Product diversity in the reaction of [(norbornadiene){CpP(iPr) 2}Rh] with alkyl iodides

Article abstract of DOI:10.1002/ejic.200600347

The reagents [(CpPR₂)Li] [R = iPr (2b), cyclohexyl (2c)] react with [(nbd)RhCl] (nbd = norbornadiene) dimer [(1a)₂] to yield the respective mononuclear complexes [(nbd)Rh(CpPR₂)] (3b,c). Subsequent treatment of 3b with a large excess of MeI led to the formation of the stable organometallic phosphonium salt [(nbd)Rh{CpP(iPr)₂Me}]I (4b). The analogous reaction of 3b with the slightly more bulky EtI or nPrI resulted in the formation of the dinuclear [μ-CpP(iPr)₂]-bridged dirhodium complex [(nbd)Rh{CpP(iPr)₂}Rh(nbd)I] (5b) and the corresponding ylides C₅H₄P(iPr)₂R¹ [R¹ = Et (6b), nPr (6c)]. The rhodium complexes 3b, 4a and 5b were characterised by X-ray crystal-structure analyses. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.

Full text of DOI:10.1002/ejic.200600347

FULL PAPER
DOI: 10.1002/ejic.200600347
Product Diversity in the Reaction of [(norbornadiene){CpP(iPr)2}Rh] with
Alkyl Iodides
Esteban Ortega,[a] Nina Kleigrewe,[a] Gerald Kehr,[a] Gerhard Erker,*[a] and
Roland Fröhlich[a]
Keywords: Rhodium / Phosphonium salts / Dimetallic complexes / Cyclopentadienyl ligands / Phosphorus ylides
The reagents [(CpPR2)Li] [R = iPr (2b), cyclohexyl (2c)] react
with [(nbd)RhCl] (nbd = norbornadiene) dimer [(1a)2] to yield
the respective mononuclear complexes [(nbd)Rh(CpPR2)]
(3b,c). Subsequent treatment of 3b with a large excess of MeI
led to the formation of the stable organometallic phospho-
nium salt [(nbd)Rh{CpP(iPr)2Me}]I (4b). The analogous reac-
tion of 3b with the slightly more bulky EtI or nPrI resulted in
the formation of the dinuclear [µ-CpP(iPr)2]-bridged dirho-
dium complex [(nbd)Rh{CpP(iPr)2}Rh(nbd)I] (5b) and the cor-
responding ylides C5H4P(iPr)2R1 [R1 = Et (6b), nPr (6c)]. The
rhodium complexes 3b, 4a and 5b were characterised by X-
ray crystal-structure analyses.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2006)
desired mononuclear complex 3a and its dinuclear adduct
5a containing an unreacted monomeric (nbd)RhCl unit
from the starting material (1a)2. These two products could
not be separated with sufficient ease, nor were we able to
convert 5a back to the desired 3a, for example by treatment
with additional 2a (Scheme 1).
Introduction
[CpRh(L)n] complexes have been of increasing interest
lately due to some remarkable reactivities, for example their
ability to catalyse selective C–H activation processes in con-
junction with R2B–BR2 reagents.[1] It may be of interest to
use Rh cyclopentadienides that bear functional groups at
their Cp rings in order to potentially facilitate such cur-
rently high activation energy C–H cleavage reactions by pre-
coordination of suitable substrates in a second coordination
sphere around the catalytically active metal centre. For that
reason, we have prepared a couple of (dialkylphosphanyl)-
cyclopentadienyl-containing rhodium(I) complexes[2] and
have encountered some unexpected features with regard to
their reactions with alkyl iodides. This will be described and
discussed in this article.
Scheme 1.
Therefore, we made a variety of changes in our synthetic
scheme and slightly changed the substituents and reagents
to eventually achieve a clean formation of mononuclear RhI
complexes of the desired type. The reagents [{CpP(iPr)2}Li]
(2b) and [(CpPCy2)Li] (2c; Cy = cyclohexyl) were prepared
as described in the literature.[5,6] The reaction of [(nbd)-
RhCl]2 [(1a)2] with 2b was carried out in THF at room tem-
perature. Removal of the solvent and extraction of the resi-
due with pentane cleanly gave the mononuclear complex
[(nbd)Rh{CpP(iPr)2}] (3b; 85% isolated yield). Complex 3b
was characterised by X-ray diffraction. Single crystals were
obtained from pentane. The structure shows a typical dis-
turbed trigonally planar coordination geometry around the
rhodium atom made up by the pair of norbornadiene C=C
double bonds [C=C(centroid)–Rh–C=C(centroid) = 70.7°]
and the substituted Cp ring [Cp(centroid)–Rh–C=C(cen-
troid) = 144.4° and 144.9°]. The norbornadiene ligand is
almost symmetrically bonded to the metal atom through its
Results and Discussion
Synthetic Developments
The (diphenylphosphanyl)cyclopentadienide anion was
prepared by treatment of CpLi with ClPPh2 followed by
deprotonation with n-butyllithium/hexane in toluene.[3]
When we wanted to attach this simple functionalised ligand
to an Rh(diene) framework, we encountered the same diffi-
culties that had previously been observed by Poilblanc et
al.[2] For example, treatment of the (nbd)RhCl (nbd = nor-
bornadiene) dimer [(nbd)RhCl]2 [(1a)2][4] with [(CpPPh2)Li]
(2a) always resulted in the formation of a mixture of the
[a] Organisch-Chemisches Institut der Universität Münster,
Corrensstrasse 40, 48149 Münster, Germany
E-mail: erker@uni-muenster.de
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E. Ortega, N. Kleigrewe, G. Kehr, G. Erker, R. Fröhlich
FULL PAPER
endo face [Rh–C14/C15 = 2.119(2), 2.127(2) Å; Rh–C18/ phosphane complex 3b as it features the same framework
C17 = 2.127(2), 2.135(2) Å]. The diisopropylphosphanyl- structure (see Figure 1 and Table 1). This similarity even ex-
substituted Cp ring is rather uniformly η5-coordinated to tends to the overall characteristics of the favoured confor-
the rhodium atom, with Rh–C(Cp) distances being in a nar- mational orientation of the Cp[P] ring system. The C1–P
row range between 2.214(2) and 2.290(2) Å.[7] In the crystal, bond in 4a is shorter [1.767(5) Å] than in 3b [1.822(2) Å]
a metal complex conformation is found that has the bulky and the phosphorus centre is tetracoordinate (Figure 2).
P(iPr)2 substituent rotated toward one side of the coordi-
nated nbd ligand, with the C1–P vector almost bisecting the
C15–Rh–C17 angle in the respective projection. The phos-
phorus centre in complex 3b is three-coordinate and prochi-
ral [C1–P–C7 = 103.1(1)°; C1–P–C6 = 99.7(1)°; C7–P–C6
= 101.9(1)°].
In solution, rotation around the Rh–Cp[P] vector is fast.
Scheme 3.
Consequently, complex 3b shows only one norbornene ole-
1
finic H NMR multiplet (δ = 3.24 ppm) representing four
protons plus a signal for the two bridgehead hydrogen
atoms (δ = 3.22 ppm). The methyl groups of the isopropyl
substituents at the prochiral phosphorus atom are pairwise
diastereotopic, as expected (13C: δ = 19.7/20.4 ppm). The
1H NMR signals of the pairs of Cp hydrogen atoms are
observed at δ = 4.93 (2 H) and 5.20 (2 H) ppm. The corre-
sponding 31P NMR resonance of 3b occurs at δ = –3.2 ppm.
The reaction of dimer (1a)2 with [(CpPCy2)Li] (2c) took
place analogously. The product [(nbd)Rh(CpPCy2)] (3c)
was isolated in 68% yield. It was characterised spectroscop-
ically and by C,H elemental analysis (for details see the Ex-
perimental Section and Scheme 2).
Figure 1. View of the molecular structure of [(nbd)Rh{CpP(iPr)2}]
(3b).
Table 1. Comparison of selected structural parameters of com-
plexes 3b, 4a and 5b.[a]
3b
4a
5b (Rh1)
5b (Rh2)
Rh–C1
2.290(2) 2.276(5) 2.291(3)
Rh–C2
Rh–C3
2.281(2) 2.256(5) 2.216(3)
2.252(2) 2.268(6) 2.256(3)
Scheme 2.
Rh–C4
2.261(2) 2.249(6) 2.256(3)
Rh–C5
C1–P
2.214(2) 2.291(5) 2.248(3) Rh2–I1
1.822(2) 1.767(5) 1.811(3) Rh2–P1
2.119(2) 2.129(6) 2.118(3) Rh2–C14b
2.127(2) 2.122(5) 2.126(3) Rh2–C15b
2.135(2) 2.122(5) 2.125(3) Rh2–C17b
2.127(2) 2.133(5) 2.105(3) Rh2–C18b
2.6624(4)
2.2992(7)
2.218(3)
2.223(3)
2.096(3)
2.105(3)
Rh1–C14
Rh1–C15
Rh1–C17
Rh1–C18
C14–C15
C17–C18
Reactions with Alkyl Iodides
We expected that the CpPR2 subunit in complex 3b, for
example, should show a typical reactivity pattern of a phos-
phorus nucleophile. Treatment with suitable alkyl electro-
philes might, therefore, yield the respective quaternized
phosphonium salts at the organometallic backbone. This
was actually observed when we treated complex 3b with
1.409(4) 1.396(9) 1.404(4) C14b-C15b 1.361(4)
1.404(4) 1.401(8) 1.403(4) C17b-C18b 1.391(4)
[a] Bond lengths [Å].
In solution, complex 4a features a typical phosphonium-
methyl iodide. Treatment of 3b with a large excess of MeI in type 31P NMR chemical shift (δ = +35.1 ppm).[9,10] Again,
pentane rapidly led to the formation of the organometallic the system is conformationally equilibrated in solution. The
phosphonium salt 4a (Scheme 3), which precipitated from isopropyl methyl groups at the prochiral phosphorus atom
the solution and was obtained as a slightly beige-coloured are pairwise diastereotopic [13C NMR: δ = 16.6/16.7 (CH3),
solid in 92% yield.[8] Slow diffusion of pentane vapour into 22.8 (d, JP,C = 49.7 Hz, CH) ppm] and there is an ad-
1
a solution of 3b in dichloromethane gave single crystals that ditional CH3 group bonded to the phosphorus centre [1H
were suitable for an X-ray crystal structure analysis. The NMR: δ = 2.24 (2JP,H = 12.5 Hz) ppm; 13C NMR: δ = 4.3
structure of phosphonium salt 4a is very similar to that of (1JP,C = 54.4 Hz) ppm].
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Reaction of [(norbornadiene){CpP(iPr)2}Rh] with Alkyl Iodides
FULL PAPER
P1 = 2.2992(7) Å; I1–Rh2–P1 = 95.76(2)°]. The resulting
bond angle at the phosphorus atom (Rh2–P1–C1) is
119.24(9)° (Figure 3).
Figure 2. Molecular structure of [(nbd)Rh{CpP(iPr)2Me}]I (4a).
The reaction of complex 3b with excess ethyl iodide un-
der similar conditions gave a different reaction product. Af-
ter removal of the volatiles in vacuo, we isolated the dinu-
clear [µ-CpP(iPr)2]-bridged dirhodium complex 5b in good
yield (86%; Scheme 4). This product was characterised
spectroscopically, by C,H elemental analysis and by X-ray
diffraction (single crystals were obtained from a pentane
solution at –30 °C).
Figure 3. Molecular structure of complex 5b.
In solution, there is again a rapid rotation around the
Rh1–Cp[P] vector, resulting in the observation of a single
1H NMR =CH resonance [δ = 3.09 (4 H) ppm] for the nbd-
1 ligand. In contrast, nbd-2, which is bonded to the dis-
torted square planar Rh2 centre, exhibits a clearly differen-
tiated pair of HC=CH 1H/13C NMR features of the double
bonds cis to I and cis to P1 [1H NMR: δ = 3.83/5.36 (each
2 H) ppm; 13C NMR: δ = 51.0/78.4 ppm], respectively.
Again, the isopropyl groups at the prochiral phosphorus
atom are pairwise diastereotopic, as expected (1H NMR: δ
= 1.12/1.36 ppm; 13C NMR: δ = 19.7/20.1 ppm). The 31P
NMR resonance of complex 5b is located at δ = +40.1 ppm.
Although the complete mechanistic elucidation of the
unexpected formation of the dinuclear product 5b must
await further detailed studies, we would like to propose a
tentative scheme for the possible formation of this product.
It may be assumed that the formation of the unexpected
product 5b might also be initiated by phosphonium salt for-
mation. The resulting intermediates (4b, 4c) seem not to
be stable under the applied reaction conditions but rather
undergo a nucleophilic displacement of the respective
(C5H4)P(iPr)2R moiety (6b, 6c) by iodide. Substitution of
the Cp-phosphonium ylides 6b, 6c might be facilitated by
their higher steric bulk as compared to the [P]-CH3 deriva-
tive 6a in 4a. In the case of 4b and 4c the nucleophilic sub-
stitution reaction probably leads to the formation of the
ethyl- or n-propyl-substituted phosphonium salts 6b or 6c,
Scheme 4.
The X-ray crystal structure analysis of 5b shows the pres- respectively, which must be assumed to be slightly more
ence of an [(nbd)Rh{CpP(iPr)2}] subunit that is structurally bulky than their methylphosphonium analogue 6a. Appar-
very similar to that found in 3b or 4a (see above and ently, the reaction in the cases 4b and 4c, in contrast to the
Table 1). The phosphorus atom of this unit coordinates to more persistent 4a, proceeds with cleavage of the Cp ligand
the Rh centre of an (nbd)RhI subunit. The norbornadiene bearing the bulky phosphonium substituent from the rho-
ligand is again endo-coordinated through both its C=C dium atom, with the possible formation of (nbd)RhI (1b).
double bonds. The rhodium centre Rh2 is distorted square- Under the applied reaction conditions, this monomeric spe-
planar coordinated by this pair of C=C double bonds and cies seems never to reach a high enough concentration to
P1 and I1 are cis to each other [Rh2–I1 = 2.6624(4), Rh2– give rise to observable dimer formation, but is apparently
Eur. J. Inorg. Chem. 2006, 3769–3774
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E. Ortega, N. Kleigrewe, G. Kehr, G. Erker, R. Fröhlich
FULL PAPER
X-ray Crystal-Structure Determinations: Data sets were collected
with a Nonius KappaCCD diffractometer equipped with a rotating
anode generator. Programs used: data collection COLLECT (Non-
ius B.V., 1998), data reduction Denzo-SMN (Z. Otwinowski, W.
Minor, Methods in Enzymology 1997, 276, 307–326), absorption
correction SORTAV (R. H. Blessing, Acta Crystallogr., Sect. A
1995, 51, 33–37; R. H. Blessing, J. Appl. Crystallogr. 1997, 30, 421–
426) and Denzo (Z. Otwinowski, D. Borek, W. Majewski, W.
Minor, Acta Crystallogr., Sect. A 2003, 59, 228–234), structure
solution SHELXS-97 (G. M. Sheldrick, Acta Crystallogr., Sect. A
efficiently trapped by the neutral starting material 3b to
yield the CpPR2-bridged dinuclear product 5b.[5,11] We have
only observed this unexpected reaction pathway in the case
of treatment of 3b with ethyl iodide or n-propyl iodide but
so far not with methyl iodide, which only gave the organo-
metallic phosphonium salt 4a that is stable under the ap-
plied reaction conditions.
In order to further support the proposed reaction course,
we treated 2b with methyl iodide, ethyl iodide and n-propyl
iodide. The corresponding trialkyl(Cp)phosphonium ylide 1990, 46, 467–473), structure refinement SHELXL-97 (G. M. Shel-
drick, University of Göttingen, 1997), graphics SCHAKAL (E.
Keller, University of Freiburg, 1997). CCDC-600987 to -600989
(for 3b, 4a and 5b, respectively) contain the supplementary crystal-
lographic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
products (6a–c) were isolated as pale-yellow solids and
characterised spectroscopically. The resulting ylide 6a fea-
tures a 31P NMR signal at δ = 24.7 ppm and a 13C NMR
resonance for the adjacent C1 ring carbon atom at δ =
1
74.0 ppm with a very characteristic JP,C coupling constant
of 104 Hz [C=P(iPr)2Me].[12,13] The ethyl-substituted
CpP(iPr)2Et ylide 6b shows an analogous 13C NMR feature
at δ = 74.3 ppm (1JP,C = 101 Hz). This signal was detected
in the crude reaction mixture obtained by treatment of
complex 2b with ethyl iodide to eventually yield 5b.
Reaction of [{CpP(iPr)2}Li] (2b) With [(nbd)RhCl]2 [(1a)2]. Forma-
tion of Complex 3b: A solution of 2b (94 mg, 0.50 mmol) in THF
(3 mL) was added to a solution of (1a)2 (115 mg, 0.25 mmol) in
THF (3 mL) at ambient temperature and the suspension was stirred
at room temperature overnight. Subsequently, the solvent was re-
moved in vacuo and the crude product was extracted through Celite
with pentane (4 mL) five times. Evaporation of the solvent yielded
the rhodium complex 3b as a yellow powder (160 mg, 0.43 mmol,
85%). Crystals suitable for X-ray crystal structure analysis were
obtained by slow evaporation of the solvent from a concentrated
pentane solution at ambient temperature. 1H NMR (500 MHz,
C6D6, 298 K): δ = 0.95 (t, J = 1.5 Hz, 2 H, CH2nbd), 1.13 (dd, J =
14.6, 7.1 Hz, 6 H, MeiPr), 1.25 (dd, J = 10.8, 6.8 Hz, 6 H, MeiPr),
1.90 (dsept, J = 7.0, 0.9 Hz, 2 H, CHiPr), 3.22 (m, 2 H, CHnbd),
3.24 (m, 4 H, =CHnbd), 4.93 (m, 2 H, Cp), 5.20 (m, 2 H, Cp) ppm.
13C{1H} NMR (125 MHz, C6D6, 298 K): δ = 19.7 (d, J = 9.3 Hz,
MeiPr), 20.4 (d, J = 17.5 Hz, MeiPr), 23.8 (d, J = 12.8 Hz, CHiPr),
30.5 (d, J = 10.5 Hz, =CHnbd), 47.0 (d, J = 2.8 Hz, CHnbd), 57.4
(d, J = 7.0 Hz, CH2nbd), 86.3 (m, Cp), 89.0 (m, Cp), 94.7 (Cp;
detected by 1H/13C ghmbc experiment) ppm. 31P{1H} NMR (C6D6,
81 MHz, 298 K): δ = –3.2 (s, PiPr2) ppm. C18H26PRh (376.27):
calcd. C 57.45, H 6.96; found C 57.49, H 6.92.
Conclusions
The reaction of [(nbd){CpP(iPr)2}Rh] (3b) with simple
alkyl iodides shows some remarkably different outcomes
depending on the bulk of the alkyl group of the RI reagent
used. The reaction with methyl iodide leads to the forma-
tion of a stable phosphonium salt 4a, whereas the analo-
gous reaction of 3b with either EtI or nPrI rapidly results
in the formation of the dinuclear product 5b. The experi-
mental characteristics of these reactions led us to assume
that in the latter cases the corresponding phosphonium
salts might also have been formed initially. However, these
slightly more bulky systems seem to be unstable with regard
to CpP(iPr)2R ylide dissociation,[14] a pathway that eventu-
ally leads to the formation of 5b. For the less bulky [(nbd)-
{CpP(iPr)2Me}Rh]I system this pathway seems not to be
readily available under our typical reaction conditions. This
specific alkyl group dependent behaviour makes the 3b +
RI reaction system a remarkable example of an observed
borderline behaviour along a threshold determined by
rather subtle differences in steric bulk.
X-ray Crystal Structure Analysis of 3b: C18H26PRh, M = 376.27,
colourless crystal 0.30×0.30×0.05 mm, a = 5.875(1), b = 10.749(1),
c = 13.870(1) Å, α = 104.53(1), β = 90.22(1), γ = 93.37(1)°, V =
846.3(2) Å3, ρcalcd. = 1.477 gcm–3, µ = 1.093 mm–1, empirical ab-
sorption correction (0.735 Յ T Յ 0.947), Z = 2, triclinic, space
¯
group P1 (no. 2), λ = 0.71073 Å, T = 198 K, ω- and φ-scans, 8037
reflections collected ( h, k, l), [(sinθ)/λ] = 0.67 Å–1, 4102 inde-
pendent (Rint = 0.034) and 3745 observed reflections [I Ն 2σ(I)],
185 refined parameters, R = 0.027, wR2 = 0.070, max. (min.) resid-
ual electron density 0.41 (–1.06) eÅ–3, hydrogen atoms calculated
and refined as riding atoms.
Experimental Section
General: All reactions involving air- or moisture-sensitive com-
pounds were carried out under an inert gas using Schlenk-type
glassware or in a glove box. Solvents were dried and distilled prior
to use. The following instruments were used for physical characteri-
sation of the compounds: Melting points: DSC 2010 TA-instru-
ments; elemental analyses: Foss-Heraeus CHNO-Rapid; MS:
Reaction of [(CpPCy2)Li] (2c) with [(nbd)Rhcl]2 [(1a)2]. Formation
of Complex 3c: According to the procedure described for the for-
mation of 3b, 3c was obtained as a yellow powder (54 mg,
0.118 mmol, 68%) from 2c (46 mg, 0.173 mmol) in THF (2 mL)
and (1a)2 (40 mg, 0.087 mmol) in THF (1 mL). The crude product
1
Micromass Quattro LC-Z electrospray mass spectrometer; NMR: was extracted three times through Celite with pentane (2 mL). H
Bruker AC 200 P (1H: 200 MHz; 13C: 50 MHz), ARX 400 (1H:
400 MHz; 13C: 100 MHz), Varian 500 INOVA (1H: 500 MHz; 13C:
125 MHz) or Varian UNITY plus 600 (1H: 600 MHz; 13C:
151 MHz). The complex [(nbd)RhCl]2 (1a)[4] and the reagents
[{CpP(iPr)2}Li] (2b)[5] and [{CpPCy2}Li] (2c)[5] were prepared ac-
cording to literature procedures.
NMR (400 MHz, C6D6, 298 K): δ = 0.97 (m, 2 H, CH2nbd), 1.11–
1.47 (m, 12 H, Cy), 1.65 (dm, J = 11.9 Hz, 2 H, Cy), 1.78 (dm, J
= 11.2 Hz, 2 H, Cy), 1.85 (m, 2 H, Cy), 1.93 (dm, J = 11.7 Hz, 2
H, Cy), 2.31 (dm, J = 11.7 Hz, 2 H, Cy), 3.25 (m, 4 H, =CHnbd),
3.24 (m, 2 H, CHnbd), 4.95 (m, 2 H, Cp), 5.18 (m, 2 H, Cp) ppm.
13C{1H} NMR (100.6 MHz, C6D6, 298 K): δ = 27.0 (s, Cy), 27.6
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Reaction of [(norbornadiene){CpP(iPr)2}Rh] with Alkyl Iodides
(d, J = 7.8 Hz, Cy), 27.8 (d, J = 11.5 Hz, Cy), 30.4 (broad d, J =
FULL PAPER
CH2nbd1), 65.1 (dd, J = 4.9, 2.1 Hz, CH2nbd2), 78.4 (dd, J = 11.4,
10.6 Hz, Cy), 30.4 (d, J = 8.7 Hz, Cy), 30.6 (d, J = 15.2 Hz, 5.5 Hz, =CHnbd2), 87.2 (dd, J = 6.1, 4.2 Hz, Cp), 88.0 (dd, J = 7.6,
=CHnbd), 34.1 (d, J = 12.8 Hz, Cy), 47.1 (d, J = 2.1 Hz, CHnbd), 3.9 Hz, Cp). 89.1 (Cp, detected by 1H/13C ghmbc experiment) ppm.
57.4 (d, J = 6.8 Hz, CH2nbd), 86.5 (m, Cp), 89.3 (dd, J = 14.6, J =
31P{1H} NMR (121.5 MHz, C6D6, 298 K): δ = 40.1 (d, J =
3.3 Hz, Cp), 95.1 (dd, J = 23.5, J = 4.6 Hz, Cp) ppm. 31P{1H} 163.4 Hz, PiPr2) ppm. C25H34IPRh2 (698.23): calcd. C 43.00, H
NMR (121.5 MHz, C6D6, 298 K): δ = –11.2 (s, PCy2) ppm.
C24H34PRh (456.39): calcd. C 63.16, H 7.51; found C 63.55, H
7.62.
4.91; found C 43.03, H 5.26.
X-ray Crystal-Structure Analysis of 5b: C25H34IPRh2, M = 698.21,
red crystal 0.20×0.20×0.10 mm, a = 10.097(1), b = 17.498(1), c =
13.770(1) Å, β = 92.85(1)°, V = 2429.8(2) Å3, ρcalcd. = 1.909 gcm–3,
µ = 2.704 mm–1, empirical absorption correction (0.614 Յ T Յ
0.774), Z = 4, monoclinic, space group P21/n (no. 14), λ =
0.71073 Å, T = 198 K, ω- and φ-scans, 16579 reflections collected
( h, k, l), [(sinθ)/λ] = 0.67 Å–1, 5968 independent (Rint = 0.030)
and 5230 observed reflections [I Ն 2σ(I)], 267 refined parameters,
R = 0.026, wR2 = 0.059, max. residual electron density 1.47
(–1.62) eÅ–3 close to iodine, hydrogen atoms calculated and refined
as riding atoms.
Reaction of 3b with Methyl Iodide. Formation of the Organometallic
Phosphonium Salt 4a: A large excess of methyl iodide (0.25 mL,
4.00 mmol) was added to a solution of 3b (35 mg; 0.09 mmol) in
pentane (5 mL). Precipitation occurred immediately and the tawny
suspension was stirred at ambient temperature for 2 h. The super-
natant was removed by filtration in air and the resulting beige filter
cake was washed carefully with pentane (1 mL). Subsequently, the
residue was dried in vacuo and 4a was obtained as a brown powder
(44 mg, 0.085 mmol, 92%). Crystals suitable for X-ray crystal
structure analysis were obtained by slow diffusion of pentane into
a concentrated solution of 4a in dichloromethane. 1H NMR
(500 MHz, CDCl3, 298 K): δ = 1.06 (t, J = 1.6 Hz, 2 H, CH2nbd),
1.43 (dd, J = 9.7, 7.1 Hz, 6 H, MeiPr), 1.47 (dd, J = 9.5, 7.1 Hz, 6
H, MeiPr), 2.24 (d, J = 12.5 Hz, 3 H, Me), 3.03 (m, 2 H, CHiPr),
3.36 (broad s, 2 H, CHnbd), 3.53 (m, 4 H, =CHnbd), 5.19 (m, 2 H,
Cp), 5.79 (m, 2 H, Cp) ppm. 13C{1H} NMR (125 MHz, CDCl3,
298 K): δ = 4.3 (d, J = 54.4 Hz, Me), 16.6 (d, J = 2.5 Hz, MeiPr),
16.7 (d, J = 2.9 Hz, MeiPr), 22.8 (d, J = 49.7 Hz, CHiPr), 35.2 (d, J
= 10.1 Hz, =CHnbd), 46.7 (d, J = 2.6 Hz, CHnbd), 58.4 (d, J =
6.9 Hz, CH2nbd), 72.8 (dd, J = 90.6, 6.0 Hz, Cp) 87.7 (dd, J = 11.6,
4.2 Hz, Cp), 92.4 (dd, J = 10.1, 3.7 Hz, Cp) ppm. 31P{1H} NMR
(CDCl3, 121.5 MHz, 298 K): δ = 35.1 (s, PiPr2) ppm. MS (ESI):
m/z calcd. 391.105 [M–I]+; found 391.00. C19H29IPRh (518.20):
calcd. C 44.03, H 5.64; found C 43.94, H 5.50.
Reaction of 3b with n-Propyl Iodide. Formation of Complexes 5b and
6c: n-Propyl iodide (7.8 µL, 13.5 mg, 0.08 mmol) was added to a
solution of 3b (30 mg, 0.08 mmol) in C6D6 (1 mL) at room tem-
perature. The reaction mixture was transferred into an NMR tube
and the reaction was monitored by NMR spectroscopy.
Reaction of [{CpP(iPr)2}Li] (2a) with Methyl Iodide. Generation of
6a: Methyl iodide (99.30 µL, 227 mg, 1.60 mmol) was added to a
solution of 2a (300 mg, 1.60 mmol) in toluene (40 mL) at room
temperature. After the reaction mixture had been stirred at ambient
temperature overnight, all volatiles were removed in vacuo. The
product was obtained as a bright yellow solid (310 mg, 0.94 mmol,
59%). M.p. 96 °C (DSC). 1H NMR [400 MHz, C6D6/TDF (4:1),
298 K]: δ = 6.66, 6.31 (each m, each 2 H, C5H4), 1.83 (dsept, JH,H
= 6.8, JP,H = 10.0 Hz, 2 H, CHiPr), 1.08 (d, JP,H = 12.0 Hz, 3 H,
Me), 0.82 (dd, JP,H = 16.2, JH,H = 6.8 Hz, 6 H, MeiPr), 0.70 (dd,
JP,H = 15.8, JH,H = 6.8 Hz, 6 H, MeiPr) ppm. 13C{1H} NMR
[100 MHz, C6D6/TDF (4:1), 298 K]: δ = 113.9 (d, J = 16.3 Hz,
C5H4), 113.3 (d, J = 13.8 Hz, C5H4), 74.0 (d, J = 104.2 Hz, C=P),
22.7 (d, J = 52.9 Hz, CHiPr), 15.6 (d, J = 1.8 Hz, MeiPr), 15.4 (d, J
= 2.1 Hz, MeiPr), 0.6 (d, J = 56.9 Hz, Me–P) ppm. 31P{1H} NMR
(81 MHz, C6D6, 298 K): δ = 24.7 (s, PiPr2) ppm. MS (ESI): m/z
calcd. 197.1459 [M + H]+; found 197.1446. C12H21P·LiI (330.12):
calcd. C 43.66, H 6.41; found C 42.61, H 6.52.
X-ray Crystal-Structure Analysis of 4a: C19H29IPRh·CH2Cl2, M =
603.13, yellow crystal 0.30×0.10×0.03 mm, a = 15.973(1), b =
10.887(1), c = 26.453(1) Å, V = 4600.1(5) Å3, ρcalcd. = 1.742 gcm–3,
µ = 2.389 mm–1, empirical absorption correction (0.534 Յ T Յ
0.932), Z = 8, orthorhombic, space group Pbca (no. 61), λ =
0.71073 Å, T = 198 K, ω- and φ-scans, 22987 reflections collected
( h, k, l), [(sinθ)/λ] = 0.66 Å–1, 5470 independent (Rint = 0.060)
and 4556 observed reflections [I Ն 2σ(I)], 231 refined parameters,
R = 0.045, wR2 = 0.146, max. (min.) residual electron density 1.75
(–0.82) eÅ–3 close to iodine, hydrogen atoms calculated and refined
as riding atoms.
Reaction of [{CpP(iPr)2}Li] (2a) with Ethyl Iodide. Generation of
6b: According to the procedure described for the generation of 6a,
6b was obtained as a colourless powder (435 mg, 1.26 mmol, 79%)
from the reaction of 2a (300 mg, 1.60 mmol) with ethyl iodide
(129 µL, 249 mg, 1.60 mmol) in toluene (40 mL). M.p. 144 °C
(DSC). 1H NMR [600 MHz, C6D6/TDF (4:1), 298 K]: δ = 6.59,
Reaction of 3b with Ethyl Iodide. Formation of Complex 5b: A large
excess of ethyl iodide (0.25 mL, 3.10 mmol) was added to a solution
of 3b (30 mg; 0.08 mmol) in toluene (3 mL) at room temperature.
After the reaction mixture had been stirred at ambient temperature
overnight, all volatiles were removed in vacuo. The obtained yellow
oil was washed twice with pentane (1 mL) and dried in vacuo. The
pure product was obtained as a yellow solid (48 mg, 0.07 mmol,
86%). Crystals suitable for X-ray crystal structure analysis were
6.28 (each m, each 2 H, C5H4), 1.99 (dsept, JP,H = 10.6, JH,H
=
7.0 Hz, 2 H, CHiPr), 1.77 (dq, JP,H = 12.7, JH,H = 7.7 Hz, 2 H,
CH2), 0.90 (dd, JP,H = 15.4, JH,H = 7.0 Hz, 6 H, MeiPr), 0.86 (q,
JP,H = JH,H = 7.7 Hz, 3 H, CH3), 0.80 (dd, JP,H = 15.4, JH,H
=
7.0 Hz, 6 H, MeiPr) ppm. 13C{1H} NMR (125 MHz, C6D6/TDF,
4:1, 298 K): δ = 113.7 (d, J = 16.7 Hz, C5H4), 113.3 (d, J = 13.3 Hz,
C5H4), 73.1 (d, J = 103.5 Hz, P=C), 22.0 (d, J = 51.8 Hz, CHiPr),
16.2 (d, J = 1.8 Hz, MeiPr), 16.0 (d, J = 1.9 Hz, MeiPr), 11.7 (d, J
= 52.9 Hz, CH2), 7.5 (d, J = 4.8 Hz, CH3) ppm. 31P{1H} NMR
(81 MHz, C6D6, 298 K): δ = 24.7 (s, PiPr2) ppm. MS (ESI): m/z
calcd. 211.1616 [M + H]+; found 211.1. C13H23P·LiI (344.15):
calcd. C 45.37, H 6.74; found C 44.45, H 6.73.
1
obtained from a pentane solution at –30 °C. H NMR (600 MHz,
C7D8, 298 K): δ = 0.90 (br., 2 H, CH2nbd1), 1.10/1.14 (each dm, J
= 8.5 Hz, each 1 H, CH2nbd2), 1.12 (dd, J = 14.5, 7.1 Hz, 6 H,
MeiPr), 1.36 (dd, J = 15.8, 7.0 Hz, 6 H, MeiPr), 2.46 (dsept, J = 7.9,
7.1 Hz, 2 H, CHiPr), 3.09 (m, 4 H, =CHnbd1), 3.08 (m, 2 H,
CHnbd1), 3.36 (br., 2 H, CHnbd2), 3.83 (m, 2 H, =CHnbd2), 4.41 (m,
2 H, Cp), 5.07 (m, 2 H, Cp), 5.36 (m, 2 H, =CHnbd2) ppm. 13C{1H}
NMR (150 MHz, C7D8, 298 K): δ = 19.7 (MeiPr), 20.1 (d, J = Reaction of [{CpP(iPr)2}Li] (2a) with n-Propyl Iodide. Generation
4.7 Hz, MeiPr), 27.9 (d, J = 24.1 Hz, CHiPr), 31.9 (d, J = 10.2 Hz,
=CHnbd1), 47.1 (d, J = 2.4 Hz, CHnbd1), 51.0 (dd, J = 2.3, 1.6 Hz,
CHnbd2), 52.2 (d, J = 11.7 Hz, =CHnbd2), 57.7 (d, J = 6.7 Hz,
of 6c: According to the procedure described for the generation of
6a, 6c was obtained as a colourless powder (470 mg, 0.76 mmol,
82%) from the reaction of 2a (300 mg, 1.60 mmol) with n-propyl
Eur. J. Inorg. Chem. 2006, 3769–3774
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3773

E. Ortega, N. Kleigrewe, G. Kehr, G. Erker, R. Fröhlich
FULL PAPER
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iodide (156.5 µL, 271 mg, 1.60 mmol) in toluene (40 mL). M.p.
101 °C (DSC). H NMR (600 MHz, C6D6/TDF (4:1), 298 K): δ =
1
6.67, 6.33 (each m, each 2 H, C5H4), 1.96 (dsept, JP,H = 10.8, JH,H
= 7.2 Hz, 2 H, CHiPr), 1.76 (m, 2 H, PCH2), 1.32 (m, 2 H, CH2),
0.90 (dd, JP,H = 15.8, JH,H = 7.2 Hz, 6 H, MeiPr), 0.79 (dd, JP,H
15.6, JH,H = 7.2 Hz, 6 H, MeiPr), 0.76 (td, JH,H = 7.1, JH,H
=
=
1.5 Hz, 3 H, CH3) ppm. 13C{1H} NMR [125 MHz, C6D6/TDF
(4:1), 298 K]: δ = 113.8 (d, J = 16.6 Hz, C5H4), 113.4 (d, J =
13.8 Hz, C5H4), 73.2 (d, J = 102.3 Hz, P=C), 22.3 (d, J = 52.3 Hz,
CHiPr), 20.9 (d, J = 51.8 Hz, PCH2), 17.1 (d, J = 4.1 Hz, CH2),
16.2 (d, J = 2.1 Hz, MeiPr), 16.0 (d, J = 2.1 Hz, MeiPr), 16.1 (d, J
= 15.3 Hz, CH3) ppm. 31P{1H} NMR [81 MHz, C6D6/TDF (4:1),
298 K]: δ = 26.1 (s, PiPr2) ppm. MS (ESI): m/z calcd. 225.18 [M +
H]+; found 456.00 [2M + H,Li]+. C14H25P·LiI (358.17): calcd. C
46.95, H 7.04; found C 47.24, H 7.34.
Acknowledgments
Financial support from the Fonds der Chemischen Industrie and
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Received: April 18, 2006
Published Online: August 3, 2006
3774
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Eur. J. Inorg. Chem. 2006, 3769–3774