Zirconium alkyl thiolate complexes:Synthesis and reactivity.Molecular structures of[Zr(η5-C5H5)2(η 2-C6H7N2S)(Me)]and[Zr(η5- C5H5)2(η1-C6H7N 2S)

Article abstract of DOI:10.1021/om960396g

The thiolate-alkylzirconocene complex Cp₂ZrMe(SR) (2) (Cp = η⁵-C₅H₅; SR = 4,6-dimethylpyrimidine-2-thiolate) can be prepared by reacting the corresponding dialkylmetallocene complex Cp₂ZrMe₂ (1) with 1 equiv of 4,6-dimethyl-2-mercaptopyrimidine. X-ray structure analysis of complex 2 revealed that the thiolate group is bonded in an η2 fashion through the sulfur and one of the nitrogen atoms. Complex 2 reacts with 2,6-dimethylphenyl isocyanide (CNXylyl) to yield the corresponding iminoacyl derivative, Cp₂Zr(η²-MeCNXylyl)-(SR) (4). The molecular structure of 4 shows that the thiolate group is η1-bonded while the iminoacyl group behaves as a bidentate ligand. Reaction of compound 2 with different acidic reagents gives formation of methane and different zirconium complexes. Reaction with HSR renders Cp₂Zr(SR)₂ (3) and with (NHEt₃)(BPh₄) the cationic complex [Cp₂Zr(SR)][BPh₄] (5). An hydride thiolate complex, Cp*₂ZrH(SR) (Cp* = η⁵-C₅Me₅) (6) can also be prepared by reaction of Cp*₂Zr with HSR by an oxidative addition reaction.

Full text of DOI:10.1021/om960396g

Organometallics 1996, 15, 4725-4730
4725
Zir con iu m Alk yl Th iola te Com p lexes: Syn th esis a n d
Rea ctivity. Molecu la r Str u ctu r es of
[Zr (η5-C5H5)2(η2-C6H7N2S)(Me)] a n d
[Zr (η5-C5H5)2(η1-C6H7N2S)(η2-CH3CNXylyl)] (Xylyl )
2,6-Dim eth ylp h en yl)
Rosa Fandos,*,† Maurizio Lanfranchi,‡ Antonio Otero,*,§
Maria Angela Pellinghelli,‡ Mar´ıa J ose´ Ruiz,† 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,
and Campus de Ciudad Real, 13071 Ciudad Real, Spain, Dipartimento di Chimica
Generale ed Inorganica, Chimica Analitica, Chimica Fisica, Universita´ degli Studi di Parma,
Centro di Studio per la Structturistica Diffractometrica del CNR, Vialle delle Scienze 78,
I-43100 Parma, Italy, and Instituto de Cata´lisis y Petroleoqu´ımica, CSIC,
Cantoblanco, 28049 Madrid, Spain
Received May 22, 1996X
The thiolate-alkylzirconocene complex Cp2ZrMe(SR) (2) (Cp ) η5-C5H5; SR ) 4,6-
dimethylpyrimidine-2-thiolate) can be prepared by reacting the corresponding dialkylmet-
allocene complex Cp2ZrMe2 (1) with 1 equiv of 4,6-dimethyl-2-mercaptopyrimidine. X-ray
structure analysis of complex 2 revealed that the thiolate group is bonded in an η2 fashion
through the sulfur and one of the nitrogen atoms. Complex 2 reacts with 2,6-dimethylphenyl
isocyanide (CNXylyl) to yield the corresponding iminoacyl derivative, Cp2Zr(η2-MeCNXylyl)-
(SR) (4). The molecular structure of 4 shows that the thiolate group is η1-bonded while the
iminoacyl group behaves as a bidentate ligand. Reaction of compound 2 with different acidic
reagents gives formation of methane and different zirconium complexes. Reaction with HSR
renders Cp2Zr(SR)2 (3) and with (NHEt3)(BPh4) the cationic complex [Cp2Zr(SR)][BPh4] (5).
An hydride thiolate complex, Cp*2ZrH(SR) (Cp* ) η5-C5Me5) (6) can also be prepared by
reaction of “Cp*2Zr” with HSR by an oxidative addition reaction.
In tr od u ction
widespread use of sulfur-containing complexes as syn-
thons for multinuclear transition metal complexes and
so a number of zirconocene thiolate complexes have been
prepared.4
Moreover, thiolate complexes are the focus of much
attention due to their relevance to the structure, bond-
ing, and function of biologically active reaction centers
such as nitrogenase or metallothioneins.5 In the last
aspect, thiolate ligands containing nitrogen atoms are
specially interesting.6
In the last few years there has been a growing interest
in transition metal thiolate complexes due to the
important role that such compounds are believed to play
as intermediates in different reactions such as desulfu-
rization of organosulfur compounds1-2 and metal-
catalyzed synthetic reactions involving C-S bond cleav-
age and formation.3 On the other hand, the propensity
of sulfur to form M(µ-SR)M′ bridges has led to the
From recent literature it appears that the number of
studies concerning the interaction modes and reactivity
of transition metal complexes containing pyridinethi-
olate and pyrimidinethiolate ligands is growing rapidly.7
Such ligands are especially interesting because (i) they
contain functional groups common in crude oils (thi-
olate-S and aromatic-N), (ii) the pyrimidine group is a
constituent of nucleic acids, and (iii) they have the
ability to chelate and bridge transition metals, allowing
access to both mononuclear and oligonuclear products.
We herein report the synthesis and reactivity of the
first examples of pyrimidinethiolate-containing zir-
conocene complexes as well as the X-ray crystal struc-
ture characterization of two of them.
† Campus de Toledo, Universidad de Castilla-La Mancha.
‡ Universita´ degli Studi di Parma.
§ Campus de Ciudad Real, Universidad de Castilla-La Mancha.
| Instituto de Cata´lisis y Petroleoqu´ımica.
X Abstract published in Advance ACS Abstracts, September 15, 1996.
(1) (a) Massoth, F. E. Adv. Catal. 1978, 27, 265. (b) Orr, W. L. Oil
Sand and Oil Shale Chemistry; Verlag Chemie: Weinheim, 1978; p
223. (c) Cyr, T. D.; Payzant, J . D.; Montgomery, D. S.; Srausz, O. P.
Org. Geochem. 1986, 9, 139. (d) Nishikota, M. Energy Fuels 1988, 2,
214.
(2) (a) Sa´nchez-Delgado, R. A. J . Mol. Catal. 1994, 86, 287. (b)
Kwart, H.; Schuit, G. C. A.; Gates, B. C. J . Catal. 1980, 61, 128. (c)
Zaera, F.; Kollin, E. B.; Gland, J . L. Surf. Sci. 1987, 184, 75. (d) Eisch,
J . J .; Hallenbeck, L. E.; Han, K. L. J . Org. Chem. 1983, 48, 2963. (e)
Antebi, S.; Alper, H. Organometallics 1986, 5, 596. (f) Angelici, R. J .
Acc. Chem. Res. 1988, 21, 387. (g) Angelici, R. J . Coord. Chem. Rev.
1990, 105, 61. (h) Chen. J .; Angelici, R. J . Organometallics 1992, 11,
992. (i) Rauchfuss, T. B. Prog. Inorg. Chem. 1991, 39, 259.
(3) (a) Okamura, H.; Miura, M.; Takei, H. Tetrahedron Lett. 1979,
43. (b) Okamura, H.; Takei, H. Tetrahedron Lett. 1979, 3425. (c)
Murahashi, S.; Yamamura, M.; Yanagisawa, K.; Mita, N.; Kondo, K.
J . Org. Chem. 1979, 44, 2408. (d) Kosugi, M.; Shimizu, T.; Migita, T.
Chem. Lett. 1978, 13. (e) Hutchins, R. O.; Learn, K. J . Org. Chem.
1982, 48, 4380. (f) Wenkert, E.; Hanna, J . M., J r.; Leftin, M. H.;
Michelotti, E. L.; Potts, K. T.; Usifer, D. J . Org. Chem. 1985, 50, 1125.
(g) Tiecco, M.; Testaferri, L.; Tingoli, M.; Chianelli, P.; Wenkert, E.
Tetrahedron Lett. 1982, 23, 4629. (h) Osakada, K.; Yamamoto, T.;
Yamamoto, A. Tetrahedron Lett. 1987, 27, 6321.
(4) Sthephan, D. W.; Nadasdi, T. T. Coord. Chem. Rev. 1996, 147,
147.
(5) (a) Dilworth, J . R.; Hu, J . Adv. Inorg. Chem. 1993, 40, 411 and
references therein.
(6) Sellmann, D.; Ruf, R.; Knoch, F.; Moll, M. Inorg. Chem. 1995,
34, 3745 and references therein.
(7) Reynolds, J . G.; Sendlinger, S. C.; Murray, A. M.; Huffman, J .
C.; Christou, G. Inorg. Chem. 1995, 34, 5745 and references therein.
S0276-7333(96)00396-2 CCC: $12.00 © 1996 American Chemical Society

4726 Organometallics, Vol. 15, No. 22, 1996
Fandos et al.
Sch em e 1
F igu r e 1. An ORTEP drawing of complex 2 with the
atomic labeling scheme (30% probability ellipsoids).
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
Resu lts a n d Discu ssion
Zr-CE(1)
Zr-CE(2)
Zr-S
2.241(4) N(1)-C(4)
2.229(5) N(2)-C(1)
2.629(1) N(2)-C(2)
2.440(2) C(2)-C(3)
2.359(4) C(3)-C(4)
1.723(3) C(2)-C(5)
1.358(4) C(4)-C(6)
1.355(4)
1.329(4)
1.343(4)
1.379(5)
1.377(4)
1.500(5)
1.504(4)
Early transition metal alkyl complexes react with
acidic reactives such as alcohols or mercaptans to the
corresponding alkane and the alkoxide or thiolate
complexes, respectively. A likely mechanism of the
protonolysis of carbon-zirconium bonds requires initial
donation of an oxygen or sulfur lone pair to the metal
center.8 This methodology is useful in the synthesis of
alkyl thiolate zirconocene complexes. 4,6-Dimethyl-2-
mercaptopyrimidine reacts with Cp2ZrMe2 (1) in 1:1
ratio according to Scheme 1.
Synthesis of Cp2ZrMe(SR) (2) was carried out with
pentane used as the solvent. Complex 2 is prepared in
high yield (92%) as a white precipitate in the reaction
solvent from which it is separated by filtration. Com-
plex 2 is air sensitive, insoluble in alkanes, sparsely
soluble in toluene and benzene, and partially soluble
in THF and acetonitrile. At room temperature, and over
a period of 48 h, complex 2 does not react with an excess
of mercaptan.
Zr-N(1)
Zr-C(7)
S-C(1
N(1)-C(1)
CE(1)-Zr-CE(2) 130.0(2)
C(1)-N(1)-C(4) 117.3(2)
CE(1)-Zr-S
CE(1)-Zr-N(1)
CE(1)-Zr-C(7)
CE(2)-Zr-S
CE(2)-Zr-N(1)
CE(2)-Zr-C(7)
S-Zr-N(1)
114.4(1)
99.0(1)
99.1(1)
115.5(1)
102.5(1)
98.5(2)
60.5(1)
72.2(1)
132.6(1)
85.5(1)
101.9(2)
140.4(2)
S-C(1)-N(1)
S-C(1)-N(2)
111.7(2)
122.4(2)
N(1)-C(1)-N(2) 125.9(3)
C(1)-N(2)-C(2) 116.5(3)
N(2)-C(2)-C(3) 121.2(3)
N(2)-C(2)-C(5) 116.4(3)
C(3)-C(2)-C(5)
C(2)-C(3)-C(4)
122.3(3)
119.9(3)
S-Zr-C(7)
N(1)-Zr-C(7)
Zr-S-C(1)
N(1)-C(4)-C(3) 119.3(3)
N(1)-C(4)-C(6) 119.2(3)
Zr-N(1)-C(1)
Zr-N(1)-C(4)
C(3)-C(4)-C(6)
121.5(3)
a
CE(1) and CE(2) are the centroids of the C(8)‚‚‚C(12) and
C(13)‚‚‚C(17) cyclopentadienyl rings, respectively.
The lack of reactivity of the remaining alkyl group
indicates that the coordination of the sulfur atom from
a second mercaptan molecule is prevented by coordina-
tion of the nitrogen atom of the pyrimidine group. This
expectation is confirmed by the structure of complex 2,
which has been determined by X-ray diffraction. X-ray-
quality crystals were prepared by slow diffusion of
pentane on a THF-saturated solution. An ORTEP
drawing of the structure of complex 2 is shown in Figure
1. Selected bond distances and angles are given in
Table 1 and atomic coordinates for all non-hydrogen
atoms appear in Table 2.
Complex 2 exhibits the typical bent metallocene struc-
ture. The cyclopentadienyl rings are bonded to the
zirconium atom in a nearly symmetric η5-fashion. The
Zr-CE1 and Zr-CE2 (CE ) ring centroid) distances of
2.241(4) and 2.229(5) Å compare well with those of other
Cp2Zr(IV) reported complexes.9
knowledge this complex, together with complex 4 (see
below), represents the first structurally characterized
pyrimidine-2-thiolate zirconium complex. The Zr, C(7),
S, and N(1) atoms are practically coplanar (max dev
0.033(4) Å for C(7)) and lie roughly in the equatorial
plane which bisects the dihedral angle formed by the
cyclopentadienyl rings. The 4,6-dimethylpyrimidine-2-
thiolate ligand chelates ligand through the N(1) and S
atoms. The four-membered ZrSC(1)N(1) ring is not
strictly planar and the dihedral angle between the
ZrSN(1) and SC(1)N(1) planes is 172.9(2)°.
The bonding of the bidentate thiolate to the metal
center can be considered as an intermediate between
the two possible bonding situations represented in
Scheme 2.10 In agreement with this proposal is that
the C(1)-S bond (1.723(3) Å) is slightly shorter than
the one observed in complex 4 (1.752(4) Å) where the
thiolate ligand is mononodentate. The value falls into
the range 1.696-1.761 Å observed in pyrimidine-2-
thiolate transition metal complexes.11
The zirconium atom is also bonded to the bidentate
4,6-dimethylpyrimidine-2-thiolate-N,S ligand and to the
carbon atom of the methyl group. To the best of our
The Zr-S bond distance (2.629(1) Å) falls into the
range 2.561-2.660 Å found in zirconocene complexes
(8) Cardin, D. J .; Lappert, M. F.; Raston, C. L. Chemistry of Organo-
Zirconium and Hafmium Compounds; Ellis Harwood Limited, Halsted
Press: New York, 1986.
(9) (a) Hunter, W. E.; Hrncir, D. C.; Vann Bynum, R.; Penttila, 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.
(10) Ciriano, M. A.; Lanfranchi, M.; Oro, L. A.; Pe´rez-Torrente, J .
J .; Tiripicchio, A.; Tiripicchio Camellini, M. J . Organomet. Chem. 1994,
469, C31.
(11) Baker, P. K.; Harman, M. E.; Hughes, S.; Hursthouse, M. B.;
Abdulmalik, K. M. J . Organomet. Chem. 1995, 498, 257.

Zirconium Alkyl Thiolate Complexes
Organometallics, Vol. 15, No. 22, 1996 4727
Sch em e 2
Sch em e 4
Sch em e 3
with N and S atoms coordinated to the metal. In Cp2-
ZrCl[SC(H)NC6H5],12 which is the only X-ray structur-
ally characterized zirconium complex containing similar
four-membered N,S chelation, the Zr-S (2.659(4) Å)
bond distance is larger than in complex 2. On the other
hand, the Zr-N bond length (2.408(9) Å) is shorter than
in complex 2 (2.440(4) Å).
Methyl groups appear as three singlets at 2.04 (3H),
1.96 (3H), and 1.78 (6H) ppm, indicating that while one
thiolate acts as a bidentate ligand the other is bonded
to the zirconium atom only by the sulfur atom.
The Zr-C7 distance (2.359(4) Å) is longer than the
one observed in Cp2ZrMe2 (2.273 Å)9a but is within the
range expected for 18 e- zirconium complexes.13
Compound 2 reacts readily in THF, at room temper-
ature, with 2,6-dimethylphenyl isocyanide in 1:1 ratio
to give the corresponding η2-iminoacyl complex 4 (Scheme
4) in 82% yield, which was isolated as the hemi-THF
adduct. It is air sensitive, moderately soluble in THF,
less soluble in toluene and other aromatic solvents, and
practically insoluble in pentane.
1
The room temperature H NMR spectrum of complex
2 (toluene-d8) shows a broad resonance at 1.85 ppm that
integrates to six protons and which is assigned to the
methyl groups attached to the phenyl ring in the
thiolate ligand. The width of the peak indicates flux-
ional behavior through which both nitrogen atoms
interchange their positions in the coordination sphere
of the zirconium atom (see Scheme 3). Variable-tem-
All spectroscopic data point to an η2-coordination of
the iminoacyl group while the thiolate acts as a mono-
dentate ligand. This is in agreement with the expecta-
tion based on the literature precedents in which early
transition metal iminoacyl complexes are described to
be normally stabilized by coordination of the nitrogen
atom to the metal center on a η2-coordination mode.14
Accordingly, the IR spectrum shows several absorptions
in the region near to 1500 cm-1 and one of them may
be assigned to the ν(CdN), and the iminoacyl carbon
appears at 241.8 ppm in the 13C{1H} NMR spectrum.15
On the other hand, the 1H NMR spectrum shows that
the two methyl groups in the pyrimidine moiety are
equivalent as they appear as a singlet at 1.92 ppm
which means free rotation around the C-S bond. In the
same way, rotation of the xylyl group is fast on the NMR
time scale and the two methyl groups are equivalent
giving a singlet at 2.17 ppm.
1
perature H NMR spectroscopy showed that at -40 °C
methyl groups are unequivalent and appear as two
singlets at 1.99 and 1.54 ppm. The peaks coalesce at
14 °C. The two site exchange equations and the
coalescence temperature of 287 K can be used to
estimate a value for ∆G‡ of 13.5 ( 2 kcal mol-1 for the
rotation. That means that although complex 2 in the
solid state is, formally, a 18 e- molecule, in solution,
due to the fluxional interchange, a free coordination
position at the metal atom could be available for some
reactions to take place.
Accordingly, when the reaction of Cp2ZrMe2 with 2
equiv of 4,6-dimethyl-2-mercaptopyrimidine is carried
out at high temperature, in refluxing toluene, it is
possible to synthesize the corresponding bis-thiolate
complex as depicted in eq 1
The structure of complex 4 has been determined by
X-ray diffraction. An ORTEP drawing is shown in
Figure 2. Selected bond distances and angles are given
in Table 3 and the atomic coordinates for all non-
hydrogen atoms appear in Table 4.
Cp2ZrMe2
Cp Zr(SR)
+ 2HSR f
+ 2MeH (1)
2
2
1
3
Like 2, complex 4 exhibits the typical bent metal-
locene structure with the cyclopentadienyl groups η5-
bonded to the Zr atom. The coordination sphere around
the metal is completed by the S atom of the monoden-
tate thiolate ligand and by the N(3) and C(7) atoms of
the η2-iminoacyl. The Zr, C(7), N(3), and S atoms are
practically coplanar and lie in the equatorial plane
which bisects the dihedral angle formed by the cyclo-
pentadienyl rings. The Zr-S bond (2.623(1) Å) is quite
Complex 3 can also be prepared by reaction of 2 with
one more equivalent of mercaptan under the same
experimental conditions. Compound 3 is insoluble in
pentane and scarcely soluble in toluene or THF. It has
been characterized by 1H NMR and IR spectroscopy and
elemental analysis.
1H NMR spectrum, at room temperature, shows
singlets at 6.23 (10H), 5.92 (1H), and 5.54 (1H) ppm
assigned to Cp and the pyrimidine protons, respectively.
(14) Durfee, L. D.; Rothwell, I. P. Chem. Rev. 1988, 88, 1059.
(15) (a) Carmona, E.; Palma, P.; Paneque, M.; Poveda, L. M.
Organometallics 1990, 9, 583. (b) Bochmann, M.; Wilson, L. M.;
Hursthouse, M. B.; Short, R. Organometallics 1987, 6, 2556.
(12) Mei, W.; Shiwei, L.; Meizhi, B.; Hefu, G.; Zhongsheng, J . J .
Organomet. Chem. 1993, 447, 227.
(13) Berg, F. J .; Petersen, J . L. Organometallics 1989, 8, 2461.

4728 Organometallics, Vol. 15, No. 22, 1996
Fandos et al.
Sch em e 5
F igu r e 2. An ORTEP drawing of complex 4 with the
atomic labeling scheme (30% probability ellipsoids).
by treatment of the well-known cationic complex [Cp2-
ZrMe(THF)][BPh4] with HS(t-C4H9). [Cp2Zr(S-t-C4H9)-
(THF)][BPh4] is unstable in THF solution, and the
decomposition occurs through cleavage of the carbon-
sulfur bond and formation of the known sulfide-bridged
dimmer [Cp2ZrS]2. Dissociation of the THF ligand is
proposed to be the step prior to the cleavage.
Ta ble 3. 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 4‚1/2C4H8Oa
Zr-CE(1)
Zr-CE(2)
Zr-S
Zr-N(3)
Zr-C(7)
S-C(1)
N(1)-C(1)
N(1)-C(4)
N(2)-C(1)
2.237(5) N(2)-C(2)
2.244(5) C(2)-C(3)
2.623(1) C(3)-C(4)
2.271(3) C(2)-C(5)
2.206(4) C(4)-C(6)
1.752(4) N(3)-C(7)
1.341(5) N(3)-C(9)
1.342(6) C(7)-C(8)
1.349(5)
1.338(5)
1.380(6)
1.373(7)
1.505(7)
1.504(7)
1.268(5)
1.439(4)
1.489(6)
Complex 5 is stable in THF solution, at room tem-
perature, at least, 24 h. The higher stability of this
complex can be explained, on one the hand, by the
strong coordination of the nitrogen atom which is
enhanced by the chelate effect. On the other hand a
possible contribution of form B to the bond (see Scheme
2) strengthens the C-S bond, preventing its cleavage.
1H NMR spectrum of 5 shows two singlets at 2.41 and
2.46 ppm, indicating that the two methyl groups are
clearly different, at room temperature. That implies
that one of the two nitrogen atoms of the pyrimidine
group is bonded to the metal and than the bond is
stronger than that in complex 2, as expected for a
cationic complex. Dissociation which would allow rota-
tion around the S-C bond and would make the two
methyl groups equivalent is not possible. The protons
from the Cp groups appear at 6.37 ppm as a singlet
which indicates that both ligands are equivalent. The
proton of the pyrimidine group appears at 5.41 ppm.
13C NMR spectrum agrees well with the proposed η2-
coordination of thiolate group. 13C NMR resonances for
C-Me pyrimidinethiolato atoms at 167.0 and 114.2 ppm
respectively suggest that an important contribution of
the bonding situation of form B (Scheme 2) may be
considered.
CE(1)-Zr-CE(2) 126.9(2)
C(1)-N(2)-C(2) 116.2(3)
CE(1)-Zr-S
105.6(1)
110.3(1)
103.2(2)
107.9(2)
116.5(2)
102.6(2)
77.2(1)
N(2)-C(2)-C(3) 122.1(4)
N(2)-C(2)-C(5) 116.5(4)
CE(1)-Zr-N(3)
CE(1)-Zr-C(7)
CE(2)-Zr-S
CE(2)-Zr-N(3)
CE(2)-Zr-C(7)
S-Zr-N(3)
S-Zr-C(7)
N(3)-Zr-C(7)
Zr-S-C(1)
C(3)-C(2)-C(5)
C(2)-C(3)-C(4)
121.4(4)
117.6(4)
N(1)-C(4)-C(3) 121.8(4)
N(1)-C(4)-C(6) 115.9(4)
C(3)-C(4)-C(6)
Zr-N(3)-C(7)
Zr-N(3)-C(9)
C(7)-N(3)-C(9) 128.0(3)
Zr-C(7)-N(3)
Zr-C(7)-C(8)
122.2(4)
70.8(2)
161.2(2)
109.9(1)
32.9(1)
111.5(1)
116.6(3)
119.7(3)
114.6(3)
125.6(3)
C(1)-N(1)-C(4)
S-C(1)-N(1)
S-C(1)-N(2)
N(1)-C(1)-N(2)
76.4(2)
156.4(3)
N(3)-C(7)-C(8) 127.1(3)
a
CE(1) and CE(2) are the centroids of the C(17)‚‚‚C(21) and
C(22)‚‚‚C(26) cyclopentadienyl rings respectively.
similar to that previously described for 2, while the
S-C(1) bond length (1.752(4) Å) is longer than the one
found in complex 2. The S-C(1) bond distance, ob-
served for complex 4, agrees well with the the un-
weighted sample mean value (1.761(20) Å) reported for
terminal arenethiolates.16 The Zr-C(7) bond distance
(2.206(4) Å) falls into the range 2.164-2.363 Å while
the Zr-N(3) bond distance (2.271(3) Å) is slightly out
of the range 2.148-2.250 Å obtained from 10 crystal
structures from CSD which contain the Cp2Zr(η2-
CdNs) moiety (Zr-C and Zr-N mean bond lengths:
2.25(6) and 2.21(3) Å, respectively). The length of the
N(3)-C(7) bond distance (1.268(5) Å) is consistent with
a double-bond character and falls into the range 1.242-
1.322 Å obtained in the above-mentioned system.
Reaction of compound 2 with [NEt3H]+[BPh4]-, in
THF, at room temperature yields the cationic complex
5 (Scheme 5).
In an effort to get a deeper insight on the reactivity
of the 4,6-dimethyl-2-mercaptopyrimidine group with
different zirconium moieties we have studied the oxida-
tive addition reactions of the thiol on Zr(II) precursors.
Reaction of “Cp*2Zr”18 with 4,6-dimethyl-2-mercap-
topyrimidine gives via oxidative addition the hydride-
thiolate complex 6 as depicted in Scheme 6.
It is a colorless compound and very soluble in most
of the common organic solvents. It has been character-
1
ized by elemental analysis, H and 13C NMR, and IR
spectroscopy. 1H NMR shows singlets at 1.89 (30H),
2.04 (3H), and 2.34 ppm (3H) corresponding to the
methyl groups in the Cp* ring and the pyrimidine
Some thiolate cationic complexes of zirconium have
been previously reported.17 They have been prepared
(17) Piers, W. E.; Koch, L.; Ridge, D. S.; MacGillivray, L. R.;
Zaworotko, M. Organometallics 1992, 11, 3148.
(18) (a) Negishi, E.; Cederbaum, F. E.; Takahashi, T. Tetrahedron
Lett. 1986, 27, 1829. (b) Negishi, E.; Swanson, D. R.; Takahashi, T. J .
Chem. Soc., Chem. Commun. 1990, 1254.
(16) Orpen , A. G.; Brammer, L.; Allen, F. H.; Kennard, O.; Watson,
D. G.; Taylor, R. J . J . Chem. Soc., Dalton Trans. 1989, S1.

Zirconium Alkyl Thiolate Complexes
Organometallics, Vol. 15, No. 22, 1996 4729
1063 (w), 1022 (m), 1010 (m), 980 (w), 951 (m), 906 (w), 894
(w), 837 (m), 811 (s), 765 (m), 668 (w), 637 (w), 594 (w), 566
(w), 549 (w), 461 (w), 420 (w), 336 (m), 228 (w), 203 (w); H
Sch em e 6
1
NMR (300 MHz, toluene-d8, -40 °C) δ 0.47 (s, 3 H, CH3Zr),
1.54 (s, 3H, CH3), 1.99 (s,, 3H, CH3), 5.42 (s, 10H, Cp), 5.62 (s,
1H, pyrimidine). Anal. Calcd for C17H20N2SZr: C, 54.36; H,
5.37; N, 7.46. Found: C, 53.93; H, 5.36; N, 7.58.
Syn th esis of Cp 2Zr (SC6H7N2)2 (3). A mixture of Cp2ZrMe2
(0.46 g, 1.83 mmol) and HS(C6H7N2) (0.51 g, 3.66 mmol) was
stirred under reflux, in 15 mL of toluene, for 3 h. The solution
was allowed to reach the room temperature, and the white
solid that formed was filtered and then washed with pentane
(2 × 5 mL) and characterized as 3: Yield 0.43 g (47%); IR
(Nujol/PET, cm-1) 2671 (w), 2329 (w), 2019 (w), 1563 (m), 1266
(s), 1241 (s), 1061 (m), 1014 (m), 967 (w), 874 (w), 820 (m),
796 (s), 764 (m), 552 (m); 1H NMR (200 MHz, C6D6) δ 1.78 (s,
6H, CH3), 2.04 (br s, 3H, CH3), 1.96 (br s, 3H, CH3), 5.54 (s,
1H, pyrimidine), 5.92 (s, 1H, pyrimidine), 6.23 (s, 10H, Cp).
Anal. Calcd for C22H24N4S2Zr: C, 52.87; H, 4.84; N, 11.21.
Found: C, 52.53; H, 4.77; N, 11.13.
moiety. It means that, at room temperature, the
thiolate ligand is bidentate, and rotation around the
C-S bond is obstructed. The aromatic proton of the
thiolate group appears at 5.49 ppm and the hydride
signal at 5.95 ppm which agrees well with the shift
expected according to that found in other hydride-
zirconocene complexes, like Cp*2ZrH(NH2)19 (4.83 ppm)
or (Cp*2ZrH)2O20 (5.50 ppm).
Syn t h esis of Cp 2Zr (η2-MeCNXylyl) (η1-SC6H 7N2)‚(1/
2C4H8O)(4‚1/2THF ). A mixture of Cp2Zr(SC6H7N2)(Me) (0.20
g, 0.53 mmol) and 2,6-dimethylphenyl isocyanide (0.07 g, 0.53
mmol) in 20 mL of THF was allowed to react at room
temperature for 5 h. After this time, the solvent was partially
evaporated under vacuum. Slow diffusion of pentane in the
saturated THF solution yielded 0.22 g of insertion product 4‚1/
2THF in 81% yield: IR (Nujol/PET, cm-1) 2360(w), 1611(m),
1599 (m), 1568 (m), 1556 (m), 1537 (m), 1532 (m), 1519 (m),
1244 (s), 1175 (m), 1159 (w), 1133 (w), 789 (s), 766 (s); 1H NMR
(200 MHz, C6D6) δ 1.44 (m, 2H, THF), 1.92 (s, 6H, CH3), 1.94
(s, 3H, CH3), 2.17 (s, 6H, CH3), 3.59 (m, 2H, THF), 5.85 (s,
10H, Cp), 6.11 (s, 1H, pyrimidine), 6.9 (m, 3H, Xylyl); 13C{H}
NMR (300 Mhz, C6D6) δ 19.2 (CH3), 23.6 (CH3), 23.8 (CH3),
25.8 (THF), 67.8 (THF), 108.7 (Cp), 112.9 (CH, pyrimidine),
125.6, 128.8 (CH, Xylyl), 130.3 (CsCH3, Xylyl), 142.8 (CsN,
Xylyl), 164.5 (CsCH3, pyrimidine), 181.4 (CsS), 241.8 (CdN).
Anal. Calcd for C28H33N3O0,5SZr: C, 61.95; H, 6.12; N, 7.74.
Found: C, 61.61; H, 6.10; N, 7.78.
Syn th esis of [Cp 2Zr (η2-SC6H7N2)][BP h 4] (5). A mixture
of complex 2 (0.51 g, 1.36 mmol) and [NEt3H][BPh4] (0.57 g,
1.36 mmol) was stirred at room temperature, in 20 mL of THF,
for 7 h. After this time, the solvent was partially evaporated
under vacuum. Slow diffusion of pentane gave 0.80 g (87%)
of the microcrystalline cationic complex 5: IR (Nujol/PET,
cm-1) 1611 (m), 1574 (m), 1567 (m), 1525 (m), 1307 (m), 1264
(m), 1228 (m), 1013 (m), 706 (s). 1H NMR (200 MHz, CD3CN)
δ 2.41 (s, 3H, CH3), 2.46 (s, 3H, CH3), 5.41 (s, 1H, pyrimidine),
6.37 (s, 10H, Cp), 6.92-7.40 (m, 20 H, Ph); 13C{H} NMR (300
MHz, CD3CN) δ 22.9 (CH3), 24.4 (CH3), 114.2 (C-CH3), 114.8
(Cp), 118.2 (CH, pyrimidine), 122.7, 126.5, 136.7 (CH, BPh4),
164.7 (1J C-B ) 49.4 Hz, C-B), 167.0 (C-CH3), 171.7 (C-S).
Anal. Calcd for BC40H37N2SZr: C, 70.67; H, 5.49; N, 4.12.
Found: C, 70.55; H, 5.60; N, 4.19.
In conclusion, we would like to call the attention to
the great potential offered by this versatile thiolate
ligand. On one hand it is possible to stabilize unsatur-
ated compounds due to the assistance of the nitrogen
atom without preventing its further reactivity and so,
it is possible to synthesize, in a stepwise manner,
monoalkyl-thiolate zirconium compounds and the cor-
responding bis-thiolate zirconium complexes. The ligand
is also useful in the stabilization of the cationic thiolate
complex, and it is able to undergo oxidative addition
reactions in a selective way. On the other hand, it can
also behave as a monodentate ligand as is the case in
the iminoacyl complex.
Exp er im en ta l Section
Gen er a l P r oced u r es. All reactions were carried out by
using Schlenk techniques. Toluene was distilled from sodium.
Pentane was distilled from sodium/potassium alloy. Diethyl
ether and THF were distilled from sodium benzophenone. All
solvents were deoxygenated prior to use.
The following reagents were prepared by literature pro-
cedures: Cp*H,21 Cp*2ZrCl2,22 Cp2ZrMe2,23 CNXylyl.24 The
commercially available compounds LiMe in diethyl ether, 4,6-
dimethyl-2-mercaptopyrimidine, Cp2ZrCl2, and tBuLi were
used as received from Aldrich.
1H and 13C NMR spectra were obtained on either 200 Gemini
or 300 Unity MHz Varian Fourier transform spectrometers.
Trace amounts of protonated solvents were used as references,
and chemical shifts are reported in units of parts per million
relative to SiMe4.
Syn th esis of Cp 2Zr (η2-SC6H7N2)(Me) (2). A mixture of
Cp2ZrMe2 (0.36 g, 1.43 mmol) and HS(C6H7N2) (0.20 g, 1.43
mmol) was stirred with 20 mL of pentane, at room temperature
for 5 h. The white precipitate was separated by filtration and
washed twice with 10 mL of pentane and vacuum dried
yielding 0.50 g (93%) of 2: IR (Nujol / PET, cm-1) 3096 (m),
3079 (m), 3056 (m), 2668 (w), 1621 (w), 1575 (s), 1526 (s), 1364
(s), 1336 (s), 1271 (s), 1235 (m), 1186 (w), 1168 (m), 1124 (w),
Syn th esis of Cp *2Zr (η2-SC6H7N2)(H) (6). To a solution
of Cp*2ZrCl2 (0.37 g, 0.85 mmol) in 10 mL of Et2O at -78 °C
t
was added 1 mL (1.70 mmol) of a pentane solution of BuLi.
The mixture was allowed to reach room temperature and to
react for 1 h. The solution was then cooled again at -78 °C
and 0.12 g (0.85 mmol) of 4,6-dimethyl-2-mercaptopyrimidine
were added. After that the cooling was removed and the
mixture was stirred at room temperature for 3 h. The solvent
was removed under vacuum, and the residue was extracted
with pentane. Partial evaporation of the solvent and cooling
at -30 °C for 24 h gave 0.20 g (47%) of a microcrystalline solid
which was characterized as 6: IR (Nujol/PET, cm-1) 1645 (w,
broad), 1570 (s), 1552 (w), 1524 (m), 1332 (m), 1259 (s), 1063
(19) Hillhouse, G. L.; Bulls, A. R.; Santarsiero, B. D.; Bercaw, J . E.
Organometallics 1988, 7, 1309.
(20) Hillhouse, G. L.; Bercaw, J . E. J . Am. Chem. Soc. 1984, 106,
5472.
(21) Burger, U.; Delay, A.; Maznot, F. Helv. Chim. Acta 1974, 57,
2106.
(22) 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.
1
(w), 1022 (m), 952 (w), 788 (w), 358 (m); H NMR (200 MHz,
C6D6) δ 1.89 (s, 30H, Cp*), 2.04 (s, 3H, CH3), 2.34 (s, 3H, CH3),
5.49 (s, 1H, C-H), 5.95 (s, 1H, Zr-H); 13C NMR (300 MHz,
(23) Samuel, E.; Rausch, M. D. J . Am. Chem. Soc. 1973, 95, 6263.
(24) Shingaki, T.; Takebayashi, M. Bull. Soc. Chem. J pn. 1963, 36,
617.
1
1
C6D6) δ 12.2 (q, J C-H ) 127.4 Hz, Cp*), 23.7 (q, J C-H ) 127.9
1
1
Hz, CH3), 24.0 (q, J C-H ) 127.4 Hz, CH3), 113.9 (d, J C-H
)

4730 Organometallics, Vol. 15, No. 22, 1996
Fandos et al.
Ta ble 5. Exp er im en ta l Da ta for th e X-r a y
Diffr a ction Stu d ies
The structures were solved by direct and Fourier methods
and refined by full-matrix least-squares methods, first with
isotropic thermal parameters and then with anisotropic ther-
mal parameters for all the non-hydrogen atoms, except the
carbon and the oxygen atoms of the solvent for 4‚1/2C4H8O.
All hydrogen atoms of 2 were clearly located in the ∆F map
and refined isotropically, while the hydrogen atoms of 4‚1/
2C4H8O (except those of the THF molecule which were not
calculated) were placed at their geometrically calculated
positions (C-H ) 0.96 Å) and refined “riding” on the corre-
sponding carbon atoms (with isotropic thermal parameters).
The final cycles of refinement were carried out on the basis of
256 (2) and 307 (4‚1/2C4H8O) variables; after the last cycles no
parameters shifted more than 0.51 (2) and 0.54 (4‚1/2C4H8O).
The biggest remaining peak in the final difference map was
equivalent to about 0.40 (2) and 0.84 (4) e/Å3. In the final
2
4‚1/2C4H8O
mol formula
mol wt
C17H20N2SZr
375.638
C26H29N3SZr‚1/2C4H8O
542.869
cryst syst
space group
monoclinic
P21/n
monoclinic
P21/c
radiation (Mo KR) λ ) 0.71073 Å graphite-monochromated
a, Å
b, Å
c, Å
â, deg
V, Å3
Z
13.905(2)
15.677(2)
7.683(1)
94.20(1)
1670.3(4)
4
8.706(2)
22.790(5)
13.607(2)
100.89(2)
2651.1(9)
4
D
calcd, g cm-3
1.494
1.360
F(000)
768
1128
cryst dimens, mm 0.15 × 0.22 × 0.25 0.20 × 0.25 × 0.30
2
-1
µ(Mo KR), cm-1
diffractometer
2θ range, deg
reflns measd
7.78
5.16
cycles of refinement a weighting scheme, w ) k[σ(Fo) + gFo
] ,
was used; at convergence the k and g values were 0.4224 and
0.0010 (2), 0.5929 and 0.0056 (4‚1/2C4H8O), respectively. The
analytical scattering factors, corrected for the real and imagi-
nary parts of anomalous dispersions.26 All calculations were
carried out on the OULD POWERNODE 6040 and ENCORE
91 of the “Centro di Studio per la Strutturistica Diffrattomet-
rica” of the CNR, Parma. The system of computer programs
SIR92,27 SHELXS-86 and SHELX-76,28 Parts29 and ORTEP30
were used.
Philips PW 1100
6-60
(h,k,l
4866
Siemens AED
6-60
(h,k,l
7718
unique total data
unique obsd data
[I g 2σ(I)]
2360
5141
goodness of fit
1.04
0.0291, 0.0336
1.07
0.0479, 0.0718
R,a Rw
b
a
b
R ) ∑| |Fo| - |Fc| |/∑|Fo|. Rw ) [∑w(|Fo| - |Fc|)2/∑w(Fo)2]1/2
.
Ack n ow led gm en t. R.F., M.J .R., and A.O. gratefully
acknowledge financial support from the DGICyT (grant
no. PB 92-0715) of Spain. M.L. and M.A.P. gratefully
acknowledge financial support from the Ministerio
dellUÄ niversita` e della Ricerca Scientifica e Tecnologica
(MURST) and the Consiglio Nazionale della Ricerca
(CNR) (Rome, Italy). P.T. gratefully acknowledges
financial support from the EU (Programme ALAMED)
Project no. C11*-CT93-0329.
169.2 Hz, CH ), 115.1 (s, Cp*), 166.1 (s, C-CH3), 169.0 (s,
C-CH3), 184.6 (S, C-S). Anal. Calcd for C26H38N2SZr: C,
62.22; H, 7.63; N, 5.58. Found: C, 62.06; H, 7.89; N, 5.30.
Gen er al P r ocedu r es Em ployed in th e Cr ystallogr aph ic
St u d ies. A single crystal of each compound was sealed in
Lindemann capillary under dry nitrogen atmosphere and used
for data collection. Crystallographic data are summarized in
Table 5.
Accurate unit cell parameters were determined by least-
squares treatment of the setting angles of 30 carefully centered
reflections in the θ range 10.8-18.5° for 2 and 11.1-18.9° for
4‚1/2C4H8O. Data (3 < θ < 30°) were collected at 22 °C on a
Philips PW 1100 single-crystal diffractometer (2) and on a
Siemens AED (4‚1/2C4H8O), using the graphite-monochromated
Mo KR radiation (λ ) 0.710 73 Å) and the θ/2θ scan method.
The reflections were collected with a variable scan speed of
3-9° min-1 and a scan width of 1.20 + 0.34 tan θ. One
standard reflection was monitored every 50 measurements;
no significant decay was noticed over the time of data collec-
tions. The individual profiles have been analyzed following
the method of Lehmann and Larsen:25 Intensities were cor-
rected for Lorentz and polarization effects. Only the observed
reflections were used in the structure refinements.
Su p p or tin g In for m a tion Ava ila ble: Tables 2 and 4,
tables of hydrogen atom coordinates, anisotropic thermal
parameters, complete bond distances and angles, and complete
crystallographic data (12 pages). Ordering information is
given on any current masthead page. A list of structure factors
is available upon request from the authors.
OM960396G
(26) International Tables for X-Ray Crystallography; Kynoch
Press: Birmingham, England, 1974; Vol. IV.
(27) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Gualiardi, A. Appl.
Crystallogr. 1993, 26, 343.
(28) Sheldrick, G. M. SHELXS-86 Program for the Solution of
Crystal Structures. University of Go¨ttingen, Go¨ttingen, Germany,
1986. Sheldrick, G. M. SHELXS-76 Program for Crystal Structure
Determination. Universty of Cambridge, Cambridge, England, 1976.
(29) Nardelli, M. Comput. Chem. 1983, 7, 95.
(25) Lehmann, M. S.; Larsen, F. K. Acta, Crystallogr., Sect. A 1974,
30, 580.
(30) J ohnson, C. K. ORTEP Report ORNL-3794, revised; Oak Ridge
National Laboratory: Oak Ridge, TN, 1965.