Synthesis of symmetrically and unsymmetrically 3,5-dimethylbenzyl- substituted 1,1′-ferrocene diamines

Article abstract of DOI:10.1016/j.jorganchem.2011.06.043

1,1′-Ferrocene diamides have shown remarkable efficacy as supporting ligands for electrophilic metal centers. While different substituents have been used, most ferrocene diamines are employed as dianionic precursors, thus limiting the possible scope and r

Full text of DOI:10.1016/j.jorganchem.2011.06.043

Journal of Organometallic Chemistry 696 (2011) 4090e4094
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis of symmetrically and unsymmetrically 3,5-dimethylbenzyl-substituted
1,10-ferrocene diamines
*
Jason A. Lee, Bryan N. Williams, Kevin R. Ogilby, Kevin L. Miller, Paula L. Diaconescu
Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
a r t i c l e i n f o
a b s t r a c t
1,10-Ferrocene diamides have shown remarkable efficacy as supporting ligands for electrophilic metal
centers. While different substituents have been used, most ferrocene diamines are employed as dianionic
precursors, thus limiting the possible scope and reactivity of these metal complexes. The use of a 3,5-
dimethylbenzyl (xylyl) substituent allowed the successful synthesis of tri- and tetra-substituted ferro-
cene 1,10-diamines, providing monoanionic and neutral pro-ligands. In addition, an unsymmetrically
disubstituted 1,10-ferrocene diamine was obtained containing both the 3,5-dimethylbenzyl and t-
butyldimethylsilyl substituents.
Article history:
Received 10 May 2011
Received in revised form
29 June 2011
Accepted 30 June 2011
Keywords:
Ferrocene
Xylyl
Ó 2011 Elsevier B.V. All rights reserved.
CeN coupling
1. Introduction
thus far, the ferrocene-based ligands synthesized by our group have
been limited to dianionic variants. Furthermore, all the pro-ligands
The utilization of 1,10-ferrocene diamides as supporting ligands
for electrophilic metal centers has seen extensive exploration by
several groups [1e32]. A variety of substituents, consisting mainly
of silyl and aryl moieties, have often been attached to the nitrogen
atoms of the 1,10-ferrocene diamides. These ligands add to the
number of excellent non-cyclopentadienyl alternatives for the
ubiquitous cyclopentadienyl group 3 metal chemistry [33e36].
Ferrocene diamides have numerous advantages: (i) cis-coordina-
tion of the two amide donors is enforced, effectively blocking one
side of the metal center; (ii) the ferrocene backbone can accom-
modate electron density changes at the metal center by varying the
geometry around iron; (iii) other ligands and substrates coordinate
perpendicularly to the plane formed by the two amide nitrogens,
iron, and the metal, giving clear access to the electrophilic center;
(iv) a weak interaction of donoreacceptor type between iron and
the electrophilic metal center is possible and might influence the
reactivity of the complex; (v) iron(II) can be oxidized to iron(III),
potentially resulting in enhanced reactivity at the electrophilic
metal center [7,16,37].
have been symmetrical with respect to the nitrogen substituents.
With this in mind, we report on achieving two goals: (1) the
expansion of 1,10-disubstituted ferrocene amides to neutral and
monoanionic variations, and (2) the synthesis of an unsymmetrical
dianionic precursor.
2. Results and discussion
2.1. Formation of 1,10-ferrocene dixylyl diamine
The synthetic procedure for the dixylyl-functionalized diamine
fc(NHXy)2 (1, fc ¼ 1,10-ferrocenylene, Xy ¼ 3,5-Me2C6H3, Eq. (1)) was
adapted from a previously reported procedure employed for
fc(NHMes)2 (Mes ¼ 2,4,6-Me3C6H2) [38]. The precursor fc(NH2)2
reacted with 3,5-dimethylbromobenzene, NaOtBu, and 1.75e4 mol%
Pd(dba)(BINAP) (dba ¼ dibenzylideneacetone, BINAP ¼ 2,20-bis
(diphenylphosphino)-1,10-binaphthyl) at 100 ꢀC in toluene for 2
days under an inert atmosphere (Eq. (1)). The product was charac-
terized by 1H and 13C NMR spectroscopy (Figs. S1 and S2) as well as
elemental analysis. Comparisons can be made between 1 and the
previously characterized fc(NHSitBuMe2)2 or fc(NHMes)2. In the 1H
NMR spectrum of 1, the ferrocene protons are split into two broad
peaks at 4.18 and 3.89 ppm, while the 1H NMR spectrum of
fc(NHSitBuMe2)2 shows two broad singlets at 3.84 and 3.82 ppm.
The 1H NMR spectrum of fc(NHMes)2 is also similar, with the
ferrocene protons located at 3.80 and 3.78 ppm. In compound 1, the
Previous research in our group has not only explored the use of
these ligands with d0fn metals, but also variation of the nitrogen
substituents [37]. While these substituents afford remarkable
alterations in reactivity, solubility, electronic and steric properties,
* Corresponding author. Tel.: þ1 310 794 4809; fax: þ1 310 206 4038.
E-mail address: pld@chem.ucla.edu (P.L. Diaconescu).
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.06.043

J.A. Lee et al. / Journal of Organometallic Chemistry 696 (2011) 4090e4094
4091
amine protons are observed at 4.56 ppm, a significant downfield
shift from the amine protons in fc(NHSitBuMe2)2, observed at
2.07 ppm, but similar to the downfield shift of the amine protons in
fc(NHMes)2, which appear at 4.05 ppm. The methyl protons in 1 are
found at 2.17 ppm, similar to the methyl protons in fc(NHMes)2,
which are found at 2.17 and 2.12 ppm. Overall, the 1H NMR spectrum
of 1 is similar to the closely related fc(NHMes)2.
xylyl and amine (NH) protons (6.51, 6.44, and 4.75 ppm) and the
corresponding N(Xy)2 protons (7.21 and 6.60 ppm).
Br
NH
NH
N
1.2 NaOtBu
(3)
Fe
Fe
1.75-4 mol%
Pd(dba)BINAP
toluene
H
N
3 NaOtBu
100 oC, 8 d
Br
1.75-4 mol %
NH2
NH
Pd(dba)BINAP
56%
3
1
Fe
Fe
(1)
+
2
toluene
100 C, 48 h
91%
NH2
NH
1
2.4. 1,10-Ferrocene monoxylyl diamine
The successful isolation and characterization of 3 led us to
investigate whether 1,10-ferrocene monoxylyl diamine, 4, could be
synthesized and isolated (Scheme 1). From fc(NH2)2, 1 equivalent of
both 3,5-dimethylbromobenzene and NaOtBu in the presence of
1.75e4 mol% Pd(dba) (BINAP) led to the formation of 4. Similar to
the incomplete conversion of 1 to 3, the formation of 4 stopped
after 70% of the initial ferrocene diamine was consumed, as
assessed by 1H NMR spectroscopy. However, much like 3, solubility
differences allowed the separation of 1 and 4, leading to the
isolation of 4 in 51% yield. As with 3, there is a reduction of
symmetry observed in the 1H NMR spectrum of 4 when compared
to the starting material. The number of peaks for the ferrocene
protons increases from 2 to 4 (3.74 and 3.66 ppm in fc(NH2)2 to 4.19,
3.91, 3.73, and 3.62 ppm in 4, Fig. S10).
2.2. 1,10-Ferrocene tetraxylyl diamine
Small amounts of byproducts present during the synthesis of 1
suggested that the amine nitrogens may be substituted with
additional xylyl groups. Indeed, from 1, an additional 2 equivalents
of 3,5-dimethylbromobenzene,
3
equivalents of NaOtBu, and
1.75e4 mol% Pd(dba)(BINAP) yielded fc(NXy2)(NXy2), 2, in 68%
yield (Eq. (2)). Compound 2 was characterized by 1H and 13C NMR
spectroscopy (Figs. S3 and S4); while the proton resonances in the
1H NMR spectrum appear to be similar to those of 1, there are
noticeable shifts of the ferrocene signals from 4.17 and 3.89 ppm in
1 to 4.26 and 4.07 ppm in 2, and the o,o0-xylyl-H signals shift from
6.52 ppm in 1 to 7.23 ppm in 2. Additionally, the disappearance of
the amine proton resonance supports the formation of 2.
2.5. Unsymmetrically substituted 1,10-ferrocene diamine
Br
With the successful isolation of 4, the isolation of an unsym-
2
metrically substituted 1,10-ferrocene diamine was explored.
NH
NH
N
N
t
3 NaOtBu
Compound 4 was combined with triethylamine and BuMe2SiCl in
(2)
Fe
Fe
dichloromethane for 14 h at room temperature to generate
fc(NHXy)(NHSitBuMe2) (5) in 60% yield (Scheme 1). Analysis of the
1H and 13C NMR spectra confirms the formation of 5 (Figs. S12 and
S13): the NH2 protons at 1.62 ppm in 4 are replaced by the amine
proton signal at 1.84 ppm and the t-butyl and methyl protons of the
t-butyldimethylsilyl substituent are found at 0.85 and 0.12 ppm,
respectively. These signals exhibit an upfield shift with respect to
fc(NHSitBuMe2)2 (amine proton signal at 2.08 ppm and t-butyl and
methyl signals at 0.93 and 0.17 ppm, respectively). In addition, the
signals for the xylyl and xylyl amine protons have shifted with
respect to the starting compound 4; while the aryl and methyl
peaks have hardly shifted from 6.64, 6.46, and 2.22 ppm in 4 to
6.64, 6.45, and 2.21 ppm in 5, the amine proton has moved upfield
from 5.68 ppm in 4 to 5.05 ppm in 5.
1.75-4 mol%
Pd(dba)BINAP
toluene
100 oC, 14 h
68%
1
2
2.3. 1,10-Ferrocene trixylyl diamine
During one of the reactions to form 2, an intermediate, the tri-
xylyl species fc(NHXy)(NXy2), 3, was observed. Separately, the
formation of 3 from 1 was monitored via 1H NMR spectroscopy, by
which it was determined that there was a 75% conversion from 1
after8 days (Eq. (3)). Attempts tooptimize the reaction conditions by
varying the amount of Pd(dba)(BINAP) did not increase conversion,
while additional equivalents of NaOtBu led to the formation of 2.
Fortunately, 3 is sparingly soluble in hexanes, unlike 1; as a conse-
quence, 3 was easily isolated in 56% yield. As expected, a reduction of
symmetry was observed in the 1H NMR spectrum of 3 compared to 1
and 2 (Fig. S5): the ferrocene proton signals have increased from 2
peaks (4.17 and 3.89 ppm) to 4 peaks (4.31, 4.17, 4.01, and 3.92 ppm).
Additionally, separate resonances are observed for the aromatic
Br
Si
Cl
NH2
NH
NH
NH
NaOtBu
1.2 Et3N
Fe
Fe
Fe
1.75-4 mol%
CH2Cl2
25 oC, 14 h
60%
NH2 Pd(dba)BINAP
toluene
100 oC, 48 h
NH2
Si
5
4
51%
Scheme 1. Synthesis of 4 and 5.

4092
J.A. Lee et al. / Journal of Organometallic Chemistry 696 (2011) 4090e4094
3. Conclusions
1H NMR (500 MHz, C6D6):
d, ppm: 6.52 (s, 4H, d), 6.46 (s, 2H, a),
4.56 (s, 2H, f), 4.17 (t, 4H, h), 3.89 (t, 4H, i), 2.17 (s, 12H, b). 13C NMR
The use of a xylyl substituent allowed the successful synthesis of
a series of 1,10-ferrocene diamines. Characterization by 1H and 13C
NMR spectroscopy indicates that the amine proton peaks of
fc(NHXy)2 (1) appear more downfield than those of the previously
(126 MHz, C6D6): d, ppm: 146.1 (e), 138.3 (c), 120.7 (a), 113.0 (d),
100.5 (g), 64.8 (i), 62.8 (h), and 21.2 (b). Anal. (%) for C26H28FeN2
Calcd: C, 73.59; H, 6.65; N, 6.60; Found: C, 73.86; H, 6.44; N, 6.42.
reported fc(NHSitBuMe2)2. Further variations from
1 led to
4.2. Synthesis of 2
fc(NXy2)2 (2) and fc(NHXy)(NXy2) (3), while reactions carried out
from fc(NH2)2 led to the formation of fc(NH2)(NHXy) 4. Compound
In a glove box, 1 (194.9 mg, 0.459 mmol) was dissolved in
w10 mL toluene. To this solution, 3,5-dimethylbromobenzene
(0.187 mL, 1.38 mmol), NaOtBu (133 mg, 1.38 mmol) and Pd(dba)
BINAP (32.1 mg, 3 mol%) were added and the solution was trans-
ferred to a Schlenk tube. The solution was stirred and heated at
100 ꢀC for 14 h, after which the tube was brought back into the
glove box and solvent was removed under reduced pressure. The
crude solid was redissolved in diethyl ether and filtered through
Celite. The filtrate was collected, solvent was removed, and the
resulting solid was dissolved in a minimal amount of hexanes. The
solution was stored at ꢁ35 ꢀC overnight, which afforded the
product as a red solid; the solid was separated by filtration, dried
under reduced pressure, and determined to be 2 via NMR spec-
troscopy. Yield: 196.6 mg, 67.7%.
4
was reacted with t-butyldimethylsilylchloride to produce
fc(NHXy)(NHSitBuMe2) 5, an unsymmetrically substituted 1,10-
ferrocene diamine that incorporates both the new xylyl substituent
and the standard t-butyldimethylsilyl substituent commonly used
in our research. Reactivity studies with a variety of metal centers
are currently in progress.
4. Experimental
All experiments were performed under a dry nitrogen atmo-
sphere using standard Schlenk techniques or in an MBraun inert-
gas glovebox. Solvents were purified using a two-column solid-
state purification system by the method of Grubbs [39] and trans-
ferred to the glovebox without exposure to air. NMR solvents were
obtained from Cambridge Isotope Laboratories, degassed, and
stored over activated molecular sieves prior to use. fc(NH2)2 was
prepared following published procedures [40], 1H and 13C NMR
spectra were recorded on Bruker300 or Bruker500 spectrometers
(supported by the NSF grant CHE-9974928) at room temperature in
C6D6 unless otherwise specified. Chemical shifts are reported with
respect to solvent residual peak, 7.16 ppm (C6D6). CHN analyses
were performed on an Exeter Analytical, Inc. CE-440 Elemental
Analyzer.
b
a
c
b
b
c
d
c
d
e
d
g
e
h
a
a
f
N
h
h
c
d
g
b
Fe
g
h
b
d
f
c
4.1. Synthesis of 1
N
e
g
e
d
d
fc(NH2)2 (200.0 mg, 0.925 mmol) was combined with 3 equiv of
c
d
c
NaOtBu
(266.8 mg,
2.776 mmol),
2.5 equiv
of
3,5-
b
c
b
a
dimethylbromobenzene (428.2 mg, 2.314 mmol), and 2.4 mol% of
Pd(dba)BINAP (21.8 mg, 0.0226 mmol) in 20 mL of toluene in
a 50 mL Schlenk tube equipped with a magnetic stir bar. The
solution was heated and stirred at 100 ꢀC for 48 h. The volatiles
were then removed under reduced pressure; the resulting orange
solid was extracted with hexanes and filtered through Celite. The
filtrate was reduced to dryness and the resulting solid was taken up
in a minimal amount of ether to obtain a concentrated solution. The
solution was then placed in a freezer at ꢁ35 ꢀC. The product
obtained from crystallization was a yellow-orange flaky solid in 91%
yield (360.2 mg, 0.844 mmol).
b
1H NMR (500 MHz, C6D6):
4.26 (m, 4H, f), 4.07 (m, 4H, g), 2.06 (s, 24H, b). 13C NMR (126 MHz,
C6D6): , ppm: 148.1 (e), 138.3 (c), 124.8 (a), 122.7 (d), 108.5 (h), 64.8
d, ppm: 7.23 (s, 8H, d), 6.59 (s, 4H, a),
d
(g), 61.1 (f), and 20.9 (b). Anal. (%): Calcd. for C42H44FeN2: C, 79.74;
H, 7.01; N, 4.43. Found: C, 79.52; H 7.05; N 3.99.
4.3. Synthesis of 3
b
a
c
In a glove box, 1 (150.2 mg, 0.354 mmol) was dissolved in
w7 mL toluene. To this solution, 3,5-dimethylbromobenzene
(0.048 mL, 0.353 mmol), NaOtBu (33.9 mg, 0.353 mmol) and
Pd(dba)BINAP (9.8 mg, 3 mol%) were added and the solution was
transferred to a Schlenk tube. The solution was stirred and heated
at 100 ꢀC for 8 days, at which time it was determined via NMR
spectroscopy that the reaction could not be pushed further. The
Schlenk tube was brought back into the glove box and the volatiles
were then removed under reduced pressure. The crude solid was
redissolved in diethyl ether and filtered through Celite. The filtrate
was collected, solvent was removed, and the resulting solid was
dissolved in a minimal amount of hexanes. The solution was
stored at ꢁ35 ꢀC overnight, which afforded the product as a red-
orange solid; the solid was separated by filtration, dried under
b
c
d
d
e
h
i
NH
i
g
f
h
Fe
h
i
g
NHf
i
h
b
e
d
d
c
c
a
b

J.A. Lee et al. / Journal of Organometallic Chemistry 696 (2011) 4090e4094
4093
reduced pressure, and determined to be 3 via NMR. Yield:
105.0 mg, 56.2%.
4.5. Synthesis of 5
In a glove box, 4 (101.1 mg, 0.314 mmol) was dissolved in w7 mL
dichloromethane in a 20 mL vial. In a separate vial, triethylamine
(0.044 mL, 0.314 mmol) and t-butyldimethylsilylchloride (43.5 mg,
0.314 mmol) were combined and dissolved in w5 mL dichloro-
methane. The solutions were combined and stirred at room
temperature for 14 h, after which the volatiles were then removed
under reduced pressure. The crude solid was suspended in hexanes,
filtered through Celite, and dried, whereupon w1 mL hexanes was
added to form a concentrated solution and stored overnight
at ꢁ35 ꢀC. An orange-yellow crystalline material was collected via
filtration, dried under reduced pressure, and identified via NMR
spectroscopy. Yield: 81.9 mg, 60.1%.
b
a
c
b
b
c
d
c
d
d
e
o
p
a
l
e
N
p
n
c
d
o
b
Fe
m
n
l
NHf
m
h
k
j
j
i
i
g
b
h
a
c
b
c
d
d
e
h
i
g
NHf
i
1H NMR (500 MHz, C6D6):
d
, ppm: 7.21 (s, 4H, d), 6.60 (s, 2H, a),
h
Fe
6.51 (s, 2H, j), 6.44 (s, 1H, g), 4.75 (s, 1H, f), 4.31 (br s, 2H, m), 4.17 (br
s, 2H, o), 4.02 (br s, 2H, n), 3.92 (br s, 2H, p), 2.15 (s, 6H, h), 2.09 (s,
k
j
l
j
NHm
12H, b). 13C NMR (126 MHz, C6D6):
d, ppm: 147.7 (e), 146.7 (k), 138.5
p
n
k
o
Si
n
(c), 138.1 (i), 125.0 (a), 122.7 (d), 120.4 (g), 112.7 (j), 100.5 (l), 65.3 (n),
64.5 (p), 64.1 (m), 60.4 (o), 21.2 (h), and 21.0 (b). Anal. (%): Calcd. for
C34H36FeN2: C, 77.27; H, 6.87; N, 5.30. Found: C, 77.76; H 6.94; N
5.08.
p
p
1H NMR (500 MHz, C6D6):
d, ppm: 6.64 (s, 2H, d), 6.45 (s, 1H, a),
4.4. Synthesis of 4
5.05 (s, 1H, f), 4.20 (d, 2H, h), 3.94 (d, 2H, i), 3.77 (m, 4H, j,k), 2.21 (s,
6H, b), 1.84 (s, 2H, m), 0.85 (s, 9H, p), 0.12 (d, 6H, n). 13C NMR
(126 MHz, C6D6): d, ppm: 147.9 (e), 138.2 (c), 119.9 (a), 112.1 (d),
106.3 (l), 96.6 (g), 65.9 (j), 65.7 (k), 63.7 (i), 59.8 (h), 26.1 (p), 21.2 (b),
17.9 (o), and ꢁ4.5 (n). Anal. (%): Calcd. for C24H34FeN2Si: C, 66.35; H,
7.89; N, 6.45. Found: C, 66.04; H 7.43; N 6.41.
In a glove box, fc(NH2)2 (250 mg, 1.146 mmol) was dissolved in
w10 mL toluene. To this solution, 3,5-dimethylbromobenzene
(0.171 mL, 1.261 mmol), NaOtBu (110.1 mg, 1.146 mmol), and
Pd(dba)BINAP (32.1 mg, 3 mol%) were added and the solution was
transferred to a Schlenk tube. The solution was stirred and heated
at 100 ꢀC for 48 h, after which the tube was brought back into the
glove box and the volatiles were then removed under reduced
pressure. The crude solid was redissolved in diethyl ether and
filtered through Celite. The filtrate was collected, volatiles were
removed, and the resulting solid was dissolved in a minimal
amount of hexanes. The solution was stored at ꢁ35 ꢀC overnight,
which afforded the product as a yellow solid; the solid was sepa-
rated by filtration, dried under reduced pressure, and determined
to be 4 via NMR spectroscopy. Yield: 187.0 mg, 50.8%.
Acknowledgement
This work was supported by the UCLA, Sloan Foundation, NSF
(Grant CHE-0847735), and DOE (Grant ER15984).
Appendix A. Supplementary information
Supplementary data associated with this article can be found in
the online version at doi:10.1016/j.jorganchem.2011.06.043.
b
a
c
b
c
d
References
d
e
k
l
NH
l
[1] A. Shafir, J. Arnold, Inorg. Chim. Acta 345 (2003) 216e220.
[2] K.L. Miller, C.T. Carver, B.N. Williams, P.L. Diaconescu, Organometallics 29
(2010) 2272e2281.
[3] K.L. Miller, B.N. Williams, D. Benitez, C.T. Carver, K.R. Ogilby, E. Tkatchouk,
W.A. Goddard, P.L. Diaconescu, J. Am. Chem. Soc. 132 (2009) 342e355.
[4] A. Shafir, J. Arnold, J. Am. Chem. Soc. 123 (2001) 9212e9213.
[5] A. Shafir, J. Arnold, Organometallics 22 (2003) 567e575.
[6] A. Shafir, M.P. Power, G.D. Whitener, J. Arnold, Organometallics 20 (2001)
1365e1369.
h
f
k
Fe
i
j
h
g
NH2
j
i
[7] P.L. Diaconescu, Acc. Chem. Res. 43 (2010) 1352e1363.
[8] U. Siemeling, T.-C. Auch, Chem. Soc. Rev. 34 (2005) 584.
[9] C.T. Carver, D. Benitez, K.L. Miller, B.N. Williams, E. Tkatchouk, W.A. Goddard,
P.L. Diaconescu, J. Am. Chem. Soc. 131 (2009) 10269e10278.
[10] C.T. Carver, P.L. Diaconescu, J. Am. Chem. Soc. 130 (2008) 7558e7559.
[11] S. Jie, P.L. Diaconescu, Organometallics 29 (2010) 1222e1230.
[12] C.T. Carver, B.N. Williams, K.R. Ogilby, P.L. Diaconescu, Organometallics 29
(2009) 835e846.
1H NMR (500 MHz, C6D6):
d, ppm: 6.64 (s, 2H, d), 6.46 (s, 1H, a),
5.68 (s,1H, f), 4.19 (br s, 2H, k), 3.91 (br s, 2H, l), 3.73 (br s, 2H, i), 3.62
(br s, 2H, j), 2.22 (s, 6H, b), 1.62 (s, 2H, g). 13C NMR (126 MHz, C6D6):
d
, ppm: 148.3 (e), 138.2 (c), 119.6 (a), 112.0 (d), 95.6 (h), 66.7 (l), 65.7
(k), 63.8 (j), 59.3 (i), and 21.2 (b). Anal. (%): Calcd. for C18H20FeN2: C,
67.52; H, 6.30; N, 8.75. Found: C, 67.92; H 6.30; N 8.74.
[13] W. Huang, C.T. Carver, P.L. Diaconescu, Inorg. Chem. 50 (2011) 978e984.
[14] C.T. Carver, P.L. Diaconescu, J. Alloys Compd. (2009) 518.

4094
J.A. Lee et al. / Journal of Organometallic Chemistry 696 (2011) 4090e4094
[15] C.T. Carver, M.J. Monreal, P.L. Diaconescu, Organometallics 27 (2008)
363e370.
[28] J. Eppinger, K.R. Nikolaides, M. Zhang-Presse, F.A. Riederer, G.W. Rabe,
A.L. Rheingold, Organometallics 27 (2008) 736e740.
[16] M.J. Monreal, C.T. Carver, P.L. Diaconescu, Inorg. Chem. 46 (2007) 7226e7228.
[17] M.J. Monreal, P.L. Diaconescu, Organometallics 27 (2008) 1702e1706.
[18] M.J. Monreal, P.L. Diaconescu, J. Am. Chem. Soc. 132 (2010) 7676e7683.
[19] M.J. Monreal, S. Khan, P.L. Diaconescu, Angew. Chem. Int. Ed. 48 (2009)
8352e8355.
[29] C.D. Varnado Jr., V.M. Lynch, C.W. Bielawski, Dalton Trans. (2009) 7253e7261.
[30] U. Siemeling, C. Farber, C. Bruhn, Chem. Commun. (2009) 98e100.
[31] V.C. Gibson, N.J. Long, E.L. Marshall, P.J. Oxford, A.J.P. White, D.J. Williams,
J. Chem. Soc., Dalton Trans. (2001) 1162e1164.
[32] B. Wrackmeyer, E.V. Klimkina, W. Milius, Eur. J. Inorg. Chem. 2008 (2008)
3340e3347.
[20] E.M. Broderick, P.L. Diaconescu, Inorg. Chem. 48 (2009) 4701e4706.
[21] E.M. Broderick, P.S. Thuy-Boun, N. Guo, C.S. Vogel, J. Sutter, J.T. Miller,
K. Meyer, P.L. Diaconescu, Inorg. Chem. 50 (2010) 2870e2877.
[22] E.M. Broderick, N.P. Gutzwiller, P.L. Diaconescu, Organometallics 29 (2010)
3242e3251.
[33] F.T. Edelmann, D.M.M. Freckmann, H. Schumann, Chem. Rev. 102 (2002)
1851e1896.
[34] N. Marques, A. Sella, J. Takats, Chem. Rev. 102 (2002) 2137e2160.
[35] W.E. Piers, D.J.H. Emslie, Coord. Chem. Rev. 233e234 (2002) 131e155.
[36] P. Mountford, B.D. Ward, Chem. Commun. (2003) 1797e1803.
[37] A.W. Wong, K.L. Miller, P.L. Diaconescu, Dalton Trans. 39 (2010) 6726e6731.
[38] J.P. Wolfe, S. Wagaw, S.L. Buchwald, J. Am. Chem. Soc. 118 (1996)
7215e7216.
ꢀ
[23] S. Duhovic, M.J. Monreal, P.L. Diaconescu, Inorg. Chem. 49 (2010) 7165e7169.
ꢀ
[24] S. Duhovic, S. Khan, P.L. Diaconescu, Chem. Commun. 46 (2010) 3390e3392.
[25] B.N. Williams, W. Huang, K.L. Miller, P.L. Diaconescu, Inorg. Chem. 49 (2010)
11493e11498.
[26] U. Siemeling, T.C. Auch, O. Kuhnert, M. Malaun, H. Kopacka, B. Bildstein,
Z. Anorg. Allg. Chem. 629 (2003) 1334e1336.
[39] A.B. Pangborn, M.A. Giardello, R.H. Grubbs, R.K. Rosen, F.J. Timmers, Organo-
metallics 15 (1996) 1518e1520.
[27] U. Siemeling, T.-C. Auch, S. Tomm, H. Fink, C. Bruhn, B. Neumann, H.-
G. Stammler, Organometallics 26 (2007) 1112e1115.
[40] A. Shafir, M.P. Power, G.D. Whitener, J. Arnold, Organometallics 19 (2000)
3978e3982.