Molybdenum complexes containing ferrocenyl-functionalised arylimido ligands; Crystal structure of 2,6-Pr2i-4-Fc-C≡C-C6H 2N(SiMe3)2

Article abstract of DOI:10.1016/S0277-5387(99)00057-1

The ferrocene-functionalised anilines 2,6-Pr₂ⁱ-4-Fc-C₆H₂NH₂ (3a), 2,6-Pr₂ⁱ-4-Fc-C₆H₂N(SiMe ₃)₂ (3b), 2,6-Pr₂ⁱ-4-Fc-C≡C-C₆H₂NH ₂ (5a) and 2,6-Pr₂ⁱ-4-Fc-C≡C-C₆H ₂N(SiMe₃)₂ (5b) (Fc=ferrocenyl) have been prepared by Pd-catalysed cross-coupling reactions. The crystal structure of 5b has been determined. The NSi₂ plane and the aryl ring plane form a dihedral angle of 89.8 °. The N atom is trigonal planar [C-N distance 1.459(4) A]. The Cp ring and the aryl ring planes, which are connected by the C≡C spacer, form a dihedral angle of 85.8 °. 3a and 5a have been utilised for the preparation of the novel redox-functionalised imido complexes [Mo(N-2,6-Pr₂ⁱ-4-Fc-C₆H₂) ₂Cl₂(DME)] (6) and [Mo(N-2,6-Pr₂ⁱ-4-Fc-C≡C-C₆H ₂)₂Cl₂(DME)] (7) (DME=1,2-dimethoxyethane). Electrochemical investigations by cyclic voltammetry revealed a pronounced interaction between the respective N functional group and the ferrocenyl moiety for all six compounds, which is largest for 6. Elsevier Science Ltd.

Full text of DOI:10.1016/S0277-5387(99)00057-1

Polyhedron 18 (1999) 1815–1819
Molybdenum complexes containing ferrocenyl-functionalised arylimido
ligands; crystal structure of 2,6-Pri2-4-Fc-C;C-C6H2N(SiMe3)2
*
Ulrich Siemeling , Beate Neumann, Hans-Georg Stammler, Oliver Kuhnert
¨
¨
¨
¨
Fakultat fur Chemie, Universitat Bielefeld, Universitatsstrasse 25, D-33615 Bielefeld, Germany
Received 30 November 1998; accepted 19 February 1999
Abstract
The ferrocene-functionalised anilines 2,6-Pr2i -4-Fc-C6H2NH2 (3a), 2,6-Pr2i -4-Fc-C6H2N(SiMe3)2 (3b), 2,6-Pri2-4-Fc-C;C-C6H2NH2
(5a) and 2,6-Pri2-4-Fc-C;C-C6H2N(SiMe3)2 (5b) (Fc5ferrocenyl) have been prepared by Pd-catalysed cross-coupling reactions. The
crystal structure of 5b has been determined. The NSi2 plane and the aryl ring plane form a dihedral angle of 89.8 8. The N atom is trigonal
˚
planar [C–N distance 1.459(4) A]. The Cp ring and the aryl ring planes, which are connected by the C;C spacer, form a dihedral angle
of 85.8 8. 3a and 5a have been utilised for the preparation of the novel redox-functionalised imido complexes [Mo(N-2,6-Pri2-4-Fc-
C6H2)2Cl2(DME)] (6) and [Mo(N-2,6-Pri2-4-Fc-C;C-C6H2)2Cl2(DME)] (7) (DME51,2-dimethoxyethane). Electrochemical inves-
tigations by cyclic voltammetry revealed a pronounced interaction between the respective N functional group and the ferrocenyl moiety
for all six compounds, which is largest for 6.
1999 Elsevier Science Ltd. All rights reserved.
Keywords: Crystal structure; Cyclic voltammetry; Ferrocene, functionalised; Imido ligand, redox-functionalised; Iron; Molybdenum
1. Introduction
glovebox. Solvents and reagents were appropriately dried
and purified by using standard procedures. NMR spectra
were recorded at 300 K with a Bruker DRX 500 spec-
trometer operating at 500.13 MHz for H; TMS was used
as external reference. Cyclic voltammograms were re-
corded with an EG&G Princeton Applied Research Poten-
tiostat/Galvanostat Model 273A; ferrocene or de-
camethylferrocene was used as internal reference. Elemen-
The great current interest in ferrocene-functionalised
ligands is mainly due to the special stereo- and redox-
chemical properties of the ferrocene moiety. Such ligands
have found widespread application for asymmetric
catalysis [1–3] and redox-chemical sensors [4–7], and
their potential for a variety of areas such as, for example,
thermotropic liquid crystals [8] and redox-tunable catalysts
[9] is starting to emerge. The vast majority of ferrocene-
functionalised ligands known to date are phosphanes and
oxygen-, nitrogen- or sulfur-containing macrocycles. In-
vestigations concerning further important ligand platforms
are still rare. We are therefore currently investigating the
use of ferrocene-functionalised (oligo-)pyridine and or-
ganoimido ligands in transition metal chemistry, and here
report on results from our imido chemistry program.
1
tal analyses were performed by the Microanalytical Lab-
i
¨
oratory of the Universitat Bielefeld. 2,6-Pr2-4-I-C6H2NH2
(2a) was prepared from commercially available 2,6-Pri2-
C6H3NH2 and iodine in a degassed aqueous solution of
NaHCO3 [19]. 2,6-Pr2i -4-I-C6H2N(SiMe3)2 (2b) was ob-
tained from 2a by a standard lithiation/silylation sequence
using lithium diisopropylamide and chlorotrimethylsilane.
Ethinylferrocene (4) [20], Pd(PPh3)4 [21] and Pd(dba)2
[22] were prepared according to published procedures.
2.1. Synthesis of 2,6-Pri2-4-Fc-C6H2NH2 (3a)
2. Experimental
ButLi (10.0 cm3 of a 1.70 M solution in pentane, 17.0
mmol) was added slowly to a stirred solution of ferrocene
(1.30 g, 7.00 mmol) in THF (50 cm3) at 2208C. The
mixture was allowed to warm to room temperature and
was stirred for 30 min. Volatile components were removed
in vacuo. The residue was dissolved in THF (30 cm3).
All manipulations were performed in an inert atmos-
phere (purified argon or dinitrogen) by using standard
Schlenk and cannula techniques or
a conventional
*Corresponding author.
0277-5387/99/$ – see front matter
PII: S0277-5387(99)00057-1
1999 Elsevier Science Ltd. All rights reserved.

1816
U. Siemeling et al. / Polyhedron 18 (1999) 1815–1819
Subsequently, a solution of ZnCl2 (0.95 g, 7.00 mmol) in
THF (10 cm3) was added. After stirring of the mixture for
30 min it was added to a solution containing 2a (1.73 g,
5.70 mmol) and a few mg of Pd(PPh3)4 in THF (35 cm3).
The resulting solution was stirred for 15 h at room
temperature and was refluxed for 1 h. It was allowed to
cool to room temperature and was then quenched with 0.10
M HCl (50 cm3) and extracted with CHCl3 (3330 cm3).
The combined organic layers were dried with Na2SO4.
Volatile components (solvents and ferrocene) were re-
moved in vacuo. The crude product was purified by
column chromatography (silica gel, eluent CHCl3) to yield
(C5H4), 84.9 (C;C), 87.2 (C;C), 113.0 (C), 126.4 (Ar
CH), 132.2 (quart Ar C), 140.4 (Cipso). Anal. Calcd for
C24H27NFe (385.3): C, 74.82; H, 7.06; N, 3.64. Found: C,
74.78; H, 7.14; N, 3.50.
2.4. Synthesis of 2,6-Pri2-4-Fc-C;C-C6H2N(SiMe3 )2
(5b)
In analogy to the preparation of 5a, compound 5b (4.15
g, 74%) was obtained as a yellow solid from 2b (3.86 g,
10.6 mmol). 1H NMR (CDCl3): d 0.07 (s, 18 H, SiMe3),
1.18 (d, 3JHH56.9 Hz,12 H, CHMe2), 3.42 (sept, 3JHH56.9
Hz, 2 H, CHMe2), 4.21 (‘t’, apparent JHH51.8 Hz, 2 H,
C5H4), 4.23 (s, 5 H, C5H5), 4.48 (‘t’, apparent JHH51.5
Hz, 2 H, C5H4), 7.17 (s, 2 H, ArH). 13Ch1Hj NMR
(CDCl3): d 2.5 (SiMe3), 25.0 (CHMe2), 27.4 (CHMe2),
65.9 (C5H4), 68.6 (C5H4), 69.9 (C5H5), 71.3 (C5H4), 86.5
(C;C), 119.1 (quart Ar C), 127.2 (Ar CH), 143.8 (quart
Ar C), 147.2 (Cipso). Anal. Calcd for C30H43NSi2Fe
(529.7): C, 68.03; H, 8.18; N, 2.64. Found: C, 67.75; H,
8.32; N, 2.56.
1
3a (2.60 g, 74%) as an orange viscous oil. H-NMR
3
(CDCl3): d 1.30 (d, JHH56.8 Hz,12 H, CHMe2), 2.93
(sept, 3JHH56.8 Hz, 2 H, CHMe2), 3.67 (br s, 2 H, NH2),
4.03 (s, 5 H, C5H5), 4.23 (s, 2 H, C5H4), 4.53 (s, 2 H,
C5H4), 7.12 (s, 2 H, ArH). 13Ch1Hj NMR (CDCl3): d 22.5
(CHMe2), 27.9 (CHMe2), 66.4 (C5H4), 68.0 (C5H4), 69.4
(C5H5), 88.8 (C5H4), 121.5 (Ar CH), 128.5 (quart Ar C),
132.2 (quart Ar C), 138.7 (Cipso). Anal. Calcd for
C22H27NFe (361.3): C,73.14; H, 7.53; N, 3.88. Found: C,
72.82; H, 7.44; N, 3.68.
2.5. Synthesis of Mo(N-2,6-Pri2-4-Fc-C6H2 )2Cl2(DME)
(6)
2.2. Synthesis of 2,6-Pri2-4-Fc-C6H2N(SiMe3 )2 (3b)
Triethylamine (0.58 g, 5.76 mmol), chlorotrimethyl-
silane (1.04 g, 9.60 mmol) and a solution of 3a (0.60 g,
1.92 mmol) in DME (10 cm3) were added sequentially to a
suspension of sodium molybdate (0.20 g, 0.96 mmol) in
DME (20 cm3) placed in a thick-walled Rotaflo ampoule.
The mixture was stirred at 608C for 15 h. Insoluble
material was filtered off and washed with DME (235
cm3). The red solution was reduced to dryness in vacuo.
The remaining solid was washed with n-hexane (335
cm3) affording 6 (0.71 g, 76%) as a deep red, mi-
crocrystalline solid. H NMR (CDCl3): d 1.11 (d, JHH5
6.3 Hz, 24 H, CHMe2), 3.80 (s, 6 H, OMe), 3.94 (m, 8 H,
CHMe2 and OCH2), 4.01 (s, 10 H, C5H5), 4.30 (s, 4 H,
C5H4), 4.61 (s, 4 H, C5H4), 7.13 (s, 4 H, ArH). 13Ch1Hj
NMR (CDCl3): d 24.9 (CHMe2), 27.2 (CHMe2), 62.1
(OMe), 66.3 (C5H4), 68.8 (C5H4), 69.3 (C5H5), 71.2
(OCH2), 85.2 (C5H4), 120.2 (Ar CH), 137.8 (quart Ar C),
144.1 (quart Ar C), 151.6 (Cipso). Anal. Calcd for
C48H60N2Cl2Fe2MoO2 (975.6): C, 59.09; H, 6.20; N,
2.87. Found: C, 59.82; H, 6.44; N, 2.90.
In analogy to the preparation of 3a, compound 3b (2.60
g, 46%) was obtained from 2b (5.00 g, 11.2 mmol) after
one crystallisation of the crude product from hot methanol.
1H NMR (CDCl3): d 0.10 (s, 18 H, SiMe3), 1.23 (d,
3JHH56.9 Hz, 12 H, CHMe2), 3.45 (sept, 3JHH56.9 Hz, 2
H, CHMe2), 3.98 (s, 5 H, C5H5), 4.26 (‘t’, apparent
J
HH51.7 Hz, 2 H, C5H4), 4.62 (‘t’, apparent JHH51.7 Hz,
2 H, C5H4), 7.12 (s, 2 H, ArH). 13Ch1Hj NMR (CDCl3): d
2.5 (SiMe3), 25.1 (CHMe2), 27.4 (CHMe2), 66.3 (C5H4),
68.5 (C5H4), 69.6 (C5H5), 86.5 (C5H4), 121.4 (Ar CH),
133.9 (quart Ar C), 141.5 (quart Ar C), 146.5 (Cipso).
Anal. Calcd for C28H43NSi2Fe (505.3): C, 66.56; H, 8.58;
N, 2.77. Found: C, 66.61; H, 8.74; N, 2.72.
1
3
2.3. Synthesis of 2,6-Pri2-4-Fc-C;C-C6H2NH2 (5a)
Pd(dba)2 (0.17 g, 0.3 mmol) was added to a degassed
solution of ethinylferrocene (4) (3.17 g, 15.1 mmol), 2a
(4.57 g, 15.1 mmol), PPh3 (0.24 g, 0.9 mmol) and CuI (30
mg, 0.2 mmol) in triethylamine (150 cm3) placed in a
thick-walled Rotaflo ampoule. The solution was stirred at
658C for 6 h. The precipitate was filtered off. Volatile
components were removed in vacuo from the filtrate. The
residue was recrystallised from n-hexane to give 5a (2.97
g, 51%) as an orange solid. 1H NMR (CDCl3): d 1.27 (d,
3JHH56.9 Hz,12 H, CHMe2), 2.86 (sept, 3JHH56.9 Hz, 2
H, CHMe2), 3.85 (br s, 2 H, NH2), 4.19 (s, 2 H, C5H4),
4.23 (s, 5 H, C5H5), 4.46 (s, 2 H, C5H4), 7.16 (s, 2 H,
ArH). 13Ch1Hj NMR (CDCl3): d 22.3 (CHMe2), 27.9
(CHMe2), 66.5 (C5H4), 68.4 (C5H4), 69.9 (C5H5), 72.2
2.6. Synthesis of Mo(N-2,6-Pri2-4-Fc-C;C-
C6H2 )2Cl2(DME) (7)
In analogy to the preparation of 6, complex 7 (1.67 g,
79%) was obtained as a deep red, microcrystalline solid
from triethylamine (1.26 g, 11.4 mmol), chlorotrimethyl-
silane (2.25 g, 20.7 mmol), 3b (1.60 g, 4.14 mmol), and
sodium molybdate (0.42 g, 2.07 mmol) in DME (55 cm3).
1H NMR (CDCl3): d 1.06 (d, 3JHH56.6 Hz, 24 H,
CHMe2), 3.51 (s, 6 H, OMe), 3.66 (s, 4 H, OCH2), 3.84

U. Siemeling et al. / Polyhedron 18 (1999) 1815–1819
1817
Table 1
Crystallographic data for compound 5b
Empirical formula
C30H43FeNSi2
529.68
Index ranges
0#h#10, 0#k#19, 222#l#22
0.610
1136
2.12–24.99
Formula weight
Space group
m, mm21
Monoclinic, P21 /c
9.185(7)
16.734(11)
19.273(12)
94.25(6)
2954(3)
F(000)
u range, deg
˚
a, A
˚
b, A
Reflections collected
Unique reflections
Data/restraints/parameters
RF /RF2 [I.2s(I)]
Goodness-of-fit on F2
5543
˚
c, A
5197 (Rint50.0375)
5197/0/317
0.0481/0.1148 (3934 reflections)
1.014
b, deg
3
˚
V, A
Z
4
3
rcalcd, g/cm3
1.191
Largest diff. peak and hole, e/A
0.293 and 20.323
˚
3
(sept, JHH56.6 Hz, 4 H, CHMe2),4.01 (s, 10 H, C5H5),
4.23 (s, 14 H, C5H5 and C5H4), 4.47 (s, 4 H, C5H4), 7.13
(s, 4 H, ArH). 13Ch1Hj NMR (CDCl3): d 24.1 (CHMe2),
27.3 (CHMe2), 62.6 (br, OMe), 64.8 (C5H4), 68.5 (C5H4),
69.5 (C5H5), 71.0 (C5H4), 86.1 (C;C), 89.2 (C;C),
121.9 (quart Ar C), 125.6 (Ar CH), 144.4 (quart Ar C),
152.2 (Cipso). Anal. Calcd for C52H60N2Cl2 Fe2MoO2
(1023.6): C, 61.02; H, 5.91; N, 2.74. Found: C, 61.63; H,
6.05; N, 2.99.
2.7. X-ray crystal structure analysis of 2,6-Pri2-4-Fc-C;
C-C6H2N(SiMe3 )2 (5b)
Scheme 1. Synthesis of the ferrocenyl-functionalised anilines 3 and 5 by
Pd-catalysed cross-coupling reactions.
A yellow crystal with dimensions 0.4030.2030.20 mm
was used for data collection at 173(2) K on a Siemens P3
four-circle diffractometer with graphite-monochromated
structure analysis. A view of the molecule is shown in Fig.
1.
The aryl unit and the ferrocenyl unit are undistorted.
Their respective C–C bond lengths are identical within
˚
Mo Ka radiation (l50.71073 A). The structure was
solved by direct methods. Programs used were Siemens
SHELXTL PLUS [23] and SHELXL 97 [24]. Full-matrix
least-squares refinement on F2 was carried out aniso-
tropically for the non-hydrogen atoms. Hydrogen atoms
were included at calculated positions using a riding model.
Further details are given in Table 1.
˚
experimental error, their average value being 1.40 A for
˚
the C6 ring and 1.42 A for the cyclopentadienyl rings. The
Cp rings are arranged in an eclipsed orientation and exhibit
an average Fe–C bond length of 2.04 A. The acetylene
˚
group is almost linear [C(1)-C(11)-C(12), 176.8(3);
C(11)-C(12)-C(13), 176.5(3)8] and has a C–C distance of
˚
3. Results and discussion
1.207(4) A; the distance between each acetylene carbon
We have investigated a number of ferrocene-bearing
2,6-diisopropylanilines as arylimido ligand precursors for
the synthesis of redox-functionalised organoimido com-
plexes. The synthesis of the anilines is outlined in Scheme
1.
Negishi coupling [10] of FcZnCl (1) with 2,6-Pri2-4-I-
C6H2NH2 (2a) and 2,6-Pri2-4-I-C6H2N(SiMe3)2 (2b)
yielded 2,6-Pr2i -4-Fc-C6H2NH2 (3a) and 2,6-Pri2-4-Fc-
C6H2N(SiMe3)2 (3b), respectively. Similarly, Sonogashira
coupling [11] of FcC;CH (4) with 2a and 2b afforded
2,6-Pri2-4-Fc-C;C-C6H2NH2 (5a) and 2,6-Pri2-4-Fc-C;C-
C6H2N(SiMe3)2 (5b), respectively. It is noteworthy that
the presence of an unprotected primary amino group in 2a
and 3a does not affect the product yields.
˚
Fig. 1. ORTEP drawing of 5b. Selected bond lengths (A) and angles
(deg): Si(1)–N(1) 1.749(3), Si(2)–N(1) 1.747(3), C(15)–C(19) 1.522(4),
C(17)–C(28) 1.522(4); Si(1)–N(1)–Si(2) 125.02(16), C(14)–C(15)–
C(19) 118.8(3), C(18)–C(17)–C(28) 118.6(3).
5b has been investigated by a single-crystal X-ray

1818
U. Siemeling et al. / Polyhedron 18 (1999) 1815–1819
atom and the sp2 carbon atom attached to it is 1.431(4)
[C(1)–C(11)] and 1.439(4) A [C(12)–C(13)], respective-
Table 2
Formal electrode potentials (in V, vs ferrocene/ferrocenium) for the
oxidation process of the present ferrocenyl-functionalised compounds in
dichloromethane solutiona
˚
ly. These values are unexceptional and compare well
with those of other structurally characterised (phenyl-
ethynyl)ferrocenes [12–14]. A striking feature of the
structure of 5b is the fact that the Cp ring plane and the
aryl ring plane, which are connected by the acetylene
spacer, are almost perpendicular to each other, their
dihedral angle being 85.88. This may be the result of
crystal packing forces, but it may also reflect an interaction
of each aromatic ring with a different one of the two
orthogonal p bonds of the acetylene unit. Although such a
perpendicular orientation is not unprecedented [12], we
note that in the majority of related compounds a more or
less coplanar arrangement of the rings has been observed
[12–14]. Owing to the severe steric congestion around the
amino group, the NSi2 plane is orthogonal to the aryl ring
plane (dihedral angle 89.8 8). The N atom is trigonal planar
(sum of angles 360 8), and the C–N distance has a value of
Compound
3a
5a
3b
5b
6
7
09
E0 / 1
20.10
10.05
20.03
10.07
10.10
10.05
10.03
10.13
10.12
10.07
09b
DE
a Conditions: 298 K; supporting electrolyte, NBu4PF6 (0.1 M); Pt disk
working electrode, Ag wire pseudo-reference electrode, Pt wire counter
electrode; scan rate, 0.1 V/s; solute concentration, 1 mM; confidence limit
0.01 V.
b Referenced to the respective parent aniline (3a or 5a).
in accord with a distorted octahedral core geometry with
cis coordinating DME and imido ligands and a trans
arrangement of the chloro ligands, as is commonly ob-
served for bis(imido) complexes of the type
[Mo(NR)2Cl2(DME)].
6 and 7 are rare examples of ferrocenyl-functionalised
transition-metal imido complexes, the only previous exam-
ple being, to the best of our knowledge, the polyoxo-
ymetallate [(FcN)Mo6O18]22 published recently by Maatta
and coworkers [17,18].
˚
1.459(4) A. In comparison, the sterically less crowded
N,N,N9,N9-tetrakis(trimethylsilyl)-para-phenylenediamine
exhibits slightly smaller values for the C–N bond length
˚
(1.44 A) and the NSi2 –C6 dihedral angle (838) [15].
Reaction of 3a and 5a under standard ‘one-pot’ con-
ditions [16] with sodium molybdate in dimethoxyethane
(DME) in the presence of triethylamine and chlorotri-
methylsilane gave the bis(imido)molybdenum complexes
[Mo(N-2,6-Pri2-4-Fc-C6H2)2Cl2(DME)] (6) and [Mo(N-
2,6-Pri2-4-Fc-C;C-C6H2)2Cl2(DME)] (7), respectively, in
high yields (Scheme 2). Their spectroscopic data are fully
The electrochemical behavior of the new ferrocene-
functionalised compounds has been investigated by cyclic
voltammetry (Table 2).
09
The DE values, referenced to the respective parent
aniline, range from 0.05 (5b) to 0.13 V (6) and prove an
interaction between the ferrocenyl unit and the N func-
tional group. Bearing in mind that the electronic influence
of the MoCl2(DME) fragment is shared between two
ferrocenyl groups in the case of the bis(imido) complexes,
one can conclude that the interaction is quite pronounced
for 7 and especially for 6, which shows the largest
0
´
DE value altogether. The fact that in comparison to the
parent anilines 3a and 5a the potentials of the silylated
derivatives 3b and 5b are shifted anodically is most likely
due to the orthogonal arrangement of the NSi2 plane and
the aromatic C6 ring plane, which effectively prevents
electron-donating nN /p-delocalisation, as is the case in the
closely related N,N,N9,N9-tetrakis(trimethylsilyl)-para-
phenylenediamine [15].
We are currently exploring the use of 6 and 7 as
precursors for redox-tunable olefin metathesis catalysts of
the type [Mo(NR1)(CHR2)(OR3)2] [16] and will report on
our findings in due course.
Supplementary data
Supplementary data concerning the crystal structure
determination of 5b are available from the CCDC, 12
Union Road, Cambridge CB2 1 EZ, UK on request,
quoting the deposition number 111895.
Scheme 2. Synthesis of complexes 6 and 7.

U. Siemeling et al. / Polyhedron 18 (1999) 1815–1819
1819
Catalyzed Cross-Coupling Reactions, Wiley-VCH, Weinheim, 1998,
ch. 1.
Acknowledgements
[11] K. Sonogashira, in: F. Diederich, P.J. Stang (Eds.), Metal-Catalyzed
Cross-Coupling Reactions, Wiley-VCH, Weinheim, 1998, ch. 5.
[12] H. Fink, N.J. Long, A.J. Martin et al., Organometallics 16 (1997)
2646.
[13] J.T. Lin, J.J. Wu, C.-S. Li, Y.S. Wen, K.-J. Lin, Organometallics 15
(1996) 5028.
This work was financially supported by the Deutsche
Forschungsgemeinschaft and the Fonds der Chemischen
Industrie. We thank Mr. Alexander Salmon for recording
the cyclic voltammograms.
[14] R.P. Hsung, C.E. Chidsey, L.R. Sita, Organometallics 14 (1995)
4808.
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