1,2,4-Triphospholyl nickel complexes: Evidence for a dimerization equilibrium that includes a σ-π rearrangement of the triphospholyl ligand

Article abstract of DOI:10.1021/om000326g

1-Trimethylstannyl-3,5-di(tert-butyl)-1,2,4-triphosphole (2) reacts efficiently with [(PPh₃)₂NiCl₂] or [(NO)(PPh₃)₂NiCl] by elimination of Me₃SnCl and formation of 3,5-di(tert-butyl)1,2,4-triphospholyl (1) nickel complexes. [(η⁵-t-Bu₂C₂P₃)(PPh₃)NiCl] (5) is a half-sandwich complex that is closely related to its carbacyclic counterpart [η⁵-Cp(PPh₃)NiCl]. The properties of the reaction product of [(NO)(PPh₃)₂NiCl] and 2, however, differ significantly from those expected for the proposed target product [(η⁵-t-Bu₂C₂P₃)(NO)Ni] (7). In the solid state and at low temperatures in solution, the dimeric σ-complex [μ,η¹:η¹(t-Bu₂C₂P₃)(NO)(PPh₃)Ni]₂ (6) is the only observable species and contains two additional PPh₃ ligands. On warming the solutions, dimer 6 dissociates PPh₃ reversibly to form a mixture of free PPh₃ and the piano-stool compound [(η⁵-t-Bu₂C₂P₃)(NO)Ni] (7) as the ambient-temperature species. This temperature-dependent and fully reversible σ-π rearrangement of the triphospholyl ligand 1 is unique for unsaturated P-heterocycles. The low-temperature complex 6 also exhibits an unusual coordination mode, as its topology is much more closely related to the N-heterocyclic Cp analogues pyrazolate and triazolate than to other P-heterocycles.

Full text of DOI:10.1021/om000326g

Organometallics 2000, 19, 4283-4288
4283
1,2,4-Tr ip h osp h olyl Nick el Com p lexes: Evid en ce for a
Dim er iza tion Equ ilibr iu m Th a t In clu d es a σ-π
Rea r r a n gem en t of th e Tr ip h osp h olyl Liga n d †
Frank W. Heinemann,‡ Hans Pritzkow,§ Matthias Zeller,‡ and Ulrich Zenneck*,‡
Institut fu¨r Anorganische Chemie, Universita¨t Erlangen-Nu¨rnberg, Egerlandstrasse 1,
91058 Erlangen, Germany, and Institut fu¨r Anorganische Chemie, Universita¨t Heidelberg,
Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
Received April 18, 2000
1-Trimethylstannyl-3,5-di(tert-butyl)-1,2,4-triphosphole (2) reacts efficiently with [(PPh3)2-
NiCl2] or [(NO)(PPh3)2NiCl] by elimination of Me3SnCl and formation of 3,5-di(tert-butyl)-
1,2,4-triphospholyl (1) nickel complexes. [(η5-t-Bu2C2P3)(PPh3)NiCl] (5) is a half-sandwich
complex that is closely related to its carbacyclic counterpart [η5-Cp(PPh3)NiCl]. The properties
of the reaction product of [(NO)(PPh3)2NiCl] and 2, however, differ significantly from those
expected for the proposed target product [(η5-t-Bu2C2P3)(NO)Ni] (7). In the solid state and
at low temperatures in solution, the dimeric σ-complex [µ,η1:η1(t-Bu2C2P3)(NO)(PPh3)Ni]2
(6) is the only observable species and contains two additional PPh3 ligands. On warming
the solutions, dimer 6 dissociates PPh3 reversibly to form a mixture of free PPh3 and the
piano-stool compound [(η5-t-Bu2C2P3)(NO)Ni] (7) as the ambient-temperature species. This
temperature-dependent and fully reversible σ-π rearrangement of the triphospholyl ligand
1 is unique for unsaturated P-heterocycles. The low-temperature complex 6 also exhibits an
unusual coordination mode, as its topology is much more closely related to the N-heterocyclic
Cp analogues pyrazolate and triazolate than to other P-heterocycles.
In tr od u ction
derivatives bind metals either by the phosphorus lone
pair as a σ-ligand or in an η5-fashion via the delocalized
aromatic π-system, depending on the metal atom and
the coligands.3 For diphospholyl complexes an interme-
diate η3-coordination mode has also been observed.4 In
recent years, a series of complexes containing the 3,5-
di(tert-butyl)-1,2,4-triphospholyl ligand (1) has been
synthesized. Most examples contain a terminal η5-
bonded ligand,2,5 and a few examples are known for
bridging µ,η5-ligands,6 including two extremely slipped
triple-deckers in which 1 functions as a µ,η5:η2-bridge.7
η1-Complexes of 1 have also been reported,8,9,10 and both
coordination modes are united in binuclear µ,η5:η1-
Phosphorus atoms as parts of unsaturated hetero-
cycles may replace CR fragments as isovalent and
isolobal building blocks, which results in the formation
of numerous organophosphorus and organometallic
phosphorus compounds in which the phosphorus atom
might be viewed as a carbon copy.1 However, in some
cases the ligating properties of oligophospha cyclopen-
tadienyl derivatives differ significantly from those of
their carbacyclic cyclopentadienyl (Cp) analogues, clear
evidence of the fact that an analogy approach in the field
of organophosphorus transition metal chemistry cannot
explain the experimental findings completely.2
(3) Mathey, F.; Fischer, J .; Nelson, J . H. Struct. Bonding 1983, 55,
153-201. Mathey, F. J . Organomet. Chem. 1994, 475, 25-30. Gar-
nowskii, A. D.; Sadimenko, A. P. Adv. Heterocyclic Chem. 1999, 72,
1-77. Arliguie, T.; Ephritikhine, M.; Lance, M.; Nierlich, M. J .
Organomet. Chem. 1996, 524, 293-297.
One fundamental difference between a phosphorus
atom and a CR unit in analogous bonding situations is
the lone pair of the phosphorus atom, which is absent
for the carbon atom in most cases. Especially in the case
of π-ligands, this may cause dramatic changes of the
ligating properties, as this lone pair may come into play
in ground-state structures as well as in transition states.
Examples have been shown for the phospholyl ligand,
which is the simplest example of a phosphorus hetero-
cyclic analogue of the Cp ligand. Thus, phospholyl
(4) Bartsch, R.; Hitchcock, P. B.; Nixon, J . F. J . Organomet. Chem.
1989, 373, C17-C20. Bartsch, R.; Hitchcock, P. B.; Nixon, J . F. J .
Chem. Soc., Chem. Commun. 1990, 472-474.
(5) Driess, M.; Hu, D.; Pritzkow, H.; Scha¨ufele, H.; Zenneck, U.;
Regitz, M.; Ro¨sch, W. J . Organomet. Chem. 1987, 334, C35-C38.
Bartsch, R.; Hitchcock, P. B.; Nixon, J . F. J . Organomet. Chem. 1988,
356, C1-C4. Callaghan, Ch.; Clentsmith, G. K. B.; Cloke, F. G. N.;
Hitchcock, P. B.; Nixon, J . F.; Vickers, D. M. Organometallics 1999,
18, 793-795. Bartsch, R.; Hitchcock, P. B.; Nixon, J . F. J . Chem. Soc.,
Chem. Commun. 1987, 1146. Bartsch, R.; Hitchcock, P. B.; Madden,
T. J .; Meidine, M. F.; Nixon, J . F.; Wang, H. J . Chem. Soc., Chem.
Commun. 1988, 1475-1476.
(6) Bo¨hm, D.; Heinemann, F.; Hu, D.; Kummer, S.; Zenneck, U.
Collect. Czech. Chem. Commun. 1997, 62, 309-317. Hitchcock, P. B.;
J ohnson, J . A.; Nixon, J . F. Organometallics 1995, 14, 4382-4389.
(7) Elvers, A.; Heinemann, F. W.; Wrackmeyer, B.; Zenneck, U.
Chem. Eur. J . 1999, 5, 3143-3153. Callaghan, C.; Nixon, J . F.
Unpublished results reported by Nixon, J . F., in ref 1, p 328.
(8) Bartsch, R.; Carmichael, D.; Hitchcock, P. B.; Meidine, M. F.;
Nixon, J . F.; Sillet, G. J . D. J . Chem. Soc., Chem. Commun. 1988,
1615-1617.
† Dedicated to Professor Dieter Sellmann on the occasion of his 60th
birthday.
* Corresponding author. Fax:
zenneck@chemie.uni-erlangen.de.
‡ Universita¨t Erlangen-Nu¨rnberg.
§ Universita¨t Heidelberg.
+
49-9131-852-7367. E-mail:
(1) Dillon, K. B.; Mathey, F.; Nixon, J . F. Phosphorus, The Carbon
Copy; J ohn Wiley & Sons: Chichester, 1998.
(2) Clark, T.; Elvers, A.; Heinemann, F. W.; Hennemann, M.; Zeller,
M.; Zenneck, U. Angew. Chem. 2000, 112, 2174-2178; Angew. Chem.,
Int. Ed. 2000, 39, 2087-2091.
10.1021/om000326g CCC: $19.00 © 2000 American Chemical Society
Publication on Web 09/08/2000

4284 Organometallics, Vol. 19, No. 21, 2000
Heinemann et al.
Sch em e 1
Sch em e 2
F igu r e 1. Molecular structure of 5 in the solid state;
hydrogen atoms are omitted for clarity.
complexes.11 As we have developed an easy access to
1-triorganylstannyl triphosphole derivatives such as
1-t r im et h ylst a n n yl-3,5-di(ter t-bu t yl)-1,2,4-t r iph os-
phole (2),7 which is an excellent starting material for
the high-yield transfer of 1, we have started a system-
atic investigation to study the ligand properties of this
phosphorus-rich cyclopentadienyl derivative in detail.
In the case of [bis{3,5-di(tert-butyl)-1,2,4-triphospholyl}-
Mn] for example,2 we have shown the electronic ground
state to be different from all known manganocene
derivatives. Evidently, in this case the triphospholyl
ligand 1 is no longer a strict analogue of Cp. In this
paper we report the preparation and properties of 3,5-
di(tert-butyl)-1,2,4-triphospholyl nickel complexes.
differences in energy for the two principal coordination
modes of 1 versus the dications of late transition metals
are not very significant.
Treatment of [(NO)(PPh3)2NiCl] with 1 equiv of 2
results in the formation of a black crystalline solid 6,
whose spectroscopic properties are in agreement with
the target piano-stool complex [(η5-t-Bu2C2P3)(NO)Ni]
(7), the analogue of 4. However, all solutions prepared
from compound 6 contain 1 equiv of free PPh3 per nickel
atom. This PPh3 cannot be removed or even reduced by
recrystallization. The empirical composition of 6 is
therefore [(t-Bu2C2P3)(NO)(PPh3)Ni]. Room-temperature
31P and 13C NMR spectra of 6 strongly favor the
proposed η5-coordination mode of ligand 1. Furthermore,
the ν(NO) frequency of 1824 cm-1 observed in solution
reproduces nearly perfectly the value found for [(η5-Cp)-
(NO)Ni],13 which speaks well for a linear, positively
charged NO ligand that donates three electrons to the
metal atom here as well. If PPh3 is a ligand of complex
6, this would require the NO to be a one-electron ligand
to limit the electron count of the central metal to 18
VE. In contrast, the ν(NO) frequency observed for the
solid is only 1751 cm-1, indicating again different
bonding types in the solid state and solution.
Resu lts a n d Discu ssion
Our experiments initially followed the chemistry of
Cp as a ligand of nickel. Targets were thus the tri-
phospholyl analogues of the half-sandwich complexes
[η5-Cp(PPh3)NiCl] (3) and [η5- Cp(NO)Ni] (4), which are
both stable 18-valence-electron (VE) compounds (Scheme
1).12,13 In agreement with this expectation, the reaction
of [(PPh3)2NiCl2] with 1-trimethylstannyl-3,5-di(tert-
butyl)-1,2,4-triphosphole (2) leads to the formation of
[(η5-t-Bu2C2P3)(PPh3)NiCl] (5) in good yield. As expected,
5 is just the triphospholyl analogue of 3 (Scheme 2). A
single-crystal X-ray diffraction study established the
molecular structure with an η5-bonded triphospholyl
ligand (Figure 1, Table 1). The structural findings are
in good agreement with the spectroscopic properties of
5. Spectra and structural features are in line with 312
and other diamagnetic 18-VE sandwich and half-
sandwich complexes of 1.2,5,14 However, in contrast with
this nickel(II) species, the heavier elements of the nickel
triad form square-planar 16-VE complexes of Pd(II) and
Pt(II) with 1 as a σ-ligand.8,9 This suggests that the
An X-ray diffraction study solved the puzzle. 6 forms
a dimeric σ-complex, which indeed includes the observed
PPh3 ligand in the solid state. The correct formula of
solid 6 is {µ[1:2-η-t-Bu2C2P3](NO)(PPh3)Ni}2 (Figure 2,
Table 2, Scheme 3).
The two equivalent nickel atoms are coordinated in
tetrahedral spheres each generated by lone pairs of one
of the two adjacent phosphorus atoms of the ligands 1,
one PPh3, and one NO ligand. There is no evidence of
any bonding interaction between the two metal atoms
(Ni-Ni ) 4.745(1) Å). The µ,η1:η1-bridging mode of the
ligands 1 within dimer 6 is almost symmetric, and a
crystallographic inversion center is located halfway
between the two metal atoms. To the best of our
knowledge, only one report on a related µ,η1:η1-bridging
mode of ligand 1 has appeared in the literature, but only
for a single bridging ligand and a low-yield side product,
not a main product as here.15 6 is therefore a rare case.
In contrast with most oligophospha cyclopentadienyl
derivatives, triphospholyl ligand 1 seems to be much
(9) Hitchcock, P. B.; Meidine, M. F.; Nixon, J . F.; Sillet, G. J . D. J .
Chem. Soc., Chem. Commun. 1990, 317-319.
(10) Hitchcock, P. B.; Matos, R. M.; Nixon, J . F. J . Organomet. Chem.
1993, 462, 319-329.
(11) Bartsch, R.; Gelessus, A.; Hitchcock, P. B.; Nixon, J . F. J .
Organomet. Chem. 1992, 430, C10-C14.
(12) Yamazaki, H.; Nishido, T.; Matsumoto, Y.; Sumida, S.; Hagi-
hara, H. J . Organomet. Chem. 1966, 6, 86-91. Hernandez, E.; Royo,
P. J . Organomet. Chem. 1985, 291, 387-392.
(13) Fischer, E. O.; J ira, R. Z. Naturforsch. 1954, 9b, 618-619.
Feltham, R. D.; Fateley, W. G. Spectrochim. Acta 1964, 20, 1081.
(14) Bartsch, R.; Hitchcock, P. B.; Madden, T. J .; Meidine, M. F.;
Nixon, J . F.; Wang, H. J . Chem. Soc., Chem. Commun. 1988, 1475-
1476.
(15) Scheer, M.; Krug, J . Z. Anorg. Allg. Chem. 1998, 624, 399-
405.

1,2,4-Triphospholyl Nickel Complexes
Organometallics, Vol. 19, No. 21, 2000 4285
F igu r e 3. Triphospholyl part of variable-temperature 31
NMR spectra (161.7 MHz) of 6/7 in [D8]toluene.
P
F igu r e 2. Molecular structure of 6 in the solid state;
hydrogen atoms are omitted for clarity.
Sch em e 3
more closely related to the N-heterocyclic Cp analogues
pyrazolate or triazolate in this specific example. These
ligands prefer σ-coordination.16 On the other hand, the
N-heterocycles are definitely anions if coordinated to
transition metals in this manner.17 If ligand 1 is
regarded as an anion in the case of binuclear complex
6, the NO ligand must be a formal nitrosyl cation. This
leads us to view the compound as a classical tetra-
hedral four-coordinate and diamagnetic 18-VE Ni(0)
species.
F igu r e 4. Concentration plot of 6 and 7 as a function of
temperature. The data are obtained from the integrated
31P NMR signals. Start concentration 0.04 mol/L 6.
Sch em e 4
A temperature-dependent 31P NMR investigation
shed more light on the problem of the disagreement
between the NMR spectra of solutions of 6 and the
structural findings for the solid state. On cooling, the
31P-signals, which are observable at room temperature,
remain in the same positions, but decrease in intensity.
They are replaced reversibly and quantitatively by a
new set of signals, which can be assigned completely to
the structure found for 6 in the solid state (Figure 3).
Thus, the solid-state dimer 6 is identical with the low-
temperature species in solution.
The signals of the ring phosphorus atoms of 6 are
clearly separated by 102 ppm, as expected for a σ-bond-
ed ligand 1,5 and the 31P signal of PPh3 is shifted from
about -7 ppm to +36 ppm, which indicates the com-
plexation to the nickel atoms. At -85 °C more than 90%
of the room-temperature species is converted into dimer
6. As the room-temperature NMR spectra may be
interpreted unambiguously to result from a 1:1 mixture
of piano-stool 7 and dissociated PPh3, the temperature-
dependent NMR spectra clearly indicate an equilibrium
between 7 and free PPh3 at the ambient-temperature
side, which corresponds to dimer 6 at the low-temper-
ature side (Scheme 4, Figure 4).
Since there is no line broadening observable in the
NMR spectra or coalescence between related signals, the
speed of the rearrangement reaction is well below the
NMR time scale. On the other hand it is rapid enough
to reach equilibrium concentrations of the two species
within the time requirements for changing the temper-
ature of the NMR sample.
The rearrangement process is assumed to be complex.
A minimum of two P-Ni bonds must be cleaved to form
a σ-complex monomer out of the dimer. The removal of
the PPh3 ligand may also be correlated to the σ-π-
rearrangement of ligand 1 to prevent extremely small
electron counts for the reactive intermediates of the
process.
(16) Van Albada, G. A.; De Graaff, R. A. G.; Haasnoot, J . G.; Reedijk,
J . Inorg. Chem. 1984, 23, 1404-1408. Reimann, C. W.; Zocchi, M. J .
Chem. Soc., Chem. Commun. 1968, 272. Lo´pez, G.; Garcia, G.; Sa´nchez,
G.; Garcia, J .; Ruiz, J .; Hermoso, J . A.; Vegas, A.; Martinez-Ripoll, M.
Inorg. Chem. 1992, 31, 1518-1523. Garnowskii, A. D.; Sadimenko, A.
P. Adv. Heterocycl. Chem. 1999, 72, 1-77.
(17) Wilkinson, G.; Gillard, R. D.; McCleverty, J . A. Comprehensive
Coordination Chemistry, The Synthesis, Reactions, Properties and
Applications of Coordination Compounds, Volume 2 Ligands, 1st ed.;
Pergamon Press: Oxford, 1987; pp 76-79.
Only irreversible σ-π rearrangements have been
reported in the literature for unsaturated P-hetero-

4286 Organometallics, Vol. 19, No. 21, 2000
Heinemann et al.
Sch em e 5
cycles. Phosphabenzene derivatives, for example, may
bind metals as η1- as well as η6-ligands. The latter
coordination mode is the thermodynamically favored
one. Nevertheless some σ-complexes are kinetically
stabilized and isolable at room temperature. To initiate
the σ-π rearrangement, high temperatures or photo-
chemical conditions are required.18 There is only one
report of a σ-π rearrangement involving a triphospholyl
ligand in the literature. A σ-complex of ligand 1 was
observed by 31P NMR to be an unstable intermediate of
the formation of [(η5-C5Me5)(η5-t-Bu2C2P3)Ru].19
While the identity of the dimer 6 is validated by its
solid-state structure, the constitution of the monomeric
species may be regarded as not fully unambiguous. To
prepare pure solutions or crystalline material of 7, the
dissociated PPh3 was trapped chemically by complex-
ation to a W(CO)5 fragment. Due to the ligand properties
of 7, an excess (OC)5W(thf) was reacted with the
equilibrium mixture of 6, 7, and PPh3. As expected, the
reaction results in the formation of monomeric nickel
nitrosyl complex 8, which contains an additional W(CO)5
unit. It is attached to one of the adjacent phosphorus
atoms of the triphospholyl ligand (Scheme 5).
F igu r e 5. Molecular structure of 8 in the solid state;
hydrogen atoms are omitted for clarity.
transition metals, the σ-interaction is thermodynami-
cally favored over the η5-bonding in the case of the nickel
nitrosyl complexes. The direct observation of an equi-
librium of a reversible σ-π rearrangement of a P-
heterocyclic ligand is as unique as the doubly bridging
mode of the heterocyclic ligands within the σ-complex
dimer [µ,η1:η1(t-Bu2C2P3)(NO)(PPh3)Ni]2 (6). 6 is more
closely related to bis-pyrazolate or bis-triazolate com-
plexes than to other complexes of unsaturated P-
heterocycles or to Cp derivatives. Thus, under the
influence of the nitrosyl ligand, the specific interaction
between Ni atoms and ligand 1 is fine-tuned in a way
that makes a richer chemistry possible than observed
for 18-VE CpNi half-sandwich complexes.
The spectroscopic properties of 8 are in agreement
with an η5-coordinated nickel center with an ABC spin
system and well-resolved 31P and 183W coupling patterns
in 31P NMR. A single-crystal X-ray diffraction study
confirmed the molecular structure of µ[1:1-5-η-t-Bu2C2P3]-
{(CO)5W}(NO)Ni}, 8 (Figure 5, Table 3).
The Ni-N-O unit is almost linear (175°), and the
nitrosyl ligand must be viewed as a three-electron donor.
The bond distances are in good agreement with those
found for the cyclopentadienyl complex 4.20 The struc-
tural findings on 8 can be regarded as proof for the
proposed structure of 7. Both are the first one-legged
piano-stool complexes of the triphospholyl ligand. As for
5, the triphospholyl complexes 8 and 7 therefore can be
regarded as analogues of their cyclopentadienyl coun-
terparts 3 and 4.
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All experiments were conducted
under nitrogen atmosphere by using standard Schlenk and
cannula techniques. Solvents were dried according to described
procedures21 and used freshly distilled from the drying agent.
[(PPh3)2NiCl2] was obtained from Fluka Chemie AG; [(NO)-
(PPh3)2NiCl] was prepared according to the literature.22 1-Tri-
methylstannyl-3,5-di(tert-butyl)-1,2,4-triphosphole (2) was pre-
pared as described previously7 and distilled in an oil pump
vacuum for purification.
[(η5-t-Bu 2C2P 3)(P P h 3)NiCl] (5). A 0.642 g sample of [(PPh3)2-
NiCl2] (0.981 mmol) is dissolved in 60 mL of dichloromethane.
An orange powder starts precipitating after some minutes. A
solution of 0.398 g of 1-trimethylstannyl-3,5-di(tert-butyl)-1,2,4-
triphosphole (2) (1.008 mmol) in 40 mL of dichloromethane is
added at 0 °C over a period of half an hour. The orange powder
redissolves and the color of the solution changes to dark red.
The solution is stirred for an additional 10 min, and the
volatile parts are removed in a vacuum. The remaining solid
is washed repeatedly with n-hexane until the solution drains
off colorless and dried in vacuo to yield 427 mg (0.727 mmol,
74%) of [(η5-t-Bu2C2P3)(PPh3)NiCl] (5).
Con clu sion s
The ligand 3,5-di(tert-butyl)-1,2,4-triphospholyl (1)
may act as a σ- or π-ligand to nickel atoms, depending
on the coligands and thus on the formal oxidation state
of the metal and on the temperature. In contrast with
a general preference of 1 to act as a π-ligand toward 3d
1
Sp ectr oscop ic Da ta for 5. H NMR (269.7 MHz, CDCl3):
δ 1.63 (s, 18H, CH3), 7.41 (m, 9H, o- and p-Ph-H), 7.78 (m,
6H, m-Ph-H). 31P{1H} NMR (161.7 MHz, CH2Cl2, 20.7 °C): δ
219.35 (dt, 2J (31P,31P) ) 30.7 Hz, 2J (31P,31P) ) 25.9 Hz, 1P,
(18) Deberitz, J .; No¨th, H. Chem. Ber. 1973, 106, 2222-2226.
Vahrenkamp, H.; No¨th, H. Chem. Ber. 1973, 106, 2227-2235. Nief,
F.; Charrier, C.; Mathey, F.; Simalty, M. J . Organomet. Chem. 1980,
187, 277-285. Fischer, J .; De Cian, A.; Nief, F. Acta Crystallogr. 1981,
B37, 1067-1071.
(19) Hitchcock, P. B.; Nixon, J . F.; Matos, R. M. J . Organomet. Chem.
1995, 490, 155-162.
(20) Ronova, I. A.; Alekseeva, N. V.; Veniaminov, N. N.; Kravers,
M. A. Zh. Strukt. Khim. 1975, 16, 476-478, and literature cited
therein.
P
ring), 106.87 (d, 2J (31P,31P) ) 25.9 Hz, 2P, Pring), 26.53 (d,
2J (31P,31P) ) 30.7 Hz, 1P, PPh3). 13C{1H} NMR (67.83 MHz,
CDCl3): δ 35.92 (dpt, Σ 3J (31P,13C) + 4J (31P,13C) ) 8.0 Hz,
2
3J (31P,13C) ) 8.3 Hz, C(CH3)3), 40.69 (d, J (31P,13C) ) 20.7 Hz,
(21) Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals, 3rd ed.; Butterworth-Heinemann: Oxford, 1988.
(22) Feltham, R. D. Inorg. Chem. 1964, 3, 116-119.

1,2,4-Triphospholyl Nickel Complexes
Organometallics, Vol. 19, No. 21, 2000 4287
Ta ble 1. Selected Bon d Len gth (Å) a n d An gles
(d eg) for 5
Ta ble 2. Selected Bon d Len gth (Å) a n d An gles
(d eg)a for 6
Ni-Cl
2.2043(5)
2.1779(5)
2.1839(7)
1.7429(17)
1.7584(17)
1.7672(18)
2.3235(5)
2.3319(5)
2.4032(5)
2.3162(17)
2.2912(17)
Ni(1)-Ni(1#)
Ni(1)-N(1)
Ni(1)-P(1)
Ni(1)-P(2#)
Ni(1)-P(4)
P(1)-P(2)
P(1)-C(2)
P(2)-C(1)
P(3)-C(1)
P(3)-C(2)
N(1)-O(1)
4.745(1)
1.662(3)
Ni-P(4)
P(1)-P(2)
P(2)-C(1)
P(3)-C(1)
P(3)-C(2)
Ni-P(1)
Ni-P(2)
Ni-P(3)
Ni-C(1)
Ni-C(2)
2.2626(11)
2.2874(11)
2.3304(11)
2.0823(14)
1.746(4)
1.741(4)
1.744(4)
1.744(4)
1.169(5)
P(4)-Ni-Cl
94.056(18)
N(1)-Ni(1)-P(1)
N(1)-Ni(1)-P(2#)
P(1)-Ni(1)-P(2#)
N(1)-Ni(1)-P(4)
P(1)-Ni(1)-P(4)
P(2#)1-Ni(1)-P(4)
Ni(1)-P(1)-P(2)
Ni(1)-N(1)-O(1)
P(1)-P(2)-C(1)
P(2)-P(1)-C(2)
P(1)-C(2)-P(3)
P(2)-C(1)-P(3)
C(2)-P(3)-C(1)
107.44(12)
111.67(12)
101.74(4)
124.56(12)
105.50(4)
103.54(4)
119.92(6)
166.4(3)
100.71(14)
100.98(14)
117.1(2)
117.5(2)
103.57(18)
C(CH3)3), 128.07 (d, J (31P,13C) ) 10.4 Hz, o- or m-Ph-C), 130.58
(d, J (31P,13C) ) 2.7 Hz, p-Ph-C), 132.51 (d, J (31P,13C) ) 19.1
Hz, i-Ph-C), 134.33 (d, J (31P,13C) ) 9.8 Hz, o- or m-Ph-C), 188.4
(not res., Cring). MS (FD+, CH2Cl2): m/z (%) 586 (100) [M]+,
262 (70) [PPh3]+. Anal. Calcd for (C28H33ClNiP4): C 57.23, H
5.66. Found: C 57.09, H 5.90.
4
1
[µ,η1:η1(t-Bu 2C2P 3)(NO)(P P h 3)Ni]2 (6). A 0.254 g (0.643
mmol) sample of 1-trimethylstannyl-3,5-di(tert-butyl)-1,2,4-
triphosphole (2) in 10 mL of dichloromethane is added at -30
°C to a solution of 0.379 g (0.584 mmol) of [(NO)(PPh3)2NiCl]
in 30 mL of dichloromethane. The color changes from greenish
blue to red. After stirring for 30 min at -30 °C and an
additional 30 min at room temperature the solvent is removed
in vacuo, and the resulting black solid is suspended in cold
n-hexane, filtered, washed again with cold n-hexane until the
solution drains off colorless, and dried in vacuo. The solid is
dissolved in a minimum amount of a toluene/n-hexane mix-
ture, and [µ,η1:η1(t-Bu2C2P3)(NO)(PPh3)Ni]2 (6) precipitates at
-18 °C and is separated from the solution, dried, and
recrystallized from dichloromethane/n-hexane mixtures. Yield
of 6: 0.238 g, 0.204 mmol, 70%.
# indicates symmetry equivalent atoms, symmetry transforma-
tions used to generate equivalent atoms: -x+1,-y+1,-z+1.
a
Ta ble 3. Selected Bon d Len gth (Å) a n d An gles
(d eg) for 8
Ni-N
N-O(1)
1.613 (17)
1.14 (2)
P(2)-P(3)
P(2)-C(2)
P(3)-C(1)
P(1)-C(1)
P(1)-C(2)
Ni-P(1)
Ni-P(2)
Ni-P(3)
Ni-C(1)
Ni-C(2)
P(3)-W
2.119 (6)
1.754 (18)
1.776 (17)
1.763 (17)
1.772 (18)
2.341 (5)
2.396 (5)
2.371 (5)
2.222 (16)
2.194 (17)
2.495 (4)
1.15 (2)
Sp ectr oscop ic Da ta for 6. 31P{1H} NMR (161.7 MHz,
[D8]toluene, -85.2 °C): [AB2X] spin system, δ 35.9 (s, 1P,
PPh3), 179.1 (s, 2P, Pring), 281.2 (s, 1P, Pring). 13C{1H} NMR
(100.4 MHz, [D8]toluene, -84.9 °C): δ 34.70 (s, C(CH3)3), 40.00
(d, J (31P,13C) ) 22.9 Hz, C(CH3)3), 132.5-128 (Ph-C, not
assigned due to overlapping solvent signals), 202.89 (d,
C-O (mean)
J (31P,13C) ) 65.0 Hz,Cring). IR (KBr): ν(NO) 1751 cm-1
.
Sp ectr oscop ic Da ta for 1:1 Mixtu r es of 7 a n d P P h 3. 1H
NMR (399.65 MHz, CDCl3, 23.9 °C): δ 1.65 (s, 18H, CH3),
7.28-7.35 (m, 15H, C5H6). 31P{1H} NMR (161.7 MHz, CDCl3,
Ni-N-O(1)
175.2 (18)
chromatographed on SiO2/5% H2O. With n-hexane as eluent
38 mg (0.059 mmol, 20.0%) of µ[1:1-5-η-t-Bu2C2P3]{(CO)5W}-
(NO)Ni} (8) is obtained as a red oil.
24.9 °C): [B2AX] spin system, δ 151.64 (pd, J (31P,31P) ) 53.9
2
Hz, 2P), 151.0 (pt, 2J (31P,31P) ) 53.9 Hz, 1P), -5.6 (s, 1P, PPh3).
31P{1H} NMR (161.7 MHz, [D8]toluene, 22.3 °C): [B2AX] spin
1
Sp ectr oscop ic Da ta for 8. H NMR (269.72 MHz, C6D6):
system, δ -5.5 (s, 1P, P(C6H5)3), 150.4 (t, J (31P,31P) ) 55 Hz,
2
δ 1.521 (s, 9H, CH3), 1.316 (s, 9H, CH3). 31P{1H} NMR (161.7
MHz, C6D6, 22.5 °C): [ABC] spin system, δ 140.6 (dd,
2J (31P,31P) ) 46.9 Hz, 2J (31P,31P) ) 55.8 Hz, 1P), 126.56 (dd,
1J (31P,31P) ) 422.0 Hz, 2J (31P,31P) ) 46.9 Hz, 1P), 116.86 (d,
1J (183W,31P) ) 224.0 Hz, dd, 1J (31P,31P) ) 422.0 Hz, 2J (31P,31P)
) 55.8 Hz, 1P). 13C{1H} NMR (100.40 MHz, C6D6, 21.7 °C): δ
198.66 (d, 1J (183W,13C) ) 151.9 Hz, d, 2J (31P,13C) ) 32.0 Hz,
CO), 196.35 (d, 1J (183W,13C) ) 126.3 Hz, d, 2J (31P,13C) ) 2.7
1P, Pring), 153.7 (d, 2J (31P,31P) ) 55 Hz, 2P, Pring). 13C{1H} NMR
(100.4 MHz, CDCl3, 25.1 °C): δ 36.66 (m, C(CH3)3), 39.04 (ddd,
2J (31P,13C) ) 16.0 Hz, Σ 2J (31P,13C) + 3J (31P,13C) ) 13.6 Hz,
C(CH3)3), 128.06 (d, 4J (31P,13C) ) 5.7 Hz, p-Ph-C), 128.28 (s,
2
m-Ph-C), 133.32 (d, J (31P,13C) ) 19.0 Hz, o-Ph-C), 136.78 (d,
1J (31P,13C) ) 10.7 Hz, i-Ph-C), 179.35 (ddd, J (31P,13C) ) 77.2
1
Hz, Σ 1J (31P,13C) + 2J (31P,13C) ) 109.8 Hz, Cring). IR (n-
hexane): ν(NO) 1824 cm-1. MS (FD+, CH2Cl2): m/z (%) 262
(100) [PPh3]+, 319 (40) [(t-Bu2C2P3)Ni(NO)]+.
1
1
Hz, CO), 175.17 (dd, J (13C,31P) ) 83.7 Hz, J (13C,31P) ) 92.2
Hz, 2J (13C,31P) ) 6 Hz, Cring), 166.81 (dd, 1J (13C,31P) ) 67.7
Hz, 1J (13C,31P) ) 86.0 Hz, 2J (13C,31P) ) 11.6 Hz, Cring), 39.2
(m, C(CH3)3), 36.2 (m, C(CH3)3). IR (n-hexane): ν(CO) 2076
(m), 1955 (s), ν(NO) 1832 (s) cm-1. MS (FD+, n-hexane): m/z
(%) 644 (100) [M]+.
µ[1:1-5-η-t-Bu 2C2P 3]{(CO)5W}(NO)Ni} (8). A 172 mg
(0.148 mmol) sample of {µ[1:2-η-t-Bu2C2P3](NO)(PPh3)Ni}2 (30)
is reacted at -40 °C with 0.86 mmol of freshly prepared
(CO)5(thf)W in 250 mL of THF. The black-green suspension is
allowed to reach room temperature, and a clear red solution
forms. After ca. 4 h the reaction is completed (checked by IR
monitoring). The solvent is removed in vacuo, the residue is
dissolved in n-hexane and filtered, and the solution is concen-
trated to 30 mL and stored overnight at -18 °C. Clear crystals
form. The brownish-red solution is separated via syringe and
the crystals are washed twice with 5 mL of -30 °C n-hexane.
The combined solutions are reduced in vacuo and column
Cr ysta l Str u ctu r e Deter m in a tion of 5 a n d 6. Crystal
data were collected on a Bruker AXS SMART 1000 diffrac-
tometer with CCD area detector (Mo KR radiation, graphite
monochromator, λ ) 0.71073 Å) at -100 °C using SMART
software.23 The reflection intensities were integrated using
(23) SMART and SAINT, NT V5.0, Area detector control and
integration software; Bruker AXS: Madison, WI, 1999.

4288 Organometallics, Vol. 19, No. 21, 2000
Ta ble 4. Cr ysta l Da ta a n d Str u ctu r e Refin em en t of 5, 6, a n d 8
Heinemann et al.
5
6
8
empirical formula
fw
C
28H33ClNiP4
C56H66N2Ni2O2P8
1164.29
C15H18NNiO6P3W
643.77
587.58
solvent
n-hexane/CH2Cl2
black fragment
173(2) K
monoclinic
P21/n
n-hexane/CH2Cl2
black fragment
173(2) K
triclinic
P1h
n-hexane
red plate
220(2) K
monoclinic
C2/c
cryst habit
temperature
cryst syst
space group
unit cell dimens
a ) 15.9255(7) Å
b ) 10.7772(5) Å
c ) 16.9237(8) Å
R ) 90°
a ) 10.7894(2) Å
b ) 11.1402(2) Å
c ) 12.4640(3) Å
R ) 102.940(1)°
â ) 101.216(1)°
γ ) 101.606(1)°
1384.47(5) Å3
1
a ) 15.628(6) Å
b ) 10.000(3) Å
c ) 29.138(10) Å
R ) 90°
â ) 97.531(1)°
γ ) 90°
â ) 90.43(3)°
γ ) 90°
volume
Z
density (calcd)
abs coeff
F(000)
2879.6(2) Å3
4
4554(3) Å3
8
1.355 g/cm3
1.004 mm-1
1224
1.396 g/cm3
0.954 mm-1
608
1.878 g/cm3
6.114 mm-1
2480
cryst size
θ range for data collection
index ranges
0.44 × 0.25 × 0.16 mm
1.65-28.29°
-21 e h e 20,
0 e k e 14,
0 e l e 21
16 925
6850 [R(int) ) 0.028]
5456
0.43 × 0.11 × 0.04 mm
1.73-28.31°
-14 e h e 13,
-14 e k e 14,
0 e l e 16
18 698
6765 [R(int) ) 0.049]
5118
0.50 × 0.24 × 0.04 mm
2.42-26.02°
-19 e h e 1,
-12 e k e 1,
-35 e l e 35
5279
4278 [R(int) ) 0.088]
2552
94.9%
no. of reflns collected
no. of ind reflns
no. of reflns with I > 2σ(I)
completeness to θ ) 28.3°
abs corr
max. and min. transmn
refinement method
no. of data/restraints/params
goodness-of-fit on F2
final R indices [I>2σ(I)]
R indices (all data)
95.6%
98.0%
semiempirical from equivalents
0.894 and 0.689
semiempirical from ψ-scans
0.399 and 0.937
0.928 and 0.744
full-matrix least-squares on F2
6765/0/324
6850/0/439
0.975
R1 ) 0.029, wR2 ) 0.071
R1 ) 0.042, wR2 ) 0.075
0.54 and -0.23 e Å-3
4278/0/250
1.049
R1 ) 0.072, wR2 ) 0.162
R1 ) 0.136, wR2 ) 0.196
1.76 and -1.68 e Å-3
1.081
R1 ) 0.051, wR2 ) 0.136
R1 ) 0.070, wR2 ) 0.141
0.98 and -0.38 e Å-3
largest diff peak and hole
23
SAINT and corrected for absorption using SADABS.24 The
structures were solved by direct methods and refined by full-
matrix least-squares against F2 with all reflections using
SHELXTL-programs.25 All non-hydrogen atoms were refined
anisotropically. All hydrogen atoms were located in difference
Fourier maps and refined isotropically. Crystal data and
experimental details are listed in Table 4.
positioned. Crystal data and experimental details are listed
in Table 4.
All peaks of significant residual electron density are to be
found close to the W atom.
Ack n ow led gm en t. This work was supported by the
Deutsche Forschungsgemeinschaft and the Fonds der
Chemischen Industrie. M.Z. is grateful for a scholarship
by the DFG-Graduiertenkolleg Phosphorchemie als
Bindeglied verschiedener chemischer Disziplinen, at the
University of Kaiserslautern, Germany. We also thank
Dr. M. Moll for the measurement of variable-tempera-
ture NMR spectra.
Cr ysta l Str u ctu r e Deter m in a tion of 8. Intensity data
were collected on a Siemens P4 diffractometer (ω scan tech-
nique, 6.0°/min, Mo KR radiation, graphite monochromator, λ
) 0.71073 Å) at 220 K using the XSCAnS 2.2026 software. The
structure was solved by direct methods and refined by full-
matrix least-squares against F2 with all reflections using
SHELXTL-programs.25 All non-hydrogen atoms were re-
fined anisotropically. All hydrogen atoms are geometrically
Su p p or tin g In for m a tion Ava ila ble: Further details of
the structure determination including tables of atomic coor-
dinates, bond distances and angles, and thermal parameters.
This material is available free of charge via the Internet at
http://pubs.acs.org.
(24) Sheldrick, G. M. SADABS, Program for scaling and correction
of area detector data; Go¨ttingen, 1996.
(25) Sheldrick, G. M. SHELXTL NT V5.1; Bruker AXS: Madison,
WI, 1999.
(26) XSCANS 2.20; Siemens Analytical X-ray Instruments: Madi-
son, WI, 1996.
OM000326G