An approach to novel complexes with a tungsten-phosphorus triple bond

Article abstract of DOI:10.1021/om990019e

The metathesis reaction of [W₂(OtBu)₆] with tBuC≡P leads to the phosphide complex [(tBuO)₃W≡P] (1), which can be stabilized when the reaction is carried out in the presence of Lewis acidic carbonyl complexes of the type [M(CO)₅thf] (M = Cr, W). However, further reaction of the metathesis products [(tBuO)₃W≡CtBu] and [(tBuO)₃W≡P→M(CO)₅] [M = W (4a), Cr (4b)] with tBuC≡P leads after subsequent 1,3-OtBu shift to the metallaphosphacyclobutadiene derivatives [(tBuO)₂W{C(tBu)}₂P(OtBu)] (2a) and [(tBuO)₂WC(tBu)P{M(CO)₅}-P(OtBu)] [M = W (5a), M = Cr (5b)]. To prevent the latter, the bulky phosphaalkyne Ar′C≡ P (Ar′ = 2,4,6-tBu₃C₆H₂) was employed in the three-component reaction instead of tBuC≡ P. Surprisingly here, a head-to-tail dimerization of Ar′C≡P occurs to give the novel phosphinidene complexes [M(CO)₄P(R′)C(Ar′)P{MCO)₅}] [M = Cr (6a), M = W (6b); R′ = 2,4-tBu₂-7-Me₂-indanyl]. In the case of [W(CO)₅thf], additionally, the complex [W(CO)₂{(η²-PCAr′)W(CO)₅} ₂] (7) is formed. The function of [W₂(OtBu)₆] in this reaction is uncertain, but stoichiometric amounts of [W₂(OtBu)₆] are essential to obtain complex 6. Reduction of the size of the alkoxide ligands by the use of [W₂(ONp)₆] (Np = CH₂tBu) in the three-component reaction with Ar′C≡P leads to the trinuclear cluster compounds [W₃〈(μ₃-P)-{W(CO) ₅}〉(μ-ONp)₃(ONp)₆] (8) and [W₃(μ₃-P)(μ-ONp)₃(ONp)₆] (9). The crucial step of the side-product free synthesis of the phosphido complexes 4 is the introduction of MesC≡P (Mes = 2,4,6-Me₃C₆H₂) into the three-component system of [W₂(OtBu)₆], RC≡P, and [W(CO)₅thf]. Comprehensive structural and spectroscopic data are given for the products. Furthermore, a ³¹P NMR experiment was conducted following the reaction of [W₂(OtBu)₆] with MesC≡P from -70°C to ambient temperature. In the range of -60 to -40°C, a singlet at 845 ppm with one pair of tungsten satellites (¹J_W,P = 176 Hz) was observed for the complex [(tBuO)₃W≡ P] (1).

Full text of DOI:10.1021/om990019e

2874
Organometallics 1999, 18, 2874-2883
An Ap p r oa ch to Novel Com p lexes w ith a
Tu n gsten -P h osp h or u s Tr ip le Bon d †
Manfred Scheer,* Peter Kramkowski, and Kay Schuster
Institut fu¨r Anorganische Chemie der Universita¨t Karlsruhe, D-76128 Karlsruhe, Germany
Received J anuary 13, 1999
The metathesis reaction of [W2(OtBu)6] with tBuCtP leads to the phosphido complex
[(tBuO)3WtP] (1), which can be stabilized when the reaction is carried out in the presence
of Lewis acidic carbonyl complexes of the type [M(CO)5thf] (M ) Cr, W). However, further
reaction of the metathesis products [(tBuO)3WtCtBu] and [(tBuO)3WtPfM(CO)5] [M ) W
(4a ), Cr (4b)] with tBuCtP leads after subsequent 1,3-OtBu shift to the metallaphosphacy-
clobutadiene derivatives [(tBuO)2W{C(tBu)}2P(OtBu)] (2a ) and [(tBuO)2WC(tBu)P{M(CO)5}-
P(OtBu)] [M ) W (5a ), M ) Cr (5b)]. To prevent the latter, the bulky phosphaalkyne Ar′Ct
P (Ar′ ) 2,4,6-tBu3C6H2) was employed in the three-component reaction instead of tBuCt
P. Surprisingly here, a “head-to-tail” dimerization of Ar′CtP occurs to give the novel
phosphinidene complexes [M(CO)4P(R′)C(Ar′)P{MCO)5}] [M ) Cr (6a ), M ) W (6b); R′ )
2,4-tBu2-7-Me2-indanyl]. In the case of [W(CO)5thf], additionally, the complex [W(CO)2{(η2-
PCAr′)W(CO)5}2] (7) is formed. The function of [W2(OtBu)6] in this reaction is uncertain,
but stoichiometric amounts of [W2(OtBu)6] are essential to obtain complex 6. Reduction of
the size of the alkoxide ligands by the use of [W2(ONp)6] (Np ) CH2tBu) in the three-
component reaction with Ar′CtP leads to the trinuclear cluster compounds [W3 (µ3-P)-
{W(CO)5} (µ-ONp)3(ONp)6] (8) and [W3(µ3-P)(µ-ONp)3(ONp)6] (9). The crucial step of the side-
product free synthesis of the phosphido complexes 4 is the introduction of MesCtP (Mes )
2,4,6-Me3C6H2) into the three-component system of [W2(OtBu)6], RCtP, and [W(CO)5thf].
Comprehensive structural and spectroscopic data are given for the products. Furthermore,
a
31P NMR experiment was conducted following the reaction of [W2(OtBu)6] with MesCtP
from -70 °C to ambient temperature. In the range of -60 to -40 °C, a singlet at 845 ppm
with one pair of tungsten satellites (1J W,P ) 176 Hz) was observed for the complex [(tBuO)3Wt
P] (1).
In tr od u ction
Complexes with terminal phosphido ligands are a new
class of compounds.1 In 1995, in the groups of Cummins2
and Schrock,3 the first examples of complexes of type A
and B, respectively, were isolated and structurally
characterized. In these compounds the metal-phospho-
rus triple bond is kinetically stabilized by the very bulky
amide ligands. Thus, they reveal exclusively end-on
reactivity.4 Our interest, however, concentrates on the
side-on reactivity of WtP triple bonds. This reactivity
pattern is satisfied by the alkoxide-substituted phos-
* To whom correspondence should be addressed: (fax) +49 (0) 721
662119; (e-mail) mascheer@achibm6.chemie.uni-karlsruhe.de.
† Dedicated to Prof. Dr. E. Niecke on the occasion of his 60th
birthday.
(1) Reviews: Scheer, M. Angew. Chem. 1995, 107, 2151-2153.
Scheer, M. Angew. Chem., Int. Ed. Engl. 1995, 34, 1997-1999. Scheer,
M. Coord. Chem. Rev. 1997, 163, 271-286.
(2) Laplaza, C. E.; Davis, W. M.; Cummins, C. C. Angew. Chem.
1995, 107, 2181-2183; Angew. Chem., Int. Ed. Engl. 1995, 34, 2042-
2043.
(3) Zanetti, N.; Schrock, R. R.; Davis, W. M. Angew. Chem. 1995,
107, 2184-2186; Angew. Chem., Int Ed. Engl. 1995, 34, 2044-2046.
(4) (a) J ohnson-Carr, M. J . A.; Lee, P. M.; Odom, A. L.; Davis, W.
M.; Cummins, C. C. Angew. Chem. 1997, 109, 110-113; Angew. Chem.,
Int. Ed. Engl. 1997, 36, 87-91. (b) J ohnson, M. J . A.; Odom, A. L.;
Cummins, C. C. J . Chem. Soc., Chem. Commun. 1997, 1523-1524. (c)
J ohnson-Carr, J . A.; Zanetti, N. C.; Schrock, R. R. J . Am. Chem. Soc.
1996, 118, 11305. (d) Scheer, M.; Mu¨ller, J .; Baum, G.; Ha¨ser, M. J .
Chem. Soc., Chem. Commun. 1998, 1051-1052.
phido complexes of type C.5 The flexibility of the
alkoxide ligands and the coordination of the lone pair
of the terminal P3- ligand to a W(CO)5 group are
characteristic for these compounds.
However, due to their high side-on reactivity, the
synthesis of type C complexes via the metathesis
reaction of [W2(OtBu)6] with phosphaalkyne in the
presence of [M(CO)5thf] (M ) Cr, W) is problematic.
Until recently we had only been able to obtain insepa-
(5) Scheer, M.; Schuster, K.; Budzichowski, T. A.; Chisholm, M. H.;
Streib, W. E. J . Chem. Soc., Chem. Commun. 1995, 1671-1672.
10.1021/om990019e CCC: $18.00 © 1999 American Chemical Society
Publication on Web 07/19/1999

Complexes with a Tungsten-Phosphorus Triple Bond
Organometallics, Vol. 18, No. 15, 1999 2875
Ta ble 1. 31P NMR Da ta of th e Com p lexes 1-9 in C6D6 a t 300 K (δ in p p m , J in Hza )
δ
1J P,P
1J W,P
[(tBuO)3WtP] 1a
845 (s)
-166.2 (s)
-170.3 (s)
-156.2 (s)
412.2 (d)
-109
176
[(tBuO)2W {C(tBu)}2P(OtBu) ] 2a
[(tBuO)2W {C(Ad)}2P(OtBu) ] 2b
[(tBuO)2W {C(Mes)}2P(OtBu) ] 2c
[(tBuO)2W C(tBu)PP(OtBu) ] 3a
435
438
213
213
[(tBuO)2W C(Mes)PP(OtBu) ] 3b
413.2 (d)
-105.9 (d)
546.0 (s)
595.4 (s)
614.0 (s)
291.7 (d)
-127.4 (d)
352.5 (d)
-130.6 (d)
421.4 (d)
-131.2 (d)
418.5 (d)
-132.6 (d)
983.8 (d)
391.9 (d)
787.3 (s)
313.9 (s)
318.1
[(tBuO)3WtPfW(CO)5] 4a
[(tBuO)3WtPfCr(CO)5] 4b
[(tBuO)3WtPfCp′′Mn(CO)2] 4c
[(tBuO)2W C(tBu)P{W(CO)5}P(OtBu) ] 5a
553 and 163
536
565.8
447
466
445
448
40.6
223 and 183
[(tBuO)2W C(tBu)P{Cr(CO)5}P(OtBu) ] 5b
[(tBuO)2W C(tBu)P{Cp′′Mn(CO)2}P(OtBu) ] 5c
[(tBuO)2W C(Ad)P{Cp′′Mn(CO)2}P(OtBu) ] 5d
[Cr(CO)4P(R′)C(Ar′)P{Cr(CO)5}] 6a
235
277
279
[W(CO)4P(R′)C(Ar′)P{W(CO)5}] 6b
186 and 117
202
250
228
45.3
[W(CO)2{η2-PCAr′)W(CO)5}2] 7
[W(µ-ONp)3(ONp)6 (µ-P){W(CO)5 ] 8
[W(µ-ONp)3(ONp)6(µ-P)] 9
165.4
273.3
437.1
[ (tBuO)2WPfW(CO)5 2] 10
220
a
In toluene-d8 at 243 K.
Sch em e 1. Meta th esis Rea ction of [W2(OtBu )6]
rable mixtures containing the desired products with a
tungsten-phosphorus triple bond, as well as four-
membered-ring derivatives which arose from the sub-
sequent cycloaddition of the phosphido and alkylidyne
complex with phosphaalkyne followed by a 1,3-OR shift.5
Herein we report how we overcame these problems and
present a new strategy for the synthesis of alkoxide-
substituted tungsten phosphido complexes under suf-
ficient exclusion of the side products.
w ith tBu CtP
Resu lts a n d Discu ssion
Tw o-Com p on en t Rea ction of [W2(OtBu )6] w ith
RCtP (R ) tBu , Mes; Mes ) 2,4,6-Me3C6H2). Inves-
tigations concerning the metathesis reaction of di-
nuclear tungsten alkoxide complexes such as [W2-
(OtBu)6] containing a tungsten-tungsten triple bond
were first performed by Schrock and co-workers. They
reported the formation of carbyne and nitrido complexes
via the conversion of these alkoxides with alkynes and
nitriles.6,7 In 1985, Becker and co-workers investigated
the metathesis reaction of [W2(OtBu)6] with tBuCtP.
They were able to isolate [(tBuO)2W{C(tBu)}2P(OtBu)]
(2a ) and had 31P NMR spectroscopic evidence for the
formation of [(tBuO)2W{(tBu)CPP(OtBu)}] (3a ). These
results led to the postulation of a phosphido complex
[(tBuO)3WtP] (1) as a possible intermediate in this
reaction (Scheme 1).8 According to the proposed reaction
pathway, the first step of the conversion is the formation
of the alkylidyne complex [(tBuO)3WtCtBu] and the
phosphido complex 1, which undergoes a further formal
cycloaddition with another equivalent of tBuCtP fol-
lowed by a 1,3-OR migration to give the four-membered-
ring derivatives 2a and 3a as the only reaction products.
For comparison we repeated this reaction in THF at
-21 °C. After workup at ambient temperature, the 31P
NMR spectrum (Table 1) of the crude reaction mixture
revealed a sharp singlet at high field (-166 ppm) which
could be assigned to 2a (50 mol % P), as well as two
doublets at 412.2 and -109 ppm (1J P,P ) 435 Hz)
indicating the formation of 3a . The doublet at downfield
(6) (a) Wengrovius, J . H.; Sancho, J .; Schrock, R. R. J . Am. Chem.
Soc. 1981, 103, 3932. (b) Schrock, R. R.; Listemann, M. L.; Sturgeoff,
L. G. J . Am. Chem. Soc. 1982, 104, 4291.
(7) Schrock, R. R.; Listemann, M. L. Organometallics 1985, 4, 74.
(8) (a) Becker, G.; Becker, W.; Knebl, R.; Schmidt, H.; Weeber, U.;
Westerhausen, M. Nova Acta Leopoldina 1985, 59, 55-67. (b) Becker,
G.; Becker, W.; Knebl, R.; Schmidt, H.; Hildenbrand, U.; Westerhausen,
M. Phosphorus Sulfur 1987, 30, 349. (c) Binger, P. In Multiple Bonds
and Low Coordination in Phosphorus Chemistry; Regitz, M., Scherer,
O. J ., Eds.; Thieme Verlag: Stuttgart, 1990; p 100.

2876 Organometallics, Vol. 18, No. 15, 1999
Scheer et al.
Sch em e 2. Th r ee-Com p on en t Rea ction betw een
[W2(OtBu )6] a n d RCtP (R ) tBu , Ad ) in th e
P r esen ce of Lew is Acid ic Ca r bon yl Com p lexes
F igu r e 1. 31P{1H} NMR spectra of the reaction between
MesCtP and [W2(OtBu)6] at different temperatures in
toluene-d8 (SF ) 101.256 MHz). For clarity, the intensity
of the starting material MesCtP at 2.5 ppm (300 K) is
reduced by ∼30%. 1, [(tBuO)3WtP]; 2c, [(tBuO)2W {C-
(Mes)}2P(OtBu) ]; 3b, [(tBuO)2W C(Mes)PP(OtBu) ].
bears one pair of tungsten satellites with a coupling
1
constant of J W,P ) 213 Hz. Those results verified
Becker’s observations and confirmed the very high
reactivity of the alkylidyne and especially of the phos-
phido complex with additional phosphaalkyne.
To gain more information on whether a phosphido
intermediate exists or not, we followed the reaction of
[W2(OtBu)6] with MesCtP (Mes ) 2,4,6-Me3C6H2) by
31P{1H} NMR spectroscopy as a function of temperature
from -70 to 25 °C.9 Indeed, a signal at 845 ppm with
one pair of tungsten satellites was detected (1J W,P ) 176
Hz), which can be assigned to the complex [(tBuO)3Wt
P] (1) (Figure 1). The 31P{1H} NMR chemical shift of 1
appears also in the downfield region as observed for the
phosphorus signal of the terminal phosphido complex
this method to the system [W2(OtBu)6]/RCtP in order
to stabilize type C complexes should be possible.
We carried out the reaction of [W2(OtBu)6] with
tBuCtP in the presence of [M(CO)5thf] at -21 °C.
Workup was conducted at 0 °C in order to prevent the
reaction of tBuCtP with [W(CO)5thf] alone.5 Small
quantities of W(CO)6 and almost the whole amount of
[(tBuO)3WtCtBu] were removed from the crude product
by sublimation under high vacuum. The 31P NMR
spectrum of the remaining product mixture reveals
signals for the WC2P four-membered-ring derivative 2a
(40-45 mol % P) as well as for the WP2C derivatives
[(tBuO)2WC(tBu)P{M(CO)5}P(OtBu)] [M ) W (5a ), M
) Cr (5b)] (30-35 mol % P). Additionally, a sharp
singlet at downfield is observed for the phosphido
complexes [(tBuO)3WtPfM(CO)5] [M ) W (4a ), Cr
(4b)] (15 mol % P).
The nature of the products indicates a similar course
of the reaction as observed without [M(CO)5thf] (Scheme
2). First the formation of [(tBuO)3WtCtBu] and the
phosphido complex [(tBuO)3WtPfM(CO)5] [M ) W
(4a ), M ) Cr (4b)] occurs. The cycloaddition of 4a ,b and
the alkylidyne complex with tBuCtP yields, after
subsequent 1,3-OR shift, the metallaphosphabutadiene
derivatives 5a ,b and 2a , respectively.13 Due to the
coordination of phosphorus to a M(CO)5 group in the
phosphido complex, a subsequent reaction can be par-
tially prevented.
1
B (M ) W)3 (1080 ppm), and the J W,P is in the same
range as found for B (138 Hz). Additionally, at 243 K
the formation of the WC2P derivative [(tBuO)2W-
{C(Mes)}2P(OtBu)] (2c) (-156.2 ppm) and at 253 K the
WCP2 ring compound [(tBuO)2W{(Mes)CPP(OtBu)}]
1
(3b) (δ ) 413.2 and -105.9 ppm; J P,P ) 438 Hz) was
observed. This indicates that the alkylidyne complex
[(tBuO)3WtCMes] is more reactive than the phosphido
complex 1. At 293 K, the phosphido complex is trans-
formed completely into the four-membered-ring deriva-
tive 3b.
Th r ee-Com pon en t Reaction between [W2(OtBu )6]
a n d RCtP in th e P r esen ce of [MLn th f] [MLn ) Cr -
(CO)5, W(CO)5, Cp ′′Mn (CO)2 (Cp ′′ ) η5-1,3-tBu 2C5-
H3)]. (a ) Rea ction s Sta r tin g fr om RCtP [R ) tBu ,
Ad (a d a m a n tyl, C10H15)]. We developed the concept
of the three-component reaction in our group in order
to investigate the transformation pathway of the P4
tetrahedron in the coordination sphere of transition
metals. By addition of Lewis acidic compounds such as
[Cr(CO)5thf] to the reaction mixtures of P4 and the
corresponding coordination compound, the lone pairs of
the Pn ligands formed first are able to coordinate to the
Cr(CO)5 moieties, and thus, intermediates can be sta-
bilized along the reaction pathway.10-12 The fundamen-
tal success in P4 chemistry implied that application of
Since the ratio of the product distribution was not
satisfactory, we increased the bulk at the phosphaalkyne
and at the carbonyl fragment using AdCtP and [Cp′′Mn-
(CO)2thf] in order to prevent the side-on reaction of the
desired products. However, a combination of both varia-
tions led only to an increased yield of the WP2C ring
(9) In the analogous 31P NMR experiment with tBuCtP, the 31P
NMR data of 1 could not be observed due to the fast consecutive
reaction of it with tBuCtP.
(10) Scheer, M.; Troitzsch, C.; J ones, P. G. Angew. Chem. 1992, 104,
1395; Angew. Chem., Int. Ed. Engl. 1992, 31, 1377-1379. Scheer, M.;
Troitzsch, C.; Hilfert, L.; Dargatz, M.; Kleinpeter, E.; J ones, P. G.;
Sieler, J . Chem. Ber. 1995, 128, 257.
(11) Scheer, M.; Becker, U.; Huffman, J . C.; Chisholm, M. H. J .
Organomet. Chem. 1993, 461, C1.
(12) Scheer, M.; Becker, U.; Chem. Ber. 1996, 129, 1307-1310.
Scheer, M.; Becker, U.; Magull, J . Polyhedron 1998, 17, 1983-1989.
(13) A 1,3-alkoxide migration is also found after the cycloaddition
of phosphaalkynes to metal alkylidenes: J amison, G. M.; Saunders,
R. S.; Wheeler, D. R.; McClain, M. D.; Loy, D. A.; Ziller, J . W.
Organometallics 1996, 15, 16-18.

Complexes with a Tungsten-Phosphorus Triple Bond
Organometallics, Vol. 18, No. 15, 1999 2877
complex is characteristic, too.16 This is demonstrated
by the comparison of coupling constant and chemical
shift in the 31P{1H} NMR spectrum of the terminal
1
phosphido ligand complex 1 (δ ) 845 ppm, J W,P ) 176
Hz) and the coordinated compounds 4a -c. The same
effect is observed for the tungsten complexes B (δ )
F igu r e 2. 31P{1H} NMR resonances of the phosphido
complexes 4a and 4b in benzene-d6 (SF ) 101.256 MHz).
derivative 5d . The best results were achieved for the
system [W2(OtBu)6]/tBuCtP/[Cp′′Mn(CO)2thf]. Accord-
ing to the 31P NMR spectrum of the crude reaction
mixture, the amount of the formed phosphido complex
[(tBuO)3WtPfMnCp′′(CO)2] (4c) could be increased to
25 mol % P. In this system, the steric demand of the
Lewis acidic carbonyl fragment is of great importance.
The phosphido complex [(tBuO)3WtPfMLn] is better
stabilized with a [Cp′′Mn(CO)2] group than with M(CO)5
(M ) Cr, W). Use of AdCtP does not seem to have any
influence on the product distribution and is not able to
inhibit the cycloaddition to any greater extent than
tBuCtP.
1080 ppm, 1J WP ) 138 Hz)3 and D (δ ) 662.6 ppm; 1J W,P
) 450 and 135 Hz).15 For the phophinidene complex E,
1
a chemical shift at 193 ppm with a J W,P of 649 Hz is
found.17 This complex possesses a linear arrangement
along the W-P-R axis, and due to coordination of the
free electron pair of the phosphinidene ligand, a formal
WtP triple bond is formed [E, d(WP) ) 2.169(1) Å; B,
d(WP) ) 2.162(4) Å]. The bent phosphinidene complex
F , however, reveals the opposite situation: the free
electron pair is localized at the P atom. Thus, the
W-P-R core is not linear, and the signal of F in the
31P NMR spectrum appears downfield at 661.1 ppm with
Complexes with alkoxide ligands are very sensitive
to moisture and oxygen. Thus, a separation of the
reaction mixture by column chromatography resulted
in an undefined decomposition of all products indepen-
dent of the type and method of preparation of the
column material employed (activated or deactivated
silica gel, Al2O3, silanized silica gel, Biobeads14). A
separation of the reaction mixture can be partially
achieved by fractional crystallization in n-pentane. In
the first fraction, unreacted [W2(OtBu)6] is removed.
From the second fraction, crystals of pure [(tBuO)2W-
(CR)2P(OtBu)] (2a ,c) (R ) tBu, Ad) can be isolated. It
was not possible to obtain crystals of any other product
from these mixtures. By fractional crystallization, how-
ever, we were able to enrich the concentration of
phosphido complex 4a -c in these solutions up to 45 mol
% P with respect to the other phosphorus-containing
species.
1
a significantly smaller coupling constant J W,P of only
153.5 Hz [F , d(WP) ) 2.349(5) Å].18
The 31P NMR spectra (Table 1) of the WC2P ring
derivatives 2a -c show high-field-shifted resonances in
the range of -156 to -160 ppm, indicating the existence
of a OtBu group bound to the P atom in all cases. For
the WCP2 complexes 3a ,b and 5a -d , two doublets at
1
downfield and high field are detected. The large J P,P
coupling constants of these compounds (435-466 Hz)
indicate the multiple-bond character of the P-P bond.
It is of interest, that the ring system in the complexes
3a ,b , which do not reveal exocyclic coordination to a
1
metal carbonyl fragment, shows smaller J P,P coupling
constants. All doublets at high field are within a small
range (-109.0 to -132.6 ppm) and can therefore be
assigned to the phosphorus bearing the OR group. The
doublets at downfield show a considerable difference in
their chemical shifts, which is due to the coordination
of this P atom to a different exocyclic metal atom of the
complex fragments MLn. Whereas the coordination to
Mn complex fragments has no considerable influence
on the 31P chemical shifts, coordination to a Cr or W
pentacarbonyl fragment causes a high field shift of
approximately 70 and 130 ppm, respectively. However,
all 1J W,P of the ring tungsten atoms with the phosphorus
are quite comparable (213-279 Hz); again, the smaller
values correspond to the complexes 3a ,b without the
exocyclic MLn moiety. Additionally, 5a further reveals
In the 31P NMR spectrum, 4a -c show a singlet at
downfield (546-614 ppm) with satellites revealing a
large coupling constant for the tungsten-phosphorus
triple bond (536-566 Hz). Due to the coordinative bond
of the lone pair of the P3- ligand to the W(CO)5 moiety
(Figure 2) for 4a , a further coupling is observed (1J W,P
) 163 Hz). Experimental and theoretical studies in our
group confirmed that, due to the linear coordination of
the lone pair of the phosphido ligand to Lewis acids, the
s-character of the WtP triple bond is dramatically
increased, and in correspondence with the Fermi contact
1
term, a drastic increase of the J W,P coupling constant
1
a J W,P of 183 Hz for its coupling of the ring phosphorus
occurs.15 A shift toward high field for the phosphorus
resonance after coordination to a Lewis acidic carbonyl
atoms to the exocyclic W(CO)5 group.
(16) Wagener, T.; Frenking, G. Inorg. Chem. 1998, 37, 1805-1811.
(17) Cowley, A. H.; Pellerin, B.; Atwood, J . L.; Bott, S. G. J . Am.
Chem. Soc. 1990, 112, 6734.
(18) Hitchcock, P. B.; Lappert, M. F.; Leung, W. P. J . Chem. Soc.,
Chem. Commun. 1987, 1282.
(14) With Biobeads, no decomposition but also no separation was
observed.
(15) Scheer, M.; Mu¨ller, J .; Ha¨ser, M. Angew. Chem. 1996, 108,
2637-2641; Angew. Chem., Int. Ed. Engl. 1996, 35, 2492.

2878 Organometallics, Vol. 18, No. 15, 1999
Scheer et al.
F igu r e 3. Molecular structure of [(tBuO)2W(CtBu)2P-
(OtBu)] (2a ) (showing 30% probability ellipsoids; hydrogen
atoms are omitted for clarity). Selected bond distances (Å)
and angles (deg): W-C(1) 1.871(5), W-C(2) 1.857(5), P(1)-
C(1) 1.814(5), P(1)-C(2) 1.822(5), P(1)-O(3) 1.648(4), C(2)-
C(7) 1.515(7), C(1)-C(3) 1.526(7), W-O(1) 1.858(4); C(2)-
P(1)-C(1) 94.3(2), C(1)-W-C(2) 91.3(2), W-C(2)-P(1)
86.3(2), P(1)-C(1)-W 86.1(2), W-O(2)-C(19) 146.3(3),
P(1)-O(3)-C(11) 124.3(3).
F igu r e 4. Molecular structure of [(tBuO)2W(CAd)2P-
(OtBu)] (2b) (showing 30% probability ellipsoids; hydrogen
atoms are omitted for clarity). Selected bond distances (Å)
and angles (deg): W-C(1) 1.871(8), W-C(2) 1.931(5), P(1)-
C(1) 1.913(10), P(1)-C(2) 1.785(6), P(1)-O(3) 1.680(8),
C(2)-C(21) 1.472(9), C(1)-C(11) 1.488(10), W-O(1) 1.883-
(7); C(2)-P(1)-C(1) 96.3(3), W-C(2)-P(1) 85.8(2), P(1)-
C(1)-W 84.0(3), C(1)-W-C(2) 92.9(3), W-O(2)-C(7) 154.0-
(7), P(1)-O(3)-C(31) 127.5(8).
The X-ray analysis of 2a (Figure 3) reveals a distorted
quadratic WC2P framework which is folded by 14.3°
along the W‚‚‚P axis. The angles deviate only slightly
from 90°. The bond lengths between the four vertexes
do not differ considerably either. The tungsten atom is
surrounded in a distorted tetrahedral manner by two
carbon and two oxygen atoms. The tungsten carbon
distances are with 1.871(5) and 1.856(5) Å, typical for
carbon-tungsten double bonds as found for [W(d
CHtBu)Cl2(CO)(PMe3)2] [d(WC) ) 1.859(4) Å]19 and
[W(C3Et3){OCH3(CF3)2}3] [d(WC) ) 1.862(17) Å].20 The
P-C distances come to 1.822(5) and 1.871(5) Å, from
which the latter corresponds to a slightly shortened P-C
single-bond distance as found in 1,3-diphosphacyclobu-
tadiene complexes (e.g., [CpCo{η4-(tBu2C2P2)}], d(PC)
) 1.797(3)-1.798(3) Å21 and [Cp*Co{η4-(tBu2C2P2)}],
d(PC) ) 1.79(1)-1.82(1) Å22). The P-O distance of
1.648(4) Å is typical for P-O single bonds. The carbon
atoms C1 and C2 are coordinated in an approximately
trigonal-planar fashion. But due to the steric hindrance
induced through the tBuO ligands at the tungsten
center and the tBu substituents at C1 and C2, the ideal
geometry is distorted.
W-C2 [1.931(9) Å] is 0.06 Å longer than the average
W-C bond length in 2a (1.8635 Å). This distance is
nevertheless still in the range of WdC double bonds as,
for example, found in [W(CtBuCCtBu)Cp(Cl)] [d(WC)
) 1.924(8) Å]23 and [W(CHCHCPhN)W(OtBu)6] [d(WC)
) 1.943(5) Å].24 Also the P-C bonds in 2b differ
considerably from each other. Whereas the bond P-C2
is with 1.785(6) Å only 0.03 Å shorter than in 2a , the
bond length of P-C1 is with 1.913(10) Å strongly
elongated. Therefore, it is rather comparable to P-C
single-bond distances as observed for the diphosphene
complex [Fe2(CO)6(PtBu)2] [d(PC) ) 1.875(7) Å].25 The
described bonding situation at the P atom induces an
asymmetry in the molecule. Therefore, 2b crystallizes
in enantiomerically pure form in the chiral space group
P212121.
(b) Rea ction s Sta r tin g fr om Ar ′CtP (Ar ′ ) 2,4,6-
tBu 3C6H2). The key challenge in the synthesis of
phosphido complexes of type C is a complete inhibition
of the subsequent cycloaddition of further phosphaalkyne.
Therefore, we employed supermesitylphosphaalkyne
Ar′CtP to prevent the latter. The conversion of [W2-
(OtBu)6] with Ar′CtP in the presence of [M(CO)5(thf)]
(M ) W, Cr) was carried out at -21 °C. The 31P{1H}
NMR spectrum of the crude reaction mixture indicated
the formation of the complex [M(CO)4P(R′)C(Ar′)P-
{M(CO)5}] (6a , M ) Cr; 6b, M ) W; R′ ) 2,4-tBu2-7-
Me2-indanyl) in addition to relatively large quantities
of unreacted Ar′CtP. The yield of 6 could be increased
when the reaction was performed at ambient temper-
ature. For the reaction starting from [W(CO)5(thf)] aside
from 6b, the spirocyclic compound 7 is also obtained in
approximately equal amounts (eq 1).
The structure of 2b (Figure 4) is similar to that of
2a , but here the WC2P ring is folded by only 9.8° along
the W‚‚‚P axis (2a , 14.3°). While 2a forms an almost
regular square, the WC2P core in 2b possesses an
irregular trapezoidal shape, and the angles as well as
the distances between the vertexes of the four-mem-
bered ring have larger deviations than observed for 2a
[2b, angle range of 84.0(3)-96.3(3)°; bond lengths,
1.785(6)-1.931(5) Å]. Especially the bond distance
(19) Schrock, R. R.; Wengrovius, J . H.; Churchill, M. R. J . Am. Chem.
Soc. 1982, 104, 1739.
(20) Schrock, R. R.; Freudenberger, J . H.; Churchill, M. R.; Rhein-
gold, A. L.; Ziller, J . W. Organometallics 1984, 3, 1563.
(21) Binger, P.; Milczarek, R.; Mynott, R.; Kru¨ger, C.; Tsay, Y.-H.;
Raabe, E.; Regitz, M. Chem. Ber. 1988, 121, 637.
(22) Hitchcock, P. B.; Maah, M. J .; Nixon, J . F. J . Chem. Soc., Chem.
Commun. 1986, 737.
(23) Schrock, R. R.; Listemann, M. L.; McCullough, L. G.; Churchill,
M. R.; Ziller, J . W. J . Am. Chem. Soc. 1983, 105, 6729.
(24) Schrock, R. R.; Pedersen, S. F.; McCullough, L. G.; Churchill,
M. R.; Ziller, J . W. Organometallics 1983, 2, 1046.
(25) Vahrenkamp, H.; Wolters, D.; Lal De, R. Z. Naturforsch. 1986,
41, 283.

Complexes with a Tungsten-Phosphorus Triple Bond
Organometallics, Vol. 18, No. 15, 1999 2879
of a five-membered indanyl ring system with ring
closure to a carbon atom. Usually, five-membered rings
containing a heteroatom (e.g., P28 or Ge29) are generated.
Recently, J ones et al. showed the formation of a six-
membered ring in a complex containing arsenic.30
Since no metathesis reaction between Ar′CtP and
[W2(OtBu)6] is observed in the three-component reaction
1, the steric hindrance of the alkoxide ligands at the
tungsten atom was reduced by using [W2(ONp)6] (Np )
CH2tBu). Under conditions identical to those described
before (-21 °C, workup at 0 °C), the reaction of [W2-
(ONp)6] with Ar′CtP in the presence of [W(CO)5thf] was
carried out (eq 2).
(2)
F igu r e 5. Molecular structure of [Cr(CO)4P(R′)C(Ar′)P-
{Cr(CO)5}] (6a ) (showing 30% probability ellipsoids; hy-
drogen atoms are omitted for clarity). Selected bond
distances (Å) and angles (deg): Cr(1)-P(1) 2.3410(7), Cr-
(1)-P(2) 2.2675(7), Cr(2)-P(1) 2.3167(7), P(1)-C(1) 1.797-
(2), P(2)-C(1) 1.712(2), P(2)-C(20) 1.864(2); Cr(1)-P(1)-
C(1) 96.63(7), P(1)-C(1)-P(2) 93.81(11), C(1)-P(2)-Cr(1)
101.97(8), P(2)-Cr(1)-P(1) 67.56(2).
The grade of conversion is relatively small, but higher
than observed for reaction 1. Complex [W3 (µ3-P)-
{W(CO)5} (µ-ONp)3(ONp)6] (8) is obtained as the main
product followed by 7, 6b, and 9. The amount of 6b
formed is higher than in the case of the reaction starting
from [W2(OtBu)6]. The yield of the spirocyclic compound
7 is similar to that of reaction 1 and 7 appears to be a
common side product of these reactions resulting from
the two-component reaction of Ar′CtP with [W(CO)5thf].
If [Cr(CO)5thf] is used in reaction 2, the grade of
conversion of Ar′CtP is increased to ∼80%, and complex
6a is formed as almost the only product. Here, the head-
to tail dimerization (eq 1) becomes the favored reaction.
Crystals of 6 and 9 are obtained by fractional crystal-
lization from n-pentane solutions of reaction 2. 9
crystallizes in the trigonal space group R3 with the
lattice constants a ) b ) 23.55(8) Å, c ) 17.97(6) Å.
Thus, 9 is identical to the complex [W3(µ3-P)(µ-ONp)3-
(ONp)6] characterized by Chisholm et al. and obtained
from the reaction of [W2L2(ONp)6] (L ) Me2NH, Py) with
white phosphorus.31 9 is soluble in all common organic
solvents and decomposes within minutes when exposed
to oxygen or moisture. The main product of reaction 2
is the complex [W3 (µ3-P){W(CO)5} (µ-ONp)3(ONp)6] (8).
However, no suitable crystals for an X-ray structure
analysis could be isolated. Nevertheless, 8 could be
synthesized independently by the reaction of [W3(µ3-P)-
(µ-ONp)3(ONp)6] with [W(CO)5thf]. The 31P NMR spec-
troscopic properties of both compounds obtained by
different routes are identical.
(1)
Complex 7 is the only product of the reaction between
[W(CO)5thf] and Ar′CtP alone.26 Obviously, the influ-
ence of [W2(OtBu)6] is responsible for a “head-to-tail”
dimerization of Ar′CtP, yielding the novel phosphini-
dene complexes 6. The function of [W2(OtBu)6], however,
is uncertain. Experiments show that stoichiometric
amounts of [W2(OtBu)6], [MCO)5thf], and Ar′CtP are
essential for the formation of 6. After the “head-to-tail-
dimerization”, the C20 atom becomes unsaturated (cf.
Figure 5). Subsequently, a C-H activation involving a
1,2-H shift from the methyl group of one of the ortho
tBu groups to C20 occurs and leads to a five-membered
ring. C-H activations are common for systems contain-
ing supermesityl groups and a heteroatom at position
one of the aromatic ring.27-29 To the best of our
knowledge, 6a ,b are the first examples for the creation
The complexes 6a ,b32 crystallize in the form of dark
green plates and are soluble in all common organic
(26) Kramkowski, P.; Scheer, M.; Baum, G. J . Organomet. Chem.
1998, 553, 511-116.
(27) Yoshifuji, M.; Sato, T.; Inamoto, N. Chem. Lett. 1988, 1735.
(28) Champion, D. H.; Cowley, A. H. Polyhedron 1985, 4, 1791.
(29) Lange, L.; Meyer, B.; du Mont, W.-W. J . Organomet. Chem.
1987, 329, C17-C20.
(30) Francis, M. D.; Hibbs, D. E.; Hursthouse, M. B.; J ones, C.;
Malik, K. M. A. J . Chem. Soc., Chem. Commun. 1996, 631.
(31) Chisholm, M. H.; Folting, K.; Pasterczyk, J . W. Inorg. Chem.
1988, 27, 3057.
(32) Properties, spectroscopic data, and X-ray structural analysis
of 6b and 7 are published in ref 26.

2880 Organometallics, Vol. 18, No. 15, 1999
Scheer et al.
solvents including n-pentane. In the solid state 6a ,b are
air stable; in solution they appear to be more sensitive.
The IR spectra reveal coupled vibrational modes for
terminal bound carbonyl groups in the region of CO
stretching frequencies. The appropriate molecular ion
peaks are observed in the mass spectra. The 31P{1H}
NMR spectrum of 6a ,b (Table 1) indicates the existence
of two chemically different phosphorus atoms. One
signal appears downfield at 983.8 and 787.3 ppm,
respectively, indicating the existence of phosphinidene
P atoms. Additionally, for 6b the satellite pattern at this
signal implies the coordination to two tungsten carbonyl
The metathesis reaction of [W2(OtBu)6] with MesCt
P in the presence of [M(CO)5thf] (M ) W, Cr) yields
almost exclusively the alkylidyne complex [(tBuO)3Wt
CMes] and the desired phosphido species [(tBuO)3Wt
PfW(CO)5] (4a ,b) (eq 3). The steric demand of the
(3)
1
fragments with J WP ) 186 and 117 Hz. This is in good
agreement with data found for other tungsten phos-
phinidene complexes (e.g., [Cp*P{W(CO)5}2], δ ) 1076.2
1
ppm, J WP ) 187.6 and 165.7 Hz;33 [2-iPr-5-MeC6H9P-
mesityl group obviously matches the requirements to
undergo metathesis and also to inhibit sufficiently the
subsequent cycloaddition with the phosphido complex.
According to the 31P{1H} NMR spectrum of the crude
reaction mixtures, only the phosphido complexes 4a ,b
(80-90 mol % P) and small amounts of the WC2P ring
derivative [(tBuO)2W(CMes)2P(OtBu)] (2c) (10-20 mol
% P) are formed. The subsequent reaction between the
phosphido complex and additional phosphaalkyne is not
observed anymore. By following reaction 3 (M ) W) by
31P{1H} NMR spectroscopy from -78 °C to room tem-
perature, it was observed that the formation of the
phosphido complex 4a is favored over the subsequent
reaction with additional phosphaalkyne at low temper-
atures. Only small amounts of the alkylidyne complex
[(tBuO)3WtCMes] react in this temperature range to
give 2c. Therefore it is essential to perform the reaction
at low temperatures until all starting material is
converted before allowing the solution to warm to room
temperature.
{W(CO)5}2], δ ) 1041 ppm, 1J WP ) 168 Hz34). The second
signal is observed at 391.9 (6a ) and 313.9 ppm (6b ),
revealing for 6b only one pair of satellites (1J WP ) 202
Hz).
The 31P{1H} NMR spectrum of 8 exhibits one singlet
at 165.4 ppm. Only one pair of satellites is observed with
1
a coupling constant J WP of 228.6 Hz, which is consistent
with a coupling of the phosphorus atom to a W(CO)5
moiety. The spectroscopic data of [W3(µ3-P)(µ-ONp)3-
(ONp)6] (9) are in very good agreement with those
determined by Chisholm.31 The 31P{1H} NMR spectrum
of 9 reveals a singlet at 273.7 ppm with one pair of
tungsten satellites. The coupling constant comes to 45.3
Hz. The mass spectrum of complex 9 shows the molec-
ular ion peak.
The molecular structure of 6a (Figure 5) reveals a
“head-to-tail dimer” of two phosphaalkyne molecules
forming a phosphinidene ligand and is isostructural to
that of 6b.26 The phosphinidene phosphorus P(1) is
bonded to the C(1) atom via a slightly shortened single
bond [1.797(2) Å]. Both phosphorus atoms P(1) and P(2)
further coordinate to a Cr(CO)4 moiety creating a planar
and slightly distorted four-membered ring. The bonding
distance between P(2) and C(1) [1.717(2) Å] corresponds
to a double bond.35 The phosphinidene phosphorus atom
P(1) additionally binds to a Cr(CO)5 fragment. Due to
the shorter metal-phosphorus bond in 6a [2.3410(7)
and 2.3167(7) Å] the angle P(2)-C(1)-P(1) is smaller
than in the W analogue 6b [96.1(3)°] by 2.3°.
(c) Rea ction s Sta r tin g fr om Mesitylp h osp h a -
a lk yn e MesCtP . The discussed results show that the
bulky supermesityl group at the phosphaalkyne does not
undergo metathesis reactions with [W2(OtBu)6]. On the
other hand, in the reaction with [W2(ONp)6], the me-
tathesis reaction seems to occur to a low extent.
However, here the tungsten alkoxide reacts further with
a phosphido complex intermediate to form the trinuclear
tungsten cluster compounds 8 and 9. Therefore, a
phosphaalkyne possessing a moderately steric bulki-
ness, which lies between those of tBuCtP and Ar′Ct
P, is needed for the metathesis reaction with [W2-
(OtBu)6]. We found that MesCtP meets all these steric
requirements.
After workup, small yellow crystals of 4a ,b could be
isolated from n-hexane solutions. They are readily
soluble in n-hexane, toluene, and THF. The compounds
are very sensitive to oxygen and moisture and decom-
pose within minutes when exposed to air. Although the
31P{1H} NMR spectra indicated a quantitative grade of
conversion and a good yield of the desired product, only
small amounts of 4a ,b could be obtained in crystalline
form due to the excellent solubility even in n-pentane.
The IR spectra in the region of the CO stretching
frequencies shows vibration modes for a distorted C4v
symmetry (2 A1 + E) of the LW(CO)5 moiety. For an
estimation of the π-acceptor ability of the phosphido
ligand, the location of the A11 band (CO ligand trans to
P
3-) is important. With 1980 and 1985 cm-1, respec-
tively, they are found to be with their π-acceptor
properties between PX3 (X ) halogen) and P(OR)3.36
The molecular structure of 4a reveals an almost linear
molecule with an angle W2-P-W1 of 174° (Figure 6).
The tungsten atom W2 in 4a is surrounded in an almost
perfect tetrahedral arrangement by its three alkoxide
ligands and one phosphido ligand with an average angle
O-W2-P of 108.1(3)°. The average angle W2-O-
C(Me3) is ∼142° and reveals that the WtP triple bond
is surrounded by the tBuO groups. This situation is also
(33) J utzi, P.; Kroos, R. J . Organomet. Chem. 1990, 390, 317-322.
(34) Hinke, A. M.; Hinke, M.; Kuchen, W. Z. Naturforsch. 1986, B
41, 629
(35) Appel, R. In Multiple Bonds and Low Coordination in Phos-
phorus Chemistry; Regitz, M., Scherer, O. J ., Eds.; Thieme Verlag:
Stuttgart, 1990; pp 160ff.
(36) Huheey, J . E.; Keiter, E.; Keiter, R. Anorganische Chemie,
Prinzipien von Struktur und Reaktivita¨t, 2nd ed.; de Gruyter: Berlin,
1995; pp 500ff.

Complexes with a Tungsten-Phosphorus Triple Bond
Organometallics, Vol. 18, No. 15, 1999 2881
F igu r e 6. Molecular structure [(tBuO)3WtPfW(CO)5]
(4a ) (showing 30% probability ellipsoids; hydrogen atoms
are omitted for clarity). Selected bond distances (Å) and
angles (deg): W(2)-P 2.132(4), W(1)-P 2.476(4), W(1)-
C(5) 1.99(2), C(5)-O(5) 1.15(2), W(2)-O(6) 1.874(13), W(2)-
O(7) 1.837(9), W(2)-O(8) 1.844(8); W(2)-P-W(1) 174.0(2),
P-W(1)-C(5) 176.5(2), W(2)-O(6)-C(6) 141.0(10), W(2)-
O(7)-C(10) 140.7(9), W(2)-O(8)-C(14) 144.3(8), P-W(2)-
O(6) 107.5(3), P-W(2)-O(7) 108.3(3), P-W(2)-O(8) 108.5-
(3).
F igu r e 7. Molecular structure [W2(OtBu)4 µ3-P{W(CO)5} ]
(10) (showing 30% probability ellipsoids; hydrogen atoms
are omitted for clarity). Selected bond distances (Å) and
angles (deg): W(2)-W(2)′ 2.8738(6), W(1)-P 2.500(2),
W(2)-P 2.272(2), W(2)-O(6) 1.824(4), W(2)-O(7) 1.823-
(4); W(2)-P-W(2)′ 77.94(5), P-W(2)-P′ 102.06(5), W(2)-
P-W(1) 147.82(8), W(2)-O(6)-C(6) 150.8(4).
form the alkylidyne complexes.41 The mass spectrum of
10 reveals the appropriate molecular ion peak. In the
region of the CO stretching frequencies of the IR
spectrum of 10, a typical pattern for a W(CO)5 group
with a local C4v symmetry is found. In the 31P NMR
spectrum of 10, in comparison to 4a , an upfield-shifted
singlet at 437.1 ppm is observed, revealing only one pair
of tungsten satellites due to the coupling to the exocyclic
W atom.
found for the alkylidyne complexes [(tBuO)3WtCR] (R
) tBu, Ph) obtained from the metathesis of [W2(OtBu)6]
with the corresponding alkynes.37
The most significant feature of the phosphido com-
plex 4a is the very short bond length W2-P of 2.132(4)
Å as the shortest distance of a W-P bond reported so
far.38 The coordinative P-W1 bond in 4a [2.476(4) Å]
is slightly shorter than is usually found for those P-W
bond lengths.39 Only in the phosphido complex [thf-
(ArO)3WtPfW(CO)5] (Ar ) 2,6-Me2C6H3) the W-P
bond length comes to 2.127(2) Å.40 Due to the low
basicity of the ArO ligands, an additional coordination
of THF to the central tungsten atom, to stabilize the
entire complex, becomes necessary, which also leads to
a slight shortening of the W-P triple bond.
Due to the high flexibility of the tBuO ligands,
however, the triple bond in 4 remains accessible, and
therefore, these compounds are highly reactive. Thus,
toluene solutions of 4a react at ambient temperature
over time under formal reductive dimerization combined
with the loss of two tBuO ligands to give dark-purple
crystals of 10 (after 4 days, 30% yield). This process is
not observed in hexane solutions of 4a . 10 is sparingly
soluble in n-hexane, CH2Cl2, Et2O, or toluene. In THF
or DMSO, decomposition is observed at ambient tem-
perature. For the formation of [W2(OtBu)4(µ-CPh)2],
thermolytic reaction conditions for the reaction of
[W2(OtBu)6] with PhCtCR are necessary, whereas at
room temperature the metathesis reaction occurs to
The molecular structure of 10 (Figure 7) reveals a
planar W4P2 framework with a central W2P2 ring. The
short W-P distances in the ring system with 2.272(2)
and 2.298(2) Å indicate a multiple-bond character,
whereas the bond length of the ring phosphorus atoms
to the exocyclic W1 atom is with 2.500(2) Å in the range
of a coordinative bond.39 The six-membered planar
framework of 10 is to a certain extent comparable to
the Re2P2W2 complex [Cp*Re(CO)2 (µ3-P)W(CO)4 ]2 (11)
synthesized by Scherer et al.42 Although this molecule
also possesses a planar W2P2 ring system, the W-P and
W-W bond lengths are considerably longer as in 10 [11,
d(W-W) ) 3.0523(7) Å; d(W-P) ) 2.439(2) and 2.440-
(2) Å]. The reason lies in the double-bond character of
the exocyclic Re-P bonds in 11 where the ring bonds
are elongated. In 10, the exocyclic bond is more a
coordinative bond. In 10, the W-W distance comes to
2.8738(6) Å and is consistent with a W-W single bond.
In [W2(OtBu)4(µ-CPh)2], this distance is 2.665(1) Å.41a
The latter compound is a side product of the cother-
molysis between [(tBuO)6W2] and PhCtCPh. Pnico-
genidene complexes of phosphorus and arsenic with
E2M2 framework were first synthesized and character-
ized by Huttner and co-workers.43
(37) Caulton, K. G.; Cayton, R. H.; Chisholm, M. H.; Huffman, J .
C.; Lobkovsky, E. B. Z. Xue, X. X. Organometallics 1992, 11, 321-
326. Cotton, F. A.; Schmotzer, W.; Shamshoum, E. S. Organometallics
1984, 3, 1770-1771.
(41) Cotton, F. A.; Schwotzer, W.; Shamshoum, E. S. Organometal-
lics 1983, 2, 1167. Cotton, F. A.; Schwotzer, W.; Shamshoum, E. S. J .
Organomet. Chem. 1985, 296, 55. [W2(OtBu)4(µ-CPh)2], d(WW) ) 2.665-
(1) Å.
(42) Scherer, O. J .; Ehses, M.; Wolmersha¨user, G. Angew. Chem.
1998, 110, 530-533; Angew. Chem., Int. Ed. Engl. 1998, 37, 507-510.
(43) Huttner, G.; Everts, K. Acc. Chem. Res. 1986, 19, 406-413 and
literature therein, especially: Lang, H.; Zsolnai, L.; Huttner, G. Angew.
Chem. 1983, 95, 1016-1017; Angew. Chem., Int. Ed. Engl. 1983, 22,
976-977. Huttner, G.; Weber, U.; Sigwarth, B.; Scheidsteger, O.; Lang,
H.; Zsolnai, L. J . Organomet. Chem. 1985, 282, 331-348.
(38) Compare to d(MP) ) 2.162(4) Å in [(N3N)WtP]3 and d(MP) )
2.169(1) Å in [(Ph2MeP)2Cl2(CO)WdPAr′].16
(39) Despite neglecting the hybridization at the P atom cf.: d(WP)
) 2.544 Å in [Ph3PfW(CO)5] (Aroney, M. J .; Buys, I. E.; Davies, M.
S.; Hambley, T. W. J . Chem. Soc., Dalton Trans. 1994, 2827); dh(WP)
) 2.445(7) Å in [W(CO)4 (η4-P4){W(CO)5}4 ] (Scheer, M.; Hermann, E.;
Sieler, J .; Oehme, M. Angew. Chem. 1991, 103, 1023-1025; Angew.
Chem., Int. Ed. Engl. 1991, 30, 969).
(40) Kramkowski, P.; Radius, U.; Baum, G.; Kaupp, M.; Scheer, M.
Chem. Eur. J ., in press.

2882 Organometallics, Vol. 18, No. 15, 1999
Ta ble 2. Cr ysta llogr a p h ic Da ta for 2a ,b, 4a , 6a , a n d 10
Scheer et al.
2a
2b
4a
6a
10
formula
Mr
C
22H45O3PW
C34H57O3PW
728.62
C17H27O8PW2
758.06
C47H58O9P2Cr2
932.87
C28H36O12P2W4
1361.91
572.40
crystal size (mm)
T (K)
space group
crystal system
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
0.50 × 0.30 × 0.15 0.15 × 0.10 × 0.08 0.08 × 0.08 × 0.04 0.65 × 0.41 × 0.11 0.46 × 0.23 × 0.08
200(1)
Pbca (No. 61)
orthorhombic
9.623(2)
18.272(3)
30.565(8)
90
200(1)
200(2)
200(1)
200(2)
P212121 (No. 19)
orthorhombic
10.141(1)
10.960(1)
31.183(4)
90
P2(1)/c (No. 14)
monoclinic
12.201(2)
10.034(2)
20.883(4)
90
94.85(3)
90
2547.4(9)
4
P1h (No. 2)
triclinic
10.6961(8)
12.5573(8)
19.3285(10)
105.931(5)
98.744(5)
91.686(7)
2460.4(3)
2
P2(1)/c (No. 14)
monoclinic
10.878(2)
16.796(3)
11.577(2)
90
114.83(3)
90
1919.6(7)
2
90
90
5374(8)
8
90
90
3465.8(6)
4
Z
F
calc (g cm-3
)
1.356
1.396
1.977
1.259
2.370
µ (mm-1
)
4.375
3.409
9.120
0.557
12.085
radiation (λ, Å)
diffractometer
2Θ range (deg)
index range
Mo KR (0.71073)
STOE STADI IV
4.46 e 2Θ e 50.06 9.9 e 2Θ e 56.12
-9ehe0
-21eke0
0ele36
STOE IPDS
STOE IPDS
STOE STADI IV
STOE STADI IV
4.12 e 2Θ e 55.02
-14ehe12
0eke21
0ele15
4394/0/214
3.92 e 2Θ e 52.02 3.38 e 2Θ e 54
-13ehe13
-14eke12
-40ele41
8295/0/361
-12ehe14
-5eke12
-25ele25
4107/0/262
-13ehe13
-16eke15
0ele24
data/restrains/parameters
independent reflections
with I > 2σ(I)
4458/0/259
10701/0/558
3212 (Rint
0.0000)
1.020
)
7506(Rint
0.0569)
1.107
)
2528 (Rint
0.0976)
1.108
)
7343(Rint
0.000)
1.017
)
3943 (Rint
0.0000)
1.107
)
goodness of fit on F2
R1,a wR2 (I > 2σ(I))
0.0301, 0.0700
0.0561, 0.0798
0.692, -1.074
0.0504, 0.1167
0.0595, 0.1259
2.225, -1.658
0.0482, 0.0853
0.0976, 0.0988
0.854, -1.182
0.0406, 0.1036
0.0807, 0.1197
0.403, -0.416
0.0264, 0.0642
0.0330, 0.0683
1.192, -1.283
b
R1,a wR2 (all data)
b
largest diff peak and hole (e Å-3
)
R ) ∑|Fo| - |Fc||/∑|Fo|. wR2 ) [∑ω(Fo - Fc2)2]/[∑(Fo2)2]1/2
.
a
b
2
Bruker IFS 28 FT-IR spectrometer. MS was measured on a
Finnigan MAT 711 at 70 eV. Elemental analyses were
performed by the analytical laboratory of the institute.
Mater ials. Unless otherwise stated, commercial-grade chemi-
cals were used without further purification. tBuCtP was
synthesized in accordance with 44. AdCtP was prepared as
described in ref 45. Ar′CtP was obtained according to ref 46.
MesCtP was synthesized as published in ref 47. [W2(OtBu)6]
and [W2(ONp)6] were synthesized by literature procedures.48
Cr ysta l Str u ctu r e An a lysis. Crystal structure analyses
were performed on a STOE IPDS (2b and 4) and a STOE
STADI IV (2a , 6a , and 10: ω-scan mode) diffractometer with
Mo KR radiation (λ ) 0.710 73 Å) with empirical absorption
corrections for 2a , 6, and 10 (ψ-scans). Machine parameters,
crystal data, and data collection parameters are summarized
in Table 2. The structures were solved by direct methods using
SHELXS-86,49a full-matrix least-squares refinement on F2 in
SHELXL-9349b with anisotropic displacement for non-H atoms.
Hydrogen atoms were located in idealized positions and refined
isotropically according to the riding model. According to the
absolute structure parameter (-0.03) complex 2b crystallizes
enantiomerically pure in the acentric space group P212121.
Rea ction of [W2(OtBu )6] w ith tBu CtP . [W2(OtBu)6] (0.65
g, 0.8 mmol) was dissolved in THF (20 mL) and cooled to -21
°C. A solution of tBuCtP (0.08 g, 0.8 mmol) in n-hexane (20
mL) was added dropwise over a period of 4 h. The reaction
mixture turns from red to dark brown. When the addition of
the phosphaalkyne was completed, the solution was allowed
Con clu sion
The results show the entire progression from the
postulation of the existence of the reactive intermediate
[(tBuO)3WtP] by Becker to the realization in a three-
component reaction as an effective method for the
synthesis of [(tBuO)3WtPfM(CO)5] (4a , M ) W; 4b,
M ) Cr) in our group. The way of understanding these
metathesis reactions demonstrates the decisive influ-
ence of the sterics of the different phosphaalkynes. Only
the use of mesitylphosphaalkyne opened the route to a
synthesis of complexes containing a tungsten-phospho-
rus triple bond with hardly any side products. Further-
more, the correct reaction procedure is of crucial im-
portance. For a maximum yield of the phosphido
complexes 4, the reaction between [W2(OtBu)6] and
MesCtP in the presence of [M(CO)5thf] (M ) W, Cr)
must be performed at low temperature until all phos-
phaalkyne has reacted in the metathesis reaction. The
total amount of the side products formed is thus reduced
to 5-10%. The successful synthesis of 4 now opens the
perspective to a comprehensive study of the reactivity
of these compounds. Due to their very high side-on
reactivity, 4a ,b can be used as a source for novel W/P-
containing heterocycles. On the other hand, these
complexes can also be applied as ligands in coordination
complexes creating novel cluster compounds. Investiga-
tion of the reaction potential of these type C complexes
has now become the exciting challenge in this field.
(44) Allspach, T.; Regitz, M.; Becker, G.; Becker, W. Synthesis 1986,
31-36.
(45) Ro¨sch, W.; Alspach, T.; Bergstra¨sser, U.; Regitz, M. In Synthetic
Methods of Organometallic and Inorganic Chemistry; Herrmann, W.
A., Ed.; G. Thieme Verlag: Stuttgart, 1996; Vol. 3, pp 11-16.
(46) Ma¨rkl, G.; Sejpka, H. Tetrahedron Lett. 1986, 27, 171.
(47) Mack, A.; Pierron, E.; Allspach, T.; Bergstra¨sser, U.; Regitz,
M. Synthesis 1998, 1305-1313.
Exp er im en ta l Section
All reactions were performed under an atmosphere of dry
argon using Schlenk and glovebox techniques. Solvents were
purified and degassed by standard procedures and distilled
prior use. NMR spectra were recorded on a Bruker AC 250
[1H, 250.13 MHz; 31P, 101.256 MHz; standard Me4Si (1H), 85%
H3PO4 (31P)]. IR spectra were recorded in Nujol or KBr on a
(48) (a) Chisholm, M. H.; Haitko, D. A.; Murillo, C. A. In Inorganic
Synthesis Fackler, J . R., Ed.; J ohn Wiley and Sons: New York 1982,
Vol. XXI, pp 51-57 and references therein.
(49) (a) Sheldrick, G. M. SHELXS-86, University of Go¨ttingen, 1986.
(b) Sheldrick, G. M. SHELXL-93, University of Go¨ttingen, 1993.

Complexes with a Tungsten-Phosphorus Triple Bond
Organometallics, Vol. 18, No. 15, 1999 2883
to warm to 0 °C. At this temperature, the solvent was reduced
to dryness in vacuo (10-3 Torr). Subsequently, [(tBuO)3Wt
CtBu] was removed by sublimation (50 °C, 10-3 Torr). The
latter compound and the residue were analyzed by NMR
spectroscopy. 31P NMR data for 2a and 3a are summarized in
Table 1. For [(tBuO)3WtCtBu]: 1H NMR (C6D6, 303 K) δ )
(s, 9H, tBu); IR (KBr) ν˜(CO) 2078 (s), 2064 (w), 2017 (s), 2003
(w), 1965 (vs, br), 1941 (vs, sh), 1915 cm-1 (s); MS (70 eV, EI)
m/z (%) 1197.2 (1) [M+], 882.5 (8) [M+ - W(CO)5], 351.7 (24)
[W(CO)6+], 288 (58) [Ar′CtP+]. 31P NMR data are summarized
in Table 1. Anal. Calcd for C47H58O9PW2 (932.91): C, 60.51;
H, 6.22. Found: C, 59.93; H, 6.13.
1
3.56 (s, 3 H, J H,W ) 7.1 Hz), 1.43 (s, 27 H); 13C{1H} NMR
Rea ction of [W2(ONp )6] w ith Ar ′CtP in th e P r esen ce
of [M(CO)5th f]. The procedure was identical to that previously
described. Instead of [W2(OtBu)6], [W2(ONp)6] (641 mg, 0.72
mmol) was used. Isolated yield: 6a , M ) Cr 150 mg (45%);
6b, M ) W 130 mg (30%). 31P NMR data are summarized in
Table 1. 9: 50 mg (5%); 1H NMR (toluene-d8, 303 K) δ ) 1.03
(18H), 1.08 (9H), 4.14 (2H), 4.2 (2H), 4.4 (2H), J H,H ) 10.8 Hz;
(C6D6, 303 K) δ ) 254.3 (s, CtBu), 80.12 (s, OCMe3), 32.76 (q,
1
1J CH ) 124 Hz, OCMe3), 31.95 (q, J CH ) 128 Hz, CMe). For
2a : 1H NMR (C6D6, 303 K) δ ) 1.57 (s, 18H), 1.34 (d, 9H, 1J P,H
) 8.6 Hz), 1.07 (s, 18 H); MS (70 eV, EI) m/z (%) 572 (18) [M+],
515 (10) [M+ - tBu], 385 (100) [{(tBuO)2WC2P}+]. Anal. Calcd
for C22H45O3PW (572.42): C, 46.16; H, 7.92. Found: C, 45.83;
H, 7.50.
MS (70 eV, EI) m/z (%) 1365.1 (7) [M+], 1294.1 (1.1) [M+
-
Tem p er a tu r e-Dep en d en t 31P {1H} NMR Sp ectr oscop ic
Mea su r em en ts of th e Rea ction betw een [W2(OtBu )6] a n d
MesCtP . [W2(OtBu)6] (240 mg, 0.3 mmol) was dissolved in
toluene-d8 (2 mL) and cooled to -196 °C. A solution of MesCt
P (49 mg, 0.3 mmol) in toluene-d8 (1 mL) was cooled to -70
°C and added. The combined solutions were allowed to warm
to -70 °C and subsequently transferred into an NMR tube.
31P{1H} NMR spectra were recorded in steps of 10 °C from
-70 °C to room temperature. The resulting data for 1, 2c, and
3b are summarized in Table 1.
Rea ction of [W2(OtBu )6] w ith RCtP in th e P r esen ce
of [MLn th f]. [W2(OtBu)6] (0.65 g, 0.8 mmol) was dissolved in
a THF solution of [M(CO)5thf] or [Cp′′Mn(CO)2thf] (20 mL of
a 0.04 M solution) and cooled to -21 °C. A solution of RCtP
(R ) tBu, 0.08 g, 0.8 mmol; R ) Ad, 0.14 g, 0.8 mmol) in
n-hexane (20 mL) was added dropwise over a period of 4 h.
The reaction mixture turns from red to dark brown. When the
addition of the phosphaalkyne was completed, the solution was
allowed to warm to 0 °C. At this temperature, all of the solvent
was removed in vacuo (10-3 Torr). Subsequently, [(tBuO)3Wt
CtBu] and [M(CO)6] or [Cp′′Mn(CO)3] was removed by subli-
mation (50 °C, 10-3 Torr). The residue was dissolved in
n-pentane (30 mL) and filtered. The solution was reduced in
vacuo to 10 mL. At 5 °C, small amounts of yellow crystals of
2a ,b were obtained. According to the 31P NMR spectra, these
solutions contained mostly 4a -c and some 5a -d . 31P NMR
data are summarized in Table 1. For 2b, Anal. Calcd for
C5H11], 840.0 (10) [W2C30H66O6+].
Reaction of [W3(µ3-P )(µ-ONp)3(ONp)6] with [W(CO)5th f].
[W3(µ3-P)(µ-ONp)3(ONp)6]31 (100 mg, 0.07 mmol) was dissolved
in toluene (5 mL). An excess of [W(CO)5thf] (10 mL of a 0.04
M solution) was added at room temperature. After 3 h the
solvent was removed in vacuo, and the residue was analyzed
by 31P{1H} NMR spectroscopy. 9: 31P{1H} NMR (C6D6, 303 K)
1
δ ) 165.4 (s, J W,P ) 228.6 Hz).
Rea ction of [W2(OtBu )6] w ith MesCtP in th e P r esen ce
of [M(CO)5th f] (M ) W, Cr ). A THF solution containing [W2-
(OtBu)6] (800 mg, 1 mmol) and [M(CO)5thf] (M ) W, Cr) (25
mL of a 0.04 M solution) was cooled to -196 °C. MesCtP (162
mg, 1 mmol) dissolved in n-hexane (20 mL) was cooled to -70
°C and added to the solid mixture. The solution was allowed
to warm to room temperature over 15 h. The solvent was
removed in vacuo and the residue was extracted with n-hexane
(30 mL). After filtration, the solvent was reduced in vacuo until
the onset of crystallization. Isolated yields: 190 mg (25%) of
4a and 125 mg (20%) of 4b. 31P NMR data are summarized in
Table 1. For 4a : 1H NMR (C6D6, 303 K) δ ) 1.43 (s); IR
(Nujol): ν˜(CO) 2071 (vs), 1980 (s), 1951 cm-1 (vs); MS (70 eV,
EI) m/z (%) 758.1 (7) [M+], 702.0 (1) [M+ - 2CO], 645.9 (3)
[M+ - 4CO], 589.9 (11) [M+ - 4CO - tBu]. Anal. Calcd for
C
17H27O8PW2 (758.07): C, 26.94; H, 3.59. Found: C, 26.56; H,
3.85. For 4b: 1H NMR (C6D6, 303 K) δ ) 1.42 (s); IR (Nujol)
ν˜(CO) ) 2064 (vs), 1985 (s), 1953 cm-1 (vs); MS (70 eV, EI)
m/z (%) 626.2 (12) [M+], 514.1 (3) [M+ - 4CO].
C
34H57O3PW (728.65): C, 56.02; H, 6.59. Found: C, 55.67; H,
6.35.
Rea ction of [W2(OtBu )6] w ith Ar ′CtP in th e P r esen ce
Red u ctive Dim er iza tion of [(tBu O)3WtP fW(CO)5]. 4a
(380 mg, 0.5 mmol) was dissolved in toluene (10 mL). After 2
days, dark purple crystals of 10 could be isolated. Isolated
yield, 60 mg (15%). 31P NMR data are summarized in Table 1.
For 10: 1H NMR (C6D6, 303 K) δ ) 1.04 (s, 9 H); IR (Nujol)
ν˜(CO) 2060 (vs), 1979 (s), 1915 cm-1 (vs); MS (70 eV, EI) m/z
of [M(CO)5th f] (M ) Cr , W). To a mixture of [W2(OtBu)6]
(569 mg, 0.72 mmol) and 24 mL of a 0.04 M solution of
[M(CO)5thf] (M ) Cr, W) in THF, a solution of Ar′CtP (200
mg, 0.72 mmol) in n-hexane (40 mL) was added dropwise over
a period of 1 h at room temperature. The solution was stirred
for an additional hour. The solvent was reduced to dryness,
and M(CO)6 was removed by sublimation (25 °C, 10-3 Torr).
The residue was dissolved in n-pentane (30 mL) and subse-
quently filtered. 6a ,b were recrystallized from n-pentane at 0
°C. Isolated yield: 6a : 120 mg (35%); 6b: 90 mg (20%). For
6a : 1H NMR (C6D6, 303 K) δ ) 7.34 (d, 2H, J ) 1.81 Hz), 6.99
(d, 2H, J ) 1.77 Hz), 1.89 (s, 9H, tBu), 1.82 (s, 9H, tBu), 1.54
(s, 6H), 1.41 (s, 9H, tBu), 1.29 (s, 9H, tBu), 1.24 (s, 9H, tBu);
IR (KBr) ν˜(CO) 2069 (w), 2062 (w), 1994 (sh), 1981 (vs), 1958
(w), 1952 cm-1 (w); MS (70 eV, EI) m/z (%) 932.9 (0.2) [M+],
905.3 (1) [M+ - CO], 288 (17.3) [Ar′CtP+], 219.7 (100) [Cr-
(CO)6+]. For 6b: 1H NMR (C6D6, 303 K) δ ) 7.715 (d, 2H, J )
1.81 Hz), 7.39 (d, 2H, J ) 1.77 Hz), 1.84 (s, 9H, tBu), 1.79 (s,
9H, tBu), 1.49 (s, 6H), 1.41 (s, 9H, tBu), 1.29 (s, 9H, tBu), 1.26
(%) 1370.0 (11) [M+], 1258.0 (4) [M+ - 4CO], 1202.0 (2) [M+
-
6CO] 1129.0 (4) [M+ - 6CO - tBuO]. Anal. Calcd for
28H36O12P2W4 (1361.93): C, 24.69; H, 2.64. Found: C, 24.06;
H, 2.85.
C
Ack n ow led gm en t. We are grateful to the Deutsche
Forschungsgemeinschaft and the Fonds der Chemischen
Industrie for comprehensive financial support.
Su p p or tin g In for m a tion Ava ila ble: Complete tables of
crystal data, atomic coordinates, H-atom parameters, bond
distances, and anisotropic displacement parameters and fully
labeled figures for 2a ,b, 4a , 6a , and 10. This material is
available free of charge via the Internet at http://pubs.acs.org.
OM990019E