Diastereoselective protonation, substitution and addition reactions at pseudotetrahedral rhenium complexes

Article abstract of DOI:10.1002/ejic.200901011

The chiral N,P ligand P(Me)(Ph)[8-(2-methylquinolinyl)] (3) was synthesized and separated into its enantiomers via diastereomeric palladium complexes. The reactions of 3 and (R_p)-3 with [CpRe(CO)(NO)(NCMe)]BF₄ (7) gave the diastereomeric complexes [CpRe(CO)(NO){P(Me)(Ph)(C₁₀H ₈N)}]BF₄ [8 and (R_Re,S_P/S _Re,S_P)-8], which, upon borohydride reduction, yielded the corresponding methyl complexes [CpRe(NO){P(Me)(Ph)(C₁₀H ₈N}(CH₃)] [9 and (R_Re,S_P/ S _Re,S_p)-9]. Treatment of 9 with HBF₄ under carefully controlled conditions gave the diastereomerically pure chelates [CpRe(NO){P(Me)(Ph)(C₁₀H₈N)}]BF₄ [(A _Re,S_P/S_Re,R_P)-10, (R ^Re,R_P/S_Re,S_P)-10 and (R _Re,S_P)-10]. The chelate ring was opened with NaSH to produce the hydrosulfido complexes [CpRe(NO)(P(Me)(Ph)(C₁₀H ₈N)](SH)] [(R_Re,S_P/S_Re,R _P)-11, (R_Re,R_P,/S_Re,S _P)-11 and (R_Re,S_P)-11]. Each step in this sequence proceeded with retention of configuration at rhenium. Complex. 11 underwent acid-promoted condensation with aldehydes to give thioaldehyde complexes [CpRe(NO)(P(Me)(Ph)(C₁₀H₈N)}(S=CHR)]BF ₄ (12a-d, R = Ph, Me, 4-C₆H₄OMe, C ₆F₅). The addition of nucleophiles X^- to 12a gave rhenium-coordinated a-chiral thiolate complexes [CpRe(NO)(P(Me)(Ph)(C ₁₀H₈N)}{SC(H)(Ph)(X)}] (13a-e, X = acac, PhCH ₂S, EtS, tBuS, CN) with 42-89% de. The thiolate can readily be cleaved from the rhenium complex by a methylation/chelate ring-closure strategy. The stereochemistry of the entire reaction sequence was corroborated, for each, step by X-ray crystallography.

Full text of DOI:10.1002/ejic.200901011

FULL PAPER
DOI: 10.1002/ejic.200901011
Diastereoselective Protonation, Substitution and Addition Reactions at
Pseudotetrahedral Rhenium Complexes
Frank Bock,[a] Frank Fischer,[a] Krzysztof Radacki,[a] and Wolfdieter A. Schenk*[a]
Dedicated to Professor Dr. R. Tacke on the occasion of his 60th birthday
Keywords: Rhenium / Chiral resolution / N,P ligands / S ligands
The chiral N,P ligand P(Me)(Ph)[8-(2-methylquinolinyl)] (3)
was synthesized and separated into its enantiomers via dia-
stereomeric palladium complexes. The reactions of 3 and
(RP)-3 with [CpRe(CO)(NO)(NCMe)]BF4 (7) gave the
(RRe,RP/SRe,SP)-11 and (RRe,SP)-11]. Each step in this se-
quence proceeded with retention of configuration at rhe-
nium. Complex 11 underwent acid-promoted condensation
with
aldehydes
to
give
thioaldehyde
complexes
diastereomeric
complexes
[CpRe(CO)(NO){P(Me)(Ph)-
[CpRe(NO){P(Me)(Ph)(C10H8N)}(S=CHR)]BF4 (12a–d, R = Ph,
Me, 4-C6H4OMe, C6F5). The addition of nucleophiles X– to
12a gave rhenium-coordinated α-chiral thiolate complexes
[CpRe(NO){P(Me)(Ph)(C10H8N)}{SC(H)(Ph)(X)}] (13a–e, X =
acac, PhCH2S, EtS, tBuS, CN) with 42–89% de. The thiolate
can readily be cleaved from the rhenium complex by a meth-
ylation/chelate ring-closure strategy. The stereochemistry of
the entire reaction sequence was corroborated for each step
by X-ray crystallography.
(C10H8N)}]BF4 [8 and (RRe,SP/SRe,SP)-8], which, upon borohy-
dride reduction, yielded the corresponding methyl com-
plexes [CpRe(NO){P(Me)(Ph)(C10H8N)}(CH3)] [9 and (RRe,SP/
SRe,SP)-9]. Treatment of 9 with HBF4 under carefully con-
trolled conditions gave the diastereomerically pure chelates
[CpRe(NO){P(Me)(Ph)(C10H8N)}]BF4
(RRe,RP/SRe,SP)-10 and (RRe,SP)-10]. The chelate ring was
opened with NaSH to produce the hydrosulfido complexes
[(RRe,SP/SRe,RP)-10,
[CpRe(NO){P(Me)(Ph)(C10H8N)}(SH)]
[(RRe,SP/SRe,RP)-11,
The high diastereoselectivity is rooted in the intramolec-
ular proton transfer from the dimethylamino sidearm of the
chiral phosphane ligand to rhenium, which is much faster
for the unlike diastereomer. Thus, starting from the mixture
(RRe,SP/SRe,SP)-1 the two enantiomerically pure dia-
stereomers (RRe,SP)-2 and (SRe,SP)-2 were obtained in 99%
ee and 93% de.[11] A considerable drawback of compounds
2 is their inertness in ligand-substitution reactions. The five-
membered chelate ring could be opened only with NaCN
under quite forcing conditions.[12] We now report on a sim-
ilar system which is reactive enough to be further elabo-
rated.
Introduction
The activation of prochiral unsaturated substrates by chi-
ral, enantiomerically pure transition metal Lewis acids is a
promising and often highly efficient strategy for enantiose-
lective synthesis.[1] The chirality may be based either on the
coordination geometry around the metal atom itself
(“metal-based chirality”) – prominent examples are the
pseudotetrahedral half-sandwich complexes [CpMn-
(CO)(NO)(PPh3)],[2] [CpFe(CO)(PPh3)(COCH3)],[3] and
[CpRe(NO)(PPh3)(CH3)][4] – or may be added through the
use of chiral ligands (“ligand-based chirality”) as exem-
plified by the pioneering work of Knowles,[5] Noyori,[6] and
Sharpless[7] on enantioselective catalysis. The two concepts
have been combined in order to study the often facile epi-
merization at the metal center[8–10] and hopefully overcome
the problems associated with it with regard to asymmetric
synthesis and catalysis.[10]
Results
Phosphane Synthesis and Enantiomer Separation
The synthesis of the new chiral phosphane 3 by nucleo-
philic substitution (Scheme 2) follows well-established
methods.[13,14]
Recently, we have found a kinetically controlled, highly
efficient chirality transfer between an amine-functionalized
phosphane ligand and the metal center (Scheme 1).[11]
Phosphane 3 is a yellow, slightly air-sensitive crystalline
solid with the expected NMR spectroscopic data, e.g. a
doublet at δ = 1.76 ppm for the PCH3 group, a singlet at δ
= 2.70 for the ArylCH3 group, and a 31P signal at δ = –33.8
ppm.
[a] Institut für Anorganische Chemie, Universität Würzburg,
97074 Würzburg, Germany
E-mail: wolfdieter.schenk@uni-wuerzburg.de
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.200901011.
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F. Bock, F. Fischer, K. Radacki, W. A. Schenk
FULL PAPER
Scheme 1.
of (SP,SC)-5 was determined crystallographically in order to
assign the configuration at phosphorus. The salt crystallized
from acetone in the triclinic space group P1 with two inde-
pendent formula units and one molecule of acetone in the
unit cell. A view of one of the cations is shown in Figure 1.
Scheme 2.
We have made several attempts to devise an enantioselec-
tive synthesis for 3. Thus (SP)-(Ph)(Me)(H3B)PH[15] was de-
protonated at –78 °C with butyllithium and added to 2-
methyl-8-chloroquinoline, but failed to react at this tem-
perature. Higher temperatures would have led to racemiza-
tion of the borane-protected lithium phosphide reagent.[15]
The reverse strategy, Br/Li exchange on 2-methyl-8-bromo-
quinoline[16] followed by reaction with various chlorophos-
phanes such as (Ph)(Me)PCl, PhPCl2, or (Et2N)2PCl never
gave any tractable results.
Figure 1. Structure of the cation of (SP,SC)-5, hydrogen atoms were
omitted for clarity. Thermal ellipsoids drawn at 50% level. Space group
(RP)-3 was finally obtained with 99% ee via dia- P1; selected distances [pm] and angles [°] (standard deviations in paren-
theses): Pd(1)–P(1) 221.74(6), Pd(1)–N(1) 223.7(2), Pd(1)–N(2)
216.8(2), Pd(1)–C(40) 199.9(3), P(1)–Pd(1)–N(1) 80.23(5), P(1)–Pd(1)–
stereomeric palladium complexes as reported by Wild et al.
for the similar 8-(methylphenylphosphanyl)quinoline.[14]
N(2) 169.58(6), P(1)–Pd(1)–C(40) 95.33(7), N(1)–Pd(1)–N(2) 103.69(8),
Reaction of the dimeric Pd complex (SC)-4 with phosphane
N(1)–Pd(1)–C(40) 174.09(9), N(2)–Pd(1)–C(40) 80.04(9).
3 followed by addition of NH4PF6 gave complex 5 as a
mixture of diastereomers in high yield (Scheme 3).
As expected, the structure is very similar to that of the
(SP,RC) diastereomer of the analogous complex of 8-(meth-
ylphenylphosphanyl)quinoline.[14] The two cations in the
unit cell differ somewhat with regard to the geometry
around the Pd atom. While the one shown in Figure 1 is
almost perfectly planar, the other one is folded with a trans
angle P–Pd–N of 156.2°. Inspection of the unit cell diagram
shows that this is caused by packing forces within the crys-
tal.
Scheme 3.
(RP)-3 was cleaved from (SP,SC)-5 by treatment with eth-
Slow crystallization of (RP,SC/SP,SC)-5 from boiling 2- ylenediamine, and the ethylenediamine palladium complex
butanone gave a 54% crop of (SP,SC)-5 which after (SC)-6 converted back to (S)-4 by reaction with 2  aqueous
recrystallization was obtained with 99% de. The structure HCl (Scheme 4).
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Stereochemistry at Pseudotetrahedral Rhenium Complexes
Figure 2. Structure of the cation of 8, hydrogen atoms were omitted
for clarity. Thermal ellipsoids drawn at 50% level. C(1) and N(1) are
disordered and were labeled arbitrarily. Space group P21/c; selected
distances [pm] and angles [°] (standard deviations in parentheses):
Re(1)–P(1) 241.41(11), Re(1)–C(1) 185.6(4), Re(1)–N(1) 184.8(4), P(1)–
Re(1)–C(1) 93.16(12), P(1)–Re(1)–N(1) 91.72(12), C(1)–Re(1)–N(1)
92.46(16).
Scheme 4.
Synthesis of Diastereomeric Rhenium Complexes
The acetonitrile complex [CpRe(CO)(NO)(NCMe)]BF4
(7) is a perfectly suited starting material for the synthesis
of chiral half-sandwich rhenium complexes.[17–19] Fusing 7
together with a slight excess of racemic 3 under vacuum and
without solvent gave a high yield of racemic 8. Similarly,
diastereomeric (RRe,SP/SRe,SP)-8 was obtained from the re-
1
action of 7 and (RP)-3 with Ͼ 98% ee (determined by H
NMR spectroscopy in the presence of Eu(tfc)3). In this case
the temperature should not exceed 90 °C to keep the phos-
phane from racemizing (Scheme 5).
Scheme 6.
Scheme 5.
The structure of racemic 8 was determined crystallo-
graphically. The compound crystallized in the space group
P21/c with the CO and NO ligands disordered. A view of
the cation is shown in Figure 2. Interatomic distances and
angles are very similar to those of analogous complexes.[4,18]
Borohydride reduction of the carbonyl ligand[17] gave the
methyl complexes 9 and (RRe,SP/SRe,SP)-9, respectively
(Scheme 6). The success of the reaction is immediately evi-
dent from the disappearance of the CO stretching absorp-
Figure 3. Structure of the compound (RRe,RP/SRe,SP)-9, hydrogen
atoms were omitted for clarity. Thermal ellipsoids drawn at 50% level.
¯
Space group P1; selected distances [pm] and angles [°] (standard devia-
tions in parentheses): Re(1)–P(1) 235.12(14), Re(1)–C(1) 227.2(8),
Re(1)–N(1) 174.3(5), N(1)–O(1) 121.0(7), P(1)–Re(1)–C(1) 84.1(2),
P(1)–Re(1)–N(1) 92.8(2), C(1)–Re(1)–N(1) 94.0(3).
1
tion in the infrared spectrum and new doublets in the H
and 13C NMR spectra typical of a Re–CH3 group.
A sample of (RRe,SP/SRe,RP)-9 (72% de) was treated at
By crystallization from toluene/pentane, 9 was partially –78 °C with 0.86 equiv. HBF4, i.e. just enough to protonate
separated into (RRe,RP/SRe,SP)-9 (87% de) and (RRe,SP/ the faster reacting[11] unlike diastereomer. The ionic product
SRe,RP)-9 (72% de). (RRe,RP/SRe,SP)-9 crystallized in the (RRe,SP/SRe,RP)-10 was crystallized by addition of diethyl
¯
triclinic space group P1, a view of the molecule is shown in ether and thus easily separated from residual (RRe,RP/
Figure 3.
SRe,SP)-9 (Scheme 7).
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F. Bock, F. Fischer, K. Radacki, W. A. Schenk
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Scheme 7.
Figure 4. Structure of the cation of (RRe,RP/SRe,SP)-10, hydrogen
atoms were omitted for clarity. Thermal ellipsoids drawn at 50% level.
Space group C2/c; selected distances [pm] and angles [°] (standard devi-
ations in parentheses): Re(1)–P(1) 231.50(9), Re(1)–N(1) 176.4(3),
Re(1)–N(2) 218.9(3), N(1)–O(1) 119.6(4), P(1)–Re(1)–N(1) 92.59(10),
P(1)–Re(1)–N(2) 81.12(8), N(1)–Re(1)–N(2) 96.68(13).
Similarly, a trace of HBF4 was added to a sample of
(RRe,RP/SRe,SP)-9 (87% de) to convert the residual unlike
diastereomer into the ring-closed ionic complex which was
precipitated and discarded. The supernatant was then
treated with more acid yielding (RRe,RP/SRe,SP)-10 with
94% de. The relative configuration of both diastereomers
1
was assigned on the basis of H-1H NOESY spectra: Both
isomers gave strong crosspeaks between the Cp signal and
the resonance of the CH3 group on the quinoline ring. For
(RRe,SP/SRe,RP)-10, additional crosspeaks connected the Cp
signal with the PCH3 signal, while for (RRe,RP/SRe,SP)-10 a
correlation was observed between the Cp ring and the ortho
protons of the PC6H5 group. This assignment was finally
corroborated by an X-ray structure determination of
(RRe,RP/SRe,SP)-10 (Figure 4).
By the two-step process outlined above a sample of non-
racemic (RRe,SP/SRe,SP)-9 was finally converted into
(RRe,SP)-10 (71% de) and (SRe,SP)-10 (92% de) (Scheme 8).
For the success of this reaction it is very important that the
amount of acid in the first step is carefully controlled.
Scheme 9.
Ring opening with the strong, soft nucleophile SH– pro- nation of the (RRe,RP/SRe,SP)-diastereomer was carried out
ceeds smoothly and stereospecifically at 0 °C (Scheme 9). as an unambiguous proof of the relative configuration at
The lower yield of enantiomerically pure (SRe,SP)-11 is rhenium and phosphorus (Figure 5).
mainly due to its good solubility in pentane which is re-
Not unexpectedly, the structure is very similar to that of
sponsible for losses during workup. The presence of the Re– the methyl complex (RRe,RP/SRe,SP)-9 (Figure 3). One note-
SH group reveals itself through a doublet (J = 13.5 Hz) in worthy difference is the large angle S(1)–Re(1)–N(1). This is
1
the H NMR spectrum near δ = 0.2. A structure determi- a common feature of all complexes [CpRe(NO)(PRЈ3)(SR)],
Scheme 8.
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Stereochemistry at Pseudotetrahedral Rhenium Complexes
A structure determination of (RRe,SP/SRe,RP)-12c was
undertaken, the major concern again being the relative con-
figuration at rhenium and phosphorus. A view of the cation
is shown in Figure 6.
Figure 5. Structure of the compound (RRe,RP/SRe,SP)-11, hydrogen
atoms were omitted for clarity. Thermal ellipsoids drawn at 50% level.
¯
Space group P1; selected distances [pm] and angles [°] (standard devia-
tions in parentheses): Re(1)–P(1) 237.11(15), Re(1)–S(1) 239.1(2),
Re(1)–N(1) 179.6(6), N(1)–O(1) 115.0(8), P(1)–Re(1)–S(1) 83.76(6),
P(1)–Re(1)–N(1) 91.8(2), S(1)–Re(1)–N(1) 98.5(2).
Figure 6. Structure of the cation of (RRe,SP/SRe,RP)-12c, hydrogen
atoms were omitted for clarity. Thermal ellipsoids drawn at 50% level.
Space group P2(1)/n; selected distances [pm] and angles [°] (standard
deviations in parentheses): Re(1)–S(1) 239.12(14), Re(1)–C(50)
223.2(5), S(1)–C(50) 173.1(6), Re(1)–P(1) 243.22(14), Re(1)–N(1)
176.0(5), N(1)–O(1) 117.4(7), S(1)–Re(1)–C(50) 43.80(15), P(1)–Re(1)–
S(1) 79.80(5), P(1)–Re(1)–C(50) 121.45(15), P(1)–Re(1)–N(1) 90.42(17).
which is caused by an antibonding interaction between the
strongly π-donating SR ligand and the HOMO–1 of the
[CpRe(NO)(PRЈ3)] complex fragment.[19–21]
Condensation reactions with a number of aldehydes were
carried out on both diastereomers of 11. The desired thioal-
dehyde complexes 12 were formed in high yields and, as
expected, with retention of configuration at rhenium
(Scheme 10).
As expected, the structure is very similar to that of
[CpRe(NO)(PPh3)(η2-S=CHPh)]BF4.[22] The S(1)–C(50)
bond is almost parallel to the Re(1)–P(1) bond such as to
maximize the interaction between the HOMO of the
[CpRe(NO)(PR3)]+ complex fragment and the π* orbital of
the thiocarbonyl group.[4] This interaction results in a
lengthening of the S(1)–C(50) bond in comparison with
2,4,6-tri(tert-butyl)thiobenzaldehyde
(160.2 pm)[23]
or
[CpRu(dppe)(η1-S=CHC6H4OMe)]PF6 (162.7 pm).[24] The
aryl group is located anti to the Cp ligand such that the
configurations at rhenium and carbon are the same.
Diastereoselective Addition of Nucleophiles
As a first test of the asymmetric induction between rhe-
nium and the thioaldehyde ligand we chose the addition
of various nucleophiles X– to both diastereomers of 12a
(Scheme 11).
The addition products were isolated in satisfactory yields.
The diastereoselectivity of the addition was only moderate.
A crystal of the major isomer of (RRe,RP/SRe,SP)-13d was
investigated by X-ray crystallography. The compound crys-
¯
tallizes in the triclinic space group P1 with two molecules
in the unit cell which are related by a center of inversion.
One of them is shown in Figure 7.
Scheme 10.
The geometry around the rhenium atom is almost iden-
As indicated in Scheme 10, the thioaldehyde complexes tical to that of (RRe,RP/SRe,SP)-11, including the typically
12 exist as rapidly equilibrating mixtures of η1 and η2 iso- large angle S(1)–Re(1)–N(1). The angles at C(50) are close
mers. This can easily be inferred from the appearance of to tetrahedral with the relative configuration at this atom
two well separated NO stretching vibrations in the infrared the same as at Re(1) and P(1).
spectra. The ratio of the isomers depends on the group R
The enantiomerically enriched addition product
and the relative configuration at rhenium and phosphorus. (SRe,SP,SC)-13b was finally chosen to explore ways to cleave
Thus, both diastereomers of 12b and the like diastereomers the thiolate ligand from the rhenium complex. Initial ex-
of 12c and 12d are essentially pure η2 isomers, both dia- periments to achieve this by protonation with CF3COOH
stereomers of 12a contain smaller fractions of the η1 iso- or HBF4 failed. Methylation however worked well. Moni-
mers, and the unlike diastereomers of 12c and 12d are toring the reaction by NMR spectroscopy indicated that a
roughly equimolar mixtures of both forms.
thioether complex was involved as an intermediate. Upon
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F. Bock, F. Fischer, K. Radacki, W. A. Schenk
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workup, however, the ring-closed complex (SRe,SP)-10a was
isolated along with the dithioacetal (S)-14 whose enantio-
meric excess was determined by chiral HPLC (Scheme 12).
Discussion
The present study was undertaken with several goals in
mind: (i) to establish a broader applicability of the dia-
stereoselective proton transfer from base-functionalized
phosphane ligands to metal centers,[11] (ii) to investigate the
stereochemical course of chelate ring-opening and -closing
reactions, and (iii) to find out whether the presence of an
additional stereogenic center might influence the diastereo-
selectivity of nucleophilic addition reactions to unsaturated
ligands. In order to arrive at unambiguous conclusions we
decided to carry the entire reaction sequence through with
both diastereomers and track the stereochemical course of
each step by X-ray crystallography.
Horner-type phosphanes PR1R2R3 are configurationally
stable at temperatures below 100 °C.[25] Thus the reactivity
of the acetonitrile complex 7 is just sufficient not to jeop-
ardize the stereochemical outcome of the substitution reac-
tion described in Scheme 5. As expected the two spectro-
scopically distinguishable diastereomers of 8 are formed
with 0% de, and any attempt to separate them by crystalli-
zation or chromatography is thwarted by the similarity of
the CO and NO ligands. By contrast, the two dia-
stereomeric methyl complexes 9 have sufficiently different
solubilities to be at least partially separated by crystalli-
zation. It should be mentioned here that the success of the
CO to methyl reduction (Scheme 6) cannot be taken for
granted. In fact, attempts to reduce complexes analogous to
8 with the ligands P(Me)(Ph)(8-quinolinyl), P(Me)(Ph)(2-
pyridyl) or P(Me)(Ph)(CH2NMe2) gave intractable mixtures
which contained little if any of the desired methyl com-
plexes.[12]
As we have pointed out in our previous communica-
tion,[11] the striking diastereoselectivity of the proton trans-
fer/methane elimination reaction of Scheme 6 and 7 rests
on a number of well-established facts: (i) The basicity of
electron-rich transition metal complexes is similar to or
even exceeds that of organic nitrogen bases;[26] (ii) the rate
of proton transfer to the metal (“kinetic basicity”) is, how-
ever, smaller by several orders of magnitude;[27,28] (iii) acid
induced methyl cleavage involves metal protonation at a site
cis to CH3 followed by reductive elimination.[29,30] As a re-
sult, a metal complex bearing an amine function on the side
arm of one of the ligands will first be protonated at nitrogen
followed by intramolecular H+ transfer to the metal.[31]
This situation is graphically illustrated in Scheme 13.
Here, K(N) and K(M) represent the (roughly similar) ba-
sicities of the nitrogen and metal centers, respectively, and
the various kx(N) and kx(M) are the corresponding rate
constants of proton transfer to nitrogen or metal, with
kx(N)ϾϾkx(M). In the absence of a basic solvent a sub-
stoichiometric amount of acid HA will be rapidly and com-
pletely consumed by the formation of the N-protonated spe-
Scheme 11.
Figure 7. Structure of the compound (RRe,RP,RC/SRe,SP,SC)-13d, hy-
drogen atoms were omitted for clarity. Thermal ellipsoids drawn at
50% level. Space group P1; selected distances [pm] and angles [°] (stan-
dard deviations in parentheses): Re(1)–P(1) 236.10(9), Re(1)–S(1)
238.53(9), Re(1)–N(1) 175.4(3), N(1)–O(1) 119.6(4), S(1)–C(50)
184.8(4), S(2)–C(50) 181.8(4), P(1)–Re(1)–S(1) 86.51(3), P(1)–Re(1)–
N(1) 89.4(1), S(1)–Re(1)–N(1) 99.0(1), S(1)–C(50)–S(2) 104.5(2).
¯
Scheme 12.
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Stereochemistry at Pseudotetrahedral Rhenium Complexes
The opening of the chelate ring by the attacking nucleo-
phile SH– proceeds with retention of configuration at the
rhenium center (Scheme 9). It is tempting to ascribe this
outcome to the configurational stability of the pyramidal
Lewis acid intermediate [CpRe(NO)(PR3)]+.[9] However, it
has already been pointed out by Gladysz et al. that substitu-
tion reactions of half-sandwich rhenium complexes
[CpRe(NO)(PPh3)(L1)]+ proceed by an associative mecha-
nism with
a
bent-nitrosyl intermediate [CpRe(N-
O)(PPh3)(L1)(L2)]+. The observed retention of configura-
tion was tentatively explained as the result of steric repul-
sions which cause the entering ligand L2 to attack from a
direction anti to the bulky PPh3 ligand.[32] For the case pre-
sented here this explanation is not quite satisfying. Inspec-
tion of a space-filling model of the cation of (RRe,RP/
SRe,SP)-10 shows that for such a mechanism both possible
sites of attack are similarly shielded. Furthermore, for the
opposite diastereomer (RRe,SP/SRe,RP)-10, where the Ph
and Me groups at phosphorus have exchanged positions,
the interstice between NO and phosphorus is even more
protected. Thus, if the selectivity were mainly determined
by steric interactions we would have to expect (i) a generally
lower diastereoselectivity, and (ii) that both diastereomers
of 10 would ring-open with significantly different selectivi-
ties, which is clearly not the case. We are left to conclude
that the origin of the high stereoselectivity of the substitu-
tion at rhenium is still an open question.
Scheme 13.
cies. In a dilute solution, the entropy-favored intramolecular
proton transfer (ki step) will be much faster than the inter-
molecular reprotonation of the conjugate base A– followed
by direct metal protonation. As the reductive elimination of
methane from rhenium is rapid even at low tempera-
tures[30,31] (i.e. kel ϾϾk–i) it follows that the intramolecular
proton transfer from nitrogen to rhenium is the rate-de-
termining step. A clue as to how this step could bring about
a high diastereoselectivity comes from an inspection of the
structure of the cation of (RRe,RP/SRe,SP)-10 (Figure 4). In
this slower formed diastereomer the phenyl group at phos-
phorus eclipses the cyclopentadienyl ligand on rhenium,
whereas in the rapidly formed (RRe,SP/SRe,RP)-diastereomer
the phenyl group eclipses the svelte NO ligand (see also
the structure determinations of both diastereomers of 2[11]).
Because the geometry of the transition state of the proton
transfer from N to Re approaches that of the final product,
it seems safe to assume that this repulsive interaction is re-
The synthesis of the thioaldehyde complexes 12a–d by
acid-promoted condensation of the Re–SH complex 11 with
aldehydes is straightforward and also more reliable than the
alternative H–-abstraction from the corresponding benzyl-
thiolate complexes.[33,34] In addition, it is also more conve-
sponsible for slowing down the proton transfer within the nient as it is based on a common rhenium complex as start-
(RRe,RP/SRe,SP) diastereomer (Scheme 14).
ing material. 12a–d exist in solution as mixtures of η1(S)
Scheme 14. For the sake of clarity, only species with (RRe)-configuration are shown.
Eur. J. Inorg. Chem. 2010, 391–402
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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397

F. Bock, F. Fischer, K. Radacki, W. A. Schenk
FULL PAPER
and η2(S=C) bonded isomers. This is a quite common phe-
nomenon and has been observed not only for rhenium com-
plexes of thioaldehydes[33,34] but also for similar complexes
of aldehydes, ketones and imines.[35–37] Such a situation is
detrimental with regard to the stereoselectivity of addition
to the coordinated π ligand, as there are three competing
pathways: backside attack at the η2(S=C) isomer and attack
on both enantiofaces of the η1(S)-bonded thioaldehyde (see
Scheme 11). Gladysz et al. have pointed out that both path-
ways may favor, if to different extents, the same dia-
stereomer of the addition products.[35,38] With diastereo-
selectivities up to 89% this hope was at least partially ful-
filled. From the fact that the diastereoselectivity of the ad-
dition to carbon is similar for both diastereomers of 12a we
conclude that the configuration at phosphorus is only of
minor importance for the outcome of the reaction.
tallized from methanol at –30 °C; yield 2.18 g (67%) light yellow
crystals.
(SP,SC)-[Pd(Me2NC12H10)(P(Me)(Ph)(C10H8N))]PF6 [(SP,SC)-5]:
Compound 3 (7.93 g, 30.0 mmol) was added at 20 °C to a suspen-
sion of (SC)-4 (10.2 g, 14.9 mmol) in methanol (120 mL). After stir-
ring for 1.5 h at this temperature, some colorless precipitate had
formed which was removed by filtration through a 0.45-µ mem-
brane filter. A solution of NH4PF6 (9.80 g, 60.0 mmol) in water
(20 mL) was added to the filtrate whereupon the product began
to crystallize. More water (250 mL) was added with stirring, the
voluminous precipitate was filtered off, washed with water, water/
methanol (1:1), and finally with diethyl ether, and dried under vac-
uum; yield 19.8 g (93%) colorless crystalline powder. This material
was dissolved in a just sufficient amount of boiling 2-butanone and
the solution allowed to slowly cool to ambient temperature. The
precipitate was collected and recrystallized from 2-butanone; yield
5.7 g (54%) yellow crystals.
(RP)-P(Me)(Ph)[8-(2-methylquinolinyl)] [(RP)-3]: Ethylenediamine
(1.35 g, 22.4 mmol) and diethyl ether (100 mL) were added to a
solution of [(SP,SC)-5] (3.20 g, 4.48 mmol) in dichloromethane
(90 mL). The mixture was stirred for 1 h at 20 °C, the colorless
precipitate filtered off, washed with diethyl ether, and dried. This
material was identified spectroscopically (1H, 31P NMR) as (SC)-
6,[14] yield 2.10 g (90%). The filtrate was taken to dryness and the
residue taken up in diethyl ether (60 mL) and water (20 mL). The
ether phase was collected, the aqueous phase extracted with diethyl
ether (2ϫ20 mL), and the combined organic phases dried with
MgSO4. Evaporation gave a colorless solid; yield 0.95 g (83%),
spectroscopically (1H, 31P NMR) identical with racemic 3. 1H
NMR in the presence of the chiral shift reagent (–)-1-(9-anthryl)-
2,2,2-trifluoroethanol gave an ee of 99%.
As a guide for further development we briefly explored
ways to remove the newly formed ligand from rhenium.
Methylation transforms the anionic ligand into a neutral
one, which, like in many other cases,[39–42] is only weakly
bound. The thioacetal ligand is then given off under mild
conditions while the chelate ring is closed with high stereo-
selectivity. The two products are easily separated on the ba-
sis of their different solubilities (Scheme 12), allowing also
the rhenium chelate to be isolated and recycled.
Experimental Section
(SC)-[(PdCl(Me2NC12H10))2] [(SC)-4]: 2  aqueous HCl (30 mL,
60 mmol) was added to a suspension of (SC)-6 (7.60 g, 14.7 mmol)
in methanol (180 mL). After 10 min a yellow solid had formed
which was filtered off, washed with methanol, and dried under vac-
uum; yield 4.87 g (97%), spectroscopically (1H NMR) identified as
(SC)-4.[14]
General: All experiments were carried out in Schlenk tubes under
nitrogen using suitably purified solvents. IR: Bruker IFS 25. 1H
NMR: Bruker AMX 400, Bruker Avance 500, Jeol JNM-LA 300,
δ values relative to TMS. 13C NMR: Bruker AMX 400, Bruker
Avance 500, Jeol JNM-LA 300, δ values relative to TMS, assign-
ments were routinely checked by DEPT procedures. In some cases
the 13C NMR signals of quaternary carbon atoms were too weak
to be detected. 31P NMR: Bruker AMX 400, Bruker Avance 500,
Jeol JNM-LA 300, δ values relative to 85% H3PO4. Elemental
analyses: Analytical Laboratory of the Institut für Anorganische
Chemie. BF4– salts occasionally give low carbon values due to trace
formation of fluorocarbon compounds which escape detection.
Spectroscopic and analytical data are listed as Supporting Infor-
mation HPLC: Daicel Chiralcel OD-H column (4.6ϫ250 mm), Ja-
sco pump, gradient unit and multi-wavelength detector. X-ray
structures: Bruker SMART APEX CCD. The following starting
materials were obtained as described in the literature: [CpRe-
(CO)(NO)(NCMe)]BF4 (7),[17] NaSH,[43] PH(Me)(Ph),[44] [(SC)-
4].[14] Acetylacetone and the thiols were converted into their so-
dium salts by adding a stoichiometric amount of sodium metal to
solutions in ethanol, followed by evaporation to dryness. All other
reagents were used as purchased.
[CpRe(CO)(NO){P(Me)(Ph)(C10H8N)}]BF4 (8): [CpRe(CO)(NO)-
(NCMe)]BF4 (7) (0.60 g, 1.37 mmol) and 3 (0.52 g, 1.96 mmol)
were fused together for 4 h at 90 °C under vacuum. After cooling
to 20 °C the mixture was taken up in THF (9 mL) and stirred until
a yellow solid had formed. This was filtered off, washed with di-
ethyl ether, and dried; yield 0.81 g (90%), yellow crystalline solid;
m.p. 167 °C.
(RRe,SP/SRe,SP)-[CpRe(CO)(NO){P(Me)(Ph)(C10H8N)}]BF4 [(RRe,SP/
SRe,SP)-8]: This compound was obtained as described above from 7
(1.90 g, 4.34 mmol) and (RP)-3 (1.30 g, 4.90 mmol); yield 2.50 g (87%),
spectroscopically identical with 8. 1H NMR in the presence of the
chiral shift reagent tris[(trifluoromethyl-hydroxymethylene)-(–)-cam-
phorato]europium gave an ee of 98%.
[CpRe(NO){P(Me)(Ph)(C10H8N)}(CH3)]
(9):
NaBH4
(0.14 g,
3.75 mmol) was added to a suspension of carbonyl complex 8 (0.71 g,
1.07 mmol) in THF (5 mL). The mixture was stirred for 3 h at 20 °C
and the solvents evaporated to dryness. The residue was dissolved in
toluene (15 mL) and filtered through a layer of celite. The filtrate was
concentrated to 8 mL and stored at –30 °C whereupon brick-red crys-
tals of (RRe,RP/SRe,SP)-9 formed. The supernatant was syringed off
and the crystals washed with pentane and dried; yield 0.26 g (85%)
red crystalline solid, 87% de (1H NMR).
P(Me)(Ph)[8-(2-methylquinolinyl)] (3): A solution of 2.5  tert-bu-
tyllithium in hexane (8.5 mL, 13.6 mmol) was added to a solution
of PH(Me)(Ph) (1.45 g, 12.4 mmol) in THF (15 mL). The resulting
red solution was added at –78 °C to a solution of 2-methyl-8-chlo-
roquinoline (2.97 g, 16.7 mmol) in THF (10 mL). After stirring for
1.5 h at –78 °C and 2 h at 20 °C water (40 mL) was added. The
resulting slurry was extracted with CH2Cl2 (4ϫ20 mL) and the The supernatant was concentrated to 4 mL and pentane (15 mL)
combined organic phases dried with MgSO4. The solvent was re-
moved under vacuum and the brownish-yellow residue recrys-
added to precipitate the orange-colored (RRe,SP/SRe,RP)-9; yield 0.13 g
(43%), orange crystalline solid, 72% de (1H NMR).
398
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© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Stereochemistry at Pseudotetrahedral Rhenium Complexes
(RRe,SP/SRe,SP)-[CpRe(NO){P(Me)(Ph)(C10H8N)}(CH3)]
[(RRe,SP/ (RRe,SP/SRe,RP)-[CpRe(NO){P(Me)(Ph)(C10H8N)}(S=CHPh)]BF4
SRe,SP)-9]: NaBH4 (0.39 g, 10.3 mmol) was added at –78 °C to a sus- [(RRe,SP/SRe,RP)-12a]: (RRe,SP/SRe,RP)-11 (1.21 g, 2.09 mmol), benzal-
pension of (RRe,SP/SRe,SP)-8 (1.95 g, 2.95 mmol) in THF (40 mL). The
mixture was stirred and warmed to 20 °C over a period of 4 h. The
solvent was removed under vacuum and the residue dissolved in tolu-
ene (25 mL) and filtered through a layer of celite. The filtrate was taken
to dryness leaving a red solid; yield 1.60 g (96%), spectroscopically
identical with 9. This material was used in the next step without further
purification.
dehyde (2.22 g, 20.9 mmol), MgSO4 (0.50 g, 4.16 mmol), THF (10 mL)
and 54% HBF4 in diethyl ether (0.61 mL, 4.66 mmol) were combined
and stirred for 10 min at 20 °C. Basic alumina (0.50 g) was added to
absorb excess acid, the solids were filtered off and rinsed with acetone
(2ϫ5 mL) and the combined filtrate taken to dryness. The residue
was recrystallized from THF (2 mL)/diethyl ether (20 mL); yield 1.48 g
(91%), yellow powder, 95% de (1H NMR); m.p. 197 °C.
(RRe,SP/SRe,RP)-[CpRe(NO){P(Me)(Ph)(C10H8N)}]BF4
[(RRe,SP/
(RRe,RP/SRe,SP)-[CpRe(NO){P(Me)(Ph)(C10H8N)}(S=CHPh)]BF4
[(RRe,RP/SRe,SP)-12a]: This compound was prepared as above from
(RRe,RP/SRe,SP)-11 (1.69 g, 2.91 mmol), benzaldehyde (3.10 g,
29.2 mmol), MgSO4 (0.70 g, 5.82 mmol) and 54% HBF4 (0.85 mL,
6.50 mmol); yield 1.81 g (82%), yellow powder, 92% de (1H NMR);
m.p. 207 °C.
SRe,RP)-10]: A solution of 54% HBF4 in diethyl ether (26 µL,
0.19 mmol) was added to a solution of (RRe,SP/SRe,RP)-9 (127 mg,
0.23 mmol, 72% de) in dichloromethane (5 mL) at –78 °C . The mix-
ture was warmed to 20 °C and diethyl ether (15 mL) added. A precipi-
tate formed which was collected by filtration, washed with pentane,
and dried under vacuum; yield 105 mg (74%), orange crystalline solid,
97% de (1H NMR); m.p. 83 °C.
(SRe,SP)-[CpRe(NO){P(Me)(Ph)(C10H8N)}(S=CHPh)]BF4 [(SRe,SP)-
12a]: This compound was prepared as above from (SRe,SP)-11 (0.38 g,
0.65 mmol), benzaldehyde (0.69 g, 6.50 mmol), MgSO4 (0.15 g,
1.25 mmol) and 54% HBF4 (0.19 mL, 2.40 mmol); yield 0.36 g (73%),
yellow powder, 95% de (1H NMR). The product is spectroscopically
identical with (RRe,RP/SRe,SP)-12a.
(RRe,RP/SRe,SP)-[CpRe(NO){P(Me)(Ph)(C10H8N)}]BF4
[(RRe,RP/
SRe,SP)-10]: A solution of 54% HBF4 in diethyl ether (8 µL,
0.06 mmol) was added to a solution of (RRe,RP/SRe,SP)-9 (255 mg,
0.454 mmol, 87% de) in dichloromethane (10 mL) at –78 °C . The
mixture was warmed to 20 °C and diethyl ether (20 mL) added. An
orange precipitate of (RRe,SP/SRe,RP)-10 formed which was filtered off
and discarded. The filtrate was evaporated to dryness and the residue
treated with 54% HBF4 (55 µL, 0.40 mmol) and worked up as de-
scribed above for (RRe,SP/SRe,RP)-10; yield 195 mg (68%), orange crys-
talline solid, 94% de (1H NMR); m.p. 194 °C.
[CpRe(NO){P(Me)(Ph)(C10H8N)}(S=CHR)]BF4 (12b–d): Common
protocol: The respective diastereomer of 11 (120 mg, 0.207 mmol), al-
dehyde (2.00 mmol), MgSO4 (80 mg, 0.66 mmol), THF (5 mL) and
54% HBF4 in diethyl ether (70 µL, 0.51 mmol) were combined and
stirred for 10 min at 20 °C. Basic alumina (100 mg) was added to ab-
sorb excess acid. The supernatant was syringed off, the solution was
filtered through a nylon syringe filter (0.45 µ) and the filtrate taken to
dryness. The residue was recrystallized from THF (1 mL)/diethyl ether
(10 mL).
(RRe,SP)-[CpRe(NO){P(Me)(Ph)(C10H8N)}]BF4 [(RRe,SP)-10]: A solu-
tion of 54% HBF4 in diethyl ether (195 µL, 1.42 mmol) was added to
a solution of (RRe,SP/SRe,SP)-9 (1.60 g, 2.84 mmol) in dichloromethane
(25 mL) at –78 °C The mixture was warmed to 20 °C, concentrated to
12 mL, and diethyl ether (40 mL) added. A dark orange precipitate
formed which was collected by filtration, washed with diethyl ether
and pentane, and dried under vacuum; yield 0.77 g (82%), brownish-
red crystalline powder, 71% de (1H NMR). The product is spectro-
scopically identical with (RRe,SP/SRe,RP)-10.
(RRe,SP/SRe,RP)-[CpRe(NO){P(Me)(Ph)(C10H8N)}(S=CHMe)]BF4
[(RRe,SP/SRe,RP)-12b]: Yield 109 mg (76%), ochre powder, 95% de (1H
NMR); m.p. 195 °C.
(RRe,RP/SRe,SP)-[CpRe(NO){P(Me)(Ph)(C10H8N)}(S=CHMe)]BF4
[(RRe,RP/SRe,SP)-12b]: Yield 112 mg (78%), yellow powder, 96% de
(1H NMR); m.p. 185 °C.
(SRe,SP)-[CpRe(NO){P(Me)(Ph)(C10H8N)}]BF4 [(SRe,SP)-10]: The fil-
trate of the previous step was evaporated to dryness, redissolved in
dichloromethane, treated with HBF4 (240 µL, 1.76 mmol) and worked
up as described above; yield 0.76 g (81%), red crystalline powder, 92%
de (1H NMR). The product is spectroscopically identical with (RRe,RP/
SRe,SP)-10.
(RRe,SP/SRe,RP)-[CpRe(NO){P(Me)(Ph)(C10H8N)}(S=CHC6H4OMe)-
]BF4 [(RRe,SP/SRe,RP)-12c]: Yield 128 mg (79%), yellow powder, 88%
de (1H NMR); m.p. 103 °C.
(RRe,RP/SRe,SP)-[CpRe(NO){P(Me)(Ph)(C10H8N)}(S=CHC6H4-
OMe)]BF4 [(RRe,RP/SRe,SP)-12c]: Yield 132 mg (81%), yellow powder,
96% de (1H NMR); m.p. 195 °C.
(RRe,SP/SRe,RP)-[CpRe(NO){P(Me)(Ph)(C10H8N)}(SH)]
[(RRe,SP/
SRe,RP)-11]: NaSH (60 mg, 1.06 mmol) was added at 0 °C to a suspen-
(RRe,SP/SRe,RP)-[CpRe(NO){P(Me)(Ph)(C10H8N)}(S=CHC6F5)]BF4
[(RRe,SP/SRe,RP)-12d]: Yield 157 mg (86%), yellow powder, 94% de
(1H NMR); m.p. 132 °C.
sion of (RRe,SP/SRe,RP)-10 (0.50 g, 0.79 mmol) in THF (15 mL) and
ethanol (1 mL). The mixture was warmed to 20 °C, stirred for 2 h, and
the solvents evaporated to dryness. The residue was dissolved in benz-
ene, filtered through Celite, and the filtrate evaporated to 2 mL. Ad-
dition of pentane (20 mL) induced the product to crystallize, which
was filtered off, washed with pentane, and dried; yield 0.32 g (70%),
brown powder, 96 % de (1H NMR); m.p. 92 °C.
(RRe,RP/SRe,SP)-[CpRe(NO){P(Me)(Ph)(C10H8N)}(S=CHC6F5)]BF4
[(RRe,RP/SRe,SP)-12d]: Yield 163 mg (86%), yellow powder, 97% de
(1H NMR); m.p. 116 °C.
[CpRe(NO){P(Me)(Ph)(C10H8N)}{SC(H)(Ph)(X)}] (13a–e): Common
protocol: The respective sodium salt NaX was added at –78 °C to
a suspension of (RRe,SP/SRe,RP)-12a or (RRe,RP/SRe,SP)-12a (150 mg,
0.20 mmol) in toluene (2 mL). The mixture was stirred for 12 h and
allowed to slowly reach room temperature. A solid was removed by
syringe filtration (0.2 µ), the filter was rinsed with toluene (3 mL) and
the clear solution concentrated under vacuum to 1 mL. Pentane
(10 mL) was slowly added at –78 °C which caused the product to crys-
tallize. The supernatant was syringed off and the residue washed with
pentane (3ϫ3 mL) and dried.
(RRe,RP/SRe,SP)-[CpRe(NO){P(Me)(Ph)(C10H8N)}(SH)]
[(RRe,RP/
S
Re,SP)-11]: This compound was prepared as above from (RRe,RP/
SRe,SP)-10; yield 0.45 g (92%), ochre powder, 94% de (1H NMR); m.p.
60 °C.
(SRe,SP)-[CpRe(NO){P(Me)(Ph)(C10H8N)}(SH)] [(SRe,SP)-11]: This
compound was prepared as above from (SRe,SP)-10 (0.76 g,
1.20 mmol) and NaSH (0.14 g, 2.40 mmol); yield 0.38 g (55%), yellow
powder, 98 % de (1H NMR). The product is spectroscopically identical
with (RRe,RP/SRe,SP)-11.
Eur. J. Inorg. Chem. 2010, 391–402
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399

F. Bock, F. Fischer, K. Radacki, W. A. Schenk
FULL PAPER
(RRe,SP/SRe,RP)-[CpRe(NO){P(Me)(Ph)(C10H8N)}{SC(H)(Ph)(acac)}] (RRe,RP/SRe,SP)-[CpRe(NO){P(Me)(Ph)(C10H8N)}{SC(H)(Ph)(acac)}]
[(RRe,SP/SRe,RP)-13a]: Yield 118 mg (77%), yellow powder, 70% de
[(RRe,RP/SRe,SP)-13a]: Yield 90 mg (59%), yellow powder, 53% de (1H
NMR); m.p. 165 °C.
(1H NMR); m.p. 167 °C.
Table 1. Details of the structure determinations of compounds 5, 8, 9, 10, 11, 12c and 13d.
5·0.5acetone
8
9
10·CHCl3
Empirical formula
Formula mass
C32.5H35F6N2O0.5P2Pd
743.97
C23H21BF4N2O2PRe
661.40
C23H24N2OPRe
561.61
C23H22BCl3F4N2OPRe
752.76
Crystal color/habit
Crystal system
Space group
yellow prism
triclinic
P1
yellow plate
monoclinic
P21/c
red block
triclinic
P1
orange block
monoclinic
C2/c
¯
a [Å]
b [Å]
c [Å]
α [°]
11.6022(4)
12.0416(5)
13.3622(5)
83.283(2)
66.151(1)
70.367(2)
1607.77(11)
1.67–26.03
–14 to 14
–14 to 14
–15 to 16
2
8.891(2)
24.452(5)
10.651(2)
90
94.910(4)
90
2307.1(9)
2.09–26.11
–10 to 10
–30 to 30
–13 to 13
4
9.277(3)
10.025(3)
13.613(4)
70.323(6)
85.212(6)
80.924(6)
1176.6(6)
2.18–26.14
–11 to 11
–12 to 12
–16 to 16
2
23.0316(16)
14.2414(10)
18.9208(13)
90
120.593(1)
90
5342.2(6)
1.76–26.09
–28 to 28
–17 to 17
–23 to 23
8
β [°]
γ [°]
V [Å3]
Θ [°]
h
k
l
Z
µ(Mo-Kα) [mm–1]
Crystal size [mm]
Dcalcd. [gcm–1]
T [K]
0.739
0.54ϫ0.36ϫ0.19
1.537
5.393
0.15ϫ0.10ϫ0.03
1.904
5.246
0.23ϫ0.19ϫ0.16
1.585
4.958
0.24ϫ0.11ϫ0.10
1.872
100(2)
173(2)
173(2)
173(2)
Reflections collected
Independent reflections
Parameter
R1 [IϾ2σ(I)]
R1 (overall)
43516
11804
793
0.0218
26041
4567
329
0.0282
16410
4666
226
0.0362
37589
5292
327
0.0255
0.0226
0.0316
0.0373
0.0287
R2 [IϾ2σ(I)]
R2 (overall)
Absolute structure parameter
Diff. peak/hole [eÅ–3]
CCDC
0.0478
0.0482
–0.012(9)
0.318/–0.514
749532
0.0661
0.0676
0.0894
0.0902
0.0582
0.0599
1.811/–0.459
749533
4.023/–1.677
749534
1.331/–0.972
749535
11·0.5C6H6
12c·0.5OEt2
13d
Empirical formula
Formula mass
C25H25N2OPReS
618.70
C32H34BF4N2O2.5PReS C33H36N2OPReS2
822.69
757.93
Crystal color/habit
Crystal system
Space group
orange plate
triclinic
P1
yellow block
monoclinic
P21/n
brown plate
triclinic
P1
¯
¯
a [Å]
b [Å]
c [Å]
α [°]
9.280(3)
10.248(4)
13.668(5)
68.784(6)
86.103(7)
80.555(6)
1195.2(7)
2.16–28.36
–12 to 12
–13 to 13
–18 to 18
2
11.9197(3)
14.3281(3)
19.0098(4)
90
100.465(1)
90
3192.62(12)
1.79–26.08
–14 to 14
–17 to 17
–23 to 23
4
9.5885(15)
12.839(2)
14.116(2)
74.461(2)
72.009(2)
87.221(2)
1591.4(4)
1.95–26.02
–11 to 11
–15 to 15
–17 to 17
2
β [°]
γ [°]
V [Å3]
Θ [°]
h
k
l
Z
µ(Mo-Kα) [mm–1]
Crystal size [mm]
Dcalcd. [gcm–1]
T [K]
5.257
0.23ϫ0.20ϫ0.08
1.719
3.980
0.39ϫ0.17ϫ0.16
1.712
4.028
0.31ϫ0.24ϫ0.16
1.582
173(2)
173(2)
173(2)
Reflections collected
Independent reflections
Parameter
R1 [IϾ2σ(I)]
R1 (overall)
32134
5946
246
0.0430
50639
6283
378
0.0397
32718
6264
354
0.0249
0.0463
0.0417
0.0267
R2 [IϾ2σ(I)]
R2 (overall)
0.1084
0.1106
0.1083
0.1099
0.0637
0.0647
Absolute structure parameter
Diff. peak/hole [eÅ–3]
CCDC
3.793/–3.178
749536
3.757/–2.203
749537
1.786/–1.029
749538
400
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© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 391–402

Stereochemistry at Pseudotetrahedral Rhenium Complexes
[2]
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(RRe,SP/SRe,RP)-[CpRe(NO){P(Me)(Ph)(C10H8N)}{SC(H)(Ph)-
(SCH2Ph)}] [(RRe,SP/SRe,RP)-13b]: Yield 115 mg (73%), ochre powder,
65% de (1H NMR); m.p. 122 °C.
[3]
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(RRe,RP/SRe,SP)-[CpRe(NO){P(Me)(Ph)(C10H8N)}{SC(H)(Ph)-
(SCH2Ph)}] [(RRe,RP/SRe,SP)-13b]: Yield 123 mg (78%), ochre powder,
89% de (1H NMR); m.p. 121 °C.
[5]
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[8]
(SRe,SP,SC)-[CpRe(NO){P(Me)(Ph)(C10H8N)}{SC(H)(Ph)(SCH2Ph)}]
[(SRe,SP,SC)-13b]: Yield 103 mg (65%), yellow powder, 70% de (1H
NMR). The product is spectroscopically (1H, 31P NMR) identical with
(RRe,RP/SRe,SP)-13b.
(RRe,SP/SRe,RP)-[CpRe(NO){P(Me)(Ph)(C10H8N)}{SC(H)(Ph)(SEt)}] [9] T. R. Ward, O. Schafer, C. Daul, P. Hofmann, Organometallics
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(RRe,RP/SRe,SP)-[CpRe(NO){P(Me)(Ph)(C10H8N)}{SC(H)(Ph)(SEt)}]
[(RRe,RP/SRe,SP)-13c]: Yield 90 mg (62%), ochre powder, 79% de (1H
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(RRe,SP/SRe,RP)-[CpRe(NO){P(Me)(Ph)(C10H8N)}{SC(H)(Ph)(StBu)}]
[(RRe,SP/SRe,RP)-13d]: Yield 108 mg (71%), ochre powder, 42% de (1H
NMR); m.p. 52 °C.
[14]
(RRe,RP/SRe,SP)-[CpRe(NO){P(Me)(Ph)(C10H8N)}{SC(H)(Ph)(StBu)}]
[(RRe,RP/SRe,SP)-13d]: Yield 114 mg (75%), ochre powder, 46% de (1H
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(RRe,SP/SRe,RP)-[CpRe(NO){P(Me)(Ph)(C10H8N)}{SC(H)(Ph)(CN)}]
[(RRe,SP/SRe,RP)-13e]: Yield 137 mg (94%), yellow crystalline solid,
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(S)-PhCH2SC(H)(Ph)(SMe) [(S)-14]: Methyl iodide (16 µL,
0.26 mmol) was added at –40 °C to a solution of (SRe,SP,SC)-13b
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to room temperature overnight. The solution was concentrated to
2 mL and extracted with pentane (4ϫ10 mL). The acetonitrile fraction
was evaporated to dryness, the residue recrystallized from dichloro-
methane (2 mL)/diethyl ether (5 mL), washed with diethyl ether, and
dried; yield 120 mg (65%), orange crystalline solid, identified by NMR
as (SRe,SP)-10a, the iodide analog of (SRe,SP)-10, 69% de. The com-
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chromatographed over silica with hexane/ethyl acetate, 20:1 as eluent;
yield 24 mg (37%), colorless oil, spectroscopically identical with an
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X-ray Structure Determinations: Single crystals were bonded to a glass
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Smart Apex CCD instrument was used for data collection (graphite
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details of the measurement are summarized in Table 1. CCDC num-
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Supporting Information (see also footnote on the first page of this arti-
cle): Spectroscopic and analytical data of the new compounds.
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