Synthesis and characterization of deuterium-labelled (fulvene)M(CO) 3 complexes (M = Cr, Mo)

Article abstract of DOI:10.1016/j.ica.2004.06.038

The preparation and characterization of a series of deuterium-labelled (fulvene)M(CO)₃ (M = Cr,Mo) complexes is reported, including (η⁵-6-dimethylaminofulvene-d₂)Cr(CO)₃ and (η⁵-6-dimethylaminofulvene-d₂)Mo(CO)₃ as well as 6,6-diphenylfulvene-d₁₀ and 6,6-diphenyl-1,2-benzofulvene- d₁₀ and their corresponding tricarbonylchromium complexes. The preparation and characterization of a series of deuterium-labelled (fulvene)M(CO)₃ (M = Cr, Mo) complexes is reported. (η⁵-6-Dimethylaminofulvene-d₂)Cr(CO)₃ and (η⁵-6-dimethylaminofulvene-d₂)Mo(CO)₃ were obtained in high yields by reacting the deuterated fulvene ligands with (MeCN)₃M(CO)₃ (M = Cr, Mo). In addition, syntheses of 6,6-diphenylfulvene-d₁₀ and 6,6-diphenyl-1,2-benzofulvene-d ₁₀ as well as the corresponding tricarbonylchromium complexes are described.

Full text of DOI:10.1016/j.ica.2004.06.038

Inorganica Chimica Acta 357 (2004) 4592–4595
www.elsevier.com/locate/ica
Note
Synthesis and characterization of
deuterium-labelled (fulvene)M(CO)3 complexes (M=Cr, Mo)
*
Frank T. Edelmann
Chemisches Institut der Otto-von-Guericke-Universita¨t Magdeburg, Universita¨tsplatz 2, 39106 Magdeburg, Germany
Received 13 February 2004; accepted 26 June 2004
Available online 28 July 2004
Abstract
The preparation and characterization of a series of deuterium-labelled (fulvene)M(CO)3 (M=Cr, Mo) complexes is reported. (g5-
6-Dimethylaminofulvene-d2)Cr(CO)3 and (g5-6-dimethylaminofulvene-d2)Mo(CO)3 were obtained in high yields by reacting the
deuterated fulvene ligands with (MeCN)3M(CO)3 (M=Cr, Mo). In addition, syntheses of 6,6-diphenylfulvene-d10 and 6,6-diphe-
nyl-1,2-benzofulvene-d10 as well as the corresponding tricarbonylchromium complexes are described.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: Deuteration; Fulvenes; Fulvene complexes; Chromium complexes; Molybdenum complexes
1. Introduction
lowed an unambiguous 1H NMR analysis of the
coordinated fulvenes.
The organometallic chemistry of pentafulvenes has
recently gained renewed interest as fulvenes have been
found to be highly versatile starting materials for the
preparation of catalytically active metallocenes. Vari-
ous olefin polymerization catalysts have been pre-
pared from fulvenes such as 6,6-dimethylfulvene or
6-dimethylaminofulvene [1–4]. (Fulvene)Cr(CO)3 com-
plexes form a well-established group of transition met-
al fulvene derivatives. Since their discovery by Fischer
et al. more than 40 years ago [5], these compounds
have been extensively investigated using spectroscopic
as well as X-ray crystallographic techniques [6]. Some
uncertainties, however, remained in the unequivocal
The 1H NMR spectra of (fulvene)Cr(CO)3 complexes
containing 6-alkyl- and 6-aryl-substituted fulvenes (1, 2)
in all cases display the sequence dH2,3 >dH1,4 for the ring
protons (AAÔXXÕ system) [6] (Scheme 1).
In the case of the 6-dimethylaminofulvene complexes
3a–c (Scheme 1), the signals of the ring protons overlap
and no definite assignment could be made. A similar
1
problem was encountered in the H NMR spectrum of
the complex (g6-6,6-diphenyl-1,2-benzofulvene)Cr(CO)3
(4) [7]. The synthesis of tricarbonylchromium complexes
of 6-dimethylaminofulvene-d2 and 6,6-diphenyl-1,2-ben-
zofulvene-d10 should allow an unambiguous assignment
1
of these H NMR spectra.
1
assignment of the H NMR signals of the coordinated
fulvene ligands. We report here the preparation and
characterization of deuterium-labelled tricarbonyl(ful-
vene)chromium and molybdenum complexes which al-
2. Experimental
All reactions involving metal carbonyl complexes
were carried out under dry nitrogen using standard
Schlenk techniques. THF was dried over Na/benzophe-
none and freshly distilled under nitrogen prior to use.
*
Tel.: +49-391-6718327; fax: +49-391-6712933.
E-mail address: frank.edelmann@vst.uni-magdeburg.de (F.T. Edel-
mann).
0020-1693/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2004.06.038

F.T. Edelmann / Inorganica Chimica Acta 357 (2004) 4592–4595
4593
4
2.3. Benzophenone-d10 (improved preparation) [11]
1: R, R' = alkyl
2: R, R' = aryl
R
3
2
3a: R = H, R' = NMe2
3b: R = SMe, R' = NMe2
3c: R, R' = NMe2
(CO)3Cr
Anhydrous AlCl3 (26 g, 0.20 mol) was added in small
increments to a stirred solution of oxalyl chloride (12.7
g, 0.10 mol) and C6D6 (25 ml, 0.28 mol) in carbon disul-
fide (50 ml). After the vigorous evolution of DCl had
ceased, the brown reaction mixture was refluxed for 2
h and evaporated to dryness. The residue was redis-
solved in diethylether (150 ml) and the solution was
poured onto 300 g of ice. The organic layer was separated,
the aqueous phase was extracted with diethylether
(3·150 ml) and the combined extracts were dried over
Na2SO4. Removal of the solvent and distillation of the
residue under vacuum (b.p. 83 ꢁC/ 10ꢀ3 torr) afforded
15.4 g (80%) of pure benzophenone-d10.
R'
1
Cr(CO)3
Ph
Ph
4
Scheme 1. (Fulvene)Cr(CO)3 complexes.
Commercially available C6D6 and dicyclopentadiene
were used without further purification. 6-Dimethylami-
nofulvene-d2 [8] and (MeCN)3M(CO)3 (M=Cr, Mo)
[9,10] were prepared as described in the literature. Al-
though benzophenone-d10 is commercially available, it
was synthesized via an improved method following a
procedure given by Staudinger [11]. IR spectra: Per-
kin–Elmer spectrometer 180 and Bio-Rad FTS 7, Nujol
mulls between KBr disks. 1H NMR spectra: and Bruker
AM-250 (250 MHz, TMS ext., 25 ꢁC).
2.4. 6,6-Diphenyl-1,2-benzofulvene-d10 (6)
A solution of sodium ethoxide was freshly prepared
from Na (2.0 g, 0.09 mol) and ethanol (100 ml). Benzo-
phenone-d10 (12.0 g, 0.06 mol) and freshly distilled ind-
ene (10.0 g, 0.09 mol) were added and the mixture was
heated to reflux for 8 h. Cooling to room temperature
gave a red-brown precipitate, which was isolated by fil-
tration and washed with ethanol (20 ml). The crude ben-
zofulvene was contaminated with a red by-product.
Purification was achieved by repeated (2·) chromato-
graphy on silica gel (toluene, column: l=20 cm, B=6
cm). Subsequent recrystallization from ethanol yielded
15.3 g (84%) of bright yellow crystals. M.p. 111 ꢁC.
Anal. Calc. for C22H6D10 (290.5): C, 90.98; H, 2.08; D,
6.94. Found: C, 92.08; H, 2.13; D 7.12%. IR (KBr):
2.1. (g5-6-Dimethylaminofulvene-d2)Cr(CO)3 (5a)
A solution of (MeCN)3Cr(CO)3 (3.73 g, 13.4 mmol)
and 6-dimethylaminofulvene-d2 (1.63 g, 13.4 mmol) in
THF (250 ml) was stirred for 3 d at room temperature.
The resulting deep red reaction mixture was filtered, 100
ml of n-heptane was added to the filtrate, and the solu-
tion was concentrated in vacuo to a total volume of 50
ml. The precipitate was isolated by filtration, washed
with n-pentane (20 ml) and dried under vacuum to give
3.16 g (91%) of glistening, dark red platelets. M.p. 238
ꢁC (dec.). Anal. Calc. for C11H9CrD2NO3 (259.2): C,
50.97; H, 3.50; D, 1.56; N, 5.40. Found: C, 51.36; H,
3.46; D, 1.54; N, 5.20%. IR (KBr): m(CO) 1904, 1816,
1
1587, 1464, 1352, 783, 764, 685, 533 cmꢀ1. H NMR
(CDCl3): d 7.32 - 6.85 (m, H-10,20,30,40); 6.73, 6.58
(AB, H-3,4, J=7 Hz) ppm. 13C NMR (CDCl3): d
146.6, 144.2, 141.9, 141.2, 138.8, 135.8 (quaternary C);
132.0–126.1 (m, C-D); 131.4, 130.3, 127.0, 124.4,
123.4, 120.7 (C–H) ppm.
1784; m(C‚N) 1622 cmꢀ1. H NMR (CDCl3): d 7.85
1
(s, H-6), 5.08 (s, H-2,3), 3.46 (s, 3H, CH3), 3.30 (s, 3H,
CH3) ppm. 13C NMR (acetone-d6): d 240.4 (CO);
155.4 (C-6); 89.9 (C-1,2,3,4); 80.8 (C-5); 47.9, 41.1
(CH3) ppm.
2.5. (g6-6,6-Diphenyl-1,2-benzofulvene-d10)Cr(CO)3 (7)
3.0 g (10.3 mmol) of 6, dissolved in THF (30 ml), was
added to a suspension of (MeCN)3Cr(CO)3 (3.05 g, 11.8
mmol) in THF (30 ml), and the mixture was stirred for
48 h at 40 ꢁC. The resulting dark red solution was fil-
tered and evaporated to dryness. The residue was redis-
solved in a minimum amount of toluene and subjected
to chromatography on silica gel (column: l=20 cm,
B=6 cm). Unreacted 6 was eluted with n-hexane. Elu-
tion with toluene produced a broad red-purple band.
Removal of the solvent in vacuo and recrystallization
of the residue from n-hexane afforded 1.50 g (34%) 7
in the form of red-purple crystals. M.p. 154 ꢁC. Anal.
Calc. for C25H6CrD10O3 (426.5): C, 70.41; H, 1.42; D,
4.73. Found: C, 70.46; H, 1.37; D, 4.56%. IR (KBr):
2.2. (g5-6-Dimethylaminofulvene-d2)Mo(CO)3 (5b)
The analogous reaction of (MeCN)3Mo(CO)3 (1.50 g,
4.9 mmol) and 6-dimethylaminofulvene-d2 (0.6 g, 5.0
mmol) afforded 1.30 g (88%) 5b as orange-red micro-
crystals. M.p. >300 ꢁC (dec.). Anal. Calc. for
C11H9D2MoNO3 (303.2): C, 43.58; H, 2.99; D, 1.33;
N, 4.62. Found: C, 45.02; H, 2.79; D, 1.24; N, 4.40%.
IR (KBr): m(CO) 1908, 1818 (sh), 1787; m(C‚N) 1616
1
cmꢀ1. H NMR (acetone-d6): d 8.02 (s, H-6); 5.67 (m,
H-1,4, ca. 30%); 5.51 (s, H-2,3); 3.42 (s, 3H, CH3),
3,28 (s, 3H, CH3) ppm. 13C NMR (acetone-d6): d
230.0 (CO); 153.6 (C-6); 93.4 (C-1,2,3,4); 87.7 (C-5);
48.3, 41.4 (CH3) ppm.
m(CO) 1948, 1863 cmꢀ1 1H NMR (CDCl3): d 6.81
.

4594
F.T. Edelmann / Inorganica Chimica Acta 357 (2004) 4592–4595
(H-4), 6.57 (H-3, AB, J=5.6 Hz), 5.62 (m, H-10), 5.30
(m, H-40), 4.96 (m, H-20,30) ppm.
D
H
5a: M = Cr
5b: M = Mo
NMe2
D
2.6. 6,6-Diphenylfulvene-d10 (8)
M(CO)3
Freshly distilled monomeric cyclopentadiene (6.0 g,
0.09 mol) was added dropwise to a stirred solution of
1.84 g Na and 15.4 g (0.08 mol) benzophenone-d10 in
dry ethanol (100 ml). After 2 h, the crystalline precipi-
tate was filtered off and recrystallized from ethanol to
give 10.8 g (56%) 8 as glistening, bright red crystals.
M.p. 79 ꢁC. IR (KBr): 1586, 1463, 1351, 783, 764, 532
1
However, the H NMR spectrum of 5a revealed that
in this complex all four ring protons accidentally display
the same chemical shift and give rise to only one broad
singlet. More helpful was the NMR analysis of the mo-
1
lybdenum analog 5b. In this case, the H NMR spec-
1
cmꢀ1. H NMR (CDCl3): d 6.64–6.56 (m, 2H, fulvene
trum showed two well-separated signals for the ring
protons. The resonance at higher frequency had only
ca. 30% intensity and was thus assigned to the 1,4-pro-
tons. This is exactly opposite to what is observed in
the case of the g6-coordinated fulvene ligands in 1 and
2 having alkyl or aryl substituents [6]. The sequence
ring-H), 6.33–6.26 (m, 2H, fulvene ring-H) ppm. 13C
NMR (CDCl3): d 151.4 (C-6); 143.5 (C-5); 140.7 (q-
C6D5); 131.9 (C-2,3); 131.3, 127.9, 126.8 (t, o,m,p-
C6D5); 124.0 (C-1,4) ppm.
2.7. (g6-6,6-Diphenylfulvene-d10)Cr(CO)3 (9)
d
H1,4 >dH2,3 was therefore assigned to all M(CO)3 com-
plexes (M=Cr, Mo, W) of 6-dimethylamino-substituted
6,6-Diphenylfulvene-d10 (8) (0.90 g; 3.7 mmol) was
added to a solution of (MeCN)3Cr(CO)3 (0.96 g, 3.7
mmol) in THF (60 ml) and the dark brown reaction mix-
ture was stirred for 24 h at room temperature. The solu-
tion was evaporated to dryness in vacuo and the residue
was washed with warm n-hexane (2·50 ml). The crude
product was redissolved in THF (20 ml). Addition of
n-hexane (20 ml) and cooling to ꢀ30 ꢁC yielded 0.40 g
(29%) very fine, olive-brown needles of 9. M.p. 203 ꢁC
(dec.). Anal. Calc. for C21H4CrD10O3 (376.4): C, 67.01;
H, 1.07; D, 5.36. Found: C, 68.22; H, 0.98; D, 4.91%.
fulvenes [6].
Benzophenone-d10 served as starting material for a
series of deuterated fulvene and benzofulvenes deriva-
tives. It was found to react cleanly with indene in the
presence of sodium ethoxide according to Scheme 2 to
give the C6D5-substituted 1,2-benzofulvene derivative
6. The separation of a strongly colored by-product
was achieved by repeated chromatography on silica-
gel. The tricarbonylchromium complex 7 was synthe-
sized by treatment of 6 with (MeCN)3Cr(CO)3 in THF
[2] (Scheme 2).
The simple 1H NMR spectrum of 7 clearly confirmed
the g6-coordination of the Cr(CO)3 group. This assign-
ment was not possible in the case of the parent 6,6-
diphenyl derivative because of overlap of the fulvene
ring resonances with the C6H5 multiplets [7]. Starting
with benzophenone-d10 and monomeric cyclopentadi-
ene, bright red 6,6-diphenylfulvene-d10 (8) was synthe-
sized in moderate yield (56%). Reaction of 8 with
(MeCN)3Cr(CO)3 in THF afforded olive-brown (g6-
IR (KBr): m(CO) 1969, 1901, 1884 cmꢀ1 1H NMR
.
(CDCl3): d 5.38 (t, 2H, fulvene ring-H), 4.63 (t, 2H, ful-
vene ring-H) ppm. 13C NMR (CDCl3): d 237.7 (CO),
140.4 (q-C6D5), 127.9 (m, o,m,p-C6D5 +C-6), 107.2 (C-
5), 93.2 (C-2,3), 88.6 (C-1,4) ppm.
3. Results and discussion
1
Treatment of 6-dimethylaminofulvene with a large
excess of CH3OD according to the literature procedure
results in ca. 70% deuterium exchange of the 1,4-protons
to give 6-dimethylaminofulvene-d2. This ligand reacted
smoothly with (MeCN)3M(CO)3 (M=Cr, Mo) to afford
the desired metal tricarbonyl complexes 5a and 5b in
high yields.
6,6-diphenylfulvene-d10)Cr(CO)3 (9, Scheme 3). The H
NMR spectrum of 9 showed only two triplets corre-
sponding to the ring protons of the fulvene ligand.
The present study shows that various specifically deu-
terium-labelled fulvene derivatives are readily accessible
via different synthetic routes. The highly reactive aceto-
nitrile complexes (MeCN)3M(CO)3 (M=Cr, Mo) are
C7H9
(C6D5)2CO
(MeCN)3Cr(CO)3
NaOEt
THF
(CO)3Cr
D5C6 C6D5
D5C6 C6D5
6
7
Scheme 2. Preparation of 6,6-diphenyl-1,2-benzofulvene-d10 and its Cr(CO)3 complex.

F.T. Edelmann / Inorganica Chimica Acta 357 (2004) 4592–4595
4595
C6D5
C6D5
C6D5
C5H6
(MeCN)3Cr(CO)3
THF
(C6D5)2CO
NaOEt
C6D5
8
Cr(CO)3
9
Scheme 3. Preparation of 6,6-diphenylfulvene-d10 and its Cr(CO)3 complex.
[2] A. Razavi, J. Ferrara, J. Organomet. Chem. 435 (1992) 299.
[3] H.G. Alt, M. Jung, W. Milius, J. Organomet. Chem. 558 (1998)
111.
the precursors of choice for synthesizing the correspond-
ing tricarbonylchromium or -molybdenum complexes.
[4] V.V. Kotov, R. Fro¨hlich, G. Kehr, G. Erker, J. Organomet.
Chem. 676 (2003) 1.
Acknowledgment
[5] E.O. Fischer, W. Semmlinger, Naturwiss 48 (1961) 525.
[6] B. Lubke, F. Edelmann, U. Behrens, Chem. Ber. 116 (1983) 11
and references cited therein.
Financial support of this work by the Deutsche Fors-
chungsgemeinschaft and the Fonds der Chemischen In-
dustrie is gratefully acknowledged.
[7] F. Edelmann, O. Koch, U. Behrens, J. Organomet. Chem. 311
(1986) 111.
[8] A. Mannschreck, U. Ko¨lle, Chem. Ber. 102 (1969) 243.
[9] D.P. Tate, W.R. Knipple, J.M. Augl, Inorg. Chem. 1 (81962)
433.
References
[10] F. Edelmann, P. Behrens, S. Behrens, U. Behrens, J. Organomet.
Chem. 309 (1986) 109.
[11] H. Staudinger, Ber. Deutsch. Chem. Ges. 41 (1908) 3558.
[1] G.S. Herrmann, H.G. Alt, M.D. Rausch, J. Organomet. Chem.
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