Metalated 1,3-azaphospholes: η1-(1H-1,3-Benzazaphosphole-P)M(CO)5 and μ2-[(1,3-Benzazaphospholide-P)(cyclopentadienide)nickel] complexes

Article abstract of DOI:10.1002/1521-3749(200213)628:13<2869::AID-ZAAC2869>3.0.CO;2-3

1H-1,3-Benzazaphospholes react with M(CO)₅(THF) (M = Cr, Mo, W) to give thermally and relatively air stable η¹-(1H-1,3-Benzazaphosphole-P)M(CO)₅ complexes. The ¹H- and ¹³C-NMR-data are in accordance with the preservation of the phosphaaromatic π-system of the ligand. The strong upfield ³¹P coordination shift, particularly of the Mo and W complexes, forms a contrast to the downfield-shifts of phosphine-M(CO)₅ complexes and classifies benzazaphospholes as weak donor but efficient acceptor ligands. Nickelocene reacts as organometallic species with metalation of the NH-function. The resulting ambident 1,3-benzazaphospholide anions prefer a μ₂-coordination of the η⁵-CpNi-fragment at phosphorus to coordination at nitrogen or a η³-heteroallyl-η⁵-CpNi-semisandwich structure. This is shown by characteristic NMR data and the crystal structure analysis of a η⁵-CpNi-benzazaphospholide. The latter is a P-bridging dimer with a planar Ni₂P₂ ring and trans-configuration of the two planar heterocyclic phosphido ligands arranged perpendicular to the four-membered ring.

Full text of DOI:10.1002/1521-3749(200213)628:13<2869::AID-ZAAC2869>3.0.CO;2-3

Metalated 1,3-Azaphospholes: η1-(1H-1,3-Benzazaphosphole-P)M(CO)5 and
µ2-[(1,3-Benzazaphospholide-P)(cyclopentadienide)nickel] Complexes
Joachim Heinicke*, a, Nidhi Guptaa, 1),Shreeyukta Singha, 1), Anushka Suranaa, Olaf Kühla, Raj K. Bansalb,
Konstantin Karaghiosoffc, Martin Vogtc
a
Greifswald, Institut für Chemie und Biochemie, Ernst-Moritz-Arndt-Universität
b Jaipur/India, Department of Chemistry, University of Rajasthan
c München, Department Chemie, Ludwig-Maximilians-Universität
Received May 30th, 2002.
Dedicated to Professor Rüdiger Mews on the Occasion of his 60th Birthday
Abstract. 1H-1,3-Benzazaphospholes react with M(CO)5(THF)
(M ϭ Cr, Mo, W) to give thermally and relatively air stable
fragment at phosphorus to coordination at nitrogen or a η3-het-
eroallyl-η5-CpNi-semisandwich structure. This is shown by charac-
teristic NMR data and the crystal structure analysis of a η5-CpNi-
benzazaphospholide. The latter is a P-bridging dimer with a planar
Ni2P2 ring and trans-configuration of the two planar heterocyclic
phosphido ligands arranged perpendicular to the four-membered
ring.
1
η1-(1H-1,3-Benzazaphosphole-P)M(CO)5 complexes. The H- and
13C-NMR-data are in accordance with the preservation of the
phosphaaromatic π-system of the ligand. The strong upfield 31P
coordination shift, particularly of the Mo and W complexes, forms
a contrast to the downfield-shifts of phosphine-M(CO)5 complexes
and classifies benzazaphospholes as weak donor but efficient ac-
ceptor ligands. Nickelocene reacts as organometallic species with
metalation of the NH-function. The resulting ambident 1,3-benz-
azaphospholide anions prefer a µ2-coordination of the η5-CpNi-
Keywords: Phosphorus heterocycles; Phosphorus ligands; Tran-
sition metals; Coordination modes; Heterophospholides
Metallierte 1,3-Azaphosphole: η1-(1H-1,3-Benzazaphosphol-P)M(CO)5 und
µ2-[(1,3-Benzazaphospholid-P)(cyclopentadienid)nickel] Komplexe
Inhaltsübersicht.
1H-1,3-Benzazaphosphole
reagieren
mit
Die resultierenden ambidenten 1,3-Benzazaphospholid-Anionen
bevorzugen eine µ2-Koordination des η5-CpNi-Fragments am
Phosphor gegenüber N-Koordination oder einer η3-Heteroallyl-η5-
CpNi-Semisandwich-Struktur. Dies wird durch charakteristische
NMR-Daten und die Ergebnisse der Strukturuntersuchung an Ein-
kristallen eines η5-CpNi-benzazaphospholids belegt. Letzteres kri-
stallisiert mit Benzol und bildet ein P-Brückendimer mit planarem
Ni2P2 Ring und trans-Konfiguration der beiden senkrecht zum
Vierring angeordneten planaren heterocyclischen Phosphidoligan-
den.
M(CO)5(THF) (M ϭ Cr, Mo, W) zu thermisch und zumindest
kurzzeitig luftstabilen η1-(1H-1,3-Benzazaphosphol-P)M(CO)5-
Komplexen. Die 1H- und 13C-NMR-Daten sind mit dem Erhalt
des phosphaaromatischen π-Systems im Liganden im Einklang.
Die starke 31P-Koordinationsverschiebung zu hohem Feld, vor al-
lem der Mo- und W-Komplexe, steht im Gegensatz zur Koordina-
tionsverschiebung zu tiefem Feld, beobachtet bei Phosphin-
M(CO)5 Komplexen, und verweist auf schwache Donator-, aber
gute Akzeptoreigenschaften der Liganden. Nickelocen reagiert als
Übergangsmetallorganyl unter Metallierung der NH-Funktion.
Introduction
research and comprise a large range of coordination types.
While phospholide and polyphospholide anions belong to
the preferred target ligands and form various types of π-
and P-coordinated complexes [1Ϫ5], the studies with isoe-
lectronic heterophospholes (heteroelement N, O ,S) are
rather limited and led mainly to P-, in case of diazaphos-
pholes also to N-coordinated species [5, 6]. π-Complexes,
except in the case of the 2-o-methoxy-phenyl substituent of
a 1,3-oxaphosphole [7], to our knowledge, are not yet
known. Only a few P-coordinated transition metal carbonyl
complexes of anellated heterophospholes have been re-
ported, e.g. (2-phenyl-1,3-benzazaphosphole)pentacarbon-
Transition metal complexes of phosphorus compounds in
low-coordination number have been the subject of extensive
1) present address: b
* Prof. Dr. J. Heinicke
Institut für Chemie und Biochemie
Ernst-Moritz-Arndt-Universität Greifswald
Soldmannstr. 16
17487 Greifswald, Germany
Fax: (ϩ49-3834) 864319
ylchromium [8] and
a phospha-indolizine pentacar-
E-mail: heinicke@uni-greifswald.de
bonylchromium complex [9]. In order to extend the know-
Z. Anorg. Allg. Chem. 2002, 628, 2869Ϫ2876  2002 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim 0044Ϫ2313/02/628/2869Ϫ2876 $ 20.00ϩ.50/0
2869

J. Heinicke, N. Gupta, S. Singh, A. Surana, O. Kühl, R. K. Bansal, K. Karaghiosoff, M. Vogt
ledge about the ligand properties of heterophospholes we
studied transition metal complexes of various anellated 1,3-
azaphospholes and reported recently on chromium-, molyb-
denum- and tungsten-carbonyl complexes of electron-poor
pyrido-anellated 1,3-azaphospholes and related hetero-
cycles [10, 11]. The ligand properties of the benzo-anellated
electron-rich 1H-1,3-azaphospholes [8,12], characterised by
sizeable upfield phosphorus chemical shifts, should be dif-
ferent. The compounds are expected to be poor donors as
the electron lone pair at phosphorus occupies a relatively
low-energy orbital (HOMOϪ2) [13], but also poor ac-
ceptors, due to the π-excess character of the five-membered
ring. In particular the relatively high π-charge density at
phosphorus should militate against back donation. In com-
plexes with the even more electron-rich anionic 1,3-benz-
azaphospholide ligands, obtained by lithiation of 1H-1,3-
benzazaphospholes [14,15], the situation is again different.
We describe here the synthesis of (1H-1,3-benzazaphospho-
le)pentacarbonylchromium, -molybdenum and -tungsten
complexes as well as of 1,3-benzazaphospholide nickel
cyclopentadienide complexes from 1 and M(CO)5(THF) or
nickelocene, respectively, and compare characteristic NMR
spectroscopic data of the neutral and anionic ligands and
their complexes.
The NH-function in the (1H-1,3-benzazaphosphole)(pen-
tacarbonyl) metal complexes 2-4 can be metallated by bulky
organolithium reagents without substantial attack at the
PϭC bond or at the carbonyl ligands. In connection with a
study on N- versus P-metallation of benzazaphospholes 1
we recently described the reaction of the tungsten com-
plexes 4a and 4b with tBuLi at low temperature and sub-
sequent reactions of the resulting benzazaphospholides
4a,b(Li) with electrophiles [14,15]. Thus, treatment of 4a
with tBuLi and subsequently with CpW(CO)3Cl gives a
mixed-valence tungsten(0)-tungsten(II) complex 5a together
with a minor product indicating some addition of tBuLi to
the PϭC bond. Lithiation of the bulkier 2-tert-butyl substi-
tuted 4b and subsequent alkylation with MeI proceeds anal-
ogously and yields with high selectivity only the product of
P-substitution (eq. 2). These reactions show that the
M(CO)5 fragment, although it blocks the electron lone pair
at the phosphorus atom, is not a suitable protecting group
for low-coordinated phosphorus. The high π-charge density
at the phosphorus atom favours further coordination at this
site with loss of aromaticity in the products [14, 15].
Results and Discussion
Synthesis
1H-1,3-Benzazaphospholes 1, now accessible by a con-
venient three-step synthesis [12], are rather unreactive
towards M(CO)6, but react readily with M(CO)5(THF)
(M ϭ Cr, Mo, W) to give the (η1-1H-1,3-benzazaphos-
phole-P)pentacarbonylchromium, -molybdenum and -tung-
sten complexes 2Ϫ4 (Scheme 1). The new complexes are
isolated as mostly yellow, in some cases brown, thermally
and, at least for a short time, air-stable solids. Attempts to
eliminate more than one equivalent of carbon monoxide in
order to achieve a higher than η1 coordination of the
benzazaphosphole to the metal, e.g. by refluxing in toluene
or xylene, did not yield defined compounds, although the
mass spectra showed intensive fragment peaks for
MϩϪ3CO. Likewise, a DTA of 4a did not exhibit sharp
decomposition points. Even heating of the benzazaphos-
pholes with (Mes)W(CO)3 (Mes ϭ mesitylene) without sol-
vent failed to give semi-sandwich complexes. In several at-
tempts involving 1b no reaction occurred at 80 °C. At
130Ϫ140 °C (Mes)W(CO)3 reacted completely, but on ex-
traction with benzene only unchanged 1b was recovered. It
is known that the stability of η5-complexes of pyrroles is
low compared to phospholide complexes [1Ϫ4]. The pyrrole
complexes usually need steric protection [16]. In the benz-
azaphospholes the formal replacement of a carbon by a
phosphorus atom in the pyrrole ring does not seem to com-
pensate for the effect of the electronegativity of nitrogen
(compared to CHϪ), but to increase the destabilisation and,
together with the anellation, to favour η1-metal carbonyl
complexes.
In the above mentioned paper [14] we also reported on
(1,3-benzazaphospholide)Fe(CO)2Cp and -W(CO)3Cp
complexes obtained by reaction of 1(Li) with the corre-
sponding organometallic halides. Now, we find that 1,3-
benzazaphospholide transition metal complexes can be syn-
thesized directly from 1 and suitable organometallic com-
pounds. Thus, reaction of 1a؊f with nickelocene in re-
fluxing xylene affords the dark violet η5-cyclopentadienyl
(benzazaphospholide)nickel complexes 6a؊f (eq. 3). The
compounds 6a-f, to our knowledge, are the first nickel com-
plexes with azaphosphol(id)e ligands. They are isolated as
violet high melting powders or microcrystalline solids, in
the case of 6e also as thin plates from THF containing
2870
Z. Anorg. Allg. Chem. 2002, 628, 2869Ϫ2876

Metalated 1,3-Azaphospholes
C6H6. Usually they incorporate solvent, which cannot be
completely removed in vacuo. The complexes 6a-f are sensi-
tive to air and traces of moisture, but to a smaller degree
than the monomeric Fe(CO)2Cp and W(CO)3Cp com-
plexes. Attempts to metallate the pentacarbonyl tungsten
complex 4b by reaction with nickelocene failed. Neither by
heating 4b with nickelocene in boiling xylene nor by ad-
dition of W(CO)5(THF) in THF to the nickel complex 6b
a defined mixed tungsten-nickel complex could be isolated.
IR spectra of 2Ϫ4, and by elemental analyses. Information
on the coordination mode is provided particularly by the
31P and 13C NMR data. The chromium complexes 2 display
very small 31P coordination chemical shifts (∆δ ϭ 4.4Ϫ8.1),
which are somewhat smaller than in LCr(CO)5 complexes
of 2,5-dimethyl-1,2,3-diazaphosphole (∆δ ϭ 13.4) [17] or
2,4,6-triphenylphosphabenzene (∆δ ϭ 19.6) [18] and much
smaller than the ∆δ values observed for phosphine ligands
with dominant donor properties such as Ph3P (∆δ ϭ 61.3)
[19,20]. The 31P resonance of the corresponding molyb-
denum and tungsten complexes is shifted to higher field (3a,
∆δ ϭ Ϫ7; 4a؊d, ∆δ ϭ Ϫ35 to Ϫ40.6) reflecting the screen-
ing of the phosphorus nucleus by the inner electrons of the
heavier metals. The shift in going from 2a to 3a is similar
to that from R3PCr(CO)5 to R3PMo(CO)5 (∆MoϪCrδ ϭ
15.7Ϫ18.2 [19]) but the shift from 3a to 4a (∆’δ ϭ 28) is
markedly larger than in the phosphine series (∆WϪMoδ ϭ
15.3Ϫ19.0 [19]). The effect of coordination on the 13C
chemical shifts (Table 1) is limited to shielding of C-2 and
C-3a in α-position to phosphorus by ∆δ ϭ Ϫ4.5 to Ϫ5.5
(Cr, Mo) or Ϫ7 (W) and to weak shielding of the carbon
nuclei in β-position (C-4, C-7a, α-C of 2-R) by ∆δ ϭ Ϫ2.
C-5 to C-7 are only little effected (∆δ ϭ 0.4 to 1.6). The
influence of the benzazaphosphole ligand on the chemical
shifts of cis- and trans-CO groups is comparable to that
caused by a triphenylphosphine ligand. The PϪC coupling
constants do not reflect the ligand properties in a simple
way, but give further evidence of P-coordination since mag-
1
nitude and sign, particularly of J(P-C), depend on the co-
ordination number of phosphorus. The observed stability
of the complexes and the shielding of the phosphorus and
carbon nuclei near phosphorus give evidence of appreciable
coordination strength with strong dominance of the ac-
ceptor properties.
NMR Spectra
The structure of the new compounds of type 2؊4 and 6 is
revealed by their typical 1H and 13C chemical shifts and 1H-
1H as well as 31P-13C coupling constants, by the molecular
and fragment ions in the mass spectra, by sharp bands at
2064Ϫ2066 (Cr) or 2071Ϫ2073 (Mo, W) and broad inten-
sive bands at ca. 1945 cmϪ1 for the M(CO)5 groups in the
The coordination properties of the lithium benzazaphos-
pholides towards M(CO)5 fragments are somewhat differ-
ent. The 31P signals, shifted only slightly upfield in 1(Li), as
compared to 1 (∆δ < 10), experience a very strong upfield
coordination shift, e.g. ∆δ(4d(Li) Ϫ 1d(Li)) ϭ Ϫ108.5 [14],
Table 1 Comparison of the 13C NMR data of the 2-methyl-1,3-benzazaphosphole compounds 1aϪ6a, δ (JPC /Hz)
compd. (solv.)
C-2
C-3a
C-4
C-5
C-6
C-7
C-7a
2-Me
CO cis/trans
1a ([D8]THF)
[12a]
174.6
(52.1)
143.0
(42.5)
128.6
(20.4)
120.2
(11.3)
124.2
(1.5)
113.9
(Ϫ)
144.2
(5.3)
17.4
(23.4)
Ϫ
2a (CDCl3)
169.8
(22.2)
137.7
(14.2)
126.4
(13.7)
121.3
(13.6)
125.7
(3.1)
114.4
(2.3)
142.2
(Ϫ)
15.8
(14.3)
215.2 (16.6)
221.0 (5.3)
3a (CDCl3)
170.1
(19.8)
137.5
(13.7)
126.3
(14.4)
121.1
(13.9)
125.3
(3.3)
114.4
(2.8)
142.3
(Ϫ)
15.7
(16.1)
204.1 (10.6)
210.9 (29.4)
4a (CDCl3)
[14]
167.6
(30.8)
136.3
(21.9)
126.5
(13.5)
121.4
(14.0)
125.8
(3.5)
114.3
(3.2)
141.9
(Ϫ)
15.8
(15.0)
194.6 (8.5)
199.8 (29.1)
5a ([D8]THF)
[15]
193.1
(15.3)
148.4
(28.7)
127.3
(14.1)
126.7
(8.2)
129.9
(1.2)
124.7
(2.0)
152.5
(16.6)
20.1
(28.8)
see in [15]
b)
6a (C6D6)
194a)
140.5a)
125.4a)
128.7
124.2
155a)
20.2
89.8c)
(t, N ϭ 25 Hz)
a) Broad signal; P,C coupling not observed. Ϫ b) Signal superimposed by those of C6D6. Ϫ c) Signal of the Cp-ligand.
Z. Anorg. Allg. Chem. 2002, 628, 2869Ϫ2876
2871

J. Heinicke, N. Gupta, S. Singh, A. Surana, O. Kühl, R. K. Bansal, K. Karaghiosoff, M. Vogt
Table 2 Comparison of the 13C NMR data of the 2-tert-butyl-1,3-benzazaphosphole compounds 1b, 4b, 1bLi, 4bLi, 6b and 7b, δ (JPC /Hz)
compd. (solv.)
C-2
C-3a
C-4
C-5
C-6
C-7
C-7a
2-C/Me3
CO cis/trans
1b ([D8]THF)
[12a]
190.2
(57.4)
140.2
(41.1)
128.6
(21.1)
120.1
(10.8)
124.3
(2.2)
113.2
(Ϫ)
142.4
(Ϫ)
35.8 (13.0)
31.4 (9.3)
Ϫ
4b (CDCl3)
181.9
(18.0)
136.5
(22.9)
126.9
(13.7)
121.3
(13.9)
125.8
(3.1)
114.4
(3.0)
141.3
(Ϫ)
36.4 (9.4)
31.5 (7.7)
195.4 (8.3)
199.8 (29.7)
1b(Li) ([D8]THF) 199.5
[15] (57.3)
147.0
(34.0)
127.4
(22.6)
116.5
(10.6)
119.7
(Ϫ)
117.9
(Ϫ)
153.1
(Ϫ)
37.7 (19.9)
33.0 (9.6)
Ϫ
4b(Li) ([D8]THF) 203.1
150.3
(9.0)
126.5
(19.0)
119.0
(9.3)
122.5
(Ϫ)
121.1
(Ϫ)
155.4
(12.3)
39.2 (22.3)
32.4 (6.7)
200.6 (1.9)
205.3 (17.3)
[15]
(35.1)
6b (CDCl3)
204.5a)
141.7
(t, N ϭ 25)
126.8
(t, N ϭ 16)
125.4a)
128.3
(Ϫ)
124.3
(Ϫ)
154.3
(t, N ϭ 14)
39.8 (Ϫ)
31.9 (Ϫ)
90.8b)
(Ϫ)
7 (C6D6)
[15]
200.9
(38.0)
139.4
(3.0)
128.5
(19.8)
126.4
(6.5)
129.8
(Ϫ)
124.8
(Ϫ)
158.8
(10.3)
40.6 (18.5)
30.9 (4.8)
Ϫ
a)
b)
Broad signal; P,C coupling not observed. Ϫ C-Atoms of the cyclopentadienyl ring.
more than double that observed for the neutral complexes.
The back donation in 4(Li) enhances the π-electron repul-
sion induced by the increased negative charge at nitrogen
and phosphorus in 1(Li) (∆δ(1d(Li)Ϫ1d) ϭ 10 to 13 for C-
2, C-3a, C-7a, 8 for C-7) and causes slight downfield coor-
dination shifts for C-2 and C-3a (∆δϭ 3Ϫ4) of 4(Li). The
13C nuclei of the benzene ring, which except for C-7 are
shielded by lithiation of the benzazaphosphole, are now
slightly deshielded on complexation of the benzazaphos-
pholide (except C-4, ∆δ ϭ 2.5Ϫ3.2).
non-aromatic 3-tert-butyl-2-methyl-1,3-benzazaphosphole 7
(Table 2) (particularly evident for C-5 and C-7a) than to
the aromatic 1H-1,3-benzazaphospholes 1 or 1(Li).
Crystal and Molecular Structure of 6e · 2 C6H6
The dimeric structure of 6 in solution, proposed on the
1
basis of the H and 13C NMR as well as MS data, is con-
firmed also for the solid state by the result of a single crystal
X-ray structure investigation of 6e. Suitable crystals were
obtained from a cooled (ϩ5 °C) solution in THF contain-
ing C6H6. 6e · 2 C6H6 crystallizes in the space group C2/m
with two formula units in the unit cell. The compound is
dimeric with the phosphorus atom of the benzazaphospho-
lide ligands bridging two NiCp fragments. This results in
the formation of a planar P2Ni2 ring with a NiϪP distance
of 216.8(1) pm. Due to the imposed crystallographic sym-
metry the molecule shows a center of inversion, located in
the middle of the P2Ni2 ring. The interannular NiϪNi dis-
tance of 330.5(1) pm indicates that there is no bonding in-
teraction between the two nickel atoms. The observed bond
lengths of the P2Ni2 ring fit well to those found in the ana-
logous phosphido bridged dinuclear NiCp-complexes,
[CpNi(PHMes)]2 (NiϪP 215.2 pm, NiϪNi 334.1 pm) [21]
and [CpNi(PPh2)]2 (NiϪP 215.6 pm, NiϪNi 335.7 pm) [22]
as well as in the tetramethylphospholyl complex [(η5-
C4Me4P)Ni(µ-C4Me4P)]2(NiϪP 217.1 pm, NiϪNi 334.0
pm) [23].
A complete change towards the electronic situation of
non-aromatic 3H-1,3-benzazaphospholes is observed in the
cyclopentadienylnickel 1,3-benzazaphospholides 6. The
triplet splitting of the NMR signals observed for the 2-
1
methyl protons in the H NMR spectra and for the reson-
ances of several ring carbon atoms in the 13C{1H} NMR
spectra of 6a and 6d (Tables 1 and 2) demonstrate the pres-
ence of two chemically, but not magnetically equivalent
phosphorus atoms in the complexes. This indicates for the
complexes 6 a dimeric structure in solution with the phos-
phorus atoms µ2-bridging the two nickel atoms and ex-
cludes monomeric structures with η3-azaphosphaallyl-like
coordination of the benzazaphospholide. The dimeric struc-
ture of 6 is further supported by the EI mass spectra of
6a,e,f, which show relatively intensive peaks attributable to
the molecular ions of dimers at sufficient vaporisation tem-
peratures (direct inlet, 300Ϫ370°C). Further evidence is
1
provided by the occurrence of two sets of signals in the H
and 13C NMR spectra with an intensity ratio of 85Ϫ90 :
15Ϫ10 %, consistent with dimers which may exist as E- and
Z-isomers. Because of the low solubility of 6 in common
aprotic organic solvents 13C NMR spectra could be ob-
tained only for 6a and 6b. However, the data allow a com-
parison with those of other metal derivatives or complexes
of the same ligand (Tables 1, 2). The coordination shifts in
the nickel complexes are different from the shifts induced
by lithiation of 1 and also different from the coordination
shifts due to the formation of the M(CO)5 complexes 2؊4.
The 13C chemical shifts of 6 are more similar to those of the
The two benzazaphospholide ligands are planar and are
arranged in a trans-fashion, perpendicular to the Ni2P2
plane. The structural parameters of the azaphosphole ring
in 6e resemble strongly those observed recently in a P-oxo-
benzazaphospholide tungsten complex [14]. In the coordi-
nated ligand the PC bonds (181.1(5) and 185.9(5) pm) are
considerably longer and the CN bond (129.1(7) pm) is con-
siderably shorter as compared to the parent 2-tert-butyl-
5-methyl-1H-1,3-benzazaphosphole (172.78(12), 178.20(12)
pm and 138.36(15) pm, respectively) [12]. These differences
indicate clearly that on complexation the delocalized π-sys-
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Z. Anorg. Allg. Chem. 2002, 628, 2869Ϫ2876

Metalated 1,3-Azaphospholes
Pentacarbonyl Complexes 2؊4
η1-(2-Methyl-1H-1,3-benzazaphosphole-P) pentacarbonyl chromium
(2a).
A solution of Cr(CO)6 (0.459 g, 2.088 mmol) in THF (200 mL)
was irradiated at ca. 15 °C using a water-cooled 250 W medium
pressure mercury immersion lamp until 47 mL of CO were col-
lected and then was added to a solution of 1a (0.312 g, 2.088 mmol)
in THF (5 mL). After 1 d at room temperature the solvent and
uncomplexed Cr(CO)6 were removed in vacuo (10Ϫ4 Torr), the resi-
due fractionally extracted with hexane, and the latter extracts
recrystallised from toluene and dried at 10Ϫ4 Torr to give pure 2a.
Yield: 0.398 g (57%) of yellow 2a, m.p. 128Ϫ131 °C.
C13H8CrNO5P (341.18); N 4.14 (calc. 4.11) %.
IR (Nujol): ν(NH) 3408 m; ν(CO) 2064 m, 1940 vs br cmϪ1. MS (70 eV, 200
°C): m/z (data for 52Cr) ϭ 341 (Mϩ, 43%), 314 (MϩϪCO, 7%), 285
(MϩϪ2CO, 37%), 257 (MϩϪ3CO, 8%), 229 (MϩϪ4CO, 34%), 201.6
(MϩϪ5CO, 100%), 149 (Lϩ, 47%), 148 (45%), 52 (Crϩ, 62%). 1H NMR
3
(CDCl3): d ϭ 2.76 (d, JPH ϭ 17.4 Hz, 3 H, Me), 7.22 (ddd, 3J ϭ 7.6, 7.3,
4JPH ϭ 3.1 Hz, 1 H, 5-H), 7.38 (t, 3J ϭ 7 Hz, 1 H, 6-H), 7.54 (d, 3J ϭ 8.6
3
Hz, 1H, 7-H), 7.94 (t, 3J ഠ JPH ϭ 7.8 Hz, 1 H, 4-H), 9.30 (1 H, NH). 13C
NMR see Table 1. 31P NMR (CDCl3): δ ϭ 79.8.
η1-(2-tert-Butyl-1H-1,3-benzazaphosphole-P) pentacarbonyl chro-
mium (2b).
2b was prepared as described for 2a from 1b (0.172 g, 0.899 mmol)
and Cr(CO)5(THF) generated by irradiation of Cr(CO)6 (0.198 g,
0.899 mmol) in THF (200 mL). Crystallization with hexane af-
forded 0.204 g (59 %) of yellow 2b, m.p. 134 °C.
C16H14NO5PCr (383.26); N 3.78 (calc. 3.65) %.
Figure 1 Molecular structure of 6e with numbering scheme in one
half of the dimer; hydrogen atoms omitted for clarity (ORTEP plot,
50 % probability). Selected bond lengths (in pm) and angles (in °):
Ni1-P1 216.8(1), P1-C1 185.9(5), P1-C7 181.1(5), N1-C1 129.1(7),
N1-C2 141.3(7), C2-C7 138.8(7), Ni1-CCp 208.3 Ϫ 211.4, Ni1-P1-
Ni1’ 99.3(1), P1-Ni-P1’ 80.7(1), C1-P1-C7 88.4(2), C7-P1-Ni1
118.0(1), P1-C1-N1 112.9(4), C1-N1-C2 113.1(5), N1-C2-C7
117.4(5), P1-C7-C2 108.1(4).
IR (Nujol): ν(NH) 3386 m; ν(CO) 2066 m, 1986 m, 1949 vs br, 1888 s cmϪ1
.
MS (70 eV, 130 °C): m/zϭ 383 (Mϩ, 59%), 327 (MϩϪ2CO, 37%), 276 (62%),
252 (100%). 1H NMR (CDCl3): δ ϭ 1.58 (9 H, CMe3), 7.24 (ddd, 3J ϭ 7.0,
7.4, 4J ϭ 2.8 Hz, 1 H, 5-H), 7.40 (t, 3J ϭ 7 Hz, 1 H, 6-H), 7.58 (d, 3J ϭ 8.3
3
Hz, 1 H, 7-H), 7.99 (t, 3J ഠ JPH ϭ 7 Hz, 1H, 4-H), 9.32 (1 H, NH). 13C
NMR (CDCl3): δ ϭ 31.4 (d, 3J ϭ 7.5 Hz, CMe3), 36.3 (d, 2J ϭ 9.6 Hz,
CMe3), 114.4 (d, 3J ϭ 2.6 Hz, C-7), 121.2 (d, 3J ϭ 13.4 Hz, C-5), 125.8 (d,
4J ϭ 3.3 Hz, C-6), 126.9 (d, 2J ϭ 13.2 Hz, C-4), 137.1 (d, 1J ϭ 15.8 Hz, C-
3a), 141.3 (s, C-7a), 186.8 (d, 1J ϭ 7.4 Hz, C-2), 215.4 (d, 2J ϭ 15.6 Hz, 4
CO), 222.1 (d, 2J ϭ 5.2 Hz, 1 CO). 31P NMR (CDCl3): δ ϭ 70.0.
tem in the azaphosphole ring in 1e is lost in favour of a
conjugated coplanar phenyl azomethine system in 6e.
η1-(2-Methyl-1H-1,3-benzazaphosphole-P) pentacarbonyl molyb-
denum (3a).
Experimental
A solution of Mo(CO)6 (0.369 g, 1.40 mmol) in THF (200 mL)
was intermittently irradiated, each irradiation followed by replacing
CO with argon, until a total of 32 mL of CO was liberated. The
solution was added to 1a (0.210 g, 1.40 mmol) dissolved in THF
(5 mL). After 1 d at room temperature the solvent was removed in
vacuo. Fractional extraction of the residue with hexane afforded in
the first fractions 0.412 g (76%) of brown 3a, m.p. 119Ϫ122 °C (the
residue was contaminated with 1a).
General considerations. All reactions were carried out in an atmos-
phere of dry argon using Schlenk techniques. THF, ether and hy-
drocarbons were dried and deoxygenated by refluxing and distil-
lation from sodium/benzophenone ketyl before use. The 1H-1,3-
benzazaphospholes 1a؊f were synthesized as reported recently [12].
[(THF)M(CO)5] [24] was prepared immediately before use, nickel-
ocene was synthesized by a known procedure [25]. Other com-
pounds were purchased. NMR spectra were measured on a multi-
nuclear FT-NMR spectrometer Bruker ARX300 at 300.1 (1H), 75.5
(13C), and 121.5 (31P) MHz. The 1H, 13C and 31P chemical shifts
are δ values, relative to Me4Si and H3PO4 (85%), respectively, as
external standards. For benzazaphospholes the atomic numbers ac-
cording to the nomenclature and for 2-phenyl substituents the indi-
ces i, o, m, p are used for assignment. Coupling constants refer
to HϪH (1H NMR) or P-C couplings (13C NMR) unless stated
otherwise, N means ͉JϩJ’͉ of pseudotriplets (X of AA’X; A,A’ ϭ
P). Mass spectra were recorded on a single-focussing mass spec-
trometer AMD40 (Intectra). Elemental analyses (C, H, N) were
carried out using an elemental analyser LECO Model CHNS-932
under standard conditions; carbon combustion of the complexes
was often incomplete. Melting points were determined in sealed
capillaries under argon and are uncorrected.
C13H8MoNO5P (385.12); C 41.49 (calc. 40.54); H 2.38 (calc. 2.09);
N 3.79 (calc. 3.64) %.
IR (Nujol): ν(NH) 3408 m; ν(CO) 2072 m, 1946 vs br cmϪ1. MS (70 eV,
190 °C): m/z (data for 98Mo) ϭ 387 (Mϩ, 7%), 331 (MϩϪ2CO, 11%), 303
(MϩϪ3CO, 10%), 275 (MϩϪ4CO, 14%), 247 (MϩϪ5CO, 13%), 245 (13%),
149 (Lϩ, 100%), 148 (87%), 107 (16%). 1H NMR (CDCl3): δ ϭ 2.77 (d,
4
3JPH ϭ 17.4 Hz, 3 H, CH3), 7.23 (td, 3J ϭ 7.4 Hz, JPH ϭ 2.6 Hz, 1 H, 5-
H), 7.38 (dd, 3J ϭ 8.2 Hz, 7.1 Hz, 1 H, 6-H), 7.54(d, 3J ϭ 8.2 Hz, 1H, 7-
3
H), 7.91 (t, 3J ഠ JPH ϭ 7.5 Hz, 1 H, 4-H), 9.25 (1 H, NH). 13C NMR see
Table 1. 31P NMR (CDCl3): δ ϭ 64.7.
η1-(2-tert-Butyl-1H-1,3-benzazaphosphole-P) pentacarbonyl tungsten
(4b).
A solution of (THF)W(CO)5 was prepared by irradiation of
W(CO)6 (0.570 g, 1.62 mmol) in THF (200 mL, 37 mL of CO
evolved) and added to a solution of 1b (0.310 g, 1.62 mmol) in
Z. Anorg. Allg. Chem. 2002, 628, 2869Ϫ2876
2873

J. Heinicke, N. Gupta, S. Singh, A. Surana, O. Kühl, R. K. Bansal, K. Karaghiosoff, M. Vogt
THF (5 mL). After 15 h at 20 °C the solvent and excess W(CO)6
C26H24N2Ni2P2 (543.82); C 58.31 (calc. 57.42); H 4.76 (calc. 4.45);
N 5.01 (calc. 5.15) %.
were removed in vacuo (10Ϫ4 Torr) and the residue was recrystal-
lised from hexane affording 0.532 g (63%) of yellow 4b, m.p.
157Ϫ159 °C.
MS (70 eV, 370 °C): m/z ϭ 546 (27%), 544 ([58Ni60Ni]Mϩ, 93%), 542 (83%),
408 (28%), 406 (77%), 404 (MϩϪ138, 100%), 149 (32%), 148 (34%), 147
(29%). 1H NMR (CDCl3): Isomer A (85Ϫ90 %) δ ϭ 3.12 (t, N ϭ 7.7 Hz, 3
H, CH3), 4.63 (s, 5 H, Cp), 7.30 (t, 3J ϭ 7.4 Hz, 1 H, 6-H), 7.45 (dd, 3J ϭ
7.8, 7.3 Hz, 1 H, 5-H ), 7.74 (d, 3J ϭ 7.8 Hz, 1 H, 7-H), 7.97 (m, 1 H, 4-H);
Isomer B (10Ϫ15 %) δ ϭ 3.01 (t, N ϭ 8 Hz, CH3), 8.07 (m, 4-H), other
signals superimposed. 13C NMR see Table 1. 31P NMR (CDCl3) δ ϭ Ϫ131.7.
C16H14NO5PW (515.10); C 37.23 (calc. 37.31); H 3.02 (calc. 2.74);
N 2.56 (calc. 2.72) %.
IR (Nujol): ν(NH) 3376 m; ν(CO) 2074 m, 1981 vs, 1945 vs, 1877 s cmϪ1
.
MS (70 eV): m/z (data for 184W) ϭ 514 (MϩϪ1, 53%), 469 (97%), 446 (57%),
420 (48%), 392 (73%), 192 (Lϩϩ1,63%), 177 (100%). 1H NMR (CDCl3): δ ϭ
4
1.59 (d, JPH ϭ 0.8 Hz, 9 H, CMe3), 7.23 (dddd, 3J ϭ 7.0, 7.4 Hz, 4JPH ϭ
5
2.9 Hz, 4J ϭ 0.9 Hz, 1 H, 5-H), 7.37 (ddt, 3J ϭ 7.0, 8.2 Hz, JPH
ഠ
4J ϭ 1.2
Compound 6b.
Hz, 1 H, 6-H), 7.57 (d, 3J ϭ 8.3 Hz, 1 H, 7-H), 7.90 (t, 3J ഠ 3JPH ϭ 7.5 Hz,
1 H, 4-H), 9.96 (1 H, NH). 13C NMR see Table 2. 31P NMR (CDCl3): δ ϭ
24.5 (1JWP ϭ 241.7 Hz).
Nickelocene (365 mg, 1.93 mmol) and 1b (370 mg, 1.93 mmol) were
heated to reflux in o-xylene (20 mL) for 3 h. Then the solvent was
removed in vacuo, and the residue was extracted with boiling hex-
ane (Soxhlet apparatus). The solvent was evaporated and the prod-
uct dried in vacuo yielding 360 mg (59 %) of 6b as dark violet
powder with m.p. >260 °C. The first extracts of 6b have a higher
content of the minor isomer B (o-xylene included in the solid),
the latter extracts are the nearly pure major isomer A of 6b. 6b is
moderately soluble in toluene or warm THF, less soluble in cold
THF.
η1-(2-Phenyl-1H-1,3-benzazaphosphole-P)pentacarbonyl tungsten
(4c).
4c was prepared as described for 4b from 1c (0.365 g, 1.73 mmol)
and W(CO)5(THF) formed on irradiation of excess W(CO)6 (0.605
g, 2.16 mmol, 38.5 mL CO evolved) in THF (200 mL). Crystalliza-
tion with hexane and drying at 10Ϫ4 Torr afforded 0.623 g (68 %)
of brown 4c, m.p. 255 °C (dec.).
C32H36N2Ni2P2 (627.98); N 4.37 (calc. 4.46) %.
C18H10NO5PW (535.11); N 2.73 (calc. 2.62) %.
IR (Nujol): ν(CO) 2073 m, 1988 sh, 1949 vs br, 1919 sh cmϪ1. MS (70 eV):
MS (70 eV, 230 °C): m/z ϭ 442 (23%), 440 (71%), 438 (monomerϩϩNiCpϩ1,
100%), 370 (13%), 368 (15%), 332 (16%), 330 (18%), 318 (18%), 317 (31%),
316 (50%), 315 (47%), 314 (monomerϩϩ1, 95%), 247 (37%), 192 (38%), 189
(29%), 177 (48%). 1H NMR (CDCl3): Isomer A δ ϭ 2.00 (s, 9 H, CMe3),
4.57 (s, 5 H, Cp), 7.31 (ddd, 3J ϭ 7.8, 7.3, 4J ϭ 1 Hz, 1 H, 6-H), 7.46 (dd,
3J ϭ 7.5, 7.0 Hz, 1 H, 5-H), 7.77 (d, 3J ϭ 7.8 Hz, 1 H, 7-H), 8.18 (m, 1H,
4-H). Isomer B δ ϭ 1.80 (s, CMe3), 4.50 (s, Cp), 7.43Ϫ7.51 (m, 5-H, 6-H),
7.77 (d, 3J ϭ 7 Hz, 7-H), 8.17 (m, 4-H). 13C NMR see Table 2. 31P NMR
(CDCl3): δ ϭ Ϫ155.4 (A); Ϫ154.2 (B).
m/z (data for 184W)
ϭ
535 (Mϩ, 26%), 479 (MϩϪ2CO, 47%), 451
(MϩϪ3CO, 23%), 423 (MϩϪ4CO, 25%), 395 (MϩϪ5CO, 21%), 212
(MϩϪW(CO)5, 100%). 1H NMR (CDCl3): δ ϭ 7.25Ϫ7.35 (m, 2 H, 5-H, 6-
H), 7.43Ϫ7.54 (m, 3 H, m-H, p-H), 7.66 (d, 3J ϭ 8.3 Hz, 1 H, 7-H), 7.74
3
3
3
(dt, JHH ϭ 8.0, 4J ഠ JPH ϭ 3.3 Hz, 2 H, o-H), 7.99 (dd, 3J, JPH ϭ 7.4,
8.4 Hz, 1 H, 4-H), 9.57 (1 H, NH). 13C NMR (CDCl3): δ ϭ 115.5 (d, 3J ϭ
3.4 Hz, C-7), 121.4 (d, 3J ϭ 14.1 Hz, C-5), 126.3 (d, 4J ϭ 2.9 Hz, C-6), 126.6
(d, 2J ϭ 12.8 Hz, C-4), 126.9 (d, 4J ϭ 10.6 Hz, C-m), 129.0 (s, C-p), 129.2
(d, 3J ϭ 21.0 Hz, C-o), 137.7 (d, 1J ϭ 22.6 Hz, C-3a), 142.7 (s, C-7a), 169.8
(d, 1J ϭ 29.2 Hz, C-2), 194.8 (d, 2J ϭ 8.2 Hz, JWC ഠ 125 Hz, 4 CO), 199.4
1
Compound 6c.
(d, 2J ϭ 30.2 Hz, 1 CO). 31P NMR (CDCl3): δ ϭ 39.8.
Nickelocene (177 mg, 0.94 mmol) and 1c (290 mg, 0.94 mmol) were
heated to reflux in o-xylene for 3 h. On cooling the solid was fil-
tered off and the solvent removed from the filtrate. Both fractions
were found to be mixtures of dark violet E/Z-6c isomers free of
unreacted 1c. The residue, containing less of the minor isomer
(roughly 8:1, by 1H integration for Cp and o-H) and more o-xylene
was further purified by extraction with hexane (Soxhlet apparatus)
and dried in vacuo.
η1-(2,5-Dimethyl-1H-1,3-benzazaphosphole-P) pentacarbonyl tung-
sten (4d).
4d was prepared as described for 4b from W(CO)6 (1.164 g, 3.30
mmol) in THF (300 mL, 74 mL of CO evolved) and 1d (360 mg,
2.20 mmol) in THF (5 mL). Crystallization with hexane gave 1.045
g (97%) of yellow 4d, m.p. 120 °C.
C36H28N2Ni2P2 (667.96); N 3.87 (calc. 4.19) %.
C14H10NO5PW (487.11); C 33.49 (calc. 34.52); H 2.19 (calc. 2.07);
N 2.52 (calc. 2.88) %.
1H NMR (CDCl3): Isomer A δ ϭ 4.47 (s, 5 H, Cp), 7.30Ϫ7.75 (aryl-H), 7.91
(d, 3J ϭ 7.5 Hz, 1 H, 7-H), 8.28 (m, 1 H, 4-H), 9.29 (dd, J ϭ 7.5, 1.5 Hz, 2
H, o-H). Isomer B δ ϭ 4.49 (s, Cp), 7.30Ϫ7.75 (aryl-H), 8.54 (m, 4-H), 8.92
(m, o-H). 31P NMR (CDCl3): δ ϭ Ϫ141.6 (minor), Ϫ144.0 (major).
IR (Nujol): ν(NH) 3402 m; ν(CO) 2073 m, 1983 m, 1944 vs br cmϪ1. MS
(70 eV, 250 °C): m/z (data for 184W) ϭ 487 (Mϩ, 94%), 431 (MϩϪ2CO,
16%), 403 (20%), 401 (23%), 375 (32%), 352 (20%), 350 (54%), 91.8 (100%).
1H NMR (CDCl3): δ ϭ 2.47 (s, 3 H, 5-Me), 2.73 (d, JPH ϭ 17.7 Hz, 3 H,
3
2-Me), 7.19 (d, 3J ϭ 8.5 Hz, 1 H, 6-H), 7.43 (d, 3J ϭ 8.5 Hz, 1 H, 7-H), 7.62
(d, 3JPH ϭ 7.7 Hz, 1 H, 4-H), 9.11 (1 H, NH). 13C NMR (CDCl3): δ ϭ 15.8
(d, 2J ϭ 14.8 Hz, 2-Me), 21.4 (5-Me), 114.0 (d, 3J ϭ 3.5 Hz, C-7), 125.7 (d,
2J ϭ 13.9 Hz, C-4), 127.6 (d, 4J ϭ 3.5 Hz, C-6), 131.1 (d, 3J ϭ 14.1 Hz, C-
5), 136.5 (d, 1J ϭ 22.1 Hz, C-3a), 140.2 (s, C-7a), 167.3 (d, 1J ϭ 30.7 Hz, C-
Compound 6d.
Nickelocene (608 mg, 3.21 mmol) and 1d (525 mg, 3.21 mmol) were
heated to reflux in o-xylene (20 mL) for 3 h. Then the solvent was
removed in vacuo and the residue repeatedly extracted with boiling
hexane yielding a violet powder of 6d containing one equivalent of
xylene and hexane per benzazaphospholide (by integration of the
1H NMR), m.p. > 240 °C.
1
2), 194.7 (d, 2J ϭ 6.2 Hz, JWC ϭ 124 Hz, 4 CO), 199.7 (d, 2J ϭ 30 Hz, 1
CO). 31P NMR (CDCl3): δ ϭ 34.8 (1JWP ϭ 241.2 Hz).
C28H28N2Ni2P2 (571.88), with 2 molecules of xylene and 2 mol-
ecules of hexane (956.44); C, 67.88 (calc. 70.32); H, 7.70 (calc.
8.01); N 2.81 (calc. 2.93) %.
Reactions of 1H-1,3-benzazaphospholes with nickelocene
Compound 6a.
Nickelocene (474 mg, 2.51 mmol) and 1a (375 mg, 2.51 mmol) were
dissolved in o-xylene (20 mL) and heated to reflux for 3 h. The
colour of the solution turned from green to violet. Then the reac-
tion mixture was filtered and the filtrate was kept cold (0Ϫ5 °C)
for 2Ϫ3 d. The precipitate was separated, washed with cold pen-
tane, and dried in vacuo (10Ϫ2 to 10Ϫ4 Torr, 2 h) to give 390 mg
(57%) of dark violet crystals of 6a, m.p. 236Ϫ240 °C, containing a
MS (70 eV, 120 °C): m/z ϭ 335 (4%), 285 (monomerϩ, 45%), 243 (100%),
[monomerϪ42 ϩ], 169 (42), 149 (80). 1H NMR (CDCl3) Isomer A (85 %)
δ ϭ 2.51 (s, 3H, 5-Me), 3.11 (t, N ϭ 8.4 Hz, 3H, 2-Me), 4.64 (s, 5H, Cp),
7.24 (d, 3J ϭ 7.9 Hz, 6-H), 7.61 (d, 3J ϭ 7.9 Hz, 1H, 7-H), 7.70 (t, N ϭ 5.5
Hz, 1H, 4-H); Isomer B (15 %) δ ϭ 2.99 (t, N ϭ 8 Hz, Me), 7.12 (d, 3J ϭ
7.3 Hz, 6-H), 7.37 (d, 3J ϭ 7.3 Hz, 7-H), 7.94 (m, 4-H). Ϫ 13C NMR
(CDCl3): δ ϭ 20.2 (2-Me), 21.4 (5-Me), 89.8 (Cp), 123.8 (C-7), 127.5 (t, N ϭ
17 Hz, C-4), 129.8 (s, C-6), 132.4 and 135.1 (C-5 and C-3a), 153.3 (C-7a),
192 (C-2). 31P NMR (CDCl3) δ ϭ Ϫ96.5.
1
small amount of xylene detected by H NMR.
2874
Z. Anorg. Allg. Chem. 2002, 628, 2869Ϫ2876

Metalated 1,3-Azaphospholes
Table 3 Crystallographic data for 6e · 2 C6H6 and details of data collection and structural refinement
empirical formula
formula weight/g·molϪ1
colour, habit
temperature/K
crystal size/mm
crystal system
C46H52N2Ni2P2
812.25
violet prism
200(2)
0.37Ϯ0.16Ϯ0.16
monoclinic
C2/m
16.8724(3)
13.6089(3)
12.2108(3)
133.4492(8)
2035.50(7)
2
F(000)
θ-range/°
index-range
856
2.24 to 27.53
Ϫ21 Յ h Յ 21
Ϫ17 Յ k Յ 17
Ϫ15 Յ l Յ 15
21687
2430
1951
0.0872
2430/0/168
1.218
0.0922, 0.1849
0.0728, 0.2041
0.956, Ϫ0.788
0.7950, 0.8958
reflections collected
independent reflections
observed reflections (>4σ)
R (int.)
data/restraints/parameter
goodness of fit F2
R1, wR2 [I > 4σ(I)]
R1, wR2 (all data)
space group
˚
a/A
˚
b/A
˚
c/A
b/°
3
˚
V/A
Z
density (calc.)/g·cmϪ3
absorb. coeff./mmϪ1
1.32527(5)
1.038
largest diff. peak, hole/e·A
min., max. transmission
Ϫ3
˚
Compound 6e.
Nonius Kappa CCD using graphite monochromated Mo-Kα-radi-
ation (λ ϭ 0.71073 A). The structure was solved by direct methods
˚
Nickelocene (266 mg, 1.41 mmol) and 1e (290 mg, 1.41 mmol) were
allowed to react in o-xylene (10 mL) and extracted with hexane
(Soxhlet apparatus) as described above to give 410 mg (88%) of
dark violet 6e, m.p. > 240 °C. 6e is soluble in C6D6 and in THF.
Small plates of 6e · 2 C6H6 crystallised within several days at room
temperature from a cooled solution (5 °C) in THF containing
C6H6.
(shelxs-97) and refined by full-matrix least-squares methods on F2
for all unique reflections (shelxl-97) [26]. The structure was solved
in the space group C2/m with disordered Cp-units and benzene
molecules. The observed disorder as well as the poor quality of the
crystal are most probably responsible for the rather high R values.
For the H(C) atoms a riding model was employed. The C atoms of
the Cp are fitted to a regular pentagon by fixing the shape but the
CϪC distances were refined freely. The crystallographic data are
listed in Table 3.
C34H40N2Ni2P2 (656.03); (C, combustion incomplete); H, 6.03
(calc. 6.15); N 4.08 (calc. 4.27) %.
MS (70 eV, 300 °C): m/z ϭ 655 ([58Ni2]Mϩϩ1, 58%), 454 (8%), 452 (16%),
450 (Mϩϩ1ϪL, 17%), 329 (9%), 327 (monomerϩ, 19%), 205 (Lϩ, 45%), 190
(LϩϪ15, 71%), 120 (83%), 87 (61%), 85 (100%). 1H NMR (CDCl3): Isomer
A (85Ϫ90 %) δ ϭ 1.99 (s, 9 H, CMe3), 2.52 (s, 3 H, 5-Me), 4.57 (s, 5 H, Cp),
7.25 (d, 3J ϭ 8.0 Hz, 1 H, 6-H), 7.65 (d, 3J ϭ 8.0 Hz, 1 H, 7-H), 7.95 (1 H,
4-H); Isomer B (10-15 %) δ ϭ 1.77 (s, CMe3), 2.65 (s, 5-Me), 4.51 (s, Cp),
8.33 (4-H), signals due to the other protons superimposed. 13C NMR
(C6D6): δ ϭ 21.6 (5-Me), 31.9 (s, CMe3), 39.7 (CMe3), 90.8 (Cp), 123.9 (C-
7), 127.1 (C-4), 129.3 (C-6), 134.9 (C-5), 141.7 (t, N ϭ 23 Hz, C-3a), 152 (C-
7a). The signal for C-2 was not observed. 31P NMR (C6D6) δ ϭ Ϫ156.0.
For selected bond lengths and angles of 6e see Figure 1. Crystallo-
graphic data for 6e have been deposited with the Cambridge Crys-
tallographic Data Centre as supplementary publication no. CCDC-
186555. Copies of the data can be obtained free of charge on appli-
cation to CCDC, 12 Union Road, Cambridge CB2 1EZ, Uk [Fax:
(int. code) ϩ44-(1223)/336-033, e-mail: deposit@ccdc.cam.ac.uk].
Acknowledgement. The authors thank the Deutsche Forschungsge-
meinschaft and the Fonds der Chemischen Industrie for the sup-
port of this work, B. Witt and Dr. M. K. Kindermann for numer-
ous NMR measurements.
Compound 6f.
Nickelocene (162 mg, 0.86 mmol) and 1f (194 mg, 0.86 mmol) were
heated to reflux in o-xylene (10 mL) for 3 h. Then the solvent was
removed in vacuo and ether (10 mL) added to the residue. After
stirring for 20 min at room temperature the brown filtrate contain-
ing unreacted 1f and a small amount of 6f were separated, and the
insoluble part was extracted with hexane (Soxhlet apparatus) to
give 205 mg (64 % ) of 6f as a dark violet powder which, after
drying in vacuo, was found to contain ca. 0.5 equivalents of hexane.
6f shrinks at 120 °C but does not melt until 250 °C.
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MS (70 eV, 370 °C): m/z ϭ 695 ([58Ni2]Mϩϩ1, 100%), 475 (20%), 473 (39%),
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C6H6
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