P-Amino-cyclopentadienylidene-phosphoranes versus P-cyclopentadienyl- iminophosphoranes-tautomeric protic forms of a new bidentate CpPN ligand system

Article abstract of DOI:10.1039/b710419g

The Staudinger reaction of cyclopentadienyl-phosphanes C₅H ₅-PMe₂ (P1), C₅H₅-PPh₂ (P2), and C₅Me₄H-PMe₂ (P3) with azides Me ₃SiN₃, 1-AdN₃ (Ad = 1-adamantyl) and DipN ₃ (Dip = 2,6-diisopropylphenyl) has been studied. The nature of the products depends on the substituents at the C5 ring, at the phosphorus and nitrogen atoms: A series of new P-amino-cyclopentadienylidene-phosphoranes 2-6 was synthesized by reactions of P1-P3 with 1-AdN₃ (2-4) and DipN ₃ (5, 6). In contrast, P-cyclopentadienyl-iminophosphoranes 1 and 7 were obtained as predominant tautomers by reaction of less CH-acidic P3 with less N-basic Me₃SiN₃ and DipN₃. Both tautomers are protonated forms of ambident, potentially chelating constrained-geometry ligands. The molecular structures of three members of this "CpPN" ligand family, 3, 4 and 6, are characterized by X-ray crystallography. The Royal Society of Chemistry.

Full text of DOI:10.1039/b710419g

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P-Amino-cyclopentadienylidene-phosphoranes versus P-cyclopentadienyl-
iminophosphoranes—tautomeric protic forms of a new bidentate
CpPN ligand system†‡§
Alex R. Petrov,a Konstantin A. Rufanov,*b,c Burkhard Ziemer,b Petra Neubauer,b Vasily V. Kotova and
Jo¨rg Sundermeyer*a
Received 11th July 2007, Accepted 24th October 2007
First published as an Advance Article on the web 10th December 2007
DOI: 10.1039/b710419g
The Staudinger reaction of cyclopentadienyl-phosphanes C5H5–PMe2 (P1), C5H5–PPh2 (P2), and
C5Me4H–PMe2 (P3) with azides Me3SiN3, 1-AdN3 (Ad = 1-adamantyl) and DipN3 (Dip =
2,6-diisopropylphenyl) has been studied. The nature of the products depends on the substituents at the
C5 ring, at the phosphorus and nitrogen atoms: A series of new P-amino-cyclopentadienylidene-
phosphoranes 2–6 was synthesized by reactions of P1–P3 with 1-AdN3 (2–4) and DipN3 (5, 6). In
contrast, P-cyclopentadienyl-iminophosphoranes 1 and 7 were obtained as predominant tautomers by
reaction of less CH-acidic P3 with less N-basic Me3SiN3 and DipN3. Both tautomers are protonated
forms of ambident, potentially chelating constrained-geometry ligands. The molecular structures of
three members of this “CpPN” ligand family, 3, 4 and 6, are characterized by X-ray crystallography.
Introduction
In the framework of our current studies on the coordination
chemistry of organophosphorus(V) ligands with ambident donor
functionalities we have focused on the development of two par-
ticular ligand types—cyclopentadienyl-phosphoranylidenes (B)1
and P-amino-cyclopentadienylidene-phosphoranes (C). The cor-
responding dianion of B and monoanion of C are isoelectronic
to the chelating dianionic cyclopentadienyl-silylamido ligand sys-
tems (A, Chart 1), which became one of the best developed classes
of chelating cyclopentadienyl-amido complexes of the early transi-
tion metals,2 the so-called “constrained-geometry catalysts” CGC
(A).3 Recently we have reported the synthesis and crystal struc-
ture of a “constrained-geometry” cyclopentadienyl-phosphazene
5
lutetium complex [(g -C5Me4PMe2NAd)Lu(CH2SiMe3)2] (Ad =
1-adamantyl).4 A representative example of this interesting ligand
system has been synthesized by the Staudinger reaction of 1-
AdN3 and C5Me4H–PMe2. From a conceptual standpoint, tri-
valent lanthanide or Group 3 metal complexes on the basis of
Chart 1 Isolobally related “constrained-geometry” complexes and cor-
responding ligand systems.
type C ligands are isolobal, in the case of the Group 3 metals
even isoelectronic, with tetra-valent Group 4 transition metal
complexes of type A ligands. Having this concept and the greater
diversity of rare-earth metals in mind, we set out to develop
convenient syntheses for a large variety of type C ligands with
different substituents at the N-, P- and C-atoms. This investigation
turned out to be an interesting case study of iminophosphorane–
aminoylide tautomerism,5 which we would like to discuss in
more detail in this report. Here we describe the general synthetic
approach for type C ligand precursors, their physicochemical
and NMR spectroscopic properties, their molecular structures,
as well as factors influencing the tautomeric equilibrium of their
protonated forms.
aFachbereich Chemie der Philipps-Universita¨t Marburg, Hans-Meerwein-
Str., 35032 Marburg, Germany. E-mail: jsu@chemie.uni-marburg.de;
Fax: +49 (0)6421 2828917; Tel: +49 (0)6421 2825693
bInstitut fu¨r Chemie, Humboldt-Universita¨t zu Berlin, Brook-Taylor-Str. 2,
12489 Berlin, Germany
cLaboratory of Coordinate Organometallic Compounds, Chair of Organic
Chemistry, Department of Chemistry of the M.V. Lomonosov State Uni-
versity of Moscow, Vorob’evy Gory, 119899 Moscow, Russia. E-mail:
k_rufanov@gmx.de; Fax: +7 495 932 8846; Tel: +7 909 631 0854
† Organophosphorus(V) ligands for coordination and organometallic
chemistry. Part 4.4.
‡ Dedicated to Dr. h.c. of the M.V. Lomonosov State University of Moscow
Prof. Jo¨rg Lorberth on the occasion of his 70th birthday.
Results
Reactions of the characteristic regioisomeric6 cyclopentadienyl-
phosphanes of increasing thermal stability—C5H5–PMe2 (P1),
§ CCDC reference numbers 263440, 284188 and 284189. For crystallo-
graphic data in CIF or other electronic format see DOI: 10.1039/b710419g
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C5H5–PPh2 (P2) and C5Me4H–PMe2 (P3)—with three representa-
tive azides—silyl azide TMSN3, alkyl azide 1-AdN3 and aryl azide
DipN3 (Dip = 2,6-diisopropylphenyl) have been studied (Chart 2).
Success in the synthesis of type II or III products crucially
depends on the relative reactivity of the phosphanes and azides
applied. In general, the reaction with the most unreactive azide
TMSN3 requires higher temperatures, that are undesirable for
the thermally more labile C5H5–phosphanes P1 and P2. These
phosphanes and even more readily the corresponding iminophos-
phoranes are prone to undergo Diels–Alder type dimerisation.9,10
Although more reactive 1-AdN3, upon reaction with P1, leads
to the formation of the desired P-amino-cyclopentadienylidene-
phosphorane 2, only traces of analytically pure 2 can be isolated
after further purification at ambient temperature. P2 is less labile
with respect to Diels–Alder dimerisation and gives smoothly lig-
and 3 in up to 69% yield. Formation of 4 from thermally stable P3
is nearly quantitative. DipN3 as the most electrophilic and reactive
azide in our series smoothly reacts with all phosphanes giving the
target “CpPN” ligands 5 and 6 in considerably higher yields.
The typical protocol employed for the synthesis of P-amino-
cyclopentadienylidene-phosphoranes employs the reaction of 0.1–
0.6 molar THF solutions of phosphanes P1–P3, prepared in situ
from C5H5Tl or C5Me4HLi with Ph2PCl or Me2PCl, with azides 1-
AdN3 and DipN3 for 12–16 h at room temperature. Reaction of P3
with TMSN3 requires higher temperatures (60 ◦C, 2 d). Complete
evaporation of solvent yields light-brown powders or oils. In
the case of crystalline products, purification is accomplished by
repetitive washing with diethyl ether or hexane or recrystallization
to give the desired ligands with 60–95% yields (Table 1). The choice
of a suitable solvent and anionic Cp synthon is very important: In
diethyl ether or hexane instead of THF, the Staudinger reaction
does not proceed with high selectively. Furthermore, the use
of common C5H5M reagents (M = Li, Na) in the P–C bond
coupling leads to impurities, that could be removed only with
an unacceptable loss of yield during work-up after the Staudinger
reaction. For thermally unstable C5H5-substituted phosphanes,
best results were obtained using THF or THF–diethyl ether and
C5H5Tl as anion source. The compounds 2–6 represent white
air-sensitive microcrystalline substances, readily soluble in THF,
CHCl3, DMSO, sparingly soluble in benzene and diethyl ether and
insoluble in hexane.
Chart 2 Representative objects chosen for this study.
The first step of the Staudinger reaction proceeds via a so-
called “Staudinger adduct” or phosphazide7 (I, Scheme 1), that
can be observed as an intermediate precipitate if these reactions
are carried out at low temperatures (0 ◦C). The second irreversible
step of dinitrogen elimination is fast and it has most probably
intramolecular character.8 Extrusion of N2 leads to formation of
iminophosphorane II, that is in tautomeric equilibrium with P-
amino-cyclopentadienylidene-phosphorane III. The other spec-
ulative pathway would first involve tautomerization of I to IV,
followed by N2 elimination and formation of III (Scheme 1).
The results of our studies on the reactivity of the
cyclopentadienyl-phosphanes P1–P3 towards the above men-
tioned azides are summarized in Table 1.
Table 1 Yields of the “CpPN” ligands as mixtures of tautomers of type
II and/or III
P1
P2
P3
This synthetic approach can be extended to other
cyclopentadienyl-phosphanes and azides, however in some of our
experiments we experienced its limitation: Reactions of sterically
demanding phosphine C5Me4H–PPh2 with the less reactive azides
TMSN3
1-AdN3
DipN3
No reaction
2, traces
5, 75%
No reaction
3, 69%
6, 85%
1, 86%
4, 95%4
7, 60%
Scheme 1
910 | Dalton Trans., 2008, 909–915
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Table 2 Selected 1H, 13C and 31P NMR spectroscopic data for 1–7 in comparison to Ph3P C5H4 (8)
=
1H
1,a C6D6
2, C6D6
3, CDCl3
4,4 C6D6
5, C6D6
6, CDCl3
7,a C6D6
8, C6D6
HCp
—
—
1.64
1.93
0.95 (12.6)
—
2.98 (25.5)
6.66
6.95
—
6.35
6.39
—
—
—
2.71 (5.8)
—
—
—
2.39
2.44
1.25 (10)
1.35b
—
6.74
6.99
—
—
1.04 (13.0)
3.21 (6.6)
—
6.37
6.49
—
—
—
4.53 (7.2)
—
—
—
6.32
6.50
—
Me–Cp
Me2P (2JH,P
1.65
1.97
1.02 (11.7)
—
—
—
)
1.21 (13.2)
1.57b
—
—
—
—
NH (2JH,P
)
all-HCp (2JH,P
)
3.37 (26.8)
13C
CCp (JC,P
)
131.3 (4.0)
139.2 (6.8)
—
63.8 (58)
1.1
113.1 (17.6)
114.4 (18.7)
86.7 (126)
—
113.8 (18.1)
116.5 (17.2)
84.0 (126)
—
117.9 (18.0)
119.7 (19.0)
77.8 (125)
—
113.6 (16.0)
114.9 (19.3)
83.1 (133)
—
114.5 (18.9)
116.9 (17.4)
83.1 (133)
—
140.0 (6.9)
142.2 (7.1)
—
63.0 (62)
−3.1
114.2 (18.0)
116.8 (15.0)
77.9 (112)
ipso-CCp (1JC,P
)
all-CCp (1JC,P
)
31P
21.0
22.0
17.6
27.4
28.9
17.4
a NMR data of the main isomer. b The 2JH,P coupling constant of NH was not observed since this signal overlaps with the aliphatic protons.
did not give acceptable yields of the desired ligands, finally,
sterically unprotected indenyl-diphenylphosphane so far failed to
give the target products of a selective Staudinger reaction. Instead
intensively green-colored waxes with complex 31P NMR spectra
were obtained.11
of signals in all spectra is supported by COSY 1H/1H and 1H/13C
experiments.
In accord with these NMR data, we suggest, that the rel-
ative Brønsted acidity of the protons in unsubstituted C5H5–
phosphazene derivatives tends to be higher than all N-organo
phosphazene N–H protons of the representative compounds
investigated here. Compounds 2, 3, 5 and 6 preferentially exist
in their thermodynamically more favorable form of type III
tautomers. The other tautomers of type II are not observed in the
proton NMR spectra. The opposite trend is observed in C5Me4H-
substituted N-silyl and N-aryl phosphazenes 1 and 7, respectively:
N-silyl derivative 1 is formed as a highly hexane soluble oil
consisting of a mixture of three isomeric P-cyclopentadienyl-
iminophosphoranes 1a–1c in a molar ratio of approximately
7 : 2 : 1. The P-allylic regio-isomer 1a is predominant. Due to the
low N-basicity of the [PNSiMe3] function and low CH-acidity,
type II isomers 1a–1c do not tend to form type III tautomer 1d in
amounts detectable by proton NMR (Scheme 2).
Discussion
Preferred tautomers—a NMR study
In the 31P NMR spectra of 2–6 only one distinct signal at dP =
25 5 ppm is observed confirming their cyclopentadienylidene-
phosphorane nature (Table 2).12 In contrast, the 31P NMR spectra
of 1 and 7 reveal several signals according to the number of
isomers present: Three isomers for 1 and two tautomers for 7
(vide infra). The predominant species in both, 1 and 7, are P-
cyclopentadienyl-iminophosphoranes with 31P resonances at dP =
0
10 ppm typical for iminophosphoranes.13,15 It is important to
note that metallation of this mixture of isomers with Lu, Li or
K alkyls leads to compounds with only one 13P NMR signal; this
serves as criterion for the purity of the mixture of regioisomers.
The 1H and 13C NMR signals of the C5H4 ring in 2–6 are in accord
with Cs symmetry of the molecules: 13C NMR resonances are up-
Interestingly, N-Dip substituted 7 with slightly higher N-
basicity is formed as a waxy solid consisting of a mixture of type
II and III tautomers—P-cyclopentadienyl-iminophosphorane 7a
and P-amino-cyclopentadienylidene-phosphorane 7b—in an ap-
proximate molar ratio of 8 : 1. Again the P-allylic regio-isomer is
the predominant species of the major tautomer 7a. As one might
anticipate, the increasing N-basicity of the phosphazene shifts
the tautomeric equilibrium towards the cyclopentadienylidene-
phosphorane form III—even with four methyl groups as ring sub-
stituents. Thus, reaction of P3 with 1-AdN3 leads to 1-adamantyl-
=
field shifted similar to the parent Ph3P C5H4 (8). No allylic ring
protons (all-HCp) can be observed, instead NH protons appear
at high field. Formulation of 1 and 7 as iminophosphoranes is
strongly supported by characteristic 2JC,P coupling constants being
considerably smaller compared to 2–6, furthermore chemical shifts
in the 1H and 13C NMR spectra of the Me4C5H moiety, correlate
well with the phosphane P314 and with the 13C resonances of the
parent 1,2,3,4-tetramethylcyclopenta-1,3-diene.15 The assignment
amino-tetramethylcyclopentadienylidene-P-phosphorane
4
in
close to quantitative yield as the only tautomer (type III) observed
in solution. This fact underlines the strong N-basicity and expected
Scheme 2
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donor strength of these ambident cyclopentadienyl-phosphazene
ligands, in particular, when C-, P- and N-substituents are alkyl
groups. Scheme 3 summarizes the trends of the favored isomers.
They are easily rationalized by the relative acidity of the Me4C5–H
and N–H protons (Scheme 3).
˚
(1.6490(12)–1.6589(13) A) are significantly longer compared
=
to structurally characterized iminophosphoranes PhN PPh3
(1.602(3) A) and 2,6-Me2PhN PPh3 (1.553(2) A). The P–
CPh bond lengths in 3 and 6 vary within 1.8111(15)–1.8138(17)
A and are nearly the same as found in Ph3P C5H4 (1.802(2)–
17
18
˚
˚
=
˚
=
˚
1.808(2) A). Other parameters such as average angles CCp–P–CPh
angles (114.3◦, 110.1◦) or CPh–P–CPh (105.73◦, 106.94◦) for P-
ꢀ
phenyl substituted 3 and 6◦are also similar to those observed
◦
=
in Ph3P C5H4 (110.2–112.6 and 105.8–109.2 ). Although both
structures show significant repulsion between phenyl groups
and the sterically hindered N-substituent, they have different
conformational positions of the R–N groups toward the Cp-ring.
In the case of 2,6-diisopropylphenyl group in 6 the R–N group
Scheme 3
has the nearly trans-orientation to the Cp-ring (C–N–P–CCp
=
153.09(11)◦) and occupies the gauche-conformation between both
Ph-groups, whereas the Ad–N group in 3 has trans-orientation
to one of the phenyl substituents (CPh–P–N–C = 164.84(15)◦)
and occupies the gauche-conformation between the Cp- and Ph-
groups.
Structures
The molecular structures of P-amino-cyclopentadienylidene-
phosphoranes 3, 4 and 6 appear to be rather similar (Fig. 1),
however certain differences are worth discussing. Suitable crystals
for X-ray structure analysis of 3 and 6 were afforded upon
crystallization from chloroform, whereas highly soluble 4 is
crystallized from less polar solvents such as benzene. Molecular
structures of 3, 4 and 6 with thermal ellipsoids of 50% probability
are shown in Fig. 1.
In the molecular structure of 4 having small methyl groups at
the P atom: the molecule is less strained, so that the Ad–N group
and the Me4C5-ring have an anti-periplanar conformation and
the H–N lies nearly under the Me4C5-ring (with a plane angle of
78.13◦ between the (H–N, N, P) and the (C5, C1, C2) planes).
Consequently an extremely high-field shifted NMR resonance for
NH (1.35 ppm) is observed as a result of the strong anisotropic
effect of the aromatic Me4C5-ring.
The P–CCp and P–N bond lengths are similar in these com-
pounds (Table 3). The P–CCp bond lengths lie in the range of
˚
Comparing the N-adamantyl structures 3 and 4 we find, that—
due to perfect negative hyperconjugation—a slightly elongated
1.7184(14)–1.7345(18) A and are only slightly longer than that
16
˚
=
in Ph3P C5H4 8 (1.718(2) A), whereas P–N bond distances
Fig. 1 ORTEP23 drawing of the molecular structures of 3, 4 and 6. All hydrogen atoms except for the N–H ones are omitted for clarity; 50% probability
thermal ellipsoids are presented for all non-hydrogen atoms.
◦
4
˚
Table 3 Selected bond distances (A), angles and torsion angles ( ) for 3, 4 and 6
3
4
6
P–CPh
P–CPh
P–CCp
P–N
1.8138(17)
1.8134(17)
1.7345(18)
1.6491(17)
1.493(2)
—
—
1.8111(15)
1.8137(15)
1.7184(14)
1.6490(12)
1.4467(18)
ꢀ
1.7239(15)
1.6589(13)
1.4821(18)
N–C
C
C
Cp–P–N
Ph–P–N, CPh –P–N
115.43(8)
103.92(8), 108.47(8)
128.00(12)
108.23(7)
109.63(8), 109.61(9)
133.77(10)
108.88(7)
106.46(6), 114.26(6)
125.60(10)
ꢀ
P–N–C
Cp–P–N–C
C
72.82(17)
167.82(14)
153.09(11)
912 | Dalton Trans., 2008, 909–915
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P–N bond in 4 corresponds with a shorter P–CCp bond, whereas
in 3 a longer P–CCp bond corresponds to a shorter P–N one.
P-(1-Adamantylamino)-dimethyl-cyclopentadienylidene-phos-
phorane (2). To a stirred suspension of TlCp (2.16 g, 8.02 mmol,
1.05 eq.) in THF (50 mL) Me2PCl (0.75 g, 7.78 mmol) was added
via a syringe keeping the temperature at 0 ◦C. The reaction mixture
was allowed to warm up to r.t. within a period of 1 h, the precipitate
of TlCl was filtered off and 1-AdN3 (1.65 g, 9.34 mmol, 1.2 eq.)
were added at once. The reaction mixture was allowed to stir for
12 h at r.t., diluted with diethyl ether (30 mL) furnishing a yellow
precipitate that was filtered off and washed with diethyl ether (3 ×
25 mL) yielding 0.55 g of a beige powder. (Yield of the crude
product: 10–15%.) Repeated crystallization from toluene gives an
Conclusion
The Staudinger reaction of cyclopentadienyl-phosphanes with
azides is a convenient protocol for the synthesis of a new class
of ambident organophosphorus(V) CpPN ligands. They occur
either in their P-amino-cyclopentadienylidene-phosphorane or in
their P-cyclopentadienyl-iminophosphorane tautomeric form. It
was found that the equilibrium between both tautomers strongly
depends on the relative Brønstead acidity of the (R)nCp–H and
RN–H protons. The iminophosphorane form is only realized in
a limited number of representatives of this CpPN ligand family
revealing a low CH-acidity and low N-basicity. Further systematic
studies on different series of new organometallic complexes of s-,
p-, d- and f-elements with this new CpPN ligand family are the
subject of our current efforts.19
1
analytically pure sample. H (300.1 MHz, C6D6): d = 1.21 (d,
2JH,P = 13.2 Hz, 6 H, PMe2), 1.36 (m, 6 H, Ad), 1.41 (m, 6 H, Ad),
1.57 (m, NH), 1.76 (m, 3 H, Ad), 6.66 (m, 2 H, HCp), 6.95 (m,
1
2 H, HCp) ppm. 13C{ H} (75.5 MHz, C6D6): d = 16.5 (d, 1JC,P
=
71 Hz, Me2P), 29.9 (s, CH2(CH-)2), 36.0 (s, CH(CH2-)3), 44.8 (d,
3JC,P = 3.9 Hz, -CCH2CH-), 52.9 (d, 2JC,P = 3.9 Hz, -NC(CH2)3-),
1
86.7 (d, JC,P = 126 Hz, ipso-CCp), 113.1 (d, J = 17.6 Hz, CCp),
114.4 (d, J = 18.7 Hz, CCp) ppm. 31P{ H} (81.0 MHz, C6D6): d =
1
21.0 ppm. EI-MS: m/z (%) = 275 (100) [M+], 141 (11.1) [M+ +
H − Ad], 135 (20) [Ad+]. C17H26NP (275.4): calcd C 74.14, H 9.44,
N 5.08; found C 73.81, H 9.05, N 5.32%.
Experimental
General considerations
All manipulations were performed under purified argon or nitro-
gen using standard high vacuum or Schlenk-tube techniques, or in
a glovebox. Solvents were dried and distilled under argon employ-
ing standard drying agents. All organic reagents were purified by
conventional methods. NMR spectra were recorded at +25 ◦C
on Bruker ARX200, Bruker AMX300, and Bruker AVANCE
DRX400 instruments. Elemental analyses were performed at the
Analytical Laboratory of the Chemistry Department/Philipps-
Universita¨t Marburg. Mass spectra were obtained on a Varian
MAT CH7A spectrometer (70 eV, EI). Starting materials 1-
P-(1-Adamantylamino)-diphenyl-cyclopentadienylidene-phos-
phorane (3). To a suspension of TlCp (1.70 g, 6.5 mmol) in THF
(50 mL) was added Ph2PCl (1.42 g, 6.4 mmol) at r.t. followed by
stirring for 1 h. The precipitate of TlCl was filtered off and washed
with THF (2 × 5 mL). To a solution of thus generated phosphane
P2 1-AdN3 (1.4 g, 7.1 mmol, 1.2 eq.) was added at once. A slightly
exothermic reaction occurs with the formation of a yellow solution
and gas evolution. The reaction mixture was stirred over night. It
was diluted with diethyl ether and the white precipitate that formed
was filtered off, washed with diethyl ether (2 × 10 mL) and dried
under vacuum to give 1.80 g of 3 in the form of white powder.
Yield: 69%. Compound is soluble in THF, CHCl3, not soluble in
AdN3,20 DipN3,21 C5Me4H–PMe2,22 C5H5–PMe2 and C5H5–PPh2
9
were prepared with minor modifications to published methods.
Ph2PCl and Me3SiN3 were used as supplied (Merck).
1
benzene, diethyl ether and hexane. H (400.1 MHz, CDCl3): d =
1.52 (m, 6 H, Ad), 1.72 (s, 6 H, Ad), 1.96 (s, 3 H, Ad), 2.71 (d,
2JH,P = 5.8 Hz, 1 H, NH), 6.35 (m, 2 H, HCp), 6.39 (m, 2 H, HCp),
Synthesis
1
N-Trimethylsilyl-P-(2,3,4,5-tetramethylcyclopenta-2,4-dienyl)-
dimethyl-iminophosphorane (1). P3 was generated from
LiC5Me4H (1.61 g, 12.6 mmol) and Me2PCl (1.27 g, 13.2 mmol,
1.05 eq.) at r.t. in diethyl ether–hexane (1 : 1, 100 mL). LiCl
was removed by filtration, solvent was carefully removed and
phosphane P3 (2.05 g, 11.3 mmol, 90%) was dissolved in toluene
(20 mL) and Me3SiN3 (2.6 g, 22.6 mmol, 2.0 eq.) was added. The
reaction mixture was stirred for 48 h at 60 ◦C. Slow evolution
of N2 was observed. All volatiles were removed under vacuum
(60 ◦C for 2 h) furnishing 2.6 g (9.7 mmol) of 1a as a transparent
7.56 (m, 6 H, Ph), 7.97 (m, 4 H, o-Ph) ppm. 13C{ H} (100.6 MHz,
CDCl3): d = 29.6 (s, CH2(CH-)2), 35.6 (s, CH(CH2-)3), 44.7 (d,
3JC,P = 4.3 Hz, -CCH2CH-), 54.1 (d, 2JC,P = 3.5 Hz, -NC(CH2-)3),
1
84.0 (d, JC,P = 126 Hz, ipso-CCp), 113.8 (d, J = 18.1 Hz, CCp),
116.5 (d, J = 17.2 Hz, CCp), 128.4 (d, J = 12.9 Hz, Ph), 129.6 (d,
J = 104 Hz, Ph), 132.1 (d, J = 2.6 Hz, Ph), 132.9 (d, J = 10.4 Hz,
1
Ph) ppm. 31P{ H} (81.0 MHz, CDCl3): d = 22.0 ppm. EI-MS:
m/z (%) = 399 (100) [M+], 335 (3) [M+ − C5H4], 265 (82) [M+ −
Ad − H]. C27H30NP (399.5): calcd C 81.17, H 7.57, N 3.51; found
C 81.38, H 7.55, N 3.58%.
1
pale yellow oil in 86% yield. H NMR (300.1 MHz, C6D6): d =
0.36 (s, 9 H, Me3Si), 0.95 (d, 2JH,P = 12.6 Hz, 6 H, PMe2), 1.64 (s,
P - (2,6 - Diisopropylphenylamino) - dimethyl - cyclopentadienyl -
idene-phosphorane (5). Phosphane P1 was generated as in the
procedure above for 2 from TlCp (2.65 g, 9.9 mmol, 1.04 eq.)
and Me2PCl (0.92 g, 9.5 mmol) at 0 ◦C. After the addition of
DipN3 (1.8 g, 10.2 mmol, 1.1 eq.) the reaction mixture was stirred
over night. Removal of solvent yields an intractable oil, that after
trituration with diethyl ether gives 2.14 g (7.1 mmol) of 5 in the
form of a slightly yellow powder. Yield: 75%. Compound is soluble
in THF, CHCl3, sparingly in benzene; not soluble in diethyl ether,
hexane. 1H (300.1 MHz, C6D6): d = 1.08 (d, 3JH,H = 6.9 Hz, 6 H,
2
6 H, Me–Cp), 1.93 (s, 6 H, Me–Cp), 2.98 (d, JH,P = 25.5 Hz, 1
1
H, all-HCp) ppm. 13C{ H} NMR (75.5 MHz, C6D6): d = 4.7 (s,
Me3Si), 11.3 (s, Me–Cp), 14.7 (s, Me–Cp), 17.5 (d, 1JC,P = 66 Hz,
Me2P), 63.8 (d, 1JC,P = 58 Hz, all-CCp), 131.3 (d, J = 4.0 Hz, CCp),
1
139.2 (d, J = 6.8 Hz, CCp) ppm. 31P{ H} NMR (81.0 MHz, C6D6):
d = 1.1 (1a), 5.6 (1b), −10.1 (1c), 1a : 1b : 1c = 7 : 2 : 1. EI-MS: m/z
(%) = 269 (4.5) [M+], 149 (63.2) [M+ − C5Me4], 148 (12.6) [M+ −
C5HMe4], 134 (77.5) [M+ − Me − C5Me4]. C14H28NPSi (269.5):
calcd C 62.41, H 10.47, N 5.20; found C 62.87, H 10.62, N 4.78%.
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2
1
3
V = 2142.5(5) A , Z = 4, Dc = 1.238 g cm−3, l(Mo-Ka) =
0.142 mm−1. Crystal dimensions 0.32 × 0.28 × 0.24 mm. Data
were collected with an area detector using x-scans at 180(2) K
on a IPDS STOE diffractometer using graphite monochromated
Me2CH-), 1.13 (d, JH,P = 13.0 Hz, 6 H, Me2P), 3.21 (d, JH,P
=
˚
3
6.6 Hz, 1 H, NH), 3.43 (sept, JH,H = 6.9 Hz, 2 H, Me2CH-),
6.74 (m, 2 H, HCp), 6.99 (m, 2 H, HCp), 6.95 (m, 1 H, p-Dip),
7.05 (m, 2 H, m-Dip) ppm. 13C{ H} (75.5 MHz, C6D6): d = 13.8
1
1
(d, JC,P = 72 Hz, Me2P), 24.2 (s, Me2CH-), 28.3 (s, Me2CH-),
˚
Mo-Ka radiation (k = 0.71073 A). The structure was solved
1
83.1 (d, JC,P = 133 Hz, ipso-CCp), 113.6 (d, J = 16.0 Hz, CCp),
by direct methods and expanded by difference-Fourier syntheses
using SHELX-97 software package.23 13689 reflections measured,
3872 unique (Rint = 0.0571), which were used in all calculations.
GoF (on F2) = 0.861. The final agreement factors were R1 = 0.0343
[I>2.00r(I)] and wR2 = 0.0699 (all).
114.9 (d, J = 19.3 Hz, CCp), 124.1 (d, J = 1.7 Hz, Dip), 127.8 (s,
Dip), 132.2 (d, J = 5.5 Hz, Dip), 148.5 (d, J = 2.6 Hz, Dip) ppm.
31P{ H} (81.0 MHz, C6D6): d = 27.4 ppm. EI-MS: m/z (%) = 301
1
(100) [M+], 286 (96) [M+ − CH3], 258 (79) [M+ − C3H7]. C19H28NP
(301.4): calcd C 75.71, H 9.36, N 4.65; found C 75.39, H 9.33, N
4.70%.
For 6. C29H32NP, M = 425.53, monoclinic, space group P21/c,
◦
˚
˚
˚
a = 9.781(2) A, b = 23.416(2) A, c = 10.692(3) A, b = 99.73(2) ,
P - (2,6 - Diisopropylphenylamino) - diphenyl - cyclopentadienyl -
idene-phosphorane (6). The same procedure as for 3 is applied
starting from TlCp (1.43 g, 5.3 mmol, 1.04 eq.), Ph2PCl (1.13 g,
5.1 mmol) and DipN3 (1.2 g, 5.9 mmol, 1.2 eq.). 1.84 g (4.3 mmol)
of 6 in the form of a colorless powder is isolated. Yield: 85%. 6
is soluble in THF, CHCl3, sparingly in benzene; not soluble in
diethyl ether, hexane. 1H NMR (300.1 MHz, CDCl3): d = 0.81 (d,
3
V = 2413.6(9) A , Z = 4, Dc = 1.171 g cm−3, l(Mo-Ka) =
˚
0.130 mm−1. Crystal dimensions 0.80 × 0.80 × 0.32 mm. Data
were collected as above. The structure was solved as above. 16848
reflections measured, 4597 unique (Rint = 0.0673), which were
used in all calculations. GoF (on F2) = 1.030. The final agreement
factors were R1 = 0.0396 [I>2.00r(I)] and wR2 = 0.1065 (all).
3JH,H = 6.9 Hz, 12 H, Me2CH-), 3.25 (sept, JH,H = 6.9 Hz, 2 H,
3
Me2CH-), 4.53 (d, 2JH,P = 7.2 Hz, 1 H, NH), 6.37 (m, 2 H, HCp),
6.49 (m, 2 H, HCp), 7.01 (d, J = 7.8 Hz, Ar), 7.21 (t, J = 7.8 Hz,
Acknowledgements
Ar), 7.36 (m, 6 H, Ph), 7.53 (m, 4 H, Ph) ppm. 13C{ H} NMR
1
Financial support by the Deutsche Forschungsgemeinschaft (Pri-
ority Program 1166) and Fonds der Chemischen Industrie is
gratefully acknowledged. K.A.R. and A.R.P. are very grateful to
Prof. Manfred Meisel (Institut fu¨r Chemie, Humboldt-Universita¨t
zu Berlin) for his munificent support during our stay at his research
group.
(75.5 MHz, CDCl3): d = 23.0 (s, Me2CH-), 28.6 (s, Me2CH-), 83.1
(d, 1JP,C = 133 Hz, ipso-CCp), 114.5 (d, J = 18.9 Hz, CCp), 116.9 (d,
J = 17.4 Hz, CCp), 123.9 (s, Dip), 126.8 (s, ipso-Dip), 128.1 (d, J =
12.4 Hz, Ph), 128.4 (s, Dip), 131.6 (d, J = 5.9 Hz, Ph), 132.5 (d, J =
2.9 Hz, Ph), 133.5 (d, J = 10.9 Hz, Ph), 148.4 (d, J = 2.5 Hz, Dip)
ppm. 31P{ H} NMR (81.0 MHz, CDCl3): d = 28.9 ppm. EI-MS:
1
m/z (%) = 425 (100) [M+], 410 (48) [M+ − CH3], 382 (47) [M+ −
C3H7]. C29H32NP (425.6): calcd C 81.85, H 7.58, N 3.29; found C
82.08, H 7.68, N 3.27%.
References
1 K. A. Rufanov, B. Ziemer, M. Hummert and S. Schutte, Eur. J. Inorg.
Chem., 2004, 4759–4763.
N-(2,6-Diisopropylphenyl)-P-(2,3,4,5-tetramethylcyclopenta-2,
4-dienyl)-dimethyl-iminophosphorane (7). The same procedure as
for 1 from P3 (2.05 g, 11.3 mmol) and DipN3 (2.52 g, 12.4 mmol,
1.1 eq.). Purification was achieved by repetitive crystallization
from hexane at −80 ◦C giving a pale rose powder. Compound
7 is very air-sensitive; highly soluble in all common solvents. The
NMR data of the main tautomer (7a) are presented (ca. 90% by
2 (a) P. J. Shapiro, E. E. Bunel, W. P. Schaefer and J. E. Bercaw,
Organometallics, 1990, 9, 867–869; (b) P. J. Shapiro, W. D. Cotter, W. P.
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Lai (Dow Chemical Co.), Eur. Pat. Appl., EP 0 416 815 A2, 1991
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1H, 31P NMR): 1H NMR (300.1 MHz, C6D6): d = 1.02 (d, 2JH,P
=
11.7 Hz, 6 H, Me2P), 1.34 (d, 3JH,H = 7.0 Hz, 12 H, Me2CH-), 1.65
(m, 6 H, Me–Cp), 1.97 (s, 6 H, Me–Cp), 3.37 (d, 2JH,P = 26.8 Hz,
3
4 Part 3: K. A. Rufanov, A. R. Petrov, V. V. Kotov, F. Laquai and J.
Sundermeyer, Eur. J. Inorg. Chem., 2005, 3805–3807.
all-HCp), 3.65 (sept, JH,H = 7.0 Hz, 2 H, Me2CH-), 7.10 (m, 1
H, p-Dip), 7.24 (m, 2 H, m-Dip) ppm. 13C{ H} NMR (75.5 MHz,
1
5 This tautomerism is precedented, see e.g.: A. S. Batsanov, M. G.
Davidson, I. Ferna´ndez, J. A. K. Howard, F. Lo´pez-Ortiz and R. D.
Price, J. Chem. Soc., Perkin Trans. 1, 2000, 4237–4239. For a more
general review on phosphorous-carbon prototropic tautomerism, see:;
T. A. Mastryukova and M. I. Kabachnik, Russ. Chem. Rev. (Engl.
Transl.), 1983, 52, 1012–1029.
6 For a recent paper addressing this regioisomerism, see: S. El Chaouch,
J.-C. Guillemin, T. Ka´rpa´ti and T. Veszpre´mi, Organometallics, 2001,
20, 5405–5412 and references therein.
7 J. R. Goerlich, M. Farkens, A. Fischer, P. G. Jones and R. Schmutzler,
Z. Anorg. Allg. Chem., 2004, 620, 707–715.
8 Y. G. Gololobov and L. F. Kasukhin, Tetrahedron, 1992, 48, 1353–1406.
9 F. Mathey and J.-P. Lampin, Tetrahedron, 1975, 31, 2685–2690.
10 Diels–Alder like dimerisation is promoted by P-oxidation of sterically
unprotected cyclopentadienyl-phosphanes (cf. ref.9) yielding a complex
mixture of isomers.
1
C6D6): d = 11.4 (s, Me–Cp), 13.8 (d, JC,P = 62 Hz, Me2P), 14.7
(s, Me–Cp), 24.2 (s, Me2CH-), 28.9 (s, Me2CH-), 63.0 (d, 1JC,P
=
62 Hz, ipso-CCp), 119.4 (d, J = 3.2 Hz, Dip), 123.0 (d, J = 2.5 Hz,
Dip), 131.4 (d, J = 3.7 Hz, CCp), 140.0 (d, J = 6.9 Hz, CCp), 142.2
(d, J = 7.1 Hz, Dip), 145.9 (d, J = 3.4 Hz, Dip) ppm. 31P{ H}
1
NMR (81.0 MHz, C6D6): d = −3.1 ppm. EI-MS: m/z (%) = 357
(1.3) [M+], 253 (10.9) [M+ − C3H7 − 4 CH3], 237 (1) (M+ − C5Me4).
C23H36NP (357.5): calcd C 77.27, H 10.15, N 3.92; found C 77.69,
H 10.23, N 3.90%.
Crystal data
For 3. C27H30NP, M = 399.49, monoclinic, space group P21/c,
11 An explanation might be a 1,3-dipolar addition of azide to the activated
double bond of the indenyl-phosphane as one of the side reactions.
◦
˚
˚
˚
a = 11.418(2) A, b = 9.773(1) A, c = 19.444(3) A, b = 99.07(2) ,
914 | Dalton Trans., 2008, 909–915
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©

View Article Online
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14 1H NMR (300.1 MHz C6D6): d = 0.83 (d, 2JH,P = 4.7 Hz, Me2P), 1.72
(s, Me–Cp), 1.92 (s, Me–Cp), 2.79 (s, all-HCp) ppm; 13C (75.5 MHz,
C6D6): d = 57.4 (d, J = 23 Hz, all-CCp), 133.6 (d, J = 2 Hz, CCp), 136.2
(d, J = 3 Hz, CCp) ppm.
22 M. Visseaux, A. Dormond, M. M. Kubicki, C. Mo¨ıse, D. Baudry and
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23 G. M. SheldrickProgram for solution of crystal structures, SHELXS-
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15 13C NMR (75.5 MHz, CDCl3): d = 11.6, 14.4, 48.2, 132.0, 136.0 ppm.
16 H. L. Ammon, G. L. Wheeler and P. H. Watts, J. Am. Chem. Soc., 1973,
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This journal is
The Royal Society of Chemistry 2008
Dalton Trans., 2008, 909–915 | 915
©