New C-tetrazolato complexes of rhodium(III), palladium(II) and gold(III)

Article abstract of DOI:10.1016/S0022-328X(00)00457-5

The azido complexes [RhCp*(μ-N₃)(N₃)]₂ (Cp* = η-C₅Me₅), trans-Rh(N₃)(CO)(PPh₃)₂, Na₂[Pd(N₃)₄], Na₂[Pd₂(μ-N₃

Full text of DOI:10.1016/S0022-328X(00)00457-5

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 613 (2000) 159–169
New C-tetrazolato complexes of rhodium(III), palladium(II) and
gold(III)
Martin Wehlan a, Renate Thiel a, Joachim Fuchs a, Wolfgang Beck b,
Wolf Peter Fehlhammer a,*
a Institut fu¨r Anorganische und Analytische Chemie der Freien Uni6ersita¨t Berlin, Fabeckstraße 34–36, D-14195 Berlin, Germany
b Department Chemie der Uni6ersita¨t Mu¨nchen, Butenandtstraße 5–13 (Haus D), D-81377 Mu¨nchen-Großhadern, Germany
Received 05 April 2000; received in revised form 30 May 2000
Abstract
The azido complexes [RhCp*(m-N3)(N3)]2 (Cp*=h-C5Me5), trans-Rh(N3)(CO)(PPh3)2, Na2[Pd(N3)4], Na2[Pd2(m-N3)2(N3)4] and
Na[Au(N3)4], prepared in situ from metal halide precursors and a three- to ten-fold excess of NaN3 in water, react with aliphatic
isocyanides to give a series of new metal–carbon bonded tetrazolato complexes. All azide ligands in the coordination sphere
undergo this cycloaddition with isocyanides except on palladium(II) where only two tetrazol-5-ato groups are formed. In the
neutral species HAu(CN4R)4 (R=tBu (2c), Cy (2d)) presumably one of the four tetrazol-5-ato groups has been protonated to
afford a tetrazol-5-ylidene (carbene) ligand. The reactivities of the isocyanides decrease in the order CNtBu\CNCy\
CN(CH2)4Cl\CN-allyl\CNCH2CO2Na; surprisingly, no reaction occurs with methylisocyanide. With tert-butyl isocyanide in
the cold, [Ru(m-N3)(N3)(h-C10H14)]2 (C10H14:4-isopropyltoluene) only reacts with cleavage of the azido bridges giving rise to
[Ru(N3)2(h-C10H14)CNtBu] (5a), while heating of the same mixture affords a second azido-isocyanide complex, trans-
[Ru(N3)2(CNtBu)4] (5b), of which an X-ray structure analysis has been carried out. In some cases the reactions proceed with N2
evolution, and rhodium complexes 6a–c are also formed probably containing cyanamido (ꢀN{R}CꢁN) or carbodiimido
(ꢀNꢂCꢂNR) ligands, respectively. © 2000 Elsevier Science B.V. All rights reserved.
Keywords: Azido complexes; C-Tetrazolato complexes; [3+2]-cycloadditions; Azido–isocyanide complexes; N2 evolution; X-ray structures
were obtained by Kim and coworkers from the corre-
sponding azide and various isocyanides [2].
1. Introduction
C-Tetrazolatorhodium(III) species, for example, were
unknown to date though the isomeric N-tetrazolates
The synthesis of metal–carbon bonded tetrazolates
from azido complexes and isocyanides — a particularly
have been prepared from azido complexes and nitriles
straightforward and elegant entry to organometallic
[3]. It is interesting to note that in the same investiga-
systems from inorganic ones — was first described by
tion the dimeric azide-bridged rhodium complex,
Beck and his group [1]. More detailed studies that also
covered mechanistic considerations made clear, how-
ever, that this new reaction does not apply to any azide
moiety, but is strongly dependent on the metal, the
[RhCp*(m-N3)(N3)]2 (Cp*=h-C5Me5), had also been
reacted with tert-butyl isocyanide in acetone, though
without leading to a defined product.
In the following we report on the reactions of the
azido complexes 1a–g (Scheme 1) with the isocyanides
CNR (R=tBu, Cy, (CH2)4Cl, allyl, CH2CO2Na, Me) in
water. For that purpose it appeared most advantageous
to prepare the azido complexes in situ from metal
halide precursors and a large excess of sodium azide in
aqueous solution, and to let them react directly with the
isocyanide. Some reactions that proceed with evolution
of dinitrogen are described.
isocyanide and even the solvent [1c]. For almost 30
years no further work has been published on this type
of chemistry to our knowledge. Only recently, however,
the complexes (Me3P)2M(Me)(CN4R) (M=Pd, Pt)
* Corresponding author. Present address: Deutsches Museum, Mu-
seumsinsel 1, D-80538 Mu¨nchen, Germany. Tel.: +49-89-2179313;
fax.: +49-89-2179425.
E-mail address: wpf@extern.lrz-muenchen.de (W.P. Fehlhammer).
0022-328X/00/$ - see front matter © 2000 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(00)00457-5

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M. Wehlan et al. / Journal of Organometallic Chemistry 613 (2000) 159–169
2. Results and discussion
has earlier been shown, however, that with the help of
large organic cations like AsPh+4 anionic perazido com-
plexes of almost any metal can easily be stabilized,
isolated and safely handled [4]. Originally, reactions of
the coordinated azide such as its cycloaddition with
isocyanides have therefore been carried out with com-
plexes of the type AsPh4[Au(N3)4] in organic solvents
[1]. To this, the procedure described here represents a
straightforward and attractive alternative leading to
simple alkali salts of C-tetrazolato complexes whose
spectra are free of superimposition by features of the
cation.
2.1. Alkali-tetrakis(tetrazolato)aurates and
tetrakis(tetrazolato)gold acids
Tetraazidoaurate(III) (1a) which is prepared in situ
from tetrachloroaurate(III) and a large excess of NaN3
in dilute aqueous solution reacts with tert-Butyl isocya-
nide with gradual decolourization of the brick-red solu-
tion to give the corresponding sodium tetrakis-
(tetrazol-5-ato)aurate(III) (2a) which separates as
colourless crystals in an almost quantitative yield. In
the solid state, Na[Au(N3)4] is extremely explosive; it
Under identical conditions cyclohexyl isocyanide to
our surprise failed to react with 1a. Still we were able to
obtain the respective lithium salt of [Au(CN4Cy)4]−
(2b) by treating Li[Au(N3)4] (again made in situ from
[AuCl4]− and LiN3) with CNCy in ethanol. While 2a
crystallizes spontaneously from the aqueous reaction
medium, 2b can be precipitated from ethanol by adding
water. Both complexes are isolated as colourless micro-
crystals which are practically insoluble in cold, yet
readily soluble in warm water. Unlike their azide pre-
cursors, they are not explosive in the solid state despite
their high content of nitrogen of about 30%. Complexes
2a and 2b can even be heated to 220°C (212°C), at
which temperatures melting sets in with decomposition
as to be seen from gas evolution. In the open flame
though, they burn rapidly with little detonations. In the
IR spectrum, the antisymmetric N3 stretching vibration
at 2030 cm−1 is clearly missing while new w(CH) bands
appear between 2900 and 3000 cm−1 (Table 1). All
protons in 2a, expectedly, give rise to only one signal
Scheme 1. Starting materials (m-N3=bridging azide; Cp*=h-C5Me5;
C10H14=4-isopropyl toluene).
Table 1
Some characteristic IR data (in KBr) of the new complexes 2–6
w(CH)
w([M]CꢁNR)
Others
2a
2b
2c
2976s
2935s
2979s
3600–2400s,vb;
1800–500m,vb
[w(NHN)]
1
2d
2938s
3600–2400s,vb;
1800–500m,vb
[w(NHN)]
(at l 1.25) in the H-NMR; the cyclohexyl groups in 2b
show the typical pattern with the ipso-H signal way off
the rest at much lower field (Table 2).
3a
3b
3c
3d
3b%
3c%
3d%
4a
4b
4c
4d
4e
5a
5b
6a
2977s
2932s
3011w, 2955s
2925s
2936s
3019w, 2960s
2929s
2975s
2934s
3004w, 2958s
2925s
2216s, 2204s
2219s, 2205s
2221s, 2210s
2197s, 2176s
1645w [w(CꢂC)]
1650w [w(CꢂC)]
2177s
2174s
2181s
2169s
2191s
2198s
2190s
1655s [w(CꢂC)]
1727s,b [w(CO2Et)]
2029s [was(N3)]
2025s [was(N3)]
2145s,
2924s
2973s
2980s
2983s, 2965s
2073s[was(NꢂCꢂN)],
[w(NꢂCꢂN)]
6b
6c
3050w, 2973s
3052w, 2965s
2205s
2201s
2135s,
2070s[was(NꢂCꢂN)],
[w(NꢂCꢂN)]
2126s,
2068s[was(NꢂCꢂN)],
[w(NꢂCꢂN)]

M. Wehlan et al. / Journal of Organometallic Chemistry 613 (2000) 159–169
161
means of 15N-NMR spectroscopy either [6]. The 13C-
NMR spectrum shows only one signal in the region for
metal-bonded carbon atoms. Though there is no further
low field-resonance that could be assigned to a carbene-
carbon atom we tentatively assume that one tetrazolato
ligand has been protonated at N-4 to give the neutral
Acidification of 2a and 2b with dilute hydrochloric
acid affords new compounds of general formula
HAu(CN4R)4 (R=tBu (2c), Cy (2d)), which are totally
insoluble in water, yet can be recrystallized from etha-
nol–water. Though one would expect the extra proton
to be bonded to one of the tetrazole nitrogens, no
w(NH) band is observed in the usual range of 32009
200 cm−1; instead two extremely broad, structured IR
absorption continua stretching from about 3600 to
2400 cm−1 and from 1800 to about 500 cm−1 can be
made out, which is characteristic of very strong intra-
or intermolecular hydrogen bridges; similar though
even lower-lying IR features have recently been ob-
served in the case of the exceedingly strong and short
intermolecular hydrogen bridges present in the ‘hydro-
gen diisocyanides’, [M]CꢁNꢀHꢀNꢁC[M] [5].
tris(tetrazol-5-ato)(tetrazolin-5-yliden)gold(III)
com-
plexes 2c and 2d. This gains support at least from the
existence of two sets of tert-butyl carbon atoms of
strikingly different intensity in the 13C-NMR spectrum
1
In the H-NMR spectra of 2c and 2d NH signals
appear at comparatively low field which also points to
hydrogen bridges. Which N atoms are involved in the
NꢀHꢀN bridging, and whether these bridges are intra-
or intermolecular, however, could not be settled by
Table 2
NMR data a
1H-NMR
13C-NMR
b
b
t
c
c
2a
2b
2c
2d
3a
1.25 (s, 36H, Bu)
1.3–2.4 (m, 40H, Cy), 4.3 (m, 4H, ipso-H(Cy))
1.3 (s, 36H, Bu), 8.2 (s, 1H, NH)
t
156.2 (AuC), 59.4 (CMe3), 32.0 (C(CH3)3)
157.0 (AuC); 52.7, 52.6, 35.3, 28.4, 28.1 (Cy)
162.3 (PdCNBut(?)), 153.4, 151.3 (PdCNt4Bu), 146.9
(PdCNtBu(?)), 60.9–57.8 (CMe3), 32.2–28.9 (C(CH3)3)
154.0, 152.2 (PdCN4Cy), 55.0–28.4 (Cy)
1.2–2.6 (m, 40H, Cy), 4.4 (m, 4H, ipso-H(Cy)), 8.25 (s, 1H, NH)
1.2, 1.35 (2s, 18H, CN4But), 1.75, 1.8 (2s, 18H, CNtBu)
3b
3c
3d
4a
4b
4c
4d
0.9–2.6 (m, 40H, Cy), 4.3 (m, 2H, ipso-H(CN4Cy)), 5.05 (m, 2H,
ipso-H(CNCy))
1.2–2.4 (m, 16H, CH2CH2CH2CH2), 2.8 (t, 4H, CN4CH2), 3.5 (t,
8H, CH2Cl), 4.8 (t, 4H, CNCH2)
152.2, 150.2 (PdCN4R), 51.0–22.8 (CH2)
2.7 (d, 4H, CN4CH2), 5.1 (t, 4H, CNCH2), 5.8–6.6 (m, 12H,
CHꢂCH2)
161.2 (PdCN–allyl), 155.8–154.1 (PdCN4–allyl), 129.3–128.4
(CH), 116.2–115.6 (CHꢂCH2), 62.9–61.7 (NCH2)
0.9 (s, 15H, Cp*), 1.25 (s, 18H, CNt4Bu), 2.05 (s, 9H, CNBut)
156.4 (d, RhCNt4Bu, 103Rh-satelites, J=44.6 Hz), 102.9 (C5Me5),
58.8, 58.6 (CMe3), 30.7, 30.2 (C(CH3)3), 9.2 (C5(CH3)5)
157.0 (d, RhCN4Cy, 103Rh-satelites, J=42.2 Hz), 103.0 (C5Me5),
52.4–28.7 (Cy), 9.1 (C5(CH3)5)
0.9 (s, 15H, Cp*), 1.3–2.5 (m, 30H, Cy), 4.1 (m, 2H,
ipso-H(CN4Cy)), 5.1 (m, 1H, ipso-H(CNCy)
0.9 (s, 15H, Cp*), 1.2–2.6 (m, 12H, CH2CH2CH2CH2), 2.8 (t, 4H, 156.8 (d, RhCN4R, 103Rh–satelites, J=44.6 Hz), 102.5 (C5Me5),
CN4CH2), 3.4 (t, 6H, CH2Cl), 4.9 (t, 2H, CNCH2)
0.9 (s, 15H, Cp*), 2.75 (d, 4H, CN4CH2), 5.1 (d, 2H, CNCH2),
5.7–6.65 (m, 9H, CHꢂCH2)
53.6–23.3 (CH2), 9.3 (C5(CH3)5)
158.2 (d, RhCN4–allyl, 103Rh–satelites, J=42.2 Hz), 103.3
(C5Me5), 132.4, 132.3 (CH), 113.2, 113.0 (CHꢂCH2), 61.1, 60.9
(NCH2)), 9.0 (C5(CH3)5)
b
c
4e
5a
1.3 (s, 15H, Cp*), 3.6 (s, 4H, CN4CH2), 5.0 (s, 2H, CNCH2)
0.9 (s, 9H, But), 1.3 (d, 6H, CH(CH3)2), 2.3 (s, 3H, C6H4CH3),
2.95 (m, 1H, CHMe2), 7.1, 7.2 (C6H4)
149.2, 136.5, 128.3, 126.1 (C6H4+RuCNtBu), 59.8 (CMe3), 34.6
(CHMe2), 30.5 (C(CH3)3), 24.7 (C6H4CH3), 21.1 (CH(CH3)2)
147.0 (RuCNtBu), 60.2 (CMe3), 31.6 (C(CH3)3)
135.4 (d, RhCNtBu, 103Rh-satelites, J=36.6 Hz), 142.5 (NCN),
138.5 (Ph, J(13C/31P)=10.1 Hz), 134.3–128.1 (Ph), 59.8 (CMe3),
29.4, 28.9 (C(CH3)3)
5b
6b
1.0 (s, 36H, But)
0.9 (s, 18H, CNBut), 1.3 (s, 9H, NCNtBu), 7.2 (m, 15H, Ph)
6c
1.3–2.4 (m, 30H, Cy), 4.6 (m, 2H, ipso-H(CNCy)), 5.2 (m, 1H,
ipso-H(NCNCy)), 7.3 (m, 15H, Ph)
137.5 (d, RhCNCy, 103Rh-satelites, J=36.8 Hz), 143.2 (NCN),
136.2 (Ph, J(13C/31P)=10.2 Hz), 133.5–127.1 (Ph), 53.1–27.0
(Cy)
a l values, solvent CDCl3, internal standard CHCl3.
b In DMSO.
c Not recorded.

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M. Wehlan et al. / Journal of Organometallic Chemistry 613 (2000) 159–169
of 2c (Table 2). Complexes with mixed carbanion/car-
Methyl isocyanide and isocyano acetate react with the
perazido palladates 1b and 1c much in the same way as
with tetraazidoaurate, viz. with gas evolution and metal
deposition. Tetraazidoplatinate(II) in aqueous solution,
on the other hand, proved totally inert towards any of
the isocyanides employed; after 24 h the solution had not
even changed colour, and only after very long standing
did platinum metal begin to deposit. These findings
should be set against the successful syntheses of C-tetra-
zolates at platinum(II) in organic media from either
azidoplatinum complexes and isocyanide, or isocyanide
complexes and free azide ions [1,10].
¸¹¹¹¹¹¹¹º
be¸n¹e ¹¹li¹ga¹n¹d¹¹sºpheres, e.g. [CoIII(CꢂNCH2CH2O)-
{CN(H)CH2CH2O}5](BPh4)2 which must have formed
from tricationic hexakis(oxazolidin-2-ylidene)cobalt by
¸¹¹¹¹¹¹º
loss of a proton, or [FeIICp(CNCH2CH2O)(CNCH2-
¸¹¹¹¹¹¹¹¹º
CH2OH){CN(H)CH2CH2O}] which assembles three dif-
ferent bonding states of 2-hydroxyethyl isocyanide in the
same coordination sphere, are well known [7]. Like other
C-tetrazolatogold complexes [8], compound 2c unfortu-
nately suffered rapid decomposition in the X-ray beam
so that the data collection was given up (Section 4).
None of the other tested isocyanides gives C-tetrazo-
lato complexes with [Au(N3)4]− under similar conditions.
Methyl isocyanide and isocyano acetate caused gas
evolution, however no well-defined products could be
isolated; rather, metal deposition occurred after some
time.
2.3. C-Tetrazolates on the
(p5-pentamethylcyclopentadienyl)rhodium system
Contrary to the foregoing, the starting material in this
paragraph, bis-m-azido(diazido)-bis(h-pentamethylcy-
clopentadienyl)dirhodium(III) (1d), is an isolable stable
compound which precipitates on mixing aqueous solu-
tions of [RhCp*Cl2]2 and NaN3 [3]. To this suspension
the isocyanides were added in a slight excess resulting in
red, and later yellow solutions from which the products
4a–e were extracted with dichloromethane. The gradua-
tion of isocyanide reactivities is about the same as in the
reactions above with the only exception that isocyanoac-
etate also reacts, though to a lesser extent. Again,
methylisocyanide is the exception in that it cleaves the
azido bridges without advancing to the steps of insertion
and cycloaddition, however. The co-existence in the same
ligand sphere of potential reaction partners in com-
pounds such as [RhCp*(N3)2(CNMe)] [3] or
[M(N3)(CO)5]− (M=Cr, Mo, W) [11], on the other
hand, is of substantial interest from a mechanistic point
of view (cf. also [4]) [12].
2.2. Reactions of isocyanides with homoleptic azido
complexes of palladium and platinum in water
Unlike in tetraazidoaurate(III) 1a only two azide
ligands per metal atom react to give C-tetrazolato species
in the perazidopalladium complexes 1b and 1c, which
have also been prepared in situ from tetrachloropalla-
date(II) and sodium azide in water; obviously, 1b and 1c
exist beside one another as both (AsPh4)2[Pd(N3)4] and
(AsPh4)2[Pd2(N3)6] are precipitated with AsPh4Cl [4].
The remaining azide ligands can be replaced by isocyan-
ide to give non-ionic compounds of the formula
Pd(CN4R)2(CNR)2 (3a–d) together with completely in-
soluble white side products, presumably coordination
polymers, which analyse as [Pd(CN4R)2] (3b%–d%) and
lack any high frequency IR bands. It is interesting to note
that the amount of by-product increases with decreasing
reactivity of the isocyanide along CNtBu\CNCy\
CN(CH2)4Cl\CN–allyl, i.e. is highest in the case of
CN–allyl. Another, yet soluble and thus probably molec-
ular type of a binary C-tetrazolate, [Hg(CN4R)2], was
obtained earlier from the reaction with loss of phosphine
of Hg(N3)2(PPh3)2 with aliphatic isocyanides [1b].
Two IR bands for the CN stretching vibration prove
the square planar complexes 3a–d to exist in the cis
configuration (Table 1). In the 1H-NMR of 3a two pairs
of signals of slightly different intensity appear instead of
the one expected for the tert-butyl groups on the equiv-
alent isocyanide and tetrazole ligands. Here, possible
explanations comprise hindered rotations about the
PdꢀC axis of the tetrazolato ligands and/or the presence
of considerable amounts of the trans isomer. More
signals than expected are also found in the 13C-NMR
spectra of 3a–d where 13C–14N coupling is known to add
to their complexity, particularly causing the [M]CNR
signals to broaden and thus to be lost in the noise (Table
2) [9].
The C-tetrazolato complexes 4a–d are soluble both in
water and in organic media, the trisodium salt 4e only
in water, DMSO and DMF, and very moderately in
methanol. Again, it should be pointed out that in organic
solvents the reaction does not proceed in a clear, straight-
forward manner [3], and that it is not transferable a priori
to other metals even if surrounded by a similar set of
ligands. Thus, for example, no C-tetrazole formation
took place in either water or dichloromethane with the

M. Wehlan et al. / Journal of Organometallic Chemistry 613 (2000) 159–169
163
average values are given for the bond lengths and
angles of the four tetrazole rings in the asymmetric
unit. In their tendency they seem to support a similar
electronic delocalisation over the five-membered ring as
has been concluded from the structure of AsPh4[Au-
(CNi4Pr)4] [8]. However, a much more precise recent
X-ray structure analysis of trans-[PdMe(CN4Cy)-
(PMe3)2] suggests a localization of p-electron density in
ruthenium complex 1e, the only products being the
mononuclear azido–isocyanide complexes [Ru(N3)2(h-
C10H14)(CNtBu)] (5a) and trans-[Ru(N3)2(CNtBu)4] (5b)
(see paragraph 2.4.).
The IR spectra of 4a–e typically show the strong
w(CN) band of the coordinated isocyanide and the
complete absence of any azide stretching vibrations.
Only two 1H-NMR signals appear for the two
nonequivalent sets of tert-butyl protons in 4a indicating
that the sterically complicated situation of the square-
planar palladium complex 2a (see above) does not
apply in the tetrahedral pseudooctahedral case here.
The two 13C lines at about l 155 are assigned to the
rhodium-bonded tetrazolato carbon atoms which expe-
rience 103Rhꢀ13C coupling with reasonable J values
(4391.5 Hz); in N,O-carbene-rhodium(III) species, for
comparison, coupling constants of about 35 Hz have
been determined [7]. The isocyanide–carbon signals
which are expected between l 130 and 150 have not
been identified with reliability, however [13]. The mass
spectra are not very revealing either; in the pos-FAB, a
line can be attributed to a dinuclear species which could
have formed by loss of the isocyanide ligand and
bridging through the C-tetrazolato groups as observed
in the related N-tetrazolato complexes [3].
the C1ꢀN1 bond and
a delocalization over the
N2ꢀN3ꢀN4 part of the ring [2], remindful of the struc-
tural peculiarities of carbenoid ‘activated’ heterocycles
[14] (Fig. 1). Due to the extensive decomposition of the
crystal during the data collection the standard devia-
tions are too high to allow any further discussion of the
bonding.
2.4. Azido–isocyanide complexes
As already mentioned, the azido-bridged bis-
(areneruthenium) complex 1e prepared in situ from
[Ru(m-Cl)(Cl)(h-C10H14)]2 (C10H14:4-isopropyltoluene)
and sodium azide only gives the bridge-opened azido-
isocyanide complex [Ru(N3)2(h-C10H14)(CNtBu)] (5a),
though with CNtBu we have chosen the most effective
isocyanide component for C-tetrazolate formation.
Both the elemental analysis and the spectroscopic data,
in particular the IR spectrum with its characteristic
bands at 2029 cm−1 for the terminal azido ligand and
at 2198 cm−1 for the CN group, are in accord with this
notation. The most interesting 13C-NMR signal, how-
ever, that of the metal-bonded isocyanide C-atom
which we expected somewhere between 140 and 165
ppm, is again absent or superimposed by the lines of
the aromatic system.
An X-ray structure analysis has been undertaken of
compound 4a which only confirms the primary atomic
linkage, however (Fig. 1). In the caption of Fig. 1,
Even by boiling the [Ru(m-Cl)(Cl)(h-C10H14)]2–N−3 –
tert-butyl isocyanide mixture in water for several hours,
C-tetrazolate formation could not be enforced; instead,
arene substitution occurred to give the mononuclear
azido–isocyanide complex trans-[Ru(N3)2(CNtBu)4]
(5b), which may be compared with the phosphane
complexes Ru(N3)2(PR3)4 [15,16]. Complex 5b is char-
acterized by its IR-active (CN)- and antisymmetric
1
(N3)-stretching vibrations, and a single H-NMR reso-
nance for the tert-butyl protons. In the 13C-NMR
spectrum, the signal for the metal-bonded carbon
atoms appears at l 147 (Tables 1 and 2).
The results of an X-ray structure analysis of com-
pound 5b which had been crystallized from an ethanolic
solution containing thiourea are shown in Fig. 2. Again
we state the close neighbourhood within the same lig-
and sphere of the cis positioned potential reaction
partners azide and isocyanide, a situation which equally
prevails in the piano stool-geometries of 5a and
[RhCp*(N3)2(CNMe)] (cf. [3]). Ruthenium resides on a
crystallographic C2 axis which lies in the RuC4 coordi-
nation plane bisecting a CꢀRuꢀC angle; the two azido
Fig. 1. ORTEP drawing of one molecule of 4a (The bonding parame-
ters of the independent second molecule in the asymmetric unit differ
,
only marginally.). Selected bond distances (A) and angles (°) (aver-
aged values over the two molecules): RhꢀCp* 2.25; RhꢀC(isocyanide)
1.92(5); RhꢀC(tetrazole) 2.03(5); CꢀN(isocyanide) 1.18(5); CꢀN1
1.40(5); N1ꢀN2 1.36(6); N2ꢀN3 1.29(6); N3ꢀN4 1.36(6); N4ꢀC 1.40(6)
(all tetrazole); RhꢀCꢀN(isocyanide) 170(3); N1ꢀCꢀN4 104(3);
CꢀN1ꢀN2 110(4); N1ꢀN2ꢀN3 106(4); N2ꢀN3ꢀN4 111(4); N3ꢀN4ꢀC
108(4) (all tetrazole).

164
M. Wehlan et al. / Journal of Organometallic Chemistry 613 (2000) 159–169
complexes of gold and palladium, but we were not able
to isolate a defined product. The situation is different in
the case of rhodium. Heating under reflux of 1d with
tert-butyl isocyanide for 5 h left a small amount of a
red crystalline product with an IR spectrum in which
the azide band is replaced by two strong bands at 2145
and 2073 cm−1. Elemental analysis and the pos-FAB
spectrum are in accord with a formulation of the com-
pound as bis{(m-tetrazolato-C,N)(cyanamido)h-pen-
tamethylcyclopentadienylrhodium(III)} (6a) though we
are aware that its dimeric nature might only be an
artefact of mass spectrometry.
The step of C-tetrazolato complexes is skipped in the
reactions of azido(carbonyl)bis(triphenylphosphine)-
rhodium (1g) with tert-butyl or cyclohexyl isocyanide,
even in the cold. In both cases, N2 evolution occurs
along with substitution of CO by isocyanide and partly
of triphenylphosphine to give the compounds 6b and 6c
together with a by-product analyzing as [Rh(N3)-
(CNR)2(PPh3)2]. The main reaction compares well to
that of azido complexes with CO to give isocyanato
species [1a][12,26] and to the formation of cyanamide
complexes from aminocarbyne precursors and free
azide [27]. There are also interesting parallels with the
recently reported conversion of N-isocyanamine deriva-
tives of chromium hexacarbonyl to the corresponding
cyanamides by reaction with secondary amines [28].
As in 5a, the presence of ꢀNꢂCꢂNR or ꢀN(R)ꢀCꢁN
ligands in the products 6b and 6c is suggested by the
particular infrared pattern in the triple bond region (see
Table 1 and above) while their composition is confir-
med by elemental analyses and correct intensity ratios
Fig. 2. ORTEP drawing of 5b×2 thiourea.
Table 3
,
Selected bond distances (A) and angles (°) of 5b×2 thiourea
RuꢀN3
RuꢀC1
RuꢀC2
C1ꢀN1
C2ꢀN2
N1ꢀC11
N2ꢀC21
N3ꢀN4
N4ꢀN5
2.14(1)
1.98(1)
1.98(1)
1.15(1)
1.16(1)
1.49(2)
1.50(2)
1.17(1)
1.18(1)
SꢀC6
C6ꢀN6
C6ꢀN7
RuꢀN3ꢀN4
RuꢀC1ꢀN1
RuꢀC2ꢀN2
C1ꢀN1ꢀC11
C2ꢀN2ꢀC21
N3ꢀN4ꢀN5
1.73(2)
1.38(2)
1.36(3)
123(1)
175(1)
173(1)
174(1)
166(2)
175(2)
1
between the aliphatic and aromatic H-NMR signals.
The 13C-NMR signal at l\140 is tentatively assigned
to the cyanamido carbon (Table 2). Unfortunately,
none of the complexes presumably containing
cyanamido ligands gave crystals suitable for X-ray
structure analyses to date.
ligands with their characteristically bent RuꢀNꢀNꢀN
atomic sequences are in trans-position. The RuꢀNꢀN
(average 123(1)°), RuꢀCꢀN (average 174(1)°), CꢀRuꢀC
(average 90(2)°) and CꢀRuꢀN (average 90(1)°) bond
,
angles as well as the RuꢀN (average 2.14(1) A) and
alternative coordination mode: [Rh]ꢀN(R)ꢀCꢁN
,
RuꢀC(isocyanide) (average 1.98(1) A) bond lengths are
within the usual ranges (Table 3). A practically identi-
,
cal RuꢀN distance (2.129(6) A) has been determined
for trans-[diazidobis{1,2-bis(diethylphosphino)ethane}
ruthenium(II)] [16], while those of other azidoruthe-
,
nium complexes vary between 2.093 and 2.136 A [17–
20]. RutheniumꢀC(isocyanide) bonds generally appear
shorter; the value found in 5b lies within the range of
,
1.86–2.05 A obtained from a literature search [21–25].
There are no unusual features in the stereochemistry
of the two accompanying molecules of thiourea whose
obvious function is to fill holes in the crystal lattice.
2.5. Reactions with e6olution of dinitrogen
As already mentioned, dinitrogen gas is evolved in
the reactions of methylisocyanide with the tetraazido
alternative coordination mode: [Rh]ꢀN(R)ꢀCꢁN

M. Wehlan et al. / Journal of Organometallic Chemistry 613 (2000) 159–169
165
3. Conclusions
15.4 mmol, 100 ml of water). Caution: Solid sodium
tetraazidoaurate is extremely explosi6e; any solution
splashed onto the wall has to be washed with water
immediately. E6en concentrated aqueous solutions of
Na[Au(N3)4] may explode! After 30 min 0.42 ml of
tert-butyl isocyanide were syringed into the reaction
mixture, which resulted in gradual decolouration of the
solution and precipitation of colourless microcrystalline
Na[Au(CNt4Bu)4]. The product was filtered off, washed
with cold water and dried in high vacuum to give 460
mg (95%) of 2a with m.p. 220°C (decomp.).
The reactions of azido complexes with isocyanides
are strongly solvent-dependent. Azidogold and palla-
dium species react in water much in the same way as in
organic solvents though some new products are ob-
tained. They are all practically nonexplosive, i.e. much
less thermally labile than the alkali perazidometallate
precursors. For the formation of C-tetrazolates of
rhodium(III), the use of water as reaction medium is
essential. The reactivity of the isocyanide increases with
its assumed nucleophilicity, i.e. in the order
CNCH2CO2Na B CN–allyl B CN(CH2)4Cl B CNCy
BCNtBu with tert-butyl isocyanide reacting almost
quantitatively. Water-soluble methyl isocyanide is an
exception in that 1-methyl-tetrazol-5-ato complexes are
only obtained in organic solvents, not in water. Some
reactions proceed with evolution of dinitrogen. Though
several observations are in favour of the formation in
rhodium complexes of cyanamido ([M]ꢀN{R}ꢀCꢁN) or
carbodiimido ligands ([M]ꢀNꢂCꢂNR), there is no un-
equivocal proof for their existence1.
Anal. Found: C, 32.98; H, 4.95; N, 30.82. Calc. for
C20H36AuN16Na (MW 720.6): C, 33.34; H, 5.04; N,
31.10%.
4.2. Lithium tetrakis(1-cyclohexyltetrazol-5-ato)-
aurate(III) (2b)
A solution of 250 mg (0.661 mmol) of K[AuCl4] in 20
ml of ethanol was added dropwise with stirring to a
solution of lithium azide (1.0 g) in the same solvent
(100 ml). After ca. 1 h 0.54 ml (3.97 mmol) of cyclo-
hexyl isocyanide were added which was followed by the
addition of 200 ml of water after the solution had
turned colourless (ca. 40 min). The solution was then
concentrated in vacuo to about 100 ml and cooled to
0°C whereupon white Li[Au(CN4Cy)4] started to pre-
cipitate which was purified in the same way as 2a.
Yield: 350 mg (65%) of 2b with m.p. 212°C (decomp.)
Anal. Found: C, 42.01; H, 5.62; N, 26.96. Calc. for
C28H44AuLiN16 (MW 808.7): C, 41.59; H, 5.48; N,
27.71%.
4. Experimental
Most reactions were run in distilled water or air; only
the reactions with the rhodium(I) complex 1g were
carried out under an atmosphere of pure argon using
Schlenk-tube techniques. The organic solvents were
dried, distilled and stored under argon. The starting
complexes [RuCl2(h-C10H14)]2 [29] (C10H14: 4-isopropyl-
toluene), [RhCp*Cl2]2 [30] and trans-[Rh(N3)(CO)-
(PPh3)2] [26b][31] were prepared by standard literature
methods, the metal chlorides (RhCl3·3H2O, RuCl3·
3H2O) and chlorometallates (K[AuCl4], Na2[PdCl4],
K2[PtCl4]) were purchased from Degussa (Hanau). IR:
Perkin–Elmer model 983 and Beckman model 4240
spectrometers. NMR: Bruker AM 270. MS (EI and
pos-FAB): Varian Mat 711, Varian Mat 112 S and
Varian Mat CH5 DF with neutral xenon source at 3
keV. Microanalyses (C, H, N): Heraeus CHN-Rapid
analyzer. Melting points (uncorrected): Gallenkamp
MFB-595 apparatus.
4.3. Tris(1-tert-Butyl-tetrazol-5-ato)(1-tert-butyl-
tetrazol-5-ylidene)gold(III) (2c) and tris(1-cyclo-
hexyl-tetrazol-5-ato)(1-cyclohexyl-tetrazol-5-ylidene)
gold(III) (2d)
Compounds 2a or 2b (0.3 mmol) were dissolved in 50
ml of warm water. To this, diluted hydrochloric acid
was added dropwise until no more white product pre-
cipitated. This was collected on a frit, washed with
water and recrystallized from ethanol–water to give 2c
(m.p. 215°C (decomp.)) or 2d (m.p. 221°C (decomp.),
respectively, in 95% yield each.
4.1. Sodium tetrakis(1-tert-butyltetrazol-5-ato)-
aurate(III) (2a)
Anal. Found for 2c: C, 33.88; H, 5.41; N, 32.12.
Calc. for C20H37AuN16 (MW 698.6): C, 34.38; H, 5.34;
N, 32.08%.
A solution of 0.25 g (0.67 mmol) of Na[AuCl4]·1/
2H2O in 20 ml of water was added dropwise with
stirring to an aqueous solution of sodium azide (1.0 g,
Anal. Found for 2d: C, 42.21; H, 5.73; N, 27.55.
Calc. C28H45AuN16 (MW 802.7): C, 41.90; H, 5.65; N,
27.92%.
A colourless crystal of 2c has been X-rayed at r.t.
resulting in a substantial decay as gathered from the
drop in intensity of the standard reflexions and its
colour change to dark-brown; the set of collected data
proved inappropriate for the structure solution.
1 Note added in proof: Recently, carbodiimide complexes have
been obtained from a palladium azide and isocyanides and crystallo-
graphically characterized: Y.-J. Kim, Y.-S. Kwak, S.-W. Lee, J.
Organomet. Chem. 603 (2000) A52.

166
M. Wehlan et al. / Journal of Organometallic Chemistry 613 (2000) 159–169
4.4. Di(tert-butyl isocyanide)bis(1-tert-butyl-tetrazol-
5-ato)palladium(II) (3a)
Compound 3d% (70%; m.p. 198°C (decomp.)): Anal.
Found: C, 32.21; H, 3.51; N, 31.54. Calc. for
C8H10N8Pd (MW 324.6): C, 29.60, H; 3.10; N, 34.52%.
To an aqueous solution of sodium azide (10.0 g
NaN3 in 100 ml of water) was added dropwise with
4.7. p-Pentamethylcyclopentadienyl(tert-butyl
isocyanide)bis(1-tert-butyl-tetrazol-5-ato)rhodium(III)
(4a)
stirring
a solution of 500 mg (1.64 mmol) of
Na2[PdCl4]·1/2H2O in 30 ml of water. After 30 min 1.06
ml (10.2 mmol) of CNtBu was transferred to the reac-
tion vessel by syringe which caused a rapid decoloura-
tion of the solution with concomitant precipitation of
the product. The colourless microcrystalline precipitate
was filtered, washed with water and dried in high
vacuum to give 0.78 g (90%) of 3a with m.p. 172°C
(decomp.).
0.53 g (0.85 mmol) of [RhCp*Cl2]2, dissolved in 50
ml of water, were dropped into a vigorously stirred
solution of sodium azide (1.0 g) in water (100 ml) which
caused the orange azido complex [RhCp*(N3)2]2 to
precipitate. After about 30 min 0.62 ml (6.0 mmol) of
tert-butyl isocyanide was added, and the red solution
was stirred for 24 h after which time it was extracted
with 2×150 ml of dichloromethane. The extract was
dried over sodium sulfate, reduced to a volume of 50
ml, and layered with ether. At −18°C yellow crystals
of 4a (m.p. 150°C (decomp.)) began to grow. Yield:
0.74 g (75%). Anal. Found: C, 52.58; H, 7.45; N, 21.94.
Calc. C25H42N9Rh (MW 571.6): C, 52.53; H, 7.41; N
22.05%.
Anal. Found: C, 45.88; H, 6.87; N, 26.68. Calc. for
C20H36N10Pd (MW 523): C, 45.93; H, 6.94; N, 26.78%.
4.5. Di(cyclohexyl isocyanide)bis(1-cyclohexyl-
tetrazol-5-ato)palladium(II) (3b), bis(4-chloro-Butyl
isocyanide)bis[1-(4-chlorobutyl)-tetrazol-5-ato]
palladium(II) (3c) and di(allyl isocyanide)bis(1-allyl-
tetrazol-5-ato)palladium(II) (3d)
In their first part, the procedures are identical to the
one described under Section 4.4. For further purifica-
tion the white precipitates were dissolved in
dichloromethane, the insoluble polymers were filtered
off, and the filtrates were concentrated to about 20 ml
and layered with diethyl ether. On cooling to −18°C
white crystals separated.
Compound 3b (65%; m.p. 160°C (decomp.)): Anal.
Found: C, 54.02; H, 7.12; N, 21.95. Calc. for
C28H44N10Pd (MW 627.1): C, 53.63; H, 7.07; N,
22.33%.
Compound 3c (45%; m.p. 165°C (decomp.)): Anal.
Found: C, 35.42; H, 4.49; N, 21.12. Calc. for
C20H32Cl4N10Pd (MW 660.8): C, 36.58; H, 4.88; N,
21.20%.
Compound 3d (20%; m.p. 147°C (decomp.)): Anal.
Found: C, 42.20; H, 4.32; N, 29.79. Calc. for
C16H20N10Pd (MW 458.8): C, 41.88; H, 4.39; N,
30.53%.
4.8. (Cyclohexyl isocyanide)bis(1-cyclohexyl-tetrazol-
5-ato)(p-pentamethylcyclopentadienyl)-rhodium(III)
(4b), (4-chlorobutyl isocyanide)bis[1-(4-chlorobutyl)-
tetrazol-5-ato](p-pentamethylcyclopentadienyl)
rhodium(III) (4c) and (allyl isocyanide)bis(1-allyl-
tetrazol-5-ato)(p-pentamethylcyclopentadienyl)
rhodium(III) (4d)
In principle, 4b–d were prepared as described for 4a
in Section 4.7, however, after being stirred for 24 h, the
solution was warmed to ca. 50°C for 1 h before it was
extracted with CH2Cl2. After drying with Na2SO4 the
organic phase was evaporated to dryness in the pres-
ence of some silica gel; the impregnated material was
then transferred to a chromatography column (silica
gel, 30×3 cm) to separate the products from the
unreacted and partly reacted starting complex. The
products were eluted with
a
1:1 mixture of
dichloromethane and diethyl ether, the solutions con-
centrated to ca. 20 ml, layered with ether, and cooled to
−18°C.
4.6. Bis(1-organyl-tetrazol-5-ato)palladium(II)
(organyl=Cy (3b%), 4-chlorobutyl (3c%), allyl (3d%))
Compound 4b (45%; m.p. 145°C (decomp.)): Anal.
Found: C, 56.29; H, 7.10; N, 19.08. Calcd. C31H48N9Rh
(MW 649.7): C 57.31; H, 7.45; N, 19.40%.
Compound 4c (40%; m.p. 142°C (decomp.)): Anal.
Found: C, 43.93; H, 5.77; N, 18.55. Calc. for
C25H39Cl3N9Rh (MW 674.9): C, 44.49; H 5.82; N,
18.68%.
Compound 4d (32%; m.p. 137°C (decomp.)): Anal.
Found: C, 51.10; H, 5.82; N; 24.16. Calc. for
C22H30N9Rh (MW 523.4): C, 50.48; H, 5.78; N,
24.08%.
The insoluble coordination polymers (cf. procedure
Section 4.5) were washed with dichloromethane and
dried in high vacuum to give white powdery materials.
Compound 3b% (30%; m.p. 225°C (decomp.)): Anal.
Found: C, 38.95; H, 6.62; N, 25.55. Calc. for
C14H22N8Pd (MW 408.8): C, 41.13; H, 5.42; N, 27.41%.
Compound 3c% (45%; m.p. 217°C (decomp.)): Anal.
Found: C, 30.32; H, 4.01; N, 25.77. Calc. for
C10H16Cl2N8Pd (MW 425.6): C, 28.22;H, 3.79; N,
26.33%.

M. Wehlan et al. / Journal of Organometallic Chemistry 613 (2000) 159–169
167
4.9. [RhCp*(CN4CH2CO2Na)2(CNCH2CO2Na)] (4e)
yellow crystals of 5b (m.p. 175°C (decomp.)) started to
separate. Yield: 0.55 g (75%).
[RhCp*Cl2]2 (1.0 g, 1.62 mmol), dissolved in 100 ml
of water, was dropped with stirring into an aqueous
solution of sodium azide (1.0 g/100 ml of H2O) which
Anal. Found: C, 45.91; H, 6.88; N, 26.52. Calc.
C20H36N10Ru (MW 517.6): C, 46.41; H, 7.01; N,
27.06%.
led to
a
suspension of the azido complex
[RhCp*(N3)2]2. To this was added a solution of 1.21 g
(11.3 mmol) of sodium isocyanoacetate in 20 ml of
water resulting in a red solution which was stirred for
24 h, shortly heated to 50°C, and then taken to dryness
in vacuo. The residue was extracted with two 100 ml
portions of methanol, and the extracts were poured into
a large volume of petroleum ether (40–60°C) in order
to precipitate the extracted material quantitatively. The
white–yellow precipitate was washed several times with
ether and redissolved in methanol. This solution was
concentrated to 50 ml, layered with 20 ml of ether, and
cooled to −18°C for 3 days. A white material sepa-
rated during this time which, however, was not the
desired product. Filtration and newly layering the
filtrate with ether then gave crystals of 4e (10%, m.p.
125°C (decomp.)).
4.12. Bis[v-(1-tert-butyl-tetrazolato)-C,N]bis-
[p-pentamethylcyclopentadienyl(tert-butyl-cyanamido)-
rhodium(III)] (6a)
[RhCp*Cl2]2 (1.0 g, 1.62 mmol), NaN3 (1.0 g in 100
ml of water) and 1.4 ml (13.5 mmol) of tert-butyl
isocyanide were combined as described for 4e and then
heated under reflux for 5 h, during which time the
colour changed to yellow and back to red. After cool-
ing to r.t. the solution was extracted twice with 150 ml
portions of dichloromethane. The organic phase was
separated, dried over sodium sulfate, concentrated to a
volume of 50 ml and layered with ether. Standing at
−18°C caused two compounds to crystallize which
could be separated mechanically: 4a (yellow), the main
product, and 6a as red crystals (5%, m.p. 115°C (de-
comp.)) sticking to the Schlenk tube walls.
Anal. Found: C, 35.99; H, 3.37; N, 18.99. Calc. for
C19H21N9Na3O6Rh (MW 643.3): C, 35.47; H, 3.29; N,
19.60%.
Table 4
Crystallographic data of complexes 4a and 5b
4.10. Diazido[p-(4-isopropyl toluene)](tert-butyl
isocyanide)ruthenium(II) (5a)
4a
5b
A solution of 0.50 g (0.82 mmol) of [RuCl2(h-
C10H14)]2 in 150 ml of water was dropped into a
vigorously stirred solution of sodium azide (1.0 g) in
water (100 ml). After 30 min 0.58 ml (5.74 mmol) of
tert-butyl isocyanide was added, and the red solution
was stirred for 3 h after which time it was extracted
with 2×150 ml of dichloromethane. The extracts were
dried over sodium sulfate, reduced to a volume of 50 ml
and layered with ether. At −18°C red crystals of 5a
(m.p. 170°C (decomp.)) began to grow. Yield: 0.62 g
(95%).
Empirical formula
C25H42N9Rh
C20H36N10Ru
+2CH4N2S
669.87
Formula weight (g mol−1
Crystal dimensions (mm)
)
571.57
0.67×0.45×0.18 0.25×0.20
×0.175
Habit and colour
Yellow plate
Triclinic
Yellow,
block-shaped
Monoclinic
P2/c (no. 13)
10.268(1)
16.248(2)
11.821(1)
90.0
112.237(8)
90.0
1825.47
4
Crystal system
Space group (no.)
(
P1 (no. 1)
,
a (A)
10.910(2)
10.944(2)
12.639(2)
84.114(12)
88.891(14)
71.774(14)
1425.65
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
Anal. Found: C, 44.44; H, 5.52; N, 24.11. Calc. for
C15H23N7Ru (MW 402.5): C, 44.77; H, 5.76; N,
24.36%.
3
,
V (A )
Z
2
4.11. Diazido[tetrakis(tert-butyl
isocyanide)]ruthenium(II) (5b)
Dcalc (g cm−3
)
1.330
Nonius CAD 4
Graphite-monochromatized Mo–Ka
2.016
Diffractometer
Radiation
,
(u=0.71069 A)
293
ꢀ–2q
252q525
5231
4944
619
0.7 (−0.7)
The red solution prepared from 0.50 g (0.82 mmol) of
[RuCl2(hꢀC10H14)]2, 1.0 g of NaN3 and 0.58 ml (5.74
mmol) of tert-butyl isocyanide in water as described
under Section 4.10 was heated under reflux for 3 h
during which time its colour changed to yellow. After
cooling to r.t. the solution was extracted twice with 150
ml portions of dichloromethane. The organic phase was
separated, dried over sodium sulfate, concentrated to a
volume of 50 ml and layered with ether. At −18°C
Temperature (K)
Scan type
Scan range (°)
Reflections
Reflections (I\3|(I))
Parameters
Residual electron density,
252q525
3354
3186
148
1.1 (−0.7)
−3
,
max (min) (e A
R (Rw)
)
0.048 (0.059)
0.088 (0.105)

168
M. Wehlan et al. / Journal of Organometallic Chemistry 613 (2000) 159–169
Anal. Found: C, 50.19; H, 6.99; N 19.03. Calc. for
5. Supplementary material
C40H66N12Rh (MW 920.9): C, 52.17; H, 7.22; N,
18.25%.
Further details of the crystal structures may be ob-
tained upon request from the Fachinformationszentrum
Karlsruhe, Gesellschaft fu¨r wissenschaftlich-technische
Information mbH, D-76344 Eggenstein-Leopoldshafen
(Germany), giving reference to the depository numbers
CSD/408269 (4a), CSD/408270 (5b) and citing the au-
thors and this paper.
4.13. Di(tert-butyl isocyanide)(tert-butyl-cyanamido)-
(triphenylphosphine)rhodium(I) (6b) and di(cyclohexyl
isocyanide)(cyclohexyl-cyanamido)(triphenylphosphine)-
rhodium(I) (6c)
To 0.77 g (1.1 mmol) of [Rh(N3)(CO)(PPh3)2] in 20
ml of toluene was added 4.4 mmol of the respective
isocyanide. After stirring for 24 h the solutions were
layered with petroleum ether and cooled to −18°C
whereupon a yellow powder began to separate. This
was extracted several times with ether, the combined
extracts were concentrated to about 10 ml and kept at
−78°C for one week to give yellow crystals.
Compound 6b (25%; m.p. 75°C): Anal. Found: C,
60.91; H, 6.62; N, 8.62; Calc. for C33H42N4PRh (MW
628.6): C, 63.05; H, 6.73; N, 8.91%.
Compound 6c (25%; m.p. 72°C): Anal. Found: C,
64.11; H, 6.89; N, 7.78: Calc. for C39H48N4PRh (MW
706.7): C, 66.28; H, 6.85; N, 7.93%.
Acknowledgements
This work was supported by the Deutsche
Forschungsgemeinschaft and the Fonds der Chemi-
schen Industrie. We are also grateful to Professor H.
Hartl at the Free University Berlin, to Dr B. Herrschaft
at the Humboldt University in Berlin for their help in
the X-ray structure determinations, to Professor H.H.
Limbach and Dr H. Benedict for 15N-NMR measure-
ments and to Manuel A. Fehlhammer for the computer
drawings.
References
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4.14. X-ray structure analyses of the complexes 4a and
5b
Suitable crystals of 4a were obtained by layering a
saturated dichloromethane solution of the complex with
diethyl ether and cooling it to −25°C. As all attempts
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data collection had failed, crystals of composition of
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(
lizes in the triclinic system P1 (No. 1) with two
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