Reactivity of cyclomanganated 2-phenylpyridine derivatives toward organolithium reagents. Synthesis of novel chelated tricarbonyl(η3-benzyl)manganese(I) complexes

Article abstract of DOI:10.1021/om970629j

Ortho-manganated 2-arylpyridine and -quinoline derivatives were treated with aryllithium reagents and subsequently with alkyl triflates to yield air-stable chelated (η³-benzyl)-tricarbonylmanganese complexes. Addition of PhLi to the cyclomanganated complex of 2-phenylpyridine [NC₅H₄-C₆H₄-Mn(CO)₄], 1, followed by methylation with MeOTf afforded a red air-stable chelated η³-benzyl, tricarbonyl{2-[(1,2-η²),_κC ^α-2-(phenylmethoxymethylene)-phenyl]pyridine- _κN}manganese(I), complex 4a. The molecular structure of 4a was established by single-crystal X-ray diffraction analysis. The study of this structure indicates a helical shape in which the manganese center adopts an octahedral configuration. Spectroscopic analysis indicates that the addition of the aryllithium reagent to 1 generates a new temperature- and air-sensitive benzoylmanganate species. The latter and other anionic acylmanganese species generated from different substrates readily decompose above a temperature of 0 °C to yield ketones and a formal [Mn(CO)₃]^- species which is believed to remain coordinated to the ancilliary pyridinyl group. The latter anionic tricarbonylmanganese species was trapped by reaction with Me₃SnCl and 2 equiv of PPh₃ to yield a mixture of mer and fac isomers of Me₃SnMn(CO)₃(PPh₃)₂. The thermal decomposition of the benzoyl-manganates into ketones via a reductive elimination step was exploited as a new synthetic route of aromatic ketones bearing a pyridyl, quinolinyl, or benzo[h]quinolinyl substitution pattern.

Full text of DOI:10.1021/om970629j

Organometallics 1997, 16, 5171-5182
5171
Rea ctivity of Cyclom a n ga n a ted 2-P h en ylp yr id in e
Der iva tives tow a r d Or ga n olith iu m Rea gen ts. Syn th esis
of Novel Ch ela ted Tr ica r bon yl(η3-ben zyl)m a n ga n ese(I)
Com p lexes
J ean-Pierre Djukic,†,†,1 Karl Heinz Do¨tz,*,† Michel Pfeffer,*,‡ Andre´ De Cian,§ and
J ean Fischer§
Kekule´-Institut fu¨r Organische Chemie und Biochemie der Universita¨t Bonn,
Gerhard-Domagk-Strasse 1, 53121 Bonn, Germany, and Laboratoire de Synthe`ses
Me´tallo-induites and Laboratoire de Cristallochimie, UMR CNRS 7513, Universite´ Louis
Pasteur, 4, rue Blaise Pascal, 67070 Strasbourg, France
Received J uly 24, 1997X
Ortho-manganated 2-arylpyridine and -quinoline derivatives were treated with aryllithium
reagents and subsequently with alkyl triflates to yield air-stable chelated (η3-benzyl)-
tricarbonylmanganese complexes. Addition of PhLi to the cyclomanganated complex of
2-phenylpyridine [NC5H4-C6H4-Mn(CO)4], 1, followed by methylation with MeOTf afforded
a red air-stable chelated η3-benzyl, tricarbonyl{2-[(1,2-η2),κCR-2-(phenylmethoxymethylene)-
phenyl]pyridine- κN}manganese(I), complex 4a . The molecular structure of 4a was
established by single-crystal X-ray diffraction analysis. The study of this structure indicates
a helical shape in which the manganese center adopts an octahedral configuration.
Spectroscopic analysis indicates that the addition of the aryllithium reagent to 1 generates
a new temperature- and air-sensitive benzoylmanganate species. The latter and other anionic
acylmanganese species generated from different substrates readily decompose above a
temperature of 0 °C to yield ketones and a formal [Mn(CO)3]- species which is believed to
remain coordinated to the ancilliary pyridinyl group. The latter anionic tricarbonylman-
ganese species was trapped by reaction with Me3SnCl and 2 equiv of PPh3 to yield a mixture
of mer and fac isomers of Me3SnMn(CO)3(PPh3)2. The thermal decomposition of the benzoyl-
manganates into ketones via a reductive elimination step was exploited as a new synthetic
route of aromatic ketones bearing a pyridyl, quinolinyl, or benzo[h]quinolinyl substitution
pattern.
In tr od u ction
aromatics display a smaller spectrum of reactivity than
other families of cyclometalated arenes.4 Indeed, most
of the reactions reported to take place with cycloman-
ganated complexes deal with photolytically or thermally
promoted insertion reactions of unsaturated hydrocar-
bons or inorganic molecules.5 The latter insertion
reactions are reported to occur mostly with chelates
derived from aromatic ketones and aldehydes. In
contrast, nitrogen-based Mn(CO)4 chelates have never
been reported to produce insertion reactions.6 In some
cases, however, cyclomanganated complexes have been
reported to display a fluxional behavior producing,
The chemistry of cyclomanganated complexes has
developed rapidly since the synthesis of the first ex-
amples of such complexes.2 Many types of aromatic
substrates are known to undergo a cyclometalation
reaction when exposed to alkylpentacarbonylmanganese
complexes under thermal conditions. For instance,
aromatics derived from N,N-dimethylbenzylamine, alkyl
benzyl thioether, 2-phenylpyridine, acetophenone, benz-
aldehyde, and diazobenzene may be readily transformed
into the corresponding cyclomanganated products when
treated with alkylpentacarbonylmanganese complexes.3
However, one must point out that cyclomanganated
(4) (a) Omae, I. Chem. Rev. 1979, 79, 287. (b) Omae, I. Organome-
tallic Intramolecular-coordination Compounds (J ournal of Organome-
tallic Chemistry library; vol. 18); Elsevier Science Publishers: Am-
sterdam, The Netherlands, 1986. (c) Ryabov, A. D. Synthesis 1985, 233.
(d) Pfeffer, M. Pure Appl. Chem. 1992, 64, 335.
(5) (a) Cooney, J . M.; Depree, C. V.; Main, L.; Nicholson, B. K. J .
Organomet. Chem. 1996, 515, 109. (b) Cooney, J . M.; Main, L.;
Nicholson, B. K. J . Organomet. Chem. 1996, 516, 191. (c) Robinson,
N. P.; Main, L.; Nicholson, B. K. J . Organomet. Chem. 1984, 364, C37.
(d) Liebeskind, L. S.; Gadaska, J . R.; McCallum, J . S.; Tremont, S. J .
J . Org. Chem. 1989, 54, 669. (e) Cambie, R. C.; Metzler, M. R.;
Rutledge, P. S.; Woodgate, P. D. J . Organomet. Chem. 1990, 381, C26.
(f) Cambie, R. C.; Metzler, M. R.; Rickard, C. E. F.; Rutledge, R. P. S.;
Woodgate, P. D. J . Organomet. Chem. 1992, 426, 213.
* Professor Dr. K. H. Do¨tz: fax, +49 228 735 813; e-mail,
doetz@snchemie1.chemie.uni-bonn.de. Dr. M. Pfeffer: fax, +33 (0)3 88
60 75 50; e-mail, pfeffer@chimie.u-strasbg.fr.
† Kekule´-Institut fu¨r Organische Chemie und Biochemie der Uni-
versita¨t Bonn.
‡ Laboratoire de Synthe`ses Me´tallo-induites.
§ Laboratoire de Cristallochimie.
X Abstract published in Advance ACS Abstracts, November 1, 1997.
(1) Fellow of the Alexander von Humbolt-Stiftung 1996-1997.
(2) Treichel, P. M. In Comprehensive Organometallic Chemistry;
Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds.; Pergamon: Oxford,
U.K., 1982; Vol. 4, pp 1-159.
(3) Flood, T. C. In Comprehensive Organometallic Chemistry II; Abel,
E. W., Stone, F. G. A., Wilkinson, G., Eds.; Pergamon: Oxford, U.K.,
1995; Vol. 6, pp 21-78.
(6) However, orthomangated triphenyl phosphite has been reported
to undergo the insertion of alkynes: Grigsby, W. J .; Main, L.;
Nicholson, B. K. Organometallics 1993, 12, 397.
S0276-7333(97)00629-8 CCC: $14.00 © 1997 American Chemical Society

5172 Organometallics, Vol. 16, No. 24, 1997
Djukic et al.
Ch a r t 1
under thermal treatment, the formal transfer of the Mn-
(CO)4 moiety from one aromatic site or ligand to
another.7
Sch em e 1
The behavior of cyclomanganated aromatic com-
pounds toward carbanionic nucleophiles has not yet
been addressed in a comprehensive way. We now
present our first results on the study of the reactivity
of carbonyl chelate manganese complexes derived from
2-arylpyridine and 2-arylquinoline toward aryllithium
compounds, and we report on the unprecedented syn-
thesis of chelated tricarbonyl(η3-benzyl)manganese com-
plexes.
Resu lts
or trialkylgermyl)manganese(I) complexes.11 To our
knowledge no other class of manganese carbonyl com-
plexes has been reported to yield carbenes via the
classical “Fischer route”. We decided therefore to apply
this methodology to a series of arylpyridine and -quino-
line tetracarbonylmanganese derivatives (Chart 1) by
reacting them with methyllithium and phenyllithium.12
Syn th esis of Ch ela ted Tr ica r bon yl(η3-ben zyl)-
m a n ga n ese Com p lexes. Our preliminary experi-
ments showed that above -60 °C the addition of
organolithium reagents to these compounds yields new
air-sensitive organometallic anionic species. Our at-
tempts to trap the intermediates resulting from the
addition of MeLi by means of alkyl triflates or trialkyl-
oxonium salts were unsuccessful (vide infra). However,
the alkylation of the intermediates resulting from the
addition of PhLi resulted in the formation of new
neutral red or orange products, which were identified
As established by the pioneering work of E. O.
Fischer, the addition of alkyl- or aryllithium nucleo-
philes to metal carbonyl complexes leads in a first step
to anionic acylmetalate complexes that may undergo
alkylation at the oxygen atom to yield ultimately metal-
carbene complexes (Scheme 1).8
At the begining of this study, our main aim was to
check the possibility of metallocarbene formation. Sev-
eral examples of manganese carbene complexes have
been reported to form via the so-called “Fischer route”
from substrates such as tricarbonyl(η5-cyclopentadienyl
or cyclohexadienyl)manganese9 complexes, decacarbo-
nyldimanganese(Mn-Mn),10 and pentacarbonyl(η1-alkyl
(7) (a) Robinson, N. P.; Main, L.; Nicholson, B. K. J . Organomet.
Chem. 1992, 430, 79. (b) Bruce, M. I.; Lidell, M. J . Snow, M. J .; Tiekink,
E. R. T. Aust. J . Chem. 1988, 41, 1407. (c) Pfeffer, M.; Urriolabeitia,
E.; Fischer, J . Inorg. Chem. 1995, 34, 643. (d) Djukic, J . P.; Maisse,
A.; Pfeffer, M.; De Cian, A.; Fischer, J . Organometallics 1997, 16, 657.
(8) (a) Fischer, E. O.; Maasbo¨l, A. Angew. Chem., Int. Ed. Engl. 1964,
3, 580. (b) Dotz, K. H., Hofmann, P., Kreissl, F. R., Schubert, U., Weiss,
K., Fischer, E. O., Eds.; Transition Metal Carbene Complexes; VCH:
Weinheim, Germany, 1983. (c) Wulff, W. D. In Comprehensive Orga-
nometallic Chemistry; Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds.;
Pergamon: Oxford, U.K., 1995; Vol. 12, p 470.
(10) Fischer, E. O.; Offhaus, E. Chem. Ber. 1969, 102, 2549.
(11) (a) Moss, J . R.; Green, M.; Stone, F. G. A. J . Chem. Soc., Dalton
Trans. 1973, 975. (b) Webb, M. J .; Stewart, R. P.; Grahams, W. A. G.
J . Organomet. Chem. 1973, 59, C21. (c) Dean, W. K.; Graham, W. A.
G. J . Organomet. Chem. 1976, 120, 73.
(9) (a) Fischer, E. O.; Maasbol, A. Chem. Ber. 1967, 100, 2445. (b)
McGeary, M. J .; Templeton, J . L. J . Organomet. Chem. 1987, 323, 199.
(c) Sheridan, J . B.; Padda, R. S.; Chaffee, K.; Wang, C.; Huang, Y.;
Lalancette, R. J . Chem. Soc., Dalton Trans. 1992, 1539.
(12) List of abbreviations: phenyllithium, PhLi; methyllithium,
MeLi; methyl trifluoromethane sulfonate, MeOTf; ethyl trifluo-
romethanesulfonate, EtOTf; tetrahydrofuran, THF; petroleum ether,
PE; bis(triphenylphosphoranylidene)ammonium chloride, PPN+Cl-.

Novel Tricarbonyl(η3-benzyl)manganese(I) Complexes
Organometallics, Vol. 16, No. 24, 1997 5173
Ta ble 2. Sin gle-Cr ysta l X-r a y Diffr a ction
Exp er im en ta l Da ta for 4a
Sch em e 2
formula
C22H16NO4Mn
413.32
monoclinic
P21/n
9.889(4)
15.776(6)
13.082(5)
110.68(2)
1909(2)
mol wt
cryst syst
space group
a (Å)
b (Å)
c (Å)
â (deg)
V (Å3)
Z
4
color
red
Ta ble 1. Yield s of Ch ela ted
(η3-Ben zyl)tr ica r bon ylm a n ga n ese Com p lexes
cryst dimens (mm)
0.35 × 0.20 × 0.15
D
calc (g cm-3
)
1.44
comp
yield (%)
comp
yield (%)
F000
848
5.878
0.58/1.00
273
1.541 84
Cu KR graphite
monochromated
Philips PW1100
θ/2θ
-10,9/0,16/0,13
3.0/54.06
2512
µ (mm-1
)
4a
4b
5a
5b
56
37
46
37
6a
6b
6c
22
20
56
transm min and max
temp (K)
wavelength (Å)
radiation
subsequently as 18-electron chelated tricarbonyl(η3-
benzyl)manganese complexes. Consequently, we fo-
cused our efforts on the reaction of aryl lithium com-
pounds with cyclomanganated substrates.
diffractometer
scan mode
hkl limits
Θ limits (deg)
no. of data measd
no. of data with I > 3σ(I)
weighting scheme
no. of variables
R
In general, the use of tetrahydrofuran as solvent was
avoided due to its reactivity toward alkyl- and aryl-
lithium reagents at room temperature. Diethyl ether
was preferred, and the experiments were performed in
a “one-pot” manner. The experiments proceeded in
three steps: first, the addition of 2 equiv of aryllithium
to a solution of the starting chelate at -60 °C; second,
the reaction at a temperature below 0 °C; and third, the
addition of an alkyl triflate at -20 °C (CF3SO2OCH3 or
CF3SO2OCH2CH3) followed by workup at room temper-
ature (Scheme 2). It turned out that the mixture of ArLi
and the starting complex had to be kept at temperatures
below 0 °C in order to suppress the formation of brown
decomposition products.
The alkylation was quite slow even when alkyl
triflates were added at room temperature. The reaction
was completed by warming the reaction medium to room
temperature. The alkylation reaction could be moni-
tored either by means of IR spectroscopy (vide infra) or
visually by following the change in color of the reaction
medium from a dark yellow-brown to an intense dark
red. The starting materials and main products are
displayed in Chart 1. All complexes were isolated as
pure compounds after chromatography on deactivated
silica gel13 with yields ranging from 20% to 56% (Table
1). Analytical characterization, e.g., elemental analysis
and/or high-resolution mass spectroscopy and 1H and
13C NMR and infrared spectroscopy, are in accord with
the proposed structures (see the Experimental Section).
Molecu la r Str u ctu r e of Com p lex 4a . Complex 4a
was synthesized by reaction of tetracarbonyl[2-(phenyl-
κC2)pyridine-κN)]manganese, 1, with phenyllithium,
followed by alkylation with methyl triflate. The pure
compound was crystallized to give bright red air-stable
crystals suitable for X-ray diffraction analysis. Acquisi-
tion parameters are displayed in Table 2. The main
interatomic distances and bond angles are given in
Tables 3 and Table 4. The molecular structure of
complex 4a indicates a particular bonding mode of the
metal center to the benzyl fragment (Figure 1). In this
complex the manganese atom meets the 18 valence
electron requirement through coordination of the benzyl
1545
4Fo2/(σ2(Fo2) + 0.0064Fo
253
)
4
0.050
0.063
1.367
0.765
Rw
GOF
largest peak in final diff (e Å-3
)
Ta ble 3. Selected In ter a tom ic Bon d Len gth s (Å)
for 4a
Mn-C1
Mn-C2
Mn-C3
Mn-C4
Mn-C5
Mn-C6
Mn-N
C1-O1
C2-O2
C3-O3
1.841(5)
1.786(5)
1.773(5)
2.104(4)
2.240(4)
2.438(4)
2.018(3)
1.133(5)
1.164(5)
1.143(5)
C4-C5
1.467(5)
1.428(5)
1.428(5)
1.418(6)
1.479(6)
1.429(6)
1.439(5)
1.357(7)
1.397(7)
1.355(6)
C4-O4
C5-C6
C5-C15
C6-C7
C6-C12
O4-C22
C12-C13
C13-C14
C14-C15
Ta ble 4. Selected In ter a tom ic Bon d An gles (d eg)
for 4a
C1-Mn-C2
C1-Mn-C3
C1-Mn-C4
C1-Mn-C5
C1-Mn-N
C2-Mn-C3
C2-Mn-C4
C2-Mn-C5
C2-Mn-N
C3-Mn-C4
C3-Mn-C5
C3-Mn-N
C4-Mn-C5
C5-Mn-N
88.4(2)
96.9(2)
168.4(2)
129.4(2)
92.2(2)
89.0(2)
93.7(2)
90.8(2)
175.0(2)
94.5(2)
133.7(2)
95.9(2)
39.3(1)
85.0(1)
C4-C5-C6
123.0(4)
121.0(4)
115.6(4)
122.1(3)
120.1(4)
117.6(4)
120.8(4)
119.8(4)
120.4(4)
123.2(4)
123.3(3)
112.6(3)
84.8(1)
C4-C5-C15
C6-C5-C15
C5-C6-C7
C5-C6-C12
C7-C6-C12
C6-C12-C13
C12-C13-C14
C13-C14-C15
C5-C15-C14
C5-C4-C16
C5-C4-O4
C4-Mn-N
moiety in a trihapto fashion implying the contribution
of π electrons from the arene ring, which therefore
suffers from a partial loss of aromaticity.
The molecular structure of the complex indicates that
the manganese center adopts an octahedral configura-
tion. Atoms N, C4, C2, and C1 are regarded as being
the equatorial components of an octahedron, while C3
and C6 occupy the axial positions. The octahedral
coordination geometry is further corroborated by the
corresponding interatomic bond angles given in Table
4.
Electronic peculiarities of the η3-benzyl bonding mode
in 4a are suggested by the slight distortions of both the
(13) We observed that activated silica could induce a significant
decomposition of the new complexes.

5174 Organometallics, Vol. 16, No. 24, 1997
Djukic et al.
nium15 (η3-benzyl) complexes that have been character-
ized by X-ray diffraction analyses. This could be
explained by a weaker bonding interaction between the
aromatic carbon atoms (e.g., C6 and C5) and the metal
center.19 Therefore, it would seem more appropriate to
consider the interaction between the manganese atom
and C6, C5, and C4 in terms of a 6,5-η2:4-η1 rather than
a 6,5,4-η3 bonding mode.20
A partial loss of aromaticity of the coordinated arene
ring can be deduced from the bond distances within the
coordinated arene. For instance, the distances C12-
C13 and C14-C15 are quite similar (mean value of 1.35
Å) but distinctly shorter than C6-C12, C13-C14, and
C5-C15 (mean value of 1.41 Å) (Figure 1). This
distortion is reminiscent of a cyclohexadiene-like ring
system.21
The chelation of the manganese center by the nitrogen
atom of the pyridyl group imposes an increased rigidity
on the whole assembly and, thus, prevents the η3-benzyl
moiety from displaying any fluxional behavior that could
be detected by NMR spectroscopy. We calculated that
the pyridyl group and the coordinated arene ring are
twisted around the C6-C7 axis by a torsion angle of
40.5°. The distortions are not limited to the twisting of
the pyridylbenzyl system. The benzylic carbon C4 does
not adopt a rigorously planar sp2 configuration and
seems to have some sp3 character. The deviation of C4
from the mean plane formed by C16-O4-C5 is esti-
mated to be 0.296 ( 0.005 Å toward the metal center.
The phenyl ring attached to C4 originating from the
organolithium nucleophile is tilted out of the mean
plane formed by the benzyl moiety (Figure 1); it lies
above the pyridyl unit and thus imposes a helical
structure on the tricyclic ligand system. This molecular
structure implies a restricted rotation of the phenyl
group as a consequence of its crowded environment, as
can be also established by temperature-dependent NMR
spectroscopy (vide infra).
Sp ectr oscop ic P r op er ties of th e Novel Ch ela ted
Tr icar bon yl(η3-ben zyl)m an gan ese Com plexes. The
complexes described herein obey the general formula
fac-LL′L′′M(CO)3. For a complex of the formula fac-
L3M(CO)3 which possesses a C3v symmetry the IR
spectrum displays two intense bands (an A1 and a
degenerated E) for the vibrations of the CO ligands.22
In the title complexes, however, the Mn(CO)3 moiety is
located in an asymmetric environment that causes the
splitting of the E band into two separate absorptions.
The intense carbonyl bands are detected for each
complex at approximately 2000 (A1), 1917, and 1898
cm-1 (split E).
F igu r e 1. ORTEP view of the molecular structure of 4a .
Ellipsoids are scaled to enclose 30% of the electronic
density. Hydrogen atoms are omitted.
benzylmetal and tricarbonylmetal substructures. How-
ever, as pointed out by one of the reviewers, in a
molecule with such low symmetry, assigning bond
parameter differences to σ-π effects is difficult without
more detailed theoretical analysis. For instance, the
C4-Mn distance of 2.104(4) Å would suggest a σ-type
bonding mode for the benzyl carbon C4 bound to the
manganese atom.14 However, a simple σ-type interac-
tion between C4 and Mn is in contradiction with the
fact that the bond distance Mn-C1 of 1.841(5) Å is
longer than the distances measured for Mn-C2 and
Mn-C3. Indeed a σ-donor ligand having weak or no
π-accepting properties should induce a shortening of the
bond between the metal and a trans CO ligand. For
instance, the Mn-C2 bond distance has a value of
1.786(5) Å, which is consistent with those reported for
Mn-CO bond distances of carbonyl carbon atoms lo-
cated trans to strong σ-donor ligands of other analogous
manganese carbonyl complexes.14 The relatively short
Mn-C2 bond distance as compared to Mn-C1 consis-
tently reflects a strong σ donation of the pyridyl nitrogen
atom. A similar conclusion cannot be drawn here for
the electronic effect of the benzylic carbon C4 over the
Mn-C1 bond distance.
The benzyl fragment is bound to manganese through
C4, C5, and C6, and the corresponding carbon-
manganese distances C4-Mn and C5-Mn are about 0.1
Å shorter than the analogous C-Re bond distances
reported for a nonchelated rhenium complex.15 It is
noteworthy that the η3-benzylic moiety is unsymmetri-
cally bound to the metal; the carbon to manganese bond
lengths decrease in the order C6-Mn > C5-Mn > C4-
Mn (Table 3). The same trend has been observed for
other ruthenium,16 rhodium,17 molybdenum,18 and rhe-
(19) Several nonchelated η3-benzyl complexes are known to possess
a fluxional behavior which is related to the weakness of the bond
between the two aromatic carbons and the metal center. Please refer
to references herein and to the following: (a) Brookhart, M.; Buck, R.
C.; Danielson, E. J . Am. Chem. Soc. 1984, 111, 567. (b) Stu¨hler, H. O.
Angew. Chem. 1980, 92, 475. (c) Crascall, L. E.; Spencer, J . L. J . Chem.
Soc., Dalton Trans. 1992, 3445. (d) Young, K. M.; Wrighton, M. S. J .
Am. Chem. Soc. 1990, 112, 157.
(20) Accordingly, complex 4a may be named by following the “hapto”
and “kappa” conventions established for chelates, e.g., tricarbonyl{2-
[(1,2-η2),κCR-2-(ph en ylm et h oxym et h ylen e)ph en yl]pyr idin e-κN}-
manganese(I) or tricarbonyl{2-[(1,2,R-η3)-phenylmethoxymethylene)-
phenyl]pyridine-κN}manganese(I). Leigh, G. J ., Ed. IUPAC Nomen-
clature of Inorganic Chemistry, Recommendations, 1990; Blackwell
Scientific Publication: Oxford, 1991.
(14) (a) Little, R. G.; Doedens, R. J . Inorg. Chem. 1973, 12, 840. (b)
Little, R. G.; Doedens, R. J . Inorg. Chem. 1973, 12, 844.
(15) Crocker, L. S.; Mattson, B. M.; Heinekey, D. M.; Schulte, G. K.
Inorg. Chem. 1988, 27, 3722.
(16) Bennett, M. A.; Goh, L. Y.; McMahon, I. J .; Mitchell, T. R. B.;
Robertson, G. B.; Turney, T. W.; Wickramasinghe, W. A. Organome-
tallics 1992, 11, 3069.
(17) Werner, H.; Scha¨fer, M.; Nu¨rnberg, O.; Wolf, I. Chem. Ber. 1994,
127, 27.
(21) (a) Lankin, D. C.; Griffin, G. W.; Bernal, I.; Korp, J .; Watkins,
S. F.; Delord, T. J .; Bhacca, N. S. Tedrahedron 1984, 40, 2829. (b) For
a similar alternating bond length in 1,3-cycloheptadiene, see: Chiang,
J . F.; Bauer, S. H. J . Am. Chem. Soc. 1966, 88, 420.
(22) Braterman, P. S. Metal Carbonyl Spectra; Academic Press:
London, 1975.
(18) Cotton, F. A.; Marks, T. J . J . Am. Chem. Soc. 1969, 91, 1339.

Novel Tricarbonyl(η3-benzyl)manganese(I) Complexes
Organometallics, Vol. 16, No. 24, 1997 5175
The intrinsic steric hindrance encountered in this type
of chelated tricarbonyl(η3-benzyl)manganese complex
has been corroborated by 1H NMR spectroscopy. In-
deed, the proton NMR spectra of complexes 4a , 5a , 5b,
6a , and 6c recorded at room temperature contain two
types of signals in the aromatic region. In addition to
well-resolved signals, broad peaks are observed, indicat-
ing a fluxional behavior within the aromatic fragment.
The well-resolved part of the spectra generally displays
a deshielded signal at around 8.3 ppm (benzyl H2) in
C6D6 that is related to the proton located ortho to the
benzylic carbon on the coordinated arene. The rest of
the signals related to the benzyl group appear for 4a at
7.35 (triplet, benzyl H3) and at 7.05 (multiplet, benzyl
H4, and H5) ppm in C6D6. The signals that belong to
the pyridyl group are usually observed in the range 6.0-
5.7 ppm in C6D6. For 4a , the pyridyl proton signals
appear at 7.23 (H6 vicinal to the nitrogen atom), 6.40
(triplet, H4), 5.85 (doublet, H3), and 5.80 (doublet, H5)
ppm. In the case of quinoline derivatives 6a -c the
spectra are more complex in the aromatic region.
However, the signals of the benzyl fragment appear at
values similar to those obtained for 4a . For the ethoxy
analogue 5b, the asymmetry of the molecule is charac-
terized by the signals of the -OCH2- diastereotopic
protons of the ethoxy group, which are detected as two
multiplets at 3.86 and 4.05 ppm, respectively. The
corresponding CH3 proton resonance appears as a single
triplet at 1.39 ppm. For the phenyl complexes 4a , 5a ,
5b, and 6a a broad peak is observed at an approximate
value of 6.6 ppm at room temperature and can be
reasonably attributed to the protons of the phenyl group
bound to the benzylic carbon. In order to ascertain its
origin we undertook the preparation of the deuterium-
labeled analogues of 4a and 6a . We first prepared a
stock solution of d5-PhLi from pentadeuteriobromoben-
zene and lithium. This reagent was then reacted with
the corresponding complexes 1 and 3 under conditions
similar to those used for the synthesis of 4a and 6a .
F igu r e 2. Temperature dependence of the 1H NMR
spectrum of compound 4a . Signals bearing an asterisk
correspond to the resonances of the protons located at the
meta and ortho positions of the phenyl ring attached to
the benzylic carbon atom.
F igu r e 3. Temperature dependence of the 13C NMR
spectrum of compound 4a . Signals bearing an asterisk
correspond to resonances of the ortho and meta carbon
atoms of the phenyl ring attached to the benzylic carbon
atom.
1
The H NMR spectra of the pure products 4b and 6b
revealed the absence of the broad peak.
The 13C NMR spectra inform also on the asymmetry
at the metal atom and denote a marked magnetic
difference of the three carbonyl carbons for 4a , 5a , and
6a . They appear as three distinct peaks at 220, 221,
and 230 ppm (for the carbonyl ligand trans to the
pyridyl nitrogen atom). The benzylic carbon substituted
by alkoxy groups and coordinated to manganese reso-
nates at around 100 ppm.
Low -Tem p er a t u r e NMR E xp er im en t s w it h 4a .
Low-temperature NMR experiments ascertained our
assignments for 4a . For instance, a 1H NMR experi-
ment carried out at 253 K with a solution of 4a in
deuterated acetone revealed four broadened but well-
defined peaks at 8.00 (doublet, Hortho), 7.26 (triplet,
Hmeta), 6.61 (triplet, Hmeta), and 6.05 ppm (doublet,
Hortho), each integrating for one proton. These four
signals can be assigned to the diastereotopic ortho and
meta protons of the phenyl group bound to the benzylic
carbon (Figure 2).
between related peaks, the signals resulting from the
coalescence of two signals were not detected in deuter-
ated acetone. The proton para at the arene ring, which
is not expected to undergo any line broadening, was
located in an intense multiplet at 7.80 ppm. Comple-
mentary 13C NMR measurements on this sample of 4a
were carried out at 213, 243, 273, and 298 K. At 243
K, five signals related to the phenyl group observed at
values of 140.7 (para), 132.3, 128.2, 127.6, and 127.1
ppm could be attributed to tertiary aromatic carbon
atoms. Four out of these five signals underwent broad-
ening upon warming of the NMR probe to 273 K. Three
broad and unresolved signals consequently appeared at
132.5, 128.0, and 127.2 ppm (Figure 3).
We attribute the dynamic behavior described above
to a restrained rotation of the phenyl group around the
Cipso-Cbenzyl bond axis. Given the large separation in
1
frequency between the H or 13C signals described here
it was difficult to establish the exact coalescence tem-
perature for a pair of structurally related NMR signals.
However, if one considers that the coalescence occurs
at a temperature of ca. 298 K, the barrier of rotation
for the phenyl moiety can be estimated to be ap-
Warming the NMR probe caused further broadening
of the latter signals at 273 K and their disappearance
at 298 K.23 Due to the large separation in frequency
proximately 14 kJ ‚mol-1
.
(23) A similar NMR dynamic effect has been reported for a strained
(porphyrinato)osmium(II) ylide; Djukic, J . P.; Young, V. G.; Woo, L.
K. Organometallics 1994, 13, 3995.
In vestiga tion s on th e Mech a n ism of F or m a tion
of (η3-Ben zyl)t r ica r b on ylm a n ga n ese Com p lexes.

5176 Organometallics, Vol. 16, No. 24, 1997
Djukic et al.
The addition of organolithium reagents such as MeLi
or PhLi to cyclomanganated complexes is expected to
yield acyltricarbonylmanganates [RC(O)Mn(CO)3L2]-
that should be detectable by various spectroscopic
methods. We monitored the reaction mixture resulting
from the action of PhLi with 1 by means of infrared
spectroscopy at 253 K using the method described by
Gladysz and co-workers.24 We noticed that shortly after
the addition of 2 equiv of PhLi to a solution of 1 in THF
(c ) 0.031 M) the color of the solution changed from pale
yellow to orange-brown. The IR spectrum of the result-
ing mixture displayed after 1 min of reaction only three
separated intense bands in the carbonyl ligand region
at 1975, 1885, and 1856 cm-1 and the absence of any
signal related to 1 (note that a THF solution of 1 gives
four bands in the IR spectrum at 2073 (w), 1988.3 (vs),
1974.6 (s), and 1933.4 (m) cm-1).
F igu r e 4. 13C NMR spectrum of Li-7 at 253 K in d8-THF.
The typical resonance of the acyl carbon appears at 313
ppm. The resonances at 222, 223, and 230 ppm are related
to the Mn(CO)3 moiety.
This experiment indicated the quantitative conversion
of the starting tetracarbonyl complex into an anionic
asymmetric tricarbonylmanganese complex. The an-
ionic nature of the intermediate may be deduced from
the decrease in wavenumbers for the CO vibration
relative to those of the substrate 1 in the same solvent.
A buildup of negative charge at the metal center lowers
the bond order of the carbonyl ligand C-O bond and
thus induces a bathochromic shift of the IR absorption
bands.
benzoylmanganese moiety of a molecule such as Li-7.
It is important to note that this absorption band was
observable only in highly concentrated solutions of the
lithium salt.
Addition of HMPA to a solution of the lithium salt
induced a bathochromic shift to give absorptions bands
at 1951.4 (strong, A), 1847.1 (strong), 1833.2 (strong),
and 1593.8 (weak) cm-1. This reflects the chelation of
the lithium cation and can be rationalized in terms of a
weaker coordination of the lithium cation to the ben-
zoylmanganate anion 7 resulting in a higher delocal-
ization of the negative charge within the tricarbonyl
manganese fragment.26 We similarly prepared the
PPN+ salt. PPN-7 was obtained as a dark red com-
pound after metathesis reaction of Li-7 with PPN+Cl-.
Its IR spectrum in CH2Cl2 at room temperature displays
bands at 1941.3 (strong, A), 1836.5 (very strong), and
1593.3 (weak) cm-1, indicating an even more pro-
nounced bathochromic shift in comparison to Li-7 due
to the pronounced ionic character of the PPN salt.
The lithium salt Li-7 was also characterized by 13C
NMR at 253 K. At this temperature the spectrum
displayed five signals above 190 ppm (Figure 4). The
first one at 195.5 ppm is attributed to benzaldehyde,
which is likely to be a decomposition product of the
reaction between the anionic intermediate 7 and the
residual water present in d8-THF. This interpretation
was corroborated by reacting a solution of PPN-7 in CH2-
Cl2 with a slight amount of water. A GC-MS analysis
of the mixture indicated the presence of significant
amounts of benzaldehyde.
The other low-field signals appear at 222.9, 223.3,
230.3, and 313.3 ppm. The first group of three signals
can reasonably be assigned to the Mn(CO)3 moiety
(Figure 4). The more deshielded 13C NMR signal at
313.3 ppm was identified as that arising from the
carbonyl carbon of the benzoyl moiety.
Although a few data are available on the 13C NMR
spectroscopic properties of neutral or anionic acylman-
ganese complexes, our results are in accord with those
reported for acetyl-, benzoyl-, and formylmanganese
complexes. For instance, the carbonyl 13C resonances
of benzoyl fragments have been detected at ca. 270 ppm
Only weak signals were detected around 1600 cm-1
.
Line rolling prevented us from ascertaining the presence
of any signal that could have been related to a benzoyl
PhCO-Mn group of a plausible benzoylmanganate in-
termediate 7 (eq 1). In the literature related to man-
ganese carbonyl complexes the CO stretching band of a
benzoyl moiety has been detected by Casey and co-
workers at around 1570 cm-1 for a compound formu-
lated as Li[cis-(CO)4Mn(COCH3)(COC6H5)] and at 1525
cm-1 for N(CH3)4[cis-(CO)4Re(CH3)(COC6H5)].25
(1)
In order to either ascertain or rule out the transitory
formation of the benzoyl tricarbonylmanganate inter-
mediate 7 in the process leading to chelated (η3-benzyl)-
tricarbonylmanganese complexes, we attempted to iso-
late the anionic intermediate described above at -30
°C. We decided first to isolate the putative lithium salt
formulated as Li-7 and then concentrated on the influ-
ence of the countercation on the IR spectrum of the
anionic intermediate. We reacted 1 equiv of PhLi with
a solution of 1 in THF at -70 °C. The temperature was
allowed to rise to -30 °C, and the solvent was removed
under reduced pressure. The IR spectrum of the result-
ing residue, dissolved in CH2Cl2, showed three bands
at 1983.2 (strong, A), 1861 (broad and very strong, E),
and 1597.6 (weak) cm-1. The last band can plausibly
be assigned to the CdO stretching vibration of a
(24) Gladysz, J . A.; Williams, G. M.; Tam, W.; J ohnson, D. L.; Parker,
D. W.; Selover, J . C. Inorg. Chem. 1979, 18, 553.
(25) (a) Casey, C. P.; Bunnell, C. A. J . Am. Chem. Soc. 1976, 98,
436. (b) Casey, C. P.; Scheck, D. M. J . Am. Chem. Soc. 1980, 102, 2733.
(26) (a) Fischer, E. O.; Offhaus, E.; Mu¨ller, J .; Nothe, D. Chem. Ber.
1972, 105, 3027. (b) Casey, C. P.; Cyr, C. R.; Anderson, R. L.; Marten,
D. F. J . Am. Chem. Soc. 1975, 97, 3053.

Novel Tricarbonyl(η3-benzyl)manganese(I) Complexes
Organometallics, Vol. 16, No. 24, 1997 5177
F igu r e 6. Alkylation of Li-7 by MeOTf at -20 °C and
formation of 4a . Plot of the concentration in 4a (M) versus
time (s).
F igu r e 5. IR monitoring of the reaction of Li-7 with
MeOTf in THF at -20 °C: formation of 4a .
tricarbonylmanganese anion which supposedly remains
coordinated to the ancilliary pyridyl nitrogen atom.
This particular process has been already established
for the thermal decomposition of acyl manganate and
-rhenate anions such as Li[cis-(CO)4Mn(COCH3)(CO-
C6H5)] and N(CH3)4[cis-(CO)4Re(CH3)(COC6H5)].25 In
order to obtain evidence for the formation of a [Mn(CO)3]-
species, we treated 2 with 1 equiv of MeLi at -30 °C
during 0.5 h in Et2O, and we injected the resulting
mixture into a solution containing 2 equiv of tri-
phenylphosphine and 1 equiv of trimethyltin chloride
at -30 °C. The temperature of the solution was allowed
to rise to room temperature in order to assist the
reductive elimination process of the benzoylmanganate
species. An abundant pale yellow precipitate was
produced within 1 h in over 91% yield. This compound
was separated from the mother liquor, purified by
chromatography on silica gel, and finally identified as
a mixture of mer- and fac-(Ph3P)2(CO)3MnSnMe3 (Scheme
3). Spectroscopic characterization was in good agree-
ment with published data.31 A GC-MS analysis of the
liquor revealed the presence of considerable amounts
of a compound which has a relative molecular mass of
196 m/e and which we identified as the ketone 8a . In
addition, an experiment was carried out with PhLi
under identical conditions, and the same bimetallic tin-
manganese complex was isolated in only 26% yield. The
GC-MS analysis of the supernatant indicated, apart
from the presence of triphenylphosphine, major amounts
of a compound having a relative molecular mass of 273
m/e; it was identified as the ketone 8b.
Syn th esis of Ar om a tic Keton es fr om Or th o-
Ma n ga n a ted P yr id in e Der iva tives. The latter series
of experiments provide relevant information regarding
the thermal stability of the anionic intermediate 7.
Formation of the ketones 8a and 8b occurs at temper-
atures above -30 °C via a process that generates a very
sensitive and electron deficient tricarbonylmanganese
anion. We decided to apply this property to the syn-
thesis of polycyclic aromatic ketones. For this purpose
we reacted compounds 1, 3, and 9 with PhLi at low
temperature (-60 °C) in Et2O and allowed the reaction
mixture to reach room temperature in order to promote
reductive elimination to afford the corresponding ke-
for [(η6-{(CO)5Mn}C(O)C6H5)Cr(CO)3]27 and at ca. 250
ppm for 4-CH3C6H4C(O)-Mn(CO)5.28 Signals at ap-
proximately 284 ppm were reported by Gladysz and co-
workers for homobimetallic anionic formylmanganese
and -rhenium complexes of the formula Li[(CO)5MM-
(CO)4{C(O)H}] (M) Mn, Re).29 In addition, the 13C
NMR resonance of the acyl moiety in [NMe4]+[(CO)5-
Cr(13C(O)Ph)]- has been detected at 306 ppm.30
In summary, IR and NMR data clearly indicate that
the reaction between PhLi and 1 at -30 °C leads to the
anionic benzoylmanganese intermediate Li-7.
R ea ct ion of t h e An ion ic In t er m ed ia t e w it h
MeOTf. A solution of Li-7 was prepared as described
above and treated with a slight excess of methyl triflate
at 253 K. This was carried out in order to obtain a
qualitative estimation of the rate of alkylation of the
putative anionic benzoylmanganese complex prepared
above. The reaction was monitored over 3 h by IR
spectroscopy. Figure 5 demonstrates the formation of
a new species whose IR absorptions at 2000, 1918, and
1900 cm-1 are consistent with the structure of a tricar-
bonylmanganese complex 4a . Compared with the gen-
eration of the benzoylmanganate intermediate, the
methylation step seems much slower. The plot of the
concentration in complex 4a versus time indicates that
the alkylation reaction requires approximately 2.5 h to
reach completion at 253 K (Figure 6).
Tr a p p in g of th e An ion ic Tr ica r bon ylm a n ga n ese
Sp ecies [Mn (CO)3]-. In our preliminary studies we
noticed that MeLi and PhLi exhibited distinctly differ-
ent behavior when reacted with 2. All of our attempts
to isolate neutral (η3-benzyl)manganese compounds
from reactions with MeLi led to very air sensitive
brownish solutions. Variation of the temperature, the
concentration of the reactants, and the nature of the
alkylating agent did not provide any stable neutral
organometallic species. We speculated whether this
might be a consequence of the propensity of acylman-
ganate anions toward reductive elimination of a ketone
and the subsequent generation of an electron deficient
(27) Lotz, S.; Schindehutte, M.; van Rooyen, P. H. Organometallics
1992, 11, 629.
(28) Sheeran, D. J .; Arenivar, J . D.; Orchin, M. J . Organomet. Chem.
1986, 316, 139.
(29) Tam, W.; Marsi, M.; Gladysz, J . A. Inorg. Chem. 1983, 22, 1413.
(30) Lee, I.; Cooper, N. J . J . Am. Chem. Soc. 1993, 115, 4389.
(31) Onaka, S.; Yoshikawa, Y.; Yamatera, H. J . Organomet. Chem.
1978, 157, 187.

5178 Organometallics, Vol. 16, No. 24, 1997
Djukic et al.
Sch em e 3
Sch em e 4
ligand located cis with respect to the better donor ligand
L.32 In our case, it is not clear yet whether the
nucleophilic ArLi reagent attacks only the axial carbonyl
ligand of the starting tetracarbonylmanganese chelate
or adds also to one of the other two equatorial CO
ligands, affording therefore a mixture of three anionic
benzoylmanganate species. To address this question
one must be able to isolate temperature-stable inter-
mediates that might be characterized by X-ray diffrac-
tion analysis. Unfortunately, all of our attempts to
crystallize the manganese anions failed to produce good
quality crystals, and so far only decomposition products
have been obtained. At this moment, we focus our
efforts on the isolation of more stable rhenium ana-
logues, which will be described elsewhere.
From our investigations we know that the anionic
benzoyl- or acetylmanganate anions may undergo re-
ductive elimination following a process similar to that
described by Casey and co-workers for the decomposi-
tion of Li[cis-(CO)4Mn(COCH3)(COC6H5)] into [Mn(CO)4]-
and acetophenone.25a The intermediate proposed by
these authors, e.g., [(CO)4Mn(C(O)Me)(Ph)]-, closely
resembles the anion 7. Related anionic rhenium spe-
cies, [(CO)4Re(C(O)Me)(Ph)]- and [(CO)4Re(C(O)Ph)-
(Me)]-,33 have been reported to yield acetophenone when
heated to 120 °C.25b
tone. After the end of the reaction the workup was
performed in air using water to neutralize unreacted
amounts of organolithium reagent and to induce the
oxidation of the sensitive Mn(I) species into the metal
oxide easily separable by filtration through Celite.
Following this procedure, three different aromatic ke-
tones, 10, 11, and 12, were synthesized in isolated yields
of 40%, 74%, and 41% after chromatographic purifica-
tion (Scheme 4). A similar experiment carried out with
3 and 2-lithionaphthalene afforded less than 5% of the
corresponding crowded aromatic ketone.
The alkylation of intermediates such as Li-7 may be
challenged by the competing reductive elimination path.
The latter process, which produces an aromatic ketone,
may in some respects lower the efficiency of the process
that yields the new (η3-benzyl)tricarbonylmanganese
complex. We speculate whether in the reaction with
MeLi a fast reductive elimination reaction prevents the
anionic acetyl intermediate from giving a (η3-benzyl)-
manganese complex. This difference of reactivity be-
tween acetyl- and benzoylmanganates has been previ-
ously addressed in part by Casey and co-workers.25a
However, in the cases presented herein a more thorough
discussion requires reliable kinetic data, which are not
available so far.
Discu ssion . The formation of the chelated (η3-
benzyl)tricarbonyl species is not a straightforward
process. As evidenced above, the first step, which
involves the addition of the aryl lithium to the tetra-
carbonylmanganese substrate, yields an anionic ben-
zoylmanganate Ar-CO-Mn intermediate. Previous
work has demonstrated that the addition of organo-
lithium reagents to metal carbonyl complexes of the
formula (CO)nML preferentially occurs at the carbonyl
(32) (a) Darensbourg, M. Y.; Conder, D. J .; Darensbourg, D. J .;
Hasday, C. J . Am. Chem. Soc. 1973, 95, 5919. (b) Dobson, G. R.;
Paxson, J . R. J . Am. Chem. Soc. 1973, 95, 5925. (c) Casey, C. P.;
Bunnell, C. A. J . Am. Chem. Soc. 1976, 98, 436.
(33) Casey, C. P.; Scheck, D. M. J . Organomet. Chem. 1977, 142,
C12.

Novel Tricarbonyl(η3-benzyl)manganese(I) Complexes
Organometallics, Vol. 16, No. 24, 1997 5179
Sch em e 5
The detailed mechanism of the formation of the (η3-
benzyl)tricarbonylmanganese complexes is still un-
known. However, we can propose two reasonable paths
that are consistent with our experimental observations
(Scheme 5) .
First, the alkylating agent may add to the oxygen
atom of the aroyl fragment to afford a reactive manga-
nese arylmethoxymethylidene species, which may un-
dergo a nucleophilic migration of the phenyl moiety of
the 2-phenylpyridine chelate from the manganese center
to the electrophilic carbene carbon atom and yield the
chelated (η3-benzyl)tricarbonylmanganese complex as
the final stable product (path A).
Alternatively, a reductive elimination pathway start-
ing from the anionic benzoylmanganate could afford an
alcoholate precursor of the neutral (η3-benzyl)tri-
carbonyl manganese complex (path B). This intermedi-
ate could also be seen as the precursor of the aromatic
ketones that we detected and isolated throughout this
work.
erable amounts of benzaldehyde that could be consid-
ered as the product of the decomposition either of a
manganese hydroxycarbene36 or of a hydridomanga-
nese(III) acyl intermediate. This latter possibility, a
known process in iron and nickel carbonyl chemistry,
implies a localization of the negative charge at the metal
center.37 In most of the cases where the yields of (η3-
benzyl)tricarbonylmanganese complexes are high after
alkylation, we observe low yields of aromatic ketones
resulting from the reductive elimination step. This
suggests that in some cases the competing reductive
elimination might be more disfavored than the forma-
tion of the η3 manganese complex arising from the same
anionic intermediate.
Con clu sion
In this paper we have reported the unprecedented
synthesis of chelated (η3-benzyl)tricarbonylmanganate
complexes starting from tetracarbonylmanganese cy-
clometalated arylpyridines and aryllithium nucleophiles
followed by alkylation. The molecular structure of
complex 4a reveals a sterically congested helical-type
assembly of aromatic rings which reveals peculiar
temperature dependent NMR properties. We have
demonstrated that the reaction of PhLi with the starting
tetracarbonylmanganese complexes generates anionic
benzoylmanganates. We have shown that one of the
side reactions that compete with the formation of the
novel benzylic η3 species is a reductive elimination
process yielding the corresponding aromatic ketones
from the anionic benzoylmanganate intermediate. We
have shown, in three cases, that this reaction path could
be exploited for the synthesis of extended aromatic
However, one might argue that the reductive elimina-
tion step yielding an aromatic ketone is a prerequisite
for the further formation of a (η3-benzyl)manganese
-
complex. In this context, an anionic (S)nMn(CO)3
species (S ) solvent, n ) 1 or 2) could act as a strong
nucleophile that adds to the carbon of the endogenous
aryl ketone. To some extent, this would be consistent
with other reports that confer to the [Mn(CO)3]- species
in the gas phase a high reactivity toward the C-H bond
activation of hydrocarbons.34,35
At this point in our studies we may rule out none of
these proposals. Qualitative experiments performed
with PPN-7 suggest that the oxygen atom of the benzoyl
group is not the only nucleophilic center. As reported
above, the treatment of PPN-7 with H2O yields consid-
(36) Fischer, E. O.; Riedel, A. Chem. Ber. 1968, 101, 156.
(37) (a) Bates, R. W. In Comprehensive Organometallic Chemistry;
Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds.; Pergamon: Oxford,
U.K., 1995; Vol. 12, pp 349-355. (b) Alper, H.; Fabre, J . L. Organo-
metallics 1982, 1, 1037. (c) Corey, E. J .; Hegedus, L. S. J . Am. Chem.
Soc. 1969, 91, 4926. (d) Semmelhack, M. F.; Tamura, R. J . Am. Chem.
Soc. 1983, 105, 4099.
(34) (a) McDonald, R. N.; J ones, M. T.; Chowdhury, A. K. J . Am.
Chem. Soc. 1992, 114, 71. (b) McDonald, R. N.; J ones, M. T.;
Chowdhury, A. K. Organometallics 1992, 11, 392. (c) McDonald, R.
N.; J ones, M. T.; Chowdhury, A. K. Organometallics 1992, 11, 356.
(35) McDonald, R. N.; J ones, M. T.; Chowdhury, A. K. Organome-
tallics 1991, 113, 476.

5180 Organometallics, Vol. 16, No. 24, 1997
Djukic et al.
Tet r a ca r b on yl[2-(4-m et h ylp h en yl-KC2)p yr id in e-KN]-
m a n ga n ese(I), Com p lex 2. Elemental anal. Calcd for
ketones containing pyridyl-type moieties.38 Several
questions concerning the mechanism of the formation
of the (η3-benzyl)manganese species remain unan-
swered, and we intend to focus our attention on these
issues in our subsequent work. We also intend to apply
the novel synthetic access to aromatic ketones to other
types of manganese chelates.
C
16H10NO4Mn: C, 57.33; H, 3.01; N, 4.18. Found: C, 57.53;
H, 3.02; N, 4.07. MS (EI): 169, 223, 251, 279, 335. High-
resolution MS (EI) calcd for C16H10NO4Mn: 334.9990. Found
(intensity (%)): 334.9999 (2.44). IR (CH2Cl2) ν(CO): 2074 (w),
1989 (s), 1976 (s), 1932 (m). 1H NMR (C6D6): δ 8.16 (d, 1H),
8.03 (s, 1H), 7.36 (d, 1H), 7.02 (d, 1H), 6.87 (d, 1H), 6.74 (t,
1H), 6.06 (t, 1H), 2.18 (s, 3H). 13C NMR (C6D6): δ 21.7, 118.8,
121.6, 124.5, 125.5, 137.2, 140.8, 142.6, 143.8, 153.5, 166.3,
174.1, 214.0, 215.0 (2CO), 220.8.
Exp er im en ta l Section
All reactions were carried out under a dry argon atmo-
sphere. 2-Phenylpyridine, 2-(4-tolyl)pyridine, 2-phenylquino-
line, methyl and ethyl trifluoromethanesulfonate, phenyllith-
ium, and methyllithium were purchased from Aldrich and
Fluka Companies. 2-Lithionaphthalene and pentadeuteri-
olithiobenzene solutions were obtained from the reactions of
2-bromonaphthalene and pentadeuteriobromobenzene, respec-
tively, with lithium metal in dry diethyl ether. Pentacarbonyl-
(R-η1-benzyl)manganese was prepared following a literature
procedure.39 All reactions involving manganese complexes
were always protected from exposure to oxygen even though
most of the isolated compounds withstood an oxygen atmo-
sphere for days without undergoing decomposition. Tetra-
hydrofuran and diethyl ether were dried over sodium ben-
zophenone ketyl under a dry argon atmosphere and distilled
prior to use. Hexane and petroleum ether were distilled over
CaH2 prior to use. Before NMR experiments were performed,
deuterated solvents were filtered through a column of activated
basic alumina, and sample tubes were purged with dry argon
to remove oxygen. Products were separated by flash chroma-
tography using deactivated silica gel (60 µm) under a dry
atmosphere of argon gas. 1H and 13C NMR spectra were
acquired on Bruker WR 250, AC 400, and DRX 500 equipment,
and chemical shifts are reported in parts per million (δ in ppm)
downfield of Me4Si. 1H NMR spectra were referenced against
the residual 1H impurity of the deuterated solvent (δ (ppm)
7.15 (C6D6); 7.24 (CDCl3); 2.05 ((CD3)2CO)), and 13C NMR
spectra were referenced against the 13C resonance of the
solvent (δ 128.0 (C6D6); 77.1 (CDCl3); 29.8, 206.0 ((CD3)2CO)).
Infrared spectra (reported in cm-1) were performed on a FT-
IR Nicolet Magna 550 spectrometer. Kinetic measurements
were done by using the method of Gladysz and co-workers.24
The ꢀl factor of the Beer-Lambert formula A ) ꢀcl was
calculated for complex 4a at a frequency of 1998.3 cm-1. Mass
spectra and high-resolution mass determination were per-
formed at the Analytical Center of the Chemical Institutes of
the University of Bonn by using the electron impact method.
Elemental analyses (reported in % mass) were performed at
the Kekule´-Institut fu¨r Organische Chemie und Biochemie der
Universita¨t Bonn, Germany, and at the Faculte´ de Chimie de
l’Universite´ Louis Pasteur, Strasbourg, France. Complex 1,
tetracarbonyl[2-(phenyl-κC2)pyridine-κN]manganese(I),40 com-
plex 9,41 and complexes 2 and 3 were prepared according to
literature methods from the uncoordinated pyridine, benzo-
[h]quinoline, and quinoline derivatives and from penta-
carbonyl(R-η1-benzyl)manganese.
Tetr acar bon yl[2-(ph en yl-KC2)qu in olin e-KN]m an gan ese-
(I), Com p lex 3. Elemental anal. Calcd for C19H10NO4Mn:
C, 61.47; H, 2.72; N, 3.77. Found: C, 61.48; H, 2.74; N, 3.68.
MS (EI): 204, 259, 200, 315, 371 m/e. IR (CH2Cl2) ν(CO): 2075
(w), 1993 (s), 1973 (s), 1930 (m) cm-1 1H NMR (C6D6): δ 8.65
.
(d, 1H), 8.29 (dd, 1H), 7.46 (dd, 1H), 7.40-7.05 (m, 7H). 13C
NMR (C6D6): δ 117.3, 124.4, 126.4, 126.7, 128.1, 128.6, 130.7,
131.1, 148.4, 150.1, 169.3, 176.7, 214.5, 215.1, 221.7.
Gen er a l P r oced u r e for th e Syn th esis of Ch ela ted
Tr ica r bon yl(η3-ben zyl)m a n ga n ese(I) Com p lexes. To a
solution of the starting manganese chelate in dry diethyl ether
was added an excess of a solution of aryllithium reagent at
-60 °C. A slight change in color from pale yellow to reddish
occurred. The resulting solution was then warmed to -30 °C,
stirred and maintained during ca. 30 min between -30 and
-20 °C. The brownish mixture was cooled down to -60 °C, a
slight excess of alkyl triflate was added to it, and the resulting
mixture was warmed slowly to room temperature. At this
stage, the reaction could be considered complete only when
the color of the solution turned to an intense dark red or
orange. The solvent was removed under reduced pressure and
the residue further dried under vacuum. The latter was
redissolved in Et2O, and deactivated silica was added to the
solution. The solvent was removed in vacuo and the coated
silica loaded on the top of a column of deactivated silica gel. A
first band of the starting manganese complex was eluted (from
30% to 50% Et2O in petroleum ether) followed by a red or
orange band of the corresponding chelated tricarbonyl(η3-
benzyl)manganese (Et2O, 100%). The solution of the latter
complex was stripped of solvent and the solid recrystallized
from hexane.
Tr ica r bon yl{2-[(1,2-η2),κCr-2-(p h en ylm eth oxym eth yl-
en e)ph en yl]pyr idin e-KN}m an gan ese(I), Com plex 4a. Com-
plex 1 (349 mg, 1.09 mmol), PhLi (1.8 M, 1.5 mL, 2.5 mmol),
and MeOTf (0.4 mL, 3.62 mmol) were used to prepare complex
4a (230 mg, 0.557 mmol). Fp: 148 °C dec. Elemental anal.
Calcd for C22H16NO4Mn: C, 63.92; H, 3.89; N, 3.38. Found:
C, 63.89; H, 3.88; N, 3.27. IR (CH2Cl2) ν(CO): 2000 (s), 1916
(s), 1899 (s) cm-1. MS (EI): 289, 244, 299, 329 (M - 3CO),
357 (M - 2CO), 385 (M - CO), 413 (M) m/e. High-resolution
MS (EI) calcd for C22H16NO4Mn: 413.0460. Found (intensity
(%)): 413.0456 (1.62). 1H NMR (C6D6, 298 K): δ 8.27 (d, 1H),
7.29 (t, 1H), 7.17 (m, 1H), 7.01 (m, 2H), 6.70 (m), 6.36 (t, 1H),
5.80 (d, 1H), 5.74 (t, 1H), 3.58 (s, 3H). 1H NMR (C3D6O, 253
K): δ 8.08 (d, 1H), 8.00 (d, 1H), 7.80 (m, 3H), 7.65 (t, 2H),
7.26 (t, 1H), 7.09 (1H), 6.93 (m, 2H), 6.61 (t, 1H), 6.05 (d, 1H),
3.44 (s, 3H). 13C NMR (CDCl3, 298 K): δ 57.7, 102.2, 110.4,
121.3, 123.2, 125.9, 127.4 (broad), 128.0, 129.9, 131.3, 134.8,
136.9, 140.5, 151.0, 220.2, 220.6, 232.0. 13C NMR (C3D6O, 243
K): δ 57.3, 103.6, 109.7, 110.2, 122.8, 124.6, 126.4, 127.1, 127.6,
128.2, 128.9, 130.9, 131.9, 132.3, 134.7, 138.5, 140.7, 151.5,
157.9, 221.0, 221.2, 232.5.
P en ta d eu ter iobr om oben zen e. This compound was pre-
pared starting from hexadeuteriobenzene by using an adapted
literature procedure.42 Elemental anal. Calcd for C6D5Br :
C, 44.47; H + 1/2D, 3.11. Found: C, 43.45; H + 1/2D, 3.05. High-
resolution MS (EI) calcd for C6D5Br: 160.9883. Found (in-
tensity (%)): 160.9889 (83.39). MS (EI): 82, 161 m/e. 13C
NMR (neat): δ 122.4, 126.3 (t, J C-D ) 50 Hz), 129.6 (t), 131.1
(t).
Tr ica r b on yl{2-[(1,2-η2),KCr-2-(p en t a d eu t er iop h en yl)-
m e t h oxym e t h yle n e ]p h e n yl]p yr id in e -KN }m a n ga n e se -
(I), Com p lex 4b. Complex 1 (263 mg, 0.82 mmol), d5-PhLi
(1 M, 1.3 mL, 1.3 mmol), MeOTf (0.22 mL, 2 mmol), and Et2O
(15 mL) were used to prepare complex 4b (126.4 mg). Fp: 148
°C dec. Elemental anal. Calcd for C22H11D5NO4Mn: C, 63.16;
(38) (a) Ahmed, M.; Kricka, L. J .; Vernon, J . N. J . Chem. Soc., Perkin
Trans. 1 1975, 71. (b) Ahmed, M.; Vernon, J . M. J . Chem. Soc., Perkin
Trans. 1 1977, 601.
(39) Bruce, M. I.; Liddell, M. I.; Pain, G. N. Inorg. Synth. 1984, 26,
172.
(40) Bruce, M. I.; Goodall, B. L.; Matsuda, I. Aust. J . Chem. 1975,
28, 1259.
(41) Bruce, M. I.; Goodall, B. L.; Stone, F. G. A. J . Organomet. Chem.
1973, 60, 343.
1
1
H + /2D, 3.86; N, 3.35. Found: C, 63.03; H + /2D, 3.87; N,
3.14. MS (EI): 209, 249, 291, 304, 334, 362, 390, 418 m/e.
High-resolution MS (EI) calcd for C22H11D5NO4Mn: 418.0768.
Found (intensity (%)): 418.0772 (1.18). 1H NMR (C6D6, 298
(42) Ghigi, E. Ber. Dtsch. Chem. Ges. 1938, 71, 684.

Novel Tricarbonyl(η3-benzyl)manganese(I) Complexes
Organometallics, Vol. 16, No. 24, 1997 5181
1919 (s), 1897 (s) cm-1 1H NMR (C6D6, 298 K): δ 8.60 (m,
K): δ 8.29 (d, 1H), 7.29 (t, 1H), 7.17 (m, 1H), 7.01 (m, 2H),
6.36 (t, 1H), 5.80 (d, 1H), 5.74 (t, 1H), 3.58 (s, 3H). 13C NMR
(CDCl3, 298 K): δ 57.7, 102.2, 110.4, 121.3, 123.2, 125.5 (t,
J C-D ) 27 Hz), 128.0, 129.9, 131.3, 134.8, 136.9, 140.5, 151.0,
220.2, 220.6, 232.0.
.
broad), 8.19 (m, broad), 7.39 (t, 1H), 7.26 (d, 1H), 7.08-6.84
(m, 5H), 6.73 (d, 1H), 6.61 (t, 1H), 6.48 (d, 1H), 6.12 (m, broad),
3.58 (s, 3H). 1H NMR (C3D6O, 253 K): δ 8.20 (d, 1H), 8.04-
8.01 (m, 3H), 7.89 (t, 1H), 7.83 (d, 1H), 7.71 (t, 1H), 7.67 (t,
1H), 7.35 (m, 5H), 7.21 (m, 2H), 7.15 (t, 1H), 6.42 (s, 1H), 3.48
(s, 3H). 13C NMR (CDCl3, 298 K): δ 58.3 (broad), 119.5, 124.1,
124.7, 125.4, 126.4, 127.1 (broad), 127.9, 129.7 (broad), 130.9,
131.4, 131.5, 131.8, 132.8, 136.9, 138.3, 146.1, 158.7, 221.1,
232.0.
X-r a y Deter m in a tion a n d P r ocessin g for 4a . Crystal
data and details of data collection for 4a are given in Table 2.
Data for 4a were collected in the ω/2θ flying step-scan mode
using Cu KR graphite-monochromated radiation (λ ) 1.5418
Å) on a red crystal of dimensions 0.15 × 0.20 × 0.35 mm3 with
a Philips PW1100/16 automatic diffractometer at room tem-
perature. Three standard reflections measured every 1 h
during the entire data collection period showed no significant
trend. The raw data were converted to intensities and
corrected for Lorentz polarization and absorption factors. The
structure was solved by the heavy atom method. After
refinement of the non-hydrogen atoms, Fourier difference
maps revealed maxima of residual electron density close to
positions expected for hydrogen atoms. Hydrogen atoms were
refined at calculated positions with a riding model in which
the C-H vector was fixed at 0.95 Å with isotropic temperature
factors such as B(H) ) 1.3Beqv(C) Å2. A final Fourier difference
map revealed no significant maxima. All calculations were
performed on a DEC Alpha 3000 computer using the Nonius
OpenMoleN package.43 Neutral atom scattering factor coef-
ficients and anomalous dispersion coefficients were taken from
a standard source.44
Tr ica r b on yl{2-[(1,2-η2),KCr-4-m et h yl-2-(p h en ylm et h -
oxym eth ylen e)p h en yl]p yr id in e-KN}m a n ga n ese(I), Com -
p lex 5a . Complex 2 (340 mg, 1.01 mmol), PhLi (1.8 M, 1.11
mL, 2 mmol), MeOTf (0.5 mL, 4.56 mmol), and Et2O (20 mL)
were used to prepare complex 5a (199.6 mg). Fp: 145-151
°C dec. Elemental anal. Calcd for C23H18NO4Mn: C, 64.65;
H, 4.25; N, 3.28. Found: C, 64.57; H, 4.24; N, 2.98. MS (EI):
223, 258, 313, 343, 371, 399, 427 m/e. High-resolution MS (EI)
calcd for C23H18NO4 Mn: 427.0616. Found (intensity (%)):
427.0608 (1.68). IR (CH2Cl2) ν(CO): 1999 (s), 1915 (s), 1896
(s) cm-1
.
1H NMR (C6D6): δ 8.29 (s, 1H), 7.31 (d, 1H), 7.26
(m, 1H), 7.13 (m, 1H), 7.02 (m, 1H), 6.83 (m, 4H), 6.50 (t, 1H),
5.95 (d, 1H), 5.88 (t, 1H), 3.78 (s, 3H), 2.30 (s, 3H). 13C NMR
(CDCl3, 298 K): δ 22.1, 57.7, 100.3, 110.0, 110.9, 121.1, 123.0,
125.8, 127.2 (broad), 129.9, 130.1, 133.2, 136.8, 140.7, 141.7,
150.9, 158.3, 221.0, 220.6, 232.0.
Tr ica r b on yl{2-[(1,2-η2),KCr-4-m e t h yl-2-(p h e n yle t h -
oxym eth ylen e)p h en yl]p yr id in e-KN}m a n ga n ese(I), Com -
p lex 5b. Complex 2 (344 mg, 1.02 mmol), PhLi (1.8 M, 1.13
mL, 2 mmol), and EtOTf (0.6 mL, 4.65 mmol), and Et2O (20
mL) were used to prepare complex 5b (158 mg). Fp: 149-
152 °C dec. Elemental anal. Calcd for C24H20NO4Mn: C,
65.31; H, 4.57; N, 3.17. Found: C, 65.02; H, 4.65; N, 2.91.
MS (EI): 223, 258, 313, 357, 385, 413, 441 m/e. High-
resolution MS (EI) calcd for C24H20NO4Mn: 441.0773. Found
(intensity (%)): 441.0774 (0.75). IR (CH2Cl2) ν(CO): 1998(s),
1916 (s), 1895 (s) cm-1 1H NMR (C6D6): δ 8.26 (s, 1H), 7.26-
.
IR Mon itor in g of th e Rea ction of P h Li w ith 1, F ol-
low ed by Alk yla tion w ith MeOTf. To a solution of complex
1 (200 mg, 0.623 mmol, 0.031 M) in THF (20 mL) was added
a solution of PhLi in a 30:70 diethyl ether-cyclohexane
mixture (2 equiv, 1.246 mmol, 0.7 mL, 1.8 M) at 253 K. The
solution was immediately monitored by IR spectroscopy. The
solution was stirred for 30 min and a slight excess of MeOTf
(0.136 mL, 1.240 mmol) was added. The plot of the concentra-
tion in 4a versus time was obtained from the CO vibration
6.91 (m, 4H), 6.24 (m), 6.39 (t, 1H), 5.84 (d, 1H), 5.78 (t, 1H),
4.05 (q, 1H), 3.86 (q, 1H), 2.22 (s, 3H), 1.39 (t, 3H). 13C NMR
(C6D6): δ 15.9, 21.4, 65.7, 100.6, 109.5, 111.8, 120.7, 122.7,
125.9, 129.9, 130.0, 133.9, 136.3, 141.6, 141.8, 151.0, 158.3,
221.1, 233.0.
Tr ica r bon yl{2-[(1,2-η2),KCr-2-(p h en ylm eth oxym eth yl-
en e)p h en yl]q u in olin e-KN}m a n ga n ese(I), Com p lex 6a .
Complex 3 (371 mg, 1 mmol), PhLi (1.8 M, 1.1 mL, 2 mmol),
MeOTf (0.5 mL, 4.56 mmol), and Et2O (20 mL) were used to
prepare complex 6a (103.7 mg). Fp: 190 °C. Elemental anal.
Calcd for C26H18NO4Mn: C, 67.39; H, 3.92; N, 3.02. Found:
C, 67.12; H, 3.90; N, 2.82. MS (EI): 217, 259, 294, 324, 349,
379, 407, 435, 463 m/e. High-resolution MS (EI) calcd for
band at 1998.3 cm-1
.
13C NMR Stu d y of th e In ter m ed ia te. To a solution of
complex 1 in Et2O was added a solution of PhLi at -60 °C.
The solution was warmed to -30 °C and kept at this temper-
ature for 30 min. At this stage the solvent was removed in
vacuo and the resulting residue washed with dry hexane and
redissolved in a commercial sample of d8-THF. At this stage
unavoidable decomposition of a part of the solution prevented
C
26H18NO4Mn: 463.0616. Found (intensity (%)): 463.0616
(1.59). IR (CH2Cl2) ν(CO): 2000 (s), 1919 (s), 1895 (s) cm-1
.
1H NMR (C6D6): δ 8.22 (m, 2H), 7.38 (t, 1H), 7.25 (d, 1H),
7.15-6.75 (m, 5H), 6.31 (m, 5H, broad Cbenzyl-Ph), 6.08 (d, 1H),
3.58 (s, 3H). 13C NMR (CDCl3): δ 57.7, 94.4, 109.0, 110.9,
119.6, 124.4, 125.4, 126.4 (broad), 126.9, 127.2, 127.3, 128.4,
131.1, 131.3, 131.7, 133.0, 138.3, 139.7, 146.2, 158.8, 220.0,
221.2, 232.0.
1
us from acquiring resolved H NMR spectra. The solution was
kept at 213 K and introduced in the probe at 243 K. Measure-
ments allowed the detection of benzaldehyde main signals at
195.5, 135.3, 128.7, and 126.9 ppm. Other signals were
attributed to the benzoylmanganate intermediate Li-7: δ 313.3
(CO-Ph), 230.3 (CO), 223.3 (CO), 222.9 (CO), 166.1, 157.5,
153.4, 145.8, 141.3, 140.1, 129.2, 127.7, 127.3, 125.3, 122.7,
121.9, 120.4, 117.9.
Tr ica r bon yl{2-[(1,2-η2),KCr-2-[(p en ta d eu ter iop h en yl)-
m et h oxym et h ylen e]p h en yl]q u in olin e-KN}m a n ga n ese-
(I), Com p lex 6b. Complex 3 (382 mg, 1.03 mmol), d5-PhLi
(1 M, 2 mL, 2 mmol), MeOTf (0.22 mL, 2 mmol), and Et2O (15
mL) were used to prepare complex 6b (97.9 mg). Fp: 190 °C.
MS (EI): 259, 299, 354, 304, 412, 468 m/e. High-resolution
MS (EI) calcd for C26H13D5NO4Mn: 468.0925. Found (inten-
sity (%)): 468.0926 (1.29). 1H NMR (C6D6): δ 8.22 (m, 2H),
7.38 (t, 1H), 7.25 (d, 1H), 7.15-6.75 (m, 5H), 6.08 (d, 1H), 3.58
(s, 3H).
Tr ica r b on yl{2-[(1,2-η2),KCr-2-(â-n a p h t h ylm e t h oxy-
m et h ylen e)p h en yl]q u in olin e-KN}m a n ga n ese(I), Com -
p lex 6c. Complex 3 (398 mg, 1.07 mmol), 2-lithionaphthalene
(0.48 M, 4.45 mL, 2.14 mmol), MeOTf (0.5 mL, 4.56 mmol),
and Et2O (20 mL) were used to prepare complex 6c (308.8 mg).
Fp: 168 °C. Elemental anal. Calcd for C30H22NO4Mn: C,
70.18; H, 3.93; N, 2.73. Found: C, 70.71; H, 4.09; N, 2.49.
MS (EI): 259, 344, 399, 429, 457, 469, 513 m/e. High-
resolution MS (EI) calcd for C30H20NO4Mn: 513.0773. Found
(intensity (%)): 513.0782 (0.36). IR (CH2Cl2) ν(CO): 2001 (s),
Meta th esis Rea ction of Li-7 a n d P P N+Cl-. Complex 1
was reacted with 1 equiv of PhLi in dry Et2O at -60 °C. The
temperature of the cooling bath was raised slowly to -30 °C
and the solvent removed under reduced pressure. The residue
was washed with hexane, and solid PPN+Cl- was added. The
solid mixture containing Li-7 was dissolved in dichloromethane
at -30 °C and stirred for a while. After filtration of the
crimson solution over Celite and evaporation of the solvent
under vacuum, PPN-7 was isolated as a dark red compound,
insoluble in diethyl ether.
Ad d ition of MeLi to 2. Tr a p p in g of “[Mn (CO)3]-”. A
(43) Fair, C. K. MolEN. An Interactive Intelligent System for Crystal
Structure Analysis; Enraf-Nonius: Delft, The Netherlands, 1990.
(44) Cromer, D. T.; Waber, J . T. International Tables for X-ray
Crystallography; The Kynoch Press: Birmingham, U.K., 1974; Vol. IV,
Tables 2.2b and 2.3.1.

5182 Organometallics, Vol. 16, No. 24, 1997
Djukic et al.
solution of 2 (405.2 mg, 1.22 mmol) in Et2O (15 mL) was
treated with MeLi (1.6 M, 0.76 mL, 1.21 mmol) at -78 °C and
the resulting mixture warmed to -30 °C. The solution was
stirred at the same temperature for 20 min and injected via a
syringe into a solution containing triphenylphosphine (641 mg,
2.44 mmol) and trimethylstannyl chloride (244 mg, 1.23 mmol)
in Et2O (10 mL) at -30 °C. The resulting mixture was allowed
to warm slowly to room temperature. After 2 h of reaction at
room temperature an abundant precipitate formed, which was
filtered off and purified further by chromatography on silica
gel (eluent: CH2Cl2). The filtrate was analyzed by the GC-
MS technique to contain ketone 8a . The yellow flaky solid
isolated after chromatographic purification was identified as
being a mixture of the mer and fac stereoisomers of (PPh3)2-
(CO)3MnSnMe3 (920 mg, 1.11 mmol, 91% yield). 1H NMR
indicates two singlets at 0.23 and 0.53 ppm, a broad multiplet
centered at 6.97 ppm, a signal at 7.38 ppm, and a triplet at
7.85 ppm. The 13C NMR spectrum displays two peaks at -3.42
and -2.97 ppm and a series of peaks at 128.4, 129.8, 129.9,
133.4 (multiplet), 134.2, 136.6 (triplet), 137.7, and 138.4 ppm
and relatively weak signals at 224.8, 226.5, 226.9, and 227.1
ppm assigned as the signals of the carbonyl ligands of the two
species. IR (CH2Cl2) ν(CO): 1981 (s), 1908 (s), 1895 (s).
Ad d ition of P h Li to 2. Tr a p p in g of “[Mn (CO)3]-”. A
similar procedure was used for the experiment with PhLi:
complex 2 (518 mg, 1.56 mmol) in 15 mL of Et2O, PhLi (1.8
M, 0.95 mL, 1.7 mmol); Me3SnCl (342 mg, 1.71 mmol), PPh3
(820 mg, 3.12 mmol) in 15 mL of Et2O. mer- and fac-(PPh3)2-
(CO)3MnSnMe3: 340 mg, 0.41 mmol, 26% yield.
154.0, 127.0, 105.0, 77.0 m/e. High-resolution MS (EI) calcd
for C18H13NO: 259.0997. Found (intensity (%)): 259.0998
(11.41). 1H NMR (CDCl3): δ 8.38 (d, 1H), 7.80 (d, 1H), 7.70
(dd, 2H), 7.63 (t, 1H), 7.57 (m, 4H), 7.40 (t, 1H), 7.29 (t, 2H),
7.02 (m, 1H). 13C NMR (CDCl3): δ 121.9, 122.7, 128.1, 128.5,
128.8, 129.1, 129.5, 130.3, 132.4, 136.3, 137.9, 139.5, 139.7,
149.1, 156.8, 198.3.
2-Qu in olin -6-ylben zop h en on e, 11. Compound 3 (371 mg,
1 mmol), PhLi (1.8 M, 0.55 mL, 1 mmol), and Et2O (15 mL)
were used to prepare compound 11 (230 mg, 74% yield). Fp:
119-120 °C. IR (neat) ν(ArCOAr′): 1666.2. MS (EI): 311
(M+), 288, 232, 204 m/e. High-resolution MS (EI) calcd for
C
22H16NO: 310.1232. Found (intensity (%)): 310.1235 (5.72).
Elemental anal. Calcd for C22H16NO: C, 85.41; H, 4.89; N,
4.53. Found: C, 85.21; H, 4.95; N, 4.62. 1H NMR (CDCl3): δ
8.04 (d, 1H), 7.91 (d, 1H), 7.72-7.61 (m, 5H), 7.62 (t, 1H), 7.54
(m, 3H), 7.40 (t, 1H), 7.28 (t, 1H), 7.19 (t, 2H). 13C NMR
(CDCl3): δ 119.9, 126.5, 127.3, 128.0, 128.8, 128.9, 129.0, 129.1,
129.2, 129.7, 130.2, 132.2, 136.7, 138.3, 139.5, 140.4, 147.4,
156.2, 198.4.
10-Ben zo[h ]qu in olin -6-ylben zop h en on e, 12. Compound
9 (500 mg, 1.35 mmol), PhLi (1.8 M, 0.8 mL, 1.44 mmol), and
Et2O (20 mL) were used to prepare compound 12 (160 mg,
41%). Fp: 148 °C. Elemental anal. Calcd for C20H13NO: C,
84.78; H, 4.62; N, 4.94. Found: C, 84.58; H, 4.68; N, 5.01. IR
(CH2Cl2) ν(ArCOAr′): 1670.4. MS (EI): 283.1 (M+), 254.1,
206.1, 178.1. High-resolution MS (EI) calcd for C20H13NO:
283.0997. Found (intensity (%)): 283.1002 (40.35). 1H NMR
(CDCl3): δ 8.48 (dd, 1H), 8.07 (dd, 1H), 8.03 (dd, 1H), 7.88 (d,
Gen er a l P r oced u r e for th e Syn th esis of F u n ction a l-
ized Ar om a tic Keton es. To a solution of the starting
complex in dry Et2O was added 1 equiv of PhLi at -60 °C.
The temperature was slowly raised to 20 °C during 2 or 3 h.
The color of the mixture changed from bright yellow to deep
orange-brown. The reaction mixture was stirred for ap-
proximately 1 h at room temperature, the vessel opened to
air, and ca. 0.5 mL of water added. The brownish suspension
that formed rapidly was filtered through a plug of Celite and
the filtrate dried over Na2SO4 and stripped of solvents. The
crude residue was then separated by silica gel chromatogra-
phy. A strong band corresponding to the organometallic
substrate was eluted with a CH2Cl2-hexane (30:70) mixture.
The organic products, e.g., the aromatic ketones, were eluted
with pure CH2Cl2, and the eluate was stripped of solvent. The
resulting oil was recrystallized from a hexane-CH2Cl2 mixture
and the purity of the solid compound checked by GC-MS.
2-P yr id in -6-ylben zop h en on e, 10. Compound 1 (424 mg,
1.31 mmol), PhLi (1.8 M, 0.73 mL, 1.30 mmol), and Et2O (20
mL) were used to prepare compound 10 (136 mg, 40% yield).
Fp: 109 °C. Elemental anal. Calcd for C22H15NO: C, 83.37;
H, 5.05; N, 5.40. Found: C, 83.37; H, 5.10; N, 5.38. IR (CH2-
Cl2) ν(ArCOAr′): 1668.2. MS (EI): 259.0 (M+), 230.1, 182.0,
1H), 7.75 (m, 4H), 7.61 (dd, 1H), 7.40 (t, 1H), 7.30 (m, 3H). 13
C
NMR (CDCl3): δ 121.7, 126.2, 126.4, 127.0, 127.8, 127.9, 128.3,
128.8, 129.0, 129.2, 131.8, 133.9, 135.4, 139.0, 139.3, 144.7,
147.2, 198.7.
Ack n ow led gm en t. We thank the Alexander von
Humboldt-Stiftung for having enabled the initiation of
this project by sponsoring one of us (J .-P. D.). We also
gratefully acknowledge the support provided by the
Centre National de la Recherche Scientifique, the Deut-
sche Forschungsgemeinschaft (SFB 334), and the Fonds
der Chemischen Industrie. We also thank Mrs. Ulrike
Weynand (University of Bonn) for carrying out the low-
temperature NMR experiments.
Su p p or tin g In for m a tion Ava ila ble: Listings of atomic
coordinates and isotropic displacement parameters, H atom
coordinates and isotropic displacement parameters, anisotropic
displacement parameters (U values), and bond distances and
angles for 4a and IR spectra of 1 (7 pages). Ordering
information is given on any current masthead page.
OM970629J