Novel access to azaphosphiridine complexes and first applications using Bronsted acid-induced ring expansion reactions

Article abstract of DOI:10.1039/b922166b

Synthesis of azaphosphiridine complexes 3a-e was achieved via thermal group transfer reaction using 2H-azaphosphirene complex 1 and N-methyl C-aryl imines 2a-e (i) or via reaction of transient Li/Cl phosphinidenoid complex 5 (prepared from dichloro(organo)phosphane complex 4) using 2a-c (ii), respectively. Reaction of complexes 3a,d and trifluoromethane sulfonic acid in the presence of dimethyl cyanamide led to a highly bond- and regioselective ring expansion yielding 1,3,4σ³λ³-diazaphosphol-2-ene complexes 8a,d after deprotonation with NEt₃. ³¹P NMR reaction monitoring revealed that protonation of complex 3a yields the azaphosphiridinium complex 6a, unambiguously identified by NMR spectroscopy at low temperature. All isolated products were characterized by multinuclear NMR spectroscopy, IR and UV/Vis (for 3a,d, 6a, 8a,d), MS and single-crystal X-ray crystallography in the cases of complexes 3b-d, 8a and 8d. DFT studies on the reaction mechanism and compliance constants of the model complex of 6a are presented.

Full text of DOI:10.1039/b922166b

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PAPER
www.rsc.org/dalton | Dalton Transactions
Novel access to azaphosphiridine complexes and first applications using
Brønsted acid-induced ring expansion reactions†
Stefan Fankel,a Holger Helten,a Gerd von Frantzius,a Gregor Schnakenburg,a Jo¨rg Daniels,a Victoria Chu,b
Christina Mu¨llera and Rainer Streubel*a
Received 22nd October 2009, Accepted 22nd December 2009
First published as an Advance Article on the web 23rd February 2010
DOI: 10.1039/b922166b
Synthesis of azaphosphiridine complexes 3a-e was achieved via thermal group transfer reaction using
2H-azaphosphirene complex 1 and N-methyl C-aryl imines 2a-e (i) or via reaction of transient Li/Cl
phosphinidenoid complex 5 (prepared from dichloro(organo)phosphane complex 4) using 2a-c (ii),
respectively. Reaction of complexes 3a,d and trifluoromethane sulfonic acid in the presence of dimethyl
3
3
cyanamide led to a highly bond- and regioselective ring expansion yielding 1,3,4s l -diazaphosphol-
2-ene complexes 8a,d after deprotonation with NEt3. 31P NMR reaction monitoring revealed that
protonation of complex 3a yields the azaphosphiridinium complex 6a, unambiguously identified by
NMR spectroscopy at low temperature. All isolated products were characterized by multinuclear NMR
spectroscopy, IR and UV/Vis (for 3a,d, 6a, 8a,d), MS and single-crystal X-ray crystallography in the
cases of complexes 3b-d, 8a and 8d. DFT studies on the reaction mechanism and compliance constants
of the model complex of 6a are presented.
for the intermediacy of azaphosphiridine complexes in thermal
Introduction
reactions of 7-phospha-norbornadiene complexes with imines17
thus confirming the proposal by Mathey and co-workers made
earlier. Recently, we provided strong NMR evidence for a complex
of type VII at low temperature and demonstrated that ring
expansion occurs selectively upon addition of a nitrile derivative.18
To the best of our knowledge, nothing is known about complexes
VIII and their chemistry.
Brønsted and Lewis acid-induced ring expansion reactions of
small, strained N-heterocycles such as 2H-azirenes (I) and
aziridines (II) (Scheme 1) enable numerous applications in organic
synthesis.1–3 Surprisingly, evidence for reaction intermediates
such as 2H-azirenium (III) or aziridinium (IV) derivatives is
scarce.4–6 Furthermore and by comparison, the chemistry of
2H-azaphosphirenes (V) and azaphosphiridines7,8 (VI) is largely
undeveloped. The synthesis of metal complexes containing ligands
V9,10 or VI11 was reported but studies on ring cleavage reactions
were focused on complexes of V.12–14 Lammertsma and coworkers
reported strong experimental15 and computational16 evidence
On the other hand, we recently reported reactions of thermally
unstable Li/Cl phosphinidenoid complexes in the synthesis of
2H-azaphosphirene19 and oxaphosphirane19-21 complexes, both
of which can be used to obtain five-membered phosphorus
heterocycles.18,22
Here, a new, facile access to azaphosphiridine metal complexes
is described, and first examples of Brønsted acid-induced ring
3
3
expansion reactions are presented that selectively yield 1,3,4s l -
diazaphosphol-2-ene complexes. In addition, computational stud-
ies provide an insight into the mechanistic aspects of the ring
expansion.
Results and discussion
Thermal reaction of 2H-azaphosphirene complex 123 with N-
methyl C-aryl imines 2a-e24-28 (Scheme 2, i) diastereoselectively
gave azaphosphiridine complexes 3a-e in good to moderate yields
(according to the method described for the synthesis of 3a11).29
Yields were significantly improved when Li/Cl phosphinidenoid
complex 5, generated from 4, was reacted with 2a–c at low
temperature (ii); in the case of 2d,e no reaction to give 3d,e was
observed.30 All complexes were isolated using low temperature
column chromatography, except for 3e, which could be obtained
after washing the crude product; selected NMR data for 3a-e are
shown in Table 1.
Scheme 1 Three-membered N-heterocycles I–IV, related N,P-heterocyles
V, VI and metal complexes thereof VII, VIII (lines denote organic
substituents; [M] = M(CO)5 of Cr, Mo, W).
aInstitut fu¨r Anorganische Chemie, Rheinische Friedrich-Wilhelms-
Universita¨t Bonn, Gerhard-Domagk-Str. 1, 53121, Bonn, Germany. E-mail:
r.streubel@uni-bonn.de; Fax: (+) 49-228-73-9616
bDepartment of Chemistry, University of Rochester, RC Box 270216,
Rochester, NY, 14627-0216
† CCDC reference numbers 743281 (3b), 743282 (3c), 743281 (3d), 695893
(8a), and 743283 (8d). For crystallographic data in CIF or other electronic
format see DOI: 10.1039/b922166b
To test our new ring expansion methodology18,22 derivatives 3a,d
were reacted with trifluoromethane sulfonic acid (triflic acid or
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Table 1 31P NMR data of 3a–e, 6a,d, 7a,a¢ and 8a,a¢,d,d¢
As a more cost-efficient alternative, rin◦g expansion induced by
oleum (w(SO3) = 0.2) was tested at -25 C, and complexes 3a,d
were used as a good case in point. C-Phenyl substituted derivative
3a showed a selective reaction via transient complexes 7a,a¢ to
yield finally complex 8a, whereas the C-ferrocenyl substituted
complex 3d gave complex 8d together with a complex exhibiting a
phosphorus resonance at 91.2 ppm (1JW, P = 275 Hz, 1JP,H = 352 Hz)
in a 1 : 1 ratio, which could not be isolated. For comparison, 1,3,4-
diazaphosphol-2-ene-P-oxides reported by Zhou et al.31 showed
phosphorus resonances in the range of 40–45 ppm.
|2J(P,H)|/Hz |2J(P,H)|/Hz
Ar No. d(31P) [ppm] |1J(W,P)|/Hz P-CHTms2
P-CH(Ar)h-
h
Ph 3ag -37.3
Fua 3bg -35.9
Thb 3cg -37.7
Fcc 3dg -40.7
Pyd 3eg -39.2
Ph 6af +45.1k
Fcc 6df +51.0k
Ph 7af,k 85.1k
269.9
271.8
269.5
265.8
267.0
298.2k
301.9k
17.7
17.5
16.4
17.8
5.4
7.0
6.6
8.3
i
i
—
—
17.3k
16.3k
h1/2 = ~16k
h1/2 = ~20k
286.5 k(major) 19.1/19.7 dd k
290.0 k(minor) 20.1 d k
Monitoring of ◦the reactions of 3a,d with triflic acid at low
temperature (-70 C, CD2Cl2) by 31P NMR spectroscopy showed
N-protonation as a first step, and thus the obtained intermediates
6a,d revealed significantly downfield shifted resonances at 45.1
f,k
Ph 7a¢ 90.2k
Ph 8ag 103.3 (major) 279.7 (major) 9.1
6.2
g
j
j
j
8a¢ 90.8 (minor) 261.9 (minor)
5.9
Fcc 8dg 101.9 (major) 278.5 (major)
j
g
j
8d¢ 96.9 (minor) 265.1 (minor)
1
and 51.0 ppm and increased JW, P couplings of about 300 Hz
a Fu = 2-furanyl. b Th = 2-thienyl. c Fc = ferrocenyl. d Py = 2-(N-methyl
pyrryl). e In C6D6. f In CD2Cl2. g In CDCl3. h From 1H NMR spectrum.
i Not isolated. j Not observed. k Recorded at 203 K.
(Table 1). In total, these 31P NMR data are very similar to those
of oxaphosphirane tungsten complexes,cf. 19-21 which illustrates a
similar influence of the cationic N(Me)H unit and the oxygen atom
1
(in oxaphosphiranes) on the P center. In the H NMR spectrum
(-70 ◦C) of the C-phenyl derivative 6a the resonance of the proton
attached to the N atom is at 8.31 ppm. The spectrum further reveals
a downfield shifted N-methyl resonance from 2.82 (3a) to 3.20 ppm
(6a). Similarly the proton bonded to the azaphosphiridine ring
carbon atom is shifted from 3.28 (3a) to 4.35 ppm (6a). Remarkably
the resonance of this proton is more deshielded in complex 6a
(3.28 ppm) than it is in complex 6d (2.89 ppm), which points to
some electron-donation of the ferrocenyl group in this case. Upon
warming to ambient temperature complexes 6a,d decomposed.
31P NMR spectroscopic monitoring of the reaction of 3a with
TfOH in the presence of dimethyl cyanamide revealed evidence
for the formation of N-protonated diastereomeric 1,3,4-diaza-
phosphol-2-ene complexes 7a,a¢ (Table 1), which, at -70 ◦C,
were observed together with 3a in a 2 : 12 : 7 ratio (3a : 7a : 7a¢).
Upon warming the resonance of 3a decreased until it vanished
at ambient temperature. Further support for the assignment of
these data to complex 7a,a¢ came from the observation that the
31P NMR resonance was shifted to lower field (by 6–12 ppm)
compared with 8a,a¢. A similar situation was found recently
for P-CH(SiMe3)2 substituted 2H-1,4,2-diazaphosphole tungsten
complexes and their N-protonated derivatives.18 Complex 7a
showed a doublet of doublets (2JPH = 19.1 and 19.7 Hz), while
7a¢ revealed a doublet (2JPH = 20.0 Hz) in the proton-coupled
31P NMR spectrum. N-Protonation also caused an increase in the
magnitude of the tungsten–phosphorus coupling constant by 10–
17 Hz. Further support for complex 6a was also obtained by MS
experiments.32
Scheme
2 Synthesis of azaphosphiridine complexes 3a–e using
2H-azaphosphirene complex 1 (i) or in situ generated complex 5 (from
4) (ii) and imines 2a–e.
TfOH) in CH2Cl2 in the presence of dimethyl cyanamide and
subsequently treated with triethylamine thus forming bond- and
regioselectively diastereomeric 1,3,4-diazaphosphol-2-ene com-
plexes 8a,a¢ (11 : 2) and 8d,d¢ (22 : 1) (Scheme 3).
In the IR spectra the absorptions due to CO stretch vibrations
are of particular interest as the normal mode of local A1 symmetry
reveals a hypsochromic shift of 2–4 cm-1 for the cationic complexes
6a,d compared to their respective neutral counterparts 3a,d.
Complexes 7a,d show a blue shift by 11–13 cm-1 compared to
8a,d. This supports the idea that protonation of the heterocyclic
ligand leads to weakening of the trans C–O bond.33 All spectra
show several overlapping bands in the region around 1900–
1960 cm-1 which did not allow a clear assignment. In all four
cases protonation causes a broadening of the bands in the region
of 1840–1980 cm-1. In the UV/Vis absorption spectra the bands of
the three-membered ring complexes 3a,d and 6a,d did not change
significantly upon protonation.
Scheme 3 Ring expansion reaction of complexes 3a,d.
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Complexes bearing aferrocenylsubstituent atthe imine 2d or the
ring system 3d, 8d were investigated by cyclic voltammetric (CV)
experiments;34 Fig. 1 shows the resulting graphs. Whereas imine 2d
shows a reversible CV (E 1 = 0.647 V), the 1,3,4-diazaphosphol-
2
2-ene complex 8d (E 1 = 0.548 V) shows a quasi-reversible and
2
the azaphosphiridine complex 3d an irreversible CV behavior and
thus only the value for Epa (0.575 V) could be determined. In total,
the three- (3d) and five-membered ring (8d) substituted ferrocene
derivatives allow a more facile oxidation than the imine 2d.
Fig. 3 Molecular structure of complex 3c in the crystal (50% probability
level, hydrogen atoms except on C(1) are omitted for clarity). Selected bond
◦
˚
lengths [A] and angles [ ]: W–P 2.4952(12), P–C(1) 1.846(4), P–N 1.725(4),
P–C(7) 1.805(4), C(1)–N 1.483(5), N–C(6) 1.468(6), C(1)–C(2) 1.475(6);
N–P–C(1) 48.94(18), C(1)–N–P 69.8(2), N–C(1)–P 61.3(2), C(1)–P–C(7)
109.7(2), N–P–C(7) 104.1(2), P–N–C(6) 124.2(3), C(1)–N–C(6) 117.2(4).
Fig. 1 Cyclic voltammetric measurements of imine 2d, complexes 3d and
8d (100 mV s-1, 3 mmol L-1 in CH2Cl2, 0.1 mol L-1 [n-Bu4N]PF6, GCE,
Pt-wire, Ag/AgCl, 2 mol L-1 LiCl in EtOH, direction of scan indicated by
the arrow.
The molecular structures of 3b-d (Fig. 2-4) and 8a,d (Fig. 5
and 6) were determined for the solid state by single-crystal
X-ray diffraction studies. Complexes 3b-d exhibit some common
structural features: a) the P–N bond length is ~10 pm shorter
than the P–C bond length, b) the P–W bond lengths are around
˚
2.50 A, c) in all three complexes the endocyclic angles at
Fig. 4 Molecular structure of complex 3d in the crystal (50% probability
phosphorus are very narrow (~49◦). The situation is markedly
different in the C-Ph, and C-Fc, P-CH(SiMe3)2 substituted 2H-
azaphosphirene tungsten complexes,9,35,36 in which the P–C and
level, hydrogen atoms except on C(1) are omitted for clarity). Selected
bond lengths [A] and angles [◦]: W(1)–P(1) 2.505(9), P(1)–C(1)
˚
1.838(5), P(1)–N(1) 1.735(4), P(1)–C(13) 1.799(6), C(1)–N(1) 1.487(6),
N(1)–C(12) 1.472(6), C(1)–C(2) 1.475(6); N(1)–P(1)–C(1) 49.08(19),
C(1)–N(1)–P(1) 69.1(3), N(1)–C(1)–P(1) 61.9(2), C(1)–P(1)–C(13)
108.0(2), N(1)–P(1)–C(13) 104.7(2), P(1)–N(1)–C(12) 123.4(3),
C(1)–N(1)–C(12) 116.0(5).
P–N bond distances are almost identical (Fc derivative: d(PN) =
˚
˚
˚
1.803(3) A, d(PC) = 1.763(4) A, Ph derivative: d(PN) = 1.796 A,
˚
d(PC) = 1.759 A; in both derivatives the d(PN) is somewhat
longer than d(PC)).9,35,36 The endocycli◦c angle at phosphorus is
significantly more acute (R = Ph:36 41.9 and R = Fc:35 42.2◦) due
to the shorter C–N bond in such complexes.
Noteworthy is also the small bond angle sum at phosphorus
(not including the W(CO)5 group) of 3b–d, which is about 261◦.
A stereochemical feature is the relative orientation of the N-Me
group in complexes 3b–d, which was found to be on the same
side of the azaphosphiridine ring plane as the W(CO)5 fragment;
this was also observed for the structure of 3acf. 11. Some structural
features of complexes 8a,d—the first transition metal complexes
of this heterocycle—are best revealed through comparison with
3a,d. Whereas the P–W and the P–C3 distances in 8a,d and 3b-d
Fig. 2 Molecular structure of complex 3b in the crystal (50% probability
level, hydrogen atoms except on C(1) are omitted for clarity). Selected
◦
˚
bond lengths [A] and angles [ ]: W–P 2.4935(8), P–C(1) 1.838(3),
P–N(1) 1.730(3), P–C(7) 1.806(3), C(1)–N(1) 1.470(5), N(1)–C(6) 1.468(5),
C(1)–C(2) 1.465(5); N(1)–P–C(1) 48.55(16), C(1)–N(1)–P 69.58(19),
N(1)–C(1)–P 61.87(18), C(1)–P–C(7) 108.56(16), N(1)–P–C(7) 103.80(15),
P–N(1)–C(6) 123.6(2), C(1)–N(1)–C(6) 117.2(3).
˚
are virtually identical, the latter is slightly elongated by ~0.05 A,
˚
and the P–C(1) bond is elongated by ~0.07 A. The bond angle
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C(2)–N(2) is in the range of a sp2-C–sp2-N double bond.38 The
endocyclic C(2)–(N1) and the exocyclic C(2)–N(3) distances are
virtually identical. In 8d the endocyclic C(2)–(N1) distance is by
˚
0.04 A longer than in 8a while the exocyclic C(2)–N(3) distance is
˚
by 0.03 A shorter.
The 1,2,4-diazaphosphol-2-ene rings in 8a and 8d show an
envelope conformation with only little deviation of the phosphorus
˚
atom (8a: 0.295, 8d: 0.505 A), from the best plane given by C(1)–
N(1)–C(2)–N(2); the relative deviation of N(1), N(2), C(1) and
˚
C(2) from the best plane is between 0.023 and 0.057 A. The ring
plane bears the N-Me group and the bulky CH(SiMe3)2 group on
the same side, which is an important hint for the ring formation
and thus for theoretical studies of the mechanism.
Apparently, the ring expansion proceeds via an acyclic interme-
diate with the N-methyl group trans to the phenyl (or ferrocenyl)
group that derives from a P–N bond cleavage. The interplanar
angles between the best plane of the five-membered heterocycle
and the ring substituents at C(1) are 88.1◦ (8a) and 76.1◦ (8d),
respectively.
Fig. 5 Molecular structure of complex 8a in the crystal (50% probability
level, except for H at C(1) all other hydrogen atoms are omitted for
◦
˚
clarity). Selected bond lengths [A] and angles [ ]: W–P 2.5286(7), P–C(3)
1.850(3), P–N(2) 1.700(3), P–C(1) 1.917(3), N(2)–C(2) 1.300(4), C(2)–N(1)
1.373(4), N(1)–C(1) 1.458(4), C(1)–C(4) 1.511(4), C(2)–N(3) 1.377(4);
C(1)–P–N(2) 93.22(13), P–N(2)–C(2) 110.1(2), N(2)–C(2)–N(1) 119.9(3),
C(2)–N(1)–C(1) 114.0(2), N(1)–C(1)–P 100.1(2).
Computational studies
A conceivable mechanism of the acid-induced ring expansion was
obtained in a theoretical study using DFT calculations on complex
9 (Scheme 4), an all-methyl substituted model system for 3a,b;
cyanamide was chosen as the nitrile component (Scheme 4 and
Tab. 2).
Fig. 6 Molecular structure of complex 8d in the crystal (50% probability
level, except for H at C(1) all other hydrogen atoms are omitted
◦
˚
for clarity). Selected bond lengths [A] and angles [ ]: W–P 2.5276(2),
P–C(3) 1.8440(1), P–N(2) 1.6909(1), P–C(1) 1.9010(1), N(2)–C(2)
1.3024(1), C(2)–N(1) 1.4190(1), N(1)–C(1) 1.4711(1), C(1)–C(4) 1.4784(1),
C(2)–N(3) 1.3484(1); C(1)–P–N(2) 92.440(3), P–N(2)–C(2) 109.655(4),
N(2)–C(2)–N(1) 120.076(5), C(2)–N(1)–C(1) 109.860(4), N(1)–C(1)–P
100.977(4).
Scheme 4 Computed pathway for the reaction of complex 9 with
cyanamide in the presence of TfOH. The sum of free energies of the
reactants 9 + TfOH + H2NCN was arbitrarily chosen as zero-point of
the DG scale.
sum at phosphorus as well as the endocyclic angle at phosphorus
is increased (300–308◦ and 92–93◦, respectively), both are effected
by the increasing ring size.
Table 2 Calculated thermochemical data ([kJ mol-1]) for reactions
shown in Scheme 4 (B3LYP/aug-TZVP/ECP-60-MWB(W), COSMO
CH2Cl2//RI-BLYP/aug-SV(P)/ECP-60-MWB(W), COSMO CH2Cl2)
In 1994, Martynov et al. published the crystal structure37 of
a 1,3,4-diazaphosphol-2-ene P-oxide. In this case the geometry
is very much dominated by the P–O bond: the P–C1 bond is
Reaction
DG‡298
DRG298
a
˚
˚
i)
9 + TfOH → [H–9][OTf]
[H–9][OTf] + H2NCN → 10
10 → 10¢
–42.1
+56.7
+1.4
-89.7
-106.6
shorter by more than 0.05 A and the P–N2 by ~0.1 A, compared
to the transition metal bound ligands (8a,d). The C1–N1 bond
ii)
iii)
iv)
v)
+73.7
a
˚
˚
is shortened by 0.03 A (8a) resp. 0.05 A (8d). The C2–N2 bond
is elongated by 0.05 A. The angle around the P-atom is by 3.5
10¢ → 11
+8.1
◦
a
˚
11 → 12
(8a) resp. 4.4◦ (8d) more acute in the P-oxide. The distances to
the nitrogen atoms around C(2) in 8a (Fig. 5) are inequivalent:
a The activation barrier was not calculated.
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In the first step the azaphosphiridine nitrogen of 9 is protonated
by triflic acid with formation of azaphosphiridinium salt [H–
9][OTf] (i) where the triflate anion remains attached through a
hydrogen bond (Fig. 7, left). Different from the situation found
for 2H-azaphosphirene18 and oxaphosphirane complexes22 upon
ring-protonation the P,N bond of [H–9][OTf] is not spontaneously
cleaved, but the phosphorus center becomes prone to a nucle-
ophilic attack of cyanamide (ii) thus leading to ring opening in
an SN 2-type fashion (TSii; Fig. 7, right). Since the attack occurs
trans to the P,N bond (for stereoelectronic reasons), inversion
of the configuration at the phosphorus results. Intermediately P-
nitrilium substituted phosphane complex 10 is formed.
Fig.
8
ZORA-DFT calculated ((B88+P86)VWN5/tz2p, COSMO
bond lengths [A] and angles [◦] of
˚
)
CH2Cl2, ADF 2007.139b
[3Me,Cr]/[H-3Me,Cr]+: P–N 1.727/1.868, P–C 1.832/1.833, N–C 1.477/1.516,
Cr–P 2.351/2.284, N–P–C 48.95/48.34, C–N–P 69.22/64.61, P–C–N
61.83/67.05; Charges (Hirshfeld): Cr +0.20/+0.21, P +0.23/+0.28, C
-0.02/+0.02, N -0.14/+0.00, H(N) -/+0.17.
Fig. 9 DFT (BVP86/tzvp, IEFPCM CH2Cl2, G0339a) compliance con-
stants [A/mdyn] of 3Me,Cr(black)/[H-3Me,Cr]+(grey).
˚
Fig. 7 Calculated structures of N-protonated azaphosphiridine complex
[H–9][OTf] with the triflate anion attached via a hydrogen bond (left) and
transition state TSii for the nucleophilic ring opening of [H–9][OTf] by
Fig. 10 Bond strengthening (+)/weakening (-) [%] upon N-protonation
(BVP86/tzvp, IEFPCM CH2Cl2, G0340a): 3Me,Cr/[H-3Me,Cr]+.
˚
cyanamide (right) (bond distances in A).
Conclusions
After a conformational change of 10 (rotation about the P,C
bond; iii) to 10¢ the latter can undergo facile cyclization to give
N1-protonated 1,3,4-diazaphosphol-2-ene complex 11 in a highly
exergonic reaction (iv). Owing to the presence of an amidine
moiety a subsequent proton transfer to N3 is highly favored (v).
Overall, due to inversion of the configuration at phosphorus in
step ii, the ring expansion reaction results in the formation of a
mixture of diastereomers 12 (4R,5R/4S,5S), which is consistent
with the experimental observations.
We have demonstrated that the use of a transient Li/Cl phos-
phinidenoid complex enables a new and facile access to aza-
phosphiridine complexes, thus facilitating research in this field.
Furthermore, we provided the first examples of Brønsted acid-
induced ring expansion reactions of azaphosphiridine complexes
that selectively yielded 1,3,4-diazaphosphol-2-ene complexes; two
of which were characterized by X-ray crystallography. 31P NMR
spectroscopic monitoring at low temperature of the protonation
reaction revealed good evidence for azaphosphiridinium com-
plexes formed in the first step; this was further supported by DFT
calculations. Compliance constants describe quantitatively the
bond strength changes occurring upon N-protonation and offer
an additional rationale for P–N bond cleavage. Computational
studies gave further insight into mechanistic aspects of the
ring expansion: the second step is a nucleophilic attack of the
nitrile at a partially positively charged phosphorus center, which
leads to P–N bond cleavage and transient formation of a P-
nitrilium substituted phosphane complex. This is followed by
facile cyclization to give a N1-protonated 1,3,4-diazaphosphol-
2-ene complex in a highly exergonic reaction. A proton transfer
from N1 to N3 follows thus forming the (more stable) amidinium
moiety, which further supports the structural assignment of
intermediates experimentally observed. After deprotonation, the
ring expansion reaction results in the formation of a mixture of
Calculated compliance constants of chromium model complexes
The influence of N-protonation on ring bond strengths of
azaphosphiridine complexes was also investigated by calculation
of P-/C-/N-methyl substituted chromium model complexes 3Me,Cr
[H-3Me,Cr]+ (Fig. 8).
,
As a measure of bond strengths DFT compliance constants40—
diagonal elements of the inverse force field—are calculated: the
stronger a bond the less compliant it is and vice versa. N-
protonation of azaphosphiridine model complex 3Me,Cr is calcu-
lated including dichloromethane as a solvent (simulated by a
polarizable continuum model) (Fig. 9, black).
N-Protonation weakens P–N by 72% and N–C by 9% while
Cr–P is enforced by 15%; P–C remains almost unchanged (Fig. 10).
+
The positive charge in [H-3Me,Cr
]
concentrates essentially on
phosphorus, which leads to enforcement of the P–Cr bond.
3476 | Dalton Trans., 2010, 39, 3472–3481
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diastereomeric 1,3,4-diazaphosphol-2-ene complexes. In total, the
reaction sequence represents a new example of click-type reactions
in organophosphorus chemistry.
ature reached -40 ◦C, then 465 mL (4.25 mmol) of N-[(furan-
2-yl)methylene]methanamine or N-methylfurfurylidenamine 2b
were slowly added. The color of the solution changed to orange.
After warming to room temperature all volatile components were
removed in vacuo (10-2 mbar). The product was obtained as a
mixture of diastereomers (ratio 5.9 : 1; major isomer: -35.9 ppm
(1J(W,P) = 271.8 Hz), minor isomer: -38.5 ppm (1J(W,P) =
277.0 Hz) and subsequently purified by column chromatography
on neutral aluminium oxide (-30 ◦C, petroleum ether/Et2O: 4/1).
The product was crystallized from Et2O at -30 ◦C.
Experimental section
General procedures
All operations were performed in an atmosphere of deoxygenated
and dried argon using standard Schlenk techniques with conven-
tional glassware. Solvents were distilled from sodium or CaH2
(CH2Cl2). 2H-Azaphosphirene complex 1 was synthesized accord-
ing to the method described in the literature.9 Melting points were
determined with a Bu¨chi apparatus Type S. The values are not
corrected. NMR data were recorded on a Bruker Avance 300
spectrometer (1H: 300.13 MHz; 13C: 75.5 MHz; 29Si: 59.6 MHz; 31P:
121.5 MHz) using C6D6, CDCl3 or CD2Cl2 as solvent and internal
standard; shifts are referenced to tetramethylsilane (1H; 13C; 29Si,
N = 19.867187 MHz), and 85% H3PO4 (31P, N = 40.480742 MHz).
Mass spectra were recorded on a Kratos Concept 1H (FAB+,
mNBA) or a MAT 95 XL Finnigan (EI, 70 eV, 184W) spectrometer
(selected data given). ESI mass spectra and ESI tandem mass
spectra were recorded on a Bruker APEX IV Fourier transform
ion cyclotron resonance (FT-ICR) mass spectrometer equipped
with an Apollo ESI source. UV/Vis spectra were recorded on
a Shimadzu UV-1650 PC spectrometer. Infrared spectra were
recorded on a Thermo Nicolet 380 FT-spectrometer (selected data
given). Elemental analyses were performed using an Elementar
Vario EL instrument. Cyclic voltammetric measurements were
performed using the EG&G-Potentiostat/Galvanostat M273 with
an Ag/AgCl reference electrode and 0.1 mol [n-Bu4N]PF6 (E1/2
values are given in mV, scan speed: 100 mV s-1).
Complex 3b. Light yellow solid, yield: 464 mg (0.74 mmol,
88%); only the analytical data of the mayor isomer are given:
1H NMR (CDCl3): d = -0.04 (s, 9H; Si(CH3)3), 0.32 (s, 9H;
2
Si(CH3)3), 1.09 (d, J(P,H) = 17.5 Hz, 1H; CH(SiMe3)2), 2.65
2
2
(d, J(P,H) = 17.5 Hz, 3H; N–CH3), 3.09 (d, J(P,H) = 7.0 Hz,
1H; P–C(H)-N), 6.18 (mc, 1H; subst. ring H3), 6.41 (mc, 1H;
subst. ring H4), 7.44 (mc, 1H; subst. ring H5); 13C{ H} NMR
1
2
(CDCl3): d = 196.2 (d, J(P,C) = 30.3 Hz; COtrans), 196.0 (dsat,
2J(P,C) = 7.6 Hz, 1J(W,C) = 125.0 Hz; COcis), 151.5 (d, 2J(P,C) =
5.5 Hz; ipso-Cfuranyl), 142.7 (d, 5J(P,C) = 2.4 Hz; C5furanyl), 110.7 (d,
4J(P,C) = 2.5 Hz; C4furanyl), 107.3 (d, J(P,C) = 4.0 Hz; C3furanyl),
3
50.1 (d, 2+3J(P,C) = 2.4 Hz; NCH3), 42.0 (d, 1+3J(P,C) = 2.2 Hz,
PCN), 19.5 (d, 2J(P,C) = 26.6 Hz; CH(SiMe3)2), 1.9 (d, 3J(P,C) =
3.7 Hz,1J(Si,C) = 52.5 Hz; Si(CH3)3), 0.8 (d, J(P,C) = 3.9 Hz,
3
1J(Si,C) = 52.6 Hz; Si(CH3)3); 29Si{ H} NMR (CDCl3): d = 0.06
1
1
2
1
(dsat, J(Si,C) = 56.0, J(P,Si) = 6.4 Hz), 1.61 (dsat, J(Si,C) =
52.3, 2J(P,Si) = 2.4 Hz); 31P{ H} NMR (CDCl3): d = -35.1
1
(dsat, 1J(W,P) = 270.7 Hz); MS (EI, 70 eV, 184W): m/z (%):
623.0 ([M]+, 39), 539.0 ([M-3CO]+, 18), 514.0 ([M-C6H7NO]+,
13), 486 ([M-C6H7NO-CO]+, 100), 458 ([M-C6H7NO-2CO]+, 20),
430 ([M-C6H7NO-3CO]+, 38), 402 ([M-C6H7NO-4CO]+, 30),
374 ([M-C6H7NO-5CO]+, 22), 358.0 ([M-C6H7NO-5CO-CH3–
H]+, 50), 110.1 ([CH(furanyl)NMe+H]+, 15), 73.1 ([Me3Si]+, 40);
elemental analysis (%) calculated for C18H26NO6PSi2W: C 34.68,
H 4.20, N 2.25; found: C 34.33, H 4.18, N 2.23.
Imines 2b–e were synthesized from common available alde-
hydes and methyl imine gas according to the literature.25-28 N-
Benzylidenmethyl imine 2a was used as purchased from Acros.
Synthesis of the complex 3a via the new method. To a solution
of 500 mg (0.85 mmol) of dichlorophosphane complex 1, 139 mL
(0.85 mmol) of 12-crown-4 and 530 mL (4.25 mmol) of N-
benzylidenmethyl imine 2a were dissolved in 30 mL of Et2O. At
-80 ◦C 0.68 mL (1.02 mmol) of tert.-butyl lithium (1.5 M in
hexanes) was slowly added. The yellow solution was stirred for
2 h and warmed up to 0 ◦C. From the resulting orange solution all
volatile components were removed in vacuo (ca. 10-2 mbar). The
product was subsequently purified by column chromatography on
neutral aluminium oxide (-30 ◦C, petroleum ether/Et2O: 5/1) and
obtained as a pale fraction.
Synthesis of complex 3c. A solution of 617 mg (1.0 mmol)
of 2H-azaphosphirene complex 1 and 250 mL (2.0 mmol) of
N-[(thiophen-2-yl)methylene]methanamine or 2-[(methylimino)-
methyl]thiophene 2c in 6.0 mL toluene is stirred for 3 h at
75 ◦C while the brown solution turned dark red. After removing
all volatile components in vacuo (10-2 mbar) the product was
subsequently purified by column chromatography on neutral
aluminium oxide (-30 ◦C, pentane–Et2O: 5/1).
Complex 3c. Light brown solid, yield: 165 mg (0.26 mmol,
1
26%); only the analytical data of the major isomer are given: H
Complex 3a. Light pale solid, yield: 390 mg (0,62 mmol, 73%)
NMR (CDCl3): d = -0.10 (s, 9H; Si(CH3)3), 0.32 (s, 9H; Si(CH3)3),
1
1
31P{ H} NMR (CDCl3): d = -37.3 (dsat, J(P,W) = 269.9 Hz),
0.89 (d, 2J(P,H) = 16.4 Hz, 1H; CH(SiMe3)2), 2.66 (d, 2J(P,H) =
1
29Si{ H} NMR (CDCl3): d = 0.06 (dsat, 1J(Si,C) = 6.7, 2J(P,Si) =
2
15.8 Hz, 3H; N–CH3), 3.12 (d, J(P,H) = 6.6 Hz, 1H; P–C(H)-
6.4 Hz), 2.26 (dsat, 1J(Si,C) = 2.7, 2J(P,Si) = 2.4 Hz); IR (Nujol):
N), 7.12 (mc, 2H; subst. ring H3/4), 7.35 (mc, 1H; subst. ring H5).
˜
n = 2072.6 (w), 2064.8 (vw, CO), 1947.5 (vs, CO), 1941.0 (vs, CO),
1
13C{ H} NMR (CDCl3): d = 196.3 (d, 2J(P,C) = 30.1 Hz; COtrans),
1914.8 cm-1 (m, CO), UV/Vis (CH2Cl2): lmax (abs.) = 237.0 nm
196.3 (dsat, 2J(P,C) = 7.7 Hz, 1J(W,C) = 125.3 Hz; COcis), 138.4 (d,
2J(P,C) = 4.6 Hz; ipso-Cthienyl), 127.8 (d, 3J(P,C) = 0.7 Hz; C3thienyl),
(2.490); other analytical data of 3a were reported earlier.11
4
5
Synthesis of complex 3b. To a solution of 500 mg (0.85 mmol)
of dichlorophosphane complex 4 and 139 mL (0.85 mmol) of
12-crown-4, dissolved in 30 mL Et2O, 0.68 mL (1.02 mmol)
of tert.-butyl lithium (1.5 M in hexanes) were slowly added at
-80 ◦C. The yellow solution was allowed to stir until the temper-
126.2 (d, J(P,C) = 0.8 Hz; C4thienyl), 121.2 (d, J(P,C) = 3.8 Hz;
C5thienyl), 52.8 (d, 2+3J(P,C) = 2.4 Hz; NCH3), 42.1 (d, 1+3J(P,C) =
2
2.4 Hz, PCN), 18.6 (d, J(P,C) = 26.9 Hz; CH(SiMe3)2), 1.9 (d,
3J(P,C) = 3.5 Hz; Si(CH3)3), 1.2 (d, 3J(P,C) = 3.9 Hz; Si(CH3)3);
29Si1H} NMR (CDCl3): d = 0.06 (dsat, J(P,Si) = 6.7 Hz), 2.08
2
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5
4
pyrryl), 123.7 (d, J(P,C) = 2.4 Hz; C5pyrryl), 107.4 (d, J(P,C) =
2
1
(dsat, J(P,Si) = .5 Hz); 31P{ H} NMR (CDCl3): d = -37.7 (dsat,
1J(W,P) = 269.5 Hz); MS (EI, 70 eV, 184W): m/z (%): 639.0
([M]+, 13), 543.0 ([M-CH(thienyl)]+, 10), 514.0 ([M-C6H7NO]+,
13), 486 ([M-C6H7NO-CO]+, 57), 458 ([M-C6H7NO-2CO]+, 20),
430 ([M-C6H7NO-3CO]+, 27), 402 ([M-C6H7NO-4CO]+, 28), 374
([M-C6H7NO-5CO]+, 20), 358.0 ([M-C6H7NO-5CO-CH3–H]+,
50), 97.0 ([CH(thienyl)+H]+, 15), 73.1 ([Me3Si]+, 40).
C
3.5 Hz; C4pyrryl), 107.1 (d, 3J(P,C) = 2.4 Hz; C3pyrryl), 50.7 (d,
2+3J(P,C) = 1.5 Hz; NCH3), 42.3 (d, 1+3J(P,C) = 2.4 Hz, PCN),
33.9 (s, N-CH3-pryrryl), 17.5 (d, 2J(P,C) = 25.6 Hz; CH(SiMe3)2),
2.0 (d, 3J(P,C) = 3.7 Hz,1J(Si,C) = 52.6 Hz; Si(CH3)3), 0.7
(d, J(P,C) = 3.8 Hz, J(Si,C) = 52.2 Hz; Si(CH3)3); 29Si{ H}
NMR (CDCl3): d = 0.06 (dsat, 2J(P,Si) = 6.9 Hz, 1J(Si,C) =
52.3 Hz), 2.20 (dsat, 2J(P,Si) = 3.1 Hz, 1J(Si,C) = 52.1 Hz);
3
1
1
Synthesis of complex 3d. A solution of 617 mg (1.00 mmol)
2H-azaphosphirene complex
31P{ H} NMR (CDCl3): d = -40.7 (dsat, 1J(W,P) = 265.8 Hz); MS
1
1 and 227 mg (1.00 mmol)
(EI, 70 eV, 184W): m/z (%): 607.1 ([M-NMe]+, 18), 122.1 ([CH(1-
Me-pyrryl)NMe]+, 18), 73.1 ([tms]+, 40); elemental analysis (%)
calculated for C19H29N2O5PSi2W: C 35.86, H 4.59, N 4.40; found:
C 35.26, H 4.64, N 4.20.
N-[(ferrocenyl)methylene]methanamine or 2-((methylimino)-
methyl)ferrocene 2d in 1.5 mL toluene is stirred for 1.5 h at
75 ◦C. The brown solution turns dark red. After removing
all volatile components in vacuo (10-2 mbar) the product is
subsequently purified by column chromatography on neutral
aluminium oxide (-30 ◦C, n-pentane).
Synthesis of 6a. To a solution of 95 mg (0.15 mmol) of
azaphosphiridine complex 3a in 0.6 mL of CD2Cl2 at -70 C in
◦
an NMR tube 13 mL (0.15 mmol) of TfOH were added. The light
yellow solution turned greenish. At -70 ◦C NMR spectra were
recorded.
Complex 3d. Orange solid, yield: 535 mg (0.72 mmol, 72%);
m.p. 99 ◦C (decomp.), 1H NMR (CDCl3): d = 0.04 (s, 9H;
Si(CH3)3), 0.35 (s, 9H; Si(CH3)3), 1.01 (d, 2J(P,H) = 17.8 Hz, 1H;
3
CH(SiMe3)2), 2.68 (d, J(P,H) = 15.7 Hz, 3H; NCH3), 2.89 (d,
Complex 6a. 1H NMR (CD2Cl2): d = 0.00 (s, 9H; Si(CH3)3),
0.59 (s, 9H; Si(CH3)3), 1.94 (d, 2J(P,H) = 17.2 Hz, 1H;
CH(SiMe3)2), 3.20 (s, br, 3H; NCH3), 4.35 (s, br, 1H; PNCH), 7.67-
2J(P,H) = 8.3 Hz, 1H; PNCH), 4.01 (mc, 2H; subst. ring), 4.05 (s,
5H; unsubst. ring), 4.13 (mc, 1H; subst. ring), 4.24 (mc, 1H; subst.
7.76 (m, br, 5H; subst. Ph-Ring), 8.31 (s, 1H; NHMe); 13C{ H}
1
2
1
ring); 13C{ H} NMR (CDCl3): d = 194.8 (d, J(P,C) = 29.4 Hz;
COtrans), 194.6 (dsat, 2J(P,C) = 7.4 Hz, 1J(W,C) = 125.4 Hz; COcis),
83.0 (s, ipso-Cferrocenyl), 67.5 (s, subst. cp ring), 67.2 (s, unsubst.
cp ring), 66.5 (s, subst. cp ring), 65.5 (s, subst. cp ring), 65.0
(s, subst. cp ring), 52.8 (d, 2+3J(P,C) = 1.9 Hz; NCH3), 40.4 (d,
1+3J(P,C) = 2.6 Hz, PCN), 17.2 (d, 2J(P,C) = 27.2 Hz; CH(SiMe3)2),
NMR (CD2Cl2): d = [COtrans was not observed] 192.7 (dsat, br,
2J(P,C) = 4 Hz, 1J(W,C) = 128 Hz; COcis), 129.1 (s, br; subst. Ph-
Ring), 128.5 (s, br; subst. Ph-Ring), 126.1 (s, br; subst. Ph-Ring),
126.0 (s, br; subst. Ph-Ring), 60.1 (s, br; PNC), 39.4 (d, br; N-CH3),
17.7 (d, br; CH(SiMe3)2), 0.0 (s, br; Si(CH3)3), -0.2 (s, br; Si(CH3)3);
29Si{ H} NMR (CD2Cl2): d = 4.95 (d, 2J(P,Si) = 7.2 Hz), 5.21 (s);
3
3
1
0.0 (d, J(P,C) = 3.2 Hz; Si(CH3)3), -0.5 (d, J(P,C) = 3.9 Hz;
31P{ H} NMR (CD2Cl2): d = 45.1 (dsat, 1J(W,P) = 298.2 Hz); IR
1
1
Si(CH3)3); 29Si{ H} NMR (CDCl3): d = 0.95 (dsat, 2J(P,Si) =
6.5 Hz), 2.34 (dsat, 2J(P,Si) = 3.2 Hz); 31P{ H} NMR (CDCl3): d =
(Nujol): n = 2074.4 (m, CO), 1987.9 (w, CO) 1939.9 cm-1 (s, broad
1
˜
1
˜
-39.2 (dsat, J(W,P) = 267.0 Hz); IR (KBr): n = 2071.3 (m, sh, CO),
CO); UV/Vis (CH2Cl2): lmax (abs.) = 296.0 (0.068), 256.5 (0.300),
1988.6 (m, CO), 1929.1 (s, CO); UV/Vis (n-pentane): lmax (abs.) =
296.0 (0.068), 256.6 (0.300), 233.0 (0.851), 209.5 nm (0.088);
MS (FAB pos., mNBA): m/z (%): 741.1 ([M+H]+, 20), 657.1
233.0 (0.851), 209.5 nm (0.088).
Synthesis of 8a. To a solution of 279 mg (0.44 mmol) of
azaphosphiridine complex 3a in 6.0 mL of CH2Cl2 39 mL
(0.48 mmol) of dimethyl cyanamide and 39 mL (0.44 mmol) of
TfOH were added. After 2 min, 62 mL (0.44 mmol) of NEt3 was
added to the solution at ambient temperature. After filtration
and removal of all volatile components in vacuo (10-2 mbar) a
mixture of diastereomers (ratio 11 : 2; major isomer: 103.3 ppm
(1J(W,P) = 281.0 Hz), minor isomer: 90.8 ppm (1J(W,P) =
269.6 Hz) was obtained. The major isomer was purified by
column chromatography on neutral aluminium oxide (-30 ◦C,
first petroleum ether/Et2O: 10/1, then pure CH2Cl2).
([M-3CO]+, 22), 599.1 ([M-5CO]+, 10), 358.0 (M-W(CO)5-tms]+,
+
=
24), 227 ([Fc-C NMe] , 100); elemental analysis (%) calculated
for C24H32FeN2O5PSi2W: C 38.88, H 4.35, N 1.89; found: C 38.76,
H 4.56, N 1.88.
Synthesis of complex 3e. A solution of 617 mg (1.0 mmol) 2H-
azaphosphirene complex 1 and 250 mL (2.0 mmol) N-[(1-methyl-
2-pyrryl)methylene]methanamine or 2-[(methylimino)methyl](N-
methyl-1H-pyrrole) 2e in 6.0 mL toluene is stirred for 3 h at
75 ◦C. The brown solution turns dark red. After removing all
volatile components in vacuo (10-2 mbar) the product is obtained
as a mixture of diastereomers (ratio >100 : 1; major isomer: -
42.0 ppm (1J(W,P) = 265.2 Hz), minor isomer: -45.7 ppm and
subsequently extracted with cold pentane. Complex decays at
-50 ◦C on neutral aluminium oxide.
Complex 8a.◦ Light orange solid, yield: 122 mg (0.17 mmol,
40%); m.p. 154 C (decomp.); 1H NMR (CDCl3): d = 0.28 (s, 9H;
Si(CH3)3), 0.40 (s, 9H; Si(CH3)3), 1.68 (d, 2J(P,H) = 9.1 Hz, 1H;
CH(SiMe3)2), 2.90 (s, 6H; N(CH3)2), 2.93 (s, 3H; NCH3), 4.85 (s,
1H, PC(H)N), 7.25 (mc, 1H; Hphenyl), 7.28 (mc, 1H; Hphenyl), 7.37(mc,
1
Complex 3e. Dark brown oil, yield: 516 mg (0.81 mmol, 81%);
only the analytical data of the major isomer are given: 1H NMR
(CDCl3): d = -0.10 (s, 9 H; Si(CH3)3), 0.34 (s, 9 H; Si(CH3)3), 1.22
(d, 2JH,P = 17.8 Hz, 1 H; PCH(SiMe3)2), 2.65 (d, 2JP,H = 16.0 Hz,
3 H; NCH3), 2.99 (d, 2JP,H = 8.8 Hz, 1 H; PCH(1-methylpyrryl)),
3.69 (s, 3 H; 1-CH3-pyrryl), 5.97 (m, 1 H; pyrryl-H3), 6.12 (m, 1 H;
2H; Hphenyl), 7.39 ppm (mc, 1H; Hphenyl); 13C{ H} NMR (CDCl3):
2
2
d = 199.8 (d, J(P,C) = 25.9 Hz; COtrans), 196.8 (dsat, J(P,C) =
8.1 Hz, 1J(W,C) = 126.7 Hz; COcis), 161.6 (d, 2+3J(P,C) = 5.2 Hz;
NCN), 136.7 (d, 2J(P,C) = 5.2 Hz; ipso-Cphenyl), 127.8 (d, 4J(P,C) =
3
1.9 Hz; meta-Cphenyl), 127.4 (d, J(P,C) = 3.3 Hz; ortho-Cphenyl),
127.2 (d, 5J(P,C) = 1.9 Hz; para-Cphenyl), 78.0 (d, 1+4J(P,C) = 5.5 Hz;
1
pyrryl-H4), 6.68 (m, 1 H; pyrryl-H5); 13C{ H} NMR (CDCl3): d =
PCN), 64.8 (s, NCH3), 39.8 (s, N(CH3)2), 39.4 (s; N(CH3)2), 31.7
2
3
196.5 (d, 2J(P,C) = 39.7 Hz; COtrans), 196.3 (dsat, 2J(P,C) = 7.7 Hz,
(d, J(P,C) = 13.9 Hz; CH(SiMe3)2), 2.5 (d, J(P,C) = 1.9 Hz;
1J(W,C) = 125.4 Hz; COcis), 127.7 (d, J(P,C) = 4.4 Hz; ipso-
Si(CH3)3), 1.7 (d, J(P,C) = 4.5 Hz; Si(CH3)3); 31P{ H} NMR
2
3
1
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1
˜
(CDCl3): d = 103.3 (dsat, J(W,P) = 281.0 Hz); IR (Nujol): n =
2067.8 (w, CO), 1985.1 (w, CO), 1929.9 cm-1 (s, CO), 1899.8 (s),
1863.3 (m); UV/Vis (n-pentane): lmax (abs.) = 297.5 (0.069), 287.0
(0.062), 258.0 (0.281), 233.0 (0.955), 212.0 nm (0.242); MS (EI,
70 eV, 184W): m/z (%):703.1 (2) [M]+, 675.2 (40) [M-CO]+, 647.2
(25) [M-2CO]+, 619.2 (100) [M-3CO]+, 563.2 (25) [M-5CO]+,
549.1 (45) [M-5CO-Me+H]+, 491.1 (30) [M-5CO-Me3Si]+, 220.1
(or triflic acid) the basis was augmented by uncontracted Gaussian
functions with an exponent of 0.0845 (one of each type), and the
nitrogen and sulfur basis sets were augmented by uncontracted
basis functions with exponents of 0.0639 (one of each type)
for nitrogen and 0.0405 (one of each type) for sulfur. For
tungsten the effective core potential ECP-60-MWB46 derived
from the Stuttgart–Dresden group was used. The influence of
the polar solvent was taken into account by employing the
COSMO approach47 with e = 8.93. For cavity construction the
atomic radii of Bondi48 were used which are obtained from
crystallographic data. For tungsten the atomic radius was set to
+
+
=
(5) M-W(CO)5-CHtms2] , 118.1 (10) [PhC NMe] , 73.1 (50)
[Me3Si]+; elemental analysis (%) calculated for C23H34N3O5PSi2W:
C 39.27, H 4.87, N 5.97; found: C 38.89, H 5.10, N 5.61.
Synthesis of 8d. To a solution of 300 mg (0.41 mmol)
azaphosphiridine complex 3d and 37 mL (0.45 mmol) dimethyl
cyanamide in 3.0 mL CH2Cl2 36 mL (0.41 mmol) TfOH and,
after 5 min, 57 mL (0.41 mmol) NEt3 were added at room
temperature. The light orange solution turned into a red brown
one. After removal of all volatile components in vacuo (10-2 mbar)
a mixture of diastereomers (ratio 22 : 1; major isomer: 103.1 ppm
(1J(W,P) = 279.8 Hz), minor isomer: 91.0 ppm (1J(W,P) =
263.5 Hz) was obtained as a brown solid and subsequently purified
by column chromatography on neutral aluminium oxide (-30 ◦C,
pure petroleum ether).
˚
2.2230 A. The stationary points were characterized by numerical
vibrational frequencies calculations using the SNF 3.3.0 program
package.49 Single point calculations were carried out using the
Three Parameter Hybrid Functional Becke350 (B3) in combination
with the correlation functional LYP43 using the valence-triple-z
basis set TZVP,51 which was augmented as specified above, and
the effective core potential ECP-60-MWB46 for tungsten. The
COSMO approach47 was employed with the same parameters as
used for the optimizations. Zero point corrections and thermal
corrections to enthalpies and free energies were adopted from the
optimizations on the RI-BLYP/aug-SV(P), ECP-60-MWB(W)
level. It has been shown that this approach is appropriate for
reactions of epoxide, aziridine and thiirane with methanethiolate.52
Complex 8d. ◦Light orange solid, yield: 97 mg (0.12 mmol,
1
29%); m.p. 167 C (decomp.); H NMR (CDCl3): d = 0.19 (s,
9H; Si(CH3)3), 0.26 (s, 9H; Si(CH3)3), 1.22 (d, 2J(P,H) = 19.3 Hz,
1H; CH(SiMe3)2), 2.91 (s, 6H; N(CH3)2), 3.30 (s, 3H; NCH3),
3.84 (s, br, 1H, PC(H)NMe), 4.07 (mc, 1H; HFc-4/5), 4.10 (s, 5H;
HFc-unsubst), 4.21 (mc, 1H; HFc-4/5), 4.35 (mc, 1H; HFc-2/3), 4.43 (mc,
X-ray crystallographic analyses of 3b,c,d and 8a,d
Suitable single crystals were obtained from concentrated n-
pentane or Et2O solutions upon decreasing the temperature from
ambient temperature to +4 ◦C. Data were collected on Nonius
KappaCCD diffractometer equipped with a low-temperature
device (Cryostream, Oxford Cryosystems) at 123(2) K using
1
1H; HFc-2/3); 13C{ H} NMR (CDCl3): d = 199.2 (d, br, 1J(W,C) =
22.7 Hz; COtrans), 196.8 (dsat, 1J(W,C) = 7.8 Hz, 2J(P,C) = 127.0 Hz,
COcis), 164.6 (s, NCN), 128.8 (s, PCN), 67.8 (s, ipso-Cferrocenyl),
68.0 (s, subst. Cp ring), 67.6 (s, not subst. Cp ring), 66.4 (s,
subst. Cp ring), 66.3 (s, subst. Cp ring), 65.9 (s, subst. Cp ring),
39.9 (s, N-CH3), 39.3 (s, N(CH3)2), 30.7 (s, CH(SiMe3)2), 2.22
˚
graphite monochromated Mo-Ka radiation (l = 0.71073 A).
The structures were solved by Patterson methods (SHELXS-
97) and refined by full-matrix least squares on F2 (SHELXL-
97).53 All non-hydrogens were refined anisotropically. The hy-
drogen atoms were included isotropically using the riding model
on the bound atoms. Absorption corrections were carried out
by integration (3c) or semi-empirically from equivalents (3b,d
and 8a,d) (min./max. transmissions = 0.28704/0.41248 (3b),
0.4876/0.6961 (3c), 0.48284/0.67580 (3d), 0.40853/0.61286 (8a),
and 0.5996/0.8877 (8d)).
1
(s, Si(CH3)3), 2.18 (s, Si(CH3)3); 29Si{ H} NMR (CDCl3): d =
2
2
1
-1.8 (d, J(P,Si) = 2.6 Hz), 1.0 (d, J(P,Si) = 4.8 Hz); 31P{ H}
NMR (CDCl3): d = 101.9 (dsat, 1J(W,P) = 278.5 Hz); IR (Nujol):
-1
˜
n = 2065.9 (m, CO), 1977.3 (m, CO) 1932.5 cm (s, CO). 1916.6
(s), 1899.0 (s); UV/Vis (n-pentane): lmax (abs.) = 296.0 (0.068),
256.0 (0.300), 233.0 (0.851), 209.5 nm (0.088); MS (EI, 70 eV,
184W): m/z (%):811.1 (15) [M]+, 783.1 (40) [M-CO]+, 727.1 (30)
[M-3CO]+, 699.1 (100) [M-4CO]+, 671.1 (20) [M-5CO]+, 657.1
(100) [M-5CO-Me+H]+, 629.1 (25) [M-Cp-Me3Si-NMe2]+, 599.1
(25) [M-Cp2Fe-CO]+, 512.0 (10) [M-5CO-CH(SiMe3)2]+, 486.0
(70) [M-5CO-Cp2Fe]+, 414.1 (10) [M-W(CO)5-Me3Si]+, 328.1 (25)
Crystal structure data of complex 3b (C18H26NO6PSi2W).
Crystal size 0.40 ¥ 0.31 ¥ 0.27 mm, triclinic, P-1, a = 9.2166(3),
˚
+
+
b = 9.7609(5), c = 15.0733(4) A, a = 73.292(2), b = 74.587(2),
=
[M-W(CO)5-CH(SiMe3)2] , 227.1 (40) [Cp2Fe–C(H) NMe] ,
143.1 (90) [M-W(CO)5-CH(SiMe3)2-Cp2Fe]+, 73.1 (100) [Me3Si]+.
Elemental analysis (%) calculated for C27H38FeN3O5PSi2W 39.96,
H 4.72, N 5.18; found: C 39.98, H 4.76, N 4.97.
◦
3
-3
˚
g = 78.755(2) , V = 1241.70(8) A , Z = 2, rc = 1.667 Mg m ,
2qmax = 56◦, collected (independent) reflections = 14037 (5794),
Rint = 0.0593, m = 4.843 mm-1, 269 refined parameters, 0 restraints,
R1 (for I > 2s(I)) = 0.0315, wR2 (for all data) = 0.0661, max./min.
-3
˚
residual electron density = 1.305/-3.531 e A .
Computational methods
DFT calculations on the mechanism of the acid-induced ring
expansion were carried out with the TURBOMOLE V5.8 program
package.41a For optimizations41b the gradient corrected exchange
functional by Becke42 (B88) in combination with the gradient
corrected correlation functional by Lee, Yang and Parr43 (LYP)
with the RI approximation44 and the valence-double-z basis set
SV(P)45 was used. For the oxygen atoms belonging to triflate
Crystal structure data of complex 3c (C18H26NO5PSSi2W). The
thiophene ring is disordered, major layer: 84%: crystal size 0.22 ¥
0.15 ¥ 0.13 mm, triclinic, P-1, a = 9.3006(4), b = 9.8061(4), c =
◦
◦
◦
˚
15.3241(6) A, a = 72.925(3) , b = 75.155(3) , g = 77.227(3) ,
3
V = 1275.21(9) A , Z = 2, rc = 1.665 Mg m-3, 2qmax
=
=
˚
56◦, collected (independent) reflections = 10310 (5790), Rint
0.0282, m = 4.794 mm-1, 289 refined parameters, 6 restraints, R1
Dalton Trans., 2010, 39, 3472–3481 | 3479
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The Royal Society of Chemistry 2010
©

View Article Online
(for I > 2s(I)) = 0.0322, wR2 (for all data) = 0.0850, max./min.
Leonard, Angew. Chem., Int. Ed. Engl., 1969, 8, 962–974; (c) T.-H.
Chuang and K. B. Sharpless, Org. Lett., 2000, 2, 3555–3557; (d) V. H.
Dahanukar and A. I. Zavialov, Curr. Opin. Drug Discov. Dev., 2002, 5,
918–927.
-3
˚
residual electron density = 1.191/-1.253 e A .
Crystal structure data of complex 3d (C24H32NO5PFeSi2W).
3
7 For 1,2l -azaphosphiridines, see: (a) E. Niecke, A. Seyer and D.-A.
Crystal size 0.20 ¥ 0.20 ¥ 0.08 mm, triclinic, P-1, a = 14.5415(2),
Wildbredt, Angew. Chem., 1981, 93, 687–688; (b) N. Dufour, A.-M.
Camminade and J.-P. Majoral, Tetrahedron Lett., 1989, 30, 4813–4814.
˚
b = 16.5338(2), c = 19.5865(2) A, a = 109.0050(7), b = 90.3535(6),
◦
3
-3
5
˚
8 For 1,2l -azaphosphiridines, see: (a) K. Burger, J. Fehn and W. Thenn,
g = 97.4184 (6) , V = 4409.30(9) A , Z = 6, rc = 1.675 Mg m ,
2qmax = 58◦, collected (independent) reflections = 49604 (22997),
Rint = 0.0853, m = 4.572 mm-1, 946 refined parameters, 0 restraints,
R1 (for I > 2s(I)) = 0.0421, wR2 (for all data) = 0.0738, max./min.
Angew. Chem., 1973, 85, 542; K. Burger, J. Fehn and W. Thenn, Angew.
Chem. Int. Ed. Engl., 1973, 12, 502–503; (b) E. Niecke and W. Flick,
Angew. Chem., 1975, 87, 355–356; E. Niecke and W. Flick, Angew.
Chem., Int. Ed. Engl., 1975, 14, 363–364; (c) E. Niecke, J. Bo¨ske, B.
Krebs and M. Dartmann, Chem. Ber., 1985, 118, 3227–3240; (d) M. J. P.
Harger and A. Williams, Tetrahedron Lett., 1986, 27, 2313–2314 (here,
the azaphosphiridine P-oxide was claimed as reactive intermediate).
9 R. Streubel, J. Jeske, P. G. Jones and R. Herbst-Irmer, Angew. Chem.,
1994, 106, 115–117; R. Streubel, J. Jeske, P. G. Jones and R. Herbst-
Irmer, Angew. Chem., Int. Ed. Engl., 1994, 33, 80–82.
-3
˚
residual electron density = 1.989/-1.823 e A .
Crystal structure data of complex 8a (C23H34N3O5PSi2W).
Crystal size 0.32 ¥ 0.24 ¥ 0.12 mm, triclinic, P-1, a = 9.8089(4),
˚
b = 10.0809(5), c = 16.4987(9) A, a = 86.801(2), b = 87.041(3),
◦
3
-3
˚
g = 66.682(3) , V = 1495.07(13) A , Z = 2, rc = 1.563 Mg m ,
2qmax = 60◦, collected (independent) reflections = 17963 (8457),
Rint = 0.0587, m = 4.032 mm-1, 325 refined parameters, 0 restraints,
R1 (for I > 2s(I)) = 0.0319, wR2 (for all data) = 0.0561, max./min.
10 For the use of Li/Cl phosphinidenoid complex 5 in the synthesis of
¨
oxaphosphirane and 2H-azaphosphirene complexes, see: A. Ozbolat,
G. von Frantzius, J. Marinas Pe´rez, M. Nieger and R. Streubel, Angew.
¨
Chem., 2007, 119, 9488–9491; A. Ozbolat, G. von Frantzius, J. Marinas
Pe´rez, M. Nieger and R. Streubel, Angew. Chem., Int. Ed., 2007, 46,
9327–9330.
-3
˚
residual electron density = 1.501/-1.330 e A .
11 R. Streubel, A. Ostrowski, H. Wilkens, F. Ruthe, J. Jeske and P. G.
Jones, Angew. Chem., 1997, 109, 409–413; R. Streubel, A. Ostrowski,
H. Wilkens, F. Ruthe, J. Jeske and P. G. Jones, Angew. Chem., Int. Ed.
Engl., 1997, 36, 378–381.
12 H. Wilkens, F. Ruthe, P. G. Jones and R. Streubel, Chem.–Eur. J., 1998,
4, 1542–1553.
13 R. Streubel, H. Wilkens, F. Ruthe and P. G. Jones, Chem. Commun.,
1999, 2127–2128.
14 R. Streubel, Coord. Chem. Rev., 2002, 227, 175–192.
15 M. J. M. Vlaar, P. Valkier, F. J. J. de Kanter, M. Schakel, A. W. Ehlers,
A. L. Spek, M. Lutz and K. Lammertsma, Chem.–Eur. J., 2001, 7,
3551–3557.
Crystal structure data of complex 8d (C27H38N3O5PSi2W).
Crystal size 0.14 ¥ 0.13 ¥ 0.03 mm, monoclinic, P21 (No. 4),
˚
a = 10.642(1), b = 13.2433(8), c = 11.749(1) A, b = 91.68(0),
V = 1655.14(27) A , Z = 2, rc = 1.628 Mg m , 2qmax = 51◦,
collected (independent) reflections = 5726 (4789), Rint = 0.0505,
m = 4.069 mm-1, 370 refined parameters, 1 restraints, R1 (for I >
2s(I)) = 0.0365, wR2 (for all data) = 0.0724, max./min. residual
3
-3
˚
-3
˚
electron density = 1.159/-1.988 e A .
16 T. P. M. Goumanns, A. W. Ehlers, M. J. M. Vlaar, S. J. Strand and K.
Lammertsma, J. Organomet. Chem., 2002, 643–644, 369–375.
17 N. H. Tran Huy, L. Ricard and F. Mathey, Heteroat. Chem., 1998, 9,
597–600.
18 H. Helten, M. Engeser, D. Gudat, R. Schilling, G. Schnakenburg, M.
Nieger and R. Streubel, Chem.–Eur. J., 2009, 15, 2602–2616.
19 A. Oezbolat, G. von Frantzius, W. Hoffbauer and R. Streubel, Dalton
Trans., 2008, 2674–2676.
20 R. Streubel, M. Bode, J. Marinas Pe´rez, G. Schnakenburg, J. Daniels,
M. Nieger and P. G. Jones, Z. Anorg. Allg. Chem., 2009, 635, 1163–1171.
21 M. Bode, J. Daniels and R. Streubel, Organometallics, 2009, 28, 4636–
4638.
Acknowledgements
Financial support by the Deutsche Forschungsgemeinschaft,
the SFB 624 “Template”, the Fonds der Chemischen Industrie
(Ke´kule grant for H. Helten) and the COST action CM0802
“PhoSciNet” is gratefully acknowledged; furthermore we thank
Prof. Dr B. Engels and the John von Neumann Institute (HBN12)
for computing time and Dr M. Engeser for FT-MS.
22 H. Helten, J. Marinas Pe´rez, J. Daniels and R. Streubel,
Organometallics, 2009, 28, 1221–1226.
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3480 | Dalton Trans., 2010, 39, 3472–3481
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=
-
2
1
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