)
[(M ꢀ 3CO)+], 302 (65) [(M ꢀ 4CO)+], 274 (100)
[(M ꢀ 5CO)+]. C19H22CrO7 (414.38).
1
212.6 (Ca, JWC = 107.7 Hz). MS (EI), m/z (%): 560 (16)
[M+], 532 (7) [(M ꢀ 2CO)+], 420 (100) [(M ꢀ 5CO)+].
UV–Vis (kmax, nm (log e) [CH2Cl2]): 435 (4.347). Anal.
Calc. for C20H24O7W (560.26): C, 42.88; H, 4.32. Found:
C, 43.05; H, 4.02%.
2.3.5. Pentacarbonyl(3-endo-bornyloxy-3-ethoxy-1,2-
propadienylidene)chromium (6a)
Orange-red oil. Yield: 1.26 g (59%). IR (THF, cmꢀ1):
m(CO) = 2083 vw, 1943 vs, 1925 sh; m(CCC) = 1982 m.
1H NMR (400 MHz, [d6]-acetone): d = 0.88 (m, 1H, H4),
0.94 (s, 3H, H7), 0.98 (s, 3H, H10), 0.99 (s, 3H, H9), 1.32
2.3.8. Pentacarbonyl(2-(ꢀ)-menthyloxycarbonyl-2-methyl-
1-ethenylidene)tungsten (7b)
Green oil. Yield: 0.62 g (23%). IR (THF, cmꢀ1):
m(CO) = 2101 m, 2028 w, 1998 s, 1973vs. 1H NMR
3
3
(m, 2H, H5), 1.48 (t, JHH = 8.0 Hz, 3H, OCH2CH3),
(250 MHz, CDCl3): d = 0.70 (d, JHH = 6.8 Hz, 3H, H7),
3
3
1.81–1.94 (m, 3H, H2/H3), 2.66 (m, 1H, H4), 4.78 (q,
0.76 (d, JHH = 7.0 Hz, 3H, H9), 0.80 (d, JHH = 7.0 Hz,
3H, H10), 0.93 (m, 2H, H5), 1.27 (m, 1H, H3), 1.43 (m,
1H, H8), 1.60 (m, 2H, H2), 1.79 (s, 3H, CbCH3), 1.83–
3
3JHH = 7.1 Hz, 2H, OCH2CH3), 5.47 (dt, JHH = 9.9 Hz,
2JHH = 4.1 Hz, 1H, H1). 13C NMR (100 MHz, [d6]-ace-
tone): d = 13.7 (OCH2CH3), 14.2 (C7), 18.9 (C9), 19.8
(C10), 27.6 (C4), 28.2 (C5), 36.7 (C2), 45.4 (C3), 48.9 (C8),
50.4 (C6), 72.4 (OCH2CH3), 93.6 (C1), 107.8 (Cb), 151.7
(Cc), 217.4 (cis-CO), 221.8 (trans-CO), 230.3 (Ca). MS
(EI), m/z (%): 426 (26) [M+], 370 (15) [(M ꢀ 2CO)+], 342
(21) [(M ꢀ 3CO)+], 314 (94) [(M ꢀ 4CO)+], 290 (100)
3
2
2.01 (m, 3H, H6 + H4), 4.72 (td, JHH = 10.2 Hz, JHH
=
4.7 Hz, 1H, H1). 13C NMR (62.5 MHz, CDCl3): d = 6.2
(CbCH3), 16.0 (C7), 20.7 (C9), 22.9 (C10), 23.1 (C5), 26.0
(C8), 31.4 (C3), 34.0 (C4), 41.0 (C2), 47.0 (C6), 75.4 (C1),
117.1 (Cb, JWC = 25.3 Hz), 166.7 (COOR), 192.1 (cis-
CO, JWC = 125.8 Hz), 205.0 (trans-CO, JWC = 95.6 Hz),
2
1
1
[(M ꢀ C10H16)+], 286 (62) [(M ꢀ 5CO)+]. UV–Vis (kmax
,
365.2 (Ca, JWC = 105.7 Hz). MS (FAB), m/z (%): 546
1

N. Szesni et al. / Inorganica Chimica Acta 359 (2006) 617–632
621
(11) [M+], 490 (17) [(M ꢀ 2CO)+], 462 (21) [(M ꢀ 3CO)+],
434 (57) [(M ꢀ 4CO)+], 406 (100) [(M ꢀ 5CO)+].
C19H22O7W (546.23).
m/z (%): 426 (13) [M+], 370 (15) [(M ꢀ 2CO)+], 314 (90)
[(M ꢀ 4CO)+], 286 (100) [(M ꢀ 5CO)+]. C20H22CrO7
(426.39).
2.3.9. Pentacarbonyl(2-ethyl-2-(ꢀ)-menthyloxycarbonyl-1-
ethenylidene)chromium (8a)
2.3.12. Pentacarbonyl(2-endo-bornyloxycarbonyl-2-methyl-
1-ethenylidene)tungsten (9b)
Green oil. Yield: 0.19 g (9%). IR (THF, cmꢀ1):
Green oil. Yield: 0.27 g (10%). IR (THF, cmꢀ1):
m(CO) = 2100 m, 2025 w, 2002 sh, 1978 vs. 1H NMR
(250 MHz, [d6]-acetone): d = 0.83 (s, 3H, H7), 0.86 (s, 3H,
H10), 0.93 (s, 3H, H9), 1.02 (m, 1H, H4), 1.17 (t,
m(CO) = 2095 m, 2036 w, 2000 sh, 1980vs. 1H NMR
3
(250 MHz, [d6]-acetone): d = 0.78 (d, JHH = 7.0 Hz, 3H,
H7), 0.88 (d, 3JHH = 7.0 Hz, 3H, H9), 0.93 (d, 3JHH = 7.0 Hz,
3
3H, H10), 1.06 (m, 2H, H5), 1.17 (t, 3H, JHH = 7.2 Hz,
3JHH = 7.2 Hz, 3H, CbCH2CH3), 1.30 (m, 1H, H5), 1.79
3
CbCH2CH3), 1.37 (m, 1H, H3), 1.48 (m, 1H, H8), 1.66 (m,
2H, H2), 1.96–2.06 (m, 3H, H6 + H4), 2.24 (q,3JHH = 7.2 Hz,
2H, CbCH2CH3), 4.82 (td, 3JHH = 10.2 Hz, 2JHH = 4.4 Hz,
1H, H1). 13C NMR (62.5 MHz, [d6]-acetone): d = 15.5
(CbCH2CH3), 17.0 (C7), 20.0 (CbCH2CH3), 21.7 (C9), 23.0
(C10), 24.5 (C5), 27.4 (C8), 32.9 (C3), 35.7 (C4), 42.7 (C2),
48.7 (C6), 75.2 (C1), 126.5 (Cb), 170.5 (COOR), 213.5 (cis-
CO), 220.3 (trans-CO), 398.4 (Ca). MS (FAB), m/z (%):
428 (19) [M+], 372 (87) [(M ꢀ 2CO)+], 344 (17)
[(M ꢀ 3CO)+], 316 (61) [(M ꢀ 4CO)+], 288 (100)
[(M ꢀ 5CO)+]. C20H24CrO7 (428.37).
(m, 1H, H5), 1.96–2.11 (m, 3H, H2/H3), 2.29 (q, JHH
=
7.4 Hz, 2H, CbCH2CH3), 2.40 (m, 1H, H4), 5.09 (m, 1H,
H1). 13C NMR (62.5 MHz, [d6]-acetone): d = 14.6 (CbCH2-
CH3), 15.6 (C7), 18.3 (C9), 19.8 (C10), 20.7 (CbCH2CH3),
28.5 (C4), 28.7 (C5), 38.1 (C2), 46.4 (C3), 49.3 (C8), 50.4
(C6), 82.1 (C1), 124.4 (Cb), 167.4 (COOR), 194.6 (cis-CO,
1JWC = 125.9 Hz), 205.3 (trans-CO), 364.9 (Ca). MS
(FAB), m/z (%): 558 (26) [M+], 446 (66) [(M ꢀ 4CO)+],
418 (100) [(M ꢀ 5CO)+]. C20H22O7W (558.24).
2.4. General procedure for the preparation of alkoxy-
substituted allenylidene complexes 10a,b and 11a,b
2.3.10. Pentacarbonyl(2-ethyl-2-(ꢀ)-menthyloxycarbonyl-
1-ethenylidene)tungsten (8b)
At ꢀ78 ꢁC, a solution of 3.1 ml of BuLi (5 mmol, 1.6 M
in hexane) was added dropwise to a solution of 0.65 g
(5 mmol) of 3-phenylpropynone in 50 ml of dry THF.
The solution was stirred for 20 min at ꢀ78 ꢁC. Then
50 ml of a solution of [(CO5)M(THF)] (M = Cr, W;
0.1 M in THF) was added. The cooling bath was removed
and the brown solution was stirred for 30 min at ambient
temperature. After removal of the solvent in vacuo, the
remaining oily residue was dissolved in 50 ml of CH2Cl2
and treated with 6 mmol of [R3O]BF4 (R = Me, Et) at
0 ꢁC. The reaction mixture was stirred for another 30 min
at 0 ꢁC and then filtered over a short column of silica at
ꢀ60 ꢁC using CH2Cl2 as the eluent. The solvent was re-
moved in vacuo and the residue chromatographed on silica
using mixtures of pentane/Et2O as the eluent.
Green oil. Yield: 0.30 g (11%). IR (THF, cmꢀ1):
m(CO) = 2100 m, 2028 w, 1996 sh, 1975vs. 1H NMR
3
(250 MHz, CDCl3): d = 0.70 (d, JHH = 7.0 Hz, 3H, H7),
3
3
0.80 (d, JHH = 7.0 Hz, 3H, H9), 0.82 (d, JHH = 7.0 Hz,
3
3H, H10), 0.93 (m, 2H, H5), 1.07 (t, 3H, JHH = 7.2 Hz,
CbCH2CH3), 1.23 (m, 1H, H3), 1.44 (m, 1H, H8), 1.59 (m,
2H, H2), 1.88–1.99 (m, 3H, H6 + H4), 2.23 (q,3JHH
=
3
7.1 Hz, 2H, CbCH2CH3), 4.71 (td, JHH = 10.2 Hz,
2JHH = 4.4 Hz, 1H, H1). 13C NMR (62.5 MHz, CDCl3):
d = 14.0 (CbCH2CH3), 16.0 (C7), 20.8 (CbCH2CH3), 22.0
(C9), 23.1 (C10), 24.5 (C5), 26.0 (C8), 31.4 (C3), 34.2 (C4),
1
41.1 (C2), 47.2 (C6), 75.2 (C1), 123.0 (Cb, JWC = 26.9 Hz),
1
166.4 (COOR), 192.4 (cis-CO, JWC = 125.9 Hz), 205.2
(trans-CO,1JWC = 96.2 Hz), 366.9 (Ca). MS (FAB), m/z
(%): 560 (8) [M+], 532 (16) [(M ꢀ 2CO)+], 448 (73)
[(M ꢀ 4CO)+], 420 (100) [(M ꢀ 5CO)+]. C20H24O7W
(560.26).
2.4.1. Pentacarbonyl(3-methoxy-3-phenyl-1,2-propadieny-
lidene)chromium (10a)
Violet solid. Yield: 0.71 g (42%); m.p. 43–44 ꢁC (dec.).
IR (THF, cmꢀ1): m(CO) = 2084 vw, 1972 vs, 1940 m;
m(CCC) = 1956 m. 1H NMR (400 MHz, [d6]-acetone):
d = 4.28 (s, 3H, OCH3), 7.21–7.33 (m, 5H, ArH). 13C
NMR (100 MHz, [d6]-acetone): d = 62.4 (OCH3), 129.5
(Cb), 128.7, 129.3, 131.1, 135.9 (4 ArC), 154.8 (Cc), 216.6
(cis-CO), 226.0 (trans-CO), 272.0 (Ca). MS (EI), m/z (%):
336 (2) [M+], 280 (8) [(M ꢀ 2CO)+], 224 (63)
2.3.11. Pentacarbonyl(2-endo-bornyloxycarbonyl-2-methyl-
1-ethenylidene)chromium (9a)
Green oil. Yield: 0.34 g (13%). IR (THF, cmꢀ1):
m(CO) = 2094 m, 2034 w, 2020 sh, 1989 vs. 1H NMR
(250 MHz, [d6]-acetone): d = 0.82 (s, 3H, H7), 0.85 (s, 3H,
H10), 0.91 (s, 3H, H9), 1.05 (m, 1H, H4), 1.18 (t,
3JHH = 7.2 Hz, 3H, CbCH2CH3), 1.29 (m, 1H, H5), 1.70
(m, 1H, H5), 1.92–2.05 (m, 3H, H2/H3), 2.26 (q,
3JHH = 7.4 Hz, 2H, CbCH2CH3), 2.33 (m, 1H, H4), 5.07
(m, 1H, H1). 13C NMR (62.5 MHz, [d6]-acetone): d =
15.5 (CbCH2CH3), 15.6 (C7), 19.8 (C9), 20.3 (C10), 20.7
(CbCH2CH3), 28.5 (C4), 28.6 (C5), 38.2 (C2), 46.4 (C3),
49.3 (C8), 50.3 (C6), 81.5 (C1), 126.5 (Cb), 170.6 (COOR),
213.4 (cis-CO), 220.1 (trans-CO), 398.0 (Ca). MS (FAB),
[(M ꢀ 4CO)+], 196 (100) [(M ꢀ 5CO)+]. UV–Vis (kmax
nm (log e) [CH2Cl2]): 576 (3.722). C15H8CrO6 (336.22).
,
2.4.2. Pentacarbonyl(3-methoxy-3-phenyl-1,2-propadieny-
lidene)tungsten (10b)
Violet solid. Yield: 1.03 g (44%); m.p. 50–51 ꢁC (dec.).
IR (THF, cmꢀ1): m(CO) = 2083 vw, 1972 s, 1939 vs;

622
N. Szesni et al. / Inorganica Chimica Acta 359 (2006) 617–632
m(CCC) = 1954 m. 1H NMR (400 MHz, [d6]-acetone):
d = 4.28 (s, 3H, OCH3), 7.21–7.40 (m, 5H, ArH). 13C
NMR (100 MHz, [d6]-acetone): d = 62.9 (OCH3), 129.4
(Cb), 128.7, 129.3, 131.1, 136.2 (4 ArC), 155.8 (Cc), 196.2
(cis-CO), 200.2 (trans-CO), 254.4 (Ca). MS (EI), m/z (%):
468 (6) [M+], 412 (11) [(M ꢀ 2CO)+], 384 (18)
[(M ꢀ 2CO)+], 343 (18) [(M ꢀ 3CO)+], 315 (100)
[(M ꢀ 4CO)+], 287 (84) [(M ꢀ 5CO)+]. UV–Vis (kmax
,
nm (log e) [CH2Cl2]): 397 (4.199). Anal. Calc. for
C20H25CrNO6 (427.42): C, 56.20; H, 5.90; N, 3.28.
Found: C, 56.22; H, 5.78; N, 3.38%.
[(M ꢀ 3CO)+], 328 (100) [(M ꢀ 5CO)+]. UV–Vis (kmax
nm (log e) [CH2Cl2]): 570 (3.881). C15H8O6W (468.07).
,
2.5.2. Pentacarbonyl(3-dimethylamino-3-(ꢀ)-menthyloxy-
1,2-propadienylidene)tungsten (12b)
Yellow solid. Yield: 0.33 g (59%); m.p. 87–89 ꢁC. IR
(THF, cmꢀ1): m(CO) = 2084 vw, 1928 vs, 1905 m;
m(CCC) = 2011 m. 1H NMR (400 MHz, [d6]-acetone):
2.4.3. Pentacarbonyl(3-ethoxy-3-phenyl-1,2-propadieny-
lidene)chromium (11a)
3
3
Violet solid. Yield: 0.45 g (26%); m.p. 57–58 ꢁC (dec.).
IR (THF, cmꢀ1): m(CO) = 2074 vw, 1974 s, 1945 vs;
m(CCC) (cmꢀ1): 1960 m. 1H NMR (400 MHz, [d6]-acetone):
d = 0.85 (d, JHH = 7.0 Hz, 3H, H7), 0.92 (d, JHH =
3
4.6 Hz, 3H, H9), 0.95 (d, JHH = 4.7 Hz, 3H, H10), 0.96
(m, 1H, H3), 1.16 (m, 2H, H5), 1.53 (m, 2H, H4), 1.74
(m, 2H, H2), 1.93 (m, 1H, H8), 2.22 (m, 1H, H6), 3.25 (s,
3H, NCH3), 3.50 (s, 3H, NCH3), 5.16 (td, 3JHH = 10.2 Hz,
2JHH = 4.4 Hz, 1H, H1). 13C NMR (100 MHz, [d6]-ace-
tone): d = 16.9 (C7), 20.8 (C9), 22.0 (C10), 24.0 (C5), 26.9
(C8), 32.1 (C3), 34.5 (C4), 37.1 (NCH3), 41.7 (C2), 41.9
3
d = 1.43 (t, JHH = 7.2 Hz, 3H, OCH2CH3), 4.70 (q,
3JHH = 7.2 Hz, 2H, OCH2CH3), 7.21–7.34 (m, 5H, ArH).
13C NMR (100 MHz, [d6]-acetone): d = 14.3 (OCH2CH3),
72.6 (OCH2CH3), 129.3 (Cb), 128.6, 129.9, 131.1, 135.9 (4
ArC), 155.0 (Cc), 216.7 (cis-CO), 225.9 (trans-CO), 269.7
(Ca). MS (EI), m/z (%): 350 (11) [M+], 294 (10) [(M ꢀ
2CO)+], 266 (5) [(M ꢀ 3CO)+], 210 (100) [(M ꢀ 5CO)+].
UV–Vis (kmax, nm (log e) [CH2Cl2]): 576 (3.375). C16H10-
CrO6 (350.25).
2
(NCH3), 47.7 (C6), 86.8 (C1), 100.0 (Cb, JWC = 25.9 Hz),
1
150.9 (Cc), 174.7 (Ca, JWC = 100.0 Hz), 197.9 (cis-CO,
1
1JWC = 124.1 Hz), 201.8 (trans-CO, JWC = 134.6 Hz).
MS (EI), m/z (%): 559 (100) [M+], 532 (73) [(M ꢀ CO)+],
419 (43) [(M ꢀ 5CO)+]. UV–Vis (kmax, nm (log e)
[CH2Cl2]): 398 (4.193). Anal. Calc. for C20H25NO6W
(559.27): C, 42.95; H, 4.51; N, 2.50. Found: C, 42.88; H,
4.47; N, 2.55%.
2.4.4. Pentacarbonyl(3-ethoxy-3-phenyl-1,2-propadienyli-
dene)tungsten (11b)
Yield: 0.89 g (37%). Identification through comparison
of its spectroscopic data with those published [29].
2.5.3. Pentacarbonyl(3-endo-bornyloxy-3-dimethylamino-
1,2-propadienylidene)chromium (13a)
2.5. Reaction of bis(alkoxy)-substituted allenylidene
complexes 5a,b and 6a,b with dimethylamine
Yellow solid. Yield: 0.47 g (99%); m.p. 99–101 ꢁC. IR
(THF, cmꢀ1): m(CO) = 2081 vw, 1933 vs, 1911 m;
m(CCC) = 2010 m. 1H NMR (400 MHz, [d6]-acetone):
d = 0.81 (s, 3H, H7), 0.84 (s, 3H, H10), 0.86 (s, 3H, H9),
1.08 (m, 2H, H5), 1.32 (m, 1H, H4), 1.66–1.92 (m, 3H,
H2/H3), 2.42 (m, 1H, H4), 3.16 (s, 3H, NCH3), 3.38 (s,
A solution of 1 mmol of the appropriate allenylidene
complex was treated at 0 ꢁC with 0.5 ml of dimethylamine.
After stirring for 2 min at ambient temperature the solvent
was removed. The residue was chromatographed on silica
at ꢀ20 ꢁC using mixtures of pentane/CH2Cl2 as the eluent.
In the cases of the menthyl-substituted allenylidene com-
plexes 12a and 12b, a second yellow band containing 2a
and 2b [24] (yields: 34% and 36%) was isolated.
3
3H, NCH3), 5.27 (d, JHH = 10.2 Hz, 1H, H1). 13C NMR
(100 MHz, [d6]-acetone): d = 13.7 (C7), 18.9 (C9), 19.8
(C10), 27.9 (C4), 28.3 (C5), 37.2 (NCH3), 37.3 (C2), 41.8
(NCH3), 45.5 (C3), 48.7 (C8), 50.1 (C6), 91.4 (C1), 102.4
(Cb), 149.4 (Cc), 197.0 (Ca), 218.8 (cis-CO), 222.4 (trans-
CO). MS (EI), m/z (%): 425 (24) [M+], 369 (13)
[(M ꢀ 2CO)+], 341 (25) [(M ꢀ 3CO)+], 313 (100)
[(M ꢀ 4CO)+], 285 (73) [(M ꢀ 5CO)+]. UV–Vis (kmax, nm
(log e) [CH2Cl2]): 398 (4.184). Anal. Calc. for C20H23-
CrNO6 (425.40): C, 56.47; H, 5.45; N, 3.29. Found: C,
56.36; H, 5.40; N, 3.40%.
2.5.1. Pentacarbonyl(3-dimethylamino-3-(ꢀ)-menthyloxy-
1,2-propadienylidene)chromium (12a)
Yellow solid. Yield: 0.26 g (61%); m.p. 111 ꢁC. IR
(THF, cmꢀ1): m(CO) = 2080 vw, 1933 vs, 1911 m;
m(CCC) = 2008 m. 1H NMR (400 MHz, [d6]-acetone):
3
3
d = 0.84 (d, JHH = 7.0 Hz, 3H, H7), 0.90 (d, JHH
=
3
4.6 Hz, 3H, H9), 0.95 (d, JHH = 4.7 Hz, 3H, H10), 0.96
(m, 1H, H3), 1.15 (m, 2H, H5), 1.59 (m, 2H, H4), 1.76
(m, 2H, H2), 1.93 (m, 1H, H8), 2.24 (m, 1H, H6), 3.21
(s, 3H, NCH3), 3.52 (s, 3H, NCH3), 5.14 (td,
2.5.4. Pentacarbonyl(3-endo-bornyloxy-3-dimethylamino-
1,2-propadienylidene)tungsten (13b)
Yellow solid. Yield: 0.55 g (99%); m.p. 69–70 ꢁC. IR
(THF, cmꢀ1): m(CO) = 2085 vw, 1928 vs, 1905 m;
m(CCC) = 2013 m. 1H NMR (400 MHz, [d6]-acetone):
d = 0.92 (s, 3H, H7), 0.95 (s, 3H, H10), 0.98 (s, 3H, H9),
1.25 (m, 2H, H5), 1.44 (m, 1H, H4), 1.76–1.97 (m, 3H,
H2/H3), 2.59 (m, 1H, H4), 3.30 (s, 3H, NCH3), 3.50 (s,
2
3JHH = 10.6 Hz, JHH = 4.2 Hz, 1H, H1). 13C NMR
(100 MHz, [d6]-acetone): d = 16.8 (C7), 20.8 (C9), 22.1
(C10), 24.1 (C5), 27.0 (C8), 32.2 (C3), 34.5 (C4), 37.0
(NCH3), 41.8 (C2), 41.8 (NCH3), 47.7 (C6), 86.4 (C1),
101.6 (Cb), 149.1 (Cc), 196.0 (Ca), 218.8 (cis-CO), 222.4
(trans-CO). MS (EI), m/z (%): 427 (19) [M+], 371 (10)
3
2
3H, NCH3), 5.35 (dt, JHH = 7.8 Hz, JHH = 2.0 Hz, 1H,

N. Szesni et al. / Inorganica Chimica Acta 359 (2006) 617–632
623
3
H1). 13C NMR (100 MHz, [d6]-acetone): d = 13.9 (C7), 19.1
(C9), 20.0 (C10), 28.0 (C4), 28.5 (C5), 37.2 (NCH3), 37.6
(C2), 42.1 (NCH3), 45.7 (C3), 48.9 (C8), 50.4 (C6), 91.9
3JHH = 7.0 Hz, 2H, OCH2CH3), 5.09 (dt, JHH = 7.4 Hz,
2JHH = 2.1 Hz, 1H, H1), 7.30 (m, 9H, ArH), 7.42 (m, 6H,
ArH). 13C NMR (100 MHz, [d6]-acetone): d = 13.8 (C7),
14.3 (OCH2CH3), 19.0 (C9), 19.8 (C10), 27.5 (C4), 28.2
(C5), 37.0 (C2), 45.5 (C3), 48.7 (C8), 50.1 (C6), 70.9
(OCH2CH3), 91.4 (C1), 113.1 (Cb), 128.9 (d, 3JPC = 9.6 Hz,
2
(C1), 101.0 (Cb, JWC = 24.9 Hz), 151.4 (Cc), 175.2 (Ca,
1
2JWC = 101.0 Hz), 198.2 (cis-CO, JWC = 124.0 Hz), 202.0
1
(trans-CO, JWC = 132.7 Hz). MS (EI), m/z (%): 557
(100) [M+], 529 (78) [(M ꢀ CO)+], 417 (49) [(M ꢀ 5CO)+].
UV–Vis (kmax, nm (log e) [CH2Cl2]): 400 (4.209). Anal.
Calc. for C20H23O6W (557.26): C, 43.11; H, 4.16; N, 2.51.
Found: C, 43.26; H, 4.14; N, 2.63%.
PArC), 130.4 (d, JPC = 1.9 Hz, PArC), 133.9 (d,
4
2JPC = 10.6 Hz, PArC), 137.4 (d, JPC = 33.7 Hz, PArC),
1
2
146.4 (Cc), 221.8 (cis-CO, JPC = 6.7 Hz), 227.5 (trans-
CO, 2JPC = 21.2 Hz), 227.5 (cis-COtrans to P, 2JPC = 2.0 Hz),
250.0 (Ca, JPC = 19.2 Hz). 31P NMR (162.0 MHz, [d6]-
2
2.6. Reaction of alkoxy-substituted allenylidene complex 10a
with dimethylamine
acetone): d = 60.4. MS (EI), m/z (%): 660 (18) [M+], 605
(100) [(M ꢀ 2CO)+], 548 (43) [(M ꢀ 4CO)+]. UV–Vis
(kmax, nm (log e) [CH2Cl2]): 481 (4.130). Anal. Calc. for
C37H37CrO6P (660.66): C, 67.27; H, 5.64. Found: C,
67.59; H, 6.03%.
2.6.1. Pentacarbonyl(3-dimethylamino-3-phenyl-1,2-propa-
dienylidene)chromium (14)
A solution of 0.34 g (1 mmol) of the allenylidene com-
plex 10a was treated with a minimum amount of dimethyl-
amine (ca. 0.3 ml) at 0 ꢁC. The solvent was immediately
evaporated and the residue chromatographed on silica at
ꢀ20 ꢁC using a mixture of pentane/CH2Cl2 as the eluent.
Yield: 0.31 g (89%). Identification through comparison of
its spectroscopic data with those published [24].
2.7.2. mer-Tricarbonyl(3-endo-bornyloxy-3-ethoxy-1,2-
propadienylidene)[bis-(triphenylphosphane)]chromium
(17)
Violet solid. Yield: 0.61 g (68%); m.p. 83 ꢁC (dec.). IR
(THF, cmꢀ1): m(CO) = 1991 w, 1882 sh, 1868 vs;
m(CCC) = 1921 m. 1H NMR (400 MHz, [d6]-acetone):
d = 0.54 (s, 3H, H7), 0.57 (s, 3H, H10), 0.63 (s, 3H, H9),
3
2.6.2. Pentacarbonyl{1,3-bis(dimethylamino)-3-phenyl-2-
propenylidene}chromium (15)
0.72 (m, 2H, H5), 0.90 (t, JHH = 7.0 Hz, 3H, OCH2CH3),
0.99–1.14 (m, 3H, H3), 1.51–1.64 (m, 3H, H2/H4), 1.96 (m,
1H, H4), 3.40 (br, 2H, OCH2CH3), 3.60 (m, 1H, H1), 7.11–
7.51 (m, 30H, ArH). 13C NMR (100 MHz, [d6]-acetone):
d = 13.0 (C7), 13.6 (OCH2CH3), 18.4 (C9), 19.0 (C10),
A solution of 0.34 g (1 mmol) of the allenylidene com-
plex 10a was treated with an excess of dimethylamine (ca
5 ml) at 0 ꢁC and stirred for 2 min at this temperature.
The solvent was evaporated and the residue chromato-
graphed on silica gel at ꢀ20 ꢁC using a mixture of
pentane/CH2Cl2 as the eluent. Yield: 0.32 g (81%). Identi-
fication through comparison of its spectroscopic data with
those published [24].
27.5 (C4), 28.2 (C5), 36.6 (C2), 44.9 (C3), 47.6 (C8), 48.9
2
(C6), 75.7 (OCH2CH3), 86.7 (C1), 131.4 (Cb, JPC
=
2.9 Hz), 127.4 (t, JPC = 8.6 Hz, PArC), 130.4 (dd,
JPC = 15.3 Hz, JPC = 34.9 Hz, PArC), 133.3 (t, JPC
=
10.5 Hz, PArC), 138.2 (t, JPC = 31.6 Hz, PArC), 152.1
1
(Cc), 226.9 (cis-CO, JPC = 29.6 Hz), 234.4 (trans-CO,
1
2.7. Photochemical reaction of bis(alkoxy)-substituted
allenylidene complex 6a with triphenylphosphine
1JPC = 34.7 Hz), 265.3 (Ca, JPC = 28.8 Hz). 31P NMR
(162.0 MHz, [d6]-acetone): d = 78.2. MS (FAB), m/z (%):
896 (6) [(M + H)+], 784 (33) [(M ꢀ 3CO + H)+], 288
(100) [(M ꢀ 3CO ꢀ 2PPh3 + H)+]. UV–Vis (kmax, nm
(log e) [CH2Cl2]): 525 (3.978). Anal. Calc. for C54H52-
CrO5P2 (894.95): C, 72.47; H, 5.86. Found: C, 72.37; H,
6.09%.
A solution containing 0.43 g (1 mmol) of allenylid-
ene(pentacarbonyl)chromium complex 6a and 0.29 g
(1.1 mmol) of triphenylphosphine in 30 ml of dry THF
was irradiated at ꢀ20 ꢁC for ca. 2 h while passing a slow
stream of argon through the solution. The solvent was re-
moved in vacuo and the residue was chromatographed on
silica at ꢀ20 ꢁC using a mixture of pentane/CH2Cl2/THF
as the eluent. The first brown fraction contained the tetra-
carbonyl allenylidene complex 16 and the violet fraction
the tricarbonyl complex 17.
2.8. Reaction of bis(alkoxy)-substituted allenylidene
complexes 5a,b with diethylaminopropyne
Solutions of 1 mmol of the allenylidene complexes 5a
or 5 b were treated at 0 ꢁC with 0.6 ml (ca. 5 mmol) of
diethylaminopropyne. The solutions were stirred at ambi-
ent temperature until all of the starting material was
consumed (as indicated by TLC). The solvent was re-
moved in vacuo and the residue chromatographed on sil-
ica gel at ꢀ20 ꢁC using mixtures of pentane/CH2Cl2 as
the eluent. The first red fraction contained the allenylid-
ene complex 18a (18b). Then, a second red band contain-
ing 19a,b and a third yellow fraction containing 20a,b
were eluted.
2.7.1. Tetracarbonyl(triphenylphosphane)(3-endo-borny-
loxy-3-ethoxy-1,2-propadienylidene)-chromium (16)
Brown oil. Yield: 0.20 g (31%). IR (THF, cmꢀ1):
1
m(CO) = 2036 m, 1910 vs, 1894 sh; m(CCC) = 1951 m. H
NMR (400 MHz, [d6]-acetone): d = 0.77 (s, 3H, H7), 0.78
(s, 3H, H10), 0.79 (s, 3H, H9), 0.98 (m, 2H, H5), 1.16 (t,
3JHH = 7.0 Hz, 3H, OCH2CH3), 1.59–1.74 (m, 3H, H2/
H3), 2.43 (m, 1H, H4), 3.48 (m, 1H, H4), 4.24 (q,

624
N. Szesni et al. / Inorganica Chimica Acta 359 (2006) 617–632
3
2.8.1. Pentacarbonyl(3-diethylamino-5-ethoxy-5-(ꢀ)-
menthyloxy-4-methyl-1,2,4-pentatrienylidene)chromium
(18a)
(400 MHz, [d6]-acetone): d = 0.68 (d, JHH = 7.2 Hz, 3H,
3
H7), 0.77 (m, 1H, H3), 0.78 (d, JHH = 7.0 Hz, 3H, H9),
0.81 (d, JHH = 7.0 Hz, 3H, H10), 0.95 (m, 2H, H5), 1.24
(m, 1H, H8), 1.33 (s, 3H, CH3), 1.34 (t, 6H, 2 NCH2CH3),
1.48 (m, 2H, H4), 1.59 (m, 1H, H6), 1.91 (m, 2H, H2), 3.81–
4.19 (m, 4H, 2 NCH2CH3), 4.61 (td, JHH = 10.3 Hz,
3
Red oil. Yield: 0.26 g (48%). IR (THF, cmꢀ1):
1
m(CO) = 2074 vw, 1933 vs, 1907 m; m(CCC) = 1996 m. H
NMR (400 MHz, [d6]-acetone): d = 0.71 (d, 3JHH = 7.0 Hz,
3
3H, H7), 0.74 (m, 1H, H3), 0.80–0.91 (m, 6H, H9, H10), 0.94
2JHH = 4.4 Hz, 1H, H1). 13C NMR (100 MHz, [d6]-ace-
tone): E/Z mixture of isomers: d = 12.1, 12.2 (NCH2CH3),
13.8, 13.9 (NCH2CH3), 16.1, 16.1 (CH3C@C), 16.2, 16.4
(C7), 21.0, 21.1 (C9), 22.1, 22.2 (C10), 23.5, 23.7 (C5),
26.1, 26.5 (C8), 32.0 (C3), 34.8, 34.9 (C4), 40.8, 41.3 (C2),
44.9, 45.0 (C6), 47.5, 47.6 (NCH2CH3), 51.6, 51.7
(NCH2CH3), 76.2, 76.3 (C1), 100.4, 101.7 (CH3C@C),
116.5, 116.6 (Cb), 155.8, 156.4 (Cc), 168.3, 168.7
(CH3C@C), 214.2, 215.4 (Ca), 218.7 (cis-CO), 224.1
(trans-CO). MS (EI), m/z (%): 511 (8) [M+], 399 (76)
3
(m, 2H, H5), 1.21 (br, 6H, 2 NCH2CH3), 1.39 (t, JHH
=
7.4 Hz, 3H, OCH2CH3), 1.56 (m, 2H, H4), 1.78 (m, 2H,
H2), 1.93 (m, 1H, H8), 2.10 (m, 1H, H6), 3.62–4.03 (m,
br, 6H, 2 NCH2CH3, OCH2CH3), 4.14 (br, 1H, H1). 13C
NMR (100 MHz, [d6]-acetone): E/Z mixture of isomers:
d = 12.6 (NCH2CH3), 13.6 (NCH2CH3), 14.3 (OCH2CH3),
14.5 (OCH2CH3), 15.3 (CH3C@C), 16.4, 16.4 (C7), 21.4
(C9), 22.4 (C10), 23.6 (C5), 26.2, 26.3 (C8), 32.1 (C3), 34.8,
34.9 (C4), 41.5, 41.7 (C2), 48.2, 49.1 (NCH2CH3), 49.0,
49.3 (C6), 67.2, 67.6 (OCH2CH3), 78.9, 79.3 (C1), 96.0,
96.7 (CH3C@C), 117.7, 118.4 (Cb), 151.4, 153.9
(CH3C@C), 155.4, 155.7 (Cc), 208.2, 208.3 (Ca), 219.0,
219.1 (cis-CO), 224.2, 224.3 (trans-CO). MS (EI), m/z
(%): 539 (11) [M+], 483 (9) [(M ꢀ 2CO)+], 455 (17)
[(M ꢀ 3CO)+], 427 (41) [(M ꢀ 4CO)+], 399 (100)
[(M ꢀ 5CO)+]. UV–Vis (kmax, nm (log e) [CH2Cl2]): 451
(4.285). Anal. Calc. for C27H37CrNO7 (539.59): C, 60.10;
H, 6.91; N, 2.60. Found: C, 59.98; H, 7.01; N, 2.73%.
[(M ꢀ 4CO)+], 371 (100) [(M ꢀ 5CO)+]. UV–Vis (kmax
,
nm (log e) [CH2Cl2]): 464 (4.302). Anal. Calc. for
C25H33CrNO7 (511.53): C, 58.70; H, 6.50; N, 2.74. Found:
C, 59.12; H, 6.56; N, 2.93%.
2.8.4. Pentacarbonyl(3-diethylamino-5-hydroxy-5-(ꢀ)-
menthyloxy-4-methyl-1,2,4-pentatrienylidene)tungsten (19b)
Red oil. Yield: 0.31 g (47%). IR (THF, cmꢀ1): m(CO) =
1
2081 vw, 1930 vs, 1905 m; m(CCC) = 1998 m. H NMR
3
(400 MHz, [d6]-acetone): d = 0.66 (d, JHH = 7.2 Hz, 3H,
3
2.8.2. Pentacarbonyl(3-diethylamino-5-ethoxy-5-(ꢀ)-
menthyloxy-4-methyl-1,2,4-pentatrienylidene)tungsten (18b)
Red oil. Yield: 0.31 g (46%). IR (THF, cmꢀ1):
H7), 0.73 (m, 1H, H3), 0.74 (d, JHH = 7.0 Hz, 3H, H9),
3
0.78 (d, JHH = 7.0 Hz, 3H, H10), 0.88 (m, 2H, H5), 1.24
(m, 1H, H8), 1.30 (s, 3H, CH3), 1.31 (t, 6H, 2 NCH2CH3),
1.44 (m, 2H, H4), 1.54 (m, 1H, H6), 1.85 (m, 2H, H2), 3.67–
1
m(CO) = 2078 vw, 1928 vs, 1901 m; m(CCC) = 1998 m. H
NMR (400 MHz, [d6]-acetone): d = 0.72 (d, 3JHH = 7.0 Hz,
3.99 (m, 4H, 2 NCH2CH3), 5.48 (td, JHH = 10.3 Hz,
3
3H, H7), 0.77 (m, 1H, H3), 0.82 (m, 6H, H9, H10), 0.98 (m,
2JHH = 4.4 Hz, 1H, H1). 13C NMR (100 MHz, [d6]-ace-
tone): E/Z mixture of isomers: d = 12.2, 12.3 (NCH2CH3),
13.7, 13.8 (NCH2CH3), 16.0, 16.1 (CH3C@C), 16.2, 16.4
(C7), 21.0, 21.0 (C9), 22.2, 22.2 (C10), 23.5, 23.7 (C5),
26.4, 26.7 (C8), 31.9, 32.0 (C3), 34.7, 34.8 (C4), 40.9, 41.4
(C2), 45.2, 45.2 (C6), 47.8, 47.9 (NCH2CH3), 51.9, 52.0
(NCH2CH3), 76.3, 76.4 (C1), 104.4, 104.8 (CH3C@C),
114.3, 114.4 (Cb), 154.4, 155.9 (Cc), 168.1, 168.5
(CH3C@C), 191.6, 192.6 (Ca), 198.0, 198.0 (cis-CO,
2H, H5), 1.24 (br, 6H,
2
NCH2CH3), 1.32 (t,
3JHH = 7.4 Hz, 3H, OCH2CH3), 1.57 (m, 2H, H4), 1.78
(m, 2H, H2), 1.95 (m, 1H, H8), 2.11 (m, 1H, H6), 3.65–
3.99 (m, br, 6H, 2 NCH2CH3, OCH2CH3), 4.10 (br, 1H,
H1) ppm. 13C NMR (100 MHz, [d6]-acetone): E/Z mixture
of isomers: d = 12.6 (NCH2CH3), 13.5 (NCH2CH3), 14.1
(OCH2CH3), 14.3 (OCH2CH3), 15.3 (CH3C@C), 16.4,
16.4 (C7), 21.4 (C9), 22.4 (C10), 23.6 (C5), 26.2 (C8), 32.1
(C3), 34.8, 34.8 (C4), 41.5, 41.6 (C2), 48.3, 49.0
(NCH2CH3), 49.3, 49.4 (C6), 67.2, 67.6 (OCH2CH3),
79.0, 79.3 (C1), 95.8, 96.5 (CH3C@C), 115.7, 116.3 (Cb),
154.0, 155.7 (Cc), 157.2 (CH3C@C), 186.4, 186.7 (Ca),
1JWC = 125.9 Hz), 203.6, 203.6 (trans-CO, 1JWC
=
130.8 Hz). MS (EI), m/z (%): 643 (11) [M+],], 531 (91)
[(M ꢀ 4CO)+], 503 (100) [(M ꢀ 5CO)+]. UV–Vis (kmax
,
nm (log e) [CH2Cl2]): 455 (4.390). Anal. Calc. for
C25H33NO7W (643.40): C, 46.67; H, 5.17; N, 2.18. Found:
C, 46.53; H, 5.37; N, 2.29%.
1
198.2, 198.2 (cis-CO, JWC = 123.1 Hz), 203.7, 203.7
1
(trans-CO, JWC = 124.0 Hz). MS (EI), m/z (%): 671 (9)
[M+], 615 (5) [(M ꢀ 2CO)+], 587 (17) [(M ꢀ 3CO)+], 5597
(56) [(M ꢀ 4CO)+], 531 (100) [(M ꢀ 5CO)+]. UV–Vis
(kmax, nm (log e) [CH2Cl2]): 443 (4.360). Anal. Calc. for
C27H37NO7W (671.44): C, 48.30; H, 5.55; N, 2.09. Found:
C, 48.30; H, 5.61; N, 2.23%.
2.8.5. Pentacarbonyl(4-diethylamino-6-(ꢀ)-menthyloxy-5-
methylpyran-2-ylidene)chromium (20a)
Yellow oil. Yield: 0.02 g (4%). IR (THF, cmꢀ1):
1
m(CO) = 2047 m, 1966 vw, 1930 vs, 1920 vs, 1907 sh. H
3
NMR (400 MHz, [d6]-acetone): d = 0.62 (d, JHH
=
3
2.8.3. Pentacarbonyl(3-diethylamino-5-hydroxy-5-(ꢀ)-
menthyloxy-4-methyl-1,2,4-pentatrienylidene)chromium
(19a)
7.2 Hz, 3H, H7), 0.74 (d, JHH = 7.4 Hz, 3H, H9), 0.75 (d,
3JHH = 7.4 Hz, 3H, H10), 0.76 (m, 1H, H3), 0.92 (m, 2H,
H5), 1.21 (t, 6H, 2 NCH2CH3), 1.36 (m, 2H, H4), 1.55 (s,
3H, CH3), 1.58 (m, 2H, H2), 1.84 (m, 1H, H8), 2.00 (m,
1H, H6), 3.32 (m, 2H, N CH2CH3), 3.50 (m, 2H,
Red oil. Yield: 0.24 g (45%). IR (THF, cmꢀ1): m(CO) =
1
2077 vw, 1935 vs, 1911 m; m(CCC) = 1996 m. H NMR

N. Szesni et al. / Inorganica Chimica Acta 359 (2006) 617–632
625
3
2
NCH2CH3), 4.55 (td, JHH = 10.2 Hz, JHH = 4.1 Hz, 1H,
173.4 (CN(CH2CH3)2, COMenthyl), 199.5 (cis-CO), 203.8
(trans-CO), 258.4 (Ca). MS (FAB), m/z (%): 643 (12)
[M+], 615 (63) [(M ꢀ 2CO)+], 587 (41) [(M ꢀ 2CO)+], 503
(29) [(M ꢀ 5CO)+], 364 (100) [(M ꢀ 5CO ꢀ C10H19)+].
C25H33NO7W (643.38).
H1), 7.30 (s, 1H, CbH). 13C NMR (100 MHz, [d6]-acetone):
d = 12.5 (NCH2-CH3), 12.6 (NCH2CH3), 16.1 (C7), 19.6
(CH3C@C), 21.0 (C9), 22.1 (C10), 23.4 (C5), 26.3 (C8), 31.9
(C3), 34.6 (C4), 41.2 (C2), 44.4, 44.4 (NCH2CH3), 47.7
(C6), 75.9 (C1), 115.2 (Cb), 145.8 (CCH3), 170.6, 171.3
(CN(CH2CH3)2, COMenthyl), 219.4 (cis-CO), 226.8
(trans-CO), 283.2 (Ca). MS (FAB), m/z (%): 511 (11)
[M+], 399 (74) [(M ꢀ 4CO)+], 371 (100) [(M ꢀ 5CO)+].
C25H33CrNO7 (511.53).
2.9. X-ray structural analyses of 3b and 12a
Single crystals suitable for X-ray structural analyses
were obtained by slow evaporation of the solvent from
solutions of 3b and 12a in CH2Cl2 at 4 ꢁC. The measure-
ments were performed with a crystal mounted on a glass
fiber on a Siemens P4 diffractometer (graphite monochro-
2.8.6. Pentacarbonyl(4-diethylamino-6-(ꢀ)-menthyloxy-5-
methylpyran-2-ylidene)tungsten (20b)
Yellow oil. Yield: 0.03 g (5%). IR (THF, cmꢀ1):
mator, Mo Ka, radiation, k = 0.71073 A). For the data
˚
1
m(CO) = 2055 m, 1964 vw, 1926 vs, 1918 vs, 1905 sh. H
collection, the Wykhoff technique was used. A semiem-
pirical absorption correction (w scan with 12 reflections)
was performed. The structures were solved by direct
methods using the SHELXTL-97 program package [30].
The position of the hydrogen atoms was calculated by
assuming ideal geometry, and their coordinates were re-
fined together with those of the attached carbon atoms
as Ôriding-modelÕ. All other atoms were refined anisotrop-
ically (see Table 1).
NMR (400 MHz, [d6]-acetone): d = 0.63 (d, 3JHH = 7.2 Hz,
3
3H, H7), 0.74 (d, JHH = 7.4 Hz, 3H, H9), 0.76 (d,
3JHH = 7.4 Hz, 3H, H10), 0.76 (m, 1H, H3), 0.94 (m, 2H,
H5), 1.22 (t, 6H, 2NCH2CH3), 1.24 (m, 2H, H4), 1.48 (s,
3H, CH3), 1.57 (m, 2H, H2), 1.84 (m, 1H, H8), 1.96 (m,
1H, H6), 3.35 (m, 2H, NCH2CH3), 3.55 (m, 2H,
3
2
NCH2CH3), 4.58 (td, JHH = 10.4 Hz, JHH = 4.4 Hz, 1H,
H1), 7.21 (s, 1H, CbH). 13C NMR (100 MHz, [d6]-acetone):
d = 12.6 (NCH2CH3), 12.8 (NCH2CH3), 16.4 (C7), 20.3
(CH3C@C), 21.1 (C9), 22.3 (C10), 23.8 (C5), 26.6 (C8),
32.0 (C3), 34.9 (C4), 41.5 (C2), 44.8, 44.9 (NCH2CH3),
47.9 (C6), 76.0 (C1), 113.6 (Cb), 145.7 (CCH3), 171.4,
3. Results and discussion
3.1. Synthesis of alkoxy-substituted allenylidene complexes
Reaction of deprotonated propynoic acid ethylester with
[(CO)5M-THF] (M = Cr, W) followed by alkylation of the
resulting alkynyl metallates [Li][(CO)5MAC„CAC(@O)
OEt] with triethyloxonium tetrafluoroborate affords the
bis(alkoxy)allenylidene complexes 1a,b (Scheme 1, route
a). In contrast to the analogous amino-substituted alleny-
lidene complexes, 1a and 1b are highly reactive. Therefore
it was not possible to isolate them in a pure form, neither
by applying chromatographic means nor by crystallization
methods. However, 1a and 1b could be characterized by
their IR spectra (1a: m(CO) = 2083 vw, 1943 vs, 1921 sh
cmꢀ1; m(CCC) = 1978 m cmꢀ1; 1b: m(CO) = 2088 vw,
1938 vs cmꢀ1; m(CCC) = 1976 m cmꢀ1).
An alternative approach to alkoxyallenylidene com-
plexes starts out from tris(ethoxy)propyne as the C3 source.
Deprotonation, reaction with the solvent complexes
[(CO)5M-THF] (M = Cr, W) and subsequent silica-in-
duced abstraction of one of the alkoxy substituents likewise
yields complexes 1a and 1b (Scheme 1, route b). This route
is comparable to that recently developed for the synthesis
of bis(amino)allenylidene complexes [31]. The IR spectra
of the crude reaction mixtures obtained by routes a and
b are identical.
Table 1
Crystal data and refinement details for compounds 3b and 12a
3b
12a
Formula
Mr
C
12H10N2O5W
C20H23CrNO6
425.39
monoclinic
P21
10.099(5)
16.878(7)
12.289(6)
90
92.90(3)
90
2092.0(16)
4
0.50 · 0.40 · 0.30
1.351
0.581
888
446.07
monoclinic
C2/c
13.484(3)
13.111(4)
9.0974(15)
90
117.571(14)
90
1425.6(5)
4
Crystal system
Space group
˚
a (A)
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
V (A )
Z
Crystal size (mm3)
0.40 · 0.30 · 0.20
2.078
8.122
qcalc (g cmꢀ3
)
l (mmꢀ1
F(000)
)
840
Diffractometer
Siemens P4
Mo Ka
0.71073
188(2)
Siemens P4
Mo Ka
0.71073
183(2)
Radiation
˚
k (A)
T (K)
Maximum 2H (ꢁ)
Index range
56
56
0 6 h 6 17,
0 6 k 6 17,
ꢀ10 6 l 6 10
1749
1681
94
0.0344
0.0857
1.053
ꢀ13 6 h 6 13,
ꢀ22 6 k 6 22,
ꢀ16 6 l 6 16
10580
9658
506
0.0584
0.1469
1.030
Due to the presence of two r-electron-withdrawing alk-
oxy substituents at Cc, complexes 1a and 1b are very reac-
tive, but are stable in solution for some periods of time.
These features render them as convenient starting com-
pounds for the synthesis of other p-donor-substituted
allenylidene complexes. For instance, addition of a
Number of data
Number of unique data
Parameters
R(F) for I > 2r > (I)
wR2(F2) for all data
Goodness-of-fit on F2

626
N. Szesni et al. / Inorganica Chimica Acta 359 (2006) 617–632
binuclear bis(allenylidene) complexes are observed. The
new allenylidene complexes are remarkably stable and do
not decompose in air within weeks. The spectroscopic data
of 3a and 3b agree with those of known bis(amino)alleny-
lidene complexes [31,33].
The molecular structure of 3b was additionally estab-
lished by an X-ray structural analysis (Fig. 1, Table 1).
Complex 3b exhibits all characteristic features of amino
allenylidene complexes. The bond C6–C7 is shorter than
that expected for a C(sp)@C(sp) bond and C7–C8 is longer
than an average C(sp)@C(sp2) bond. The distances agree
well with those usually observed in other aminoallenylidene
complexes [21c,24,31–34] indicating considerable electron
transfer from the amino substituents to the metal center.
As a result, the trans-CO bond is markedly longer than
the average cis-CO bond. The imidazolidin-2-ylidene ring
is almost planar and eclipsed with respect to the cis-CO
ligands.
The high reactivity of the bis(alkoxy)allenylidene com-
plexes 1a and 1b towards nucleophiles is due to the electro-
philicity of the terminal carbon atom of the allenylidene
chain. DFT-calculations on the series of substituted chro-
mium pentacarbonyl allenylidene complexes [(CO)5Cr@
C@C@C(R1)R2; R1 = Ph, OMe, NMe2; R2 = Ph, OMe,
NMe2] indicate that the LUMO is predominantly localized
at Ca and Cc of the allenylidene ligand and that there is a
significant positive charge accumulation at Cc of bis(alk-
oxy)allenylidene complexes due to the two electronegative
substituents [4k,33]. The orbital coefficient of the LUMO
is larger at Cc than at Ca. The problems connected with
the high electrophilicity can be circumvented by using
bulky alkoxy substituents that kinetically stabilize the
complexes.
When propynoic acid (ꢀ)-menthylester or -endo-borny-
lester are used as the starting alkynes instead of the ethy-
lester, the bis(alkoxy)-substituted allenylidene complexes
4a,b–6a,b are formed. In contrast to 1a and 1b, these com-
plexes are stable in a pure form as well as in solution for
several hours at room temperature. Therefore, they could
be isolated as red oils in 6–59% yield (Scheme 3) and could
Scheme 1.
minimum amount of dimethylamine to the reaction mix-
tures instantaneously led to the formation of the
amino(alkoxy)allenylidene complexes 2a and 2b [24]
(Scheme 2) via displacement of one of the ethoxy substitu-
ents by dimethylamide. Cc-substitution of a p-donor group
is a well documented reactivity pattern of heteroatom-
substituted allenylidene complexes [32,33]. The reaction is
highly selective. Addition of the amine across the Ca–Cb
bond of the allenylidene ligand as is usually observed with
diarylallenylidene complexes was not observed under the
reaction conditions employed.
The substitution of both alkoxy groups can also be
achieved. The reaction of complexes 1a and 1b with
N,N0-dimethylethylenediamine (DMEDA) yields the bis-
(amino)allenylidene complexes 3a and 3b. In 3a and 3b,
the Cc atom of the allenylidene ligand is incorporated into
a five-membered heterocycle (Scheme 2).
At room temperature the reaction is complete within a
few seconds. Complexes 3a and 3b are isolated as the only
product. Neither addition of the amine across the Ca–Cb
bond to give a,b-unsaturated carbene complexes nor an
intramolecular cyclization (1,3-addition) to give a heterocy-
clic carbene complex or an intermolecular reaction to give
NMe2
HNMe2
(CO)5M
C
C
C
OEt
OEt
OEt
2a,b
(CO)5M
C
C
C
Me
N
1a,b
DMEDA
Fig. 1. Structure of complex 3b in the crystal (ellipsoids drawn at 50%
(CO)5M
C
C
C
˚
level, hydrogen atoms omitted for clarity). Selected bond lengths (A) and
N
angles (ꢁ) are: W1–C1 2.041(7), W1–C2 2.047(7), W1–C5 2.018(9), W1–C6
2.157(9), C6–C7 1.225(13), C7–C8 1.408(12), C8–N1 1.331(7); W1–C6–C7
180.0(2), C6–C7–C8 180.0(3), C7–C8–N1 124.7(4); C9–N1–C8–N1A
ꢀ3.5(3).
Me
M = Cr (a), W (b)
3a,b
Scheme 2.

N. Szesni et al. / Inorganica Chimica Acta 359 (2006) 617–632
627
The IR spectra show a typical pentacarbonyl pattern in
the region of 1900–2100 cmꢀ1, the position of the CO
absorptions being similar to those of [(CO)5Cr@C@
C(COOMe)CH@CHCOOMe] [5b]. The resonance of the
Ca atom in the 13C NMR spectra is characteristically
shifted downfield and agrees well with that of other penta-
carbonyl vinylidene complexes of chromium or tungsten
[40].
When the propynoic acid esters are replaced by phenyl-
propynone as the C3 source, mono(alkoxy)allenylidene
complexes are obtained. Deprotonation of 1-phenylpropy-
none, followed by reaction with [(CO)5M-THF] (M = Cr,
W) and alkylation with trialkyloxonium tetrafluoroborate,
affords the allenylidene complexes 10a,b and 11a,b as deep
violet, temperature-sensitive compounds in 26–44% yield
(Scheme 4). Complex 11b has previously been prepared
by a different method [29].
3.2. Spectroscopic properties of alkoxyallenylidene
complexes
Scheme 3.
be characterized by spectroscopic means and by elemental
analysis. Samples can be stored at ꢀ30 ꢁC for weeks with-
out any decomposition. As a by-product, the vinylidene
complexes 7a,b–9a,b could be isolated (yield: 9–23%).
Complexes 7a,b–9a,b are isomers of 4a,b–6a,b and result
from alkylation at the nucleophilic Cb atom of the alkynyl
metallate intermediates instead of at the carbonyl oxygen.
Cb alkylation of alkynyl ligands is well-known and has
been used for the preparation of vinylidene complexes
[4,35–37]. The reaction of electrophiles with alkynyl com-
plexes of ruthenium and osmium derived from propynoic
acid esters exclusively yields vinylidene complexes [37].
However, when the same methodology is applied to the
synthesis of amino-substituted allenylidene complexes, nei-
ther vinylidene complexes nor follow-up products can be
detected. According to DFT calculations [38], vinylidene
complexes of the type 7a,b–9a,b are more stable than the
corresponding allenylidene complexes 4a,b–6a,b, very
likely due to the strong acceptor properties of the alkoxy-
carbonyl substituent in 7a,b–9a,b. The reverse is true for
the amino-substituted complexes [(CO)5Cr@C@C@
C(NMe2)R] versus [(CO)5Cr@C@C{C(@NMe)R}Me].
From DFT calculations already carried out earlier by Re
et al. [39], it follows that pentacarbonyl metallacumulenes
with an even number of carbon atoms in the chain are sta-
bilized by p-acceptor substituents and odd-numbered
metallacumulenes by p-donor substituents. Therefore,
these calculations indicate that the observed preferential
or even exclusive (OR = OR0 = OMe, OEt) formation of
the allenylidene isomer is the result of a kinetic control in
the alkylation of propynoic acid ester metallates. However,
when bulky substituents OR are employed Cb-substitution
successfully competes with O-alkylation.
The electronic structure and the spectroscopic properties
of allenylidene complexes strongly depend on the substitu-
ents at the terminal carbon atom [4h,4k,21c,39,41]. In
complexes having weak donor groups, the cumulenylidene
resonance form (I) dominates. When enhancing the p-
donor propensity of the substituents, the zwitterionic
alkynyl resonance form (II) (Scheme 5) increasingly
contributes to the overall bonding in the MC3 fragment.
The m(CCC) absorption in the IR-spectra and the reso-
nance of the metal-bound Ca atom in the 13C NMR spectra
have turned out to be excellent probes for determining the
effect of substituents on the electronic structure of alleny-
lidene complexes. In Figs. 2 and 3, the m(CCC) absorption
of the chromium complexes and the 13C-resonance of the
Ca atom are plotted against the sum of the Hammett
constants [rp(R1) + rp(R2)]. Both sets of data correlate
(1) BuLi
(2) (CO)5M[THF]
Ph
O
Ph
H
C
C
C
(CO)5M
C
C
C
(3) [R3O]BF4
OR
10a,b, 11a,b
M = Cr ( ), W ( )
a
b
R = Me ( ), Et (
10 11
)
Scheme 4.
The vinylidene complexes 7a,b–9a,b are unstable and
decompose within minutes at room temperature. There-
fore, they were identified by their IR and NMR spectra.
Scheme 5.

628
N. Szesni et al. / Inorganica Chimica Acta 359 (2006) 617–632
3.3. Reactivity
The influence of two alkoxy substituents on the reactiv-
ity of the new allenylidene complexes towards nucleophiles
was investigated by employing N- and P-nucleophiles as
well as the electron-rich alkyne diethylaminopropyne.
Whereas bis(aryl)-substituted allenylidene complexes
add amines across the Ca–Cb bond of the allenylidene li-
gand to give a,b-unsaturated carbene complexes [6,8–
10b,42], p-donor-substituted allenylidene complexes show
a strong preference for addition of the amines to the termi-
nal carbon atom of the MC3 unit [32]. Addition is usually
followed by elimination of a former substituent. Cc-substi-
tution is likewise observed in the reaction of dimethyla-
mino(aryl)allenylidene complexes with a large excess of a
primary amine [32].
Fig. 2. Correlation between the m(CCC) absorption of the allenylidene
complexes of chromium and the Hammett constants rp.
When a slight excess of dimethylamine is added to a
solution of the bis(alkoxy)allenylidene complexes 5a,b or
6a,b, one of the two alkoxy substituents is displaced and
dimethylamino(alkoxy)allenylidene complexes are formed
(Scheme 6, see also Scheme 2).
The reaction is complete within seconds as indicated by
IR spectroscopy. Only one product, the bornyloxy(dimeth-
ylamino)allenylidene complex 13a (13b), is formed in the
reaction of the bornyloxy(ethoxy)allenylidene complex
6a,b with dimethylamine. Surprisingly, substitution of the
sterically less demanding ethoxy group is favored. In con-
trast, a mixture of two allenylidene complexes, 2a,b and
12a,b, is obtained from the reaction of the ethoxy(menthyl-
oxy)allenylidene complex 5 with dimethylamine. Again,
displacement of the sterically less demanding ethoxy group
dominates. The ratio of isomers is approximately
12a,b:2a,b = 2:1. Both reactions are highly selective. Addi-
tion of the amine to the Ca–Cb bond is not observed, nei-
ther in 5a,b or 6a,b nor in one of the products 12a,b,
13a,b, or 2a,b.
Fig. 3. Correlation between the 13C-resonance of the Ca atom and the
Hammett constants rp.
reasonably well. Deviations are presumably due to different
steric requirements of R1 and R2 that in some cases prevent
optimal overlap of the lone electron pair at R1/R2 and the
p-orbital of the chain. As expected, the m(CCC) absorption
of the bis(amino)-substituted complex 3 is found at highest
energy (Fig. 2).
The amino(alkoxy)allenylidene complexes were charac-
terized spectroscopically and by elemental analyses. The
structure of 12a was additionally established by an X-ray
analysis (Fig. 4, Table 1). All data are similar to those of
other amino(alkoxy)allenylidene complexes [24].
In a similar fashion, the reaction of the meth-
oxy(phenyl)allenylidene complex 10a with a minimum
amount of dimethylamine proceeds by substitution of the
The 13C-resonance of the Ca atom shifts towards higher
field with increasing p-donor propensity of R1 or/and R2
(Fig. 3).
NMe2
In the UV–Vis spectra, the absorption at longest wave-
length that is assigned to a metal-to-ligand charge transfer
(MLCT) likewise depends on the substitution pattern.
Increasing the donor propensity of the substituents gives
rise to a shift of the MLCT absorption towards shorter
wavelength.
In general, the relevant data of the alkoxyallenylidene
complexes are found in between those of bis(aryl)- and
bis(amino)-substituted allenylidene complexes. This
indicates an enhanced contribution of the cumulene-like
resonance structure and implies a higher reactivity when
compared to aminoallenylidene complexes.
(CO)5M
C
C
C
OR
12a,b, 13a,b
OEt
OR
HNMe2
(CO)5M
C
C
C
OEt
5a,b, 6a,b
(CO)5M
C
C
C
NMe2
2a,b
M = Cr ( ), W ( )
a
b
R = (-)-menthyl ( , ), endo-bornyl ( ,
5 12 6 13
)
Scheme 6.

N. Szesni et al. / Inorganica Chimica Acta 359 (2006) 617–632
629
OEt
(CO)4(PPh3)Cr
C
C
C
C
C
OBornyl
16
OEt
ν
h , PPh3
(CO)5Cr
C
C
C
+
OBornyl
OEt
6a
(CO)3(PPh3)2Cr
C
OBornyl
17
Scheme 8.
amino(alkyl)- and -(aryl)allenylidene complexes even at
elevated temperatures. Upon irradiation, one or two CO-
ligands are displaced by the phosphine donors yielding
tetracarbonyl(phosphine)- or tricarbonyl{bis(phosphine)}
allenylidene complexes, respectively [44].
Analogously to aminoallenylidene complexes, com-
pound 6a does not react thermally with triphenylphos-
phine. However, irradiation in the presence of a slight
excess of the phosphine yields complexes 16 and 17 in, after
chromatographic workup, 31% (16) and 68% (17) yield,
respectively (Scheme 8).
Fig. 4. Structure of complex 12a in the crystal (ellipsoids drawn at 50%
˚
level, hydrogen atoms omitted for clarity). Selected bond length (A) and
angles (ꢁ): Cr1–C1 1.874(6), Cr1–C2 1.886(6), Cr1–C3 1.900(6), Cr1–C4
1.879(6), Cr1–C5 1.846(7), Cr1–C6 1.996(6), C6–C7 1.228(8), C7–C8
1.366(7), C8–N1 1.298(7), C8–O6 1.319(7); Cr1–C6–C7 176.1(5), C6–C7–
C8 171.1(6), C7–C8–N1 123.0(5), C7–C8–O6 122.6(5), N1–C8–O6
114.3(5).
The complexes 16 and 17 are stable when handled in an
inert atmosphere. The IR spectra of the complexes indicate
a cis arrangement of the phosphine and the allenylidene
ligand in 16 and a mer conformation of the three carbonyl
ligands in 17. These conclusions are supported by the
NMR spectra of the complexes and are in agreement with
results on related complexes [44]. Due to the enhanced elec-
tron density at the metal through coordination of the phos-
phine, the resonance of the metal-bound carbon atom is
significantly shifted downfield compared to that of the
starting compound (d = 230 ppm for 6a; 250 ppm for 16;
265 ppm for 17), indicating reduced contribution of the
zwitterionic alkynyl resonance form to the overall bonding
description. The conclusion is confirmed by the shift of the
m(CCC) absorption in the IR spectra towards lower wave
numbers. As expected, the effect is more pronounced for
the tricarbonyl complex 17 than for 16.
alkoxy group to give the dimethylamino(phenyl)allenylid-
ene complex 14 (Scheme 7).
However, when the amine is used in excess, additionally
the a,b-unsaturated carbene complex 15 is formed. Com-
pound 15 is finally obtained as the sole product when dim-
ethylamine is used in at least 2-fold excess and prolonged
reaction times are employed. Obviously, substitution of
the terminal alkoxy substituent is much faster than addi-
tion across the Ca–Cb bond of the allenylidene ligand. This
agrees well with the results of studies on the reactivity of
other p-donor-substituted allenylidene complexes [24,32].
Bis(aryl)-substituted allenylidene complexes add triphe-
nylphosphine to either the a- or the c-carbon atom of the
allenylidene chain to give allenylphosphine or c-phos-
phinoalkynyl complexes [5c,9e,43]. In contrast, tertiary
phosphines do not add to the cumulenylidene ligand of
In the reaction of bis(aryl)allenylidene complexes with
diethylaminopropyne, two different isomeric complexes
are formed: (a) alkenylallenylidene complexes by insertion
of the C„C bond of the alkyne into the CbACc bond of
the allenylidene ligand [6b,45] and (b) cyclobutenylidene
complexes via formal [2+2]-cycloaddition of the C„C
bond to the Ca–Cb bond [6b]. The product ratio depends
on the polarity of the solvent, the temperature, and the
electronic properties of the cumulenylidene substituents.
Increasing the p-donor propensity of the Cc substituents
shifts the product ratio towards alkenylallenylidene com-
plexes [6b].
Ph
Ph
HNMe2
(CO)5Cr
C
C
C
(CO)5Cr
C
C
C
OMe
NMe2
10a
14
HNMe2
NMe2
C
(CO)5Cr
NMe2
C
C
The results of the reaction of the allenylidene com-
plexes 5a and 5b with diethylaminopropyne are in line
with these observations. Two alkenylallenylidene com-
plexes are formed in almost equal amounts. The product
H
Ph
15
Scheme 7.

630
N. Szesni et al. / Inorganica Chimica Acta 359 (2006) 617–632
of a regiospecific insertion of the ynamine into the Cb–Cc
bond (18a,b, Scheme 9) is isolated in 46–48% yield and
its ‘‘hydrolysis product’’ 19a,b in 45–47% yield. Com-
plexes 19a,b presumably arise from the hydrolysis of
18a,b by traces of water present in the solvent. In addi-
tion, traces of the pyranylidene complexes 20a,b (4–5%)
are also isolated. Complexes 20a,b are presumably
formed by an intramolecular cyclization of 19a,b. Prod-
ucts of a formal [2+2]-cycloaddition are not detected.
A possible mechanism for the cyclization process is out-
lined in Scheme 10. Hydrolysis of the Ce-bound ethoxy
group in 18a,b gives 19a,b (step a). Subsequent tautomer-
ization of the allenylidene complex, presumably by a pro-
tonation/deprotonation sequence, affords a vinylidene
complex (steps b and c). The isomerization is finally fol-
lowed by a 1,6-cyclization (step d) to form the product
complex 20a,b. The mechanistic proposal is supported by
the following observation. When catalytic amounts of
hydrochloric acid are added to a solution of pure alkenyl-
allenylidene complex 18a,b, only the pyranylidene complex
20a,b is obtained albeit in low yield. In contrast, bases do
not induce cyclization. Several investigations concerning
mechanistic aspects of the formation of pyranylidene com-
plexes support the proposed reaction pathway [46]. Never-
theless, other mechanisms are also conceivable.
NEt2
NEt2
(CO)5M
C
C
C
C
C
C
(CO)5M
C
C
C
Me
C
Me
Menthyl-O
EtO
OEt
O-Menthyl
(E)-s-cis-18
(Z)-s-cis-18
Scheme 11.
The alkenylallenylidene complexes exhibit all spectro-
scopic features that are characteristic for amino-substituted
allenylidene complexes. The NMR spectra indicate that in
solution, two isomers of 18a and 18b are present in a ratio
of approximately 1:1. Usually, alkenylallenylidene com-
plexes selectively adopt the s-cis-conformation in solution
as well in the solid state [7a,31]. Therefore, the two isomers
of 18a and 18b very likely differ in the relative orientation
of OEt and OMenthyl at the C@C bond of the s-cis-con-
former (Scheme 11). Obviously, none of these isomers is
significantly favored at room temperature.
In summary, alkoxyallenylidene complexes are readily
accessible by the methodology successfully applied to
the synthesis of aminoallenylidene complexes. The spec-
troscopic data indicate an enhanced contribution of the
cumulenylidene resonance form to the overall bonding
description when compared to their amino-stabilized
counterparts and a reduced contribution when compared
to the corresponding diarylallenylidene complexes. Thus,
as far as the bonding within the allenylidene ligand is con-
cerned, alkoxyallenylidene complexes are intermediate in
between diamino- and diarylallenylidene complexes. The
reactivity trends are comparable to those of aminoalleny-
lidene complexes and deviate from those of diarylalleny-
lidene complexes. In contrast, the thermal stability is
more similar to that of diarylallenylidene complexes.
However, the higher reactivity compared to aminoalleny-
lidene complexes renders alkoxyallenylidene complexes as
very convenient starting compounds for derivatizing
allenylidene complexes.
OEt
NEt2
C-NEt2
Me-C
C
(CO)5M
C
C
C
+
(CO)5M
C
C
C
C
Me
OMenthyl
,
5a b
Menthyl-O
OEt
18a,b
NEt2
H
NEt2
C
C
(CO)5M
C
C
C
O
C
C
C
Me
+ (CO)5M
C
Me
C
Menthyl-O
OH
OMenthyl
19a,b
20a,b
Scheme 9.
4. Supplementary material
Crystallographic data for the structural analyses of com-
plexes 3b and 12a have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publica-
tion nos. CCDC 277967 (3b) and CCDC 277968 (12a).
Copies of the data can be obtained free of charge on appli-
cation to CCDC, 12 Union Road, Cambridge CB2 1EZ,
UK (fax: +44 1223 336033; e-mail deposit@ccdc.cam.ac.uk
or www: http://www.ccdc.cam.ac.uk).
Acknowledgment
Support of these investigations by the Wacker-Chemie
GmbH (gift of chemicals) is gratefully acknowledged.
Scheme 10.

N. Szesni et al. / Inorganica Chimica Acta 359 (2006) 617–632
631
´
´
´
(d) M.A. Esteruelas, A.V. Gomez, A.M. Lopez, M. Olivan, E. Onate,
˜
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