Five- and six-coordinate hydridorhodium(III) complexes containing metalated Schiff-bases as ligands

Article abstract of DOI:10.1016/j.ica.2003.12.018

The reactions of either [RhCl(C₈H₁₄) ₂]₂ (2) or [RhCl(C₂H₄) ₂]₂ (3) with Schiff-bases 1a-d derived from 2-aminopyridine afford, in the presence of four equivalents of PiPr₃, the octahedral chloro(hydrido)rhodium(III) complexes [{(C₅H ₄N)N=C(C₆H₄R)}RhHCl(PiPr₃) ₂] (4a-d) in which the metalated Schiff-base behaves as a chelating ligand. Treatment of 4a (R=H) with NaI and CF₃SO₃Tl produce the corresponding derivatives [{(C₅H₄N)N=C(C ₆H₅)}RhHX(PiPr₃)₂] (5, 6) by salt metathesis. The triflato compound 6 reacts with nBu₄NF·xH ₂O to give [{(C₅H₄N)N=C(C₆H ₅)}RhHF(PiPr₃)₂] (7). While attempts to eliminate HCl from 4a failed, the reaction of 4a with AgPF₆ generates the five-coordinate cationic complex [{(C₅H₄N)N=C(C ₆H₅)}RhH(PiPr₃)₂]PF₆ (8) which adds one equivalent of acetonitrile to give [{(C₅H ₄N)N=C(C₆H₅)}RhH(NCCH₃)(PiPr ₃)₂]PF₆ (9). Treatment of 4a with either nBu₂Mg or LiAlH₄ affords the dihydridorhodium(III) compound [{(C₅H₄N)N=C(C₆H₅)}RhH ₂(PiPr₃)₂] (10) being also accessible from 8 and nBu₂Mg.

Full text of DOI:10.1016/j.ica.2003.12.018

Inorganica Chimica Acta 357 (2004) 2855–2862
www.elsevier.com/locate/ica
Five- and six-coordinate hydridorhodium(III) complexes containing
metalated Schiff-bases as ligands
*
Andreas Meiswinkel, Helmut Werner
Institut fu€r Anorganische Chemie, Universit€at W€urzburg, Am Hubland, W€urzburg D-97074, Germany
Received 11 December 2003; accepted 18 December 2003
Available online 21 January 2004
Abstract
The reactions of either [RhCl(C8H14)2]2 (2) or [RhCl(C2H4)2]2 (3) with Schiff-bases 1a–d derived from 2-aminopyridine afford, in the
presence of four equivalents of PiPr3, the octahedral chloro(hydrido)rhodium(III) complexes [{(C5H4N)N@C(C6H4R)}RhHCl-
(PiPr3)2] (4a–d) in which the metalated Schiff-base behaves as a chelating ligand. Treatment of 4a (R@H) with NaI and CF3SO3Tl
produce the corresponding derivatives [{(C5H4N)N@C(C6H5)}RhHX(PiPr3)2] (5, 6) by salt metathesis. The triflato compound 6 reacts
withnBu4NF ꢀ xH2O togive[{(C5H4N)N@C(C6H5)}RhHF(PiPr3)2](7). Whileattemptstoeliminate HClfrom 4a failed, thereactionof
4a with AgPF6 generates the five-coordinate cationic complex [{(C5H4N)N@C(C6H5)}RhH(PiPr3)2]PF6 (8) which adds one equivalent
of acetonitrile to give [{(C5H4N)N@C(C6H5)}RhH(NCCH3)(PiPr3)2]PF6 (9). Treatment of 4a with either nBu2Mg or LiAlH4 affords
the dihydridorhodium(III) compound [{(C5H4N)N@C(C6H5)}RhH2(PiPr3)2] (10) being also accessible from 8 and nBu2Mg.
Ó 2004 Elsevier B.V. All rights reserved.
Keywords: Rhodium; Schiff-bases; Phosphine complexes; Hydrido complexes; Ligand substitution
1. Introduction
mentioned trans-configurated compounds trans-
[RhCl(@CRR0)(PR3)2]. Therefore, we attempted to pre-
pare carbenerhodium(I) complexes of type B (see Scheme
1) by using octahedral rhodium(III) derivatives of type A
as the starting materials. Some representatives of these
compounds with Y ¼ Cl, Br, I and CN have already been
described in the literature [4]. We anticipated that, by
replacing the anionic ligand Y for a better leaving group
such as triflate, the reductive elimination of HY is fa-
vored and by subsequent reaction of the intermediate
with RX the desired product would be formed. When we
started this project we took into consideration that work
Recently, we reported on the preparation of carbene-
rhodium(I) complexes of the general composition trans-
[RhCl(@CRR0)(L)2] with L ¼ PR3, AsR3 and SbR3,
which were obtained by ligand exchange from trans-
[RhCl(@CRR0)(SbiPr3)2] as the precursor [1]. Although
these complexes, having a 16-electron count, can be re-
garded as relatives of the Grubbs-type carbenes [RuCl2-
(@CHR)(PR3)2], they are catalytically inactive in olefin
metathesis [2]. They react, however, with ethene or pro-
pene by C–C coupling generating trisubstituted olefins
such as RR0C@CHCH3 (from ethene) or RR0C@CH-
C2H5 (from propene) as the dominating products [1,3].
Following this work, we became interested to find out
whether four-coordinate rhodium carbenes with two
phosphine ligands in cis-disposition would behave in a
different way toward olefins compared with the above-
€
by Rudler and coworkers [5] and Dotz and coworkers [6]
has shown that Fischer-type carbenes of composition C
(see Scheme 1) react with 2-aminopyridine by ether
cleavage and displacement of one CO group to give the
chelating aminocarbene complexes D in excellent yield.
2. Results and discussion
* Corresponding author. Tel.: +49-931-888-5270; fax: +49-931-888-
4623.
The preparation of the Schiff-bases 1a–d, used as
substrates for the synthesis of the required rhodium
E-mail address: helmut.werner@mail.uni-wuerzburg.de (H. Wer-
ner).
0020-1693/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2003.12.018

2856
A. Meiswinkel, H. Werner / Inorganica Chimica Acta 357 (2004) 2855–2862
imine-CH proton at low field (d ca. 9.1–9.5 ppm) and the
X
resonance for the corresponding @CH carbon atom at d
ca. 160–164 ppm.
R
N
N
N
N
- HY
+ RX
L
Taking into account that most of the previous work
concerned to the reactivity of rhodium carbenes trans-
[RhCl(@CRR0)(PR3)2] has been carried out with the
bis(triisopropylphosphine) derivatives [3,7], we decided
to choose the dinuclear complex [RhCl(PiPr3)2]2 as the
precursor for compounds of type A. Since this complex
is extremely air-sensitive, it was generated in situ from
either [RhCl(C8H14)2]2 (2) or [RhCl(C2H4)2]2 (3) and
four equivalents of PiPr3 as the starting materials [8].
Stirring a solution of [RhCl(PiPr3)2]2 in THF with the
Schiff-bases 1a–d for 18 h at room temperature produces
the chloro(hydrido)rhodium(III) complexes 4a–d, which
were isolated as yellow, slightly air-sensitive solids in 63–
83% yield (Scheme 3). Under argon they can be stored
for weeks without decomposition. The 1H NMR spectra
of 4a–d display the hydride signal at around d )12.6
ppm, while the 13C NMR spectra show a resonance for
the metal-bound carbon atom at d ca. 230 ppm, the
latter being split into a doublet of triplets due to 13C–
103Rh and 13C–31P couplings. Since the 31P NMR
spectra of 4a–d display a single resonance (doublet),
there is no doubt that the two phosphine ligands are
trans-disposed.
L
Rh
L
Y
Rh
Ar
Ar
L
H
B
A
H
R
N
N
N
NH2
OEt
R
- EtOH
- CO
(CO)
(CO)
5M
4M
C
D
Scheme 1.
complexes, followed established routes. Similarly to
benzaldehyde, the corresponding derivatives ArCHO
(Ar ¼ p-C6H4OMe, m-C6H4NO2, p-C6H4Me) react with
2-aminopyridine in toluene under reflux to give com-
pounds 1b–d in 51–77% yield (Scheme 2). Typical fea-
tures in the NMR spectra of 1a–d are the signal for the
In contrast to what we expected, the chloro(hydrido)
complexes 4a–d are completely inert toward Broensted
bases. Treatment of 4a–d with NaH, DBU, DABCO or
K2CO3 does not lead to deprotonation or elimination of
HCl but leaves the starting materials unreacted. Com-
pounds 4a–d are also inert toward HCl and methyl
sulfate. Under the conditions used (benzene or nitro-
methane as solvent, room temperature, time of reaction
6–12 h), no protonation or methylation at the imine-
nitrogen atom could be observed. Compound 4a reacts
slowly with an excess of methyl iodide to give, however,
instead of an N-methylated cationic species the hyd-
rido(iodo) complex 5. A more convenient procedure to
O
N
N
∆T
+
H
Ar
N
NH2
Ar
- H2O
H
1a-d
Ar
1a
C6H5
1b p-C6H4OMe
1c m-C6H4NO2
1d p-C6H4Me
Scheme 2.
N
N
L
2 PiPr3
1a-d
2 PiPr3
1/2 [RhCl(C8H14)2]2
1/2 [RhCl(C2H4)2]2
Cl Rh
1d
Ar
L
H
3
2
(L = PiPr3)
Ar
4a
4b
4c m-C6H4NO2
4d p-C6H4Me
C6H5
p-C6H4OMe
Scheme 3.

A. Meiswinkel, H. Werner / Inorganica Chimica Acta 357 (2004) 2855–2862
2857
obtain 5 consists of the metathetical reaction of 4a with
NaI in benzene, which affords the product as an orange
solid in 82% yield. The NMR data of 5 are quite similar
to those of 4a and are in agreement with the proposed
structure (see Scheme 4).
triflate for fluoride and that all attempts to prepare 7
directly from 4a and nBu4NF ꢀ xH2O or CsF failed.
To obtain a four-coordinate rhodium(I) compound
[{(C5H4N)N@C(C6H5)}Rh(PiPr3)2], considered to be
a potential precursor for the preparation of rhodium
carbenes of type B (see Scheme 1), a stepwise elimina-
tion of Clꢁ and Hþ from 4a has also been attempted.
The reaction of 4a with AgPF6 in acetone proceeds
rather quickly and gives, after separation of AgCl and
recrystallisation of the crude product from acetone/
pentane, the five-coordinate complex 8 in moderate
yield (Scheme 5). The yield can be improved if an
equimolar amount of methyl iodide is added to the re-
action mixture. We assume that under these conditions
initially a substitution of chloride for iodide takes place
and that the subsequent formation of AgI facilitates the
process.
Owing to the ionic nature, compound 8 is readily
soluble in acetone, nitromethane, dichloromethane and
THF, but almost insoluble in benzene and other hy-
drocarbons. Conductivity measurements in nitrometh-
ane confirm the presence of a 1:1 electrolyte. The
formation of a cationic complex is also indicated by the
1H and 31P NMR spectra, in which both the signal for
the hydridic proton and that for the two equivalent
phosphorus atoms are shifted to lower fields compared
with 4a. In the 13C NMR spectrum of 8 the resonance
for the imine-carbon nuclei appears at d 202.3 ppm and
is thus shifted upfield compared with 4a.
The chloro ligand of 4a can also be replaced by tri-
flate. By using CF3SO3Tl as the substrate and acetone as
the solvent, the reaction is much faster than that of 4a
with NaI and gives the substitution product 6 in 69%
yield. The triflato complex 6, being also an orange solid,
is significantly less stable than the chloro or iodo
counterparts and decomposes even under argon in 2–3
days. While 6 is a non-electrolyte in benzene, conduc-
tivity measurements suggest that in nitromethane a
dissociation of the triflate anion occurs and a solvated
cation is formed. Treatment of 6 with nBu4NF ꢀ xH2O in
benzene leads to substitution of the triflato ligand for
fluoride and affords the fluoro(hydrido) complex 7 in
86% yield. The presence of a covalent Rh–F bond in 7 is
illustrated by the doublet-of-doublet resonance in the
31P NMR spectrum and the splitting of the hydride
1
signal into a doublet of doublets of triplets in the H
NMR spectrum. The formation of 7 from 6 is reminis-
cent to recent work from our group which showed that
metalla-cumulenes of the composition trans-[RhF-
(@C@CHR)(PiPr3)2] (R@H, tBu, Ph) are accessible via
the corresponding triflatorhodium complexes as inter-
mediates [9,10]. We note that the reaction of 6 with KF
or CsF in benzene does not lead to the replacement of
N
MX
nBu4NF
(X = Tfl)
N
N
N
N
N
L
L
L
- MCl
Cl Rh
X
Rh
H
F
L
Rh
H
Ph
Ph
Ph
L
L
H
7
4a
5, 6
(L = PiPr3)
X
I
5
6
CF3SO3 (Tfl)
Scheme 4.
PF6
PF6
CH3CN
AgPF6
- AgCl
N
L
Cl Rh
N
N
N
N
N
L
L
CH3CN
Rh
H
Rh
H
Ph
Ph
Ph
L
L
L
H
9
4a
8
(L = PiPr3)
Scheme 5.

2858
A. Meiswinkel, H. Werner / Inorganica Chimica Acta 357 (2004) 2855–2862
The open coordination site in the cation of 8 can
the substitution products 5–7 in good yields. The Rh–Cl
bond in 4a is also split by AgPF6 to afford the five-
coordinate cationic complex 8 having an open coordi-
nation site. The reaction of either 4a or 8 with nBu2Mg
leads to the formation of the dihydridorhodium(III)
compound 10 which is rather inert and does not elimi-
nate H2 to give a rhodium(I) complex with the two PiPr3
ligands in cis-disposition.
easily be occupied by acetonitrile. As has been shown by
an experiment carried out in an NMR-tube, treatment
of a solution of 8 in CD2Cl2 with a fivefold excess of
MeCN generates in a few seconds the octahedral com-
1
plex 9 which has been characterized by H, 13C and 31P
NMR spectroscopy. Typical features are the hydride
resonance (doublet of triplets) at d )12.84 ppm (see 7: d
)10.53 ppm) and the signal for the metal-bound car-
bon atom (also a doublet of triplets) at d 226.4 ppm (see
7: d 202.3 ppm). When we attempted to remove the
volatiles and isolate compound 9, the precursor 8 was
regenerated.
3. Experimental
All experiments were carried out under an atmo-
sphere of argon by Schlenk techniques. The starting
materials 1a [12], 2 [13] and 3 [14] were prepared as
described in the literature. PiPr3 was a commercial
product from Strem. IR spectra were recorded on a
Bruker VECTOR 22 FT-IR spectrometer and NMR
spectra at room temperature (r.t.) on Bruker AC 200
and AMX 400 instruments. Abbreviations used: s, sin-
glet; d, doublet; t, triplet; q, quartet; sept, septet; m,
multiplet; br, broadened signal; vt, virtual triplet;
The Rh–H bond in the cation of 8 is remarkably
strong and thus all attempts to abstract a proton from 8
by using KOtBu or NaOH and a phase-transfer reagent
such as tribenzylethylammonium chloride (TEBA) re-
mained unsuccessful. The reaction of either 8 or 4a with
nBu2Mg does also not lead to compound [{(C5H4N)N@
CPh}Rh(PiPr3)2] but affords the dihydrido complex 10
instead (Scheme 6). The yield can be improved from 60–
65% up to 80% (isolated product) if LiAlH4 is used as
the hydride source. Compound 10 is a yellow oil that is
readily soluble in all common organic solvents. The
5
1
3
N ¼ 3JðPHÞ þ JðPHÞ or JðPCÞ þ JðPCÞ. Conductiv-
ity measurements were carried out with a Schott Kon-
duktometer CG 851. Melting points were determined by
Differential Thermal Analysis (DTA). The mass spec-
trum of 8 was measured on a Finnigan 90 MAT
instrument.
1
proposed structure is particularly supported by the H
NMR spectrum which displays in the high-field region
two signals (both doublets of doublets of triplets) at d
)9.61 and )16.03 ppm indicating that the two hydrido
ligands are in different environments. Taking into con-
sideration that the trans influence of the iminoacyl
group is presumably much stronger than that of pyri-
dine [11], we assume that the signal at d )9.61 should be
assigned to the hydride trans to nitrogen and the signal
at d )16.03 trans to carbon. The resonance of the C-
bound carbon atom appears in the 13C NMR spectrum
of 10 as a doublet of triplets at d 274.4 ppm due to 13C–
103Rh and 13C–31P couplings.
In summarizing the present work has shown that al-
though hydridorhodium(III) complexes of type A with
L ¼ PiPr3 are easily accessible from Schiff-bases derived
from 2-aminopyridine, the Rh–H bond is exceedingly
strong and thus all attempts to eliminate HCl from 4a or
CF3SO3H from 6 remained unsuccessful. However, the
chloro ligand in the starting material 4a can be smoothly
replaced by soft as well as by hard Lewis bases to give
3.1. Preparation of 2-(C5H4N)N@CHC6H4-p-OMe (1b)
A solution of 4.67 g (49.6 mmol) of 2-aminopyridine
in 100 ml of toluene was treated with 6.75 g (49.6 mmol)
of p-methoxybenzaldehyde and two drops of concen-
trated H2SO4. After the reaction mixture was refluxed
for 6 h at a water condenser, it was brought to r.t. The
solvent was evaporated in vacuo and the oily residue
was distilled at 7 ꢂ 10ꢁ2 mbar. At 139–141 °C a colorless
oil was obtained which transformed at r.t. to a white
solid; yield 5.36 g (51%), m.p. 54 °C. Anal. Calc. for
C13H12N2O: C, 73.57; H, 5.70; N, 13.20. Found: C,
1
73.29; H, 5.97; N, 12.85%. H NMR (C6D6, 200 MHz):
d 9.52 (s, 1H, N@CH), 8.42 (m, 1H, C5H4N), 7.92 (m,
2H, C6H4), 7.38, 7.14 (both m, 1H each, C5H4N), 6.68
(m, 2H, C6H4), 6.63 (m, 1H, C5H4N), 3.16 (s, 3H,
PF6
nBu2Mg
nBu2Mg
N
N
N
N
N
N
L
L
L
(or LiAlH4 )
H
Rh
Cl Rh
Rh
Ph
Ph
Ph
L
L
L
H
H
H
4a
10
8
(L = PiPr3)
Scheme 6.

A. Meiswinkel, H. Werner / Inorganica Chimica Acta 357 (2004) 2855–2862
2859
OCH3). 13C NMR (C6D6, 50.3 MHz): d 163.5 (s, NCN),
162.7 (s, N@CH), 162.4 (s, COCH3), 149.7, 138.3 (both
s, C5H4N), 132.3 (s, C6H4), 130.4 (s, CC@N), 122.1,
121.4 (both s, C5H4N), 115.0 (s, C6H4), 55.3 (s, OCH3).
0.98 [both dvt, 18 H each, N ¼ 13.3 Hz, 3J(HH) ¼
7.0 Hz, PCHCH3], )12.61 [dt, 1H, 2J(PH) ¼ 14.9 Hz,
1J(RhH) ¼ 13.7 Hz, RhH]. 13C NMR (C6D6, 100.6
1
2
MHz): d 230.4 [dt, J(RhC) ¼ 34.6 Hz, J(PC) ¼ 7.1 Hz,
RhC], 168.7 (s, NCN), 150.7 (s, C5H4N), 145.5 [d,
2J(RhC) ¼ 4.1 Hz, CC@N], 137.7 (s, C5H4N), 130.6,
128.3 (both s, C6H5), 127.3, 120.2, 117.5 (all s, C5H4N
and C6H5), 25.9 (vt, N ¼ 20:4 Hz, PCHCH3), 20.0, 19.7
(both s, PCHCH3). 31P NMR (C6D6, 162.0 MHz): d
3.2. Preparation of 2-(C5H4N)N@CHC6H4-m-NO2 (1c)
This compound was prepared as described for 1b,
with 3.73 g (39.6 mmol) of 2-aminopyridine and 5.98 g
(39.6 mmol) of m-nitrobenzaldehyde as starting materi-
als. Yellow solid, yield 4.95 g (55%), m.p. 87 °C. Anal.
Calc. for C12H9N3O2: C, 63.43; H, 3.99; N, 18.49.
1
35.6 [d, J(RhP) ¼ 109.3 Hz].
3.5. Preparation of [{(C5H4N)N@C(C6H4-p-OMe)}-
RhHCl(PiPr3)2] (4b)
1
Found: C, 63.00; H, 4.19; N, 18.30%. H NMR (C6D6,
200 MHz): d 9.17 (s, 1H, N@CH), 8.52 (m, 1H, C6H4),
8.35 (m, 1H, C5H4N), 7.72 (br m, 2H, C6H4), 7.28, 7.13
(both m, 1H each, C5H4N), 6.64 (br m, 2H, C5H4N and
C6H5). 13C NMR (C6D6, 50.3 MHz): d 160.2 (s,
N@CH), 160.1 (s, NCN), 149.2 (s, C5H4N), 148.8 (s,
CNO2), 138.1 (s, C5H4N), 137.7 (s, CC@N), 134.2,
129.3, 125.7, 124.1, 122.7, 121.4 (all s, C5H4N and
C6H5).
This compound was prepared as described for 4a,
with 626 mg (0.87 mmol) of 2, 370 mg (1.74 mmol) of 1b
and 0.67 ml (3.48 mmol) of PiPr3 as starting materials.
Yellow solid; yield 828 mg (71%), m.p. (decomposition)
136 °C. Anal. Calc. for C31H54ClN2OP2Rh: C, 55.48; H,
8.11; N, 4.17. Found: C, 55.22; H, 7.70; N, 4.69%. IR
(KBr): m(RhH) 2095 cmꢁ1. 1H NMR (C6D6, 200 MHz):
d 9.92 (m, 1H, C5H4N), 8.98 (m, 2H, C6H4), 7.77, 7.22
(both m, 1H each, C5H4N), 6.91 (m, 2H, C6H4), 6.68
(m, 1H, C5H4N), 3.25 (s, 3H, OCH3), 2.49 (m, 6H, PCH
CH3), 1.08, 1.02 [both dvt, 18 H each, N ¼ 13:7 Hz,
3J(HH) ¼ 7.0 Hz, PCHCH3], )12.57 [dt, 1H,
2J(PH) ¼ 14.8 Hz, 1J(RhH) ¼ 13.9 Hz, RhH]. 13C NMR
(C6D6, 50.3 MHz): d 229.0 [dt, 1J(RhC) ¼ 33.1 Hz,
2J(PC) ¼ 6.4 Hz, RhC], 168.8 (s, NCN), 162.2 (s,
COCH3), 150.7 (s, C5H4N), 138.1 [d, 2J(RhC) ¼ 7.6 Hz,
CC@N], 137.6 (s, C5H4N), 128.3, 112.5 (both s, C6H4),
119.6, 117.1 (both s, C5H4N), 54.8 (s, OCH3), 26.0 (vt,
N ¼ 20:4 Hz, PCHCH3), 20.0, 19.7 (both s, PCHCH3).
31P NMR (C6D6, 81.0 MHz): d 35.6 [d, 1J(RhP) ¼ 109.3
Hz].
3.3. Preparation of 2-(C5H4N)N@CHC6H4-p-Me (1d)
This compound was prepared as described for 1b,
with 7.53 g (80.0 mmol) of 2-aminopyridin and 9.53 g
(80.0 mmol) of p-methylbenzaldehyde as starting mate-
rials. White solid, yield 12.05 g (77%), m.p. 62 °C. Anal.
Calc. for C13H12N2: C, 79.56; H, 6.16; N, 14.27. Found:
C, 79.65; H, 5.95; N, 14.19%. 1H NMR (C6D6, 200
MHz): d 9.51 (s, 1H, N@CH), 8.41 (m, 1H, C5H4N),
7.90 (m, 2H, C6H4), 7.36, 7.16 (both m, 1H each,
C5H4N), 6.93 (m, 2H, C6H5), 6.65 (m, 1H, C5H4N), 2.00
(s, CH3). 13C NMR (C6D6, 50.3 MHz): d 162.7 (s,
N@CH), 161.6 (s, NCN), 149.1 (s, C5H4N), 142.2 (s,
CCH3), 137.8 (s, C5H4N), 134.3 (s, CC@N), 129.9, 129.7
(both s, C6H5), 121.7, 120.8 (both s, C5H4N), 21.4
(CH3).
3.6. Preparation of [{(C5H4N)N@C(C6H4-m-NO2)}-
RhHCl(PiPr3)2] (4c)
3.4. Preparation of [{(C5H4N)N@C(C6H5)}RhHCl-
(PiPr3)2] (4a)
This compound was prepared as described for 4a,
with 395 mg (0.55 mmol) of 2, 250 mg (1.10 mmol) of 1c
and 0.42 ml (2.20 mmol) of PiPr3 as starting materials.
Yellow solid; yield 626 mg (83%), m.p. (decomposition)
144 °C. Anal. Calc. for C30H51ClN3O2P2Rh: C, 52.52;
H, 7.49; N, 6.12. Found: C, 52.16; H, 7.70; N, 5.74%. IR
(KBr): m(RhH) 2091 cmꢁ1. 1H NMR (C6D6, 200 MHz):
d 9.87 (br m, 2H, C5H4N and C6H4), 8.99, 7.92 (both m,
1H each, C6H4), 7.71, 7.19 (both m, 1H each, C5H4N),
6.90 (m, 1H, C6H4), 6.67 (m, 1H, C5H4N), 2.36 (m, 6H,
PCHCH3), 0.98, 0.94 [both dvt, 18 H each, N ¼ 12:8 Hz,
A solution of 856 mg (1.19 mmol) of 2 and 435 mg
(2.39 mmol) of 1a in 30 ml of THF was treated with 0.91
ml (4.77 mmol) of PiPr3 and stirred for 18 h at r.t. The
solution was concentrated to ca. 4 ml in vacuo and, after
it was cooled to )20 °C, 5 ml of pentane was added. A
yellow solid precipitated, which was washed twice with
2-ml portions of pentane ()20 °C) and dried; yield 1.164
g (76%), m.p. (decomposition) 131 °C. Anal. Calc. for
C30H52ClN2P2Rh: C, 56.21; H, 8.18; N, 4.37; Rh, 16.05.
Found: C, 56.08; H, 8.34; N, 4.45; Rh, 16.40%. IR
(KBr): m(RhH) 2093 cmꢁ1. 1H NMR (C6D6, 400 MHz):
d 9.87 (m, 1H, C5H4N), 8.90 (m, 2H, C6H5), 7.75 (m,
1H, C5H4N), 7.35–7.15 (br m, 4H, C5H4N and C6H5),
6.71 (m, 1H, C5H4N), 2.44 (m, 6H, PCHCH3), 1.02,
2
3J(HH) ¼ 6.9 Hz, PCHCH3], )12.57 [dt, 1H, J(PH) ¼
1
14.8 Hz, J(RhH) ¼ 13.9 Hz, RhH]. 13C NMR (C6D6,
50.3 MHz): d 231.1 [dt, 1J(RhC) ¼ 34.9 Hz, 2J(PC) ¼ 7.6
Hz, RhC], 168.4 (s, NCN), 150.8 (s, C5H4N), 148.2 (s,
2
CNO2), 146.5 [d, J(RhC) ¼ 4.9 Hz, CC@N], 139.1 (s,
C6H4), 137.9 (s, C5H4N), 128.3, 127.8, 124.9, 120.7,

2860
A. Meiswinkel, H. Werner / Inorganica Chimica Acta 357 (2004) 2855–2862
118.2 (all s, C5H4N and C6H4), 26.0 (vt, N ¼ 22:0 Hz,
PCHCH3), 19.9, 19.6 (both s, PCHCH3). 31P NMR
(C6D6, 81.0 MHz): d 35.9 [d, J(RhP) ¼ 104.2 Hz].
31P NMR (C6D6, 81.0 MHz): d 31.0 [d, 1J(RhP) ¼ 106.8
Hz].
1
3.9. Preparation of [{(C5H4N)N@C(C6H5)}RhH(j1-
O3SCF3)(PiPr3)2] (6)
3.7. Preparation of [{(C5H4N)N@C(C6H4-p-Me)}-
RhHCl(PiPr3)2] (4d)
A solution of 385 mg (0.60 mmol) of 4a in 20 ml of
acetone was treated with 212 mg (0.60 mmol) of
CF3SO3Tl and stirred for 30 min at r.t. The solvent was
evaporated in vacuo and the residue was extracted with
10 ml of benzene. The extract was concentrated to ca. 2
ml in vacuo. After addition of 2 ml of pentane at )20 °C,
an orange-yellow solid precipitated, which was washed
twice with 1-ml portions of pentane ()20 °C) and dried;
yield 313 mg (69%), m.p. (decomposition) 96 °C. Anal.
This compound was prepared as described for 4a,
either (a) with 441 mg (0.62 mmol) of 2, 240 mg (1.23
mmol) of 1d and 0.47 ml (2.46 mmol) of PiPr3 or (b)
with 107 mg (0.28 mmol) of 3, 108 mg (0.55 mmol) of 1d
and 0.21 ml (1.10 mmol) of PiPr3 as starting materials.
Yellow solid; yield 596 mg (74%) according to (a) and
227 mg (63%) according to (b), m.p. (decomposition) 99
°C. Anal. Calc. for C31H54ClN2P2Rh: C, 56.84; H, 8.31;
N, 4.28. Found: C, 56.38; H, 8.43; N, 4.26%. IR (KBr):
Calc. for C31H52F3N2O P2RhS: C, 49.34; H, 6.94; N,
3
1
m(RhH) 2097 cmꢁ1. H NMR (C6D6, 200 MHz): d 9.92
3.71; S, 4.25. Found: C, 48.94; H, 7.20; N, 3.67; S,
4.31%. Conductivity: K(CH3NO2) 72 cm2 ꢀ Xꢁ1 ꢀ molꢁ1
(m, 1H, C5H4N), 8.91 (m, 2H, C6H4), 7.77, 7.21 (both
m, 1H each, C5H4N), 7.11 (m, 2H, C6H4), 6.68 (m, 1H,
C5H4N), 4.28 (s, 3H, CH3), 2.47 (m, 6H, PCHCH3),
;
K(C6H6) 0 cm2 ꢀ Xꢁ1 ꢀ molꢁ1 IR (Nujol): m(RhH) 2114,
m(S@Oasym) 1339, m(S@Osym) 1236 cmꢁ1. H NMR (ac-
1
3
1.08, 1.01 [both dvt, 18H each, N ¼ 12:8 Hz, J(HH) ¼
etone-d6, 200 MHz): d 8.98 (m, 1H, C5H4N), 8.05 (m,
2H, C6H5), 7.92, 7.67 (both m, 1H each, C5H4N), 7.35–
7.10 (br m, 4H, C5H4N and C6H5), 1.99 (m, 6H,
PCHCH3), 0.79, 0.72 [both dvt, 18H each, N ¼ 13:8 Hz,
3J(HH) ¼ 6.9 Hz, PCHCH3], )10.93 [dt, 1H,
2J(PH) ¼ 11.8 Hz, 1J(RhH) ¼ 19.7 Hz, RhH]. 13C NMR
(C6D6, 100.6 MHz): d 213.0 [dt, 1J(RhC) ¼ 40.3 Hz,
2J(PC) ¼ 8.2 Hz, RhC], 164.7 (s, NCN), 152.4 (s,
C5H4N), 141.9 (br s, CC@N), 138.7 (s, C5H4N), 132.5
(br s, C6H5), 131.3, 127.5 (both s, C6H5), 121.3 [q,
1J(FC) ¼ 320.2 Hz, CF3], 121.0, 119.7 (both s, C5H4N),
25.8 (vt, N ¼ 20:4 Hz, PCHCH3), 16.8, 16.4 (both s,
PCHCH3). 31P NMR (C6D6, 162.0 MHz): d 42.4 [d,
1J(RhP) ¼ 109.3 Hz].
7.8 Hz, PCHCH3], )12.56 [dt, 1H, 2J(PH) ¼ 14.8 Hz,
1J(RhH) ¼ 14.0 Hz, RhH]. 13C NMR (C6D6, 50.3
2
MHz): d 230.3 [dt, 1J(RhC) ¼ 34.3 Hz, J(PC) ¼ 7.7 Hz,
RhC], 168.8 (s, NCN), 150.7 (s, C5H4N), 142.6 [d,
3J(RhC) ¼ 3.8 Hz, CC@N], 140.7 (s, CCH3), 137.6 (s,
C5H4N), 128.5, 127.5 (both s, C6H4), 120.0, 117.3 (both
s, C5H4N), 53.5 (s, CH3), 25.9 (vt, N ¼ 20:4 Hz,
PCHCH3), 20.0, 19.7 (both s, PCHCH3). 31P NMR
1
(C6D6, 81.0 MHz): d 35.6 [d, J(RhP) ¼ 107.6 Hz].
3.8. Preparation of [{(C5H4N)N ¼ C(C6H5)}RhHI-
(PiPr3)2] (5)
A solution of 180 mg (0.28 mmol) of 4a in 10 ml of
benzene was treated with 502 mg (3.35 mmol) of NaI
and stirred for 18 h at r.t. The reaction mixture was
filtered and the filtrate was concentrated to ca. 2 ml in
vacuo. After the addition of 5 ml of pentane at )20 °C,
an orange solid precipitated, which was washed twice
with 2-ml portions of pentane ()20 °C) and dried; yield
168 mg (82%), m.p. (decomposition) 120 °C. Anal. Calc.
for C30H52IN2P2Rh: C, 49.19; H, 7.15; N, 3.82. Found:
C, 49.49; H, 7.09; N, 4.22%. IR (KBr): m(RhH) 2128
3.10. Preparation of [{(C5H4N)N@C(C6H5)}RhHF-
(PiPr3)2] (7)
A solution of 137 mg (0.18 mmol) of 6 in 10 ml of
benzene was treated with 324 mg (ca. 1.05 mmol) of
nBu4NF ꢀ xH2O ðx ꢃ 2:67Þ and stirred for 15 min at r.t.
After the solution was washed twice with 5-ml por-
tions of water, the organic phase was separated and
dried with MgSO4. The solution was filtered, the filtrate
was brought to dryness in vacuo and the remaining
orange oil dried; yield 97 mg (86%). Anal. Calc. for
C30H52FN2P 2Rh: C, 57.69; H, 8.39; N, 4.48. Found: C,
57.20; H, 8.73; N, 4.32%. 1H NMR (C6D6, 400 MHz): d
9.31 (m, 1H, C5H4N), 8.87 (m, 2H, C6H5), 7.77 (m, 1H,
C5H4N), 7.32–7.21 (br m, 3H, C6H5), 7.19, 6.69 (both
m, 1H each, C5H4N), 2.23 (m, 6H, PCHCH3), 1.09, 0.97
[both dvt, 18H each, N ¼ 13:8 Hz, 3J(HH) ¼ 7.1 Hz,
PCHCH3], )11.55 [ddt, 1H, 2J(PH) ¼ 14.2 Hz,
cmꢁ1 1H NMR (C6D6, 200 MHz): d 10.45 (m, 1H,
.
C5H4N), 8.94 (m, 2H, C6H5), 7.73 (m, 1H, C5H4N),
7.40–7.10 (br m, 4H, C5H4N and C6H5), 6.55 (m, 1H,
C5H4N), 2.54 (m, 6H, PCHCH3), 1.03, 1.00 [both dvt,
18H each, N ¼ 12:8 Hz, 3J(HH) ¼ 7.9 Hz, PCHCH3],
2
1
)13.43 [dt, 1H, J(PH) ¼ 14.7 Hz, J(RhH) ¼ 15.7 Hz,
RhH]. 13C NMR (C6D6, 50.3 MHz): d 230.4 [dt,
1J(RhC) ¼ 34.1 Hz, 2J(PC) ¼ 7.3 Hz, RhC], 168.7 (s,
2
NCN), 153.1 (s, C5H4N), 144.4 [d, J(RhC) ¼ 7.7 Hz,
2
CC@N], 138.1 (s, C5H4N), 130.9, 128.3 (both s, C6H5),
127.8, 120.4, 118.4 (all s, C5H4N and C6H5), 27.9 (vt,
N ¼ 20:4 Hz, PCHCH3), 20.8, 20.0 (both s, PCHCH3).
1J(RhH) ¼ 15.8 Hz, J(FH) ¼ 7.9 Hz, RhH]. 13C NMR
(C6D6, 100.6 MHz): d 231.7 (m, RhC), 168.0 (s, NCN),
149.8 (s, C5H4N), 145.8 (br s, CC@N), 137.3 (s,

A. Meiswinkel, H. Werner / Inorganica Chimica Acta 357 (2004) 2855–2862
2861
C5H4N), 132.2, 130.3, 127.3 (all s, C6H5), 120.1, 117.8
(both s, C5H4N), 24.8 (vt, N ¼ 20:4 Hz, PCHCH3), 19.5,
19.4 (both s, PCHCH3). 19F NMR (C6D6, 376.6 MHz):
d )334.9 (br m). 31P NMR (C6D6, 162.0 MHz): d 40.2
2J(PC) ¼ 6.1 Hz, RhC], 168.6 (s, NCN), 150.7 (s,
2
C5H4N), 144.4 [d, J(RhC) ¼ 7.1 Hz, CC@N], 141.1 (s,
C5H4N), 132.9, 129.2 (both s, C6H5), 123.3, 121.5, 188.8
(all s, C5H4N and C6H5), 118.6 (s, NCCH3), 27.5 (vt,
N ¼ 21:8 Hz, PCHCH3), 20.8, 20.6 (both s, PCHCH3),
3.3 (s, NCCH3). 31P NMR (CD2Cl2, 81.0 MHz): d 36.5
1
2
[dd, J(RhP) ¼ 110.2 Hz, J(FP) ¼ 13.5 Hz].
1
1
3.11. Preparation of [{(C5H4N)N ¼ C(C6H5)}RhH-
(PiPr3)2]PF6 (8)
[d, J(RhP) ¼ 103.7 Hz, PiPr3], )144.3 [sept, J(FP) ¼
711.7 Hz, PF6ꢁ].
A solution of 174 mg (0.27 mmol) of 4a in 10 ml of
acetone was first treated with 0.02 ml (0.32 mmol) of
methyliodide and then dropwise with a solution of
69 mg (0.27 mmol) of AgPF6 in 5 ml of acetone at r.t.
A pale yellow solid precipitated which was sepa-
rated from the solution by filtration on Celite. The so-
lution was brought to dryness in vacuo and the residue
was recrystallized from 10 ml of acetone/pentane (1:2)
to give a yellow microcrystalline solid; yield 137 mg
(67%), m.p. (decomposition) 183 °C. Anal. Calc. for
C30H52F6N2P3Rh: C, 48.01; H, 6.98; N, 3.73; Rh,
13.71%. Found: C, 47.97; H, 6.79; N, 3.68; Rh, 13.89%.
MS (FAB, 2-nitrophenyloctylether): m=z 605 (Mþ).
Conductivity: K(CH3NO2) 104 cm2 ꢀ Xꢁ1 ꢀ molꢁ1. IR
3.13. Preparation of [{(C5H4N)N@C(C6H5)}RhH2-
(PiPr3)2] (10)
Method a: A solution of 57 mg (0.09 mmol) of 4a in 5
ml of benzene was treated with 0.2 ml of a 1.0 M solu-
tion of nBu2Mg in hexane (0.20 mmol) at r.t. The so-
lution was stirred for 15 min and the volatiles were
evaporated in vacuo. The residue was extracted with 10
ml of pentane, the extract was concentrated to ca. 2 ml
and the solution was chromatographed on Al2O3 (neu-
tral, activity grade V, height of column 4 cm). With
pentane, a yellow fraction was eluted which gave a yel-
low oil after evaporation of the solvent; yield 33 mg
(61%).
(KBr): m(RhH) 2109 cmꢁ1
.
1H NMR (CD2Cl2, 400
Method b: A solution of 131 mg (0.20 mmol) of 4a in
10 ml of diethyl ether was treated with 50 mg of LiAlH4
and stirred for 30 min at r.t. The solvent was evaporated
in vacuo and the residue was extracted with 10 ml of
benzene. After the extract was brought to dryness in
vacuo, a yellow oil was obtained; yield 98 mg (81%).
Method c: A solution of 52 mg (0.06 mmol) of 8 in 5
ml of benzene was treated with 0.13 ml of a 1.0 M so-
lution of nBu2Mg in hexane (0.13 mmol) at r.t. The
suspension was stirred for 1 h and the volatiles were
evaporated in vacuo. The residue was extracted with 10
ml of pentane, the extract was concentrated to ca. 2 ml
and the solution was chromatographed on Al2O3 (neu-
tral, activity grade V, height of column 4 cm). With
pentane, a yellow fraction was eluted which gave a yel-
low oil after evaporation of the solvent; yield 36 mg
(65%). Anal. Calc. for C30H53N2P2Rh: C, 59.40; H, 8.81;
N, 4.62. Found: C, 59.01; H, 9.07; N, 4.23%. IR (KBr):
MHz): d 8.83 (m, 1H, C5H4N), 8.19 (m, 2H, C6H5),
8.05, 7.86 (both m, 1H each, C5H4N), 7.51–7.43 (br m,
2H, C5H4N and C6H5), 7.37 (m, 2H, C6H5), 2.16 (m,
6H, PCHCH3), 0.98, 0.90 [both dvt, 18H each, N ¼ 14:1
Hz, 3J(HH) ¼ 7.4 Hz, PCHCH3], )10.53 [dt, 1H,
2J(PH) ¼ 10.9 Hz, 1J(RhH) ¼ 21.1 Hz, RhH]. 13C NMR
1
(CD2Cl2, 100.6 MHz): d 202.3 [dt, J(RhC) ¼ 37.6 Hz,
3J(PC) ¼ 5.1 Hz, RhC], 162.5 [d, 3J(RhC) ¼ 2.1 Hz,
NCN], 151.2, 141.7 (both s, C5H4N), 139.9 [d,
3J(RhC) ¼ 5.1 Hz, CC@N], 133.7 [d, 3J(RhC) ¼ 10.2 Hz,
C6H5], 133.6, 129.7 (both s, C6H5), 124.2, 122.9 (both s,
C5H4N), 26.7 (vt, N ¼ 22:4 Hz, PCHCH3), 20.5, 20.4
(both s, PCHCH3). 31P NMR(CD2Cl2, 81.0 MHz): d
41.5 [d, 1J(RhP) ¼ 113.4 Hz, PiPr3], )144.3 [sept,
1J(FP) ¼ 713.0 Hz, PF6ꢁ].
3.12. Generation of [{(C5H4N)N ¼ C(C6H5)}RhH-
(NCCH3)(PiPr3)2]PF6 (9)
1
m(RhH) 2096 cmꢁ1. H NMR (C6D6, 400 MHz): d 8.97
(m, 2H, C6H5), 8.73, 7.95 (both m, 1H each, C5H4N),
7.44 (m, 2H, C6H5), 7.26 (m, 1H, C6H5), 7.22, 6.42
(both m, 1H each, C5H4N), 1.89 (m, 6H, PCHCH3),
In an NMR tube, a solution of 21 mg (0.03 mmol) of
8 in 0.5 ml of CD2Cl2 was treated with 0.005 ml (0.15
1
3
mmol) of acetonitrile at r.t. The H, 13C and 31P NMR
1.06, 0.96 [both dvt, 18H each, N ¼ 14:2 Hz, J(HH) ¼
spectra revealed that compound 9 was formed. If the
solvent was evaporated in vacuo, the starting material 8
7.1 Hz, PCHCH3], )9.61 [ddt, 1H, 2J(PH) ¼ 18.5 Hz,
1J(RhH) ¼ 9.8 Hz, 2J(HH) ¼ 8.2 Hz, RhH], )16.03 [ddt,
1H, 2J(PH) ¼ 16.4 Hz, 1J(RhH) ¼ 16.4 Hz, 2J(HH) ¼ 8.2
Hz, RhH]. 13C NMR (C6D6, 100.6 MHz): d 274.4 [dt,
1J(RhC) ¼ 29.2 Hz, 2J(PC) ¼ 7.3 Hz, RhC], 171.8 (s,
1
was regenerated. Data for 9: H NMR (CD2Cl2, 400
MHz): d 8.89 (m, 1H, C5H4N), 8.30 (m, 2H, C6H5),
7.94, 7.79 (both m, 1H each, C5H4N), 7.45-7.25 (br m,
4H, C5H4N and C6H5), 2.13 (m, 6H, PCHCH3), 2.10 (s,
3H, CH3CN), 1.03, 0.98 [both dvt, 18H each, N ¼ 13:3
Hz, 3J(HH) ¼ 6.9 Hz, PCHCH3], )12.84 [dt, 1H,
2J(PH) ¼ 13.0 Hz, 1J(RhH) ¼ 13.3 Hz, RhH]. 13C NMR
2
NCN), 151.5 (s, C5H4N), 149.3 [d, J(RhC) ¼ 3.8 Hz,
CC@N], 136.3 (s, C5H4N), 132.2, 129.5, 127.4 (all s,
C6H5), 121.7, 116.5 (both s, C5H4N), 26.9 (vt, N ¼ 22:8
Hz, PCHCH3), 20.1, 19.6 (both s, PCHCH3). 31P NMR
1
1
(CD2Cl2, 100.6 MHz): d 226.4 [dt, J(RhC) ¼ 36.1 Hz,
(C6D6, 162.0 MHz): d 61.1 [d, J(RhP) ¼ 111.9 Hz].

2862
A. Meiswinkel, H. Werner / Inorganica Chimica Acta 357 (2004) 2855–2862
[4] (a) J.W. Suggs, S.D. Cox, Organometallics 1 (1982) 402;
Acknowledgements
(b) A. Albinati, C. Arz, P.S. Pregosin, J. Organomet. Chem. 335
(1987) 379.
Financial support from the Fonds der Chemischen
Industrie and BASF AG, Ludwigshafen, is gratefully
acknowledged. We also thank Mrs. R. Schedl and Mr.
C.P. Kneis for elemental analyses and DTA measure-
ments, Dr. G. Lange and Mr. F. Dadrich for the mass
spectrum, and Dr. J. Wolf for valuable advice.
[5] B. Denise, P. Dubost, A. Parlier, M. Rudler, H. Rudler, J.C.
Daran, J. Vaissermann, F. Delgado, A.R. Arevalo, R.A. Toscano,
C. Alvarez, J. Organomet. Chem. 418 (1991) 377.
€
[6] K.H. Dotz, A. Rau, K. Harms, Chem. Ber. 125 (1992) 2137.
[7] H. Werner, J. Organomet. Chem. 500 (1995) 331.
€
[8] H. Werner, J. Wolf, A. Hohn, J. Organomet. Chem. 287 (1985)
395.
[9] J. Gil-Rubio, B. Weberndorfer, H. Werner, J. Chem. Soc., Dalton
€
Trans. (1999) 1437.
[10] J. Gil-Rubio, M. Laubender, H. Werner, Organometallics 19
(2000) 1365.
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