Optically active transition-metal complexes, 8. - Transition-metal complexes of the optically active cyclopentadienyl ligand PinCp: Crystal structure of (S(Re))-(η5-PinCp)Re(No)(PPh3)[CONHCH(CH3)C10H7

Article abstract of DOI:10.1002/(sici)1099-0682(199909)1999:9<1497::aid-ejic1497>3.0.co;2-6

The synthesis of (η⁵-PinCp*)Re(CO)₃ [PinCp* = tetramethyl(pinanyl)cyclopentadienyl] is described. Successive substitution of two CO ligands by NO⁺ and PPh₃ generates a 1.1 diastereomeric mixture of chiral-at-met

Full text of DOI:10.1002/(sici)1099-0682(199909)1999:9<1497::aid-ejic1497>3.0.co;2-6

FULL PAPER
Optically Active Transition-Metal Complexes, 8[°]
Transition-Metal Complexes of the Optically Active
Cyclopentadienyl Ligand PinCp*: Crystal Structure of
(SRe)-(η5-PinCp*)Re(NO)(PPh3)[CONHCH(CH3)C10H7]
Albrecht Salzer,*[a] Annegret Hosang,[a] Jutta Knuppertz,[a] and Ulli Englert[a]
Dedicated to Professor Helmut Werner on the occasion of his 65th birthday
Keywords: Half-sandwich complexes / Molybdenum / Optically active complexes / Rhenium / Tungsten
The synthesis of (η5-PinCp*)Re(CO)3 [PinCp*
=
tetra-
analysis. By treating the (SRe)-amide with CF3CO2H and
NaBF4, (SRe)-(PinCp*)Re(CH3)(NO)(PPh3) can be generated.
Protolysis of this compound with HBF4/Et2O in CD2Cl2 at –
methyl(pinanyl)cyclopentadienyl] is described. Successive
substitution of two CO ligands by NO+ and PPh3 generates
a 1:1 diastereomeric mixture of chiral-at-metal [(SRe)/(RRe)-
(PinCp*)Re(CO)(NO)(PPh3)]BF4. The diastereomers are
converted with sodium methoxide into the derivative
“esters” (SRe)/(RRe)-(PinCp*)Re(COOCH3)(NO)(PPh3), and
then with (+)-(R)-(1-naphthylethyl)amine to the “amides”
(SRe)/(RRe)-(PinCp*)Re(NO)(PPh3)[CONHCH(CH3)C10H7]
[(SRe)/(RRe) = 1:1]. Fractional crystallisation separates the
(SRe) isomer with an optical purity of Ͼ 98%. The latter
compound has been characterized by X-ray structure
78 °C leads to the solvent-stabilized complex (SRe)-[(PinCp*
–
)Re(NO)(PPh3)(ClCD2Cl)]+BF4
.
The
thermal
and
configurational stability of this chiral Lewis acid is
investigated at various temperatures. The syntheses of
[PinCp*RhCl2]2, PinCp*TiCl3 and PinCp*M(CO)2(NO) (M =
Mo, W) are also described. Starting with PinCp*
M(CO)2(NO), the relatively stable 16-VE complexes PinCp*
MCl2(NO) and PinCp*W(CH2SiMe3)2(NO) are synthesized.
figuration at the stereogenic metal centre up to their de-
composition points at Ϫ20°C.
Introduction
Recently, Gladysz et al.[7] have extended their studies to
the peralkylated derivative (SRe)-[(η5-C5Me5)Re(NO)-
(PPh3)(ClCD2Cl)]ϩBF4Ϫ, under the assumption that peral-
kylated ligands should enhance the thermal and configura-
tional stability of the chiral Lewis acid by either shielding
the central metal atom through the bulk of the ligand, or by
stabilizing the cationic centre through the electron-donating
effect of the five alkyl groups. Surprisingly, they found that
Chiral Lewis acids, derived from transition-metal com-
plexes, play an increasingly important role in enantioselec-
tive organic synthesis.[1Ϫ4] Both their thermal as well as
their configurational stability are essential for their appli-
cation as catalysts in asymmetric synthesis. While Gladysz
et al.[4] have investigated the stability of the chiral-at-metal
Lewis acid (SRe)-[(η5-C5H5)Re(NO)(PPh3)(ClCD2Cl)]ϩ
BF4Ϫ, our group has studied the behaviour of a chiral
Lewis acid incorporating an optically active cyclopen-
tadienyl ligand, namely (SRe)-[(η5-PCp)Re(NO)(PPh3)-
decomposition
of
(SRe)-(η5-C5Me5)Re(NO)(PPh3)-
(ClCD2Cl)]ϩBF4Ϫ seems to occur even below Ϫ35°C. They
also noticed that products formed by addition of nucleo-
philes at lower temperatures were only recovered with a
maximum enantiomeric purity of 90%. Because spectro-
scopic methods for directly determining the conformational
stability of enantiomers are limited, Gladysz et al. were not
able to fully rationalize their observations.
Ϫ
(ClCD2Cl)]ϩ-BF4 (PCp ϭ “pinene-fused cyclopenta-
dienyl”).[5][6] Gladysz determined the configurational sta-
Ϫ
bility of (SRe)-[(η5-C5H5)Re(NO)(PPh3)(ClCD2Cl)]ϩBF4
by either investigating the optical purity of the decompo-
sition products formed after warming above Ϫ20°C, or by
analysing the products generated when nucleophiles are ad-
As our previous work[6] had shown that the fate of a
stereogenic metal centre could be easily monitored by low-
temperature NMR spectroscopy when an optically active
cyclopentadienyl ligand is present, we also investigated the
synthesis and stability of a chiral Lewis acid derived from
a peralkylated, optically active ligand such as PinCp*
[PinCp* ϭ tetramethyl(pinenyl)cyclopentadienyl], a ligand
that has been first introduced by Lai et al.[8] This ligand,
like PCp used by us before, should serve as an internal chi-
ral probe to directly determine the stability of peralkylated
derivatives of GladyszЈ chiral Lewis acids. We also wanted
ded at low temperatures. The configurational stability of
Ϫ
(SRe)-[(η5-PCp)Re(NO)(PPh3)(ClCD2Cl)]ϩBF4
,
on the
other hand, was determined by low-temperature 31P-NMR
spectrocopy, where the optically active cyclopentadienyl li-
gand served as an internal spectroscopic probe of dia-
stereomeric purity. Both systems show no inversion of con-
[°]
Part 7: Ref.[27]
[a]
Institut für Anorganische Chemie, RWTH Aachen,
D-52056 Aachen, Germany
Fax: (internat.) ϩ 49-(0)241/888-8288
E-mail: albrecht.salzer@ac.rwth-aachen.de
Eur. J. Inorg. Chem. 1999, 1497Ϫ1505
WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999
1434Ϫ1948/99/0909Ϫ1497 $ 17.50ϩ.50/0
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A. Salzer, A. Hosang, J. Knuppertz, U. Englert
FULL PAPER
to show that this ligand could be universally used as a chiral spectra each have two sets of signals due to the two dia-
replacement for Cp* by incorporating it into a series of stereomers. The signals of the diastereomeric CO ligands
other organometallic compounds.
are quite interesting, because they appear as two doublets
at δ ϭ 202, each with a coupling constant of 8.3 Hz. There
was, unexpectedly, only one signal for both diastereomers
in the 31P-NMR spectrum, both in [D6]acetone and in
[D3]nitromethane.
Results and Discussion
1. Synthesis of a Diastereomeric Mixture of
(SRe)/(RRe)-(η5-PinCp*)Re(CH3)(NO)(PPh3)
The ligand PinCp* was prepared from optically active
(ϩ)-pinanaldehyde,[9] which was oxidized to the (ϩ)-car-
boxylic acid and then converted in several steps into a per-
alkylated cyclopentadiene ligand, as described by Lai for
the other enantiomer[8] (Scheme 1).
Scheme 2
The reduction of the CO ligand to a methyl group was
achieved in a two-step reaction with Li(C2H5)BH3 and
BH3·THF.[11] After workup, (SRe)/(RRe)-(η5-PinCp*)-
Re(CH3)(NO)(PPh3) (4a/4b) was obtained as a red powder.
The IR spectrum had one characteristic band for the NO
ligand, while the 1H- and 13C-NMR spectra again con-
tained two sets of signals for the two diastereomers. In the
1H-NMR spectrum, the four methyl groups of the five-
membered ring and the three methyl groups of the pinanyl
part of each diastereomer overlapped. These signals there-
fore cannot be assigned unambiguously. Two signals, one at
δ ϭ 25.7 and one at δ ϭ 23.4, appeared in the 31P-NMR
Scheme 1
Following the same method as before,[6] (η5-PinCp*)- spectrum of the diastereomeric complexes. Because one of
Re(CO)3 (1) was synthesized in good yield by reaction of these signals is sharp and the other one is broad, it appears
[Re(CO)3(THF)2]Cl with PinCp*Li in THF (Scheme 2). Be- as if one of the two diastereomers is undergoing hindered
cause the peralkylated ligand has homotopic faces, only one ligand rotation. Measurements at low temperature con-
product is generated and no separation step is required. In firmed that the broadened signal disappears below 0°C; two
line with the work of Gladysz et al.,[10] the tricarbonyl com- new signals, at a 3.5:1 ratio, appeared below Ϫ25°C. The
plex was treated with freshly prepared NOBF4 in CH2Cl2 sharp signal for the other diastereomer is retained through-
at 0°C to form [(η5-PinCp*)Re(CO)2(NO)]ϩ (2) as yellow out this experiment. That the original spectrum was ob-
crystals after workup. The two diastereotopic CO groups served again after the NMR sample was warmed up, con-
could now be distinguished in the 13C-NMR spectrum as firms that hindered ligand rotation is a likely explanation
two singlets. Because PPh3 is less π-accepting than CO, the for this phenomenon. It is interesting, but not yet explained
second CO ligand could not be substituted directly. In a why the two diastereomers should show such disparate be-
first step, one of the CO groups had to be oxidized with haviour and which type of rotation is involved.
iodosobenzene in acetonitrile. The intermediate acetonitrile
The two signals of 4a/4b appeared in a ratio of 1:1 in
complex was then treated with an excess of PPh3 to give a the 31P-NMR spectrum, at room temp. The optically active
diastereomeric mixture of (SRe)/(RRe)-[(η5-PinCp*)- PinCp* ligand therefore caused no asymmetric induction at
Ϫ
Re(CO)(NO)(PPh3)]ϩBF4 (3a/3b), which was obtained in the rhenium stereogenic centre. A reason for this may be
excellent yield and purity. The IR spectrum contains two the high temperature required for the substitution of the
1
bands for the CO and NO ligands. The H- and 13C-NMR second CO group.
1498
Eur. J. Inorg. Chem. 1999, 1497Ϫ1505

Optically Active Transition-Metal Complexes, 8
FULL PAPER
2. Resolution of Optically Active
soluble than the mixed products (SRe,Ramid
)
and
(SRe)-(PinCp*)Re(CH3)(NO)(PPh3) (4a)
(RRe,Samid).[7] The pinanyl substituent in 6a adopts a con-
formation in which the methyl group points away from the
metal centre and the dimethylmethylene bridge lies parallel
to the plane of the cyclopentadienyl ring. This is very simi-
lar to the stereochemistry found in LaiЈs molybdenum com-
pound.[8]
Usually, mixtures of diastereomers can be separated by
fractional crystallization or by chromatography. In our case,
fractional crystallization was not possible because of the
poor crystallinity of the mixture of (SRe)/(RRe)-(η5-PinCp*)-
Re(CH3)(NO)(PPh3). Also, no solvent mixture could be
found to separate the diastereomers by preparative MPLC.
We therefore followed the route of Gladysz et al. for the
separation of (SRe)/(RRe)-(η5-C5Me5)Re(CH3)(NO)(PPh3)[7]
by using a suitable derivative.
The starting material for the separation was the complex
Ϫ
(SRe)/(RRe)-[(η5-PinCp*)Re(CO)(NO)(PPh3)]ϩBF4
(3a/
3b), which was treated with sodium methoxide in methanol
to give the methyl ester (SRe)/(RRe)-[(η5-PinCp*)Re(CO-
OMe)(NO)(PPh3) (5a/5b) in excellent yield (Scheme 3). The
31P-NMR spectrum contained two sharp singlets in a ratio
of 1:1. We could determine the ratio of the two dia-
stereomers by using the two singlets of the methoxy groups
at δ ϭ 3 in the 1H-NMR spectrum. The CO groups appear
in the 13C-NMR spectrum as two doublets at δ ϭ 203 and
202, with JCϪP ϭ 13.8 Hz.
Figure 1. Crystal structure of (SRe)-(η5-PinCp*)Re(NO)(PPh3)-
[CONHCH(CH3)C10H7] (6a)
The enantiomerically pure amide was treated with tri-
fluoroacetic acid at 0°C, which recovered the cationic, op-
tically pure carbonyl complex, which was then isolated as
the tetrafluoroborate salt (SRe)-[(η5-PinCp*)Re(CO)-
Ϫ
NO(PPh3)]ϩBF4 (3a). By following this procedure with
the other diastereomer, recovered by concentration of the
mother liquor of the resolution step, the (RRe)-carbonyl
complex could also be obtained in 80% optical purity. The
reduction of pure 3a to the methyl complex 4a was carried
out as described above for the diastereomeric mixture. The
31P-NMR spectrum of (SRe)-(η5-PinCp*)Re(CH3)(NO)-
(PPh3) (4a) shows the broadened signal of the diastereomer
undergoing hindered rotation. This signal, upon cooling,
underwent the same changes as described before.
3. Formation and Stability of the Diastereomeric
Scheme 3
Mixture of (SRe)/(RRe)-[(η5-PinCp*)-
Ϫ
Re(NO)(PPh3)(ClCD2Cl)]؉BF4 (7a/7b) and
Its Optically Pure (SRe) Isomer
The methyl ester complexes were then treated with com-
mercially available (ϩ)-(R)-(1-naphthyl)ethylamine in
CH2Cl2 to obtain the amide complexes 6a/6b. The solvent
was evaporated and the residual orange oil was stirred in n-
The chiral Lewis acid (SRe)/(RRe)-[(η5-PinCp*)-
Ϫ
hexane. An orange solid separated, which was collected by Re(NO)(PPh3)(ClCD2Cl)]ϩBF4 (7a/7b) was generated as
filtration, and recrystallized from benzene/n-hexane as crys- described before.[5][12] The diastereomers were dissolved in
tals of one single diastereomer in an optical purity of > CD2Cl2 in an NMR tube and treated with HBF4 at Ϫ78°C.
98%, as determined by 1H- and 31P-NMR spectra The 31P-NMR spectrum, measured directly after shaking
(Scheme 3).
the reaction mixture, had three sharp signals of different
This less soluble diastereomer was identified by a crystal- intensity at δ ϭ 14, assignable to the two diastereomeric
structure determination to be (SRe)-(η5-PinCp*)Re(NO)- cations where one cation is a mixture of two rotamers. Ad-
(PPh3)[CONHCH(CH3)C10H7] (6a) (Figure 1). These ob- ditional signals appeared at δ ϭ 15 and 11 and seem to be
servations agree with GladyszЈ findings for (η5-C5Me5)Re- decomposition products. When the solution was warmed,
(NO)(PPh3)[CONHCH(CH3)C10H7], where the symmetri- one of the three signals of the chiral Lewis acid remained
cal products (SRe,Samid) and (RRe,Ramid) were also more unchanged, while the two others became broad. This behav-
Eur. J. Inorg. Chem. 1999, 1497Ϫ1505
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A. Salzer, A. Hosang, J. Knuppertz, U. Englert
FULL PAPER
iour is similar to that of the diastereomeric mixture of the
The chiral Lewis acid decomposition products whose sig-
complex (SRe)/(RRe)-[(η5-PinCp*)Re(CH3)(NO)(PPh3) de- nals were observed at δ ϭ 15 appeared to be more stable.
scribed above. Warming to Ϫ20°C resulted in a rapid de- By comparing[12][13] the 31P-NMR and IR data of the anal-
crease in the intensity of the three signals and a concomi- ogous PCp and Cp* complexes, we deduced this species to
tant growth of the signals at δ ϭ 11 and 15. The signal at be a diastereomeric mixture of (SRe)/(RRe)-(η5-PinCp*)-
δ ϭ 11 appeared as two singlets in a ratio of 1:1, one of ReCl(NO)(PPh3) (8a/8b). This could have formed directly
them sharp, the other one broadened.
by nucleophilic substitution of the stabilizing solvent mol-
We then repeated the same experiment with optically ecule by a chloride anion, available from a small amount of
pure (SRe)-[(η5-PinCp*)Re(CH3)(NO)(PPh3). We expected DCl in the solvent. On the other hand, it could have formed
to see only the two signals of the (SRe) isomer, but surpris- by loss of CD2Clϩ from the ReIII species. We favour the
ingly we also immediately observed the third signal due to second pathway because the signal at 1746 cmϪ1 disappears
the second diastereomer. This indicates that inversion at the in favour of the signal at 1641 cmϪ1 (Scheme 4).
metal centre starts taking place directly after mixing the
compounds at Ϫ80°C. A noticeable amount of decompo-
sition products was also observed at this temperature. At
Ϫ60°C, the two diastereomers approached a ratio of 1:1,
which was reached at Ϫ40°C. At Ϫ20°C, the cation had
completely disappeared and the two signals at δ ϭ 11 were
again apparent as one sharp and one broadened signal. The
IR spectrum of the reaction mixture, measured at room
temperature, contained two NO signals, one at 1746 cmϪ1
,
and one at 1641 cmϪ1; they are assigned to the main de-
composition products at δ ϭ 11 and 15.
These results clearly show that the chiral Lewis acid
Ϫ
(SRe)-[(η5-PinCp*)Re(NO)(PPh3)(ClCD2Cl)]ϩBF4 has an
extremely low configurational stability. Even at Ϫ80°C, a
small amount of the inversion product can be detected and
at Ϫ40°C complete inversion has occurred. These con-
clusions could be drawn solely on the basis of low-tempera-
ture 31P-NMR spectroscopy and they confirm the results
obtained by Gladysz et al. for the Cp* complex. GladyszЈ
observations, that the optically purity of the Lewis acid di-
minishes on reaction with another nucleophile can now be
explained: Inversion at the metal centre already starts oc-
curring shortly before the CD2Cl2 ligand is exchanged for
a new nucleophile.
Scheme 4
To confirm this, we synthesized the chloride complex in-
dependently, following the route that Gladysz used for the
Cp* complex.[13] After formation of the chiral Lewis acid,
methyltriphenylphosphonium iodide was added. The solu-
tion turned red and the product could be identified by IR,
1H-, 13C-, 31P-NMR, and MS data to be the expected chlo-
ride species (8a/8b). The IR and 31P-NMR signals were
identical to those of the previous NMR experiments. The
31P-NMR spectrum of 8a/8b contained a sharp and a broad
signal. The broadened signal disappeared upon cooling be-
low 0°C and two new signals appeared upon further cool-
ing. The sharp signal does not change during this time. The
same behaviour was previously observed for (SRe)/(RRe)-
[(η5-PinCp*)Re(CH3)(NO)(PPh3). Again, a hindered ligand
rotation associated most likely with the bulky PinCp* li-
gand occurs within the (SRe) isomer, but not in the case of
the (RRe) isomer. It remains unclear why this phenomenon
should so persistently be restricted to only one of the two
diastereomers.
To find an explanation for the thermal and configura-
tional
instability
of
the
complex
[(η5-Cp*)-
Re(NO)(PPh3)(ClCD2Cl)]ϩBF4Ϫ, Gladysz et al. examined
the products formed on warming the solution. They found
that oxidative addition of the dichloromethane fragment
takes place to give the cationic complex [(η5-PinCp*)-
Re(NO)(PPh3)(CD2Cl)Cl]ϩBF4Ϫ. This ReIII species gives
rise to a singlet at δ ϭ 11 in its 31P-NMR spectrum and an
NO band at 1739 cmϪ1 in its IR spectrum. It was rational-
ized that the electron-rich permethylated complex confers
stability to this unexpected ReIII species; this favours the
formation of a higher oxidation species, which, contrary to
expectations, lowers the stability of the chiral Lewis acid.
As we also saw two signals at δ ϭ 11 in the 31P-NMR
spectra and a signal at 1746 cmϪ1 in the IR spectra, we
tried to isolate [(η5-PinCp*)Re(NO)(PPh3)(CD2Cl)Cl]ϩ-
4. Synthesis of Other Metal Complexes of the Chiral
Cyclopentadienyl Ligand PinCp*
Ϫ
BF4 by dissolving the dried residue of the NMR sample
in a small amount of THF and precipitating it with ether.
A solid appeared, which dissolved again after being stirred
As rhodium complexes with a chiral cyclopentadienyl li-
for a short time. If this precipitate was in fact the ReIII gand are known to be useful in asymmetric hydrogen-
species, of which we are sure, it must be quite unstable in ations,[14] we also synthesized a corresponding PinCp*
the case of the PinCp* complex.
complex. We prepared [PinCp*RhCl2]2 (9) by heating
1500
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Optically Active Transition-Metal Complexes, 8
FULL PAPER
RhCl3·3H2O and PinCp*H in methanol under reflux for a
few days (Scheme 5). After the solvent was evaporated, a
red solid was collected in reasonable yields, which was
1
characterized by H- and 13C-NMR spectroscopy and el-
emental analysis. We are currently trying to perform these
experiments in the presence of zeolites to prepare a corre-
sponding “ship-in-the-bottle” complex and to test 9 as a
catalyst precursor in enantioselective hydrogenation.
Scheme 5
Chiral cyclopentadienyl ligands are also often attached
to early transition metals like Ti, Zr, and Hf.[15] Such com-
plexes may be efficient Ziegler-Natta polymerization cata-
lysts, or catalyse enantioselective synthesis. We prepared the
complex (PinCp*)TiCl3 (10) by treating TiCl3·3THF with
PinCp*Li in DME under reflux.[16] After workup, a red
1
solid was isolated and characterized by H- and 13C-NMR
and MS data to be PinCp*TiCl3. Extraction of the remain-
ing solid with CCl4 did not lead to the isolation of the ex-
pected doubly substituted product (PinCp*)2TiCl2. The re-
Scheme 7
action with PinCp* therefore takes a different route from sponding molybdenum compounds,[20] we restricted our in-
that with Cp*, where Cp*2TiCl2 is the major product under vestigations to the former. The NO group of the dialkylated
the same reaction conditions (Scheme 6).
product (PinCp*)W(NO)(CH2SiMe3)2 (15) has an IR ab-
sorption at 1582 cmϪ1 which agrees with a weakening of
the NϪO bond as found by Legdzins et al. in crystal struc-
1
tures. The H- and 13C-NMR spectra contain two signals
for the diastereotopic SiMe3 groups. The compound does
not appear to be as stable in solution as the corresponding
Cp* complex, but it can be stored at room temperature as
a solid. We could also obtain a monoalkylated product as
a red oil by using only half an equivalent of the magnesium
reagent and strict temperature control, but this product was
Scheme 6
Legdzins et al. have prepared many complexes with the too unstable to be isolated and fully characterized in ana-
14-VE backbone CpЈM(NO) [M ϭ Mo, W; CpЈ ϭ C5H5 or lytically pure form.
C5Me5].[17] Their aim was to synthesize stable 16-VE com-
We also tried to generate a new stereogenic centre at the
plexes of the type CpЈM(NO)(R)(RЈ), where the alkyl or metal atom by a thermal or photochemical substitution of
aryl substituents could be equivalent or different from each one of the CO groups in (PinCp*)W(CO)2(NO). Brunner[21]
other. To synthesize such a complex with the chiral ligand had reported an efficient substitution of PPh3 for CO to
PinCp* we followed the procedure published for Cp*.[18] generate the complex CpMo(CO)(NO)(PPh3) in refluxing
[(η5-PinCp*)M(CO)3]Ϫ was synthesized by treating M(CO)6 toluene. He obtained quantitative yields, while another
with PinCp*Li in THF. The anion was then directly con- group[22] claimed that this substitution does not take place
verted into the neutral, coordinatively saturated complexes even at very high temperatures. We treated (PinCp*)Mo-
(η5-PinCp*)M(CO)2(NO) (11,12) without further purifi- (CO)2(NO) with PPh3 in refluxing toluene over several
cation by treating the tricarbonyl complex with Diazald. hours. No substitution could be observed, which may be
The product was purified by sublimation and excess Diaz- either because the PinCp* ligand is more electron-donating
ald was separated by column chromatography (hexane/ or because of steric hindrance. A photochemical ligand ex-
ether, 4:1). The reaction of the nitrosyl complexes with PCl5 change also did not occur by irradiation in toluene, where
in ether yielded the 16-VE complexes (PinCp*)MCl2(NO) after one hour the starting material had completely decom-
(13,14) as poorly soluble, green solids (Scheme 7).
posed.
The nitrosyl dichloride complex was alkylated with
PinCpH* also reacts with carbonyliron and -ruthenium
(Me3SiCH2)2Mg·(dioxane)2 at very low temperatures.[19] As complexes to form dimeric carbonyl complexes. These will
the Cp* tungsten complex was more stable than the corre- be described elsewhere.
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A. Salzer, A. Hosang, J. Knuppertz, U. Englert
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1.26 (s, 3 H, H-9), 1.19 (s, 1 H), 1.16 (s, 3 H, H-8), 1.02 (d, JHϪH ϭ
7.0 Hz, 2 H). Ϫ 13C NMR (CDCl3): δ ϭ 198.1 (CO), 105.5, 100.9,
98.4, 96.9 (C5Me4), 49.2 (C-5), 43.2 (C-1), 39.42, 34.4 (C-2/6/10),
39.1 (br., C-3), 33.9 (C-4), 28.7, 23.5 (C-8/9), 21.2 (C-7), 12.0, 10.9,
10.8 (C5Me4). Ϫ C22H29O3Re (527.66): calcd. C 50.08, H 5.54;
found C 50.08, H 5.52.
Conclusion
The optically active peralkylated ligand PinCp*H can be
introduced into a series of metal complexes of titanium,
molybdenum, tungsten, rhenium and rhodium. In most
cases, these new complexes have properties similar to those
of the corresponding Cp* complexes. The PinCp* ligand
can serve as an internal spectroscopic probe for the configu-
rational stability of the chiral-at-metal Lewis acid [PinCp*
ReNO(PPh3)(ClCD2Cl)]ϩ.
Ϫ
[(η5-PinCp*)Re(CO)2(NO)]؉BF4
(2): Compound
1
(2.30 g,
4.36 mmol) was dissolved in 100 mL of CH2Cl2 and cooled to 0°C.
Freshly prepared NOBF4 (0.79 g, 6.77 mmol) was added in small
portions and CO started to evolve immediately. After 3 h of stir-
ring, the solution was poured into 300 mL of diethyl ether and a
light yellow precipitate formed. The solid was collected by filtration
and washed with diethyl ether. Recrystallisation from CH2Cl2/n-
hexane gave a yellow compound 2; yield: 2.63 g (4.27 mmol, 98%).
Experimental Section
Ϫ IR (hexane): ν˜(CO) ϭ 2093 (s), 2040 (s); ν˜(NO) ϭ 1799 (m) cmϪ1
.
General Remarks: All experiments were performed under purified
nitrogen using standard vacuum-line and Schlenk-tube techniques.
Diethyl ether and THF were distilled from sodium benzophenone
ketyl. Acetonitrile and dichloromethane were distilled from calcium
hydride. Dimethoxyethane (DME) and n-hexane were dried with
Ϫ 1H NMR ([D6]acetone): δ ϭ 3.37 (q, J ϭ 9.5 Hz, 1 H, H-4), 2.64
(s, 3 H, C5Me4), 2.57 (s, 3 H, C5Me4), 2.50 (d, JHϪH ϭ 2.8 Hz, 6
H, 2ϱ C5Me4), 2.47 (m, 1 H), 2.35 (m, 2 H), 2.12 (m, 1 H), 1.99
(m, 2 H), 1.30 (s, 3 H, H-9), 1.28 (s, 1 H), 1.22 (s, 3 H, H-8), 1.12
(d, JHϪH ϭ 7.0 Hz, 3 H, H-7). Ϫ 13C NMR ([D6]acetone): δ ϭ
187.0, 186.9 (CO), 112.1, 109.2 (C5Me4), 49.9 (C-5), 43.8 (C-1/3),
40.1, 38.3, 34.9 (C-2/6/10), 35.2 (C-4), 29.0, 23.7 (C-8/9), 21.4 (C-
7), 11.9, 11.7, 10.5, 10.3 (C5Me4). Ϫ C21H29BF4NO3Re (616.47):
calcd. C 40.91, H 4.74, N 2.27; found C 40.56, H 2.25, N 2.25.
molecular sieves. [Re(CO)3(THF)2]Cl,[23] NOBF4,[24] iodosoben-
[26]
zene,[25] [(Me3Si)CH2Mg]·(dioxane)2
and PinCp*[8] were pre-
pared as described in the literature. (ϩ)-3-Formylpinane was a gift
from BASF. Ϫ Infrared spectra were recorded with a PerkinϪ
Elmer 1750 FT spectrophotometer as solutions in n-hexane,
CH2Cl2, or DME in NaCl cells. Ϫ NMR spectra were recorded
with either a Varian VXR 300 or a Varian Unity 500 spectrometer
in CDCl3 or C6D6 unless otherwise stated. 1H- and 13C-NMR spec-
tra were referenced to tetramethylsilane (TMS) or from internal
solvent peaks; 31P-NMR spectra were referenced to H3PO4 (exter-
nal). All 13C- and 31P-NMR data are of proton-decoupled (broad-
band) spectra.
Ϫ
(SRe)/(RRe)-[(η5-PinCp*)Re(CO)(NO)(PPh3)]؉BF4 (3a/3b): The
nitrosyl complex 2 (2.56 g, 4.16 mmol) was dissolved in 50 mL of
acetonitrile and freshly prepared iodosobenzene (1.05 g,
4.78 mmol) was added at 0°C. CO2 evolution started immediately
and the solution was stirred until the solid had dissolved (about
1.5 h). The solution was filtered through 2 cm of silica gel and after
evaporation
of
the
solvent
(SRe)/(RRe)-[(η5-PinCp*)Re-
Ϫ
(CH3CN)(NO)(PPh3)]ϩBF4 was obtained as a brown oil. Ϫ
IR (CH3CN): ν˜(CO) ϭ 2010 (s), ν˜(NO) ϭ 1743 cmϪ1. Ϫ The oil was
dissolved in 2-butanone and PPh3 (1.33 g, 5.09 mmol) was added
in small portions while stirring. The dark-brown mixture was re-
fluxed for 12 h and the solvent was removed afterwards by vacuum
distillation. The residue was recrystallized from acetone/Et2O; yield
(؉)-(1S,2S,3S,5R)-Pinane-3-carboxylic Acid: (ϩ)-3-Formylpinane
(49.8 g, 0.30 mol) was dissolved in acetone and treated slowly with
a cold saturated aqueous solution of KMnO4 (31.6 g, 0.2 mol). The
solution was stirred for 2 h at room temperature and the precipitate
of MnO2 was filtered off with a Buchner funnel, and through Ce-
lite/cotton wool. The solution was treated with solid KOH to an
approximate pH value of 12 and extracted 3 times with ether. After
acidification with concd. HCl, the aqueous solution was again ex-
tracted 3 times with ether. The organic phases were combined and
dried with MgSO4. The solvent was evaporated under reduced
pressure in a rotary evaporator, leaving a pale-yellow oil, yield
52.8 g (0.29 mol, 98%). This product was used for the further syn-
thesis of PinCp*.[8]
of yellow 3a/3b: 3.18 g (3.74 mol, 90%). Ϫ IR (CH2Cl2): ν˜(CO)
ϭ
2005 (s), ν˜(NO) ϭ 1747 (s) cmϪ1. Ϫ 1H NMR ([D6]acetone): δ ϭ
7.70Ϫ7.50 (m, 30 H, PPh3), 3.45 (q, JHϪH ϭ 9.46 Hz, 1 H, H-4),
3.40 (q, JHϪH ϭ 7.02, 1 H, H-4Ј), 2.85 (s, 3 H), 2.50 (s, 3 H), 2.46
(m, 1 H), 2.38 (m, 3 H), 2.31 (s, 3 H), 2.27 (s, 3 H), 2.16 (m, 3 H),
2.00 (m, 2 H), 1.86 (s, 3 H), 1.71 (s, 3 H), 1.51 (s, 3 H), 1.33(s, 1
H), 1.30 (m, 6 H), 1.27 ( s, 3 H), 1.24 (s, 3 H), 1.12 (m, 6 H). Ϫ
13C NMR ([D6]acetone): δ ϭ 201.8 (d, JCϪP ϭ 12.6 Hz, CO), 201.4
(d, JCϪP ϭ 12.6 Hz, COЈ), 134.3 (d, JCϪP ϭ 11.4 Hz, C-b), 134.1
(d, JCϪP ϭ 11.4 Hz, C-bЈ), 133.3 (dd, JCϪP ϭ 6.6 Hz, C-d/dЈ), 131.2
(d, JCϪP ϭ 12.6 Hz, C-a/aЈ), 130.7 (d, JCϪP ϭ 11.4 Hz, C-c), 130.6
(d, JCϪP ϭ 11.4 Hz, C-cЈ), 115.5, 114.7, 109.7, 107.5, 106.0
(C5Me4), 50.2 (C-5/5Ј), 44.4 (br. s, C-3/3Ј), 43.9, 43.7 (C-1/1Ј), 40.2,
40.1 (C-10/10Ј), 37.8, 36.3 (C-4/4Ј), 35.9, 35.6, 34.9 (C-2/2Ј/6/6Ј),
29.4, 29.0, 23.9, 23.7 (C-8/8Ј/9/9Ј), 21.8, 21.7 (C-7/7Ј), 15.1, 11.8,
11.6, 10.2, 10.0, 9.8, 9.4 (C5Me4). Ϫ 31P NMR ([D6]acetone): δ ϭ
12.9. Ϫ C38H44BF4NOPRe (834.71): calcd. C 53.65, H 5.21, N
1.65; found C 52.98, H 5.22, N 1.64.
[(η5-PinCp*)Re(CO)3 (1): PinCp*H (5.16 g, 20.0 mmol) was dis-
solved in 80 mL of THF and cooled to ؊78°C. nBuLi (1.6  in hex-
ane, 20 mmol, 12.5 mL) was added by syringe while the solution
was stirred. The mixture was allowed to warm to room temperature
and was then refluxed for 14 h. PinCp*Li precipitated as a white
solid. The solvent was removed by vacuum distillation and the
product was washed twice with 100 mL of n-hexane. The white
solid was dissolved in 50 mL of THF, cooled to 0°C, and a solution
of 20.0 mmol of [Re(CO)3(THF)2]Cl in THF was added dropwise.
The solution was then refluxed for 12 h and, after cooling to room
temperature, the solvent was removed by vacuum distillation. The
residue was extracted with hot n-hexane and filtered hot through
Celite. After concentrating the solution, the product precipitated at
(SRe)/(RRe)-(η5-PinCp*)Re(CH3)(NO)(PPh3) (4a/4b): The dia-
stereomeric mixture of 3 (1.56 g, 1.83 mmol) was suspended in
Ϫ30°C as an off-white solid; yield: 10.00 g (19.0 mmol, 95%). Ϫ 50 mL of THF and 3.7 mL of Li(C2H5)3BH in THF (1  in THF,
IR (n-hexane): ν˜(CO) ϭ 2014 (s), 1923 (s) cmϪ1. Ϫ 1H NMR
3.7 mmol) was injected. The precipitate dissolved slowly, while the
(CDCl3): δ ϭ 2.94 (q, JHϪH ϭ 9.5 Hz, 1 H, H-4), 2.38 (m, 1 H), colour of the solution became honey-brown. Then 9.2 mL of
2.27 (s, 3 H, C5Me4), 2.21 (s, 3 H, C5Me4), 2.17 (d, JHϪH ϭ 7.3 Hz, 0.776  BH3·THF in THF (7 mmol) was added. H2 evolution oc-
6 H, C5Me4), 2.08 (m, 3 H, H-9), 1.90 (t, JHϪH ϭ 5.5 Hz, 2 H),
curred immediately and the solution was stirred for 30 min. The
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Eur. J. Inorg. Chem. 1999, 1497Ϫ1505

Optically Active Transition-Metal Complexes, 8
FULL PAPER
solvent was then removed and the residue extracted with toluene
and passed through a short silica gel column. The solvent was eva-
porated to give complex 4a/4b as a red powder; yield 1.31 g
de. Ϫ IR (CH2Cl2): ν˜(NO) ϭ 1624 (s), ν˜(CO) ϭ 1533 (m) cmϪ1. Ϫ
1H NMR (CDCl3): δ ϭ 8.16 (d, JHϪH ϭ 7.32 Hz, 1 H), 7.78 (d,
JHϪH ϭ 7.94 Hz, 1 H), 7.67 (dd, JHϪH ϭ 1.83 Hz, JϽinf'HϪHϽ/
(1.74 mmol, 95%). Ϫ IR (hexane): v(NO) ϭ 1634 (s) cmϪ1. Ϫ 1H INF' ϭ 6.91 Hz, 1 H), 7.55 (t, JHϪH ϭ 8.55 Hz, 6 H, H-b), 7.39
NMR (CDCl3): δ ϭ 7.50Ϫ7.32 (m, 30 H, PPh3), 3.22 (q, JHϪH
ϭ
(m, 13 H, H-c/d/naphthyl), 5.76 (quint, JHϪH ϭ 6.87 Hz, 1 H,
9.46 Hz, 1 H, H-4), 3.13 (q, JHϪH ϭ 9.46 Hz, 1 H, H-4Ј), 2.38 (m, NCH), 5.26 (s, 1 H, NH), 3.08 (q, JϽinf'H&NDASH;HϽ/INF' ϭ
2 H), 2.28 (m, 2 H), 2.21 (m, 2 H), 2.06 (s, 3 H), 2.00(m, 1 H), 1.90 9.36 Hz, 1 H, H-4), 2.17 (t, JHϪH ϭ 7.48 Hz, 2 H), 2.10 (s, 3 H,
(m, 4 H), 1.82 (s, 3 H), 1.80 (s, 3 H), 1.53(s, 3 H), 1.50 (s, 3 H),
1.29Ϫ1.23 (6 s, 18 H), 1.11 (d, JHϪH ϭ 7.02 Hz, 3 H), 1.06 (d, 1 H), 1.52 (s, 3 H, CH3), 1.43 (s, 1 H), 1.26 (s, 1 H), 1.18 (s, 3 H,
JHϪH ϭ 7.02 Hz, 3 H), 0.84 (d, JHϪP ϭ 7.02, 3 H, ReϪMe), 0.79 CH3), 1.10 (s, 3 H, CH3), 1.05 (s, 3 H, CH3), 0.95 (s, 3 H, CH3),
(d, JHϪP ϭ 7.02 Hz, 3 H, ReϪMeЈ), 0.68 (s, 3 H), 0.5 (s, 3 H). Ϫ 0.84 (d, JHϪH ϭ 6.41, 1 H), 0.78 (d, JHϪH ϭ 6.71 Hz, 3 H,
13C NMR (CDCl3): δ ϭ 136.4, 136.0 (d, JCϪP ϭ 47.7 Hz, C-a), NCCH3). Ϫ 13C NMR (CDCl3): δ ϭ 199.5 (d, JHϪH ϭ 11.6 Hz,
136.0, 135.6 (d, 47.7 Hz, C-aЈ), 134.08, 134.01 (d, JCϪP ϭ 9.8 Hz, CO), 141.4 (C-Naph1), 134.2 (C-NCH), 133.9 (C-a PPh3), 131.3
C-b), 134.04, 133.96 (d, 10.4 Hz, C-bЈ), 129.5 (C-d/dЈ), 128.1, 128.0 (C-Naph8/9), 139.8, 128.3, 128.2, 128.1 (d, JHϪH ϭ 9.8 Hz), 127.1,
(C-c/cЈ), 107.5, 105.9, 103.7, 103.6, 100.4, 96.6, 95.6, 94.7 (C5Me4), 125.7, 125.3, 125.2, 124.5, 122.2 (CH-Naph, PPh3), 111.7, 101.1,
49.6, 49.5 (C-5/5Ј), 43.8 (br., C-3/3Ј), 43.2, 43.1 (C-1/1Ј), 39.6, 39.5 98.6 (C5Me4), 49.3 (C-5), 43.9, 42.9 (C-3/NaphCH3), 43.5 (C-1),
(C-10/10Ј), 35.7, 35.4, 34.8, 34.6,34.4 (C-4/4Ј/2/2Ј/6/6Ј), 28.9, 23.6, 39.3, 34.8, 34.4 (C-2/6/10), 35.0 (C-4), 28.8, 23.4 (C-8/9), 20.3 (C-
23.5 (C-8/8Ј/9/9Ј), 21.6, 21.5 (C-7/7Ј), 11.9,11.8, 10.8, 10.7, 10.6,
7), 12.0, 11.5, 10.2, 8.1 (C5Me4). Ϫ 31P NMR (CDCl3): δ ϭ 19.5.
7.6, 7.3 (C5Me4), Ϫ22.7 (d, JCϪP 7.0 Hz, ReϪMe), Ϫ24.7 (d, Ϫ C50H46O2N2PRe (924.10): calcd. C 64.29, H 6.04, N 3.00; found
CϪP ϭ 7.2 Hz, ReϪMe). Ϫ 31P NMR (C6D6): δ ϭ 25.7 (br.), 23.4. C 64.19, H 6.11, N 3.04.
CH3), 2.03 (s, 3 H, CH3), 1.89 (m, 1 H), 1.78 (t, JHϪH ϭ 5.56 Hz,
J
Ϫ C38H47NOPRe (750.92): calcd. C 60.78, H 6.31, N 1.87; found
C 59.96, H 6.33, N 1.87
(SRe)/(RRe)-(η5-PinCp*)Re(COOCH3)(NO)(PPh3) (5a/5b): The dia-
stereomeric mixture of 3a/3b (1.04 g, 1.23 mmol) was dissolved in
30 mL of dichloromethane and 2.7 mL of 4.37  sodium methoxide
(SRe)-(η5-PinCp*)Re(NO)(PPh3)(CH3) (4a): The optically pure am-
ide 6a (0.34 g, 0.36 mmol) was dissolved in 5 mL of dichlorometh-
ane and CF3COOH (68.0 mL, 0.90 mmol) was added dropwise at
0°C. The solution was stirred at this temperature for 10 min; the
orange colour changed to yellow. The solvent was removed and the
in MeOH (10.68 mmol) was added while stirring. The progress of residue was dissolved in 5 mL of MeOH. Then NaBF4 (0.075 g,
the reaction was monitored by IR spectroscopy. After the disap-
pearance of the starting material, the solvent was removed. The
residue was extracted with hot n-hexane, filtered and concentrated.
Slow cooling gave a yellow precipitate which was purified by wash-
0.72 mmol), dissolved in 2 mL of water, was added dropwise. An
additional 6 mL of water was then added and a yellow precipitate
formed. Stirring was continued for 15 min, the solid was collected
by filtation and dried in vacuo. Yield of 3a (SRe)-[(η5-PinCp*)-
Ϫ
ing with a small amount of n-hexane. Yield of 5a/5b: 1.15 g Re(CO)(NO)(PPh3)]ϩBF4
: 0.30 g (0.36 mmol, 99%). Ϫ
13C
(1.14 mmol, 93%). Ϫ IR (CH2Cl2): ν˜(NO) ϭ 1646 (s), ν˜(COOMe)
ϭ
NMR ([D6]acetone): δ ϭ 206.0 (CO), 134.3, 134.1 (d, JCϪP
ϭ
1576 (m) cmϪ1. Ϫ IR (MeOH): ν˜(NO) ϭ 1663 (s), ν˜(COOMe) ϭ 1550 11.5 Hz, C-b), 133.3 (C-d), 131.5 (C-a), 130.7, 130.5 (d, JCϪP
ϭ
(m) cmϪ1. Ϫ 1H NMR (CDCl3): δ ϭ 7.47 (m, 12 H, PPh3), 7.36(m, 11.4 Hz, C-c), 116.9, 116.1, 110.2, 107.6, 106.3 (C5Me4), 50.4 (C-
18 H, PPh3), 3.27 (q, JHϪH ϭ 9.46 Hz, 1 H, H-4), 3.17 (q, JHϪH ϭ 5), 44.3 (br., C-3), 43.9 (C-1), 40.2 (C-10), 36.5 (C-4), 36.0, 35.0 (C-
9.46 Hz, 1 H, H-4Ј), 3.03 (s, 3 H, OCH3), 2.98 (s, 3 H, OCH3), 2.36 2/6), 38.9, 23.9 (C-8/9), 21.8 (C-7), 12.3, 11.7, 10.1, 9.6 (C5Me4). Ϫ
(m, 3 H), 2.25 (s, 4 H), 2.16 (s, 2 H), 2.07 (m, 3 H), 1.97 (s, 1 H), The yellow precipitate of 3a was dissolved in 20 mL of THF and
1.91 (m, 2 H), 1.87 (s, 6 H), 1.72 (s, 3 H), 1.47 (s, 2 H), 1.31 (s, 2
0.71 mL of Li[(C3H5)3BH] in THF (1  in THF, 0.71 mmol) was
H), 1.29 (s, 1 H), 1.28 (s, 3 H), 1.24 (s, 6 H), 1.21 (m, 1 H), 1.16 added. After 20 min of stirring, 1.25 mL of BH3·THF (0.94  in
(s, 9 H), 1.08 (d, JHϪH ϭ 7.02 Hz, 3 H), 1.02 (d, JHϪH ϭ 7.02 Hz, THF, 1.34 mmol) was added dropwise. While the solution was
3 H), 0.95 (d, 3 H). Ϫ 13C NMR (CDCl3): δ ϭ 203.2 (d, JCϪP
13.7 Hz, CO), 202.6 (d, JCϪP ϭ 13.7 Hz, CO), 135.0 (d, JCϪP
25 Hz, C-a), 134.6 (d, JCϪP ϭ 25 Hz, C-aЈ), 134.2, 134.1 (d, JCϪP ϭ
3.8 Hz, C-b), 134.1, 134.0 (d, JCϪP ϭ 3.8 Hz, C-bЈ), 130.0, 129.9
ϭ
stirred for 30 min, it turned red. The solvent was removed in vacuo,
the residue taken up in toluene and passed through 3 cm of silica
gel. After evaporating the solvent in vacuo, the red solid was recrys-
tallized from n-hexane. Yield of 4a: 0.26 g (0.34 mmol, 95%). Ϫ IR
ϭ
(C-d/dЈ), 128.1, 128.0 (C-c/cЈ), 111.2, 110.6, 104.5, 104.1, 100.1, (n-hexane): nu tilde(NO) ϭ 1634 (s) cmϪ1. Ϫ 1H NMR (CDCl3):
100.0 (C5Me4), 49.7, 49.5, 49.4, 49.1 (C-5/5Ј/OCH3/OCH3Ј), 44.5, δ ϭ 7.50Ϫ7.32 (m, 15 H, PPh3), 3.22 (q, JHϪH ϭ 9.46 Hz, 1 H, H-
44.1 (br., C-3/3Ј), 43.3, 43.2 (C-1/1Ј), 39.6, 39.5 (C-10/10Ј), 36.5, 4), 2.38 (m, 1 H), 2.28 (m, 1 H), 2.21 (m, 1 H), 2.06 (s, 1 H), 2.00
35.4 (C-4/4Ј), 34.8, 34.7, 34.4, 34.3 (C-2/2Ј/6/6Ј), 28.8, 28.7, 23.6,
(m, 1 H), 1.90 (m, 1 H), 1.82 (s, 3 H), 1.50 (s, 3 H), 1.29 (s, 3 H),
23.4 (C-8/8Ј/9/9Ј), 21.7, 21.6 (C-7/7Ј), 11.9, 11.8, 11.6, 11.1, 10.9, 1.23 (s, 3 H), 1.06 (d, JHϪH ϭ 7.02 Hz, 3 H), 0.84 (d, JHϪP ϭ 7.02,
9.9, 8.9, 8.7 (C5Me4/C5Me4Ј). Ϫ 31P NMR (CDCl3): δ ϭ 18.7, 3 H, ReMe), 0.5 (s, 3 H). Ϫ 13C NMR (CDCl3): δ ϭ 136.4, 136.1
18.1. Ϫ C39H47NO3PRe (794.97): calcd. C 58.92, H 5.96, N 1.76;
found C 58.88, H 5.89, N 1.74.
(d, JCϪP ϭ 47.6 Hz, C-a), 134.1, 134.0 (d, JCϪP ϭ 10.4 Hz, C-b),
129.6 (C-d), 128.1, 128.0 (d, JCϪP ϭ 9.8 Hz, C-c), 96.6, 94.7
(C5Me4), 49.6 (C-5), 43.6 (br., C3), 43.1 (C-1), 39.6 (C-10), 35.4
(C-4), 34.9, 34.4 (C-2/6), 28.0, 23.6 (C-8/9), 21.6 (C-7), 11.8, 10.8,
10.6, 7.3 (C5Me4), 22.7, Ϫ22.8 (d, JCϪP ϭ 6.5 Hz, ReCH3). Ϫ 31P
NMR (CDCl3): δ ϭ 24.8 (br.) (25°C); 25.4 (br.), 23.1 (br.)
(Ϫ20°C); 25.5, 23.1 (Ϫ50°C). Ϫ C38H47NOPRe (750.92): calcd. C
60.78, H 6.31, N 1.87; found C 60.82, 6.38, N 1.85.
(SRe)/(RRe)-(η5-PinCp*)Re(NO)(PPh3)[CONHCH(CH3)C10H7]
(6a/6b): Compound 5a/5b (1.02 g, 1.28 mmol) was dissolved in
30 mL of CH2Cl2 and (ϩ)-(R)-1-(1-naphthyl)ethylamine (0.42 mL,
2.56 mmol) was added dropwise via a syringe. The solution was
stirred at room temperature until the reaction was completed (reac-
tion monitoring by IR spectroscopy). The solvent was then re-
moved and the oily residue was stirred in n-hexane until a yellow
precipitate formed. The solid was collected by filtration and recrys-
Ϫ
(SRe)/(RRe)-[(η5-PinCp*)Re(NO)(PPh3)(ClCD2Cl)]؉BF4
(7a/7b)
(NMR Experiment): A 5-mm NMR tube was filled with a solution
tallized from CH2Cl2/n-hexane. After a few days, orange crystals of of 4a/4b (60.0 mg, 0.08 mmol) in 0.7 mL of CD2Cl2. The NMR
(SRe)-(η5-PinCp*)Re(NO)(PPh3)[CONHCH(CH3)C10H7] (6a) had tube was cooled to Ϫ78°C and 11 µL of HBF4·Et2O (54% in Et2O,
formed. Yield: 0.35 g (0.38 mmol, 60%) of optical purity: > 98%
0.081 mmol) was added by syringe. The tube was sealed, shaken
1503
Eur. J. Inorg. Chem. 1999, 1497Ϫ1505

A. Salzer, A. Hosang, J. Knuppertz, U. Englert
FULL PAPER
quickly and a 31P-NMR spectrum was measured at Ϫ80°C im-
2.22Ϫ2.17 (m, 1 H), 2.13 (m, 1 H), 1.90 (m, 1 H), 1.80 (m, 1 H),
mediately. Ϫ 31P NMR (CD2Cl2): δ ϭ 14.7, 14.3, 14.2 (Ϫ80°C); 1.28 (s, 3 H), 1.26 (m, 2 H), 1.23 (s, 3 H), 0.95 (d, JHϪH ϭ 7.02 Hz,
14.6, 14.1, 14.0 (Ϫ60°C); 14.5 (v br.), 14.0, (br.), 13.9 (Ϫ40°C); 3 H). Ϫ 13C NMR (CDCl3): δ ϭ 148.8, 141.2, 137.9, 137.1, 134.3
13.9 (v br.), 13.8 (Ϫ20°C).
(C5Me4), 49.4 (C-5), 43.8 (br., C-3), 42.6 (C-1), 39.6 (C-10), 37.6
(C-4), 34.4, 33.5 (C-2/6), 28.8, 23.5 (C-8/9), 21.7 (C-7), 16.6, 15.6,
15.2, 14.0 C5Me4). Ϫ MS (EI): m/z (%): 375 (7) [Mϩ Ϫ Cl], 256
(80) [PinCp*ϩ]. Ϫ C19H29Cl2Ti (411.7): calcd.: C 55.43, H 7.10;
found C 56.18, H 7.21.
Ϫ
(SRe)-[(η5-PinCp*)Re(NO)(PPh3)(ClCD2Cl)]؉BF4
(7a) (NMR
Experiment): Optically pure 4a was treated the same way as the
diastereomeric mixture. Ϫ 31P NMR (CD2Cl2): δ ϭ 14.7, 14.3
(Ϫ80°C); 14.6, 14.1 (Ϫ60°C); 14.5 (v br.), 14.0, (br.) (Ϫ40°C); 13.9
(v br.) (Ϫ20°C).
(η5-PinCp*)Mo(CO)2(NO) (11): PinCp*Li (3.54 g, 13.41 mmol)
was dissolved in THF and, after addition of Mo(CO)6 (3.33 g;
13.41 mmol), the reaction mixture was heated under reflux for 12 h.
After cooling the solution, Diazald (2.7 g, 12.60 mmol), dissolved
in 10 mL of THF, was added dropwise, so that the temperature
did not exceed room temp. Stirring was continued for 3 h, with a
continuous slight flow of nitrogen over the solution. The solvent
was distilled off and the residue was sublimed at 140°C and 10Ϫ3
bar. The sublimed product was then purified by chromatography
(Al2O3; hexane/ether, 4:1) to give red crystals after evaporation of
the solvent. Yield: 3.60 g (8.19 mmol, 65%). Ϫ IR (hexane): ν˜(CO) ϭ
(SRe)/(RRe)-(η5-PinCp*)ReCl(NO)(PPh3) (8a/8b): Complexes 4a/4b
(60 mg, 0.08 mmol) were dissolved in 10 mL of CH2Cl2 and cooled
to Ϫ78°C. 11.8 µL HBF4·Et2O (54% in Et2O, 0.087 mmol) was
added by syringe and the mixture was stirred at this temperature
for 10 min. Then [Ph3PCH3]ϩIϪ (39.5 mg, 0.098 mmol) was added
and the cooling bath was removed. The solution was warmed to
room temperature, passed through 3 cm of silica gel and dried.
Yield of a red solid 8a/8b: 49.3 mg (0.06 mmol, 80%). Ϫ IR
(CH2Cl2) ν˜(NO) ϭ 1641 cmϪ1. Ϫ 1H NMR (CDCl3): δ ϭ 7.60Ϫ7.52
(m, 6 H, H-b), 7.37 (m, 9 H, H-c/d), 3.14 (q, JHϪH ϭ 9.46 Hz, 1
H, H-4), 3.06 (q, JHϪH ϭ 9.46 Hz, 1 H, H-4Ј), 2.49 (m, 1 H), 2.34
(m, 2 H), 2.29 (m, 1 H), 2.20 (m, 2 H), 2.05 (m, 4 H), 1.96 (s, 1
H), 1.92 (m, 1 H), 1.89 (m, 2 H), 1.75 (s, 3 H), 1.73 (s, 3 H), 1.65
(s, 3 H), 1.3 (s, 3 H), 1.28Ϫ1.16 (6s, 18 H), 1.14 (d, JHϪH ϭ 6.7 Hz,
3 H), 1.11 (d, 7.0 Hz, 3 H), 0.85 (m, 3 H), 0.78 (s, 3 H). Ϫ 13C
NMR (CDCl3): δ ϭ 134.32, 134.24 (d, JCϪP ϭ 10.4 Hz, C-b),
134.29, 134.21 (d, JCϪP ϭ 9.9 Hz, C-bЈ), 130.0 (C-d/dЈ), 128.3,
128.2 (C-c/cЈ), 115.9, 115.5, 107.9, 105.3, 103.8, 97.3, 95.7, 93.2,
90.7 (C5Me4), 49.5, 49.3 (C-5/5Ј), 43.3 (br., C-3/3Ј), 43.0, 42.9 (C-
1
2004 (s), 1930 (s), ν˜(NO) ϭ 1667 cmϪ1. Ϫ H NMR (CDCl3): δ ϭ
3.03 (q, JHϪH ϭ 9.77 Hz, 1 H, H-4), 2.37 (m, 1 H) 2.17 (s,3 h), 2.12
(m, 3 H), 2.07 (s, 3 H), 2.03 (s, 3 H), 2.03 (s, 3 H), 1.85 (m, 2 H),
1.26 (s, 3 H), 1.21 (m, 1 H), 1.17 (s, 3 H) 1.02 (d, JHϪH ϭ 7.02 Hz,
3 H). Ϫ 13C NMR (CDCl3): δ ϭ 230.7, 230.6 (CO), 114.8, 108.2,
106.0, 105.1 (C5Me4), 49.2 (C-5), (43.5 (br., C-3) 43.1 (C-1) 39.5
(C-2/6), 38.0 (C-10), 34.5 (C-4), 28.8, 23.5 (C-8,9), 21.5 (C-7), 12.1,
12.0, 10.9, 10.8 (C5Me4). Ϫ C21H29NO3Mo (439.4): calcd.: C 57.40,
H 6.65, N 3.19; found: C 57.62, H 6.72, N 3.15.
1/1Ј), 39.5 (C-10/10Ј), 36.4, 34.7, 34.5, 34.3 (C-2/2Ј/6/6Ј), 34.9 (C- (η5-PinCp*)W(CO)2NO (12): (η5-PinCp*)W(CO)2NO (12) was
4/4Ј), 28.8, 28.7, 23.5, 23.4 (C-8/8Ј/9/9Ј), 21.6, 21.4 (C-7/7Ј), 12.1, prepared in a similar way to 11 from PinCp*Li (3.00 g 11.40 mmol)
11.6, 11.4, 10.9, 10.7, 10.6, 8.4, 7.0 (C5Me4/C5Me4Ј). Ϫ 31P NMR
(CDCl3): δ ϭ 17.0 (br.), 15.2 (25°C); 17.5 (v br.), 15.4 (0°C); 18.1
and W(CO)6 (4.05 g, 11.50 mmol) after 5 d of reflux. Diazald
(2.44 g, 11.4 mmol) was added as before. Yield: 3.61 g (6.84 mmol,
(br.), 16.3 (v. br.), 15.5 (Ϫ25°C); 18.4, 16.6, 15.6 (Ϫ50°C). Ϫ MS 60%), red crystals. Ϫ IR (hexane): ν˜(CO) ϭ 1995 (s), 1918 (s),
(EI); m/z (%): 771 (10) [Mϩ].
ν˜(NO) ϭ 1661 cmϪ1. Ϫ 1H NMR (CDCl3): δ ϭ 3.03 (q, JHϪH
ϭ
9.2 Hz, 1 H, H-4), 2.35 (m, 1 H) 2.27 (s, 3 H), 2.18 (s, 3 H), 2.14
(s, 3 H), 2.10 (s, 3 H), 1.89 (m, 2 H), 1.25 (s, 3 H), 1.19 (m, 1 H),
1.16 (s, 3 H) 0.99 (d, JHϪH ϭ 7.0 Hz, 3 H). Ϫ 13C NMR (CDCl3):
δ ϭ 222.4 ( 2CO), 113.4, 106.4, 104.6, 104.0 (C5Me4), 49.4 (C-5),
(43.4 (C-3) 43.2 (C-1) 39.4 (C-10) )34.8 (C-2/6), 34.5 (C-4), 28.8,
23.4 (C-8,9), 21.1 (C-7), 11.8, 10.7, 10.6 (C5Me4). Ϫ C21H29NO3W
(527.31): calcd.: C 47.83, H 5.54, N 2.66; found C 48.51, H 5.61,
N 2.70.
[(η5-PinCp*)2RhCl2]2 (9): PinCp*H (2.00 g, 7.70 mmol) was dis-
solved in 50 mL of methanol and Rh3·3H2O (0.96 g, 37.4% Rh,
3.50 mmol) was added. The light red solution was refluxed for 5 d
and the solvent was concentrated to 10 mL afterwards. Storage at
5°C for several hours gave a red solid, which was filtered, washed
with diethyl ether and dried. Compound 9 can be recrystallized
from CH2Cl2/Et2O. Yield of the red solid 9: 1.52 g (1.76 mmol,
1
50%). Ϫ H NMR (CDCl3): δ ϭ 2.82 (q, JHϪH ϭ 9.46 Hz, 1 H,
H-4), 2.49 (m, 1 H), 2.35 (m, 1 H), 2.06 (m, 2 H), 1.90 (m, 2 H),
(η5-PinCp*)MoCl2(NO) (13): Compound 11 (0.85 g, 1.94 mmol)
1.83 (s, 3 H), 1.80 (s, 3 H), 1.65 (s, 3 H), 1.61 (s, 3 H), 1.24 (s, 3 was dissolved in ether and treated slowly at 0°C with solid PCl5
H), 1.14 (s, 3 H), 0.95 (d, JHϪH ϭ 10.1 Hz), 0.98 (d, JHϪH ϭ 6.7 Hz). (0.40 g, 1.94 mmol). Stirring was continued for 12 h at room temp.;
Ϫ
13C NMR (CDCl3): δ ϭ 100.1, 98.2, 96.3, 93.1, 90.8 (C5Me4), the solution turned a vivid green with a green solid precipitate.
48.8 (C-5), 42.2 (C-1), 41.3 (br., C-3), 39.6, 34.3 (C-2/6), 32.7 (C-
After addition of 30 mL of hexane, the volume was reduced to
4), 32.5 (C-10), 28.8, 23.5 (C-8/9), 21.6 (C-7), 11.6, 11.1, 10.0, 9.2 10 mL under vacuum. The green solid was filtered, washed with a
(C5Me4). Ϫ C38H58Cl4Rh2 (862.5): calcd.: C 52.92, H 6.78; found small amount of cold ether and dried. Yield 0.75 g (1.65 mmol,
C 53.41, H 6.75.
85%). Ϫ IR (THF): ν˜(CO) ϭ 1660 cmϪ1. Ϫ 1H NMR (CDCl3): δ ϭ
3.13 (q, JHϪH ϭ 9.46 Hz, 1 H, H-4), 2.38 (m, 1 H), 2.23 (s, 3 H),
2.19 (m, 3 H), 2.10 (s, 3 H), 2.06 (m, 3 H) 1.95 (s, 3 H) 1.86 (m, 2
(η5-PinCp*)TiCl3 (10): PinCp*Li (0.86 g, 3.46 mmol) was dissolved
in DME and TiCl3·3THF (0.43 g, 1.15 mmol) was added at Ϫ78°C.
The solution was warmed to room temp. and refluxed for 2 d.
Concd. HCl (2.7 mL) was added carefully at Ϫ30°C, followed by
10 mL of chloroform. The layers were separated and the organic
layer was dried with NaSO4. The solvent was removed and the
nearly dry residue was transferred to a Soxhlet extractor. The ex-
traction was performed with pentane saturated with HCl gas. The
red solution, obtained after 30 min, was dried and a red solid was
H), 1.26 (s, 3 H), 1.18 (m, 1 H) 1.14 (s, 3 H) 1.00 (d, JHϪH
ϭ
7.02 Hz), 3 H). Ϫ 13C NMR (CDCl3): δ ϭ 127.0, 125.8, 124.6,
119.1 (C5Me4), 49.2 (C-5), 43.1 (br., C-3) 42.4 (C-1), 39.5, 34.5 (C-
2/6), 34.9 (C-4). 33.2 (C-10) 28.8, 23.4 (C-8/9), 21.8 (C-7), 12.9,
12.6, 10.7, 10.3 (C5Me4). Ϫ MS: m/z (%): 455 (20) [Mϩ], 425 (95)
[Mϩ Ϫ NO], 385 (25) [Mϩ Ϫ 2 Cl]. Ϫ C19H29Cl2NOMo (454.27):
calcd.: C 48.88, H 6.60; found C 48.63, H 6.49.
obtained. Yield of the red solid 10: 0.13 g (0.32 mmol, 28%). Ϫ 1H (η5-PinCp*)WCl2(NO) (14): Compound 12 (1.07 g, 2.03 mmol) was
NMR (CDCl3): δ ϭ 3.63 (q, JHϪH ϭ 9.46 Hz, 1 H, H-4), 2.67 (s, dissolved in ether and was treated slowly at 0°C with solid PCl5
3 H), 2.47 (s, 3 H), 2.46 (s, 3 H), 2.43Ϫ2.34 (m, 1 H), 2.27 (s, 3 H), (0.42 g, 2.03 mmol). Reaction and workup as above. Yield
1504
Eur. J. Inorg. Chem. 1999, 1497Ϫ1505

Optically Active Transition-Metal Complexes, 8
FULL PAPER
0.95 g(1.75 mmol, 86%). Ϫ IR (THF): ν˜(CO) ϭ 1632 cmϪ1. Ϫ 1H
graphic Data centre as supplementary publication no. CCDC-
NMR (CDCl3): δ ϭ 3.15 (q, JHϪH ϭ 9.53 Hz, 1 H, H-4), 2.42 (s, 114499. Copies of the data can be obtained free of charge on appli-
3 H), 2.25 (s, 3 H), 2.21 (s, 3 H), 2.15 (m, 2 H), 2.04 (m, 3 H) cation to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [Fax:
2.02Ϫ1.78 (m, 4 H) 1.86 (m, 2 H), 1.26 (s, 3 H), 1.21 (m, 1 H) 1.16 (internat.) ϩ 44-1223/336-033; E-mail: deposit@ccdc.cam.ac.uk].
(s, 3 H) 1.00 (d, JHϪH ϭ 7.02 Hz, 3 H). Ϫ 13C NMR (CDCl3): δ ϭ
124.2, 123.2, 119.3, 117.3 (C5Me4), 49.9 (C-5), 43.4 (br., C-3) 43.1
(C-1), 39.9, 35.5 (C-2/6), 34.4 (C-4). 33.2 (C-10) 29.0, 23.6 (C-8/9),
Acknowledgments
21.8 (C-7), 12.5, 12.3, 10.8, 10.3 (C5Me4). Ϫ MS: m/z (%): 543 (40)
The authors gratefully acknowledge financial support by the Deut-
[Mϩ], 490 (70) [Mϩ Ϫ Cl, Ϫ NO], 385 (30) [Mϩ Ϫ 2 Cl, Ϫ NO].
sche Forschungsgemeinschaft (DFG) within the Collaborative Re-
Ϫ C19H29Cl2NOW (542.18): calcd.: C 40.78, H 5.51; found C 40.52,
search Centre (SFB) 380: “Asymmetric Syntheses with Chemical
H 5.39.
and Biological Means”, and by the Fonds der Chemischen Indu-
strie.
(η5-PinCp*)W(CH2SiMe3)2NO (15): Compound 14 (346.9 mg,
0.64 mmol)
and
[(CH3)3Si(CH2)2Mg]·(dioxan)2
(246.1 mg,
0.64 mmol) were mixed as solids in a Schlenk tube. After cooling
to Ϫ196°C, 20 mL of THF was slowly condensed into the tube
under vacuum. After waiting for 10 min, the Schlenk tube was
transferred into a Dewar cooled to Ϫ78°C. The temperature was
allowed to rise to Ϫ50°C and kept at this temperature for 12 h.
The solution assumed a deep purple colour. The solvent was evapo-
rated at 0°C, the residue taken up in cold ether and filtered at
Ϫ20°C through Celite. A purple residue was obtained after evapor-
ating the solvent at 0°C, yield 315.9 mg (0.51 mmol, 80%). Ϫ IR
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
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1
(hexane): ν˜(CO) ϭ 1582 (s) cmϪ1. Ϫ H NMR (C6D6): δ ϭ 3.03 (q,
JHϪH ϭ 9.15 Hz, 1 H, H-4), 2.28 (m, 2 H), 2.13 (m, 1 H), 1.90 (s,
3 H), 1.82 (s, 3 H), 1.78 (m, 1 H), 1.71 (d, JHϪH ϭ 11.58, 1 H, H-
a1), 1.68 (S, 3 H), 1.66 (d, JHϪH ϭ 11.29 Hz, 1 H, H-b1), 1.49 (s,
3 H), 1.33Ϫ1.22 (m, 2 H), 1.17 (s, 3 H), 1.10 (m, 1 H), 1.08 (s, 3
H), 0.93 (d, JHϪH ϭ 7.01 Hz, 3 H), 0.38 (2 s, 18 H, SiMe3), Ϫ1.21
(d, JHϪH ϭ 11.29 Hz, 1 H, H-b2), Ϫ1.29 (d, JHϪH ϭ 11.58 Hz, 1
H, H-a2). Ϫ 13C NMR (C6H6): δ ϭ 119.2, 117.2, 113.6, 112.2
(C5Me4), 65.2, 63.4, (2 ϫ C-11), 49.6 (C-5), 43.0 (br., C-3), 42.8
(C-1), 39.5, 35.0 (C-2/6), 34.9 (C-4), 30.1 (C-10), 28.9, 23.5 (C-8/
9) 21.8 (C-7), 14.3, 12.0, 9.7, 9.5 (C5Me4), 1.41, 1.37 (SiMe3). Ϫ
C27H51NOSi2W (645.72): calcd. C 49.28, H 8.11; found C 49.64,
H 8.23.
J. A. Gladysz, Y.-H. Huang, F. Niedercorn, A. M. Arif, J. Or-
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[15]
[16]
X-ray Crystallographic Study: (SRe)-[(η5-PinCp*)Re(COOMe)NO-
(PPh3) (5a) crystallizes in the orthorhombic space group P212121
(no. 19). Crystal data: C50H56N2O2PRe, formula mass 934.19 g
[17]
[18]
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molϪ1, a ϭ 11.522(5), b ϭ 18.789(2), c ϭ 20.116(6) A, V ϭ 4355(2)
˚
3
A , Z ϭ 4, dcalcd. ϭ 1.425 g cmϪ3, µ(Mo-Kα) ϭ 29.02 cmϪ1
,
˚
F(000) ϭ 1904. Intensity data were collected at 203 K on an orange
rod of approximate dimensions 0.47 ϫ 0.18 ϫ 0.15 mm with an
ENRAF-Nonius CAD4 diffractometer in the ω mode up to θmax ϭ
26°. A total of 11726 reflections were corrected for Lorentz and
polarization effects and for absorption (numerical by Gaussian in-
tegration;[28] min. transmission 0.5339, max. transmission 0.6826).
After averaging symmetry-equivalent data, the structure was
solved[29] by Patterson and subsequent Fourier difference synthesis.
Full-matrix least-squares refinement on F[29] of 428 variables for
7010 independent observations with I > 1.0 σ(I) converged at R ϭ
0.057, Rw ϭ 0.058 [wϪ1 ϭ σ2(Fo)], GOF ϭ 1.338. During refinement
the naphtyl moiety was treated as a rigid group, all other non-
hydrogen atoms were assigned anisotropic displacement param-
eters, and hydrogen atoms were included as riding in calculated
[19]
[20]
[21]
[22]
[23]
[24]
[25]
[26]
[27]
[28]
[29]
H. Saltzman, J. G. Sharefkin, in Organic Syntheses (Ed.: H. E.
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533, 131Ϫ141.
˚
positions [CϪH ϭ 0.98 A, Uiso(H) ϭ 1.3 Ueq(C)]. A final Fourier
P. Coppens, L. Leiserowitz, D. Rabinovich, Acta Crystallogr.
1965, 18, 1035Ϫ1038.
difference synthesis showed a residual electron density of ca. 3
ENRAF-Nonius, SDP Version 5.0, Delft, The Netherlands,
1989.
Ϫ3
˚
eA in the region of the disordered naphtyl moiety. Crystallo-
graphic data (excluding structure factors) for the structure reported
in this paper have been deposited with the Cambridge Crystallo-
Received February 22, 1999
[I99061]
Eur. J. Inorg. Chem. 1999, 1497Ϫ1505
1505