Synthesis and characterization of organorhodium(I) complexes with the tridentate ligand 2,6-bis(diphenylphosphanylmethyl)pyridine [Rh(PNP)R] (R = CH3, C6H5) and their reactivity toward ethylene and protic acids

Article abstract of DOI:10.1002/(SICI)1099-0682(199810)1998:10<1425::AID-EJIC1425>3.0.CO;2-R

The organorhodium(I) complexes [Rh(PNP)R] [PNP = 2,6-bis(diphenylphosphanylmethyl)pyridine, R = CH₃ (3a), C₆H₅ (3b)] were synthesized from [Rh(PNP)(C₂H₄)IBF₄ (1a) and LiR and characterized by ³¹P-, ¹H-, and ¹³C-NMR spectroscopy and EI mass spectrometry. In a THF solution saturated with ethylene 3a and 3b form the five-coordinate ethylene organorhodium(I) complexes [Rh(PNP)R(C₂H₄)] (5a, b). The stable monohydridorhodium(III) complex [Rh(PNP)ClH-(CH₃CN)]SO₃CF₃ (7) was obtained by the reaction of [Rh(PNP)Cl] with HSO₃CF₃ in a solution of THF/acetonitrile and characterized by X-ray crystallography. In a THF solution the organorhodium(I) complexes 3a, b react upon the addition of either HSO₃CF₃ or HNMe₃Cl with the immediate release of the respective hydrocarbon HR.

Full text of DOI:10.1002/(SICI)1099-0682(199810)1998:10<1425::AID-EJIC1425>3.0.CO;2-R

FULL PAPER
Complex Catalysis, LIV[᭛]
Synthesis and Characterization of Organorhodium(I) Complexes with the
Tridentate Ligand 2,6-Bis(diphenylphosphanylmethyl)pyridine [Rh(PNP)R]
(R ؍ CH3, C6H5) and Their Reactivity toward Ethylene and Protic Acids
Christine Hahna, Michael Spieglerb, Eberhardt Herdtweckb, and Rudolf Taube*b
Institut für Anorganische Chemie, Universität Würzburga,
Am Hubland, D-97074 Würzburg, Germany
E-mail: christine.hahn@mail.uni-wuerzburg.de
Anorganisch-Chemisches Institut, Technische Universität Münchenb,
Lichtenbergstraße 4, D-85747 Garching, Germany
Fax: (internat.) ϩ 49(0)89/289-13473
Received April 27, 1998
Keywords: Organorhodium(I) complexes / Tridentate ligand / Protolysis / Reductive elimination / C–H coupling
The organorhodium(I) complexes [Rh(PNP)R] [PNP = 2,6-
bis(diphenylphosphanylmethyl)pyridine, R = CH3 (3a), C6H5
(3b)] were synthesized from [Rh(PNP)(C2H4)]BF4 (1a) and LiR
and characterized by 31P-, 1H-, and 13C-NMR spectroscopy
and EI mass spectrometry. In a THF solution saturated with
ethylene 3a and 3b form the five-coordinate ethylene
organorhodium(I) complexes [Rh(PNP)R(C2H4)] (5a, b). The
stable monohydridorhodium(III) complex [Rh(PNP)ClH-
(CH3CN)]SO3CF3 (7) was obtained by the reaction of
[Rh(PNP)Cl] with HSO3CF3 in a solution of THF/acetonitrile
and characterized by X-ray crystallography. In
a THF
solution the organorhodium(I) complexes 3a, b react upon
the addition of either HSO3CF3 or HNMe3Cl with the
immediate release of the respective hydrocarbon HR.
The hydroamination of ethylene was first achieved at Scheme 1
room temp. and normal pressure by a cationic ethylenerho-
dium(I) complex [Rh(PPh3)2(Me2CO)(C2H4)]PF6[1]. How-
ever, the low productivity of this rhodium complex catalyst
could not be improved by variation of the ligand sphere[2]
.
Therefore we started upon a series of model studies to in-
vestigate the reaction mechanism of the rhodium complex
catalyzed hydroamination of olefins, trying to trace system-
atically those reaction steps considered crucial for the cata-
lytic cycle by the use of the [2,6-bis(diphenylphosphanyl-
methyl)pyridine]rhodium(I) complex fragment [Rh(PNP)]ϩ
as a stable structural moiety for the respective model com-
pounds. The hypothetical reaction mechanism of the cata-
lyses is formulated in Scheme 1.
It was recently found that model complexes of the type
A [Rh(PNP)(olefin)]X (olefin ϭ ethylene, styrene; X ϭ BF4,
PF6, SO3CF3) are only in a thermodynamic equilibrium
with the corresponding amine complex E. In this case no
indication of a nucleophilic attack of the secondary amine
at the CϪC double bond could be detected[3]. On the other
hand the nucleophilic attack of secondary amines (HNR2)
was succesful with related dicationic olefin palladium(II)
complexes [Pd(PNP)(olefin)]BF4 (olefin ϭ ethylene, styr-
ene), however the PdϪC σ-bond in the formed (β-amino-
ethyl)palladium(II) complexes [Pd(PNP)(CHRЈCH2NR2)]-
BF4 (RЈ ϭ H, Ph) is so stable that it can not be cleaved
protolytically under the reaction conditions[4]
.
It is known from other rhodium-catalyzed reactions, such
as the hydrogenation of olefins[5][6], that the cleavage of the
RhϪC σ-bond and the formation of the CϪH bond can be
realized by intramolecular reductive elimination, which is
proposed as the product-forming step, cf. the formation of
the ethylamine, shown as the step C ǞD in Scheme 1.
In this paper we report on the synthesis of related orga-
norhodium(I) model complexes [Rh(PNP)R] (R ϭ CH3,
C6H5) which were used to characterize the stability of the
[᭛] Part LIII: R. Taube, H. Windisch, H. Hemling, H. Schumann,
J. Organomet. Chem. 1998, 555, 201Ϫ210.
Eur. J. Inorg. Chem. 1998, 1425Ϫ1432
WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1998
1434Ϫ1948/98/1010Ϫ1425 $ 17.50ϩ.50/0
1425

C. Hahn, M. Spiegler, E. Herdtweck, R. Taube
FULL PAPER
RhϪC σ-bond. For this purpose their reactivities toward plexes which are obtained in good yields are reddish/brown
ethylene and protic acids were investigated, and these re- air-sensitive solids which are soluble in THF and toluene,
sults are presented here.
moderately soluble in ethanol, and insoluble in diethyl
ether. In contrast to the structurally analogous organorhod-
ium(I) complexes [Rh(PPh3)3R], which form spontaneously
the ortho-metallated product [Rh(o-C6H4PPh2)(PPh3)2] by
release of the respective hydrocarbon HR [7], the complexes
3a, b are quite stable as solid compounds under an inert
gas, as well as in solution at room temp.
Results and Discussion
Synthesis and Characterization of [Rh(PNP)R]
The organorhodium(I) complexes [Rh(PNP)R] [R ϭ
CH3 (3a), C6H5 (3b)] were synthesized from the cationic
ethylenerhodium(I) complex [Rh(PNP)(C2H4)]BF4 (1a)[3]
with slightly more than three equiv. of the corresponding
organyllithium compound, cf. Eq. 1.
However, only a few stable square-planar alkyl- and ar-
ylrhodium(I) complexes of the type [Rh{RЈP(CH2CH2-
CH2PPh2)2}R] (RЈ ϭ tBu, Ph) are known[8]. The ortho-met-
allation of a PPh group in these complexes as well as in 3a,
b is obviously prevented by the chelating structure of the
tridentate ligand.
The complexes 3a, b were characterized by 31P-, 1H-, and
13C-NMR spectroscopy and by EI mass spectrometry. In
the 31P-NMR spectra a doublet was found at δ ϭ 28.9
(JPϪRh ϭ 177 Hz) for 3a, and at δ ϭ 20.6 (JPϪRh ϭ 180 Hz)
for 3b. These signals are shifted upfield and have a larger
phosphorus-rhodium coupling constant compared to those
of the related cationic (PNP)rhodium(I) complexes
[Rh(PNP)L]X (L ϭ HNR2, py, CH3CN, DMSO, olefin;
X ϭ BF4, PF6, SO3CF3) which are found in the region of
δ ϭ 31Ϫ41 with coupling constants of 126Ϫ157 Hz[3][9]
.
1
The H-NMR signal for the methyl group of 3a at δ ϭ
0.19 (JHϪP ϭ 6.2 Hz; JHϪRh ϭ 1.7 Hz), as well as the corre-
sponding 13C-NMR signal at δ ϭ Ϫ20.8 (JCϪP ϭ 11.7 Hz;
JCϪRh ϭ 24.6 Hz), is shifted upfield in comparison to that
found for the intermediate 2a. The characteristic virtual
triplet for the methylene group of the PNP ligand appears
The intermediates 2a, b formed were characterized in situ
by NMR spectroscopy. The 31P-NMR spectrum of the reac-
tion solution of 1a with 3.1 equiv. of LiCH3 in [D8]THF
shows one doublet at δ ϭ 17.2 (JPϪRh ϭ 148 Hz) which is
shifted upfield by about 11 ppm compared to the starting
1
at δ ϭ 3.88 in the H-NMR spectrum, and at δ ϭ 46.8 in
the 13C-NMR spectrum.
1
The H-NMR signals for the phenyl moiety of 3b are
found at δ ϭ 6.45, 6.57, and 7.36, and in the 13C-NMR
spectrum the corresponding signals are observed at δ ϭ
1
complex 1a. In the H-NMR spectrum of this solution a
1
119.0, 125.2, 140.9. While in the H-NMR spectrum of 3b
signal is found at δ ϭ 0.30 (td, JHϪP ϭ 4.9 Hz, JHϪRh ഠ 1
Hz, CH3) for the methyl group coordinated at the rhodium
centre. The corresponding 13C signal for the methyl group
appears at δ ϭ Ϫ15.4 (dt, JCϪP ϭ 10.3 Hz, JCϪRh ϭ 27.5
Hz).
the characteristic virtual triplet for the methylene group at
δ ϭ 4.02 is shifted slightly downfield compared to that of
3a, the corresponding 13C-NMR signal appears at the same
chemical shift (δ ϭ 46.8) as is found for 3a.
In the EI mass spectra of 3a and 3b the respective peaks
[M]ϩ and [M Ϫ R]ϩ could be observed.
1
A virtual triplet in the H-NMR spectrum at δ ϭ 3.34
has an intensity of 2 H, consistent with deprotonated meth-
ylene groups of the PNP ligand in 2a, while the correspond-
ing 13C signal is observed at δ ϭ 58.0 (vt, N ϭ 24.6 Hz),
which is shifted downfield in comparison to that of 1a (δ ϭ
43.9, vt, N ϭ 10.9 Hz). Thus, the NMR data suggests the
formation of 2a.
The formation of the analogous phenyl compound 2b is
suggested by the 31P-NMR-spectroscopic investigation of a
reaction solution of 1a and 3.2 equiv. of LiC6H5 in THF,
where again one doublet is observed, at δ ϭ 16.7, showing
A further piece of evidence for the formation of the two-
fold deprotonated intermediate 2a is given by the reaction
of 3a with two equiv. of CH3Li, cf. Eq. 2.
By the reaction of 2a with D2O the corresponding two-
fold deuterated methyl complex 4 is obtained and charac-
1
terized by H-NMR spectroscopy, where the signal for the
methylene group is observed at δ ϭ 3.87 with half the inten-
sity found in the spectrum of 3a. Accordingly, in the mass
spectrum of 4, the peaks for [M]ϩ and [M Ϫ CH3]ϩ appear
at the corresponding m/z values which are higher by two
units than those found for 3a.
the same phosphorus-rhodium coupling constant (JPϪRh
148 Hz) as that found for 2a.
ϭ
Upon reprotonation with ethanol or water these inter-
This deprotonation reaction was also described for the
mediates 2a, b are converted into the neutral organorhodi- structurally related [2,6-bis(diphenylphosphanylmethyl)-
um(I) complexes 3a, b. The methyl and the phenyl com- phenyl](methyl)platinum(II) complex, where an analogous
1426
Eur. J. Inorg. Chem. 1998, 1425Ϫ1432

Complex Catalysis, LIV
FULL PAPER
flected by the decreased phosphorus-rhodium coupling
constants.
The behaviour of the solution of 3b (under ethylene in
[D8]THF and during the cooling) was monitored by a dy-
namic proton-NMR experiment. The chemical shifts of the
spectra run in the temperature range room temp. to Ϫ80°C
are summarized in Table 1.
By cooling the sample the average signal for the ethylene
becomes very broad. The coalescence temp. lies between
Ϫ20°C and Ϫ40°C. At Ϫ60°C a broad signal at δ ϭ 5.36
for the free ethylene, and two broad signals at δ ϭ 2.48 and
1.85 for the coordinated ethylene, are visible and the signal
for the methylene protons of the PNP ligand at δ ഠ 4.1
begins to split into two signals. By cooling to Ϫ80°C the
signals for free and coordinated ethylene become sharper,
which indicates a slow exchange relative to the NMR time
scale. At this temperature the five-coordinate complex 5b
has a relatively stable coordination geometry which is no
longer of C2v symmetry, consequently the signals for the
methylene protons become inequivalent and there is a split
into two doublets at δ ϭ 4.16 and 4.06 (JHϪH ϭ 14.8 Hz).
When the solvent was removed under vacuum from a
solution of 5a or 5b a red solid remained, identified as 3a
or 3b, respectively. This indicates a weak coordination of
the ethylene at the organorhodium(I) complexes. No indi-
cation of an insertion of the ethylene into the RhϪC σ-
bond could be observed, under these conditions, for either
3a or 3b.
twofold deprotonated complex is obtained by the reaction
with two equiv. of CH3Li[10]
.
Reactivity of [Rh(PNP)R] toward Ethylene
Since the possibility of an insertion of an ethylene mol-
ecule into the RhϪC bond (cf. Scheme 1: e.g. in B) has to
be taken into consideration as a side reaction during the
hydroamination of ethylene, the investigation of the reactiv-
ity of the organorhodium(I) complexes 3a, b toward ethyl-
ene was included in the model studies.
When a solution of 3a or 3b in THF saturated with ethyl-
ene was cooled down its colour changed reversibly from red
(at room temp.) to orange-red (at Ϫ78°C). The formation
of the corresponding five-coordinate ethylene organorhodi-
Synthesis and Structure of [Rh(PNP)ClH(CH3CN)]SO3CF3
1
um(I) complexes 5a, b (cf. Eq. 3) is suggested by H-NMR
In the proposed catalytic cycle of the hydroamination of
ethylene (cf. Scheme 1) the liberation of the ethylamine
from the (β-ammonioethyl)rhodium(I) complex B is as-
sumed to be achieved by oxidative addition of the proton
of the β-ammonio group at the rhodium centre, forming the
spectroscopy at room temp.: In addition to the slightly
shifted signals for the coordinated PNP ligand and the or-
gano moiety (see Experimental Section), relatively broad
average signals at δ ϭ 5.08 and δ ϭ 4.36 are found for
the methyl and phenyl complexes respectively, indicating an
exchange between free and coordinated ethylene (the chemi-
cal shift of the average signal depends on the concentration
of free ethylene).
(β-aminoethyl)(hydrido)rhodium(III) complex
C
from
which the product is reductively eliminated in an irrevers-
ible reaction step.
As is known (monohydrido)rhodium(III) complexes can
be obtained by the oxidative addition of protic acids to rho-
dium(I) complexes[11][12], which is demonstrated here by the
reaction of [Rh(PNP)Cl] (6)[13] with HSO3CF3, cf. Eq. 4.
The (chloro)(hydrido)rhodium(III) complex [Rh(PNP)-
ClH(CH3CN)]SO3CF3 (7) obtained was isolated as an air-
stable pale yellow solid and characterized by IR and 1H-
NMR spectroscopy. In the IR spectrum the band at 2138
cmϪ1 is assigned to the RhϪH vibration, the two bands at
2293 and 2366 cmϪ1 are observed for the end-on coordi-
In the 31P-NMR spectra of these solutions the doublets nated acetonitrile[14], and the corresponding bands for the
at δ ϭ 39.0 (JPϪRh ϭ 152 Hz) and 27.5 (JPϪRh ϭ 171 Hz) triflate anion (see Experimental Section) suggest its non-
are observed at room temp. for the methyl and phenyl com- coordination[15]. The 1H-NMR signal of the hydrido ligand
plexes 5a, b respectively; these are show a remarkable down- appears at δ ϭ Ϫ15.99 as a broad triplet, while for the coor-
field shift compared to those found for 3a, b. These features dinated acetonitrile a singlet is observed at δ ϭ 1.48. For
are in agreement with the coordination of an ethylene mol- the inequivalent methylene protons of the PNP ligand the
ecule. As a consequence of the increased coordination num- corresponding two doublets of virtual triplets appear at δ ϭ
ber the phosphorusϪrhodium bond becomes weaker, as re- 4.22 and 4.83.
Eur. J. Inorg. Chem. 1998, 1425Ϫ1432
1427

C. Hahn, M. Spiegler, E. Herdtweck, R. Taube
Table 1. Dynamic H-NMR experiment of the solution of [Rh(PNP)(C6H5)] (3a) in [D8]THF under ethylene (500 MHz)
FULL PAPER
1
T [°C]
py-4
(t)
PPh, Ph
(m)
Ph
(m)
CH2
C2H4
free
coord.
23
0
Ϫ20
Ϫ40
Ϫ60
7.52
7.52
7.52
7.54
7.56
7.08Ϫ7.34
7.02Ϫ7.26
7.00Ϫ7.28
6.99Ϫ7.30
6.99Ϫ7.31
6.48Ϫ6.57
6.50Ϫ6.57
6.50Ϫ6.58
6.51Ϫ6.58
6.54Ϫ6.59
4.05 vt
4.20 br.
3.96 br.
3.9 br.
4.07 br.
4.09 br.
4.10 br.
5.3 br.
2.5 br.
2.50 br., 1.86 br.
4.12 br.
5.36 br.
4.09 br.
Ϫ70
7.57
6.99Ϫ7.36
6.52Ϫ6.59
4.15 d
5.40 br.
2.48 br., 1.85 br.
4.07 d
JHϪH ϭ 14.8 Hz
4.16 d
Ϫ80
7.58
6.99Ϫ7.36
6.52Ϫ6.60
5.41 br.
2.48 d, 1.84 d
JHϪH ϭ 14.8 Hz
4.06 d
JHϪH ϭ 14.8 Hz
Figure 1. Platon[16] drawing of the complex cation [Rh(PNP)ClH-
(CH3CN)]ϩ of 7
Single crystals of complex 7 were obtained from the
mother liquor (THF/CH3CN/diethyl ether) which stood
three days at room temp. The molecular structure of the
complex cation [Rh(PNP)ClH(CH3CN)]ϩ is shown in Fig-
˚
ure 1. The RhϪCl distance [2.3480(7) A] is identical with
that found for the chlororhodium(I) complex [Rh(PNP)Cl]
˚
˚
[2.344(2) A], while the RhϪN(1) distance [2.1451(19) A] is
significantly longer than the corresponding RhϪN bond
˚
length [1.984(3) A] found in the (acetonitrile)rhodium(I)
First HSO3CF3 was added to a solution of 3a or 3b in
THF. In the case of the methyl complex 3a the release of
the methane was observed immediately, visible as an evol-
ution of gas, whereas from the phenyl complex 3b the corre-
sponding benzene was detected by gas chromatography of
the reaction solution. However, no defined RhI complex
could be isolated from the reaction solution. Obviously, the
remaining [Rh(PNP)]ϩ fragment (analogous to D, Scheme
1) cannot be stabilized either by the solvent (THF) or by
complex [Rh(PNP)(CH3CN)]BF4[9] due to the strong trans
influence of the hydrido ligand. The RhIII(PNP) fragment
in 7 exhibits practically the same features of the bonding
parameters as found in the RhI(PNP) fragment in 6 and in
other RhI(PNP) complexes[3][9]
.
Reactivity of [Rh(PNP)R] toward Protic Acids
Analogous to the formation of the hydridorhodium(III) the triflate anion. Decomposition of the reaction solution
complex 7, the reaction of the organorhodium(I) complexes occurred and the formation of the dinuclear complex
3a, b with protic acids can be used as a simplified reaction [Rh2(PNP)3](SO3CF3)2 (8)[3] was detected by 31P NMR.
model for the product-forming steps (B Ǟ C Ǟ D in
However, when some acetonitrile was added to the reac-
Scheme 1). It is of interest to investigate the protolysis of tion solution after the protolysis the corresponding cationic
[Rh(PNP)R], in one case in the presence of a weak coordi- acetonitrile complex 9[9] could be isolated, cf. Eq. 5.
nating anion XϪ such as CF3SO3Ϫ, and in another case
According to the last step of the catalytic cycle (D Ǟ A,
with a stronger coordinating anion such as ClϪ. Thus, the Scheme 1) the remaining [Rh(PNP)]ϩ fragment can also be
proposed hydrido organorhodium(III) intermediates, either trapped with ethylene by formation of the cationic ethylene
five-coordinate I or six-coordinate II (cf. Scheme 2), might complex 1b[3], cf. Eq. 6.
show different reactivities concerning the reductive elimi-
When cyclooctadiene was added after the protolyses of
nation of the hydrocarbon HR (discussed in detail by 3b a dinuclear COD complex 10 was obtained, cf. Eq. 7,
1
Milstein[6]).
1428
which was fully characterized by 31P-, H-, and 13C-NMR
Eur. J. Inorg. Chem. 1998, 1425Ϫ1432

Complex Catalysis, LIV
FULL PAPER
˚
Table 2. Selected bond lengths [A] and angles [°] for [Rh(PNP)ClH(CH3CN)]SO3CF3 (7)
RhϪCl(1)
2.3480(7)
2.1451(19)
1.828(2)
166.90(2)
91.95(5)
84.53(6)
92.83(7)
RhϪP(1)
RhϪN(2)
2.3013(7)
RhϪP(2)
2.2863(6)
1.841(3)
RhϪN(1)
2.0656(17)
P(1)ϪC(1)
P(2)ϪC(7)
P(1)ϪRhϪP(2)
ClϪRhϪN(1)
P(1)ϪRhϪN(2)
N(1)ϪRhϪN(2)
ClϪRhϪP(1)
ClϪRhϪN(2)
P(2)ϪRhϪN(1)
96.77(2)
175.06(5)
96.85(5)
ClϪRhϪP(2)
P(1)ϪRhϪN(1)
P(2)ϪRhϪN(2)
93.42(2)
91.02(5)
84.82(5)
Scheme 2
ing the protolysis reaction described above might be postu-
lated. Furthermore, the reductive elimination step from this
complex seems to proceed without any kinetic inhibition,
independent of the coordinating ability of the anion in the
Brönsted acid used for protolysis.
Conclusions
The synthesis of the new organorhodium(I) complexes
[Rh(PNP)R] (R ϭ CH3, C6H5) succeeded by the reaction
of the cationic ethylene complex [Rh(PNP)(C2H4)]BF4 with
three equiv. of LiR. Organorhodium complexes containing
deprotonated methylene groups of the PNP ligand occur
as intermediates, which can be reprotonated with ethanol
or water.
The square-planar coordination geometry of the organo-
rhodium complexes is stabilized by the chelating structure
of the tridentate PNP ligand, which avoids the release of
the hydrocarbon HR by ortho-metallation of a PPh moiety.
The organorhodium(I) complexes [Rh(PNP)R] react with
ethylene by the formation of five-coordinate complexes
[Rh(PNP)R(C2H4)] in which the ethylene is weakly coordi-
nated and can be removed under vacuum. No indication of
an insertion of the ethylene in the RhϪC σ-bond could be
observed, which may be important to exclude the oligomer-
ization of ethylene as a side reaction of the hydroamination.
As was shown a stable (monohydrido)rhodium(III) com-
plex [Rh(PNP)ClH(CH3CN)]SO3CF3 can be obtained by
oxidative addition of HSO3CF3 to the chlororhodium(I)
complex [Rh(PNP)Cl]. Upon protolysis with HSO3CF3 of
the organorhodium(I) complexes [Rh(PNP)R] the hydro-
carbons RH are liberated, and it is possible to trap the re-
maining RhI complex fragment with olefins, so the cationic
olefin complex can be regenerated, which is as expected for
the starting complex in the catalytic cycle of the hydroami-
nation of olefins.
spectroscopy (see Experimental Section). Thus, it is shown
that the regeneration of the cationic olefin complex is pos-
sible after the elimination of the hydrocarbon, which is of
great importance for the catalysis.
In another experiment trimethylammonium chloride was
added to a solution of 3a or 3b. In both cases the respective
hydrocarbon was also released immediately while the chlo-
rorhodium(I) complex 6 formed, which is poorly soluble in
THF, began to precipitate and was filtered off after 4 h with
a yield of 80Ϫ90%, cf. Eq. 8.
Independently, if a protic acid with a weakly coordinating
(HSO3CF3) or a stronger coordinating anion (HNMe3Cl)
is used, the protolytic reaction of the organorhodium(I)
complexes [RhPNP)R] [proceeding by intermediate forma-
tion of corresponding hydrido-organorhodium(III) com-
plex] leads immediately in each case to the reductive elimi-
nation of the hydrocarbon HR. These results also suggest
that the reductive elimination of the ethylamine (cf. Scheme
Since a (hydrido)(phenyl)rhodium(III) complex [Rh- 1) may proceed irreversibly and without kinetic inhibition,
(PMe3)2(CO)(C6H5)HCl] could be detected upon the reac- which is essential for a product-forming step closing the
tion of [Rh(PMe3)2(CO)(C6H5)] with HCl, although only in catalytic cycle. The proposed reaction mechanism for the
solution at Ϫ40°C by NMR spectroscopy[17], the formation hydroamination of olefins finds strong chemical support
of a hydrido organo-PNPϪrhodium(III) intermediate dur- from these model reactions.
Eur. J. Inorg. Chem. 1998, 1425Ϫ1432
1429

C. Hahn, M. Spiegler, E. Herdtweck, R. Taube
FULL PAPER
We thank Dr. A. Porzel of the Institut für Pflanzenbiochemie of
and dried under vacuum. The crude product was recrystallized in
the University of Halle for the measurement of the dynamic pro- hot THF giving 2.1 g of 3b (3.2 mmol, 75%), reddish/brown solid,
ton-resonance experiment and the Deutsche Forschungsgemein-
schaft (Sonderforschungsbereich 347 of the University of Würzburg) 20.6 (d, JPϪRh ϭ 180 Hz). Ϫ H NMR ([D8]THF): δ ϭ 4.02 (vt,
temp. of decomposition 215Ϫ220°C. Ϫ 31P NMR ([D8]THF): δ ϭ
1
for financial support.
NHϪP ϭ 3.8 Hz, 4 H, CH2), 6.45 (t, JHϪH ϭ 7.0 Hz, 1 H, Hpara),
6.57 (t, JHϪH ϭ 7.2 Hz, 2 H, Hmeta), 7.21 (m, 14 H, PPh, 3,5-py),
7.36 (d, JHϪH ϭ 7.3 Hz, 2 H, Hortho), 7.50 (m, 8 H, PPh), 7.60 (t,
J
HϪH ϭ 7.6 Hz, 1 H, 4-py). Ϫ 13C NMR ([D8]THF): δ ϭ 46.8 (vt,
Experimental Section
NCϪP ϭ 9.9 Hz, CH2), 119.0 (s, Cpara), 120.9 (vt, NCϪP ϭ 5.2 Hz,
C3,5-py), 125.24 (s, Cmeta), 128.5 (vt, NCϪP ϭ 4.6 Hz, PCmeta), 129.3
(s, PCpara), 133.5 (s, C4-py), 133.6 (vt, NCϪP ϭ 6.9 Hz, PCortho),
137.9 (vt, NCϪP ϭ 16.1 Hz, PCipso), 140.9 (vt, NCϪP ϭ 3.8 Hz,
Cortho), 160.9 (vt, NCϪP < 3 Hz, C2,6-py). Ϫ EI MS; m/z (100): 655
(6.7) [M]ϩ, 578 (0.1) [M Ϫ C6H5]ϩ. Ϫ C37H32NP2Rh (655.52):
calcd. C 67.79, H 4.92, N 2.14, Rh 15.70; found C 63.92 (premature
decomposition of the sample), H 5.03, N 1.91, Rh 15.58.
General: All reactions were carried out under dry and oxygen-
free argon or ethylene. Ethanol, acetone, CDCl3 and [D6]acetone
˚
were refluxed over 4-A molecular sieves and made oxygen-free by
bubbling argon through the liquid. THF and diethyl ether were
refluxed in the presence of Na/benzophenone and [D8]THF in the
presence of K/Na alloy. Acetonitrile and DMSO were dried over
˚
4-A molecular sieves and distilled before use. HSO3CF3, LiCH3
and LiC6H5 were obtained from Fluka. Ϫ IR: KBr pellets with a
Perkin-Elmer FT-IR 16 spectrometer. Ϫ 1H, 13C{1H}, and 31P{1H}
NMR: Varian Gemini 300 NMR spectrometer (300, 75, and 121
MHz respectively), 1H- and 13C-NMR shifts were referenced to the
resonance of the residual protons of the solvents, the 31P-NMR
shifts were referenced to external 85% H3PO4. Ϫ Dynamic proton
NMR: Varian Unity 500 NMR spectrometer (500 MHz). Ϫ EI
MS: AMD 402 spectrometer (AMD Intectra) at 70 eV. Ϫ (C, H,
and N): LECO CHN 932 analyzer. Rh elemental analysis was de-
termined using a photometric method[18]. The Chrompack gas-
chromatograph CP 9000 was used for the identification of liquid
organic compounds.
Alternatively the complexes could be obtained by reprotonation
with 5 equiv. of H2O which were added directly to the red reaction
solution (2a or 2b). The crude products 3a, b precipitated after a
few minutes from the THF solution and were isolated in yields of
about 65%.
NMR-Spectroscopic Characterization of [ Rh{2,6-( Ph2PCHLi) 2-
( NC5H3) }( R) ] [ R ϭ CH3 (2a), C6H5 (2b)]
2a: (a) [Rh(PNP)(C2H4)]BF4 (148 mg, 0.21 mmol, 1a) was dis-
solved in 1 ml of [D8]THF and 3.1 equiv. of solid LiCH3 (0.66
mmol, obtained from 0.41 ml of a 1.6  Et2O solution by removing
the solvent) were added at Ϫ78°C and warmed up to room temp.
The NMR spectra, which were measured instantly from the red
solution obtained are consistent with 2a. Ϫ 31P NMR ([D8]THF):
Syntheses: [Rh(PNP)(C2H4)]BF4 (1a) was prepared according to
the procedure described in ref.[3]
.
[ Rh( PNP) ( CH3) ] (3a): 10.5 ml of a 1.6  LiCH3 solution in
diethyl ether (3.2 equiv.) was added slowly at Ϫ78°C to a suspen-
sion of 3.6 g (5.2 mmol) of [Rh(PNP)(C2H4)]BF4 (1a) in 20 ml of
THF. The mixture was warmed up to room temp. and stirred for
a further 10 min to give a red solution. The solvent was removed
under reduced pressure. 20 ml of ethanol was added dropwise
slowly at Ϫ78°C to the remaining red crystalline solid with rigor-
ous stirring. After stirring for another 20 min at room temp., the
reddish/brown solid was filtered off, washed with ethanol (2 ϫ),
then with diethyl ether and dried under vacuum. After recrystalli-
zation of the crude product in hot THF, 2.2 g of 3a (3.7 mmol,
71%), reddish/brown solid was isolated, temp. of decomposition
220Ϫ230°C. Ϫ 31P NMR ([D8]THF): δ ϭ 28.89 (d, JPϪRh ϭ 177
1
δ ϭ 17.2 (d, JPϪRh ϭ 148 Hz). Ϫ H NMR ([D8]THF): δ ϭ 0.30
3
(td, JHϪP ϭ 4.9 Hz, JHϪRh ഠ 1 Hz, 3 H, CH3), 3.34 (vt, NHϪP
ϭ
3.8 Hz, 2 H, CH), 5.10 (d, JHϪH ϭ 7.6 Hz, 2 H, 3,5-py), 6.06 (t,
JHϪH ϭ 7.6 Hz, 1 H, 4-py), 6.92Ϫ7.05 (m, 12 H, PPh), 7.72 (m, 8
2
H, PPh). Ϫ 13C NMR ([D8]THF): δ ϭ Ϫ15.4 (dt, JCϪP ϭ 10.3
Hz, JCϪRh ϭ 27.5 Hz, CH3), 58.0 (vt, NCϪP ϭ 24.6 Hz, CH), 92.3
(vt, NCϪP ϭ 8.0 Hz, C3,5-py), 126.1 (s, PCpara), 127.2 (vt, NCϪP
ϭ
4.2 Hz, PCmeta), 131.0 (s, C4-py), 132.5 (vt, NCϪP ϭ 6.6 Hz, PCortho),
148.6 (vt, NCϪP ϭ 14.4 Hz, PCipso), 171.6 (vt, NCϪP < 3 Hz,
C2,6-py).
(b) [Rh(PNP)(CH3)] (197 mg, 0.33 mmol, 3a) was dissolved in 1
ml of [D8]THF and 2.2 equiv. of solid CH3Li (0.73 mmol, obtained
from 0.46 ml of a 1.6  Et2O solution by removing the solvent)
were added at Ϫ78°C and warmed up to room temp. The obtained
red solution was instantly characterized by NMR spectroscopy.
The 31P-, 1H-, and 13C-NMR spectra are identical with those found
for the reaction solution of 1a and 3.1 equiv. of CH3Li described
in (a).
3
Hz). Ϫ 1H NMR([D8]THF): δ ϭ 0.19 (td, JHϪP ϭ 6.2 Hz,
JHϪRh ϭ 1.7 Hz, 3 H, CH3), 3.88 (vt, NHϪP ϭ 3.9 Hz, 4 H, CH2),
7.07 (d, JHϪH ϭ 7.6 Hz, 2 H, 3,5-py), 7.30 (m, 12 H, PPh), 7.49 (t,
JHϪH ϭ 7.6 Hz, 1 H, 4-py), 7.78 (m, 8 H, PPh). Ϫ 13C
2
NMR([D8]THF): δ ϭ Ϫ20.8 (dt, JCϪP ϭ 11.7 Hz, JCϪRh ϭ 24.6
Hz, CH3), 46.8 (vt, NCϪP ϭ 9.7 Hz, CH2), 120.8 (vt, NCϪP ϭ 5.1
Hz, C3,5-py), 128.6 (vt, NCϪP ϭ 4.4 Hz, PCmeta), 129.3 (s, PCpara),
131.4 (s, C4-py), 133.6 (vt, NCϪP ϭ 7.5 Hz, PCortho), 138.3 (vt,
NCϪP ϭ 14.9 Hz, PCipso), 159.9 (vt, NCϪP < 3 Hz, C2,6-py). Ϫ EI
2b: The reaction solution of 1a and 3.2 equiv. of C6H5Li (1.8 
solution in Et2O/cyclohexane) in THF prepared in the same man-
ner as described for 2a was characterized by 31P NMR (with exter-
nal ref. C6D6): δ ϭ 16.7 (d, JPϪRh ϭ 148 Hz).
MS; m/z (%): 593 (100) [M]ϩ, 578 (62) [M Ϫ CH3]ϩ.
Ϫ
C32H30NP2Rh (593.45): calcd. C 64.77, H 5.10, N 2.36, Rh 17.34;
found C 64.26, H 5.04, N 2.63, Rh 17.88.
Reaction of 2a with D2O: 5 equiv. of D2O were added to a solu-
tion of 2a in THF, which was prepared from 3a and 2.2 equiv. of
[ Rh( PNP) ( C6H5) ] (3b): The complex 3b was prepared in the CH3Li as described above. The reddish/brown crystalline solid
same manner as described for 3a from 3 g (4.3 mmol) of 1a in 20 which was precipitated was filtered off washed with ethanol and
ml of THF and 7.5 ml of a ca. 1.8  Et2O/cyclohexane solution of diethyl ether and dried under vacuum. The H-NMR spectrum of
1
LiC6H5 (13.4 mmol, 3.1 equiv.). When the solvent was removed
from the red solution, a red oil remained which was treated with
20 ml of ethanol at Ϫ78°C by rigorously stirring, giving a reddish/
the solid is consistent with [Rh{2,6-(Ph2PCHD)2(NC5H3)}(CH3)]
(4). For the deuterated methylene group a multiplet at δ ϭ 3.87
was found with an intensity of 2 H. All other signals of 4 agree
brown suspension. After stirring for another 20 min, the solid was with those of 3a. Ϫ EI MS of 4; m/z (%): 595 [M]ϩ (81), 580 [M
filtered off washed with ethanol (3 ϫ)and then with diethyl ether
Ϫ CH3]ϩ (53).
1430
Eur. J. Inorg. Chem. 1998, 1425Ϫ1432

Complex Catalysis, LIV
FULL PAPER
Reaction of 3a, b with Ethylene: The complexes 3a, b were dis-
solved in [D8]THF. The solutions were saturated with ethylene at
of THF. After 5 min, 1.6 ml (12.6 mmol) of cyclooctadiene (COD)
was added and stirred for 30 min while an orange yellow solid
Ϫ78°C. The five-coordinate complexes [Rh(PNP)R(C2H4)] [R ϭ crystallized slowly from the solution. The solid was filtered off the
CH3 (5a), C6H5 (5b)] were identified by 31P- and 1H-NMR spec-
troscopy.
next day. For recrystallization the solid was dissolved in acetone
and precipitated after addition of diethyl ether to the solution. The
crystalline solid was filtered off, washed with diethyl ether and
dried under vacuum. The solid was characterized as
[Rh2(PNP)2(COD)](SO3CF3)2 (10) which was isolated in a yield of
520 mg (0.66 mmol, 53%), temp. of decomposition 232°C. Ϫ 31P
1
5a: 31P NMR ([D8]THF): δ ϭ 39.0 (d, JPϪRh ϭ 152 Hz). Ϫ H
3
NMR ([D8]THF): δ ϭ Ϫ0.54 (td, JHϪP ϭ 7.3 Hz, JHϪRh ϭ 1.5
Hz, 3 H, CH3), 4.04 (vt, NHϪP ϭ 3.0 Hz, 4 H, CH2), 5.08 (br.,
average signal for free and coord. C2H4), 7.12Ϫ7.62 (m, 23 H,
PPh, py).
1
NMR ([D6]acetone): δ ϭ 41.2 (d, JPϪRh ϭ 142 Hz). Ϫ H NMR
([D6]acetone): δ ϭ 1.18 (m, 4 H, COD), 2.25 (m, 4 H, COD), 4.09
(m, 4 H, COD), 4.36 (vt, NHϪP ϭ 3.6 Hz, 4 H, CH2), 7.37Ϫ7.81
(m, 23 H, PPh, py). Ϫ 13C NMR ([D6]acetone): δ ϭ 44.7 (vt,
NCϪP ϭ 11.5 Hz, CH2), 77.8 (d, JCϪRh ϭ 12 Hz), 122.7 (vt, NCϪP
< 3 Hz, C3,5-py), 129.9 (vt, NCϪP ϭ 4.2 Hz, PCmeta), 131.0 (vt,
NCϪP ϭ 15.8 Hz, PCipso), 132.2 (s, PCpara), 134.5 (vt, NCϪP ϭ 6.6
Hz, PCortho), 141.7 (s, C4-py), 161.9 (vt, NCϪP < 3 Hz, C2,6-py). Ϫ
C72H66F6N2O6P4Rh2S2 (1563.15): calcd. C 55.31, H 4.26, N 1.79,
Rh 13.17; found C 54.91, H 4.26, N 1.65, Rh 13.07.
1
5b: 31P NMR ([D8]THF): δ ϭ 27.5 (d, JPϪRh ϭ 171 Hz). Ϫ H
NMR ([D8]THF): δ ϭ 4.05 (vt, NHϪP ϭ 3.0 Hz, 4 H, CH2), 4.36
(br., average signal for free and coord. C2H4), 6.45 (t, JHϪH ϭ 7.3
Hz, 1 H, Hpara), 6.55 (t, JHϪH ϭ 7.3 Hz, 2 H, Hmeta), 7.07Ϫ7.40
(m, 23 H, PPh, 3,5-py, Hortho), 7.54 (t, JHϪH ϭ 7.9 Hz, 1 H, 4-py).
[ Rh( PNP) ClH( CH3CN) ] SO3CF3 (7): 0.2 ml of HSO3CF3 was
added to a suspension of 345 mg (0.56 mmol) of [Rh(PNP)Cl][9][13]
in 5 ml of THF and 1 ml of acetonitrile. The mixture changed its
colour to pale yellow. After filtration of the solution, diethyl ether
was added dropwise and a yellow/brown oil precipitated which
crystallized to a pale yellow solid. The crude product was filtered
off, washed with diethyl ether (2 ϫ), and recrystallized in acetone/
diethyl ether to give 290 mg of 7 (0.38 mmol, 67%), temp. of de-
composition 160Ϫ170°C. Ϫ IR (KBr): ν˜ ϭ 2366 cmϪ1, 2293
(CH3CN); 2138 (RhϪH); 1602, 1568 (py); 1261, 1223, 1159, 1030,
Reactivity of 3a, b toward HNMe3Cl: 48 mg (0.5 mmol) of
HNMe3Cl, dissolved in 2 ml of THF, was added to a solution of
0.5 mmol of 3a or 3b, dissolved in 8 ml of THF. A red crystalline
solid precipitated and, in the case of the methyl complex 3a, an
evolution of gas was observed immediately. In the reaction solution
of 3b benzene was detected by gas chromatography. After 4 h, the
red solid was filtered off, washed with THF and diethyl ether and
dried under vacuum. The solid was identified in each case as
[Rh(PNP)Cl][9][13] (6) by 31P-NMR and IR spectroscopy (yield:
80Ϫ90%).
1
2
638, 572 (SO3CF3). Ϫ H NMR (CDCl3): δ ϭ Ϫ15.9 (t, JHϪP
ϭ
9.5 Hz, 1 H, RhH), 1.49 (s, 3 H, NCH3) 4.22 (dvt, JHaϪHb ϭ 17.8
Hz, NHϪP ϭ 4.6 Hz, 2 H, CHa), 4.83 (dvt, JHaϪHb ϭ 17.8 Hz,
NHϪP ϭ 4.6 Hz, 2 H, CHb), 7.41Ϫ7.94 (m, 23 H, PPh, py).
Crystal-Structure Determination of 7: A single crystal of approxi-
mate dimensions 0.64 ϫ 0.28 ϫ 0.08 mm was mounted inside a
Lindemann glass capillary. Crystal data and structure refinement
details are given in Table 3.
Reactivity of 3a, b toward HSO3CF3: (a) 1 equiv. of HSO3CF3
was added to a solution of 1 mmol of 3a or 3b in 8 ml of THF.
In the case of the reaction with 3a the evolution of methane was
immediately visible. In the reaction solution of 3b benzene was cor-
respondingly detected by gas chromatography. By addition of di-
ethyl ether to the respective reaction solutions dark red oil precipi-
tated giving reddish/brown solids upon removal of the solvent in
vacuum. The solids obtained from both reaction solutions contain
the dinuclear complex [Rh2(PNP)3](SO3CF3)2 (8) among decompo-
sition products; detected by 31P-NMR spectroscopy (δ ϭ 43.9 dd,
Table 3. Crystal data and structure refinement for 7
Formula
C34H31ClF3N2O3P2RhS
805.00
Molecular mass
Crystal system
Space group
triclinic
¯
P1 (I. T. No. 2)
˚
a [A]
9.2052(5)
JP(a)ϪRh ϭ 139 Hz, JP(a)ϪP(b) ϭ 39 Hz; δ ϭ 26.4, dt JP(b)ϪRh
169 Hz)[3]
ϭ
˚
b [A]
12.6582(8)
.
˚
c [A
15.7936(10)
α [°]
β [°]
γ [°]
79.231(7)
(b) In presence of CH3CN: After the protolysis of 3a or 3b with
HSO3CF3 (see above), 1 ml of acetonitrile was added to the reac-
tion solution and stirred for 20 min at room temp. Upon dropwise
addition of diethyl ether an orange/brown oil precipitated which
crystallized after 1 d to give a brown/yellow solid which was filtered
off washed with diethyl ether and dried under vacuum. In each
74.202(6)
77.905(6)
V [A3]
1714.9(2)
˚
Z
2
D(calcd.) [g cmϪ3
]
]
1.559
µ (Mo-Kα) [cmϪ1
F(000)
7.8
816
1
case the solid was analyzed by H-NMR spectroscopy as the pure
Θ range [°]
T [K]
Reflections, collected
2.28Ϫ25.60
acetonitrile complex [Rh(PNP)(CH3CN)]SO3CF3 (9) when com-
pared to the spectrum of an authentic sample prepared according
to the procedure in the literature[9] (yield: 50Ϫ60%).
193
10392
Independent reflections
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2σ(I)]
R indices (all data)
5972
5972/0/548
(c) In presence of ethylene: After the protolysis of 3a or 3b with
HSO3CF3 (see above), the reaction solution was stirred for 20 min
under ethylene at Ϫ78°C. The mixture was warmed up to room
temp. Upon addition of diethyl ether to the solution an orange
yellow crystalline solid precipitated which was filtered off, washed
with diethyl ether and dried under vacuum. The solid was identified
as the pure ethylene complex [Rh(PNP)(C2H4)]SO3CF3 (1b) by 1H-
NMR spectroscopy when compared to an authentic sample[3]
(yield: 60Ϫ80%).
0.948
R1 ϭ 0.0249, wR2 ϭ 0.0571
R1 ϭ 0.0337, wR2 ϭ 0.0588
ϩ0.53; Ϫ0.62
Largest diff peak and hole [e AϪ3
]
˚
The data were measured with a STOE IPDS[18] using graphite-
˚
monochromated Mo-Kα radiation (λ ϭ 0.71073 A). A decay correc-
tion using the program DECAY[19] was applied. The structure was
solved by direct methods[20], completed by subsequent difference
Fourier syntheses, and refined by full-matrix least-squares pro-
(d) In the presence of COD: 114 µl of HSO3CF3 was added to a
solution of 830 mg (1.26 mmol) of [Rh(PNP)(C6H5)] (3b) in 8 ml cedures[21]. Final cycles of refinement converged at R1 ϭ Σ(ʈFo͉ Ϫ
Eur. J. Inorg. Chem. 1998, 1425Ϫ1432
1431

C. Hahn, M. Spiegler, E. Herdtweck, R. Taube
FULL PAPER
͉Fcʈ)/Σ͉Fo͉ ϭ 0.0249 and wR2 ϭ [Σw(Fo Ϫ Fc2)2/Σw(Fo2)2]1/2
[6]
[7]
2
D. Milstein, Acc. Chem. Res. 1984, 17, 221Ϫ226.
ϭ
[7a] W. Keim, J. Organomet. Chem. 1968, 14, 179Ϫ184. Ϫ [7b] C.
S. Cundy, M. F. Lappert, R. Pearce, J. Organomet. Chem. 1973,
59, 161Ϫ166.
0.0571 for 4931 observed reflections [I > 2σ(I)]. All non-hydrogen
atoms were refined with anisotropic displacement coefficients. All
hydrogen atom positions were found in the difference map calcu-
lated from the model containing all non-hydrogen atoms. The hy-
drogen positions were refined with individual isotropic temperature
parameters. Crystallographic data (excluding structure factors) for
the structures reported in this paper have been deposited with the
Cambridge Crystallographic Data Centre (CCDC-101416). Copies
of the data can be obtained free of charge on application to CCDC,
12 Union Road, Cambridge CB2 1EZ, UK [Fax: (internat.) ϩ 44-
1223/336-033, E-mail: deposit@ccdc.cam.ac.uk].
[8] [8a]
L. Dahlenburg, C. Prengel, Organometallics 1984, 3,
[8b]
934Ϫ936. Ϫ
L. Dahlenburg, C. Prengel, J. Organomet.
Chem. 1983, 241, 27Ϫ36.
[9]
C. Hahn, J. Sieler, R. Taube, Polyhedron 1998, 17, 1183Ϫ1193.
F. Gorla, L. M. Venanzi, A. Albinati, Organometallics 1994,
13, 43Ϫ54.
[10]
[11]
[12]
[13]
T. E. Nappler, D. W. Meek, R. M. Kirchner, J. A. Ibers, J. Am.
Chem. Soc. 1973, 95, 4194Ϫ4210.
J. A. Tiethof, J. L. Peterson, D. W. Meek, Inorg. Chem. 1976,
15, 1365Ϫ1370.
G. Vasapollo, P. Giannoccaro, C. F. Nobile, A. Sacco, Inorg.
Chim. Acta 1981, 48, 125Ϫ128.
[14]
[15]
[16]
B. N. Storhoff, H. C. Lewis, Coord. Chem. Rev. 1977, 23, 1Ϫ29.
M. Aresta, E. Quaranta, Organometallics 1993, 12, 2032Ϫ2043.
A. L. Spek, “PLATON-92”, Acta Crystallogr., Sect. A 1990,
46, C34.
[1]
[1a] R. Taube in Applied Homogeneous Catalysis with Organome-
tallic Compounds (Eds.: B. Cornils, W. A. Herrmann), Verlag
[1b]
Chemie, Weinheim, 1996, vol. 1, pp. 507. Ϫ
D. Steinborn,
J.-J. Brunet, D.
[1c]
[17]
[18]
[19]
[20]
R. Taube, Z. Chem. 1986, 26, 349Ϫ359. Ϫ
S. E. Boyd, L. D. Field, T. W. Hambley, Organometallics 1992,
12, 1720Ϫ1724.
Neibecker, F. J. Niedercorn, J. Mol. Catal. 1989, 49, 235Ϫ259.
[1d]
Ϫ
E. Krukowka, R. Taube, D. Steinborn, DD 296 909 A5
B. Lange, Z. J. Vejdelek, Kolorimetrische Analyse, Verlag
Chemie, 1982, p. 232.
[1e]
(10. 11. 88), 1988; Chem. Abstr. 1992, 116, 213993b. Ϫ
Brunet, Gazz. Chim. Ital. 1997, 127, 111Ϫ118.
J.-J.
IPDS Operating System Version 2.8. STOE&CIE. GmbH,
Darmstadt, Gemany, 1997.
[2]
[2a] E. Krukowka, Dissertation, TH Merseburg, 1985. Ϫ [2b] R.
Taube, Arbeits- und Ergebnisbericht 1992/1993/1994 des SFB
347 (Universität Würzburg): Selektive Reaktionen Metall-akti-
vierter Moleküle, p. 573.
A. Altomare, G. Cascarano, C. Giacovazzo, A. Guargliardi, M.
C. Burla, G. Polidori, M. Camalli SIR-92, University of Bari,
Italy, 1992.
[3]
[4]
[21]
C. Hahn, J. Sieler, R. Taube, Chem. Ber. 1997, 130, 393Ϫ345.
C. Hahn, A. Vitagliano, F. Giordano, R. Taube, Organometal-
lics 1998, 17, 2060Ϫ2066.
G. M. Sheldrick SHELXL-93, in Crystallographic Computing 3
(Eds.: G. M. Sheldrick, C. Krüger, R. Goddard), Oxford Uni-
versity Press, England, 1993, pp. 175Ϫ189.
[98113]
[5]
J. Halpern, Pure Appl. Chem. 1983, 55, 99Ϫ106.
1432
Eur. J. Inorg. Chem. 1998, 1425Ϫ1432