Perfluorobenzyl complexes of cobalt and rhodium. Unusual coupling between pentafluorophenyl and pentamethylcyclopentadienyl rings

Article abstract of DOI:10.1021/om9607255

Oxidative addition of perfluorobenzyl iodide to [M(η⁵-C₅R₅)(CO)₂] (M = Co, R = H, Me; M = Rh, R = Me) in benzene affords the perfluorobenzyl complexes [M(η⁵-C₅R₅)(CF₂C ₆F₅)I-(CO)] (M = Co, R = H (1a), Me (2a); M = Rh, R = Me (2b)). Further reaction of 1a or 2a with PMe₃ in benzene results in a substitution reaction to give complexes [Co(η⁵-C₅R₅)-(CF₂C ₆F₅)I(PMe₃)] (R = H (3a), Me (4a)) . While the reaction of (pentamethylcyclopentadienyl)cobalt complex 2a with PMe₃ in benzene gives 4a, the analogous reaction in THF results in alkyl C-H activation and aryl C-F activation, with coupling of the pentamethylcyclopentadienyl ligand and the perfluorobenzyl ligand, to give 9a. Similarly, the reaction of 2a with PMe₂Ph in THF affords the analogous ring-coupled complex 9b, while reaction of the cyclopentadienyl analogue 1a with PMe₂Ph affords the simple substitution product 5a. In contrast to the reactions of the (pentamethylcyclopentadienyl)cobalt complexes, reaction of the rhodium analogue 2b with PMe₃ or PMe₂Ph result in a simple substitution to give [Rh(η⁵-C₅Me₅)(CF₂C ₆F₅)I(L)] (L = PMe₃ (5a) PMe₂Ph (5b)). Attempts to purify complexes 9 result in facile hydrolysis of the CF₂ group to give acyl complexes 10. A mechanism is proposed for this coupling reaction, and an analogue 13 of a proposed cationic intermediate has been isolated and shown to react with iodide to afford 10, via 9a. Heating of 2a results in a different coupling reaction to afford the organic cyclopentadiene 14. The solid state structures of 3a, 5b, and 10b were determined by X-ray crystallography.

Full text of DOI:10.1021/om9607255

5678
Organometallics 1996, 15, 5678-5686
P er flu or oben zyl Com p lexes of Coba lt a n d Rh od iu m .
Un u su a l Cou p lin g betw een P en ta flu or op h en yl a n d
P en ta m eth ylcyclop en ta d ien yl Rin gs
Russell P. Hughes* and Danielle C. Lindner
Department of Chemistry, Burke Chemistry Laboratory, Dartmouth College,
Hanover, New Hampshire 03755-3564
Arnold L. Rheingold and Glenn P. A. Yap
Department of Chemistry, University of Delaware, Newark, Delaware 19716
Received August 22, 1996X
Oxidative addition of perfluorobenzyl iodide to [M(η5-C5R5)(CO)2] (M ) Co, R ) H, Me; M
) Rh, R ) Me) in benzene affords the perfluorobenzyl complexes [M(η5-C5R5)(CF2C6F5)I-
(CO)] (M ) Co, R ) H (1a ), Me (2a ); M ) Rh, R ) Me (2b)). Further reaction of 1a or 2a
with PMe3 in benzene results in a substitution reaction to give complexes [Co(η5-C5R5)-
(CF2C6F5)I(PMe3)] (R ) H (3a ), Me (4a )) . While the reaction of (pentamethylcyclopenta-
dienyl)cobalt complex 2a with PMe3 in benzene gives 4a , the analogous reaction in THF
results in alkyl C-H activation and aryl C-F activation, with coupling of the pentameth-
ylcyclopentadienyl ligand and the perfluorobenzyl ligand, to give 9a . Similarly, the reaction
of 2a with PMe2Ph in THF affords the analogous ring-coupled complex 9b, while reaction of
the cyclopentadienyl analogue 1a with PMe2Ph affords the simple substitution product 5a .
In contrast to the reactions of the (pentamethylcyclopentadienyl)cobalt complexes, reaction
of the rhodium analogue 2b with PMe3 or PMe2Ph result in a simple substitution to give
[Rh(η5-C5Me5)(CF2C6F5)I(L)] (L ) PMe3 (5a ) PMe2Ph (5b)). Attempts to purify complexes 9
result in facile hydrolysis of the CF2 group to give acyl complexes 10. A mechanism is
proposed for this coupling reaction, and an analogue 13 of a proposed cationic intermediate
has been isolated and shown to react with iodide to afford 10, via 9a . Heating of 2a results
in a different coupling reaction to afford the organic cyclopentadiene 14. The solid state
structures of 3a , 5b, and 10b were determined by X-ray crystallography.
In tr od u ction
instances. In contrast to the usual requirements for
such hydrolysis reactions, we have observed an unusu-
ally facile hydrolysis reaction of benzylic C-F bonds in
some of these complexes, and in one cobalt system, an
unusually facile activation of an aryl C-F bond has been
observed.
The recent commercial availability of perfluorobenzyl
iodide prompted us to explore the synthesis and chem-
istry of perfluorobenzyl complexes of the transition
metals. Except for the (perfluorobenzyl)cadmium and
(perfluorobenzyl)copper reagents prepared by Burton
and co-workers,1 no (perfluorobenzyl)metal complexes
appear to have been reported thus far. Here we describe
the synthesis and structure of some cobalt and rhodium
perfluorobenzyl complexes of the general formula [M(η5-
C5R5)(CF2C6F5)I(L)] (M ) Co, Rh; R ) H, Me; L ) CO,
PMe3, PMe2Ph). While intramolecular and intermo-
lecular activation of aryl C-F bonds by transition metal
centers has been observed in a number of systems,2
activation of saturated C-F bonds has proven to be
more difficult and seems to require a strongly reducing
environment.3 Similarly, while the hydrolysis of transi-
tion metal-CF3 groups to give carbonyl ligands has been
observed in several systems,4-6 the reaction usually
requires the presence of a strong Lewis acid like BF3,4a
SbF5,4b or SiMe3,5 although there are some indications
that H+ can act as the initial fluoride acceptor in some
Resu lts a n d Discu ssion
Perfluorobenzyl compounds of cobalt (1a , 2a ) and
rhodium (2b) were readily prepared by the oxidative
addition of perfluorobenzyl iodide to [M(η5-C5R5)(CO)2]
(M ) Co, R ) H, Me; M ) Rh, R ) Me) in benzene at
room temperature, in the manner previously reported
for oxidative addition of fluoroalkyl iodides to [M(η5-
C5H5)(CO)2] (M ) Co,7 Rh8). The reactions were moni-
X Abstract published in Advance ACS Abstracts, December 1, 1996.
(1) Burton, D. J .; Yang, Z. Y.; Platonov, V. J . Fluorine Chem. 1994,
66, 23-24.
(2) Kiplinger, J . L.; Richmond, T. G.; Osterberg, C. E. Chem. Rev.
1994, 94, 373-431.
(3) Harrison, R. G; Richmond, T. G. J . Am. Chem. Soc. 1993, 115,
5303-5304. Kiplinger, J . L.; Richmond, T. G. Ibid. 1996, 118, 1805-
1806. Burdeniuc, J .; Crabtree, R. H. Ibid. 1996, 118,2525-2526.
tored by solution IR and 19F NMR spectroscopies to
ensure that the complete reaction had occurred. The
structures of compounds 1 and 2 were confirmed by H
1
S0276-7333(96)00725-X CCC: $12.00 © 1996 American Chemical Society

Perfluorobenzyl Complexes of Cobalt and Rhodium
Organometallics, Vol. 15, No. 26, 1996 5679
Ta ble 1. In fr a r ed Str etch in g F r equ en cies (νCO) of
CO Liga n d s in P er flu or oben zyl a n d Oth er
P er flu or oa lk yl Com p lexes of Coba lt a n d Rh od iu m
νCO (cm-1) (CH2Cl2)
ref
Co(C5H5)(CF2C6F5)(I)(CO) (1a )
Co(C5H5)(CF3)(I)(CO)
Co(C5H5)(C2F5)(I)(CO)
Co(C5Me5)(CF2C6F5)(I)(CO) (2a )
Co(C5Me5)(CF(CF3)2)(I)(CO)
Rh(C5Me5)(CF2C6F5)(I)(CO) (2b)
Rh(C5H5)(C2F5)(I)(CO)
2080
2073
2080a
2044
2062
2056
2098a
7a
7a
7b
8
a
Infrared reported in CS2.
troscopically and by elemental analysis. The solid state
structure of 3a was also obtained by X-ray diffraction.
Crystallographic information for the structure deter-
mination of 3a is given in Table 2, and a list of selected
bond lengths and angles is provided in Table 3. An
ORTEP plot with atom labeling scheme is shown in
Figure 1. Discussion of the solid state structure is
deferred until later.
and 19F NMR spectroscopy, IR spectroscopy, and el-
emental analysis. The 19F NMR spectra of all perfluo-
robenzyl complexes are similar, showing a characteristic
AB splitting pattern for the diastereotopic fluorines of
the R-CF2 group located downfield of the 2:1:2 pattern
of the three aromatic fluorine resonances between -140
and -160 ppm. The R-CF2 resonances exhibit a large
geminal coupling constant, J AB, ranging from 205 to 250
Hz, and each shows a triplet coupling to the two ortho
fluorines of the aromatic ring. As an example, the 19F
NMR spectrum of 1a exhibits an AB splitting pattern,
at δ -25.6 (dt, Fa) and -31.5 (dt, Fb) with the fluorine
atoms on the aromatic ring appearing at δ -137.0,
-153.7, and -162.5 in the expected 2:1:2 ratio. The
pentafluorophenyl ring rotates freely about the CF2-
C6F5 bond on the NMR time scale, as evidenced from
the NMR equivalence of the two ortho fluorines, even
on cooling to -60 °C, and their triplet coupling to each
of the CF2 fluorines. That this triplet coupling is of a
different magnitude to each CF2 fluorine suggests (not
unexpectedly) that the conformational ground state of
the molecule does not have the plane of the fluoroaryl
group bisecting the CF2 group. In the rhodium analogue
1,c any 103Rh coupling to the CF2 fluorines is too small
to be resolved.
The spectroscopic data obtained for the solution
structure are consistent with the solid state structure.
The presence of PMe3 is manifested in the 19F NMR
spectrum as an additional doublet, 31P coupling to the
AB resonances of the diastereotopic CF2 fluorines. In
these substitution products (3, 4, and 5), one of the CF2
fluorine atoms couples to 31P more strongly than the
other. The 31P{1H} NMR resonances corresponding to
the cobalt substitution complexes are very broad, pre-
sumably as a result of the quadrupolar 59Co isotope (I
7
) /2),10 whereas those of the analogous rhodium com-
plexes appear as the expected doublet of doublets, due
to coupling with 103Rh and one fluorine of the CF2 group.
The preparations of complexes 5 by reaction of 1a or
2b with PMe2Ph were similar to those of 3 and 4, and
the characterization methods were analogous. As ex-
The infrared spectra of 1 and 2 each show a single
high-frequency band characteristic of a single CO ligand
bound to Co(III) or Rh(III), and the results are listed in
Table 1 with those of other perfluoroalkyl analogues for
comparison.
Reactions of 1 and 2 with 1 equiv of PMe3 in benzene
solution result in simple CO substitution to give 3 and
4, respectively, in good yield. As expected for fluoroalkyl
ligands,9 no products resulting from the migratory
insertion of CO into the fluoroalkyl-metal bond were
observed. Complexes 3 and 4 were characterized spec-
pected, the methyl groups of the PMe2Ph ligand are
diastereotopic in complexes 5, each methyl group ap-
1
pearing as a doublet in the H NMR spectrum [J HP
)
Ta ble 2. Cr ysta llogr a p h ic Da ta for 3a , 5b, a n d 10b
3a
10b
5b
formula
formula weight
space group
a, Å
C
544.1
P21/c
10.422(3)
15H14CoF7IP
C25H25CoF4IOP
634.3
P21/n
11.188(5)
C25H26F7IPRh
720.2
P21/c
8.778(3)
b, Å
11.830(3)
17.405(7)
14.170(2)
c, Å
14.573(4)
12.651(5)
21.145(4)
â, deg
100.160(2)
1768.5(8)
94.16(4)
2457(2)
100.05(4)
2590(1)
V, Å3
Z
4
4
4
cryst color
D (calc), g cm-3
µ (Mo KR), cm-1
temp, K
radiation
R(F), %a
R(wF), %a
brown
2.043
28.71
293
Mo KR (λ ) 0.710 73 Å)
3.94
4.80
black
1.715
20.66
296
red
1.847
19.76
296
Mo KR (λ ) 0.710 73 Å)
3.76
4.51
Mo KR (λ ) 0.710 73 Å)
4.46
5.16
a
Quantity minimized ) ∑w∆2; R ) ∑∆/∑(Fo); R(w) ) ∑∆w1/2/∑(Fo‚w1/2), ∆ ) |(Fo - Fc)|

5680 Organometallics, Vol. 15, No. 26, 1996
Hughes et al.
F igu r e 1. ORTEP drawing and labeling scheme for 3a .
Ellipsoids are drawn at 35% probability.Hydrogens have
been omitted for clarity.
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 3a
F igu r e 2. ORTEP drawing and labeling scheme for 5b.
Ellipsoids are drawn at 35% probability.Hydrogens have
been omitted for clarity.
Co-I
2.583(1)
1.990(7)
2.074(8)
2.105(8)
1.815(8)
1.811(9)
1.390(7)
1.342(8)
1.343(9)
1.536(10)
1.392(9)
1.358(11)
1.368(10)
1.406(13)
1.402(11)
Co-P
2.204(2)
2.118(10)
2.059(8)
2.129(9)
1.813(9)
1.376(9)
1.343(9)
1.358(9)
1.335(8)
1.388(9)
1.379(11)
1.363(10)
1.395(12)
1.402(12)
1.397(12)
Co-C(1)
Co-C(8)
Co-C(9)
Co-C(10)
Co-C(12)
P-C(14)
Ta ble 4. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 5b
Co-C(11)
P-C(13)
Rh-I
2.706(1)
2.190(11)
2.217(9)
Rh-P
2.305(3)
P-C(15)
F(1)-C(1)
F(3)-C(3)
F(5)-C(5)
F(7)-C(7)
C(2)-C(3)
C(3)-C(4)
C(5)-C(6)
C(8)-C(9)
C(9)-C(10)
C(11)-C(12)
Rh-C(30)
Rh-C(22)
Rh-C(24)
P-C(7)
Rh-C(21)
Rh-C(23)
Rh-C(25)
P-C(8)
2.153(10)
2.251(10)
2.251(11)
1.804(12)
1.486(14)
1.327(12)
1.386(15)
1.365(18)
1.389(14)
1.405(16)
1.334(23)
1.373(21)
1.350(17)
1.392(15)
F(2)-C(1)
F(4)-C(4)
F(6)-C(6)
C(1)-C(2)
C(2)-C(7)
C(4)-C(5)
C(6)-C(7)
C(8)-C(12)
C(10)-C(11)
2.255(11)
1.804(10)
1.815(10)
1.257(14)
1.374(15)
1.361(18)
1.348(17)
1.356(15)
1.334(13)
1.327(17)
1.331(15)
1.329(15)
1.334(15)
P-C(6)
C(30)-C(16)
C(30)-F(32)
C(1)-C(6)
C(3)-C(4)
C(5)-C(6)
C(11)-C(16)
C(12)-C(13)
C(13)-C(14)
C(14)-C(15)
C(15)-C(16)
C(30)-F(31)
C(1)-C(2)
C(2)-C(3)
C(4)-C(5)
C(11)-C(12)
C(11)-F(1)
C(12)-F(2)
C(13)-F(3)
C(14)-F(4)
C(15)-F(5)
I-Co-P
90.5(1)
92.4(2)
99.8(3)
135.3(3)
127.2(3)
151.4(2)
94.5(3)
39.7(3)
152.8(2)
65.2(4)
39.4(3)
137.1(3)
38.7(4)
I-Co-C(1)
97.5(2)
97.6(2)
160.5(3)
89.0(3)
38.8(3)
114.8(2)
66.6(3)
113.0(2)
97.4(3)
64.9(3)
86.8(2)
130.4(3)
64.5(3)
P-Co-C(1)
I-Co-C(8)
P-Co-C(8)
I-Co-C(9)
C(1)-Co-C(9)
I-Co-C(10)
C(1)-Co-C(10)
C(9)-Co-C(10)
P-Co-C(11)
C(8)-Co-C(11)
C(10)-Co-C(11)
P-Co-C(12)
C(8)-Co-C(12)
C(10)-Co-C(12)
Co-P-C(13)
C(13)-P-C(14)
C(13)-P-C(15)
Co-C(1)-F(1)
F(1)-C(1)-F(2)
F(1)-C(1)-C(2)
C(1)-C(2)-C(3)
C(3)-C(2)-C(7)
F(3)-C(3)-C(4)
F(4)-C(4)-C(3)
C(3)-C(4)-C(5)
F(5)-C(5)-C(6)
F(6)-C(6)-C(5)
C(5)-C(6)-C(7)
F(7)-C(7)-C(6)
C(1)-Co-C(8)
P-Co-C(9)
C(8)-Co-C(9)
P-Co-C(10)
C(8)-Co-C(10)
I-Co-C(11)
C(1)-Co-C(11)
C(9)-Co-C(11)
I-Co-C(12)
I-Rh-P
91.3(1)
89.7(3)
112.3(3)
130.2(3)
132.3(4)
96.5(3)
156.1(4)
35.8(4)
146.9(3)
60.7(4)
I-Rh-C(30)
97.1(3)
151.8(3)
98.2(4)
94.0(3)
37.4(4)
109.6(3)
61.9(4)
91.0(3)
122.7(5)
60.3(4)
117.7(3)
95.1(4)
61.1(4)
35.0(5)
115.7(4)
114.6(3)
104.0(5)
111.6(7)
105.9(7)
P-Rh-C(30)
I-Rh-C(21)
P-Rh-C(21)
I-Rh-C(22)
C(30)-Rh-C(22)
I-Rh-C(23)
C(30)-Rh-C(23)
C(22)-Rh-C(23)
P-Rh-C(24)
C(21)-Rh-C(24)
C(23)-Rh-C(24)
P-Rh-C(25)
C(21)-Rh-C(25)
C(23)-Rh-C(25)
Rh-P-C(7)
C(30)-Rh-C(21)
P-Rh-C(22)
C(21)-Rh-C(22)
P-Rh-C(23)
C(1)-Co-C(12)
C(9)-Co-C(12)
C(11)-Co-C(12)
Co-P-C(14)
C(21)-Rh-C(23)
I-Rh-C(24)
65.8(3)
38.5(3)
C(30)-Rh-C(24)
C(22)-Rh-C(24)
I-Rh-C(25)
114.5(3)
104.6(4)
101.3(4)
114.8(5)
102.6(5)
105.6(5)
122.8(6)
114.8(6)
116.4(6)
119.3(7)
119.9(7)
120.9(7)
119.9(7)
119.5(7)
116.0(6)
111.9(3)
120.7(3)
101.8(4)
110.0(4)
116.5(5)
106.2(5)
122.3(6)
121.1(6)
122.5(7)
120.8(7)
119.1(7)
120.0(7)
120.6(6)
120.7(6)
123.2(6)
Co-P-C(15)
37.4(4)
149.6(3)
37.3(5)
C(14)-P-C(15)
Co-C(1)-F(2)
Co-C(1)-C(2)
F(2)-C(1)-C(2)
C(1(-C(2)-C(7)
F(3)-C(3)-C(2)
C(2)-C(3)-C(4)
F(4)-C(4)-C(5)
F(5)-C(5)-C(4)
C(4)-C(5)-C(6)
F(6)-C(6)-C(7)
F(7)-C(7)-C(2)
C(2)-C(7)-C(6)
C(30)-Rh-C(25)
C(22)-Rh-C(25)
C(24)-Rh-C(25)
Rh-P-C(8)
61.2(4)
117.2(4)
102.2(5)
101.0(5)
117.2(7)
C(7)-P-C(8)
C(7)-P-C(6)
Rh-C(30)-C(16)
C(16)-C(30)-F(31) 110.0(9)
C(16)-C(30)-F(32) 105.9(8)
Rh-P-C(6)
C(8)-P-C(6)
Rh-C(30)-F(31)
Rh-C(30)-F(32)
F(31)-C(30)-F(32) 105.3(9)
C(2)-C(1)-C(6)
C(2)-C(3)-C(4)
C(4)-C(5)-C(6)
P-C(6)-C(5)
121.1(10) C(1)-C(2)-C(3)
120.4(12)
119.2(12) C(3)-C(4)-C(5)
121.8(11) P-C(6)-C(1)
123.7(8) C(1)-C(6)-C(5)
120.7(11)
119.6(8)
116.6(9)
118.0(11)
C(12)-C(11)-C(16) 123.2(11) C(12)-C(11)-F(1)
11.1 (5a ) and 10.5 (5b) Hz]. Curiously, the benzylic CF2
resonances of 5b appear as a broad singlet. Rapid
inversion of configuration at the metal center is pre-
cluded by the observation of diastereotopic Me groups
for the PMe2Ph ligand (vide supra); the CF2 fluorines
are likely to have approximately coincidental chemical
shifts. To confirm its identity, the solid state structure
of 5b was also determined by X-ray diffraction. Crys-
tallographic information for the structure determination
of 5b is given in Table 2, and a list of selected bond
lengths and angles is given in Table 4. An ORTEP plot
C(16)-C(11)-F(1)
C(11)-C(12)-F(2)
118.8(9)
118.4(13) C(13)-C(12)-F(2)
C(11)-C(12)-C(13) 121.0(13)
120.5(11)
121.7(13)
C(12)-C(13)-C(14) 119.2(12) C(12)-C(13)-F(3)
C(14)-C(13)-F(3)
C(13)-C(14)-F(4)
119.1(14) C(13)-C(14)-C(15) 119.4(12)
120.4(12) C(15)-C(14)-F(4)
120.0(13)
115.6(10)
C(14)-C(15)-C(16) 124.4(12) C(14)-C(15)-F(5)
C(16)-C(15)-F(5)
120.0(9)
with atom labeling scheme is presented in Figure 2.
The solid state structures of 3a and 5b show some
similarities and some significant differences. In both
complexes, the metal has a pseudooctahedral geometry

Perfluorobenzyl Complexes of Cobalt and Rhodium
Organometallics, Vol. 15, No. 26, 1996 5681
with the cyclopentadienyl ligand occupying three fac
coordination sites. Interligand bond angles I-Co-P,
I-Co-C(1), and P-Co-C(1) for 3a and I-Rh-P, I-Rh-
C(30), and P-Rh-C(30) for 5b are approximate 90°. For
cobalt complex 3a , the Co-C(1) distance (1.990(7) Å) is
similar to the Co-CF2 distances in the cobalt n-
perfluoropropyl complexes reported by J ablonski and
co-workers: [Co(η5-indenyl)(n-C3F7)I(Ph2PNHCH(CH3)-
(Ph))] ) 1.962(2) Å,11 [Co(η5-indenyl)(n-C3F7)I(PMe3)-
(P(O)(OMe)2)] ) 1.972(4) Å, [Co(η5-indenyl)(n-C3F7)
I(PMe3)(P(O)Ph(OMe))] ) 1.987(7) Å, [Co(η5-indenyl)(n-
C3F7)I(PMe2Ph)(P(O)Ph(OMe))] ) 1.979(5) Å, and [Co-
(η5-C5H5)(n-C3F7)I(PMe3)(P(O)Ph(OMe))] ) 1.968(4) Å.12
The Co-P distance in 3a (2.210(2) Å) is also similar to
the Co-P distances in the (n-perfluoropropyl)cobalt
complexes mentioned above.12 In contrast, the Rh-CF2
distance in 5b is significantly longer than that in [Rh-
(C5H5)(C2F5)I(CO)]13 (2.190(11) vs 2.08(3) Å) and longer
than those in the metallacyclic complexes 6 (2.075(6),
2.024(6) Å), 7 (2.013(5) Å), and 8 (2.034(4) Å).14 On the
metal-CF2-Cipso found in 3a (116.5(5)°) and 5b
(117.2(7)°). Further manifestation of the high p-char-
acter inthe carbon orbitals to fluorine and the cor-
respondingly high s-character in the carbon orbital to
the metal is provided in a comparison of the structure
of 3a with a different complex, described below.
Comparison of 3a and 5b also reveals some differ-
ences in their solid state structures. The C-F distances
in the CF2 group in 5b (1.257(14), 1.327(12) Å) are
significantly shorter than those in 3a (1.376(9), 1.390(7)
Å). The conformation of the perfluorobenzyl ligand is
also quite different. In 3a , the pentafluorophenyl ring
is directed away from the trimethylphosphine ligand,
as expected, but also tilts toward the cyclopentadienyl
ring, with F(7) being particularly close. While the
H-atoms on the cyclopentadienyl carbons of 3a were not
located crystallographically, assumption of a reasonable
C-H bond length of 1.00 Å for the H-atoms bound to
C(10) and C(11) brings these H-atoms within 2.53 and
2.59 Å, respectively, of F(7), distances less than the sum
of the van der Waals’ radii (2.67 Å), indicative of weak
intramolecular hydrogen bonding.17 This interaction is
far too weak to have any effect on the conformational
dynamics of the pentafluorophenyl ring in solution,
where it rotates freely on the NMR time scale (vide
supra), but it may be a factor in favoring the solid state
conformation. In contrast, and not unexpectedly, the
perfluorobenzyl ligand in 5b adopts a conformation in
which the pentafluorophenyl ring tilts away from the
much bulkier pentamethylcyclopentadienyl (Cp*) ligand.
Even so, there are some necessarily close H‚‚‚F contacts
in this structure; making analogous assumptions as to
the positions of the H-atoms, the ortho fluorine F(1)
must be within 2.60 Å of a H-atom on C(35), the benzylic
fluorine F(32) must be within 2.27 Å of the very same
H-atom, and the other benzylic fluorine, F(31), is within
2.25 Å of a H-atom on the phosphorus methyl carbon
C(8). Thus, weak hydrogen bonding interactions may
be important in defining thepreferred conformations of
these molecules; certainly H-F distances of this mag-
nitude have been interpreted similarly in organic sys-
tems.18
other hand, the Rh-P bond distance in 5b (2.305(3) Å)
is significantly shorter than those in 6 (2.386(2), 2.400(2),
2.378(2) Å) or 8 (2.362(1), 2.379(1), 2.367(1) Å).14 The
expected higher p-character in the carbon orbitals to
fluorine is reflected in the typically acute bond angles15,16
in the CF2 groups of 3a (102.6(5)°) and 5b (105.3(5)°),
with correspondingly more obtuse angles between the
While the cobalt complex 2a reacts with PMe3 in
benzene to give 4a , the corresponding reaction in THF
results in a completely different pathway, in which a
coupling of one methyl group of the pentamethylcyclo-
pentadienyl ligand with one ortho position of the per-
fluorobenzyl ligand has occurred, affording 9a . Hydro-
gen fluoride is evolved and was identified in the volatiles
trapped from the reaction mixture by 19F NMR (THF)
at δ -194.2 (J HF ) 438 Hz).19 The structural assign-
ment for 9a is based on the spectroscopic evidence and
on the X-ray structure of a derivative described below.
(4) (a) Richmond, T. G.; Crespi, A. M.; Shriver, D. F. Organometallics
1984, 3, 314-319. (b) Reger, D. L.; Dukes, M. D. J . Organomet. Chem.
1978, 153, 67.
(5) Koola, J . D.; Roddick, D. M.Organometallics 1981, 10, 591-597.
(6) Michelin, R. A.; Ros, R.; Guadalupi, G.; Bombieri, G.; Benetollo,
F.; Chapius, G. Inorg. Chem. 1989, 28, 840-846.
(7) (a) King, R.; Treichel, P.; Stone, F. G. A. J . Am. Chem. Soc. 1961,
83, 3593. (b) King, R. B.; Efraty, A.; Douglas, W. M. J . Organomet.
Chem. 1973, 56, 345-355.
(8) McCleverty, J .; Wilkinson, G. J . Chem. Soc. 1964,4200-4203.
(9) Connor, J . A.; Zafarani-Moattar, M. T.; Bickerton, J .; El Saied,
N. I.; Carson, R.; Al Takhin, G.; Skinner, H. A. Organometallics 1982,
1, 1166. Calderazzo, F. Angew. Chem. 1977, 89, 305.
(10) Friebolin, H. Basic One-and Two-Dimensional NMR Spectro-
scopy; VCH Verlagsgesellschaft: Weinheim, FRG, 1991, p 344.
(11) J ablonski, C.; Zhou, Z.; Bridson, J . N. J . Organomet. Chem.
1992, 429, 379-389.
(12) Zhou, Z.; J ablonski, C.; Bridson, J . Organometallics 1994, 13,
781-794.
(13) Churchill, M. R. Inorg. Chem. 1965, 4, 1734-1739.
(14) Hughes, R. P.; Rose, P. R.; Rheingold, A. L. Organometallics
1993, 12, 3109-3117.
The 19F NMR spectrum of 9a shows diastereotopic CF2
fluorines but only four aromatic fluorine resonances of

5682 Organometallics, Vol. 15, No. 26, 1996
Hughes et al.
for any ring-coupling products was obtained in the
reactions of the rhodium analogue 2b.
Complexes 9 were difficult to purify owing to rapid
conversion to new compounds 10 via hydrolysis of the
CF2 group to a ketone; notably, this hydrolysis reaction
proceeded even under “anhydrous” conditions, but could
be inhibited by adding excess CaCO3 to the reaction
mixtures. The slightly more stable 9a could be crystal-
F igu r e 3. ORTEP drawing and labeling scheme for 10b.
Ellipsoids are drawn at 35% probability. Hydrogens have
been omitted for clarity.
Ta ble 5. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 5b
Co-I
2.595(1)
2.071(4)
2.168(4)
2.128(5)
1.824(6)
1.822(6)
1.367(7)
1.322(7)
1.418(7)
1.507(7)
1.498(7)
1.505(7)
1.507(7)
1.513(7)
1.387(7)
1.351(9)
1.375(7)
Co-P
2.210(2)
2.067(4)
2.182(5)
1.972(5)
1.817(6)
1.118(6)
1.356(8)
1.343(7)
1.408(7)
1.431(6)
1.405(7)
1.434(7)
1.511(8)
1.372(8)
1.390(9)
1.391(9)
1.520(7)
Co-C(1)
Co-C(2)
lized for microanalysis, whereas 9b converted too rap-
idly to 10b in solution. In contrast to progenitors 9, the
solution IR spectra of 10 reveal bands at ca. 1610 cm-1
for the acyl group and the 19F NMR spectra lack
resonances due to the CF2 group. The solid state
structure of 10b was also obtained and confirms the
structure indicated by the solution data. The crystal-
lographic information for the structure determination
of 10b is given in Table 2, and a list of selected bond
lengths and angles is given in Table 5. An ORTEP plot
with atom labeling scheme is presented in Figure 3.
Once again, the metal has a pseudooctahedral geom-
etry with the Cp ligand occupying three fac coordination
sites and interligand bond angles I-Co-P, I-Co-C(17),
and P-Co-C(17) of approximately 90°. The distance
from the metal to the three-coordinate acyl carbon in
10b, Co-C(17) (1.972(5) Å), is identical within experi-
mental error to that between cobalt and the four-
coordinate fluorobenzylic carbon in 3a, Co-C(1) (1.990(7)
Å). This perhaps emphasizes the increased s-charac-
ter expected in the carbon orbital to cobalt in 3a ,
induced by the presence of two fluorines.
Co-C(3)
Co-C(4)
Co-C(17)
P-C(19)
Co-C(5)
P-C(18)
P-C(26)
O(1)-C(17)
F(2)-C(13)
F(4)-C(15)
C(1)-C(5)
C(2)-C(3)
C(3)-C(4)
C(4)-C(5)
C(5)-C(9)
C(11)-C(12)
C(12)-C(13)
C(14)-C(15)
C(16)-C(17)
F(1)-C(12)
F(3)-C(14)
C(1)-C(2)
C(1)-C(10)
C(2)-C(6)
C(3)-C(7)
C(4)-C(8)
C(10)-C(11)
C(11)-C(16)
C(13)-C(14)
C(15)-C(16)
I-Co-P
93.8(1)
145.8(1)
106.9(1)
132.4(1)
65.4(2)
97.9(1)
65.4(2)
37.7(2)
154.4(1)
66.3(2)
38.8(2)
89.8(1)
98.1(2)
152.5(2)
116.8(2)
101.6(3)
102.6(3)
69.8(2)
108.6(4)
126.4(4)
70.1(2)
107.2(4)
126.4(4)
66.5(2)
108.5(4)
125.4(4)
70.6(3)
107.7(4)
126.5(4)
68.2(3)
I-Co-C(1)
120.3(1)
157.5(1)
40.1(2)
94.2(1)
39.4(2)
115.6(1)
65.5(2)
91.2(1)
39.2(2)
64.5(2)
90.5(1)
87.8(2)
136.4(2)
115.3(2)
115.6(2)
113.8(2)
104.7(3)
72.6(3)
125.4(3)
124.9(4)
74.1(2)
128.7(3)
125.7(4)
71.7(3)
133.7(3)
125.6(4)
68.5(3)
130.5(3)
125.6(5)
72.6(3)
131.1(4)
P-Co-C(1)
I-Co-C(2)
P-Co-C(2)
C(1)-Co-C(2)
P-Co-C(3)
I-Co-C(3)
C(1)-Co-C(3)
I-Co-C(4)
C(2)-Co-C(3)
P-Co-C(4)
C(1)-Co-C(4)
C(3)-Co-C(4)
P-Co-C(5)
C(2)-Co-C(4)
I-Co-C(5)
C(1)-Co-C(5)
C(3)-Co-C(5)
I-Co-C(17)
C(2)-Co-C(5)
C(4)-Co-C(5)
P-Co-C(17)
C(1)-Co-C(17)
C(3)-Co-C(17)
C(5)-Co-C(17)
Co-P-C(19)
C(2)-Co-C(17)
C(4)-Co-C(17)
Co-P-C(18)
Compounds 10 represent the products of an unusual,
but not unprecedented, coupling of a methyl group of
Cp* with a pentafluorophenyl ring. Saunders and co-
workers20 recently reported a similar intramolecular
coupling in the reaction of [Rh(η5-C5Me5)Cl2]2 with 1,2-
bis[bis(pentafluorophenyl)phosphino]ethane to give 11,
crystallographically characterized as its BF4- salt. This
C(18)-P-C(19)
C(18)-P-C(26)
Co-C(1)-C(2)
C(2)-C(1)-C(5)
C(2)-C(1)-C(10)
Co-C(2)-C(1)
C(1)-C(2)-C(3)
C(1)-C(2)-C(6)
Co-C(3)-C(2)
C(2)-C(3)-C(4)
C(2)-C(3)-C(7)
Co-C(4)-C(3)
C(3)-C(4)-C(5)
C(3)-C(4)-C(8)
Co-C(5)-C(1)
Co-P-C(26)
C(19)-P-C(26)
Co-C(1)-C(5)
Co-C(1)-C(10)
C(5)-C(1)-C(10)
Co-C(2)-C(3)
Co-C(2)-C(6)
C(3)-C(2)-C(6)
Co-C(3)-C(4)
Co-C(3)-C(7)
C(4)-C(3)-C(7)
Co-C(4)-C(5)
Co-C(4)-C(8)
C(5)-C(4)-C(8)
Co-C(5)-C(4)
Co-C(5)-C(9)
equal intensity; the doublet of doublets of doublets
pattern for one of the CF2 resonances indicates that only
one ortho fluorine atom is coupling to the R-CF2 group
product is the result of coupling of two methyl groups
with two fluoroaryl carbon atoms, resulting in two new
.
The 1H NMR spectrum shows four inequivalent
methyl groups for the tetramethylcyclopentadienyl ligand,
two inequivalent, strongly coupled (J AB ) 15.6 Hz)
methylene hydrogens, and a doublet at δ 1.30 for the
PMe3 ligand. An analogous product 9b is observed in
the reaction of 2a and PMe2Ph in THF and has been
characterized similarly spectroscopically. No evidence
(15) Smart, B. E. In The Chemistry of Functional Groups, Supple-
ment D: Patai, S., Rappoport, Z., Eds.; J ohn Wiley & Sons: New York,
1983; Chapter 14.
(16) Bernett, W. A. J . Org. Chem. 1969, 34, 1772. Bondi, A. J . Phys.
Chem. 1964, 68, 441.
(17) Smart, B. E. Organofluorine Chemistry; Banks, R. E., Smart,
B. E., Tatlow, J . C., Eds.; Plenum Press: New York, 1994; p 69.

Perfluorobenzyl Complexes of Cobalt and Rhodium
Organometallics, Vol. 15, No. 26, 1996 5683
Sch em e 1
Sch em e 2
C-C bonds between the respective ortho aryl carbon
atoms and the exocyclic carbons of Cp*. The HF which
presumably must also accompany this coupling reaction
was not identified. The authors suggest an electron
transfer initiated mechanism involving the initial trans-
fer of an electron from the Cp* ring to the fluoroarene;20
an analogous pathway has been proposed for the C-F
activation observed in the reaction of C6F6 with IrMe-
(PEt3)3.21 However, the latter reaction involves an Ir(I)
precursor, whereas the metal center in the precursors
for 11 or 9 are formally in the M(III) oxidation state
and would be less likely to reduce a fluoroarene. A more
likely pathway available in our system would involve
deprotonation of a methyl group on the Cp* ring to give
a fulvene intermediate, followed by nucleophilic addi-
tion-elimination of fluoride from the ortho-position of
the pentafluorophenyl ring as shown in Scheme 1.
However, as noted by the authors who prepared 11,20
deprotonation of the Cp* ligand to give fulvene-
rhodium complexes requires a strong base22 and it is
not obvious what that base may be in their system; a
similar concern pertains to formation of complexes 9.
We speculate in Scheme 1 that a trace of base (B) can
initiate the reaction, and then the fluoride ion that is
produced can act as a base giving HF, which we have
observed (vide supra), thereby propagating the reaction.
Surprisingly, treatment of either the starting material
2a or the simple substitution product 4a with bases such
CO. The solution IR spectrum of 13 shows a carbonyl
band at 2060 cm-1 compared to starting complex 2a
(2044 cm-1), consistent with a cationic cobalt center in
13, and the NMR spectra are very similar to others
described herein. In support of our hypothesis, the
treatment of 13 with bis(triphenylphosphine)nitro-
gen(1+) iodide [PPN+I-] in attempts to give 12 instead
affords the ring coupling to give 10a as the major
product, presumably via 9a , as well as small amounts
of 2a and 4a . Apparently iodide can act as either the
nucleophile or the initiating base in this reaction.
Why is there no observed ring coupling during the
substitution reactions of the rhodium analogue 2b,
especially in view of the facility of an analogous coupling
in the related system to afford 11? In the putative
progenitor for rhodium complex 11, one pentafluorophe-
nyl group on each phosphorus must be in close proximity
to the Cp* ligand, with a restricted conformational
flexibility being imposed by coordination of the chelating
diphosphine. In complex 2a , the smaller cobalt center
is also expected to be sterically congested, with the Cp*
and pentafluorophenyl group spending some of their
time in close proximity. In the rhodium derivatives, the
larger metal center means a longer distance between
Cp* and the pentafluorophenyl ring, without significant
conformational restraints imposed on the perfluoroben-
zyl ligand. So, even if deprotonation of a methyl group
can occur during the substitution mechanism of 2b, any
t
as LDA, N(iPr)2Et, or BuLi did not result in coupling
of the two rings, indicating that if deprotonation of the
pentamethylcyclopentadienyl ligand is indeed a crucial
step, it must occur at some intermediate stage in the
overall substitution reaction rather than directly from
starting material 2a or substitution product 4a .
A reasonable intermediate in the substitution reaction
would result from substitution of phosphine for I- in
2a to give cation 12 as shown in Scheme 2. Indeed,
J ablonski and co-workers12 have investigated the reac-
tions of [Co(η5-C5H5)(n-C3F7)(I)(L)] (L ) P(OMe)3, PMe3)
with PR(OMe)2 (R ) OMe, Ph) which afford analogous
ionic species. We expect the methyl protons in cation
12 to be more acidic than those in starting material 2a
or product 4a deprotonatation occurs more easily, and
the resultant carbanion can then initiate the observed
coupling reaction. Although attempts to isolate 12, or
to observe it during the course of the reaction, were
(20) Atherton, M. J .; Fawcett, J .; Holloway, J . H.; Hope, E. G.;
Karacar, A.; Russell, D. R.; Saunders, G. C. J . Chem. Soc., Chem.
Commun. 1995, 191-192. Atherton, M. J .; Fawcett, J .; Holloway, J .
H.; Hope, E. G.; Karacar, A.; Russell, D. R.; Saunders, G. C. J . Chem.
Soc., Dalton Trans. 1996, 3215-3220.
-
(21) Blum, O.; Frolow, F.; Milstein, D.
J Chem. Soc., Chem.
unsuccessful, the BF4 analog 13 was readily synthe-
Commun. 1991, 258.
sized from reaction of 4a with AgBF4 in the presence of
(22) Gusev, O. V.; Sergeev, S.; Saez, I. M.; Maitlis, P. M. Organo-
metallics 1994, 13, 2059. Miguel-Garcia, J . A.; Maitlis, P. M. J . Chem.
Soc., Chem. Commun. 1990, 1472-1473. Glueck, D. S.; Bergman, R.
G. Organometallics 1990, 9 , 2862-2863.
(18) Huang, J .; Hedberg, K. J . Am. Chem. Soc. 1989, 111, 6909.
(19) Muenter, J . S.; Klemperer, W. J . Chem. Phys. 1970, 52, 6033.

5684 Organometallics, Vol. 15, No. 26, 1996
Hughes et al.
Braun drybox. 1H NMR (300 MHz), 19F NMR (282.2 MHz),
and 31P NMR (121.4 MHz) spectra were recorded on a Varian
Unity Plus 300 FT spectrometer at 23 °C; coupling constants
were recorded in Hz. 1H NMR chemical shifts were recorded
in deuteriobenzene as ppm downfield from tetramethylsilane,
unless otherwise stated, and referenced to the solvent. 19F
NMR chemical shifts were recorded in deuteriobenzene, unless
otherwise stated, as ppm and internally referenced to CFCl3.
Chemical shifts for 31P{1H} NMR were recorded in deuteri-
obenzene, unless otherwise stated, as ppm and externally
referenced to 85% H3PO4. The infrared spectra were recorded
on a Perkin-Elmer FTIR 1600 Series spectrometer. Micro-
analyses were performed by Schwarzkopf Microanalytical
Laboratory, Woodside, NY.
Rea gen ts. PMe3 (Aldrich), C6F5CF2I (PCR), PMe2Ph, Co2-
(CO)8, and pentamethylcyclopenta-1,3-diene (Strem), [Co-
(C5H5)(CO)2] (Aldrich or Strem), 1, 3-cyclohexadiene (Lancast-
er), AgBF4 [Ato-Chem (North America)], and CO (Matheson)
were purchased commercially. [Co(C5Me5)(CO)2],24 [Co(C5R5)-
(CO)(PMe2Ph) ] (R ) H, Me),25 and [Rh(C5Me5)(CO)2]26 were
prepared according to literature methods. (Ph3PdNdPPh3)+I-
[PPN+I-] was prepared by anion exchange from the corre-
sponding chloride, which was obtained from J ohnson-Matthey.
Hydrocarbon and ethereal solvents were distilled under dini-
trogen from sodium or sodium/potassium alloy and benzophe-
none ketyl, and halogenated solvents were distilled from
calcium hydride. Deuterated solvents were purchased from
ISOTEC, Inc., or Cambridge Isotope Laboratories.
resultant nucleophilic attack on the pentafluorophenyl
ring is likely to be entropically disfavored compared to
2a .
The facility of hydrolysis of the CF2 group in com-
plexes 9 is also remarkable when compared to the lack
of hydrolytic reactivity of the CF2 groups in complexes
1-5. By analogy with previously studied reactions of
this type, we assume that such hydrolysis requires the
presence of a fluoride acceptor (a Lewis or protic acid)
and, of course, the adventitious moisture as the source
of the oxygen atom in the final product. The pathway
by which compounds 9 are formed also yields HF as a
reaction product, and we suggest that this can initiate
the hydrolysis mechanism in a manner similar to those
suggested in the literature.4,23 Traces of HF act as the
initial fluoride acceptor to give a carbocation that is
stabilized by π-back-bonding from the metal. Nucleo-
philic attack on carbon by adventitious water, followed
by loss of 2 equiv of HF, affords the final ketone product
and generates more HF to act as a fluoride abstractor.
We have shown previously14 that even glass surfaces
that have been flame dried can still infuse sufficient
water as a reagent to a reactive center, especially on
the small scales on which these reactions are performed.
Protection of the glass surface by silylation, or some
other method of isolating the contained solution from
the surface, is essential to exclude such moisture. A
more detailed study on the role of trace protic acids,
fluoride acceptors, and surface moisture on the hydroly-
sis reactions of saturated fluorocarbons is underway in
our laboratories and will be published in due course.
Finally we have observed that heating 2a at 80 °C
for prolonged periods in benzene solution results in a
direct coupling reaction of the perfluorobenzyl and
pentamethylcyclopentadienyl ligands to give cyclopen-
tadiene 14 in 20% yield. The diene was characterized
(η5 -C y c lo p e n t a d ie n y l)io d o (p e r flu o r o b e n zy l)c a r -
bon ylcoba lt(III) (1a ). [Co(C5H5)(CO)2] (641 mg, 3.56 mmol)
was dissolved in benzene (35 mL), C6F5CF2I (930 mg, 2.70
mmol) was added, and the reaction mixture was stirred at
room temperature (46 h). Volatiles were removed under
vacuum leaving behind a green-black solid, which was dis-
solved in diethyl ether. The solution was filtered via cannula,
and the filtrate was concentrated. The product crystallized
from ethyl ether at -78 °C as dark brown crystals (1.02 g,
76%). Mp: 118-119 °C. 1H NMR (C6D6) δSPCLN 4.49 (s, 5H,
C5H5). 19F NMR (C6D6) δSPCLN -25.6 (dt, J F ) 207, J F
F
F
cc′
a
b
a
) 30, 1F, Fa), -31.5 (dt, J F ) 207, J F cc′ ) 33, 1F, Fa), -137.0
F
F
b
a
b
(m, 2F, Fcc′), -153.7 (t, J FF ) 21, 1F, Fe), -162.5 (m, 2F, Fdd′).
IR (CH2Cl2): νCO ) 2080 cm-1. Anal. Calcd for C13H5CoF7IO:
C, 31.48; H, 1.02. Found: C, 31.55; H, 1.10.
(η5-P e n t a m e t h ylcyclop e n t a d ie n yl)iod o(p e r flu or o-
ben zyl)ca r bon ylcoba lt(III) (2a ). A solution of [Co(C5Me5)-
(CO)2] (2.70 g, 10.8 mmol) in benzene (70 mL) was treated with
C6F5CF2I (3.82 g, 11.1 mmol), and the mixture was stirred at
room temperature (1 h). Similar workup gave the product as
black crystals (5.70 g, 93%). Mp: 126-128 °C. 1H NMR (C6D6)
δ: 1.49 (15H, C5Me5). 19F NMR (C6D6) δ: -50.6 (d, J F b ) 217,
F
1
a
by H and 19F NMR spectroscopy and gas chromatog-
J F
) 27, 1F, Fa), -58.4 (d, J F ) 217, J F
) 36, 1F, Fb),
F
F
F
b cc′
a
cc′
a
b
1
raphy/mass spectrometry (GC/MS). The H NMR (C6D6)-
-136.1 (m, 2F, Fcc′), -155.1 (t, J FF ) 21, 1F, Fe), -163.3 (m,
2F, Fdd′). IR (CH2Cl2): νCO ) 2044 cm-1
Anal. Calcd for
18H15CoF7IO: C, 38.19; H, 2.67. Found: C, 38.59; H, 2.62.
(η5-P e n t a m e t h ylcyclop e n t a d ie n yl)iod o(p e r flu or o-
spectrum reveals three singlets in a 1:2:2 ratio corre-
sponding to the methyl groups, and the 19F NMR (C6D6)
reveals the expected four different types of fluorine
resonances. The CF2 resonance in 14 is shifted upfield
from its position in the starting material. The three
resonances due to the aromatic fluorine substituents
appeared in positions similar to those of complexes
described previously. GC/MS data reveal that the high-
est molecular weight ion peak corresponded to the
molecular weight of the coupled organic fragment.
.
C
ben zyl)ca r bon ylr h od iu m (III) (2b). A solution of [Rh(C5-
Me5)(CO)2] (162 mg, 0.551 mmol) in benzene (10 mL) was
treated with C6F5CF2I (232 mg, 0.673 mmol), and the mixture
was stirred at room temperature (14 h). Volatiles were
removed under vacuum, and the resultant red-orange solid was
dissolved in CH2Cl2. The solution was filtered via cannula and
concentrated, and hexane was layered gently on top of the CH2-
Cl2. The product crystallized at -20 °C as deep red crystals
(284 mg, 85%). Mp: 146-147 °C. 1H NMR (C6D6) δ: 1.53
(15H, C5Me5). 19F NMR (C6D6) δ: -44.1 (dt, J F ) 211, J F
Exp er im en ta l Section
F
F
cc′
a
b
a
) 23, 1F, Fa), -53.6 (dt, J F ) 211, J F cc′ ) 35, 1F, Fb), -136.6
F
F
b
a
b
Gen er a l Con sid er a tion s. All reactions were performed
in oven-dried glassware using standard Schlenk techniques
under an atmosphere of dinitrogen, which had been deoxy-
genated over BASF catalyst and dried over Aquasorb or in a
(m, 2F, Fcc′), -155.2 (t, J FF ) 20, 1F, Fe), -163.1 (m, 2F, Fdd′).
(24) Frith, S. A.; Spencer, J . L. Inorg. Syn. 1990, 28, 273-285.
(25) Werner, H.; Heiser, B.; Klingert, B.; Dolfel, R. J . Organomet.
Chem. 1982, 240, 179-190.
(26) Maitlis, P. M.; Kang, J . W. J . Organomet. Chem. 1971, 26, 393-
399.
(23) Clark, G. R.; Hoskins, S. V.; Roper, W. R. J . Organomet. Chem.
1982, 234, C9-C12.

Perfluorobenzyl Complexes of Cobalt and Rhodium
Anal. Calcd for C18H15F7-
Organometallics, Vol. 15, No. 26, 1996 5685
IR (CH2Cl2): νCO ) 2056 cm-1
.
NMR (C6D6) δ: 1.37 (d, J HRh ) 3.3, 15H, C5Me5), 1.71(d, J HP
) 10.5, 3H, C5Me5), 1.81 (d, J HP ) 10.5, 3H, C5Me5), 7.04 (m,
3H, PMe2Ph), 7.72 (m, 3H, PMe2Ph). 19F NMR (C6D6) δ: -45.7
(br s, 2F, Fa, Fb), -139.7 (m, 2F, Fcc′), -159.0 (t, 1F, Fe), -165.1
(m, 2F, Fdd′). 31P{1H} NMR (C6D6) δ: 15.40 (dd, J PRh ) 160,
J PF ) 73, PMe2Ph). Anal. Calcd for C25H26F7IPRh: C, 41.69;
H, 3.64. Found: C, 41.62; H, 3.66.
IORh: C, 35.44; H, 2.48. Found: C, 35.36; H, 2.66.
(η5 -C y c lo p e n t a d ie n y l)io d o (p e r flu o r o b e n zy l)(t r i-
m eth ylp h osp h in e)coba lt(III) (3a ). A solution of 1a (500
mg, 1.01 mmol) in benzene (30 mL) was treated with PMe3
(105 µL, 1.01 mmol), and the mixture was stirred at room
temperature (6 h). The reaction mixture was filtered via
cannula, and the volatiles were removed under vacuum leaving
behind a green-black solid (390 mg, 71%). Crystals for X-ray
diffraction were obtained from an ethyl ether solution which
was cooled to 10 °C. Mp: 136-137 °C. 1H NMR (C6D6) δ:
1.24 (9H, J HP ) 11.4, PMe3), 4.50 (5H, C5H5). 19F NMR (C6D6)
Rea ction of 2a w ith P Me3 in THF To Give 9a . A solu-
tion of 2a (1.00 g, 1.77 mmol) in THF (40 mL) was treated
with PMe3 (0.185 mL, 1.77 mmol), and the mixture was stirred
at room temperature (20 h). Volatiles were removed under
vacuum and trapped in a Schlenk flask that was cooled with
liquid nitrogen. A 19F NMR spectrum of the volatiles showed
a resonance at δ -194.2 (d, J FH ) 438), consistent with the
presence of HF. The residual green-black solid was dissolved
in CH2Cl2 and filtered, and the filtrate was layered with
hexanes. The product crystallized at -78 °C to afford 9a (462
mg, 44%). 1H NMR (C6D6) δ: 0.92 (s, 3H, C5Me4CH2), 0.96 (s,
3H, C5Me4CH2), 1.30 (d, J HP ) 9.9, 9H, PMe3), 1.48 (s, 3H,
δ: -35.9 (dtd, J F ) 240, J F
) 22, J F ) 7, 1F, Fa), -50.5
F
b cc′
F
F
P
a
a
b
a
cc′
(ddt, J F ) 240, J F ) 60, J F
) 30, 1F, Fb), -138.5 (m,
F
P
a
b
b
2F, Fcc′), -157.3 (t, J FF ) 20, 1F, Fe), -163.6 (m, 2F, Fdd′);
31P{1H} NMR (C6D6) δ 17.37 (br s, PMe3). Anal. Calcd for
C
15H14CoF7IP: C, 33.11; H, 2.59. Found: C, 33.09; H, 2.64.
(η5-P e n t a m e t h ylcyclop e n t a d ie n yl)iod o(p e r flu or o-
ben zyl)(tr im eth ylp h osp h in e)coba lt(III) (4a ). A solution
of 2a (4.20 g, 7.60 mmol) in benzene (50 mL) was treated with
PMe3 (0.789 mL, 7.60 mmol), and the mixture was stirred at
room temperature (6 h). Volatiles were removed under
vacuum to leave a dark solid, which was dissolved in CH2Cl2
and filtered, and the filtrate was layered with hexanes. The
product crystallized at -60 °C to afford dark orange crystals
(3.87 g 83%). Mp: 149-152 °C. 1H NMR (C6D6) δ: 1.28 (d,
J HP ) 10.2, 9H, PMe3), 1.41 (s, C5Me5). 19F NMR (C6D6) δ:
-49.5 (d, J F ) 260, Fa), -54.9 (ddt, J F ) 260, J F ) 76,
C5Me4CH2), 1.56 (d, J HP ) 3.3, 3H, C5Me4CH2), 2.88 (d, J AB
15.6, HA, C5Me4CH2), 3.23 (d, J AB ) 15.6, HB, C5Me4CH2). 19F
NMR (C6D6) δ: -45.6 (d, J F ) 211, Fa), -58.3 (ddd, J F
)
)
F
F
b
a
b
a
211, J F ) 92, J F ) 31, Fb), -139.4 (dm, J F ) 91, F1),
F
P
F
1 b
b
1
b
-147.3 (dd, J F ) 23, J F ) 12, F4), -157.5 (t, J F ) 22,
F2), -158.3 (t, J F ) 21, F3). 31P{1H} NMR (C6D6) δ3: 16.31
F
F
F
2
4
3
4
1
F
3
2
(br s, PMe3). Anal. Calcd for C20H23CoF6IP: C, 40.43; H, 3.90.
Found: C, 40.82; H, 3.96.
Hyd r olysis of 9a To Give 10a . An NMR sample of 9a
(23 mg, 0.040 mmol) was dissolved in C6D6 (0.7 mL) and
monitored by 19F and 1H NMR. The compound slowly but
completely hydrolyzed to the acyl complex 10a over 5 days.
1H NMR (C6D6) δ: 0.82 (s, 3H, C5Me4CH2), 1.02 (s, 3H, C5Me4-
CH2), 1.28 (d, J PH ) 10.2, 9H, PMe3), 1.53 (s, 3H, C5Me4CH2),
1.87 (s, C5Me4CH2), 2.11 (d, J AB ) 15.9, 1H, C5Me4CH2), 3.21
(d, J AB ) 15.9, 1H, C5Me4CH2). 19F NMR (C6D6) δ: -145.1 (dd,
J F ) 24, J F ) 14, F1), -149.9 (dd, J F ) 22, J F ) 14,
F
F
a b
P
a
b
J F
) 37, Fb), -138.1 (m, 2F, Fcc′), -158.6 (t, J FF )b20, 1F,
F
b
cc′
Fe), -165.0 (m, 2F, Fdd′). 31P{1H} NMR (C6D6) δ: 13.24 (br s,
PMe3). Anal. Calcd for C20H24CoF7IP: C, 39.11; H, 3.94.
Found: C, 39.00; H, 4.16.
(η5-P e n t a m e t h ylcyclop e n t a d ie n yl)iod o(p e r flu or o-
ben zyl)(tr im eth ylp h osp h in e) r h od iu m (III) (4b). A solu-
tion of 2b (52 mg, 0.085 mmol) in benzene (1 mL) was treated
with PMe3 (8.8 µL, 0.085 mmol), and the mixture was stirred
at room temperature (1 h). Volatiles were removed under
vacuum to afford the product as a red-orange solid (47 mg,
84%). Mp: 168-170 °C. If necessary, this compound can be
recrystallized from CH2Cl2 and hexanes at -20 °C. 1H NMR
(C6D6) δ: 1.31 (d, J HP ) 10.8, 9H, PMe3), 1.53 (d, J HRh ) 3.3,
15H, C5Me5). 19F NMR (C6D6) δ: -44.6 (d, J F ) 248, Fz),
F
F
F
F
1
1
2
1
4
4
3
F4), -157.9 (t, J F
) 22, F2), -159.1 (t, J F
) 422, F3).
F
F
2
3
3
2
31P{1H}NMR (C6D6) δ: 23.41 (br s, PMe2Ph). IR (CH2Cl2): νCdO
) 1610 cm-1
.
Rea ction of 2a w ith P Me2P h To Give 9b. A solution of
2a (1.00 g, 1.77 mmol) in THF (50 mL) was treated with PMe2-
Ph (380 µL, 2.66 mmol), and the mixture was stirred at room
temperature (19 h). Volatiles were removed under vacuum
leaving behind 9b as a green-black solid (1.14 g, 98%). 1H
NMR (C6D6) δ: 0.39 (d, J HP ) 2.4, 3H, C5Me4CH2), 0.73 (s, 3H,
C5Me4CH2), 1.40 (s, 3H, C5Me4CH2), 1.58 (d, J HP ) 3.6, 6H,
PMe2Ph, C5Me4CH2), 1.80 (d, J HP ) 9.9, 3H, PMe2Ph), 2.90 (d,
J AB ) 15.9, 1H, C5Me4CH2), 3.21 (d, J AB ) 15.9, 1H, C5Me4CH2),
7.07 (m, PMe2Ph, 3H), 7.70 (m, PMe2Ph, 2H). 19F NMR (C6D6)
δ: -44.9 (d, J F ) 206, 1F, Fa), -59.3 (ddd, J F ) 206, J F
F
a
b
-52.6 (ddtd, J F ) 248, J F ) 87, J F
) 35, J F ) 12, 1F,
F
P
F
Rh
b
a
b
b
b
cc′
Fb), -139.3 (m, 2F, Fcc′), -158.4 (t, J FF ) 23, 1F, Fe), -164.7
(m, 2F, Fdd′). 31P{1H}NMR (C6D6) δ: 8.70 (dd, J PRh ) 151, J PF
) 76, PMe3). Anal. Calcd for C20H24F7IPRh: C, 36.50; H, 3.68.
Found: C, 36.48; H, 3.98.
(η5 -C y c lo p e n t a d i e n y l)i o d o (p e r flu o r o b e n z y l)(d i -
m eth ylp h en ylp h osp h in e)coba lt(III) (5a ). A solution of 1a
(200 mg, 0.402 mmol) in benzene (5 mL) was treated with
PMe2Ph (57 µL, 0.402 mmol), and the mixture was stirred at
room temperature (2 h). Volatiles were removed under
vacuum, and the resultant black solid was dissolved in a
minimal amount of CH2Cl2 and then filtered via cannula.
Hexane was gently layered on top of the CH2Cl2 solution. The
product crystallized at -78 °C as black needles (184 mg, 75%).
1H NMR (C6D6) δ: 1.58 (d, J HP ) 11.1, 3H, PMe2Ph), 1.76 (d,
J HP ) 11.1, 3H, PMe2Ph), 4.44 (s, 5H, C5H5), 7.05 (m, 3H,
PMe2Ph), 7.62 (m, 2H, PMe2Ph). 19F NMR (C6D6) δ: -34.6
F
F
F
b 1
a
b
a
b
) 91, J F ) 37, 1F, Fb), -139.1 (dm, J F ) 91, 2F, F1), -147.3
P
F
b
b
1
(dd, J F ) 22, J F ) 13, 1F, F4), -157.5 (t, J F ) 21, 2F,
F
F
F
2 3
4
3
1
F2), -158.2 (t, J F 4 ) 21, 2F, F3). 31P{1H} NMR (C6D6) δ: 23.58
F
3
2
(br s, PMe2Ph). Satisfactory microanalysis could not be
obtained for this complex due to facile hydrolysis of the CF2
group.
Hyd r olysis of 9b To Give 10b. A solution of 9b (125 mg,
0.190 mmol) in CH2Cl2 (50 mL) was stirred at room temper-
ature (14 h). The volatiles were removed under vacuum
leaving 10b as a black solid in quantitative yield. The solid
was recrystallized from CH2Cl2 and hexanes to afforded black
cubic crystals. 1H NMR (C6D6) δ: 0.58 (d, J HP ) 3.3, 3H, C5Me4-
CH2), 0.66 (s, 3H, C5Me4CH2), 1.46 (s, 3H, C5Me4CH2), 1.69 (d,
J HP ) 10.2, 3H, PMe2Ph), 1.70 (d, J PH ) 10.2, 3H, PMe2Ph),
1.81 (d, J HP ) 3.3, 3H, C5Me4CH2), 2.17 (d, J AB ) 16.3, 1H,
C5Me4CH2), 3.19 (d, J AB ) 16.3, 1H, C5Me4CH2), 7.08 (m, 3H
PMe2Ph), 7.90 (m, 2H, PMe2Ph). 19F NMR (C6D6) δ: -143.5
(dt, J F ) 236, J F
) 22, 1F, Fa), -49.3 (ddt, J F ) 236,
F
F
F
a b
b
a
cc′
J F )a61, J F
) 33, 1F, Fb), -137.4 (m, 2F, Fcc′), -157.2 (t,
P
F
b
b
cc′
J FF ) 21, 1F, Fe), -163.6 (m, 2F, Fdd′). 31P{1H} NMR (C6D6)
δ: 21.42 (br s, PMe2Ph). Anal. Calcd for C20H16CoF7IP: C,
39.63; H, 2.66. Found: C, 39.41; H, 2.65.
(η5-P e n t a m e t h ylcyclop e n t a d ie n yl)iod o(p e r flu or o-
ben zyl)(d im eth ylp h en ylp h osp h in e)r h od iu m (III) (5b). A
solution of 2b (50 mg, 0.085 mmol) in benzene (1 mL) was
treated with PMe2Ph (11.7 µL, 0.345 mmol), and the mixture
was stirred at room temperature (6 h). Removal of the
volatiles under vacuum left behind a red-orange solid which
was recrystallized from CH2Cl2 and methanol at -20 °C to
yield deep red crystals (30 mg, 51%). Mp: 147-149 °C. 1H
(dd, J F ) 24, J F ) 14, F1), -149.9 (dd, J F ) 21, J F
)
F
F
F
F
4 1
1
2
1
4
4
3
14, F4), -157.5 (t, J F ) 22, F2), -158.4 (t, J F ) 21, F3).
F
F
2
3
3
2
31P{1H} NMR (C6D6) δ: 26.83 (br s, PMe2Ph). IR(CH2Cl2): νCdO
) 1617 cm-1. Anal. Calcd for C25H25CoF4IOP: C, 47.34; H,
3.97. Found: C, 47.41; H, 3.91.

5686 Organometallics, Vol. 15, No. 26, 1996
Hughes et al.
(η5-P en ta m eth ylcyclop en ta d ien yl)(p er flu or oben zyl)-
ca r bon yl(tr im eth ylp h osp h in e)coba lt(III) tetr a flu or obo-
r a te (13). A Schlenk flask containing a solution of 4a (1.50
g, 2.44 mmol) in CH2Cl2 (80 mL) was flushed with CO for 3
min. After CO was bubbled through the solution for another
5 min, AgBF4 (475 mg, 2.44 mmol) was added, and the mixture
was stirred (7 min) with continued bubbling of CO. The
mixture was then stirred at room temperature (4 h) with no
further CO passage. The reaction mixture was transferred
to a glass frit by cannula and filtered to give a clear red-yellow
solution. Volatiles were removed, the residue was dissolved
in CH2Cl2 (25 mL), and the product was precipitated by adding
ether (70 mL). The yellow-orange mixture was filtered via
cannula, and the product was washed with ether (3 × 5 mL),
dried under a flow of N2, and then dried under vacuum to yield
1.23 g (84%) of a yellow-orange powder. 1H NMR (CDCl3) δ:
1.68 (s, C5Me5), 1.78 (d, J PH ) 11.1, PMe3). 19F NMR (CDCl3)
purified by chromatography (silica gel, 1.5 × 20 cm, -40 °C)
to yield 40 mg (20%) of white solid 14. 1H NMR (C6D6) δ: 1.26
(s, 3H), 1.33 (s, 6H), 1.88 (s, 6H). 19F NMR (C6D6) δ: -90.9
(t, J FF ) 27 Hz, 2F, CF2), -138.1 (m, 2Fortho), -152.3 (t, J )
23 Hz, 1Fpara), -163.4 (m, 2Fmeta). GC/MS m/z 352.10 M+
(C11H15F7).
Cr ysta llogr a p h ic Stu d ies. Crystal data collection and
refinement parameters are given in Table 2. The systematic
absences in the diffraction data are uniquely consistent for
the reported space groups. The structures were solved using
direct methods, completed by subsequent difference Fourier
syntheses, and refined by full-matrix least-squares procedures.
Semiempirical absorption corrections were applied to the data
sets. All non-hydrogen atoms were refined with anisotropic
displacement coefficients. Hydrogen atoms were treated as
idealized contributions.
All software and sources of the scattering factors are
contained in the SHELXTL PLUS (4.2) program library (G.
Sheldrick, Siemens XRD, Madison, WI).
δ: -29.6 (dm, J F ) 236, Fa), -52.9 (ddt, J F ) 236, J FbP
)
F
F
b
a
b
a
47, J F
) 43, Fb), -140.2 (m, 2F, Fcc′), -151.3 (t, J FF ) 23
F
b
cc′
1F, Fe), -151.6 (s, BF4), -160.4 (m, 2F, Fdd′). 31P{1H} NMR
(C6D6) δ: 24.80 (s, PMe3). IR(CH2Cl2): νCO ) 2060 cm-1. Anal.
Calcd for C21H24BCoF11P: C, 41.89; H, 4.02. Found: C, 41.60;
H, 4.04.
Ack n ow led gm en t. R.P.H. acknowledges generous
financial support from the U.S. Air Force Office of
Scientific Research and the Petroleum Research Fund,
administered by the American Chemical Society. D.C.L.
acknowledges support via the Department of Defense
Augmentation Award for Scientific and Engineering
Research Training Program. A loan of rhodium chloride
from J ohnson-Matthey Aesar/Alfa is also gratefully
acknowledged.
Rea ction of 13 w ith P P N+I-. A cloudy yellow-orange
suspension of 13 (115 mg, 0.191 mmol) in THF (10 mL) was
treated with PPN+I- (500 mg, 0.751 mmol). The reaction
mixture changed color to yellow-green. After 16 h, the mixture
was filtered, the filtrate evaporated to dryness, and the residue
redissolved in CH2Cl2. Unreacted starting material was
precipitated with ether, the mixture was filtered, and the
filtrate was evaporated to dryness under vacuum. The 19F
NMR spectrum of the residue showed the three major products
10a , 2a , and 4a in an 18:3:1 ratio.
Su p p or tin g In for m a tion Ava ila ble: Tables of fractional
atomic coordinates, bond lengths, bond angles, anisotropic
displacement coefficients, H-atom coordinates, and isotropic
displacement coefficients for complex 3a , 5b, and 10b (21
pages). Ordering information is given on any current mast-
head page.
Th er m olysis of 2a To Give 14. A solution of 2a (1.00g,
1.77 mmol) in benzene (40 mL) was stirred at reflux (60 h).
The solution was filtered via cannula, and volatiles were
removed under vacuum. The crude residue (200 mg) was
OM9607255