1-Dialkylamino-1-phospha-[1]ferrocenophanes - Synthesis and characterisation

Article abstract of DOI:10.1016/S0022-328X(99)00078-9

1-Diisopropylamino-1-phospha-[1]ferrocenophane, fc[P-NⁱPr₂] (1), has been prepared from 1,1′-dilithioferrocene and diisopropylamino-dichlorophosphane. A complete set of NMR data (¹H-, ¹³C-, ¹⁵N-, ³¹P-NMR) supports the monomeric structure of 1 in solution, which has been confirmed by an X-ray structure analysis for the solid state. The nitrogen atom is in a planar environment (sum of angles 359.3°); the distorted sandwich structure contains ecliptic cyclopentadienyl rings which include an angle of α=27.89°. The reactions of 1 with sulfur, selenium and bis(triphenylphosphane)(ethene)platinum(0) are discussed.

Full text of DOI:10.1016/S0022-328X(99)00078-9

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Journal of Organometallic Chemistry 582 (1999) 352–357
1-Dialkylamino-1-phospha-[1]ferrocenophanes—synthesis and
characterisation
Max Herberhold *, Frank Hertel, Wolfgang Milius, Bernd Wrackmeyer
Laboratorium fu¨r Anorganische Chemie, Uni6ersita¨t Bayreuth, Postfach 10 12 51, D-95440 Bayreuth, Germany
Received 19 November 1998
Abstract
1-Diisopropylamino-1-phospha-[1]ferrocenophane, fc[PꢀNiPr2] (1), has been prepared from 1,1%-dilithioferrocene and diiso-
propylamino-dichlorophosphane. A complete set of NMR data (1H-, 13C-, 15N-, 31P-NMR) supports the monomeric structure of
1 in solution, which has been confirmed by an X-ray structure analysis for the solid state. The nitrogen atom is in a planar
environment (sum of angles 359.3°); the distorted sandwich structure contains ecliptic cyclopentadienyl rings which include an
angle of h=27.89°. The reactions of 1 with sulfur, selenium and bis(triphenylphosphane)(ethene)platinum(0) are discussed.
© 1999 Elsevier Science S.A. All rights reserved.
Keywords: Ferrocene; [1]Ferrocenophane; Phosphorus; NMR; X-Ray analysis
1. Introduction
2. Results and discussion
Structural distortions in [1]ferrocenophanes as com-
pared with ferrocene have recently attracted consider-
able interest [1,2]. The synthetic potential due to the
strained bonding situation in such compounds has been
exploited in insertion reactions [3,4] and in ring-opening
polymerisations (ROP) [4–10], which can be conducted
under thermal [7,8], anionic [9] or coordination-
catalysed [10] conditions. Although 1-organo-1-phos-
pha-[1]ferrocenophanes have been known since 1980
[11,12], the first P-functionally substituted derivative,
1-chloro-1-phospha-[1]ferrocenophane (fc[PꢀCl]) was
prepared and structurally characterised only recently
[8]. However, it appears that its limited stability in
solution may prevent a more widespread synthetic ap-
plication. We report here on the synthesis and charac-
terisation of the first 1-amino-substituted 1-phospha-
[1]ferrocenophanes.
2.1. Synthesis and reacti6ity of 1-diisopropylamino-1-
phospha-[1]ferrocenophane (1) and 1-(2,2,6,6,-tetra-
methylpiperidino)-1-phospha[1]ferrocenophane (2)
In principle, the reaction of 1,1%-dilithioferrocene
with amino-dichlorophosphanes, R2NꢀPCl2, should
provide a straightforward route to 1-amino-1-phospha-
[1]ferrocenophanes, fc[PꢀNR2]. However, so far only
dichlorophosphanes bearing a bulky diisopropylamino-
or 2,2,6,6-tetramethylpiperidino group, respectively,
could be converted to the desired [1]ferrocenophanes 1
and 2 (Scheme 1). The analogous reaction with diethyl-
amino-dichlorophosphane was not successful.
The [1]ferrocenophanes 1 and 2 were isolated as
dark-red solids which, in pure crystalline state, can be
handled in air. Their solutions in hexane or benzene are
stable for weeks at room temperature if air and mois-
ture are rigorously excluded. However, THF solutions
of 1 decompose within several hours, and 1 is converted
into a brown insoluble solid. Some typical reactions of
1 are presented in Scheme 2.
* Corresponding author. Tel.: +49-921-552-540; fax: +49-921-
552-157.
E-mail address: max.herberhold@uni-bayreuth.de (M. Herberhold)
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00078-9

M. Herberhold et al. / Journal of Organometallic Chemistry 582 (1999) 352–357
353
are based on 2D 1H/1H COSY and NOESY and 13C/1H
HETCOR spectra. In the case of 1, the Hahn-echo
extended (HEED [15]) INEPT experiment [16] is readily
applied to record the 15N satellites and to measure the
1
isotope induced chemical shift D14/15N(31P) at natural
abundance in the 31P-NMR spectra with high accuracy
(91 ppb). This technique suppresses the intensity of
the parent signal belonging to the 31P–14N isotopomer
(Fig. 1). The normal 31P{1H}-NMR spectra serve for
detecting the 13C and 15N satellites and for determining
with slightly lower accuracy (92 ppb), using more
spectrometer time, both D12/13C(31P) and D14/15N(31P)
as shown for 2 in Fig. 2. The 15N satellites are signifi-
cantly sharper than the 13C satellites since the latter
belong to the 13C–31P–14N isotopomer in which the
31P-NMR signals are broadened by partially relaxed
1
1
Scheme 1.
Like other phosphanes, 1 reacts with sulfur and
selenium in a 1:1 ratio to give the sulfide 3 and the
selenide 4, respectively. There was no reaction of 1 with
tellurium at room temperature or after heating in ben-
zene at 60°C for several minutes. The potential of 1 as
a ligand in transition metal complexes has been tested
scalar 31P–14N coupling. The magnitude of 1D14/15
-
N(31P) is in the range known for aminophosphanes
1
[15,17]. However, D12/13C(31P) is more negative than in
comparable organophosphanes (e.g. Ph3P: 1D12/13
-
C(31P)= −22.7 ppb [18]). Although the data set avail-
able for these parameters is still limited, the outlook is
promising since it appears that extreme bonding situa-
tions, such as in [1]ferrocenophanes, are reflected by
noticeable changes in the magnitude of isotope induced
chemical shifts. Therefore, it might be worthwhile to
in the reaction of
1
with bis(triphenylphos-
phane)(ethene)platinum, Pt(PPh3)2C2H4. A mixture of
two platinum complexes 5 and 6 is obtained, indepen-
dent of the molar ratio of the reactants and of the
reaction conditions. This mixture is stable in solution
for several weeks, even in the presence of an excess of
1.
1
determine D12/13C(M) for M=13C, 29Si, 119Sn in other
[1]ferrocenophanes.
The formation of the sulfide 3 and the selenide 4
follows unambiguously from the NMR data (Section
3), the [1]ferrocenophane structure being retained. Simi-
larly, this strained structure is retained in the platinum
complexes 5 and 6, although one might have expected
that insertion into one of the PꢀC bonds could have
taken place (cf. [3,4]). However, complementary 31P-
and 195Pt-NMR data (Section 3) provide clear evidence
for the presence of a two-coordinate (5) and a three-co-
ordinate Pt(0) complex (6). The magnitude of the cou-
2.2. NMR Spectra of 1 and 2 and of some deri6ati6es
of 1 in solution
A fairly complete NMR data set of 1 and 2 proves
that they possess monomeric structures in solution
(Table 1). The inversion at the phosphorus atom in
both 1 and 2 is apparently slow on the NMR time
1
scale, and four different H and 13C signals are there-
fore observed for the ferrocene core; the assignments
Scheme 2.

354
M. Herberhold et al. / Journal of Organometallic Chemistry 582 (1999) 352–357
Table 1
NMR dataa of the 1-dialkylamino-1-phospha-[1]ferrocenophanes 1 and 2
No.
l
1H (C5H4)
l
1H (NR2)
l
13C (C5H4)
l
13C (NR2)
l
31Pb
l
15N
1
4.37 (2/7)
4.30 (3/8)
4.16 (4/9)
4.36 (5/10)
3.47 (11.5) CH
1.22 (B1) (Me)
78.1 (7.8) (2/7)
78.2 (1.0) (3/8)
75.1 (12.1) (4/9)
76.1 (49.0) (5/10)
34.7 (53.2) (1/6)
49.5 (10.1) (CH)
24.2 (8.1) (Me)
31.1
−310.6
(64.7)
2
4.49 (2/7)
4.16 (3/8)
4.01 (4/9)
4.37 (5/10)
1.41 (B1) (Me)
1.36 (B1) (CH2)
1.18 (B1) (ꢀCH2ꢀ)
79.8 (11.7) (2/7)
76.9 (3.0) (3/8)
74.5 (16.6) (4/9)
79.1 (68.0) (5/10)
40.9 (69.6) (1/6)
57.3 (12.5) NC
28.3
−286.5
(86.4)
42.7 (2.3) (CꢀCH2)
32.6 (13.2) (CꢀMe)
17.6 (0.8) (ꢀCH2ꢀ)
1
a The numbering scheme corresponds to that of the molecular structure of 1 (Fig. 3). Coupling constants J(31P, H), J(31P,13C) and J(31P, 15N)
are given in parentheses.
b Isotope induced chemical shifts; 1: 1D12/13C(31P)=−40.092 ppb; 1D14/15N(31P)=−35.091 ppb (Hahn-echo experiment; Fig. 1); 2:
1D12/13C(31P)=−35.792 ppb; 1D14/15N(31P)=−39.092 ppb (Fig. 2).
1
pling constants J(195Pt, 31P) is typical of Pt(0) com-
plexes, and the 195Pt resonances at low frequency (l195
Pt: −502.7) and high frequency (l195 Pt: −28.6) are
characteristic of two-coordinate and three-coordinate
Pt(0) phosphane complexes, respectively [19].
The angles i which describe the inclination of the
C(1)ꢀP and C(6)ꢀP connections relative to their respec-
tive cyclopentadienyl planes are significantly larger
(41.2° average in 1) than the analogous angles in the
t
other fc[PꢀR] complexes (R=Cl [8], Bu [13], and Ph
[13,14]) where average i values between 31.9 and 32.8°
have been observed. Apparently, the phosphorus atom
in fc[PꢀNiPr2] (1) is shifted closer to the ferrocenophane
cave although the iron atom tries to avoid close Fe···P
contacts. The distance of the Fe atom from the line
connecting the two midpoints of the cyclopentadienyl
rings, Z(1) and Z(6), is 30.4 pm in fc[PꢀNiPr)2] (1) as
compared with 27.7(8) pm in fc[PꢀCl] [8]; the distances
FeꢀZ(1) (163.8 pm) and FeꢀZ(6) (163.3 pm) are very
close to the value of 166 pm in ferrocene [20]. Both
cyclopentadienyl rings are planar (within experimental
2.3. X-ray structural analysis of fc[PꢀNiPr2] (1)
Dark red prisms of 1 were grown from hexane solu-
tion in the refrigerator (8°C). The complex 1 crystallises
in the monoclinic system with four molecules in the unit
cell. The distorted sandwich structure of 1 is shown in
Fig. 3; selected bond lengths and angles are given in
Table 2.
The nitrogen atom of the diisopropylamino group
has a planar environment, the sum of the angles at N
being 359.3°. The plane containing P, N, C(11), C(14)
and also the two single hydrogen atoms of the iso-
propyl substituents forms an angle of 8.3° with the Fe,
P, N plane and is arranged almost perpendicular (82.1°)
with respect to the line connecting C(1) and C(6). This
indicates that the lone pair of electrons at the nitrogen
atom can interact (n–s*) with the PꢀC(1) and PꢀC(6)
bonds.
Table 3 contains a collection of typical molecular
parameters of 1 together with those of related 1-phos-
pha-[1]ferrocenophanes, fc[PꢀR], which have been
structurally characterised by X-ray crystallography.
The molecular distortions in phospha-[1]ferro-
cenophanes, fc[PꢀR], can be conveniently described
[1a,8] by a set of four angles (h, i, l and q) which are
defined in Fig. 4.
Compared with 1-chloro-1-phospha-[1]ferroceno-
phane, fc[PꢀCl] [8], the (non-bonding) iron–phosphorus
distance in 1 is slightly longer (280.2(1) versus 271.5(6)
pm, Table 3), and concomitantly, both the angles l at
iron and q at phosphorus in 1 become slightly smaller.
Fig. 1. 103.1 MHz 31P-NMR spectrum of fc[PꢀNiPr2] (1) in C6D6,
recorded by using the HEED-INEPT pulse sequence with 1H decou-
pling [15] (Hahn-echo delay of 0.18 s; result of 200 transients,
spectrometer time 8 min). The 15N satellites are marked by asterisks
(1D14/15N(31P)= −35.091 ppb).

M. Herberhold et al. / Journal of Organometallic Chemistry 582 (1999) 352–357
355
Table 2
Selected bond lengths and angles in fc[PꢀNiPr2] (1)
Bond lengths (pm)
Fe···P
FeꢀC(1)
FeꢀC(2)
FeꢀC(3)
FeꢀC(4)
FeꢀC(5)
PꢀC(1)
NꢀC(11)
280.2(1)
197.7(2)
201.6(2)
208.8(3)
208.9(3)
203.1(2)
187.4(2)
147.1(3)
PꢀN
166.9(2)
198.2(2)
200.8(2)
207.6(3)
208.5(3)
203.0(1)
185.5(2)
148.7(2)
FeꢀC(6)
FeꢀC(7)
FeꢀC(8)
FeꢀC(9)
FeꢀC(10)
PꢀC(6)
NꢀC(14)
Bond angles (°)
Fe···PꢀN
C(1)ꢀPꢀN
C(6)ꢀPꢀN
C(1)ꢀPꢀC(6)
125.3(1)
110.0(1)
109.8(1)
88.8(1)
PꢀNꢀC(11)
PꢀNꢀC(14)
C(11)ꢀNꢀC(14)
125.0(1)
117.9(1)
116.4(2)
Fig. 2. 202.5 MHz 31P{1H}-NMR spectrum of 2 showing the parent
line together with 13C and 15N satellites (2716 transients; 2 h of
spectrometer time). Note that the 15N satellites (marked by asterisks;
1D14/15N(31P)= −3992 ppb) are much sharper than the 13C satel-
lites for 1J(31P, 13C(1,6)) (marked by open circles; 1D12/13C(31P)= −
3692 ppb) and 2J(31P, 13C(2,7)) (marked by arrows; 2D12/13C-
3. Experimental
3.1. Materials and instruments
(
31P)B2 ppb).
All reactions were performed in an atmosphere of
dry nitrogen, using carefully dried solvents and oven-
dried glassware. Starting materials such as ferrocene,
BuLi in hexane (1.6 M) and PCl3 were used as commer-
cial products; the amino-dichlorophosphanes [21] and
1,1%-dilithioferrocene [22] were prepared following the
literature procedures. EI–MS (70 eV): Varian MAT
CH7 with direct inlet. 1H-, 13C-, 15N- (INEPT refocused
error), and they are arranged in an ecliptic position, the
angle ~ describing the deviation from the ideal ecliptic
arrangement being only 1.4°.
[16], based on J(15N, H)=2.5 Hz, H decoupled) and
31P-NMR spectra were measured using Bruker ARX
250 and DRX 500 instruments, equipped with multinu-
clear units; chemical shifts are given with respect to
Me4Si [l 1H(C6D5H)=7.15, (C6D5CD2H)=2.03: l
13C(C6D6)=128.0, (C6D5CD3)=20.4], neat MeNO2 (l
15N=0 for J(15N)=10.136767 MHz), H3PO4 85%(aq.)
[l 31P=0 for J(31P)=40.480747 MHz], and l 195Pt=0
for J(195Pt)=21.4 MHz.
3
1
1
3.2. 1-Diisopropylamino-1-phospha-[1]ferrocenophane,
fc[PꢀNiPr2] (1)
A suspension of fcLi2(TMEDA) (11.4 mmol) in hex-
ane (200 ml) is cooled to −78°C and a solution of
iPr2NꢀPCl2 (2.30 g; 11.4 mmol) in hexane (30 ml) is
added dropwise. The reaction mixture is allowed to
warm up to 15°C, and insoluble material is immediately
removed by filtration. The filtrate is kept at −78°C for
12 h to give deep red needles of 1 [1.33 g; 42%; m.p.
dec.=133°C] which are dried in vacuo after decanting
the reddish solution. EI–MS: m/z (%)=315 (100)
[M+], 230 (40) [fcPMe+], 215 (50) [fcP+].
1-(2,2,6,6-Tetramethylpiperidino)-1-phospha-[1]ferro-
cenophane, fc[Pꢀtmp] (2), was obtained in the same
way as a bright red powder [yield 50%; m.p. dec.=
116°C], using 2,2,6,6-tetramethylpiperidino-dichloro-
Fig. 3. Two views of the molecular structure of fc[PꢀNiPr2] 1.

356
M. Herberhold et al. / Journal of Organometallic Chemistry 582 (1999) 352–357
Table 3
Characteristic molecular parameters in 1-phospha-[1]ferrocenophanes, fc[PꢀR]
R=Cl
R=tBu
R=Ph
R=Ph
R=NiPr2
[8]
[13]
[14]
[13]
This work
Bond lengths (pm)
Fe···P
FeꢀC(1)
FeꢀC(6)
C(1)···C(6)
PꢀC(1)
271.5(6)
276.3(1)
198.3(3)
197.8(4)
263.3(5)
185.4(3)
187.0(4)
277.4(3)
197.5(9)
198.3(9)
261.9(12)
183.6(9)
184.9(10)
277.4(1)
198.2(4)
197.9(4)
263.2(6)
184.9(5)
185.0(5)
280.2(1)
197.7(2)
198.2(6)
261.0(2)
187.4(2)
185.5(2)
195.4(17)
196.0(14)
260.6(17)
184.0(15)
183.4(20)
PꢀC(6)
Bond angles (°)a
h
27.0(6)
31.9(7)
160.4(6)
90.1
27.1
32.8
159.8
90.5(2)
26.7
32.5
160
90.6(3)
26.9
32.3
159.8
90.7(2)
27.8
i(average)
l
41.2(2)
157.1
88.8(1)
r
a See Fig. 4.
phosphane. EI–MS: m/z (%)=355 (82) [M+], 230
Structure solution and refinement: after applying
Lorentz, polarisation, and absorption corrections (C-
scans, min/max transmission factors: 0.4224/0.4556) the
position of Fe could be found by Patterson synthesis,
and the remaining atoms were located by consecutive
(100) [fcPMe+], 215 (68) [fcP+].
3.3. Reactions of 1 with sulfur, selenium and
[Pt(PPh3)2(C2H4)]
difference Fourier synthesis (Siemens SHELXTL-PLUS);
all non-hydrogen atoms were refined anisotropically;
the hydrogen atoms (on calculated positions) were
The reactions were carried out on a small scale in
NMR tubes. The sulfide 3 and the selenide 4 were
formed quantitatively, and in the case of the platinum
complex, a mixture of the Pt(0) complexes 5 and 6 was
identified. The latter reaction was carried out by mixing
the components either at room temperature or at −
78°C; the result was the same.
treated isotropically applying the riding model with a
2
,
fixed temperature factor (0.08 A ); refinement of 173
parameters converged at R/wR-values of 0.037/0.041;
the max/min residual electron density was 0.55/−0.32
−3
,
e A
.
3: 31P-NMR: l 31P=65.4. 4: 31P-NMR: l 31P=54.7,
1J(77Se, 31P)=792 Hz; 5: 31P-NMR: l 31P=97.6 d
(2J(31P, 31P)=68.0 Hz), [1J(195Pt, 31P)=4320 Hz] 1-
phospha-[1]ferrocenophane; 36.5 d (2J(31P, 31P)=68.0
Hz), [1J(195Pt, 31P)=3525 Hz] PPh3; 195Pt-NMR: l
195Pt= −502.7 dd [1J(195Pt, 31P)=4320 and 3525 Hz];
6: l 31P=119.0 t (2J(31P, 31P)=172.0 Hz), [1J(195Pt,
31P)=5336 Hz] 1-phospha-[1]ferrocenophane; 50.8 d
(2J(31P, 31P)=172.0 Hz), [1J(195Pt, 31P)=4135 Hz]
PPh3; 195Pt-NMR: l 195Pt= −28.6 dt [1J(195Pt, 31P)=
5336 (d) and 4135 Hz (t)].
4. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC No. 107105. Copies of this infor-
mation can be obtained free of charge from The Direc-
tor, CCDC, 12 Union Road, Cambridge, CB2 1EZ,
UK (fax: +44-1223-336-033; e-mail: deposit@ccdc.
cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
3.4. X-ray structure analysis of fc[PꢀNiPr2] (1)
The crystal of C16H22FeNP was a dark red prism
with dimensions 0.25×0.20×0.12 mm3; space group
P21/c (monoclinic) with lattice parameters a=
1895.6(2), b=754.5(2), c=1089.1(2) pm, i=95.62(2)°,
and Z=4; absorption coefficient 1.062 mm−1. Data
collection: Siemens P4 diffractometer (Mo–Ka radia-
tion, u=71.073 pm, graphite monochromator); T=
296 K; 7946 reflections measured with ꢀ scan mode in
the range 3°52r555°; 3554 independent reflections
and 3029 were assigned to be observed (Fo]3.0 |(Fo)).
Fig. 4. Assignments of angles in [1]ferrocenophanes (see Table 3).

M. Herberhold et al. / Journal of Organometallic Chemistry 582 (1999) 352–357
357
Soc. 116 (1994) 12 121. (c) Y. Ni, R. Rulkens, I. Manners, J.
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Support of this work by the Deutsche Forschungsge-
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gratefully acknowledged.
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