P-coligand tuning of the haptotropic metal migration in phenanthrene chromium complexes

Article abstract of DOI:10.1021/om900057a

The hydroquinoid phenanthrene Cr(CO)₃ complex 1, directly accessible from the benzannulation of pentacarbonyl[(methoxy)-1-naphthylcarbene] chromium with 3-hexyne as the kinetically favored isomer, and its thermodynamically stable haptotropomer

Full text of DOI:10.1021/om900057a

Organometallics 2009, 28, 3473–3484
3473
P-Coligand Tuning of the Haptotropic Metal Migration in
Phenanthrene Chromium Complexes
Oliver Joistgen,† Anja Pfletschinger,‡ Jan Ciupka,‡ Michael Dolg,‡ Martin Nieger,§,#
Gregor Schnakenburg,§ Roland Fro¨hlich, Olga Kataeva, and Karl Heinz Do¨tz*,†
Kekule´-Institut fu¨r Organische Chemie und Biochemie, Rheinische Friedrich-Wilhelms-UniVersita¨t, Bonn,
Gerhard-Domagk-Strasse 1, D-53121 Bonn, Germany, Institut fu¨r Theoretische Chemie, UniVersita¨t zu
Ko¨ln, Greinstrasse 4, D-50939 Ko¨ln, Germany, Institut fu¨r Anorganische Chemie, Rheinische
Friedrich-Wilhelms-UniVersita¨t, Bonn, Gerhard-Domagk-Strasse 1, D-53121 Bonn, Germany, Laboratory
of Inorganic Chemistry, Department of Chemistry, UniVersity of Helsinki, FIN-00014, Finland, and
Organisch-Chemisches Institut, UniVersita¨t Mu¨nster, Corrensstrasse 40, D-48149 Mu¨nster, Germany
ReceiVed January 26, 2009
The hydroquinoid phenanthrene Cr(CO)3 complex 1, directly accessible from the benzannulation of
pentacarbonyl[(methoxy)-1-naphthylcarbene]chromium with 3-hexyne as the kinetically favored isomer,
and its thermodynamically stable haptotropomer 2 undergo a photoinduced substitution of one CO ligand
for phosphines and phosphites PR3 (R ) Me, OMe, Ph, OPh) to give (η6-phenanthrene)Cr(CO)2PR3
complexes 3-10. Upon warming chromium complexes 3-6, a haptotropic metal migration affords
regioisomers 7-10 in up to 79% yield bearing the chromium fragment coordinated to the terminal
unsubstituted phenanthrene ring. The rearrangements have been monitored by IR and NMR spectroscopy.
Kinetic NMR experiments in noncoordinating solvents such as hexafluorobenzene reveal first-order kinetics
in line with an intramolecular metal shift along the extended π-system. The metal migration can be
tuned by the P-based coligand as demonstrated by rate constants differing by 2 orders of magnitude and
by barriers of activation differing by 15 kJ mol-1, respectively. A quantitative analysis (QALE) of these
ligand effects suggests that the rearrangement is controlled by both electronic and steric properties of the
P-coligand. The molecular structures of the complexes 3, 4, and 6-10 were established by single-crystal
X-ray analysis. Quantum chemical DFT calculations provide a mechanistic rationale of the haptotropic
migration in naphthalene and phenanthrene Cr(CO)2PR3 complexes.
tricarbonyl(η6-naphthalene)chromium complexes2 but more
recently has been extended to fused arenes such as phenan-
threne,3 naphthobenzofuran, and naphthobenzothiophene.4 The
mechanism of the haptotropic metal migration has been
investigated using experimental and theoretical methods. EHMO
and, more recently, DFT calculations suggested that the metal
shift in tricarbonyl(η6-naphthalene)chromium complexes does
not follow the least motion pathway across the ring junction
but rather occurs along the periphery of the naphthalene system
with a η4-trimethylene methane complex type transition state.1a,d,e,5
A similar metal migration principle has been revealed for
tricarbonyl(η6-phenanthrene)chromium3,6 and complexes with
Introduction
Transition metal complexes with unsaturated ligands such as
polycyclic arenes or oligoenes offering more than one coordina-
tion site are able to undergo a metal shift along the π-skeleton.
This rearrangement is usually referred to as a haptotropic metal
migration and has been studied for several metals as well as
for different ligand systems.1 Although this phenomenon is
known for several kinds of metal complexes, it has been most
intensively studied in tricarbonyl(η6-arene)chromium complexes
due to their easy accessibility via Cr(CO)3 transfer procedures.
Early research focused mainly on η6-η6-rearrangements in
* Corresponding author. Fax: (+49) 228 735813. E-mail: doetz@
uni-bonn.de.
(2) (a) Cunningham, S. D.; Öfele, K.; Willeford, B. J. Am. Chem. Soc.
1983, 105, 3724. (b) Do¨tz, K. H.; Dietz, R. Chem. Ber. 1977, 110, 1555.
(c) Do¨tz, K. H.; Stinner, C. Tetrahedron: Asymmetry 1997, 8, 1751–1756.
(d) Ku¨ndig, E. P.; Peret, C.; Spichiger, S.; Bernadinelli, G. J. Organomet.
Chem. 1985, 286, 183–200. (e) Kriss, R. U.; Treichel, P. M. J. Am. Chem.
Soc. 1986, 108, 853–855. (f) Oprunenko, Y. F.; Malyugina, S. G.; Ustynyuk,
Y. A.; Ustynyuk, N. A.; Kravtsov, D. N. J. Organomet. Chem. 1988, 338,
357–368.
† Kekule´-Institut fu¨r Organische Chemie und Biochemie, Rheinische
Friedrich-Wilhelms-Universita¨t.
‡ Universita¨t zu Ko¨ln.
§ Institut fu¨r Anorganische Chemie, Rheinische Friedrich-Wilhelms-
Universita¨t.
# University of Helsinki.
Universita¨t Mu¨nster.
(1) For reviews see: (a) Albright, T. A.; Hofmann, P.; Hoffmann, R.;
Lillya, C. P.; Dobosh, P. A. J. Am. Chem. Soc. 1983, 105, 3396–3411. (b)
Ku¨ndig, E. P.; Desorby, V.; Grivet, C.; Spichiger, S. Organometallics 1987,
6, 1173. (c) Morris, M. J. In ComprehensiVe Organometallic Chermistry
II; Abel, E. W., Stone, F. G. A., Wilkinson, G. Eds.; Pergamon Press: New
York, 1995; Vol. 5, pp 501-504. (d) Oprunenko, Y. F. Russ. Chem. ReV.
2000, 69, 683–704. (e) Do¨tz, K. H.; Stendel. J., Jr. In Modern Arene
Chemistry; Astruc, D. Eds.; Wiley-VCH: Weinheim, Germany, 2002. (f)
Do¨tz, K. H.; Wenzel, B.; Jahr, H. C. Chromium-Templated Benzannulation
and Haptotropic Metal Migration. Top. Curr. Chem. 2004, 248, 63–103.
(g) Gridnev, I. D. Coord. Chem. ReV. 2008, 252, 1798–1818.
(3) (a) Do¨tz, K. H.; Stendel, J., Jr.; Mu¨ller, S.; Nieger, M.; Ketrat, S.;
Dolg, M. Organometallics 2004, 24, 3219–3228. (b) Do¨tz, K. H.; Stendel,
J., Jr.; Nieger, M. Z. Anorg. Allg. Chem. 2009, 635, 221–237.
(4) (a) Do¨tz, K. H.; Jahr, H. C.; Nieger, M. J. Organomet. Chem. 2002,
641, 185–194. (b) Schneider, J. F.; Na¨ttinen, K.; Lewall, B.; Nieger, M.;
Niecke, E.; Do¨tz, K. H. Eur. J. Org. Chem. 2005, 1541–1560.
(5) (a) Ref 1a. (b) Oprunenko, Y. F.; Akhmedov, N. G.; Laikov, D. N.;
Malyugina, S. G.; Mstislavsky, V. I.; Roznyatovsky, V. A.; Ustynyuk, Y. A.;
Ustynyuk, N. A. J. Organomet. Chem. 1999, 583, 136–145.
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6102.
10.1021/om900057a CCC: $40.75
2009 American Chemical Society
Publication on Web 05/08/2009

3474 Organometallics, Vol. 28, No. 12, 2009
Joistgen et al.
Scheme 1. Synthesis of Kinetic and Thermodynamic Tricarbonyl(η6-phenanthrene)chromium Complexes 1 and 2
Scheme 2. Synthesis of P-Based Phenanthrene Chromium
more extended arene platforms.7 A competitive scenario for a
metal transfer in fused arenes from one ring to another may be
Complexes 3-10
based on an intermolecular, a dissociative, or a decomplexation/
recomplexation mechanism depending on the reaction conditions
used for the regioisomerization. High concentrations and
elevated temperatures favor an intermolecular mechanism in
which the chromium fragment is directly transferred from one
arene to another, while a dissociative and a decomplexation/
recomplexation mechanism are supported by coordinating
solvents in which the metal fragment is completely disconnected
from the arene and transferred via solvent-stabilized intermedi-
ates to the other coordination site or to another arene.8 To
preserve the chiral information implemented in enantiopure
planar-chiral tricarbonyl(η6-arene)chromium complexes, non-
coordinating or weakly coordinating solvents and only moderate
temperatures should be applied, which allow for intramolecular
haptotropic rearrangements.2b
We aim at a systematic tuning of the haptotropic metal
migration along polycyclic arene platforms following different
approaches. A variation of the arene substitution pattern and
thus of the electronic properties of the coordinated π-ligand in
hydroquinoid (η6-naphthalene)-9 and (η6-phenanthrene)-Cr(CO)3
complexes3 has been demonstrated to allow for a control of the
metal labeling of an aromatic ring in fused arenes.13 Reaction
of pentacarbonyl[methoxy(1-naphthylcarbene)]chromium with
3-hexyne, carried out under kinetic control, affords exclusively
the [(η6-1,2,3,4,4a,10a)-phenanthrene]chromium complex 1,
which, upon warming, rearranges nearly quantitatively to its
thermodynamic haptotropomer 2 (Scheme 1).3
For the synthesis of the chromium phosphine and phosphite
complexes 3-10 tricarbonyl chromium complexes 1 and 2 have
been subjected to a photoinduced decarbonylation in tetrahy-
drofuran at low temperature.14 The coordinatively unsaturated
dicarbonylchromium complex intermediate is stabilized by
tetrahydrofuran to give a labile dicarbonyl(THF)chromium
complex. Subsequent substitution of the labile tetrahydrofuran
ligand for trimethylphosphite, trimethylphosphine, triphenylphos-
phite, and triphenylphosphine at room temperature afforded
phosphine and phosphite complexes 3-10 in 28-75% yield
(Scheme 2).
haptotropic migration rates.3 Alternatively, the metal shift has
been governed by an adjustment of the electronic properties of
the metal fragment by tuning the coligand sphere as shown for
enantiopure planar-chiral tricarbonyl(η6-naphthalene)chromium
complexes,10 which resulted in the elaboration of a stereospecific
organometallic switch with retention of configuration.11 More
recently, a σ-π-switch was developed based on an azaborine
chromium complex.12 In this paper, we concentrate on the in-
fluence of the chromium coligand sphere and report on the
haptotropic migration in phenanthrene Cr(CO)3 complexes
controlled by phosphines and phosphites differing in their
electronic and steric properties.
Results and Discussion
Synthesis of Phenanthrene Cr(CO)2PR3 Complexes. The
chromium-templated benzannulation of an arylcarbene ligand
by an alkyne and carbon monoxide allows for a regiospecific
Each pair of phosphine or phosphite chromium complexes
represents a pair of haptotropomers in which the complexes 3-6
are the kinetically more stable isomers. In order to evaluate the
role of the P-ligand in the metal migration, complexes 3-6 were
(7) (a) Sola, M.; Robles, J.; Jimenez-Halla, J. O. C. J. Phys. Chem. A
2008, 112, 1202. (b) Sola, M.; Robles, J.; Jimenez-Halla, J. O. C.
Organometallics 2008, 27, 5230–5240.
(8) For examples of a metal transfer from one arene ring to another in
biphenyl and diphenylether Cr(CO)3 complexes at considerably higher
temperatures (140-205 °C) suggesting an intermolecular decomplexation-
recomplexation pathway, see: (a) Oprunenko, Y. F.; Shapshnikova, I. A.;
Ustynyuk, Y. A. Metalloorg. Khim. 1991, 4, 1377–1390. (b) Rose-Munch,
F.; Rose, E.; Semra, A. J. Chem. Soc., Chem. Commun. 1986, 1108–1109.
(9) Do¨tz, K. H.; Szesni, N.; Nieger, M.; Na¨ttinen, K. J. Organomet.
Chem. 2003, 671, 58–74.
(10) (a) Do¨tz, K. H.; Jahr, H. C.; Nieger, M. Chem. Eur. J. 2005, 11,
5333–5342. (b) Do¨tz, K. H.; Jahr, H. C. Chem. Rec. 2004, 4, 61–71.
(11) Do¨tz, K. H.; Jahr, H. C.; Nieger, M. Chem. Commun. 2003, 2866–
2867.
(13) For reviews see: (a) Do¨tz, K. H. Angew. Chem., Int. Ed. Engl.
1984, 23, 587–608; Angew. Chem. 184, 96, 573-594. (b) Wulff, W. D. In
ComprehensiVe Organometallic Chemistry; Abel, E. W., Stone, F. G. A.,
Wilkinson, G. Eds.; Pergamon Press: Oxford, 1995, Vol. 12, pp 469-547.
(c) Minatti, A.; Do¨tz, K. H. Top. Organomet. Chem. 2004, 13, 123–156.
(d) Do¨tz, K. H.; Stendel, J., Jr. In Modern Arene Chemistry; Astruc, D.
Ed.; Wiley-VCH: Weinheim (Bergstr.), 2002; pp 250-296. (e) Do¨tz, K. H.;
Tomuschat, P. Chem. Soc. ReV. 1999, 28, 187–198.
(14) (a) Strohmeier, W. Angew. Chem., Int. Ed. Engl. 1964, 11, 730–
737; Angew. Chem. 1964, 21, 873-881. (b) Cais, M.; Kaftory, M.; Kohn,
D. H.; Tatarsky, D. J. Organomet. Chem. 1979, 184, 103–112. (c) For an
oxidative displacement of a CO ligand by a phosphine or phosphite in arene
complexes, see: Rose-Munch, F.; Susanne, C.; Renard, C.; Rose, E.;
Vaisserman, J. J. Organomet. Chem. 1996, 519, 253–259.
(12) Pan, J.; Kampf, J. W.; Ashe, A. J., III. Organometallics 2006, 25,
197–202.

P-Coligand Tuning
Organometallics, Vol. 28, No. 12, 2009 3475
Table 1. Thermo-induced Haptotropomerization of Complexes 3-6,
Monitored via IR
A1
B1
T
time
yield
[%]b
a
a
complex
PR3
[cm-1
]
[cm-1
]
[°C]b
[min]b
3
7
4
8
5
9
6
10
P(OMe)3
P(OMe)3
P(OPh)3
P(OPh)3
PMe3
PMe3
PPh3
PPh3
1897
1907
1903
1922
1878
1897
1878
1901
1849
1859
1853
1870
1830
1847
1830
1857
120
90
90
75
30
60
64
79
23
54
90
90
a Measured in petroleum ether at room temperature. b Reaction
conditions and yields for the thermally induced metal migration.
Scheme 3. Thermo-induced Haptotropomerization of Com-
plexes 3-6
Figure 1. Molecular structure of P(OMe)3 complex 3. Hydrogen
atoms have been omitted for clarity. Displacement parameters are
drawn at the 50% probability level. Selected bond distances [Å]:
Cr1-P1 2.2275(7), Cr1-C1 2.236(2), Cr1-C2 2.225(2), Cr1-C3
2.263(2), Cr1-C4 2.238(2), Cr1-C4A 2.293(2), Cr1-C10A
2.293(2), Cr1-ZAr 1.753(2), Cr1-C1A 1.821(3), Cr1-C1B 1.818(3).
Selected torsion angle [deg]: C4-C4A-C4B-C5 9.6(4).
Table 2. 1H NMR Coordination Shifts in Haptotropomers 7-10
complex
H5 [ppm]
H6/H7 [ppm]
H8 [ppm]
a
7
7.50
7.00
7.21
7.17
5.28/5.19
4.63/4.41
5.23/5.06
4.96/4.65
5.62
4.95
5.94
5.06
8a
9b
10a
a In CDCl3. b In CD2Cl2.
subjected to a thermo-induced isomerization in di-n-butyl ether
at temperatures between 90 and 120 °C over a period of 30 -
90 min to form the thermodynamic haptotropomers 7-10. The
metal migration was monitored by infrared spectroscopy focus-
ing on the hypsochromic shift of the A1 bands of the carbonyl
ligands (Table 1). The reaction was stopped when the starting
material was consumed or when rapid decomposition was
indicated by formation of Cr(CO)6. After chromatographic
workup the thermodynamic haptotropomers 7-10 were isolated
in 23-79% yield. The low yield of the trimethylphosphine
complex 9 was due to rapid decomposition, which forced us to
stop the reaction after 30 min (Scheme 3). The coordination of
the chromium fragment to the unsubstituted terminal benzene
ring is further demonstrated by the characteristic upfield shift
1
of the benzene hydrogen atoms in the H NMR spectra of
complexes 7-10 (Table 2).
Figure 2. Molecular structure of P(OPh)3 complex 4. Hydrogen
atoms have been omitted for clarity. Displacement parameters are
drawn at the 50% probability level. The numbering of atoms differs
from that used in the NMR characterization. Selected bond distances
[Å]: Cr1-P1 2.2088(6), Cr1-C4 2.300(2), Cr1-C3 2.247(2),
Cr1-C2 2.198(2), Cr1-C1 2.190(2), Cr-C10B 2.252(2), Cr1-C4A
2.309(2), Cr1-ZAr 1.740(1), Cr1-C1A 1.818(2), Cr1-C1B 1.826(2).
Selected torsion angle [deg]: C10-C10A-C10B-C1 12.0(3).
Molecular Structures. The molecular structures of the
phenanthrene complexes were determined by single-crystal
X-ray crystallography (Figures 1-7). Suitable crystals of
complexes 3, 4, and 6-10 were obtained by slow evaporation
of the solvent (dichloromethane or diethyl ether). All arene
platforms deviate from planarity with torsion angles of 8.1-12°
at the inner phenanthrene bay induced by the methoxy sub-
stituent. No obvious correlation of the conformation of the
chromium tripod with the nature of the P-ligand is observed.
In the majority of the complexes the relative position of the
Cr-P bond is eclipsed to one of the coordinated arene carbon
atoms. In the kinetically favored P(OMe)3 complex 3 the Cr-P
bond is eclipsed to C4 and adopts a position away from the
bulky silyl group. In contrast, in complexes 4 and 6, revealing
a staggered conformation with respect to the carbon atoms C4
and C4a, the PPh3 and the P(OPh)3 ligands are orientated above
the silyl group. In the thermodynamically favored haptotro-
pomers 7, 9, and 10 the P(OMe)3, PMe3, and PPh3 ligands lie
above the inner bay of the phenanthrene skeleton, whereas the
P(OPh)3 ligand in complex 8 points toward the periphery of
the arene system.15 The Cr-P bond lengths generally range
between 2.20 and 2.31 Å, with the longest distances found for
the better P-donor ligands PMe3 and PPh3 in complexes 9 and
6/10. The Cr-C bond lengths of the coordinated arene ring vary
between 2.18 and 2.34 Å, indicating that chromium is not
located above the center of the arene plane but rather shifted
away from the ring junction to the π-periphery independent from
the conformation of the chromium tripod. In complexes 4 and

3476 Organometallics, Vol. 28, No. 12, 2009
Joistgen et al.
The rate constants and free energies of activation determined
for the metal migration in the phenanthrene Cr(CO)2PR3
complexes 3-6 indicate that the nature of the phosphorus ligand
plays a significant role in the tuning of the haptotropic migration.
In order to elucidate the contribution of steric and electronic
effects of the P-ligand, we applied the QALE method16 for the
correlation of the free energy of activation ∆Gq with the cone
angle θ17 and the Tolman electronic parameter ꢀ18 derived from
the A1(CO) stretching frequency of Ni(CO)3PR3 complexes (Table
6, eq 1).16
∆Gq ) a(θ) + b(ꢀ) + c19
(1)
A multiple regression for the set of the four phosphorus
ligands applied demonstrates that the haptotropic migration is
controlled by both steric and electronic effects quantified by a
) -0.3559 kJ mol-1 K-1, b ) -0.5028 kJ mol-1 cm-1, and c
) 159.2577 kJ mol-1 (Figure 12). This correlation may serve
as a rationale for the experimental observation that sterically
demanding ligands with considerable acceptor properties ac-
celerate the metal migration, while small and electron-rich
ligands slow it down.
Quantum Chemical Calculations on the Haptotropo-
merization. Density functional calculations have been per-
formed in order to provide a more detailed insight into the course
of the haptotropomerization of chromium fragments modified
by P-coligands, in particular into the structures and relative
energies of the haptotropomers and the relevant transition states.
This work extends previous studies on tricarbonyl phenanthrene
complexes (Scheme 4).3
Figure 3. Molecular structure of PPh3 complex 6. Hydrogen atoms
have been omitted for clarity. Displacement parameters are drawn
at the 50% probability level. The numbering of atoms differs from
that used in the NMR characterization. Selected bond distances
[Å]: Cr1-P1 2.3180(5), Cr1-C4 2.3367(15), Cr1-C3 2.2690(16),
Cr1-C2 2.1969(16), Cr1-C1 2.1848(16), Cr1-C10B 2.2592-
(15), Cr1-C4A 2.2966(15), Cr1-ZAr 1.751(1), Cr1-C1A 1.8224(18),
Cr1-C1B 1.8115(17). Selected torsion angle [deg]: C10-C10A-
C10B-C1 -10.4(2).
Because of the drastically increased number of atoms resulting
from the substitution of one carbon monoxide by a phosphine
or phosphite coligand, most calculations were carried out for
naphthalene complexes expecting that the trends for the energy
barriers for the metal migration along naphthalene and phenan-
threne platforms are similar.20 The results of corresponding
model calculations are compiled in Table 7. The energy barriers
∆E(TS/S) are given with respect to the thermodynamically less
favored starting haptomer S. The relative energies ∆E(NS/S)
are those of the less stable kinetic haptomer S with respect to
the more stable regioisomer NS obtained from the thermo-
induced metal migration.
A comparison of the barriers for the substituted (R1 ) OMe,
R2 ) Et) and the unsubstituted (R1 ) R2 ) H) system reveals
that the substitution leads to a significant decrease in the energy
barriers of about 20 kJ mol-1 for all four ligands L. The energies
of the transition states for the substituted naphthalene show that
the highest barrier (119.7 kJ mol-1) is found for L ) PMe3,
which is the sterically least demanding coligand. Correspond-
ingly the lowest energy barrier was determined for L ) P(OPh)3.
In the calculations a clear trend of the energy barrier height
due to the steric demand of the coligand is found, decreasing
in the order PMe3 > P(OMe)3 > PPh3 > P(OPh)3 (see Figure
13). This trend is perfectly in line with the experimentally
determined energy barriers. The energy barriers of the substi-
6, containing bulky phosphorus ligands, the silyl protective
group adopts an anti conformation relative to the chromium
fragment, whereas the smaller trimethylphosphite ligand prefers
a syn conformation, as shown in complex 3. In the rearranged
Cr(CO)2PR3 complexes 7, 9, and 10 the phosphorus ligands
point inside the phenanthrene system, while an outside orienta-
tion is observed for the P(OPh)3 complex 8. The crystallographic
data for all complexes are summarized in Tables 3 and 4.
Kinetic Studies of the Coligand-Controlled Haptotropo-
merization. In order to elaborate the role of the P-coligand in
the haptotropic metal migration, the rate constants and the
activation barriers were determined by a kinetic NMR study.
To secure an intramolecular course of the metal rearrangement,
the reactions were performed at 75 °C in a noncoordinating
solvent such as hexafluorobenzene using an external standard.
Figures 8-11 show the concentration profiles for the rearrange-
ments and the kinetic plots. The experiments reveal first-order
kinetics expected for an intramolecular haptotropic metal
migration in all Cr(CO)2PR3 complexes. Compared to the parent
Cr(CO)3 complex 1 the metal shift observed for complexes 4
and 6, bearing the bulky and acceptor-type ligands triphenyl-
phosphine and triphenylphosphite, is approximately 4-5 times
faster, and the activation energy is decreased by ca. 5 kJ/mol
(Table 5). In contrast, the smaller and better donor ligands
trimethylphosphite and trimethylphosphine in complexes 3 and
5 slow down the haptotropic migration by the factor of 3 and
35 according to an increase of the free energy of activation by
3 and 10 kJ/mol, respectively.
(16) (a) Giering, W. P.; Prock, A.; Wilson, M. R. Organometallics 2002,
21, 2758–2763. (b) Giering, W. P.; Prock, A.; Wilson, M. R.; Fernandez,
A. L. Organometallics 2001, 20, 3429–3435. (c) Giering, W. P.; Prock,
A.; Liu, H. Y.; Rahman, M. M. Organometallics 1987, 6, 650–658.
(17) (a) Tolman, C. A. Chem. ReV. 1977, 77, 313–348. (b) Bunten, K. A.;
Chen, L.; Fernandez, A. L.; Poe¨, A. J. Coord. Chem. ReV. 2002, 233-234,
41–51.
(18) (a) Bartik, T.; Himmler, T.; Schulte, H. G.; Seevogel, K. J.
Organomet. Chem. 1984, 272, 29–41. (b) Ku¨hl, O. Coord. Chem. ReV. 2005,
249, 693–704.
(15) Molecular structures showing the projection of the chromium tripod
onto the phenanthrene platform are depicted in the Supporting Information.
For a conformational study of Cr(CO)3 complexes of O-silylated phenol
derivatives, see: (a) Levisalles, J.; Rose-Munch, F.; Rose, E.; Semra, A.;
Garcia Oricain, J.; Jeannin, Y.; Robert, F. J. Organomet. Chem. 1987, 328,
109–122.
(19) θ is a measure of the steric property of the ligands provided by
Tolman’s cone angle, while ꢀ is the electronic parameter.

P-Coligand Tuning
Organometallics, Vol. 28, No. 12, 2009 3477
Figure 4. Molecular structure of P(OMe)3 complex 7. Hydrogen atoms have been omitted for clarity. Displacement parameters are
drawn at the 50% probability level. The numbering of atoms differs from that used in the NMR characterization. Selected bond
distances [Å]: Cr1-P1 2.2272(4), Cr1-C10A 2.2608(12), Cr1-C10 2.1811(13), Cr1-C9 2.2027(14), Cr1-C8 2.2004(13), Cr1-C7
2.2170(13), Cr1-C6A 2.2453(13), Cr1-ZAr 1.704(1), Cr1-C1A 1.8280(14), Cr1-C1B 1.8349(15). Selected torsion angle [deg]:
C10-C10A-C10B-C1 9.6(2).
Figure 5. Molecular structure of P(OPh)3 complex 8. Hydrogen atoms have been omitted for clarity. Displacement parameters are drawn
at the 50% probability level. Selected bond distances [Å]: Cr1-P1 2.204(4), Cr1-C4B 2.289(3), Cr1-C5 2.232(6), Cr1-C6 2.2179(5),
Cr1-C7 2.2040(5), Cr1-C8 2.1793(3), Cr1-C8A 2.1940(4), Cr1–ZAr 1.713, Cr1-C22 1.8303(3), Cr1-C23 1.7858(5). Selected torsion
angle [deg]: C4-C4A-C4B-C5 8.158(3).
tuted naphthalene complexes exhibit a nearly perfect linearity.
This indicates that an increasing size of the coligand leads to a
decrease of the energy barrier assisted by the electronic effect
resulting from the incorporation of an oxygen functionality
pointing in the same direction.
The calculated structures of naphthalene complexes bearing
different phosphorus ligands are presented in Figure 14. In
the transition states, the chromium adopts a trimethylen-
emethane-like coordination to the arene; alternating positions
of the methoxy substituents relative to the chromium unit
were found for the complexes bearing the sterically less
demanding ligands PMe3 and P(OMe)3, while the more bulky
(20) Note that for the haptotropic migration of Cr(CO)3 the transition state
barriers for the unsubstituted phenanthrene (128.0 and 122.2 kJ mol-1) were
calculated very close to the one for naphthalene (125.9 kJ mol-1): Ketrat, S.;
Mu¨ller, S.; Dolg, M. J. Phys. Chem. A 2007, 111, 6094–6102.

3478 Organometallics, Vol. 28, No. 12, 2009
Joistgen et al.
Figure 6. Molecular structure of PMe3 complex 9. Hydrogen atoms have been omitted for clarity. Displacement parameters are drawn at
the 50% probability level. The numbering of atoms differs from that used in the NMR characterization. Selected bond distances [Å]:
Cr1-P15 2.3135(9), Cr1-C1 2.181(3), Cr1-C2 2.176(3), Cr1-C3 2.204(3), Cr1-C4 2.201(3), Cr1-C11 2.269(3), Cr1-C14 2.241(3),
Cr1-ZAr 1.701, Cr1-C19 1.820(3), Cr1-C21 1.822(3). Selected torsion angle [deg]: C5-C12-C11-C4 -9.3(4).
Table 3. Crystallographic Data for Complexes 3, 4, and 6
3
4
6
empirical formula
M [g/mol]
T [K]
C30H43CrO7PSi C45H49CrO7PSi C45H49CrO4PSi
626.70
123(2)
812.90
123(2)
764.90
123(2)
λ [Å]
Mo KR 0.71073 Mo KR 0.71073 Mo KR 0.71073
cryst syst
space group
a [Å]
monoclinic
P21/c (no. 14)
15.4755(4)
9.4598(3)
21.3731(6)
90
triclinic
triclinic
j
j
P1 (no. 2)
P1 (no. 2)
9.3080(1)
11.1984(2)
21.5305(5)
80.901(1)
84.642(1)
65.482(1)
2015.21(6)
2
9.4311(1)
11.9278(1)
19.7424(3)
73.265(1)
83.572(1)
68.017(1)
1972.16(4)
2
b [Å]
c [Å]
R [deg]
ꢁ [deg]
98.010(2)
90
γ [deg]
V [Å3]
3098.39(15)
4
Z
cryst size [mm]
0.40 × 0.25 ×
0.30 × 0.15 ×
0.35 × 0.10 ×
0.10
0.05
0.05
F(calcd) [g/cm]
1.343
0.503
1328
1.340
0.404
856
1.288
0.403
808
µ [mm-1
F(000)
]
θ range [deg]
3.29 to 25.03
-18 e h e 13 -11 e h e 11 -12 e h e 12
-10 e k e 11 -13e k e 13
-25 e l e 24
11 831
2.96 to 25.03
3.17 to 27.47
index ranges
-15 e k e 15
-25 e l e 25
32 884
-25 e l e 25
17 177
total reflns
unique reflns
R(int)
5059
0.0304
7042
0.0326
8873
0.0388
R for (I > 2σ(I))
0.0380
0.0904
0.0339
0.0845
0.994
0.307/-0.312
0.0347
0.0911
1.050
0.341/-0.383
Figure 7. Molecular structure of PPh3 complex 10. Hydrogen atoms
have been omitted for clarity. Displacement parameters are drawn
at the 50% probability level. The numbering of atoms differs from
that used in the NMR characterization. Selected bond distances [Å]:
Cr1-P1 2.3195(8), Cr1-C7 2.183(2), Cr1-C8 2.182(2), Cr1-C9
2.216(2), Cr1-C10 2.229(2), Cr1-C10A 2.346(2), Cr1-C6A
2.277(2), Cr1-ZAr 1.736(1), Cr1-C1A 1.812(2), Cr1-C1B 1.826(2).
Selected torsion angle [deg]: C10-C10A-C10B-C1 -7.5(3).
wR2 (all data)
goodness of fit on F2 1.037
largest diff peak
0.324/-0.354
and hole [e Å-3
]
the P-coligands P(OMe)3 and PPh3, which count 65 and 83
atoms, respectively. The relative energies, using the same
conventions as for Table 6, are listed in Table 8.
The values presented in Table 8 show that compared to
naphthalene complexes the situation is more complicated in
phenanthrene compounds due to the increased number of
transition states. Nevertheless, it can be stated that the energy
barriers are in the range of the experimental values and
decrease significantly when the bulk of the migrating group
ligands PPh3 and P(OPh)3 induce a conformation bearing both
methoxy groups opposite the chromium fragment.
In order to confirm that the naphthalene system is an adequate
model to describe the experimental findings, we calculated all
relevant structures for the two phenanthrene complexes bearing

P-Coligand Tuning
Organometallics, Vol. 28, No. 12, 2009 3479
Table 4. Crystallographic Data for Phenanthrene Complexes 7-10
7
8
9
10
empirical formula
M [g/mol]
T [K]
C30H43CrO7PSi
626.70
123(2)
C45H49CrO7PSi
812.90
123(2)
C30H43CrO4PSi
578.70
223(2)
C45H49CrO4PSi
764.90
123(2)
λ [Å]
Mo KR 0.71073
monoclinic
P21/c (no. 14)
14.3749(1)
17.3537(1)
13.2375(1)
90
108.132(1)
90
3138.21(4)
4
Mo KR 0.71073
monoclinic
P21/c (no. 14)
26.672(5)
11.080(2)
14.165(5)
90
98.120(9)
90
4144.2(18)
4
Mo KR 0.71073
monoclinic
P21/c (no. 14)
14.813(1)
17.070(1)
13.084(1)
90
108.11(1)
90
3144.5(4)
4
Mo KR 0.71073
cryst syst
space group
a [Å]
triclinic
j
P1 (no. 2)
8.9334(3)
14.0088(5)
17.0355(8)
88.580(2)
75.167(2)
73.085(2)
1968.88(13)
2
b [Å]
c [Å]
R [deg]
ꢁ [deg]
γ [deg]
V [Å3]
Z
cryst size [mm]
F(calcd) [g/cm]
0.40 × 0.20 × 0.10
0.16 × 0.08 × 0.04
0.40 × 0.30 × 0.20
0.30 × 0.10 × 0.05
1.326
1.303
1.222
1.290
µ [mm-1
F(000)
]
0.497
1328
0.393
1712
0.484
1232
0.404
808
θ range [deg]
2.98 to 27.48
-18 e h e 18
-22 e k e 22
-17 e l e 17
64 161
2.40 to 25.00
-28 e h e 31
-12 e k e 13
-15 e l e 15
16 905
1.87 to 30.42
-21 e h e 20
-23 e k e 23
-18 e l e 18
21 961
2.98 to 25.03
-10 e h e 10
-16 e k e 16
-18 e l e 20
16 563
index ranges
total reflns
unique reflns
7165
6279
9291
6924
R(int)
0.0390
0.2538
0.066
0.0434
R for (I > 2σ(I))
0.0277
0.0793
1.051
0.328/-0.385
0.1050
0.2803
0.935
0.391/-0.276
0.0622
0.1791
0.998
0.406/-0.804
0.0368
0.0756
0.903
0.311/-0.420
wR2 (all data)
goodness of fit on F2
largest diff peak and hole [e Å-3
]
increases, confirming that the use of the model system
naphthalene produces reliable results. The calculation of the
minimum structure of the middle ring complex M resulted
in a rather small energy difference between complexes M
and S, especially for L ) PPh3. This may be a reason for the
acceleration of the migration for the bulkier metal fragments
as found in the experiments.
In order to evaluate the quality of the theoretical approach,
a comparison of selected bond lengths is presented in Table
9 for L ) PPh3. In general, there is a very good agreement
of the calculated and the experimentally obtained structure
with maximum deviations of about 0.05 Å. The orientation
of the methoxy and ethyl substituents is identical in the
calculations and the X-ray structure; that is, both methoxy
groups and one ethyl group of the substituted ring point to
the opposite side of the coordinated chromium fragment. We
note that other orientations of these substituents might lead
to local minima that are several kJ/mol higher in energy.
Conclusion
A study of the haptotropic metal migration in Cr(CO)2PR3
complexes of phenanthrene demonstrated that the exchange
of a carbonyl ligand of Cr(CO)3-phenanthrene complexes for
a phosphorus ligand can be applied to tune the metal shift
depending on the steric and electronic effects of the coligand.
The Cr(CO)2PR3 (R ) OMe, Me, Ph, OPh) complexes were
prepared via photoinduced ligand substitution of Cr(CO)3-
phenanthrene complexes in tetrahydrofuran. A kinetic analy-
sis of the haptotropic metal migration via NMR spectroscopy
in hexafluorobenzene reveals that the migration is first order.
The contribution of steric and electronic ligand effects to
the metal isomerization has been investigated using the QALE
method. Bulky ligands such as P(OPh)3 or PPh3 accelerate
the metal isomerization, and small or electron-rich ligands
such as P(OMe)3 or PMe3 slow it down. The DFT calculations
support the experimental work. The results for a smaller
Figure 8. Concentration profile and kinetic plot for the rearrangement of the trimethylphosphite complex 3.

3480 Organometallics, Vol. 28, No. 12, 2009
Joistgen et al.
Figure 9. Concentration profile and kinetic plot for the rearrangement of the triphenylphosphite complex 4.
Figure 10. Concentration profile and kinetic plot for the rearrangement of the trimethylphosphine complex 5.
Figure 11. Concentration profile and kinetic plot for the rearrangement of the triphenylphosphine complex 6.
was dried by distillation from calcium hydride, petroleum ether by
distillation from lithium aluminum hydride, and tetrahydrofuran and
di-n-butyl ether by distillation from sodium. Deuterated solvents and
hexafluorobenzene were saturated with argon using three cycles of
freeze, pump, and thaw before use. P(OMe)3, P(OPh)3, PPh3, and PMe3
(1 M solution in THF) were used as received from Fluka. Macherey
Nagel silica gel 60 (0.015-0.025 mm) was used for column chroma-
model system (naphthalene instead of phenanthrene) exhibit
a clear linearity of the energy barriers with respect to the
size of the coligand.
Experimental Section
General Procedures. All reactions were carried out under an argon
atmosphere using conventional Schlenk techniques. Dichloromethane

P-Coligand Tuning
Organometallics, Vol. 28, No. 12, 2009 3481
Table 5. Rate Constants and Activation Barriers (with standard
deviations) of the Haptotropic Migration in Complexes 3-6
Table 7. Calculated Energy Barriers and Relative Energies of the
Naphthalene Complexes Depicted in Scheme 4a
Cr(CO)2L
T [K]a
k [s-1
]
∆Gq [kJ mol-1
]
R1 ) OMe, R2 ) Et
R1 ) R2 ) H
∆Gq
difference
L) P(OMe)3
L ) P(OPh)3
L ) PPh3
348
348
348
348
348
(5.26(0.2) × 10-4
(7.36(0.3) × 10-3
(7.46(0.5) × 10-3
(4.55(0.3) × 10-5
(1.6(0.2) × 10-3
107.5 ( 0.3
99.89 ( 0.3
99.85 ( 0.3
114.3 ( 0.3
104.3 ( 0.3
L
exptl ∆E (TS/S) calc/exptl ∆E (NS/Sb)
∆E(TS/S)
PMe3
114.3
P(OMe)3 107.5
119.7
114.3
110.5
104.2
106.3
5.4
6.8
10.7
4.3
-23.0
-15.5
-25.5
-25.5
-11.3
137.7
132.6
133.5
128.0
122.2
L ) PMe3
L ) COb
PPh3
P(OPh)3
CO
99.85
99.89
104.3
a T ) 348 K measured in C6F6. b Ref 3.
2.0
Table 6. Free Energy of Activation of the Haptotropomerization of
Complexes 3-6, Cone Angles, and Electronic Parameters for the
PR3 Ligands Applied
a A single-point calculation with the solvent model COSMO has been
performed for all structures. Experimentally determined free energies of
activation ∆Gq for the related phenanthrene systems from Table 5 are
b
∆Gq [kJ mol-1
]
θ [deg]a
ꢀ [cm-1
]
given for comparison. All energies are listed in kJ mol-1 b NS:
.
PR3
Cr(CO)2L is coordinated to the nonsubstituted ring, S: Cr(CO)2L is
coordinated to the hydroquinoid ring.
P(OMe)3
P(OPh)3
PPh3
107.5 ( 0.3
99.89 ( 0.3
99.85 ( 0.3
114.3 ( 0.3
107
128
145
118
24.10
30.20
13.25
8.55
PMe3
a Cone angles taken from ref 17. b Electronic parameters taken from
ref 18a.
Figure 13. Relative energies of the transition states of all four
phosphorus ligands for substituted (2) and unsubstituted (9)
naphthalene.
10), 7.68 (d, 3JHH ) 7.7 Hz, 1H, H8), 7.59 (m, 1H, H6/7), 7.53 (m,
1H, H6/7), 7.42 (d, 3JHH ) 9.3 Hz, 1H, H9/10), 3.75 (s, 3H, OCH3),
3.08 (d, 2JHP ) 11.2 Hz, 9H, P(OMe3)3), 2.85-2.65 (m, 4H, CH2),
Figure 12. QALE correlation: Fit of experimental ∆Gq values vs
a(θ) + b(ꢀ) + c.
3
3
Scheme 4. Schematic Representation of the Calculated
Naphthalene and Phenanthrene Complexes
1.44 (t, JHH ) 7.52 Hz, 3H, CH3), 1.39 (t, JHH ) 7.52 Hz, 3H,
CH3), 1.11 (s, 9H, C(CH3)3), 0.42 (s, 3H, SiCH3), 0.36 (s, 3H,
2
SiCH3) ppm. 13C NMR (100 MHz, CDCl3): δ 239.0 (d, JCP
)
2
33.9 Hz, Cr(CO)), 238.3 (d, JCP ) 33.1, Cr(CO)), 132.7, 131.2
(2C, C1/4), 130.2, 129.0 (ArC), 128.6, 127.9 (ArCH), 127.2 (d,
3JHP ) 4 Hz, ArCH), 126.9, 123.3 (ArCH), 105.1, 100.6, 93.2, 92.9
3
(ArC), 62.7 (OCH3), 50.1 (d, JCP ) 2 Hz, P(OCH3)3), 26.3
(C(CH3)3), 21.5, 20.9 (CH2), 19.1 (C(CH3)3), 16.3, 16.0 (CH3), -1.9
(SiCH3), -2.6 (SiCH3) ppm. 31P NMR (202 MHz, CDCl3): δ 215.1
ppm. MS (EI): m/z (%) ) 626 (68) [M+], 595 (22) [M+ - OMe],
570 (20) [M+ - 2CO], 446 (30) [M+ - 2CO - P(OMe)3], 394
(100) [M+ - Cr(CO)2P(OMe)3], 379 (30) [M+ - Cr(CO)2P(OMe)3
- Me], 176 (8) [Cr(CO)2P(OMe)3+], 73 (30) [SiMe3+]. HR-MS:
calcd for C30H43CrO7PSi 626.19208, found 626.19160.
tography. Infrared spectra were recorded on a Nicolet Magna 550.
NMR spectra were measured on Bruker DRX-300, -400, and -500
spectrometers at room temperature. Mass spectra (EI-MS) were
recorded on a Kratos MS 50.
General Procedure for the Synthesis of Cr(CO)2PR3
Phenanthrene Complexes. 1 mmol of complex 1 or 2 was
dissolved in 50 mL of THF and irradiated 3 h with a HPK 125
medium-pressure mercury lamp at -40 °C. The phosphite or
phosphine was added as a solution in tetrahydrofuran, and the
reaction mixture was allowed to warm to room temperature and
stirred for 2 h. All volatile components were removed, and the
residue was subjected to column chromatography.
Dicarbonyl(trimethylphosphite)[(η6-1,2,3,4,4A,10A)-1-tert-bu-
tyldimethylsilyloxy-2,3-diethyl-4-methoxyphenanthrene]chromi-
um (3). Yield: 420 mg (67%). Rf ) 0.5 (CH2Cl2). Yield: 420 mg
(67%). Rf ) 0.5 (CH2Cl2). IR (PE): ν(CdO) 1897 (vs, A1), 1888 (vs,
A1), 1849 (m), 1839 (s, B1) cm-1. 1H NMR (400 MHz, CDCl3): δ
9.18 (d, 3JHH ) 8.5 Hz, 1H, H5), 7.71 (d, 3JHH ) 9.3 Hz, 1H, H9/
Dicarbonyl(triphenylphosphite)[(η6-1,2,3,4,4A,10A)-1-tert-bu-
tyldimethylsilyloxy-2,3-diethyl-4-methoxyphenanthrene]chromi-
um (4). Yield: 436 mg (57%). Rf ) 0.4 (2:1 petroleum ether/
CH2Cl2). IR (PE): ν(CdO) 1903 (vs, A1), 1853 (s, B1) cm-1. 1H NMR
(400 MHz, CDCl3): δ 9.16 (dd, 3JHH ) 7.2 Hz, 4JHH ) 1.9 Hz, 1H,
H5), 7.63-7.51 (m, 4H), 7.16-7.06 (m, 7H), 6.83-6.77 (m, 6H),
3.80 (s, 3H, OCH3), 2.92 (m, 2H, CH2), 2.65 (m, 2H, CH2), 1.40
(t, 3JHH ) 7.5 Hz), 1.32 (t, 3JHH ) 7.5 Hz), 1.05 (s, 9H, C(CH3)3),
0.35 (s, 3H, SiCH3), 0.28 (s, 3H, SiCH3). 13C NMR (100 MHz,
2
2
CDCl3): δ 238.2 (d, JCP ) 30.7 Hz, Cr(CO)), 237.7 (d, JCP
)
2
31.2 Hz, Cr(CO)), 152.2 (d, JCP ) 10.1 Hz, POC), 133.4 (C1/
C4), 131.7 (C1/C4), 130.8 (CAryl), 129.6 (CAryl), 128.8 (POC-CHAryl),
128.3, 127.6, 127.3, 126.7, 123.6 (5C, CHAryl), 123.2 (POC-CHAryl),

3482 Organometallics, Vol. 28, No. 12, 2009
Joistgen et al.
Figure 14. Calculated structures for 1,4-dimethoxy-2,3-diethylnaphthalene Cr(CO)2PR3 complexes.
Table 8. Relative Energies of the Transition States for the
Migration of the Cr(CO)2L Fragment on the Phenanthrene Platform
Table 9. Comparison of Selected Bond Lengths of the
1,4-Dimethyl-2,3-diethylphenanthrene-Cr(CO)2PPh3 Complex (bond
lengths in Å)
a All values in kJ mol-1 b Transition state could not be found. c M:
.
Cr(CO)2L is coordinated to the middle ring.
(18) [M+ - 2CO], 539 (5) [M+ - 2CO - P(OPh)2], 446 (5) [M+
- 2CO - P(OPh)3], 394 (100) [M+ - Cr(CO)2P(OPh)3], 362 (45)
121.7 (CHAryl), 121.0 (POC-CHAryl), 107.6, 100.9, 96.4, 92.3 (C2,
C3, C4a, C10a), 63.7 (OCH3), 26.3 (3C, C(CH3)3), 21.3, 20.6 (CH2),
19.1 (C(CH3)3, 16.3, 15.6 (CH3), -2.3, -2.5 (SiCH3). 31P NMR
(202 MHz, CDCl3): δ 189.9. MS (EI): m/z (%) 812 (7) [M+], 756
(21) Ahlrichs, R.; et al. Turbomole 5, Institut fu¨r Physikalische Chemie;
Universita¨t Karlsruhe, 2002.

P-Coligand Tuning
Organometallics, Vol. 28, No. 12, 2009 3483
[Cr(CO)2P(OPh)3+], 310 (22) [P(OPh)3+], 217 (65) [P(OPh)2+]. HR-
MS: calcd for C45H49CrO7PSi 812.23903, found 812.23944.
Dicarbonyl(trimethylphosphine)[(η6-1,2,3,4,4A,10A)-1-tert-bu-
tyldimethylsilyloxy-2,3-diethyl-4-methoxyphenanthrene]chromi-
um (5). Yield: 220 mg (38%). Rf ) 0.4 (1:1 petroleum ether/
CH2Cl2). IR (PE): ν(CdO) 1878 (vs, A1), 1830 (s, B1) cm-1. 1H NMR
(500 MHz, CD2Cl2): δ 9.16 (d, 3JHH ) 8.3 Hz, 1H, H5), 7.68 (dd,
-3.3 (SiCH3) ppm. 31P NMR (202 MHz, CDCl3): δ 219.8 ppm.
MS (EI): m/z (%) 626 (20) [M+], 595 (10) [M+ - OMe], 570 (100)
[M+ - 2CO], 446 (65) [M+ - 2CO - P(OMe)3], 394 (60) [M+ -
Cr(CO)2P(OMe)3], 379 (15) [M+ - Cr(CO)2P(OMe)3 - Me], 293
t
(20) [M+ - Cr(CO)2P(OMe)3 - Me - Bu], 265 (5) [M+
-
Cr(CO)2P(OMe)3 - Me - tBu - Et], 176 (10) [Cr(CO)2P(OMe)3+],
73 (30) [SiMe3+]. HR-MS: calcd for C30H43CrO7PSi 626.19208,
found 626.1928.
4
3
3JHH ) 7.6 Hz, JHH ) 1.6 Hz, 1H, H8), 7.63 (d, JHH ) 9.3 Hz,
3
Dicarbonyl(triphenylphosphite)[(η6-4B,5,6,7,8,8A)-1-tert-butyldi-
methylsilyloxy-2,3-diethyl-4-methoxyphenanthrene]chromium (8).
Yield: 520 mg (64%). Rf ) 0.3 (2:1 petroleum ether/CH2Cl2). IR
(PE): ν(CdO) 1922 (vs, A1), 1870 (s, B1) cm-1. 1H NMR (300 MHz,
CDCl3): δ 7.51 (d, 3JHH ) 9.2 Hz, 1H, H9/10), 7.22-6.95 (m, 16H),
6.60 (d, 3JHH ) 9.2 Hz, 1H, H9/10), 4.95 (d, 6.4 Hz, 1H, H8), 4.63
(m, 1H, H6/7), 4.41 (m, 1H, H6/7), 3.60 (s, 3H, OCH3), 2.77-2.55
1H, H9/10), 7.66-7.57 (m, 2H, H6/7), 7.24 (d, JHH ) 9.3 Hz,
1H, H9/10), 3.82 (s, 3H, OCH3), 3.02-2.9 (m, 1H, CH2), 2.8-2.63
3
3
(m, 3H, CH2), 1.42 (t, JHH ) 7.5 Hz, 3H, CH2CH3), 1.40 (t, JHH
3
) 7.5 Hz, 3H, CH2CH3), 1.11 (s, 9H, C(CH3)3), 0.95 (d, JPH
)
7.8 Hz, 9H, P(CH3)3), 0.37 (s, 3H, SiCH3), 0.34 (s, 3H, SiCH3)
ppm. 13C NMR (125 MHz, CD2Cl2): δ 239.6 (d, JCP ) 21.1 Hz,
1
1
Cr(CO)), 238.9 (d, JCP ) 21.1 Hz, Cr(CO)), 132.5 (C1/4), 130
3
3
(C1/4), 129.4, 129.2 (2C, C4b/8a), 127.8, 127.6, 126.7, 126.5, 124.5,
123.9 (6C, ArCH), 102.4, 99.5, 93.8, 90.9 (4C, C4a, C10a, C3,
C2), 62.9 (OCH3), 25.7 (C(CH3)3), 21.2, 20.2 (2CH2), 18.6 (d, 1JCP
) 22.5 Hz, P(CH3)3), 18.5 (C(CH3)3), 16.4, 15.4 (2CH2CH3), -3.2
(2 Si(CH3)) ppm. 31P NMR (202 MHz, CD2Cl2): δ 35.0 ppm. MS
(EI): m/z (%) 578 (1) [M+], 522 (15) [M+ - 2CO], 446 (4) [M+ -
(m, 4H, CH2), 1.12 (t, JHH ) 7.3 Hz, 3H, CH3), 1.01 (t, JHH
)
7.4 Hz, 3H, CH3), 0.96 (s, 9H, C(CH3)3), 0.02 (s, 3H, SiCH3), -0.01
(s, 3H, SiCH3). 13C NMR (75 MHz, CDCl3): δ 236.1 (d, JCP
)
2
2
32.3 Hz, Cr(CO)), 235.9 (d, JCP ) 32.9 Hz, Cr(CO)), 152.4 (d,
2JCP ) 7.2 Hz, POC), 151.5, 146.3 (C1/4), 137.2, 133.8 (CAryl),
129.3 (POCCH), 124.99 (C9/10), 124.96 (C), 124.4 (C9/10), 123.9
2CO - PMe3], 394 (100) [M+ - Cr(CO)2PMe3], 379 (39) [M+
-
3
(POCCH), 121.9 (C), 121.8 (d, JCP ) 4.8 Hz, POCCH), 100.8,
Cr(CO)2PMe3 - CH3]. HR-MS: calcd for C30H43CrO4PSi 578.2073,
100.1, 90.9, 89.3, 88.8 (C5/6/7/8/4b/8a), 61.21 (OCH3), 26.1
(C(CH3)3), 20.7, 20.3 (CH2), 18.7 (C(CH3)3), 15.8, 14.6 (CH3), -3.2,
-3.3 (SiCH3). 31P NMR (202 MHz, CDCl3): δ 204.2. MS (EI):
m/z (%) 812 (7) [M+], 756 (30) [M+ - 2CO], 539 (5) [M+ - 2CO
found 578.2075.
Dicarbonyl(triphenylphosphine)[(η6-1,2,3,4,4A,10A)-1-tert-bu-
tyldimethylsilyloxy-2,3-diethyl-4-methoxyphenanthrene]chromi-
um (6). Yield: 458 mg (60%). Rf ) 0.6 (2:1 petroleum ether/
CH2Cl2). IR (PE): ν(CdO) 1891 (vs, A1), 1886 (s), 1843 (s, B1), 1835
- P(OPh)2], 446 (5) [M+ - 2CO - P(OPh)3], 394 (100) [M+
-
Cr(CO)2P(OPh)3], 362 (40) [Cr(CO)2P(OPh)3+], 310 (40)
[P(OPh)3+], 217 (50) [P(OPh)2+]. HR-MS: calcd for C45H49CrO7PSi
812.23903, found 812.24004.
1
3
(s, B1) cm-1. H NMR (300 MHz, CDCl3): δ 9.08 (d, JHH ) 8.1
3
4
Hz, 1H, H5), 7.66 (dd, JHH ) 7.6 Hz, JHH ) 1.7 Hz, 1H, H6/8),
3
Dicarbonyl(trimethylphosphine)[(η6-4B,5,6,7,8,8A)-1-tert-bu-
tyldimethylsilyloxy-2,3-diethyl-4-methoxyphenanthrene]chromi-
um (9). Yield: 162 mg (28%). Rf ) 0.5 (1:1 petroleum ether/
CH2Cl2). IR (PE): ν(CdO) 1897 (vs, A1), 1847 (s, B1) cm-1. 1H NMR
7.59 (d, JHH ) 9.3 Hz, 1H, H9/10), 7.57-7.44 (m, 7H), 7.37 (d,
3JHH ) 9.3 Hz, 1H, H9/10), 7.33-7.20 (m, 9H), 3.71 (s, 3H, OCH3),
2.90-2.50 (m, 4H, 2CH2CH3), 1.29 (t, 3JHH ) 7.45 Hz, 3H, CH3),
3
1.28 (t, JHH ) 7.5 Hz, 3H, CH3), 1.04 (s, 9H, C(CH3)3), 0.29 (s,
3H, SiCH3), 0.28 (s, 3H, SiCH3) ppm. 13C NMR (125 MHz, CDCl3):
3
(500 MHz, CD2Cl2): δ 7.67 (d, JHH ) 9.2 Hz, 1H, H9/10), 7.26
2
2
3
δ 242.9 (d, JCP ) 19.7 Hz, Cr(CO)), 242.5 (d, JCP ) 19.2 Hz,
Cr(CO)), 137.9 (d, 1JCP ) 32 Hz, 3PC), 133.6 (d, 2JCP ) 10.6 Hz,
6PCCH), 132.6 (C1/4), 130.1, 129.7 (2C, C4b/8a), 128.6 (C1/4),
128.4, 128.3, 128.2 (3C, ArCH), 128.1 (3 PCCH-CHCH), 127.7
(ArCH), 127.1 (d, 3JCP ) 8.6 Hz, 6PCCHCHCH), 126.4, 122.6 (2C,
ArCH), 102.5, 99.5, 94.4, 92.9 (4C, C2, C3, C4a, C10a), 61.9
(OCH3), 26.5 (C(CH3)3), 21.4, 21.3 (2C, CH2CH3), 19.3 (C(CH3)3),
16.1, 15.9 (2C, CH2CH3), -1.9, -2.5 (2C, SiCH3) ppm. 31P NMR
(202 MHz, CDCl3): δ 88.9 ppm. MS (EI): m/z (%) 762 (40) [M+],
708 (60) [M+ - 2CO], 446 (8) [M+ - 2CO - PPh3], 394 (100)
[M+ - Cr(CO)2PPh3], 379 (30) [M+ - Cr(CO)2PPh3 - CH3], 262
(90) [PPh3+]. HR-MS: calcd for C45H49CrO4PSi 764.25429, found
764.25282.
(d, JHH ) 9.2 Hz, 1H, H9/10), 7.23-7.19 (m, 1H, H5), 5.49 (d
3
4
3
“t”, JHH ) 6.0 Hz, JHH ) 1.3 Hz, JHP ) 1.3 Hz, 1H, H8), 5.23
(m, 1H, H6/7), 5.06 (m, 1H, H6/7), 3.75 (s, 3H, OCH3), 3.0-2.75
3
3
(m, 4H, CH2), 1.28 (t, JHH ) 7.5 Hz, 3H, CH2CH3), 1.17 (t, JHH
2
) 7.5 Hz, 3H, CH2CH3), 1.14 (s, 9H, C(CH3)3), 0.88 (d, JHP
)
7.8 Hz, 9H, P(CH3)3), 0.20 (s, 3H, s, 3H, SiCH3), 0.16 (s, 3H,
SiCH3) ppm. 13C NMR (125 MHz, CD2Cl2): δ 240.4 (d, JCP
)
1
21.6 Hz, Cr(CO)), 238.3 (d, 1JCP ) 21.1 Hz, Cr(CO)), 151.0 (C4),
146.1 (C1), 136.9, 133.0 (2C, C2/3), 126.3 (C9/10), 125.2 (C4a/
10a), 122.6 (C9/10), 122.0 (C4a/10a), 101.2, 100.7 (2C, C4b/8a),
89.4, 86.9, 85.5, 83.9 (4C, C5/6/7/8), 61.3 (OCH3), 25.9 (C(CH3)3),
20.7, 20.3 (2 CH2), 20.1 (d, 1JCP ) 23 Hz, P(CH3)3), 18.6 (C(CH3)3),
15.9, 14.9 (2 CH3), -3.0, -3.9 (2 SiCH3) ppm. 31P NMR (202
MHz, CD2Cl2): δ 39.0 ppm. MS (EI): m/z (%) 578 (5) [M+], 522
(30) [M+ - 2CO], 446 (5) [M+ - 2CO - PMe3], 394 (100) [M+
- Cr(CO)2PMe3], 379 (39) [M+ - Cr(CO)2PMe3 - CH3], 308 (20)
[M+ - Cr(CO)2PMe3 - tBu - Et]. HR-MS: calcd for C30H43CrO4-
PSi 578.2073, found 578.2079.
Dicarbonyl(trimethylphosphite)[(η6-4B,5,6,7,8,8A)-1-tert-bu-
tyldimethylsilyloxy-2,3-diethyl-4-methoxyphenanthrene]chromi-
um (7). Yield: 470 mg (75%). Rf ) 0.5 (CH2Cl2). IR (PE): ν(CdO)
1
1907 (vs, A1), 1859 (s, B1) cm-1. H NMR (400 MHz, CDCl3): δ
7.70 (d, 3JHH ) 9.4 Hz, 1H, H9/10), 7.50 (ddd, 3JHH ) 6.9 Hz, 3JHP
4
3
) 3.8 Hz, JHH ) 0.9 Hz 1H, H5), 7.13 (d, JHH ) 9.4 Hz, 1H,
Dicarbonyl(triphenylphosphine)[(η6-4B,5,6,7,8,8A)-1-tert-bu-
tyldimethylsilyloxy-2,3-diethyl-4-methoxyphenanthrene]chromi-
um (10). Yield: 430 mg (57%). Rf ) 0.4 (2:1 petroleum ether/
CH2Cl2). IR (PE): ν(CdO) 1901 (vs, A1), 1857 (s, B1) cm-1. 1H NMR
H9/10), 5.62 (d, 3JHH ) 6.3 Hz, 1H, H8), 5.28 (m, 1H, H6/7), 5.19
3
(m, 1H, H6/7), 3.79 (s, 3H, OCH3), 3.28 (d, JHP ) 11.3 Hz, 9H,
P(OMe)3), 2.93-2.71 (m, 4H, 2CH2), 1.28 (t, 3JHH ) 7.44 Hz, 3H,
3
CH3), 1.14 (t, JHH ) 7.44 Hz, 3H, CH3), 1.08 (s, 9H, C(CH3)3),
3
(500 MHz, CDCl3): δ 7.63 (d, JHH ) 9.3 Hz, 1H, H9/10),
0.16 (s, 3H, SiCH3), 0.14 (s, 3H, SiCH3) ppm. 13C NMR (100 MHz,
7.30-7.22 (m, 15H, 3C6H5), 7.17 (d, 3JHH ) 7.1 Hz, 1H, H5), 6.78
(d, 3JHH ) 9.3 Hz, 1H, H9/10), 5.06 (d, 3JHH ) 6.41 Hz, 1H, H8),
2
2
CDCl3): δ 237.9 (d, JCP ) 32.9 Hz, Cr(CO)), 237.2 (d, JCP
)
31.7 Hz, Cr(CO)), 151.7 (ArC, C1/4), 146.1 (ArC, C1/4), 136.9
(ArCH), 133.4 (ArCH), 125.6 (ArCH), 125.0 (ArC), 123.7 (ArC),
100.6 (d, 3JCP ) 1.2 Hz, ArC), 100.3 (ArC), 90.1, 88.7, 88.0, 87.6
3
3
4.96 (“t”, JHH ) 5.6 Hz, 1H, H6/7), 4.65 (“t”, JHH ) 6.14 Hz,
1H, H6/7), 3.76 (s, 3H, OCH3), 2.93-2.78 (m, 4H, CH2), 1.26 (t,
3JHH ) 7.4 Hz, 3H, CH2CH3), 1.12 (t, 3JHH ) 7.4 Hz, 3H, CH2CH3),
1.13 (s, 9H, C(CH3)3), 0.19 (3H, SiCH3), 0.17 (3H, SiCH3) ppm.
13C NMR (125 MHz, CDCl3): δ 240.7 (d, 2JCP ) 20.1 Hz, Cr(CO)),
240.3 (d, 2JCP ) 20.1 Hz, Cr(CO)), 151.4, 146.2 (C1/4), 139.0 (d,
3
(4C, ArC), 61.3 (OCH3), 50.7 (d, JCP ) 3 Hz, P(OMe)3), 26.1
(C(CH3)3), 20.7, 20.3 (CH2), 18.7 (C(CH3)3), 15.9, 14.8 (CH3), -3.2,
2
(22) Becke, A. D. Phys. ReV. A 1988, 38, 3098–2100.
1JCP ) 33.1 Hz, 3PC), 136.8 (ArC), 133.0 (d, JCP ) 11.0 Hz,

3484 Organometallics, Vol. 28, No. 12, 2009
Joistgen et al.
3
6PCCH), 128.6 (3PCCHCHCH), 127.6 (d, JCP ) 8.6 Hz, 6PC-
relativistic pseudopotential for the transition metal Cr (ecp-10-
mdf),24 together with the appropriate TZVP valence basis sets. For
C, H, O, and P a SV(P) basis set was used as implemented in
TURBOMOLE. All stationary states on the energy hypersurface
were confirmed and characterized by analyzing the Hessian matrix.
In order to take the presence of a solvent into account, for all
structures a single-point calculation has been performed with a
conductor-like screening model (COSMO)25 assuming a dielectric
constant ꢀ ) 2, with default parameters as implemented in
TURBOMOLE.
Crystal Structure Determination. Single crystals of complexes
3, 4, and 6-10 suitable for X-ray structure determination were
grown from diethyl ether or dichloromethane solutions. Data have
been collected on a Nonius Kappa CCD diffractometer at 123 K
(223 K for 9) using Mo KR radiation (λ ) 0.71073 Å). Crystal
data, data collection parameters, and results of the analyses are listed
in Tables 2 and 3. Direct methods (SHELXS-97)26 were used for
structure solution, and refinement was carried out using SHELXL-
97 (full-matrix least-squares on F2).26 Hydrogen atoms were refined
using a riding model. CCDC-716539 (3), CCDC-716540 (4),
CCDC-716541 (6), CCDC-716542 (7), CCDC-725613 (8), CCDC-
725374 (9), and CCDC-716543 (10) contain the supplementary
crystallographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
CHCHCH), 125,5 (C9/10), 125.1 (C4a/10a), 123.8 (C9/10), 122.6
(C4a/10a), 100.2, 98.6 (2C, C4b, C8a), 91.8, 88.8, 88.4, 88.3 (4C,
C5, C6, C7, C8), 61.3 (OCH3), 26.1 (C(CH3)3), 20.7, 20,3 (2C,
CH2CH3), 18.7 (C(CH3)3), 16.0, 14.8 (2C, CH2CH3), -3.1, -3.2
(2C, SiCH3) ppm. 31P NMR (202 MHz, CDCl3): δ 93.0 ppm. MS
(EI): m/z (%) 762 (1) [M+], 394 (100) [M+ - Cr(CO)2PPh3], 379
(40) [M+ - Cr(CO)2PPh3 - CH3], 262 (90) [PPh3+]. HR-MS: calcd
for C45H49CrO4PSi 764.25429, found 764.2543.
General Procedure for the Haptotropic Rearrangement of
Complexes 3-6. A solution of 1 mmol of complex 3-6 in 30-50
mL of n-Bu2O was warmed to 120 °C. The reaction was monitored
by IR spectroscopy and stopped when the IR bands of the starting
complex could no longer be detected or rapid decomposition started,
as indicated by the formation of Cr(CO)6. All volatiles were
removed under high vacuum, and the residue was purified by
column chromatography. Reaction conditions and yields: Isomer-
ization of 3 to 7 (T ) 120 °C, t ) 90 min, yield: 64%),
isomerization of 4 to 8 (T ) 90 °C, t ) 75 min, yield: 79%),
isomerization of 5 to 9 (T ) 90 °C, t ) 30 min, yield:
23%), isomerization of 6 to 10 (T ) 90 °C, t ) 60 min, yield:
54%).
Kinetic NMR Studies of the Haptotropomerization. Concen-
trated solutions of Cr(CO)2PR3-phenanthrene complexes in hexaflu-
orobenzene were saturated with argon by three freeze-pump-thaw
cycles prior to use. The solutions were filtered into a NMR tube
under argon. After sealing the tubes the samples were warmed to
75 ( 0.1 °C, and NMR spectra were recorded in intervals between
5 and 30 min. The ratio of the two regioisomers was determined
by integration of the methylene protons of the silyl group.
Computational Details. All calculations have been performed
using the program package TURBMOLE (Version 5.10).21 The
optimizations have been done using gradient-corrected density
functional theory (Becke/Perdew 1988/1986 exchange-correlation
functional)22,23 in combination with an energy-consistent scalar-
Acknowledgment. Financial support of this work provided
by the Deutsche Forschungsgemeinschaft (SFB 624 “Tem-
plates”) is gratefully acknowledged.
Supporting Information Available: 1H and 13C NMR, MS
spectra, crystallographic data of compounds 3, 4, and 6-10 (CIF
format), and molecular structures showing the projection of the
chromium tripod onto the phenanthrene platform are depicted. This
materialisavailablefreeofchargeviatheInternetathttp://pubs.acs.org.
OM900057A
(23) (a) Perdew, J. P. Phys. ReV. B 1986, 33, 8822–8824. (b) Perdew,
J. P. Phys. ReV. B 1986, 34, 7406.
(24) Dolg, M.; Wedig, U.; Stoll, H.; Preuss, H. J. Chem. Phys. 1987,
86, 866–872.
(25) (a) Klamt, A.; Schüuermann, G. J. Chem. Soc., Perkin Trans. 2
1993, 799. (b) Klamt, A. J. Phys. Chem. 1995, 99, 2224–2235.
(26) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112–122.