Reductive elimination of [Ph2C=C=CHPR3]BF4 from the rhodium(III)-allenyl derivatives [Rh(acac){CH=C=CPh2}(PR3)2]BF4 (PR3 = PCy3, PiPr3)

Article abstract of DOI:10.1021/om970567x

The olefinic unit of the complexes Rh(acac)(cyclooctadiene)(PR₃) (PR₃ = PCy₃ (1), PiPr₃ (2)) is displaced by 1,1-diphenyl-2-propyn-1-ol, to afford Rh(acac){η²-HC=CC(OH)Ph₂}(PR₃)

Full text of DOI:10.1021/om970567x

4572
Organometallics 1997, 16, 4572-4580
Red u ctive Elim in a tion of [P h 2CdCdCHP R3]BF 4 fr om th e
Rh od iu m (III)-Allen yl Der iva tives
[Rh (a ca c){CHdCdCP h 2}(P R3)2]BF 4 (P R3 ) P Cy3, P iP r 3)
Miguel A. Esteruelas,* Fernando J . Lahoz, Marta Mart´ın, Enrique On˜ate, and
Luis A. Oro*
Departamento de Qu´ımica Inorga´nica, Instituto de Ciencia de Materiales de Arago´n,
Universidad de Zaragoza-CSIC, 50009 Zaragoza, Spain
Received J uly 7, 1997X
The olefinic unit of the complexes Rh(acac)(cyclooctadiene)(PR3) (PR3 ) PCy3 (1), PiPr3
(2)) is displaced by 1,1-diphenyl-2-propyn-1-ol, to afford Rh(acac){η2-HCtCC(OH)Ph2}(PR3)
(PR3 ) PCy3 (3), PiPr3 (4)). At 60 °C, in toluene as solvent, and in the presence of 1 equiv
of phosphine, complexes 3 and 4 evolve into Rh(acac)H{CtCC(OH)Ph2}(PR3)2 (PR3 ) PCy3
(5), PiPr3 (6)). At -78 °C, the treatment of complex 5 with HBF4‚OEt2 leads to the
allenylphosphonium compound [Rh(acac){η2-CH(PCy3)dCdCPh2}(PCy3)]BF4 (7). The X-ray
crystal structure analysis of 7 reveals that the coordination geometry around the rhodium
center is almost square-planar with the CH(PCy3)dC bond disposed perpendicular to the
coordination plane of the rhodium center. The allenylphosphonium ligand of 7 is easily
displaced by carbon monoxide, to give Rh(acac)(CO)(PCy3) (8) and [Ph2CdCdCHPCy3]BF4
(9). At -78 °C, the protonation of complex 6 leads to the five-coordinate rhodium(III)-
allenyl derivative [Rh(acac){CHdCdCPh2}(PiPr3)2]BF4 (10), which evolves in solution into
[Rh(acac){η2-CH(PiPr3)dCdCPh2}(PiPr3)]BF4 (11). For this isomerization first-order con-
stants kobs were obtained in CD2Cl2, which give activation parameters of ∆Hq ) 23 ( 2 kcal
mol-1 and ∆Sq ) 2 ( 2 cal K-1 mol-1. Similarly to 7, the reaction of complex 11 with carbon
monoxide affords Rh(acac)(CO)(PiPr3) (12) and [Ph2CdCdCHPiPr3]BF4 (13).
In tr od u ction
plexes PdI(CHdCHCO2R)(PPh3)2, on heating in benzene
at 75-80 °C, formed PdI{η2-CH(PPh3)dCHCO2R}(PPh3)
(R ) Me, Et). The X-ray investigation of PdI{η2-
CH(PPh3)dCHCO2Me}(PPh3) reveals that the carbon-
carbon double bond of the alkenylphosphonium ligand
lies in the coordination plane, and therefore, the com-
plex can be regarded as a palladium(0) derivative.
Previously, Guerchais and co-workers2a had observed
that the complex W(η5-C5H5)(CHdCHCN)(CO)2(PPh3)
similarly evolves into W(η5-C5H5)(CO)2{η2-CH(PPh3)d
CHCN}.
Reductive elimination, the reverse of oxidative addi-
tion, leads to the extrusion of an X-Y fragment from a
LnM(X)(Y) (or [LnM(X)(Y)]+) complex. For mononuclear
compounds, these reactions involve a decrease of 2 in
the oxidation number of the metallic center and a
decrease in coordination number for the metal.1
In general, reductive elimination takes place when X
and Y are one-electron ligands and, in this way, the X-Y
fragments are neutral molecules (eqs 1 and 2). The
In the search for transition-metal complexes which
are catalytically active for the addition of germanes and
stannanes to alkynes, we have recently reported on the
reactivity of the (acetylacetonato)rhodium compound
Rh(acac)(cyclooctene)(PCy3), which is formed by ligand
displacement from Rh(acac)(cyclooctene)2 and PCy3.3
The cyclooctene compound Rh(acac)(cyclooctene)(PCy3)
reacts with HGeEt3 to give Rh(acac)H(GeEt3)(PCy3) and
with HSnPh3 to afford Rh(acac)H(SnPh3)(PCy3). The
hydrido-germyl complex reacts with methyl propiolate
and phenylacetylene to give square-planar complexes,
Rh(acac){η2-CH(GeEt3)dCHR}(PCy3), containing the
corresponding germane-olefin. In contrast to the case
for Rh(acac)H(GeEt3)(PCy3), the related reactions with
Rh(acac)H(SnPh3)(PCy3) lead to rhodium(III) alkenyl-
stannyl derivatives, which are stable and do not evolve
by reductive elimination of the stannaolefins.4
extrusion of [A-X]+ cations as results of the elimination
of a one-electron ligand and a two-electron molecule (eqs
3 and 4) is uncommon. Although, it was not rationalized
as a reductive process, eq 3 has been previously ob-
served in a few cases for neutral complexes.2 In 1985,
Rubinskaya and co-workers2b reported that the com-
The olefinic unit of Rh(acac)(cyclooctene)(PCy3) can
be also easily displaced by strong π-acceptor ligands
X Abstract published in Advance ACS Abstracts, September 1, 1997.
(1) Crabtree, R. H. The Organometallic Chemistry of the Transition
Metals; Wiley: New York, 1988; Chapter 6.
(2) (a) Scordia, H.; Kergoat, R.; Kubicki, M. M.; Guerchais, J . E.;
L’Haridon, P. Organometallics 1983, 2, 1681. (b) Rybin, L. V.; Petrov-
skaya, E. A.; Rubinskaya, M. I.; Kuz’mina, L. G.; Struchkov, Yu. T.;
Kaverin, V. V.; Koneva, N. Yu. J . Organomet. Chem. 1985, 288, 119.
(3) Esteruelas, M. A.; Lahoz, F. J .; On˜ate, E.; Oro, L. A.; Rodr´ıguez,
L.; Steinert, P.; Werner, H. Organometallics 1996, 15, 3436.
(4) Esteruelas, M. A.; Lahoz, F. J .; On˜ate, E.; Oro, L. A.; Rodr´ıguez,
L. Organometallics 1996, 15, 3670.
S0276-7333(97)00567-0 CCC: $14.00 © 1997 American Chemical Society

Rhodium(III)-Allenyl Derivatives
Organometallics, Vol. 16, No. 21, 1997 4573
Sch em e 1a
of the complex Rh(acac)(cyclooctene)(PCy3) (1) and the
related derivative Rh(acac)(cyclooctene)(PiPr3) (2) can
be displaced by 1,1-diphenyl-2-propyn-1-ol to afford the
π-alkyne compounds Rh(acac){η2-HCtCC(OH)Ph2}(PR3)
(PR3 ) PCy3 (3), PiPr3 (4)). The reactions were carried
out at -78 °C, in pentane as solvent, and the reaction
products were isolated as yellow solids in 71% (3) and
63% (4) yields.
The IR spectra of 3 and 4 display two strong ν(CO)
absorptions between 1582 and 1521 cm-1, indicating
that the acetylacetonato ligand is coordinated in a κ2-
oxygen bonding mode.5 The π-coordination of the
alkynol is also supported by the IR spectra, in which
the CtC stretching frequency is found at 1831 (3) and
1821 (4) cm-1, shifted 286 (3) and 296 (4) cm-1 to lower
wavenumbers in comparison with the free alkynol (2117
cm-1). In agreement with the square-planar coordina-
1
tion of the rhodium atom, the H NMR spectra display
two singlets between 1.83 and 1.53 ppm for the protons
of the methyl groups of the acetylacetonato ligand. The
resonances due to the OH and HCt protons appear at
5.78 and 4.41 ppm (3) and at 5.74 and 4.37 ppm (4), as
singlets. The 13C{1H} NMR spectra agree well with the
1H NMR spectra. Thus, they contain two singlets
between 188 and 183 ppm for the carbon atoms of the
carbonyl groups of the â-diketonato ligand, and a singlet
and a doublet, both at about 27 ppm, for the carbon
atoms of the methyl groups of the same ligand. In the
13C{1H} NMR spectra of both compounds, the resonance
of the HCt carbon atom appears at 69.4 ppm as a
double doublet with Rh-C and P-C coupling constants
of about 16 and 6 Hz, respectively, whereas the other
acetylenic carbon atom gives rise at about 90 ppm to a
doublet with a Rh-C coupling constant of about 16.5
Hz. The 31P{1H} NMR spectra of 3 and 4 contain
doublets at 50.6 (3) and 60.3 (4) ppm with Rh-P
coupling constants of 176.5 and 178.3 Hz, respectively.
At 60 °C, in toluene as solvent, and in the presence
of 1 equiv of phosphine, complexes 3 and 4 evolve into
the six-coordinate hydrido-alkynyl species Rh(acac)-
H{CtCC(OH)Ph2}(PR3)2 (PR3 ) PCy3 (5), PiPr3 (6)),
which were isolated as white solids in 59% (5) and 51%
(6) yields.
a
For 1, 3, and 5, PR3 ) PCy3; for 2, 4, and 6, PR3 ) PiPr3.
such as carbon monoxide, dimethyl acetylenedicarbox-
ylate, and methyl propiolate. Although the bis(phos-
phine) complex Rh(acac)(PCy3)2 is not accessible by
direct reaction from Rh(acac)(cyclooctene)(PCy3), it can
be prepared by addition of PCy3 to Rh(acac){η2-HCt
CCO2Me}(PCy3). Rh(acac)(PCy3)2 does not react with
molecular hydrogen and terminal alkynes by oxidative
addition. However, the rhodium(III) compounds Rh-
(acac)HX(PCy3)2 (X ) H, CtCR) are obtained by addi-
tion of HX to Rh(acac)(cyclooctene)(PCy3) in the pres-
ence of a stoichiometric amount of the phosphine. The
protonation of the hydrido-alkynyl derivatives with
HBF4‚OEt2 affords the cationic five-coordinate alkenyl
complexes [Rh(acac){(E)-CHdCHR}(PCy3)2]BF4 (R )
Cy, H).3
As a continuation of our work in this field, we have
now studied the reactivity of Rh(acac)(cyclooctene)(PCy3)
and the related triisopropylphosphine derivative Rh-
(acac)(cyclooctene)(PiPr3) toward 1,1-diphenyl-2-propyn-
1-ol. During this study, we have prepared the hydrido-
alkynyl complexes Rh(acac)H{CtCC(OH)Ph2}(PR3)2 and
observed that their protonations with HBF4‚OEt2 afford
the allenylphosphonium derivatives [Rh(acac){η2-CH-
(PR3)dCdCPh2}(PR3)]BF4. In this paper, we report
evidence to prove that the formation of the allenylphos-
phonium derivatives is a result of the reductive elimina-
tion of the allenylphosphonium cation from the cationic
(allenyl)rhodium(III) derivatives [Rh(acac){CHdCd
CPh2}(PR3)2]BF4 (PR3 ) PCy3, PiPr3).
The most noticeable features of the IR spectra of 5
and 6 in KBr are two bands between 2130 and 2109
cm-1, which were assigned to the ν(Rh-H) and ν(CtC)
vibrations. The presence of an alkynyl ligand in these
compounds is also supported by the 13C{1H} NMR
spectra. The signals of the R-C carbon atoms appear
at about 97 ppm as double triplets with Rh-C and P-C
coupling constants of about 50 and 17 Hz, respectively,
while the â-C carbon atoms give rise to doublets at 106.2
(5) and 107.3 (6) ppm with Rh-C coupling constants of
about 10 Hz and the γ-C carbon atoms display singlets
1
at 75.5 (5) and 75.7 (6) ppm. In the H NMR spectra,
the resonances of the hydrido ligands are observed in
the high-field region at -19.23 (5) and -18.99 (6) ppm,
as double triplets with Rh-H and P-H coupling con-
stants of about 18 and 12 Hz, respectively. The pres-
ence of only one hydrido ligand in 5 and 6 was inferred
from the 31P{1H} NMR spectra, which contain at 37.7
(5) and 47.3 (6) ppm doublets with Rh-P coupling
constants of 101.9 and 102.9 Hz, respectively, in agree-
Resu lts a n d Discu ssion
Syn th esis a n d Ch a r a cter iza tion of Rh (a ca c){η2-
HCtCC(OH)P h 2}(P R3) an d Rh (acac)H{CtCC(OH)-
P h 2}(P R3)2 (P R3 ) P Cy3, P iP r 3). These compounds
were prepared according to Scheme 1. The olefinic unit
(5) Oro, L. A.; Carmona, D.; Esteruelas, M. A.; Foces-Foces, C.; Cano,
F. H. J . Organomet. Chem. 1986, 307, 83.

4574 Organometallics, Vol. 16, No. 21, 1997
Esteruelas et al.
Sch em e 2
F igu r e 1. Molecular drawing for the complex [Rh(acac){η2-
CH(PCy3)dCdCPh2}(PCy3)]BF4 (7).
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for th e Com p lex
[Rh (a ca c){η2-CH(P Cy3)dCdCP h 2}(P Cy3)]BF 4 (7)
Bond Lengths
Rh-C(1)
2.130(7)
1.969(7)
2.083(5)
2.040(5)
2.285(2)
1.276(9)
1.387(11)
1.512(11)
O(2)-C(52)
C(52)-C(53)
C(52)-C(55)
C(1)-P(1)
C(1)-C(2)
C(2)-C(3)
C(3)-C(4)
C(3)-C(10)
1.279(9)
Rh-C(2)
1.388(11)
1.489(11)
1.809(7)
1.401(10)
1.344(10)
1.486(10)
1.506(10)
Rh-O(1)
Rh-O(2)
Rh-P(2)
O(1)-C(54)
C(53)-C(54)
C(54)-C(56)
Bond Angles
ment with the mutually trans disposition of the phos-
phine ligands. Under off-resonance conditions these
signals split into double doublets due to the P-H
coupling. These spectroscopic data agree well with
those previously reported for the hydrido-alkynyl com-
plexes Rh(acac)H(CtCR)(PCy3)2 (R ) Ph, Cy, SiMe3),
which were prepared by reaction of 1 with the corre-
sponding alkyne in the presence of tricyclohexylphos-
phine, as has been previously mentioned.4 Then, we
proposed that the formation of these compounds in-
volves the coordination of phosphine to five-coordinate
hydrido-alkynyl intermediates of the type Rh(acac)H-
(CtCR)(PCy3). The formation of 5 and 6, with 3 and 4
and phosphine as starting materials, is new evidence
in favor of this proposal.
P r oton a tion of 5. Treatment of complex 5 with 1
equiv of HBF4‚OEt2 in dichloromethane at -78 °C leads
to a red-orange solution, which changes color to yellow
by slow heating to room temperature. From the yellow
solution, a yellow solid in 89% yield was obtained by
addition of diethyl ether. The solid was characterized
as the allenylphosphonium complex [Rh(acac){η2-CH-
(PCy3)dCdCPh2}(PCy3)]BF4 (7; see Scheme 2) by el-
emental analysis, IR and 1H, 13C{1H}, and 31P{1H} NMR
spectroscopy, and a X-ray diffraction study. Although
at -78 °C the solution is red-orange, the spectroscopic
data obtained from the solid isolated at this temperature
are the same as those of 7. This complex is also
obtained from the reaction of 5 with DBF4‚D2O, indicat-
ing that the hydrido ligand of 5 becomes a part of the
allenyl ligand of 7.
P(2)-Rh-O(1)
P(2)-Rh-O(2)
P(2)-Rh-M(1)a
O(1)-Rh-O(2)
O(1)-Rh-M(1)
O(2)-Rh-M(1)
C(1)-Rh-C(2)
Rh-C(1)-C(2)
Rh-C(2)-C(1)
Rh-C(1)-P(1)
173.2(2)
86.5(2)
95.1(2)
88.4(2)
90.9(3)
166.7(3)
39.7(3)
63.9(4)
76.4(4)
124.2(4)
Rh-C(2)-C(3)
135.0(6)
148.5(7)
127.2(5)
121.9(7)
120.7(7)
117.5(6)
107.5(3)
113.9(3)
109.6(3)
C(1)-C(2)-C(3)
C(2)-C(1)-P(1)
C(2)-C(3)-C(4)
C(2)-C(3)-C(10)
C(4)-C(3)-C(10)
C(1)-P(1)-C(16)
C(1)-P(1)-C(22)
C(1)-P(1)-C(28)
a
M(1) is the midpoint of the allenylphosphonium ligand C(1)-
C(2) double bond.
is almost square planar with the C(1)-C(2) double bond
disposed perpendicular to the coordination plane of the
rhodium. If M(1) is the midpoint of the C(1)-C(2)
double bond, the deviations from the best plane are
0.0082(6) Å (Rh), 0.014(2) Å (P(2)), -0.448(5) Å (O(2)),
0.122(5) Å (O(1)), and -0.0011(3) Å (M(1)). The â-dike-
tonato bite angle (O(1)-Rh-O(2) ) 88.4(2)°) is similar
to the values found in related chelated rhodium com-
plexes,3,4,6 whereas the P(2)-Rh-M(1) angle (95.1(2)°)
slightly deviates from the ideal value of 90°, probably
as a result of the steric hindrance experienced by the
phosphine and allenylphosphonium ligands, which are
mutually cis-disposed. The C(1)-C(2) and C(2)-C(3)
bond lengths are 1.401(10) and 1.344(10) Å, respectively.
The elongation of the C(1)-C(2) bond upon coordination
of the allenylphosphonium ligand to the rhodium atom
is accompanied by a bending of the C(1)-C(2)-C(3)
angle to 148.5(7)°. Although transition-metal allenyl-
(6) (a) Leipold, J . G.; Lamprecht, G. J .; Van Zgl, G. J . Inorg. Chim.
Acta 1985, 96, L31. (b) Van Zgl, G. J .; Lamprecht, G. J .; Leipold, J . G.
Inorg. Chim. Acta 1985, 102, L1. (c) Duan, Z.; Hampden-Smith, M. J .;
Duester, E. N.; Rheingold, A. L. Polyhedron 1994, 13, 609.
A view of the molecular geometry of 7 is shown in
Figure 1. Selected bond distances and angles are listed
in Table 1. The coordination around the rhodium center

Rhodium(III)-Allenyl Derivatives
Organometallics, Vol. 16, No. 21, 1997 4575
F igu r e 2. HETCOR NMR spectrum of [Rh(acac){η2-CH(PCy3)dCdCPh2}(PCy3)]BF4 (7) in CD2Cl2 at 293 K.
phosphonium complexes have not been previously re-
ported, one can find examples of structurally charac-
terized M(η2-R2CdCdCR2) compounds.7 For these
compounds the degree of elongation of the coordinated
carbon-carbon double bond agrees well with that found
in 7 (between 0.10 and 0.03 Å), and the elongation is
also accompanied by a similar bending of the allene
ligand (between 160 and 140°).
In agreement with the sp2 character of C(1), the value
of the C(2)-C(1)-P(1) angle is 127.2(5)°. The rhodium-
allenylphosphonium coordination exhibits Rh-C dis-
tances of 2.130(7) Å (Rh-C(1)) and 1.969(7) Å (Rh-
C(2)), which agree well with those found in rhodium(I)-
olefin complexes (mean values 2.10 Å).8 The P(1)-C(1)
bond length of 1.809(7) Å is close to that observed in
W(η5-C5H5)(CO)2{η2-CH(PPh3)dCHCN} (1.802(3) Å)2a
and is significantly greater than the values found for
PdC double bonds (for example, 1.640(6) Å in (CH3)3-
PdCH2)9 or for partial phosphorus-carbon double bonds
(between 1.68 and 1.78 Å).2a
In addition, it should be mentioned that the Rh-O(2)
bond distance (O trans to C(1)-C(2), 2.040(5) Å) is about
0.04 Å shorter than the Rh-O(1) bond length (O trans
to P(2), 2.083(5) Å), probably as a result of the different
trans influences of the allenylphosphonium and phos-
phine ligands. The same situation, with similar Rh-O
bond lengths, has been found in the related rhodium(I)
complex Rh(acac){η2-CH(GeEt3)dCHCO2Me}(PCy3).4
In agreement with the κ2-oxygen coordination bonding
mode of the acetylacetonato ligand in 7, and the salt
character of the compound, the IR spectrum in KBr
shows two strong ν(CO) bands at 1576 and 1522 cm-1
and an absorption due to the [BF4]- anion centered at
1056 cm-1. In the 13C{1H} NMR spectrum, the most
noticeable resonances are those corresponding to the R-,
â-, and γ-C carbon atoms of the allenylphosphonium
ligand. The resonance due to C(1) appears at -1.2 ppm
as a doublet of doublets of doublets with Rh-C, P(1)-
C, and P(2)-C coupling constants of 13.8, 54.3, and 2.3
Hz, respectively. The resonance corresponding to C(2)
is observed at 162.7 ppm, also as a doublet of doublets
of doublets but with a Rh-C coupling constant of 24.7
Hz and the same value (5.9 Hz) for the P(1)-C and
P(2)-C coupling constants. The resonance due to C(3)
appears at 132.2 ppm as a doublet with a Rh-C
coupling constant of 6.0 Hz. According to the HETCOR
spectrum shown in Figure 2, the HC(PCy3)dC reso-
(7) (a) Okamoto, K.; Kai, Y.; Yasuoka, N.; Kasai, N. J . Organomet.
Chem. 1974, 65, 427. (b) Foxman, B. J . Chem. Soc., Chem. Commun.
1975, 221. (c) Yasuoka, N.; Morita, M.; Kai, Y.; Kasai, N. J . Organomet.
Chem. 1975, 90, 111. (d) Briggs, J . R.; Crocker, C.; McDonald, W. S.;
Shaw, B. L. J . Chem. Soc., Dalton Trans. 1981, 121. (e) Lundquist, E.
G.; Folting, K.; Streib, W. E.; Huffman, J . C.; Eisenstein, O.; Caulton,
K. G. J . Am. Chem. Soc. 1990, 112, 855. (f) Pu, J .; Peng, T.-S.; Arif, A.
M.; Gladysz, J . A. Organometallics 1992, 11, 3232. (g) Werner, H.;
Schwab, P.; Mahr, N.; Wolf, J . Chem. Ber. 1992, 125, 2641. (h) Werner,
H.; Schneider, D.; Schulz, M. J . Organomet. Chem. 1993, 451, 175. (i)
Lee, L.; Wu, I.-Y.; Lin, Y.-C.; Lee, G.-H.; Wang, Y. Organometallics
1994, 13, 2521.
1
nance appears in the H NMR spectrum at 2.25 ppm,
as a doublet of doublets of doublets with P(1)-H, Rh-
H, and P(2)-H coupling constants of 8.4, 2.7, and 2.5
(8) Allen, F. H.; Davies, J . E.; Galloy, J . J .; J ohnson, O.; Kennard,
O.; Macrae, C. F.; Mitchell, E. M.; Mitchell, G. F.; Smith.; Watson, D.
G. J . Chem. Inf. Comput. Sci. 1991, 31, 187.
(9) Ebsworth, E. A. V.; Fraser, T. E.; Rankin, D. W. H. Chem. Ber.
1977, 110, 3494.

4576 Organometallics, Vol. 16, No. 21, 1997
Esteruelas et al.
Hz, respectively. The 31P{1H} NMR spectrum shows
two doublets at 44.4 (P(2)) and 39.9 (P(1)) ppm, with
Rh-P coupling constants of 158.8 and 5.3 Hz.
Sch em e 3
The allenylphosphonium ligand of 7 is easily displaced
by carbon monoxide. By passage of a slow stream of
this gas through a dichloromethane solution of 7 the
previously reported carbonyl complex Rh(acac)(CO)(P-
Cy3)3 (8) and the salt [Ph2CdCdCHPCy3]BF4 (9) are
formed.
Salt 9 was isolated as a white solid in 75% yield and
characterized by elemental analysis and IR and 1H,
13C{1H}, and 31P{1H} NMR spectroscopy. The presence
of the allenyl unit in the compound is supported by the
CdCdC stretching frequency in the IR spectrum at
1928 cm-1 and three doublets in the 13C{1H} NMR
spectrum at 215.9 (J PC ) 3.2 Hz), 113.6 (J PC ) 13.3 Hz),
and 73.3 (J PC ) 78.3 Hz) ppm for the â-, γ-, and R-C
allenyl carbon atoms, respectively, which are in agree-
ment with the 13C{1H} data reported for other allene-
1
phosphine derivatives.10 In the H NMR spectrum the
most noticeable resonance is at 6.38 ppm, and it appears
as a doublet with a P-H coupling constant of 7.8 Hz.
This signal was assigned to the CHPCy3 proton. The
31P{1H} NMR spectrum shows a singlet at 30.2 ppm.
In addition, it should be mentioned that the reso-
nances of R- and â-carbon atoms of the allenyl unit in
the 13C{1H} NMR spectrum of compound 7 show an
unusually long slide toward high field, as a result of the
coordination to the rhodium atom. The same phenom-
enon has been previously observed for the coordination
of simple allene ligands.6h,11
P r oton a tion of 6. Treatment of complex 6 with 1
equiv of HBF4‚OEt2 in dichloromethane at -78 °C leads
to a red-orange solution, from which the allenyl complex
[Rh(acac){CHdCdCPh2}(PiPr3)2]BF4 (10; see Scheme 3)
was isolated as a red-orange solid in 63% yield, by
addition of diethyl ether.
The IR spectrum of 10 in KBr strongly supports the
presence of the allenyl ligand, showing the CdCdC
stretching frequency at 1885 cm-1. This spectrum also
contains two ν(CO) bands at 1569 and 1523 cm-1 in
agreement with the κ2-oxygen coordination bonding
mode of the acetylacetonato group. Furthermore, the
spectrum shows an absorption due to the [BF4]- anion
with Td symmetry centered at 1055 cm-1, indicating
that, although the metallic center of 10 is coordinatively
unsaturated, the anion is not coordinated to the rho-
dium atom.
The presence of the allenyl ligand in 10 is also
supported by the 13C{1H} NMR spectrum at -40 °C,
which shows two singlets at 189.6 and 119.0 ppm for
the â- and γ-C carbon atoms, respectively, and a double
triplet at 67.1 ppm with Rh-C and P-C coupling
constants of 35.5 and 8.3 Hz for the R-C carbon atom.
The 13C{1H} NMR spectrum also supports the square-
pyramidal geometry proposed in Scheme 3. In agree-
ment with the apical position of the allenyl group, the
spectrum shows singlets for both carbonyl and both
methyl carbon atoms of the acetylacetonato ligand, at
1
185.8 and 26.8 ppm, respectively. The H NMR spec-
trum at -40 °C agrees well with the 13C{1H} NMR
spectrum at the same temperature, containing only one
singlet at 1.70 ppm for the methyl protons. The
resonance of the RhCHd proton appears at 7.22 ppm
as a double triplet with Rh-H and P-H coupling
constants of 3.3 and 9.3 Hz, respectively. In accordance
with the presence of two chemically equivalent phos-
phine ligands in 10, the 31P{1H} NMR spectrum at -40
°C shows a doublet at 41.1 ppm, with an Rh-P coupling
constant of 135.7 Hz.
The related alkenyl complex [Rh(acac){(E)-CHdCH-
Cy}(PCy3)2]BF4, which was prepared similarly to 10 by
protonation of the hydrido-alkynyl compounds Rh-
(acac)H(CtCCy)(PCy3)2 with HBF4‚OEt2, also has a
square-pyramidal geometry with the η1-carbon ligand
in the apical position, as was established by X-ray
diffraction analysis.3 However, in the stannyl-allenyl
complex Rh(acac)(SnPh3){CHdCdCPh2}(PCy3), the al-
lenyl ligand occupies a site of the base of the pyramid.4
There are a variety of η1-allenyl transition-metal
complexes known, but most have been prepared by
oxidative addition of propargyl or allenyl halides to
electron-rich metal centers.12 Werner has observed that
the osmium alkynyl-hydrido complexes OsHCl{CtCC-
(OH)Ph2}(NO)(PR3)2 react with acidic alumina to afford
(10) (a) Schmidbaur, H.; Pollok, T.; Reber, G.; Mu¨ller, G. Chem. Ber.
1987, 120, 2015. (b) Manhart, S.; Schier, A.; Paul, M.; Riede, J .;
Schimdbaur, H. Chem. Ber. 1995, 128, 365.
(11) (a) Wolf, J .; Zolk, R.; Schubert, U.; Werner, H. J . Organomet.
Chem. 1988, 340, 161. (b) Rappert, T.; Nu¨rnberg, O.; Werner, H.
Organometallics 1993, 12, 1359. (c) Schneider, D.; Werner, H. Orga-
nometallics 1993, 12, 4420. (d) Binger, P.; Langhauser, F.; Wedemann,
P.; Gabor, B.; Mynott, R.; Kru¨ger, C. Chem. Ber. 1994, 127, 39.

Rhodium(III)-Allenyl Derivatives
Organometallics, Vol. 16, No. 21, 1997 4577
the allenylosmium(II) derivatives OsCl2{CHdCdCPh2}-
(NO)(PR3)2 (PR3 ) PiPr3, PPhiPr2).13 Fisher has also
reported that the allenylidene complex Cr(CO)5{dCd
CdC(C6H4NMe2-p)2} adds phosphine at the R-C carbon
atom to give Cr(CO)5{η1-C(PR3)dCdC(C6H4NMe2-p)2}
(PR3 ) PMe3, PHPh2, PH2Me).14 In the same sense,
Gimeno has observed that [Ru(η-C9H7){CtCC(PMe3)-
Ph2}(dppm)]PF6 isomerizes in tetrahydrofuran solution
to the thermodynamically stable product [Ru(η-C9-
H7){C(PMe3)dCdCPh2}(dppm)]PF6,15 and we have
described that the deprotonation of R,â-unsaturated al-
koxycarbene, (alkylthio)carbene, and 2-azaallenyl com-
plexes also yields allenyl derivatives.16
At room temperature, complex 10 evolves in dichlo-
romethane as solvent into the allenylphosphonium-
rhodium(I) derivative [Rh(acac){η2-CH(PiPr3)dCdCPh2}-
(PiPr3)]BF4 (11; see Scheme 3), which was isolated as a
yellow solid in 90% yield by addition of diethyl ether.
In the IR spectrum of 11, the most noticeable features
are the two ν(CO) bands of the acetylacetonato ligand
at 1575 and 1520 cm-1 and the absorption due to the
F igu r e 3. Stacked 1H NMR spectra illustrating the
isomerization of complex 10 to 11 in CD2Cl2 at 309 K.
[BF4]- anion with Td symmetry centered at 1053 cm-1
.
In the 1H NMR spectrum the CH(PiPr3) resonance
appears at 2.32 ppm as a doublet of doublets of doublets
with P-H, Rh-H, and P′-H coupling constants of 9.0,
3.0, and 2.1 Hz, respectively. The 13C{1H} NMR spec-
trum shows the resonances due to the R-, â-, and γ-C
carbon atoms of the allenylphosphonium ligand at -1.7,
162.2, and 132.8 ppm. The first resonance appears as
a doublet of doublets of doublets with P-C, Rh-C, and
P′-C coupling constants of 56.5, 14.0, and 2.9 Hz. The
second resonance is also observed as a doublet of
doublets of doublets, but with a Rh-C coupling constant
of 25.2 Hz, and the same value (6.1 Hz) for the P-C
and P′-C coupling constants, whereas the third reso-
nance is a doublet with a Rh-C coupling constant of
5.8 Hz. The 31P{1H} NMR spectrum shows two doublets
at 54.6 (PiPr3) and 50.8 ppm (CHPiPr3), with Rh-P
coupling constants of 158.8 and 6.2 Hz, respectively.
1
The isomerization of 10 into 11 was followed by H
F igu r e 4. Eyring plot of the first-order rate constants (kobs
for the isomerization of 10 to 11 in CD2Cl2.
)
NMR spectroscopy by measuring the disappearance of
the CH resonance of the acetylacetonato ligand as a
function of time. As shown in Figure 3, the decrease of
10 (with the corresponding increase of 11) in dichlo-
romethane-d2 is an exponential function of time, in
agreement with a first-order process. The values ob-
tained for the first-order rate constant kobs in the
temperature range studied are reported in Table 2. The
activation parameters of the reaction were obtained
from the Eyring analysis shown in Figure 4, giving
values of ∆Hq ) 23 ( 2 kcal mol-1 and ∆Sq ) 2 ( 2 cal
Ta ble 2. Ra tes of Isom er iza tion of Com p lex 10 to
11 in CD2Cl2
temp (K)
kobs (105 s-1
)
313
309
301
297
293
93.1 ( 5.5
67.1 ( 4.0
21.7 ( 1.3
16.0 ( 0.9
6.2 ( 0.4
therefore, that the reductive elimination of the allen-
ylphosphonium cation is a concerted process. In agree-
ment with this, we have also observed that the forma-
tion of 11 is not affected by the presence of tricyclo-
hexylphosphine.
K-1 mol-1
. The activation entropy is nearly zero,
suggesting that the isomerization is intramolecular and,
(12) (a) J acobs, T. L. The Chemistry of the Allenes; Lamor, S. R.,
Ed.; Academic Press: London, 1982; Vol. 2, p 334. (b) Schuster, H. F.;
Coppola, G. M. Allenes in Organic Chemistry; Wiley-Interscience: New
York, 1984. (c) Wojcicki, A.; Shuchart, C. E. Coord. Chem. Rev. 1990,
105, 35. (d) Keng, R.-S.; Lin, Y.-C. Organometallics 1990, 9, 289. (e)
Shuchart, C. E.; Willis, R. R.; Wojcicki, A. J . Organomet. Chem. 1992,
424, 185. (f) Wouters, J . M. A.; Klein, R. A.; Elsevier, C. J .; Ha¨ming,
L.; Stam, C. H. Organometallics 1994, 13, 4586.
(13) Werner, H.; Flu¨gel, R.; Windmu¨ller, B.; Michenfelder, A.; Wolf,
J . Organometallics 1995, 14, 612.
(14) Fischer, H.; Reindl, D.; Troll, C.; Leroux, F. J . Organomet.
Chem. 1995, 490, 221.
Although attempts to isolate a compound related to
10 with tricyclohexylphosphine have been unsuccessful,
even at -78 °C, it is reasonable to assume that the
formation of 7 by protonation of 5 also goes through a
five-coordinate allenyl intermediate, [Rh(acac){CHdCd
CPh2}(PCy3)2]+, which rapidly isomerizes into 7. Two
differences seem to exist between tricyclohexylphos-
phine and triisopropylphosphine. The first phosphine
appears to have a larger cone angle and a greater donor
power than the second one.17
(15) Cardieno, V.; Gamasa, M. P.; Gimeno, J .; Lastra, E. J . Orga-
nomet. Chem. 1994, 474, C27.
(16) Esteruelas, M. A.; Go´mez, A. V.; Lahoz, F. J .; Lo´pez, A. M.;
On˜ate, E.; Oro, L. A. Organometallics 1996, 15, 3423.

4578 Organometallics, Vol. 16, No. 21, 1997
Esteruelas et al.
75.1 (s, C-OH), 69.4 (dd, J RhC ) 15.9 Hz, J PC ) 5.9 Hz, HCtC),
31.7 (d, J PC ) 24.8 Hz, PCy3), 29.9, 29.1, 28.1, 27.9, and 26.8
(all s, PCy3), 27.4 (d, J PC ) 5.5 Hz, CH3 of acac), 26.9 (s, CH3
of acac).
P r ep a r a t ion of R h (a ca c){η2-H CtCC(OH )P h 2}(P iP r 3)
(4). This compound was prepared as described for 3, using 2
(118.1 mg, 0.25 mmol) and 1,1-diphenyl-2-propyn-1-ol (52.1 mg,
0.25 mmol) as starting materials: yellow solid. Yield: 90 mg
(63%). Anal. Calcd for C29H40O3PRh: C, 61.05; H, 7.07.
Found: C, 60.74; H, 6.85. IR (KBr, cm-1): ν(OH) 3255, ν(CtC)
1821, ν(CO)acac 1582 and 1521. 1H NMR (300 MHz, C6D6, 293
The allenylphosphonium ligand of 11 can be displaced
by carbon monoxide, to afford Rh(acac)(CO)(PiPr3) (12)
and [Ph2CdCdCHPiPr3]BF4 (13). Salt 13 was isolated
as a white solid in 68% yield. The spectroscopic data
obtained for 13 agree well with those of 9. The presence
of the allenyl unit is supported by the CdCdC stretch-
ing frequency in the IR spectrum at 1932 cm-1 and three
doublets in the 13C{1H} NMR spectrum at 217.0 (J PC
)
3.2 Hz), 114.6 (J PC ) 12.9 Hz), and 72.8 (J PC ) 79.7 Hz)
ppm for the â-, γ-, and R-C allenyl carbon atoms,
respectively. In the 1H NMR spectrum the CHPiPr3
resonance appears at 6.21 ppm, as a doublet with a P-H
coupling constant of 7.8 Hz. The 31P{1H} NMR spec-
trum shows a singlet at 40.8 ppm.
K): δ 8.08 (d, 4H, J HH ) 6.9 Hz, Ho-Ph), 7.19 (dd, 4H, J HH
)
J HH′ ) 6.9 Hz, Hm-Ph), 7.05 (dd, 2H, J HH ) 6.9 Hz, Hp-Ph), 5.74
(s, 1H, OH), 5.13 (s, 1H, CH of acac), 4.37 (s, 1H, HCt), 1.79
(m, 3H, PCHCH3), 1.77 and 1.56 (both s, 6H, CH3 of acac),
0.99 (dd, 18H, J PH ) 12.9 Hz, J HH ) 7.2 Hz, PCHCH3). 31P{1H}
NMR (121.4 MHz, C6D6, 293 K): δ 60.3 (d, J RhP ) 178.3 Hz).
13C{1H} NMR (75.4 MHz, C6D6, 293 K): δ 187.4 and 184.2
(both s, CO of acac), 147.9 (br, Cipso-Ph), 127.7 (s, Co-Ph), 127.6
Con clu d in g Rem a r k s
This study has revealed that the protonation of the
hydrido-alkynyl complexes Rh(acac)H{CtCC(OH)Ph2}-
(PR3)2 (PR3 ) PCy3, PiPr3) with HBF4‚OEt2 leads to the
allenyl derivatives [Rh(acac){CHdCdCPh2}(PR3)2]BF4,
as a result of the dehydration of the alkynyl group in
the acid medium and the migration of the hydrido ligand
to the R-C carbon atom of the alkynyl. The five-
coordinative allenyl derivatives evolve by reductive
elimination of [Ph2CdCdCHPR3]+ into the square-
planar allenylphosphonium complexes [Rh(acac){η2-
CH(PR3)dCdCPh2}(PR3)]BF4. The isomerization is
intramolecular, suggesting that the reductive elimina-
tion of the allenylphosphonium cation is a concerted
process.
(s, Cm-Ph), 126.7 (s, Cp-Ph), 99.7 (s, CH of acac), 89.6 (d, J RhC
)
17.4 Hz, HCtC), 75.4 (s, C-OH), 69.4 (dd, J RhC ) 15.5 Hz, J PC
) 5.9 Hz, HCtC), 27.5 (d, J PC ) 5.3 Hz, CH3 of acac), 26.9 (s,
CH3 of acac), 22.6 (d, J PC ) 23.2 Hz, PCHCH3), 19.4 (s,
PCHCH3).
P r ep a r a tion of Rh (a ca c){CtCC(OH)P h 2}H(P Cy3)2 (5).
To a solution of PCy3 (70.1 mg, 0.25 mmol) in 15 mL of toluene
was added 3 (141.6 mg, 0.25 mmol). After the mixture was
stirred for 30 min at 60 °C, a solid was formed. The solvent
was removed in vacuo, and the residue was treated with
pentane to give a white solid. Yield: 143 mg (59%). Anal.
Calcd for C56H85O3P2Rh: C, 69.26; H, 8.82. Found: C, 69.07;
H, 8.51. IR (KBr, cm-1): ν(OH) 3480, ν(RhH) 2120, ν(CtC)
2130, ν(CO)acac 1599 and 1512. 1H NMR (300 MHz, CDCl3,
293 K): δ 7.59 (d, 4H, J HH ) 8.1 Hz, Ho-Ph), 7.15 (m, 6H,
H
m,p-Ph), 5.13 (s, 1H, CH of acac), 1.91-0.92 (m, 66H, C6H11),
Exp er im en ta l Section
1.88 and 1.67 (both s, 6H, CH3 of acac), -19.23 (dt, 1H, J RhH
) 18.0 Hz, J PH ) 12.1 Hz, RhH), signal of OH not observed.
All reactions were carried out under an atmosphere of argon
by using Schlenk-tube techniques. Solvents were dried by the
usual procedures and distilled under argon prior to use. The
starting materials Rh(acac)(C8H14)(PR3) (R ) Cy (1), iPr (2))
were prepared by a published method.3 The reagent 1,1-
diphenyl-2-propyn-1-ol was a commercial product from ABCR.
IR spectra were recorded on a Perkin-Elmer 883 spectrom-
eter and the NMR spectra on Varian UNITY 300, Varian
GEMINI 2000 300 MHz, and Bruker ARX 300 instruments.
The probe temperature of the NMR spectrometers was cali-
brated against a methanol standard. The 13C NMR signals
were assigned by DEPT experiments (vt ) virtual triplet; N
31P{1H} NMR (121.4 MHz, CDCl3, 293 K): δ 37.7 (d, J RhP
)
101.9 Hz, dd in off-resonance). 13C{1H} NMR (75.4 MHz,
CDCl3, 293 K): δ 187.9 and 184.1 (both s, CO of acac), 148.2
(s, Cipso-Ph), 127.2 (s, Co-Ph), 126.9 (s, Cm-Ph), 126.1 (s, Cp-Ph),
106.2 (d, J RhC ) 9.8 Hz, RhCtC), 99.4 (s, CH of acac), 97.2
(dt, J RhC ) 50.3 Hz, J PC ) 16.8 Hz, RhCtC), 75.5 (s, C-OH),
33.3 (vt, N ) 18.9 Hz, PCy3), 29.2 and 29.1 (both s, PCy3), 28.5
(s, CH3 of acac), 27.9 (m, PCy3), 26.7 (s, PCy3).
P r ep a r a tion of Rh (a ca c){CtCC(OH)P h 2}H(P iP r 3)2 (6).
This compound was prepared as described for 5, using PiPr3
(46 mL, 0.25 mmol) and 4 (142.6 mg, 0.25 mmol) as starting
materials: white solid. Yield: 93 mg (51%). Anal. Calcd for
1
) 3J PH + 5J PH or J PC + 3J PC, respectively). C and H analyses
C
38H61O3P2Rh: C, 62.46; H, 8.42. Found: C, 62.27; H, 8.19.
were carried out with a Perkin-Elmer 2400 CHNS/O mi-
croanalyzer.
IR (KBr, cm-1): ν(OH) 3342, ν(CtC) 2119, â(RhH) 2109,
ν(CO)acac 1598 and 1515. 1H NMR (300 MHz, C6D6, 293 K): δ
7.88 (d, 4H, J HH ) 7.7 Hz, Ho-Ph), 7.17-7.06 (m, 6H, Hm,p-Ph),
5.14 (s, 1H, CH of acac), 2.69 (s, 1H, OH), 2.35 (m, 6H,
PCHCH3), 1.85 and 1.63 (both s, 6H, CH3 of acac), 1.25 (dvt,
18H, N ) 13.5 Hz, J HH ) 6.9 Hz, PCHCH3), 1.21 (dvt, 18H, N
P r ep a r a t ion of R h (a ca c){η2-H CtCC(OH )P h 2}(P Cy3)
(3). A solution of compound 1 (148.2 mg, 0.25 mmol) in 15
mL of pentane was cooled to -78 °C, and then a stoichiometric
amount of 1,1-diphenyl-2-propyn-1-ol (52.1 mg, 0.25 mmol) was
added. After the mixture was stirred for 1 h, a yellow solid
was formed. The solid was separated by decantation, washed
with pentane, and dried in vacuo. Yield: 123 mg (71%). Anal.
Calcd for C38H52O3PRh: C, 66.08; H, 7.59. Found: C, 65.69;
H, 7.24. IR (KBr, cm-1): ν(OH) 3395, ν(CtC) 1831, ν(CO)acac
1574 and 1521. 1H NMR (300 MHz, C6D6, 293 K): δ 8.10 (d,
4H, J HH ) 7.5 Hz, Ho-Ph), 7.20 (br, 4H, Hm-Ph), 7.05 (br, 2H,
) 13.5 Hz, J HH ) 6.6 Hz, PCHCH3), -18.99 (dt, 1H, J RhH
)
18.6 Hz, J PH ) 12.6 Hz, RhH). 31P{1H} NMR (121.4 MHz,
C6D6, 293 K): δ 47.3 (d, J RhP ) 102.9 Hz, dd in off-resonance).
13C{1H} NMR (75.4 MHz, C6D6, 293 K): δ 188.8 and 185.0
(both s, CO of acac), 148.9 (s, Cipso-Ph), 127.7 (s, Co-Ph), 127.2
(s, Cm-Ph), 126.5 (s, Cp-Ph), 107.3 (d, J RhC ) 9.6 Hz, RhCtC),
99.9 (s, CH of acac), 96.7 (dt, J RhC ) 47.0 Hz, J PC ) 17.4 Hz,
RhCtC), 75.7 (s, C-OH), 28.9 and 28.0 (both s, CH3 of acac),
23.6 (vt, N ) 20.3 Hz, PCHCH3), 19.2 and 19.1 (both s,
PCHCH3).
H
p-Ph), 5.78 (s, 1H, OH), 5.12 (s, 1H, CH of acac), 4.41 (s, 1H,
HCt), 1.83 and 1.53 (both s, 6H, CH3 of acac), 1.80-1.11 (m,
33H, C6H11). 31P{1H} NMR (121.4 MHz, C6D6, 293 K): δ 50.6
(d, J RhP ) 176.5 Hz). 13C{1H} NMR (75.4 MHz, toluene-d8,
233 K): δ 187.4 and 183.9 (both s, CO of acac), 149.1 and 147.2
(both s, Cipso-Ph), 127.8, 127.6, 127.5, 126.8, and 126.7 (all s,
P r ep a r a tion of [Rh (a ca c){η2-CH(P Cy3)dCdCP h 2}(P -
Cy3)]BF 4 (7). A solution of 5 (242.8 mg, 0.25 mmol) in 5 mL
of dichloromethane was cooled to -78 °C, and then a stoichio-
metric amount of HBF4‚OEt2 (37 µL, 0.27 mmol) was added.
A change from yellow to red-orange occurred almost instan-
taneously. The solution turns yellow by slow heating to room
C
o,m,p-Ph), 99.8 (s, CH of acac), 90.1 (d, J RhC ) 16.0 Hz, HCtC),
(17) Li, C.; Ogasawara, M.; Nola, S. P.; Caulton, K. G. Organome-
tallics 1996, 15, 4900.

Rhodium(III)-Allenyl Derivatives
Organometallics, Vol. 16, No. 21, 1997 4579
temperature. The solvent was removed in vacuo, and the
residue was washed with diethyl ether to give a yellow solid.
Yield: 232 mg (89%). Anal. Calcd for C56H84BF4O2P2Rh: C,
64.62; H, 8.13. Found: C, 64.52; H, 7.91. IR (KBr, cm-1):
ν(CO)acac 1576 and 1522, ν(BF4) 1056. 1H NMR (300 MHz,
CD2Cl2, 293 K): δ 7.40-7.12 (m, 10H, Ph), 5.78 (s, 1H, CH of
acac), 2.25 (ddd, 1H, J PH ) 8.4 Hz, J RhH ) 2.7 Hz, J P′H ) 2.5
Hz, CH(PCy3)), 2.02 (br, 6H, CH3 of acac), 1.78-1.04 (m, 66H,
C6H11). 31P{1H} NMR (121.4 MHz, CD2Cl2, 293 K): δ 44.4 (d,
1J RhP ) 158.8 Hz, Rh(PCy3)), 39.9 (d, 2J RhP ) 5.3 Hz, CH(PCy3)).
13C{1H} NMR (75.4 MHz, CD2Cl2, 293 K): δ 187.4 (br, CO of
acac), 162.7 (ddd, J RhC ) 24.7 Hz, J PC ) J P′C ) 5.9 Hz,
CH(PCy3)dCdC), 141.1 and 140.1 (both s, Cipso-Ph), 132.3 (d,
J RhC ) 6.0 Hz, CH(PCy3)dCdC), 130.7, 129.9, 128.7, 128.5,
128.3, and 128.0 (all s, Co,m,p-Ph), 101.0 (s, CH of acac), 33.0
(br, PCy3), 32.2 (d, J PC ) 23.0 Hz, PCy3), 29.7 and 29.6 (both
s, PCy3), 28.2 (d, J PC ) 9 Hz, PCy3), 28.1 (d, J PC ) 9.6 Hz,
PCy3), 26.0 (br, CH3 of acac), 26.6 and 25.8 (both s, PCy3), -1.2
(ddd, J PC ) 54.3 Hz, J RhC ) 13.8 Hz, J P′C ) 2.3 Hz,
CH(PCy3)dCdC).
CD2Cl2, 293 K): δ 7.50-7.11 (m, 10H, Ph), 5.78 (s, 1H, CH of
acac), 2.46 (m, 3H, PCHCH3), 2.32 (ddd, 1H, J PH ) 9.0 Hz,
J RhH ) 3.0 Hz, J P′H ) 2.1 Hz, CH(PiPr3)), 2.15 (m, 3H,
PCHCH3), 2.05 (br, 6H, CH3 of acac), 1.18 (dd, 9H, J PH ) 14.4
Hz, J HH ) 7.2 Hz, PCHCH3), 1.18 (dd, 9H, J PH ) 13.8 Hz, J HH
) 7.2 Hz, PCHCH3), 1.14 (dd, 9H, J PH ) 12.3 Hz, J HH ) 7.5
Hz, PCHCH3), 1.06 (dd, 9H, J PH ) 13.8 Hz, J HH ) 7.2 Hz,
PCHCH3). 1H NMR (300 MHz, CD2Cl2, 213 K): δ 2.04 and
1.98 (both s, 6H, CH3 of acac). 31P{1H} NMR (121.4 MHz,
1
CD2Cl2, 293 K): δ 54.6 (d, J RhP ) 158.8 Hz, Rh(PiPr3)), 50.8
2
(d, J RhP ) 6.2 Hz, CH(PiPr3)). 13C{1H} NMR (75.4 MHz,
CD2Cl2, 293 K): δ 187.7 and 186.9 (both br, CO of acac), 162.2
(ddd, J RhC ) 25.2 Hz, J PC ) 6.1 Hz, CH(PiPr3)dCdC), 141.3
and 140.8 (both s, Cipso-Ph), 132.8 (d, J RhC ) 5.8 Hz, CH-
(PiPr3)dCdC), 130.5, 129.3, 128.8, 128.5, 128.3, and 127.9 (all
s, Co,m,p-Ph), 101.0 (s, CH of acac), 27.4 and 27.0 (both br, CH3
of acac), 22.8 (d, J PC ) 40.5 Hz, PCHCH3), 22.4 (d, J PC ) 24.2
Hz, PCHCH3), 19.6 and 19.3 (both s, PCHCH3), 18.5, 17.9, and
17.8 (all d, J PC ) 3.8 Hz, PCHCH3), -1.7 (ddd, J PC ) 56.5 Hz,
J RhC ) 14.0 Hz, J P′C ) 2.9 Hz, CH(PiPr3)dCdC). 13C{1H} NMR
(75.4 MHz, CD2Cl2, 233 K): δ 187.5 and 186.5 (both s, CO of
acac), 27.2 (d, J PC ) 4.8 Hz, CH3 of acac), 26.7 (s, CH3 of acac).
Rea ction of 11 w ith CO. A stream of CO was passed
through a solution of compound 11 (200.1 mg, 0.25 mmol) in
10 mL of dichloromethane for 5 min. A change from yellow
to light yellow occurred almost instantaneously. Then the
solvent was removed in vacuo, and the addition of pentane
caused the precipitation of a white solid, which was washed
with pentane. The pentane solution was concentrated in vacuo
to produce a residue, which was identified as Rh(acac)-
(CO)(PiPr3) (12). The white solid was identified as [Ph2Cd
CdCHPiPr3]BF4 (13). Spectroscopic data for 12 are as fol-
lows: 1H NMR (300 MHz, CD2Cl2, 293 K): δ 5.45 (s, 1H, CH
of acac), 2.37 (m, 3H, PCHCH3), 2.03 and 1.85 (both s, 3H,
CH3 of acac), 1.31 (dd, 18H, J PH ) 14.1 Hz, J HH ) 7.2 Hz,
PCHCH3). 31P{1H} NMR (121.4 MHz, CD2Cl2, 293 K): δ 70.6
(d, J RhP ) 167.0 Hz). 13C{1H} NMR (75.4 MHz, CD2Cl2, 293
K): δ 191.7 (dd, J RhC ) 77.4 Hz, J PC ) 23.0 Hz, RhCO), 188.1
and 185.4 (both s, CO of acac), 100.5 (s, CH of acac), 27.9 (d,
J PC ) 5.3 Hz, CH3 of acac), 27.2 (s, CH3 of acac), 24.5 (d, J PC
) 25.6 Hz, PCHCH3), 19.9 (s, PCHCH3). Data for 13 are as
follows: yield: 74 mg (68%). Anal. Calcd for C24H32BF4P: C,
65.77; H, 7.36. Found: C, 65.44; H, 6.95. IR (KBr, cm-1):
ν(CdCdC) 1932, ν(BF4) 1054. 1H NMR (300 MHz, CD2Cl2,
293 K): δ 7.45-7.31 (m, 10H, Ph), 6.21 (d, J PH ) 7.8 Hz,
CHPiPr3), 2.80 (m, 3H, PCHCH3), 1.37 (dd, 18H, J PH ) 16.8
Hz, J HH ) 7.2 Hz, PCHCH3). 31P{1H} NMR (121.4 MHz,
CD2Cl2, 293 K): δ 40.8 (s). 13C{1H} NMR (75.4 MHz, CD2Cl2,
Rea ction of 7 w ith CO. A stream of CO was passed
through a solution of compound 7 (260.2 mg, 0.25 mmol) in
10 mL of dichloromethane for 5 min. A change from yellow
to light yellow occurred almost instantaneously. Then the
solvent was removed in vacuo, and the addition of pentane
caused the precipitation of a white solid, which was washed
with pentane. The pentane solution was concentrated in vacuo
to produce a residue, which was identified as Rh(acac)(CO)(P-
Cy3) (8).3 The white solid was identified as [Ph2CdCdCHPCy3]-
BF4 (9). Yield: 105 mg (75%). Anal. Calcd for C33H44BF4P:
C, 70.97; H, 7.94. Found: C, 70.60; H, 7.64. IR (KBr, cm-1):
ν(CdCdC) 1928, ν(BF4) 1066. 1H NMR (300 MHz, CDCl3, 293
K): δ 7.45-7.27 (m, 10H, Ph), 6.38 (d, J PH ) 7.8 Hz, CHPCy3),
2.51-1.10 (m, 33H, C6H11). 31P{1H} NMR (121.4 MHz, CDCl3,
293 K): δ 30.2 (s). 13C{1H} NMR (75.4 MHz, CDCl3, 293 K):
δ 215.9 (d, J PC ) 3.2 Hz, CdCdCH), 132.4 (d, J PC ) 5.5 Hz,
C
ipso-Ph), 129.2 and 128.5 (both s, Co,m,p-Ph), 113.6 (d, J PC ) 13.3
Hz, CdCdCH), 73.3 (d, J PC ) 78.3 Hz, CdCdCH), 31.0 (d,
J PC ) 41.4 Hz, PCy3), 26.6, 26.5, 26.4, 26.2, and 25.2 (all s,
PCy3).
P r ep a r a t ion of [R h (a ca c)(CHdCdCP h 2)(P iP r 3)2]BF 4
(10). A solution of 6 (182.7 mg, 0.25 mmol) in 5 mL of
dichloromethane was cooled to -78 °C, and then a stoichio-
metric amount of HBF4‚OEt2 (37 µL, 0.27 mmol) was added.
A change from yellow to red-orange occurred almost instan-
taneously. The solvent was removed in vacuo, and the residue
was washed with diethyl ether at -78 °C to give a red-orange
solid. Yield: 126 mg (63%). Anal. Calcd for C38H60BF4-
O2P2Rh: C, 57.01; H, 7.55. Found: C, 56.54; H, 7.09. IR (KBr,
cm-1): ν(CdCdC) 1885, ν(CO)acac 1569 and 1523, ν(BF4) 1055.
1H NMR (300 MHz, CD2Cl2, 293 K): δ 7.8-7.4 (m, 10H, Ph),
7.22 (dt, 1H, J PH ) J P′H ) 9.3 Hz, J RhH ) 3.3 Hz, RhCHdCdC),
5.52 (s, 1H, CH of acac), 2.81 (m, 6H, PCHCH3), 1.85 (br, 6H,
CH3 of acac), 1.44 (dvt, 18H, N ) 13.7 Hz, J HH ) 6.5 Hz,
PCHCH3), 1.42 (dvt, 18H, N ) 13.7 Hz, J HH ) 6.4 Hz,
PCHCH3). 1H NMR (300 MHz, CD2Cl2, 233 K): δ 1.70 (s, 6H,
CH3 of acac). 31P{1H} NMR (121.4 MHz, CD2Cl2, 233 K): δ
41.1 (d, J RhP ) 135.7 Hz). 13C{1H} NMR (75.4 MHz, CD2Cl2,
233 K): δ 189.6 (s, RhCHdCdC), 185.8 (s, CO of acac), 137.1
(s, Cipso-Ph), 128.7 (s, Co-Ph), 128.6 (s, Cm-Ph), 128.2 (s, Cp-Ph),
293 K): δ 217.0 (d, J PC ) 3.2 Hz, CdCdCH), 132.5 (d, J PC
)
5.6 Hz, Cipso-Ph), 129.6 and 128.9 (both s, Co,m,p-Ph), 114.6 (d,
J PC ) 12.9 Hz, CdCdCH), 72.8 (d, J PC ) 79.7 Hz, CdCdCH),
22.2 (d, J PC ) 42.9 Hz, PCHCH3), 16.7 (s, PCHCH3).
Cr ysta l Da ta for 7. Crystals suitable for the X-ray
diffraction study were obtained by slow diffusion of pentane
into a saturated solution of 7 in dichloromethane. A summary
of crystal and refinement data is reported in Table 3. An
unstable yellow irregular block of approximate dimensions 0.67
× 0.65 × 0.15 mm was mounted on a glass fiber at low
temperature. A set of randomly searched reflections in the
range 20 e 2θ e 36° showed strong reflections, from which a
group of 48 were carefully centered and used to obtain by least-
squares methods the unit cell dimensions. A Siemens-STOE
AED four-circle diffractometer was used for data acquisition
(ω/2θ scans), with graphite-monochromated Mo KR radiation
and 2θ range 3 e 2θ e 45° (-20 e h e 19, 0 e k e 15, 0 e l
e 27). A total of 8736 reflections were measured; from 8513
unique reflections (Rmerge ) 0.05), 7601 having Fo > 0 were
used in the refinement. Three orientation and intensity
standards were monitored every 55 min; no significant varia-
tion was observed. Reflections were also corrected by a
semiempirical method (ψ-scans).18
119.0 (s, RhCHdCdC), 100.2 (s, CH of acac), 67.1 (dt, J RhC
)
35.5 Hz, J PC ) 8.3 Hz, RhCHdCdC), 26.8 (s, CH3 of acac),
26.1 (m, PCHCH3), 20.7 and 19.8 (both s, PCHCH3).
P r ep a r a t ion of [R h (a ca c){η2-CH (P iP r 3)dCdCP h 2}-
(P iP r 3)]BF 4 (11). A solution of 10 (200.1 mg, 0.25 mmol) in
10 mL of dichloromethane was stirred for 30 min at 35 °C.
Then the solvent was removed in vacuo, and the addition of
diethyl ether caused the precipitation of a orange-yellow solid.
The solid was decanted and washed with diethyl ether.
Yield: 180 mg (90%). Anal. Calcd for C38H60BF4O2P2Rh: C,
57.01; H, 7.55. Found: C, 56.74; H, 7.31. IR (KBr, cm-1):
ν(CO)acac 1575 and 1520, ν(BF4) 1053. 1H NMR (300 MHz,

4580 Organometallics, Vol. 16, No. 21, 1997
Esteruelas et al.
-
Ta ble 3. Cr ysta l Da ta a n d Da ta Collection a n d
Refin em en t Da ta for
cupancy factors. The BF4 anion was also observed to be
severely disordered. A common B-F unit, and three sites for
the other three fluorines, were included in the model estab-
lished for the anion. The refinement of this group includes
restrictions of bond distances, angles, and thermal parameters
(SHELX93 facilities).19 The occupancy factors for the latter
disordered groups were estimated on the basis of the thermal
parameters and refined (anion) or maintained fixed (solvent)
during refinement. Anisotropic thermal parameters were used
for all non-hydrogen atoms; and hydrogens, except those
bonded to disordered groups, were included in calculated
positions19 riding on carbon atoms with isotropic thermal
parameters related to bonded atoms. Final R(F, Io > 2.0σ(Io))
and Rw(F2, all reflections with Fo > 0) values were 0.0638 and
0.1677. All calculations were performed by the SHELXTL (v.
5) system of computer programs.20
[Rh (a ca c){η2-CH(P Cy3)dCdCP h 2}(P Cy3)]BF 4 (7)
Crystal Data
formula
C
56H84BF4O2P2Rh‚1.55CH2Cl2‚
0.25C5H12
mol wt
color, habit
cryst size, mm
symmetry
space group
a, Å
1190.565
yellow, irregular block
0.67 × 0.65 × 0.15
monoclinic
P21/n (No. 14)
18.700(3)
14.041(3)
25.701(4)
90
b, Å
c, Å
R, deg
â, deg
105.05(2)
90
6517(2)
γ, deg
V, Å3
Kin etic An a lysis. The isomerization of complex 10 to 11
was followed quantitatively by 1H NMR spectroscopy in
CD2Cl2. The decrease of the intensity of the CH signal of acac
in complex 10 was measured automatically at intervals in a
Varian GEMINI 2000 spectrometer. The rate constants and
the errors were obtained by fitting the data to an exponential
decay function, using the routine programs of the spectrom-
eter. Activation parameters ∆Hq and ∆Sq were obtained by a
least-squares fit of the Eyring plot. Error analysis assumed
a 6.0% error in the rate constant (the maximum value found
in the experimental determinations) and 1 K in the temper-
ature. Errors were computed by published methods.21
Z
D
4
calc, g cm-3
1.213
Data Collection and Refinement
diffractometer
λ(Mo KR), Å; technique
monochromator
µ, mm-1
four-circle Siemens-STOE AED
0.710 73; bisecting geometry
graphite oriented
0.49
scan type
ω/2θ
2θ range, deg
temp, K
3 e 2θ e 45°
200
no. of data collcd
no. of unique data
no. of params refined
R1a (F2 > 2σ(F2))
wR2b (all data (Fo g 0))
Sc
8736
8513 (Rint ) 0.0508)
925
0.0638
0.1677
1.070
Ack n ow led gm en t. We thank the DGICYT (Projects
PB 94-1186 and PB 95-0806, Programa de Promocio´n
General del Conocimiento).
a
b
2
R1(F) ) ∑||Fo| - |Fc||/∑|Fo|. wR2(F2) ) {∑[w(Fo - Fc2)2]/
∑[w(Fo2)2]}1/2
.
c GOF ) S ) {∑[w(Fo - Fc2)2]/(n - p)}1/2, where n
2
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
coordinates, thermal parameters, distances and angles, and
interatomic distances for 7 (15 pages). Ordering information
is given on any current masthead page.
is the number of observed reflections and p is the number of refined
parameters.
The structure was solved by Patterson (rhodium atom) and
conventional Fourier techniques. A zone of disordered solvent
was found close to the inversion center. This disorder was
modeled with seven molecules of CH2Cl2 (with two sites for
some atoms) and one molecule of pentane with partial oc-
OM970567X
(19) Sheldrick, G. SHELXTL-93: Program for Crystal Structure
Refinement; Intitu¨t fu¨r Anorganische Chemie der Universita¨t, Go¨t-
tingen, Germany, 1993.
(20) Sheldrick, G. M. SHELXTL (v. 5); Siemens Analytical X-ray
Instruments, Madison, WI, 1994.
(18) North, A. C. T.; Phillips, D. C.; Matthews, S. F. Acta Crystal-
logr., Sect. A 1969, 24, 351.
(21) Morse, P. M.; Spencer, M. O.; Wilson, S. R.; Girolami, G. S.
Organometallics 1994, 13, 1646.