Synthesis and reactivity of 2-iodophosphinines

Article abstract of DOI:10.1021/om9505322

The synthesis of 2-iodophosphinines 5 (a, parent compound; b, 4,5-dimethyl derivative) and of their pentacarbonyltungsten complexes 7 is described starting from dichloro-(diiodomethyl)phosphine (2), which was prepared via alkylation of phosphorus trichloride with (diiodomethyl)magnesium chloride (1). The halogen-metal exchange reactions of 5a/b and 7a/b are reported: the lithiation reactions of 5a/b with n-BuLi were not successful. In contrast, the complexes 7a/b were converted to the corresponding lithium derivatives 11a/b with n-BuLi in THF at -100 °C. Derivatization of 11a/b with triphenyltin chloride furnished 13a/b, respectively. The reaction of 5b with magnesium in THF at room temperature led to the formation of 3,4-dimethylphosphinine (18) (41.5%), 4,4′,5,5′-tetramethyl-2,2′-biphosphinine (16) (1.3%), and 2-(iodomagnesio)-4,5-dimethylphosphinine (17) (19.2%); 37% of the starting material had decomposed. In a reaction with zinc, 5b gave the organozinc derivatives 20 or 21 in THF/TMEDA or DMF, respectively. The same zinc insertion procedures were applied to 7b but did not furnish the pentacarbonyltungsten complexes 22 or 24 in a clean fashion. However, 22 could be prepared via complexation of 20 with (acetonitrile)-pentacarbonyltungsten (6).

Full text of DOI:10.1021/om9505322

794
Organometallics 1996, 15, 794-801
Syn th esis a n d Rea ctivity of 2-Iod op h osp h in in es
Herman T. Teunissen and Friedrich Bickelhaupt*
Scheikundig Laboratorium, Vrije Universiteit, De Boelelaan 1083,
1081 HV Amsterdam, The Netherlands
Received J uly 11, 1995X
The synthesis of 2-iodophosphinines 5 (a , parent compound; b, 4,5-dimethyl derivative)
and of their pentacarbonyltungsten complexes 7 is described starting from dichloro-
(diiodomethyl)phosphine (2), which was prepared via alkylation of phosphorus trichloride
with (diiodomethyl)magnesium chloride (1). The halogen-metal exchange reactions of 5a /b
and 7a /b are reported: the lithiation reactions of 5a /b with n-BuLi were not successful. In
contrast, the complexes 7a /b were converted to the corresponding lithium derivatives 11a /b
with n-BuLi in THF at -100 °C. Derivatization of 11a /b with triphenyltin chloride furnished
13a /b, respectively. The reaction of 5b with magnesium in THF at room temperature led
to the formation of 3,4-dimethylphosphinine (18) (41.5%), 4,4′,5,5′-tetramethyl-2,2′-biphos-
phinine (16) (1.3%), and 2-(iodomagnesio)-4,5-dimethylphosphinine (17) (19.2%); 37% of the
starting material had decomposed. In a reaction with zinc, 5b gave the organozinc derivatives
20 or 21 in THF/TMEDA or DMF, respectively. The same zinc insertion procedures were
applied to 7b but did not furnish the pentacarbonyltungsten complexes 22 or 24 in a clean
fashion. However, 22 could be prepared via complexation of 20 with (acetonitrile)-
pentacarbonyltungsten (6).
In tr od u ction
mental details. Furthermore, metalation reactions of
these compounds with n-butyllithium, magnesium, and
zinc are described.
The synthesis of phosphinine derivatives, which was
first reported by Ma¨rkl in 1966,1 is usually achieved by
a multistep procedure in which the phosphinine is
prepared from non-phosphaaromatic prcursors.2 In
principle, preparation of a new phosphinine via chemical
modification of a halophosphinine might be an interest-
ing approach to obtain a variety of functionalized
phosphinines. Along this line, Mathey et al. investiga-
ted the chemistry of 2-chloro- and 2-bromophosphin-
ines.3 As we were interested in phosphinines function-
alized at the 2-position, we focused our attention on the
synthesis and reactivity of 2-iodo derivatives in the hope
that the enhanced reactivity of the carbon-iodine bond
would open new perspectives for investigations on
2-halophosphinines in general. In preliminary com-
munications4 we reported on the synthesis of 2-iodo-
phosphinines and on several exploratory results con-
cerning their reactivity. In this paper we wish to report
the synthesis of 2-iodophosphinines 5a /b and their
pentacarbonyltungsten complexes 7a /b with full experi-
While halogen-metal exchange with organolithium
reagents and the preparation of Grignard reagents is
well-known, direct zinc insertion into C-X bonds is less
common. However, recently, Knochel provided some
important contributions to the preparation of organozinc
compounds.5 One of these5a concerns the preparation
of arylzinc iodides in DMF or DMAC (dimethylaceta-
mide) via direct zinc insertion into an aryl-iodine bond.
Another zinc insertion into an sp2-hybridized C-X bond
was reported by J iang and Xu.6 With 2-bromotrifluo-
ropropene as the substrate, they investigated a variety
of solvents (Et2O, THF, DME, and DMF) and a zinc/
silver couple in the presence or absence of TMEDA. It
was found that in the presence of TMEDA (1 equiv) in
THF, DME, or Et2O, the corresponding organozinc
derivative was obtained in high yield while poor results
were obtained in DMF.
Resu lts a n d Discu ssion
* To whom correspondence should be addressed. E-mail: bicklhpt@
chem.vu.nl.
Iod op h osp h in in es. The synthesis of 2-iodophos-
phinines and their pentacarbonyltungsten complexes
was achieved by the Diels-Alder approach developed
by Mathey for the corresponding chlorine and bromine
derivatives3a and is outlined in Scheme 1.
The precursor 2 was prepared by alkylation of phos-
phorus trichloride with the magnesium carbenoid 1. The
freshly prepared solution of 17 was frozen in liquid
nitrogen at -196 °C. Then a Schlenk tube containing
X Abstract published in Advance ACS Abstracts, December 15, 1995.
(1) Ma¨rkl, G. Angew. Chem. 1966, 78, 907.
(2) Ma¨rkl, G. In Multiple Bonds and Low Coordination in Phospho-
rus Chemistry; Regitz, M., Scherer, O. J ., Eds.; Thieme Verlag:
Stuttgart, Germany, 1990; pp 220-257.
(3) (a) Le Floch, P.; Mathey, F. Tetrahedron Lett. 1989, 30, 817. (b)
Le Floch, P.; Ricard, L.; Mathey, F. Polyhedron 1990, 9, 991. (c) Le
Floch, P.; Carmichael, D.; Mathey, F. Organometallics 1991, 10, 2432.
(d) Le Floch, P.; Carmichael, D.; Mathey, F. Bull. Soc. Chim. Fr. 1992,
129, 291. (e) Le Floch, P.; Carmichael, D.; Mathey, F. Phosphorus
Sulfur 1993, 76, 33. (f) Le Floch, P.; Ricard, L.; Mathey, F. J . Chem.
Soc., Chem. Commun. 1993, 789. (g) Le Floch, P.; Carmichael, D.;
Ricard, L.; Mathey, F. J . Am. Chem. Soc. 1993, 115, 10665. (h) Le
Floch, P.; Kolb, A.; Mathey, F. J . Chem. Soc., Chem. Commun. 1994,
2065. (i) Trauner, H; Le Floch, P.; Lefour, J . M.; Ricard, L.; Mathey,
F. Synthesis 1995, 717.
(5) (a) Majid, T. N.; Knochel, P. Tetrahedron Lett. 1990, 31, 4413.
(b) Berk, S. C.; Yeh, M. C. P.; J eong, N.; Knochel, P. Organometallics
1990, 9, 3053. (c) Rozema, M. J .; Sidduri, A. R.; Knochel, P. J . Org.
Chem. 1992, 57, 1956. (d) Tucker, C. E.; Majid, T. N.; Knochel, P. J .
Am. Chem. Soc. 1992, 114, 3983.
(6) J iang, B.; Xu, Y. J . Org. Chem. 1991, 56, 7336.
(7) Seyferth, D.; Lambert, R. L. J . Organomet. Chem. 1973, 54, 123.
(4) (a) Teunissen, H. T.; Bickelhaupt, F. Tetrahedron Lett. 1992, 33,
3537. (b) Teunissen, H. T.; Bickelhaupt, F. Bull. Soc. Chim. Belg. 1992,
101, 609. (c) Bickelhaupt, F. Pure Appl. Chem. 1993, 65, 621. (d)
Teunissen, H. T.; Bickelhaupt, F. Phosphorus Sulfur 1993, 76, 75.
0276-7333/96/2315-0794$12.00/0 © 1996 American Chemical Society

2-Iodophosphinines
Organometallics, Vol. 15, No. 2, 1996 795
Sch em e 1
Sch em e 2
Sch em e 3
freshly distilled, frozen (-196 °C) phosphorus trichloride
(13 equiv) was attached up side down on top of the
frozen solution of 1. The Schlenk tube was allowed to
warm such that phosphorus trichloride was dropping
at its melting point (-112 °C) down on top of the frozen
solution of 1. After the phosphorus trichloride had been
added, the cooling bath was removed and the reaction
mixture warmed to -100 °C. At this temperature, the
mixture began to melt and the reaction could occur in
the presence of a large excess of phosphorus trichloride,
which was expected to suppress di- and trialkylation.
In spite of its successful synthesis from 1, 2 (δ(31P) 155.2
ppm) could not be purified by distillation or crystalliza-
tion. Therefore, the subsequent Diels-Alder reactions
with a 1,3-butadiene were carried out with freshly
prepared crude 2, which, according to 31P NMR spec-
troscopy, was approximately 70% pure.
close to the value of benzene8 (57.0 Hz) and confirms
the electronic delocalization within the aromatic ring.
Furthermore, the 1J (CC) values involving the methyl
groups (42.6-43.67 Hz) are very close to those in
o-xylene8 (44.2 Hz). The pentacarbonyltungsten com-
1
plexes 7a (δ(31P) 202 ppm, J (PW) ) 286 Hz) and 7b
1
(δ(31P) 185 ppm, J (PW) ) 280.4 Hz) were prepared in
moderate to high yield by reacting 5a ,b with (acetoni-
trile)pentacarbonyltungsten9 (6) in THF at room tem-
perature (7a ) or 45-50 °C (7b) (Scheme 1). In these
reactions, a small excess of 6 (about 10%) was necessary
to drive the complexation to completion.
The Diels-Alder reactions were carried out at rela-
tively low temperatures: -5 °C for 1,3-butadiene (a
series, 23 equiv) and 0 °C for 2,3-dimethylbutadiene (b
series, 20 equiv). A large excess of triethylamine (a ,
11 equiv; b, 17 equiv) was added to a solution of 2 in
the diene to generate the unstable phosphaalkene 3 and
to aromatize its primary Diels-Alder adducts 4; to
achieve this, the reaction mixture was allowed to warm
slowly to room temperature.
The aromatization of 4 was monitored by 31P NMR
spectroscopy. The aromatization of 4a required less
than 16 h. On the other hand, 55 h stirring at room
temperature was necessary to convert 4b (δ(31P) 94
ppm) to 5b. The 2-iodophosphinines were isolated by
distillation under high vacuum in a yield of 32% (5b,
yellow crystals (δ(31P) 216 ppm)) and 10% (5a , yellow
liquid (δ(31P) 233 ppm)) relative to iodoform, the precur-
sor of 1 (Scheme 1).7 Whereas 5b was isolated in pure
form, 5a was slightly contaminated with 1,1-diiodo-
isobutane (5-10%) which is formed as a byproduct,
presumably in the preparation of 1 from iodoform and
isopropylmagnesium chloride (Scheme 1). Distillative
separation of 1,1-diiodoisobutane was easy for 5b but
impossible in the case of 5a .
In the reactivity studies, the attention was focused
on the dimethyl derivatives 5b and 7b, as 5b could be
obtained in pure form and in higher yield. Furthermore,
its synthesis is less complicated than that of 5a because
of the easy handling of 2,3-dimethyl-1,3-butadiene
compared with 1,3-butadiene.
Attempts to prepare the η6 complex 9 by heating 5b
for several hours under reflux in di-n-butyl ether with
hexacarbonylchromium analogous to the procedures of
No¨th10 failed; besides decomposition products of 5b, only
the η1 complex 8 (δ(31P) 231 ppm) was formed (Scheme
2). Apart from decomposition, the lack of steric hin-
drance at positions 2 and 6 of the phosphinine ring
probably is an important factor for this failure.11
Compound 8 was isolated in low yield (12%) and was
fully characterized by NMR and MS spectroscopy.
Or ga n olith iu m Der iva tives. Toward 1.6 M n-
BuLi, there are some interesting differences in behavior
between uncoordinated 2-iodophosphinines 5 and their
pentacarbonyltungsten complexes 7. As outlined in
Scheme 3, the lithiation of uncoordinated 2-iodophos-
phinines did not occur, whereas the pentacarbonyltung-
sten complexes showed the expected iodine-lithium
exchange. Reaction of 1.6 M n-BuLi (1 equiv) with 5a /b
in THF was performed at -100 °C. After 0.5 h of
Phosphinines 5 were fully characterized by NMR, MS,
and elemental analysis. The NMR assignments were
supported by 2D NMR techniques. While HH COSY,
CH COSY, COLOC, and 1D NOE did not distinguish
between C4 and C5 in 5b, INADEQUATE solved this
(8) Wray, V. Prog. Nucl. Magn. Reson. Spectrosc. 1979, 13, 177.
(9) Marinetti, A.; Bauer, S.; Ricard, L.; Mathey, F. Organometallics
1990, 9, 793.
(10) Deberitz, J .; No¨th, H. Chem. Ber. 1970, 103, 2541.
(11) Nainan, K. C.; Sears, C. T. J . Organomet. Chem. 1978, 148,
C31.
1
problem conveniently. The J (CC) values of the phos-
phinine ring lie in the range 55.3-58.7 Hz, which is

796 Organometallics, Vol. 15, No. 2, 1996
Teunissen and Bickelhaupt
Sch em e 4
stirring of the black reaction mixtures at temperature
below -80 °C, a quench reaction with ClSnR′3 (R′ ) Ph
(5b), R′ ) CH3 (5a )) was carried out. After warming of
the samples to room temperature, 31P NMR spectro-
scopy indicated complete decomposition in the case of
5b and the formation of many non-phosphaaromatic
compounds with a poor signal to noise ratio in the case
of 5a . In the latter case, the experiment was not
conclusive with respect to the lithiation of 5a , because
of the presence of 1,1-diiodoisobutane.
The lithiation of the pentacarbonyltungsten com-
plexes was successful, and the organolithium phosphin-
ines 11a /b could be detected by low-temperature 31P
NMR spectroscopy. The thermal decomposition of 11a /b
was followed as a function of temperature; 11b (δ(31P)
163.4 ppm, 1J (PW) ) 239.8 Hz) turned out to decompose
at -70 °C. In the 31P NMR spectra, signals appeared
between 0 and -100 ppm and around 240 ppm. At room
temperature the most important signals were located
at 242 and 7 ppm with a rather unsatisfactory signal
to noise ratio. The signal at 242 ppm did not show
tungsten satellites so this compound might be the
Fischer carbene 12 (Scheme 3), which could be formed
by an intramolecular attack of the C-Li bond on CO.
Such intramolecular reaction would result in a strained
four-membered ring system, which opens by disruption
of the coordination between phosphorus and tungsten;
it is reasonable to assume that the resulting vacant
coordination site at tungsten is filled by a Lewis base
such as THF or CO to furnish an 18 electron species as
indicated. The spectroscopic detection of 11a was more
difficult as its formation was not selective and the
thermal stability rather low. The first recorded spec-
trum at -85 °C showed the presence of 11a (δ(31P) 176.9
ppm, 1J (PW) ) 235.2 Hz) and many signals in the region
of 8 to -52 ppm. The spectrum recorded at -80 °C
showed already substantial decomposition, thus indicat-
ing that methyl groups at the 4- and 5-positions lead to
increased stability of (organometallic) phosphinine de-
rivatives. Both organolithium derivatives were quenched
with triphenyltin chloride at -90 or -100 °C, and the
organotin derivatives 13a /b were isolated in pure form
and were fully characterized. The yield of 13b was
moderate (48%), but 13a was obtained in a rather
disappointing yield (4%). The steric shielding of the
2-position of the phosphinine by the W(CO)5 moiety
might be responsible for a rather slow reaction of
triphenyltin chloride. The competition between decom-
position of 11a /b on the one hand and nucleophilic
substitution at tin on the other is more detrimental for
11a than for 11b. Mathey et al. encountered similar
unexpected difficulties in quench reactions of a molyb-
denum-coordinated 2-lithiophosphinine.3d Apparently,
substituents can have a substantial influence on the
effectiveness with which an organolithiophosphinine is
derivatized. In addition, the purification of 13a turned
out to be difficult; many crystallizations were required
before it was isolated in pure form.
phinines3b toward lithiation at the 2-position;3c it was
suggested that this stabilization is less pronounced in
the pentacarbonyltungsten complex in which the aro-
maticity of the phosphinine ring is somewhat reduced.12
We propose that, in 2-iodophosphinines 5a /b, reaction
with the organolithium reagents results in a competition
between nucleophilic attack at phosphorus and halogen-
metal exchange. Due to the interaction between the
2-halogen substituent and the phosphinine ring, which
seems operational in 2-iodophosphinines, too, the reac-
tion is dominated by nucleophilic attack at phosphorus
to give 14 (Scheme 4).13 Possibly, decomposition pro-
ceeds via cleavage of the C-I bond, which leads to the
formation of 15, a phosphinin-2-ylidene derivative which
has been shown to be a local minimum by ab initio
calculations.14 Its polymerization may be the cause of
decomposition; Scheme 4 shows only this decomposition
pathway, but others are conceivable. Apparently, nu-
cleophilic attack at phosphorus is less competitive in 7,
probably for steric reasons.
In conclusion, the halogen-lithium exchange of nei-
ther 5a /b nor the 2-bromo- or 2-chlorophosphinines3b
could be achieved. In contrast, the pentacarbonyltung-
sten complexes 7a /b are easily converted to the corre-
sponding 2-lithiophosphinines 11a /b by n-BuLi. The
pentacarbonyltungsten complex of a 2-bromophosphin-
ine has been reported to undergo halogen-metal ex-
change in reaction with phenyllithium;3c so in this
respect our 2-iodophosphinines do not exhibit unique
behavior.
Or ga n om a gn esiu m Der iva tives. In contrast to the
iodine-lithium exchange, reaction of 5b with magne-
sium was slightly more successful in leading to the
formation of three products, along with substantial
decomposition (Scheme 5). The best results were ob-
tained in THF, using three times sublimed magnesium
rather than commercial magnesium turnings. The
magnesium was first activated with 1,2-dibromoethane;
after cooling of the reaction mixture to room tempera-
ture, 5b was added and the reaction was followed by
31P NMR spectroscopy. Two of the products were
known: 3,4-dimethylphosphinine (18, δ(31P) 191 ppm)15
and 4,4′,5,5′-tetramethyl-2,2′-biphosphinine (16, δ(31P)
181.3 ppm).16 This compound was unambiguously
identified by its proton-coupled 31P NMR spectrum
which showed an AA′BB′XX′ system. With the PH
The question why halogen-lithium exchange is not
successful in the case of 5a /b, whereas for the pentac-
arbonyltungsten complexes, notably 7b, it is achieved
rather easily, is difficult to answer. Mathey et al.
suggested that a strong stabilizing interaction between
the phosphaaromatic system and the halogen (Cl, Br)
could account for the inertness of free 2-halophos-
(12) Alcaraz, J . M.; Mathey, F. Tetrahedron Lett. 1984, 25, 207.
(13) Reference 2, p 239.
(14) Nyulaszi, L; Szieberth, D; Veszpremi, T. J . Org. Chem. 1995,
60, 1647.
(15) Alcaraz, J . M.; Mathey, F. Tetrahedron Lett. 1984, 25, 4659.
(16) Le Floch, P.; Carmichael, D.; Ricard, L.; Mathey, F. J . Am.
Chem. Soc. 1991, 113, 667.

2-Iodophosphinines
Organometallics, Vol. 15, No. 2, 1996 797
Sch em e 5
Sch em e 6
Ta ble 1. Rela tive In ten sities of 31P NMR Sign a ls
d u r in g th e Rea ction of 5b w ith Ma gn esiu m in THF
time (h)
5b
18
16
17
2.5
5.75
21.0
25.0
6.50
0.34
0
1
1
1
1
0
0
1.83
1.57
0.59
1.04a
0.16
0
0.20a
a
Due to the relatively large line width of 18, these figures are
not a good indication for relative amounts; actually, these amounts
are smaller.
Finally, the Grignard reagent 17 decomposed slowly at
room temperature.
coupling constants given by Mathey for 16,16 simulation
of the proton-coupled 31P NMR spectrum exactly repro-
duced the experimentally obtained pattern. The third
product was the desired phosphinine Grignard reagent
17 (δ(31P) 229.0 ppm). This compound was identified
by a reaction with triphenyltin chloride which gave the
organotin derivative 19 (δ(31P) 222.0 ppm), identical
with a product obtained via an independent route.4a
Several observations may be of interest. First, it is
remarkable that hardly any reaction occurred with
diethyl ether instead of THF as solvent. Also, the
degree of decomposition of 5b increased when activation
of magnesium with 1,2-dibromoethane was carried out
in the presence of 5b. Finally, when magnesium salts,
formed by activation of magnesium with 1,2-dibromo-
ethane, were removed by washing with THF, the
reaction on subsequent addition of 5b was very slow.
This observation may indicate an initiating17 or cata-
lytic18 role of magnesium bromide in the reaction of
magnesium with 5b. By calibration with triphenylphos-
phine as an internal standard, the absolute yields of 18,
16, and 17 were found to be 41.5, 1.3, and 19.2%,
respectively; more than one-third (37%) of 5b had
decomposed.
The reaction of 5b with magnesium in the presence
of triphenylphosphine turned out to be considerably
slower (see Experimental Section) than in the absence
of triphenylphosphine. A reaction mixture consisting
of magnesium (4.11 mmol) in THF (5 mL) was activated
with 1,2-dibromoethane (2.32 mmol). After addition of
5b (1.16 mmol), the reaction was followed by 31P NMR
spectroscopy at room temperature during 25 h. The
course of the reaction is presented in Table 1.
From Table 1 it follows that the conversion of 5b is
complete within 21 h. Furthermore, it is remarkable
that the formation of 16 does not occur in the initial
phase of the reaction but only after the amount of 5b
has diminished substantially and approaches zero.
The course of the reactions discussed above are
challenging from a mechanistic point of view. The
formation of 18 and 17 can be explained by the radical
mechanism of Grignard reagent formation.17-19 The
obvious possibility that 16 might be formed by a
coupling reaction between 5b and 17 is ruled out by the
observation that 16 is not formed in the initial phase
when 5b and 17 are abundant. The alternative forma-
tion of 16 by nucleophilic attack of 17 on 18 is unlikely
because nucleophilic attack on the phosphinine ring
occurs at the phosphorus center.13 More likely is the
assumption that 17 decomposes (possibly under the
influence of magnesium bromide and the excess of
magnesium) under the formation of the 2-phosphininyl
radical, which will yield 16 by radical coupling and 18
by hydrogen abstraction from the solvent.
Mathey et al. described that 2-chloro-4,5-dimeth-
ylphosphinine did not show any reaction with magne-
sium in refluxing THF under ultrasonic irradiation;3b
the 2-bromo derivative proved to be equally inert. A
reinvestigation showed that, in reaction of 2-bromo-4,5-
dimethylphosphinine with magnesium alone, the phos-
phinine Grignard reagent could not be generated
efficiently.3d,e On the other hand, trapping of the in situ
generated Grignard species with silicon electrophiles
under Barbier conditions lead to the formation of
functionalized phosphinines in good yields.3d,e There-
fore, the reaction of 5b with magnesium is the first
example of the direct reaction leading to an observable
phosphinine Grignard reagent (17); this is possibly a
consequence of the high reactivity of the carbon-iodine
bond. However, interesting as the formation of 17 and
that of 16 from 5b may be from a mechanistic point of
view, their yield is too low for preparative applications.
Or ga n ozin c Der iva tives. The course of the meta-
lation of 5b with zinc in THF/TMEDA or DMF is
depicted in Scheme 6. In THF, the selective formation
of 20 (δ(31P) 220.5 ppm) occurred at room temperature
by reaction of 5b with zinc dust (1.8 equiv) in the
(17) Kharasch, M. S.; Reinmuth, O. Grignard Reactions of Non
Metallic Substances; Prentice-Hall: New York, 1954; p 56.
(18) Garst, J . F.; Lawrence, K. E.; Batlow, R.; Boone, J . R. Inorg.
Chim. Acta 1994, 222, 365.
(19) (a) Walborsky, H. M. Acc. Chem. Res. 1990, 23, 286. (b)
Bickelhaupt, F. J . Organomet. Chem. 1994, 475, 1.

798 Organometallics, Vol. 15, No. 2, 1996
Teunissen and Bickelhaupt
Con clu sion s
presence of TMEDA (1 equiv). The reaction required
20 h, after which the conversion of 5b to 20 (and traces
of 18) was complete. The NMR spectroscopic charac-
terization of 20 was performed on crystals obtained after
cooling its THF solution for several days to -70 °C.
Without TMEDA, zinc insertion of 5b did not occur.
Even prolonged heating of 5b in THF at 60 °C with zinc
dust resulted only in slow reduction of 5b to 18.
In DMF, the conversion of 5b to 21 (δ(31P) 222.6 ppm)
and traces of 18 was achieved by reaction with zinc dust
(2.8 equiv) during 20 h at room temperature. The
organometallic phosphinine derivative turned out to be
very stable; a sealed tube containing 21 in DMF-d7
(prepared for NMR characterization) remained practi-
cally unchanged after several months at room temper-
ature.
The synthesis of 2-iodophosphinines and their pen-
tacarbonyltungsten complexes is an interesting expan-
sion of the chemistry of halophosphinines. The unique
properties of the 2-iodophosphinines were illustrated by
the synthesis of organozinc derivatives 20-22, which
cannot be obtained from the 2-bromo or 2-chloro ana-
logues.
Exp er im en ta l Section
Gen er a l P r oced u r es. All oxygen- and/or water-sensitive
reactions were carried out under dry nitrogen with oven-dried
glassware and oxygen-free, dry solvents. THF was distilled
first from NaH and finally from Na/benzophenone. Pentane
was distilled from LiAlH4, and CH2Cl2 was distilled from P2O5.
Triethylamine was distilled from CaH2, and PCl3 was distilled
before use. A solution of 1.6 M n-BuLi in hexane was
commercially available and used as received. Sublimed mag-
nesium was kindly provided by G. Schat. 2-Chloropropane and
2,3-dimethyl-1,3-butadiene were distilled before use. TMEDA
was distilled from Na. DMF was distilled and stored on 4 Å
molecular sieves. Zinc powder was activated with dilute HCl
and thoroughly washed with oxygen-free water, ethanol, THF,
and pentane.
NMR spectra were recorded at a Bruker AC 200 spectrom-
eter at 200 MHz (1H) or 50.32 MHz (13C). For 31P NMR
spectroscopy a Bruker WM 250 was used operating at 100.26
MHz. Incidentally, 1H, 13C, or 31P NMR experiments were
carried out with a Bruker MSL 400, operating at 400 MHz
(1H), 100.64 MHz (13C), or 161.9 MHz (31P). The coupling
constants (J ) are given in Hz.
The direct inlet mass spectra were measured with a Finni-
gan MAT 90 (Bremen FRG), source temperature 150 °C (70
eV IP). The GCMS spectra were measured with a Hewlett
Packard 5970 MSD equipped with a 5890 GC with 50 m CP
Sil 5CB column. In the mass spectra, the appropriate isotope
pattern was observed unless otherwise stated.
Elemental analysis were carried out by Micro Analytisches
Labor Pascher in Remagen, Germany. Melting points (uncor-
rected) were determined with melting point equipment of
Pleuger after Dr. Tottoli.
Dich lor o(d iiod om eth yl)p h osp h in e (2). A solution of
isopropylmagnesium chloride, prepared from Mg (twice sub-
limed, 5.37 g, 221 mmol), isopropyl chloride (35 mL, 274 mmol),
and THF (60 mL), was added dropwise with a syringe to a
solution of iodoform (80.46 g, 204 mmol) in THF (400 mL) at
-95 °C. The resulting dark red solution was frozen with liquid
nitrogen to -196 °C. Then a Schlenk tube containing freshly
distilled PCl3 (230 mL, 2.636 mol) was frozen with liquid
nitrogen, too, and attached upside down upon the solid reaction
mixture. By spontaneous warming, the PCl3 was allowed to
flow down slowly on top of the carbenoid mixture which was
kept at -196 °C. After complete addition, the reaction mixture
was allowed to warm to -100 °C and mechanical stirring was
commenced as soon as possible. The reaction mixture became
yellow and a large amount of colorless precipitate was formed
within 15 min. The reaction mixture was warmed to -40 °C
during 4 h and then quickly to room temperature, while the
color changed gradually from yellow to brown orange. The
volatile compounds were removed under reduced pressure, and
the residue was extracted three times with pentane (640 mL)
and filtered. After concentration of the pentane extracts to
300 mL, another filtration was carried out. Further removal
of pentane from the filtrate under vacuum furnished crude 2
as a red brown oil. Attempted purification via distillation or
crystallization did not improve the purity significantly. There-
fore, the subsequent Diels-Alder reactions with a 1,3-buta-
diene were carried out with freshly prepared crude 2, which,
on the basis of 31P NMR spectroscopy was approximately 70%
pure. The main impurity, δ(31P) 175 ppm, is presumably a
These results on zinc insertion reactions of 5b are
unique, as attempted insertion reactions with the
2-chloro and 2-bromo derivatives were unsuccessful.3b
Comparison of the zinc insertions into iodobenzene and
5b shows the latter to be more reactive; iodobenzene is
converted to phenylzinc iodide for only 80% during 22
h at 55 °C in DMF.5a As the zinc insertion in THF/
TMEDA has been described for an olefinic system only,6
a direct comparison is not possible. Therefore, we
carried out a zinc insertion with iodobenzene in THF/
TMEDA at room temperature and quenched the reac-
tion mixture with bromine; according to GCMS analysis,
zinc insertion had not occurred. A possible explanation
for these differences in reactivity between 5b and
iodobenzene might be the increased electron acceptor
properties of the phosphinine ring compared with those
of the benzene ring.20 As the rate-determining step in
the zinc insertion reaction is presumably a single
electron transfer from zinc to the arene ring,5a 5b would
be expected to react faster than iodobenzene.
Whereas the zinc insertion into 5b is successful in
DMF and THF/TMEDA, the corresponding tungsten
complex 7b showed a disappointing behavior under the
same reaction conditions. The desired zinc complexes
22 and 24 were not formed selectively; the 31P NMR
spectra showed many signals in the region 0-200 ppm.
A different approach for the preparation of 22 and 24
is the reaction of 20 or 21 with (acetonitrile)pentacar-
bonyltungsten 6 (Scheme 6). This strategy failed in
DMF; 24 was not obtained, but slow decomposition of
21 occurred. In THF/TMEDA, however, 22 (δ(31P) 174.5
1
ppm, J (PW) ) 249.7 Hz) was formed from 20 (contain-
ing a small amount of 18) in moderate yield. The
complexation procedure at room temperature required
20 to 30 h stirring when carried out with 1 equiv of 6
(yield 68-70%). With an excess (13%) of 6, the com-
plexation was complete within 15 h, and the yield was
slightly higher (78%). Other phosphinines present in
the final reaction mixture were 7b (5.6%), 18 (4.3%),
and 23 (3.5%). The formation of 22 was supported by
1H and 13C NMR spectra which were recorded in THF-
d8. Unfortunately, 22 decomposed slowly at room
temperature. Following this process by NMR showed
that, after 7 days, 22 was no longer present; 23 and two
unidentified products (δ(31P) 60.8 ppm, 1J (PW) ) 260.4
1
Hz; 61.5 ppm, J (PW) ) 259.5 Hz) were formed.
(20) Elschenbroich, C.; Nowotny, M.; Metz, B.; Massa, W.; Graulich,
J . Angew. Chem. 1991, 103, 601.

2-Iodophosphinines
Organometallics, Vol. 15, No. 2, 1996 799
compound R-PCl2, but it was not identified. Data for 2 are as
follows. NMR (C6D6): δ(1H) 4.34 (d, 2J (PH) ) 17.1); δ(13C-
{1H}) -19.1 (dd, 1J (PC) ) 84.9, {1J (CH) ) 167.5}); δ(31P{1H})
155.2. HRMS (m/ e): calcd for CH35Cl2I2P, 367.7280; found,
367.7256. MS (EI): m/ e 368 ([M]+, 54), 333 ([M - Cl]+, 15),
241 ([M - I]+, 98), 206 ([M - 2Cl - I]+, 15).
(η1-2-Iod op h osp h in in e)p en ta ca r bon yltu n gsten (7a ). A
solution of (acetonitrile)pentacarbonyltungsten (6) (7.2 g, 19.7
mmol) and 5a (4.02 g, 16.3 mmol) in THF (150 mL) was stirred
at room temperature for 49 h. After 31 h, 0.44 g of 6 (1.2
mmol) was added to drive the complexation of 5a toward
completion. Afterward, the dark green solution was evapo-
rated and the residue was extracted with pentane (600 mL).
Crystallization by cooling the extract to -70 °C furnished pure
7a as brown yellow crystals (dec 81 °C) in a yield of 48% (4.31
g, 7.9 mmol). Data for 7a are as follows. NMR (C6D6): δ(1H)
6.20 (tdd, 4J (PH) ) 8.0, 3J (HH5) ) 8.1, 3J (HH3) ) 8.8, 4J (HH6)
) 1.3, 1H, H4), 6.89 (dddd, 3J (PH) ) 22.7, 3J (HH6) ) 10.1,
3J (HH4) ) 8.1, 4J (HH3) ) 1.0, 1H, H5), 7.48 (ddd, 2J (PH) )
26.4, 3J (HH5) ) 10.1, 4J (HH4) ) 1.3, 1H, H6), 7.68 (ddd, 3J (PH)
) 16.3, 3J (HH4) ) 8.8, 4J (HH5) ) 1.0, 1H, H3); δ(13C{1H}) 120.8
(dddt, 1J (PC) ) 2.0, {3J (CH4) ) 10.5}, {3J (CH6) ) 13.4},
2-Iod op h osp h in in e (5a ). Compound 2 was prepared as
described above from iodoform (177.2 g, 450 mmol). In this
case, commercial isopropylmagnesium chloride was used.
Crude 2 was obtained in a yield of 63% (104 g, 0.28 mol). Then
1,3-butadiene (350 g, 6.5 mol) was condensed into the reaction
vessel. After dropwise addition of approximately 1 equiv of
NEt3 (39 mL, 0.28 mol) at -5 °C, a large amount of brown-
red precipitate was formed in the yellow solution. As this
made stirring difficult, THF (270 mL) was added. Then the
rest of the NEt3 (400 mL, 2.88 mol) was added dropwise within
3 h. Meanwhile, the temperature was allowed to rise to room
temperature. After 16 h, the heterogeneous yellow brown
mixture was evaporated and the residue extracted six times
with pentane (800 mL). The combined extracts were concen-
trated to 100 mL and filtered. Distillation, first under normal
pressure and finally under vacuum, furnished 5a (slightly
contaminated with 1,1-diiodoisobutane) as a yellow liquid (bp
45 °C/4 × 10-3 mbar) in a yield of 10% (10.8 g, 0.044 mol).
Data for 5a are as follows. NMR (C6D6): δ(1H) 6.61 (ddt,
4J (PH) ) 4.3, 4J (HH6) ) 1.0, 3J (HH5) ) 8.4, 3J (HH3) ) 8.6,
1H, H4), 7.27 (apparent q, 3J (PH) ) 8.6, 3J (HH4) ) 8.4, 3J (HH6)
) 10.1, 1H, H5), 7.94 (ddd, 2J (PH) ) 38.8, 3J (HH5) ) 10.1,
3
{2J (CH2) ) 2.9}, {4J (CH5) ) 2.9}, C2), 127.6 (dddd, J (PC) )
29.0, {1J (CH) ) 163.2}, {3J (CH6) ) 8.8}, {2J (CH3 or CH5) )
1.5}, C4), 135.7 (ddddd, 2J (PC) ) 16.5, {1J (CH) ) 161.1},
{3J (CH3) ) 8.2}, {2J (CH6 or CH4) ) 1.2}, {2J (CH4 or CH6) )
2.3}, C5), 146.2 (dddt, 2J (PC) ) 13.3, {1J (CH) ) 165.2},
{3J (CH5) ) 8.5}, {4J (CH6) ) 1.4}, {2J (CH4) ) 1.4}, C3), 153.0
(ddddd, 1J (PC) ) 12.4, {1J (CH) ) 162.5}, {3J (CH4) ) 9.1},
2
{2J (CH5) ) 2.1}, {4J (CH3) ) 1.5}, C6), 194.4 (d, J (PC) ) 9.3,
1J (WC) ) 125.0, CO [cis]), 198.5 (d, 2J (PC) ) 33.0, CO [trans]);
δ(31P{1H}) 201.5 (1J (PW) ) 285.6). HRMS calcd for C10H4O5-
IP182W, 543.8323; found, 543.832. MS (EI): m/ e 546 ([M]+,
55), 518 ([M - CO]+, 3), 490 ([M - 2CO]+, 42), 462 ([M -
3CO]+, 31), 434 ([M - 4CO]+, 34), 406 ([M - 5CO]+, 100). Anal.
Calcd for C10H4IO5PW: C, 22.0; H, 0.74; P, 5.67; I, 23.25; W,
33.68. Found: C, 21.85; H, 0.76; P, 5.46; I, 22.0; W, 33.8.
3
3
4J (HH4) ) 1.0, 1H, H6), 7.95 (dd, J (PH) ) 5.3, J (HH4) ) 8.6,
1H, H3); δ(13C{1H}) 124.9 (dt, 1J (PC) ) 77.5, {3J (CH6) ) 12.1},
{3J (CH4) ) 12.1}, C2), 130.7 (dddd, J (PC) ) 18.6, {1J (CH) )
3
159.6}, {3J (CH6) ) 8.8, 2J (CH3 or CH5) ) 2.0}, C4), 131.8 (ddd,
2J (PC) ) 13.3, {1J (CH) ) 158.3}, {3J (CH) ) 7.4}, C5), 143.4
(dddt, 2J (PC) ) 14.5, {1J (CH) ) 164.1}, {3J (CH5) ) 7.8},
{2J (CH4) ) 1.4}, {4J (CH6) ) 1.4}, C3), 159.4 (ddd, 1J (PC) )
60.5, {1J (CH) ) 165.6}, {3J (CH4) ) 9.0}, C6); δ(31P{1H}) 233.1.
MS (EI): m/ e 222 ([M]+, 20), 95 ([M - I]+, 18). HRMS (m/ e):
calcd for C5H4IP, 221.9094; found, 221.907. Anal. Calcd for
C5H4IP: C, 27.06; H, 1.82. Found: C, 26.94; H, 2.14.
(η1-2-Iod o-4,5-d im e t h ylp h osp h in in e )p e n t a ca r b on -
yltu n gsten (7b). During 18 h, a THF solution (200 mL) of
7b (3.7 g, 14.8 mmol) and 6 (6.4 g, 17.5 mmol) was heated to
45-50 °C. After removal of THF under reduced pressure, the
residue was extracted with pentane (200 mL) and crystallized
by cooling the extract to -70 °C. Pure 7b was obtained as
brown yellow crystals (dec 126-7 °C) in a yield of 86% (7.36
g, 12.8 mmol). Data for 7b are as follows. NMR (C6D6): δ(1H)
1.50 (s, 3H, 5-CH3), 1.54 (d, 5J (PH) ) 6.4, 3H, 4-CH3), 7.54 (d,
2J (PH) ) 25.6, 1H, H6), 7.73 (d, 3J (PH) ) 17.4, 1H, H3); δ(13C-
{1H}) 21.1 (ddq, 4J (PC) ) 4.0, {3J (CH) ) 4.0}, {1J (CH) )
127.5}, 4-CH3), 22.4 (ddq, 3J (PC) ) 9.5, {3J (CH) ) 6.4},
{1J (CH) ) 128.0}, 5-CH3), 117.0 (t, 1J (PC) ) 6.6, {3J (CH) )
2-Iod o-4,5-d im et h ylp h osp h in in e (5b ). To the crude
mixture of 2, freshly distilled 2,3-dimethyl-1,3-butadiene (300
mL, 2.65 mol) was added. After cooling of the mixture to 0
°C, NEt3 (300 mL, 2.16 mol) was added dropwise during 5 h.
A brown precipitate was formed, and the reaction mixture
became red. The temperature was then raised gradually to
room temperature. During 55 h the reaction was followed by
31P NMR spectroscopy, which indicated the conversion of 4b
(δ(31P) 94 ppm) to 5b (impurity at (δ(31P) 95 ppm, 7%). After
the mixture was stirred, the volatile fraction was removed
under vacuum. The residue was extracted four times with
pentane (600 mL) and filtered. After concentration of the
combined pentane fractions to 150 mL and filtration, the
filtrate was subjected to distillation, first at atmospheric
pressure to remove pentane and then under vacuum to obtain
5b. A second distillation furnished pure 5b as yellow crystals
(mp 30 °C; bp 76 °C/10-3 mbar) in a yield of 32% (16.4 g, 65.7
mmol) relative to iodoform. Data for 5b are as follows. NMR
(C6D6): δ(1H) 1.69 (d, 5J (PH) ) 3.7, 3H, 4-CH3), 1.74 (s, 3H,
5-CH3), 7.69 (d, 2J (PH) ) 38.6, 1H, H6), 7.96 (d, 3J (PH) ) 5.6,
3
2
6.6}, C2), 138.7 (d, J (PC) ) 26.2, C4), 146.7 (d, J (PC) ) 16.7,
2
C5), 148.1 (ddq, J (PC) ) 13.3, {1J (CH) ) 161.9}, {3J (CH) )
5.5}, C3), 152.5 (ddq, 1J (PC) ) 14.7, {1J (CH) ) 158.4}, {3J (CH)
2
1
) 5.2}, C6), 194.7 (d, J (PC) ) 9.3, J (WC) ) 125.1, CO [cis]),
198.7 (d, 2J (PC) ) 32.3, 1J (WC) ) 148.2, CO [trans]); δ(31P-
{1H}) 184.6 (1J (PW) ) 280.4). HRMS (m/ e): calcd for C12H8-
IO5PW, 571.8636; found, 571.861. MS (EI): m/ e 574 ([M]+,
32), 518 ([M - 2CO]+, 18), 490 ([M - 3CO]+, 62), 462 ([M -
4CO]+, 20), 434 ([M - 5CO]+, 62). Anal. Calcd for C12H8IO5-
PW: C, 25.11; H, 1.41; I, 22.11; P, 5.40; W, 32.03. Found: C,
25.36; H, 1.47; I, 21.8; P, 5.46; W, 31.5.
(η1-2-Iod o-4,5-d im e t h ylp h osp h in in e )p e n t a ca r b on -
ylch r om iu m (8). A mixture of di-n-butyl ether (50 mL), 5b
(0.38 g, 1.5 mmol), and Cr(CO)6 (0.49 g, 2.2 mol) was heated
at 140 °C for 5.5 h. A black precipitate was formed in the
dark green solution. Removal of solvent under reduced
pressure was followed by extraction of the residue with
pentane (100 mL). Crystallization by cooling the extract to
-70 °C furnished pure 8 as yellow crystals (dec 101 °C) in a
yield of 12% (0.08 g, 0.18 mmol). Data for 8 are as follows.
4
1H, H3); δ(13C{1H}) 21.5 (dq, J (PC) ) 1.9, {1J (CH) ) 127.2},
1J (CC4) ) 43.7, 4-CH3), 22.7 (ddq, 3J (PC) ) 3.4, {3J (CH) ) 6.3},
{1J (CH) ) 127.0}, 1J (CC5) ) 42.6, 5-CH3), 121.0 (dd, 1J (PC) )
1
3
71.4, {3J (CH) ) 12.7}, J (CC3) ) 55.6, C2), 141.4 (d, J (PC) )
1
1
2
17.5, J (CC3) ) 58.7, J (C4-CH3) ) 43.7, C4), 141.9 (d, J (PC)
) 14.8, 1J (C5-CH3) ) 42.6, 1J (CC6) ) 55.3, C5), 145.7 (ddq,
NMR (C6D6): δ(1H) 1.50 (s, 3H, 5-CH3), 1.55 (d, J (PH) ) 6.2,
5
2J (PC) ) 15.2, {1J (CH) ) 165.8}, {3J (CH) ) 5.4}, J (CC4) )
3H, 4-CH3), 7.58 (d, J (PH) ) 26.2, 1H, H6), 7.70 (d, J (PH) )
16.7, 1H, H3); δ(13C{1H}) 21.0 (ddq, 4J (PC) ) 3.9, {3J (CH) )
4.5}, {1J (CH) ) 127.4}, 4-CH3), 22.5 (ddq, 3J (PC) ) 9.1,
1
2
3
58.7, J (CC2) ) 55.6, C3), 159.7 (ddq, J (PC) ) 56.9, {1J (CH)
) 152.8}, {3J (CH) ) 5.0},1J (CC5) ) 55.3, C6); δ(31P{1H}) 216.2.
HRMS (m/ e): calcd for C7H8IP, 249.9407; found, 249.9446.
MS (EI): m/ e 250 ([M]+, 62), 123 ([M - I]+, 11). Anal. Calcd
for C7H8IP: C, 33.63; H, 3.23; I, 50.76; P, 12.39. Found: C,
33.58; H, 3.20; I, 50.4; P, 12.6.
1
1
{3J (CH) ) 6.3}, {1J (CH) ) 127.8}, 5-CH3), 118.9 (d, J (PC) )
1
3
2
2.5, C2), 138.6 (d, J (PC) ) 25.5, C4), 146.4 (d, J (PC) ) 17.0,
C5), 148.8 (ddq, J (PC) ) 14.1, {1J (CH) ) 161.8}, {3J (CH) )
2
5.4}, C3), 153.0 (ddq, J (PC) ) 8.8, {1J (CH) ) 157.8}, {3J (CH)
1

800 Organometallics, Vol. 15, No. 2, 1996
Teunissen and Bickelhaupt
4
) 5.1}, C6), 214.9 (d, 2J (PC) ) 17.2, CO [cis]), 220.9 (d, 2J (PC)
) 3.8, CO [trans]); δ(31P{1H}) 230.9. MS (EI): m/ e 442 ([M]+,
22), 414 ([M - CO]+, 3), 386 ([M - 2CO]+, 13), 358 ([M -
3CO]+, 15), 330 ([M - 4CO]+, 31), 302 ([M - 5CO]+, 100), 250
([M - Cr(CO)5]+, 11). Anal. Calcd for C12H8CrIO5P: C, 32.60;
H, 1.82; I, 28.71; P, 7.01. Found: C, 32.36; H, 1.84; I, 27.10;
P, 7.43.
(η1-2-Lith iop h osp h in in e)p en ta ca r bon yltu n gsten (11a ).
A solution of 7a (0.15 g, 0.27 mmol) in THF (3.0 mL) was cooled
to -100 °C. After addition of 1.6 M n-BuLi (0.25 mL, 0.40
mmol), the mixture was vigorously stirred while the temper-
ature was maintained between -90 and -100 °C. The
resulting black solution was subjected to low temperature 31P
NMR measurements. NMR (THF) for 11: δ(31P{1H}) 176.9
(1J (PW) ) 235.2).
129.8 (dt, J (SnC) ) 11.7, {1J (CH) ) 159.6}, {3J (CH) ) 7.0},
SnPh3 para-C), 137.5 (d, 2J (SnC) ) 38.4, {1J (CH) ) 157.0},
3
3
SnPh3 ortho-C), 136.9 (d, J (PC) ) 35.4, C4), 137.9 (d, J (PC)
) 2.7, J (119SnC) ) 551.0, J (117SnC) ) 526.5, SnPh3 ipso-C),
148.5 (d, 2J (PC) ) 15.5, C5) 149.2 (ddq, 2J (PC) ) 20.8, {1J (CH)
) 157.1}, {3J (CH) ) 5.4}, C3), 154.1 (ddq, 1J (PC) ) 10.4,
3J (SnC) ) 37.6, {1J (CH) ) 158.4}, {3J (CH) ) 5.4}, C6), 159.0
1
1
(d, J (PC) ) 25.5, J (119SnC) ) 404.6, J (117SnC) ) 385.5, C2),
1
1
1
195.7 (d, 2J (PC) ) 9.2, 1J (WC) ) 124.5, CO [cis]), 198.0 (d,
2J (PC) ) 28.7, J (WC) ) 145.9, CO [trans]); δ(31P{1H}) 180.5
1
(2J (P117Sn) ) 186.9, 2J (P119Sn) ) 195.8, 1J (PW) ) 266.2);
δ(119Sn) -107.6. HRMS (m/ e): calcd for C30H23O5P120Sn182W,
795.9814; found, 795.984. MS (EI): m/ e 798 ([M]+, 28), 770
([M - CO]+, 6), 712 ([M - 3CO]+, 42), 656 ([M - 5CO]+, 64),
579 ([M - 5CO - Ph]+, 5). Anal. Calcd for C30H23O5PSnW:
C, 45.22; H, 2.89. Found: C, 45.28; H, 3.29.
(η1 -2-(T r i p h e n y ls t a n n y l)p h o s p h i n i n e )p e n t a c a r -
bon yltu n gsten (13a ). A solution of 7a (1.12 g, 2.05 mmol)
in THF (10 mL) was cooled to -100 °C. Then 1.6 M n-BuLi
(1.3 mL, 2.08 mmol) was added during 30 s while the
temperature was maintained at -100 °C. After 2 min, a
solution of ClSnPh3 (0.90 g, 2.34 mmol) in THF (2 mL) was
added during 10 s. Then the dark red reaction mixture was
allowed to warm to room temperature. Evaporation of the
reaction mixture under reduced pressure was followed by
extraction of the residue with pentane (50 mL). Crystallization
by cooling the extract to -70 °C furnished pure 13a as light
brown crystals (dec 67 °C) in a yield of 4% (0.07 g, 0.09 mmol)
relative to 7a . Data for 13a are as follows. NMR (C6D6): δ(1H)
2-(Iod om a gn esio)-4,5-d im eth ylp h osp h in in e (17) a n d
4,4′,5,5′-Tetr a m eth yl-2,2′-bip h osp h in in e (16). (a ) In th e
Absen ce of Tr ip h en ylp h osp h in e. To a mixture consisting
of Mg (three times sublimed, 0.10 g, 4.11 mmol) and THF (5
mL) was added 1,2-dibromoethane (0.2 mL, 2.32 mmol). After
the exothermal activation of Mg, the mixture was cooled to
room temperature and 5b (0.29 g, 1.16 mmol) was added
during stirring. The reaction mixture became black, and a
dark brown precipitate was formed. After 25 h of stirring at
room temperature, 31P NMR spectroscopy indicated the pres-
ence of 17, 16, and 18 in a ratio of 19.2:3.6:18.4.
(b) In th e P r esen ce of Tr ip h en ylp h osp h in e. Reliable
indications concerning the yield of the products and the degree
of decomposition of 5b were obtained by carrying out a reaction
with triphenylphosphine as internal standard, assuming that
triphenylphosphine is inert under the reaction conditions.
Therefore, the relative molar ratio of 5b and triphenylphos-
phine was related to their relative intensity in a 31P NMR
spectrum, recorded before the reaction of 5b with magnesium.
An intensity ratio of 3.22:1 (5b:triphenylphosphine) cor-
responded to a molar ratio of 1:1. This ratio, deduced from
5b, was applied to all phosphinine derivatives formed later.
In this experiment, magnesium (6.17 mmol) was activated with
1,2-dibromoethane (4.48 mmol) in THF (10 mL) in the presence
of triphenylphosphine (0.95 mmol). After cooling of the
mixture to room temperature, 5b (1.12 mmol) was added after
which the reaction was followed by 31P NMR spectroscopy.
After 6 days of stirring at room temperature, the black reaction
mixture, in which a dark brown precipitate was present,
contained 18, 16, and 17 in an absolute yield of 41.5, 1.3, and
19.2%. More than one-third (37%) of 5b had decomposed.
Another 6 days later, only 0.11 mmol (10%) of phosphinines
was left: predominantly 18 and hardly any 16 and 17. Data
for 17 are as follows. NMR (THF): δ(31P{1H}) 229.0 ({2J (PH)
4
3
3
6.70 (q, J (PH) ) 7.8, J (HH5) ) 7.8, J (HH3) ) 7.8, 1H, H4),
7.00-7.30 (m, 9H, meta,para-SnPh3), 7.40-7.60 (m, 7H, ortho-
3
3
SnPh3 + H5), 7.95 (dd, J (PH) ) 27.3, J (HH) ) 7.8, 1H, H3),
8.40 (dd, J (PH) ) 24.1, J (HH5) ) 10.2, 1H, H6); δ(13C) 126.5
2
3
(d, J (PC) ) 39.4, C4), 129.2 (s, J (119SnC) ) 54.6, J (117SnC)
3
3
3
4
) 52.5, SnPh3 meta-C), 129.9 (s, J (SnC) ) 11.9, SnPh3 para-
C), 135.2 (d, 2J (PC) ) 31.8, C5), 137.5 (s, 2J (SnC) ) 39.8, SnPh3
ortho-C), 137.7 (d, 3J (PC) ) 2.7, 1J (119SnC) ) 553.1, 1J (117SnC)
) 528.7, SnPh3 ipso-C), 147.1 (d, 2J (PC) ) 20.7, 2J (SnC) ) 11.8,
C3), 154.5 (d, 1J (PC) ) 7.9, 3J (SnC) ) 34.0, C6), 162.7 (d, 1J (PC)
2
1
) 30.2, C2), 195.4 (d, J (PC) ) 9.1, J (WC) ) 124.9, CO [cis]),
197.8 (d, 2J (PC) ) 29.2, CO [trans]); δ(31P{1H}) 195.4 (2J (P119Sn)
) 193.7, J (P117Sn) ) 185.5, J (PW) ) 269.7). HRMS (m/ e):
calcd for C28H19O5P116Sn184W, 765.9501; found, 765.949. MS
(EI): m/ e 768 ([M]+, 14), 684 ([M - 3CO]+, 32), 628 ([M -
5CO]+, 42). Anal. Calcd for C28H19O5PSnW: C, 43.73; H, 2.49.
Found: C, 43.54; H, 2.61.
2
1
(η1-2-Lit h io-4,5-d im et h ylp h osp h in in e)p en t a ca r b on -
yltu n gsten (11b). A solution of 7b (0.10 g, 0.17 mmol) in
THF (2.5 mL) was cooled to -100 °C. After addition of 1.6 M
n-BuLi (0.11 mL, 0.18 mmol), the mixture was vigorously
stirred while the temperature was maintained between -90
and -100 °C. The resulting dark red solution was subjected
to low-temperature 31P NMR measurements. NMR (THF) for
11b: δ(31P{1H}) 163.4 (1J (PW) ) 239.8).
3
) J (PH) ) 26.7}). Data for 16 are as follows. NMR (C6D6):
δ(31P{1H}) 181.3. HRMS (m/ e): calcd for C14H16P2, 246.0727;
found, 246.0752. MS (EI): m/ e 246 ([M]+, 100), 231 ([M -
CH3]+, 33).
(η1-2-(Tr ip h en ylst a n n yl)-4,5-d im et h ylp h osp h in in e)-
p en ta ca r bon yltu n gsten (13b). To a cooled solution (-95
°C) of 7b (0.88 g, 1.53 mmol) in THF (10 mL) was added 1.6
M n-BuLi (0.95 mL, 1.52 mmol) during 10 min. After 20 min
of stirring, ClSnPh3 (0.62 g, 1.61 mmol) was added to the dark
red solution. After being stirred for 10 min at -90 °C, the
reaction mixture was allowed to warm to room temperature.
The solvents were removed from the resulting dark red
solution, and the residue was extracted with pentane (50 mL).
Crystallization by cooling the extract to -70 °C furnished pure
13b as yellow crystals (mp 144-5 °C) in a yield of 49% (0.60
g, 0.75 mmol) relative to 7b. Data for 13b are as follows. NMR
(C6D6): δ(1H) 1.67 (d, 5J (PH) ) 6.2, 3H, 4-CH3), 1.77 (s, 3H,
5-CH3), 7.20-7.35 (m, 9H, meta,para-SnPh3), 7.60-7.75 (m,
6H, ortho-SnPh3), 7.86 (d, 3J (PH) ) 29.5, 3J (SnH) ) 66.6, 1H,
H3), 8.36 (d, 2J (PH) ) 23.7, 4J (SnH) ) 23.8, 1H, H6); δ(13C-
(4,5-Dim eth ylph osph in in yl-κC2)(iodo)(TMEDA)zin c (20).
A reaction mixture consisting of 5b (1.88 g, 7.52 mmol),
TMEDA (2.29 g, 19.7 mmol), and zinc powder (2.86 g, 43.7
mmol) in THF (12 mL) was stirred for 19 h at room temper-
ature. Approximately 8 mL of this solution was cooled to -70
°C. After several days, a precipitate was formed consisting of
dark gray crystals, contaminated with some light brown
powder and a small amount of zinc dust. After removal of
supernatant, the precipitate was dried and subjected to NMR
analysis. Data for 20 are as follows. NMR (C6D6): δ(1H) 1.88
(s, 4H, NCH2), 2.15 (s, 12H, NCH3), 2.20 (s, 3H, 5-CH3), 2.24
5
2
(d, J (PH) ) 3.4, 3H, 4-CH3), 8.67 (d, J (PH) ) 31.9, 1H, H6),
8.81 (d, 3J (PH) ) 18.7, 1H, H3), ratio TMEDA/20 1:1; δ(13C)
22.4 (d, 3J (PC) ) 1.8, 5-CH3), 23.6 (d, 4J (PC) ) 1.8, 4-CH3),
49.0 (s, NCH3), 56.8 (s, NCH2), 136.3 (d, 3J (PC) ) 29.8, C4),
141.5 (d, 2J (PC) ) 15.1, C3), 147.9 (d, 2J (PC) ) 16.3, C5), 155.0
4
{1H}) 21.6 (dq, J (PC) ) 4.0, {1J (CH) ) 127.5}, 4-CH3), 23.0
(dq, 3J (PC) ) 8.2, {1J (CH) ) 127.5}, 5-CH3), 129.2 (d, 3J (119SnC)
(d, J (PC) ) 63.2, C6), 183.4 (d, J (PC) ) 86.6, C2); δ(31P{1H})
1
1
3
) 54.4, J (117SnC) ) 52.4, {1J (CH) ) 157.3}, SnPh3 meta-C),
220.5.

2-Iodophosphinines
Organometallics, Vol. 15, No. 2, 1996 801
2-(Iod ozin cio)-4,5-d im eth ylp h osp h in in e (21). A mix-
ture containing 5b (0.18 g, 0.7 mmol), zinc powder (0.19 g, 2.8
mmol), and DMF-d7 (1 mL) was stirred at room temperature
for 15 h. Then the dark red solution was separated from the
excess of zinc powder and placed in an NMR tube which was
subsequently sealed. Data for 21 are as follows. NMR (DMF-
d7): δ(1H) 2.32 (d, 5J (PH) ) 3.3, 3H, 4-CH3), 2.35 (s, 3H,
5-CH3), 8.14 (d, 3J (PH) ) 18.8, 1H, H3), 8.42 (d, 2J (PH) ) 31.6,
in the dark red solution. Of this solution a small amount (2
mL) was evaporated under reduced pressure. Subsequent
NMR measurements indicated complete decomposition after
7 days at room temperature. Data for 22 are as follows. NMR
(THF-d8): δ(1H) 2.22 (s, 3H, 5-CH3), 2.52 (d, 5J (PH) ) 9.9, 3H,
4-CH3), 2.49 (s, 12H, NCH3), 2.68 (s, 4H, NCH2), 8.16 (d, 3J (PH)
) 40.4, 1H, H3), 8.26 (d, 2J (PH) ) 21.2, 1H, H6); δ(13C) 21.9
(d, 4J (PC) ) 4.2, 4-CH3), 22.8 (d, 3J (PC) ) 6.9, 5-CH3), 49.2 (s,
4
3
1H, H6); δ(13C{1H}) 20.7 (dddq, J (PC) ) 1.7,{3J (CH) ) 6.0},
NCH3), 57.3 (s, NCH2), 134.5 (d, J (PC) ) 42.1, C4), 145,4 (d,
3
2
{4J (CH) ) 0.9}, {1J (CH) ) 125.6}, 4-CH3), 20.9 (dddq, J (PC)
2J (PC) ) 16.5, C5), 149.0 (d, J (PC) ) 24.1, C3), 154.3 (s, C6),
) 1.4, {3J (CH) ) 6.8}, {4J (CH) ) 1.4}, {1J (CH) ) 126.0},
180.2 (d, J (PC) ) 45.3, C2), 197.6 (d, J (PC) ) 9.5, CO [cis]),
200.8 (d, 2J (PC) ) 24.1, CO [trans]); δ(31P{1H}) 174.6 (1J (PW)
) 249.7).
1
2
3
2
5-CH3), 133.8 (d, J (PC) ) 29.7, C4), 139.6 (d, J (PC) ) 14.7,
C5), 143.8 (ddq, J (PC) ) 16.5), {1J (CH) ) 152.9}, {3J (CH) )
2
5.1}, C3), 154.2 (ddq, 1J (PC) ) 64.0, {1J (CH) ) 149.0}, {3J (CH)
) 5.1}, C6), 184.4 (d, J (PC) ) 86.6, C2); δ(31P{1H}) 222.6.
1
Ack n ow led gm en t. We are grateful to Dr. B. L. M.
van Baar for measuring the HRMS spectra and to Dr.
F. J . J . de Kanter for the NOE and INADEQUATE
experiments.
[(4,5-D i m e t h y lp h o s p h i n i n y l-1KP ,2KC 2 )p e n t a c a r -
bon yltu n gsten ](iod o)(TMEDA)zin c (22). A solution of 20
(3.16 mmol) in THF (6.2 mL) was added to a solution of 6 (1.17
g, 3.21 mmol) in THF (2 mL). After 23 h of stirring at room
temperature, a small amount of yellow precipitate was formed
OM9505322