New chiral zwitterionic iron hydride complexes with 'ephosium' and 'valphosium' ligands

Article abstract of DOI:10.1016/S0022-328X(98)00686-X

New chiral cationic phosphinite ligands based on ephedrine or valinol skeletons, and corresponding zwitterionic hydridotricarbonylferrate complexes are described. IR data indicate an unusual cis-H-Fe-P arrangement in these complexes, and NMR studies show

Full text of DOI:10.1016/S0022-328X(98)00686-X

Journal of Organometallic Chemistry 566 (1998) 117–123
New chiral zwitterionic iron hydride complexes with ‘ephosium’ and
‘valphosium’ ligands
Jean-Jacques Brunet, Remi Chauvin *, Je´roˆme Chiffre, Sandrine Huguet, Pascale Leglaye
Laboratoire de Chimie de Coordination du CNRS, UPR 8241 lie´e par con6entions a` l’Uni6ersite´ Paul Sabatier et a` l’Institut National Polytechnique,
205 Route de Narbonne, 31077 Toulouse cedex, France
Received 26 February 1998
Abstract
New chiral cationic phosphinite ligands based on ephedrine or valinol skeletons, and corresponding zwitterionic hydridotricar-
bonylferrate complexes are described. IR data indicate an unusual cis-H–Fe–P arrangement in these complexes, and NMR
2
studies show an unusual variation of JPH with temperature and solvent. The possibility that both these rare features are dictated
by a stabilizing back folding of the [NMeR2]+ terminus onto the [FeH]− center is discussed. © 1998 Elsevier Science S.A. All
rights reserved.
Keywords: Carbonylferrates; Chiral phosphinite-ammoniums; Ephedrine; Valinol; Zwitterionic hydrides
1. Introduction
Baird-type cationic phosphines [1], the counterparts
of the well studied sulfonated, carboxylated and phos-
phonated anionic phosphines, have recently attracted a
renewed interest for performing catalysis in aqueous
medium [2,3]. In the search for asymmetric versions of
hydrosoluble transition metal catalysts, chiral cationic
phosphine ligands have received some attention [4].
This kind of ligands may also find applications in a
recently disclosed possible strategy for controlling an
asymmetric transformation through the use of a disym-
metric ligand: PꢀE+ chelating an anionic metal center
by a P:“M− dative bond on one side and by a weaker
E+…M− interaction on the other [5]: although the
latter interaction is schematized as an electrostatic at-
traction between formal atomic charges, it must be
more generally regarded as a contact ion pairing which
should be tightened by chelation (Fig. 1). The dative–
* Corresponding author. Fax: +33 05 61553003; e-mail: chauvin
@lcctoul.lcc-toulouse.fr
Fig. 1. Putative ‘chiral zwitterionic control’ strategy in asymmetric
reduction by a transition metal hydride.
0022-328X/98/$19.00 © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(98)00686-X

118
J.-J. Brunet et al. / Journal of Organometallic Chemistry 566 (1998) 117–123
Scheme 1. Synthesis of diphenylephosium ligands and their hydridotricarbonylferrate complex: (i) RX=MeI or Br(CH2)5Br; (ii) KPF6, H2O; (iii)
Ph2PNEt2,CH3CN, reflux; (iv) KHFe(CO)4, THF, r.t.
electrostatic chelation mode should exhibit peculiar
properties to be compared with those of the classical
dative–dative chelation mode of hemilabile ligands
such as phosphine ethers and alcohols.
dipolar solvent where the putative zwitterionic control
strategy of Fig. 1 is more questionable. Nevertheless,
3a·HFe(CO)3 can also be used in sursaturated THF
solution, before triggering crystallization of freshly pre-
pared complex: using this in situ method, trifluoroace-
tophenone has been reduced to PhCH(OH)CF3 with
60% conversion and 60% yield (20°C, 24 h), but with
no significant e.e. Under the basic conditions used,
epimerization of configurationally fragile products can-
not be ruled out, but before studying further the poten-
tial of the strategy, more lipophilic chiral zwitterionic
complexes were needed. Two possibilities were envi-
sioned: one is still based on the ephedrine skeleton
quaternized by higher alkyl groups and the other on the
more aliphatic valinol skeleton.
Few alkaloid-derived PIII-ammonium compounds are
known [6], and within this prospect, cationic chiral
phosphinites derived from ephedrine and named ‘N,N-
dimethyl-R2-ephosiums’
R2P–O–CHPh–CHMe–
NMe3+ have been reported (R=Ph, NMe2,
(NMeCH2CH2MeN)1/2, OH). Zwitterionic hydridotri-
carbonylferrate complexes of such ligands have been
prepared [5], and we report here on preliminary reduc-
tion tests using these complexes and on complementary
synthetic and analytic studies.
2. Reducing properties of
N,N-dimethyldiphenylephosium
hydridotricarbonylferrate
3. N,N-(1,5-pentylene)-diphenylephosium and its
hydridotricarbonylferrate complex
The complex 3a·HFe(CO)3 was obtained from
KHFe(CO)4 and 3a·PF6 as yellow crystals deposited
from THF solution [5]. The solid is insoluble in water,
methanol and isopropanol, and only slightly soluble in
ethanol, THF, dichloromethane and acetonitrile [7].
Although reduction of electron-poor ketones by
KHFe(CO)3L complexes (L=CO, P(OMe)3) proceeds
readily in methanol [8], preliminary attempts of asym-
metric reduction were conducted in homogeneous
DMSO solution. It was found that benzil was reduced
to benzoin PhC(O)CH(OH)Ph (20°C, 24 h) in 66%
yield and 100% selectivity, but with 0.4% e.e. only.
Although the [HFe(CO)3P]−…[NMe4]+ contact inter-
action in THF is not readily removed by DMSO (as
compared with the [HFe(CO)3P]−…Na+ contact inter-
action: see last section and ref. [9](a)), the intramolecu-
lar ion pairing is likely to be perturbed by this highly
Our first targets are ephosium ligands with a nitrogen
atom quaternized by alkyl groups larger than the initial
methyl groups. The flexibility of large alkyl sub-
stituents, however, is anticipated to dilute the eventual
conformation controlling the reduction of a prochiral
substrate: a substituted six-membered ring has a re-
stricted freedom degree, and we tackled the synthesis of
3b·PF6, the piperidinium homologue of the ephosium
3a·PF6 (Scheme 1).
N,N-(1,5-pentylene)-ephedrinium 2b*PF6 was pre-
pared in 81% yield from 1,5-dibromopentane and (−)-
ephedrine 1, followed by anion exchange of 2b·Br with
the hexafluorophosphate anion. The product reacted
slowly with excess Ph2PNEt2 in refluxing acetonitrile
for 4 days to afford the desired diphenylephosium
hexafluorophosphate 3b·PF6 in 90% yield. Attempts to
reduce the reaction time by heating neat reactants

J.-J. Brunet et al. / Journal of Organometallic Chemistry 566 (1998) 117–123
119
Table 1
i-(aminophosphine)–phosphinite (‘ValNOP’) have
been reported [13]. A related quaternary i-phos-
phinite–ammonium is now described (Scheme 2).
Under Eschweiler-Clarke conditions, (−)-valinol
leads to (−)-N,N-dimethyl valinol 5 in 74% yield [14].
Quaternization of 5 by methyl iodide occurs slowly in
71% yield. The primary alcohol function of N,N,N-
trimethylvalinolium iodide 6·I reacts with excess
2
Solvent dependence ꢀ JPHꢀ at 20°C of zwitterionic diphenylephosium
hydridotricarbonylferrates
2
2
NMR solvent
CD3CN (ꢀ JPHꢀ Hz)
[D8]THF (ꢀ JPHꢀ Hz)
3a·HFe(CO)3
3b·HFe(CO)3
25.8
28.0
34.9
36.5
Ph2PNEt2
in
acetonitrile
to
give
‘N,N,N-
resulted in the formation of the ene–ammonium side-
product 4b·PF6 [10]. The phosphinite–ammonium salt
3b·PF6 displaces both the potassium and one carbonyl
ligand of KHFe(CO)4 in THF to give the new zwitteri-
trimethyldiphenyl–valphosium’ iodide 7·I in 96% yield.
This phosphinite–ammonium reacts with KHFe(CO)4
in THF to give the zwitterionic complex, 7·HFe(CO)3
in 97% yield (in a mixture with 0.2 equivalents of KI).
Spectroscopic properties of 7·HFe(CO)3 are similar to
those of 3a·HFe(CO)3 and 3b·HFe(CO)3, and similar
structural features of these complexes are likely.
Surprisingly, the solid complex is still insoluble in
most organic solvents. Nevertheless, 7·HFe(CO)3 pro-
vides an example of a second structural kind of chiral
zwitterionic complex, the characterization of which is
compared below with that of the first structural kind
based on the ephedrine backbone.
onic
diphenylephosium
hydridotricarbonylferrate
3b·HFe(CO)3, which crystallizes from a sursaturated
THF solution at −20°C (in mixture with 0.6 equiva-
lents of KPF6: 79% yield). NMR characteristics of
3a·HFe(CO)3 and 3b·HFe(CO)3 are similar. In particu-
lar, the IR spectra suggest that they both adopt a
cis-H–Fe–P configuration (A%, A% and A%% bands). The
1
2
cis-geometry has been confirmed by single crystal X-ray
analysis for 3a·HFe(CO)3 [5]. Another unusual feature
2
of these complexes is the dependence of the ꢀ JPH
ꢀ
coupling constants on the solvent: the magnitude of
2
ꢀ JPHꢀ is lowered by about 9 Hz while increasing the
5. VTP-NMR study of the zwitterionic complexes
dielectric constant from 7 (THF) to 36 (acetonitrile) at
room temperature (Table 1). The dielectric constant is
known to vary as the reciprocal of the temperature [11],
2
Although the ꢀ JPH
ꢀ
coupling constant of
2
7·HFe(CO)3 in CD3CN at 25°C (10.8 Hz) is half that
of 3a·HFe(CO)3, both vary with temperature and
moreover at the same rate, ca 0.15 Hz K−1 (Fig. 2).
and, indeed, ꢀ JPHꢀ also decreases with temperature in a
given solvent (see last but one section): the possibility
of a relationship between this phenomenon and the
unusual cis-H–Fe–P geometry is discussed below.
Despite interesting structural features, the piperi-
dinium derivative is still not very soluble and the use of
a more lipophilic chiral backbone had to be explored.
2
Such behaviour of ꢀ JPHꢀ has been previously evidenced
in non-zwitterionic phosphane–hydridotricarbonylfer-
rate complexes having the classical trans-H–Fe–P ge-
ometry [15]: the occurrence of an equilibrium between
several stereoisomers or of a tight intermolecular ion-
pair interaction were ruled out, and this phenomenon
was explained by a dielectric constant-induced variation
of the Hax–Fe–COeq angle while maintaining the over-
all C36 symmetry. Nonetheless, ammonium cations were
shown to give intermolecular contact ion-pairing inter-
actions with [HFe(CO)3L]− anions which can be de-
tected by IR spectroscopy [9]: it is therefore reasonable
4. N,N,N-trimethyl-diphenylvalphosium and its
hydridotricarbonylferrate complex
Natural amino acid-derived aminoalcohols have been
widely used for the synthesis of chiral auxiliaries. Start-
ing from valinol, a i-aminophosphine (‘Valphos’) [12],
a secondary i-phosphinite–amine (‘ValNHOP’) and a
to
infer
that
intramolecular
ammonium–
Scheme 2. Synthesis of a diphenylvalphosium ligand and a zwitterionic complex. (i)CH2O/HCO2H, 100°C, 2 h, 74%. (ii) CH3I, ether, 90 h, 71%.
(iii) Ph2PNEt2, CH3CN, 19 h, 96%. (iv) KHFe(CO)4, THF, 25°C, 15 h, 97%.

120
J.-J. Brunet et al. / Journal of Organometallic Chemistry 566 (1998) 117–123
2
Fig. 2. ꢀ JPHꢀ versus temperature between −50 and +100°C in CD3CN or [D6]DMSO for the diphenylephosium complex 3a·HFe(CO)3 and the
diphenylvalphosium complex 7·HFe(CO)3. The average slope is 0.15 Hz K−1
.
[HFe(CO)3L]− interactions could be enhanced enough
to be detected by VTP-NMR spectroscopy. The dielec-
tric constant effect can also be a priori invoked here for
open-[+NꢀPFeH−…solvent]
= closed-[ꢀN+…−HFePꢀ]+solvent.
2
explaining the variation of ꢀ JPHꢀ with temperature, but
This hypothesis also partially accounts for the ob-
served shift and broadening of the hydride resonances at
low temperature (in contrast with the sharp lines ob-
served in the NMR spectra of non-zwitterionic
[HFe(CO)3P]− complexes at low temperature [15]), al-
though no decoalescence could be obtained above −
50°C. More subtle effects of the [FeH]−…solvent
interaction in the open form may also superimpose, but
their magnitude should be relatively weak according to
previous results on the non-zwitterionic cis-phosphane-
hydridocarbonylferrate complex [HFe(CO)3{P(OPh3}]−
,[PPN]+ [15,16]. Likewise, the presence of 0.2
equivalents of KI in the 7·HFe(CO)3 sample should not
this phenomenon was claimed to occur specifically with
trans-[HFe(CO)3L]− anions and not with their cis-con-
geners [15]: indeed, the only known phosphanehydri-
2
dotricarbonylferrate complex with a non-variable ꢀ JPH
ꢀ
is [HFe(CO)3{P(OPh3}]− which precisely exhibits an
unusual cis-geometry [16]. The zwitterionic complexes
3a·HFe(CO)3 and 7·HFe(CO)3 are thus original
phoshane–hydridotricarbonylferrates displaying both a
2
cis-H–Fe–P geometry and a dependence of ꢀ JPHꢀ with
solvent and temperature.
The cis-geometry could be dictated by a stabilizing
effect of an intramolecular interaction which could not
take place in a trans isomer owing to a steric hindrance
of the equatorial carbonyl ligands. Within this context,
2
influence the JPH values: in cat+,[HM(CO)nP]− salts,
the cation has been recognized to exert a weak influence
2
2
on JPH: ꢀD2JPHꢀB2 Hz for M=Fe [15,9](a)[18], Cr, W
the variation of ꢀ JPHꢀ would reveal a variation of the
[19], when cat+ =K+, Na+, Et4N+, PPN+, Li+). The
nature of hydridocarbonylate–ammonium contact in
solution cannot be detailed further [9](a)[20]. However,
H–Fe–P angle with the temperature-dependent average
opening of a seven-membered chelation ring with a
hemilabile electrostatic edge [HFe]−…+[N] [17]. This
average opening can be controlled not only by the
temperature but also by the relative energy of competi-
tive HFe−…solvent (and/or N+…solvent) interactions:
a
multisite docking of Me4N+onto an external
[HFe(CO)3P]− anion has been proposed to occur in
THF at both a [FeCO] level and the [Fe–H] level [15a]:
an intramolecular contact of this type is found in the
solid state structure of 3a·HFe(CO)3 [5] and could be
entropically favored in solution, even in polar solvents
such as acetonitrile and dimethylsulfoxide.
2
the dependence of ꢀ JPHꢀ with both the temperature and
the solvent can therefore be explained by an effect of the
solvent dielectric constant on the shift of the
equilibrium:

J.-J. Brunet et al. / Journal of Organometallic Chemistry 566 (1998) 117–123
121
6. Conclusion
Fe(CO)5 (Fluka) and KOH (technical 86%, Prolabo)
according to literature procedures [18].
Two kinds of chiral zwitterionic hydride complexes
of iron with phophinite–ammonium ligands 3a, 3b and
7, which are readily derived from commercially avail-
able optically pure ephedrine and valinol, have been
compared. However, chiral phosphinites are sensitive to
nucleophilic attack and protic cleavage. Akin cationic
phosphines with three P–C bonds would require fur-
ther preparation steps, but should be stable in alcoholic
medium where asymmetric reduction has better chance
to succeed. However, unlike phosphites [18] and phos-
phinites [21], phosphines require that they cannot be
anchored directly to the hydridotricarbonylferrate moi-
ety by CO-substitution from KHFe(CO)4 [22], and a
specific synthetic strategy is needed [23].
Beyond coordination chemistry and a possible use in
asymmetric reduction of dipolar substrates, chiral
cationic phosphanes could serve as ligands for the
design of novel catalysts: whereas dative bonds are
generally assumed to govern the stereoselectivity of
transition metal catalysis, electrostatic interactions play
a key role in stereoselective transformations occurring
in enzyme pockets. Coordination chemistry of zwitteri-
onic transition metallates with chiral ligands paves the
way to the design of chiral reactants or catalysts based
on a hybrid concept, where both dative and electro-
static interactions would take place.
7.1. N,N-(1,5-pentylene)ephedrinium
hexafluorophosphate 2b ·PF6
(−)-Ephedrine 1 (16.60 g, 100 mmol) and 1.5-dibro-
mopentane (14.6 g, 63 mmol) were dissolved in 50 ml of
refluxing toluene. After 15 h, a white solid had de-
posited and the reaction medium was cooled to r.t. and
the solid mixture of 2b·Br and 1·HBr was filtered. A
50 ml sample of 5N aqueous NaOH was added to a
slurry of the solid in 10 ml of water, which was then
washed with ether (3×20 ml: one equivalent of base
ephedrine was recovered from ether). The aqueous so-
lution was then dropwise acidified to pH=7 with con-
centrated HCl. A sample of 9.20 g KPF6 (50 mmol) was
added and a white solid filtered and dried (15.37 g,
81%). C15F6H24NOP (379.3): Calcd.: C, 47.50; H, 6.38;
N, 3.69%; found: C, 47.48; H, 6.49; N, 3.64%. 31P{1H}-
NMR: l= −139.1 (hept, 1JPF=705 Hz). 1H-NMR:
3
l=1.14 (d, JHH=6.8 Hz, 3H; CCH3
6
); 1.71–1.85 (m,
3
6H; CH2
5.7 Hz, 2H; NCH2
3.64 (m, 1 H; H
3JHH=3.9 Hz, 1 H; H
13C{1H}-NMR: l=6.55 (CC
(CH2CH2CH2); 45.26 (NCH3); 60.62 (NC
(NCH2); 69.39 (CHN); 73.91 (CHO); 126.67 (Cortho);
6
CH2
6
CH2
6
); 3.08 (s, 3H; NCH3
); 3.57 (t, 3JHH=5.7 Hz, 2H; NCH2
CCH3); 4.50 (1 H; OH); 5.52 (d,
CPh); 7.32–7.38 (m, 5 H; Ph).
H3); 20.43, 20.82, 21.50
H2); 61.42
6 ); 3.34 (t, JHH=
6
6 );
6
6
6
6
6
6
6
6
6
6
6
6
128.81 (Cpara); 129.40 (Cmeta); 142.12 (Cipso).
7. Experimental
7.2. N,N-(1,5-pentylene)-diphenylephosium
hexafluorophosphate 3b ·PF6
All experiments were carried out with standard vac-
uum line techniques under an argon atmosphere. THF
and ether were distilled under argon and over Na/ben-
zophenone, toluene over sodium and acetonitrile over
P2O5 before use. Commercial synthesis grade pentane,
dichloromethane, methanol and ethanol were degassed
by bubbling argon before use. Elemental analyses were
performed at the Service de Microanalyse du L.C.C.
Optical rotations were measured in a 1 dm cell with a
Perkin Elmer 241 polarimeter. IR spectra were recorded
on a Perkin-Elmer 1725X FT-IR spectrometer using
CaF2 windows. NMR spectra were recorded on a
2b·PF6 (1.65 g, 4.36 mmol) were dissolved in a
refluxing solution of Ph2PNEt2 (3.36 g, 13.1 mmol) in
15 ml of acetonitrile. The reaction was monitored by 1H
and 31P-NMR: after 100 h, the solution was cooled and
evaporated. The yellow residue was washed with ether
(2×50 ml, then 2×25 ml). 8 ml of a 7/1 THF/ether
mixture are added: an orange oil deposited which was
separated and dried (2.22 g; 90%). C15F6H24NOP
(563.51): Calcd.: C, 57.55; H, 5.90; N, 2.49%; found: C,
57.82; H, 5.91; N, 2.48%. 31P{1H}-NMR: l= −139.1
1
1
Brucker AC 200 spectrometer: at 200 MHz for H, 81
(hept, JPF=705 Hz, 1P; PF6−); 116.3 (s, 1P; Ph2P).
MHz for 31P and 50 MHz for 13C, in CD3CN as solvent
unless otherwise noted. Positive chemical shifts at low
field are expressed in ppm by internal reference to TMS
1H-NMR: l=1.41 (d, 3JHH=6.8 Hz, 3H; CCH3
6
6
);
);
1.51–1.75 (m, 6H; CH2
3.12–3.25 (m, 5H; CH2NCH2
3JPH=7.5 Hz, 1H; H
CPh); 7.28–7.60 (m, 15 H; Ph).
13C{1H}-NMR: l=7.27 (CC
H3); 20.17, 20.43, 21.14
(CH2CH2CH2); 44.43 (NCH3); 60.00 (NCH2); 61.17
(NC HN); 77.12 (d,
H2); 75.26 (d, 3JPC=5.8 Hz; C
2JPC=22.4 Hz; C
HOP); 127.5–141.0 (aromatic C with
6
CH2
6
CH2
6
); 2.75 (s, 3H; NCH3
CMe); 5.61 (d, broad,
6
6
, H
6
1
for H and 13C and by external reference to 85% H3PO4
6
in D2O for 31P. (−)-Ephedrine, (−)-valinol and
chlorodiphenylphosphine were purchased from Aldrich.
Ph2PNEt2 was prepared from Ph2PCl and two equiva-
lents of diethylamine in ether: 31P{1H}-NMR: l=66.6.
1H-NMR: l=0.93 (t, 3JHH=7.1 Hz; 6H), 3.07 (dq,
3JPH=9.7 Hz, 3JHH=7.1 Hz; 4H), 7.28–7.45 (10H).
THF solutions of KHFe(CO)4 were prepared from
6
6
6
6
6
6
6
6
6
a complex degenerated spectrum of four singlets for
PhC+four pairs of diastereoisomeric doublets for
Ph2P).

122
J.-J. Brunet et al. / Journal of Organometallic Chemistry 566 (1998) 117–123
Heating of the neat reactants at 100–110°C under
formic acid (8.41 g, 182.8 mmol) were heated at 100°C
for 2 h. The solution was cooled to r.t. and 30 ml of 5
N aqueous NaOH was added. After extraction with
ether (3×30 ml), the organic phase was washed with 20
ml of 5 N aqueous NaOH and then water (2×20 ml),
dried over MgSO4 and evaporated to dryness. A spec-
troscopically pure yellow oil 5 was obtained and used
as such in the next step (4.46 g; 74%). h2D5= −3.2°
vacuum resulted in the formation of 3b·PF6 in 50%
yield, along with ca 20% of the ene–ammonium 4b·PF6
which is purified as a white powder washed with ethyl
acetate, and identified by NMR: 31P{1H}-NMR: l= −
139.1 (hept, 1JPF=705 Hz). 1H-NMR: l=1.79–1.9
(m, 6H; CH2
3H; NCH3); 3.31 (dt; 2H axial or equatorial) and 3.92
(dt; 2H equatorial or axial) (2JHH=12.7 Hz, 4H;
N(CH2)2); 7.04 (broad, 1H; HCꢀ); 7.3–7.6 (m, 5H;
phenyl). 13C{1H}-NMR: l=12.71 (CC
H3); 20.78
(CH2CH2CH2); 53.54 (NCH3); 60.83 (N(CH2)2) 106.93
(ꢀCH); 127–140 (aromatic C and ꢀCN+).
6 CH6 2CH6 2); 2.06 (s, 3H; ꢀCCH6 3); 3.15 (s,
6
1
3
(neat). H-NMR: l=0.80 (d, JHH=5.4 Hz, 3H; CH3
6
);
3
6
6
0.92 (d, JHH=5.4 Hz, 3H; CH3
CH(CH3)2); 2.10 (m, 1H; CH
3.05 (broad, 1H; OH); 3.10–3.50 (m, JHH=4.3 Hz,
3JHH=10.6 Hz, JHH=8.1 Hz, 2H; CH2OH). 13C{1H}-
NMR: l=19.98 (CCH3); 22.15 (CH3); 28.30 (CHMe2);
41.47 (N(CH3)2); 59.46 (CH2OH); 71.48 (CHNMe2).
6
); 1.79 (sept. d, 1H;
6 N); 2.31 (s, 6H; N(CH6 3)2);
6
6
3
6
6
6
6
6
6
3
6
6
6
By comparison, the NMR data for 4a·PF6 obtained
as a side product of 3a·PF6 under similar conditions
6
6
6
6
6
6
are: 31P{1H}-NMR: l= −139.1 (hept, JPF=705 Hz).
1
l=2.12 (s, 3H; ꢀCCH3
6 ); 3.29 (s, 9H; N(CH6 3)3); 7.07
(broad, 1H; HCꢀ); 7.4–7.5 (m, 5H; phenyl).
6
7.5. N,N,N-trimethyl6alinolium iodide 6 ·I
CH3I (6.34 g, 45 mmol) was added into a solution of
5 (3.91 g, 29.8 mmol) in 20 ml of ether. The solution
was stirred for 15 h, and a white solid was filtered and
dried (2.76 g; 34%). Another 4 ml of CH3I was added
to the ether filtrate which was stirred for an additional
72 h. The solution was again filtered, the solid was
dried (2.97 g; 37%) and combined with the first crop
(5.74 g; 71%). C8H20INO (273.16): Calcd.: C, 35.18; H,
7.38; N, 5.13%: found C, 35.31; H, 7.37; N, 5.12%.
7.3. N,N-(1,5-pentylene)diphenylephosium
hydridotricarbonylferrate 3b ·HFe(CO)3
’
3b PF6 (0.84 g, 1.5 mmol) were dissolved in a solu-
tion of KHFe(CO)4 (0.31 g, 1.5 mmol) in 10 ml of
THF. The solution turned brown–yellow. After stirring
for 4 h, KPF6 was filtered. After 4 weeks at −20°C, a
yellow powder deposited from the red supernatant liq-
uid, which was filtered. After drying, 0.837 g of mate-
rial was obtained. NMR spectra indicate the presence
of residual THF (0.5 equivalents) and PF6− anion. For
1
[h]2D5= +10.2° (c=1.05, CH3CN). H-NMR: l=0.98
3
3
(d, JHH=6.8 Hz, 3H; CH3
3H; CH3); 2.39 (m, 1H; CH
N(CH3)3); 3.32 (m, 1H; CHN); 3.95 (broad, 3H; OH
and CH H3); 23.13
2OH). 13C{1H}-NMR: l=17.75 (C
(CH3); 26.83 (CHMe2); 53.41 (N(CH3)3); 56.21
(CH2OH); 80.13 (CHN).
6
); 1.05 (d, JHH=7.1 Hz,
6
6
(CH3)2); 3.14 (s, 9H;
C30FeH34NO4P(C4H8O)0.5(KPF6)0.6
(705.54,
79%):
6
6
6
Calcd.: C, 54.43; H, 5.43; N, 1.98%; found: C, 54.44; H,
5.40; N, 2.03%. Mp=72–76°C (dec.). IR (THF):
6
6
6
6
6
6
w(CO)=1946 (m; A% band), 1853 (s; A%% band), 1830
6
1
(m; A2% band) cm−1
;
w(FeH)=1888 (m) cm−1
.
31P{1H}-NMR: l=191.7 (s). H-NMR: l= −9.21 (d,
1
2JPH=28.0 Hz, 1H; FeH. In [D8]THF, 2JPH=36.5 Hz);
7.6. N,N,N-trimethyl-diphenyl6alphosium iodide 7 ·I
3
1.54 (d, JHH=6.8 Hz, 3H; CCH3); 1.6–1.9 (m, 6H;
(CH2)3); 2.93 (s, 3H; NCH3); 3.25 (m, 2H; CH2
6
N+);
6·I (1.40 g, 5.12 mmol) and Ph2PNEt2 (2.079 g, 8.20
mmol) were dissolved in 20 ml of refluxing acetonitrile.
After 19 h, the solution was cooled to r.t. and evapo-
rated to dryness. The pale yellow oil was stirred with
ether (3×20 ml) for 15 h: the resulting white solid was
filtered and dried (2.25 g; 96%). C20H29INOP (457.34):
Calcd.: C, 52.53; H, 6.39; N, 3.06%; found: C, 51.88; H,
3.51 (q, 3JHH=6.8 Hz, 1H; H
6
CMe); 3.70 (m, 2H;
3
CH2
7.0–8.0 (15H; aromatic CH
(CCH3); 20.28, 20.59, 21.32 (C
(broad +NCH3); 60.51, 61.03 (+N(C
2JPC=1.3 Hz); 75.95 (s, broad, JPCB2 Hz; CH
6 6
N+); 6.59 (d, broad, JPH=9.0 Hz, 1H; H
CPh);
6
). 13C{1H}-NMR: l=7.77
6
6
H2C
H2)2); 74.41 (d,
N+);
6 H2C6 H2,); 44.51
6
6
3
6
127.6–141.0 (aromatic C with a complex degenerated
spectrum of four singlets for PhC+four pairs of
diastereoisomeric doublets for Ph2P). 224.24 (2JPCB2
6.23; N, 3.06%. [h]2D5= −7.2° (c=1.05, CH3CN).
1
31P{1H}-NMR: l=123.4 (s, Ph2P
6
). H-NMR: l=0.94
3
3
(d, JHH=6.7 Hz, 3H; CH3
3H; CH3
N(CH3)3); 3.49 (m, 1H; CH
CH2
OP). 13C{1H}-NMR: l=17.46 (C
26.76 (CHMe2); 53.31 (N(CH3)3); 64.17 (d, JPC=22.5
Hz; CH2OP); 80.01 (d, JPC=9.1 Hz; CHN); 129.16–
6
C); 1.01 (d, JHH=7.1 Hz,
Hz; C
6
O).
6
C); 2.40 (m, 1H; CH
N); 4.02–4.30 (m, 2H;
H3); 22.70 (CH3);
6 Me2); 3.10 (s, 9H;
6
6
6
6
6
2
7.4. N,N-dimethyl6alinol 5
6
6
3
6
6
A mixture of 96% (−)-valinol (4.91 g, 45.7 mmol),
37% aqueous formaldehyde (3.43 g, 114.3 mmol) and
131.10 (aromatic C: four pairs of diastereoisomeric
doublets for Ph2P).

J.-J. Brunet et al. / Journal of Organometallic Chemistry 566 (1998) 117–123
123
[4] (a) U. Nagel, E. Kinzel, Chem. Ber. 119 (1986) 1731. (b) I. Toth,
B.E. Hanson, Tetrahedron Assym. 1 (1990) 895.
[5] J.-J. Brunet, R. Chauvin, G. Commenges, B. Donnadieu, P.
Leglaye, Organometallics 15 (1996) 1752.
7.7. N,N,N-trimethyl-diphenyl6alphosium
hydridotricarbonylferrate 7 ·HFe(CO)3
A solution of KHFe(CO)4 (1.12 g, 5.4 mmol) in 2.5
ml of THF was added to a solution of 7·I (2.11 g, 4.62
mmol) in 2.5 ml of THF. After stirring for 15 h, the
brown solution was filtered. Ether (4 ml) was added
and the solution was cooled to −20°C: after 10 days, a
solid had separated, which was dried (2.121 g; 97%).
[6] For quinine derivatives, see: (a) K.N. Gavrilov, I.S. Mikhel,
D.V. Lechkin, G.I. Timofeeva, Phosphorus, Sulfur, Silicon 108
(1996) 285. (b) E.E. Nifantyev, M.K. Gratchev, Tetrahedron
Lett. 36 (1995) 1727.
[7] The previous unreported optical rotation has been measured:
[h]25
D= −7.2° (c=0.19, CH3CN).
[8] J.-J. Brunet, R. Chauvin, F.B. Kindela, D. Neibecker, Tetrahe-
dron Lett. 47 (1994) 8801.
[9] (a) C.E. Ash, T. Delord, D. Simmon, M.Y. Darensbourg,
Organometallics 5 (1986) 17. (b) M. Darensbourg, H. Barros, C.
Borman, J. Am. Chem. Soc. 88 (1977) 1647.
[10] On the synthesis of ene–ammoniums, see for example: E. Elkik,
Bull. Soc. Chim. Fr. (1969) 903.
[11] J. Wymann Jr., J. Am. Chem. Soc. 58 (1936) 1482.
[12] T. Hayashi, M. Konishi, M. Fukushima, K. Kanahira, T. Hioki,
M. Kumada, J. Org. Chem. 48 (1983) 2195.
Elemental
analysis
consistent
with
C23H30FeNO4P(KI)0.2 (504.52): Calcd.: C, 54.50; H,
5.97; N, 2.76%; found: C, 54.53; H, 5.73; N, 2.65%.
[h]25578= +7°, [h]52456= +16° (c=0.2; DMSO). IR
(THF): w(CO)=1939 (m), 1846 (s), 1830 (sh) cm−1
;
w(FeH)=1883 (m) cm−1
.
31P{1H}-NMR: l=195.23
1
2
(Ph2P
6
). H-NMR: l= −8.84 (d, JHP=10.8 Hz, 1H;
FeH); 0.97 (d, 3JHH=6.7 Hz, 3H; CH3
3JHH=7.0 Hz, 3H; CH3
); 2.38 (m, 1H; CH
(s, 9H; N(CH3)3); 3.46 (m, 1H; CHN); 4.10–4.34 (2H;
CH2OP); 7.30–7.75 (5H; C6H5
). 13C{1H}-NMR: l=
17.55 (CH3C); 23.05 (CH3C); 27.30 (CHMe2); 53.47
(N+(CH3)3); 59.63 (d, 2JPC=6.6 Hz; C
H2OP); 80.64 (d,
3JPC=9.2 Hz; C
HN); 128.54–146.05 (aromatic C with
6
); 1.05 (d,
6 Me2); 3.08
[13] A. Mortreux, F. Petit, G. Buono, G. Pfeiffer, Bull. Soc. Chim.
Fr. (1987) 631.
6
[14] Although the obtained dimethylvalinol is optically active (h2D5
=
6
6
−3.2° (neat)), the possibility of a partial epimerization through
an internal iminium intermediate could be a priori considered:
6
6
6
6
6
H2Cꢀ+NMeC*H(i-Pr)CH2OH = Me2N+ꢀC(i-Pr)CH2OH
6
6
6
Dimethylation of (S)-valine by H2CO/H2/Pt–C followed by
LiAlH4 reduction of the acid led to (−)-valinol with h2D5= −
3.68° (neat), but no precision on the e.e. was given [11]. Previous
studies, however, indicated that substitution at asymmetric h-
carbons of primary amines is not sufficient to bring about a
significant isomerization unless this carbon is benzylic (methyla-
tion of optically pure 1-phenylethylamine occurs with 61% e.e.:
(a) A.C. Cope, E. Ciganeck, L.J. Fleckenstein, M.A.P.
Meisinger, J. Am. Chem. Soc. 82 (1960). Eschweiler-Clarke
a complex degenerated spectrum of four singlets for
PhC+four pairs of diastereoisomeric doublets for
2
Ph2P); 223.12 (d, JPC=11.2 Hz; gated spectrum: dd,
2JCH=12.6 Hz; C
6 O).
Acknowledgements
conditions have also been used for dimethylation of
D-penicil-
lamine which is structurally closely related to valinol: the e.e. is
82% and the authors ‘suspect that partial racemization occurs,
although this has neither been proved nor have exhaustive
attempts been made to avoid racemization’. (b) J.H. Griffin,
R.M. Kellogg, J. Org. Chem. 50 (1985) 3261. A similar e.e. for
5 is likely.
The authors wish to thank the Centre National de la
Recherche Scientifique, and Ms L. Noe´ for performing
elemental analyses.
[15] C.E. Ash, M.Y. Darensbourg, M.B. Hall, J. Am. Chem. Soc. 109
(1987) 4173.
References
[16] C.E. Ash, C.M. Kim, M.Y. Darensbourg, A.L. Rheingold, In-
org. Chem. 26 (1987) 1357.
[1] (a) R.T. Smith, R.K. Ungar, L.J. Sanderson, M.C. Baird,
Organometallics 2 (1983) 1138. (b) E. Renaud, R.B. Russel, S.
Fortier, S.J. Brown, M.C. Baird, J. Orgonomet. Chem. 419
(1991) 403. (c) E. Renaud, M.C. Baird, J. Chem. Soc. Dalton
Trans. (1992) 2905.
[2] See for example: (a) W.A. Herrmann, C.W. Kohlplainter,
Angew. Chem. Int. Ed. Engl. 32 (1993) 1524. (b) I.T. Horvath
(Ed.), Catalysis in Water. J. Mol. Cat. A 116 (1997). (c) H.
Gulyas, P. Arva, J. Bakos, J. Chem. Soc. Chem. Commun.
(1997) 2385.
[3] For recent examples, see: (a) D.J. Brauer, J. Fisher, S. Kucken,
K.P. Langhans, O. Stelzer, N. Weferling, Z. Naturforsch, B.
Chem. Soc. 49 (1994) 1511. (b) I. Kovacs, M.C. Baird, J.
Organomet. Chem. 502 (1995) 87. (c) B. Mohr, D.M. Lynn,
R.H. Grubbs, Organometallics 15 (1996) 4317.
[17] In 3a·HFe(CO)3, the electrostatic pairing in solution has been
indicated by
a measure of a
large 1H-NOE (36%) from
[N(CH3)3]+ onto [FeH]− [5].
[18] J.-J. Brunet, G. Commenges, F.B. Kindela, D. Neibecker,
Organometallics 11 (1992) 3023.
[19] S.C. Kao, M.Y. Darensbourg, W. Schenk, Organometallics 3
(1984) 871.
[20] M.Y. Darensbourg, J.M. Hanckel, Organometallics 1 (1982) 82.
[21] J.-J. Brunet, R. Chauvin, B. Donnadieu, P. Leglaye, D.
Neibecker, submitted for publication in this journal (1998).
[22] J.-J. Brunet, G. Commenges, F.B. Kindela, D. Neibecker,
Organometallics 11 (1992) 1343.
[23] J. Chiffre, S. Huguet, P. Leglaye, R. Chauvin, unpublished
results.
.