Insertion of imines and carbon monoxide into manganese-alkyl bonds: Synthesis and structure of a manganese-α-amino acid derivative

Article abstract of DOI:10.1021/om000745d

Two new routes have been developed to generate manganese-chelated amides from imine and carbon monoxide building blocks. The reaction of (CO)₅MnR (R = CH₃, Ph) with (p-tolyl)(R¹)=NR² (R¹ = H, ^tBu; R² = alkyl, H) results in the generation of the cyclometalated imine complexes (CO)₄Mn[η²-4-CH₃-2- (C(R¹)=NR²)-C₆H₃] in 50-84% isolated yield. However, when the reaction of (p-tolyl)(H)C=NCH₃ with (CO)₅MnCH₃ is performed in the presence of AlCl₃, the product of sequential carbon monoxide and imine insertion is generated in 35% yield: (CO₄)Mn[η²-C(H)(p-tolyl)N (CH₃)COCH₃]. The addition of PPh₃ to the latter complex results in replacement of a carbonyl ligand and formation of the isolable fac-(CO)₃(PPh₃)- Mn[η²-C(H)(p-tolyl)N(CH₃)COCH₃]. In an alternative route to metal-bound amides, the oxidative addition of the N-acyl iminium salt (p-tolyl)(H)C=N(CH₃)COPh⁺Cl^- to (CO)₅Mn^-Na⁺ has been found to lead to the generation of the product of subsequent CO insertion, (CO₄)Mn- [η²-COC(H)(p-tolyl)N(CH₃)COPh]. The latter represents the first example of a acyl-bound transition-metal-chelated α-amino acid complex and has been characterized by X-ray crystallography. Preliminary reactivity studies demonstrate that (CO)₄Mn[η²-COC(H)(p-tolyl)N(CH₃)COPh] reacts with PPh₃ to generate the unchelated cis-(CO)₄(PPh₃)Mn[COC-(H)(p-tolyl)N(CH₃)COPh], while reaction with NaBH₄ leads to the liberation of the amide (p-tolyl)CH₂N(CH₃)COPh, rather than the amino acid residue.

Full text of DOI:10.1021/om000745d

1128
Organometallics 2001, 20, 1128-1136
In ser tion of Im in es a n d Ca r bon Mon oxid e in to
Ma n ga n ese-Alk yl Bon d s: Syn th esis a n d Str u ctu r e of a
Ma n ga n ese-r-Am in o Acid Der iva tive
Danny Lafrance, J ason L. Davis, Rajiv Dhawan, and Bruce A. Arndtsen*
Department of Chemistry, McGill University, 801 Sherbrooke Street West,
Montreal, Quebec, Canada H3A 2K6
Received August 28, 2000
Two new routes have been developed to generate manganese-chelated amides from imine
and carbon monoxide building blocks. The reaction of (CO)5MnR (R ) CH3, Ph) with (p-
t
tolyl)(R1)dNR2 (R1 ) H, Bu; R2 ) alkyl, H) results in the generation of the cyclometalated
imine complexes (CO)4Mn[η2-4-CH3-2-(C(R1)dNR2)-C6H3] in 50-84% isolated yield. However,
when the reaction of (p-tolyl)(H)CdNCH3 with (CO)5MnCH3 is performed in the presence of
AlCl3, the product of sequential carbon monoxide and imine insertion is generated in 35%
yield: (CO)4Mn[η2-C(H)(p-tolyl)N(CH3)COCH3]. The addition of PPh3 to the latter complex
results in replacement of a carbonyl ligand and formation of the isolable fac-(CO)3(PPh3)-
Mn[η2-C(H)(p-tolyl)N(CH3)COCH3]. In an alternative route to metal-bound amides, the
oxidative addition of the N-acyl iminium salt (p-tolyl(H)CdN(CH3)COPh+Cl- to (CO)5Mn-Na+
has been found to lead to the generation of the product of subsequent CO insertion, (CO)4Mn-
[η2-COC(H)(p-tolyl)N(CH3)COPh]. The latter represents the first example of a acyl-bound
transition-metal-chelated R-amino acid complex and has been characterized by X-ray
crystallography. Preliminary reactivity studies demonstrate that (CO)4Mn[η2-COC(H)(p-
tolyl)N(CH3)COPh] reacts with PPh3 to generate the unchelated cis-(CO)4(PPh3)Mn[COC-
(H)(p-tolyl)N(CH3)COPh], while reaction with NaBH4 leads to the liberation of the amide
(p-tolyl)CH2N(CH3)COPh, rather than the amino acid residue.
Sch em e 1
In tr od u ction
The sequential insertion of carbon monoxide and
imines into metal-carbon bonds provides a potential
method to generate metal-bound amides (1) and the
related metalated R-amino acid (2) complexes (Scheme
1). These represent important intermediates in the
development of metal-mediated routes to construct
amino acid derivatives from simple and flexible imine/
CO building blocks.1 Indeed, complexes analogous to 2
have been postulated as intermediates in the cobalt- and
palladium-catalyzed synthesis of R-amino acids from
aldehydes, amides, and CO.2 Nevertheless, while the
insertion chemistry of olefins and carbon monoxide has
been thoroughly explored,3 much less is known about
the analogous insertion of imines. Recently, we and
others reported that the sequential insertion of carbon
monoxide and imine can be achieved with palladium
complexes of the form L2Pd(CH3)(RNdC(H)R′)+X-
(L2 ) bidentate ligand; R ) alkyl, aryl; R′ ) aryl; X )
noncoordinating anion), providing the first well-defined
examples of imine insertion into a late-metal-carbon
bond.1a,b This process has since been elaborated to the
analogous nickel complexes.4 These reactions have
allowed for the construction of metal-bound R-amides
(1); however, the products were found to be completely
inert to the subsequent insertion of CO. To our knowl-
edge, metalated R-amino acid derivatives of the form of
2 have not been previously prepared via sequential
imine/carbon monoxide insertion.5
(1) (a) Dghaym, R. D.; Yaccato, K. J .; Arndtsen, B. A. Organome-
tallics 1998, 17, 4. (b) Kacker, S.; Kim, J . S.; Sen, A. Angew. Chem.,
Int. Ed. 1998, 37, 1251. (c) Cavallo, L. J . Am. Chem. Soc. 1999, 121,
4238.
(2) (a) Beller, M.; Eckert, M. Angew. Chem., Int. Ed. 2000, 39, 1010.
(b) Beller, M.; Eckert, M.; Vollmuller, F.; Bogdanovic, S.; Geissler, H.
Angew. Chem., Int. Ed. Engl. 1997, 36, 1494. (c) Beller, M.; Eckert,
M.; Holla, E. W. J . Org. Chem. 1998, 63, 5658. (d) Dyker, G. Angew.
Chem., Int. Ed. Engl. 1997, 36, 1700.
(3) (a) Drent. E.; Budzellar, P. H. M. Chem. Rev. 1996, 96, 663. (b)
Rix, F. C.; Brookhart, M.; White, P. S. J . Am. Chem. Soc. 1996, 118,
4746 and references therein. (c) Sen, A. Acc. Chem. Res. 1993, 26, 303.
(d) J ohnson, J . K.; Ittel, S. D.; Brookhart, M. Chem. Rev. 2000, 100,
1169.
A rationale put forward for the lack of CO insertion
in the palladium and nickel versions of complex 1 was
that strong chelation of the amide oxygen blocks the
empty coordination site required for CO coordination.
(4) Davis, J . L.; Arndtsen, B. A. Organometallics 2000, 19, 4657.
10.1021/om000745d CCC: $20.00 © 2001 American Chemical Society
Publication on Web 02/22/2001

A Manganese-R-Amino Acid Derivative
Organometallics, Vol. 20, No. 6, 2001 1129
Sch em e 2
With this in mind, we reasoned that the use of metal-
carbonyl complexes for sequential CO/imine insertion
would result in the formation of the metal-R-amide
complex with a cis-coordinated carbon monoxide ligand
(1; L ) CO), which may more readily undergo subse-
quent CO insertion. Manganese carbonyl complexes
have been demonstrated to undergo the sequential
insertion of carbon monoxide with olefins and alkynes
to generate five-membered metallacycles analogous to
1a -c.6 In addition, imine insertion into the metal-acyl
bonds of (CO)xMCOR (M ) Mn, Co) has been postulated
in several reports.7 These suggest that (CO)5Mn-R (R
) CH3, C6H5) may be prime candidates to mediate the
sequential insertion of carbon monoxide and imines to
generate metal-bound R-amino acid products.
We report below the results of our investigation on
the insertion of imines with manganese carbonyl com-
plexes. These show an unusual discrimination between
imine C-H bond activation and insertion that can be
controlled by the addition of external Lewis acids. We
also report a mild oxidative addition route to these
products of CO/imine insertion. The latter has allowed
the factors which affect the subsequent CO insertion
chemistry to be explored and has ultimately led to the
first crystallographic characterization of a manganese-
bound R-amido-substituted acyl derivative (2).
Complexes 6a -c have been fully characterized in
analogy to previously reported arene-metalated imine
complexes.9 Notably, three distinct aromatic resonances
1
are observed in the H NMR of these complexes (e.g.,
6a : δ 7.72 (s, 1H), δ 7.48 (d, 1H), δ 6.96 (d, 1H)),
demonstrating that metalation of the p-tolyl aromatic
ring has occurred. In addition, the imine hydrogen
(dCH) is shifted downfield from that in the free imine
(1H NMR (CD3CN): 6a , δ 8.48 (s); 5a , δ 8.20), consistent
with chelation of the imine nitrogen to manganese.10
The cis-substituted Mn(CO)4 unit is observed in both
the IR (6a : 2075 (m), 1966 (m), 1910 cm-1 (s)) and 13C
NMR (6a : δ 220.2, 214.6, 213.5).
Resu lts
Rea ctivity of (CO)5Mn -R (R ) CH3, C6H5) w ith
Im in es. Manganese carbonyl complexes of the form
(CO)5Mn-R (3, R ) CH3; 4, R ) Ph) are known to
undergo facile insertion of carbon monoxide in the
presence of added ligands to generate the corresponding
manganese-acyl complexes.8 Thus, our first attempts
to achieve sequential CO/imine insertion involved the
simple reaction of (CO)5Mn-R with imines. The addi-
tion of imines 5a -c to (CO)5Mn-CH3 (3) in CH3CN
followed by warming to 70 °C leads to the formation of
a new organometallic complex. However, rather than
generating the product of imine insertion, the ortho-
metalated products 6a -c are isolated in 50-84% yield
(Scheme 2). Identical products were observed upon the
reaction of 5a -c with (CO)5Mn-Ph (4).
The C-H activation of aromatic imines by alkylman-
ganese carbonyl complexes is not a new reaction. Bruce
and co-workers have reported that the reaction of Ph-
(H)CdNPh with (CO)5MnCH2Ph leads to the generation
of a product analogous to 6.9 In these studies, arene
metalation is postulated to occur via the initial displace-
ment of CO and imine coordination to (CO)4MnCH2Ph,
followed by C-H bond activation (either via a σ-bond
metathesis or oxidative addition/reductive elimination
mechanism) and elimination of alkane. An analogous
process is likely active in the reaction of 3 and 4 with
imines. Monitoring the reaction of (CO)5Mn-Ph (4) with
5a -c by 1H NMR (CD3CN) reveals the quantitative
formation of benzene in addition to 4a -c.
In the case of the less sterically encumbered imine
(5) Complexes of this form have been previously generated via
alternative routes: (a) Severin, K.; Bergs, R.; Beck, W. Angew. Chem.,
Int. Ed. 1998, 37, 1634 and references therein. (b) Nagy-Gergely, I.;
Szalontai, G.; Ungvary, F.; Marko, L.; Moret, M.; Sironi, A.; Zucchi,
C.; Sisak, A.; Tschoerner, M.; Martinelli, A.; Sorkau, A.; Palyi, G.
Organometallics 1997, 16, 2740. (c) Petri, W.; Beck, W. Chem. Ber.
1984, 117, 3265. (d) Hungate, R. W.; Miller, F.; Goodman, M. S.
Tetrahedron Lett. 1988, 29, 4273. (e) Amiens, C.; Balavoine, G.; Guibe,
F. J . Organomet. Chem. 1993, 443, 207.
(6) (a) DeShong, P.; Sidler, D. R.; Rybczynski, P. J .; Slough, G. A.;
Rheingold, A. L. J . Am. Chem. Soc. 1988, 110, 2575. (b) DeShong, P.;
Slough, G. A.; Rheingold, A. L. Tetrahedron Lett. 1987, 28, 2229. (c)
DeShong, P.; Slough, G. A. Organometallics 1984, 3, 636. (d) Booth,
B. L.; Gardner, M.; Haszeldine, R. N. J . Chem. Soc., Dalton Trans.
1975, 1856. (e) DeShong, P.; Slough, G. A. Tetrahedron Lett. 1987, 28,
2233.
(7) (a) Reduto, A. C.; Hegedus, L. S. Organometallics 1995, 14, 1586.
(b) Vaspallo, G.; Alper, H. Tetrahedron Lett. 1988, 29, 5113. (c) Alper,
H.; Amaratunga, S. J . Org. Chem. 1982, 47, 3595. (d) Muller, F.; van
Koten, G.; Vrieze, K.; Heijdenrijk, D. Organometallics 1989, 8, 33.
(8) (a) Kraihanzel, C. S.; Maples, P. K. Inorg. Chem. 1968, 7, 1806
and references therein. (b) Calderazzo, F. Angew. Chem., Int. Ed. Engl.
1977, 16, 299. (c) Noack, K.; Calderazzo, F. J . Organomet. Chem. 1967,
10, 101. (d) Flood, T. C. In Topics in Organic and Organometallic
Stereochemistry; Goeffroy, G. L., Ed.; Wiley: New York, 1981; Vol. 12,
p 83. (e) Flood, T. C.; J ensen, J . E.; Statler, J . A. J . Am. Chem. Soc.
1981, 103, 4410.
1
5c, monitoring its reaction with 3 by H NMR reveals
the quantitative formation of intermediate 7c at ambi-
ent temperature, which has been characterized to be the
σ-coordinated imine complex cis-(CO)4Mn(COCH3)-
[HNd(Tol)tBu] (Scheme 2). The formation of the acyl
1
ligand in 7c can be clearly observed in the H (δ 2.78
(s, 3H)) and 13C NMR (δ 275.1), and the imine hydrogen
1
is shifted downfield in the H NMR (δ 10.76 (s, 1H)),
consistent with imine σ-coordination. Warming of com-
plex 7c in CD3CN to 70 °C for 20 h leads to the
generation of 6c in 84% isolated yield, presumably via
the loss of CO followed by imine C-H activation.
(9) (a) Bennett, R. L.; Bruce, M. I.; Goodall, B. L.; Iqbal, M. Z.; Stone,
F. G. A. J . Chem. Soc., Dalton Trans. 1972, 1787. (b) Bruce, M. I.;
Goodall, B. L.; Iqbal, M. Z.; Stone, F. G. A. J . Chem. Soc., Dalton Trans.
1971, 1595. (c) Bennett, R. L.; Bruce, M. I.; Matsuda, I. Aust. J . Chem.
1975, 28, 1265.
(10) (a) Lenges, C. P.; Brookhart, M.; White, P. S. Angew. Chem.,
Int. Ed. 1999, 38, 552. (b) Knight, D. A.; Dewey, M. A.; Stark, G. A.;
Bennet, B. K.; Arif, A. M.; Gladysz, J . A. Organometallics 1993, 12,
4523.

1130 Organometallics, Vol. 20, No. 6, 2001
Lafrance et al.
Sequ en tia l CO/Im in e In ser tion vs Cyclom eta la -
tion : In flu en ce of Lew is Acid s. Mechanistic studies
on the insertion of imines into palladium-acyl bonds
have demonstrated that this reaction proceeds via the
initial σ-coordination of imine to the palladium center,
followed by a migratory insertion reaction.11 These
studies also suggested that the nucleophilic attack of
the imine on the acyl ligand carbon may lead to
generation of the insertion product and that increasing
the electrophilicity of the acyl ligand can facilitate this
transformation. The observation of intermediate 7c in
the reaction of imine with complex 3 shows that a
similar σ-coordination of imines cis to an acyl ligand can
be obtained with manganese complexes. However, the
decarbonylation of 7c followed by C-H bond activation
occurs at a faster rate than imine insertion into the
manganese-acyl bond. Considering the mechanism of
imine insertion with palladium complexes, it was rea-
soned that factors which increase the electrophilicity of
the acyl ligand in these manganese complexes (i.e., 7c)
may make imine insertion more favorable than C-H
bond activation. Since Lewis acids are well-known to
interact with manganese-acyl ligands,12 the influence
of AlCl3 on the reaction with imines was examined.
The addition of imine 5a to complex 3 in the presence
of 1 equiv of AlCl3 in CD3CN followed by monitoring
the reaction by 1H NMR reveals the formation of a new
product (8a , 35% NMR yield) over the course of 24 h
(eq 1). Of note, no evidence for the formation of the
Mn[η2-C(H)TolN(CH3)COCH3]. The nonaromatic 1H NMR
resonances for 9a are similar to those observed in 8a
(δ 4.60 (d, 1H, Mn-CH), δ 2.98 (s, 3H, NCH3), δ 2.23
(s, 3H, COCH3), δ 2.05 (s, 3H, C6H4CH3)), with the
three-bond coupling of the phosphine ligand to Mn-CH
clearly evident (3J P-C ) 18.5 Hz). The IR of 9a demon-
strates the presence of the fac-substituted manganese
center (νCO 1996 (s), 1904 (vs), 1873 cm-1 (vs)). In
addition, the amide carbonyl vibration in 9a is observed
at 1600 cm-1, which is a low frequency compared to that
of free amides (νCO 1630-1680 cm-1). The latter is a
characteristic of chelation of the amide oxygen to the
manganese center and is directly analogous to that
previously observed for chelated amides in 1a -c.1,4 The
structure of 9a was further confirmed by X-ray struc-
tural analysis of a related derivative (vide infra).
The generation of manganese-chelated amide prod-
ucts upon addition of Tol(H)CdNMe (5a ) to (CO)5Mn-
CH3 (3) in the presence of AlCl3 shows that the
sequential insertion of CO and imine into manganese-
carbon bonds is a viable reaction pathway. The role of
AlCl3 in this process will be discussed in a later section.
Nevertheless, the product 8a is formed in low yield and
could only be isolated as triphenylphosphine derivative
9a . This limited our ability to directly examine its
subsequent insertion chemistry and its potential as an
intermediate on the pathway towards manganese-bound
R-amino acid derivatives (2; Scheme 1). Thus, we
became interested in alternative, higher yield, routes
to complexes analogous to 8.
cyclometalated product 6a was observed. The reaction
of imine 5b with 3 and AlCl3 also does not lead to imine
C-H activation; however, this reaction yields a complex
1
mixture of products.13 The H NMR of 8a shows that
the former imine hydrogen (dCH) shifted upfield to δ
5.09 (s, 1H), consistent with a reduction in the CdN
bond, and the formation of new NCH3 (δ 2.98 (s, 3H)),
COCH3 (δ 2.23 (s, 3H)) and C6H4CH3 (δ 2.05 (s, 3H))
resonances. These data are directly analogous to those
observed for the palladium-chelated R-amide complex
(bipy)Pd[η2-CH(Tol)N(CH3)COCH3]+OTf-1a and allow a
preliminary structural assignment of 8a as the product
of carbon monoxide and imine insertion into the man-
ganese-methyl bond of 3.
Attempts to isolate complex 8a were unsuccessful.
However, the addition of 1 equiv of PPh3 to the reaction
mixture results in an immediate effervescence, due to
CO loss, and the quantitative conversion of 8a to its
phosphine-substituted derivative 9a (eq 2). The latter
could be isolated upon crystallization at -30 °C from
CH3CN and has been characterized as fac-(CO)3(PPh3)-
Oxid a tive Ad d ition of N-Acyl Im in iu m Sa lts to
(CO)5Mn -: Syn th esis of r-Am id o-Su bstitu ted Acyl
Com p lexes. It is known that the carbonylmanganate
anion, (CO)5Mn-, can be used to generate Mn-R bonds
via the nucleophilic displacement of halides from RX.14
This suggests an alternative route to complexes analo-
gous to 8, which could occur by reaction of (CO)5Mn-Na+
(11) with N-acyl iminium chloride salts.15 Iminium salt
12 can be easily prepared in situ by reaction of imine
with the appropriate acid chloride, in analogy to litera-
ture procedures.16 The addition of 12 to (CO)5Mn-Na+
(11) in CH3CN results in the immediate precipitation
of NaCl and the clean formation of a new manganese-
containing product. However, rather than generating a
complex analogous to 8, this reaction results in the
formation of the new manganese-chelated R-amido acyl
complex 13 (Scheme 3).
Complex 13 can be isolated by crystallization from
acetonitrile at -30 °C. The 1H NMR of 13 shows the
(11) Dghaym, R. D.; Dhawan, R.; Arndtsen, B. A. Submitted for
publication.
(12) (a) Butts, S. B.; Strauss, S. H.; Holt, E. M.; Strimson, R. E.;
Alcock, N. W.; Shriver, D. F. J . Am. Chem. Soc. 1980, 102, 5093. (b)
Butts, S. B.; Holt, E. M.; Strauss, S. H.; Alcock, N. W.; Strimson, R.
E.; Shriver, D. F. J . Am. Chem. Soc. 1979, 101, 5864. (c) Richmond, T.
G.; Basolo, F.; Shriver, D. F. Inorg. Chem. 1982, 21, 1272.
(13) A complex analogous to 8a was detected in the 1H NMR of the
reaction mixture in ca. 10% yield but could not be isolated to allow
complete characterization.
(14) Crabtree, R. H. The Organometallic Chemistry of the Transition
Metals; Wiley: New York, 1995; p 50.
(15) The analogous oxidative addition of N-phthaloylmethyl choride
to metal carbonyl complexes has been reported to yield complexes
analogous to 8.5a-c
(16) Ratts, K.; Chupp, J . J . Org. Chem. 1974, 39, 3745.

A Manganese-R-Amino Acid Derivative
Organometallics, Vol. 20, No. 6, 2001 1131
Sch em e 3
formation of new NCH3 (δ 3.16 (3H)) and C6H4CH3 (δ
2.31 (3H)) resonances. In addition, a new signal at δ
4.54 (s, 1H) is observed, which is assigned to the former
iminium hydrogen in 12. This chemical shift is signifi-
cantly upfield of that in 12 (7-8 ppm) and is similar to
that observed in 8a , suggesting that 13 may be simply
the product of (CO)5Mn- displacement of Cl- in 12.
However, the 13C NMR of 13 is quite diagnostic for the
structure shown. This reveals four separate metal-
carbonyl ligand resonances (δ 218.1, 213.1, 212.2, 210.1),
demonstrating the presence of a cis-substituted (CO)4Mn
fragment rather than a pentacarbonylmanganese cen-
ter. A new amide resonance is observed at δ 178.0, once
again consistent with chelation of the amide oxygen to
the manganese center. The 13C NMR also reveals the
presence of a manganese-acyl ligand in 13 (δ 269.9 (s)).
This acyl ligand would arise from the insertion of carbon
monoxide into the manganese-carbon bond of the
addition product.
F igu r e 1. Crystal structure of (CO)4Mn[η2-COCH(Tol)N-
(CH3)COPh] (13). Selected bond lengths (Å) and angles
(deg): Mn(1)-C(1), 1.854(5); Mn(1)-C(2), 1.780(4); Mn(1)-
C(3), 1.860(5); Mn(1)-C(4), 1.862(4); Mn(1)-C(5), 2.017-
(4); Mn(1)-O(6), 2.040(2); C(1)-O(1), 1.128(4); C(2)-O(2),
1.149(4); C(3)-O(3), 1.136(5); C(4)-O(4), 1.131(4); C(5)-
O(5), 1.210(4); C(7)-O(6), 1.259(4); C(7)-N(1), 1.326(4);
C(5)-Mn(1)-O(6), 88.30(13); C(7)-N(1)-C(8), 122.9(3);
C(7)-N(1)-C(6), 122.4(3); C(8)-N(1)-C(6), 114.5(3).
Sch em e 4
The generation of complex 13 upon addition of N-acyl
iminium salt 12 to 11 likely arises from the rapid
insertion of carbon monoxide into the metal-carbon
bond generated by nucleophilic displacement of Cl- by
(CO)5Mn-. To further probe the mechanism of this
process, the reaction was examined by low-temperature
NMR. The addition of 11 and 12 in CD3CN at -40 °C
followed by 1H NMR analysis reveals the immediate
formation of a reaction intermediate, which has been
preliminarily assigned as complex 14 (Scheme 3).
Notably, this product displays new NCH3 (δ 3.02) and
C6H4CH3 (δ 2.35) resonances and the presence of a
CH(Tol) resonance at δ 5.94. The upfield shift in the
CH signal from 12 demonstrates that reduction of the
CdN has occurred upon addition to (CO)5Mn- and is
in a region similar to that observed for complexes 8a
and 9a . Complex 14 is the only intermediate observed
and is rapidly converted to the product of CO insertion
into the Mn-C bond (13) upon warming to -15 °C.
Cr ysta llogr a p h ic Ch a r a cter iza tion of Com p lex
13. Crystals of complex 13 suitable for X-ray diffraction
can be grown from acetonitrile at -40 °C, and its
formulation as illustrated in Scheme 4 is confirmed by
X-ray crystallography. As shown in Figure 1, 13 has a
pseudo-octahedral geometry about the metal center. The
Mn-carbonyl bond lengths are similar for three of the
carbonyl ligands (ca. 1.86 Å); however, the carbonyl
ligand trans to the amide oxygen has a shortened Mn-
C(2) bond (1.780(4) Å). This is accompanied by a slight
lengthening of the C(2)-O(2) bond (1.149(4) Å), relative
to the other carbonyl C-O bonds (ca. 1.13 Å). This can
be attributed to the π-donor ability of the oxygen ligand,
which increases back-bonding to the trans carbonyl
ligand.
The chelation of the amide oxygen to the Mn center
creates a six-membered metallacycle. Interestingly, the
amide nitrogen is essentially planar (sum of bond angles
359.8°), and the N(1)-C(7) bond length of 1.326(4) Å is
shorter than the C-N bond distance in formamide
(C-N ) 1.368 Å)17 and closer in length to a typical
carbon-nitrogen double bond (1.30 Å). In addition, the
carbonyl bond length (C(7)-O(6) ) 1.259(4) Å), is
lengthened from that found in typical amides (forma-
mide: CdO ) 1.212 Å). These data are indicative of a
significant contribution of resonance structure 13′ to the
overall structure of the complex.
To our knowledge, complex 13 is the first example of
a crystallographically characterized acyl-bound transi-
tion metal R-amino acid derivative.5 Importantly, this
complex can be generated from simple imine, carbon
monoxide, and acid chloride building blocks. Therefore,
(17) CRC Handbook of Chemistry and Physics, 81th ed.; Kide, D.
R., Ed.; CRC Press: Cleveland, OH, 2000; p 9-1.

1132 Organometallics, Vol. 20, No. 6, 2001
Lafrance et al.
a preliminary examination of the reactivity of 13 toward
external substrates has been performed.
Dech ela t ion of 13 w it h P P h 3. In contrast to the
behavior of the five-membered metallacycle 8a , the
addition of 1 equiv of PPh3 to complex 13 does not lead
to displacement of a carbonyl ligand and instead leads
to the formation of a new complex (15) in 70% NMR
yield. Complex 15 can be isolated as a pale yellow solid
and has been characterized as the product of dechelation
of the amide ligand by coordination of PPh3 (eq 3). The
F igu r e 2. Crystal structure of fac-(CO)3(PPh3)Mn[η2-CH-
(Tol)N(CH3)COPh] (9d ). Selected bond lengths (Å) and
angles (deg): Mn(1)-C(1), 1.814(2); Mn(1)-C(2), 1.775(2);
Mn(1)-C(3), 1.812(2); Mn(1)-C(4), 2.128(2); Mn(1)-P(1),
2.3690(9); Mn(1)-O(4), 2.0242(14); C(1)-O(1), 1.149(2);
C(2)-O(2), 1.155(2); C(3)-O(3), 1.154(2); C(5)-O(4), 1.270-
(2); C(5)-N(1), 1.31(2); C(4)-Mn(1)-O(4), 80.12(7); C(5)-
N(1)-C(6), 123.4(2); C(5)-N(1)-C(4), 115.59(12); C(6)-
N(1)-C(4), 117.8(2).
formulation of 15 is supported by the 13C NMR, which
shows four separate metal-carbonyl resonances:
δ
2
2
216.9 (d, J P-C ) 32 Hz), δ 216.2 (d, J P-C ) 84 Hz), δ
2
2
214.6 (d, J P-C ) 76 Hz), and δ 213.2 (d, J P-C ) 59
Hz), confirming that the (CO)4Mn fragment remains
intact and phosphine is bound to the metal center. The
final coordination site on manganese is occupied by the
acyl ligand. This can be clearly observed in the 13C NMR
signal for the acyl carbon (δ 267.5 (d)), which has strong
two-bond coupling to the phosphine ligand (2J P-C ) 50
Hz). The dechelation of the amide ligand is also evident
from 13C NMR, in which the amide carbonyl resonance
(δ 170.8) is shifted upfield from that in 7a and 8a and
is instead similar to that observed in free amides (δ 171).
The facile dechelation of the amide oxygen from 13
is surprising when compared to the reactivity of complex
8a , which does not undergo amide dechelation and
instead loses carbon monoxide upon PPh3 addition.
Thus, while the chelation of the amide in the five-
membered ring of 8a is quite robust, the added flex-
ibility of the six-membered chelate appears to result in
a weaker Mn-O bond that can be broken by strong
ligands.
nuclear NMR and IR. The NMR data for 8d are almost
identical with those of its methyl analogue 8a , with the
diagnostic Mn-CH resonance shifted upfield of free
imine to δ 5.09 (s) (8a : δ 5.09). The 13C NMR of 8d
reveals the disappearance of the manganese-acyl reso-
nance at δ 269.9, confirming that decarbonylation has
occurred. In addition, the amide resonance is once again
downfield of the free amide (δ 179.9), demonstrating
that the carbonyl oxygen remains chelated to the
manganese center after CO loss. All other data are
consistent with the structure as shown.
As with 8a , the addition of PPh3 to a CD3CN solution
of 8d leads to an immediate displacement of carbon
monoxide and the quantitative generation of the phos-
phine-substituted complex 9d . Complex 9d can be
isolated as yellow crystals by crystallization from ac-
etonitrile at -40 °C, and its structure as fac-(CO)3-
(PPh3)Mn[η2-C(H)TolN(CH3)COPh] has been confirmed
by X-ray crystallography (Figure 2).
This structure demonstrates that carbon monoxide
deinsertion has occurred from 13 to generate the five-
membered amide-chelated complex. The geometry about
manganese is near octahedral and clearly shows the fac
orientation of the three carbonyl ligands about the metal
center. As with complex 13, the carbonyl ligand trans
to the oxygen ligand displays a shortened Mn-C(2) bond
(1.775(2) Å) relative to the other carbonyl ligands (M-
C(1) ) 1.814(2) Å; Mn-C(3) ) 1.812(2) Å), suggestive
of the stronger back-bonding with this CO ligand. The
shortened amide N(1)-C(5) bond length (1.313(2) Å) and
lengthened C(5)-O(4) bond (1.270(2) Å) are consistent
with a strong chelation of the amide oxygen to the
manganese center, in which a resonance structure
similar to 13′ is strongly contributing to the overall
structure of the complex.
Deca r bon yla tion of Com p lex 13. Complex 13 has
been found to be susceptible to CO deinsertion in the
absence of strong ligands. The warming of complex 13
in CD3CN to 50 °C for 15 min results in a rapid
decarbonylation of the complex to form 8d in 40% NMR
yield (Scheme 4). Similarly, the reaction of imines 5a -c
with complex 13 in CD3CN also results in the slow loss
of carbon monoxide and generation of complex 8d . Thus,
it appears that the weaker coordinating imine cannot
stabilize the dechelated version of complex 13 in analogy
to PPh3 (15) and, instead, leads to CO deinsertion and
formation of the stable five-membered metallacycle.
This process also occurs more rapidly than imine
insertion into the Mn-acyl bond of 13. The decarbony-
lation of 13 appears to be irreversible, and the addition
of up to 1000 psi of CO to 8d does not lead to the
regeneration of complex 13.
Complex 8d can be partially isolated by extraction
with pentane and has been characterized by multi-

A Manganese-R-Amino Acid Derivative
Organometallics, Vol. 20, No. 6, 2001 1133
Sch em e 5
Sch em e 6
Clea va ge of th e Mn -C Bon d in Com p lex 13.
Preliminary attempts to liberate the R-amino acid unit
from the metal center in 13 show that decarbonylation
to generate the five-membered chelate ring occurs prior
to cleavage of the manganese-acyl bond. Thus, the
oxidation of complex 13 with I2 in CH3CN, followed by
workup under hydrolytic conditions, yields p-tolualde-
hyde and the amide (CH3)HNCOPh. These products
would arise from hydrolysis of the N-acyl iminium iodide
salt 16 (Scheme 5). Considering that oxidation of the
manganese center by I2 likely causes the displacement
of CO ligands, the generation of 16 presumably occurs
via initial CO loss from the Mn center, followed by CO
deinsertion and cleavage of the Mn-C bond. Similarly,
the reduction of 13 with NaBH4 leads to the formation
of amide 17 (70% NMR yield). Once again, this product
shows that CO deinsertion from 13 occurs prior to
rupture of the Mn-C bond.
acid present. Considering that the insertion of Tol(H)Cd
NCH3 into the manganese-acyl bond occurs under
much milder conditions (ambient temperature) than
cyclometalation (70 °C), the influence of AlCl3 likely
occurs as anticipated: by lowering the barrier for imine
insertion from intermediate 7. This does not allow the
higher barrier C-H activation chemistry to compete
with insertion. The ability of AlCl3 to lower the kinetic
barrier to imine insertion likely arises from its ability
to coordinate to the acyl ligand oxygen,12 thereby
creating a more electrophilic acyl ligand in 18. Thus, it
appears that, provided the acyl ligand is sufficiently
electrophilic, these neutral manganese complexes be-
have in a fashion similar to cationic group 10 metals
and undergo imine insertion into the metal-acyl bond
under relatively mild conditions.
Discu ssion
Sequ en tial CO/Im in e In ser tion with (CO)5Mn CH3.
While olefins and alkynes have been previously exam-
ined for migratory insertion into the manganese-acyl
bonds of (CO)5MnCOR,6 our observation of the forma-
tion of 8a upon reaction of Tol(H)CdNCH3 (5a ) with
(CO)5Mn-CH3 in the presence of AlCl3 represents the
first well-defined example of sequential carbon monox-
ide and imine insertion with a neutral metal complex.
Structurally, this sequential insertion occurs to generate
a manganese-chelated product that is directly analogous
to those observed with alkenes and alkynes.6 A similar
amide chelation has also been noted in the only other
reports of imine insertion reactions with cationic pal-
ladium and nickel complexes (Scheme 1).1,4 As demon-
strated by in the X-ray structure of 9d (Figure 2), this
chelation is strongly resonance stabilized, generating a
robust and nearly planar five-membered metallacycle.
This chelation undoubtedly provides a further thermo-
dynamic driving force for imine insertion.
In contrast to the behavior of the cationic palladium
and nickel complexes, imine insertion into the manga-
nese-acyl bond of (CO)4Mn(COR) is only observed in
the presence of AlCl3. The ability of the Lewis acid to
completely divert the reactivity of Tol(H)CdNCH3 with
methylmanganese pentacarbonyl (3) from cyclometala-
tion to sequential insertion has, to our knowledge, not
been previously noted. A reasonable rationale for this
behavior is summarized in Scheme 6. The formation of
intermediate 7c upon reaction of imine 5c with 3
demonstrates that the complex cis-(CO)4Mn(COCH3)-
(imine) can be generated both with and without Lewis
CO In ser tion in to (CO)n Mn CH(Tol)N(CH3)COR
(8 a n d 14). The oxidative addition of N-acyl iminium
chloride salts to (CO)5Mn-Na+ provides an alternative
route to generate manganese-bound amides similar to
those obtained from sequential imine/CO insertion. In
contrast to what has been observed from imine/CO
insertion, this oxidative addition route results in the
immediate insertion of carbon monoxide into the Mn-C
bond, forming the six-membered metallacycle 13. Thus,
not only is CO insertion into the R-amido substituted
manganese-alkyl complex possible but it occurs under
very mild conditions. By way of comparison, CO inser-
tion into the Mn-CH3 bond of (CO)5MnCH3 (3) under
1 atm of CO is only 75% complete at 25 °C after 24 h.18
Similarly, Beck and co-worker have reported that the
less basic R-amide-substituted phthalimidomethyl-
manganese complex requires high CO pressure to
undergo carbonylation.5c The rapid insertion of CO at
-15 °C in complex 14 is likely related to the ability of
the amide oxygen to undergo rapid intramolecular
chelation to the manganese center. This would allow for
the rapid trapping of the product of CO insertion into
the Mn-C bond of complex 14.
(18) Determined by monitoring the reaction of methylmanganese
carbonyl (27 mg, 0.12 mmol) in 0.5 mL of CD3CN under 1 atm of CO
by 1H NMR.

1134 Organometallics, Vol. 20, No. 6, 2001
Lafrance et al.
Sch em e 7
The difference in CO insertion propensity between the
similar R-amido-substituted manganese complexes ob-
tained from oxidative addition (14) and sequential
imine/CO insertion (8a ) likely arises from the structure
of these complexes. The oxidative addition route gener-
ates the R-amido-substituted manganese-alkyl complex
in a nonchelated form (14) and bound to a pentacarbonyl
manganese center (Scheme 7). In order for the amide
oxygen to chelate to the Mn center from 14, carbon
monoxide must first insert into the Mn-C bond, and
this is subsequently trapped out as 13. This contrasts
with the imine insertion route, in which the migration
of the σ-bound imine from cis-(CO)4Mn(COCH3)(H3CNd
C(H)Tol) (7a ) generates an unsaturated tetracarbonyl
center, in which the amide oxygen can undergo rapid
chelation to form a five-membered metallacycle. Con-
sidering the greater stability of the five-membered
amide-chelated metallacycle (vide infra), these data
strongly argues that efforts toward utilizing sequential
imine/CO insertion to generate R-amino acid derivatives
may be greatly facilitated by the generation of unch-
elated insertion products.
Rela tive Sta bility of th e F ive- a n d Six-Mem -
ber ed Meta lla cycles. Depending upon he synthetic
route employed, either the five- (complex 8) or six-
membered (complex 13) amide-chelated metallacycles
can be generated as the initial isolated product. How-
ever, the five-membered metallacycle is the thermody-
namically more stable form of the two complexes. This
is clearly demonstrated in the thermal reactivity of 13,
which undergoes irreversible CO loss upon warming to
generate complex 8d . The greater stability of the five-
membered metallacycles may be related to the ability
of the five-membered ring to achieve amide chelation
to the manganese center stronger than that of the more
flexible six-membered metallacycle. This is not evident
in the crystal structures of the complexes, which show
similar Mn-O bond distances in both 13 and 9d (13,
2.040(2) Å; 9d , 2.0242(14) Å). However, it is revealed
in their reactivity toward phosphine ligands. In contrast
to the six-membered metallacycle in 13, which under-
goes reaction with PPh3 to generate the nonchelated
phosphine-substituted analogue 8d , PPh3 does not
cleave the amide chelation from the five-membered
metallacycles and, instead, results in the displacement
of a CO ligand. The propensity of complex 13 to undergo
rapid CO deinsertion is further demonstrated in our
preliminary attempts to liberate the R-amino acid unit
from the manganese center with I2 and NaBH4, which
instead results in the decarbonylation of 13 prior to
cleavage of the Mn-C bond (Scheme 5).
Con clu sion
In conclusion, two new routes have been developed
to generate manganese-chelated amides: the sequential
insertion of carbon monoxide and imine into manganese-
methyl bonds and the oxidative addition of N-acyl
iminium salts to (CO)5Mn-. Structural characterizations
of the products of both these reactions demonstrate the
strong propensity of the amide ligand to coordinate to
the manganese center to generate five- and six-mem-
bered metallacycles, respectively. In the case of oxida-
tive addition, this chelation is accompanied by CO
insertion, allowing the synthesis and structural char-
acterization of a novel manganese-chelated R-amino acid
derivative. The propensity of the latter complex to
undergo CO deinsertion has hindered our preliminary
attempts to liberate the organic amino acid fragment
from the metal center. Nevertheless, the reactivity of
this six-membered metallacycle with strong ligands
implies it may be possible to stabilize this complex and
selectively cleave the manganese-acyl bond. Consider-
ing that this would allow for the controlled synthesis of
R-amino acids from simple imine, carbon monoxide, and
acid chloride building blocks, efforts along these lines
are currently being pursued in our laboratory.
Exp er im en ta l Section
Unless otherwise noted, all manipulations were carried out
under an inert atmosphere in a Vacuum Atmosphere 553-2
drybox or by using standard Schlenk or vacuum-line tech-
niques. NMR spectra were obtained on a 270 MHz J EOL NMR.
IR spectra were obtained on a Bruker IFS-48 spectrometer.
X-ray analyses were performed on either an Enraf-Nonius
CAD4 with Cu KR radiation (9d ) or a Rigaku diffractometer

A Manganese-R-Amino Acid Derivative
Organometallics, Vol. 20, No. 6, 2001 1135
with Mo KR radiation (13). Elemental analyses were performed
by Laboratoire d’analyse elementaire de l’Universite de Mon-
treal, Montreal, Quebec, Canada, or by QTI, Whitehouse, NJ .
Unless otherwise specified, all reagents were purchased
from commercial suppliers and used without further purifica-
tion. Liquids were freeze-pump-thawed three times to degas
before use. Diethyl ether was distilled from sodium benzophe-
none. Pentane, methylene chloride, and chlorobenzene were
distilled from CaH2. Deuterated solvents were dried as their
protonated analogues but were vacuum-transferred from the
drying agent. UHP grade carbon monoxide was obtained from
Matheson. Manganese carbonyl was obtained from Strem
Chemical Co. and used without further purification. Imines
were prepared by reaction of p-tolualdehyde and the appropri-
ate amine in diethyl ether at room temperature for 1 day in
the presence of 4 Å molecular sieves. N-Acyl iminium salt 12
was generated in situ by the reaction of benzoyl chloride with
MeNdC(H)Tol, in analogy to literature procedures.16 (CO)5-
MnR (R ) CH3, Ph)19 and (CO)5MnNa19 were prepared by
literature procedures.
The ether was removed in vacuo, and the crude product was
recrystallized from 5 mL of pentane at -30 °C overnight. The
light yellow crystals were collected by filtration, washed with
cold pentane, and dried under vacuum, yielding 6c (117 mg,
34% yield). IR (KBr): 3372 (s), 2970 (m), 2074 (s), 1983 (vs),
1898 (s), 1569 (s), 1449 (m), 1360 (m), 1189 (m), 1140 (m), 1041
1
(w), 962 (m), 852 (m), 646 (s), 544 (m) cm-1. H NMR (C6D6):
δ 8.13 (s, 1H), 7.66 (s, 1H, NH), 7.57 (d, 1H), 6.75 (d, 1H), 2.13
(s, 3H, Tol), 0.77 (s, 9H). 13C NMR (C6D6, 5 °C): δ 220.0, 215.7,
214.5, 197.8, 183.0, 142.9, 141.8, 141.0, 130.0, 124.2, 39.6, 27.9,
21.3.
Syn th esis of (CO)4Mn [η2-CH(Tol)N(CH3)COCH3] (8a ).
Methylmanganese pentacarbonyl (200 mg, 0.95 mmol), Tol-
(H)CdNMe (127 mg, 0.95 mmol), and AlCl3 (127 mg, 0.965
mmol) were dissolved in 20 mL of acetonitrile, and the solution
was stirred at room temperature for 24 h. 1H NMR of the
reaction mixture reveals the formation of 8a in 30% yield.
1
Attempts to isolate 8a were unsuccessful. H NMR (CD3CN):
δ 7.04 (d, 2H), 6.89 (d, 2H), 5.09 (s, 1H, Mn-CH), 2.98 (s, 3H,
NCH3), 2.23 (s, 3H, COCH3), 2.05 (s, 3H, Tol).
Syn t h esis of fa c-(CO)3(P P h 3)Mn [η2-CH (Tol)N(CH 3)-
COCH3] (9a ). Methylmanganese pentacarbonyl (200 mg, 0.95
mmol), Tol(H)CdNMe (127 mg, 0.95 mmol) and AlCl3 (127 mg,
0.965 mmol) were dissolved in 20 mL of acetonitrile, and the
solution was stirred at room temperature for 24 h. A 3 mL
acetonitrile solution of triphenylphosphine (250 mg, 0.95
mmol) was added to the reaction mixture, resulting in an
immediate effervesence. After 15 min of stirring, the solution
was concentrated in vacuo until the appearance of a solid
precipitate, and the solution placed at -30 °C overnight. The
pale yellow powder was collected, washed with cold diethyl
ether, and dried under vacuum, yielding 9a (122 mg, 22%
yield). Anal. Found: C, 66.33; H, 5.14; N, 2.56. Calcd: C, 66.55;
H, 5.06; N, 2.43. IR (KBr): 1996 (s), 1904 (vs), 1873 (vs), 1600
Syn th esis of (CO)4Mn [η2-2-(CHdNCH3)-5-(CH3)C6H3]
(6a ). Methylmanganese pentacarbonyl (200 mg, 0.95 mmol)
and Tol(H)CdNMe (127 mg, 0.95 mmol) were dissolved in 5
mL of acetonitrile, and the solution was heated to 70 °C for
24 h. The solution was concentrated in vacuo until the
appearance of a solid and then cooled to -30 °C overnight.
The yellow crystals formed were collected by filtration, washed
with cold diethyl ether, and dried under vacuum, yielding 6a
(190 mg, 67% yield). Anal. Found: C, 52.16; H, 3.35; N, 4.63.
Calcd: C, 52.19; H, 3.37; N, 4.68. IR (KBr): 2075 (m), 1966
(m), 1910 (s), 1614 (m), 1581 (m), 1431 (w), 1134 (m), 1033
1
(m), 808 (m), 633 (s), 546 (m) cm-1. H NMR (CD3CN): δ 8.31
(s, 1H, HCdN), 7.72 (s, 1H), 7.48 (d, 1H), 6.96 (d, 1H), 3.60 (s,
3H, NCH3), 2.36 (s, 3H, Tol). 13C NMR (C6D6, 5 °C): δ 220.2,
21.6, 181.5, 176.1, 145.4, 142.1, 141.3, 128.6, 124.8, 51.4, 21.7.
Syn th esis of (CO)4Mn [η2-2-(CHdNCH2P h )-5-(CH3)C6H3]
(6b). Methylmanganese pentacarbonyl (200 mg, 0.95 mmol)
and Tol(H)CdNCH2Ph (197 mg, 0.95 mmol) were dissolved in
5 mL of acetonitrile, and the solution was heated to 70 °C for
72 h. The solution was removed in vacuo, and the residual oil
was dissolved in 3 mL of pentane and cooled to -30 °C
overnight. The yellow crystals formed were collected by
filtration, washed with cold diethyl ether, and dried under
vacuum, yielding 6b (251 mg, 70% yield). Anal. Found: C,
60.72; H, 3.48; N, 3.71. Calcd: C, 60.81; H, 3.76; N, 3.73. IR
(KBr): 2071 (s), 1994 (vs), 1974 (s), 1936 (s), 1604 (s), 1580
(s), 1545 (m), 1452 (m), 1345 (m), 1064 (m), 1032 (m), 742 (m),
1
(m), 1505 (w), 1434 (w), 1089 (w), 679 (m), 520 (m) cm-1. H
3
NMR (C6D6): δ 7.69 (m, 8H), 6.9-7.5 (m, 11H), 4.60 (d, J P-H
) 19 Hz, 1H), 2.22 (s, 3H, NCH3), 1.85 (s, 3H, Tol), 1.09 (s,
3H, COCH3). 31P NMR (C6D6): δ 53.97.
Syn th esis of (CO)4Mn [η2-COCH(Tol)N(CH3)COP h ] (13).
Sodium manganese pentacarbonyl (500 mg, 2.29 mmol) and
Tol(H)CN(CH3)COPh+Cl- (630 mg, 2.29 mmol) were stirred
in 10 mL of acetonitrile for 2 min, and the cloudy yellow
solution was quickly filtered through Celite (to remove NaCl).
The solution was concentrated in vacuo until the appearance
of a yellow solid precipitate, and the cold solution was filtered
through a fritted Buchner funnel. The pale yellow powder was
collected, washed with cold diethyl ether, and dried under
vacuum, yielding 13 (520 mg, 52% yield). Anal. Found: C,
58.07; H, 3.80; N, 3.18. Calcd: C, 58.21; H, 3.72; N, 3.23. IR
(KBr): 2076 (m), 1987 (vs), 1630 (m), 1582 (s), 1494 (w), 1013
1
640 (s), 546 (m) cm-1. H NMR (CD3CN): δ 8.53 (s, 1H, HCd
N), 7.71 (s, 1H), 7.58 (d, 1H), 7.28-7.44 (m, 5H, Ph), 6.99 (d,
1H), 4.92 (s, 2H, NCH2Ph), 2.36 (s, 3H, Tol). 13C NMR (C6D6,
5 °C): δ 220.3, 214.2, 182.5, 175.9, 145.2, 142.1, 141.9, 135,8,
129.4, 128.7, 128.5, 124.9, 67.8, 21.8.
1
(m), 912 (w), 698 (m), 638 (m), 532 (m) cm-1. H NMR (CD3-
CN): δ 7.57 (m, 5H, Ph), 7.21 (d, 2H, Tol), 7.07 (d, 2H, Tol),
4.54 (s, 1H, Mn-CH), 3.16 (s, 3H, NCH3), 2.31 (s, 3H, Tol).
13C NMR (C6D6, 5 °C): δ 269.9, 218.1, 213.1, 212.2, 210.1,
178.0, 137.7, 133.8, 131.2, 130.9, 129.7, 128.7, 127.5, 126.0,
83.0, 41.4, 20.8.
Syn th esis of (CO)4Mn [η2-2-(C(tBu )dNH)-5-(CH3)C6H3]
(6c). Methylmanganese pentacarbonyl (180 mg, 0.86 mmol)
t
and Bu(Tol)CdNH (151 mg, 0.86 mmol) were dissolved in 10
mL of acetonitrile and stirred for 15 min. An aliquot of the
solution was removed and analyzed by IR and NMR, revealing
the quantitative formation of complex 7c. Anal. Found: C,
56.54; H, 4.73; N, 4.00. Calcd: C, 56.32; H, 4.73; N, 4.10. IR
(KBr): 3128 (w), 2971 (w), 2065 (m), 1954(vs), 1920 (vs), 1608
(s), 1476 (w), 1388 (w), 1242 (w), 1076 (m), 822 (m), 641 (s),
Syn th esis of cis-(CO)4(P P h 3)Mn [η2-COCH(Tol)N(CH3)-
COP h ] (15). Sodium manganese pentacarbonyl (300 mg, 1.38
mmol) and Tol(H)CN(CH3)COPh+Cl- (378 mg, 1.38 mmol)
were mixed in 10 mL of acetonitrile for 2 min, and the cloudy
yellow solution was quickly filtered through Celite (to remove
NaCl). A 10 mL acetonitrile solution of triphenylphosphine
(362 mg, 1.28 mmol) was added to the reaction mixture, and
the solution was stirred for 2 h at 0 °C. The pale yellow solid
was collected by filtration, washed with cold diethyl ether, and
dried under vacuum, yielding 15 (237 mg, 37% yield). Complex
15 proved too unstable for elemental analyses and was
therefore characterized by spectroscopic methods. See the
Supporting Information for 1H and 13C NMR spectra. IR
(KBr): 2063 (m), 1962 (vs), 1939 (vs), 1624 (s), 1434 (m), 1389
1
546 (m) cm-1. H NMR (C6D6): δ 10.76 (s, 1H, NH), 6.91 (d,
2H), 6.67 (d, 2H), 2.78 (s, 3H, COCH3), 2.06 (s, 3H, Tol), 0.86
(s, 9H). 13C NMR (C6D6, 5 °C): δ 275.1, 220.1, 213.7, 211.2,
197.9, 188.7, 138.9, 136.4, 129.0, 126.6, 50.1, 43.1, 27.4, 20.9.
The reaction solution was warmed to 70 °C for 20 h. The
solvent was removed in vacuo, the residue was dissolved in
diethyl ether, and this solution was filtered through Celite.
(19) Hermann, B. Synthetic Method of Organometallic and Inorganic
Chemistry; Stuttgart: New York, 1996; Vol. 7, p 92.
(m), 1328 (m), 1063 (w), 997 (m), 633 (s), 520 (m) cm-1 1H
.

1136 Organometallics, Vol. 20, No. 6, 2001
Lafrance et al.
Ta ble 1. Cr ysta llogr a p h ic Deta ils for Com p lexes
9d a n d 13
NMR (C6D6): δ 7.76-7.86 (m, 6H), 7.40-7.48 (m, 2H), 7.32
(s, 1H), 7.26 (d, 2H), 7.02-7.13 (m, 8H), 6.93-7.02 (m, 5H),
2.53 (s, 3H, NCH3), 2.02 (s, 3H, Tol). 31P NMR (C6D6): 52.05.
9d
13
2
13C NMR (C6D6, 5 °C): δ 267.6 (d, J P-C ) 50 Hz), 216.9 (d,
empirical formula
fw
C
37H31NMnNO4P
C21H16NMnNO6
433.29
2
2
2J P-C ) 32 Hz), 216.2 (d, J P-C ) 84 Hz), 214.6 (d, J P-C ) 76
639.57
2
Hz), 213.3 (d, J P-C ) 59 Hz), 170.7, 138.0 (d, J P-C ) 54 Hz),
temp, K
wavelength, Å
cryst syst
space group
a (Å)
230(2)
293(2)
135.2, 134.6, 134.0 (d, J P-C ) 38 Hz), 132.5, 130.5, 129.9 (d,
J P-C ) 27 Hz), 129.7, 128.9, 128.4 (d, J P-C ) 27 Hz), 83.0 (d,
3J P-C ) 10 Hz), 36.0, 20.9.
1.540 56
monoclinic
P21/c
14.975(5)
13.004(5)
17.838(7)
0.709 30
triclinic
P1h
10.309(5)
10.518(3)
11.002(4)
75.09(3)
62.73 (2)
85.46 (4)
1023.6 (7)
2
Syn t h esis of (CO)4Mn [η2-CH (Tol)N(CH3)COP h ] (8d ).
Sodium manganese pentacarbonyl (500 mg, 2.29 mmol) and
Tol(H)CN(CH3)COPh+Cl- (400 mg, 1.46 mmol) were mixed in
10 mL of acetonitrile, and the solution was stirred at 50 °C
for 15 min. The solvent was removed, and the residue was
dissolved in 10 mL diethyl ether. The red solution was filtered
through Celite, diluted with 20 mL of pentane, and allowed
to stand at ambient temperature for 24 h. The solution was
filtered (to remove a red impurity), the solvent was removed
in vacuo, and the product was extracted with 20 mL of
pentane. Evaporation of the pentane solution yielded 8d as a
yellow powder with approximately 95% purity by 1H NMR (250
mg, 43% yield). See the Supporting Information for 1H and
13C NMR spectra. IR (KBr): 2014 (s), 1979 (vs), 1951 (vs), 1913
(s), 1589 (w), 1559 (m), 1508 (m), 1474 (w), 1070 (m), 710 (m),
b (Å)
c (Å)
R (deg)
â (deg)
111.76 (3)
γ (deg)
V (Å3)
3226 (2)
4
1.317
4.129
1328
Z
d(calcd) (Mg m-3
)
1.406
0.681
444
µ (mm-1
F(000)
)
no. of rflns collected
no. of indep rflns
15 711
6114
8042
4021
θ
min, θmax (deg)
3.17, 69.87
0.860
2.00, 25.96
1.040
goodness of fit on F2
R (I > 2σ(I))
R1 ) 0.0303,
wR2 ) 0.0669
R1 ) 0.0455,
wR2 ) 0.0692
-0.350, 0.358
R1 ) 0.0601,
wR2 ) 0.1081
R1 ) 0.1122,
wR2 ) 0.1216
-0.381, 0.384
R (all data)
639 (s) cm-1 1H NMR (C6D6): δ 7.09 (m, 2H), 7.01 (m, 5H),
.
6.90 (m, 2H), 5.04 (s, 1H, Mn-CH), 2.49 (s, 3H, NCH3), 2.16
(s, 3H, Tol). 13C NMR (C6D6): δ 220.8, 214.8, 212.8, 179.9,
148.8, 1233.1, 132.8, 130.6, 129.5, 128.3, 127.6, 67.5, 38.5, 20.8.
min, max ∆F (e/Å3)
were solved with direct methods using SHELXS9622 and
difmap synthesis using SHELXL96.23 All non-hydrogen atoms
were refined anisotropically, and the hydrogen atoms were
refined isotropically. Hydrogen atoms in 9d were calculated
at idealized positions using a riding model with different C-H
distances for the types of hydrogens. Hydrogen atoms in 13
were constrained to the parent site using a riding model. The
isotropic displacement factors were adjusted to a value 50%
higher than that of the parent site (methyl) and 20% higher
(others). A final verification of possible voids was performed
using the VOID routine of the PLATON program.20
Syn t h esis of fa c-(CO)3(P P h 3)Mn [η2-CH (Tol)N(CH 3)-
COP h ] (9d ). Complex 15a (200 mg, 0.50 mmol) and triph-
enylphosphine (132 mg, 0.50 mmol) were dissolved in 10 mL
acetonitrile, and the mixture was stirred for 2 h at 0 °C. The
pale yellow solid precipitate was collected by filtration and
washed with cold diethyl ether to yield 9d (140 mg, 52% yield).
Complex 9d proved too unstable for elemental analyses and
was therefore characterized by spectroscopic methods. See the
Supporting Information for 1H and 13C NMR spectra. IR
(KBr): 3013 (w), 2002 (s), 1902 (vs), 1868 (vs, 1601 (s), 1504
(m), 1433 (m), 1162 (w), 1089 (m), 1016 (w), 820 (m), 755 (m),
Ack n ow led gm en t. We thank Dr. Anne-Marie Le-
buis for determination of the crystal structure of com-
plexes 13, Dr. Celine Pearson for the crystal structure
of 9d , and the NSERC (Canada) and FCAR (Quebec)
for their financial support of this research. D.L. thanks
FCAR for a graduate fellowship.
699 (s), 518 (s) cm-1
.
1H NMR (C6D6): δ 7.70-7.88 (m, 6H),
3
7.22 (m, 3H), 6.85-7.08 (m, 15H), 4.59 (d, J P-H ) 18 Hz, 1H,
Mn-CH), 2.22 (s, 3H, NCH3), 2.14 (s, 3H, Tol). 31P NMR
(C6D6): 55.57. 13C NMR (C6D6, 5 °C): δ 226.8 (d, J P-C ) 84
2
Hz), 220.6 (d, 2J P-C ) 146 Hz), 217.9 (d, 2J P-C ) 84 Hz), 150.0
2
(d, J P-C ) 30 Hz), 133.8, 133.6, 133.1, 132.1, 130.2, 129.8,
129.1, 128.4 (d, 1J P-C ) 35 Hz), 127.6, 74.8 (d, 4J P-C ) 49 Hz),
Su p p or tin g In for m a tion Ava ila ble: Tables giving X-ray
structural data for complexes 9d and 13 and figures giving
NMR spectra of complexes 8d , 9d , and 15. This material is
available free of charge via the Internet at http://pubs.acs.org.
38.6, 21.0.
X-r a y Cr ysta llogr a p h ic Stu d y of fa c-(CO)3(P P h 3)Mn -
[CH(Tol)N(CH3)COP h ] (9d) an d (CO)4Mn [η2-COCH(Tol)N-
(CH3)COP h ] (13). Crystals of 9d and 13 for diffraction
analysis were grown by cooling an acetonitrile solution and
mounted on a capillary. X-ray data for 9d were collected at
230 K on a Enraf-Nonius CAD4 with Cu KR radiation. X-ray
data for 13 were collected at 293 K on a Rigaku diffractometer
with Mo KR radiation. The crystal, data collection, and
refinement parameters are collected in Table 1. The space
groups were confirmed by the PLATON program.20 Data
reduction was performed using NRCVAX.21 The structures
OM000745D
(20) Spek, A. L. PLUTON Molecular Graphics Program, J uly 1995
version; University of Utrecht, Utrecht, Holland.
(21) Gabe, E. J .; Le Page, Y,.; Charland, J .-P.; Lee, F. L.; White, P.
S. J . Appl. Crystallogr. 1989, 22, 384.
(22) Sheldrick, G. M. Program for the Solution of Crystal Structures;
University of Gottingen, Gottingen, Germany, 1996.
(23) Sheldrick, G. M. Program for Structure Analysis; University
of Gottingen, Gottingen, Germany, 1996.