Synthesis and characterization of half-sandwich Ir and Ru complexes containing Mnt ligand (Mnt = maleonitriledithiolate)

Article abstract of DOI:10.1016/j.inoche.2007.07.023

The reaction of [Cp^*IrCl₂]₂ and [(p-Cymene)RuCl₂]₂ with disodium maleonitriledithiolate (Na₂Mnt) yield the 16-electron complexes Cp^*Ir(Mnt) (1) and [(p-Cymene)Ru(Mnt)] (2). Compl

Full text of DOI:10.1016/j.inoche.2007.07.023

Inorganic Chemistry Communications 10 (2007) 1222–1225
www.elsevier.com/locate/inoche
Synthesis and characterization of half-sandwich Ir and Ru
complexes containing Mnt ligand (Mnt = maleonitriledithiolate)
*
Wei-Guo Jia, Ying-Feng Han, Jia-Sheng Zhang, Guo-Xin Jin
Shanghai Key Laboratory of Molecular Catalysis and Innovative Material, Department of Chemistry, Fudan University, 200433 Shanghai, PR China
Received 8 June 2007; accepted 26 July 2007
Available online 3 August 2007
Abstract
The reaction of [Cp*IrCl2]2 and [(p-Cymene)RuCl2]2 with disodium maleonitriledithiolate (Na2Mnt) yield the 16-electron complexes
Cp*Ir(Mnt) (1) and [(p-Cymene)Ru(Mnt)] (2). Complexes 1 and 2 can further react with PPh3 to form the corresponding 18-electron
complexes Cp*Ir(Mnt)PPh3 (3) and [(p-Cymene)Ru(Mnt)PPh3] (4). All complexes have been fully characterized by IR and NMR spec-
troscopy, as well as elemental analysis. The molecular structures of 1 and 4 have been confirmed by X-ray crystallography.
Ó 2007 Elsevier B.V. All rights reserved.
Keywords: Iridium; Ruthenium; Half-sandwich complexes; Maleonitriledithiolate ligand; Structure
Dithiolene compounds as ligands have been extensively
studied over the past 40 years due to their non-innocent
bonding with transition metals [1,2]. In particular, a series
of transition metal complexes with Mnt lignand (Mnt =
maleonitriledithiolate) have been under considerable
debate owing to their novel properties such as redox, mag-
netism, conducting and non-linear optics [3]. Compared
with Ni and Cu complexes containing the Mnt ligand
which have been extensively studied [4], the half-sandwich
transition metal complexes containing Mnt ligand have rel-
atively rarely been investigated [5]. In previous work, we
have already reported the synthesis of the 16-electron
‘‘pseudo-aromatic’’ half-sandwich complexes [Cp*M{E2C2-
(B10H10)}] (M = Co, Rh, Ir; E = S, Se), [(p-Cymene)Ru
{E2C2(B10H10)}] (E = S, Se) [6], and suggests that this spe-
cies may be promising for further transformations owing to
its electron deficiency at the metal center. These complexes
have been used as models to study the Lewis base adduct
containing N or N-heterocyclic carbene ligands to form sta-
ble 18-electron complexes which have mono-, bi-, tri- and
tetra- nuclear molecular structures [7].
Aiming at the development of versatile and rational
methods for the synthesis of 16-electron half-sandwich
Cp*Ir(III) and (p-Cymene)Ru(II) complexes, Na2Mnt has
been chosen as dithiolene ligand. The red complex
Cp*Ir(Mnt) (1) and dark-red [(p-Cymene)Ru(Mnt)] (2)
were synthesized by the reaction of the half-sandwich irid-
ium dichloride complex [{Cp*IrCl(l-Cl)}2] [8] and ruthe-
nium dichloride complex [{(p-Cymene)RuCl(l-Cl)}2] [9]
with disodium maleonitriledithiolate (Na2Mnt) [10] in eth-
anol solution. The complexes 1 and 2 can further react with
PPh3 to give the complexes Cp*Ir(Mnt)PPh3 (3) [11] and
[(p-Cymene)Ru(Mnt)PPh3] (4), respectively (Scheme 1).
The complex 3 is known, but the synthetic method for 3
in this paper is different from the literature reported [5b].
The new complexes 1, 2 and 4 are neutral and air-stable
in solid state. They can be soluble in polar organic solvents,
such as THF, DMF and CH2Cl2. The IR spectra of these
complexes in the solid state all exhibit intense C„N
stretching at about 2200 cmÀ1. The molecular structures
of 1 and 4 have been determined by X-ray single crystal dif-
fraction method. The single crystals of 1 and 4 were
obtained by slow diffusion of hexane into a concentrated
solution of the corresponding complex in dichloromethane
at room temperature, respectively [12].
*
Corresponding author. Tel.: +86 21 65643776; fax: +86 21 65641740.
E-mail address: gxjin@fudan.edu.cn (G.-X. Jin).
1387-7003/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2007.07.023

W.-G. Jia et al. / Inorganic Chemistry Communications 10 (2007) 1222–1225
1223
Cl
Cl
Cl
M
M
+ Na2Mnt
+ PPh3
S
M
M
S
PPh3
S
C
S
C
C
Cl
C
NC
NC
CN
CN
M = Ir (3)
M = Ir (1)
= Cp*
= p-Cymene M = Ru (2)
= Cp*
= p-Cymene M = Ru (4)
Scheme 1. Synthesis of complexes 1, 2, 3 and 4.
The iridium(III) center in complex 1 adopts a two-leg-
ged piano-stool conformation with five-coordinate geome-
try, assuming the Cp* ligand functions as three coordinate
ligand (Fig. 1). The mononuclear 16-electron dithiolene
complex 1 corresponds to point group symmetry C2v with
two perpendicular mirror planes, in which the two essen-
tially planar five-membered rings Cp* and IrS2C2 are
arranged perpendicular to each other with the dihedral
angle being 88.449(181)°. It is interesting that the complex
1 contains an almost planar metallacycle IrC2S2. The five-
membered ring is bent with a dihedral angle along SÁ Á ÁS
vector of 178.73(16)°, which can be also found in the com-
plex Cp*Ir[C2S2(B10H10)] (178.07°) [13]. The Ir–S bond
˚
lengths (av. 2.2284(19) A) are significantly shorter than in
the 18-electron oligosulfide precursor complex Cp*IrP-
˚
Me3(SH)2 (av. 2.375 A) [14], but comparable with the
corresponding Ir–S bond distances in the 16-electron
complexes Cp*Ir[S2C2(COOMe)2] (av. 2.233 A) [15],
˚
Fig. 2. Four units in stacking of the complex 1. All hydrogen atoms are
omitted for clarity. Ir, C, N and S atoms are represented by pink, gray,
blue, and yellow. (For interpretation of the references to color in this
figure legend, the reader is referred to the web version of this article.)
Cp*Ir[C2S2(B10H10)] (av. 2.263 A) [13] and Cp*Ir(S2C6H4)
˚
˚
(av. 2.248 A) [16].
There are two pairs of independent molecules in the unit
cell of 1 (Fig. 2). The structure is similar to Cp*Ir[C2S2-
(B10H10)]. The two molecules adopt the different tropism
and form rectangular hole along the b-axis in the packing
structure, the distances between the two N atoms of Mnt
ligand and the least-square plane of Cp* (plane C) are
˚
˚
of four C atoms of Mnt ligand are 3.6224 A (3.5196 A,
˚
˚
˚
3.5447 A, 3.6991 A, 3.7264 A). The two planes C4N2 and
Cp* dihedral angle is 8.637(345)°, which shows the p–p
stacking interaction. The neighboring molecules of 1 are
paired and staggered in face to face fashion along the C–
C edge of Mnt ligand forming the two parallel planes
˚
3.3300 and 3.3745 A, respectively, and the average lengths
˚
(planes A and B) with an average separation of 3.7450 A,
which indicates the presence of weak p–p stacking interac-
tion (Fig. 2). The two different kinds of intracyclic p–p
interaction decide the special packing shape.
In Fig. 3, the ruthenium(III) center adopts a three-leg-
ged piano-stool conformation in complex 4 that possess a
p-Cymene ruthenium half-sandwich tripod structure in
which two legs are sulfur atoms from the Mnt chelate
ligand and the third leg is phosphorous from the PPh3
ligand.
The complex 2 takes up PPh3 to give coordinative satu-
rated 18-electron products, in which the dihedral angle
RuS2/S2C2 along the SÁ Á ÁS vector is 178.659(99)°, and the
dihedral angle between the p-Cymene fragment and the
five-membered ring of RuS2C2 is 54.595(231)°, which is devi-
ated from the vertical plane because of the repulsion from the
Fig. 1. Molecular structure of the Cp*Ir(mnt) (1); all hydrogen atoms are
omitted for clarity. Selected distances (A) and angels (°): Ir(1)–S(1)
2.2254(19), Ir(1)–S(2) 2.2314(19), C(1)–C(2) 1.337(10); S(1)–Ir(1)–S(2)
88.58(7).
˚
˚
PPh3 ligand. The Ru–S bond lengths (av. 2.3531(13) A) are

1224
W.-G. Jia et al. / Inorganic Chemistry Communications 10 (2007) 1222–1225
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Fig. 3. Molecular structure of the p-CymeneRu(mnt)PPh3 (4); All
˚
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slightly shorter than the corresponding complex (p-Cymene)
Ru[S2C2(B10H10)](PMe3) (av. 2.392(1) A) [17].
˚
In summary, half-sandwich Ir and Ru complexes with
Mnt ligands have been synthesized and characterized.
The 16-electron complexes Cp*Ir(mnt) (1) and [(p-Cyme-
ne)Ru(mnt)] (2) react with PPh3 to form the corresponding
18-electron complexes Cp*Ir(Mnt)PPh3 (3) and [(p-Cyme-
ne)Ru(Mnt)PPh3] (4). The preparation of another 18-elec-
tron Mnt complexes of Ir and Ru with the Lewis base
containing N of poly-pyridine or C of N-heterocyclic car-
bene ligands are now in progress.
[6] (a) G.X. Jin, Coord. Chem. Rev. 248 (2004) 587;
(b) G.X. Jin, in: C.G. Screttas, B.R. Steele (Eds.), Perspectives in
Organometallic Chemistry, RSC Cambridge Press, Cambridge, UK,
2003, p. 47.
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188;
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Acknowledgements
Financial support by the National Science Foundation
of China for Distinguished Young Scholars (20531020,
20421303), by the National Basic Research Program of
China (2005CB623800) and by Shanghai Science and Tech-
nology Committee (05JC14003, 06XD14002) is gratefully
acknowledged.
(g) M. Herberhold, G.X. Jin, H. Yan, W. Milius, B. Wrackmeyer,
Eur. J. Inorg. Chem. (1999) 873;
(h) S.Y. Cai, J.Q. Wang, G.X. Jin, Organometallics 24 (2005) 4226;
(i) G.X. Jin, J.Q. Wang, Dalton Trans. (2006) 86;
(j) S.Y. Cai, Y.J. Lin, G.X. Jin, Dalton Trans. (2006) 912;
(k) J.Q. Wang, G.X. Jin, Inorg. Chem. Commun. 10 (2007) 463.
[8] C. White, A. Yates, P.M. Maitlis, Inorg. Synth. 29 (1992) 228.
[9] M.A. Bennett, T.N. Huang, T.W. Matheson, A.K. Smith, Inorg.
Synth. 21 (1982) 74.
[10] A. Davison, R.H. Holm, Inorg. Synth. 10 (1982) 8.
[11] Synthesis of 1: [Cp*IrCl2]2(398 mg, 0.5 mmol) was added to a solution
of Na2Mnt (186 mg, 1 mmol) in degassed ethanol (50 mL) in a
Schlenk tube and kept at room temperature to stir for 16 h. The color
of the solution changed slowly from orange-yellow to red. After
removal of the solvent, the residue was redissolved in 3 mL of
dichloromethane and chromatographed on silica gel. Elution with
Appendix A. Supplementary material
CCDC 649877 contains the supplementary crystallo-
graphic data for this paper. These data can be obtained free
of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.
html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK, fax:
(+44) 1223-336-033, or e-mail: deposit@ccdc.cam.ac.uk.
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.inoche.2007.
07.023.
dichloromethane gave
a red zone. Evaporation under reduced
pressure and crystallization from CH2Cl2/hexane afford 1(384 mg
82%). Anal. Calcd. for C14H15IrN2S2(%): C 35.96, H 3.23, N 5.99.
Found: C 35.62, H 3.46, N 5.88, 1H NMR (500 M CDCl3, ppm):
d = 2.19 (s, g5-C5H5, 10H). IR (KBr disk): m = 2205 cmÀ1 (–CN).
Synthesis of 2: [(p-Cymene)RuCl2]2(306 mg, 0.5 mmol) was added to a
solution of Na2Mnt (186 mg, 1 mmol) in degassed ethanol (50 mL) in
a Schlenk tube and kept at room temperature to stir for 16 h. The
color of the solution changed slowly from red to dark-red. After
removal of the solvent, the residue was redissolved in 3 mL of
dichloromethane and chromatographed on silica gel. Elution with
dichloromethane gave a dark-red zone. Evaporation under reduced
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W.-G. Jia et al. / Inorganic Chemistry Communications 10 (2007) 1222–1225
1225
pressure and crystallization from CH2Cl2/hexane afford 2(285 mg
76%). Anal. Calcd. for C14H14RuN2S2(%): C 44.78, H 3.75, N 7.46
Found: C 44.62, H 3.79, N 7.39 . 1H NMR (500 M CDCl3, ppm):
d = 1.14 (m, (CH3)2, 6H), 1.70 (s, CH3, 3H), 2.71 (br, CH, 1H), 5.04
(d, aromatic, 2H), 5.45 (d, aromatic, 2H), IR (KBr disk): m = 2196
(–CN) cmÀ1. Synthesis of 4: [p-CymeneRu(Mnt)] (38 mg, 0.1 mmol)
was added to a solution of PPh3 (26.2 mg, 0.1 mmol) in dichloro-
methane (20 mL) and kept at room temperature to stir for 4 h. After
removal of the solvent. The residue was crystallization from CH2Cl2/
hexane afford 4 (57.3 mg 90%). Anal. Calcd. for C32H29RuN2S2P (%):
C 60.17, H 4.73, N 4.38. Found: C 60.22, H 4.80, N 4.30. 1H NMR
(500 MHz, CDCl3, ppm): d = 1.12 (m, (CH3)2, 6H), 1.69 (s, CH3, 3H),
2.71 (br, CH, 1H), 5.00 (d, aromatic, 2H), 5.44 (d, aromatic, 2H), 7.46
(br, (C6H5)3, 15H). IR (KBr disk): m = 2193 cmÀ1 (–CN).
deposited in the Cambridge Crystallographic Data Center, CCDC
649877(1) and 649878 (4) for complexes 1 and 4. Data for the crystal
structure analysis of complex 1 (C14H15IrN2S2, Mr = 467.60) crystal-
ꢀ
˚
lized in the triclinic space group P1 with a = 8.835(3) A,
˚
˚
b = 12.992(4) A, c = 14.453(5) A
,
˚
a = 98.399(4)°, b = 97.728(4)°,
c = 106.045 (4)°, V = 1550.4(9) A , Z = 4, Dc = 2.003 g cmÀ3
,
3
R1 = 0.0367, wR2 = 0.0868 for final data and R1 = 0.0480,
wR2 = 0.0899 for final all data, GOF = 0.983; data for the crystal
structure analysis of complex 4 (C33H31Cl2N2PRuS2, Mr = 722.66)
crystallized in the monoclinic space group P2(1)/n with
˚
˚
˚
a = 12.060(7) A, b = 17.698(10) A, c = 15.478(9) A, b = 96.227(9)°,
3
V = 3284(3) A , Z = 4, Dc = 1.462 g cmÀ3
, R1 = 0.0514, wR2 =
˚
0.1055 for final data and R1 = 0.0896; wR2 = 0.1164 for final all
data, GOF = 0.913.
[12] Diffraction data of 1 and 4 were collected on a Bruker Smart APEX
CCD diffractometer with graphite-monochromated Mo Ka radiation
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142.
˚
(k = 0.71073 A). All the data were collected at room temperature and
the structures were solved by direct methods and subsequently refined
on F2 by using full-matrix least-squares techniques (SHELXL),
SADABS absorption corrections were applied to the data, all non-
hydrogen atoms were refined anisotropically, and hydrogen atoms
were located at calculated positions. Crystallography data (excluding
structure factors) for the structures reported in this paper have been