A sandwich zwitterionic ruthenium complex bearing a cyanamido group

Article abstract of DOI:10.1021/om400547r

A sandwich zwitterionic ruthenium complex (4) was prepared by an intramolecular 1,3-dipolar cycloaddition of the ruthenium azido isocyanide [CpMe₅Ru(CNAr)₂N₃] (2). The reaction involved a formal 1,3-migration mechanism along a highly conjugated system linking to a cyanamido group.

Full text of DOI:10.1021/om400547r

Communication
pubs.acs.org/Organometallics
A Sandwich Zwitterionic Ruthenium Complex Bearing a Cyanamido
Group
Junfei Li,†,‡ Wenying Kuai,†,‡ Weiping Liu,§ and Wenjun Zheng*,†,‡,∥
‡
†Institute of Organic Chemistry and School of Chemical and Materials Science, Shanxi Normal University, Gongyuan Street 1,
Linfen, Shanxi Province 041004, People’s Republic of China
§State Key Laboratory for Platinum Group Metals, Kunming Institute of Precious Metals, Kunming, Yunnan Province 650106,
People’s Republic of China
∥Key Laboratory of Magnetic Molecules and Magnetic Information Material, Ministry of Education, People’s Republic of China
S
* Supporting Information
ABSTRACT: A sandwich zwitterionic ruthenium complex (4) was
prepared by an intramolecular 1,3-dipolar cycloaddition of the
ruthenium azido isocyanide [CpMe5Ru(CNAr)2N3] (2). The reaction
involved a formal 1,3-migration mechanism along a highly conjugated
system linking to a cyanamido group.
he design and construction of reactive charge-neutral
products of π-bonded cyanamido allyl metal intermediates
Tzwitterionic platinum-group-metal complexes have at- such as 4 have not been isolated and characterized structurally
before the present work.
As shown in Scheme 1, the complex [Cp*RuL2Cl] (1; L =
CNAr, Ar = 2,6-dimethylphenyl) was easily obtained by the
tracted considerable interest over the past few years because
some such complexes have a high potential as catalysts in varied
organic transformations.1−4 For instance, while zwitterionic
rhodium(I) complexes have shown divergent reactivity, such as
in the hydrosilylation of ketones,2a diboration of vinylarenes,2b
hydroformylation of olefins,2c,d and tandem cyclohydrocarbo-
nylation/CO insertion of α-imino alkynes,2g several zwitter-
ionic ruthenium(II) complexes3 have been recently applied to
the activation in the atom transfer radical addition of CCl4,4a
the geminal Si−H bond of an organosilane,4b the ring-opening
metathesis polymerization of cyclooctene,4c reversible H2
splitting,4d and so on.4d
Scheme 1. Preparation of Complexes 1−4
On the other hand, 1.3-dipolar cycloaddition of metal azido
and isocyanides is one of the routes to the preparation of
transition-metal cyanamido complexes with terminal nitrogen
coordination as well as C-bonded tetrazolato compounds,5
where cyanamido complexes are regarded as the thermolysis
products of the C-bonded tetrazolato compounds.5a,f−h
Recently, it has been postulated that π-bonded cyanamido
allyl metal intermediates might isomerize in solution and might
play a key role in the metal-catalyzed (especially palladium-
catalyzed) preparation of organic cyanamides.6 Due to the
importance of cyanamides for heterocyclic compounds in the
fields of organic and inorganic chemistry,7 the inferred
mechanism of the isomerized π-bonded cyanamido allyl metal
intermediates is significant in understanding the formation of
cyanamides6 as well as cyanamido complexes.5 However, such
species have not been evidenced experimentally to date. Herein,
we report a half-sandwich cyanamido ruthenium compound (3)
and one sandwich arene ruthenium complex with a cyanamido
anion group (4), both of which likely derive from isomerized π-
bonded cyanamido allyl ruthenium intermediates. Probably
owing to their high reactivity, the formal 1,3-isomerized
8
reaction of [Cp*RuCl]4 and 2 equiv of 2,6-dimethylphenyl
isocyanide (L) in CH2Cl2 in 94.4% yield as dark orange crystals
(Scheme 1).9 The ruthenium azido complex [Cp*RuL2N3] (2)
was further synthesized by the salt elimination reaction of 1 and
NaN3 in dry ethanol as a orange solid in 90.1% yield.10 The
intramolecular [3 + 2] cycloaddition occurred when 2 was
refluxed in o-xylene for 4 days in the presence of additional 0.6
equiv of 2,6-dimethylphenyl isocyanide (L) (Scheme 1). The
reaction led to the formation of 3 and 4 as a mixture ([3]/[4] =
4/1), which was further isolated in good to fair yield (63.0% for
3, 24.8% for 4), respectively.11 Alternatively, the reaction may
be performed within 5 h at 200 °C in a sealed evacuated Carius
tube by using 1,2,4,5-tetramethylbenzene as solvent. Complexes
Received: June 13, 2013
© XXXX American Chemical Society
A
dx.doi.org/10.1021/om400547r | Organometallics XXXX, XXX, XXX−XXX

Organometallics
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3 and 4 are readily soluble in THF and chlorinated solvents but
only somewhat soluble in ether.
The elemental analysis results are in complete agreement
with the formulas of compounds 1−4.12 The 1H NMR (CD3Cl,
23 °C) spectrum of complex 3 shows signals at δ 1.91 (s), 2.31
(s), 2.40 (s), 6.55−6.81 (m), and 7.06 (s) ppm that are
assigned to CpMe5, NCNAr, and CNAr groups, respectively.
Two resonances at δ 117.98 and 170.60 ppm in the 13C{1H}
NMR spectrum evidenced the NCN and Ru−CN groups. The
NCN stretching vibrations in the IR spectrum appear at
1598 (m) and 2164 (m) cm−1, while the band at 2363(w) cm−1
is attributed to CN of the coordinated acetonitrile.13 The H
1
Figure 2. ORTEP drawing of complex 4 with thermal ellipsoids drawn
at the 30% probability level. Hydrogen atoms are omitted for clarity.
Selected bond lengths (Å) and angles (deg): Ru(1)−C(11) =
2.194(2), Ru(1)−C(6) = 2.235(5), Ru(1)−C(1) = 2.360(1), C(1)−
N(1) = 1.360(9), N(1)−C(9) = 1.297(7), C(9)−N(2) = 1.149(8);
C(1)−N(1)−C(9) = 127.48(9), N(2)−C(9)−N(1) = 169.97(2).
NMR spectrum (CD2Cl2, 23 °C) of compound 4 is, however,
quite different from that of 3 and shows one set of signals at δ
1.82 (s, 15 H), 2.14 (s, 6 H), and 4.95 (m, 3 H) ppm. The
upfield resonance at δ 4.95 (m) is assigned to the protons on
the η6-coordinated phenyl ring, suggesting the formation of a
metal arene complex. The 13C{1H} NMR spectrum shows the
upfield signals of the carbon atoms on the phenyl ring at about
δ 90 ppm. The broad resonance at δ 131.54 ppm is assigned to
the NCN group. The −NCN stretching vibration of 4 in
the IR spectrum appears at 2096 (m) cm−1 but bands without
stretching appear at about 2360 and 1600 cm−1.
An X-ray crystal structure determination of 1−4 was carried
out.12,13 In the structures of complexes 1−3, the Ru center is
coordinated by two CNAr units, one chloro for 1 (azido for 2
or NCNAr for 3), and one η5-CpMe5 group. The overall
geometry about ruthenium exclusively featured a typical “piano
stool” conformation (Figure 1).13 The bond distances (Ru(1)−
N(1) bond length (1.360(9) Å, vs N(1)−C(9) = 1.297(7) Å)
and C(9)−N(2) (1.149(8) Å) and the smaller bond angle at
N(1) (C(1)−N(1)−C(9) = 127.48(9)°, vs N(2)−C(9)−N(1)
= 169.97(2)°) are indicative of C(1)−N(1) single-bond
character. The difference between Ru(1)−C(1) (2.360(1) Å)
and the average Ru(1)−C bond length in the phenyl ring
(2.235(5) Å) is 0.12(2) Å. The packing structure of 4 showed
that the cyanamido group was neither affected by any packing
force from the group and atoms nor oriented to the metal
center of a neighboring molecule. The amino nitrogen atom
(N(1)) of the cyanamido group has therefore one lone pair of
electrons that seems to conjugate with both cyano and arene
groups. Since the C(1) atom is almost coplanar, the phenyl ring
must remain aromatic to comply with the 4n + 2 rule; complex
4 is thus a zwitterionic species with an anionic NCN−
functional group. Ruthenium arene complexes with an anionic
functional group on the phenyl ring are rare, and only a few
structurally characterized examples such as [CpRu(η6-
C6H5BPh3)], [(η6-C6H5BPh2H)Ru(PMe3)2(SiMe3)], [(η6-
C6H5BPh3)RuH(depe)], and [(η6-C6H5BPh3)Ru((1−3,5,6-η)-
C8H11)] as well as [CpMe5Ru(η6-PhCOO)], [(η5-C8H11)Ru-
(η6-PhSO3)], and [(η5-C5H4OH)Ru(η6-p-MeC6H4SO3)] are
known.14,15 However, it is notable that the significantly longer
Ru(1)−C(1) bond length may indicate another resonance form
of 4: namely, a η5 species containing a CN−CN group,
similar to that found in [CpMe5Ru(η5-C5F5CO)].14n−p
The mechanism for the formation of 3 and 4 seems to be an
alternative three-step mechanism involving intermediates A−C
at high temperatures (Scheme 2). The C-bonded tetrazolato
ruthenium complex (A) forms and then decomposes at high
temperatures to give a π-bonded cyanamido allyl metal
intermediate (B). It seems reasonable that a formal 1,3-
migration of the [Ru]L2 unit would occur along the allyl group
in B to give complexes 3 and 4.16a It seems that 3 is a kinetic
product and 4 is a thermodynamic species.16b However, we
could not observe the proton resonances of these intermediates
in the 1H NMR spectra at varying temperatures (100−145 °C),
indicating that they are all unstable at high temperatures.16 We
also investigated the possible equilibrium between complexes 3
and 4. Compound 3 only converted to compound 4 (only
about 5% yield) slightly when an o-xylene-d10 solution of 3 was
heated at 145 °C in a sealed combustion tube for 100 h. In
contrast, compound 4 is quite stable and could not convert to
compound 3 even after 150 h under similar conditions.16
Figure 1. ORTEP drawing of complex 3 with thermal ellipsoids drawn
at the 30% probability level. Hydrogen atoms are omitted for clarity.
Selected bond lengths (Å) and angles (deg): Ru(1)−C(30) =
2.237(5), Ru(1)−C(1) = 1.931(3), Ru(1)−N(3) = 2.080(3), N(3)−
C(19) = 1.152(5), C(19)−N(4) = 1.269(1), N(4)−C(20) =
1.391(2); C(10)−Ru(1)−C(1) = 90.85(5), C(10)−Ru(1)−N(3) =
90.84(1), Ru(1)−C(1)−N(1) = 178.15(9), Ru(1)−N(3)−C(19) =
170.16(5), N(3)−C(19)−N(4) = 170.16 (5), C(19)−N(4) −C(20) =
128.28(4).
N(3) = 2.080(3) Å and Ru(1)−C(1) = 1.931(3) Å) and bond
angles (C(10)−Ru(1)−C(1) = 90.85(5)° and C(10)−Ru(1)−
N(3) = 90.84(1)°) at ruthenium in 3 are comparable to those
found in 1 and 2.12,13
In contrast to the piano-stool structures of 1−3, the X-ray
analysis clearly revealed that 4 is a sandwich molecule with [η5-
(CpMe5)]− and [η6-(arene)NCN]− moieties (Figure 2).12,13
The carbon atom (C(6)) deviation from the least-squares plane
of phenyl ring is only 0.0331° (0.0105 Å), and the angle
between two best planes of the ligand rings is 0.41°, so that the
sandwich is almost perfectly stacked parallel. The longer C(1)−
B
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Advanced Technology for Comprehensive Utilization of
Platinum Metals.
Scheme 2. Suggested Mechanism for the Formation of
Complexes 3 and 4
REFERENCES
■
(1) (a) Crabtree, R. H. The Organometallic Chemistry of the Transition
Metals; Wiley: Hoboken, NJ, 2005. (b) Stradiotto, M.; Hesp, K. D.;
Lundgren, R. J. Angew. Chem., Int. Ed. 2010, 49, 494−512.
(2) (a) Hesp, K. D.; McDonald, R.; Ferguson, M. J.; Stradiotto, M. J.
Am. Chem. Soc. 2008, 130, 16394−16406. (b) Dai, C.-Y.; Robins, E.
G.; Scott, A. J.; Clegg, W.; Yufit, D. S.; Howard, J. A. K.; Marder, T. B.
Chem. Commun. 1998, 1983. (c) Amer, I.; Alper, H. J. Am. Chem. Soc.
1990, 112, 3674−3676. (d) Park, H. S.; Alper, H. J. Am. Chem. Soc.
1999, 121, 11697−11703. (e) Monteil, F.; Matsuda, I.; Alper, H. J. Am.
Chem. Soc. 1995, 117, 4419−4420. (f) van den Hoven, B. G.; Alper, H.
J. Am. Chem. Soc. 2001, 123, 1017−1022. (g) van den Hoven, B. G.;
Alper, H. J. Am. Chem. Soc. 2001, 123, 10214−10220.
(3) (a) Rankin, M. A.; Schatte, G.; McDonald, R.; Stradiotto, M. J.
Am. Chem. Soc. 2007, 129, 6390−6391. (b) Lundgren, R. J.; Rankin,
M. A.; McDonald, R.; Schatte, G.; Stradiotto, M. Angew. Chem., Int. Ed.
In summary, an intramolecular 1,3-dipolar cycloaddition of
the azido metal isocyanide 2 occurred to afford the two
isomeric cyanamido ruthenium complexes 3 and 4, the latter of
which is a zwitterionic ruthenium complex with a non-
coordinating cyanamido group that has potential in organic
transformations.4 The formation of isomers 3 and 4 suggested
2007, 46, 4732−4735. (c) Samuel, C.; Tortoioli, S.; Muller, J.; Linder,
̈
D.; Buron, F.; Lacour, J. Angew. Chem., Int. Ed. 2007, 46, 8979−8982.
(d) Annibale, V. T.; Song, D.-T. Chem. Commun. 2012, 48, 5416−
5418. (e) Rankin, M. A.; McDonald, R.; Ferguson, M. J.; Stradiotto,
M. Angew. Chem., Int. Ed. 2005, 44, 3603−3606. (f) He, X. D.;
Chardret, B.; Dahan, F.; Huang, Y. S. Organometallics 1991, 10, 970−
979. (g) Stebler-Roethlisberger, M.; Salzer, A.; Buergi, H. B.; Ludi, A.
Organometallics 1986, 5, 298−302. (h) Koelle, U.; Weissschaedel, C.;
Englert, U. J. Organomet. Chem. 1995, 490, 101−109. (i) Dioumaev, V.
K.; Ploessl, K.; Carroll, P. J.; Berry, D. H. Organometallics 2000, 19,
3374−3378. (j) Kruger, G. J.; Preez, L.; Haines, R. J. J. Chem. Soc.,
Dalton Trans. 1974, 1302−1305. (k) Gemel, C.; LaPensee, A.;
Mauthner, K.; Mereiter, K.; Schmid, R.; Kirchner, K. Monatsh. Chem.
1997, 128, 1189−1199. (l) Ashworth, T. V.; Nolte, M. J.; Reimann, R.
H.; Singleton, E. J. Chem. Soc., Chem. Commun. 1977, 937−939.
(m) Winter, R. F.; Hornung, F. M. Inorg. Chem. 1997, 36, 6197−6204.
(4) (a) Lundgren, R. J.; Rankin, M. A.; McDonald, R.; Stradiotto, M.
Organometallics 2008, 27, 254−258. (b) Rankin, M. A.; Maclean, D. F.;
Gabriele, S.; McDonald, R.; Stradiotto, M. J. Am. Chem. Soc. 2007, 129,
15855−15864. (c) Hans, M.; Willem, Q.; Wouters, J.; Demonceau, A.;
Delaude, L. Organometallics 2011, 30, 6133−6142. (d) Stepowska, E.;
Jiang, H.; Song, D.-T. Chem. Commun. 2010, 46, 556−558. (e) Amouri,
H.; Caspar, R.; Gruselle, M.; Duhayon, C. G.; Boubekeur, K.; Lev, D.
A.; Collins, L. S. B.; Grotjahn, D. B. Organometallics 2004, 23, 4338−
4341. (f) Amouri, H.; Vaissermann, J.; Rager, M. N.; Grotjahn, D. M.
Organometallics 2000, 19, 1740−1748. (g) Bras, J. L.; Amouri, H.;
Vaissermann, J. Organometallics 1998, 17, 1116−1121. (h) Amouri, H.;
Besace, Y.; Bras, J. L. J. Am. Chem. Soc. 1998, 120, 6171−6172.
(5) (a) Kim, Y.-J.; Kwak, Y.-S.; Joo, Y.-S.; Lee, S.-W. Dalton Trans.
2002, 144−151. (b) Kim, Y.-J.; Joo, Y.-S.; Han, J.-T.; Han, W.-S.
Dalton Trans. 2002, 3611−3618. (c) Fehlhammer, W. P.; Dahl, L. F. J.
Am. Chem. Soc. 1972, 94, 3370−3377. (d) Beck, W.; Burger, K.;
Fehlhammer, W. P. Chem. Ber. 1971, 104, 1816−1825. (e) Beck, W.;
Fehlhammer, W. P. Angew. Chem., Int. Ed. Engl. 1967, 6, 169−170.
(f) Kim, Y.-J.; Chang, X.-H.; Han, J.-T.; Lim, M. S.; Lee, S. W. Dalton
Trans. 2004, 3699−3708. (g) Chang, X.-H.; Kim, M.-Y.; Kim, Y.-J.;
Huh, H. S.; Lee, S. W. Dalton Trans. 2007, 792−801. (h) Kim, Y.-J.;
Lee, K.-E.; Jeon, H.-T.; Huh, H. S.; Lee, S. W. Inorg. Chim. Acta 2008,
361, 2159−2165 and references therein.
2
5
that a metal 1,3-migration to N or even to N occurred
probably via the π-allyl ruthenium cyanamido intermediate B
after the breakdown of the tetrazolato ring. The migration to
2N may be regarded as a formal Curtius rearrangement,17 while
5
the migration to N, however, was never observed due to a
bulky substituent on the nitrogen atom. In addition, the
structure of 4 rendered a unique example that may give insight
into the bonding capability of the phenylcyanamido ligand with
transition metals, which usually presents a terminal or side-on
cyanamido coordination with metals.18a The successful
preparation and structural characterization of 4 may thus
open a path to the preparation of novel sandwich zwitterionic
phenylcyanamide complexes with specific electronic and
magnetic communication properties.18
ASSOCIATED CONTENT
* Supporting Information
■
S
Text, figures, tables, and CIF files giving crystal data, structure
solution and refinement details, atomic coordinates, bond
lengths and angles, and anisotropic thermal parameters for 1−
4, experimental details, and NMR spectra. This material is
available free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*E-mail for W.Z.: wjzheng@sxnu.edu.cn.
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
(6) (a) Kamijo, S.; Jin, T.; Yamamoto, Y. Angew. Chem., Int. Ed. 2002,
41, 1780−1782. (b) Kamijo, S.; Jin, T.; Yamamoto, Y. J. Am. Chem.
Soc. 2002, 124, 11940−11945. (c) Kamijo, S.; Jin, T.; Yamamoto, Y. J.
Am. Chem. Soc. 2001, 123, 9453−9454. (d) Kamijo, S.; Jin, T.; Huo,
Z.-B.; Yamamoto, Y. J. Org. Chem. 2004, 69, 2386−2393. (e) Hirai, T.;
Han, L.-B. J. Am. Chem. Soc. 2006, 128, 7422−7423. (f) Kamijo, S.; Jin,
T.; Huo, Z.-B.; Yamamoto, Y. J. Am. Chem. Soc. 2003, 125, 7786−
7787. (g) Kamijo, S.; Jin, T.; Yamamoto, Y. J. Org. Chem. 2002, 67,
7413−7417. (h) Kamijo, S.; Jin, T.; Huo, Z.-B.; Yamamoto, Y.
Tetrahedron Lett. 2002, 43, 9707−9710. (i) Kamijo, S.; Jin, T.;
W.Z. gratefully acknowledges financial support from the
Program for the Top Young and Middle-aged Innovative
Talents of Higher Learning Institutions of Shanxi (TYMIT
2011), the Doctoral Foundation of the Chinese Education
Ministry (Grant No. 20111404110001), the National Natural
Science Foundation of China (NSFC; Grant No. 21272143),
the Program for Changjiang Scholar and Innovative Research
Team in University (IRT1156), the State R&D Program of
China (No. 2012BAE06B08), and the State Key Laboratory of
C
dx.doi.org/10.1021/om400547r | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Communication
Yamamoto, Y. Tetrahedron Lett. 2004, 45, 689−691. (j) Ohtaka, M.;
Nakamura, H.; Yamamoto, Y. Tetrahedron Lett. 2004, 45, 7339−7341.
(7) Reviews of the preparation and reactions of cyanamides:
(a) Lantzsch, R. In Methoden der Organischen Chemie (Houben-
Weyl); Hagemann, H., Ed.; Georg Thieme Verlag: Stuttgart, Germany,
1983; Vol. E4, pp 974−999. (b) Grundmann, C. In Methoden der
Organischen Chemie (Houben-Weyl); Falbe, J., Ed.; Georg Thieme
Verlag: Stuttgart, Germany, 1985; Vol. E5, pp 1611−1658.
H, 6.72; N, 7.21. Single crystals suitable for X-ray diffraction analysis
were obtained from a mixture of CH2Cl2 and THF (4/6) at ambient
temperature.
(12) See the Supporting Information for the plots of compounds 1
and 2.
(13) Sheldrick, G. M. SHELXL-97; Program for Crystal Structure
Refinement; University of Gottingen, Gottingen, Germany, 1997.
(14) (a) Wang, T.; Pranckevicius, C.; Lund, C. L.; Sgro, M. J.;
Stephan, D. W. Organometallics 2013, 32, 2168−2177. (b) Zaitsev, A.
B.; Caldwell, H. F.; Pregosin, P. S.; Veiros, L. F. Chem. Eur. J. 2009, 15,
6468−6477. (c) He, X. D.; Chardret, B.; Dahan, F.; Huang, Y. S.
Organometallics 1991, 10, 970−979. (d) Stebler-Roethlisberger, M.;
Salzer, A.; Buergi, H. B.; Ludi, A. Organometallics 1986, 5, 298−302.
(e) Koelle, U.; Weissschaedel, C.; Englert, U. J. Organomet. Chem.
1995, 490, 101−109. (f) Dioumaev, V. K.; Ploessl, K.; Carroll, P. J.;
Berry, D. H. Organometallics 2000, 19, 3374−3378. (g) Kruger, G. J.;
Preez, L.; Haines, R. J. J. Chem. Soc., Dalton Trans. 1974, 1302−1305.
(h) Gemel, C.; LaPensee, A.; Mauthner, K.; Mereiter, K.; Schmid, R.;
Kirchner, K. Monatsh. Chem. 1997, 128, 1189−1199. (i) Ashworth, T.
V.; Nolte, M. J.; Reimann, R. H.; Singleton, E. J. Chem. Soc., Chem.
Commun. 1977, 937−939. (j) Winter, R. F.; Hornung, F. M. Inorg.
Chem. 1997, 36, 6197−6204. (k) Gooch, A. B.; Griffin, R. G.; Johnson,
C., Jr.; Chang, R. J. Am. Chem. Soc. 1971, 93, 2820−2821. (l) Chaudret,
B.; He, X.-D.; Huang, Y.-S. J. Chem. Soc., Chem. Commun. 1989, 1844−
1846. (m) Damas, A. E.; Ventura, B.; Axet, M. R.; Esposti, A. D.;
Chamoreau, L. M.; Barbieri, A.; Amouri, H. Inorg. Chem. 2010, 49,
10762−10764. (n) Damas, A.; Ventura, B.; Moussa, J.; Esposti, A. D.;
Chamoreau, L. M.; Barbieri, A.; Amouri, H. Inorg. Chem. 2012, 51,
1739−1750. (o) Hughes, R. P.; Zheng, X. M.; Morse, C. A.; Curnow,
O. J.; Lomprey, J. R.; Rheingold, A. L.; Yap, G. P. A. Organometallics
1998, 17, 457−465. (p) Hughes, R. P.; Kowalski, A. S. Organometallics
1998, 17, 270−273. (q) Curnow, O. J.; Hughes, R. P. J. Am. Chem. Soc.
1992, 114, 5895−5897.
(8) Fagan, P. J.; Ward, M. D.; Calabrese, J. C. J. Am. Chem. Soc. 1989,
111, 1698−1719.
(9) Preparation of 1: to a mixture of [(η5-CpMe5)RuCl]4 (0.89 g,
0.82 mmol) and CNAr (1.41 g, 10.70 mmol) was added CH2Cl2 (25
mL) via a syringe. After the solution was stirred for 24 h, the volatile
components were removed under reduced pressure. The resulting
residue was washed with n-hexane (5 × 10 mL) to give 1 as a pure
orange solid (1.65 g, 94.4%). Mp: 162 °C. 1H NMR (CD3Cl, 23 °C):
δ 1.89 (s, 15 H, CpCH3), 2.43 (s, 12 H, ArCH3), 7.05 (s, 6 H, Ar H)
ppm. 13C{1H} NMR (CD3Cl, 23 °C): δ 10.32 (s, CpCH3), 19.17 (s,
PhCH3), 94.49 (s, CpCCH3), 126.65, 127.60, 134.26, 171.69 (5s, C on
the phenyl rings) ppm. Anal. Calcd for C28H33ClN2Ru: C, 62.20; H,
6.15; N, 12.95. Found: C, 61.80; H, 6.19; N, 12.56. Single crystals
suitable for X-ray diffraction analysis were obtained from a mixture of
CH2Cl2 and n-hexane (1/3) at −25 °C.
(10) Preparation of 2: to a mixture of 1 (0.36 g, 0.73 mmol) and
NaN3 (0.19g, 2.92mmol) was added dry ethanol (30 mL) via a syringe.
After it was refluxed for 6 h, the solution was cooled to room
temperature. The volatile components were removed under reduced
pressure, and the resulting residue was extracted with CH2Cl2. The
solution was filtered, and the filtrate was concentrated to ca. 5 mL to
afford a bright red crystalline solid in the presence of n-hexane (5 mL)
(0.31 g, 90.1%). Mp: 148 °C. 1H NMR (CD3Cl, 23 °C): δ 1.90 (s, 15
H, CpCH3), 2.47 (s, 12 H, ArCH3), 7.10 (s, 6 H, Ar H) ppm. 13C{1H}
NMR (CD3Cl, 23 °C): δ 10.29 (s, CpCH3), 19.11 (s, ArCH3), 94.69
(s, CpCMe), 126.83, 127.60, 129.47, 134.36, 170.57 (5s, C on the
phenyl rings) ppm. IR (KBr, cm−1): 3171 (m), 2104 (s), 2019 (s),
1589 (w), 1261 (m), 1025 (m), 773 (m), 723 (m), 672 (m), 512 (m);
Anal. Calcd for C28H33N5Ru: C, 62.20; H, 6.15; N, 12.95. Found: C,
61.80; H, 6.19; N, 12.56. Single crystals suitable for X-ray diffraction
analysis were obtained from a mixture of THF and Et2O (1/2) at −5
°C.
(11) Preparation of 3 and 4: a suspension of 2 (2.16 g, 4.0 mmol) in
o-xylene (80 mL) was refluxed for 4 days under an argon atmosphere.
The volatile components were removed under reduced pressure. The
resulting residue was extracted with cold THF (0 °C, 3 × 10 mL), and
the solvent was then removed under high vaccum. The resulting
yellow solid was washed with Et2O to afford 3 as a spectrally pure
solid. Single crystals suitable for X-ray diffraction analysis were
obtained from a mixture of THF and Et2O (1/2) at room temperature
(1.62 g, 63%). Mp: 191 °C. 1H NMR (CD3Cl, 23 °C): δ 1.91 (s, 15H,
CpCH3), 2.31 (s, 6 H, ArCH3), 2.40 (s, 12 H, ArCH3), 6.54−6.56 (m,
1 H, NCCAr H), 6.80 (d, 2 H, NCNAr H), 7.06 (s, 6 H, CNAr H)
ppm. 13C{1H} NMR (CD3Cl, 23 °C): δ 10.46 (s, CpCH3), 19.04 (s,
ArCH3), 19.66 (s, ArCH3), 95.98 (s, CpCMe), 117.76 (s, CRu),
126.85, 127.64, 127.71, 129.70, 130.46, 134.52, 147.10 (overlapped,
Ar), 170.60 (s, NCN). IR (KBr, cm−1): 2362 (w), 2164 (s), 2043 (s),
1589 (m), 1262 (m), 1189 (m), 1082 (m), 1029 (m), 768 (s), 753 (s),
669 (s), 522 (m), 504 (s). Anal. Calcd for C37H42N4Ru: C, 69.02; H,
6.58; N, 8.70. Found: C, 69.20; H, 6.54; N, 8.69. Single crystals
suitable for X-ray diffraction analysis were obtained from a mixture of
CH2Cl2 and Et2O (1/3) at −5 °C. The resulting residue after
extraction with cold THF was dissolved in CH2Cl2 and THF (4/6) to
give 4 as colorless crystals at −30 °C (0.62 g, 24.8%). Mp: 351 °C dec.
1H NMR (CD3Cl, 23 °C): δ 1.82 (s, 15 H, CpCH3), 2.17 (s, 6 H,
ArCH3), 4.93 (t, 1 H, NCCAr H), 5.08 (d, 2 H, NCNAr H). 13C{1H}
NMR (CD3Cl, 23 °C): δ 10.10 (s, CpCH3), 17.56 (s, ArCH3), 88.37
(s, CpCMe), 80.48, 90.48, 92.09 (3s, overlapped, Ph), 131.54 (br,
NCN). IR (KBr, cm−1): 3158 (s), 2096 (m), 2044 (s), 1303 (s), 1259
(s), 1152 (s), 1019 (s), 798 (m), 722 (s), 669 (m), 588 (m). Anal.
Calcd for C19H24N2Ru: C, 59.51; H, 6.83; N, 7.30. Found: C, 59.32;
(15) The ionic complex [AsPh4]+[L]− (HL = 2-cyanaminofluoren-9-
one) was reported: Adams, C. J. Chem. Soc., Dalton Trans. 1999,
2059−2064.
(16) (a) Zheng, W. Unpublished results. Similarily, we obtained the
azido isocyanide ruthenium complex [CpMe5RuL2N3] (2′; L =
tBuNC). When 2′ was heated to 120 °C, the two ruthenium
c o m p o u n d s [ C p M e 5 R u L 2 N  C  N t B u ] ( 3 ′ ) a n d
[CpMe5RuL2N(tBu)CN] (4′) were isolated and structurally
characterized (17.0% for 3′ and 26.9% for 4′). To elucidate their
formation, an o-xylene-d10 solution of 3′ or 4′ was warmed and
monitored by 1H NMR spectroscopy. After the solutions were heated
to 120 °C (6 h for 4′ or 12 h for 3′), the isomerization of 3′ or 4′
occurred (3′ ⇌ 4′, Keq(296 K) = [3′]/[4′] = 1.6). Crystal data for 3′:
C25H42N4Ru, Mr = 499.70, monoclinic, C2/c, a = 32.591(6) Å, b =
9.2223(15) Å, c = 20.877(3) Å; β = 111.504(3)°; Crystal data for 4′:
C25H42N4Ru, Mr = 499.70, orthorhombic, Pna21, a = 14.226(3) Å, b =
10.1943(17) Å, c = 19.184(3) Å, α = β = γ = 90°. (b) Mori, S.;
Mochida, T. Organometallics 2013, 32, 283−288.
(17) (a) He, Z.; Zajdlik, A.; St. Denis, J. D.; Assem, N.; Yudin, A. K. J.
Am. Chem. Soc. 2012, 134, 9926−9929. (b) Yagupolskii, L. M.;
Shelyazhenko, S. V.; Maletina, I. I.; Petrik, V, N.; Rusanov, E. B.;
Chernega, A. N. Eur. J. Org. Chem. 2001, 1225−1233. (c) Smith, P. A.
S.; Leon, E. J. Am. Chem. Soc. 1958, 80, 4647−4654.
(18) (a) Crutchley, R. J. Coord. Chem. Rev. 2001, 219−221, 125−155.
(b) Fabre, M.; Bonvoisin, J. J. Am. Chem. Soc. 2007, 129, 1434−1444.
(c) Harb, C.; Kravtsov, P.; Choudhuri, M.; Sirianni, E.; Yap, G. P. A.;
Lever, A. B. P.; Crutchley, R. J. Inorg. Chem. 2013, 52, 1621−1630.
D
dx.doi.org/10.1021/om400547r | Organometallics XXXX, XXX, XXX−XXX