Phosphinoalkyne additions to (η5-C5H5)2Rh 2(μ-CO)(μ-η2:η2-CF 3C2CF3): Facile conversion of coordinated phosphinoalkynes to phosphino-enone ligands on a Rh-Rh bond

Article abstract of DOI:10.1021/om960830e

The phosphinoalkynes Ph₂PC≡CR (R = H, Me, CF₃, Bu^t, Ph, and PPh₂) behave as tertiary phosphines in their reactions with the dirhodium complex (η⁵-C₅H₅)₂Rh ₂(μ-CO)(μ-η²:η²-CF ₃C₂-CF₃) (1). All six addition products (η₅-C₅H₅)₂Rh ₂(CO)(μ-η¹:η¹-CF₃C ₂CF₃)(η¹-Ph₂PC≡CR) (4) have been isolated and fully characterized. The bis(diphenylphosphino)alkyne Ph₂PC≡CPPh₂ also forms a tetranuclear complex (5) in which each phosphorus coordinates to a dirhodium unit. With the exception of 4 when R = H, the solid complexes are relatively stable. However, when solutions of two of the complexes (R = Me, Ph) are left in the presence of both silica and oxygen, there is oxygen transfer to an alkyne carbon accompanied by an intramolecular condensation reaction to generate a phosphino-enone ligand. The structure of one of these oxidation products, (η⁵-C₅H₅)₂Rh ₂(μ-C(CF₃)C(CF₃)C{C(O)R}PPh₂) (6, R = Ph), has been established by X-ray crystallography. Prior oxidation of the phosphinoalkynes to give Ph₂P-(O)C≡CR and subsequent reaction with 1 leads to the formation of typical alkyne addition products.

Full text of DOI:10.1021/om960830e

Organometallics 1997, 16, 1531-1537
1531
P h osp h in oa lk yn e Ad d ition s to
(η5-C5H5)2Rh 2(µ-CO)(µ-η2:η2-CF 3C2CF 3): F a cile Con ver sion
of Coor d in a ted P h osp h in oa lk yn es to P h osp h in o-En on e
Liga n d s on a Rh -Rh Bon d
Ron S. Dickson,* Tania de Simone, Richard J . Parker, and Gary D. Fallon
Department of Chemistry, Monash University, Clayton, Victoria 3168, Australia
Received September 30, 1996X
The phosphinoalkynes Ph2PCtCR (R ) H, Me, CF3, But, Ph, and PPh2) behave as tertiary
phosphines in their reactions with the dirhodium complex (η5-C5H5)2Rh2(µ-CO)(µ-η2:η2-CF3C2-
CF3) (1). All six addition products (η5-C5H5)2Rh2(CO)(µ-η1:η1-CF3C2CF3)(η1-Ph2PCtCR) (4)
have been isolated and fully characterized. The bis(diphenylphosphino)alkyne Ph2PCtCPPh2
also forms a tetranuclear complex (5) in which each phosphorus coordinates to a dirhodium
unit. With the exception of 4 when R ) H, the solid complexes are relatively stable. However,
when solutions of two of the complexes (R ) Me, Ph) are left in the presence of both silica
and oxygen, there is oxygen transfer to an alkyne carbon accompanied by an intramolecular
condensation reaction to generate a phosphino-enone ligand. The structure of one of these
oxidation products, (η5-C5H5)2Rh2(µ-C(CF3)C(CF3)C{C(O)R}PPh2) (6, R ) Ph), has been
established by X-ray crystallography. Prior oxidation of the phosphinoalkynes to give Ph2P-
(O)CtCR and subsequent reaction with 1 leads to the formation of typical alkyne addition
products.
In tr od u ction
to generate separate phosphido and acetylide frag-
ments.15,16 An example of this type of behavior is found
in the reactions of Ph2PCtCR (R ) Ph, Pri, But) with
M3(CO)12 (M ) Fe, Ru, Os) where the substituted cluster
M3(CO)11(Ph2PCtCR) is formed initially, but oxidative
insertion into the P-C bond accompanied by cluster
fragmentation then gives the binuclear products M2-
(CO)6(µ2-η1:η2-CtCR)(µ2-PPh2).17
A wide variety of ligands and some transient species
have been added coordinatively to the dirhodium com-
plex (η5-C5H5)2Rh2(µ-CO)(µ-η2:η2-CF3C2CF3) (1).1 For
example, the reactions with tertiary phosphanes, PR3,
give the inert products (η5-C5H5)2Rh2(CO)(PR3)(µ-η1:η1-
CF3C2CF3).2 In other reactions, the added substrate
reacts further with the existing ligands to form con-
densed ligands. This occurs, for instance, in the reac-
tions between 1 and various alkynes, which give prod-
ucts containing bridging metallacyclopentadiene (2) or
dimetallacycloheptadienone (3) units.3-5 Recently, we
The bis(diphenylphosphino)alkyne Ph2PCtCPPh2 is
potentially even more versatile in its coordination
behavior. This compound often coordinates exclusively
from one or both phosphorus atoms. Even with Co2-
(CO)8, which is especially prone to form µ-alkyne
complexes,18 Ph2PCtCPPh2 gives phosphane substitu-
tion products.19 The complex W(CO)(S2CNEt2)2(η2-Ph2-
PCtCPPh2) provides a rare example of coordination
from the alkyne function of Ph2PCtCPPh2.20 There are
also examples of P-C bond cleavage in some reactions
of bis(phosphino)alkynes and clusters.21
(5) Dickson, R. S.; Gatehouse, B. M.; J ohnson, S. H. Acta Crystal-
logr.. 1977, B33, 319.
(6) de Simone, T.; Dickson, R. S.; Skelton, B. W.; White, A. H. Inorg.
Chim. Acta 1995, 240, 323.
(7) Carty, A. J .; J acobson, S. E.; Simpson, R. T.; Taylor, N. J . J .
Am. Chem. Soc. 1975, 97, 7254.
(8) Taylor, N. J .; Carty, A. J . J . Chem. Soc., Dalton Trans. 1976,
799.
(9) Sappa, E. J . Chem. Soc., Dalton Trans. 1989, 601.
(10) Braga, D.; Benvenutti, M. H. A.; Grepioni, F.; Vargas, M. D. J .
Chem. Soc., Chem. Commun. 1990, 1730.
(11) Carty, A. J .; Paik, H. N. J . Organomet. Chem. 1974, 70, C17.
(12) Carty, A. J .; Patel, H. A., Hota, N. K. J . Organomet. Chem.
1973, 50, 247.
investigated some reactions of 1 with phosphinoalkynes
Ph2P(CH2)nCtCR. In these systems, coordination oc-
curs exclusively from phosphorus.6
In other studies, phosphinoalkynes of the type Ph2-
PCtCR have been shown to react with mononuclear
and polynuclear complexes in a number of ways. Co-
ordination can be from phosphorus only7-10 or from
phosphorus and the alkyne,11-14 but in other cases,
these ligands undergo cleavage of the P-C(alkyne) bond
* Author to whom correspondence should be addressed. Email:
r.s.dickson@sci.monash.edu.au.
(13) Carty, A. J .; Paik, N. N.; Ng, T. W. J . Organomet. Chem. 1974,
74, 279.
(14) Sappa, E. J . Organomet. Chem. 1985, 297, 103.
(15) Carty, A. J . Pure Appl. Chem. 1982, 54, 10.
(16) Carty, A. J .; Nucciarone, D.; MacLaughlin, S. A.; Taylor, N. J .
Organometallics 1988, 7, 106.
X Abstract published in Advance ACS Abstracts, March 1, 1997.
(1) Dickson, R. S. Polyhedron 1991, 10, 1995.
(2) Dickson, R. S.; Oppenheim, A. P.; Pain, G. N. J . Organomet.
Chem. 1982, 224, 377.
(3) Baimbridge, W. C.; Dickson, R. S.; Fallon, G. D.; Grayson, I.;
Nesbit, R. J .; Weigold, J . Aust. J . Chem. 1986, 39, 1187.
(4) Dickson, R. S.; McLure, F. I.; Nesbit, R. J . J . Organomet. Chem.
1988, 349, 413.
(17) Cherkas, A. A.; Randall, L. H.; MacLaughlin, S. A.; Mott, G.
N.; Taylor, N. J .; Carty, A. J . Organometallics 1988, 7, 969.
(18) Dickson, R. S.; Fraser, P. J . Adv. Organomet. Chem. 1974, 12,
323.
S0276-7333(96)00830-8 CCC: $14.00 © 1997 American Chemical Society

1532 Organometallics, Vol. 16, No. 8, 1997
Dickson et al.
the solvent under reduced pressure gave (η5-C5H5)2Rh2(CO)(µ-
η1:η1-CF3C2CF3)(η1-Ph2PCtCBut) (4, R ) But; 72 mg, 78%) as
red-orange crystals. Anal. Calcd for C33H29F6OPRh2: C, 50.0;
H, 3.7; F, 14.4; P, 3.9. Found: C, 50.2; H, 3.6; F, 14.1; P, 3.8.
This diversity in coordination behavior demonstrated
by phosphinoalkynes, plus the extensive and interesting
reaction chemistry reported for P-coordinated phos-
phinoalkynes,7,8,22 prompted us to explore the reactions
between these ligands and 1. In this paper, we describe
the results of our investigations.
MS, m/ z: 792 (4, [M]+), 764 (20, [M - CO]+), 233 (80, [C10H10
-
Rh]+), 168 (40, [C5H5Rh]+), 57 (100, [C2H2P]+). IR (CH2Cl2),
cm-1: ν(CO) 1985 (vs), ν(CtC) 2208 (w) and 2169 (m). 1H
NMR (CDCl3, 300 MHz): δ 1.29 (s, 9H, CH3), 5.10 (s, 5H,
2
Exp er im en ta l Section
C5H5), 5.14 (d, J RhH ) 1.7 Hz, 5H, C5H5), 7.3-7.5 (m , 8H,
ortho- and meta-H of C6H5), 7.92 (m, 2H, para-H of C6H5). 19F
NMR (CDCl3, 282 MHz): two isomers were evident in the ratio
95:5; major isomer δ -51.7 (q, 5J FF ) 11.4 Hz, 3F, CF3), -55.0
Gen er a l P r oced u r es. All reactions were carried out under
an atmosphere of purified nitrogen in oven-dried Schlenk
flasks. Purification of some products was achieved by pre-
parative-scale thin layer chromatography (TLC), which was
carried out on 20 cm by 20 cm glass plates with a 1:1 silica
gel G-HF254 mixture (type 60, Merck) as the adsorbent. All
separations were achieved on deactivated plates, obtained by
drying at room temperature only. Microanalyses were per-
formed by the Campbell Microanalytical Laboratory, Univer-
sity of Otago, New Zealand. Melting points were determined
on a Buchi melting point apparatus using analytically pure
samples and are uncorrected.
5
3
4
(qdd, J FF ) 11.4 Hz, J RhF ) J PF ) 3.3 Hz, 3F, CF3); minor
5
3
isomer δ -51.1 (qd, J FF ) 11.3 Hz, J RhF ) 3.0 Hz, 3F, CF3),
5
3
4
-55.0 (qdd, J FF ) 11.3 Hz, J RhF ) J PF ) 3.3 Hz, 3F, CF3).
31P{1H} NMR (CDCl3, 162 MHz, 297 K): δ 28.3 (br m, PPh2).
P h 2P CtCCF 3. Upon dropwise addition of a solution of Ph2-
PCtCCF3 (44 mg, 0.158 mmol) in dichloromethane (5 mL) to
a stirred solution of 1 (82 mg, 0.156 mmol) in dichloromethane
(25 mL), there was an instant color change from green to
orange. The solvent was removed under reduced pressure to
give (η5-C5H5)2Rh2(CO)(µ-η1:η1-CF3C2CF3)(η1-Ph2PCtCCF3) (4,
R ) CF3; 126 mg, 100%) as orange crystals. Anal. Calcd for
In str u m en ta tion . Solution infrared spectra (KBr win-
dows) were obtained using a Perkin Elmer 1600 Fourier
transform spectrometer. NMR spectra were measured on a
Bruker AC 200, AM 300, or RDX 400 spectrometer. Deuter-
ated solvents (CDCl3, toluene-d8) were used as internal locks.
Chemical shifts are in parts per million from internal Me4Si
C
30H20F9OPRh2: C, 44.8; H, 2.5; F, 21.3; P, 3.9. Found: C,
44.5; H, 2.5; F, 21.0; P, 3.8. MS, m/ z: 804 (<1, [M]+), 776 (6,
[M - CO]+), 526 (11, [M - Ph2PC2CF3]+), 233 (100, [C10H10
-
Rh]+), 168 (29, [C5H5Rh]+). IR (CH2Cl2), cm-1: ν(CO) 1993
(vs), ν(CtC) 2218 (w). 1H NMR (CDCl3, 400 MHz): δ 5.10 (s,
5H, C5H5), 5.25 (d, 2J RhH ) 1.5 Hz, 5H, C5H5), 7.3-7.6 (m, 8H,
ortho- and meta-H of C6H5), 7.83 (m, 2H, para-H of C6H5). 19F
1
for H and 13C, from CCl3F for 19F, and from external 85% H3-
PO4 for 31P; in all cases, a positive chemical shift denotes a
resonance downfield from the reference. Electron impact mass
spectra were obtained by using a TRIO-1 GCMS spectrometer
operating at 70 eV and a 200 °C inlet temperature.
NMR (CDCl3, 376.5 MHz): two isomers were evident in the
5
ratio 93:7; major isomer δ -51.8 (s, 3F, CF3), -52.0 (q, J FF
)
11.2 Hz, 3F, CF3), -56.0 (m, 3F, CF3); minor isomer δ -51.6
Ma ter ia ls. Acetone was analytical-grade reagent; hydro-
carbons and dichloromethane were purified by distillation
under nitrogen from the appropriate drying agent.23 All
solvents were stored in the dark over activated 4 Å molecular
sieves and were purged with nitrogen prior to use. (η5-C5H5)2-
Rh2(µ-CO)(µ-η2:η2-CF3C2CF3) was prepared as described in ref
24.
5
(q, J FF ) 10.8 Hz, 3F, CF3), -52.6 (s, 3F, CF3), -55.5 (m, 3F,
CF3). 31P{1H} NMR (CDCl3, 162 MHz, 297 K): δ 36.9 (d, 1J RhP
) 194 Hz, PPh2)sthe signal emerges from a broader doublet
centered at δ 35.2.
P h 2P CtCP P h 2. The dropwise addition of Ph2PCtCPPh2
(36 mg, 0.135 mmol) dissolved in dichloromethane (2 mL) to a
stirred solution of 1 (77 mg, 0.146 mmol) in dichloromethane
(15 mL) resulted in an instant color change from green to
orange. Removal of the solvent under reduced pressure gave
a red residue. Workup by TLC with a 3:1 mixture of petroleum
ether and dichloromethane as the eluent gave two major
bands. An orange band was extracted with dichloromethane,
and the solvent was removed under reduced pressure to yield
orange crystals of (η5-C5H5)2Rh2(CO)(µ-η1:η1-CF3C2CF3)(η1-Ph2-
PCtCPPh2) (4, R ) PPh2; 69 mg, 51%). Anal. Calcd for
The alkynes Ph2PCtCR (R ) H, Ph, PPh2) were prepared
by the dropwise addition of PPh2Cl to the appropriate alkynyl-
Grignard RCtCMgX following the method described by Char-
rier.25 The other alkynes Ph2PCtCR (R ) But, Me, CF3) were
prepared in similar manner from the alkynyl-lithium reagent
and PPh2Cl by the method described by Carty.26 Treatment
of Ph2PCtCR (R ) Me, Ph) with H2O2 in glacial acetic acid
gave the phosphine oxides Ph2P(O)CtCR.25 All of the phos-
phinoalkynes and the oxides were spectroscopically character-
ized by MS and IR and multinuclear NMR spectroscopies.
Rea ction s of (η5-C5H5)2Rh 2(µ-CO)(µ-η2:η2-CF 3C2CF 3) (1)
w ith P h osp h in oa lk yn es. P h 2P CtCBu t. A solution of Ph2-
PCtCBut (36 mg, 0.135 mmol) in dichloromethane (2.0 mL)
was added dropwise to a stirred solution of 1 (61 mg, 0.116
mmol) in dichloromethane (5.0 mL). The green solution
immediately turned to a dark orange color. The solvent was
removed under reduced pressure, and the red residue was
purified by TLC with a 3:1 mixture of petroleum ether and
dichloromethane as the eluent. A major orange band devel-
oped and was extracted with dichloromethane. Removal of
C
41H30F6OP2Rh2: C, 53.5; H, 3.3; F, 12.4; P, 6.8. Found: C,
53.7; H, 3.3; F, 12.5; P, 6.4. MS, m/ z: 920 (<1, [M]+), 892
(<1, [M - CO]+), 526 (6, [M - Ph2PCtCPPh2]+), 498 (<1, [M
- Ph2PCtCPPh2 - CO]+), 394 (30, [Ph2PCtCPPh2]+), 233 (62,
[C10H10Rh]+), 168 (100, [C5H5Rh]+). IR (CH2Cl2), cm-1: ν(CO)
1987 (vs), ν(CtC) 2111 (w). 1H NMR (CDCl3, 400 MHz): δ
2
3
5.00 (s, 5H, C5H5), 5.18 (dd, J RhH ) 1.6 Hz, J PH ) 0.3 Hz,
5H, C5H5), 7.2-7.6 (m, 16H, ortho- and meta-H of C6H5), 7.83
(m, 4H, para-H of C6H5). 19F NMR (CDCl3, 376.5 MHz): δ
-52.0 (q, J FF ) 10.7 Hz, 3F, CF3), -55.3 (m, 3F, CF3). 31P-
5
{1H} NMR (CDCl3, 162 MHz, 297 K): δ 27.6 (br d, J RhP
)
1
189 Hz, 1P, PPh2), -30.8 (s, 1P, uncoordinated PPh2).
Similar workup of a second orange band gave an orange
solid, which was characterized spectroscopically as [(η5-C5H5)2-
Rh2(CO)(µ-η1:η1-CF3C2CF3)]2(η1:η1-Ph2PCtCPPh2) (31 mg, 15%).
IR (CH2Cl2), cm-1: ν(CO) 1991 (vs), ν(CtC) 2116 (w) . 1H
NMR (CDCl3, 400 MHz): δ 4.92 (s, 5H, C5H5), 4.95 (s, 5H,
C5H5), 5.23 (d, J RhH ) 1.2 Hz, 5H, C5H5), 5.25 (d, J RhH ) 1.3
Hz, 5H, C5H5), 7.3-7.7 (m, 20H, C6H5). 19F NMR (CDCl3, 282
MHz): δ -52.3 (m, 3F, CF3), -55.3 (br m, 3F, CF3). 31P{1H}
NMR (CDCl3, 162 MHz, 297 K): δ 17.6 (br d, PPh2).
P h 2P CtCP h . In similar manner, a mixture of Ph2PCtCPh
(45 mg, 0.157 mmol) and 1 (82 mg, 0.155 mmol) in dichlo-
romethane (20 mL) was stirred for a few minutes. The green
solution immediately turned to a reddish color. The reaction
(19) Carty, A. J .; Ng, T. W. J . Chem. Soc., Chem. Commun. 1970,
149.
(20) Went, M. J .; Nickel, T. M.; Yau, S. Y. W. J . Chem. Soc., Chem.
Commun. 1989, 775.
(21) Adams, C. J .; Bruce, M. I.; Horn, E.; Skelton, B. W.; Tiekink,
E. R. T.; White, A. H. J . Chem. Soc., Dalton Trans. 1993, 3299.
(22) Carty, A. J .; Taylor, N. J .; J ohnson, D. K. J . Am. Chem. Soc.
1979, 101, 5422.
(23) Amarego, W. F. L.; Perrin, D. D.; Perrin, D. R. Purification of
Laboratory Chemicals, 2nd ed.; Pergamon: Oxford, 1980.
(24) Dickson, R. S.; J ohnson, S. H.; Pain, G. M. Organomet. Synth.
1988, 4, 283.
2
2
(25) Charrier, C.; Chodkiewicz, W.; Cadiot, P. Bull. Soc. Chim. Fr.
1966, 3, 1002.
(26) Carty, A. J .; Hota, N. K.; Ng, T.; Patel, A. Can. J . Chem. 1971,
49, 2706.

Conversion of Coordinated Phosphinoalkynes
Organometallics, Vol. 16, No. 8, 1997 1533
mixture was filtered, and the solvent was then removed from
the filtrate under reduced pressure. The residue was washed
with cold pentane. This gave orange crystals of (η5-C5H5)2-
Rh2(CO)(µ-η1:η1-CF3C2CF3)(η1-Ph2PCtCPh) (4, R ) Ph; 123
mg, 97%). Anal. Calcd for C35H25F6OPRh2: C, 51.8; H, 3.1;
F, 14.0. Found: C, 52.3; H, 3.3; F, 13.5. MS, m/ z: 812 (5,
[M]+), 784 (100, [M - CO]+), 233 (10, [C10H10Rh]+). IR (CH2-
dichloromethane to which some silica gel (ca. 0.3 g) was added.
The suspension was then stirred at room temperature for 18
h without protection from the air. Periodic monitoring by
infrared spectroscopy indicated a gradual increase in the
intensity of the acyl carbonyl absorption near 1660 cm-1
.
Further TLC of the material with a 3:1 mixture of petroleum
ether and dichloromethane as the eluent separated two orange
bands. Each was extracted with dichloromethane. The in-
frared spectrum of the first extract indicated it was still a
mixture of 4 and the new product. Evaporation of solvent gave
8 mg of residue. Evaporation of solvent from the second
extract gave an orange crystalline solid, which was identified
as (η5-C5H5)2Rh2(µ-C(CF3)C(CF3)C{C(O)Me}PPh2) (6, R ) Me;
57 mg, 60%), mp 280 °C. Anal. Calcd for C29H23F6OPRh2: C,
47.2; H, 3.1; F, 15.4; P, 4.2. Found: C, 47.0; H, 3.2; F, 15.5;
P, 4.4. MS, m/ z: 738 (100, [M]+), 661 (60, [M - Ph]+). IR
(CH2Cl2), cm-1: ν(CO) 1661 (m). 1H NMR (CDCl3, 400 MHz):
Cl2), cm-1
:
ν(CO) 1986 (vs), ν(CtC) 2176 (m). 1H NMR
2
(CDCl3, 400 MHz): δ 5.11 (s, 5H, C5H5), 5.21 (d, J RhH ) 1.5
Hz, 5H, C5H5), 7.3-7.5 (m , 13H, ortho- and meta-H of C6H5),
7.99 (m, 2H, para-H of C6H5). 19F NMR (CDCl3, 376.5 MHz):
two isomers were evident in the ratio 96:4; major isomer δ
5
5
-51.7 (q, J FF ) 11.2 Hz, 3F, CF3), -55.2 (qdd, J FF ) 11.2
3
Hz, J RhF
)
4J PF ) 3.5 Hz, 3F, CF3); minor isomer δ -51.6
(poorly resolved m, 3F, CF3), -54.7 (poorly resolved m, 3F,
CF3). 31P{1H} NMR (CDCl3, 162 MHz, 297 K): δ 30.8 (d, 1J RhP
) 170 Hz, PPh2).
4
2
δ 2.08 (d, J PH ) 1.6 Hz, 3H, CH3), 5.17 (d, J RhH ) 1.0 Hz,
P h 2P CtCMe. When a solution of Ph2PCtCMe (39 mg,
0.174 mmol) in dichloromethane (8 mL) was added dropwise
to a stirred solution of 1 (90 mg, 0.171 mmol) in dichlo-
romethane (20 mL), the green solution instantly turned to a
reddish color. After filtration of the reaction mixture and
removal of the solvent under reduced pressure, the residue
was washed with cold pentane. This gave (η5-C5H5)2Rh2(CO)(µ-
η1:η1-CF3C2CF3)(η1-Ph2PCtCCH3) (4, R ) Me; 129 mg, 100%)
as orange crystals. Anal. Calcd for C30H23F6OPRh2: C, 48.0;
H, 3.1; F, 15.2; P, 4.1. Found: C, 47.9; H, 2.9; F, 15.1; P, 4.2.
MS, m/ z: 750 (10, [M]+), 722 (60, [M - CO]+), 233 (100,
[C10H10Rh]+), 168 (22, [C5H5Rh]+). IR (CH2Cl2), cm-1: ν(CO)
1985 (vs), ν(CtC) 2205 (w). 1H NMR (CDCl3, 400 MHz): δ
2
5H, C5H5), 5.46 (d, J RhH ) 0.8 Hz, 5H, C5H5), 7.2-7.5 (m ,
8H, ortho- and meta-H of C6H5), 7.74 (m, 2H, para-H of C6H5).
19F NMR (CDCl3, 282 MHz): δ -46.4 (qdd, J FF ) 12.4 Hz,
5
4J PF
)
3J RhF ) 3.4 Hz, 3F, CF3), -51.0 (qd, J FF ) 12.4 Hz,
5
3J RhF ) 1.0 Hz, 3F, CF3). 31P{1H} NMR (CDCl3, 162 MHz, 297
1
K): δ 62.0 (d, J RhP ) 153 Hz, PPh2).
R ) P h . A similar experiment was performed with (η5-
C5H5)2Rh2(CO)(µ-η1:η1-CF3C2CF3)(η1-Ph2PCtCPh) (4, R ) Ph).
TLC of the complex (40 mg, 0.129 mmol) with a 3:1 mixture
of petroleum ether and dichloromethane as the eluent sepa-
rated a major orange band from trace amounts of yellow and
orange compounds, which were rejected. After 2.5 h, the major
orange band was extracted with dichloromethane and the
solvent was removed under reduced pressure. This gave dark
orange crystals of (η5-C5H5)2Rh2(µ-C(CF3)C(CF3)C{C(O)Ph}-
PPh2) (6, R ) Ph; 36 mg, 91%), mp ∼210 °C. Anal. Calcd for
4
2.04 (d, J PH ) 3.5 Hz, 3H, CH3), 5.09 (s, 5H, C5H5), 5.17 (d,
2J RhH ) 1.7 Hz, 5H, C5H5), 7.2-7.5 (m , 8H, ortho- and meta-H
of C6H5), 7.93 (m, 2H, para-H of C6H5). 19F NMR (CDCl3, 376.5
MHz): two isomers were evident in the ratio 96:4; major
5
3
C
34H25F6OPRh2: C, 51.0; H, 3.2; F, 14.2. Found: C, 50.8; H,
isomer δ -52.0 (qd, J FF ) 11.5 Hz, J RhF ) 1.6 Hz, 3F, CF3),
3.2; F, 14.1. MS, m/ z: 800 (28, [M]+), 723 (20, [M - Ph]+). IR
5
3
4
-55.1 (qdd, J FF ) 11.5 Hz, J RhF ) J PF ) 3.5 Hz, 3F, CF3);
minor isomer δ -51.9 (qd, J FF ) 11.4 Hz, J RhF ) 3.0 Hz, 3F,
CF3), -54.7 (qdd, J FF ) 11.4 Hz, J RhF ) J PF ) 3.6 Hz, 3F,
CF3). 31P{1H} NMR (CDCl3, 162 MHz, 297 K): δ 30.9 (d, 1J RhP
) 188 Hz, PPh2).
(CH2Cl2), cm-1: ν(CO) 1660 (m). 1H NMR (CDCl3, 300 MHz):
δ 5.13 (d, J RhH ) 1.5 Hz, 5H, C5H5), 5.49 (d, J RhH ) 0.8 Hz,
5H, C5H5), 6.8-7.7 (m, 15H, C6H5). 19F NMR (CDCl3, 282
MHz): δ -45.9 (q, J FF ) 14.7 Hz, 3F, CF3), -49.6 (qd, J FF
5
3
2
2
5
3
4
5
5
)
14.7 Hz, J RhF ) 2.5 Hz, 3F, CF3). 31P{1H} NMR (CDCl3, 162
MHz, 297 K): δ 60.2 (dd, 1J RhP ) 153 Hz, 2J RhP ) 3.2 Hz, PPh2).
F u r th er In vestiga tion of F a ctor s Affectin g th e Con -
ver sion of 4 to 6, R ) P h ; O2. Oxygen was bubbled through
a solution of 4 (3 mg) in dichloromethane for 1 h. The reaction
solution was stirred at room temperature for a further 15 h.
An infrared spectrum of the solution showed that 4 was the
only species present.
3
P h 2P CtCH. Ph2PCtCH (21 mg, 0.100 mmol) was dis-
solved in dichloromethane (5 mL) and added dropwise to a
stirred solution of 1 (53 mg, 0.101 mmol) in dichloromethane
(10 mL). The green solution instantly changed to a red color.
Immediate removal of the solvent under reduced pressure left
a red-brown residue. NMR results indicated that the product
was not pure, but attempts to purify it by recrystallization or
TLC resulted in further decomposition. The orange complex
was characterized spectroscopically as (η5-C5H5)2Rh2(CO)(µ-
η1:η1-CF3C2CF3)(η1-Ph2PCtCH). MS, m/ z: 736 (<1, [M]+),
708 (<2, [M - CO]+), 233 (100, [C10H10Rh]+). IR (CH2Cl2),
cm-1: ν(CO) 1988 (s), ν(CtC) 2057 (w). 1H NMR (toluene-d8,
300 MHz): δ 4.30 (s, 1H, CtC-H), 4.95 (s, 5H, C5H5), 5.04 (d,
2J RhH ) 1.7 Hz, 5H, C5H5), 6.9-7.8 (m, 10H, C6H5). 19F NMR
H2O. The complex 4 (4 mg) was dissolved in dichlo-
romethane (10 mL) containing some added water (0.5 mL).
Nitrogen was bubbled through the mixture, and it was then
stirred at room temperature for 15 h. The mixture was dried
over calcium chloride and filtered. An infrared spectrum of
the filtrate established that only unchanged 4 was present.
SiO2. Oven dried silica (0.5 g) was added to a solution of 4
(4 mg) in dichloromethane (10 mL). The solution was stirred
for 15 h under a nitrogen atmosphere. The silica was removed
by filtration. An infrared spectrum of the filtrate revealed only
unchanged 4.
SiO2 + H2O. A slurry containing 4 (4 mg), silica (0.5 g),
dichloromethane (10 mL), and water (0.5 mL) was stirred
under nitrogen for 15 h. Filtration followed by infrared
examination showed that no reaction had occurred.
SiO2 + O2. Oxygen was bubbled through a slurry contain-
ing 4 (5 mg) and silica (0.5 g) in dichloromethane (10 mL).
The slurry was stirred for 15 h under an oxygen atmosphere
and was then filtered. An infrared spectrum of the filtrate
showed the presence of 6 (R ) Ph, medium intensity ν(CO)
absortion at 1661 cm-1) and a trace of unchanged 4 (weak ν-
(CO) absortion at 1985 cm-1).
5
(toluene-d8, 282 MHz): δ -49.6 (q, J FF ) 11.3 Hz, 3F, CF3),
5
3
4
-53.5 (qdd, J FF ) 11.3 Hz, J RhF ) J PF ) 3.3 Hz, 3F, CF3).
31P{1H} NMR (toluene-d8, 162 MHz, 297 K): δ 31.4 (br d, 1J RhP
) 181 Hz, PPh2).
Con ver sion of (η5-C5H5)2Rh 2(CO)(µ-η1:η1-CF 3C2CF 3)(η1-
P h 2P CtCR) (4) to (η5-C5H5)2Rh 2(µ-C(CF3)C(CF3)C{C(O)R}-
P P h 2) (6). R ) Me. A spectroscopically pure sample of (η5-
C5H5)2Rh2(CO)(µ-η1:η1-CF3C2CF3)(η1-Ph2PCtCMe) (4, R ) Me)
(97 mg, 0.129 mmol) was chromatographed by TLC with a 3:1
mixture of petroleum ether and dichloromethane as the eluent.
The chromatogram was left to develop for 1 h; this separated
three bands from an immobile base band containing decom-
position material. A minor purple band was rejected. The two
major bands were individually extracted with dichloromethane,
and solvent was removed under reduced pressure. The first
extract (orange) was identified as unchanged 4 (4 mg). The
infrared spectrum of the second extract (87 mg) indicated it
was a mixture of 4 and a new compound with an acyl carbonyl
Com p a r ison of Exten t of Con ver sion of 4 w ith R ) P h
a n d 4 w ith R ) Me. Samples of 4 with R ) Ph (6 mg) and
4 with R ) Me (6 mg) were applied to separate halves of a
absorption near 1660 cm-1
. This extract was dissolved in

1534 Organometallics, Vol. 16, No. 8, 1997
Dickson et al.
Ta ble 1. Cr ysta l Da ta a n d Exp er im en ta l Deta ils
formula
fw
Rh2C34H25F6OP
800.4
cryst syst
space group
cell dimens
triclinic
P1h
a
b
c
14.165(2) Å
11.707(1) Å
9.522(1) Å
71.893(5)°
83.693(4)°
86.801(8)°
1491.4(3) Å3, 2
1.78, 1.78(1) g cm-3
792
R
â
γ
cell vol, Z
density (calcd, obs)
F(000)
abs coeff
Mo KR radiation
temp
1.21 mm-1
(λ ) 0.7107 Å)
20(1) °C
F igu r e 1. Molecular structure of (η5-C5H5)2Rh2(µ-C(CF3)C-
(CF3)C{C(O)Ph}PPh2) (6; R ) Ph) showing the atom
labeling scheme; the cyclopentadienyl rings (C(25)-C(29))
and (C(30)-C(34)) are omitted for clarity.
single TLC plate. The complexes were slowly eluted with a
3:1 mixture of petroleum ether and dichloromethane without
protection from the air. After 60 min, the plate was removed
from the eluent mix. The chromatogram for 4 with R ) Me
showed three orange bands which were extracted together.
Analysis of the combined extract by 19F NMR spectroscopy
established that the mixture contained 20% 4 and 80% 6. For
6, R ) Ph, the chromatogram showed one major orange band
and several minor bands, which were rejected. Extraction of
the orange band followed by 19F NMR analysis showed that it
contained only 6.
Ta ble 2. Selected Bon d Len gth s (Å) for 6 (R ) P h ),
w ith Esd Va lu es in P a r en th eses
Rh(1)-P
2.187(1)
2.037(4)
2.6751(4)
2.105(4)
2.047(4)
2.148(4)
2.941(1)
C(2)-C(3)
C(3)-C(5)
C(5)-C(6)
C(6)-O
1.385(7)
1.468(6)
1.524(7)
1.207(5)
1.493(6)
1.815(4)
1.828(4)
1.836(4)
Rh(1)-C(2)
Rh(1)-Rh(2)
Rh(2)-C(2)
Rh(2)-C(3)
Rh(2)-C(5)
Rh(2)‚‚‚P
C(6)-C(7)
P-C(5)
Rea ction s of 1 w ith P h 2P (O)CtCR. P h 2P (O)CtCP h .
Ph2P(O)CtCPh (31 mg, 0.103 mmol) was dissolved in dichlo-
romethane (3 mL) and added dropwise to a stirred solution of
1 (24 mg, 0.045 mmol) in dichloromethane (5 mL). The green
solution was stirred for 24 h; during this time, the color of the
solution changed to a red-brown color. The solvent was
removed under reduced pressure, and the residue was purified
by TLC with a 1:1:1 mixture of petroleum ether, acetone, and
diethyl ether as the eluent. After the major red-orange band
was extracted with acetone and the solvent was removed under
reduced pressure, (η5-C5H5)2Rh2[µ-η1:η1:η2:η2-C4(CF3)2{P(O)-
Ph2}(Ph)CO] (2, 17 mg, 45%) was obtained as red-brown
crystals. MS, m/z: 828 (12, [M]+), 800 (14, [M - CO]+), 751
(8, [M - Ph]+). IR (CH2Cl2) cm-1: ν(CO) 1712 (m), ν (PdO)
1184 (m). 1H NMR (CDCl3, 300 MHz): δ 5.49 (s, 5H, C5H5),
5.71 (s, 5H, C5H5), 7.0-7.95 (m, 15H, C6H5). 19F NMR
P-C(13)
P-C(19)
from the calculated Bragg scattering angle at a scan rate of
0.05° s-1
A total of 8699 unique data were collected,
.
((h,(k,+l), 5458 of which were considered to be observed (I
g 3σ(I)]) and used in the final refinement. Three standard
reflections monitored every 4 h showed no significant variation
in intensity over the data collection period. Crystal data are
given in Table 1. The cell parameters were determined from
24 accurately centered reflections measured in the range 18°
< 2θ e 40° and were refined by least-squares methods using
the standard Philips program.
Intensity data were processed as described previously.27
A
face-indexed numerical absorption correction was applied28 on
six crystal faces, the maximum and minimum transmission
factors being 0.844 and 0.778, respectively. The atomic
scattering factors for neutral atoms were corrected for anoma-
lous dispersion.29 All calculations were performed on a VAX
6250 computer. The program used for least-squares refine-
ment was SHELX-76.28
5
5
(CDCl3,): δ -48.9 (q, J FF ) 11.3 Hz, 3F, CF3), -54.9 (q, J FF
) 11.3 Hz, 3F, CF3). 31P{1H} NMR (CDCl3, 162 MHz): δ 31.6
(s, Ph2PdO).
P h 2P (O)CtCMe. Ph2P(O)CtCMe (20 mg, 0.083 mmol)
was dissolved in dichloromethane (4 mL) and added dropwise
to a stirred solution of 1 (21 mg, 0.040 mmol) in dichlo-
romethane (5 mL). The green solution was stirred for 4 days;
the color of the final solution was orange. The solvent was
removed under reduced pressure. The residue was dissolved
in dichloromethane, and hexane was added to precipitate out
excess Ph2P(O)CtCMe, which was removed by filtration. The
red filtrate was evaporated to dryness, yielding red crystals
of (η5-C5H5)2Rh2{µ-η1:η1:η4-C4(CF3)2{P(O)Ph2}Me} (3, 14 mg,
49%). MS, m/ z: 729 (42, [M]+), 723 (3, [M - Me]+), 710 (6,
[M - F]+), 673 (30, [C24H18R2F6PO]+), 233 (100, [C10H10Rh]+),
168 (48, [C5H5Rh]+). IR (CH2Cl2) cm-1: ν(PdO) 1198 (s). 1H
The structure was solved by conventional Patterson and
Fourier methods. Final refinement was by full-matrix least-
squares employing anisotropic thermal parameters for all non-
hydrogen atoms and a single isotropic thermal parameter for
hydrogen (which refined to 0.070(3) Å2) positioned in geo-
metrically idealized positions (d(C-H) ) 0.96 Å). At conver-
gence (398 variables, 5458 observed data), R was 0.039 and
Rw ) 0.039, where Rw ) ∑|Fo - Fc|)w1/2/∑|Fo|w1/2 and w )
[σ2(Fo)]-1. The goodness of fit value ([∑w(|Fo| - |Fc|)2/(Nobs
-
params)]1/2) was 1.31. The highest peak in the difference
4
N
NMR (CDCl3, 300 MHz): δ 2.15 (d, J PH ) 2.1 Hz, 3H, CH3),
Fourier synthesis was 0.94 e‚Å-3
.
2
4.68 (s, 5H, C5H5), 5.77 (d, J RhH ) 0.6 Hz, 5H, C5H5), 7.42-
7.87 (m, 10H, C6H5). 19F NMR (CDCl3, 282 MHz): δ -48.1
(q, 5J FF ) 13.6 Hz, 3F, CF3), -50.1 (q, 5J FF )13.6 Hz, 3F, CF3).
31P{1H} NMR (CDCl3, 162 MHz): δ 32.9 (s, Ph2PdO).
Final atomic parameters are given in the Supporting
Information, selected bond lengths in Table 2 and selected
bond angles in Table 3. Figure 1 shows the atomic labeling
scheme used.
X-r a y Str u ctu r e Deter m in a tion . Crystals of 6 (R ) Ph)
were grown by slow evaporation of the solvent from a solution
in dichloromethane. A representative dark red tabular crystal
of approximate dimensions (0.16 × 0.18 × 0.26 mm) was used
for data collection. Intensity measurements were made on a
Philips PW1100 diffractometer using graphite-monochromated
Mo KR radiation with 6° < 2θ e 60°, operating in an ω scan
mode with a symmetric scan range of ((0.75 + 0.15 tan θ)
(27) Fallon, G. D.; Gatehouse, B. M. J . Solid State Chem. 1980, 34,
193.
(28) Sheldrick, G. M. SHELX-76 Program for Crystal Structure
Determination; Cambridge University: Cambridge, England, 1975.
(29) International Tables for X-ray Crystallography; Ibers, J . A.,
Hamilton, W. C., Eds.; Kynoch Press: Birmingham, England, 1974;
Vol. IV.

Conversion of Coordinated Phosphinoalkynes
Organometallics, Vol. 16, No. 8, 1997 1535
Ta ble 3. Selected Bon d An gles (d eg) for 6 (R )
P h ), w ith Esd Va lu es in P a r en th eses
C(2)-Rh(1)-P
83.0(1)
50.9(1)
73.7(0)
39.0(2)
40.9(2)
77.2(1)
69.1(2)
48.7(1)
78.4(1)
110.6(2)
108.8(2)
C(5)-P-Rh(1)
C(13)-P-C(19)
C(13)-P-Rh(1)
C(19)-P-Rh(1)
C(2)-C(3)-C(5)
C(3)-C(5)-C(6)
C(3)-C(5)-P
100.0(1)
103.0(2)
115.4(1)
118.9(2)
115.4(3)
125.0(3)
110.1(3)
120.9(3)
120.4(4)
120.4(4)
119.2(3)
C(2)-Rh(1)-Rh(2)
P-Rh(1)-Rh(2)
C(3)-Rh(2)-C(2)
C(3)-Rh(2)-C(5)
C(3)-Rh(2)-Rh(1)
C(2)-Rh(2)-C(5)
C(2)-Rh(2)-Rh(1)
C(5)-Rh(2)-Rh(1)
C(5)-P-C(13)
C(6)-C(5)-P
O-C(6)-C(7)
O-C(6)-C(5)
C(7)-C(6)-C(5)
C(5)-P-C(19)
Resu lts
F or m a tion of th e Com p lexes (η5-C5H5)2Rh 2(CO)-
(µ-η1:η1-CF 3C2CF 3)(η1-P h 2P CtCR), R ) Bu t, CF 3 or
P P h 2. When Ph2PCtCBut was added to 1 in dichlo-
romethane, the color of the solution changed immedi-
ately from green to red. Chromatographic workup
yielded (η5-C5H5)2Rh2(CO)(µ-η1:η1-CF3C2CF3)(η1-Ph2-
PCtCBut), which was isolated as red-orange crystals
in almost 80% yield. Formation of this complex occurs
without the loss of ligands from 1 and involves the well-
established 90° rotation of the alkyne.1 The product has
been fully characterized by elemental analysis and
various spectroscopic techniques, which indicate that
the phosphinoalkyne is attached exclusively from phos-
phorus. Thus, the 31P{1H} NMR spectrum exhibits a
doublet resonance at δ 28.3 with a rhodium-phosphorus
coupling of 188 Hz, and there is a free alkyne stretching
absorption in the IR spectrum at 2169 cm-1. The IR
spectrum also shows a terminal carbonyl absorption at
1985 cm-1. These and other spectroscopic results are
consistent with the structure of 4 with R ) But, which
is analogous to those established for other complexes
of the type (η5-C5H5)2Rh2(CO)(µ-η1:η1-CF3C2CF3)(L).2,30
In these complexes, the preferred orientation of CO and
F igu r e 2. Variable temperature 31P{1H} NMR spectra for
(η5-C5H5)2Rh2(CO)(µ-η1:η1-CF3C2CF3)(η1-Ph2PCtCR): (a) R
) But, (b) R ) Me.
F igu r e 3. Fischer projection down the P-Rh bond of one
rotamer of complex 4.
of the coordinated phosphinoalkyne about the Rh-P
bond. From steric considerations, three orientations of
the phosphinoalkyne would be favored. One of these is
represented in Figure 3; the others are generated by
120° rotations of one set of ligands. At elevated tem-
peratures, rotation would be rapid, leading to a sharp
doublet in the NMR spectrum. At reduced temperature,
one conformer could be frozen out, again generating a
sharp doublet. The doublet would be broad and poorly
resolved at intermediate temperatures. It is interesting
to note that restricted rotation about Rh-P bonds has
been observed previously for the complexes (η5-C5Me5)-
Rh{P(p-tolyl)3}(C6F5)Br32 and (η5-C5H5)2Rh2(CO)(µ-η1:
η1-CF3C2CF3){P(p-tolyl)3}.33
An analogous complex (4, R ) CF3) was obtained in
quantitative yield when Ph2PCtCCF3 was added to 1.
Spectroscopic results indicated a 93:7 ratio of trans to
cis isomer for this orange complex.
When Ph2PCtCPPh2 was added to 1, the complex 4
with R ) PPh2 was formed as orange crystals in greater
than 50% yield. Again, the spectroscopic results (see
L is trans, but in the present case, the 19F NMR
spectrum shows that a small amount of the correspond-
ing cis isomer is also present, with the ratio of trans:cis
being 95:5. We have not previously seen evidence for
both cis and trans isomers of the complexes (η5-C5H5)2-
Rh2(CO)(µ-η1:η1-CF3C2CF3)(L) when L is a tertiary
phosphane. However, when L ) CO, the two isomers
can be separated by TLC and the cis isomer transforms
to the trans isomer when left in solution.31
The 31P{1H} NMR spectrum of 4 (R ) But) showed
an unusual temperature dependence, which is illus-
trated in Figure 2. The doublet is sharp and well-
resolved at low temperature (-83 °C) but is broad and
unresolved near room temperature. When the solution
is warmed further, the peaks begin to sharpen again.
We suggest that these changes can be related to rotation
(30) Bixler, J . W.; Bond, A. M.; Dickson, R. S.; Fallon, G. D.; Nesbit,
R. J .; Pateras, H. Organometallics 1987, 6, 2508.
(31) Dickson, R. S.; Gatehouse, B. M.; Nesbit, M. C.; Pain, G. N. J .
Organomet. Chem. 1981, 215, 97.
(32) J ones, W. D.; Feher, F. J . Inorg. Chem. 1984, 23, 2376.
(33) Paravagna, O. M.; Dickson, R. S. Unpublished observation.

1536 Organometallics, Vol. 16, No. 8, 1997
Dickson et al.
Experimental Section) were consistent with the pro-
posed structure. At -50 °C, the 31P{1H} NMR spectrum
shows a doublet at δ 27.6, with Rh-P coupling of 189
Hz, and a singlet at δ -30.8. This clearly indicates that
only one phosphorus atom is coordinated to rhodium.
Again, the doublet broadens significantly as the tem-
perature of the solution is raised toward room temper-
ature, but the resonance for the uncoordinated phos-
phorus remains sharp.
A second product is isolated from this reaction, and
it has been characterized spectroscopically as [(η5-
C 5 H 5 )2 R h 2 (C O )(µ-η1 :η1 -C F 3 C 2 C F 3 )]2 (η1 :η1 -P h 2 -
PCtCPPh2) (5). The 31P{1H} NMR spectrum of this
spectra, no absorptions are observed for a terminal
carbonyl or a free CtC bond; there is however, an
absorption within the region of 1660-1695 cm-1 which
1
is attributed to a ketonic carbonyl. In the H and 19F
NMR spectra, there are two cyclopentadienyl and two
trifluoromethyl resonances consistent with an unsym-
metrical structure. There is a doublet resonance near
δ 61-64 in the 31P{1H} NMR spectra with rhodium-
phosphorus couplings of 127 (R ) H) and 167 (R ) Ph)
Hz. These chemical shifts are moved about 30 ppm
downfield from those for the initial complexes 4.
At face value, these data are consistent with the
formal loss of C in the conversion of 4 to 6. This
probably arises through the loss of CO and the gain of
O. However, the precise nature of the new ligand in 6
is difficult to visualize. Since it was not possible to
deduce the structure of 6 from the spectroscopic evi-
dence, determination of the molecular structure of one
of the complexes (R ) Ph) was undertaken by X-ray
crystallography. Figure 1 shows a molecular core
diagram of the structure of the complex (6, R ) Ph). It
demonstrates that components of the phosphinoalkyne
and the fluorinated alkyne have condensed to form a
unit of the type C(CF3)dC(CF3)C{C(dO)R}PPh2. The
new ligand is attached to the Rh-Rh bond as shown in
Figure 4. The P and C(2) ends of the ligand are
σ-attached to one rhodium atom, and there is an η2:η1-
linkage of C(2)-C(3)-C(5) to the second rhodium atom.
The incorporation of a ketonic function in the new ligand
is of particular interest; the ketonic oxygen is not
involved in the attachment. Although the source of the
oxygen in the ligand has not been determined, we favor
a concerted pathway involving the loss of the terminal
carbonyl in 4, transfer of an oxygen atom from the
oxygenated silica surface to the â-carbon of the phos-
phinoalkyne, and condensation of the phosphino-ketone
and hexafluorobut-2-yne units. The overall process is
outlined in Figure 5.
5
product shows a single broad doublet at δ 17.6, but other
spectroscopic properties are similar to those of 4 with
R ) PPh2. The isolated yield of 5 was 15%. The
complex 5 is presumably formed by the further reaction
of 4 (R ) PPh2) with 1. Similar reactions have been
observed with (η5-C5H5)2Rh2(CO)(µ-η1:η1-CF3C2CF3)(L),
where L is a bis(phosphine) of the type Ph2P(CH2)n-
PPh2.34
Rea ction of 1 w ith P h 2P CtCR (R ) P h , Me, H).
Each of the phosphinoalkynes Ph2PCtCR (R ) Ph, Me,
H) adds coordinatively to 1 to give the appropriate
addition product 4. The complex 4 with R ) H could
not be obtained analytically pure because it decomposed
when kept in solution during attempted recrystalization
and chromatography. The spectroscopic results for
these complexes (see Experimental Section) are similar
to those previously discussed for 4 with R ) But. The
31P{1H} NMR spectra for the complexes 4 with R ) Ph
and Me display the same type of temperature depen-
dence as described previously for 4 with R ) But and
PPh2). However, the extent of line broadening at
intermediate temperatures depends on the mass of the
alkyne substituent. The spectra for 4 with R ) But and
4 with R ) Me are compared in Figure 2. Presumably,
there is a shallower energy well for the rotation when
the substituent has a lower mass.
It is known that the uncoordinated triple bonds in
coordinated phosphinoalkynes are susceptible to nu-
cleophilic attack. For example, phosphino-enolates are
formed by the controlled hydrolysis of complexes of the
type cis-[MCl2(Ph2PCtCCF3)2], where M ) Pd or Pt.7,8
We have also previously reported the transfer of oxygen
atoms from silica to ligand atoms during the chromato-
graphic workup of the complex (η5-C5H5)2Rh2{η1:η1: η2-
C(CF3)C(CF3)C(H)C(But)}; in this case, the product
incorporates an unsaturated keto-ether.35 There are
also many examples of condensation reactions between
hexafluorobut-2-yne and transient species coordinated
to the Rh-Rh bond in intermediates derived from 1.36
An alternative pathway involving cleavage of the P-C
and/or CtC bonds and CO insertion is much less likely
because it involves the need for elimination of one of
the alkyne carbons.
When the complexes 4 with R ) Ph and Me are
stirred in solution in the presence of chromatographic
silica and oxygen, there is a transformation to new
complexes of the formula (η5-C5H5)Rh2(µ-C(CF3)C(CF3)C-
{C(O)R}PPh2) (6). A molecular ion is observed for these
(34) County, G. R.; Dickson, R. S.; Fallon, G. D.; J enkins, S. M.;
J ohnson, J . J . Organomet. Chem. 1996, 296, 279.
(35) Dickson, R. S.; Fallon, G. D.; McLure, F. I.; Nesbit, R. J .
Organometallics 1987, 6, 215.
(36) See, for example: Dickson, R. S.; Fallon, G. D.; Nesbit, R. J .;
Pain, G. N. Organometallics 1985, 4, 355. Dickson, R. S.; Fallon, G.
D.; J enkins, S. M.; Nesbit, R. J . Organometallics 1987, 6, 1240.
Dickson, R. S.; Nesbit, R. J .; Pateras, H.; Patrick, J . M.; White, A. H.
J . Organomet. Chem. 1984, 265, C25. Dickson, R. S.; Nesbit, R. J .;
Pateras, H.; Baimbridge, W. Organometallics 1985, 4, 2128.
(37) Braunstein, P.; Chauvin, Y.; Mercier, S.; Saussine, L.; De Cian,
A.; Fischer, J . J . Chem. Soc., Chem. Commun. 1994, 2203.
complexes in the mass spectrum. In the infrared

Conversion of Coordinated Phosphinoalkynes
Organometallics, Vol. 16, No. 8, 1997 1537
ing that some phosphino-enolato ruthenium(II) com-
plexes react with alkynes to form ligands of the type
C(H)dC(R)CR′{CdO)R′′}PPh2, which are closely related
to the one in our complex. However, in the ruthenium
complex, the new ligand is η3-coordinated with attach-
ments from P, C, and a ketonic oxygen.39
Rea ction s of 1 w ith P h 2P (O)CtCR. Before the
structure of 6 was established, it seemed possible that
oxygen addition was to the phosphorus atom. To help
assess this idea, the reactions of 1 with two phosphine
oxides Ph2P(O)CtCR (R ) Ph, Me) were investigated.
These reactions occurred slowly at room temperature,
and the phosphine oxides behaved as alkynes. Different
products were obtained for the two systems.
F igu r e 4. Representation of the bonding in complex 6 (R
) Ph).
The reactions with Ph2P(O)CtCPh yielded the di-
metallapentadienone product (η5-C5H5)2Rh2{µ-η1:η2:η2:
η1-C4(CF3)2(Ph2PO)(Ph)CO} in 45% yield. Spectroscopic
data indicates that this has the structure of 2 (R, R′ )
Ph2PO, Ph). The cyclometallabutadiene complex (η5-
C5H5)2Rh2{µ-η2:η4-C4(CF3)2(Ph2PO)(Me)} was obtained
in 49% yield from the reaction with Ph2P(O)tCMe.
Ack n ow led gm en t. We thank the Australian Re-
search Council for financial support.
F igu r e 5. Pathway for the conversion of 4 to 6; cyclopen-
tadienyl groups omitted for clarity.
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
positional coordinates, anisotropic thermal parameters, bond
lengths, and bond angles, as well as a complete structural
diagram for 6 (R ) Ph) (13 pages). Ordering information is
given on any current masthead page.
We are aware of several examples of metal complexes
containing related phosphino-enolato ligands. These
are formed by reaction of nickel complexes with phena-
cylidenetriphenylphosphoranes, Ph3PdCHC(dO)R,37 or
of rhodium complexes with â-keto phosphines, Ph2PCH-
(R)C(dO)R′,38 and in each case, there is a three-electron
P-O chelation of the ligand to the metal. It is interest-
OM960830E
(38) Demerseman, B.; Guilbert, B.; Renouard, C.; Gonzalez, M.;
Dixneuf, P. H.; Masi, D.; Mealli, C. Organometallics 1993, 12, 3906.
(39) Crochet, P.; Demerseman, B. Organometallics 1995, 14, 2173.