3H-benzophosphepine complexes: Versatile phosphinidene precursors

Article abstract of DOI:10.1021/ja054885w

The synthesis of a variety of benzophosphepine complexes [R = Ph, t-Bu, Me; ML_n = W(CO)₅, Mo(CO)₅, Cr(CO)₅, Mn(CO)₂Cp] by two successive hydrophosphinations of 1,2-diethynylbenzene is discussed in det

Full text of DOI:10.1021/ja054885w

Published on Web 11/10/2005
3H-Benzophosphepine Complexes: Versatile Phosphinidene
Precursors
Mark L. G. Borst,† Rosa E. Bulo,†,‡ Danie`le J. Gibney,† Yonathan Alem,†
Frans J. J. de Kanter,† Andreas W. Ehlers,† Marius Schakel,† Martin Lutz,§
Anthony L. Spek,§ and Koop Lammertsma*,†
Contribution from the Department of Chemistry, Faculty of Sciences, Vrije UniVersiteit,
De Boelelaan 1083, NL-1081 HV, Amsterdam, The Netherlands, and the BijVoet Center for
Biomolecular Research, Crystal and Structural Chemistry, Utrecht UniVersity, Padualaan 8,
NL-3584 CH, Utrecht, The Netherlands
Received July 21, 2005; E-mail: k.lammertsma@few.vu.nl
Abstract: The synthesis of a variety of benzophosphepine complexes [R ) Ph, t-Bu, Me; MLn ) W(CO)5,
Mo(CO)5, Cr(CO)5, Mn(CO)2Cp] by two successive hydrophosphinations of 1,2-diethynylbenzene is
discussed in detail. The first hydrophosphination step proceeds at ambient temperature without additional
promoters, and subsequent addition of base allows full conversion to benzophosphepines. Novel benzeno-
1,4-diphosphinanes were isolated as side products. The benzophosphepine complexes themselves serve
as convenient phosphinidene precursors at elevated, substituent-dependent temperatures (>55 °C). Kinetic
and computational analyses support the proposal that the phosphepine-phosphanorcaradiene isomerization
is the rate-determining step. In the absence of substrate, addition of the transient phosphinidene to another
benzophosphepine molecule is observed, and addition to 1,2-diethynylbenzene furnishes a delicate bidentate
diphosphirene complex.
Scheme 1. Synthesis of Benzophosphepine Complexes 1a
Introduction
Phosphines are valuable organometallic ligands and are
important in catalysts for stereoselective organic reactions. In
a continuous demand for atom-efficient, fast, and versatile routes
to functionalized phosphines, their reaction with unsaturated
bonds (hydrophosphination), especially under catalytic condi-
tions,1,2 is gaining attention. While radical-initiated3 and base-
promoted4,5 hydrophosphinations are already known for decades,
mechanistic knowledge is required to take better advantage of
the more readily occurring reactions when the phosphine is
complexed to BH36 or transition metals,7-9 which both activate
a (i) THF, rt, 12h. (ii) KOH, rt.
the P-H bond.10 This understanding can aid in the design of
selective hydrophosphination catalysts.
Because of our recent interest in benzophosphepine complexes
1 (Scheme 1),11 we were attracted to a report by Ma¨rkl and
co-workers12 on the base-catalyzed hydrophosphination of
diethynylbenzene 2 with primary phosphines 3. We found that
base (KOH) is required only for full conversion when com-
plexed phosphines are used and that reaction proceeds exclu-
sively in a trans fashion at ambient temperatures. The present
study gives mechanistic details and also insight into the use of
the product.
† Vrije Universiteit.
‡ Present address: ETH Zurich, Switzerland.
§ Utrecht University.
(1) For reviews: (a) Wight, D. K.; Glueck D. S. In Catalytic Heterofunction-
alization; Togni, A. Gru¨tzmacher, H., Eds.; Wiley-VCH: Weinheim, 2001;
Chapter 5, p 143. (b) Tanaka, M. Top. Curr. Chem. 2004, 232, 25. (c)
Alonso, F.; Beletskaya, I. P.; Yus, M. Chem. ReV. 2004, 104, 3079.
(2) (a) Ohmiya, H.; Yorimitsu, H.; Oshima, K. Angew. Chem., Int. Ed. 2005,
44, 2368. (b) Sadow, A. D.; Haller, I.; Fadini, L.; Togni, A. J. Am. Chem.
Soc. 2004, 126, 14704.
(3) (a) Mitchell, T. N.; Heesche, K. J. Organomet. Chem. 1991, 409, 163. (b)
Heesche-Wagner, K.; Mitchell, T. N. J. Organomet. Chem. 1994, 468, 99.
(c) Uriarte, R.; Mazanec, T. J.; Tau, K. D.; Meek, D. W. Inorg. Chem.
1980, 19, 79. (d) Schoufs, M.; Meijer, J.; Vermeer, P.; Brandsma, L. Rec.
TraV. Chim. Pays-Bas 1974, 93, 241.
(4) (a) Bunlaksananusorn, T.; Knochel, P. J. Org. Chem. 2004, 69, 4595. (b)
Ma¨rkl, G.; Baier, H.; Liebl, R. Synthesis 1977, 842. (c) King, R. B. Acc.
Chem. Res. 1972, 5, 177.
(5) (a) Malysheva, S. F.; Sukhov, B. G.; Larina, L. I.; Belogorova, N. A.;
Gusarova, N. K.; Trofimov, B. A. Russ. J. Gen. Chem. 2001, 71, 1907. (b)
Khachatryan, R. A.; Grigoryan, N. Y.; Indzhikyan, M. G. Russ. J. Gen.
Chem. 1994, 64, 1134.
(6) (a) Mimeau, D.; Gaumont, A.-C. J. Org. Chem. 2003, 68, 7016. (b) Mimeau,
D.; Delacroix, O.; Gaumont, A.-C. Chem. Commun. 2003, 2928. (c) Soulier,
E.; Yaouanc, J.-J.; Laurent, P.; des Abbayes, H.; Cle´ment, J.-C. Eur. J.
Org. Chem. 2000, 3497.
(7) With base: (a) Malisch, W.; Klu¨pfel, B.; Schumacher, D.; Nieger, M. J.
Organomet. Chem. 2002, 661, 95. (b) Adams, H.; Bailey, N. A.; Blenkiron,
P.; Morris, M. J. J. Chem. Soc., Dalton Trans. 2000, 3074. Mo-CCH: (c)
Adams, H.; Atkinson, M. T.; Morris, M. J. J. Organomet. Chem. 2001,
633, 125.
(8) With radical initiation: Lang, H.; Lay, U. J. Organomet. Chem. 1992, 441,
389.
(9) Without additives: Leoni, P.; Pasquali, M.; Sommovigo, M.; Albinati, A.;
Lianza, F.; Pregosin, P. S.; Ru¨egger, H. Organometallics 1993, 12, 4503.
(10) Frenking, G.; Wichmann, K.; Fro¨hlich, N.; Grobe, J.; Golla, W.; Le Van,
D.; Krebs, B.; La¨ge, M. Organometallics 2002, 21, 2921.
(11) Borst, M. L. G.; Bulo, R. E.; Winkel, C. W.; Gibney, D.; Schakel, M.;
Ehlers, A. W.; Lammertsma, K. J. Am. Chem. Soc. 2005, 127, 5800.
(12) Ma¨rkl, G.; Burger, W. Tetrahedron Lett. 1983, 2545.
9
10.1021/ja054885w CCC: $30.25 © 2005 American Chemical Society
J. AM. CHEM. SOC. 2005, 127, 16985-16999
16985

A R T I C L E S
Borst et al.
Scheme 2. Isomerization of Benzophosphepines 1 and Generation of Phosphinidenes
Scheme 3. Synthesis of 1,2-Diethynylbenzenea
Benzophosphepines have synthetic potential, because they
rearrange to the phosphanorcaradienes 4, cf. the cyclohepta-
triene-norcaradiene valence isomerization.13 Phosphanorcara-
dienes themselves are unstable and dissociate into naphthalene
and phosphinidene complexes [R-PdMLn] (5), which are the
phosphorus analogues of carbenes (Scheme 2).14 Apart from a
separate class of isolable positively charged complexes,15
electrophilic phosphinidene complexes are transient reagents that
display a rich and versatile chemistry,16 but their access has
been restricted to only a few synthetic routes,17 of which the
cheletropic elimination from 7-phosphanorbornadiene complexes
6 is the most used one.18 Even this reaction is limited to group
6 (Cr, Mo, W) transition-metal-carbonyl complexes and by the
reaction temperature of 110 °C. Using CuCl as catalyst lowers
the reaction temperature, but it likely also changes the nature
of the reagent.19 Benzophosphepine 1 offers advantages because
of its short, convergent synthesis with the phosphorus group
being introduced in the last step; access to a broader range of
transition-metal complexes; a more modest decomposition
temperature of 75-80 °C; and a simpler workup procedure.11
The applicability of this new complexed phosphinidene precur-
sor will be further detailed with additional mechanistic insights.
a (i) (1) LDA, -78 °C; (2) (NH4)2SO4 aq, -78 °C. (ii) (1) KOtBu, -78
°C; (2) H2O, -78 °C.
the most attractive one, but it requires better access to the
dialkyne. An improved synthesis starts with the Corey-Fuchs
one-carbon homologation21 of commercially available o-phthal-
dialdehyde (7) to give tetrabromide 8, followed by debromi-
nation using LDA to furnish diethynylbenzene 2 in 91% overall
yield (Scheme 3). Bases such as n-BuLi are less selective.
Surprisingly, treatment of 8 with KO-t-Bu at -78 °C gave
quantitatively the known22 1,2-bis(bromoethynyl)benzene 9,
whereas other aromatic bromoalkynes are reported to undergo
smooth conversion to terminal alkynes under similar condi-
tions.23
Results and Discussion
We pursued the procedure reported by Ma¨rkl et al.12 for the
uncomplexed benzophosphepines, but the addition of the various
complexed phosphines 3 to diethynylbenzene 2 showed unsat-
isfactory reproducibility on using KOH with 18-crown-6 in
toluene, likely because of its heterogeneous character. This
problem was solved by using THF/KOH instead, thereby
eliminating the use of the crown ether (Table 1, method A).
Unfortunately, similar to the original prodedure, yields never
exceeded 50%, despite full consumption of 8 in ca. 10 min.
Moreover, this method proved inadequate for the synthesis of
3-amino derivative 1g because of the instability of the Et2NPH2-
W(CO)5 complex (3g) in THF. This limitation could be
overcome by eliminating the use of base entirely for the first
hydrophosphination reaction. Thus, monitoring by 31P NMR
spectroscopy of the careful addition of an ethereal solution of
3g to a THF solution of diethynylbenzene showed the appear-
ance of a major resonance at 21 ppm (d, 1JPH ) 381 Hz), which
we assign to the intermediate cis-vinylphosphine complex 11g
(Scheme 4, Table 1), and a smaller one at 56 ppm. On addition
of KOH, full conversion resulted in the evolution of the signal
at 21 ppm into the one at 56 ppm. Workup of the reaction
Synthesis of Benzophosphepine Complexes. Of the two
reported syntheses12,20 leading to 3H-benzophosphepines, the
base-catalyzed hydrophosphination of 1,2-diethynylbenzene is
(13) Jarzeˆcki, A. A.; Gajewski, J.; Davidson, E. R. J. Am. Chem. Soc. 1999,
121, 6928 and references therein.
(14) Dillon, K. D.; Mathey, F.; Nixon, J. F. In Phosphorus: The Carbon Copy;
Wiley: Chichester, 1998.
(15) (a) Graham, T. W.; Cariou, R. P.-Y.; Sa´nchez-Nieves, J.; Allen, A. E.;
Udachin, K. A.; Regragui, R.; Carty, A. J.; Organometallics 2005, 24, 2023.
(b) Sa´nchez-Nieves, J.; Sterenberg, B. T.; Udachin, K. A.; Carty, A. J. J.
Am. Chem. Soc. 2003, 125, 2404. (c) Sterenberg, B. T.; Udachin, K. A.;
Carty, A. J. Organometallics 2003, 22, 3927. (d) Sterenberg, B. T.; Udachin,
K. A.; Carty, A. J. Organometallics 2001, 20, 2657. (e) Sterenberg, B. T.;
Udachin, K. A.; Carty, A. J. Organometallics 2001, 20, 4463. (f) Sterenberg,
B. T.; Carty, A. J. J. Organomet. Chem. 2001, 617-618, 696.
(16) For recent reviews: (a) Lammertsma, K. Top. Curr. Chem. 2003, 229, 95.
(b) Lammertsma, K.; Vlaar, M. J. M.; Eur. J. Org. Chem. 2002, 1127. (c)
Mathey, F.; Tran Huy, N. H.; Marinetti, A. HelV. Chim. Acta 2001, 84,
2938.
(17) (a) Wit, J. B. M.; van Eijkel, G. T.; de Kanter, F. J. J.; Schakel, M.; Ehlers,
A. W.; Lutz, M.; Spek, A. L.; Lammertsma, K. Angew. Chem., Int. Ed.
1999, 38, 2596. (b) Wit, J. B. M.; van Eijkel, G. T.; de Kanter, F. J. J.;
Schakel, M.; Ehlers, A. W.; Lutz, M.; Spek, A. L.; Lammertsma, K.
Tetrahedron 2000, 56, 137. (c) Borst, M. L. G.; van der Riet, N.; Lemmens,
R. H.; de Kanter, F. J. J.; Schakel, M.; Ehlers, A. W.; Mills, A. M.; Lutz,
M.; Spek, A. L.; Lammertsma, K. Chem. Eur. J. 2005, 11, 3631. (d)
Streubel, R.; Wilkens, H.; Ostrowski, A.; Neumann, C.; Ruthe, F.; Jones,
P. G. Angew. Chem., Int. Ed. Engl. 1997, 36, 1492. (e) Wilkens, H.; Ruthe,
F.; Jones, P. G.; Streubel, R. Chem. Commun. 1998, 1529. (f) Mercier, F.;
Deschamps, B.; Mathey, F. J. Am. Chem. Soc. 1989, 111, 9098.
(18) Marinetti, A.; Mathey, F.; Fischer, J.; Mitschler, A. J. Am. Chem. Soc.
1982, 104, 4484.
(20) Yasuike, S.; Kiharada, T.; Tsuchiya, T.; Kurita, J. Chem. Pharm. Bull. 2003,
51, 1283.
(21) Corey, E. J.; Fuchs, P. L. Tetrahedron Lett. 1972, 3769.
(22) Bowles, D. M.; Anthony, J. E. Org. Lett. 2000, 2, 85.
(23) Michel, P.; Gennet, D.; Rassat, A. Tetrahedron Lett. 1999, 8575.
(19) Lammertsma, K.; Ehlers, A. W.; McKee, M. L. J. Am. Chem. Soc. 2003,
125, 14750.
9
16986 J. AM. CHEM. SOC. VOL. 127, NO. 48, 2005

3H-Benzophosphepine Complexes
A R T I C L E S
Table 1. Yields and 31P NMR Chemical Shifts of 3H-Benzophosphepine Complexes 1 (Scheme 4)
31Pc (ppm)
R
MLn
Aa (%)
Bb (%)
1
11
3
1JPHd (Hz)
byproducte
a
b
c
d
e
f
Ph
Ph
Ph
Ph
Me
t-Bu
NEt2
W(CO)5
Mo(CO)5
MnCp(CO)2
Cr(CO)5
W(CO)5
W(CO)5
W(CO)5
47
40
35
37
47
41
-
74
67
-
-14.8
5.8
64.0
23.1
-34.2
10.5
-43
-23
-
-89
-69
+2f
-38
-122
-48
-14
365
345
-
-
A: 10
-
39
19
-
+2
352
348
-
A: polymer?
-69
-
+21
A: 10
-
-
g
40
+56.8
381
c
a Method A, using KOH from the start. b Method B, using KOH only for completing the conversion of 11 to 1. 31P NMR chemical shift recorded in
d
CDCl3 for 1 and THF for 11 and 3. 31P NMR coupling constants for 11. e Only when identified. f We assign the +2 ppm signal to (PhPH2)MnCp(CO)2
instead of the reported (PhPH2)2MnCp(CO) (ref 24).
Scheme 4. Synthesis of Benzophosphepines 1, with (A) and without (B) Initial Base, and Side Product
mixture gave the desired 3-aminobenzophosphepine W(CO)5
complex 3g in 40% yield as yellow crystals. The same one-pot
sequential process, using base to complete the conversion of
11 to 1, also worked well for the syntheses of several of the
other 3H-benzophosphepine complexes listed in Table 1 (method
B) and for some (1a,b) with better yields.
diphosphinane). The meso and one of the rac-isomers that were
formed could be isolated by chromatography. The 31P NMR
resonances at -15.0 and -16.6 ppm (JPP ) 17.4 Hz) for the
meso-isomer consist of double doublets, indicating nonequiva-
lent phosphorus atoms. The rac-isomer shows a single 31P NMR
resonance at -15.7 ppm, but the complexity of its W-satellites
is consistent with the presence of two phosphorus atoms. Also
Tolerance of this method to variation of both transition-metal
complexes [M(CO)5 (M ) Cr, Mo, W) and MnCp(CO)2] and
substituents (Ph, Me, t-Bu, and NEt2) at the phosphorus center
is evident (Table 1). Noteworthy is molybdenum complex 1b
(yellow crystals), because the corresponding phospha-
norbornadiene 6b is difficult to synthesize (29%), as traces of
Mo(CO)6 catalyze the polymerization of acetylenedicarboxylate.
Therefore and because of the stability of the final products, most
phosphinidene chemistry has revolved around the W(CO)5
1
the H NMR spectrum of the symmetric 10e (rac) isomer is
less complex compared to the asymmetric meso-isomer. The
bridgehead protons give a single resonance at δ 3.64 ppm with
a large 2JHP of 22.7 Hz and smaller 3JHH coupling constants of
5.3 and 2.1 Hz. Two resonances are observed at 2.67 and 2.54
ppm for the endo- and exo-protons at C3 and C6. All other
NMR data of these stable compounds that have melting points
>170 °C are consistent with the bicyclo[2.2.2]octane structure
10e.
1
complexes. The H NMR characteristics for 1d with H(2) and
2
H(4) resonances at 6.18 ppm, a sizable JHP coupling constant
In the X-ray crystal structure of rac-10e, the molecule has
an approximate, noncrystallographic C2 symmetry. Deviations
from the exact symmetry are due to a different arrangement of
the W(CO)5 groups, which are both located over the ring system
(Figure 1). The P-CH3 bond distances are relatively short
[1.826(3) and 1.822(3) Å] compared to the P-C bonds in the
1,4-diphosphinane part [1.854(3)-1.865(3) Å]. The arrangement
around the bridge-head carbon C11 is nearly tetrahedral (Σ
329.4°) and the C-C bonds of the benzene-ring [all 1.386(4)-
1.395(4) Å] are indicative of electron delocalization.
3
of 24.1 Hz, and a JHH of 12.4 Hz for the cis-olefin are also
representative for the other benzophosphepine complexes. Using
method A enables the synthesis of the sterically demanding tert-
butyl derivative (1f, orange crystals), whereas amino derivative
1g is accessible via method B, as discussed. The large difference
in 31P NMR chemical shifts between the methyl and tert-butyl
derivatives (1e, -34.5 ppm; 1f, 10.5 ppm) is due to the
substituent effect, which is even more pronounced in the
phosphine complexes 3. The low-field 31P NMR chemical shift
of 1g (56.8 ppm) indicates significant shielding due to electron
donation of the nitrogen.
Mo(CO)5-complexed diphosphinanes (rac- and meso-10b)
were likewise obtained as byproducts (12%) in the synthesis of
1b (also method A) and isolated by fractional crystallization.
The rac-isomer has a 31P NMR resonance at δ 19.7 ppm and
the asymmetric meso-isomer has two at 27.2 and 25.1 ppm with
a 3JPP coupling of 11.7 Hz. The molecular structure in the crystal
of meso-10b (mp >116 °C), shown in Figure 2, is similar to
that of rac-10e, but the pseudosymmetric bonds and angles differ
slightly due to the asymmetry of the molecule, which has slightly
longer bonds around the P2 than the P1 atom.
Side-Product Formation and Mechanism. The synthesis
of 3-methyl-3H-benzophosphepine complex 1f gives 10e as
byproduct in about 10%, which we believe to be the first
complexed 2,5-diphosphabicyclo[2.2.2]octane25 (or benzeno-1,4-
(24) Rehder, D.; Kec¸eci, A. Inorg. Chim. Acta 1985, 103, 173.
(25) 2,5-Diphosphabicyclo[2.2.2]octane as a structural motive can be recognized
in several polycyclic compounds. See: (a) Ma¨rkl, G.; Beckh, H. J.; Mayer,
K. K.; Ziegler, M. L.; Zahn, T. Angew. Chem., Int. Ed. Engl. 1987, 26,
236. (b) Kojima, T.; Ishioka, Y.; Matsuda, Y. Chem. Commun. 2004, 366.
9
J. AM. CHEM. SOC. VOL. 127, NO. 48, 2005 16987

A R T I C L E S
Borst et al.
The uncatalyzed reaction of phosphine complexes 3 with 1,2-
diethynylbenzene 2 (method B) is truly remarkable because so
far all reported hydrophosphinations that used complexed
phosphines required heat, base, and/or radical initiators,7,26
except for a report on the room-temperature reaction of ethylene
with a Pd-phosphine complex9 and the facile reaction of a
bridged phosphine diiron complex with phenylacetylene.27
The first part of the explanation became apparent on mixing
equimolar amounts of PhPH2-W(CO)5 and PhPD2-W(CO)5
in anhydrous THF. 31P NMR monitoring showed slow H-D
exchange, forming PhPHD-W(CO)5 with a characteristic triplet
at -90 ppm, which signifies phosphine disproportionation. The
Figure 1. Displacement ellipsoid plot (50% probability level) of rac-10e.
Hydrogen atoms are omitted for clarity. Selected bond distances (Å), angles
(deg), and torsion angles (deg): P1-W1, 2.5058(7); P2-W2, 2.5048(7);
P1-C11, 1.860(3); P2-C21, 1.854(3) P1-C26, 1.861(3); P2-C16, 1.865(3);
P1-C15, 1.826(3); P2-C25, 1.822(3); C11-C12, 1.513(3); C12-C22,
1.395(4); C12-C13, 1.393(4); P1-C11-C12, 105.66(17); P2-C21-C22,
105.32(17); P1-C11-C16, 113.85(17); P2-C21-C26, 113.71(17); C11-
C12-C13, 123.2(2); C19-W1-P1-C15, 12.35(13); C27-W2-P2-C25,
11.57(13); C16-C11-C12-C13, -118.3(3); C15-P1-C11-C16, 45.8(2);
P1-C11-C12-C13, 118.5(3).
1
second indicator is the deshielded H NMR chemical shift of
the 1,2-diethynylbenzene 2 (3.33 ppm, tCH), which suggests
an activated acetylenic group similar to benzoylacetylene (3.44
ppm),28 which readily undergoes phosphine catalyzed addi-
tions.29 Under the same experimental conditions, phenylphos-
phine 3a reacted hardly with phenylacetylene (3.03 ppm), giving
<1% of vinylphosphine, while p-diethynylbenzene (3.27 ppm)
was only slightly less reactive than 2. The third, important lead
was the NMR identification of vinylphosphine 11d in the
reaction of PhPH2-Cr(CO)5 with 2 (Scheme 4), even though it
could not be obtained free of benzophosphepine complex 1d.
The olefinic protons showed a NOE interaction and a coupling
constant (12.5 Hz) that are consistent with a cis olefin. The 31
P
NMR chemical shift at 4.3 ppm is similar to the radical-initiated
hydrophosphination product (+3.4, 1JPH ) 356 Hz) of PhPH2-
Cr(CO)5 (3d) with phenylacetylene, which reportedly has a cis
configuration (3JHH ) 13 Hz).8 Further, 31P NMR monitoring
of the reaction of 3d with 2 in the presence of the radical initiator
AIBN showed conversion of the phosphine (3d) to vinylphos-
phine 11d. Some benzophosphepine 1d [δ(31P) 23.1] was also
formed, but it was not stable at the temperatures required for
radical formation (50-60 °C). Finally, 31P NMR monitoring
of the deuteriophosphination of 2 with PhPD2-W(CO)5 (3h)
(with incomplete conversion) showed the formation of only two
D-containing products, 1,5-dideuteriophosphepine 1h (-14.8
ppm, 95% D-label, 14% isolated yield) and a product with a
Figure 2. Displacement ellipsoid plot (50% probability level) of meso-
10b. Hydrogen atoms are omitted for clarity. Selected bond distances (Å),
angles (deg), and torsion angles (deg): P1-Mo1, 2.5099(9); P2-Mo2,
2.5237(9); P1-C11, 1.826(3); P2-C22, 1.830(4); P1-C1, 1.850(4); P2-
C8, 1.861(3); P1-C9, 1.855(4); P2-C10, 1.863(4); C1-C10, 1.533(5); C1-
C2, 1.515(5); C2-C7, 1.396(5); C2-C3, 1.393(5); P1-C1-C2, 104.4(2);
C2-C1-C10, 112.6(3); Mo1-P1-C1, 119.35(11); Mo2-P2-C8,
116.53(11); P1-C1-C2-C3, 116.2(3).
1
chemical shift at -43.9 ppm (t, JPD 55 Hz) that we assign to
11h.
Consequently, we surmise that the hydrophosphination in
THF starts by some disproportionation of phosphine complex
3 into 12 and 13 of which the phosphide anion attacks the
activated acetylenic carbon of 2 to form vinyl anion 14 that is
then protonated (by 12) to give cis-vinylphosphine 11 (Scheme
6). The fact that the phenylphosphine complexes give better
yields than the alkylphosphines (Table 1) supports the dispro-
portionation mechanism as the phenyl group stabilizes the
charged phosphorus center better.
Reactivity and Kinetics of Benzophosphepines. All the
benzophosphepine complexes 1 are phosphinidene precursors,
as shown by their reaction at 80-85 °C (120 °C for 1f) with
diphenylacetylene and trans-stilbene that afforded the expected
phosphirenes 15 and phosphiranes 16, respectively, in (very)
Application of the benzeno-1,4-diphosphinane frame, be it
decomplexed, can be envisioned both as a novel ligand system
and as a supramolecular building block. Its formation can be
explained by successive attacks of two phosphide complexes
on diethynylbenzene 2. The yields increased with an excess of
the phosphine complex. The first phosphide attacks a terminal
acetylenic carbon in either an anti (a) or syn (b) fashion (Scheme
5). Route b gives a cis-vinylphosphide complex that undergoes
intramolecular hydrophosphination to form benzophosphepine
1. Anti attack leads to a trans-olefin that cannot undergo ring-
closure and is therefore subject to attack by a second phosphide
complex, either before or after protonation. When this occurs
in a syn fashion ring-closure at the benzylic carbon will give
the Markovnikov addition product, and subsequent protonation
allows the other phosphorus atom to perform a similar addition
to yield 1,4-diphosphinane 10. When the second phosphide
enters in an anti-fashion, which may even be sterically preferred,
the resulting bis(trans-vinylphosphide) is unable to ring-close
and may lead to polymeric structures and loss of material.
(26) (a) Kalinina, I.; Donnadieu, B.; Mathey, F. Organometallics 2005, 24, 696.
(b) Huttner, G.; Mu¨ller, H.-D.; Friedrich, P.; Ko¨lle, U. Chem. Ber. 1977,
110, 1254.
(27) Sugiura, J.; Kakizawa, T.; Hashimoto, H.; Tobita, H.; Ogino, H. Organo-
metallics 2005, 24, 1099.
(28) Noro, M.; Masuda, T.; Ichimura, A. S.; Koga, N.; Iwamura, H. J. Am.
Chem. Soc. 1994, 116, 6179.
(29) Lu, X.; Zhang, C.; Xu, Z. Acc. Chem. Res. 2001, 34, 535.
9
16988 J. AM. CHEM. SOC. VOL. 127, NO. 48, 2005

3H-Benzophosphepine Complexes
A R T I C L E S
Scheme 5. Proposed Mechanism for the Formation of Diphoshabicyclo[2.2.]octanes 10
Scheme 6. Proposed Mechanism for the Uncatalyzed Formation of Vinylphosphine Complexes
Scheme 7. Phosphinidene Addition Reactions for 1 with Yields in Parentheses for Those Using 6
Table 2. Half-life Times of Benzophosphepines 1 in the Presence
of Diphenylacetylene and the Rate Constants for the
Decomposition of 1e in the Presence of Diphenylacetylene
good yields (Scheme 7). The values in parentheses refer to the
reported yields for the reaction with phosphanorbornadiene
complex 6.18,30
half-life determination
rate constant determination for 1e
Particularly complexed aminobenzophosphepines are interest-
ing precursors to aminophosphinidene complexes, which could
be trapped upon thermolysis of aminophosphirane complexes
in high yields.17c The amine group in these trapping products
is easily replaced, as has been shown, for example, for the
corresponding amino phosphirene that converts to the chloro
derivative on treatment with dry HCl.31 We found an unexpected
functionalization of the known32 aminophosphirene 15g during
its purification over silica, on which it partially converted to
the yet unknown hydroxyphosphirene complex 15i. This yellow
solid (mp 122-124 °C) has a rather shielded 31P NMR chemical
t1
k
/
2
1
phosphepine 1
T (
°
C)
(min)
T (
°
C)
(10-5 L mol-1 s-
)
a
b
d
e
f
75
75
75
203
111
142
633
344
70
80
90
100
1.00
3.18
9.45
24.9
75a
115
Ea (kcal/mol)
26.3 ( 0.3
a Derived from an Arrhenius plot.
by more than 3 times, and that for the tert-butyl derivative 1f
is about twice as much at the higher temperature of 115 °C.
The kinetics was determined by 31P NMR for methyl derivative
1e at four different temperatures (Table 2) from which an
activation energy is derived of 27.0 ( 0.3 kcal/mol, which is 6
kcal/mol less than for the related decomposition of 7-phenyl-
7-phosphanorbornadiene complex 6.33 The activation enthalpy
is calculated to be 26.3 ( 0.3 kcal/mol, with a small entropy of
activation of -5.1 ( 0.9 eu. The rate constants were independent
of either the concentration (5.1, 2.6, or 1.0 equiv) or the nature
of the substrate (phenylacetylene, trans-stilbene, or aniline) in
the reaction mixture as graphically shown in Figure 3. This
behavior is similar to that reported for 6.30,34
1
shift at -78.1 ppm with a large JPW of 319.6 Hz.
The reaction of the benzophosphepine complexes 1 with
phenylacetylene in toluene is a first-order process for the release
of the phosphinidene moiety from 1 that depends more on the
substituent than on the transition-metal group. The half-life
times, summarized in Table 2, are at 75 °C, similar for the
phenyl derivatives 1a, b, d; the t1/2 for Mn complex 1c could
not be determined accurately due to the broadness of the NMR
signals, but the onset of the reaction starts similarly to 1a at
about 50 °C. Methyl substitution (1e) increases the half-life time
(30) Marinetti, A.; Mathey, F. Organometallics 1984, 3, 456.
(31) Deschamps, B.; Mathey, F. Synthesis 1995, 941.
(32) Deschamps, B.; Mathey, F. New J. Chem. 1988, 12, 755.
(33) Marinetti, A.; Charrier, C.; Mathey, F.; Fischer, J. Organometallics 1985,
4, 2134.
9
J. AM. CHEM. SOC. VOL. 127, NO. 48, 2005 16989

A R T I C L E S
Borst et al.
Figure 3. Kinetic plots of the decomposition of 1e at 80 °C in the presence of (left) aniline (b), or 5.1 (O) or 2.6 (1) equiv of stilbene, or (right) 5.1 (b),
2.6 (1), or 1.0 (O) equiv of diphenylacetylene.
Table 3. B86-P88/TZP Energies (in kcal/mol) Relative to eq-I
entry
MLn
R
annelated
syn-II
synTS
ax-I
TS-flip
eq-I
antiTS
anti-II
1
2
3
4
5
6
7
-
H
H
H
-
-
-4.2
4.4
3.0
2.8
3.3
10.6
15.5
15.1
13.5
15.3
19.3
26.1
0.0
1.3
1.5
2.0
0.9
-1.3
0.4
6.3
5.9
6.2
5.5c
4.1c
2.7
2.8
0.0
0.0
0.0
0.0
3.7c
0.0
0.0
9.7
-4.7
3.1
2.3
2.0
7.2
Cr(CO)5
W(CO)5
Cr(CO)5
Cr(CO)5
-
13.6
13.7
d
-
Pha
Phb
H
-
-
yes
yes
21.4c
18.0
24.1
9.6
19.1
8.5
17.6
Cr(CO)5
H
a Perpendicular to the P-W bond. b Parallel to the P-W bond; values relative to eq-I, entry 4. c No frequencies. d No convergence.
Figure 4. Energy diagram for the relationship of phosphine-Cr(CO)5 (I) and phosphanorcaradiene-Cr(CO)5 (II).
To better understand the relationship between the benzo-
phosphepine and 7-phosphanorbornadiene complexes, we used
density functional theory (B86-P88) for several parent phos-
phinidene complexes. Their energetic data are summarized in
Table 3. The relationship is graphically depicted in Figure 4
for the parent phosphepine-Cr(CO)5 (labeled I). Its two
conformations with the transition metal group in either an axial
(ax) or equatorial position (eq) interconvert via a ring-flip with
a small energy barrier of only 5.9 kcal/mol. Each rearranges in
a symmetry-allowed disrotatory process to the corresponding
syn- or anti-phosphanorcaradiene complex (labeled II), but these
processes are endothermic by about 3 kcal/mol with barriers of
nearly 14 kcal/mol. The higher barrier for ax-I f syn-II may
stem from steric interactions between the metal group and the
cyclohexadiene ring.
The influence of the transition group on the energy profile is
important but does not discirminate between the metals (entries
2 and 3 of Table 3). Complexation destabilizes norcaradiene II
with respect to phosphepine I and to a smaller extent the
transition state for the electrocyclization. Thus, whereas the
rearrangement is exothermic for the uncomplexed phosphepine
(entry 1), which is indeed an elusive species,12,20,35 metal
complexation results in an endothermic rearrangement. The
(35) (a) Ma¨rkl, G.; Schubert, H. Tetrahedron Lett. 1970, 1273. (b) Ma¨rkl, G.;
Burger, W. Angew. Chem., Int. Ed. Engl. 1984, 23, 894.
(34) Marinetti, A.; Mathey, F. Organometallics 1982, 1, 1488.
9
16990 J. AM. CHEM. SOC. VOL. 127, NO. 48, 2005

3H-Benzophosphepine Complexes
A R T I C L E S
Figure 5. Schematic representation of the interaction of the Walsh orbitals
of phosphanorcaradiene II with the orbitals of chromium-pentacarbonyl
group.
Scheme 8. Reaction of Phosphinidene 5a with
Diphenyldiacetylene at (a) 55 °C with CuICl and (b) 110 °C
Figure 6. Displacement ellipsoid plot (50% probability level) of rac-19.
Hydrogen atoms are omitted for clarity. Selected bond distances (Å), angles
(deg), and torsion angles (deg): W1-P1, 2.4905(11); W2-P2, 2.4765(10);
P1-C11, 1.803(4); P1-C12, 1.799(4); C11-C12, 1.325(6); C21-C22,
1.326(6); C12-C22, 1.423(6); C11-P1-C12, 43.18(18); C21-P2-C22,
43.27(18); C11-C12-C22-C21, -176.1(6); C12-C11-C13-C18, -3.2(9);
C22-C21-C23-C28, -178.6(6).
complex 1e. This is also consistent with the observation that
the decomposition of 1e is neither catalyzed by metals (PdCl2,
Pd/C, CuSO4) nor by (Lewis) bases (KOH, Et3N, BPh3).
Addition to Diynes. Next to turn to is the window within
(some of) the benzophosphepines complexes 1 are usable. After
all, the electrophilic phosphinidene complexes may add to the
CdC bonds that 1 possesses and to the CtCH bonds of their
starting material (2). We address these aspects starting with a
1,3-diyne. It has been shown that the “classical” 7-phospha-
norbornadiene complex 6a gives different products depending
on the manner in which it is used (Scheme 8). At ca. 55 °C,
using Cu(I)Cl as catalyst,18 [1 + 2]-adduct 17 is the primary
product. In selected cases, depending on the substituents R and
R′, a second [PhPW(CO)5] inserts into a C-P bond to give
1,2-diphosphetes 18.39 Instead, without using a catalyst (110
°C), a second alkyne addition takes place and gives bis-
phosphirenes 19.40 Diphosphene complex 20 is typically ob-
served as a byproduct, resulting from the decomposition of 6a.33
Benzophosphepines 1a (2.2 equiv) reacted at 60 °C with
diphenyl-1,3-butadiyne to give the rac-bis-phosphirene 19a (δ
31P -137.3 ppm) as orange needles in 11% yield, a trace of the
meso-isomer (δ31P -137.1 ppm), and 28% of monoadduct 1739a
(28%). The low yield of the diadduct is likely due to steric
hindrance, which is evident from the single X-ray crystal
structure analysis of the rac-isomer (Figure 6). In the crystal,
the molecule of 19 has only C1 symmetry. Conjugation of the
two phosphirene double bonds is apparent from the short
connecting C12-C22 bond [1.423(6) Å], similar to that reported
for the di-SiMe3 derivative.40 In 19 conjugation is extended to
the phenyl substituents, which lie almost in the same plane as
the two phosphirene rings [torsion angles of -3.2(9)° and
-178.6(6)°].
influence of the transition metal is evident. Coordination of the
phosphorus atom to the transition metal results in strong
σ-bonding with electron transfer from the ligand to the metal
together with weaker π-back-bonding due to electron donation
of the metal into the unoccupied orbitals of the ligand.36 The
P-metal σ-bond diminishes the strength of the phosphirane C-C
bonding orbital (Figure 5a), while π-back-donation enhances
the antibonding nature of the distal C-C bond (Figure 5b). Both
effects stabilize the phosphepine over the norcaradiene struc-
ture.37
Substituting hydrogen for a phenyl group decreases the barrier
for electrocyclization slightly (e1.0 kcal/mol, entries 4 and 5).
The phenyl group can adopt two conformations, either perpen-
dicular or parallel to the P-W bond, the latter of which is found
in the crystal structure of W(CO)5-benzophosphepine 1a, but
the difference is marginal for ax-I and syn-II; for the equatorial/
anti pair, a parallel orientation results in an unfavorable
interaction of the phenyl group with the phosphepine ring,
leading to considerably higher energies. The effect of benz-
annellation is far more pronounced, raising the cyclization
barrier by about 10 to 26.1 kcal/mol for forming syn-benzo-II
from ax-benzo-I (entry 6, Table 3), because benzophos-
phanorcaradiene benefits far less from electron delocalization
than benzophosphepine. Dissociation of syn-benzo-II into
Cr(CO)5-phosphinidene and naphthalene is endothermic by
14.9 kcal/mol, but is likely more favorable when the entropy
term is included.38 Recent DFT calculations on W(CO)5-
complexed phosphinidenes suggest a small barrier for this
process (6.7 kcal/mol).19
In summary, ring-closure of metal-complexed benzophos-
phepine I appears to be the rate-determining step, which is in
compliance with the kinetic data and with the experimental
activation energy of 27.0 kcal/mol for reaction of the W(CO)5-
The question arises of the fate of the reactive phosphinidene
in the absence of a substrate. For precursor 6a this results mostly
(36) Goumans, T. P. M.; Ehlers, A. W.; van Hemert, M. C.; Rosa, A.; Baerends,
E.-J.; Lammertsma, K. J. Am. Chem. Soc. 2003, 125, 3558.
(37) Gu¨nther, H. Tetrahedron Lett. 1970, 5173.
(38) Bulo, R. E. Ph.D. thesis, Vrije Universiteit, Amsterdam (NL), The
Netherlands, 2004.
(39) (a) Tran Huy, N. H.; Ricard, L.; Mathey, F. Organometallics 1997, 16,
4501. (b) Wang, B.; Nguyen, K. A.; Srinivas, N.; Watkins, C. L.; Menzer,
S.; Spek, A. L.; Lammertsma, K. Organometallics 1999, 18, 796.
(40) Tran Huy, N. H.; Ricard, L.; Mathey, F. J. Chem. Soc., Dalton Trans. 1999,
2409-2410.
9
J. AM. CHEM. SOC. VOL. 127, NO. 48, 2005 16991

A R T I C L E S
Borst et al.
Table 4. 31P NMR Chemical Shifts (ppm), Assignments, and
Intensities of the Isomers of 21
21
δ
3JPP (Hz)
W(CO)5P2
W(CO)5P1
rel int
a
b
c
-8.4, -126.9
-6.6, -118.8
-15.5, -123.4
-16.4, -127.9
14.7
11.7
11.4
14.6
endo
endo
exo
endo
exo
exo
0.46
1.00
0.59
<0.1
d
exo
endo
Scheme 9. Reaction of Phosphinidene 5a in the Presence of 1a
at 60 °C
in diphosphene 20, which often is also a byproduct of the
addition reactions. Monitoring by 31P NMR the decomposition
of benzophosphepine 1a in toluene at 60 °C for 3 days likewise
resulted in the formation of 20 (10% by 31P NMR), confirming
the intermediacy of the same reagent, but in addition gave other
products (70% by 31P NMR) that were also observed in the
reaction with diphenyldiacetylene. Analysis of the reaction
mixture (see the Experimental Section) showed the presence
of the four isomers of phosphirane complex 21 (characteristics
are summarized in Table 4) that must result from addition of
[PhPW(CO)5] to one of the double bonds of phosphepine 1a
(Scheme 9). The addition underscores the olefinic nature of the
phosphepine ring of 1a as additions to aromatic rings are rare.41
Characteristic in the 31P NMR spectrum of the major isomer
21b are the double doublets at -6.6 and -118.8 ppm with a
3JPP coupling constant of 11.7 Hz, which enables the assignment
of the other isomers as they have different 31P NMR chemical
shifts (Table 4). The fact that both the endo and exo orientations
of the W(CO)5P2 moiety are observed is in accord with the
calculated modest energy barrier between the axial and equato-
rial conformations of benzophosphepine complexes. The as-
signment of 21b was confirmed by a single-crystal X-ray
structure determination, which is shown in Figure 7. The
W(CO)5 moiety of the phosphepine ring is positioned axially,
just as in 1a, and that of the phosphirane is exo-substituted.
The P-phenyl substituent is parallel to the almost planar seven-
membered ring, thereby rotated by about 90° from its perpen-
dicular position in 1a. The P-C bond lengths [1.840(2) and
1.839(2) Å] and the C1-P-C2 bond angle [48.74(9)°] for the
phosphirane ring are in the expected range.42
Figure 7. Displacement ellipsoid plot (50% probability level) of 21b.
Hydrogen atoms are omitted for clarity. Selected bond distances (Å), angles
(deg), and torsion angles (deg): W1-P1, 2.4681(5); W2-P2, 2.4960(5);
P1-C1, 1.840(2); P2-C1, 1.814(2); P1-C2, 1.860(2); P2-C10, 1.799(2);
C3-C8, 1.412(3); C1-P1-C2, 48.74(9); C1-P2-C10, 106.17(10); P1-
C1-P2, 128.77(12); P1-C2-C3, 130.22(16); C11-P1-C1-P2, 11.47(18);
P2-C1-C2-P1, -122.23(16); C8-C9-C10-P2, 4.4(4); P2-C1-C2-
C3, 0.4(3); C28-W2-P2-C17, 46.02(11); C23-W1-P1-C11, 122.53(12).
part is due to the limited stability of 2 at elevated temperatures.
For 23 steric hindrance plays a role. The X-ray crystal structure
of rac-23 shows a slightly deformed Mo(CO)5 moiety (Figure
8). The CdC bonds of the phosphirenes are conjugated with
each other via the connecting benzene ring, as signified by the
small dihedral angles and the short C1-C7 [1.456(3) Å] and
C2-C9 [1.457(3) Å] bonds. Still, steric bulk prevents the
benzene and phosphirene rings to lie in the same plane, causing
the P1-phosphirene ring to be tilted by 20°. The other
characteristic data of rac-23 in solution (31P δ -135.5 ppm)
resemble those of a similar phosphirene molybdenum complex.43
Reactivity of a Manganese Phosphinidene. So far we
discussed the benzophosphepines 1 as precursors for electro-
philic phosphinidenes, such as [RPM(CO)5], but because of its
convenient synthesis, access to species with other philicities can
be envisioned. We will elaborate on this aspect for manganese
benzophosphepine 1c, on which we reported only briefly in an
earlier communication.11 Presumably [Ph-PdMn(CO)2Cp] (5c)
has strongly reduced electrophilic character, since the philicity
of a phosphinidene complex [RPdMLn] is known to change
profoundly on replacing electron-withdrawing (e.g. CO) for
electron-donating ligands, such as the cyclopentadienyl ring
(Cp).44 In fact, a number of very stable, highly nucleophilic
phosphinidene complexes with rather limited reactivity have
To further establish the reaction window within which the
benzophosphepine complexes can be used, it is of interest to
verify to what extent they can react with their precursor, 1,2-
diethynylbenzene 2. For this purpose we applied the molybde-
num complex 1b that gave both the monoadduct 22 (49%) and
the diadduct 23 (40%) in modest yields (Scheme 10), which in
(41) (a) Bulo, R. E.; Trion, L.; Ehlers, A. W.; de Kanter, F. J. J.; Schakel, M.;
Lutz, M.; Spek, A. L.; Lammertsma, K. Chem. Eur. J. 2004, 10, 5332. (b)
Bulo, R. E.; Ehlers, A. W.; de Kanter, F. J. J.; Wang, B.; Schakel, M.;
Lutz, M.; Spek, A. L.; Lammertsma, K. Chem. Eur. J. 2004, 10, 2732. (c)
van Eis, M. J.; Komen, C. M. D.; de Kanter, F. J. J.; de Wolf, W. H.;
Lammertsma, K.; Bickelhaupt, F.; Lutz, M.; Spek, A. L. Angew. Chem.,
Int. Ed. 1998, 37, 1547. (d) Svara, J.; Mathey, F. Organometallics 1986,
5, 1159.
(42) Mathey, F.; Regitz, M. Three-membered rings. In Phosphorus-Carbon
Heterocyclic Chemistry: The Rise of a New Domain; Mathey, F., Ed.;
Elsevier: Oxford; 2001; p 17-55.
(43) Marinetti, A.; Fischer, J.; Mathey, F. J. Am. Chem. Soc. 1985, 107, 5001.
(44) Ehlers, A. W.; Baerends, E. J.; Lammertsma, K. J. Am. Chem. Soc. 2002,
124, 2831.
9
16992 J. AM. CHEM. SOC. VOL. 127, NO. 48, 2005

3H-Benzophosphepine Complexes
A R T I C L E S
Scheme 10. Reaction of Benzophosphepine 1b with 1,2-Diethynylbenzene
been reported.45 Because both CO and Cp ligands are present
in 5c, it is of interest to explore its reactivity.
phosphirene, which has a Mn-P bond length [2.1961(6) Å]
similar to that of the benzophosphepine complex 1c11 and
likewise has its P-phenyl group oriented parallel to this bond.
The phosphirene bond lengths and angles are in the expected
range.42 Conjugation between the C1-phenyl group and the
phosphirene ring is suggested by the small torsion angle of
5.6(3)°.
Phosphinidene complex 5c was found to be not nucleophilic
enough to react with benzophenone to form a phosphaalkene46
nor to be electrophilic enough to yield a P-O ylide either.47
And although reaction with trans-stilbene did not take place,
addition to phenylacetylene did occur to give the first manganese-
complexed phosphirene (24) in 81% yield (Scheme 11). The
increased electron donation from the transition metal fragment
of the yellow product (mp 105 °C) is apparent from the 31P
NMR chemical shift at -59.0 ppm, which is significantly
deshielded from that for the phosphirene-M(CO)5 (M ) W,
Mo) complexes. Phosphirene 24 shows a doublet for its olefinic
2
proton at 8.52 ppm with a large JHP of 19.3 Hz. An X-ray
crystal structure (Figure 9) supports the formation of the
Figure 9. Displacement ellipsoid plot (50% probability level) of 24.
Selected bond distances (Å), angles (deg), and torsion angles (deg): Mn1-
P1, 2.1961(5); P1-C1, 1.7896(16); P1-C2, 1.7781(18); C1-C2, 1.310(2);
Mn-C15, 1.7691(18); Mn-C16, 1.7633(18); C15-O1, 1.157(2); C1-P1-
C2, 43.08(8); Mn1-P1-C1, 125.48(5); C16-Mn1-P1-C9, -47.71(8);
C2-C1-C3-C4, 5.6(3).
The reduced reactivity of [Ph-PdMn(CO)2Cp] (5c) is
reminiscent to that of [i-Pr2N-PdFe(CO)4], which adds to
alkynes and to terminal olefins, but not to di- or higher
substituted ones.17a-c Reaction of benzophosphepine 1c in
1-hexene at 70 °C gave nearly quantitatively (98%) in a 1:1.4
mixture the anti-:syn-phosphirane complexes 25 as a yellow
oil (Scheme 11). The 31P NMR chemical shifts of 23 (-77.5/-
Figure 8. Displacement ellipsoid plot (50% probability level) of rac-23.
Hydrogen atoms are omitted for clarity. Selected bond distances (Å), angles
(deg), and torsion angles (deg): Mo1-P1, 2.5180(6); Mo2-P2, 2.4885(7);
P1-C7, 1.808(2); P1-C8, 1.795(3); P2-C9, 1.808(3); P2-C10, 1.781(3);
C7-C8, 1.311(4); C9-C10, 1.311(4); C1-C7, 1.456(3); C1-C2, 1.416(3);
C2-C9, 1.457(3); C2-C3, 1.398(3); C7-P1-C8, 42.66(11); C9-P2-C10,
42.85(12); C2-C1-C7, 123.7(2); C2-C9-C10, 139.6(2); P2-C9-C2,
152.85(19); C2-C1-C7-P1, 177.1(2); C2-C1-C7-C8, 21.2(6); C7-
C1-C2-C9, 5.1(4); C1-C2-C9-C10, 177.2(3); C1-C2-C9-P2, -5.0(6);
C23-Mo1-P1-C11, 42.02(12); C31-Mo2-P2-C17, 122.98(12).
(45) For examples: (a) Hitchcock, P. B.; Lappert, M. F.; Leung, W.-P. J. Chem.
Soc., Chem. Commun. 1987, 1282. (b) Ho, J.; Rousseau, R.; Stephan, D.
W. Organometallics 1994, 13, 1918. (c) Cummins, C. C.; Schrock, R. R.;
Davis, W. M. Angew. Chem., Int. Ed. 1993, 32, 756. (d) Freundlich, J. S.;
Schrock, R. R.; Davis, W. M. J. Am. Chem. Soc. 1996, 118, 3643. (e)
Melenkivitz, R.; Mindiola, D. J.; Hillhouse, G. L. J. Am. Chem. Soc. 2002,
124, 3846. (f) Termaten, A. T.; Nijbacker, T.; Schakel, M.; Lutz, M.; Spek,
A. L.; Lammertsma, K. Organometallics 2002, 21, 3196. (g) Termaten, A.
T.; Schakel, M.; Ehlers, A. W.; Lutz, M.; Spek, A. L.; Lammertsma, K.
Chem. Eur. J. 2003, 9, 3577. (h) Waterman, R.; Hillhouse, G. L. J. Am.
Chem. Soc. 2003, 125, 13350. (i) Basuli, F.; Bailey, B. C.; Huffman, J. C.;
Baik, M. H.; Mindiola, D. J. J. Am. Chem. Soc. 2004, 126, 1924.
(46) Breen, T. L.; Stephan, D. W. J. Am. Chem. Soc. 1995, 117, 11914. The
high reactivity of the Zr-complex may be due to loss of a ligand (16-electron
species) and/or oxophilicity of the Zr-center.
Scheme 11. Reactions of Phosphinidene 5c Expelled from
Manganese Benzophosphepine 1c
(47) Streubel, R.; Ostrowski, A.; Wilkens, H.; Ruthe, F.; Jeske, J.; Jones, P. G.
Angew. Chem., Int. Ed. 1997, 36, 2427.
9
J. AM. CHEM. SOC. VOL. 127, NO. 48, 2005 16993

A R T I C L E S
Borst et al.
shifts are internally referenced to the solvent for 1H (CDCl3, 7.25 ppm;
C6D6, 7.15 ppm) and 13C (CDCl3, 77.0 ppm; C6D6, 128 ppm) and
externally for 31P to 85% H3PO4.
72.7 ppm) are at distinctly higher field than that of phosphirene
complex 24 (-59.0 ppm), while the phosphorus in a phosphirene
is usually more deshielded than in a less condensed phosphirane.
The Mn(CO)2Cp-complexed phosphiranes 25 are stable at room
temperature, which differs from the Fe(CO)4-complexed ones
that are amenable to retroaddition of the phosphinidene.17a-c It
is evident that 5c still shows electrophilic behavior, albeit less
than 1a,b.
1,2-Bis(2′,2′-dibromoethenyl)benzene (8). Triphenylphosphine (27.52
g, 104.9 mmol) was added portionwise to a cold (0 °C) solution of
tetrabromomethane (17.39 g, 52.4 mmol) in 250 mL of dichloro-
methane. The resulting orange-red solution was stirred at room
temperature for 20 min. After cooling to 0 °C a solution of 3.07 g
(22.8 mmol) of o-phthaldialdehyde in 100 mL of dichloromethane was
added slowly and the mixture was stirred in the dark at room
temperature for 2 h. The reaction mixture was extracted with distilled
water (2 × 100 mL) and the water layers washed with dichloromethane
(2 × 50 mL). The combined organic layers were dried (MgSO4) and
concentrated. Pentane (7 × 150 mL) was added and the resulting
suspension was decanted after stirring. After addition of another 150
mL of pentane to the suspension it was filtered and all pentane fractions
were combined, concentrated, and purified by column chromatography
(SiO2, 1% Et2O in pentane, Rf ) 0.5), yielding a yellow oil (9.85 g,
22.1 mmol, 97%). 13C NMR (CDCl3): δ 135.4 (CHd), 134.58 (ipso-
ArC), 128.8 (o-ArC), 128.4 (m-ArC), 93.1 (dCBr2). 1H NMR
(CDCl3): δ 7.47-7.56 (m, 2H, o-ArH), 7.42 (s, 2H, CHd), 7.35-
7.39 (m, 2H, m-ArH). HRMS Calcd for C10H679Br281Br2: 445.716 20.
Found: 445.717 01. MS m/z (%): 446 (5) [M+], 367 (20) [M+ - Br],
Conclusion
We have demonstrated the accessibility of 3H-benzo-
phosphepine complexes for a variety of metals and substituents
under mild conditions in acceptable yields. As side products in
the synthesis of benzophosphepines, novel benzeno-1,4-diphos-
phinanes were isolated. All of the benzophosphepine complexes
eliminate electrophilic phosphinidene complexes at elevated
temperatures, as demonstrated by trapping experiments and
kinetic analysis and as confirmed by calculations on the
proposed mechanism. Compared to others, the lower reaction
temperature of this method to generate phosphinidenes enabled
the synthesis of a delicate diphosphirene complex. Decomposi-
tion of benzophosphepines 1 in the absence of a substrate present
results in addition of the phosphinidene complex to the a CdC
bond of another phosphepine molecule. Currently, we are
exploring the use of phosphepines, complexed with other
transition-metal groups and Lewis acids, to enlarge their scope
and applicability.
286 (100) [M+
-
81Br - 79Br], 126 (38) [M+ - Br4].
1,2-Diethynylbenzene (2). n-BuLi (48.8 mL, 78.1 mmol, 1.6 M in
hexanes) was added to a cold (-78 °C) solution of 10.3 mL (78.1 mmol)
of diisopropylamine in 250 mL of THF. After warming up to room
temperature the solution was added carefully to a cold (-78 °C), well-
stirred solution of 5.82 g (13.0 mmol) of 8 in 50 mL of THF. After 20
min of stirring at -78 °C, the reaction was quenched with 130 mL of
sat. aq. (NH4)2SO4 and stirred for 2 h at room temperature. The reaction
mixture was poured out in 200 mL of pentane, the organic layer was
separated and washed with water, dried (MgSO4), concentrated, and
purified using column chromatography (SiO2, 1% Et2O in pentane, Rf
) 0.42), yielding a colorless liquid (1.54 g, 12.2 mmol, 94%). 1H NMR
(CDCl3): δ 7.48-7.54 (m, 2H, o-ArH), 7.27-7.34 (m, 2H, m-ArH),
3.33 (s, 2H, CH).
1,2-Bis(bromoethynyl)benzene (9). To a cold (-78 °C) solution
of 8 (0.3 mmol) in THF (3 mL) was added KO-t-Bu (0.5 g, 5.3 mmol).
After 5 min, brine (3.8 mL) was added and the solution was allowed
to warm to room temperature. The organic layer was separated and
the water layer extacted with diethyl ether (3 × 5 mL). The combined
organic layers were dried (Na2SO4), and after evaporation of the solvent,
the crude product was purified by filtration over a short silica plug,
eluting with 1% Et2O in pentane, yielding a clear oil (0.084 g, 0.3
mmol, ∼100%). 13C NMR (CDCl3): δ 132.8 (s, ArC), 128.7 (s, ArC),
126.2 (s, ipso), 78.8 (s, Ar-Ct), 54.5 (s, tCBr).1H NMR (CDCl3):
δ 7.37-7.41 (m, 2H, ArH), 7.21-7.25 (m, 2H, ArH).
Experimental Section
Calculations. All geometry optimizations were performed with the
ADF48 program, using a triple ú basis set with polarization functions,
the local density approximation (LDA) in the Vosko-Wilk-Nusair
parametrization49 with nonlocal corrections for exchange (Becke88)50
and correlation (Perdew86)51 included in a self-consistent manner, and
the analytical gradient method of Versluis and Ziegler.52 Minima were
confirmed to have only a positive force constant and the transition
structures to have only one imaginary value using the Gaussian98
program package,53 using geometries optimized with the BP86 exchange-
correlation potentials and the LANL2DZ basis set for chromium or
tungsten and 6-31G(d) for all other elements.
Synthesis. All experiments were performed under an atmosphere
of dry nitrogen. All solvents were distilled from LiAlH4 (pentane,
diethyl ether), sodium benzophenone (THF), or P2O5 (dichloromethane)
before use. Diisopropylamine was distilled from KOH. W(CO)5-
(MePH2), W(CO)5tBuPH2, and Cr(CO)5(PhPH2) were synthesized
according to literature procedures.54 The synthesis of W(CO)5(Et2NPH2)
(3g) has been described briefly before.55 All other compounds were
purchased and used as such. NMR spectra were recorded on Bruker
AC 200 (1H, 13C), Bruker WM 250 (1H, 13C, 31P), and Bruker MSL
400 MHz (1H, 13C) spectrometers, IR spectra on a Mattson-6030 Galaxy
FT-IR spectrophotometer, and high-resolution mass spectra (HRMS)
were recorded on a Finnigan MAT 900 spectrometer. NMR chemical
(N,N-Diethylamino)phosphine Pentacarbonyltungsten(0) (3g). To
a solution of dichloro(N,N-diethylamino)phosphine56 (1.76 g, 10.1
mmol) in THF (80 mL) was added a mixture of W(CO)5AcCN and
W(CO)5NMe3 (3.75 g, 10.0 mmol). The resulting green solution was
protected from light and stirred for 3 days at 45 °C. The mixture was
concentrated and filtered over a short silica plug, eluting with diethyl
ether. Evaporation gave a yellow powder (3.57 g, 7.5 mmol, 75%). 31
P
1
NMR (CDCl3): δ 124.01 (1JPW ) 378.5 Hz). H NMR (CDCl3): δ
(48) ADF program, version 2003.01: (a) te Velde, G.; Bickelhaupt F. M.;
Baerends, E. J.; Fonseca-Guerra, C.; van Gisbergen, S. J. A.; Snijders, J.
G.; Ziegler, T. J. Comput. Chem. 2001, 22, 931. (b) Fonseca-Guerra, C.;
Visser, O.; Snijders, J. G.; Baerends, E. J. In METECC-95; Clementi, E.,
Corongiu, C., Eds.; STEFF; Cagliari, Italy, 1995; p 307.
(49) Vosko, S. H.; Wilk, L.; Nusair, M. Can. J. Phys. 1992, 99, 84.
(50) Becke, A. D. Phys. ReV. A 1988, 38, 3098.
(51) Perdew, J. P. Phys. ReV. B 1986, 33, 8822.
(52) (a) Fan, L.; Versluis, L.; Ziegler, T.; Baerends, E. J.; Raveneck, W. Int. J.
Quantum. Chem.; Quantum. Chem. Symp. 1988, S22, 173. (b) Versluis,
L.; Ziegler, T. J. J. Chem. Phys. 1988, 322, 88.
3.44-3.59 (m, 4H, CH2N), 1.25 (m, 6H, CH3).
To a cold (0 °C), stirred suspension of LiAlH4 (0.58 g, 15.3 mmol)
in diethyl ether (20 mL) was carefully added a solution of dichloro-
(N,N-diethylamino)phosphine pentacarbonyltungsten(0) (3.64 g, 7.3
mmol) in diethyl ether (24 mL). After 1 h of stirring at room
temperature, acrylonitrile was added (1.0 mL), the suspension was
filtrated, and the solvent was evaporated, yielding a yellow oil (1.76
g, 4.1 mmol, 56%), which was immediately dissolved in diethyl ether.
31P NMR (Et2O): δ -12.1 (1JPW ) 245.0 Hz)
(53) Frisch, M. J.; et al. Gaussian 98, Revision A.3, 1998.
(54) Marinetti, A.; Bauer, S.; Ricard, L.; Mathey, F. Organometallics 1990, 9,
793.
(55) Mercier, F.; Mathey, F. J. Chem. Soc., Chem. Commun. 1984, 782.
(56) Perich, J. W.; Johns, R. B. Synthesis 1988, 142.
9
16994 J. AM. CHEM. SOC. VOL. 127, NO. 48, 2005

3H-Benzophosphepine Complexes
A R T I C L E S
P,P-Dideuteriophenylphosphine Pentacarbonyltungsten(0) (3h).
Compound 3a (0.71 g, 1.6 mmol) was dissolved in THF (3 mL), D2O
(1.8 mL) was added, and the resulting mixture was stirred well. THF
was evaporated, pentane added, and the D2O layer separated. 31P NMR
analysis of the pentane layer showed incomplete conversion, so pentane
was evaporated and the procedure repeated twice. Upon complete
conversion the pentane layer was filtered over little Na2SO4 and
(KBr): ν ) 2067.8 (s), 1913.5 (s) (CtO) cm-1. HRMS Calcd for
C16H11O5PW: 497.9853, found: 497.9839. MS m/z (%): 498 (57) [M+],
414 (100) [M+ - 3CO], 356 (85) [M+ - H2 - 5CO], 128 (17) [C10H8+].
3-t-Butyl-3H-3-benzophosphepine Pentacarbonyltungsten(0) (1f)
was synthesized according to the general synthesis, with 1.75 h of
stirring, to give orange plates (41%). Mp: 95 °C. 31P NMR (CDCl3):
δ 10.5 (1JPW ) 233.4 Hz). 13C NMR (CDCl3): δ 199.8 (d, 2JCP ) 20.4
2
2
concentrated. At -20 °C light yellow plates were formed (0.52 g, 1.2
Hz, COax); 197.0 (d, JCP ) 6.8 Hz, COeq), 140.9 (d, JCP ) 3.9 Hz,
1
mmol, 72%). Mp: 47-48 °C. 31P NMR (C6D6): δ -89.6 (q, JPD
)
C1, C5), 136.5 (d, 3JCP ) 3.6 Hz, C5a, C9a), 133.7 (s, C6, C9), 128.6
52.9 Hz, 1JPW ) 220.5 Hz, int 100, PD2), -88.9 (t, 1JPD ) 52.9 Hz, int
1
1
(s, C7, C8), 123.2 (d, JCP ) 31.5 Hz, C2, C4), 33.6 (d, JCP ) 26.6
Hz, CMe3), 26.6 (d, 2JCP ) 5.1 Hz, CH3). 1H NMR (CDCl3): δ 7.26-
7.34 (m, 4H, H(C6-C9)), 7.03 (ddd, 3JHP ) 31.2 Hz, 3JHH ) 13.6 Hz,
4, PHD). 13C NMR (C6D6): δ 198.4 (d, JCP ) 21.8 Hz, COax), 195.8
2
(d, 2JCP ) 6.9 Hz, 1JCW ) 125.0 Hz, COeq), 132.7 (d, 2JCP ) 11.4 Hz,
4
3
5JHH ) 2.9 Hz, 2H, H1+H5), 5.92 (dd, JHP ) 19.4 Hz, JHH ) 13.6
Hz, 2H, H2+H4), 1.34 (d, JHP ) 14.9 Hz, 9H, CH3). IR (KBr): ν )
2
3
o-ArC), 130.5 (d, JCP ) 2.3 Hz, p-ArC), 129.0 (d, JCP ) 10.4 Hz,
m-ArC), 125.3 (d, 1JCP ) 48.1 Hz, ipso-ArC). 1H NMR (C6D6): δ 6.94-
7.05 (m, 2H, o-H), 6.86-6.91 (m, 3H, m+p-H), 4.73 (dm, 1JHP ) 344.1
Hz, rel int 0.02, PHD). IR (KBr): ν ) 2076.6 (m), 1996.6 (m), 1949.7
(s), 1913.7 (s) (CtO) cm-1. HRMS Calcd for C11H5D2O5PW:
435.966 39. Found: 435.967 26. MS m/z (%): 436 (48) [M+], 380 (52)
[M+ - 2CO], 350 (92) [M+ - 3CO - D], 348 (100) [M+ - 3CO -
D2], 320 (50) [M+ - 4CO - D2], 292 (70) [M+ - 5CO - D2].
General Synthesis of 3H-3-Benzophosphepine Complexes 1.
Method A (with Base). The appropriate phosphine complex (1 mmol)
and 1,2-diethynylbenzene (1.5 mmol) were dissolved in THF (11.75
mL) followed by addition of freshly ground KOH (79 mg). Almost
immediately a color change took place, and after completion of the
reaction, the mixture was filtered over a short silica column, the solvent
was evaporated, and the excess 1,2-diethynylbenzene distilled off at
50 °C/1 mmHg. The crude product was purified by column chroma-
tography (toluene:pentane ) 1:4) and subsequently crystallized from
diethyl ether:pentane ) 1:4 at -20 °C.
3
2068.0 (s), 1995.4 (s), 1981.6 (s), 1944.7 (s), 1920.6 (sh), 1904.5 (s)
(CtO) cm-1. HRMS Calcd for C19H17WPO5: 540.032 35. Found:
540.031 04.
3-Diethylamino-3H-3-benzophosphepine Pentacarbonyltung-
sten(0) (1g). A solution of 3g (0.33 mmol, 1.3 mL, 0.25 M in Et2O)
was added slowly with stirring to a solution of 2 (25 mg, 0.20 mmol)
in THF (0.4 mL) at room temperature. The reaction mixture was stirred
overnight, freshly ground KOH (30 mg) was added, and after 2.25 h
filtered over a short silica plug. After evaporation the crude product
was purified by column chromatography (SiO2, 1:4 ) toluene:pentane)
and crystallization (Et2O:pentane ) 1:4) to give yellow blocks (40%).
Mp: 97 °C (dec). 31P NMR (CDCl3): δ 56.8 (1JPW ) 261.0 Hz). 13C
2
2
NMR (CDCl3): δ 200.3 (d, JCP ) 21.2 Hz, COax), 196.6 (d, JCP
)
)
1
3
7.2 Hz, JCW ) 126.2 Hz, COeq), 137.4 (s, C1, C5), 136.3 (d, JCP
3.8 Hz, C5a, C9a), 133.5 (s, C6, C9), 130.8 (d, JCP ) 38.9 Hz, C2,
C4), 128.3 (s, C7, C8), 42.7 (d, JCP ) 5.8 Hz, CH2), 14.6 (d, JCP
2.8 Hz, CH3). H NMR (CDCl3): δ 7.24-7.28 (m, 4H, H(C6-C9)),
1
2
3
)
1
Method B (without Initial Base). The appropriate phosphine
complex (1 mmol) and 1,2-diethynylbenzene (1.3 mmol) were dissolved
in THF (11.75 mL). After 2-3 h freshly ground KOH (50 mg) was
added. Workup was as above.
3
3
4
6.83 (ddd, JHP ) 35.0 Hz, JHH ) 13.2 Hz, JHH ) 3.1 Hz, 2H,
2
3
H1+H5), 5.87 (dd, JHP ) 15.6 Hz, JHH ) 13.2 Hz, 2H, H2+H4),
3.30 (dq, 3JHP ) 11.9 Hz, 3JHH ) 7.0 Hz, 4H, CH2), 1.15 (t, 3JHH ) 7.0
Hz, 6H, CH3). IR (KBr): ν ) 2071.2 (m), 1986.7 (s), 1938.7 (sh),
1917.7 (s) (CtO) cm-1. HRMS Calcd for C19H18NO5P182W: 553.040 51.
Found: 553.040 61. Calcd for C19H18NO5P186W: 557.04666. Found:
557.04644. MS m/z (%): 555 (48) [M+], 471 (100) [M+ - 3CO], 415
(50) [M+ - 5CO], 128 (72) [C10H8+].
3-Phenyl-1,5-dideuterio-3H-benzophosphepine Pentacarbonyl-
tungsten(0) (1h). To a solution of 3h (135 mg, 0.31 mmol) in THF
(5.7 mL) was added 1,2-diethynylbenzene (0.8 mL, 0.5 M in THF, 0.4
mmol). The mixture was stirred for 1 day at room temperature and 7
h at 35 °C, followed by filtration over a silica plug and purification by
column chromatography (1:4 ) toluene:pentane, then 2:3 ) toluene:
pentane). 1h was obtained in pure form by crystallization (-20 °C)
from 1:4 ) Et2O:pentane to give light yellow plates (25 mg, 0.044
mmol, 14%, >94% D2). Mp: 110 °C (dec). 31P NMR (CDCl3): δ
-14.8 (1JPW ) 236.8 Hz). 13C NMR (CDCl3): δ 199.6 (d, 2JCP ) 20.5
Hz, COax), 196.4 (d, 2JCP ) 7.0 Hz, 1JCW ) 126.0 Hz, COeq), 140.3 (t,
1JCD ) 24 Hz, C1, C5), 136.4 (d, 3JCP ) 4.7 Hz, C5a, C9a), 135.5 (d,
3-Phenyl-3H-3-benzophosphepine Pentacarbonylchromium(0) (1d)
was synthesized according to the general synthesis, with 10 min of
stirring, to give yellow plates (37%). Mp: 114 °C (dec). 31P NMR
(CDCl3): δ 23.1. 13C NMR (CDCl3): δ 221.6 (d, 2JCP ) 7.4 Hz, COax),
2
2
216.3 (d, JCP ) 13.6 Hz, COeq), 141.0 (d, JCP ) 3.4 Hz, C1, C5),
3
1
136.6 (d, JCP ) 4.4 Hz, C5a, C9a), 135.8 (d, JCP ) 41.5 Hz, ipso-
4
2
ArC), 132.4 (d, JCP ) 0.8 Hz, C6, C9), 131.1 (d, JCP ) 11.0 Hz,
4
3
o-ArC), 129.7 (d, JCP ) 2.2 Hz, p-ArC), 128.4 (d, JCP ) 9.6 Hz,
m-ArC), 128.1 (s, C7, C8), 126.6 (d, 1JCP ) 32.6 Hz, C2, C4). 1H NMR
(CDCl3): δ 7.56-7.64 (m, 2H, o-ArH), 7.14-7.37 (m, 5H, m+p-
2
ArH+H1+H5), 7.29 (s, 4H, H(C6-C9)), 6.18 (dd, JHP ) 24.1 Hz,
2
1JCP ) 46.2 Hz, ipso-C), 132.7 (s, C6, C9), 132.2 (d, JCP ) 12.2 Hz,
3JHH ) 12.4 Hz, 2H, H2+H4). IR (KBr): ν ) 2063.9 (s), 1924.0 (s),
1898.7 (s) (CtO) cm-1. HRMS Calcd for C21H13CrPO5, 427.9906.
Found 427.9886. MS m/z (%): 428 (16) [M+], 288 (100) [M+ - 5CO],
160 (55) [M+ - 5CO - C10H8], 128 (16) [C10H8+].
4
3
o-ArC), 130.2 (d, JCP ) 2.1 Hz, p-ArC), 128.6 (d, JCP ) 10.0 Hz,
m-ArC), 128.1 (s, C7, C8), 127.3 (d, 1JCP ) 36.6 Hz, C2, C4). 1H NMR
(CDCl3): δ 7.70-7.75 (m, 2H, o-ArH), 7.37-7.47 (m, 3H, m+p-ArH),
2
7.31 (s, 4H, H6-H9), 6.10 (d, JHP ) 21.3 Hz, 2H, H2+H4). IR
3-Methyl-3H-3-benzophosphepine Pentacarbonyltungsten(0) (1e)
was synthesized according to the general synthesis, but with 2 equiv
of 1,2-diethynylbenzene and 10 min of stirring, to give large light yellow
needles (47%). Mp: 105-106 °C (dec). 31P NMR (CDCl3): δ -34.2
(KBr): ν ) 2069.2 (m), 1948.0 (s), 1928 (s) (CtO) cm-1. HRMS
Calcd for C21H11D2O5WP: 562.013 34. Found: 562.013 59. MS m/z
(%): 562 (35) [M+], 478 (100) [M+ - 3CO], 420 (100) [M+ - 5CO
- D/H2], 130 (100) [C10H6D2+].
2
(1JPW ) 231.3 Hz). 13C NMR (CDCl3): δ 199.8 (d, JCP ) 19.6 Hz,
2
COax), 196.3 (d, JCP ) 7.1 Hz, COeq), 140.1 (s, C1, C5), 136.7 (d,
1,4-Dimethyl-2,5-[1,2]benzeno-1,4-diphosphinane Bis(pentacar-
bonyltungsten(0)) (10e). Compounds 3e (185 mg, 0.497 mmol) and 2
(50 mg, 0.4 mmol) were dissolved in THF (5.8 mL). Freshly ground
KOH (70 mg) was added, and the solution turned immediately red.
After stirring overnight the red and cloudy solution was filtered over
silica, eluted with THF, and concentrated. The residue was purified by
3JCP ) 5.6 Hz, C5a, C9a), 132.4 (s, C6, C9), 128.0 (s, C7, C8), 129.8
(d, 1JCP ) 35.9 Hz, C2, C4), 18.7 (d, 1JCP ) 33.9 Hz, CH3P). 1H NMR
3
3
(CDCl3): δ 7.33 (s, 4H, H6-H9), 7.06 (ddd, JHP ) 33.8 Hz, JHH
)
12.7 Hz, 4JHH ) 2.3 Hz, 2H, H1+H5), 5.93 (dd, 2JHP ) 18.7 Hz, 3JHH
) 12.7 Hz, 2H, H2+H4), 1.91 (d, JHP ) 7.4 Hz, 3H, CH3P). IR
2
9
J. AM. CHEM. SOC. VOL. 127, NO. 48, 2005 16995

A R T I C L E S
Borst et al.
column chromatography (toluene:pentane:THF ) 17:66:1), yielding
several fractions. The first fraction (Rf ) 0.57) contained benzophos-
phepine 1e (50.3 mg, 25%). Fraction 2 (Rf ) 0.36) contained mainly
(∼75%) meso-10e, part of which could be obtained pure after succesive
crystallizations from hexane/dichloromethane. Fraction 3 (Rf ) 0.13)
was rac-10e (54.1 mg, 14%). Small, yellowish needles could be
obtained from chloroform or diethyl ether.
COax), 205.0 (d, 2JCP ) 8.8 Hz, COeq), 204.5 (d, 2JCP ) 9.1 Hz, COeq),
1
1
138.0 (d, JCP ) 24.6 Hz, ipso-C), 136.7 (d, JCP ) 32.8 Hz, ipso-C),
136.4 (m, C7), 133.0 (d, 2JCP ) 7.0 Hz, C8), 128.1-129.8 (m, C9-12
1
2
1
+ ArC), 38.1 (dd, JCP ) 13.5 Hz, JCP ) 5.2 Hz, C5), 36.6 (dd, JCP
2
1
2
) 14.3 Hz, JCP ) 6.0 Hz, C2), 27.0 (dd, JCP ) 20.0 Hz, JCP ) 9.1
Hz, C6), 26.1 (dd, JCP ) 15.3 Hz, JCP ) 5.6 Hz, C3). 1H NMR
1
2
(CDCl3): δ 6.79-7.60 (m, 14H, H9-H12 + ArH), 4.12-4.21 (m,
2
3
1H, H2), 3.85 (ddm, JHP ) 19.9 Hz, JHH ) 6.4 Hz, H5), 3.29 (ddm,
2JHH ) 14.6 Hz, 3JHH ) 1.2 Hz, 1H, H3a), 2.89 (ddm, 2JHH ) 14.6 Hz,
3JHH ) 7.1 Hz, 1H, H3b), 2.72-2.84 (m, 2H, H6a-b). IR (KBr): ν )
2071.0 (m), 1991.2 (m), 1930.1 (s), 1914.1 (s) (CtO) cm-1. MS m/z
(%): 822 (18) [M+], 738 (30), [M+ - 3CO], 444 (50) [M+
Mo(CO)10], 346 (100) [M+ - Mo2(CO)10], 149 (100) [C9H10P+].
rac-10b: Mp: 116 °C (dec). 31P NMR (CDCl3): δ 19.7 (1JPMo
-
)
26.2 Hz).13C NMR (CDCl3): δ 209.8 (d, 2JCP ) 24.8 Hz, COax), 204.5
1
2
3
(m, COeq), 136.8 (d, JCP ) 25.0 Hz, ipso-ArC), 135.8 (t, JCP ) JCP
) 3.3 Hz, C7, C8), 129.6 (s, C10, C11), 128.5-129.2 (m, C9, C12,
o+m+p-ArC), 37.5 (m, C2, C5), 27.4 (m, C3, C6). 13C NMR
3
meso-10e: Mp: 174-175 °C. 31P NMR (CDCl3): δ -15.0 (d, JPP
) 17.4 Hz, 1JPW ) 246.9 Hz), -16.6 (d, 3JPP ) 17.4 Hz, 1JPW ) 235.0
Hz). 13C NMR (CDCl3): δ 198.6 (d, 2JCP ) 23.5 Hz, COax), 197.6 (d,
2
(CDCl3): δ 209.8 (d, JCP ) 24.8 Hz, COax), 204.5 (m, COeq), 136.8
(d, JCP ) 25.0 Hz, ipso-ArC), 135.8 (t, JCP ) JCP ) 3.3 Hz, C7,
C8), 129.6 (s, C10, C11), 128.5-129.2 (m, C9, C12, o+m+p-ArC),
2
1
2JCP ) 22.2 Hz, COax), 196.7 (d, JCP ) 6.7 Hz, JCW ) 118.1 Hz,
1
2
3
2
1
COeq), 196.0 (d, JCP ) 7.1 Hz, JCW ) 132.6 Hz, COeq), 135.8 (m,
2
3
C7), 134.3 (dd, JCP ) 6.6 Hz, JCP ) 1.8 Hz, C8), 129.0-129.2 (m,
C9-C11), 128.0 (t, 3JCP ) 4JCP ) 3.2 Hz, C12), 39.1 (dd, 1JCP ) 20.4
Hz, 2JCP ) 5.7 Hz, C5), 38.5 (dd, 1JCP ) 19.8 Hz, 2JCP ) 5.8 Hz, C2),
1
37.5 (m, C2, C5), 27.4 (m, C3, C6). H NMR (CDCl3): δ 7.45-7.57
(m, 4H, H9-H12), 7.20-7.27 (m, 6H, m+p ArH), 6.95-7.00 (m, 4H,
o-ArH), 4.14 (ddd, 2JHP ) 22.3 Hz, 3JHH ) 5.2 Hz, 3JHH ) 2.3 Hz, 2H,
1
2
1
30.0 (dd, JCP ) 26.9 Hz, JCP ) 6.0 Hz, C6), 29.1 (dd, JCP ) 21.6
2
3
3
H2, H5), 3.11 (ddd, JHH ) 14.5 Hz, JHP ) 3.3 Hz, JHH ) 2.3 Hz,
2H, H3a, H6a), 2.53 (ddd, 2JHP ) 21.8 Hz, 2JHH ) 14.5 Hz, 3JHH ) 5.2
Hz, 2H, H3b, H6b). IR (KBr): ν ) 2070.3 (s), 1988.6 (sh), 1939.9
(m), 1916.1 (s) (CtO) cm-1. HRMS Calcd for C32H20O10P2Mo2,
821.8640. Found 821.8803. MS m/z (%): 822 (50) [M+], 738 (72) [M+
- 3CO], 682 (60) [M+ - 5CO], 542 (15) [M+ - 10CO], 444 (50)
[M+ - Mo(CO)10], 346 (100) [M+ - Mo2(CO)10].
Hz, 2JCP ) 5.5 Hz, C3), 22.1 (d, 1JCP ) 28.7 Hz, CH3P4), 19.9 (d, 1JCP
1
) 18.4 Hz, CH3P1). H NMR (CDCl3): δ 7.37-7.43 (m, 3H, H9-
H11), 7.19-7.21 (m, 1H, H12), 3.67 (dddd, JHP ) 19.9 Hz, JHP
5.0 Hz, JHH ) 5.1, JHH ) 2.1 Hz, 1H, H2), 3.40 (ddm, JHP ) 19.9
Hz, JHH ) 4.1 Hz, H5), 2.77 (dddm, JHP ) 7.5 Hz, JHH ) 15.1 Hz,
3JHH ) 2.1 Hz, 1H, H3a), 2.61 (dm, 3JHH ) 4.1 Hz, 2H, H6a-b), 2.07
(d, 2JHP ) 6.1 Hz, 3H, CH3P1), 1.98 (ddm, 2JHH ) 15.1 Hz, 3JHH ) 5.1
2
3
)
3
3
2
3
3
2
11d: Isolated with phosphepine 1d. Data obtained from differential
2
Hz, 1H, H3b), 1.04 (d, JHP ) 5.9 Hz, 3H, CH3P4). IR (KBr): ν )
1
spectra. 31P NMR (CDCl3): δ 4.3 (d, JPH ) 348 Hz). 1H NMR
2068.0 (s), 1982.0 (s), 1952.3 (sh), 1939.6 (sh), 1921.3 (sh), 1910.6
(sh), 1899.9 (s) (CtO) cm-1. HRMS Calcd for C22H16W2P2O10,
869.9237. Found 869.92623. MS m/z (%): 870 (100) [M+], 786 (92)
[M+ - 3CO], 758 (52) [M+ - 4CO].
3
3
(CDCl3): δ 7.50 (ddm, JHP ) 28.9 Hz, JHH ) 12.8 Hz, 1H, Ar-
CHd), 7.27-7.57 (m, 9H, ArH), 6.29 (ddd, 2JHP ) 25.7 Hz, 3JHH(C)
)
3
1
12.8 Hz, JHH(P) ) 11.2 Hz, 1H, dCH-P), 6.17 (ddd, JHP ) 347.7
3
4
Hz, JHH ) 11.2 Hz, JHH ) 1.0 Hz, 1H, PH), 3.27 (s, 1H, CCH). IR
(KBr): ν ) 3301.06 (w), 2957.6 (w), 2942.6 (w), 2863.3 (w), 2063.4
(m, CtO), 1983.5 (sh, CtO), 1937.4 (s, CtO), 1260.5 (w), 1093.9
(br, m), 1022.3 (br, m), 799.6 (m), 762.3 (w), 627.0 (s), 650.9 (s, CCH)
rac-10e: Mp: 170 °C (dec). 31P NMR (CDCl3): δ -15.7 (1JPW
)
249.2 Hz). 13C NMR (CDCl3): δ 198.7 (m, COax), 196.0 (m, COeq),
136.0 (m, C7, C8), 129.6 (m, C10, C11), 129.1 (m, C9, C12), 38.4 (m,
1
C2, C5), 28.6 (m, C3, C6), 19.0 (m, CH3). H NMR (CDCl3): δ 7.40
cm-1
.
2
3
3
(s, 4H, H9-H12), 3.64 (ddd, JHP ) 22.7 Hz, JHH ) 5.3 Hz, JHH
)
2.1 Hz, 2H, H2, H5), 2.67 (ddm, 2JHH ) 14.9 Hz, 3JHH ) 2.1 Hz, 2H,
H3a, H6a), 2.54 (ddm, 2JHH ) 14.9 Hz, 3JHH ) 5.3 Hz, 2H, H3b, H6b).
2.07 (d, 2JHP ) 6.1 Hz, 6H, CH3P). IR (KBr): ν ) 2068.1 (m), 1985.4
(m), 1926.4 (s), 1909.8 (s), 1895.0 (s) (CtO) cm-1. HRMS Calcd for
C22H16W2P2O10: 869.9238. Found: 869.9254. MS m/z (%): 870 (<1)
[M+], 590 (<1) [M+ - 10CO], 472 (20) [M+ - 10CO - CH3 - C8H7],
430 (100) [W2P2+].
Evidence for Disproportionation of 3a. A mixture of 3a (10.5 mg,
0.024 mmol) and 3h (10.9 mg, 0.025 mmol) was dissolved in THF
(0.5 mL). The resulting solution was monitored by 31P NMR. Alongside
the signals attributed to 3a (-89.4 ppm, s) and 3h (-90.6, q, JPD
53.7 Hz) the signal of PhPHD-W(CO)5 grew in: -90.0 (t, JPD
1
)
)
1
53.7 Hz). After 2 h an equilibrium is reached, with the following
intensities: PH2:PHD:PD2 ) 1.0:0.4:0.7.
General Procedure for Phosphinidene Reactions. The benzophos-
phepine complex and substrate were dissolved in dry toluene (20 mL/
mmol) and placed in an oil bath at the reaction temperature until
completion. The solvent was evaporated, followed by sublimation of
naphthalene at 60 °C/1-2 mmHg. The residue was purified by column
chromatography (pentane, then pentane:Et2O ) 1:4) when necessary
and/or crystallization (pentane, -20 °C).
1,4-Diphenyl-2,5-[1,2]benzeno-1,4-diphosphinane Bis(pentacar-
bonylmolybdenum(0)) (10b). To a suspension of KOH (0.24 g) in
THF (16.0 mL) was added simultaneously a solution of 2 (0.85 mmol,
0.5 M in THF, 1.7 mL) and 3b (1.47 mmol, 0.49 M in THF, 3.0 mL).
The solution turned red immediately and was stirred overnight at room
temperature. After filtration over a short silica plug and evaporation
of the solvent, the crude product mixture was separated by column
chromatography (Et2O:pentane ) 1:4), yielding several fractions. The
first fraction (Rf ) 0.57) contained mostly benzophosphepine 1b, which
was purified by crystallization (43.1 mg, 0.091 mmol, 11%). The second
fraction (Rf ) 0.43, 106 mg) was a mixture of the benzophosphepine
(5%) and the two isomers of 10b (rac, 67%; meso, 29%). rac-10b could
be isolated in pure form after fractional crystallization from DCM/
pentane. meso-10b could be obtained almost pure (>95%), also by
crystallization from DCM/pentane.
15d:18 1.5 equiv of tolane and 11 h at 85 °C gave yellow crystals
(75%). 31P NMR (CDCl3): δ -109.2.13C NMR (CDCl3): δ 220.3 (d,
2
1
2JCP ) 5.8 Hz, COax), 216.3 (d, JCP ) 16.4 Hz, COeq), 138.7 (d, JCP
) 1.9 Hz, ipso-ArP), 130.9 (d, 2JCP ) 14.4 Hz, o-ArP), 130.6 (s, p-ArC),
130.4 (d, JCP ) 5.0 Hz, o-ArC), 130.3 (d, JCP ) 2.3 Hz, p-ArP),
129.3 (d, 1JCP ) 12.4 Hz, Cd), 129.3 (d, 4JCP ) 0.7 Hz, m-ArC), 128.6
(d, JCP ) 9.7 Hz, m-ArP), 127.4 (d, JCP ) 6.9 Hz, ipso-ArC). H
NMR (CDCl3): δ 7.88-7.92 (m, 4H, ArH), 7.45-7.58 (m, 8H, ArH),
7.27-7.35 (m, 3H, ArH).
3
4
3
2
1
meso-10b: Colorless blocks. Mp: 163 °C (dec). 31P NMR (CDCl3):
3
3
δ 27.2 (d, JPP ) 11.7 Hz), 25.1 (d, JPP ) 11.7 Hz). 13C NMR
16d:30 2.9 equiv of trans-stilbene and 11 h at 85 °C gave a light-
yellow solid (∼100%), which after crystallization became yellow
(CDCl3): δ 209.8 (d, 2JCP ) 25.2 Hz, COax), 208.9 (d, 2JCP ) 24.0 Hz,
9
16996 J. AM. CHEM. SOC. VOL. 127, NO. 48, 2005

3H-Benzophosphepine Complexes
A R T I C L E S
1
needles (70%). 31P NMR (CDCl3): δ -72.5. H NMR (CDCl3): δ
3
2
6.98-7.50 (m, 15H, ArH), 3.97 (dd, JHH ) 10.0 Hz, JHP ) 8.1 Hz,
3
1H, H(trans-Cr)), 3.55 (d, JHH ) 10.0 Hz, 1H, H(cis-Cr)).
15e:18 1.1 equiv of diphenylacetylene and 24 h at 80 °C gave small,
light yellow crystals (65%). 31P NMR (CDCl3): δ -167.9 (1JPW
)
261.2 Hz).1H NMR (CDCl3): δ 7.85-7.89 (m, 4H, o-ArH), 7.50-
2
7.57 (m, 6H, m+p-ArH), 1.70 (d, JHP ) 5.6 Hz, 3H, CH3P).
16e:30 2.9 equiv of trans-stilbene and 26 h at 85 °C gave a light
1
yellow oil (89%). 31P NMR (CDCl3): δ -138.8 (1JPW ) 261 Hz). H
NMR (CDCl3): δ 7.28-7.41 (m, 10H, ArH), 3.45 (d, 3JHH ) 9.5 Hz,
3
2
1H, CH), 3.34 (dd, JHH ) 9.5 Hz, JHP ) 8.0 Hz, 1H, CH), 1.25 (d,
2JHP ) 6.4 Hz, 3H, Me).
15f: 1.5 equiv of diphenylacetylene and 26 h at 120 °C gave orange
crystals (66%). Mp: 110 °C (dec). 31P NMR (CDCl3): δ -125.7 (1JPW
21a: 6.9 mg, 5%. Rf ) 0.24, crystals from Et2O:pentane, -20 °C.
3
Mp: 153-158 °C (dec).57 31P NMR (CDCl3): δ -8.4 (d, JPP ) 14.7
2
) 247.1 Hz). 13C NMR (CDCl3): δ 198.0 (d, JCP ) 29.3 Hz, COax),
1
3
1
Hz, JPW ) 239 Hz, PA), -126.9 (d, JPP ) 14.7 Hz, JPW ) 263 Hz,
2
196.5 (d, 2JCP ) 7.9 Hz, COeq), 130.6 (d, 1JCP ) 12.8 Hz, Cd), 130.4
PB). 13C NMR (CDCl3): δ 198.6 (d, JCP ) 21 Hz, COaxA), 197.4 (d,
2JCP ) 34 Hz, COaxB), 196.2 (d, 2JCP ) 6.8 Hz, COeqA), 195.3 (d, 2JCP
3
4
(s, p-ArC), 130.1 (d, JCP ) 4.6 Hz, o-ArC), 129.3 (d, JCP ) 0.4 Hz,
) 7.4 Hz, COeqB), 143.2 (pseudo-s, C1), 141-1-141.4 (m, ipso-ArA),
2
1
m-ArC), 128.5 (d, JCP ) 7.2 Hz, ipso-ArC), 37.7 (d, JCP ) 2.9 Hz,
3
CP), 28.3 (d, JCP ) 8.9 Hz, CH3).1H NMR (CDCl3): δ 7.84-7.88
2
135.6-135.9 (m, C5a, C9a), 134.8 (pseudo-s, C9), 134.2 (d, JCP
)
3
3
4.0 Hz, C6), 130.9-131.1 (m), 130.5 (s), 130.1 (d, JCP ) 10.6 Hz,
(m, 4H, o-ArH), 7.48-7.55 (m, 6H, m+p-ArH), 1.14 (d, JHP ) 17.4
m-ArB), 129.2-129.4 (m), 127.6 (d, JCP ) 2.3 Hz, C8), 124.1 (dd,
5
Hz, 9H, CH3). IR (KBr): ν ) 2067.6 (w), 1980.9 (w), 1927.2 (s),
1917.4 (s) (CtO) cm-1. HRMS Calcd for C23H19WPO5: 590.0479.
Found: 590.0458. MS m/z (%): 590 (49) [M+], 449 (100) [M+ - 5CO
- H], 393 (39) [M+ - 5CO - C4H9].
1JCP ) 37.5 Hz, 3JCP ) 4.7 Hz, C2), 43.0 (m, C4), 36.7 (d, 1JCP ) 16.5
Hz, C5). H NMR (CDCl3): δ 7.99-8.03 (m, 2H, o-ArPA), 7.64-
1
7.68 (4H, m+pArA, H6), 7.32-7.42 (m, 8H, ArBH, H7-H9), 7.08 (dd,
3JHP ) 35.6 Hz, JHH ) 13.7 Hz, 1H, H1), 6.35 (m, 1H, H2), 3.71-
3
15g:32 1.6 equiv of diphenylacetylene and 11.5 h at 85 °C gave
3.83 (m, 1H, H5), 3.02-3.10 (m, 1H, H4). IR (KBr): ν ) 2066.7 (m),
1990.5 (m), 1948.14 (s), 1929.4 (s), 1912.4 (sh) (CtO) (cm-1). HRMS
Calcd for C32H18O10P2W2: 991.939 38. Found: 991.9394. MS m/z
yellow crystals (61%). 31P NMR (CDCl3): δ -100.8 (1JPW ) 299.7
Hz). 1H NMR (CDCl3): δ 7.83 (d, 3JHH ) 7.0 Hz, 4H, o-ArH), 7.43-
3
7.57 (m, 6H, m+p-ArH), 2.90-3.04 (m, 4H, NCH2), 0.98 (t, JHH
)
(%): 992 (3) [M+], 712 (12) [M+ - 10CO], 558 (37) [M+
-
7.0 Hz, 6H, CH3).
PhPH2W(CO)5], 476 (78) [M+ - 3CO-PhPW(CO)5], 418 (80) [M+
- 5CO-PhPH2W(CO)5], 128 (100) [C10H8+].
15i: Chromatography of 15g over SiO2 eluting with THF gave a
yield that depends on the time on the column. Crystallization from
The third fraction (Rf ) 0.16, 10%) gave 25.2 mg (17%) of a mixture
of 21b-c. Colorless blocks of 21b from Et2O:pentane ) 1:4.
pentane yielded yellow blocks. Mp: 122-124 °C. 31P NMR (CDCl3):
2
δ -78.1 (1JPW ) 319.6 Hz). 13C NMR (CDCl3): δ 198.3 (d, JCP
)
21b: mp 158-160 °C (dec).57 31P NMR (CDCl3): δ -6.6 (d, 3JPP
)
38.4 Hz, COax), 195.2 (d, 2JCP ) 9.8 Hz, COeq), 147.7 (d, 1JCP ) 15.0
11.7 Hz, 1JPW ) 235 Hz, PA), -118.8 (d, 3JPP ) 11.7 Hz, 1JPW ) 263
Hz, PB). 13C NMR (CDCl3): δ 199.3 (d, 2JCP ) 21.1 Hz, COaxA), 197.5
(d, 2JCP ) 32.6 Hz, COaxB), 196.3 (d, 2JCP ) 6.6 Hz, COeqA), 195.3 (d,
Hz, Cd), 131.1 (s, p-ArC), 129.9 (d, 3JCP ) 5.7 Hz, o-ArC), 129.4 (s,
2
1
m-ArC), 127.7 (d, JCP ) 4.9 Hz, ipso-ArC). H NMR (CDCl3): δ
7.89-7.92 (m, 4H, o-ArH), 7.49-7.58 (m, 6H, m+p-ArH), 2.60
(s, broad, 1H, OH). IR (KBr): ν ) 3524.8 (w), 3461.5 (m) (OH),
2074.5 (m), 1988.8 (m), 1933.9 (s) (CtO) cm-1. HRMS Calcd for
C19H11WPO6: 549.9803. Found: 549.98002. MS m/z (%): 550 (30)
[M+], 410 (100) [M+ - 5CO], 209 (86) [PhCC(P)Ph+], 178 (63)
[PhCCPh+].
1
2JCP ) 7.9 Hz, COeqB), 139.9 (pseudo-s, C1), 137.3 (d, JCP ) 45.6
Hz, ipso-ArA), 135.0 (m, C5a, C9a), 134.4-134.5 (m, C6,C9), 131.5
2
4
(d, JCP ) 11.0 Hz, o-ArB), 131.1 (ipso-ArB),58 130.8 (d, JCP ) 2.0
Hz, p-ArB), 130.4 (d, JCP ) 2.1 Hz, p-ArA), 129.5 (d, JCP ) 9.2 Hz,
m-ArA), 129.4 (s, C7), 128.8 (d, 3JCP ) 9.9 Hz, m-ArB), 128.5 (d, 2JCP
) 9.7 Hz, o-ArA), 127.4 (d, 5JCP ) 2.8 Hz, C8),123.3 (dd, 1JCP ) 37.5
4
3
3
1
1
Hz, JCP ) 2.9 Hz, C2), 45.9 (dd, JCP ) 27.1 Hz, JCP ) 15.0 Hz,
rac-19: A mixture of 1a (70.3 mg, 0.304 mmol) and diphenyldi-
acetylene (28.5 mg, 0.141 mmol) in toluene (2.9 mL) was heated at 60
°C for 3 days. The solvent was evaporated, naphthalene sublimed (50
°C, 1-2 mmHg), and the crude product purified by chromatography
(SiO2, dichloromethane:pentane ) 1:9). The monoadduct elutes first,
followed by the main isomer, to yield 16.1 mg (0.015 mmol, 11%) as
yellow needles. Mp: 152 °C (dec). 31P NMR (CDCl3): δ -137.3 (1JPW
1
1
C4), 37.9 (d, JCP ) 16.0 Hz, C5). H NMR (CDCl3): δ 7.79-7.85
(m, 2H, o-ArA), 7.72 (d, 3JHH ) 8.0 Hz, H6), 7.64-7.69 (m, 2H, m-ArA),
7.56-7.58 (m, 1H, p-ArA), 7.35-7.38 (m, 1H, H7), 7.20-7.28 (m,
2H, 8+p-ArB), 7.00-7.02 (m, 2H, m-ArA), 6.97 (d, JHH ) 8.0 Hz,
3
H9), 6.51-6.55 (m, 2H, o-ArB), 5.90 (dd, 3JHP ) 36.6 Hz, 3JHH ) 13.9
2
3
4
Hz, 1H, H1), 5.60 (ddd, JHP ) 16.5 Hz, JHH ) 13.9 Hz, JHH ) 2.0
Hz, 1H, H2), 3.64-3.70 (m, 3JHH ) 12.9 Hz, 1H, H5), 3.19-3.22 (m,
2
) 274 Hz).13C NMR (CDCl3): δ 197.1 (d, JCP ) 32.5 Hz, COax),
4
3JHH ) 12.9 Hz, JHH ) 2.0 Hz, 1H, H4). IR (KBr): ν ) 2067.9 (m),
2
1998.8 (w), 1979.4 (m), 1932.9 (s), 1922.8 (s), 1906.2 (s) (CtO) cm-1
.
195.3 (pseudo-t, JCP ) 4.0 Hz, COeq), 137.0 (m, C3,C3′), 134.0 (m,
ipso-ArP), 132.1 (s), 131.3-131.7 (m), 129.6 (s), 129.0 (m), 126.5
HRMS Calcd for C32H18O10P2W2: 991.939 38. Found: 991.939 54. MS
m/z (%): 992 (3) [M+], 964 (34) [M+ - CO], 476 (96) [M+ - 3CO
-PhPW(CO)5], 418 (100) [M+ - 5CO - PhPH2W(CO)5].
2
(pseudo-t, JCP ) 3.2 Hz ipso-ArC), 115.3 (m, C2,C2′). 1H NMR
(CDCl3): 7.80-7.86 (m, 4H, o-ArH), 7.38-7.58 (m, 16H, ArH). IR
(KBr): ν ) 2073.3 (m), 1995.7 (m), 1986.8 (m), 1924.5 (s) (CtO)
cm-1. MS: MS m/z (%): 1066 (3) [M+], 870 (3) [M+ - 7CO], 786
(5) [M+ - 10CO], 352 (67) [W(CO)6+], 296 (48) [W(CO)4+], 268 (100)
[W(CO)3+], 184 (20) [W+].
3
1
21c: 31P NMR (CDCl3): δ -15.5 (d, JPP ) 11.4 Hz, JPW ) 247
3
1
Hz, PA), -123.4 (d, JPP ) 11.3 Hz, JPW ) 268 Hz, PB).
The fourth fraction gave 6.0 mg of impure 21d. 31
P NMR (CDCl3):
3
3
δ -16.4 (d, JPP ) 14.6 Hz, PA), -127.9 (d, JPP ) 14.6 Hz, PB).
21: A solution of 1a (84.1 mg, 0.150 mmol) in toluene (1.4 mL) is
heated at 60 °C for 64 h. After evaporation of the solvent the crude
mixture is separated by column chromatography (SiO2, 30 g, starting
with 5% Et2O in pentane, increasing to 10%). 4% of benzophosphepine
1a is regenerated (Rf ) 0.37).
(57) The crystals of 21a,b shrink upon slowly heating to 125 °C, but do not
melt or turn black. Above the mentioned temperature they turn black.
Melting occurs on more rapid heating (>145 °C), but without a defined
temperature rage.
(58) This ipso-carbon was only seen in the HMBC spectrum, because it is very
small and obscured by neighboring signals.
9
J. AM. CHEM. SOC. VOL. 127, NO. 48, 2005 16997

A R T I C L E S
Borst et al.
22: 2 (1.4 mmol) and 1b (199.5 mg, 0.422 mmol) were heated in
toluene (10 mL) at 75 °C for 17 h. The solvent was evaporated and
Found: 386.0247. MS m/z (%): 386 (26) [M+], 330 (100) [M+ - 2CO],
264 (32) [M+ - 2CO - C5H6], 228 (88) [M+ - 2CO - PhCCH].
25: A solution of 1c (50.4 mg, 0.122 mmol) in 1-hexene (1.0 mL)
was heated under reflux at 75 °C for 2 days. After evaporation of the
solvent the crude product was purified by chromatography (SiO2, 1:4
) toluene:pentane) yielding a yellow oil (43.8 mg, 0.119 mmol, 98%).
Data in square brackets refer to the minor anti-isomer. 31P NMR (C6D6):
δ -77.5 [-72.7]. 13C NMR (C6D6): δ 231.3 (broad, CO), 140.8 [136.7]
(d, 1JCP ) 25.4 [24.7] Hz, ipso-C), 131.3 [132.7] (d, 2JCP ) 11.3 [10.7]
4
Hz, o-ArC), 129.1 [129.4] (d, JCP ) 2.4 [2.3], p-ArC), 128.5 [128.4]
3
(d, JCP ) 9.5 [9.4] Hz, m-ArC), 81.4 [81.5] (s, Cp), 32.4 [32.3] (d,
the crude residue purified by column chromatography (SiO2, 1% Et2O
in pentane, 20% Et2O in pentane). Crystallization from pentane (-20
°C) yielded red needles (97 mg, 0.206 mmol, 49%). Mp: 65 °C. 31P
NMR (CDCl3): δ -131.3. 13C NMR (CDCl3): δ 208.8 (d, 2JCP ) 33.6
2
3JCP ) 7.6 [4.8] Hz, CH2CH2CHP), 31.1 [30.9] (d, JCP ) 1.9 [4.7]
Hz, CH2CH3), 24.2 [23.8] (d, 1JCP ) 11.7 [13.1] Hz, CHP), 22.9 [22.6]
(s, CH2CH3), 15.5 [13.9] (d, 1JCP ) 11.6 [12.0] Hz, CH2P), 14.3 [14.0]
1
(s, CH3). H NMR (C6D6): δ 7.28-7.35 (m, 2H, o-ArH), 6.91-7.03
2
1
Hz, COax), 205.0 (d, JCP ) 11.2 Hz, COeq), 138.9 (d, JCP ) 2.2 Hz,
(m, 3H, m+p-ArH), 4.16 [4.10] (d, 2JHP ) 2.0 [2.1] Hz, 5H, Cp), 1.01-
1
4
ipso-ArC), 135.6 (d, JCP ) 13.6 Hz, CCd), 133.9 (d, JCP ) 0.5 Hz,
3
1.44 (m, unresolved), 0.92 [0.71] (t, JHH ) 7.1 [7.3] Hz, 3H, CH3),
3
2
C3), 131.3 (d, JCP ) 4.0 Hz, C6), 131.3 (d, JCP ) 17.0 Hz, o-ArC),
130.6 (s, p-ArC), 130.4 (d, JCP ) 2.5 Hz, C5), 129.3 (d, JCP ) 0.7
Hz, C4), 128.4 (d, JCP ) 10.2 Hz, m-ArC), 127.5 (d, JCP ) 6.9 Hz,
C1), 123.7 (d, JCP ) 3.8 Hz, C2), 120.7 (d, JCP ) 12.4 Hz, dCH),
0.64 (t, 3JHH ) 7.5 Hz, 1H, HCHP). IR (KBr): ν ) 1935.7 (s), 1866.3
4
5
(s) (CtO) cm-1. HRMS Calcd for C19H22MnPO2: 368.073 79.
3
2
Found: 368.073 62. MS m/z (%): 368 (18) [M+], 312 (48) [M+
2CO], 228 (100) [M+ - 2CO - C6H12].
-
3
1
1
2
83.9 (s, CCH), 81.5 (-CCH). H NMR (CDCl3): δ 8.56 (d, JHP
)
X-ray Crystallography. Crystal Structure Determination of rac-
10e. C22H16O10P2W2, fw ) 869.99, yellowish needle, 0.48 × 0.06 ×
0.06 mm3, monoclinic, P21/c (no. 14), a ) 6.7509(4) Å, b ) 14.9157(8)
Å, c ) 26.1982(13) Å, â ) 92.038(2)°, V ) 2636.3(2) Å3, Z ) 4, F )
2.192 g/cm3. A total of 49 511 reflections up to a resolution of (sin
θ/λ)max ) 0.65 Å-1 were measured on a Nonius KappaCCD diffrac-
tometer with rotating anode and graphite monochromator (λ ) 0.710 73
Å) at a temperature of 150(2) K. An absorption correction based on
multiple measured reflections was applied (µ ) 8.89 mm-1, 0.19-
22.3 Hz, 1H, dCH), 7.62-7.70 (m, 2H, H3+H6), 7.37-7.49 (m, 7H,
ArH), 3.38 (s, 1H, CCH). IR (KBr): ν ) 2073.5 (m), 1994.0 (m),
1920.3 (s) (CtO) cm-1. HRMS Calcd for C21H11MO5P: 471.939 82.
Found: 471.940 52. MS m/z (%): 472 (10) [M+], 332 (100) [M+
-
5CO], 126 (46) [C10H6+].
23: To a solution of 22 (97 mg, 0.206 mmol) in toluene (4.0 mL)
was added 1b (117.0 mg, 0.248 mmol, 1.2 eq) and the resulting mixture
0.59 correction range). There were 6046 unique reflections (Rint
)
0.047). The structure was solved with automated Patterson methods59
and refined with SHELXL-9760 on F2 of all reflections. Non-hydrogen
atoms were refined with anisotropic displacement parameters. All
hydrogen atoms were located in the difference Fourier map and refined
as rigid groups, and 327 parameters were refined with no restraints.
R1/wR2 [I > 2σ(I)]: 0.0176/0.0383. R1/wR2 [all refl]: 0.0226/0.0401.
S ) 1.115. Residual electron density was between -1.08 and 0.58 e/Å3.
Geometry calculations, drawings, and checking for higher symmetry
were performed with the PLATON package.61
was heated at 65 °C for 24 h. The solvent was evaporated and the
crude product purified by chromatography (1:4 ) Et2O:pentane). The
combined yield of both isomers was 86 mg (43%). The rac-compound
could be obtained pure after crystallization from Et2O/pentane (yel-
lowish plates). rac-22: 15%. Mp: 133 °C (dec). 31P NMR (CDCl3): δ
-135.5. 13C NMR (CDCl3): δ 208.3 (d, 2JCP ) 34.0 Hz, COax), 204.8
Crystal Structure Determination of meso-10b. C32H20Mo2O10P2,
fw ) 818.30, colorless block, 0.21 × 0.12 × 0.06 mm3, monoclinic,
P21/c (no. 14), a ) 9.0413(1) Å, b ) 21.6707(3) Å, c ) 17.8474(3)
Å, â ) 111.9773(5)°, V ) 3242.75(8) Å3, Z ) 4, F ) 1.676 g/cm3. A
total of 38 814 reflections up to a resolution of (sin θ/λ)max ) 0.60
Å-1 were measured on a Nonius KappaCCD diffractometer with rotating
anode and graphite monochromator (λ ) 0.710 73 Å) at a temperature
of 150(2) K. An absorption correction based on multiple measured
reflections was applied (µ ) 0.93 mm-1, 0.87-0.95 correction range).
There were 5864 unique reflections (Rint ) 0.071). The structure was
solved with direct methods62 and refined with SHELXL-9760 on F2 of
all reflections. Non-hydrogen atoms were refined with anisotropic
displacement parameters. All hydrogen atoms were located in the
difference Fourier map. H atoms at C1, C8, C9, and C10 were refined
freely with isotropic displacement parameters; all other H atoms were
refined as rigid groups. A total of 439 parameters were refined with
no restraints. R1/wR2 [I > 2σ(I)]: 0.0326/0.0706. R1/wR2 [all refl]:
0.0596/0.0827. S ) 1.051. Residual electron density was between -0.57
2
1
(d, JCP ) 11.1 Hz, COeq), 137.9 (d, JCP ) 2.6 Hz, ipso-ArC), 135.6
1
3
(d, JCP ) 15.5 Hz, C-Cd), 133.3 (d, JCP ) 5.3 Hz, C3+C6), 131.7
(s, p-ArC), 131.5 (d, 2JCP ) 17.2 Hz, o-ArC), 130.8 (d, 4JCP ) 2.4 Hz,
C4+C5), 128.6 (d, 3JCP ) 10.3 Hz, m-ArC), 126.8-127.0 (m, C1+C2),
121.5 (d, 1JCP ) 12.1 Hz, dCH). 1H NMR (CDCl3): δ 8.47 (d, 2JHP
)
22.0 Hz, 2H, dCH), 7.78-7.84 (m, 2H, H3+H6), 7.57-7.63 (m, 2H,
H4+H5), 7.30-7.48 (m, 10H, ArH). IR (KBr): ν ) 2073.4 (m), 1991.9
(m), 1925.1 (s) (CtO) cm-1. MS: 817 (<0.001) [M+ - H], 266 (100)
[M+ - Mo2(CO)10 - C6H6]. Anal. Calcd (%) for C32H16Mo2O10P2: C,
47.20; H, 1.98. Found: C, 46.27; H, 2.25.
24: 2.5 equiv of phenylacetylene and 6 h at 95 °C gave yellow blocks
(81%). Mp: 105 °C. 31P NMR (CDCl3): δ -59.0. 13C NMR (CDCl3):
2
δ 144.3 (s, ) CPh), 142.1 (s, ipso-ArP), 131.1 (d, JCP ) 14.1 Hz,
3
o-ArP), 130.6 (s, p-ArC), 129.8 (d, JCP ) 4.1 Hz, o-ArC), 129.6 (d,
(59) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.; Garcia-
Granda, S.; Gould, R. O.; Smits, J. M. M.; Smykalla C. The DIRDIF99
program system, Technical Report of the Crystallography Laboratory,
University of Nijmegen, The Netherlands, 1999.
3
4JCP ) 2.5 Hz, p-ArP), 129.1 (s, m-ArC), 128.0 (d, JCP ) 10.0 Hz,
2
m-ArP), 127.5 (d, JCP ) 6.0 Hz, ipso-ArC), 124.1 (s, HCd), 81.7 (s,
Cp). 1H NMR (CDCl3): δ 8.52 (d, 2JHP ) 19.3 Hz, dCH), 7.52-7.71
(m, 2H, dC(o-ArH)), 7.41-7.52 (m, 5H, ArH), 7.29-7.32 (m, 3H,
m+p-Ar(P)H), 4.51 (d, 2JHP ) 2.4 Hz, 5H, Cp). IR (KBr): ν ) 1932.6
(s), 1856.2 (s) (CtO) cm-1. HRMS Calcd for C21H16MnPO2: 386.0268.
(60) Sheldrick G. M. SHELXL-97. Program for crystal structure refinement;
Universita¨t Go¨ttingen: Germany, 1997.
(61) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7-13.
(62) Sheldrick G. M. SHELXS-97. Program for crystal structure solution;
Universita¨t Go¨ttingen: Germany, 1997.
9
16998 J. AM. CHEM. SOC. VOL. 127, NO. 48, 2005

3H-Benzophosphepine Complexes
A R T I C L E S
and 0.69 e/Å3. Geometry calculations, drawings, and checking for higher
symmetry were performed with the PLATON package.61
based on multiple measured reflections was applied (µ ) 0.92 mm-1
,
0.50-0.95 correction range). There were 7481 unique reflections (Rint
) 0.049). The structure was solved with automated Patterson methods59
and refined with SHELXL-9760 on F2 of all reflections. Non-hydrogen
atoms were refined with anisotropic displacement parameters. All
hydrogen atoms were located in the difference Fourier map. H atoms
at C8 and C10 were refined freely with isotropic displacement
parameters; all other H atoms were refined as rigid groups. A total of
423 parameters were refined with no restraints. R1/wR2 [I > 2σ(I)]:
0.0338/0.0873. R1/wR2 [all refl]: 0.0425/0.0935. S ) 1.038. Residual
electron density was between -1.36 and 1.10 e/Å3. Geometry calcula-
tions, drawings, and checking for higher symmetry were performed
with the PLATON package.61
Crystal Structure Determination of 24. C21H16MnO2P, fw )
386.25, yellow block, 0.36 × 0.15 × 0.12 mm3, triclinic, P1h (no. 2), a
) 9.2488(1), b ) 10.0296(1), c ) 10.8435(2) Å, R ) 110.0434(9), â
) 95.2573(10), γ ) 105.1996(8)°, V ) 893.42(2) Å3, Z ) 2, F ) 1.436
g/cm3. A total of 16 043 reflections up to a resolution of (sin θ/λ)max
) 0.65 Å-1 were measured on a Nonius KappaCCD diffractometer
with rotating anode and graphite monochromator (λ ) 0.710 73 Å) at
a temperature of 150(2) K. An absorption correction based on multiple
measured reflections was applied (µ ) 0.84 mm-1, 0.85-0.91 correction
range). There were 4040 unique reflections (Rint ) 0.047). The structure
was solved with automated Patterson methods59 and refined with
SHELXL-9760 on F2 of all reflections. Non-hydrogen atoms were
refined with anisotropic displacement parameters. All hydrogen atoms
were located in the difference Fourier map. Phenyl H atoms were refined
as rigid groups; all other H atoms were refined freely with isotropic
displacement parameters. A total of 250 parameters were refined with
no restraints. R1/wR2 [I > 2σ(I)]: 0.0289/0.0680. R1/ wR2 [all refl]:
0.0380/0.0731. S ) 1.038. Residual electron density was between -0.28
and 0.43 e/Å3. Geometry calculations, drawings, and checking for higher
symmetry were performed with the PLATON package.61
Crystal Structure Determination of rac-19. C38H20O10P2W2, fw
) 1066.18, yellow needle, 0.39 × 0.06 × 0.06 mm3, triclinic, P1h (no.
2), a ) 8.0153(3) Å, b ) 10.6946(4) Å, c ) 22.3651(5) Å, R )
88.441(2)°, â ) 83.323(2)°, γ ) 79.194(1)°, V ) 1870.34(10) Å3, Z
) 2, F ) 1.893 g/cm3. A total of 44 445 reflections up to a resolution
of (sin θ/λ)max ) 0.65 Å-1 were measured on a Nonius KappaCCD
diffractometer with rotating anode and graphite monochromator (λ )
0.710 73 Å) at a temperature of 150(2) K. An absorption correction
based on multiple measured reflections was applied (µ ) 6.29 mm-1
,
0.37-0.69 correction range). There were 8531 unique reflections (Rint
) 0.045). The structure was solved with automated Patterson methods59
and refined with SHELXL-9760 on F2 of all reflections. Non-hydrogen
atoms were refined with anisotropic displacement parameters. All
hydrogen atoms were introduced in calculated positions and refined as
rigid groups and 469 parameters were refined with no restraints. R1/
wR2 [I > 2σ(I)]: 0.0295/0.0542. R1/wR2 [all refl]: 0.0463/0.0580. S
) 1.200. Residual electron density was between -0.96 and 1.10 e/Å3.
Geometry calculations, drawings and checking for higher symmetry
were performed with the PLATON package.61
Crystal Structure Determination of 21b. C32H18O10P2W2, fw )
992.10, colorless block, 0.42 × 0.24 × 0.18 mm3, triclinic, P1h (no. 2),
a ) 10.4762(1) Å, b ) 11.3603(1) Å, c ) 14.8964(1) Å, R )
103.5604(4)°, â ) 99.8561(5)°, γ ) 103.9820(4)°, V ) 1622.87(2)
Å3, Z ) 2, F ) 2.030 g/cm3. A total of 47 067 reflections up to a
resolution of (sin θ/λ)max ) 0.65 Å-1 were measured on a Nonius
KappaCCD diffractometer with rotating anode and graphite monochro-
mator (λ ) 0.710 73 Å) at a temperature of 150(2) K. An absorption
correction based on multiple measured reflections was applied (µ )
7.24 mm-1, 0.15-0.27 correction range). There were 7450 unique
reflections (Rint ) 0.029). The structure was solved with automated
Patterson methods59 and refined with SHELXL-9760 on F2 of all
reflections. Non-hydrogen atoms were refined with anisotropic dis-
placement parameters. All hydrogen atoms were located in the
difference Fourier map. H atoms at C1, C2, C9, and C10 were refined
freely with isotropic displacement parameters; all other H atoms were
refined as rigid groups. A total of 431 parameters were refined with
no restraints. R1/wR2 [I > 2σ(I)]: 0.0155/0.0334. R1/wR2 [all refl]:
0.0173/0.0339. S ) 1.105. Residual electron density between -0.61
and 0.89 e/Å3. Geometry calculations, drawings and checking for higher
symmetry were performed with the PLATON package.61
Acknowledgment. This work was supported by the Council
for Chemical Sciences of The Netherlands Organization for
Scientific Research (NWO/CW). We thank Dr. M. Smoluch and
Dr. H. Zappey for exact mass determinations.
Note Added after ASAP Publication: In the version
published on the Internet November 10, 2005, there was an error
in the caption for Figure 3. This has been corrected in the version
published November 14, 2005, and in the print version.
Crystal Structure Determination of rac-23. C32H16Mo2O10P2, fw
) 814.27, yellowish plate, 0.42 × 0.33 × 0.06 mm3, triclinic, P1h (no.
2), a ) 9.2748(4) Å, b ) 12.0660(6) Å, c ) 15.2717(6) Å, R )
90.529(2)°, â ) 98.060(1)°, γ ) 104.808(2)°, V ) 1634.16(12) Å3, Z
) 2, F ) 1.655 g/cm3. A total of 36 889 reflections up to a resolution
of (sin θ/λ)max ) 0.65 Å-1 were measured on a Nonius KappaCCD
diffractometer with rotating anode and graphite monochromator (λ )
0.710 73 Å) at a temperature of 150(2) K. An absorption correction
Supporting Information Available: The calculated energies
and xyz-coordinates of the species discussed and details of the
single-crystal X-ray structure determinations (CIF files). This
material is available free of charge via the Internet at
http://pubs.acs.org.
JA054885W
9
J. AM. CHEM. SOC. VOL. 127, NO. 48, 2005 16999