Rhodium(I) complexes with π-coordinated arylallene. Structures in the solid state and in solution and reaction with arylallene to give rhodacyclopentane

Article abstract of DOI:10.1021/om970931s

Reactions of phenylallene and of (4-fluorophenyl)allene with [Rh(μ-Cl)(PMe₃)₂]₂ (Rh: arylallene = 1:1) give Rh(I) complexes with π-coordinated arylallene, RhCl(η²-CH₂=C=CHAr)-(PMe₃)₂ (1a, Ar = C₆H₅; 1b, Ar = C₆H₄F-p). X-ray crystallography of 1a,b has established their square-planar coordination around the rhodium center, which is bonded to the 2,3-double bond of the arylallene. The aryl group of the ligand and the Rh center are situated on the same side of the uncoordinated 1,2-double bond. The position of an ortho hydrogen of the phenyl group in the ligand suggests an agostic interaction between the C-H group and the Rh center. Dissolution of 1a in benzene results in equilibration with its isomer 3a, which does not have a close contact between the ortho C-H group of the ligand and the Rh center. The ¹H NMR spectra of an equilibrated mixture in the temperature range 30-55 °C afford thermodynamic parameters for 3a?1a of ΔH°= -5.0 kJ mol^-1 and ΔS° = -8 J mol^-1 K^-1. The arylallenes react also with RhCl(PMe₃)₃ in a 1.2:1 molar ratio to yield pentacoordinated Rh(I)-arylallene complexes, RhCl(η²-CH₂=C=CHAr)(PMe₃)₃ (2a, Ar = C₆H₅; 2b, Ar = C₆H₄F-p). A crystallographic study of 2b shows a distorted trigonalbipyramidal coordination around the Rh center, which is bonded to equatorial Cl, PMe₃, and 2,3-η²-CH₂=C=CHAr ligands and to two apical PMe₃ ligands. The 4-fluorophenyl group of the ligand and the Rh center are situated on opposite sides of the uncoordinated C=C double bond. Complex 2a is in equilibrium with its isomer 4a, which shows dynamic NMR behavior on the NMR time scale. Reactions in a 3:1 molar ratio give rhodacyclopentanes, mer-Rh[CH₂C(=CHAr)C(=CHAr)CH₂]Cl(PMe₃) ₃ (5a, Ar = C₆H₅; 5b, Ar = C₆H₄F-p) as the main product. Complex 5a is also obtained from reaction of phenylallene with 2a. Reactions of (4-fluorophenyl)allene with RhCl(PEt₃)₃, RhCl{P(i-Pr)₃}₂, and RhCl(PPh₃)₃ proceed smoothly to give the corresponding Rh(I)-(4-fluorophenyl)allene complexes, RhCl(η²-CH₂=C=CHC₆H₄F-p)(PR ₃)₂ (6, R = Et; 7, R = i-Pr; 8, R = Ph). The ¹H NMR spectra of the complexes and X-ray crystallography of 8 indicate square-planar coordination around the Rh center, which is bonded to the 2,3-double bond of the arylallene.

Full text of DOI:10.1021/om970931s

Organometallics 1998, 17, 2037-2045
2037
Rh od iu m (I) Com p lexes w ith π-Coor d in a ted Ar yla llen e.
Str u ctu r es in th e Solid Sta te a n d in Solu tion a n d
Rea ction w ith Ar yla llen e To Give Rh od a cyclop en ta n e
J un-Chul Choi, Susumu Sarai, Take-aki Koizumi, Kohtaro Osakada,* and
Takakazu Yamamoto*
Research Laboratory of Resources Utilization, Tokyo Institute of Technology,
4259 Nagatsuta, Midori-ku, Yokohama 226-8503, J apan
Received October 27, 1997
Reactions of phenylallene and of (4-fluorophenyl)allene with [Rh(µ-Cl)(PMe3)2]2 (Rh:
arylallene ) 1:1) give Rh(I) complexes with π-coordinated arylallene, RhCl(η2-CH2dCdCHAr)-
(PMe3)2 (1a , Ar ) C6H5; 1b, Ar ) C6H4F-p). X-ray crystallography of 1a ,b has established
their square-planar coordination around the rhodium center, which is bonded to the 2,3-
double bond of the arylallene. The aryl group of the ligand and the Rh center are situated
on the same side of the uncoordinated 1,2-double bond. The position of an ortho hydrogen
of the phenyl group in the ligand suggests an agostic interaction between the C-H group
and the Rh center. Dissolution of 1a in benzene results in equilibration with its isomer 3a ,
which does not have a close contact between the ortho C-H group of the ligand and the Rh
1
center. The H NMR spectra of an equilibrated mixture in the temperature range 30-55
°C afford thermodynamic parameters for 3a T1a of ∆H° ) -5.0 kJ mol-1 and ∆S° ) -8 J
mol-1 K-1. The arylallenes react also with RhCl(PMe3)3 in a 1.2:1 molar ratio to yield
pentacoordinated Rh(I)-arylallene complexes, RhCl(η2-CH2dCdCHAr)(PMe3)3 (2a , Ar )
C6H5; 2b, Ar ) C6H4F-p). A crystallographic study of 2b shows a distorted trigonal-
bipyramidal coordination around the Rh center, which is bonded to equatorial Cl, PMe3,
and 2,3-η2-CH2dCdCHAr ligands and to two apical PMe3 ligands. The 4-fluorophenyl group
of the ligand and the Rh center are situated on opposite sides of the uncoordinated CdC
double bond. Complex 2a is in equilibrium with its isomer 4a , which shows dynamic NMR
behavior on the NMR time scale. Reactions in a 3:1 molar ratio give rhodacyclopentanes,
mer-Rh[CH2C(dCHAr)C(dCHAr)CH2]Cl(PMe3)3 (5a , Ar ) C6H5; 5b, Ar ) C6H4F-p) as the
main product. Complex 5a is also obtained from reaction of phenylallene with 2a . Reactions
of (4-fluorophenyl)allene with RhCl(PEt3)3, RhCl{P(i-Pr)3}2, and RhCl(PPh3)3 proceed
smoothly to give the corresponding Rh(I)-(4-fluorophenyl)allene complexes, RhCl(η2-
1
CH2dCdCHC6H4F-p)(PR3)2 (6, R ) Et; 7, R ) i-Pr; 8, R ) Ph). The H NMR spectra of the
complexes and X-ray crystallography of 8 indicate square-planar coordination around the
Rh center, which is bonded to the 2,3-double bond of the arylallene.
In tr od u ction
give the polymer formulated as -[CH2-C(dCHPh)]n-.3
Use of RhH(PPh3)4 or CoH(N2)(PPh3)3 as the catalyst
Rh(I) complexes catalyze polymerization or cyclooli-
gomerization of 1,2-dienes depending on auxiliary ligands
of the complexes and reaction conditions. Catalysts
such as RhCl(PPh3)3, [RhCl(CH2dCH2)2]2-PPh3 mix-
ture, and [RhCl(CO)2]2-PPh3 mixture lead to cyclooli-
gomerization of 1,2-propadiene.1 Chlorocarbonylrhodium-
(I) complexes, [RhCl(CO)2]2, RhCl(CO)3, and RhCl(CO)2-
(PPh3), have a tendency to initiate allene polymerization
rather than cyclooligomerization.2 Phenylallene under-
goes polymerization in the presence of [RhCl(CO)2]2 to
improves the polymer yield.4
Detailed studies of the reaction of 1,2-dienes with
chlororhodium(I) complexes in equimolar amounts or in
low substrate/catalyst ratios could provide a clue to
reactions that initiate the polymerization and oligomer-
ization of 1,2-dienes. There seem to be several possible
reactions of 1,2-dienes and chlororhodium(I) complexes
in stoichiometric amounts: (i) π-coordination of a CdC
double bond to Rh center, (ii) insertion of a double bond
into the Rh-Cl bond, and (iii) 2:1 cycloaddition to give
a five-membered rhodacyclopentane, as depicted in
Scheme 1.
(1) (a) J ones, F. N.; Lindsey, R. V. J . Org. Chem. 1968, 33, 3838. (b)
Otsuka, S.; Nakamura, A.; Tani, K.; Ueda, S. Tetrahedron Lett. 1969,
297. (c) Otsuka, S.; Nakamura, A.; Minamida, H. J . Chem. Soc., Chem.
Commun. 1969, 191. (d) Scholten, J . P.; van der Ploeg, H. J .
Tetrahedron Lett. 1972, 1685.
Insertion of allene into the Rh-Cl bond (ii) and
(2) (a) Otsuka, S.; Nakamura, A. J . Polym. Sci., Part B: Polym. Lett.
1967, 5, 973. (b) Scholten, J . P.; van der Ploeg, H. J . J . Polym. Sci.,
Polym. Chem. Ed. 1972, 10, 3067. (c) Scholten, J . P.; van der Ploeg,
H. J . J . Polym. Sci., Polym. Chem. Ed. 1973, 11, 3205.
(3) Leland, J .; Boucher, J .; Anderson, K. J . Polym. Sci., Polym.
Chem. 1977, 15, 2785.
(4) Choi, J .-C.; Osakada, K.; Yamaguchi, I.; Yamamoto, T. Appl.
Organomet. Chem. 1997, 11, 957.
S0276-7333(97)00931-X CCC: $15.00 © 1998 American Chemical Society
Publication on Web 04/17/1998

2038 Organometallics, Vol. 17, No. 10, 1998
Choi et al.
Sch em e 1
F igu r e 1. ORTEP drawing of (a) RhCl(η2-CH2dCdCHPh)-
(PMe3)2 (1a ) and (b) RhCl(η2-CH2dCdCHC6H4F-p)(PMe3)2
(1b) at 50% probability level. Hydrogens are omitted for
simplicity.
cyclometalation (iii) would initiate the catalytic polym-
erization and cyclooligomerization, respectively. π-Co-
ordination of allene or related cumulenes to transition
metals is known for Ni(0), Pt(0), Fe(0), and Rh(I)
complexes,5 although it is less common than coordina-
tion of alkenes. The Ni(0)-allene complex is regarded
as an intermediate in the reaction of allene with a
Ni(0) complex with CO2 and HOMe to give methyl
methacrylate.5f Insertion of a double bond of allene into
a Pd-Cl bond gives the corresponding π-allylic com-
plex.6 There have been fewer reports on metallacycle
formation from the 2:1 reaction of allene and transition
metal complexes7 than on cyclometalation of alkenes
and various transition metals such as Ti, Ta, Co, Ir, and
Ni.8 In this paper, we report preparation and structure
of π-coordinated arylallene-Rh(I) complexes containing
auxiliary phosphine ligands. Their further reaction
with arylallene to give a rhodacyclopentane is also
described. A part of this work has been reported in a
preliminary form.9
plexes, RhCl(η2-CH2dCdCHAr)(PMe3)2 (1a , Ar ) C6H5;
1b, Ar ) C6H4F-p), as pale yellow crystals.
Figure 1 shows X-ray crystal structures of 1a ,b,
which, as expected, are similar. Selected bond distances
and angles are summarized in Table 1. The Rh center
has a square-planar coordination, with two PMe3 ligands
at mutually trans positions. The molecules contain a
crystallographic mirror plane including Rh, Cl, and
carbon atoms of the coordinated arylallene molecule.
The uncoordinated CdC double bond of 1a ,b has the
phenyl group and the Rh center on the same side.
Nonbonding distances between an ortho hydrogen of the
phenyl group and the Rh center (1a , 2.75 Å; 1b, 2.66 Å)
are less than the expected sum of van der Waals radii
of H and 4d transition metals and imply the presence
of an agostic interaction between the C-H group and
the metal center.10
Resu lts
Rh od iu m (I) Com p lexes Ha vin g a π-Coor d in a ted
Ar yla llen e Liga n d . Reactions of phenylallene and of
(4-fluorophenyl)allene with [Rh(µ-Cl)(PMe3)2]2 (Rh:aryl-
allene ) 1:1) give phenylallene-coordinated Rh(I) com-
RhCl(PMe3)3 reacts with equimolar arylallenes in
hexane to give RhCl(η2-CH2dCdCHAr)(PMe3)3 (2a , Ar
) C6H5; 2b, Ar ) C6H4F-p). The coordination geometry
(5) (a) Chisolm, M. H.; Clark, H. C.; Hunter, D. H. J . Chem. Soc.,
Chem. Commun. 1971, 809. (b) Bright, D.; Mills, O. S. J . Chem. Soc.
(A) 1971, 1979. (c) Hagelee, L.; West, R.; Calabrese, J .; Norman, J . J .
Am. Chem. Soc. 1979, 101, 4888. (d) Stang, P. J .; White, M. R.; Maas,
G. Organometallics 1983, 2, 720. (e) White, M. R.; Stang, P. J .
Organometallics 1983, 2, 1654. (f) Hoberg, H.; Oster, B. W. J .
Organomet. Chem. 1984, 266, 321.
(6) (a) Schultz, R. G. Tetrahedron Lett. 1964, 301. (b) Schultz, R. G.
Tetrahedron 1964, 20, 2809. (c) Lupin, M. S.; Shaw, B. L. Tetrahedron
Lett. 1965, 883. (d) Hegedus, L. S.; Kambe, N.; Tamura, R.; Woodgate,
P. D. Organometallics 1983, 2, 1658.
(7) (a) Ingrosso, G.; Immirzi, A.; Porri, L. J . Organomet. Chem. 1973,
60, C35. (b) Ingrosso, G.; Porri, L.; Pantini, G.; Racanelli, P. J .
Organomet. Chem. 1975, 84, 75. (c) Immirzi, A. J . Organomet. Chem.
1974, 81, 217. (d) Barker, G. K.; Green, M.; Howard, J . A. K.; Spencer,
J . L.; Stone, F. G. A. J . Chem. Soc., Dalton Trans. 1978, 1839. (e) Uhlig,
E.; Walther, D. Coord. Chem. Rev. 1980, 33, 3 and references therein.
(f) Winchester, W. R.; Gawron, M.; Palenik, G. J .; J ones, W. M.
Organometallics 1985, 4, 1894.
(8) (a) Fraser, A. R.; Bird, P. H.; Bezman, S. A.; Shapley, J . R.; White,
R.; Osborn, J . A. J . Am. Chem. Soc. 1973, 95, 597. (b) McDermott, J .
X.; Wilson, M. E.; Whitesides, G. M. J . Am. Chem. Soc. 1976, 98, 6529.
(c) Grubbs, R. H.; Miyashita, A. J . Organomet. Chem. 1978, 161, 371.
(d) McLain, S. J .; Wood, C. D.; Schrock, R. R. J . Am. Chem. Soc. 1979,
101, 4558. (e) Cohen, S. A.; Auburn, P. R.; Bercaw, J . E. J . Am. Chem.
Soc. 1983, 105, 1136. (f) Binger, P.; Martin, T. R.; Benn, R.; Rufinska,
A.; Schroth, G. Z. Naturforsch. 1984, 39B, 993. (g) Mashima, K.;
Takaya, H. Organoetmallics 1985, 4, 1464.
of 2b around the Rh center in Figure 2 can be rational-
ized as a distorted trigonal bipyramid containing phos-
phorus atoms (P1 and P3) occupying two apical posi-
tions. Carbon atoms bonded to the metal center (C1 and
C2) are included in the equatorial coordination plane.
Elongation of the C1-C2 bond (1.42 Å) compared to the
C2-C3 bond (1.34 Å) and CdC double bonds of common
organic molecules and bend in the C1dC2dC3 fragment
(142°) suggest significant back-donation, which is com-
mon to most late transition metal complexes containing
a π-coordinated CdC double bond. The 4-fluorophenyl
(10) (a) Brookhart, M.; Green, M. L. H. J . Organomet. Chem. 1983,
250, 395. (b) Brookhart, M.; Green, M. L. H.; Wong, L.-L. Prog. Inorg.
Chem. 1988, 36, 1. (c) Crabtree, R. H. Chem. Rev. 1985, 85, 245. (d)
Hall, C.; Perutz, R. N. Chem. Rev. 1996, 96, 3125.
(9) Osakada, K.; Choi, J .-C.; Sarai, S.; Koizumi, T.; Yamamoto, T.
Chem. Commun. 1997, 1313.

Rh(I) Complexes with π-Coordinated Arylallene
Organometallics, Vol. 17, No. 10, 1998 2039
Ta ble 1. Selected Bon d Dista n ces (Å) a n d An gles (d eg) of 1a , 1b, 2a , 2b, a n d 8
1a
1b
2a a
2b
8
Rh-Cl
Rh-P1
Rh-P2
Rh-P3
Rh-C1
Rh-C2
C1-C2
C2-C3
C3-C4
2.391(6)
2.303(3)
2.386(4)
2.308(2)
2.540(2)
2.320(2)
2.323(2)
2.325(2)
2.126(7)
1.988(6)
1.406(9)
1.353(9)
1.477(10)
2.549(4)
2.320(5)
2.336(4)
2.308(4)
2.15(1)
1.97(2)
1.42(2)
1.34(2)
1.48(2)
2.361(2)
2.346(2)
2.336(2)
2.07(2)
2.01(2)
1.35(2)
1.35(3)
1.46(2)
2.08(1)
1.99(1)
1.41(2)
1.31(1)
1.44(2)
2.094(5)
2.004(6)
1.384(4)
1.321(8)
1.460(7)
Cl-Rh-P1
Cl-Rh-P2
Cl-Rh-P3
P1-Rh-P2
P1-Rh-P3
P2-Rh-P3
P1-Rh-P1*
Cl-Rh-C1
Cl-Rh-C2
C1-Rh-C2
C1-C2-C3
C2-C3-C4
C3-C4-C5
87.5(2)
87.94(9)
84.79(7)
97.80(7)
83.36(7)
96.74(7)
162.98(7)
96.94(7)
83.6(1)
98.2(2)
84.9(2)
97.0(2)
163.3(2)
96.6(2)
88.88(6)
90.33(7)
170.55(6)
174.8(3)
161.2(5)
160.3(6)
38.5(7)
152(1)
175.8(2)
161.2(5)
158.2(3)
40.5(5)
146(1)
118.3(2)
158.0(2)
39.8(3)
142.1(7)
126.9(7)
122.3(7)
117.6(4)
157.4(5)
39.9(5)
142(1)
125(1)
120(1)
163.3(2)
157.2(2)
39.4(2)
152.2(6)
124.3(5)
123.5(6)
131(1)
123(1)
127(1)
124(1)
a
Taken from ref 9.
F igu r e 2. ORTEP drawing of RhCl(η2-CH2dCdCHC6H4F-
p)(PMe3)3 (2b ) at 50% probability level. Hydrogens are
omitted for simplicity.
1
F igu r e 3. (b) H (400 MHz) and (a) 31P{1H} (160 MHz)
NMR spectra of a C6D6 solution of an equilibrated mixture
of 1a at 25 °C. Peaks with an arrow are due to 3a generated
in the solution through isomerization of 1a . The solvent
peak is marked with an asterisk.
group and Rh center exist on opposite sides of the
uncoordinated CdC bond, thus reducing steric conges-
tion between the aryl group and a PMe3 ligand within
the equatorial coordination plane. These crystallo-
graphic results of 2b are similar to those of 2a reported
in a preliminary communication.9
tively. The 13C{1H} NMR spectrum also shows signals
due to the two isomeric complexes. The signal of the
ortho carbons of the major complex appears at a higher
magnetic field position (δ 127.6) than that of the meta
carbon signal (δ 128.4), while the minor complex shows
the ortho and meta carbon signals at δ 128.8 and 125.7,
respectively. The 1J (CH) value of the C-H group at the
ortho position of the major complex (157 Hz) is smaller
than those of the ortho C-H group of the minor isomer
(160 Hz) and of uncoordinated phenylallene (160 Hz).
The 13C{1H} NMR data of the ortho C-H group,
including the upfield shift of the peak and the relatively
Although 1a and 2a are isolated as crystals, the NMR
spectra of the complexes in solution demonstrate the
presence of an equilibration of the complexes with their
isomers. Figure 3 shows the 1H and 31P{1H} NMR
spectra of a C6D6 solution of 1a . The 31P{1H} NMR
spectrum contains two pairs of signals with different
intensities at δ -8.5 and -7.7, indicating the existence
of two Rh complexes. The peak intensity ratio varies
reversibly depending on temperature due to equilibrium
1
1
smaller J (C-H) value, suggests that 1a has a C-H‚‚‚
between 1a and its isomer. The H NMR spectrum at
Rh agostic interaction.12 The minor isomer 3a is as-
25 °C shows two signals due to a vinylic CH hydrogen
of the phenylallene ligand at δ 6.70 and 6.64 in a 74:26
peak area ratio and those due to the ortho phenyl
hydrogens at δ 8.58 and 7.45 in a similar ratio.11 Peaks
of the meta and para hydrogens of the two complexes
are observed as two pairs of partly overlapped two
triplet signals at δ 7.26-7.29 and 7.06-7.08, respec-
signed to a structure without an agostic interaction
1
(Scheme 2), based on the J (CH) value and NMR data
similar to those of 1a , except for the 1H NMR peak
position of the ortho hydrogens. The different structures
of 1a and 3a arise from opposite coordination modes of
the 2,3-double bond plane of the ligand. The Rh center
(11) Peak area of the 1H NMR signal at δ 8.58 corresponds to two
hydrogens of 1a in the solution. Rotation of the C-C single bond
between allenyl and phenyl groups seems to occur much faster than
the NMR time scale.
(12) The 1J (CH) value is obtained as average of that of the two ortho
C-H groups of the ligand. The coupling constants of the C-H groups
with and without the agostic interaction are estimated as 154 and 160
Hz, respectively.

2040 Organometallics, Vol. 17, No. 10, 1998
Choi et al.
F igu r e 5. 31P{1H} NMR spectra (160 MHz) of an equili-
brated mixture of 4a and 2a at (a) 25, (b) 40, (c) 50, (d) 55,
and (e) 60 °C. Peaks with asterisks are due to 4a and 4a ′.
F igu r e 4. 1H NMR spectra (400 MHz) of an equilibrated
mixture of (4a + 4a ′) and 2a at (a) 30, (b) 40, (c) 50, and
(d) 60 °C. Peaks with an asterisk are due to the ortho, meta,
and C(Ph)(H)d hydrogens of 4a and 4a ′. The peak due to
the para hydrogen of 4a is overlapped with the correspond-
ing peak of 2a .
Sch em e 3
Sch em e 2
of 1a faces the phenyl group, whereas it is at the reverse
side of the CdC double bond in 3a . Since the ratio of
the two isomers reaches ca. 76:24 in a short period (<10
min) after dissolution of single crystals of 1a in benzene-
d6 at room temperature and does not change further,
rapid equilibrium exists between 1a and 3a (Scheme
2). A linear van’t Hoff plot obtained from temperature-
dependent changes in the relative peak area ratio of
ortho hydrogens of 1a and 3a gives the thermodynamic
parameters of the reaction, ∆H° ) -5.0 kJ mol-1 and
spectrum at 25 °C shows a doublet of doublets (δ -2.1)
and a doublet of triplets (δ -18.1) due to the major
complex 2a and two new broad signals at δ -5.6 and
-24.1 assigned to the newly formed complex 4a , as
shown in Figure 5. The breadth of the new peaks at δ
-24.1 suggests exchange of the PMe3 ligands on the
NMR time scale at the newly formed complex. Raising
the temperature causes a decrease in the relative
intensity of the peak due to 2a , accompanied by broad-
ening of the new peaks. At 50-60 °C, the signal at δ
-5.6 shows a significant increase in its intensity,
whereas the signal at δ -24.1 becomes negligible.
Scheme 3 depicts a plausible reaction scheme to
account for the NMR results. Complex 2a undergoes a
reversible isomerization to 4a , which is further equili-
brated with 4a ′ a stereoisomer of 1a through partial
liberation of PMe3. The new 31P{1H} NMR peaks at δ
-24.1 and -5.6 are assigned to the PMe3 ligand
coordinated to 4a and 4a ′ and are broadened due to the
above dissociative exchange of PMe3 ligands on the
NMR time scale, whereas the peaks due to 2a do not
∆S° ) -8 J mol-1 K-1
.
The NMR spectrum of a solution of 2a containing a
small amount of added PMe3 ([PMe3]/[2a ] ) 0.1) shows
the presence of 2a as the sole Rh-containing species
after 1 h below 0 °C. Dissolution of 2a in benzene at
25 °C causes the appearance of new NMR signals.
Figure 4 shows the temperature-dependent changes in
1
the H NMR spectra of the benzene-d6 solution of 2a ;
the new peaks indicated with asterisks. The intensity
of the new peaks (δ 8.47 and 7.42) due to ortho and meta
hydrogens of the newly formed complex increases,
accompanied by peak sharpening on raising the tem-
perature. One of the new peaks at δ 8.47 can be
assigned to an ortho hydrogen of a complex containing
an agostic interaction with the Rh center by comparing
its position with that of 1a (δ 8.58). The 31P{1H} NMR

Rh(I) Complexes with π-Coordinated Arylallene
Organometallics, Vol. 17, No. 10, 1998 2041
Ch a r t 1
show such broadening. More facile dissociation of PMe3
from 4a than that from 2a is attributed to stabilization
of 4a ′ by an agostic interaction between an ortho C-H
group and the Rh center. At 25 °C, the dissociation of
PMe3 from 4a is less extensive, and the 31P{1H} NMR
spectrum shows the peaks at δ -24.1 and δ -5.6 in ca.
2:1 area ratio. At higher temperature, broadening of
the 31P{1H} NMR signals renders comparison of the
relative peak intensity difficult, although dissociation
of PMe3 ligand would be more extensive than that at
25 °C. The 31P NMR peak assigned to liberated PMe3
is not detected.13
1H NMR signals due to the CH2 hydrogens at δ 3.02
and 2.11 are assigned respectively to the CH2 group
trans to PMe3 and to that trans to Cl ligand. The 13C-
{1H} NMR spectrum shows the signals due to C(Ar)Hd
carbons and dC< carbons as two pairs of signals whose
positions and coupling constants give reasonable as-
signment of each signal. That â-carbon signal of 5a
appears at a very low magnetic field position, which
seems to reflect low electron density at the carbon, in
analogy to the corresponding carbon of free allenes.
These features imply that the carbon atoms of rhoda-
cyclopentane have the character of unreacted allene.
Complex 5b gives NMR spectra similar to those of 5a
and is proposed to have the same five-membered met-
allacycle structure.
To confirm the liberation of PMe3 from 4a , the 1H
NMR peaks in the equilibrated mixture were compared
at 25-60 °C. An apparent equilibrium constant, Kapp
,
defined as ([4a ] + [4a ′])/[2a ], is plotted against 1/T, and
the plots give a linear van’t Hoff type correlation. The
thermodynamic parameters calculated from Kapp contain
positive reaction enthalpy and entropy (∆H°app ) 27.3
kJ mol-1 and ∆S°app ) 74 J mol-1 K-1 at 273 K),
consistent with the equilibrium involving dissociation
of PMe3 (Scheme 3).
The reactions of phenylallene with RhCl(PMe3)3 shown
in eqs 2 and 3 led to the isolation of 2a and of 5a ,
respectively. The results are rationalized by assuming
that each reaction gives two Rh complexes, whose ratio
depends on the relative amounts of phenylallene and
RhCl(PMe3)3. NMR measurement of the reaction mix-
tures in several phenylallene/Rh ratios revealed the
formation of several complexes, including 2a and 5a .
Reaction of phenylallene with RhCl(PMe3)3 in a 0.5:1
molar ratio gave a mixture of Rh(I)-phenylallene
complexes as the product, (4a :2a ) 10:90 after 11 h).
An equimolar reaction for 47 h afforded 4a , 2a , and 5a
in a 10:59:31 molar ratio. An increase in the amount
of phenylallene to 2 and 3 equiv compared to the Rh
complex caused a shift of the product ratio to 6:15:79
and 0:18:82, respectively.
Complex 2b, prepared from the reaction of (p-fluo-
rophenyl)allene with RhCl(PMe3)3, also shows NMR
spectra containing peaks of 4b and 4b ′ which are in
equilibrium with 2b.
Rea ction s of Ar yla llen e w ith Rh Cl(P Me3)3 To
Give Rh od a cyclop en ta n e. Reactions of phenylallene
and of (4-fluorophenyl)allene with RhCl(PMe3)3 in a 3:1
molar ratio result in isolation of mer-Rh[CH2C(dCHAr)C-
(dCHAr)CH2]Cl(PMe3)3 (5a , Ar ) C6H5; 5b, Ar )
C6H4F-p) in 79% and 75% yields, as shown in eq 3.
The reaction mixtures contain several minor products
that were removed from the product during the recrys-
tallization process. 1H NMR peaks at δ 5.42(s),
5.29(s), 3.64 (m), and 2.32 (m) and 31P{1H} NMR peaks
at δ -9.1 (dd, J (PRh) ) 112 Hz, J (PP) ) 31 Hz) and
-23.0 (dt, J (PRh) ) 87 Hz, J (PP) ) 31 Hz) in the bulk
reaction product were observed with small peak intensi-
ties (<5% of the Rh complexes). The similarlity of the
peak pattern to that of 5a suggests that the signals are
due to a structural isomer of 5a . Chart 1 depicts a
possible structure of the isomer 5a ′ containing an E
double bond and a Z double bond in the metallacycle
part. The other possible rhodacyclopentane with two
Z double bonds would be highly congested around the
s-cis diene unit.
The reaction of phenylallene with 2a was examined
to obtain insight on the mechanism of reactions 2 and
3. Figure 6 shows changes in the amount of the
complexes in the reaction with a 2:1 molar ratio. The
initial reaction mixture contains complexes 2a and 4a ,
the latter of which is formed through isomerization of
2a . The amount of 5a increases gradually to 80% of all
X-ray crystallography of 5a shows octahedral coordina-
tion around the Rh center with three PMe3 ligands at
meridional sites and the five-membered metallacycle
having two phenylmethylidene substituents.9 The 31P-
{1H} NMR spectrum of 5a shows a doublet of doublets
(δ -5.7) and a doublet of triplets (δ -20.8) in a 2:1 peak
area ratio. The former signal is assigned to two mutu-
ally trans P nuclei and the latter to a P nucleus trans
1
to a CH2 group bonded to the Rh center. The H NMR
spectrum gives rise to two PMe3 hydrogen signals in a
1:2 area ratio, the larger of which appears as an
apparent triplet due to virtual coupling. The above
NMR results are consistent with the meridional coor-
dination of the PMe3 ligands around the metal center.
The 13C{1H} NMR spectrum shows signals due to the
CH2 carbons bonded to Rh at δ 22.13 and 13.67. The
former peak, with a large J (CP) value (83 Hz), is
assigned to the carbon bonded at the trans position of
PMe3 and the latter to the carbon trans to the Cl ligand.
Based on the 1H-13C COSY NMR spectrum, the two
the Rh complexes and does not change further.
A
(13) The absence of the 31P{1H} NMR peaks of free PMe3 and of 4a ′
can be accounted for by a small amount of the complex in the reaction
mixture or its rapid equilibrium with 4a . It is not clear whether 4a ′
has a similar structure to 1a or not because comparison of the 31P NMR
peak positions of 1a and of 4a ′ is not feasible.
similar reaction, with addition of a small amount of
PMe3, ([PMe3]/[2a ] ) 0.2), does not form the rhodacy-
clopentane, even after 14 h.14 The rhodacyclopentane
formation probably involves initial ligation of phenyl-

2042 Organometallics, Vol. 17, No. 10, 1998
Choi et al.
Sch em e 4
plexes with other phosphine ligands, RhCl(PEt3)3, RhCl-
[P(i-Pr)3]2, and RhCl(PPh3)3, react with (4-fluorophenyl)-
allene to give Rh(I) complexes containing a π-coordinated
phenylallene molecule, 6, 7, and 8, respectively, as
shown in eq 4. Complex 7 was prepared from the
reaction of CH2dCdCHC6H4F-p with RhCl(H)(SiPh3)-
[P(i-Pr)3]2, accompanied by elimination of the hydro-
silylation product of the arylallene. Reaction 4 does not
give any other inorganic products including rhodacy-
clopentane, even when excess (4-fluorophenyl)allene is
used. Figure 7 shows the X-ray structure of the square-
planar complex 8 with Rh and the aryl group on opposite
sides of the uncoordinated CdC double bond, as with
3a . The appearance of the CH2 hydrogens of coordi-
nated allene molecule at high magnetic field positions
(δ 1.4-2.5) in 6, 7, and 8 indicates coordination of the
2,3-CdC double bond rather than the 1,2-CdC double
F igu r e 6. Time course of the reaction of 2a and phenyl-
allene in a 1:2 molar ratio in benzene-d6 at 25 °C.
allene to RhCl(PMe3)3 to give complexes 4a and 2a ,
followed by reaction of another phenylallene molecule
to the Rh complexes, leading to cyclometalation, as
depicted in Scheme 4. Inhibition of the metallacycle
formation by PMe3 suggests that the reaction requires
dissociation of PMe3 to allow π-coordination of the
second phenylallene ligand. The agostic interaction of
a phenyl C-H group with the Rh center in 4a may help
to dissociate a PMe3 from the complex and enhance the
metallacycle formation.
1
bond. The H NMR peaks due to the phenyl hydrogens
of 6-8 appear at positions similar to those found for
3a .
P r epar ation of Rh (I)-Ar ylallen e Com plexes with
Oth er P h osp h in e Liga n d s. Chlororhodium(I) com-
Discu ssion
(14) In the preliminary communication (ref 9), we reported that
reaction of phenylallene with 2a does not give the rhodacyclopentane
5a . Further investigation has revealed that it is due to contamination
of PMe3 that hampers the metallacycle formation. Reaction using the
complex purified by repeated recrystallization gives 5a at room
temperature, as shown in the present paper, while addition of PMe3
stops formation of 5a . Results of measurement of the equilibrium
constant of PMe3 dissociation from 2a in the previous report are also
unreliable.
Reactions of arylallene with Rh(I) complexes give
several types of products, depending on the conditions
and auxiliary phosphine ligands. Both π-coordination
and metallacycle formation occur at the 2,3-CdC double
bond of the substrates, probably because it is sterically
less hindered than the 1,2-CdC double bond and

Rh(I) Complexes with π-Coordinated Arylallene
Organometallics, Vol. 17, No. 10, 1998 2043
Sch em e 5
depicts two possible mechanisms for the isomerization.
The smooth conversion between the isomers is ac-
counted for by reversible change of the coordination side
of the 2,3-double bond through an intramolecular path-
way involving a transition state whose Rh center is
coordinated to the 1,2-double bond of the ligand (i).
Another pathway, involving dissociation of phenylallene
ligand (ii), is less plausible because the three-coordi-
nated Rh(I) complex with compact PMe3 ligands would
be extremely unstable.
F igu r e 7. ORTEP drawing of RhCl(η2-CH2dCdCHPh)-
(PPh3)2‚THF (8‚THF) at 30% probability level. Hydrogen
atoms and atoms of the solvent molecule are omitted for
simplicity.
The Rh center of complex 4a with 18 electrons
undergoes partial dissociation of a PMe3 ligand, trig-
gered by agostic interaction of an ortho hydrogen of the
phenylallene ligand to afford 4a ′. The labile Rh-P bond
caused by the agostic interaction may be an important
factor to promote the reaction of 2a with phenylallene
to give the metallacycle 5a . Both the agostic interaction
and rhodacyclopentane formation are unique to PMe3
ligands because the reaction of arylallene with Rh(I)
complexes with more bulky phosphine ligands RhCl-
(PR3)3 (R ) Et, i-Pr, Ph) gives only Rh(I) complexes, with
structure similar to that of 3a .
Ch a r t 2
because the resulting products contain efficient π-con-
jugation between the aryl group and the uncoordinated
1,2-double bond. The results of the structural study of
1a , including close contact of an ortho hydrogen of aryl
group with Rh in the crystal structure and smaller
1J (CH) of the ortho C-H group than that of 3a and
uncoordinated phenylallene, indicate the presence of an
agostic interaction both in the solid state and in solu-
tion. The 16-electron Rh center with square-planar
coordination is conductive to the approach of the C-H
group at the apical position. The geometry of the C-H
group and metal center in 1a is closer to an end-on type
interaction than to a side-on type (Chart 2).10c The
much smaller ∆H° for isomerization from 3a to 1a (-5.0
kJ mol-1) than already reported formation enthalpies
of metal alkane complexes with a side-on type coordina-
tion mode10d indicates that the agostic interaction shown
in this system is thermodynamically favored to a limited
extent. The shift of the 1H NMR peak to a low magnetic
field position does not agree with previously reported
C-H‚‚‚M interactions, which often result in a peak shift
to high magnetic field positions due to its partial hydrido
character. Elucidation of the reason for the uncommon
1H NMR peak shift related to the weak agostic inter-
action of the aromatic C-H group in the present study
would require further study.15
Exp er im en ta l Section
Gen er a l Con sid er a tion s, Mea su r em en t, a n d Ma ter ia ls.
Manipulations of the Rh complexes were carried out under
nitrogen or argon using standard Schlenk techniques. RhCl-
(PMe3)3, [Rh(µ-Cl)(PMe3)2]2, RhCl(PPh3)3, RhCl[P(i-Pr)3]2,
RhClH(SiPh3)[P(i-Pr)3]2, and arylallenes were prepared ac-
cording to the literature.16 NMR spectra (1H, 13C, and 31P)
were recorded on a J EOL EX-400 spectrometer. 31P{1H} NMR
spectra were referenced to external 85% H3PO4. Elemental
analyses were carried out by using a Yanaco MT-5 CHN
autocorder.
P r ep a r a tion of 1a a n d 1b. To a toluene (5 mL) solution
of [Rh(µ-Cl)(PMe3)2]2 (282 mg, 0.98 mmolRh) was added
phenylallene (113 mg, 0.97 mmol) at room temperature. The
solution changed color from orange red to yellow on stirring.
After 10 h, the solvent was evaporated to dryness. The
resulting oily product was washed with hexane repeatedly to
give a yellow solid (328 mg, 83%). Recrystallization from a
THF-hexane mixture afforded 1a as pale yellow crystals (198
mg, 50%). Anal. Calcd for C15H26ClP2Rh: C, 44.30; H, 6.44.
Found: C, 44.21; H, 6.54.
Rapid and reversible isomerization between 1a and
3a is observed above room temperature. Scheme 5
The NMR spectra of a solution of 1a shows the signals of
an equilibrated mixture of 1a and 3a . 1H NMR (400 MHz in
C6D6): δ 0.91 (apparent triplet due to virtual coupling, 18H,
(15) Previous reports on hydrogen bond of OH and NH groups of
organic molecule and metal center of several organotransition metal
complexes have shown downfiled shift of the 1H NMR peaks of O-H
and N-H hydrogen. See: Brammer, L.; Zhao, D.; Ladipo, F. T.;
Braddock-Wilking, J . Acta Crystallogr. 1995, B51, 632. Zhao, D.;
Ladipo, F. T.; Braddock-Wilking, J .; Brammern L.; Sherwood, P.
Organometallics 1996, 15, 1441 and references therein. The polar
metal-hydrido interaction seems to be not related to the interaction
of C-H group and Rh-PMe3 complexes in the present study.
(16) (a) Price, R. T.; Andersen, R. A.; Muetterties, E. L. J . Orga-
nomet. Chem. 1989, 376, 407. (b) J ones, R. A.; Real, F. M.; Wilkinson,
G.; Galas, A. M. R.; Hursthouse, M. B.; Malik, K. M. A. J . Chem. Soc.,
Dalton Trans. 1980, 511. (c) Werner, H.; Wolf, J .; Ho¨hn, A. J .
Organomet. Chem. 1985, 287, 395. (d) Moore, W. R.; Ward, H. R. J .
Org. Chem. 1962, 27, 4179. (e) Osakada, K.; Koizumi, T.; Yamamoto,
T. Organometallics 1997, 16, 2063.

2044 Organometallics, Vol. 17, No. 10, 1998
Choi et al.
P(CH3)3), 2.26 (m, CH2d (3a )), 2.32 (m, CH2d (1a )), 6.64 (m,
dCH- (3a )), 6.70 (m, dCH- (1a )), 7.06 (t, J ) 7 Hz, para
(3a ), 7.08 (t, J ) 7 Hz, para (1a ), 7.26 (t, J (HH) ) 7 and 8 Hz,
meta (3a )), 7.29 (t, J (HH) ) 7 and 8 Hz, meta (1a )), 7.45 (d,
J (HH) ) 7 Hz, ortho (3a )), 8.58 (d, J (HH) ) 7 Hz, ortho (1a )).
31P{1H} NMR (160 MHz in C6D6) δ -8.5 (d, 1a , J (RhP) ) 117
Hz), -7.7 (d, 3a , J (RhP) ) 117 Hz). 13C{1H} NMR (100 MHz
in CD2Cl2): δ 12.0 (apparent triplet due to virtual coupling,
P(CH3)3 (3a )), 12.5 (apparent triplet due to virtual coupling,
P(CH3)3 (1a )), 14.0 (CH2d (3a )), 14.6 (CH2d (1a )), 110.3 (CHd
(3a )), 110.6 (d, J (RhC) ) 4 Hz, CHd (1a )), 125.1 (1J (CH) )
161 Hz, para (3a )), 125.7 (1J (CH) ) 161 Hz, para (1a ) and
meta (3a )), 127.6 (1J (CH) ) 157 Hz, ortho (1a )), 128.4 (1J (CH)
) 160 Hz, meta (1a )), 128.8 (1J (CH) ) 160 Hz, ortho (3a )),
137.2 (ipso (3a )), 140.0 (ipso (1a )), 170.8 (dCd (3a )), 174.5 (d,
J (RhC) ) 25 Hz, dCd (1a )).
J (PH) ) 7 Hz), 1.76 (ddd, 2H, CH2), 5.81 (s, 1H, CH), 6.99 (t,
2H, J (HH) ) J (HF) ) 7 Hz, meta), 7.43 (dd, J (HH) ) 8 Hz,
J (HF) ) 5 Hz, ortho (2b)), 8.36 (br, ortho (4b + 4b′)). 31P{1H}
NMR (160 MHz in C6D6 at 25 °C): δ -2.1 (dd, J (PRh) ) 102
Hz, J (PP) ) 37 Hz(2b)), -5.5 (br, (4b + 4b′)), -17.9 (dt, J (PRh)
) 129 Hz, J (PP) ) 37 Hz, (2b)) -24.4 (br (4b + 4b′)).
P r ep a r a tion of 5a a n d 5b. To a toluene (8 mL) solution
of RhCl(PMe3)3 (158 mg, 0.43 mmol) was added phenylallene
(150 mg, 1.3 mmol) at room temperature. The solution
changed color from pale yellow to pale brown, which was
accompanied by deposition of an off-white solid. After 8 h,
the solid product was collected by filtration and dried in vacuo
to give 5a as colorless crystals (203 mg, 79%). Anal. Calcd
for C27H43ClP3Rh: C, 54.15; H, 7.24. Found: C, 54.18; H, 7.20.
1H NMR (400 MHz in C6D6 at 25 °C): δ 0.93 (d, 9H, P(CH3)3,
J (PH) ) 6 Hz), 1.10 (apparent triplet due to virtual coupling,
18H, P(CH3)3), 2.11 (m, 2H, CH2 trans to Cl), 3.02 (td, 2H, CH2
trans to P, J (PH) [or J (RhH)] ) 9 and 9 Hz), 6.48, (s, 1H, CH
trans to Cl), 6.59 (s, 1H, CH trans to PMe3), 7.06 (t, 2H, para,
J (HH) ) 7 Hz), 7.26 (t, 4H, meta, J (HH) ) 7 Hz), 7.59 (d, 2H,
ortho trans to Cl, J (HH) ) 7 Hz), 7.81 (d, 2H, ortho trans to
PMe3, J (HH) ) 7 Hz). 13C{1H} NMR (100 MHz in CD2Cl2 at
25 °C): δ 13.67 (ddt, CH2-Rh trans to Cl, J ) 26, 6, and 6
Hz), 14.39 (apparent triplet due to virtual coupling, P(CH3)3),
13.67 (d, P(CH3)3, J (CP) ) 17 Hz), 22.13 (m, CH2Rh trans to
PMe3, J (CP) ) 83 Hz), 115.81 (d, CHdCCH2Rh, trans to PMe3,
J ) 6 Hz), 118.07 (s, CHdCCH2Rh, trans to Cl), 125.45 (para,
trans to Cl), 125.62 (para, trans to PMe3), 128.25 (meta, trans
to Cl), 128.43 (meta, trans to PMe3), 129.53 (ortho, trans to
Cl), 129.59 (ortho, trans to PMe3), 139.92 (ipso, trans to Cl),
140.45 (ipso, trans to PMe3), 159.56 (d, CCH2Rh trans to Cl, J
) 7 Hz), 160.01 (d, CCH2Rh trans to PMe3, J ) 13 Hz). 31P-
{1H} NMR (160 MHz in C6D6 at 25 °C): δ -5.7 (dd, J (PRh) )
110 Hz, J (PP) ) 31 Hz), -20.8 (dt, J (PRh) ) 86 Hz, J (PP) )
31 Hz).
The equilibrium constants between 1a and 3a were deter-
1
mined by comparison of the H NMR peak area ratio of ortho
hydrogens of the phenylallene ligand of 1a and 3a as follows.
K ) [1a ]/[3a ] ) 2.69 (303 K), 2.62 (308 K), 2.45 (318 K), 2.36
(323 K), and 2.33 (328 K).
Complex 1b was prepared analogously (45% after recrys-
tallization). Anal. Calcd for C15H25ClFP2Rh: C, 42.43; H, 5.93.
Found: C, 42.30; H, 6.22. The NMR spectra of a solution of
1b shows the signals of an equilibrated mixture of 1b and 3b.
1H NMR (400 MHz in C6D6): δ 0.90 (apparent triplet due to
virtual coupling, 18H, P(CH3)3), 2.16 (m, CH2d (3b)), 2.29 (m,
CH2d (1b)), 6.51 (m, dCH- (3b)), 6.57 (m, dCH- (1b)), 6.93
(m, meta (1b and 3b)), 7.22 (br, ortho (3b)), 8.41 (dd, J (HH) )
J (HF) ) 7 Hz, ortho (1b)). 31P{1H} NMR (160 MHz in C6D6):
δ -8.6 (d, J (RhP) ) 117 Hz, (1b)), -7.7 (d, J (RhP) ) 117 Hz
(3b)).
P r ep a r a tion of 2a a n d 2b. To a hexane (8 mL) dispersion
of RhCl(PMe3)3 (115 mg, 0.31 mmol) was added phenylallene
(44 mg, 0.38 mmol) at room temperature to dissolve the
complex. Stirring the solution caused gradual separation of
a yellow solid. After 26 h, the solid product was collected by
filtration and dried in vacuo (119 mg, 78%). Recrystallization
from a THF-hexane mixture afforded 2a as yellow crystals
(85 mg, 56%). Anal. Calcd for C18H35ClP3Rh: C, 44.78; H,
7.31. Found: C, 44.39; H, 7.31.
The NMR spectra of a solution of 2a show the signals of an
equilibrated mixture of 2a and 4a . 1H NMR (400 MHz in C6D6
at 25 °C): δ 1.09 (apparent triplet due to virtual coupling, 18H,
P(CH3)3), 1.14 (d, 9H, J (PH) ) 7 Hz, P(CH3)3), 1.86 (ddd, 2H,
CH2), 5.94 (s, CH (2a )), 6.78 (br, CH (4a + 4a ′)), 7.06 (t, 1 H,
J (HH) ) 7 Hz, para), 7.32 (t, J (HH) ) 7 Hz, meta (2a )), 7.42
(br, meta, (4a + 4a ′)), 7.66 (d, J (HH) ) 7 Hz, ortho (2a )), 8.47
(br, ortho (4a + 4a ′)). 13C{1H} NMR (100 MHz in CD2Cl2 at
25 °C): δ 9.8 (dt, CH2Rh, J ) 50 and 5 Hz), 15.0 (apparent
triplet due to virtual coupling, P(CH3)3), 20.1 (d, J ) 17 Hz),
P(CH3)3), 114.2 (d, J ) 11 Hz, CHPh)C), 124.2 (para), 125.7
(ortho), 128.5 (meta), 139.7 (ipso), 167.9 and 168.1 (CCH2Rh).
The 13C NMR peaks due to the minor isomer 4a were either
not observed due to low solubility of the complex or overlapped
with the peaks of 2a . 31P{1H} NMR (160 MHz in C6D6 at 25
°C): δ -2.1 (dd, J (PRh) ) 104 Hz, J (PP) ) 37 Hz, (2a )), -5.6
(br, (4a + 4a ′)), -18.1 (dt, J (PRh) ) 133 Hz, J (PP) ) 37 Hz
(2a )), -24.1 (br, (4a + 4a ′)).
Complex 5b was prepared analogously (75%). Anal. Calcd
for C27H41ClF2P3Rh: C, 51.08; H, 6.51. Found: C, 51.13; H,
6.41. 1H NMR (400 MHz in C6D6 at 25 °C): δ 0.92 (d, 9H,
P(CH3)3, J (PH) ) 7 Hz), 1.08 (apparent triplet due to virtual
coupling, 18H, P(CH3)3), 1.96 (m, 2H, CH2 trans to Cl), 2.87
(td, 2H, CH2 trans to P, J (PH) [or J (RhH)] ) 9 and 9 Hz),
6.31, (s, 1H, CH trans to Cl), 6.41 (s, 1H, CH trans to PMe3),
6.89 (t, 4H, meta, J (HH) ) J (HF) ) 8 Hz), 7.35 (dd, 2H, ortho
trans to Cl, J (HH) ) 9 Hz, J (HF) ) 6 Hz), 7.58 (d, 2H, ortho
trans to PMe3, J (HH) ) 7 Hz). 31P{1H} NMR (160 MHz in
C6D6 at 25 °C): δ -5.6 (dd, J (PRh) ) 110 Hz, J (PP) ) 31 Hz),
-17.9 (dt, J (PRh) ) 86 Hz, J (PP) ) 31 Hz).
P r ep a r a tion of 6. To a pentane (5 mL) solution of RhCl-
(PEt3)3 (147 mg, 0.42 mmol) was added (4-fluorophenyl)allene
(67 mg, 0.50 mmol) at room temperature. A yellow solid was
soon separated from the solution. After 1 h, the solid product
was collected by filtration and dried in vacuo (145 mg).
Recrystallization from a toluene-pentane mixture afforded 6
as yellow crystals (57 mg, 27%). Anal. Calcd for C21H37ClFP2-
Rh: C, 49.57; H, 7.32; Cl, 6.96. Found: C, 49.41; H, 7.45; Cl,
6.64. 1H NMR (400 MHz in C6D6) δ 0.94 (apparent triplet due
to virtual coupling, 18H, CH3), 1.50 (m, 12H, PCH2), 2.24 (m,
2H, dCH2), 6.50 (m, 1H, CdCH), 6.92 (dd, 2H, J (HH) ) J (HF)
) 9 Hz), 7.20 (dd, 2H, J (HH) ) 9 Hz, J (HF) ) 6 Hz). 31P{1H}
NMR (160 MHz in C6D6): δ 18.7 (d, J (RhP) ) 117 Hz).
P r ep a r a tion of 7. To a hexane (5 mL) suspension of RhCl-
(H)(SiPh3)[P(i-Pr)3)]2 (145 mg, 0.20 mmol) was added (4-
fluorophenyl)allene (135 mg, 1.01 mmol) at room temperature.
The solution soon changed color from purple to yellow, which
was accompanied by deposition of a yellow solid. After
evaporation of the solvent under vacuum, the resulting yellow
solid was recrystallized from a THF-hexane mixture to give
Apparent equilibrium constants between 2a and a mixture
1
of 4a and 4a ′ were determined by comparison of the H NMR
signals of dCHPh hydrogen of 2a with that of ortho hydrogens
of 4a and 4a ′. Kapp ) ([4a ] + [4a ′])/[2a ] ) 0.149 (303 K), 0.178
(308 K), 0.212 (313 K), 0.248 (318 K), 0.295 (323 K), 0.331 (328
K), and 0.403 (333 K).
Complex 2b was prepared analogously (71% after recrys-
tallization). Anal. Calcd for C18H34ClFP3Rh: C, 43.18; H, 6.84.
Found: C, 43.25; H, 7.16. The NMR spectra of a solution of
2b shows the signals of an equilibrated mixture of 2b and 4b.
1H NMR (400 MHz in C6D6 at 25 °C): δ 1.08 (apparent triplet
due to virtual coupling, 18H, P(CH3)3), 1.14 (d, 9H, P(CH3)3,
7 as yellow crystals (57 mg, 48%). Anal. Calcd for C27H49
-
ClFP2Rh: C, 54.68; H, 8.32; Cl, 5.97. Found: C, 55.08; H, 8.55;
Cl, 5.44. 1H NMR (400 MHz in C6D6): δ 1.24 (apparent triplet
due to virtual coupling, 36H, CH3), 2.30 (br, 6H, PCH), 2.51

Rh(I) Complexes with π-Coordinated Arylallene
Organometallics, Vol. 17, No. 10, 1998 2045
Ta ble 2. Cr ysta l Da ta a n d Deta ils of Str u ctu r e Refin em en t of 1a , 1b, 2b, a n d 8
compound
formula
mol wt
cryst syst
space group
a (Å)
1a
1b
2b
8‚THF
C
15H26ClP2Rh
C15H25ClFP2Rh
424.66
C18H34ClFP3Rh
500.74
C49H45ClFP2RhO
869.20
406.68
orthorhombic
Pnma (No. 62)
13.238(5)
13.474(7)
10.311(4)
orthorhombic
Pnma (No. 62)
13.362(6)
13.530(7)
10.466(5)
orthorhombic
P212121 (No. 19)
12.823(6)
15.964(4)
11.518(4)
monoclinic
P21/n (No. 14)
17.522(7)
10.514(9)
23.41(1)
99.24(4)
4253
4
5.79
1792
1.357
0.3 × 0.5 × 0.7
5.0-55.0
10 324
5585
496
0.054
0.049
2.25
b (Å)
c (Å)
â (deg)
U (Å3)
Z
1839
4
1892
4
2357
4
µ (cm-1
F(000)
)
12.32
832
1.469
0.4 × 0.5 × 0.5
5.0-55.0
2415
747
103
0.059
0.030
1.93
12.09
864
1.491
0.2 × 0.4 × 0.4
5.0-55.0
2484
1067
113
0.051
0.035
2.11
10.46
1032
1.411
0.3 × 0.4 × 0.4
5.0-55.0
3065
1259
217
0.050
0.035
1.33
Dcalcd (g cm-3
)
cryst size (mm3)
2θ range (deg)
no. of unique reflns
no. of used reflns
no. of variables
R
a
Rw
GOF
a
Weighting scheme [σ(Fo)2]-1
.
(br, 2H, dCH2), 6.60 (br, 1H, dCH), 6.90 (d, 2H, meta, J (HH)
) J (HF) ) 9 Hz), 7.17 (d, 2H, ortho, J (HH) ) 9 Hz, J (HF) )
6 Hz). 31P{1H} NMR (160 MHz in C6D6): δ 32.6 (d, J (RhP) )
117 Hz).
and the ω-2θ method. Empirical absorption correction (ψ
scan method) of the collected data was applied. Table 2
summarizes crystal data and details of data refinement.
Calculations were carried out by using the teXsan program
package on a VAX-II computer. Atomic scattering factors were
taken from the literature.17 A full-matrix least-squares refine-
ment was used for non-hydrogen atoms with anisotropic
thermal parameters. Hydrogen atoms, except for vinyl hy-
drogen of the ligands of 3a , were located by assuming ideal
positions (d ) 0.95 Å) and were included in the structure
calculation without further refinement of the parameters.
Positions of the hydrogens of phenylallene molecule of 3a were
determined by D-Fourier map and were not refined further.
P r ep a r a tion of 8. To a toluene (10 mL) dispersion of RhCl-
(PPh3)3 (310 mg, 0.34 mmol) was added (4-fluorophenyl)allene
(54 mg, 0.40 mmol) at room temperature. The solution
gradually changed color from purple to yellow. After 17 h,
the solvent was evaporated to dryness. Addition of hexane to
the resulting yellow product caused separation of a yellow
solid, which was recrystallized from a CH2Cl2-hexane mixture
to afford 8 as yellow crystals (190 mg, 71%). Anal. Calcd for
C45H37ClFP2Rh: C, 67.81; H, 4.68. Found: C, 67.50; H, 4.99.
1H NMR (400 MHz in CD2Cl2): δ 1.42 (br, 2H, CH2d), 6.36
(br, 1H, dCH), 6.60 (d, 2H, ortho, J (HH) ) 7 Hz), 6.77 (dd,
2H, J (HH) ) J (HF) ) 7 Hz), 7.3 (m, 18H, C6H5), 7.7 (m, 12H,
C6H5). 31P{1H} NMR (160 MHz in CD2Cl2): δ 27.7 (d, J (RhP)
) 125 Hz). Single crystals for X-ray crystallography were
obtained in a THF solvated form from further recrystallization
of the complex from THF-hexane.
Ack n ow led gm en t. This work was financially sup-
ported by a Grant-in-Aid for Scientific Research from
the Ministry of Education, Science, Sports, and Culture,
J apan.
Su p p or tin g In for m a tion Ava ila ble: Crystallographic
data of the complexes 1a , 1b, 2b, and 8 (21 pages). Ordering
information is given on any current masthead page.
Cr ystal Str u ctu r e Deter m in ation . Crystals were mounted
in glass capillary tubes under argon. The unit cell parameters
were obtained by least-squares refinement of 2θ values of 25
reflections with 25° e 2θ e 35°. Intensities were collected on
a Rigaku AFC-5R automated four-cycle diffractometer by using
graphite-monochromated Mo KR radiation (λ ) 0.710 69 Å)
OM970931S
(17) International Tables for X-ray Crystallography; Kynoch: Bir-
mingham, England, 1974; Vol. IV.