Oxidative Addition Reactions of Organorhodium(I) Complexes Containing the Tridentate Ligand 2,6-Bis(diphenylphosphanylmethyl)pyridine (R=CH3, C6H5) with Iodine and Methyl Iodide and Investigation of the Reductive Elimination

Article abstract of DOI:10.1002/(SICI)1099-0682(199903)1999:3<435::AID-EJIC435>3.0.CO;2-H

As part of studies aimed at delineating the mechanism of the rhodium complex-catalyzed hydroamination of olefins, the model complexes (R=CH3 1a, C6H5 1b) have been investigated with regard to oxidative addition reactions. The reaction of I2 wit

Full text of DOI:10.1002/(SICI)1099-0682(199903)1999:3<435::AID-EJIC435>3.0.CO;2-H

FULL PAPER
Complex Catalysis 55[°]
Oxidative Addition Reactions of Organorhodium(I) Complexes Containing the
Tridentate Ligand 2,6-Bis(diphenylphosphanylmethyl)pyridine [Rh(PNP)R]
(R ؍ CH3, C6H5) with Iodine and Methyl Iodide and Investigation
of the Reductive Elimination
Christine Hahn,[a] Michael Spiegler,[b] Eberhardt Herdtweck,[b] and Rudolf Taube*[b]
Dedicated to Professor Helmut Werner on the occasion of his 65th birthday
Keywords: Rhodium(III) complexes / Tridentate ligand / Oxidative addition / Reductive elimination / C–C coupling
As part of studies aimed at delineating the mechanism of the
rhodium complex-catalyzed hydroamination of olefins, the
model complexes [Rh(PNP)R] (R = CH3 1a, C6H5 1b) have
been investigated with regard to oxidative addition
reactions. The reaction of I2 with 1a leads to both trans- and
rhodium(III) complexes 2a,b and 3a,b have been
characterized by 31P-, 1H-, and 13C-NMR spectrometry, as
well as by EI mass spectrometry. The hydrocarbons RCH3 are
reductively eliminated in the reaction of [Rh(PNP)(CH3)RI]
(3a,b) with TlBF4 in acetone, while the reaction of 3b and
cis-[Rh(PNP)(CH3)I2] (trans: 2a, cis: 2aЈ), whereas with 1b TlBF4 in THF/CH3CN leads to the stable rhodium(III)
only trans-[Rh(PNP)(C6H5)I2] (2b) is obtained. The
rhodium(III) complexes [Rh(PNP)(CH3)RI] (3a,b) are formed
by the reaction of 1a,b with CH3I. The new organo-
complex [Rh(PNP)(CH3)(C6H5)(CH3CN)]BF4 (5). Complex 5
has been characterized by X-ray crystallography.
dition of the protic acid, could not be isolated or detected
in these cases, a stable monohydrido chloro rhodium(III)
complex [Rh(PNP)HCl(CH3CN)]SO3CF3 is accessible by
oxidative addition of HSO3CF3[4] to the related chloro rho-
dium(I) complex [Rh(PNP)Cl].[3b,5] Since the oxidative ad-
dition and the reductive elimination involved in numerous
other rhodium-complex catalyzed processes are of general
importance[6] it seemed therefore interesting to study these
reaction steps at the [Rh(PNP)]ϩ fragment.
In this paper, we report on oxidative addition reactions of
the organorhodium(I) complexes [Rh(PNP)R] (R ϭ CH3,
C6H5) with I2 and CH3I, as well as on the conditions under
which the obtained diorganorhodium(III) complexes
[Rh(PNP)(CH3)RI] undergo reductive elimination.
Introduction
Detailed model studies have been initiated aimed at eluci-
dating the reaction mechanism of the rhodium complex-
catalyzed hydroamination of ethylene.[1] For the first time,
the process was shown to be catalyzed by a cationic ethylene
rhodium(I) complex under normal conditions.[2] For these
studies, model complexes containing the 2,6-bis(diphen-
ylphosphanylmethyl)pyridine-rhodium(I) fragment [Rh-
(PNP)]ϩ as a stable structural unit were synthesized and
characterized.[3]
Since the formation and cleavage of an RhϪC σ-bond
is expected to play an essential role in this catalytic cycle,
organorhodium(I) complexes [Rh(PNP)R] (R ϭ CH3,
C6H5) were synthesized and investigated with regard to the
coordination of ethylene and protolysis. It was found that
with protic acids such as HSO3CF3 and [HN(CH3)3]Cl,
these organorhodium(I) complexes react by immediate re-
lease of the hydrocarbon HR, presumably via reductive
elimination from an initially formed hydrido organorho-
dium(III) complex.[4]
Results and Discussion
Oxidative Addition Reactions of [Rh(PNP)R]
(R ؍ CH3, C6H5) with I2 and CH3I
While a hydrido organorhodium(III) complex, which
might have been expected to be formed by oxidative ad-
In order to show that stable PNP-organorhodium(III)
complexes are accessible, the reactivity of organorhodi-
um(I) complexes 1a,b with iodine and methyl iodide, which
are known as suitable reagents for oxidative addition to
rhodium(I) complexes,[7] was investigated. Both organorho-
dium(I) complexes 1a,b were found to react smoothly with
iodine to give the corresponding rhodium(III) complexes
[Rh(PNP)I2R] 2 [Eqs. (1) and (2)], which were isolated as
brown, air-stable solids.
[°]
Part 54: See ref.[4]
[a]
`
Dipartimento di Chimica, Universita di Napoli “Federico II”
via Mezzocannone 4, I-80134 Napoli, Italy
E-mail: chahn@chemna.dichi.unina.it
Anorganisch-Chemisches Institut, Technische Universität
München
Lichtenbergstraße 4, D-85747 Garching, Germany
Fax: (internat.) ϩ49 (0)89/28913473
[b]
Eur. J. Inorg. Chem. 1999, 435Ϫ440
WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999
1434Ϫ1948/99/0303Ϫ0435 $ 17.50ϩ.50/0
435

C. Hahn, M. Spiegler, E. Herdtweck, R. Taube
FULL PAPER
The 31P-NMR signals observed at δ ϭ 26.5 (JPϪRh ϭ 120
Hz) for 3a and at δ ϭ 30.5 (JPϪRh ϭ 119 Hz) for 3b are
downfield shifted in comparison to the signals of the corre-
sponding diiodo complexes 2a and 2b. The increased phos-
phorus-rhodium coupling constants in 3a,b in comparison
to those in 2a,b may be arised by coordination of the more
basic methyl ligand instead of one iodo ligand, respectively.
In the 1H-NMR spectrum of the dimethyl complex 3a, two
discrete methyl signals are observed at δ ϭ Ϫ0.35 and δ ϭ
1.02, suggesting the coordination of two distinct methyl
groups in a mutual cis-arrangement. This is confirmed by
the resonances of the methylene protons of the PNP ligand,
which appear as two doublets of pseudo triplets at δ ϭ 4.31
and 4.66, consistent with the inequivalence of the methylene
protons arising from the cis orientation of the methyl
groups. Accordingly, in the 13C-NMR spectrum, two dis-
crete signals for the methyl groups are observed at δ ϭ
Ϫ14.5 and 6.9.
In the case of the methyl complex, the formation of the
trans as well as of the cis addition product (2a and 2aЈ,
respectively) was established by NMR spectrometry. The
two isomers constantly crystallize as a mixture, however, no
further attempts were made to separate 2a and 2aЈ by other
methods. In the 31P-NMR spectrum, two doublets are ob-
served at δ ϭ 14.3 (JPϪRh ϭ 99 Hz) for 2a and at δ ϭ 23.3
(JPϪRh ϭ 106 Hz) for 2aЈ, in an intensity ratio of 3:2. The
phosphorus-rhodium coupling constants are markedly
lower in comparison to those in the organorhodium(I) com-
plexes 1a,b, indicating the RhIII oxidation state.[8] Accord-
1
ingly, in the H-NMR spectrum, two discrete methyl group
1
signals are observed at δ ϭ 1.99 for 2a and at δ ϭ 0.43 for
2aЈ, with the same relative intensities of 3:2. The corre-
sponding characteristic signal patterns of the methylene
protons of the PNP ligand, a pseudo triplet at δ ϭ 4.84 for
2a and two doublets of pseudo triplets at δ ϭ 4.49 and 4.80
for 2aЈ, are consistent with the symmetry of these trans and
cis isomers. In the 13C-NMR spectrum, two discrete signals
at δ ϭ Ϫ18.4 and δ ϭ 8.7 are observed for the methyl
groups, while for the methylene groups of the PNP ligand,
two signals appear at δ ϭ 44.7 and δ ϭ 46.7, showing
slightly different intensities.
The phenyl complex 1b forms exclusively the trans ad-
dition product 2b on reaction with iodine [Eq. (2)]. The
31P-NMR spectrum exhibits only one doublet at δ ϭ 18.8
(JPϪRh ϭ 105 Hz). The pseudo triplet for the methylene
group is seen at δ ϭ 4.90 in the 1H-NMR spectrum, consist-
ent with the C2 symmetry of the trans-diiodo complex 2b.
The 1H-NMR signals of the phenyl moiety in 2b are slightly
downfield shifted compared to those found for 1b, appear-
ing at δ ϭ 6.88 and 7.96.
The H-NMR signal of the methyl group in the methyl
phenyl complex 3b appears at δ ϭ 0.35, while the phenyl
group gives rise to multiplets at δ ϭ 6.90 and 7.68. The
typical signal pattern for the non-equivalent methylene pro-
tons, as observed for 3a, is seen in the spectrum of 3b at
δ ϭ 4.34 and 4.80. The 13C-NMR signal for the methyl
group in 3b appears at δ ϭ 8.8, while the phenyl group
signals are seen at δ ϭ 121.5, 125.9, and 142.3.
In the mass spectra of 3a and 3b, peaks are observed
corresponding to the fragments [M Ϫ CH3]ϩ, [M Ϫ CH3
Ϫ R]ϩ, and [M Ϫ CH3 Ϫ R Ϫ I]ϩ. Additionally, in the
mass spectrum of 3b, a peak at m/z ϭ 91 can be observed,
attributable to [C7H7]ϩ. This suggests that toluene is re-
ductively eliminated from the methyl phenyl complex 3b fol-
lowing CϪC bond formation.
Investigation of the Reductive Elimination of
Hydrocarbons by C؊C Bond Formation from
[Rh(PNP)(CH3)RI]BF4 3a,b
In the mass spectra of 2a,aЈ (analyzed as an isomeric mix-
ture) and of 2b, peaks are observed corresponding to the
In a manner analogous to the reductive elimination of
fragments [M Ϫ I]ϩ, [M Ϫ R]ϩ, [M Ϫ I Ϫ R]ϩ, [M Ϫ I Ϫ the hydrocarbon from the proposed hydrido organorho-
I]ϩ, and [M Ϫ I Ϫ I Ϫ R]ϩ. Additionally in the mass spec- dium(III) intermediates by formation of a CϪH bond,[4,9]
trum of 2a,aЈ, a peak at m/z ϭ 142 is found, which can be the reactivity of the diorganorhodium(III) complexes 3a, b
assigned to [CH3I]ϩ as the product of reductive elimination. was investigated. The aforementioned mass spectral obser-
The reactions of 1a,b with methyl iodide [Eq. (3)] led to vation of toluene generation from 3b gave a prior indication
the diorganorhodium(III) complexes [Rh(PNP)(CH3)RI] of CϪC bond formation between the two organo moieties.
3a,b, which were isolated as pale-yellow air-stable solids and After addition of TlBF4 to a solution of 3a or 3b in acetone,
1
characterized by 31P-, H-, and 13C-NMR spectrometry, as TlI precipitated while the solution changed colour from
well as by mass spectrometry.
pale yellow to dark-red during 1Ϫ2 days indicating the
436
Eur. J. Inorg. Chem. 1999, 435Ϫ440

Complex Catalysis 55
FULL PAPER
change of the oxidation state from RhIII to RhI. Indeed, the
For the coordinated acetonitrile in 5, a singlet is observed
1
hydrocarbon which is formed by reductive elimination from at δ ϭ 1.45 in the H-NMR spectrum, while in the 13C-
3a and 3b, respectively [Eq. (4)], has been proved. Carrying NMR spectrum, two signals are observed at δ ϭ 2.0 and
out the reaction of 3a and TlBF4 in [D6]acetone in a sealed 128.5. In the IR spectrum, the two bands characteristic of
NMR tube the singlet of the liberated ethane could be ob- end-on coordinated acetonitrile[9] are seen at ν˜ ϭ 2281 and
1
served in the H-NMR spectrum while the signals of com- 2376 cmϪ1. The coordination of the pyridine of the PNP
plex 3a disappeared. Whereas the toluene reductively elim- ligand is indicated by two bands at ν˜ ϭ 1574 and 1606
inated from 3b was detected in the filtrate of the reaction cm
,
Ϫ1 [11] while a strong band at ν˜ ϭ 1062 cmϪ1 is character-
Ϫ
solution by gas chromatography. The dark colour of the istic of the non-coordinated BF4 anion.[12]
solutions indicated a decomposition reaction, most likely as
Single crystals of 5 of X-ray quality were obtained from
a consequence of the weak coordination of the acetone, a solution of the complex in acetone overlayered with di-
which does not have sufficient donor strength to stabilize ethyl ether. X-ray crystal structure analysis confirmed the
the remaining [RhI(PNP)]ϩ fragment. In order to prove that cis-arrangement of the organo moieties in the octahedral
the rhodium was present in the ϩI oxidation state, some complex cation of 5, which is an essential structural pre-
DMSO was added to the solution. The corresponding requisite for the reductive elimination of toluene. The mo-
stable rhodium(I) complex [Rh(PNP)(DMSO)]BF4 4 was lecular structure of the complex cation [Rh(PNP)-
obtained, which was identified by comparison of its 31P- (CH3)(C6H5)(CH3CN)]ϩ is shown in Figure 1.
NMR spectrum with that of an authentic sample (cf.
Comparing the rhodium-carbon distances of the σ-
bonded methyl and phenyl groups [RhϪC(3) 2.085(3),
RhϪC(11) 2.049(3)], only a very slight difference is appar-
ent. The small difference in bond lengths of the two types
of RhϪC bond may be viewed as reflecting the differential
trans influence of the N(sp2) and N(sp) atoms of the coordi-
nated pyridine moiety and acetonitrile ligand, respectively,
which gives rise to an extension of the RhϪC(sp2) bond
and a shortening of the RhϪC(sp3) bond. However, it may
also be viewed as merely following the expected trend that
the sp2 carbon atom has a shorter distance to the rhodium
atom than the sp3 carbon atom.
ref.[3b]).
Clearly, the cleavage of the iodo ligand from the octa-
hedral diorganorhodium(III) complex 3a,b leads to a kine-
tically unstable five-coordinate complex, which cannot be
stabilized by the weakly coordinating acetone used as sol-
vent. This confirms the dissociative mechanism of the re-
ductive elimination.[9]
However, when the reaction of 3b with TlBF4 was carried
out in the presence of the more strongly coordinating aceto-
nitrile, a stable six-coordinate methyl phenyl acetonitrile
rhodium(III) complex [Rh(PNP)(CH3)(C6H5)(CH3CN)]-
BF4 5 was obtained [Eq. (5)], which was isolated as an air-
stable, white, crystalline solid and characterized by 31P-,
1H-, and 13C-NMR spectrometry, as well as by X-ray crys-
tal structure analysis.
Furthermore, it is interesting to compare the molecular
structure of 5 with that of the related cationic RhIII complex
[Rh(PNP)ClH(CH3CN)]SO3CF3,[4] which contains the
same structural unit [RhIII(PNP)(CH3CN)]ϩ, but with the
hydrido ligand coordinated trans to the acetonitrile ligand.
In both complexes, the N atom of the coordinated aceto-
nitrile shows an identical distance to the rhodium atom of
˚
2.14 A, as a result of the comparable trans influence of the
methyl and hydrido ligands. However, the distance of the
pyridine N atom to the rhodium atom in 5 is significantly
˚
longer [RhϪN(2) 2.152(2) A] than the corresponding
RhϪN(py) distance in the hydrido chloro RhIII complex
[4]
˚
[RhϪN(2) 2.0656(17) A]. This is consistent with the ex-
pected stronger trans influence of the phenyl group, which
has a lower electronegativity than the chloro ligand coordi-
nated trans to the pyridine. The end-on coordinated aceto-
nitrile shows an almost linear arrangement of
RhϪN(1)ϪC(1)ϪC(2) [C(1)ϪN(1)ϪRh 172.0(2)°, N(1)Ϫ
C(1)ϪC(2) 178.4(4)°], as was also found in the cationic
In the 31P-NMR spectrum of 5, the doublet at δ ϭ 32.7 RhIII complex [Rh(PNP)ClH(CH3CN)]SO3CF3,[4] as well
(JPϪRh ϭ 117 Hz) is somewhat downfield shifted compared as in the cationic rhodium(I) complex [Rh(PNP)(CH3CN)]-
to the corresponding signal in the iodo complex 3b. While BF4.[3b]
1
the H- and 13C-NMR signals of the phenyl moiety appear
at approximately the same chemical shifts as found for 3b,
Conclusions
the signals for the methyl moiety of 5 are somewhat upfield
shifted in both the 1H- (δ ϭ 0.09) and the 13C-NMR spectra
The organorhodium(I) complexes [Rh(PNP)R] smoothly
(δ ϭ 2.0), compared to those in 3b. This may be interpreted undergo oxidative addition reactions with I2 and CH3I to
in terms of the differential trans influence of the respective give the stable organorhodium(III) complexes [Rh(PNP)-
trans-coordinated ligands (IϪ 3b; CH3CN 5).
RI2] and [Rh(PNP)(CH3)RI], respectively.
Eur. J. Inorg. Chem. 1999, 435Ϫ440
437

C. Hahn, M. Spiegler, E. Herdtweck, R. Taube
FULL PAPER
Figure 1. PLATON[13] drawing of the structure of the complex cation of [Rh(PNP)(C6H5)(CH3)(CH3CN)]BF4 5. Selected bond lengths
˚
[A] and angles [°]: RhϪN(1) 2.142(3), RhϪN(2) 2.152(2), RhϪC(3) 2.082(3), RhϪC(11) 2.049(3), RhϪP(1) 2.2913(9), RhϪP(2) 2.3098(8),
P(1)ϪC(10) 1.848(5), P(2)ϪC(4) 1.835(3); P(1)ϪRhϪP(2) 164.58(3), N(1)ϪRhϪP(1) 93.92(7), N(1)ϪRhϪP(2) 89.55(7), N(1)ϪRhϪN(2)
88.56(9), C(3)ϪRhϪC(11) 91.77(12), N(1)ϪRhϪC(3) 176.65(11), N(2)ϪRhϪC(11) 179.9(2), C(1)ϪN(1)ϪRh 172.0(2),
N(1)ϪC(1)ϪC(2) 178.4(4).
Varian Gemini 300 NMR spectrometer. The 1H- and 13C-NMR
It was shown that the diorganorhodium(III) complexes
shifts were referenced to the solvent signals, while the 31P-NMR
[Rh(PNP)(CH3)RI], in which the organo moieties are coor-
shifts were referenced to external 85% H3PO4. Ϫ A Chrompack CP
dinated in a cis arrangement, CϪC bond formation leading
9000 gas chromatograph was used for the identification of liquid
to the reductive elimination of the hydrocarbons RCH3 is
organic compounds. Ϫ EI mass spectra were recorded on an AMD
possible. This was realized by cleavage of the iodo ligand
402 spectrometer (AMD Intectra) at 70 eV. Ϫ C,H,N elemental
with TlBF4 in the presence of acetone. Acetone is too
analyses were carried out on a LECO CHN 932 analyzer, while Rh
weakly coordinating as a ligand to stabilize the resulting
five-coordinate diorganyl rhodium(III) complex. However,
when the reaction is carried out in the presence of the more
strongly coordinating CH3CN, the stable six-coordinate
acetonitrile complex [Rh(PNP)(CH3)(C6H5)(CH3CN)]BF4
is formed, confirming the dissociative mechanism of the re-
ductive elimination.
The smooth oxidative addition reactions of the model
compounds [Rh(PNP)R], and the stability as well as the
reactivity of the Rh-C σ-bond in the rhodium-PNP com-
plexes suggests that rhodium(I) has the potential to catalyze
the hydroamination of olefins according to the proposed
catalytic reaction mechanism.[4]
was determined using a photometric method.[14]
Synthesis of [Rh(PNP)RI2] (R ؍ CH3 trans: 2a, cis: 2aЈ; C6H5 2b):
237 mg of I2 (0.93 mmol) in 2 mL of THF was added to a solution
of 552 mg (0.93 mmol) of 1a in 4 mL of THF. After a few seconds,
a brown, microcrystalline solid precipitated, and the reaction mix-
ture was stirred for 10 min. After a further 30 min (without stir-
ring), the solid was filtered off and washed with THF and diethyl
ether. The crude product was recrystallized from refluxing THF.
The recrystallized product was washed twice with THF and twice
with diethyl ether and dried in vacuo.
2a (trans)/2aЈ (cis): Yield: 498 mg (0.59 mmol, 63%); m.p.
295Ϫ298°C (dec.). Ϫ C32H30I2NP2Rh (846.90): calcd. C 45.34, H
4.52, N 1.90, Rh 12.15; found C 45.43, H 4.33, N 1.73, Rh 12.03.
Ϫ
31P NMR (CD2Cl2): δ ϭ 14.3 (d, JPϪRh ϭ 99 Hz, trans), 23.3
(d, JPϪRh ϭ 106 Hz, cis). Ϫ 1H NMR (CD2Cl2): δ ϭ 0.43 (td,
JHϪP ϭ 6.2 Hz, JHϪRh ϭ 2.2 Hz, 3 H, CH3, cis), 1.99 (td, JHϪP
4.8 Hz, JHϪRh ϭ 2.2 Hz, 3 H, CH3, trans), 4.49 (d ps. t, JHaϪHb
17.3 Hz, NHϪP ϭ 4.4 Hz, 2 H, CHa, cis), 4.80 (d ps. t, JHaϪHb
ϭ
ϭ
ϭ
Experimental Section
All reactions were carried out under dry argon. Acetone, [D6]ace-
tone, CD2Cl2, and CDCl3 were refluxed over 4-A molecular sieves
and purged of oxygen by bubbling argon. THF and diethyl ether
were refluxed over Na/benzophenone. Acetonitrile, DMSO, and
˚
17.3 Hz, NHϪP ϭ 5.6 Hz, 2 H, CHb, cis), 4.84 (vt, NHϪP ϭ 4.6 Hz,
4 H, CHa, trans), 7.36Ϫ8.20 (m, PPh, py, trans/cis). Ϫ 13C NMR
(CD2Cl2): δ ϭ Ϫ18.4 (dt, JCϪP ϭ 8.9 Hz, JCϪRh ϭ 16.1 Hz, CH3,
trans), 8.7 (dt, JCϪP ϭ 4.0 Hz, JCϪRh ϭ 20.2 Hz, CH3, cis), 44.7
(ps. t, N ϭ 13.0 Hz, CH2, trans), 46.7 (ps. t, N ϭ 15.5 Hz, CH2,
cis), 121.3 (ps. t, N ϭ 5.0 Hz, C3,5-py), 121.5 (ps. t, N ϭ 5.0 Hz,
C3,5-py), 127.9 (ps. t, N ϭ 5.6 Hz, PCmeta, trans) 127.9 (ps. t, N ϭ
5.0 Hz, PCmeta, cis), 128.3 (ps. t, N ϭ 4.6 Hz, PCmeta, cis), 130.0 (s,
˚
methyl iodide were dried over 4-A molecular sieves and distilled
prior to use.
Infrared spectra were recorded from KBr pellets on a Perkin-Elmer
FT-IR 16 spectrometer. Ϫ The H-, 13C{1H}-, and 31P{1H}-NMR
1
spectra were recorded at 300, 75, and 121 MHz, respectively, on a
438
Eur. J. Inorg. Chem. 1999, 435Ϫ440

Complex Catalysis 55
PCpara, trans), 130.2 (s, PCpara, cis), 130.5 (s, PCpara, cis), 132.3 (ps. (CD2Cl2): δ ϭ 8.8 (dt, JCϪP ϭ 5.5 Hz, JCϪRh ϭ 26.7 Hz, CH3),
FULL PAPER
t, N ϭ 4.7 Hz, PCortho, cis), 132.9 (ps. t, N ϭ 5.0 Hz, PCortho, trans),
133.9 (ps. t, N ϭ 5.0 Hz, PCortho, cis), 138.2 (s, C4-py, cis), 138.5 (s,
46.3 (ps. t, N ϭ 14.1 Hz, CH2), 121.1 (ps. t, N ϭ 5.1 Hz, C3,5-py),
121.5 (s, Ph), 125.9 (s, Ph), 127.5 (ps. t, N ϭ 5.0 Hz, PCmeta), 128.2
C4-py, trans), 159.3 (ps. t, N < 3 Hz, C2,6-py, cis), 162.1 (ps. t, N < 3 (ps. t, N ϭ 4.7 Hz, PCmeta), 129.9 (s, PCpara), 130.0 (s, PCpara), 133.1
Hz, C2,6-py, trans). Ϫ EI-MS: m/z (%): 832 (0.1) [M Ϫ CH3]ϩ, 719 (ps. t, N ϭ 5.1 Hz, PCortho), 134.2 (ps. t, N ϭ 5.6 Hz, PCortho), 138.0
(1.2) [M Ϫ I]ϩ, 705 (100) [M Ϫ CH3 Ϫ I]ϩ, 578 (21) [M Ϫ CH3 Ϫ (s, C4-py), 142.3 (ps. t, N ϭ 4.0 Hz, Ph), 159.7 (ps. t, N < 3 Hz,
I Ϫ I]ϩ, 142 (16) [CH3I]ϩ.
C2,6-py). Ϫ EI-MS: m/z (%): 781 (0.1) [M Ϫ CH3]ϩ, 719 (0.8) [M Ϫ
C6H5]ϩ, 705 (100) [M Ϫ CH3 Ϫ C6H5]ϩ, 578 (17) [M Ϫ CH3
C6H5 Ϫ I]ϩ, 91 (57) [C7H8 Ϫ H]ϩ.
Ϫ
The synthesis of 2b was carried out in the same manner as de-
scribed for 2a/aЈ, starting from 572 mg (0.87 mmol) of 1b in 4 mL
of THF and 222 mg of I2 dissolved in 2 mL of THF. Yield: 565
mg (0.62 mmol, 71%); m.p. 293°C (dec.). Ϫ C37H32I2NP2Rh
(909.33): calcd. C 48.87, H 3.55, N 1.54, Rh 11.32; found C 49.05,
Reactivity of 3a and 3b Toward TlBF4: (a) A mixture of 20 mg
(0.027 mmol) of 3a and 8 mg (0.027 mmol) of TlBF4 in 0.7 mL of
[D6]acetone was shaken in a sealed NMR tube over 2 days. While
H 3.95, N 1.31, Rh 11.42. Ϫ 31P NMR (CD2Cl2): δ ϭ 18.8 (d, TlI precipitated the solution changed colour to dark-red. In the
1
JPϪRh ϭ 105 Hz). Ϫ H NMR (CD2Cl2): δ ϭ 4.90 (ps. t, NHϪP
ϭ
1H-NMR spectrum a singlet is found at δ ϭ 0.82 for ethane,
4.7 Hz, 4 H, CH2), 6.88 (m, 3 H, Ph), 7.26Ϫ7.38 (m, 20 H, PPh), whereas the signals of 3a completely disappeared.
7.60 (d, JHϪH ϭ 7.7 Hz, 2 H, 3,5-py), 7.82 (t, JHϪH ϭ 7.7 Hz, 1
78 mg (0.27 mmol) of TlBF4 was added to a solution of 215 mg
H, 4-py), 7.96 (m, 2 H, Ph). Ϫ 13C NMR (CD2Cl2): δ ϭ 48.1 (ps.
t, N ϭ 15.7 Hz, CH2), 121.5 (ps. t, N ϭ 5.3 Hz, C3,5-py), 122.7 (s,
Ph), 125.9 (s, Ph), 127.7 (ps. t, N ϭ 5.0 Hz, PCmeta), 130.3 (s,
PCpara), 134.3 (ps. t, N ϭ 4.7 Hz, PCortho), 135.9 (ps. t, N ϭ 24.5
Hz, PCipso), 138.8 (s, C4-py), 147.2 (ps. t, N ϭ 4.3 Hz, Ph), 160.4
(ps. t, N < 3 Hz, C2,6-py). Ϫ EI-MS: m/z (%): 832 (0.4) [M Ϫ
C6H5]ϩ, 781 (12.5) [M Ϫ I]ϩ, 705 (100) [M Ϫ I Ϫ C6H5]ϩ, 655
(1.4) [M Ϫ I Ϫ I]ϩ, 578 (27) [M Ϫ I Ϫ I Ϫ C6H5]ϩ.
(0.27 mmol) of 3b in 5 mL of acetone. After stirring overnight, a
yellow precipitate of TlI was filtered off. Toluene was detected in
the dark-red filtrate by means of gas chromatography. Upon ad-
dition of 0.5 mL of DMSO, the solution became orange-red in
colour. The DMSOϪrhodium(I) complex [Rh(PNP)(DMSO)]BF4
(4) was detected by 31P-NMR spectroscopy (in acetone/external
C6D6: δ ϭ 40.2, JPϪRh ϭ 148 Hz). This was consistent with an
authentic sample, which was prepared from [Rh(PNP)(C2H4)]BF4
and DMSO.[3b]
Synthesis of [Rh(PNP)(CH3)RI] (R ϭ CH3 3a, C6H5 3b): To a solu-
tion of 571 mg (0.96 mmol) of 1a in 6 mL of THF was added 60
µl of CH3I (Rh/CH3I ϭ 1:1). After a few seconds, a pale-yellow
microcrystalline solid precipitated and the reaction mixture was
stirred for 10 min. After a further 30 min (without stirring), the
solid was filtered off and washed with THF and diethyl ether. The
crude product was recrystallized by extraction with refluxing THF.
The recrystallized product was washed twice with THF, twice with
diethyl ether, and dried in vacuo.
(b) In the Presence of CH3CN: 322 mg (0.4 mmol) of 3b was sus-
pended in a mixture of 7 mL of THF and 1 mL of acetonitrile. To
this was added 120 mg of TlBF4 and the mixture was stirred over-
night. A yellow precipitate of TlI was deposited, which was filtered
off. Diethyl ether was added dropwise to the pale-yellow filtrate,
resulting in the precipitation of a white, crystalline solid. This was
filtered off, washed with diethyl ether, and dried in vacuo. The solid
was characterized as [Rh(PNP)(CH3)(C6H5)(CH3CN)]BF4 (5):
3a: Yield: 390 mg (0.53 mmol, 55%); m.p. 214Ϫ220°C (dec.). Ϫ Yield: 271 mg (0.34 mmol, 85%); m.p. 146°C (dec.).
Ϫ
C33H33INP2Rh (735.39): calcd. C 53.90, H 4.52, N 1.90, Rh 13.99; C40H38BF4N2P2Rh (798.41): calcd. C 60.17, H 4.80, N 3.51, Rh
found C 53.62, H 4.46, N 1.79, Rh 14.36. Ϫ 31P NMR (CD2Cl2):
12.89; found C 60.30, H 5.28, N 3.75, Rh 12.57. Ϫ 31P NMR
1
δ ϭ 26.5 (d, JPϪRh ϭ 120 Hz). Ϫ H NMR (CD2Cl2): δ ϭ Ϫ0.35 (CDCl3): δ ϭ 32.7 (d, JPϪRh ϭ 117 Hz). Ϫ 1H NMR (CDCl3): δ ϭ
(td, JHϪP ϭ 6.4 Hz, JHϪRh ϭ 2.2 Hz, 3 H, CH3), 1.02 (td, JHϪP
5.2 Hz, JHϪRh ϭ 2.1 Hz, 3 H, CH3), 4.31 (d ps. t, JHaϪHb ϭ 16.6
ϭ
0.09 (td, JHϪP ϭ 6.6 Hz, JHϪRh ϭ 1.5 Hz, 3 H, CH3), 1.45 (s, 3 H,
NCH3), 4.30 (d ps. t, JHaϪHb ϭ 17.5 Hz, NHϪP ϭ 4.3 Hz, 2 H,
Hz, NHϪP ϭ 4.2 Hz, 2 H, CHa), 4.66 (d ps. t, JHaϪHb ϭ 16.6 Hz, CHa), 4.47 (d ps. t, JHaϪHb ϭ 17.5 Hz, NHϪP ϭ 4.2 Hz, 2 H, CHb),
NHϪP ϭ 4.9 Hz, 2 H, CHb), 7.32Ϫ7.41 (m, 12 H, PPh), 7.50 (d,
6.95 (m, 3 H, Ph), 7.07Ϫ7.40 (m, 22 H, PPh, Ph), 7.75 (d, JHϪH ϭ
JHϪH ϭ 7.6 Hz, 2 H, 3,5-py), 7.73 (t, JHϪH ϭ 7.6 Hz, 1 H, 4-py), 7.7 Hz, 2 H, 3,5-py), 7.99 (t, JHϪH ϭ 7.7 Hz, 1 H, 4-py). Ϫ 13C
7.79 (m, 8 H, PPh). Ϫ 13C NMR (CD2Cl2): δ ϭ Ϫ14.5 (dt, JCϪP ϭ NMR (CDCl3): δ ϭ 2.03 (s, NCH3), 2.03 (m, overlapped with the
7.1 Hz, JCϪRh ϭ 22.4 Hz, CH3), 6.9 (dt, JCϪP ϭ 6.3 Hz, JCϪRh
26.0 Hz, CH3), 44.9 (ps. t, N ϭ 13.6 Hz, CH2), 120.8 (ps. t, N ϭ
5.0 Hz, C3,5-py), 127.9 (ps. t, N ϭ 5.0 Hz, PCmeta), 128.2 (ps. t, N ϭ
ϭ
NCH3 signal, CH3), 44.7 (ps. t, N ϭ 13.7 Hz, CH2), 120.4 (s, Ph),
122.5 (ps. t, N ϭ 5.6 Hz, C3,5-py), 127.2 (s, Ph), 128.5 (br, CN),
128.7 (br, PCmeta), 130.7 (s, PCpara), 130.8 (s, PCpara), 131.7 (ps. t,
4.3 Hz, PCmeta), 129.4 (s, PCpara), 130.1 (s, PCpara), 131.8 (ps. t, N ϭ N ϭ 18.3 Hz, PCipso), 132.7 (ps. t, N ϭ 5.7 Hz, PCortho), 132.9 (ps.
4.8 Hz, PCortho), 134.3 (ps. t, N ϭ 5.8 Hz, PCortho), 137.4 (s, C4-py), t, N ϭ 5.6 Hz, PCortho), 138.1 (ps. t, N < 4.0 Hz, Ph), 139.6 (s,
159.3 (ps. t, N < 3 Hz, C2,6-py). Ϫ EI-MS: m/z (%): 719 (2) [M Ϫ C4-py), 159.1 (ps. t, N < 3 Hz, C2,6-py). Ϫ IR (KBr): ν˜ ϭ 2281, 2376
CH3]ϩ, 705 (100) [M Ϫ CH3 Ϫ CH3]ϩ, 578 (15) [M Ϫ CH3 Ϫ CH3 cmϪ1 (CH3CN); 1574, 1606 (py); 1062 (BF4).
Ϫ I]ϩ.
Crystal Structure Determination of Compound 5: Crystal Data:
3b: The complex was obtained in the same manner as described for
3a, starting from 692 mg (1.05 mmol) of 1b and 66 µl of CH3I in monoclinic, P21/n (No. 14), a ϭ 12.6065(6), b ϭ 24.5689(10), c ϭ
C40H38BF4N2P2Rh · (C4H10O)0.8, formula weight 857.79 g molϪ1
,
3
˚ ˚
13.5059(9) A, β ϭ 102.356(6)°, V ϭ 4086.3(4) A , Z ϭ 4, dcalc ϭ
7 mL of THF. Ϫ Yield: 528 mg (0.66 mmol, 63%); m.p. 186Ϫ195°C
(dec.). Ϫ C38H35INP2Rh (797.46): calcd. C 57.23, H 4.42, N 1.76, 1.394 g cmϪ3, F(000) ϭ 1767. Ϫ Data Collection: STOE-IPDS,[14]
Rh 12.90; found C 56.75, H 4.60, N 1.56, Rh 12.46. Ϫ 31P NMR
Mo-Kα radiation (graphite monochromator, λ ϭ 0.71073 A), crys-
˚
(CD2Cl2): δ ϭ 30.5 (d, JPϪRh ϭ 119 Hz). Ϫ H NMR (CD2Cl2): tal size 0.34 ϫ 0.30 ϫ 0.26 mm3, T ϭ 193(2) K, scan range 2.0 <
δ ϭ 0.35 (td, JHϪP ϭ 6.4 Hz, JHϪRh ϭ 2.2 Hz, 3 H, CH3), 4.34 (d θ < 25.7°; intensities were measured for 31092 reflections with 7411
ps. t, JHaϪHb ϭ 16.9 Hz, NHϪP ϭ 4.3 Hz, 2 H, CHa), 4.80 (d ps. t, unique reflections, of which 5469 were considered observed [I Ն
JHaϪHb ϭ 16.6 Hz, NHϪP ϭ 4.8 Hz, 2 H, CHb), 6.90 (m, 3 H, Ph), 2σ(I)]. The reflections were corrected for Lorentz and polarization
7.11Ϫ7.38 (m, 20 H, PPh), 7.56 (d, JHϪH ϭ 7.7 Hz, 2 H, 3,5-py), effects; µ ϭ 0.55 mmϪ1, no absorption correction. Ϫ Structural
7.68 (m, 2 H, Ph). 7.83 (t, JHϪH ϭ 7.7 Hz, 1 H, 4-py). Ϫ 13C NMR Analysis and Refinement: Preliminary positions of heavy atoms
1
Eur. J. Inorg. Chem. 1999, 435Ϫ440
439

C. Hahn, M. Spiegler, E. Herdtweck, R. Taube
FULL PAPER
[2]
[3]
were found by direct methods,[16] while positions of the other non-
hydrogen atoms were determined from subsequent difference Four-
ier synthesis coupled with initial isotropic least-squares refine-
ment.[17] An additional diethyl ether solvent molecule was located
in the asymmetric unit and refined with 80% partial occupancy.
With the exception of those of the solvent molecule, all hydrogen
atoms were found in a difference Fourier map and refined with
individual isotropic temperature parameters. Refinement: Full-ma-
trix least-squares on F2; 7070 reflections; 649 refined parameters;
final R1 ϭ 0.0333, wR2 ϭ 0.0806, goodness-of-fit on F2 ϭ 1.040.
E. Krukowka, R. Taube, D. Steinborn, DD 296 909 A5
(10.11.88), 1988; Chem. Abstr. 1992, 213993b.
[3a] C. Hahn, J. Sieler, R. Taube, Chem. Ber. 1997, 130, 939Ϫ945.
[3b]
Ϫ
C. Hahn, J. Sieler, R. Taube, Polyhedron 1998, 17,
1183Ϫ1193.
[4]
[5]
[6]
C. Hahn, M. Spiegler, E. Herdtweck, R. Taube, Eur. J. Inorg.
Chem. 1998, 1425Ϫ1432.
G. Vasapollo, P. Giannoccaro, C. F. Nobile, A. Sacco, Inorg.
Chim. Acta 1981, 48, 125Ϫ128.
J. P. Collman, L. S. Hegedus, J. R. Norton, R. G. Finke, Prin-
ciples and Aplications of Organotransition Metal Chemistry, Uni-
versity Science Books, Mill Valley, CA, 1987.
[7] [7a]
T. E. Nappler, D. W. Meek, R. M. Kirchner, J. A. Ibers, J.
Am. Chem. Soc. 1973, 95, 4194Ϫ4210. Ϫ [7b] J. A. Tiethof, J. L.
Peterson, D. W. Meek, Inorg. Chem. 1976, 15, 1365Ϫ1370.
P. S. Pregosin, R. W. Kunz in 31P and 13C NMR of Transition
Metal Phosphine Complexes (Eds.: P. Diehl, E. Fluck, R. Kos-
feld), Springer-Verlag, Berlin, Heidelberg, New York, 1979,
vol. 16.
Crystallographic data (excluding structure factors) for the structure
reported in this paper have been deposited with the Cambridge
Crystallographic Data Centre (CCDC-100736). Copies of the
data can be obtained free of charge on application to CCDC,
12 Union Road, Cambridge CB2 1EZ, U.K. [Fax: (internat.)
ϩ 44-1223/336033; E-mail: deposit@ccdc.cam.ac.uk].
[8]
[9]
D. Milstein, Acc. Chem. Res. 1984, 17, 221Ϫ226.
B. N. Storhoff, H. C. Lewis, Coord. Chem. Rev. 1977, 23, 1Ϫ29.
W. V. Dahlhoff, S. M. Nelson, J. Chem. Soc. (A) 1971,
2184Ϫ2190.
[10]
[11]
[12]
[13]
W. Beck, K. Sünkel, Chem. Rev. 1988, 88, 1405Ϫ1421.
A. L. Spek, “PLATON-92”, Acta Crystallogr. Sect. A 1990,
46, C34.
Acknowledgments
We thank the Deutsche Forschungsgemeinschaft (Sonderfor-
schungsbereich 347 of the University of Würzburg) for financial
support.
[14]
[15]
[16]
B. Lange, Z. J. Vejdelek, Kolorimetrische Analyse, Verlag
Chemie, Weinheim, 1982, p. 232.
IPDS Operating System Version 2.8., STOE & CIE GmbH,
Darmstadt, Germany, 1997.
A. Altomare, G. Cascarano, C. Giacovazzo, A. Guargliardi, M.
C. Burla, G. Polidori, M. Camalli, SIR-92, University of Bari,
Italy, 1992.
[1]
[1a] R. Taube in Applied Homogeneous Catalysis with Organome-
tallic Compounds (Eds.: B. Cornils, W. A. Herrmann), Verlag
[1b]
[17]
Chemie, Weinheim, 1996, vol. 1, pp. 507. Ϫ
D. Steinborn,
G. M. Sheldrick, SHELXL-93, in Crystallographic Computing
3 (Ed.: G. M. Sheldrick, C. Krüger, R. Goddard), Oxford Uni-
versity Press, England, 1993, pp. 175Ϫ189.
Received June 6, 1998
[1c]
R. Taube, Z. Chem. 1986, 26, 349Ϫ359. Ϫ
J.-J. Brunet, D.
Neibecker, F. J. Niedercorn, J. Mol. Catal. 1989, 49, 235Ϫ259.
[1d]
[1e]
Ϫ
J.-J. Brunet, Gazz. Chim. Ital. 1997, 127, 111Ϫ118. Ϫ
T. E. Müller, M. Beller, Chem. Rev. 1998, 98, 675Ϫ703.
[I98181]
440
Eur. J. Inorg. Chem. 1999, 435Ϫ440