Reactivity of cyclocobaltated benzylamine derivatives toward terminal alkynes

Article abstract of DOI:10.1021/om000053p

The cyclocobaltated complexes [(η⁵-C₅H₅)Co(4-RC₆H ₃CH₂NMe₂-C²,N)I] (1; R = H, Me, F) reacted with terminal alkynes such as R′C≡CH (2; R′ = ^tBu, SiMe₃) to afford a mixture of the two compounds {(η⁵-C₅H₅)Co[η⁵-C ₅H₄CH=CR′(4-R-2-(CH₂NMe ₂)C₆H₃)]}⁺PF₆^- (3) and (E)-CHR′=CH(4-R-2-(CH₂NMe₂)C₆H ₃) (4) in a ca. 1:1 ratio. The reaction is rationalized by assuming that insertion of the alkyne into the Co-C bond of 1 occurred with no regio-selectivity, leading to two unstable regioisomers; a selective migration of the less hindered alkenyl-Co derivative to a Cp unit followed by migration of the monosubstituted Cp ring thus obtained to another cobalt center afforded 3, whereas compound 4 should be obtained via protiodemetalation of the other isomer formed.

Full text of DOI:10.1021/om000053p

Organometallics 2000, 19, 1935-1939
1935
Rea ctivity of Cyclocoba lta ted Ben zyla m in e Der iva tives
tow a r d Ter m in a l Alk yn es
Mario Roberto Meneghetti,†,‡ Mary Grellier,† Michel Pfeffer,*,† and J ean Fischer§
Laboratoire de Synthe`ses Me´tallo-Induites and Laboratoire de Cristallochimie et Chimie
Structurale, UMR 7513 du CNRS, 4, rue Blaise Pascal, 67000 Strasbourg, France
Received J anuary 21, 2000
The cyclocobaltated complexes [(η5-C5H5)Co(4-RC6H3CH2NMe2-C2,N)I] (1; R ) H, Me, F)
t
reacted with terminal alkynes such as R′CtCH (2; R′ ) Bu, SiMe3) to afford a mixture of
the two compounds {(η5-C5H5)Co[η5-C5H4CHdCR′(4-R-2-(CH2NMe2)C6H3)]}+PF6- (3) and (E)-
CHR′dCH(4-R-2-(CH2NMe2)C6H3) (4) in a ca. 1:1 ratio. The reaction is rationalized by
assuming that insertion of the alkyne into the Co-C bond of 1 occurred with no regio-
selectivity, leading to two unstable regioisomers; a selective migration of the less hindered
alkenyl-Co derivative to a Cp unit followed by migration of the monosubstituted Cp ring
thus obtained to another cobalt center afforded 3, whereas compound 4 should be obtained
via protiodemetalation of the other isomer formed.
In tr od u ction
and nitriles that involves Co(III) metallacyclic interme-
diates is rather representative of these properties.3
In line with our present investigation it was found
that cobalt(I) derivatives made with orthometalated
azobenzene ligands displayed interesting reactivity
when reacted with activated alkynes. Thus, Bruce and
co-workers reported the first insertion reaction between
[(phenylazo)phenyl-C2,N]tricarbonylcobalt, containing a
C,N-coordinated azobenzene ligand, and hexafluoro-
butyne, as shown in eq 1.4 However, this result seemed
Transition-metal-mediated organic synthesis with
compounds in which metals take part in a ring system,
i.e. metallacycles, is an important line of research of our
group.1 These compounds have indeed proved to be
effective in heterocycle synthesis, and among these
compounds, palladium derivatives have been shown to
display a large variety of processes in both bulk and fine
chemicals. We have thus long been interested in the
reactions of cyclopalladated amines with internal alkynes,
which have afforded important pathways to the syn-
theses of heterocyclic compounds.
One recent aim of our search was to determine to
what extent other transition-metal complexes can dis-
play analogous (and perhaps complementary) behavior
to their cyclopalladated counterparts. We have already
demonstrated that pseudotetrahedral ruthenacycle de-
rivatives of Ru(C6H4CH2NMe2)Cl(η6-C6H6) react with
disubstituted alkynes to afford heterocyclic compounds
bound to Ru(0) complexes. The organic product was
readily obtained under smooth oxidation conditions, and
hence, this method may become useful for the synthesis
of 2,3-disubstituted isoquinolinium derivatives.2
(1)
It has been shown on many occasions that the
chemistry of organometallic derivatives of cobalt is very
rich, leading, in several instances, to the formation of
carbon-carbon and carbon-heteroatom bonds. Of the
many examples that may illustrate this point, the
synthesis of pyridines via cyclotrimerization of alkynes
to be limited to this alkyne, as Pauson et al. failed to
extend it to less activated alkynes such as dimethyl
acetylenedicarboxylate and phenylacetylene.5
We have recently demonstrated that organometallic
compounds of Co(III) containing a metallacyclic unit
could be readily synthesized by transmetalation reac-
tions of lithiated tertiary amines. These reactions af-
forded a large variety of stable pseudotetrahedral
† Laboratoire de Synthe`ses Me´tallo-Induites.
‡ Permanent address: Laboratorio de Catalise Molecular, IQ/
UFRGS, Av. Bento Gonc¸alves, 9500-Porto Alegre, Brazil.
§ Laboratoire de Cristallochimie et Chimie Structurale.
(1) (a) Ryabov, A. D. Synthesis 1985, 233. (b) Pfeffer, M. Pure Appl.
Chem. 1992, 64, 335. (c) Spencer, J .; Pfeffer, M. In Advances in Metal-
Organic Chemistry; Liebeskind, L. S., Ed.; J AI Press: London, 1998;
Vol. 6, p 103.
(3) (a) Bonnemann, H. Angew. Chem., Int. Ed. Engl. 1985, 24, 248.
(b) Hillard, R. L.; Parnell, C. A.; Vollhardt, K. P. C. Tetrahedron 1983,
905.
(2) (a) Abbenhuis, H. C. L.; Pfeffer, M.; Sutter, J .-P.; De Cian, A.;
Fischer, J .; J i, H. L.; Nelson, J . H. Organometallics 1993, 12, 4464.
(b) Pfeffer, M.; Sutter, J .-P.; Urriolabeitia, E. P. Inorg. Chim. Acta 1996,
249, 63. (c) Ferstl, W.; Sakodisnkaya, I. K.; Beydoun-Sutter, N.; Le
Borgne, G.; Pfeffer, M.; Ryabov, A. D. Organometallics 1997, 16, 411.
(4) (a) Bruce, M. I.; Goodall, B. L.;. Redhouse, A. D.; Stone, F. G. A.
J . Chem. Soc., Chem. Commun. 1972, 1228. (b) Bruce, M. I.; Goodall,
B. L.; Stone, F. G. A. J . Chem. Soc., Dalton Trans. 1975, 1651.
(5) J anecki, T.; Pauson, P. L.; Pietrzykowski, A. J . Organomet.
Chem. 1987, 325, 247.
10.1021/om000053p CCC: $19.00 © 2000 American Chemical Society
Publication on Web 04/14/2000

1936 Organometallics, Vol. 19, No. 10, 2000
Meneghetti et al.
organocobalt compounds, in which the cobalt is a stereo-
genic center. These compounds are isoelectronic and
structurally analogous to the ruthenacycles mentioned
above, and therefore these organocobalt compounds
were excellent candidates for the research field we are
interested in. In this paper we thus describe the result
of the reactions between these complexes and terminal
alkynes leading to organic and organometallic deriva-
tives that are without precedent in this chemistry.
The structures of compounds 4 were easily deduced
from their 1H and 13C{1H} NMR spectra and mass
1
spectroscopy. In H NMR, the olefinic unit displayed a
3
large J H-H coupling constant (16-19 Hz), which is
diagnostic of their trans geometry, and the CH2NMe2
unit displayed nondiastereisotopic signals typical of a
symmetrical molecule.
All of the compounds 3 were characterized by 1H and
13C{1H} NMR spectroscopy. The combustion analysis
proved, however, to be somewhat frustrating for all
these compounds. The amount of carbon found was often
lower than the calculated amount, despite all our efforts
to crystallize the compounds and/or to dry the obtained
crystals in vacuo. However, this is a feature that has
been encountered several times for related ruthenium
or palladium compounds containing PF6 as a counter-
anion. Since (i) the N and H analyses were correct, (ii)
one compound (3a ) has been unambiguously character-
ized by a X-ray diffraction analysis (see below), and (iii)
Resu lts a n d Discu ssion
While investigating the reactivity of the new series
of organocobalt complexes6 with alkynes we have ob-
served that neutral cobaltacyclic complexes of type 1
display an amazing reactivity toward alkynes. No reac-
tion at all was observed between 1 and any internal
alkynes. However, in marked contrast to what we found
in many instances with the corresponding palladium
and ruthenium complexes, we have now observed that
only terminal alkynes lead to interesting reactions.
Terminal alkynes with bulky donor substituents gave
the best results, leading to the formation of an organic
product together with a cobaltocenium derivative as
shown in eq 2.
1
no other species could be seen on the H NMR spectra
of the compounds, we may consider that these unsatis-
factory C analyses do not hamper the characterization
1
of the compounds 3. The H NMR spectra revealed the
existence of two Cp rings bonded to the metal in which
one of them is monosubstituted. The resulting diastereo-
topicity of their methylenic groups, evidenced by the
presence of well-defined AB spin systems in their 1H
NMR spectra, can only occur if important steric effects
are present, since the molecules display a formal plane
of symmetry. Thus, although there is conjugation be-
tween the Cp′ ring, the vinyl group, and the phenyl ring,
the most favored conformation must be clinal.7 Steric
repulsion between the (dimethylamino)methyl and tert-
butyl groups is sufficient to offset the energy lost on
conjugation and to result in a nonplanar structure.
To establish with assurance which factors are respon-
sible for such atropisomerism, the solid-state structure
of 3a was elucitated via a single-crystal X-ray diffraction
study. The molecular structure is represented in Figure
1, together with the adopted numbering scheme. Se-
lected bond distances and angles are shown in Table 1.
According to this study, the molecular structure of 3a
clearly reveals the presence of a cationic fragment
typical of a cobaltocene geometry in which the cobalt-
(III) center is located between two almost parallel
Cp rings. In addition, the Z stereochemistry of the
vinyl group was unambiguously established. Restricted
rotation about a single bond must occur around the
C17-C12 bond. In the solid state the dihedral angle
between C13-C12 and C17-C18 is 101°. Such strong
steric effects are present also in solution, thus explain-
ing the presence of a diastereotopic methylene group.
These two classes of products, 3 and 4, were both
isolated in yields close to 50%, which indicates that they
probably are the only products of the reaction. In other
words, no metalated C,N-coordinated ligands seem to
have been lost during the reaction. Considering that in
3 and 4 the R groups are on the carbon atom which is
respectively adjacent and remote from the aryl ring,
there is probably no regioselectivity in the alkyne
insertion reaction leading to the intermediate organo-
cobalt species. Thus, a 1,2-insertion should lead to
(2)
We have found that such reactions do not depend on
the substitution at the para position with respect to the
Co-C bond for the series of cyclometalated amines used,
as neither the yield nor the selectivities of the reaction
have been significantly modified.
In a typical experiment 1a was dissolved in CH2Cl2,
and an excess of HCtCtBu was added at room temper-
ature. This afforded, after 16 h, a mixture of the two
main products 3 and 4. The latter was extracted in
hexane, whereas 3 was dissolved in water, affording a
yellow solution which led in the presence of KPF6 to a
light yellow powder which was very stable toward
hydrolysis and air.
(6) Meneghetti, M. R.; Grellier, M.; Pfeffer, M.; Dupont, J .; Fischer,
J . Organometallics 1999, 18, 5560.
(7) Bassindale, A. The Third Dimension in Organic Chemistry;
Wiley: Chichester, U.K., 1984.

Cyclocobaltated Benzylamine Derivatives
Organometallics, Vol. 19, No. 10, 2000 1937
internal ones), we are inclined to believe that the second
hypothesis is the one that should be operative.
The two intermediates, which both contained seven-
membered cobaltacyclic rings, formed soon after the in-
sertion of the alkyne and are then likely to be unstable,
leading to rearrangements. According to the yields of
the products 3 and 4, it is likely that this rearrangement
should be somehow concerted: the alkenyl group at-
tached to Co in A should migrate to a Cp ring, a feature
that is in line with previous observations made by
Maitlis8 and Werner,9 whereas the alkenyl-Co bond in
B is cleaved by the proton produced during the process.
At this stage it is of course not possible to draw any
likely reaction path that would explain this rather
efficient transfer of a Cp ring from one Co to the other
one. We have just checked that the solvent is not the
source of proton, as using deuterated solvent and water
afforded no evidence of D-labeled products. Further
work is obviously necessary to rationalize this reaction
sequence.
Con clu sion
F igu r e 1. ORTEP view of the cationic part of compound
3a .
It appears from the present study that Co(III) species
with ortho-chelating arylamine ligands display lower
reactivity in reactions with alkynes when compared to
their palladated and ruthenated counterparts; however,
this is compensated by the fact that terminal alkynes
lead to clean reactions with the cobalt derivatives as
opposed to the Pd and Ru complexes, which react only
with internal alkynes.
Ta ble 1. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for 3a
Co-C(Cp)av
Co-C(Cp′)av
Co-Cpa a
2.01(2)
2.01(2)
1.64(2)
1.62(2)
1.37(3)
1.41(2)
1.47(2)
C11-C12
C12-C17
C-C(Ph)av
C18-C23
C23-N
1.33(2)
1.53(2)
1.36(2)
1.56(2)
1.48(2)
1.40(2)
b
Co-Cp′a
C-C(Cp)av
C-C(Cp′)av
C6-C11
N-C24
Exp er im en ta l Section
Cpa-Co-Cp′a
C7-C6-C11
179(2)
C12-C17-C22
C17-C18-C19
C17-C18-C23
C19-C18-C23
C18-C23-N
C13-C12-C17-C18
C11-C12-C18-C18
116(1)
All reactions were performed in Schlenk flasks under oxygen
and water-free nitrogen. CH2Cl2 was dried over P2O5 and
122(1)
131(1)
128(1)
121(1)
121(1)
117(1)
122(1)
117(1)
121(1)
119(1)
111(1)
101(2)
-80(2)
C10-C6-C11
C6-C11-C12
C11-C12-C13
C11-C12-C17
C13-C12-C17
C12-C17-C18
1
distilled under nitrogen. The H NMR spectra were recorded
at 300.13 MHz and 13C{1H} NMR spectra at 75.47 MHz on a
FT-Bruker instrument (AC-300) and externally referenced to
TMS. Chemical shifts (δ) and coupling constants (J ) are
expressed in ppm and Hz, respectively. All mass spectra were
performed by the Laboratory of Molecular Catalysis da Uni-
versidade Federal do Rio Grande do Sul. Column chromatog-
raphy was carried out on alumina 90 (activity II-III mesh;
0.063-0.200 mm) from Merck.
a
b
Cpa is the centroid of Cp. Cp′a is the centroid of Cp′.
Ch a r t 1. P r op osed In ter m ed ia tes for th e
F or m a tion of 3 a n d 4
Syn th eses. [Co(η5-C5H5){η5-C5H4[CHdC(tBu )(C6H4CH2-
NMe2)]}]P F 6 (3a ) a n d tr a n s-tBu CHdCHC6H4CH2NMe2
(4a ). tert-Butylacetylene (1.0 mL, 8.0 mmol) was added to a
stirred solution of 1a (0.770 g, 2.00 mmol) in CH2Cl2 (20 mL)
at room temperature. After 20 h the volatiles were removed
in vacuo, affording a light green solid. The crude product was
washed with two solvents in order to extract the different
products. First, it was washed with hexane (5 × 50 mL). From
the combined organic solutions an organic product was isolated
after concentration in vacuo. This product was subjected to
flash chromatography over alumina using CH2Cl2 as eluent,
allowing the migration of a red-brown band corresponding to
the compound 4a . After solvent evaporation, the organic
product was dried in vacuo, affording 4a as red-brown oil.
Second, the crude product was now washed with water (8 ×
25 mL) and, into the combined yellow aqueous solutions, an
excess of KPF6 was added. Immediately, a yellow precipitate
was formed. After 15 min the precipitate thus obtained was
filtered and washed with water (10 mL) and hexane (30 mL).
After recrystallization in CH2Cl2/hexane and drying in vacuo,
cobaltocenium derivatives 3, whereas a 2,1-insertion
should afford the organic product derivatives 4 (Chart
1). The insertion should occur via either cleavage of the
iodide-Co bond or decoordination of the nitrogen atom
from Co in order to coordinate the alkyne to the Co
center prior to the insertion/migration process. As the
use of cationic species did apparently not increase the
reactivity of these complexes toward alkynes (including
(8) Roe, D. M.; Maitlis, P. M. J . Chem. Soc. A 1971, 3173.
(9) Werner, H.; Hofmann, W. Angew. Chem. 1977, 89, 835.

1938 Organometallics, Vol. 19, No. 10, 2000
Meneghetti et al.
Ta ble 2. X-r a y Exp er im en ta l Da ta Collection a n d
Str u ctu r e Refin em en t Deta ils for 3a
3a was isolated as a light yellow powder. Yield: 0.416 g (38%
from 1a ) for 3a and 0.186 g (43% from 1a ) for 4a .
3a : Anal. Calcd for C25H31CoF6NP (490.21): C, 54.65; H,
5.69; N, 2.55. Found: C, 49.01; H, 5.16; N, 2.14. 1H NMR
(CDCl3): δ 7.60 (m, 1H, Ar); 7.43 (m, 2H, Ar); 7.11 (m, 1H,
Ar); 6.42 (s, 1H, HCd); 5.77, 5.70, 5.30, and 4.07 (4 br s, 4H,
C5H4); 5.50 (s, 5H, C5H5); 3.16 and 2.97 (AB spin system, 2H,
CH2N, 2J H-H ) 13.9); 2.01 (s, 6H, NMe2); 1.21 (s, 9H, C(CH3)3).
13C{1H} NMR (acetone-d6): δ 158.06 and 117.65 (CdCH);
139.52, 133.14, 130.07, 129.35, 128.95, and 128.63 (C6H4);
102.85, 85.06, 84.28, and 81.05 (C5H4); 86.00 (C5H5); 60.55
(CH2N); 44.59 (NMe2); 38.47 (C(CH3)3); 29.79 (C(CH3)3).
Crystal Data
formula
mol wt
cryst syst
space group
a (Å)
b (Å)
c (Å)
V (Å3)
C25H31CoF6NP
549.43
orthorhombic
Pca21
13.533(3)
11.858(3)
16.132(3)
2588(1)
4
Z
color
1
4a : C15H23N (217.18), MS m/z (M+) 217. H NMR (CDCl3):
yellow
3
cryst dimens (mm)
0.30 × 0.25 × 0.20
δ 7.43 (d, 1H, Ar, J H-H ) 8.0); 7.30-7.05 (m, 3H, Ar); 6.73
Dcalcd (g cm-3
F(000)
)
1.41
3
and 6.08 (2d, 2H, HCdCH, J H-H ) 16.1); 3.38 (s, 2H, CH2N);
2.23 (s, 6H, NMe2); 1.15 (s, 9H, C(CH3)3). 13C{1H} NMR
(acetone-d6): δ 142.91 and 123.28 (HCdCH); 138.65, 136.44,
130.59, 127.64, 126.68, and 125.96 (C6H4); 62.45 (CH2N); 45.13
(NMe2), 33.68 (C(CH3)3); 29.61 (C(CH3)3).
1136
0.781
0.9277/1.0000
µ (mm-1
)
min/max transmissn
Data Collection
temp (K)
wavelength (Å)
radiation
294
0.71073
Mo KR
(graphite monochromated)
MACH3 Nonius
θ-2θ
-14 to 0/0-16/0-20
In all cases reported below the cobaltocenium derivative and
the organic product were obtained using a workup similar to
that used for the synthesis of 3a and 4a .
[Co(η5-C5H5){η5-C5H4[CHdC(tBu )(C6H3(CH3)CH2NMe2)]}]-
P F 6 (3b) a n d tr a n s-tBu CHdCHC6H3(CH3)CH2NMe2 (4b).
1b (0.800 g, 2.00 mmol) reacts with tert-butylacetylene (1.0
mL, 8.00 mmol) to give 3b and 4b as a light yellow solid and
a brown oil, respectively. Yield: 0.320 g of 3b (28% from 1b)
and 0.210 g of 4b (45% from 1b).
diffractometer
scan mode
hkl limits
θ limits (deg)
no. of data measd
no. of data with I > 3σ(I)
weighting scheme
no. of variables
R
2.5-26.28
2973
1209
4Fo2/(σ2(Fo2) + 0.0064Fo
)
4
3b: Anal. Calcd for C26H33CoF6NP (563.16): C, 55.42; H,
5.90; N, 2.49. Found: C, 47.56; H, 5.17; N, 1.88. 1H NMR
(acetone-d6): δ 7.55 (s, 1H, Ar); 7.44 (br s, 2H, Ar); 6.73 (s,
1H, HCd); 5.89, 5.72, 5.53, and 4.43 (4 br s, 4H, C5H4); 5.74
(s, 5H, C5H5); 4.11 and 3.76 (AB spin system, 2H, CH2N, 2J H-H
) 15.0); 2.57 (s, 6H, NMe2); 2.43 (s, 3H, CH3);1.22 (s, 9H,
C(CH3)3). 13C{1H} NMR (acetone-d6): δ 157.59 and 118.00 (Cd
CH); 139.15, 136.40, 131.15, 130.35, 129.82, and 129.32 (C6H4);
102.67, 85.28, 85.09, 84.38, and 81.17 (C5H4); 85.96 (C5H5);
60.12 (CH2N), 44.35 (NMe2), 38.56 (C(CH3)3), 29.73 (C(CH3)3),
20.87 (CH3).
306
0.053
0.068
1.403
0.323
Rw
GOF
largest peak in final diff map
(e Å-3
)
2J C-F ) 7.0); 116.43 (d, J C-F ) 21.1), 114.08 (d, J C-F ) 21.1)
(C6H3), 143.19, 122.04 (HCdCH), 61.61 (CH2N), 45.09 (NMe2),
33.64 (C(CH3)3), 29.39 (C(CH3)3).
[Co(η5-C5H 5){η5-C5H 4[CH dC(SiMe3)C6H 4CH 2NMe2)]}]-
P F 6 (3d ) a n d tr a n s-SiMe3CHdCHC6H4CH2NMe2 (4d ). 1a
(0.770 g, 2.00 mmol) reacts with (trimethylsilyl)acetylene (1.4
mL, 8.00 mmol) to give 3d and 4d as a light yellow solid and
a brown oil, respectively. Yield: 0.339 g of 3d (30% from 1a )
and 0.168 g (36% from 1a ).
3d : Anal. Calcd for C24H31F6NPSi (506.19): C, 50.98; H,
5.53; N, 2.48. Found: C, 44.66; H, 4.98; N, 1.75. 1H NMR
(CDCl3): δ 7.34 (m, 3H, Ar); 6.89 (d, 1H, Ar, 3J H-H ) 7.1); 6.64
(s, 1H, HCd); 5.67 (br s, 2H, C5H4); 5.42 (br s, 1H, C5H4); 4.49
(s, 1H, C5H4); 5.55 (s, 5H, C5H5); 3.03 and 2.97 (AB spin system,
2
2
4b:
C
16H25N (231.20), MS m/z (M+) ) 231. 1H NMR
3
(CDCl3): δ 7.34 (d, 1H, Ar, J H-H ) 7.8); 7.06 (s, 1H, Ar); 7.01
(d, 1H, Ar, 3J H-H ) 7.8); 6.68 and 6.05 (2d, 2H, HCdCH, 3J H-H
) 16.1); 3.38 (s, 2H, CH2N); 2.31 (s, 3H, CH3); 2.25 (s, 6H,
NMe2); 1.12 (s, 9H, C(CH3)3). 13C{1H} NMR (acetone-d6): δ
141.95 and 123.17 (HCdCH); 136.29, 135.98, 135.80, 131.25,
128.30, and 125.90 (C6H3); 62.45 (CH2N); 45.16 (NMe2); 33.62
(C(CH3)3); 29.70 (C(CH3)3); 20.77 (CH3).
[Co(η5-C5H5){η5-C5H4[CHdC(tBu )(C6H3(F )CH2NMe2)]}]-
P F 6 (3c) a n d tr a n s-tBu CHdCHC6H3(F )CH2NMe2 (4c). 1c
(0.806 g, 2.00 mmol) reacts with tert-butylacetylene (1.0 mL,
8.00 mmol) to give 3c and 4c as a light yellow solid and a
brown oil, respectively. Yield: 0.211 g of 3c (28% from 1c) and
0.204 g of 4c (43% from 1c).
3c: Anal. Calcd for C25H30CoF7NP (567.13): C, 52.92; H,
5.33 N, 2.47. Found: C, 52.19; H, 5.21; N, 2.22. 1H NMR
(CDCl3): δ 7.37 (m, 1H, Ar); 7.14 (m, 2H, Ar); 6.46 (s, 1H,
HCd); 5.72, 5.61, 5.36, and 4.23 (4 br s, 4H, C5H4); 5.54 (s,
2
2H, CH2N, J H-H ) 13.2); 2.02 (s, 6H, NMe2); 0.17 (s, 9H,
Si(CH3)3). 13C{1H} NMR (acetone-d6): δ 154.98 and 127.95
(CdCH); 142.07, 130.28, 129.97, 129.72 and 129.47, 128.11
(C6H4); 100.92, 85.56, 85.46, 84.78, and 81.80 (C5H4); 86.09
(C5H5); 60.27 (CH2N); 44.38 (NMe2); -1.83 (Si(CH3)3).
4d :
C
14H23NSi (233.16), MS m/z (M+) ) 233. 1H NMR
3
(CDCl3): δ 7.56 (d, 1H, Ar, J H-H ) 6.2); 7.36 and 6.38 (2d,
3
5H, C5H5); 3.14 and 2.90 (AB spin system, 2H, CH2N, 2J H-H
)
2H, HCdCH, J H-H ) 19.2); 7.30-7.15 (m, 3H, Ar); 3.45 (s,
2H, CH2N); 2.25 (s, 6H, NMe2); 0.16 (s, 9H, Si(CH3)3). 13C{1H}
NMR (acetone-d6): δ 142.48 and 127.73 (HCdCH); 138.93,
136.75, 130.78, 130.28, 127.73, and 125.65 (C6H4); 62.29
(CH2N); 44.97 (NMe2); -1.49 (Si(CH3)3).
14.5); 2.01 (s, 6H, NMe2); 1.19 (s, 9H, C(CH3)3). 13C{1H}
NMR (acetone-d6): δ 157.82 and 117.84 (CdCH); 164.54 (d,
3
1J C-F ) 244.1); 139.09, 135.05, 131.44 (d, J C-F ) 7.0); 116.10
(d, 2J C-F ) 23.5), 114.75 (d, 2J C-F ) 21.1) (C6H4); 102.86, 85.06,
84.91, 84.29, and 81.11 (C5H4); 85.90 (C5H5); 60.84 (CH2N);
45.07 (NMe2); 38.416 (C(CH3)3); 29.82 (C(CH3)3).
X-r a y Deter m in a tion of 3a a n d P r ocessin g. Crystals
suitable for X-ray analysis were grown by slow diffusion of
n-hexane into a solution of 3a in dichloromethane as yellow
needles. Crystal data and details of data collection for 3a are
given in Table 2. The crystals displayed a low diffracting
power, which explains the rather low values of the observed/
collected data and of the parameter/data ratios. Data were
collected in the θ/2θ mode using Mo KR graphite-monochro-
mated radiation (λ ) 0.710 73 Å) on a yellow crystal of
4c:
(CDCl3): δ 7.38 (dd, 1H, Ar, J H-H ) 8.6, J H-F ) 5.7);
C
15H22FN (235.17), MS m/z (M+) ) 235. 1H NMR
3 4
3
4
7.02 (dd, 1H, Ar, J H-F ) 9.8, J H-H ) 2.8); 7.01 (dt, 1H, Ar,
3J H-F
)
4J H-H ) 8.6, J H-H ) 2.8); 6.62 and 6.03 (2d, 2H,
3
HCdCH, 3J H-H ) 16.0); 3.41 (s, 2H, CH2N); 2.27 (s, 6H, NMe2);
1.12 (s, 9H, C(CH3)3). 13C{1H} NMR (acetone-d6): δ 162.00
1
3
(d, J C-F ) 241.8); 139.00 (d, J C-F ) 7.0); 134.70, 127.80 (d,

Cyclocobaltated Benzylamine Derivatives
Organometallics, Vol. 19, No. 10, 2000 1939
dimensions 0.20 × 0.25 × 0.30 mm3 with a Nonius MACH3
automatic diffractometer at room temperature. Three standard
reflections measured every 1 h during the entire data collection
period showed no significant trend. The raw data were con-
verted to intensities and corrected for Lorentz polarization and
absorption factors, the latter coming from the ψ-scan data of
seven reflections. The structure was solved by direct methods.
After refinement of the non-hydrogen atoms, difference Fourier
maps revealed maxima of residual electron density close to
positions expected for hydrogen atoms. Hydrogen atoms were
refined at calculated positions with a riding model in which
the C-H vector was fixed at 0.95 Å with isotropic temperature
factors such as B(H) ) 1.3[Beqv(C)] Å2. The absolute structure
was determined by refining Flack’s x parameter. A final
Fourier difference map revealed no significant maxima. All
calculations were performed on a DEC Alpha 3000 computer
using the Nonius OpenMoleN package.10 Neutral atom scat-
tering factor coefficients and anomalous dispersion coefficients
were taken from a standard source.11
Ack n ow led gm en t. Financial support of this work
through a grant to M.R.M. by the French/Brazilian
exchange program CAPES-COFECUB (Project 188/96)
is gratefully acknowledged.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystallo-
graphic data, atomic coordinates, anisotropic thermal param-
eters, bond lengths and angles, and hydrogen atom parameters
for 3a . This material is available free of charge via the Internet
at http://pubs.acs.org.
OM000053P
(10) OpenMoleN, Interactive Structure Solution; Nonius BV, Delft,
The Netherlands, 1997.
(11) (a) Cromer, D. T.; Waber, J . T. International Tables for X-ray
Crystallography; 1974; Kynoch Press: Birmingham, U.K., 1974; Vol.
IV, Table 2.2b. (b) Ibid., Table 2.3.1.