Amide complexes of zirconium, rhodium, and iridium: Synthesis and reactivity. X-ray crystal structures of (η5-C5H5)2Zr(NHC 6H4-o-SMe)2 and [Rh(μ-SC6H4-o-NHMe)(COD)]2

Article abstract of DOI:10.1021/om9709805

The reaction of Cp₂ZrCl₂ (Cp = η⁵-C₅H₅) with 2 equiv of the lithium amide derivative LiNHC₆H₄-o-SMe affords the new zirconium complex Cp₂Zr(NHC₆H₄-o-SMe)₂ (2). The structure of 2 has been determined by X-ray diffraction. When the reaction is carried out in an 1:1 ratio, the complex Cp₂ZrCl(NHC₆H₄-O-SMe) (3) is generated as the major product. Reaction of Cp*₂Zr (Cp* = η⁵-C₅Me₅) with 2-(methylmercapto)aniline yields a hydride-amide complex Cp*₂ZrH(NHC₆H₄) (4). Reaction of complex 2 with [RhCl(COD)]₂ generates complex 3 and the new rhodium amide complex Rh(NHC₆H₄-o-SMe)(COD), which has been also directly synthesized by reacting [RhCl(COD)]₂ with LiNHC₆H₄-o-SMe. Thermolysis of complex 6, at 100°C, produces to a new rhodium thiolate complex [Rh(μ-SC₆H₄-o-NHMe)-(COD)]₂ (5). Its structure has been determined by X-ray diffraction methods. Reaction of [IrCl(COD)]₂ with LiNHC₆H₄-o-SMe gives the iridium(III) complex Ir(Me)(SC₆H₄NH)(COD) (7) by oxidative addition of the S-Me bond.

Full text of DOI:10.1021/om9709805

Organometallics 1998, 17, 1465-1470
1465
Am id e Com p lexes of Zir con iu m , Rh od iu m , a n d Ir id iu m :
Syn th esis a n d Rea ctivity. X-r a y Cr ysta l Str u ctu r es of
(η5-C5H5)2Zr (NHC6H4-o-SMe)2 a n d
†
[Rh (µ-SC6H4-o-NHMe)(COD)]2
Rosa Fandos,‡ Mart´ın Mart´ınez-Ripoll,§ Antonio Otero,*,| Mar´ıa J ose´ Ruiz,‡
Ana Rodr´ıguez,§,| and Pilar Terreros
Departamento de Quı´mica Inorga´nica, Orga´nica y Bioqu´ımica, Universidad de Castilla-La
Mancha, Facultad de Quı´micas, Campus de Toledo, C/ S. Lucas, 6, 45001 Toledo, Spain,
Campus de Ciudad Real, 13071 Ciudad Real, Spain, Instituto de Qu´ımica Fı´sica
(Rocasolano), CSIC, C/ Serrano 119 Madrid, Spain, and Instituto de Cata´lisis y
Petroleoquı´mica, CSIC, Cantoblanco, 28049 Madrid, Spain
Received November 7, 1997
The reaction of Cp2ZrCl2 (Cp ) η5-C5H5) with 2 equiv of the lithium amide derivative
LiNHC6H4-o-SMe affords the new zirconium complex Cp2Zr(NHC6H4-o-SMe)2 (2). The
structure of 2 has been determined by X-ray diffraction. When the reaction is carried out
in an 1:1 ratio, the complex Cp2ZrCl(NHC6H4-o-SMe) (3) is generated as the major product.
Reaction of “Cp*2Zr” (Cp* ) η5-C5Me5) with 2-(methylmercapto)aniline yields a hydride-
amide complex Cp*2ZrH(NHC6H4) (4). Reaction of complex 2 with [RhCl(COD)]2 generates
complex 3 and the new rhodium amide complex Rh(NHC6H4-o-SMe)(COD), which has been
also directly synthesized by reacting [RhCl(COD)]2 with LiNHC6H4-o-SMe. Thermolysis of
complex 6, at 100 °C, produces to a new rhodium thiolate complex [Rh(µ-SC6H4-o-NHMe)-
(COD)]2 (5). Its structure has been determined by X-ray diffraction methods. Reaction of
[IrCl(COD)]2 with LiNHC6H4-o-SMe gives the iridium(III) complex Ir(Me)(SC6H4NH)(COD)
(7) by oxidative addition of the S-Me bond.
In tr od u ction
Moreover, in recent years, transition metal complexes
with ligands containing dissimilar donor atoms such as
sulfur and nitrogen have been widely investigated,
primarily for their applications in the synthesis of
early-late transition metal heterometallic complexes.7
Such ligands would be capable of forming strong bonds
with early transition metals in their higher oxidation
state through the nitrogen atom, while the sulfur atom
would assist the formation of the heterometallic complex
by forming a stable bond to the late transition metal
center.
In the past few years, there has been a growing
interest in the chemistry of transition metal amide
complexes studied mainly for early transition metals in
a high oxidation state.1 Only a limited number of
complexes of late transition metals in high oxidation
states have been reported and even fewer in their lower
one.2 Some of these derivatives can act as catalysts in
hydroammination processes,3 furthermore, they can be
used as precursors in the synthesis of imide4 complexes,
which are the focus of much attention because of their
reactivity and applications to organic transformations5
and to the synthesis of heterometallic complexes.6
We have undertaken the synthesis of zirconium
complexes with 2-(methylmercapto)anilide as the amide
† Dedicated to Prof. P. Royo on the occasion of his 60th birthday.
‡ Universidad de Castilla-La Mancha, Campus de Toledo.
§ Instituto de Qu´ımica F´ısica (Rocasolano).
(4) (a) Wigley, D. E. Prog. Inorg. Chem. 1994, 42, 239. (b) Ye, C. Q.;
Sharp, P. R. Inorg. Chem. 1995, 34, 55. (c) Tejel, C.; Shi, Y.-M.; Ciriano,
M. A.; Edwards, A. J .; Lahoz, F. J .; Oro, L. A. Angew. Chem., Int. Ed.
Engl. 1996, 35, 633.
(5) (a) Nugent, W. A.; Mayer, J . M. Metal-Ligand Multiple Bonds;
J ohn Wiley & Sons: New York, 1988. (b) Cozzi, P. G.; Veya, P.; Floriani,
C.; Rotzinger, F. P.; Chiesivilla, A.; Rizzoli, C. Organometallics 1995,
14, 4092. (c) Catellani, M.; Chiusoli, G. P.; Costa, M. J . Organomet.
Chem. 1995, 500, 69. (d) Casalnuovo, A. L.; Calbrese, J . C.; Milstein,
D. J . Am. Chem. Soc. 1988, 110, 6738. (e) Loeber, C.; Wieser, C.; Matt,
D.; Decian, A.; Fischer, J .; Toupet, L. Bull. Soc. Chim. Fr. 1995, 132,
166. (f) Sawamura, M.; Hamashima, H.; Shinoto, H.; Ito, Y. Tetrahe-
dron Lett. 1995, 36, 6479. (g) Padwa, A.; Hertzog, D. L.; Nadler, W. R.
J . Org. Chem. 1994, 59, 7072.
(6) See, for example: (a) Baranger, A. M.; Hollander, F. J .; Bergman,
R. G. J . Am. Chem. Soc. 1993, 115, 7890. (b) Baranger, A. M.; Bergman,
R. G. J . Am. Chem. Soc. 1994, 116, 3822. (c) Tracy, A.; Baranger, A.
M.; Bergman, R. G. J . Am. Chem. Soc. 1995, 117, 1163. (d) Tracy, A.;
Baranger, A. M.; Bergman, R. G. Angew. Chem., Int. Ed. Engl. 1996,
118, 653.
| Universidad de Castilla-La Mancha, Campus de Ciudad Real.
Instituto de Catalisis y Petroleoqu´ımica.
(1) Chisholm, M. H. in Comprehensive Coordination Chemistry;
Wilkinson, G., Ed.; Pergamon Press: Oxford, England, 1987; Vol. 2, p
161.
(2) (a) Bryndza, H. E.; Tam, W. Chem. Rev. 1988, 88, 1163. (b)
Fryzuk, M. D.; Montgomery, C. D. Coord. Chem. Rev. 1989, 95, 1. (c)
Schrock, R. D.; Acc. Chem. Rev. 1997, 30, 9. (d) Kolel-Veetil, M. K.;
Rheingold, A. L.; Ahmed, K. J . Organometallics 1993, 12, 3439. (e)
Kolel-Veetil, M. K.; Rahim, M.; Edwards, A. J .; Rheingold, A. L.;
Ahmed, K. J . Inorg. Chem. 1992, 31, 3877. (f) Rahim, M.; Bushweller,
C. H.; Ahmed, K. J . Organometallics 1994, 13, 4952. (g) Rahim, M.;
White, C.; Rheingold, A. L.; Ahmed, K. J . Organometallics 1993, 12,
2401. (h) Glueck, D. S.; Newman Winslow, L. J .; Bergman, R. G.
Organometallics 1991, 10, 1462. (i) Glueck, D. S.; Bergman, R. G.
Organometallics 1991, 10, 1479.
(3) Collman, J . P.; Hegedus, L. S.; Norton, J . R.; Finke, R. G.
Principles and Applications of Organotransition Metal Chemistry;
University Science Books: Mill Valley, CA, 1987.
(7) (a) Bader, A.; Lindner, E. Coord. Chem. Rev. 1991, 91, 27. (b)
Murray, S. G.; Hartley, F. R. Chem. Rev. 1981, 81, 365.
S0276-7333(97)00980-1 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 03/15/1998

1466 Organometallics, Vol. 17, No. 8, 1998
Fandos et al.
ligand containing dissimilar donor atoms with the aim
of bonding the sulfur atom to a rhodium or iridium
center and forming heterometallic complexes. Such
complexes are particularly interesting because of their
relevance in understanding and modeling the key
processes involved in metal-catalyzed hydrodesulfur-
ization.8
Herein, we report the synthesis and characterization
of some amide complexes of zirconium and their reactiv-
ity toward [Rh(µ-Cl)(COD)]2 as well as the synthesis of
an amide complex of rhodium and its thermolysis
reaction through a sulfur-carbon bond cleavage process.
Resu lts a n d Discu ssion
Syn th esis of th e Zir con iu m Com p lexes. Lithium
amides have been shown to react with early transition
metal chlorides to provide metal amides in high yield.9
This methodology is useful in the synthesis of bis-amide
complexes, such as Cp2Zr(NHR)2 (Cp ) η5-C5H5). In this
way, reaction of Cp2ZrCl2 (1) with 2 equiv of lithium
2-(methylmercapto)phenylamide in THF at room tem-
perature afforded the zirconium bis-amide complex 2
in 76% yield (eq 1).
Cp2ZrCl2 + 2LiNH(C6H4-o-SMe) f
1
Cp2Zr(NHC6H4-o-SMe)2 + 2LiCl (1)
F igu r e 1. ORTEP drawing of complex 2 with the atom-
labeling scheme.
2
The yellow complex 2 is air sensitive, soluble in THF
Ta ble 1. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) (w ith Esd s in P a r en th eses) for 2a
and toluene, and partially soluble in pentane. It has
1
been characterized by H and 13C NMR and IR spec-
Zr(1)-CE(1)
Zr(1)-CE(2)
Zr(1)-N(4)
Zr(1)-N(5)
N(4)-C(1)
2.2338(4)
2.2324(4)
2.122(3)
2.110(4)
1.378(5)
S(2)-C(2)
S(2)-C(7)
S(3)-C(9)
S(3)-C(14)
N(5)-C(8)
1.768(6)
1.807(6)
1.770(5)
1.790(6)
1.399(5)
troscopy (see Experimental Section), and its structure
1
has been determined by X-ray diffraction. The H and
13C NMR spectra show that both amide groups are
equivalent, pointing to the nonexistence, in solution, of
bonding between the sulfur atoms and the zirconium
center. In the same way, both cyclopentadienyl groups
are equivalent.
CE(1)-Zr(1)-CE(2) 128.33(2) N(4)-Zr(1)-N(5)
98.90(14)
Zr(1)-N(5)-C(8) 133.6(3)
Zr(1)-N(4)-C(1)
134.7(3)
a
CE(1) and CE(2) are the centroids of the C15‚‚‚C19 and
C20‚‚‚C24 cyclopentadienyl rings, respectively.
The bonding mode in complex 2 is confirmed by its
structure in the solid state, which has been determined
by X-ray diffraction. X-ray-quality crystals were grown
by slow diffusion of pentane on a THF-saturated solu-
tion. An ORTEP drawing of the structure is shown in
Figure 1. Selected bond distances and angles are given
in Table 1.
Complex 2 exhibits the typical bent metallocene
structure. The cyclopentadienyl rings are bonded to the
zirconium atom in a nearly symmetric η5-fashion. The
Zr(1)-CE(1) and Zr(1)-CE(2) (CE ) ring centroid)
distances of 2.2338(4) and 2.2324(4) Å compare well
with those of other Cp2Zr(IV) complexes.10
133.6(3)°, respectively, and could indicate a π-bonding
contribution between the N and the zirconium atom.
The phenyl groups are pointing away from each other,
and the methylmercapto moieties are oriented in such
a way that steric interactions are reduced to the
minimum. Zr-S distances are very long, and therefore,
existence of a Zr-S bond, in the solid state, can also be
ruled out.
Reaction of Cp2ZrCl2 (1) with 1 equiv of lithium
2-(methylmercapto)phenylamide afforded the mono-
amide complex 3 (eq 2). When the reaction is carried
The zirconium atom is also bonded to both amide
ligands through N(4) and N(5) with bond distances of
2.122(3) and 2.110(4) Å, respectively, which are in the
range expected for Zr(IV) amide complexes.11 Angles
Zr(1)-N(4)-C(1) and Zr(1)-N(5)-C(8) are 134.7(3)° and
Cp2ZrCl2 + Li(NHC6H4-o-SMe) f
1
Cp2ZrCl(NHC6H4-o-SMe) + LiCl (2)
3
(8) (a) Prins, R.; De Beer, V. H. J .; Somorjai, G. A. Catal. Rev.-Sci.
Eng. 1989, 31, 1. (b) Angelici, R. J . Acc. Chem. Res. 1988, 21, 387.
(9) Lappert, M. F.; Power, P. P.; Sanger, A. R.; Srivastava, R. C.
Metal and Metalloid Amides; J ohn Wiley & Sons: New York, 1980.
(10) See, for example: (a) Hunter, W. E.; Hrneir, D. C.; Vann
Bynum, R.; Pentila, R. A.; Atwood, J . L. Organometallics 1983, 2, 750.
(b) J effrey, J .; Lappert, M. F.; Luong-Thi, N. T.; Webb, M.; Atwood, J .
L.; Hunter, W. E. J . Chem. Soc., Dalton Trans. 1981, 1593.
(11) (a) Feldman, J .; Calabrese, J . C. J . Chem. Soc., Chem. Commun.
1991, 135 (b) Walsh, P. J .; Carney, M. J .; Bergman, R. G. J . Am. Chem.
Soc. 1991, 113, 6343. (c) Sun Yeoul, L.; Bergman, R. G. J . Am. Chem.
Soc. 1995, 117, 5877. (d) Lafeber, G.; Arndt, P.; Tillac, A.; Baumann,
W.; Kempe, R.; Burkalov, V. V.; Rosenthal, U. Organometallics 1995,
14, 3090. (e) Linderberg, F.; Hey-Hawkins, E.; Baum, G. 1. Naturfor-
sch., Teil B 1995, 50, 1359.

Amide Complexes of Zr, Rh, and Ir
Organometallics, Vol. 17, No. 8, 1998 1467
Sch em e 1
out by addition of complex 1 to the lithium amide
solution, complex 2 is quantitatively formed instead of
complex 3. To avoid the second chloride substitution,
the reaction has to be carried out by slow addition of
the lithium amide solution to the zirconium complex
solution, and even under these conditions, complex 3 is
always isolated contaminated with ca. 15% of the
disubstituted compound 2. Nevertheless, it was possible
to characterize it spectroscopically.
The bright yellow complex 3 is extremely air sensitive,
soluble in THF and toluene, and partially soluble in
1
pentane. Its H NMR spectrum shows singlets at 1.98,
5.88, and 7.65 (broad signal) ppm, which are assigned
to the methyl group, the cyclopentadienyl rings, and the
proton bonded to the nitrogen atom, respectively. The
high-field shift of the methyl signal suggests that there
is no bond between the sulfur atom and the zirconium
center. Aromatic protons appear as multiplet signals
between 6.81 and 7.49 ppm. The 13C{1H} NMR spec-
trum is consistent with the bonding mode proposed on
F igu r e 2. ORTEP drawing of complex 5 with the atom-
labeling scheme.
to room temperature, amber-colored crystals which were
identified, by an X-ray diffraction study, as a rhodium-
(I) thiolate dimer complex 5 (Scheme 2).
An ORTEP view of the molecule with the atom-
labeling scheme is shown in Figure 2. Table 2 lists the
most significant intramolecular distances and bond
angles with their standard deviations.
1
the basis of the H NMR spectrum.
In an effort to gain deeper insight on the bonding
modes of the 2-(methylmercapto)amide group, the reac-
tion between “Cp*2Zr” (Cp* ) η5-C5Me5) (generated in
situ by reaction of Cp*2ZrCl2 and 2 equiv of LitBu) and
2-(methymercapto)aniline has been carried out and
gives, through an oxidative-addition process, the hy-
dride-amide complex 4.
The crystal structure shows that coordination around
each rhodium atom is approximately square planar. Two
bridging sulfur atoms and a chelating cyclooctadiene are
bonded to each metal atom. The Rh2S2 ring is puckered,
the dihedral angle between the S(2)-Rh(1)-S(21) and
S(2)-Rh(11)-S(21) planes being 145.80(5)°. The amine-
thiolate bridging groups are in a syn configuration with
respect to the four-membered ring Rh2S2 core.
The Rh-S bond lengths (Rh(1)-S(2) ) 2.351(2) Å, Rh-
(1)-S(21) ) 2.362(2) Å) are in the short range of bond
lengths found for binuclear thiolate-bridged complexes;
the longest related bond was reported for [Rh(µ-SC6F5)-
(COD)]2 (average 2.41 Å),13 and the shortest was re-
ported for [Rh(µ-S(CH2)3NMe2)(COD)]2 (average 2.34
Å).14 The Rh-C bond distances fall in the range 2.139-
(9)-2.177(10) Å, which are normal values for Rh(I)
complexes containing COD ligands trans to S donor
atoms.15
Complex 4 was isolated as a pale yellow solid, and it
is air sensitive and very soluble in most organic solvents.
It has been characterized by elemental analysis and IR
1
1
and H and 13C NMR spectroscopic techniques. The H
NMR spectrum shows singlets at 1.83 and 2.31 ppm
which correspond to the Cp* ligand and the methyl
group bonded to the sulfur atom, respectively. The
spectrum also shows two more signals at 3.18 and 4.20
ppm assigned to the NH and hydride groups. Both
signals are in the expected range,12 but it was not
possible to unequivocally assign them. Furthermore,
aromatic protons give rise to multiplet signals between
6.43 and 7.11 ppm. The signal attributed to the methyl
group is located at a relatively low field when compared
with that in other zirconium complexes reported in this
paper. It might be indicative of the existence of an
interaction between the sulfur atom and the zirconium
center in this complex. In the same way, the 13C NMR
spectrum shows that the carbon atoms directly bonded
to the sulfur atom are shifted to lower field than that
in other zirconium complexes.
Complex 5 is air stable and rather insoluble in toluene
or pentane and has been characterized by 1H NMR and
1
IR spectra. The H NMR spectrum of complex 5 shows
signals for the cyclooctadiene ligand at 1.60 and 2.12
(13) Cruz-Garritz, C.; Rodr´ıguez, B.; Torrens, H.; Leal, J . Transition
Met. Chem. 1984, 9, 284.
(14) Polo, A.; Claver, C.; Castillo´n, S.; Ruiz, A. Organometallics 1992,
11, 3525.
(15) (a) Claver, C.; Ruiz, A.; Masdeu, A.; Vin˜as, J .; Saballs, T.; Lahoz,
F.; Plau, F. J . Organomet. Chem. 1989, 373, 269. (b) Pinillos, M. T.;
J arauta, M. P.; Oro, L. A.; Tiripicchio, A.; Tiripicchio-Camellini, M. J .
Organomet. Chem. 1988, 339, 181.
Rea ction of Cp 2Zr (NHC6H4-o-SMe)2 (2) w ith [Rh -
(µ-Cl)(COD)]2. Complex 2 reacts with [Rh(µ-Cl)-
(COD)]2 in toluene, at 100 °C, to give, by slow cooling
(12) Hillhouse, G. L.; Bercaw, J . E. J . Am. Chem. Soc. 1984, 106,
5472.

1468 Organometallics, Vol. 17, No. 8, 1998
Fandos et al.
Sch em e 2
at 4.30 ppm. 13C NMR data are consistent with the
proposed bonding mode.
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) (w ith Esd s in P a r en th eses) for 5
Rh(1)-C(11)
Rh(1)-C(12)
Rh(1)-C(15)
Rh(1)-C(16)
S(2)-C(3)
2.139(9)
2.169(9)
2.134(10)
2.177(10)
1.773(9)
Rh(1)-S(2)
Rh(1)-S(21)
C(8)-N(9)
2.351(2)
2.362(2)
1.384(12)
1.432(14)
According to these results, we can conclude that the
first step of the reaction between complex 2 and [Rh-
(µ-Cl)(COD)]2 is the transfer of the amide ligand from
the zirconium center to the rhodium and of the chloride
from the rhodium to the zirconium atoms to yield
complex 6 and Cp2ZrCl(NHC6H4-o-SMe) (3).
N(9)-C(10)
C(3)-S(2)-Rh(1)
Rh(1) -S(2)- Rh(11)
S(2)-Rh(1)-S(21)
115.0(3)
N(9)-C(8)-C(3)
120.9(9)
95.30(9) C(8)-N(9)-C(10) 122.0(9)
78.69(9)
To verify the next reaction step, a solution of complex
6 in toluene-d8 was heated to 100 °C for 1 h, and at the
same time, in an independent experiment, a 1:2 mixture
of [Rh(µ-Cl)(COD)]2 and Cp2Zr(NHC6H4-o-SMe)2 was
also dissolved in toluene-d8 and heated to the same
temperature. After 2 h, the signals assigned to the
rhodium thiolate complex 5 appear, indicating that the
transformation has taken place in both cases, ap-
proximately in a 43% yield. From these results one can
conclude that the zirconium complexes play no role in
the thermal rearrangement of 6 to give the thiolate
complex 5. Such rearrangement can take place through
an oxidative addition of the S-Me bond at the rhodium-
(I) atom followed by a reductive-elimination step to form
the N-Me bond (Scheme 2). Attempts to isolate or
detect the possible rhodium(III) intermediate complex,
by heating it up at a lower temperature, have been
unsuccessful.
(methylene) and 4.12 ppm (olefinic protons). The thi-
olate moiety exhibits a doublet at 2.80 ppm assigned to
the methyl group, a broad signal at 3.65 ppm due to
the amminic proton, and several multiplet signals
between 6.38 and 7.07 ppm for the aromatic protons.
To establish the mechanism of the unexpected reac-
tion, we carried out the experiment in an NMR tube
with toluene-d8 as the solvent. After 30 min at room
temperature, the 1H NMR spectrum shows that the
starting compounds [Rh(µ-Cl)(COD)]2 and the zirconium
complex 2 react in a practically quantitative way to form
Cp2ZrCl(NHC6H4-o-SMe) (3) and a new rhodium com-
plex that was identified as [Rh(NHC6H4-o-SMe)(COD)]
(6) on the basis of their spectroscopic data (see below).
To confirm the formation of the rhodium amide
complex 6, its synthesis was alternatively carried out
by reacting [Rh(µ-Cl)(COD)]2 with Li(NHC6H4-o-SMe),
prepared in situ (Scheme 2).
Complex 6 was isolated as a green compound that is
air stable in the solid state, and it has been character-
ized by elemental analysis and 1H and 13C NMR and
IR spectroscopies. It is rather soluble in THF and
toluene, only sparsely soluble in pentane. 1H NMR
shows that the olefinic protons of the COD group give
rise to two different multiplet signals at 3.72 and 4.49
ppm, indicating different groups in a trans position,
suggesting coordination of the sulfur atom as drawn in
Scheme 2. The methylene groups appear at 1.85 and
2.23 ppm as complex signals. The singlet at 1.95 ppm
can be assigned to the methyl group bonded to the sulfur
atom, and the aromatic protons appear as multiplet
signals between 6.38 and 7.07 ppm. Finally, the proton
bonded to the nitrogen atom gives rise to a broad signal
Rea ction of [Ir (µ-Cl)(COD)]2 w ith Li(NHC6H4-o-
SMe). Considering the evolution of complex 6 to a
thiolate compound, which involves a sulfur-carbon bond
breaking, we decided to further explore the reactivity
of the 2-(methylmercapto)phenylamide ligand with an
iridium center, which could stabilize higher oxidation
states better than rhodium.
In this context, we carried out the reaction between
[Ir(µ-Cl)(COD)]2 and Li(NHC6H4-o-SMe), prepared in
situ in THF at room temperature (Scheme 2), which
renders complex 7 as a purple crystalline solid. This
compound was shown to be the most stable one under
these conditions. It can be described as Ir(Me)(SC6H4-
o-NH)(COD), as a result of the proposed oxidative
addition on the initially formed Ir(NHC6H4-o-SMe)-
(COD) complex.

Amide Complexes of Zr, Rh, and Ir
Organometallics, Vol. 17, No. 8, 1998 1469
LiMe in diethyl ether, RhCl3‚nH2O, Cp2ZrCl2, LitBu, and Lin-
Bu were used as received from Aldrich.
1H and 13C NMR measurements were obtained on either a
200 Gemini or 300 Unity Varian Fourier transform spectrom-
eter. Trace amounts of protonated solvents were used as
references, and chemical shifts are reported in units of parts
per million relative to SiMe4.
Complex 7 is very soluble in THF or toluene and
partially soluble in pentane. It has been characterized
1
1
by IR and H and 13C NMR spectroscopies. Its H NMR
spectrum shows a singlet signal at 1.09 ppm which is
assigned to methyl group, and the 13C NMR spectrum
shows the resonance of the carbon atom of the methyl
group at 54.1 ppm.16 Both values indicate that the
methyl group is no longer bonded to the sulfur atom but
to the iridium center, and therefore, an oxidative
addition of the S-Me bond has taken place. Besides,
both the 1H and 13C NMR spectra indicate that the
environment of the COD group is asymmetric, giving
place to four different signals for the olefinic protons
as well as for the olefinic carbon atoms.
Syn th esis of Cp 2Zr (NHC6H4-o-SMe)2 (2). To a solution
of 2-(methylmercapto)aniline (0.5 mL, 3.9 mmol) in 5 mL of
Et2O, 2.5 mL of LinBu (1.6 M) was added. The reaction
mixture was allowed to react at room temperature for 30 min
and then cooled at -78 °C, and 0.58 g (2.0 mmol) of Cp2ZrCl2
was added. Subsequently, the cooling bath was removed and
the mixture was stirred at room temperature for 1 h. After
this time, the solvent was removed under vacuum and the
residue extracted with 2 × 20 mL of toluene at 80 °C. The
filtrate was pumped dry and washed with 2 × 10 mL of
pentane to yield 0.75 g (76%) of 2. IR (Nujol/PET) polyeth-
ylene, cm-1): 3618 (w), 3302 (m), 1611 (m), 1587 (m), 1564
(m), 1288 (s), 1262 (s), 1018 (m), 854 (w), 827 (s), 808 (s), 768
(m). 1H NMR (C6D6): δ 2.07 (s, 6 H, CH3), 3.70 (br, 2 H, N-H),
5.82 (s, 10 H, Cp), 6.64, 7.36 (m, 8 H, C6H4). 13C{1H} NMR
(C6D6): δ 16.7 (s, CH3), 110.8 (s, Cp), 119.0, 120.4, 128.5, 130.5
(s, CH), 122.9 (s, C-N), 155.9 (s, C-S). Anal. Calcd for
On the basis of these results with the iridium com-
plex, we can establish that in the reaction of 2 and [Rh-
(µ-Cl)(COD)]2, the formation of 5 can take place by a
reductive elimination in the undetected Rh(Me)(SC6H4-
o-NH)(COD).
Con clu d in g Rem a r k s
In this paper we have reported the synthesis of some
zirconium amide complexes, accessible by halide dis-
placement or by N-H oxidative addition of 2-(meth-
ylmercapto)aniline to “Cp*2Zr”. We have studied the
reaction of Cp2Zr(NHC6H4-o-SMe)2 with [Rh(µ-Cl)-
(COD)]2, which occurs with transfer of the amide ligand
from the zirconium to the rhodium atom to form an
rhodium amide complex Rh(NHC6H4-o-SMe)(COD) while
the chloride ligand is transferred to the zirconium
yielding complex 3. This reactivity is particularly
intriguing because bonds between hard ligands and soft
late transition metals are unfavorable. That is why
there are not many amide complexes of low oxidation
state metals known and bidentate phosphine-amide
ligands have been used to prepare amide complexes of
these metals. In our case, coordination of the soft base
(S) to rhodium or iridium may assist the concomitant
coordination of the amide group, hard base, forming a
five-membered ring, stabilizing complex 6. When the
rhodium amide thioether complex 6 is heated to 100 °C,
conversion to the bridged thiolate complex, 5, takes
place. However, it was not possible to detect the
postulated Rh(III) intermediate compound, whereas for
iridium, this is the most stable compound. Oxidative
addition of the S-Me bond can possibly take place,
rendering the alkyl-amide-thiolate Ir(III) complex.
The bond between the amide group and iridium in the
3+ oxidation state could account for a N(pπ)-Ir(dπ)
interaction, making complex 7 the most stable one.
C
24H26N2S2Zr: C, 57.90; H, 5.26; N, 5.63. Found: C, 57.60;
H, 5.30; N, 5.60.
Syn th esis of Cp 2Zr Cl(NHC6H4-o-SMe) (3). A solution of
Li(NHC6H4-o-SMe), prepared in situ by reaction of 2-(meth-
ylmercapto)aniline (0.2 mL, 1.6 mmol) with LinBu (1 mL, 1.6
mmol) in 5 mL of Et2O, was slowly added to a suspension of
Cp2ZrCl2 (0.47 g, 1.6 mmol) in Et2O at 0 °C. Then the mixture
was stirred at room temperature for 1 h, and the solvents were
removed under vacuum. The residue was extracted with
toluene (2 × 10 mL), and after filtration, the toluene was
evaporated and the yellow solid was washed with pentane and
dried under vacuum to give 0.34 g (54%) of product 3. 1H NMR
(C6D6): δ 1.98 (s, 3 H, CH3), 5.88 (s, 10 H, Cp), 6.81-7.49 (m,
4 H, CH), 7.65 (br, 1H, NH). 13C{1H} NMR (C6D6): δ 15.9 (s,
CH3), 112.6 (s, Cp), 121.4, 123.4, 127.4, 127.7 (s, CH), 125.5
(s, C-N), 155.0 (s, C-S).
Syn th esis of Cp *2Zr H(NHC6H4-o-SMe) (4). A suspension
of Cp*2ZrCl2 (0.97 g, 2.2 mmol) in 5 mL of THF was treated
with 2.6 mL (4.5 mmol) of LitBu (1.7 M in hexane), and the
mixture was stirred at room temperature for 30 min. After
this time, it was cooled to -78 °C and 0.28 mL (2.2 mmol) of
2-(methylmercapto)aniline was added, the cooling bath re-
moved, and the mixture stirred at room temperature for 1 h.
The solvents were evaporated under vacuum, the residue was
extracted with pentane (2 × 10 mL), and the solution was
evaporated to ca. 1 mL and cooled at -30 °C for 24 h, yielding
0.77 g (69%) of 4. IR (Nujol/PET, cm-1): 3717 (w), 3684 (m),
3486 (w), 3361 (w), 3289 (w), 1611 (s), 1584 (s), 1565 (m), 1308
(s), 1255 (s), 1031 (m), 854 (s), 518 (s). 1H NMR (C6D6): δ
1.83 (s, 30 H, Cp*), 2.31 (s, 3 H, CH3), 3.18, 4.20 (br, 1 H, N-H,
Zr-H), 6.43, 7.11 (m, 4 H, CH). 13C{1H} NMR (C6D6): δ 11.5
(s, Cp*), 11.9 (s, CH3), 115.3 (s, Cp*), 111.8, 115.8, 127.6, 128.7
(s, CH), 129.2 (s, C-N), 159.5 (s, C-S). Anal. Calcd for
Exp er im en ta l Section
C
27H38NSZr: C, 64.74; H, 7.85; N, 2.79. Found: C, 64.25; H,
7.80; N, 2.75.
Gen er a l P r oced u r es. All reactions and product manipu-
lations were carried out under dry nitrogen using standard
Schlenk and drybox techniques. Toluene was distilled from
sodium, pentane from sodium/potassium alloy, and diethyl
ether and THF from sodium benzophenone, under nitrogen.
All solvents were deoxygenated prior to use.
The following reagents were prepared by literature
procedures: Cp*H,17 Cp*2ZrCl2,18 and [Rh(µ-Cl)(COD)]2.19 The
commercially available compounds 2-(methylmercapto)aniline,
Syn th esis of [Rh (µ-SC6H4-o-NHMe)(COD)]2 (5). To a
mixture of [Rh(µ-Cl)(COD)]2 (0.095 g, 0.19 mmol) and Cp2Zr-
(NHC6H4-o-SMe)2 (0.19 g, 0.38 mmol), 3 mL of toluene was
added and the solution was heated under reflux for 24 h. After
this time, the solution was allowed to reach room temperature
slowly, yielding crystals of 5 (83 mg, 62%). IR (Nujol/PET,
cm-1): 3387 (w), 3242 (m), 1573 (s), 1451 (m), 1298 (m), 1274
(m), 859 (m), 443 (m). 1H NMR (C6D6): δ 1.60 (m, 8 H, COD),
3
2.12 (m, 8 H, COD), 2.80 (d, J H-H ) 5.1 Hz, 6 H, CH3), 3.65
(br, 2 H, NH), 4.12 (m, 8 H, COD), 6.38-7.07 (m, 8 H, CH).
Anal. Calcd for C30H32N2S2Rh2: C, 51.58; H, 5.77; N, 4.0.
Found: C, 51.75; H, 5.84; N, 3.72.
(16) Fryzuk, M. D.; J oshi, K. Organometallics 1989, 8, 722.
(17) Burger, U.; Dealy, A.; Maznot, F. Helv. Chim. Acta 1974, 57,
2106.

1470 Organometallics, Vol. 17, No. 8, 1998
Fandos et al.
Ta ble 3. Exp er im en ta l Da ta for th e X-r a y
Syn th esis of Rh (NH-C6H4-o-SMe)(COD) (6). To a solu-
tion of 2-(methylmercapto)aniline (40 µL, 0.32 mmol) in 5 mL
of Et2O, 0.2 mL (0.32 mmol) of LinBu (1.6 M in hexane) was
added and the mixture was stirred for 30 min. After this time,
the solution was cooled to -78 °C and 0.079 g (0.16 mmol) of
[Rh(µ-Cl)(COD)]2 was added. The cooling bath was then
removed, and the solution was stirred at room temperature
for 30 min. The solvents were evaporated under vacuum, and
the residue was extracted with 5 mL of toluene. After
filtration, the solvent was removed under vacuum and the
residue washed with 2 mL of pentane to yield 0.08 g (71%) of
complex 6. IR (Nujol/PET, cm-1): 3611 (w), 3335 (w), 1597
(m), 1354 (m), 1328 (m), 1308 (m), 860 (m), 466 (m). 1H NMR
(C6D6): δ 1.85 (m, 4 H, COD), 1.95 (s, 3 H, CH3), 2.23 (m, 4 H,
COD), 3.72 (m, 2 H, COD), 4.30 (br, 1 H, N-H), 4.49 (m, 2 H,
COD), 6.38-6.07 (m, 4 H). 13C{1H} NMR (C6D6): 23.8 (s, CH3),
Diffr a ction Stu d ies
5
2
mol formula
mol wt
C
30H40N2S2Rh2
C24H26N2S2Zr
497.81
698.58
cryst syst
space group
radiation (Mo KR)
a, Å
monoclinic
I2/a
orthorrombic
P212121
λ ) 0.710 70 Å
11.265(2)
13.016(3)
19.823(6)
105.15(2)
2805.5(12)
4
8.2307(8)
14.7894(9)
18.684(2)
b, Å
c, Å
â, deg
V, Å3
2274.3(4)
4
6.80
Z
µ cm-1
13.48
1.654
D
calcd, g cm-3
1.454
F(000)
1424
1024
1
30.4, 32.0 (s, COD), 71.9 (d, J Rh-C ) 11.1 Hz, COD), 84.8 (d,
cryst dimens, mm
θ range, deg
index ranges
0.15 × 0.20 × 0.40
2.13-25.02
0 e h e 13,
0 < k e 15,
-23 e l e 22
2469
0.53 × 0.25 × 0.16
2.18-25.03
0 e h e 9,
0 < k e 17,
0 e l e 22
2294
1J Rh-C ) 12.1 Hz, COD), 117.5 (s, C-N), 112.7, 115.9, 130.5,
131.6 (s, CH), 165.0 (s, C-S). Anal. Calcd for C15H16NSRh:
C, 51.58; H, 5.77; N, 4.00. Found: C, 51.71; H, 5.43; N, 3.90.
Syn th esis of Ir (Me)(SC6H4-o-NH)(COD) (7). To a solu-
tion of 2-(methylmercapto)aniline (47 µL, 0.38 mmol) in 5 mL
of THF was added 0.23 mL (0.37 mmol) of LinBu (1.6 M in
hexanes), and the mixture was stirred at room temperature
for 30 min. After this time, the solution was cooled to -78
°C, and 0.125 g (0.19 mmol) of [Ir(µ-Cl)(COD)]2 was added. The
cooling bath was then removed, and the solution was stirred
at room temperature for another 30 min. Solvents were
evaporated under vacuum, and the residue was extracted with
5 mL of toluene. After filtration, the solvent was partially
evaporated and could be isolated by slow diffusion pentane,
0.130 g (79%) of complex 7, as purple crystals. IR (Nujol/PET,
cm-1): 3304 (m), 1573 (m), 1302 (m), 897 (m), 764 (s), 762 (s),
460 (m).1H NMR (C6D6): δ 1.09 (s, 3H, Ir-Me), 1.65-2.26 (m,
8H, CH2), 3.75 (m, 1H, dCH), 3.89 (m, 1H, dCH), 4.73 (m,
1H, dCH), 5.51 (m, 1H, dCH), 6.95 (m, 1H, Ph), 7.05 (m, 1H,
Ph), 7.15 (m, 1H, Ph), 8.05 (m, 1H, Ph), 8.69 (br, 1H, NH).
13C{1H} NMR (C6D6): 24.7 (s, CH2), 30.4 (s, CH2), 31.2 (s, CH2),
32.6 (s, CH2), 54.1 (s, Me), 69.1 (s, dCH), 72.8 (s, dCH), 78.9
(s, dCH), 84.1 (s, dCH), 117.9, 118.5, 124.6, 132.6 (s, CH),
143.5 (s, N-C), 163.0 (s, S-C). Anal. Calcd for C15H16NSIr:
C, 41.07; H, 4.59; N, 3.19. Found: C, 40.98; H, 4.57; N, 3.16.
X-r a y Cr ysta llogr a p h ic An a lysis for 2 a n d 5. Crystal-
lographic data are summarized in Table 3. Diffraction data
were obtained at 298 K on a Enraf-Nonius CAD-4 diffracto-
meter with graphite-monochromated Mo KR radiation using
a ω/2θ scan technique. Cell parameters were determined by
a least-squares fit on 25 reflections. Data were corrected for
Lorentz and polarization effects, and a semiempirical absorp-
tion correction was carried out on the basis of an azimuthal
scan.20 For complex 5, the asymmetric unit comprised one
independent half molecule. The structures were solved by
direct methods, SIR92.21 Refinement was carried out by full-
total no. of
unique data
goodness of fit
1.145
0.0644, 0.1354
0.764 and -0.738
0.727
0.0228, 0.0572
0.203 and -0.281
b
R,a Rw
largest diff peak
and hole, e Å-3
matrix least-squares techniques SHELXL-93.22 All non-
hydrogen atoms were refined with anisotropic thermal pa-
rameters. The hydrogen atoms were included in calculated
positions, except the NH hydrogen for complex 5 which was
located in a difference map and refined freely. Weights were
optimized in the final refinement cycles. Other detailed data
are supplied in the Supporting Information.
Ack n ow led gm en t. R.F., M.J .R., and A.O. gratefully
acknowledge financial support from the Direccio´n Gen-
eral de Ensen˜anza Superior (DGES) (Grant No. PB95-
0023-CO1) of Spain, and P. T. acknowledges support for
EU (Program ALAMED; Project No. CI1*-CT93-0329).
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal-
lographic details, atomic coordinates, bond lengths and angles,
and anisotropic and isotropic displacement parameters for 2
and 5 (13 pages). Ordering information is given on any current
masthead page.
OM9709805
(19) Chatt, J .; Venanzi, L. M. J . Chem. Soc. 1957, 4735.
(20) North, A. C. T.; Phillips, D. C.; Mathews, F. S. Acta Crystallogr.
1968, A24, 351.
(21) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A.;
Burla, M. C.; Polidori, G.; Camalli, M. J . Appl. Crystallogr. 1994, 435.
(22) Sheldrick, G. M. Program for Refinement of Crystal Structures
from Diffraction Data; University of Go¨ttingen: Go¨ttingen, Germany,
1993.
(18) Manriquez, J . M.; McAlister, D. R.; Rosenberg, E.; Shiller, A.
M.; Williamson, K. L.; Chan, S. I.; Bercaw, J . E. J . Am. Chem. Soc.
1978, 100, 3078.