Novel dirhodium complexes derived from phosphaalkynes

Article abstract of DOI:10.1021/om990516v

Phosphaalkynes, P≡CR (R = Bu^t, 1-adamantyl), react rapidly with the dirhodium compound [Rh₂(η⁵-C₅H₅) ₂(μ-CO)(μ-η²-CF₃C≡CCF ₃)], affording the η⁴:

Full text of DOI:10.1021/om990516v

4838
Organometallics 1999, 18, 4838-4844
Novel Dir h od iu m Com p lexes Der ived fr om
P h osp h a a lk yn es
David E. Hibbs, Michael B. Hursthouse, Cameron J ones,* and Anne F. Richards
Department of Chemistry, University of Wales, Cardiff, P.O. Box 912, Park Place,
Cardiff CF1 3TB, United Kingdom
Matthew D. Francis†
Department of Chemistry, University of Wales, Swansea, Singleton Park,
Swansea SA2 8PP, United Kingdom
Ronald S. Dickson*
Department of Chemistry, Monash University, Clayton, Melbourne, Victoria 3168, Australia
Peter C. J unk
Department of Chemistry and Chemical Engineering, J ames Cook University, Townsville,
Queensland 4811, Australia
Received J uly 6, 1999
Phosphaalkynes, PtCR (R ) But, 1-adamantyl), react rapidly with the dirhodium
compound [Rh2(η5-C5H5)2(µ-CO)(µ-η2-CF3CtCCF3)], affording the η4: η1 mono(phosphacy-
clobutadienyl) complexes [Rh(η5-C5H5){µ-η4:η1-PC3R(CF3)2}{Rh(CO)(η5-C5H5)}] (R ) But, Ad).
Reaction of one of these complexes (R ) But) with [W(CO)5(THF)] leads to the novel,
crystallographically characterized “flyover” compound [Rh2(η5-C5H5)2{µ-(1,2,4-η): (1,3,4-η)-
PC3But(CF3)2}{W(CO)5}]. Both react with [Fe2(CO)9], affording the dirhodium phosphacy-
clobutenyl complexes [Rh2(η5-C5H5)2(CO){µ-η1:η3-PC3R(CF3)2}{Fe(CO)4}] (R ) But, Ad).
Spectroscopic analysis suggests the last two complexes exist in two isomeric forms in solution.
One complex (R ) Ad) has been characterized by an X-ray diffraction study.
In tr od u ction
phaalkynes and other unsaturated systems (alkynes for
example) are comparatively rare. Indeed, there are only
a limited number of mono(phosphacyclobutadiene) com-
plexes known, e.g. [Co(η5-C5H5){η4-PC(But)C2(SiMe3)2}]7
and [Rh(η5-C5H5){η4-PC(R)C2Ph2}] (R ) But, NPri-
SiMe3).8 More recently, J ohnson, Nixon, and co-workers
have reported the coupling between phosphaalkynes
and acetylenes in the coordination sphere of transition-
metal carbonyl clusters.9,10 To expand on this area, we
have studied the reactivity of phosphaalkynes with the
dimeric rhodium complex [Rh2(η5-C5H5)2(µ-CO)(µ-η2-
CF3CtCCF3)] (1). This system was chosen because of
its well-documented reactivity toward alkynes in which
the products critically depend on the nature of the
alkyne (Scheme 1).11 Pentanedione complexes are fa-
vored with alkyl-substituted alkynes, whereas metal-
lacyclopentadiene complexes are preferred for more
polar alkynes. In this paper we report on the reactivity
of phosphaalkynes with 1 and discuss the unusual
reactivity of the products with some metal carbonyls.
The coordination chemistry of phosphaalkynes (Pt
CR) is of considerable interest and has been reviewed
extensively.1 A particular feature of these compounds
is their ability to undergo facile cyclization reactions
within the coordination sphere of transition metals, and
in this respect their behavior is similar to that of
alkynes.2 Via this route, many metal-coordinated phos-
phorus-containing heterocycles have been prepared, e.g.
1,2- and 1,3-diphosphacyclobutadienes3,4 and 1,3,5-
triphospha-2,4,6-tri-tert-butylbenzene.5,6 In contrast,
however, cyclooligomerization reactions between phos-
(1) (a) Nixon, J . F. Chem. Rev. 1988, 88, 1327. (b) Nixon, J . F. Chem.
Soc. Rev. 1995, 24, 319. (c) Nixon, J . F. Coord. Chem. Rev. 1995, 145,
201. (d) Dillon, K. B., Mathey, F., Nixon, J . F. Phosphorus: The Carbon
Copy; Wiley: New York, 1998; Chapter 4. (e) Regitz, M.; Binger, P.
Angew. Chem., Int. Ed. Engl. 1988, 27, 1484. (f) Regitz, M. Chem. Rev.
1990, 90, 191. (g) Gaumont, A. C.; Denis, J . M. Chem. Rev. 1994, 94,
1413. (h) Multiple Bonds and Low Coordination in Phosphorus
Chemistry; Regitz, M., Scherer, O. J ., Eds.; Thieme: Stuttgart,
Germany, 1990; p 58ff.
(2) Schore, N. E. Chem. Rev. 1988, 88, 1081.
(3) Binger, P.; Glaser, G.; Albus, S.; Kru¨ger, C. Chem. Ber. 1995,
128, 1261.
(4) Hitchcock, P. B.; Maah, M. J .; Nixon, J . F. J . Chem. Soc., Chem.
Commun. 1986, 737.
(5) Binger, P.; Leininger, S.; Stannek, J .; Gabor, B.; Mynott, R.;
Bruckmann, J .; Kru¨ger, C. Angew. Chem., Int. Ed. Engl. 1995, 34,
2227.
(7) Regitz, M.; Binger, P.; Milczarek, R.; Mynott, R. J . Organomet.
Chem. 1987, 323, C35.
(8) Binger, P.; Haas, J .; Herrmann, A. T.; Langhauser, F.; Kru¨ger,
C. Angew. Chem., Int. Ed. Engl. 1991, 30, 310.
(9) Benvenutti, M. H. A.; Hitchcock, P. B.; Nixon, J . F.; Vargass,
M. D. J . Chem. Soc., Chem. Commun. 1994, 1869.
(10) Nowotny, M.; J ohnson, B. F. G.; Nixon, J . F.; Parsons, S. Chem.
Commun. 1998, 2223.
(6) Tabellion, F.; Nachbauer, A.; Leininger, S.; Peters, C.; Preuss,
F.; Regitz, M. Angew. Chem., Int. Ed. Engl. 1998, 37, 1233.
(11) Dickson, R. S. Polyhedron 1991, 10, 1995 and references
therein.
10.1021/om990516v CCC: $18.00 © 1999 American Chemical Society
Publication on Web 10/21/1999

Dirhodium Complexes Derived from Phosphaalkynes
Organometallics, Vol. 18, No. 23, 1999 4839
Sch em e 1
Sch em e 2
in the same range as those seen for other one-bond
interactions between an sp2-hybridized phosphorus and
a rhodium center, e.g. 218.5 Hz in the phosphaalkene
complex [Rh(η1-MesPdCPh2)Cl(PPh3)2].12 Similarly, the
1
latter coupling is comparable with the J P-Rh couplings
seen in other systems containing a phosphacyclobuta-
diene unit η4 bound to a Rh(η5-C5H5) moiety, e.g. 37.3
Hz in [Rh(η5-C5H5){η4-PC(But)C2Ph2}].8 The resolution
of the doublet of doublets into individual quartets is due
to the coupling between the phosphorus and the proxi-
mate CF3 group (3J PF ) 7.6 Hz). There is also evidence
for a further coupling, but this is not clearly resolved,
4
and it presumably arises from the J PF interaction of
the phosphorus center with the more distant of the two
CF3 groups. These observations are reflected in the 19F
NMR spectrum, which shows two poorly resolved mul-
tiplets, namely a quartet at -52.6 ppm (5J FF ) 5.6 Hz)
and a pseudo quintet at -54.0 ppm (J ≈ 6 Hz). A further
spectroscopic feature of interest is the resonance for the
carbon of the terminal CO group at 195 ppm in the 13C
2
1
NMR spectrum. Both J PC and J RhC couplings of 32 and
83 Hz, respectively, are clearly visible. The latter
coupling is in the range normally seen for one-bond
interactions between a rhodium center and a terminal
CO group (ca. 55-85 Hz).13
Resu lts a n d Discu ssion
Treatment of the dimeric rhodium complex [Rh2(η5-
C5H5)2(µ-CO)(µ-η2-CF3CtCCF3)] (1) with the phos-
phaalkynes PtCR (R ) But, 1-adamantyl (Ad)) in
hexane at -20 °C followed by warming to room tem-
perature afforded the red air- and moisture-stable
complexes 2 and 3, respectively (Scheme 2), which were
purified by recrystallization and isolated in ca. 50%
yield. Both 2 and 3 were characterized by multinuclear
NMR spectroscopy, mass spectrometry, and infrared
spectroscopy. Additionally, the solid-state structure of
2 was determined by a single-crystal X-ray diffraction
study. The spectroscopic data for 2 and 3 indicate that
they are isostructural. Moreover, the NMR spectroscopic
data for 2 are consistent with it retaining its solid-state
structure in solution.
The solid-state structure of complex 2 is shown in
Figure 1 with salient bond distances and angles col-
lected in Table 1. The η4-phosphacyclobutadiene ring is
essentially planar and contains delocalized carbon-
phosphorus and carbon-carbon bonds. The phosphorus-
carbon bond lengths of the ring (P(1)-C(1) ) 1.806(6)
Å, P(1)-C(3) ) 1.789(7) Å) are longer than expected for
carbon-phosphorus double bonds (ca. 1.67 Å)14 but
shorter than typical phosphorus-carbon single bonds
(ca. 1.85 Å).14 Similarly, the carbon-carbon bond lengths
(C(1)-C(2) ) 1.459(9) Å, C(2)-C(3) ) 1.456(8) Å) are
shorter than expected for carbon-carbon single bonds
(cf. C(1)-C(5) ) 1.522(9) Å) but longer than expected
The 31P NMR spectrum of complex 2 consists of a
doublet of doublets of quartets centered at 23.5 ppm.
The two large couplings of 251 Hz and 42.9 Hz can be
assigned respectively to the σ and π one-bond interac-
tions with the rhodium centers. The former coupling is
(12) Eshtiagh-Hosseini, H.; Kroto, H. W.; Nixon, J . F.; Maah, M. J .
J . Chem. Soc., Chem. Commun. 1981, 199.
(13) Goodfellow, R. J . In Multinuclear NMR; Mason, J ., Ed.; Plenum
Press: New York, 1987; p 552ff.
(14) See ref 1d, p 96.

4840 Organometallics, Vol. 18, No. 23, 1999
Hibbs et al.
Sch em e 3
which simultaneously causes the bridging carbonyl
ligand to become terminal at the adjacent rhodium site.
A [2 + 2] cycloaddition reaction between the phos-
phaalkyne and perfluorobutyne ligand forms the phos-
phacyclobutadiene ring, which inserts between the two
rhodium centers to form the final product.
F igu r e 1. Molecular structure of complex 2.
Ta ble 1. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) in Com p lex 2
When CO is bubbled through a solution of complex
2, 31P{1H} NMR spectroscopic monitoring indicates the
emergence of a doublet at -42.6 ppm (J PRh ) 34 Hz)
with an accompanying decrease in the intensity of the
resonance for complex 2. The doublet presumably arises
from complex 4, in which the (η5-C5H5)RhCO fragment
is lost as [Rh(η5-C5H5)(CO)2] (Scheme 3). The 31P NMR
data for complex 4 are consistent with those of similar
known species, e.g. [Rh(η5-C5H5){PC(But)C2Ph2}] (δ
Distances
C(1)-P(1)
P(1)-C(3)
C(3)-C(2)
C(2)-C(1)
Rh(2)-C(1)
Rh(2)-C(2)
Rh(2)-C(3)
Rh(2)-P(1)
Rh(1)-P(1)
Rh(1)-C(20)
1.806(6)
1.789(7)
1.456(8)
1.459(9)
2.165(6)
2.090(6)
2.105(6)
2.316(2)
2.174(2)
1.831(7)
Rh(2)-C(10)
Rh(2)-C(11)
Rh(2)-C(12)
Rh(2)-C(13)
Rh(2)-C(14)
Rh(1)-C(15)
Rh(1)-C(16)
Rh(1)-C(17)
Rh(1)-C(18)
Rh(1)-C(19)
2.195(8)
2.167(8)
2.194(8)
2.228(8)
2.203(8)
2.246(6)
2.282(6)
2.218(7)
2.297(7)
2.256(7)
1
-48.75 ppm, J PRh ) 37.3 Hz).8 The process appears to
be reversible, since removal of volatiles from the solution
leads to a residue shown by 31P{1H} NMR spectroscopy
to be entirely complex 2.
Angles
P(1)-C(1)-C(2)
92.5(4)
8.4(5)
Rh(2)-C(1)-C(2)
Rh(2)-C(1)-P(1)
Rh(2)-C(2)-C(1)
Rh(2)-C(2)-C(9)
Rh(2)-CF(2)-C(3)
Rh(2)-C(3)-C(2)
Rh(2)-C(3)-C(4)
67.2(3)
70.7(2)
72.8(4)
125.5(5)
70.2(4)
69.1(4)
125.8(5)
72.5(2)
C(1)-C(2)-C(3)
C(2)-C(3)-P(1)
C(3)-P(1)-C(1)
Rh(1)-P(1)-C(3)
Rh(1)-P(1)-C(1)
P(1)-Rh(1)-C(20)
The apparent lability of the (η5-C5H5)RhCO moiety
opened up the possibility of displacing it with other
metal fragments. To this end, the reactivity of complexes
2 and 3 with either [W(CO)5(THF)] or [Fe2(CO)9] was
examined with some interesting results. Stirring a
solution of 2 with [W(CO)5(THF)] led to an orange
solution from which the “flyover” complex 5 was isolated
by chromatographic workup and purified by recrystal-
lization in 25% yield from hexane (Scheme 4).
93.3(4)
75.7(3)
137.0(2)
145.6(2)
89.8(2)
Rh(2)-P(1)-Rh(1) 136.06(8) Rh(2)-C(3)-P(1)
Rh(2)-C(1)-C(5) 128.7(4)
for localized carbon-carbon double bonds (ca. 1.30-1.34
Å). The observation that the bond lengths are closer to
the single-bond rather than the double-bond distances
is a consequence of the increase in single-bond character
arising from the donation of π electron density from the
phosphacyclobutadiene ring to the rhodium center. A
similar lengthening of the phosphorus-carbon double
bonds of phosphaalkenes is observed upon η2 coordina-
tion to metal centers.15 The rhodium-phosphorus σ
bond distance of 2.174(2) Å is comparable with that of
2.178(8) Å in the related hexarhodium complex [Rh2-
The 31P{1H} NMR spectrum of 5 consists of a doublet
1
of doublets at 189.5 ppm with J PRh couplings of 63.7
and 44.4 Hz. The presence of two rhodium-phosphorus
couplings suggests that as well as the rhodium-
phosphorus σ bond there is also a π interaction between
the PdC functionality of the flyover backbone and the
adjacent rhodium center. Coordination of a phosphorus-
carbon double bond in a π fashion usually causes
reduction in the 31P{1H} chemical shift of the phospho-
rus, relative to the uncoordinated system. This leads to
the conclusion that if the 1-phosphabutadiendiyl back-
bone of 5 were devoid of this π interaction, then its 31P
chemical shift would be higher, perhaps somewhere in
excess of 300 ppm. This is indeed the region expected
Cl2{Rh(η5-C5H5)(η4-P2C2But )}4].16
2
The formations of 2 and 3 can perhaps be explained
by a mechanism which involves the initial coordination
of the phosphaalkyne unit to a rhodium center in 1
(15) Mathey, F. New J . Chem. 1987, 11, 585.
(16) Hitchcock, P. B.; Maah, M. J .; Nixon, J . F.; Woodward, C. J .
Chem. Soc., Chem. Commun. 1987, 844.

Dirhodium Complexes Derived from Phosphaalkynes
Organometallics, Vol. 18, No. 23, 1999 4841
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) in Com p lex 5
Sch em e 4
Distances
P(1)-C(11)
C(11)-C(13)
C(13)-C(12)
C(12)-Rh(1)
P(1)-Rh(2)
Rh(1)-Rh(2)
Rh(2)-C(6)
Rh(2)-C(7)
1.739(8)
1.512(11)
1.404(10)
2.001(9)
2.290(2)
2.6542(10)
2.211(9)
2.258(9)
Rh(2)-C(8)
Rh(2)-C(9)
Rh(2)-C(10)
Rh(1)-C(1)
Rh(1)-C(2)
Rh(1)-C(3)
Rh(1)-C(4)
Rh(1)-C(5)
2.220(10)
2.193(11)
2.204(10)
2.230(10)
2.220(10)
2.185(10)
2.223(9)
2.248(9)
Angles
W(1)-P(1)-Rh(2)
Rh(2)-P(1)-C(11)
Rh(1)-P(1)-C(11)
P(1)-C(11)-C(14)
P(1)-C(11)-C(13)
132.41(10) C(11)-C(13)-C(19) 124.5(7)
87.6(3)
65.0(3)
C(11)-C(13)-C(12) 104.3(7)
C(19)-C(13)-C(12) 128.6(8)
133.2(7)
101.1(5)
C(8)-C(12)-C(13)
C(13)-C(12)-Rh(1)
131.1(8)
99.9(6)
C(18)-C(12)-Rh(1) 126.5(6)
C(13)-C(11)-C(14) 124.1(7)
C(11)-P(1)-W(1) 138.6(3)
bridged by a phosphabutadienediyl group which spans
in a “flyover” manner. The phosphorus center is ad-
ditionally coordinated to a W(CO)5 moiety. Similar
dirhodium “flyover” complexes have been observed by
Dickson and co-workers, although the bridging unit
usually contains one more bridging atom than is ob-
served in complex 5, e.g. [Rh2(η5-C5H5)2{µ-(1,2,5-η):
(1,4,5-η)-C4Me2(CF3)2CO}].18,19 Related iron complexes
have also been reported.20 The bridging backbone of
complex 5 consists of an alkenyl (C(12)-C(13)) and a
phosphaalkenyl (P(1)-C(11)) unit connected by a short
carbon-carbon single bond (C(11)-C(13)). The phos-
phorus-carbon distance (P(1)-C(11) ) 1.739(8) Å) is
intermediate between the expected values for phospho-
rus-carbon single bonds and phosphorus-carbon double
bonds. Likewise, the alkenyl distance (C(12)-C(13) )
1.404(10) Å) is intermediate of the values seen for
carbon-carbon single and double bonds, whereas C(11)-
C(13) (1.512(11) Å) is in the region expected for a
carbon-carbon single bond. These features suggest that
the flyover backbone of 5 is comprised of localized double
bonds which are slightly elongated as a consequence of
their π interactions with the rhodium centers. The
rhodium-rhodium distance of 2.6542(10) Å is unre-
markable and is typical of that seen between two singly
bonded rhodium sites.21
The reaction between 2 or 3 with [Fe2(CO)9] in hexane
led to the air-stable red complexes 6 and 7, respectively,
the latter of which was purified by recrystallization from
diethyl ether (Scheme 5). The 31P{1H} NMR spectrum
of 6 consists of a doublet of doublets at 54 ppm, the 1J PRh
F igu r e 2. Molecular structure of complex 5.
2
and J PRh couplings being 171.8 and 81.2 Hz, respec-
tively. These data suggest the presence of one com-
pound, as shown in Scheme 5. An examination of the
19F, 1H, and 13C NMR spectra, however, indicate a more
complex picture. Complex 6 would be expected to give
rise to one tert-butyl resonance and two cyclopentadienyl
for metallophosphaalkenyl systems (ca. 300-600 ppm)17
to which 5 is notionally related. The 31P{1H} NMR
spectrum of 5 shows no evidence of fluorine-phosphorus
coupling. This is reflected in the 19F NMR spectrum,
which shows two barely resolved multiplets (J < 6 Hz)
due only to fluorine-fluorine coupling.
The structure of 5 in the solid state (Figure 2) was
elucidated from a single-crystal X-ray diffraction study
with pertinent bond distances and angles collected in
Table 2. The structure displays a (η5-C5H5)2Rh2 unit
1
resonances in its H NMR spectrum. Instead, there are
two tert-butyl and four cyclopentadienyl resonances that
are nearly overlapping, a situation which is also evident
in the 13C NMR spectrum of 6. Moreover, the 19F NMR
(18) Corrigan, P. A.; Dickson, R. S.; J ohnson, S. H.; Pain, G. N.;
Yeoh, Y. Aust. J . Chem. 1982, 35, 2203.
(17) (a) Bedford, R. B.; Hill, A. F.; J ones, C. Angew. Chem., Int. Ed.
Engl. 1996, 35, 547. (b) Gudat, D.; Niecke, E.; Malisch, W.; Hofmockel,
U.; Quashie, S.; Cowley, A. H.; Arif, A. M.; Krebs, B.; Dartmann, M.
J . Chem. Soc., Chem. Commun. 1985, 1687. (c) Gudat, D.; Niecke, E.;
Arif, A. M.; Cowley, A. H.; Quashie, S. Organometallics 1986, 5, 593.
(19) Dickson, R. S.; Gatehouse, B. M.; J ohnson, S. H. Acta Crystal-
logr. 1977, B33, 319.
(20) Piron, J .; Piret, P.; Meunier-Piret, J .; Van Meerssche, Y. Bull.
Soc. Chim. Belg. 1968, 78, 121.
(21) Cowie, M.; Dwight, S. K. Inorg. Chem. 1980, 19, 209.

4842 Organometallics, Vol. 18, No. 23, 1999
Hibbs et al.
Sch em e 5
F igu r e 4. Molecular structure of complex 7.
Ta ble 3. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) in Com p lex 7
Distances
Rh(1)-C(13)
Rh(1)-C(12)
Rh(1)-C(11)
P(1)-C(11)
C(11)-C(12)
C(12)-C(13)
C(13)-P(1)
P(1)-Rh(1)
P(1)-Rh(2)
P(1)-Fe(1)
Rh(2)-Rh(1)
2.14(1)
2.08(1)
2.20(1)
1.858(9)
1.40(1)
Rh(2)-C(6)
Rh(2)-C(7)
Rh(2)-C(8)
Rh(2)-C(9)
Rh(2)-C(10)
Rh(1)-C(1)
Rh(1)-C(2)
Rh(1)-C(3)
Rh(1)-C(4)
Rh(1)-C(5)
2.29(1)
2.19(1)
2.25(1)
2.26(1)
2.31(1)
2.27(2)
2.221(2)
2.18(1)
2.20(2)
2.19(2)
1.47(1)
1.878(8)
2.683(3)
2.282(3)
2.255(3)
2.7457(9)
F igu r e 3. Possible isomers of complexes 6 and 7 in
solution.
spectrum shows not two but four multiplets, i.e., two
pairs within a narrow bracket of 4 ppm. The NMR
spectra of the related complex 7 reveal a similar
situation, although the 1H and 13C spectra are some-
what less informative because of the complex multiplets
arising from the adamantyl groups. On the basis of
these observations, we suggest that in solution com-
plexes 6 and 7 exist in two isomeric forms in an
approximately 1:1 ratio (Figure 3). It is clear that these
isomers do not cocrystallize, since the X-ray structure
of 7 (vide infra) shows the presence of only one isomer.
The two isomers have slightly differing environments
for the C5H5, But or Ad, CF3, and P sites. That only one
signal is seen in the 31P{1H} spectra of both complexes
is believed to be entirely coincidental.
The X-ray structure of 7 and relevant bond lengths
and angles are shown in Figure 4 and Table 3, respec-
tively. The molecular structure of 7 consists of a
phosphacyclobutenyl group bridging a rhodium-rhod-
ium moiety in an unusual η1: η3 fashion. Each rhodium
bears a η5-cyclopentadienyl group, and a terminal CO
group is bound to Rh(2). The η1-P ligation is in the form
of a σ bond between P(1) and Rh(2) (P(1)-Rh(2) )
2.282(3) Å), while the η3 attachment arises from the
interaction of Rh(1) with the allylic system defined by
C(11), C(12), and C(13). The long phosphorus-carbon
distances in the phosphacyclobutenyl ring (P(1)-C(11)
) 1.858(9) Å, P(1)-C(13) ) 1.878(8) Å) correspond to
single bonds and clearly indicate that there is no
delocalization over the C(11)-P(1)-C(13) region of the
ring. The individual distances between the allylic
carbons and the rhodium center Rh(1) differ signifi-
Angles
92.9(6) Rh(2)-P(1)-Fe(1)
P(1)-C(11)-C(12)
123.0(1)
105.4(4)
115.5(4)
90.4(4)
C(11)-C(12)-C(13) 101.6(7) Rh(2)-P(1)-C(11)
C(12)-C(13)-P(1)
C(13)-P(1)-C(11)
P(1)-Rh(2)-Rh(1)
90.0(5) Fe(1)-P(1)-C(13)
73.3(4) P(1)-Rh(2)-C(30)
63.7(4) Rh(1)-Rh(2)-C(30)
81.1(5)
cantly (Rh(1)-C(11) ) 2.20(1) Å, Rh(1)-C(12) ) 2.08(1)
Å, Rh(1)-C(13) ) 2.14(1) Å) but span a range similar
to that for the analogous distances seen in a related
rhodium-phosphacyclobutenyl complex reported by
Binger et al. (mean Rh-C distance ) 2.221 Å)8 and in
other rhodium allyl systems, e.g. [RhCl2(Ph3As)2(η3-
C4H7)] (mean Rh-C distance 2.246 Å).22 The carbon-
carbon bond lengths of the allylic system (C(11)-C(12)
) 1.40(1) Å, C(12)-C(13) ) 1.47(1) Å) are both inter-
mediate between carbon-carbon single- and double-
bond lengths, even though they are marginally different.
The Rh-Rh distance of 2.7457(9) Å is longer than that
in the previous two systems but is still within the range
seen for Rh-Rh single bonds (ca. 2.617-2.842 Å).21
The formation of both 6 and 7 can possibly be
attributed to the displacement of the CpRh(CO) frag-
ment from 2 or 3 by an Fe(CO)4 fragment. This would
allow the generated rhodium fragment to form a rhod-
ium-rhodium bond and the final products. A compound
similar to 6 but with a coordinated W(CO)5 moiety
instead of an Fe(CO)4 group may be viewed as a possible
intermediate to 5. Such an intermediate could rearrange
to 5 by ring cleavage and the formation of a bond
(22) Hewitt, T. G.; de Boer, J . J .; Anzenhofer, K. Acta Crystallogr.
1970, B26, 1244.

Dirhodium Complexes Derived from Phosphaalkynes
Organometallics, Vol. 18, No. 23, 1999 4843
to leave a clear red solution. The resulting solution was stirred
at room temperature for 24 h. Volatiles were then removed in
vacuo and the residue recrystallized from hexane to afford 3
as large red crystals (0.07 g, 0.1 mmol, 52%); mp 100-103 °C.
NMR (C6D6, 298 K): 1H (400 MHz) δ 1.6-2.0 (m, 15H, Ad-H),
5.2 (s, 5H, C5H5), 5.3 (s, 5H, C5H5); 13C (100.6 MHz) δ 28.5 (s,
Ad-CH), 36.2 (s, Ad-CH2), 42.7 (s, Ad-CH2), 82.6 (s, C5H5), 87.9
between the CF3-substituted ring carbon adjacent to the
phosphorus center and the rhodium center coordinated
to the allyl fragment. Elimination of the CO group would
be necessary to maintain the electron count at each
rhodium center.
2
1
Exp er im en ta l Section
(s, C5H5), 194.9 (dd, CO, J PC ) 32 Hz, J RhC ) 83.9 Hz), CF3
and PC3But(CF3)2 ring carbons unobserved; 19F (376.4 MHz)
Gen er a l Con sid er a tion s. All procedures were conducted
using conventional Schlenk or glovebox techniques under an
atmosphere of high-purity argon or dinitrogen in flame-dried
glassware. Hexane and diethyl ether were refluxed over
sodium-potassium alloy under nitrogen for at least 12 h before
being distilled and freeze-thaw-degassed before use. NMR
spectra were recorded in dry degassed C6D6 on a Bruker WM-
250 or AC-400 spectrometer. 31P{1H} and 19F NMR spectra
were referenced to 85% H3PO4 and CFCl3, respectively, as
external references. 1H and 13C spectra were referenced to the
5
3
δ -52.2 (quartet, CF3, J FF ) 6.5 Hz), -53.9 (m, CF3, J PF
≈
5J FF ≈ 8 Hz); 31P{1H} (101.4 MHz) δ 22.5 (ddq, J PRh ) 251
and 43.1 Hz, 3J PF ) 7.6 Hz). FAB mass spectrum (25 kV): 704
([M]+, 44%), 676 ([M - CO]+, 69%). IR (ν/cm-1): 1976 (s). Anal.
Found: C, 44.43; H, 3.50. Calcd for C26H25Rh2PF6O: C, 44.34;
H, 3.58.
1
Syn th esis of [Rh 2(η5-C5H5)2{µ-(1,2,4-η):(1,3,4-η)-P C3Bu t-
(CF 3)2}{W(CO)5}] (5). [W(CO)6] (0.09 g, 0.256 mmol) in THF
(40 mL) was irradiated (254 nm) for 6 h. Compound 2 (0.08 g,
0.128 mmol) in THF (10 mL) was added to the resulting yellow
solution of [W(CO)5(THF)] and the mixture stirred for 48 h.
Volatiles were then removed in vacuo, and the residue was
extracted with hexane and filtered. The filtrate was evaporated
and the residue chromatographed (Kieselgel, hexane/Et2O
95%/5%). Compound 5 was collected as an orange fraction (0.03
g, 0.033 mmol, 25%); mp 168 °C dec. NMR (C6D6, 298 K): 1H
(400 MHz) δ 1.10 (s, 9H, But), 5.09 (s, 5H, C5H5), 5.11 (s, 5H,
C5H5); 13C (100.6 MHz) δ 29 (s, C(CH3)3), 38.8 (s, C(CH3)3),
88.2 (s, C5H5), 88.7 (s, C5H5), 197.4 (d, W(CO), cis-2J PC ) 6.1
Hz), 200.0 (d, W(CO), trans-2J PC ) 29 Hz), CF3 and PC3But-
(CF3)2 phosphabutadienyl carbons unobserved; 19F (376.4 MHz)
1
residual solvent resonances (128 ppm for 13C; 7.14 ppm for H).
Mass spectra were recorded on a VG-Autospec FAB instrument
(Cs+ ions, 25 kV, 3-nitrobenzyl alcohol matrix). Melting points
were recorded in capillaries sealed under argon. Infrared
spectra were recorded on a Perkin-Elmer 1725-X Fourier
transform instrument. A reproducible elemental analysis of 6
proved difficult to obtain, as its high solubility in all organic
solvents made it difficult to purify by recrystallization. Al-
though compounds 5 and 7 have relatively high melting points,
they appear to slowly decompose at room temperature. As a
result, accurate elemental analyses on these compounds
proved difficult to obtain, but those which were are included
below. [Rh2(η5-C5H5)2(µ-CO)(µ-η2-CF3CtCCF3)] (1) and the
phosphaalkyne PtCAd were prepared according to the pub-
lished procedures.23,24 PtCBut was prepared by a modifica-
tion25 of the literature procedure.26 Fe2(CO)9 was purchased
from Aldrich and used without further purification.
Syn th esis of [Rh (η5-C5H5){µ-η4:η1-P C3Bu t(CF 3)2}{Rh -
(CO)(η5-C5H5)}] (2). To a stirred solution of [Rh2(η5-C5H5)2-
(µ-CO)(µ-η2-CF3CtCCF3)] (1; 0.1 g, 0.19 mmol) in hexane (5
mL) at -20 °C was added the phosphaalkyne PtCBut (0.02
g, 32.3 µL, 0.2 mmol). When it was warmed, the initial green
solution became cloudy with a yellow precipitate which disap-
peared upon reaching room temperature to leave a clear red
solution. The resulting solution was stirred at room temper-
ature for 24 h. Volatiles were then removed in vacuo, and the
residue was recrystallized from hexane to afford 2 as large
red crystals (0.06 g from two crops, 0.1 mmol, 50.4%); mp 128-
130 °C. NMR (C6D6, 298 K): 1H (400 MHz) δ 1.07 (s, 9H, But),
5.09 (s, 5H, C5H5), 5.18 (s, 5H, C5H5); 13C (100.6 MHz) δ 30.8
5
δ -53.0 (quartet, CF3, J FF ≈ 6.5 Hz), -57.3 (quartet, CF3,
5J FF ≈ 6.5 Hz no P-F coupling observed); 31P{1H} (101.4 MHz)
1
δ 189.5 (dd, J PRh ) 63.7 and 44.4 Hz). FAB mass spectrum
(25 kV): 922 ([M]+, 1%), 865 ([M - 2CO]+, 3%), 781 ([M -
5CO]+, 5%), 597 ([M - W(CO)5]+, 5%); IR (ν/cm-1): 1942.9 (s),
1959.8 (s), 2067.8 (m). Anal. Found: C, 29.24; H, 1.6. Calcd
for C24H19Rh2PF6O5W: C, 31.26; H, 2.08.
Syn th esis of [Rh 2(η5-C5H5)2(CO){µ-η1:η3-P C3Bu t(CF 3)2}-
{F e(CO)4}] (6). To a stirred solution of compound 2 (0.143 g,
0.23 mmol) in THF (2 mL) was added [Fe2(CO)9] (0.089 g, 0.24
mmol). The resulting mixture was stirred for 24 h, during
which time a clear red solution formed. Volatiles were removed
in vacuo, the residue was chromatographed (Kieselgel, hexane/
Et2O 1/3), and the two isomers of 6 (see Results and Discus-
sion) were collected as a purple-red fraction (0.046 g, 0.058
mmol, 25%). The compound proved difficult to recrystallize
because of its high solubility; mp 116-119 °C. NMR (C7D8,
298 K): 1H (400 MHz) δ 1.21 (s, 9H, But), 1.13 (s, 9H, But),
5.03 (s, 5H, C5H5), 5.05 (s, 5H, C5H5), 5.06 (s, 5H, C5H5), 5.11
(s, 5H, C5H5); 13C (100.6 MHz) δ 31.9 (s, C(CH3)3), 32.2 (s,
C(CH3)3), 32.8 (d, C(CH3)3, 2J PC ) 6 Hz), 33.5 (d, C(CH3)3, 2J PC
) 6 Hz), 86.6 (s, C5H5), 87.3 (s, C5H5), 92.0 (s, C5H5), 92.3 (s,
C5H5), 215.5 (dd, FeCO, J ) 33 and 19 Hz); 19F (376.4 MHz)
δ -49.1 (m, CF3, J ≈ 6 Hz), -50.7 (m, CF3, J ≈ 7 Hz), -52.3
3
2
(d, C(CH3)3, J PC ) 6.5 Hz), 32.7 (d, C(CH3)3, J PC ) 6.5 Hz),
86.5 (s, C5H5), 88.0 (s, C5H5), 195 (dd, CO, 2J PC ) 32 Hz, 1J RhC
) 83 Hz), CF3 and PC3But(CF3)2 ring carbons unobserved; 19
F
5
(376.4 MHz) δ -52.6 (quartet, CF3, J FF ) 5.6 Hz), -54.0 (m,
3
CF3, J PF
≈
5J FF ≈ 6 Hz); 31P{1H} (101.4 MHz) δ 23.5 (ddq,
1J PRh ) 251 and 42.9 Hz, J PF ) 7.6 Hz). FAB mass spectrum
(25 kV): 626 ([M]+, 22%), 598 ([M - CO]+, 55%). IR: (ν/cm-1):
1974 (m), 1964 (m). Anal. Found: C, 38.42; H, 2.97. Calcd for
C20H19Rh2PF6O: C, 38.4; H, 3.06.
3
5
5
(quartet, CF3 J FF ≈ 7 Hz), -53.0 (quartet, CF3, J FF ≈ 7 Hz);
31P{1H} (101.4 MHz) δ 53.8 (dd, 1J PRh ) 171.8 Hz, 2J PRh ) 81.2
Hz). FAB mass spectrum (25 kV): 794 ([M]+, 4%), 766 ([M -
CO]+, 13%), 710 ([M - 3CO]+, 46%), 682 ([M - 4CO]+, 16%),
654 ([M - 5CO]+, 5%), 626 ([M - Fe(CO)4]+, 14%), 598 ([M -
Fe(CO)5]+, 14%). IR (ν/cm-1): 2036 (m), 2014 (w), 2000 (w),
1936 (s), 1926 (s).
Syn t h esis of [R h (η5-C5H 5){µ-η4:η1-P C3Ad (CF 3)2}{R h -
(CO)(η5-C5H5)}] (3). To a stirred solution of [Rh2(η5-C5H5)2-
(µ-CO)(µ-η2-CF3CtCCF3)] (1; 0.1 g, 0.19 mmol) in hexane (5
mL) at -20 °C was added a solution of the phosphaalkyne Pt
CAd (0.0338 g, 0.19 mmol) in hexane (5 mL). Upon warming,
the initial green solution became cloudy with a yellow pre-
cipitate, which disappeared upon reaching room temperature
Syn th esis of [Rh 2(η5-C5H5)2(CO){µ-η1: η3-P C3Ad (CF 3)2}-
{F e(CO)4}] (7). To a stirred solution of compound 3 (0.07 g,
0.099 mmol) in hexane (10 mL) was added [Fe2(CO)9] (0.036
g, 0.099 mmol). The resulting mixture was stirred at room
temperature for 24 h. Volatiles were then removed in vacuo,
and the residue was extracted with Et2O and filtered to give
a red solution. Concentration of the filtrate followed by slow
cooling to -30 °C afforded two isomers of compound 7 as red
crystals (0.054 g, 0.062 mmol, 62.3%); mp 131-133 °C. NMR
(C6D6, 298 K): 1H (400 MHz) δ 1.55-2.1 (m, 30 H, Ad-H), 5.06
(23) Dickson, R. S.; J ohnson, S. H.; Pain, G. N. Organomet. Synth.
1988, 4, 283.
(24) Allspach, T.; Becker, G.; Becker, W.; Regitz, M. Synthesis 1986,
31.
(25) Francis, M. D. Ph.D. Thesis, University of Wales, 1998.
(26) Becker, G.; Schmidt, H.; Uhl, G.; Uhl, W. Inorg. Synth. 1990,
27, 243.

4844 Organometallics, Vol. 18, No. 23, 1999
Hibbs et al.
Ta ble 4. Cr ysta llogr a p h ic Da ta for Com p lexes 2, 5,
a n d 7
(s, 5H, C5H5), 5.07 (s, 5H, C5H5), 5.09 (s, C5H5), 5.13 (s, C5H5);
13C (100.6 MHz) δ 28.5 (s, Ad-CH), 28.9 (s, Ad-CH), 35.9 (s,
Ad-CH2), 36.2 (s, Ad-CH2), 42.1 (s, Ad-CH2), 42.6 (s, Ad-CH2),
85.8 (s, C5H5), 86.5 (s, C5H5), 91.6 (s, C5H5), 92.1 (s, C5H5);
215 (dd, FeCO, J ) 39 and 17 Hz); 19F (376.4 MHz) δ -50.2
(m, CF3, J ≈ 7 Hz), -51.7 (m, CF3, J ≈ 7 Hz), -52.8 (quartet,
2
5
7
formula
C
20H19F6O-
PRh2
C24H19F6O5- C30H25O5F6-
PRh2W PFeRh2
922.03 872.2
Mr
626.14
5
5
CF3, J FF ) 6.9 Hz), -53.5 (quartet, CF3, J FF ) 7.6 Hz); 31P-
a, Å
b, Å
c, Å
10.043(2)
10.484(1)
11.271(1)
109.03(1)
104.89(2)
91.27(1)
1076.9(3)
triclinic
0.710 69
150(2)
9.5180(11)
18.1260(9)
16.118(2)
90
101.940(11) 99.12(1)
90
2820.6(5)
monoclinic
0.710 69
150(2)
P21/n
9.246(1)
10.07(1)
17.881(1)
91.70(1)
1
2
{1H} (101.4 MHz) δ 51 (dd, J PRh ) 194 Hz, J PRh ) 83 Hz).
FAB mass spectrum (25 kV): 872 ([M]+, 3%), 844 ([M - CO]+,
10%), 788 ([M - 3CO]+, 42%), 760 ([M - 4CO]+, 15%), 732
([M - 5CO]+, 8%), 704 ([M - Fe(CO)4]+, 7%), 676 ([M - Fe-
(CO)5]+, 24%); IR (ν/cm-1): 2041 (m), 1992 (w), 1937 (s), 1926
(m). Anal. Found: C, 42.8; H, 2.03. Calcd for C30H25FeO5-
PRh2F6: C, 41.3; H, 2.89.
R, deg
â, deg
γ, deg
V, Å3
cryst syst
λ, Å
T, K
space group
Z
110.34(3)
1534.9(3)
triclinic
0.710 73
296(2)
P1h
X-r a y Str u ctu r e Deter m in a tion s. Crystals of 2 and 5
suitable for X-ray structure determination were mounted in
silicone oil. Intensity data were measured on a FAST27 area
detector diffractometer using Mo KR radiation. Both structures
were solved by heavy-atom methods (SHELXS-8628) and
refined by least squares using the SHELXL-9329 program. The
structures were refined on F2 using all data. Neutral-atom
complex scattering factors were employed.30 Empirical absorp-
P1h
2
4
2
size
0.25 × 0.35 × 0.25 × 0.20 × 0.42 × 0.52 ×
0.30
red
0.30
orange
55.50
0.44
red
color
µ, cm-1
16.66
16.6
2θ range, deg
1.99-24.98
2.25-25.04
2-50
5743
3654
407
no. of rflns collected 4353
9059
tion corrections were carried out by the DIFABS method.31
A
no. of rflns obsd
params varied
R (I > 2σ(I))
Rw
2988
274
3943
355
crystal of 7 was mounted on a glass fiber, and X-ray data were
collected on an Enraf-Nonius CAD4 diffractometer using Mo
KR radiation. The structure was solved and refined using the
Xtal 3.4 program system.32 Crystal data and details of data
collections and refinement are given in Table 4. Molecular
structures are shown in Figures 1, 2, and 4. Anisotropic
thermal parameters were refined for all non-hydrogen atoms.
0.0489
0.1255
0.0339
0.0681
0.075
0.085
The hydrogen atoms in all structures were included in
calculated positions (riding model).
Ack n ow led gm en t. We gratefully acknowledge the
financial support of the Engineering and Physical
Sciences Research Council (A.F.R.) and the University
of Wales (M.D.F.).
(27) Darr, J . A.; Drake, S. A.; Hursthouse, M. B.; Malik, K. M. A.
Inorg. Chem. 1993, 32, 5704.
(28) Sheldrick, G. M. Acta Crystallogr., Sect. A 1990, 46, 467.
(29) Sheldrick, G. M., SHELXL-93 Program for Crystal Structure
Refinement; University of Go¨ttingen, Go¨ttingen, Germany, 1993.
(30) “International Tables for X-ray Crystallography”, Ibers, J . A.;
Hamilton, W. C. (Eds.), Kynoch Press: Birmingham, England, 1974,
Vol. 4.
(31) Walker, N. P. C.; Stuart, D. Acta Crystallogr. 1983, A39, 158
Adapted for FAST geometry by: Karavlov, A. I. University of Wales,
Cardiff, Wales, 1991.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data, positional and thermal parameters, and bond angles and
distances for 2, 5, and 7. This material is available free of
charge via the Internet at http://pubs.acs.org.
(32) Hall, S. R.; King, G. S. D.; Stewart, J . M. Xtal 3.4 User’s Manual,
UWA: Lamb, 1995.
OM990516V