Titanium and zirconium complexes of the N,N′-bis(2,6-diisopropylphenyl)-1,4-diaza-butadiene ligand: Syntheses, structures and uses in catalytic hydrosilylation reactions

Article abstract of DOI:10.1039/c4dt02013h

We report here a number of dianionic 1,4-diaza-1,3-butadiene complexes of titanium and zirconium synthesised by a salt metathesis reaction. The reaction of either CpTiCl₃ or Cp₂TiCl₂ with the dilithium salt of N,N′-bis(2,6

Full text of DOI:10.1039/c4dt02013h

Dalton
Transactions
View Article Online
View Journal | View Issue
PAPER
Titanium and zirconium complexes of the
N,N’-bis(2,6-diisopropylphenyl)-1,4-diaza-
butadiene ligand: syntheses, structures and uses
in catalytic hydrosilylation reactions†
Cite this: Dalton Trans., 2014, 43,
14876
Srinivas Anga, Kishor Naktode, Harinath Adimulam and Tarun K. Panda*
We report here a number of dianionic 1,4-diaza-1,3-butadiene complexes of titanium and zirconium syn-
thesised by a salt metathesis reaction. The reaction of either CpTiCl3 or Cp2TiCl2 with the dilithium salt of
N,N’-bis(2,6-diisopropylphenyl)-1,4-diaza-1,3-butadiene [1; abbreviated (Dipp)2DADLi2] afforded the mono-
cyclopentadienyl titanium complex [η5-CpTi((Dipp)2DAD)Cl] (2) bearing a dianionic ene-diamide ligand, while
the analogous reaction of zirconocene dichloride (Cp2ZrCl2) with the dilithium salt 1 gave the bis-cyclopen-
tadienyl zirconium complex [Cp2Zr{(Dipp)2DAD}] (3). The metal dichloride complexes [Ti((Dipp)2DAD)Cl2] (4)
and [{(Dipp)2DADZrCl(μ-Cl)}2(κ3-Cl)(Li)(OEt2)2] (5) were obtained by the reaction of 1 and anhydrous metal
tetrachloride in a 1 : 1 molar ratio in diethyl ether at room temperature. Meanwhile, the homoleptic titanium
complex [Ti{((Dipp)2DAD)}2] (6) was isolated in good yield by the treatment of 1 with TiCl4 in a 1 : 2 molar ratio
in diethyl ether. The complexes 2 and 5 were further reacted with neosilyl lithium to afford mono- and bis-
alkyl complexes of titanium [η5-CpTi{(Dipp)2DAD}(CH2SiMe3)] (7) and zirconium [Zr{(Dipp)2DAD}(CH2SiMe3)2]
(8) respectively. Molecular structures of the complexes 2, 3, and 5–8 in the solid states were confirmed by
single crystal X-ray diffraction analysis. The solid state structures of all the complexes reveal that the metal
ions are chelated through the amido-nitrogen atoms and the olefinic carbons of the [(Dipp)2DAD]2− moiety,
satisfying the σ2,π coordination mode. Compound 8 was used as a catalyst for the intermolecular hydrosilyl-
ation reaction of a number of olefins, and moderate activity of catalyst 8 was observed.
Received 3rd July 2014,
Accepted 7th August 2014
DOI: 10.1039/c4dt02013h
www.rsc.org/dalton
specifically tailored to allow applications in areas such as the
activation of small, poorly reactive molecules, homogeneous
Introduction
Amido metal chemistry of the early transition metals has catalysis, or organic synthesis.3 Recently the use of diamide
achieved significant momentum in the last 25 years with the ligands has gained more importance in early transition metal
design of novel amido ligands.1 It was observed that, in the chemistry for the stabilization of group 4 and 5 metal com-
early stages of this field of study, most researchers focused on plexes, due to their ability to chelate metal centers with higher
cyclopentadienyl-analogous amido ligands for comparison oxidation numbers through the formation of dianionic forms.4
with, and for further investigation of, the well-known cyclopen- Metal complexes with these bis (amido) ligands exhibit a
tadienyl moiety.2 Amido–metal bonds are thermodynamically closer relationship to the metallocenes and particularly to the
stable and less labile compared to metal–carbon bonds. constrained-geometry half-sandwich amido–metal complexes,
However, nowadays the stable amido–metal bond is utilized in which have been studied as potential catalysts for homo-
amido–metal chemistry to produce well-defined reaction geneous Ziegler–Natta polymerization.5 The chelating diamide
centers in transition metal complexes. In this way, the reactiv- complexes of titanium and zirconium serve as precursors for
ity of the resulting early transition metal compounds can be the highly active and living polymerization of olefins.6 The
potential advantage of the bis (amido) metal system relative to
the metallocene or the half-sandwich amido–metal complexes
is their lower formal electron count which results in a more
electrophilic and therefore potentially more active catalyst frag-
ment.7 Since the α-diimine ligand, 1,4-disubstituted diazabuta-
diene (DAD), was synthesized and utilized in the early 1960s,8
various substituted DAD ligands have been synthesized by a
number of research groups, even today, as it can be reduced to
Department of Chemistry, Indian Institute of Technology Hyderabad, Ordnance
Factory Estate, Yeddumailaram 502205, Telangana State, India.
E-mail: tpanda@iith.ac.in; Fax: +91(40) 2301 6032; Tel: +91(40) 2301 6036
†Electronic supplementary information (ESI) available: X-ray crystallographic
files for 2, 3 and 5–8 in CIF format and Table S1. CCDC 1011649–1011654. For
ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/
c4dt02013h
14876 | Dalton Trans., 2014, 43, 14876–14888
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
DADLi2) (1) and CpTiCl3 in a 1 : 1 molar ratio in diethyl ether
at room temperature, followed by re-crystallisation from ether
at −35 °C (see Scheme 1). The titanium complex 2 could also
be obtained by the reaction of 1 and titanocene dichloride
(Cp2TiCl2) under similar reaction conditions. Thus under the
reaction conditions, one cyclopentadienyl moiety underwent
elimination from Cp2TiCl2 to LiCp along with one equivalent
LiCl. Such phenomenon was recently observed by Sun et al.
while treating triscyclopentadienyl yttrium with a lithium
amidinate ligand.25 In contrast, the reaction of zirconocene
dichloride (Cp2ZrCl2) with dianionic lithium salt 1 afforded
the corresponding bis-cyclopentadienyl zirconium complex
[Cp2Zr{(Dipp)2DAD}] (3) in good yield by elimination of two
equivalents of lithium chloride (see Scheme 1). Both the tita-
nium and zirconium complexes were characterized by spectro-
scopic techniques and the solid states of the complexes 2 and
3 were established by X-ray diffraction analysis. In 1H NMR
spectra measured in C6D6, the resonances of the Cp protons in
2 appear at 6.17 ppm as a sharp singlet. The signals for the
analogous Cp protons in complex 3 are observed at 5.62 and
5.56 ppm, indicating two different chemical environments for
the two cyclopentadienyl rings. The sharp singlets at 6.16 ppm
for 2 and 5.35 ppm for 3 are assigned to the olefinic protons of
the respective DAD ligand backbone. Therefore the resonances
for the olefinic protons in 2 are significantly low field shifted
compared to those of bis-cyclopentadienyl complex 3. Two
septets for each complex (3.51 and 2.33 ppm for 2 and 3.71
and 2.92 ppm for 3) are observed for the isopropyl groups of
the 2,6-diisopropylphenyl moiety present in the DAD ligand.
The presence of two distinct septets in each complex can be
explained by the asymmetric attachment of the DAD ligand in
each case. The isopropyl methyl protons show four doublet
resonances with a coupling constant of 6.8 Hz in 2, due to the
restricted rotation around the respective carbon nitrogen bond
of the DAD ligand moiety; this indicates the presence of non-
equivalent 2,6-diisopropylphenyl groups. However, in 3, we
observed two doublets for one set of diastereotopic isopropyl
CH3 groups, indicating the presence of equivalent 2,6-diisopro-
pylphenyl groups. In proton decoupled 13C NMR spectra for 2,
the resonances at 114.6 ppm and 108.3 ppm represent the C5
of the Cp moiety and the olefinic carbons of the DAD ligand.
For zirconium compound 3, the 13C{1H} NMR signals are
114.3 and 110.1 ppm for the two Cp rings and 106.7 ppm
Chart 1 Different coordination modes of the DAD ligand.
generate a diamido ligand.9 The diversity in coordination and
redox properties of this ligand has resulted in a high level of
interest in these compounds, which have already proved to
have wide-ranging uses in the areas of both fundamental and
applied research.10 The neutral DAD molecule includes two
lone electron pairs of nitrogen atoms and π-electrons of the
multiple imine (N–C) bonds, and this molecule can act as both
a σ- and π-donor, and coordinate to the metal atom as a
neutral ligand.11 Although the dianionic DAD ligands preferen-
tially coordinate to early transition metals and alkaline metals
in σ2- and σ2,π-coordination modes,12–14 in many cases the
DAD ligands coordinate to group 3 metal atoms as a σ2-mono-
anion,15 and, in addition, both monoanionic and dianionic
coordination modes were observed for alkaline-earth metals,
group 12, and group 13 metal complexes.16,17 The possible
flexible coordination modes depending on the types and redox
properties of the central metal are shown in Chart 1.
The DAD ligand is widely utilized not only for early tran-
sition metals,18,19 f-block metals,20 and late transition
metals,21 but also for s-block and p-block main-group
elements.22–24 In the majority of these complexes, the DAD
ligands are coordinated in their dianionic form as chelating
enediamides to the metal (mode D) and therefore are reminis-
cent of diamide ligands.
To get more insight into the structure–reactivity relation-
ships of early transition metal DAD complexes, and to explore
their applications in organic transformations, we have studied
this chemistry further. In this context, we present the synthesis
of a number of dianionic 1,4-diaza-1,3-butadiene complexes with
the molecular compositions [η5-CpTi((Dipp)2DAD)Cl] (2), [Cp2Zr-
((Dipp)2DAD)] (3), [Ti((Dipp)2DAD)Cl2] (4), [{(Dipp)2DADZrCl-
(μ-Cl)}2(κ3-Cl)(Li)(OEt2)2] (5), [Ti{((Dipp)2DAD)}2] (6), [η5-CpTi-
((Dipp)2DAD)(CH2SiMe3)] (7), [Zr{(Dipp)2DAD)}-(CH2SiMe3)2] (8).
The solid state structures of complexes 2–3 and 5–8 are also
reported. The catalytic hydrosilylation of various alkenes using
complex 8 as a catalyst is also presented.
1
for the olefinic carbon atoms. All of the H and 13C–{1H} NMR
signals are in agreement with the values reported in the
literature.14
The molecular structure of the air- and moisture-sensitive
complexes 2–3 were established by single crystal X-ray diffrac-
tion analysis. The complex 2 crystallizes in the monoclinic
space group P21/c and has four independent molecules in the
unit cell (Fig. 1). The zirconium complex 3 crystallizes in the
ˉ
triclinic space group P1 and has two independent molecules
Results and discussion
Cyclopentadienyl metal complexes
along with one molecule of diethyl ether in the unit cell as a
solvate (Fig. 2). The details of the structural and refinement
The cyclopentadienyl titanium complex [η5-CpTi((Dipp)2DAD)- parameters of the crystal structures of 2–3 are given in
Cl] (2) was isolated in good yield from the reaction of (Dipp)2- Table TS1 in the ESI.† Complex 2 is monomeric and the
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 14876–14888 | 14877

View Article Online
Paper
Dalton Transactions
Scheme 1 Syntheses of titanium and zirconium complexes 2–6 from 1.
coordination polyhedron is formed by the chelation of two The geometry around the titanium ion can be best described
amido nitrogen atoms of the dianionic DAD ligand, η5-coordi- as pseudo tetrahedral, considering the η5-Cp ring as a pseudo-
nation of one cyclopentadienyl moiety, and one chloride atom. monodentate ligand. The Ti–N distances [1.928(2) and 1.922(2) Å]
Fig. 1 ORTEP drawing of 2 showing the atom labelling scheme; ellip-
soids are drawn to encompass 30% probability. Selected bond lengths
[Å] or angles [°]: Ti1–N1 1.928(2), Ti1–N2 1.922(2), Ti1–Cl1 2.3283(8),
Ti1–C27 2.331(3), Ti1–C31 2.338(3), Ti1–C28 2.342(3), Ti1–C30 2.352(3),
Ti1–C29 2.358(3), Ti1–C1 2.427(3), Ti1–C2 2.433(3), N1–C1 1.389(3), N1–
C3 1.429(3), N2–C2 1.383(3), N2–C15 1.437(3), C1–C2 1.382(4), N2–Ti1–
N1 89.90(9), N2–Ti1–Cl1 109.42(7), N1–Ti1–Cl1 109.33(7), N2–Ti1–C1
64.88(8), N1–Ti1–C1 34.86(9), Cl1–Ti1–C1 94.15(6), C27–Ti1–C1 117.84(10),
C2–N2–Ti1 34.57(8), N1–Ti1–C2 65.43(9), Cl1–Ti1–C2 93.91(6), C27–
Ti1–C2 118.68(10), C1–Ti1–C2 33.05(8), C1–N1–Ti1 92.60(15).
Fig. 2 ORTEP drawing of 3 showing the atom labelling scheme; ellip-
soids are drawn to encompass 30% probability. Selected bond lengths
[Å] or angles [°]: Zr1–N1 2.1050(14), Zr1–N2 2.1406(14), Zr1–C1 2.5928(17),
Zr1–C2 2.5977(16), Zr1–C36 2.5223(19), Zr1–C32 2.5303(18), Zr1–C33
2.5344(18), Zr1–C34 2.5398(19), Zr1–C35 2.5310(18), Zr1–C28 2.5898(19),
Zr1–C29 2.5943(19), Zr1–C31 2.5985(18), N1–C1 1.392(2), N1–C3
1.436(2), N2–C2 1.389(2), N2–C15 1.434(2), C1–C2 1.377(2), N1–Zr1–N2
84.08(5), N1–Zr1–C1 32.41(5), N2–Zr1–C1 60.62(5), N1–Zr1–C2)
60.77(5), C1–N1–Zr1 93.46(10), C3–N1–Zr1 148.42(11), C2–N2–Zr1
92.28(10), C15–N2–Zr1 145.87(11).
14878 | Dalton Trans., 2014, 43, 14876–14888
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
are close to that of the Ti–N covalent bond. The Ti–C(Cp)
distances, ranging from 2.331(3) to 2.358(3) Å, are within the
agreement of reported Ti–C(Cp) values. The zirconium
complex 3 is also monomeric, bearing two η5-Cp moiety
and one DAD ligand. The geometry around the zirconium
ion is pseudo tetrahedral, considering the η5-Cp ring as a
pseudo-monodentate ligand. The Zr–N distances [2.105(1) and
2.141(1) Å] are slightly longer than the Ti–N distances, due to
the larger ion radius of Zr(IV) ion, however they are in agree-
ment with the Zr–N covalent bonds reported in the literature.
The Zr–C(Cp) distances [2.52(2) to 2.590(2) Å] are also slightly
longer than the Ti–C(Cp) distances, but are in the range of the
Zr–C(Cp) distances reported for other zirconocene com-
plexes.26 Notably, the coordination of the dianionic DAD
ligands in complex 2 and 3 are similar, and both complexes
Fig. 3 ORTEP drawing of 5 showing the atom labelling scheme; ellip-
soids are drawn to encompass 30% probability. Selected bond lengths
[Å] or angles [°]: Zr2–N3 2.044(3), Zr2–N4 2.050(3), Zr2–C4 2.472(4),
Zr2–C3 2.472(4), Zr2–Cl5 2.4951(10), Zr2–Cl1 2.5687(9), Zr2–Cl3
2.6569(9), Zr2–Cl4 2.7194(10), Zr1–N1 2.044(3), Zr1–N2 2.045(3), Zr1–
Cl2 2.4215(10), Zr1–C1 2.481(4), Zr1–C2 2.485(4), Zr1–Cl3 2.6377(10),
Zr1–Cl1 2.7047(9), Zr1–Cl4 2.7079(10), Cl4–Li1 2.4468, Cl5–Li1 2.382(9),
C41–N4 1.430(5), C5–N2 1.437(5), C4–N4 1.402(5), N1–C17 1.435(5),
C2–N2 1.401(5), N3–C3 1.398(5), N3–Zr2–N4 87.82(13), N3–Zr2–C4
63.83(13), C4–Zr2–C3 32.18(13), N3–Zr2–Cl5 92.82(10), N4–Zr2–Cl5
95.04(9), C4–Zr2–Cl5 118.76(9), C3–Zr2–Cl5 117.80(9), N3–Zr2–Cl1
100.66(10), N4–Zr2–Cl1 105.87(9), C4–Zr2–Cl1 85.76(9), C3–Zr2–Cl1
83.66(9), Cl5–Zr2–Cl1 155.39(3), N3–Zr2–Cl3 175.09(10), N4–Zr2–Cl3
96.97(9), C4–Zr2–Cl3 119.96(9), C3–Zr2–Cl3 148.01(9), Cl5–Zr2–Cl3
87.86(3), Cl1–Zr2–Cl3 77.02(3), N3–Zr2–Cl4 97.74(10), N4–Zr2–Cl4
173.77(9), C4–Zr2–Cl4 151.35(10), C3–Zr2–Cl4 122.22(10), Cl5–Zr2–Cl4
81.94(3), Cl1–Zr2–Cl4 75.95(3), Cl3–Zr2–Cl4 77.53(3), N1–Zr1–N2
88.01(14), N1–Zr1–Cl2 105.15(11), N2–Zr1–Cl2 104.96(10), Cl2–Zr1–C2
87.92(11), N2–Zr1–Cl3 96.64(10), Cl2–Zr1–Cl3 90.97(3), C1–Zr1–Cl3
159.12(11), C2–Zr1–Cl3 127.24(10), N1–Zr1–Cl1 86.96(10), N2–Zr1–Cl1
91.85(10), Cl2–Zr1–Cl1 159.40(3), C1–Zr1–Cl1 110.24(11), C2–Zr1–Cl1
112.56(10), Cl3–Zr1–Cl(1) 75.05(3).
form
a five-membered diazametallacyclopentene structure
(Ti1–N1–C1–C2–N2 for 2 and Zr1–N1–C1–C2–N2 for 3). Both
metallacycles are folded and the dihedral angles between the
N1–M–N2 and N1–C1–C2–N2 planes are 50.62° (for 2) and
50.30° (for 3). In complex 2, the distances between the tita-
nium ion and C1vC2 are short enough [2.427(3) and 2.433(3)
Å] for π bonding to display the σ2,π-enediamide mode of the
DAD ligand. However, no such π interactions between the
zirconium ion and the olefinic carbon atoms are observed in
the molecular structure. Thus for complex 3, the DAD ligand
displayed only a σ2-diamide mode (C in Chart 1). Nevertheless,
DAD ligation can be described as the elongation of the C–N
bond [1.389(3) and 1.383(3) Å for 2; 1.392(2) and 1.389(2) Å
for 3] and the shortening of the C–C bond [1.382(4) Å for 2;
1.377(2) Å for 3] i.e. a long–short–long sequence compared to
the neutral DAD ligand. Similar coordination behavior has
also been observed in recently reported DAD lanthanide
complexes.14
Metal dichloride complexes
with four independent molecules in the unit cell. The incor-
poration of lithium chloride into the coordination sphere of
metal complexes is commonly reported in the literature, due to
the smaller size of lithium.27 Lithium chloride incorporated com-
plexes [{(Me3SiNPPh2)2CH}-Yb(μ-Cl)2LiCl(THF)2], [(η5-C5Me5)2-
Nd(μ-Cl)2Li(THF)2]28 and [{(Me3SiNPPh2)2CH}Yb(μ-Cl)2LiCl-
(THF)2] have been reported by us and others.29 The solid state
structure of complex 5 is given in Fig. 3 and the details of
the structural parameters are given in Table TS1 in the ESI.†
Zirconium complex 5 has a dimeric structure bearing the DAD
ligand and four bridging chloride atoms. One terminal chlor-
ide atom Cl2 is attached with the second zirconium atom to
make both the zirconium centers non symmetric. However,
the geometry of each metal ion can be best described as dis-
torted octahedral. In this complex, the lighter alkali metal
lithium coordinates to one zirconium through two μ-chlorine
atoms, along with two solvent diethyl ether molecules coordi-
nating to the lithium atom. The geometry around the lithium
can be considered as distorted tetrahedral. Three four-
membered metallacycles, Li1–Cl5–Zr2–Cl4, Zr1–Cl1–Zr2–Cl3
and Zr1–Cl3–Zr2–Cl4, are formed by the μ-bridging of three
chlorine atoms (Cl1, Cl3, Cl5) and one κ3 chlorine (Cl4) toward
Upon treating 1 with MCl4 (M = Ti and Zr) either in toluene (in
the case of Ti) at −78 °C or in diethyl ether (in the case of Zr)
at room temperature, a DAD titanium dichloride complex
[Ti((Dipp)2DAD)Cl2] (4) and an ‘ate’ complex for zirconium
[{(Dipp)2DADZrCl(μ-Cl)}2(κ3-Cl)(Li)(OEt2)2] (5) were obtained
respectively in good yields. Both the complexes 4 and 5 were
characterized by spectroscopic and combustion analyses. The
solid state structure of complex 5 was established by single
1
crystal X-ray diffraction analysis. In the H NMR spectrum of 5
in C6D6, a sharp singlet was observed at δ 5.81 ppm (6.18 ppm
for 4), which was assigned to the olefinic protons of the DAD
ligand backbone; a broad signal was observed at δ 3.31 ppm
(2.98 ppm for 4); and two doublet resonances of a constant
5.6 Hz appeared at δ 1.20 and 1.01 ppm (1.14 ppm for 4),
respectively, due to the CH hydrogen and isopropyl methyl
hydrogen atoms of the ligand. The above values are quite
similar to the corresponding values of compounds 2 and 3
(see above).
The lithium chloride incorporated compound [{(Dipp)2-
DADZrCl(μ-Cl)}2(κ3-Cl)(Li)(OEt2)2] was re-crystallized from diethyl
ether; this crystallizes in the monoclinic space group P21/c along
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 14876–14888 | 14879

View Article Online
Paper
Dalton Transactions
the lithium and zirconium atoms, with a distance of 3.665(1)
Å, and between two zirconium atoms, with a distance of
3.737(1) Å, respectively. One chloride atom is terminally
bonded with the zirconium atom Zr1, making the two metal
ions asymmetric in nature. The terminal Zr–Cl2 bond length
(2.422(2) Å) is significantly shorter than the bridging Zr–Cl dis-
tances (2.495(3) to 2.719 (2) Å). The Zr–N distances [Zr1–N1
2.044(3), Zr1–N2 2.045(3), Zr2–N3 2.044(3), Zr2–N4 2.050(3) Å]
are slightly shorter, due to the presence of electron-withdraw-
ing chloride ions, than that for complex 3, where electron-
donating cyclopentadienyl moieties are present. Two zirco-
nium metallacycles present in the dimeric structure of 5 are
folded and the DAD ligands satisfy the σ2,π-enediamide mode
of coordination to the zirconium ion, with a long–short–long
sequence within the ligand fragments [N1–C1 1.394(5), N2–C2
1.401(5), C3–N3 1.398(5), C4–N4 1.402(5), C1–C2 1.364(6),
C3–C4 1.370(6) Å].
Fig. 4 ORTEP drawing of 6 showing the atom labelling scheme; ellip-
soids are drawn to encompass 30% probability. Selected bond lengths
[Å] or angles [°]: Ti1–N1 1.9675(14), Ti1–N2 1.9196(14), Ti1–N3 1.9282(14),
Ti1–N4 1.9566(13), Ti1–C1 2.3941(17), Ti1–C2 2.3841(18), Ti1–C3
2.3722(17), Ti1–C4 2.3942(17), N1–C1 1.390(2), N1–C5 1.431(2), N2–C2
1.399(2), N2–C17 1.431(2), N3–C3 1.391(2), N3–C29 1.4333(19), N4–C4
1.392(2), N4–C41 1.4292, C1–C2 1.366(3), C3–C4 1.377(2), N2–Ti1–N3
112.80(6), N2–Ti1–N4 116.40(6), N3–Ti1–N4 91.26(6), N2–Ti1–N1
90.85(6), N3–Ti1–N1 118.87(6), N4–Ti1–N1 128.30(6), N2–Ti1–C3
146.47(6), N3–Ti1–C3 35.91(5), N1–Ti1–C3 113.88(6), N3–Ti1–C2
147.10(6), N4–Ti1–C2 111.07(6), C3–Ti1–C2 176.90(6), N3–Ti1–C1
150.94(6), N4–Ti1–C1 115.68(6), C3–Ti1–C1 145.59(6), C2–Ti1–C1 33.21
(6), N2–Ti1–C4 148.58(6), N1–Ti1–C4 117.62(6).
Homoleptic complex
The bis-DAD titanium complex [Ti-{(Dipp)2DAD}2] (6) was iso-
lated by the treatment of 1 with TiCl4 in a 1 : 2 molar ratio, by
the elimination of LiCl. The corresponding complex of zirco-
nium was also recently synthesized by the reaction reduction
of the neutral DAD ligand followed by a reaction with zirco-
1
nium tetrachloride.30 The complex 6 was characterized by H,
13C{1H} NMR spectroscopy and combustion analysis, and its
molecular structure was established by single crystal X-ray
diffraction analysis. The 1H NMR spectra of the complex 6
show two sets of signals for each DAD ligand. Four doublets at
δ 1.24, 1.21, 1.17 and 1.15 ppm in a 12 : 12 : 12 : 12 ratio, and a
coupling constant of 4.8 Hz in each case can be assigned to
the resonances of 48 methyl protons distributed in four diiso-
propylphenyl moieties. The magnetically asymmetric protons
indicate that the orientations of the two DAD ligands must be
in different planes. The resonances for the olefinic protons of
the two DAD ligands’ backbones are observed at δ 6.18 and
6.05 ppm as doublets, indicating a clear distinction between
the two ligands’ magnetic environments. However two multi-
plets at δ 3.12 and 2.95 ppm are obtained for the eight isopro-
pyl protons, due to the overlapping of two closely associated
septets for each DAD ligand. In proton decoupled 13C NMR
spectra, we observed that the characteristic peaks for the two
DAD ligands match with complexes 2 and 4 (see the Experi-
mental section).30
1.957(13) Å] are similar to those of complex 2 and can be
considered as covalent bonds. The Ti–C distances [Ti1–C1
2.394(17), Ti1–C2 2.384(18), Ti1–C3 2.372(17), 2.394(17) Å] are
sufficiently shorter, considering the σ bonds between the
metal ion and the CvC backbone of the ligands. Two folded
metallacycles Ti1–N1–C1–C2–N2 and Ti1–N3–C3–C4–N4 are
formed by the ligation of two dianionic DAD ligands which
satisfy the σ2,π-enediamide mode of coordination to the zirco-
nium ion, with a long–short–long sequence within the ligand
fragments [N1–C1 1.390(3), C1–C2 1.366(3) N2–C2 1.399(2);
C3–N3 1.391(2), C3–C4 1.377(2), C4–N4 1.392(2) Å]. A dihedral
angle of 59.2° was observed between the two planes containing
N1, C1, C2, N2 atoms and N3, C3, C4, N4 atoms present in
the two ligands. The center metal titanium ion is 1.104 and
1.101 Å, respectively, away from the above-mentioned two
planes.
Metal mono- and bis-alkyl complexes
The X-ray quality crystal of titanium complex 6 was re-crys- To learn more about the reactivity of metal halide complexes 2
tallized from diethyl ether at −35 °C as a red crystal. Com- and 5, we were interested in synthesizing their alkyl deriva-
pound 6 crystallizes in the monoclinic space group P21/c with tives. Metal alkyl complexes are important precursors to cata-
four independent molecules in the unit cell. The solid state lysts for a number of organic transformations.31 To explore the
structure of complex 6 is given in Fig. 4 and details of the reactivity of titanium and zirconium halide complexes 2 and 5,
structural parameters are given in Table TS1 in the ESI.† All we decided to isolate the corresponding metal alkyl complexes.
the hydrogen atoms were located in the Fourier difference map Both the complexes 2 and 5 were reacted with trimethylsilyl-
and were subsequently refined. The coordination polyhedron methyl lithium in diethyl ether as a solvent to afford the
is formed by four amido nitrogen atoms from the two DAD corresponding mono-alkyl [η5-CpTi((Dipp)2DAD)(CH2SiMe3)]
ligands. The geometry around the titanium ion is best (7) and bis-alkyl [Zr-{(Dipp)2DAD}(CH2SiMe3)2] (8) complexes,
described as distorted tetrahedral. The Ti–N distances [Ti1–N1 respectively, in good yields after re-crystallisation from hexane
1.968(14), Ti1–N2 1.920(14), Ti1–N3 1.928(14) and Ti–N4 at −35 °C (Scheme 2). Compounds 7 and 8 are soluble in THF,
14880 | Dalton Trans., 2014, 43, 14876–14888
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
Fig. 5 ORTEP drawing of 7 showing the atom labelling scheme; ellip-
soids are drawn to encompass 30% probability. Selected bond lengths
[Å] or angles [°]: Ti1–N1 1.945(2), Ti1–N2 1.928(2), Ti1–C(3) 2.367(3), Ti1–
C4 2.382(3), Ti1–C5 2.383(3), Ti1–C6 2.361(3), Ti1–C7 2.347(3), Ti1–C8
2.174(3), Ti1–C1 2.377(3), Ti1–C2 2.375(2), Si3–C8 1.851(3), N1–C1 1.386(3),
N1–C24 1.438(3), N2–C2 1.381(3), N2–C12 1.440(3), C1–C2 1.375(3),
N2–Ti1–N1 90.77(9), N2–Ti1–C8 109.56(10), N1–Ti1–C8 104.87(9), N2–
Ti1–C1 66.27(9), N1–Ti1–C1 35.67(8), N2–Ti1–C2 35.54(8), N1–Ti1–C2
66.42(9), C24–N1–Ti1 150.38(17), C12–N2–Ti1 146.16(17).
Scheme 2 Syntheses of titanium and zirconium alkyl complexes 7–8.
toluene and hydrocarbon solvents like pentane and hexane.
Both air- and moisture-sensitive complexes were characterized
by spectroscopic analysis and the solid state structures of the
complexes 7–8 were established by single crystal X-ray diffrac-
tion analysis.
cyclopentadienyl chemistry of these elements, to the best of
our knowledge complexes 7–8 represent the first titanium and
zirconium alkyl complexes containing a dianionic 1,4-diaza-
1,3-butadiene ligand and a neosilyl group attached to it.18c
Therefore, their molecular structures in the solid state were
determined by X-ray diffraction analysis. Both the titanium
and zirconium complexes 7 and 8 crystallize in the monoclinic
space group P21/c and have four molecules of either 7 or 8 in
the respective unit cells. The details of the structural para-
meters are given in Table TS1 in the ESI.† The solid state struc-
tures of complexes 7 and 8 are shown in Fig. 5 and 6,
respectively. The coordination polyhedron of half sandwich
titanium alkyl complex 7 is formed by η5 coordination of
the cyclopentadienyl ring with an average Ti–C(Cp) distance
of 2.368 Å, which is similar to the corresponding value in com-
pound 2 (2.344 Å) and other titanocene complexes in the
literature.33 Beside the Cp ring, the DAD ligand is chelated in
a dianionic ene-diamide canonical form to the titanium
ion through two amido-nitrogen atoms, and one neosilyl
(Me3SiCH2) group is ligated to the center metal through a
carbon atom. The DAD ligand is folded to have a titanium
olefin interaction, which is observed in all of the DAD metal
complexes reported in this work. In contrast, the zirconium
coordination sphere in 8 is constructed by a folded DAD
ligand moiety similar to compound 7, and two neosilyl groups.
The Ti–C(CvC) distances in 7 [2.377(3) and 2.375(2) Å] are
slightly shorter than those in complex 2 [2.427(3) and 2.433(3)
Å]. In contrast, the Zr–C(CvC) distances in 8 [2.521(3) and
2.529(3) Å] are slightly longer than in the starting material 5
[2.471–2.485 Å]. Nevertheless, in both complexes they can be
considered as M–C π bonds between the titanium (for 7) and
zirconium (for 8), and the olefinic carbon atoms of the DAD
The 1H NMR spectrum of 7 in C6D6 is very similar to the
spectrum recorded for complex 2, exhibiting four characteristic
doublet resonances in a 6 : 6 : 6 : 6 ratio for the four different
types of isopropyl methyl groups present in the DAD ligand,
along with two high field septet resonances at 3.25 and
2.42 ppm for the isopropyl –CH hydrogen atoms. Thus it is
evident that the chemical and magnetic environments of iso-
propyl methyl and –CH protons are different due to the pres-
ence of the alkyl group attached to the titanium ion. Between
two sharp singlets, the signal at δ 6.19 ppm can be assigned to
the five protons present in the cyclopentadienyl ring, whereas
the signal at δ 5.95 ppm was confirmed for the olefinic
protons (CvC) of the DAD ligand. For the neosilyl (CH2SiMe3)
group in 7, one singlet at δ 0.18 ppm (SiMe3) and one singlet
at δ −0.46 ppm is observed at high field, which can be
1
assigned to methylene (CH2) hydrogen atoms. In the H NMR
spectrum, zirconium bis-alkyl complex 8 exhibits two doublets
at δ 5.97 and 5.91 ppm, assignable to the olefinic protons of
the DAD ligand backbone and two septets at δ 3.54 and
3.17 ppm for two chemically different isopropyl –CH protons,
while four doublet resonances with a coupling constant of
6.8 Hz appeared at δ 1.33, 1.22, 1.10 and 0.92 ppm in a
6 : 6 : 6 : 6 ratio for the methyl protons of the ligand. In
addition, two singlets at δ 0.10 and 0.03 ppm were observed
for the two neosilyl (CH2SiMe3) groups present in 8. Similar
chemical shift values for the neosilyl groups (δ 0.13 and
0.04 ppm) were reported for Cp″2Zr(CH2SiMe3)2 (Cp″
CH2vCHCH2C5H4) by Piers et al.32
Although there has been ongoing interest in the alkyl com-
plexes of group 4 organometallics, and particularly in the
=
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 14876–14888 | 14881

View Article Online
Paper
Dalton Transactions
atoms, and this plane is orthogonal to the cyclopentadienyl
plane. The center metal titanium possesses distorted pseudo-
tetrahedral geometry if we consider Cp− as a pseudo-mono-
dentate ligand. The fourth coordination site of the titanium
atom in 7 (third and fourth for zirconium complex 8) is occu-
pied by a neosilyl group and the Ti–C bond distance of
2.174(3) Å is within the range of Ti–C distances reported for
titanium alkyl complexes.34 The Zr–C distances of 2.236(3) and
2.240(3) Å are also in the accepted range for reported organo-
zirconium complexes.35
Catalytic hydrosilylation of alkenes
The catalytic addition of an organic silane Si–H bond to
alkenes or alkynes (hydrosilylation) to give silicon-containing
molecules is of great interest.36 Currently, most organosilanes
are made using multistep syntheses that produce significant
amounts of waste. Therefore, hydrosilylation offers an attrac-
Fig. 6 ORTEP drawing of 8 showing the atom labelling scheme; ellip-
soids are drawn to encompass 30% probability. Selected bond lengths
[Å] or angles [°]: Zr1–N1 2.048(2), Zr1–N2 2.055(2), Zr1–C31 2.236(3),
Zr1–C27 2.240(3), Zr1–C2 2.529(3), Zr1–C1 2.521(3), C2–C1 1.361(4),
N1–C1 1.411(4), N1–C3 1.436(3), N2–C2 1.405(3), N2–C15 1.431(3), Si1– tive alternative route to obtain silicon-containing molecules
C(27) 1.860(3), Si2–C31 1.858(3), N1–Zr1–N2 87.93(9), N1–Zr1–C31
115.33(10), N2–Zr1–C31 114.07(11), N1–Zr1–C27 114.69(10), N2–Zr1–
C27 115.79(10), C31–Zr1–C27 108.18(11), N1–Zr1–C2 63.00(9), N2–Zr1–
C2 33.73(9), C31–Zr1–C2 102.88(10), C27–Zr1–C2 145.20(10), N1–Zr1–
that are important for the preparation of fine chemicals and
pharmaceuticals. It has been demonstrated that group 3 metal
complexes with Cp37,38 and non-Cp39,40 ligands are efficient
catalysts or precatalysts for the hydrosilylation of olefins, and
C1 34.03(9), N2–Zr1–C1 62.75(9), C31–Zr1–C1 103.27(10), C27–Zr1–C1
144.72(10), C2–Zr1–C1 31.27(9), C3–N1–Zr1 149.68(19), C1–N1–Zr1 the mechanism is generally believed to involve the insertion of
91.68(16), C2–N2–Zr1 91.96(16), C15–N2–Zr1 146.9(2).
the olefin into the M–Si or M–H bond of a metal-silyl or metal-
hydride species, followed by σ-bond metathesis.40,41 In our
study, the mono and bis(neosilyl) complexes 7 and 8 proved to
ligand. Thus in both complexes 7 and 8, the DAD ligand main-
tained its σ2,π-enediamide mode of coordination to the metal
ion with a long–short–long sequence within the ligand frag-
ments [N1–C1 1.386(3), C1–C2 1.375(3), C2–N2 1.381(3) Å for 7
and N1–C1 1.411(4), C1–C2 1.361(4), C2–N2 1.405(3) Å for 8].
One four-membered metallacycle in each complex (Ti1–N1–
C1–C2 for 7 and Zr1–N1–C1–C2 for 8) is formed by the coordi-
nation of the DAD ligand to the metal ion. The titanium ion is
1.108 Å away from the plane containing the N1–C1–C2 and N2
be highly efficient pre-catalysts for the intermolecular hydro-
silylation of hexene and octene, using a small excess (10%) of
phenylsilane (PhSiH3) and 5 mol% catalyst loadings. However
it was observed that complex 7 is poorly active for intermolecu-
lar hydrosilylation and thus the screening was tested using
only zirconium complex 8.
Selected data obtained from the catalytic hydrosilylation
reaction of various alkenes with respect to complex 8 are given
in Table 1. In entries 1–3 and 6–7, the substrates (1-hexene,
Table 1 Catalytic hydrosilylation reactions
Product selectivity
(n and iso)
Time
(h)
Olefin conversion
(%)
Entry
Alkene
Product
n-
Iso-
1
1
2
3
4
2
2
100
100
100
26
99
99
99
99
1
2
1
24a
1
5
6
n + iso
24a
2
99
27
99
73
1
100
7
8
2
100
86
99
99
1
1
24
The reaction was done in C6D6 at r.t. The conversion and product selectivity was calculated from 1H NMR.a 60 °C.
14882 | Dalton Trans., 2014, 43, 14876–14888
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
1-octene, vinyl cyclohexane, 1,5-hexadiene and 1-bromopen- room temperature. The reaction mixture was then stirred for
tene) essentially show complete conversion to the corres- another 12 h. A white precipitate was formed and was filtered
ponding organosilanes in 2 hours at ambient temperature, as through a G4-frit and dried in vacuo. Red crystals were
1
judged by H NMR spectroscopy. Full selectivity for the n-pro- obtained after re-crystallization from diethyl ether at −35 °C.
ducts and no side reactions were observed (for example iso- Yield was 0.223 g (80%). Compound 2 was soluble in THF and
1
products, hydrogenation, alkene dimerization, and/or dehydro- toluene. H NMR (400 MHz, C6D6, 25 °C): δ 7.18–7.14 (m, 4H,
genative coupling of organosilanes). In the case of using do- ArH), 7.07–7.04 (m, 2H, ArH), 6.17 (s, 5H, Cp-H), 6.16 (s, 2H,
decene as the substrate, only 26% conversion was observed CH), 3.51 (sept, 2H, CH (CH3)2), 2.33 (sept, 2H, CH (CH3)2),
after 24 hours even at an elevated temperature (entry 4). The 1.28 (d, J = 6.8 Hz, 6H, CH (CH3)2), 1.21 (d, J = 6.8 Hz, 6H, CH
lower activity of dodecene in contrast to those of 1-hexene and (CH3)2), 1.13 (d, J = 6.8 Hz, 6H, CH (CH3)2), 1.08 (d, J = 6.8 Hz,
1-octene is not surprising. It seems that the presence of a 6H, CH (CH3)2)ppm. 13C{1H} NMR (100 MHz, C6D6, 25 °C):
longer alkyl chain in dodecene causes its sluggish reactivity in δ 149.1 (ArC), 143.7 (ArC), 124.5 (ArC), 123.5.9 (ArC), 114.6
catalytic hydrosilylation. When we tried the hydrosilylation (Cp-C), 108.3 (CvC), 27.7, 27.6, 26.0, 25.4, 24.0, 23.9 (CH, CH3)
reaction using 8 in combination with B(C6F5)3, the reactivity ppm. FT-IR (selected frequencies): ˜ν = 2960 (ArC–H), 2861
slightly improved in entry 4; however, it still remains lower (C–H), 1622(CvC), 1459, 1258, 798, 753 cm−1. Elemental
than those of 1-hexene and 1-octene. Styrene gave a complete analysis calculated (%) for C31H41ClN2Ti (524.98): C 70.92,
conversion to a mixture of products (27% n-product and 73% H 7.87, N 5.34; found C 70.38, H 7.29, N 4.93.
iso-product) after 24 hours at room temperature (entry 5). We
Preparation of [η5-Cp2Zr{(Dipp)2DAD}] (3). In a 25 mL
also screened the alkenes with a halo functionality as sub- Schlenk flask, a suspension of 154 mg Cp2ZrCl2 (0.531 mmol)
strates, and observed that even 1-bromopentene can be com- in 3 mL diethyl ether was added dropwise to the freshly pre-
pletely converted to the corresponding n-product in 2 hours at pared diethyl ether (10 mL) solution of dilithium complex
room temperature (entry 7), while 1-bromohexene shows 86% [Li2(Dip)2DAD] (1) (200 mg, 0.531 mmol) at room temperature.
conversion even after 24 hours at the same temperature (entry The reaction mixture was then stirred for another 12 h. The
8). The lower reactivity for 1-bromohexene can be explained white precipitate of LiCl was filtered through a G4-frit and
by the deactivation of the catalyst due to the presence of the dried in vacuo. Red crystals were obtained after re-crystalliza-
bromine atom, followed by a sluggish reactivity towards hydro- tion from diethyl ether at −35 °C. Yield was 203 mg (82%).
silylation. Thus a sluggish reactivity in the hydrosilylation of 1H NMR (400 MHz, C6D6, 25 °C): δ 7.02–6.90 (m, 6H, ArH),
the olefins is observed in the zirconium bis-alkyl complex 8 5.62 (s, 5H, Cp-H), 5.56 (s, 5H, Cp-H), 5.35 (s, 2H, CH), 3.71
compared to catalysts known in the literature.40
(sept, 2H, CH (CH3)2), 2.92 (sept, 2H, CH (CH3)2), 1.14 (d, J =
6.8 Hz, 6H, CH (CH3)2), 1.11 (d, J = 6.8 Hz, 6H, CH (CH3)2),
1.08 (d, J = 6.8 Hz, 6H, CH (CH3)2), 1.01 (d, J = 6.8 Hz, 6H, CH
(CH3)2) ppm. 13C{1H}NMR (100 MHz, C6D6, 25 °C): δ 148.9
(ArC), 145.7 (ArC), 142.7 (ArC), 125.6 (ArC), 124.7 (ArC), 123.6
(ArC), 114.3 (Cp-C), 110.1 (Cp-C) 106.7 (CvC), 27.8 (CH), 27.1,
Experimental
General consideration
All manipulations of air-sensitive materials were performed 27.0, 25.5, 24.9, 24.2 (CH3). ppm. FT-IR (selected frequencies):
with the rigorous exclusion of oxygen and moisture in flame- ˜ν = 2960 (ArC–H), 2863 (C–H), 16 257 (CvC), 1434, 1255, 795,
dried Schlenk-type glassware, either on a dual manifold 778 cm−1. Elemental analysis calculated (%) for C40H56N2OZr
Schlenk line interfaced with a high vacuum (10−4 torr) line, or (3·THF 672.09): C 71.48, H 8.40, N 4.17; found: C 70.89, H
in an argon-filled M. Braun glovebox. Diethyl ether was pre- 7.93, N 3.88.
dried over Na wire and distilled under nitrogen from sodium
Preparation of [Ti{(Dipp)2DAD}Cl2] (4). To a solution of
and benzophenone ketyl prior to use. Hydrocarbon solvents freshly prepared dilithium complex [Li2(Dip)2DAD] (1)
(toluene, hexane and n-pentane) were distilled under nitrogen (200 mg, 0.531 mmol) in toluene (10 mL) was added slowly a
from LiAlH4 and stored in the glovebox. 1H NMR (400 MHz) solution of TiCl4 (1 M in toluene, 0.53 mL, 0.26 mmol) at
and 13C{1H} (100 MHz), spectra were recorded on a BRUKER −78 °C. The mixture was slowly allowed to warm to room temp-
AVANCE III-400 spectrometer. A BRUKER ALPHA FT-IR was erature and was stirred for another 12 h. A white precipitate
used for the FT-IR measurements. Elemental analyses were was formed and was filtered through a G4-frit and dried
performed on a BRUKER EURO EA at the Indian Institute of in vacuo, resulting in a dark brown solid which was washed
Technology, Hyderabad. The (Li2DippDAD)42 and [LiCH2- with hexane and dried under vacuum. Yield was 178 mg
SiMe3]43 were prepared according to the literature procedures. (68%). 1HNMR (400 MHz, C6D6, 25 °C): δ 7.08–7.00 (m, 6H,
TiCl4, ZrCl4, CpTiCl3, Cp2TiCl2, Cp2ZrCl2 and the NMR sol- Ph) 6.18 (s, 2H, CH), 2.98 (br, 4H, CH(CH3)2), 1.14 (d, J =
vents CDCl3 and C6D6 were purchased from Sigma Aldrich.
6.2 Hz, 24H, CH(CH3)2). 13CNMR (100 MHz, C6D6, 25 °C):
Preparation of [η5CpTi{(Dipp)2DAD}Cl] (2). In a pre-dried δ 148.1(ipso-C), 142.9 (o-C), 128.5 (Ph) 123.9 (Ph), 123.9 (Ph),
Schlenk flask, 0.117 g (0.531 mmol) of CpTiCl3 in 3 mL of 105.2 (CvC), 28.3 (CH), 24.6 (CH3). FT-IR (selected fre-
diethylether was placed and to this, freshly prepared diethyl quencies): ˜ν = 2961, 2865, 1622, 1459, 1258, 798, 753 cm−1
.
ether (10 mL) solution of dilithium complex [Li2(Dip)2DAD] (1) Elemental analysis calculated (%) for C26H36Cl2N2Ti (495.35):
(200 mg, 0.531 mmol) was added dropwise with stirring at C 63.04, H 7.33, N 5.66; found: C 62.84, H 7.01, N 5.41.
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 14876–14888 | 14883

View Article Online
Paper
Dalton Transactions
Preparation of [{(Dipp)2DADZrCl(μ-Cl)}2(κ3-Cl)(Li)(OEt2)2] (5). (Cp-C), 109.4 (CvC), 28.0, 27.6, 27.0, 25.3, 24.5, 23.1 (CH,
In a Schlenk flask, a suspension of 124 mg ZrCl4 (0.531 mmol) CH3), 46.8 (Ti–CH2), 1.4 (Si–CH3) ppm. FT-IR (selected frequen-
in 3 mL diethyl ether was added dropwise to the freshly pre- cies): ˜ν = 2961 (ArC–H), 2865(C–H), 1622 (CvC), 1459, 1258,
pared diethyl ether (10 mL) solution of dilithium complex 798, 753 cm−1
. Elemental analysis calculated (%) for
[Li2(Dipp)2DAD] (1) (200 mg, 0.531 mmol) at room tempera- C35H52N2SiTi (576.75): C 72.89, H 9.09, N 4.86; found C 72.07,
ture. The reaction mixture was then stirred for another 12 h. H 8.83, N 4.32.
The white precipitate of LiCl was filtered through a G4-frit and
Preparation of [Zr((Dipp)2DAD)(CH2SiMe3)2] (8). To a solu-
dried in vacuo Yellow crystals were obtained after re-crystalliza- tion of 5 (80 mg, 0.067 mmol) in diethyl ether (3 mL) was
1
tion from diethyl ether at −35 °C. Yield was 270 mg (85%). H added
a
pre-cooled solution of LiCH2SiMe3 (29 mg,
NMR (400 MHz, C6D6, 25 °C): δ 7.15 (m, 6H, ArH), 5.81 (s, 2H, 0.134 mmol) in diethyl ether (3 mL) at an ambient temperature
CH), 3.31 (br, 4H, CH (CH3)2), 1.20 (d, J = 5.6 Hz, 12H, CH for 6 h. LiCl was removed by filtration, after evaporation of the
(CH3)2), 1.01 (d, J = 5.6 Hz, 12H, CH (CH3)2) ppm. 13C {1H} solvent, resulting in a red oily compound which was re-crystal-
NMR (100 MHz, C6D6, 25 °C): δ 147.7 (ipso-ArC), 144.1 (o-ArC), lized from pentane at −35 °C to give yellow crystals. Yield was
143.3 (o-ArC) 126.8 (m-ArC), 124.1 (m-ArC), 105.8 (CvC), 28.1 65 mg (65%). 1HNMR (C6D6, 400 MHz): δ 7.26–7.08 (m, 6H,
(CH), 26.4, 24.3 (CH3) ppm. FT-IR (selected frequencies): ˜ν = Ph), 5.97(d, J = 3.6 Hz, 1H, CH), 5.91(d, J = 3.6 Hz, 1H, CH),
2961 (ArC–H), 2928 (ArC–H), 2866 (C–H), 1622 (CvC), 1439, 3.54 (sept, 2H, CH(CH3)2), 3.17 (sept, 2H, CH(CH3)2), 1.33 (d,
1212, 796, 754 cm−1. Elemental analysis calculated (%) for J = 6.8 Hz, 6H, CH(CH3)2), 1.22 (d, J = 6.8 Hz, 6H, CH(CH3)2),
C60H92Cl5LiN4O2Zr2 (1268.05): C 56.83, H 7.31, N 4.42; found: 1.10 (d, J = 6.8 Hz, 6H, CH(CH3)2), 0.92 (d, J = 6.8 Hz, 6H, CH-
C 56.29, H 6.88, N 4.02.
(CH3)2), 0.10 (s, 18H, Si(CH3)3), 0.03 (s, 4H, CH2) ppm.
Preparation of [Ti{(Dipp)2DAD}2] (6). A freshly prepared 13CNMR (C6D6, 100 MHz): δ 147.4 (ipso-C), 143.0 (o-C), 125.8
diethyl ether (10 mL) solution of dilithium complex [Li2(Dip)2- (Ph), 124.9 (Ph), 124.6 (Ph), 123.9 (Ph), 110.2(CvC), 109.1
DAD] (1) (200 mg, 0.531 mmol) was charged with an ether (CvC), 34.4 (Zr–CH2), 28.7, 28.0, 26.6, 24.9, 24.8, 24.4 (CH,
solution of TiCl4 in toluene (1 M, 0.26 mL, 0.26 mmol) at CH3), 1.3 (SiMe3) ppm. FT-IR (selected frequencies): ˜ν = 2958,
−78 °C. The mixture was slowly allowed to warm to room temp- 2896, 2869, 1624, 1459, 1247, 1045, 858, 830 cm−1. Elemental
erature and was kept under stirring for another 12 h. The analysis calculated (%) for C34H58N2Si2Zr (642.22): C 63.59, H
white precipitate of LiCl was filtered through a G4-frit and 9.10, N 4.36; found C 62.98, H 8.79, N 4.02.
dried in vacuo. Red crystals were obtained after re-crystalliza-
1
Typical procedure for catalytic hydrosilylation of alkenes
tion from diethyl ether at −35 °C. Yield was 153 mg (73%). H
NMR (400 MHz, C6D6, 25 °C): δ 7.12–6.98 (m, 12H, ArH), 6.18 An NMR tube was charged in the glovebox with
8
(d, J = 3 Hz, 2H, CH), 6.06 (d, J = 3 Hz, 2H, CH), 3.12 (sept, 4H, (0.018 mmol), PhSiH3 (0.407 mmol), olefin (1-hexene or
(CH(CH3)2), 2.95 (sept, 4H, (CH(CH3)2), 1.24 (d, J = 4.8 Hz, 1-octene, 0.370 mmol), and C6D6 (3 mL). The tube was closed
12H, CH (CH3)2), 1.21 (d, J = 4.8 Hz, 12H, CH (CH3)2), 1.17 (d, and taken out of the glovebox. The disappearance of the sub-
J = 4.8 Hz, 12H, CH (CH3)2), 1.15 (d, J = 4.8 Hz, 12H, CH strates and formation of new organosilanes could be con-
(CH3)2) ppm. 13C{1H} NMR (100 MHz, C6D6, 25 °C): δ 148.9 veniently monitored using 1H NMR spectroscopy.
(ipso-ArC), 144.1 (o-ArC), 143.3 (o-ArC), 124.4 (ArC), 123.6 (ArC),
X-Ray crystallographic studies of 2, 3 and 5–8
112.3 (CvC), 28.7 (CH), 27.5, 26.7, 25.6, 24,3, 23.1 (CH3) ppm.
FT-IR (selected frequencies): ˜ν = 2961 (ArC–H), 2865(C–H), Single crystals of compounds 2, 3, 5 and 6 were grown from
1622(CvC), 1459, 1258, 798, 753 cm−1. Elemental analysis cal- diethyl ether at −35 °C under an inert atmosphere. Com-
culated (%) for C52H72N4Ti (801.01): C 77.97, H 9.06, N 6.99; pounds 7 and 8 were grown from either hexane (for 7) or
found: C 77.51, H 8.75, N 6.44.
pentane (for 8) at −35 °C under an inert atmosphere. For com-
Preparation of [η5-CpTi{(Dipp)2DAD}(CH2SiMe3)] (7). To a pounds 2, 3 and 5–8, a crystal of suitable dimensions was
solution of 2 (82 mg, 0.156 mmol) in diethyl ether (3 mL) was mounted on a CryoLoop (Hampton Research Corp.) with a
added
a
pre-cooled solution of LiCH2SiMe3 (15 mg, layer of light mineral oil, and placed in a nitrogen stream at
0156 mmol) in diethyl ether (3 mL), and the reaction mixture 150(2) K. All measurements were made on an Agilent Super-
was stirred at an ambient temperature for 6 h. LiCl was nova X-calibur Eos CCD detector with graphite-monochromatic
removed by filtration and the filtrate was evaporated to Cu-Kα (1.54184 Å) radiation. Absorption corrections were per-
dryness, resulting in a light orange solid residue which was re- formed on the basis of multi-scans. Crystal data and structure
crystallized from hexane at −35 °C to give yellow crystals. Yield refinement parameters are summarised in Table TS1 in the
was 80 mg (88%). 1H NMR (400 MHz, C6D6, 25 °C): δ 7.16–7.14 ESI.† The structures were solved by direct methods (SIR92)44
(m, 4H, ArH), 7.08–707 (m, 2H, ArH), 6.19 (s, 5H, Cp-H), 5.95 and refined on F2 by the full-matrix least-squares method,
(s, 2H, CH), 3.25 (sept, 2H, CH(CH3)2), 2.42 (sept, 2H, CH- using SHELXL-97.45 Non-hydrogen atoms were anisotropically
(CH3)2), 1.32 (d, J = 8 Hz, 6H, CH(CH3)2), 1.16 (d, J = 8 Hz, 6H, refined. H atoms were included in the refinement in calculated
CH(CH3)2), 1.11 (d, J = 4 Hz, 6H, CH(CH3)2), 1.09 (d, J = 4 Hz, positions riding on their carrier atoms. No restraint has been
6H, CH(CH3)2), 0.18 (s, 9H, Si(CH3)3), −0.46 (s, 2H, CH2) ppm. made for any of the compounds. The function minimised was
13C{1H} NMR (100 MHz, C6D6): δ 149.3 (ipso-ArC), 144.5 [∑w(Fo − Fc ) ] (w = 1/[σ2(Fo ) + (aP)2 + bP]), where P = (max
2
2 2
2
(o-ArC), 142.8 (ArC), 126.5 (ArC), 124.1(ArC), 123.9 (ArC), 112.2 (Fo ,0) + 2Fc )/3 with σ2(Fo ) from counting statistics. The func-
2
2
2
14884 | Dalton Trans., 2014, 43, 14876–14888
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
2
tions R1 and wR2 were (∑||Fo| − |Fc||)/∑|Fo| and [∑w(Fo
−
Organometallics, 1997, 16, 1392; (i) L. T. Armistead,
P. S. White and M. R. Gagné, Organometallics, 1998, 17,
216; ( j) T. H. Warren, R. R. Schrock and W. M. Davis, Orga-
nometallics, 1998, 17, 308; (k) Y.-M. Jeon, S. J. Park, J. Heo
and K. Kim, Organometallics, 1998, 17, 3161; (l) C. H. Lee,
Y.-H. La, S. J. Park and J. W. Park, Organometallics, 1998,
17, 3648; (m) Y.-M. Jeon, J. Heo, W. M. Lee, T. Chang and
K. Kim, Organometallics, 1999, 18, 4107; (n) C. H. Lee,
Y.-H. La and J. W. Park, Organometallics, 2000, 19, 344;
(o) C. Lorber, B. Donnadieu and R. Choukroun, Organome-
tallics, 2000, 19, 1963.
Fc ) /∑(wFo )]1/2, respectively. The ORTEP-3 program was used
to draw the molecule. Crystallographic data (excluding struc-
ture factors) for the structures reported in this paper have
been deposited with the Cambridge Crystallographic Data
Centre as a supplementary publication, with the CCDC no.
1011649–1011654.
2 2
4
Conclusion
In this contribution, we have presented homoleptic and het-
eroleptic titanium and zirconium complexes with dianionic
1,4-diaza-1,3-butadiene in the backbone, to explore their
coordination modes in straightforward synthesis. The titanium
and zirconium alkyl complexes were also synthesized from the
respective chloride complexes 2 and 5 and trimethylsilylmethyl
lithium. In the solid state structures of all the DAD complexes,
it was observed that the dianionic 1,4-diaza-1,3-butadiene
ligand displayed a σ2,π-enediamide mode towards the titanium
and zirconium centers with a long–short–long sequence
within the ligand fragments. The metal alkyl complexes were
tested as catalysts for the intermolecular hydrosilylation of
alkenes, and moderate activity was observed for the zirconium
complex 8.
5 (a) P. J. Shapiro, E. Bunel, W. P. Schaefer and J. E. Bercaw,
Organometallics, 1990, 9, 867; (b) D. D. Devore,
F. J. Timmers, D. L. Hasha, R. K. Rosen, T. J. Marks,
P. A. Deck and Ch. L. Stern, Organometallics, 1996, 15,
3132; (c) P.-J. Sinnema, L. van der Veen, A. L. Spek,
N. Feldman and J. H. Teuben, Organometallics, 1997, 16,
4245; (d) J. Okuda, Th. Eberle and Th. P. Spaniol, Chem.
Ber., 1997, 130, 209; (e) L. Schwink, P. Knochel, T. Eberle
and J. Okuda, Organometallics, 1998, 17, 7; (f) Th. Eberle,
Th. P. Spaniol and J. Okuda, Eur. J. Inorg. Chem., 1998, 237.
6 (a) J. D. Scollard, D. H. McConville, N. C. Payne and
J. J. Vittal, Macromolecules, 1996, 29, 5241; (b) J. D. Scollard
and D. H. Mc-Conville, J. Am. Chem. Soc., 1996, 118, 10008;
(c) J. D. Scollard, D. H. McConville and St. J. Rettig, Organo-
metallics, 1997, 16, 1810.
7 V. C. Gibson, B. S. Kimberley, A. J. P. White, D. J. Williams
and Ph. Howard, J. Chem. Soc., Chem. Commun., 1998, 313.
8 G. van Koten and K. Vrieze, Adv. Organomet. Chem., 1982,
21, 151.
9 (a) St. L. Latesky, A. K. McMullen, G. P. Niccolai and
I. P. Rothwell, Organometallics, 1985, 4, 1896;
(b) F. G. N. Cloke, H. C. de Lemos and A. A. Sameh,
Acknowledgements
This work was supported by the Council of Scientific and
Industrial Research (CSIR) scheme (no. 01(2530)/11/EMRI) and
a start-up grant from IIT Hyderabad. S. A. and A. H. thank
CSIR, India and K. N. thanks the University Grant Commission
(UGC), India, for their PhD fellowships.
J.
Chem.
Soc.,
Chem.
Commun.,
1986,
1344;
(c) L. R. Chamberlain, L. D. Durfee, Ph. E. Fanwick,
L. M. Kobriger, St. L. Latesky, A. K. McMullen, B. D. Steffey,
I. P. Rothwell, K. Folting and J. C. Huffman, J. Am. Chem.
Soc., 1987, 109, 6068; (d) B. Hessen, J. E. Bol, J. L. de Boer,
A. Meetsma and J. H. Teuben, J. Chem. Soc., Chem.
Commun., 1989, 1276; (e) H. tom Dieck, H. J. Rieger and
G. Fendesak, Inorg. Chim. Acta, 1990, 177, 191;
(f) W. A. Herrmann, M. Denk, W. Scherer and
F.-R. Klingan, J. Organomet. Chem., 1993, 444, C21;
(g) F. J. Berg and J. L. Petersen, Organometallics, 1993, 12,
3890; (h) K. Dreisch, C. Andersson and C. Stalhandske,
Polyhedron, 1993, 12, 303 and 1335. (i) L. G. Hubert-Pfalz-
graf, A. Zaki and L. Toupet, Acta Crystallogr., Sect. C: Cryst.
Struct. Commun., 1993, 49, 1609; ( j) L. Kloppenburg and
J. L. Petersen, Organometallics, 1997, 16, 3548; (k) R. Leigh
Huff, S.-Y. S. Wang, K. A. Abboud and J. M. Boncella, Orga-
nometallics, 1997, 16, 1779; (l) M. J. Scotta and
S. J. Lippard, Organometallics, 1997, 16, 5857; (m) T. Zippel,
P. Arndt, A. Ohff, A. Spannenberg, R. Kempe and
U. Rosenthal, Organometallics, 1998, 17, 4429;
(n) M. G. Thorn, Ph. E. Fanwick and I. P. Rothwell, Organo-
metallics, 1999, 18, 4442.
Notes and references
1 Review: R. Kempe, Angew. Chem., Int. Ed., 2000, 39, 468.
2 (a) A. Togni and L. M. Venanzi, Angew. Chem., Int. Ed.,
1994, 33, 497; (b) M. F. Lappert, P. P. Power, A. R. Sanger
and R. C. Srivastava, Metal and Metalloid Amides, Ellis
Norwood, Chichester, UK, 1980.
3 G. J. P. Britovsek, V. C. Gibson and D. F. Wass, Angew.
Chem., Int. Ed., 1999, 111, 428.
4 (a) W. A. Herrmann, M. Denk, R. W. Albach, J. Behm and
E. Herdtweck, Chem. Ber., 1991, 124, 683; (b) T. H. Warren,
R. R. Schrock and W. M. Davis, Organometallics, 1996, 15,
562; (c) K. Aoyagi, P. K. Gantzel, K. Kalai and T. D. Tilley,
Organometallics, 1996, 15, 923; (d) S. Tinkler, R. J. Deeth,
D. J. Duncalf and A. McCamley, J. Chem. Soc., Chem.
Commun., 1996, 2623; (e) J. D. Scollard, D. H. McConville
and J. J. Vittal, Organometallics, 1997, 16, 4415;
(f) A. D. Horton and J. de With, Organometallics, 1997, 16,
5424; (g) N. A. H. Male, M. Thornton-Pett and
M. Bochmann, J. Chem. Soc., Dalton Trans., 1997, 2487;
(h) B. Tsuie, D. C. Swenson, R. F. Jordan and J. L. Petersen,
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 14876–14888 | 14885

View Article Online
Paper
Dalton Transactions
10 (a) J. Scholz, M. Dlikan, D. Ströhl, A. Dietrich,
H. Schumann and K.-H. Thiele, Chem. Ber., 1990, 123,
(g) J. Scholz, H. Görls, H. Schumann and R. Weimann,
Organometallics, 2001, 20, 4394.
2279; (b) J. Scholz, A. Dietrich, H. Schumann and 16 (a) F. S. Mair, R. Manning, R. G. Pritchard and J. E. Warren,
K.-H. Thiele, Chem. Ber., 1991, 124, 1035; (c) R. Goddard,
C. Krüger, G. A. Hadi, K.-H. Thiele and J. Scholz, Z. Natur-
forsch., B: Chem. Sci., 1994, 49, 519; (d) J. Scholz, B. Richter,
R. Goddard and C. Krüger, Chem. Ber., 1993, 126, 57;
(e) B. Richter, J. Scholz, B. Neumüller, R. Weimann and
H. Schumann, Z. Anorg. Allg. Chem., 1995, 621, 365;
(f) H. Görls, B. Neumüller, A. Scholz and J. Scholz, Angew.
Chem., Int. Ed., 1995, 34, 673.
Chem. Commun., 2001, 1136; (b) R. J. Baker, R. D. Farley,
C. Jones, M. Kloth and D. M. Murphy, J. Chem. Soc., Dalton
Trans., 2002, 3844; (c) R. J. Baker, C. Jones and
D. M. Murphy, Chem. Commun., 2005, 1339; (d) X.-J. Yang,
J. Yu, Y. Liu, Y. Xie, H. F. Schaefer, Y. Liang and B. Wu,
Chem. Commun., 2007, 2363; (e) C. Jones, A. Stasch and
W. D. Woodul, Chem. Commun., 2009, 113.
17 Acenaphthene-based DAD complexes: (a) I. L. Fedushkin,
A. A. Skatova, V. A. Chudakova, N. M. Khvoinova,
A. Y. Baurin, S. Dechert, M. Hummert and H. Schumann,
Organometallics, 2004, 23, 3714; (b) I. L. Feduchkin,
N. M. Khvoinova, A. Y. Baurin, G. K. Fukin, V. K. Cherkasov
and M. P. Bubnov, Inorg. Chem., 2004, 43, 7807;
(c) I. L. Fedushkin, V. A. Chudakova, A. A. Skatova,
N. M. Khvoinova, Y. A. Kurskii, T. A. Glukhova, G. K. Fukin,
S. Dechert, M. Hummert and H. Schumann, Z. Anorg. Allg.
Chem., 2004, 630, 501; (d) I. L. Fedushkin, V. A. Chudakova,
A. A. Skatova and G. K. Fukin, Heteroat. Chem., 2005, 16,
663; (e) H. Schumann, M. Hummert, A. N. Lukoyanov and
I. L. Fedushkin, Organometallics, 2005, 24, 3891;
(f) A. N. Lukoyanov, I. L. Feduchkin, H. Schumann and
M. Hummert, Z. Anorg. Allg. Chem., 2006, 632, 1471;
(g) I. L. Fedushkin, V. M. Makarov, E. C. E. Rosenthal and
G. K. Fukin, Eur. J. Inorg. Chem., 2006, 827;
(h) I. L. Fedushkin, M. Hummert and H. Schumann,
Eur. J. Inorg. Chem., 2006, 3266; (i) H. Schumann,
M. Hummert, A. N. Lukoyanov and I. L. Fedushkin, Chem.
– Eur. J., 2007, 13, 4216; ( j) I. L. Feduchkin, A. A. Skatova,
O. V. Eremenko, M. Hummert and H. Schumann, Z. Anorg.
Allg. Chem., 2007, 633, 1739; (k) I. L. Fedushkin,
A. N. Tishkina, G. K. Fukin, M. Hummert and
H. Schumann, Eur. J. Inorg. Chem., 2008, 483;
(l) I. L. Feduchkin, A. G. Morozov, M. Hummert and
H. Schumann, Eur. J. Inorg. Chem., 2008, 1584;
(m) I. L. Fedushkin, A. S. Nikipelov, A. A. Skatova,
O. V. Maslova, A. N. Lukoyanov, G. K. Fukin and
A. V. Cherkasov, Eur. J. Inorg. Chem., 2009, 3742;
(n) I. L. Fedushkin, A. G. Morozov, V. A. Chudakova,
G. K. Fukin and V. K. Cherkasov, Eur. J. Inorg. Chem., 2009,
4995.
11 (a) K. Vrieze, J. Organomet. Chem., 1986, 300, 307;
(b) H. Bock and H. tom Dieck, Chem. Ber., 1967, 100, 228.
12 (a) I. L. Fedushkin, N. M. Khvoinova, A. A. Skatova and
G. K. Fukin, Angew. Chem., Int. Ed., 2003, 42, 5223;
(b) I. L. Fedushkin, A. A. Skatova, V. K. Cherkasov,
V. A. Chudakova, S. Dechert, M. Hummert and
H. Schumann, Chem.
–
Eur. J., 2003, 9, 5778;
(c) I. L. Fedushkin, A. A. Skatova, M. Hummert and
H. Schumann, Eur. J. Inorg. Chem., 2005, 1601;
(d) I. L. Fedushkin, A. A. Skatova, G. K. Fukin, M. Hummert
and H. Schumann, Eur. J. Inorg. Chem., 2005, 2332;
(e) I. L. Fedushkin, A. N. Lukoyanov, M. Hummert and
H. Schumann, Z. Anorg. Allg. Chem., 2008, 634, 357;
(f) Y. Liu, P. Yang, J. Yu, X.-J. Yang, J. D. Zhang, Z. Chen,
H. F. Schaefer and B. Wu, Organometallics, 2008, 27, 5830.
13 (a) A. Galindo, A. Ienco and C. Mealli, New J. Chem., 2000,
24, 73; (b) P. J. Daff, M. Etienne, B. Donnadieu,
S. Z. Knottenbelt and J. E. McGrady, J. Am. Chem. Soc.,
2002, 124, 3818; (c) M. Ghosh, S. Sproules, T. Weyhermüller
and K. Wieghardt, Inorg. Chem., 2008, 47, 5963;
(d) M. Ghosh, T. Weyhermüller and K. Wieghardt, Dalton
Trans., 2008, 5149.
14 (a) K. Mashima, Y. Matsuo and K. Tani, Chem. Lett., 1997,
767; (b) K. Mashima, Y. Matsuo and K. Tani, Organometal-
lics, 1999, 18, 1471; (c) Y. Matsuo, K. Mashima and K. Tani,
Angew. Chem., Int. Ed., 2001, 40, 960; (d) T. K. Panda,
H. Kaneko, O. Michel, H. Tsurugi, K. Pal, K. W. Törnroos,
R. Anwander and K. Mashima, Organometallics, 2012, 31,
3178; (e) T. K. Panda, H. Kaneko, K. Pal, H. Tsurugi and
K. Mashima, Organometallics, 2010, 29, 2610; (f) S. Anga,
R. K. Kottalanka, T. Pal and T. K. Panda, J. Mol. Struct.,
2013, 1040, 129.
15 (a) A. A. Trifonov, E. N. Kirillov, S. Dechert, H. Schumann 18 For recent examples, see: (a) C. Stanciu, M. E. Jones,
and M. N. Bochkarev, Eur. J. Inorg. Chem., 2001, 2509;
(b) A. A. Trifonov, Y. A. Kurskii, M. N. Bochkarev,
S. Muehle, S. Dechert and H. Schumann, Russ. Chem. Bull.,
2003, 52, 601; (c) A. A. Trifonov, E. A. Fedorova,
V. N. Ikorskii, S. Dechert, H. Schumann and
P. E. Fanwick and M. M. Abu-Omar, J. Am. Chem. Soc.,
2007, 129, 12400; (b) K. A. Kreisel, G. P. A. Yap and
K. H. Theopold, Inorg. Chem., 2008, 47, 5293 and references
therein. (c) F. Amor, P. G. Sal, P. Royo and J. Okuda, Organo-
metallics, 2000, 19, 5168.
M. N. Bochkarev, Eur. J. Inorg. Chem., 2005, 2812; 19 (a) K. Mashima and A. Nakamura, J. Organomet.
(d) P. Cui, Y. Chen, G. Wang, G. Li and W. Xia, Organometal-
lics, 2008, 27, 4013. For lanthanide complexes having
μ-dianionic DAD ligands: (e) A. A. Trifonov, L. N. Zakharov,
M. N. Bochkarev and Y. T. Struchkov, Russ. Chem. Bull.,
1994, 43, 148; (f) H. Görls, B. Neumüller, A. Scholz and
J. Scholz, Angew. Chem., Int. Ed. Engl., 1995, 34, 673;
Chem., 2001, 621, 224; (b) Y. Matsuo, K. Mashima and
K. Tani, Organometallics, 2002, 21, 138; (c) H. Tsurugi,
T. Ohno, T. Yamagata and K. Mashima, Organometallics,
2006, 25, 3179; (d) H. Tsurugi, T. Ohno, T. Kanayama,
R. A. Arteaga-Müller and K. Mashima, Organometallics,
2009, 28, 1950; (e) H. Tsurugi, T. Saito, H. Tanahashi,
14886 | Dalton Trans., 2014, 43, 14876–14888
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
J. Arnold and K. Mashima, J. Am. Chem. Soc., 2011, 133,
18673.
Organomet. Chem., 1994, 36, 283; (c) H. Schumann, Angew.
Chem., Int. Ed., 1984, 23, 474.
20 For recent examples, see: (a) A. A. Trifonov, E. A. Fedorova, 28 A. L. Wayda and W. J. Evans, Inorg. Chem., 1980, 19, 2190.
G. K. Fukin, E. V. Baranov, N. O. Druzhkov and 29 T. K. Panda, M. T. Gamer and P. W. Roesky, Inorg. Chem.,
M. N. Bochkarev, Chem.
(b) J. A. Moore, A. H. Cowley and J. C. Gordon, Organometal- 30 C. Stanciu, M. E. Jones, P. E. Fanwick and M. M. Abu-
lics, 2006, 25, 5207; (c) A. A. Trifonov, I. A. Borovkov, Omar, J. Am. Chem. Soc., 2007, 129, 12400.
E. A. Fedorova, G. K. Fukin, J. Larionova, N. O. Druzhkov 31 (a) P. L. Watson and G. W. Parshall, Acc. Chem. Res., 1985,
–
Eur. J., 2006, 12, 2752;
2006, 45, 910.
and V. K. Cherkasov, Chem. – Eur. J., 2007, 13, 4981;
(d) M. D. Walter, D. J. Berg and R. A. Andersen, Organo-
metallics, 2007, 26, 2296; (e) T. V. Mahrova, G. K. Fukin,
A. V. Cherkasov, A. A. Trifonov, N. Ajellal and
J.-F. Carpentier, Inorg. Chem., 2009, 48, 4258;
(f) H. Kaneko, H. Nagae, H. Tsurugi and K. Mashima,
J. Am. Chem. Soc., 2011, 133, 19626 and references therein.
18, 51; (b) F. T. Edelmann, Top. Curr. Chem., 1996, 179, 247;
(c) S. Hong and T. J. Marks, Acc. Chem. Res., 2004, 37, 673;
(d) H. Kaneko, H. Tsurugi, T. K. Panda and K. Mashima,
Organometallics, 2010, 29, 3463; (e) S. Ge, A. Meetsma and
B. Hessen, Organometallics, 2008, 27, 3131; (f) H. Tsurugi,
K. Yamamoto, H. Nagae, H. Kaneko and K. Mashima,
Dalton Trans., 2014, 43, 2331 and references therein.
21 For representative examples, see: (a) D. J. Tempel, 32 R. Spence and W. E. Piers, Organometallics, 1995, 14, 4617.
L. K. Johnson, R. L. Huff, P. S. White and M. Brookhart, 33 Selected references. (a) F. A. Cotton, J. L. Calderon,
J. Am. Chem. Soc., 2000, 122, 6686; (b) L. Johansson,
O. B. Ryan and M. Tilset, J. Am. Chem. Soc., 1999, 121,
1974; (c) L. Johansson, M. Tilset, J. A. Labinger and
J. E. Bercaw, J. Am. Chem. Soc., 2000, 122, 10846;
(d) L. Johansson and M. Tilset, J. Am. Chem. Soc., 2001,
123, 739; (e) A. H. Zhong, J. A. Labinger and J. E. Bercaw,
J. Am. Chem. Soc., 2002, 124, 1378.
B. G. DeBoer and J. Takats, J. Am. Chem. Soc., 1971, 93,
3592; (b) A. Clearfield, D. K. Warner, C. H. Saldarriaga-
Molina, R. Ropal and I. Bernal, Can. J. Chem., 1975, 53,
1622; (c) K. P. Stahl, G. Boche and W. Massa, J. Organomet.
Chem., 1984, 227, 113; (d) M. Tamm, S. Randoll,
T. Banneberg and E. Herdtweck, Chem. Commun., 2004,
876; (e) I. A. Guzei, A. Mitra and L. C. Spencer, Cryst.
Growth Des., 2009, 9, 2287.
22 For selected examples, see: (a) J. Yu, X.-J. Yang, Y. Liu,
Z. Pu, Q.-S. Li, Y. Xie, H. F. Schaefer and B. Wu, Organo- 34 Selected references. (a) I. W. Bassi, G. Allegra,
metallics, 2008, 27, 5800; (b) Y. Liu, S. Li, X. J. Yang, P. Yang
and B. Wu, J. Am. Chem. Soc., 2009, 131, 4210;
(c) M. Bhadbhade, G. K. B. Clentsmith and L. D. Field,
Organometallics, 2011, 29, 6509; (d) Y. Liu, Y. Zhao,
X. J. Yang, S. Li, J. Gao, P. Yang, Y. Xia and B. Wu, Organo-
metallics, 2011, 30, 1599. and references therein. .
R. Scordamaglia and G. Chioccola, J. Am. Chem. Soc., 1971,
93, 3787; (b) P. J. Wilson, A. J. Blake, P. Mountford and
M. Schröder, J. Organomet. Chem., 2000, 600, 71;
(c) F. Basuli, B. C. Bailey, J. Tomaszewsky, J. C. Huffman
and D. J. Mindiola, J. Am. Chem. Soc., 2003, 125, 6052;
(d) T. Agapie, L. M. Henling, K. G. DiPasquale,
A. L. Rheingold and J. E. Bercaw, Organometallics, 2008, 27,
6245; (e) S. Kleinhenz and K. Seppelt, Chem. – Eur. J., 1999,
5, 3573; (f) A. Noor, W. P. Kretschmer, G. Glatz and
R. Kempe, Inorg. Chem., 2011, 50, 4598; (g) C. Yélamos,
M. J. Heeg and C. H. Winter, Organometallics, 1999, 18,
1168.
23 (a) R. J. Baker, A. J. Davis, C. Jones and M. Kloth,
J. Organomet. Chem., 2002, 656, 203; (b) R. J. Baker,
C. Jones, M. Kloth and D. P. Mills, New J. Chem., 2004, 28,
207; (c) R. J. Baker, C. Jones and M. Kloth, Dalton Trans.,
2005, 2106.
24 For acenaphthene-based DAD complexes of group 2 metals,
see: (a) I. L. Fedushkin, A. A. Skatova, V. A. Chudakova, 35 Selected references. (a) S. L. Latesky, A. K. McMullen,
G. K. Fukin, S. Dechert and H. Schumann, Eur. J. Inorg.
Chem., 2003, 3336; (b) I. L. Fedushkin, A. G. Morozov,
O. V. Rassadin and G. K. Fukin, Chem. – Eur. J., 2005, 11,
5749; (c) I. L. Fedushkin, A. A. Skatova, S. Y. Ketkov,
O. V. Eremenko, A. V. Piskunov and G. K. Fukin, Angew.
Chem., Int. Ed., 2007, 46, 4302; (d) I. L. Fedushkin,
O. V. Eremenko, A. A. Skatova, A. V. Piskunov, G. K. Fukin,
S. Y. Ketkov, E. Irran and H. Schumann, Organometallics,
2009, 28, 3863 and references therein.
G. P. Niccolai, I. P. Rothwell and J. C. Huffman, Organo-
metallics, 1985, 4, 902; (b) J. Z. Cayias, E. A. Babaian,
D. C. Hrncir, S. G. Bott and J. L. Atwood, J. Chem. Soc.,
Dalton Trans., 1996, 2743; (c) H. Tsurugi, Y. Matsuo,
T. Yamagata and K. Mashima, Organometallics, 2004, 23,
2797; (d) Yu.-C. Hu, C.-C. Tsai, W.-C. Shih, G. P. A. Yap and
T.-G. Ong, Organometallics, 2010, 29, 516; (e) S. El-Kurdi
and K. Seppelt, Chem. – Eur. J., 2011, 17, 3556; (f) Y. Rong,
A. Al-Harbi and G. Parkin, Organometallics, 2012, 31, 8208.
25 J. Liu, F. Pan, S. Yao, X. Min, D. Cui and Z. Sun, Organo- 36 (a) T. Hiyama and T. Kusumuto, in Comprehensive Organic
metallics, 2014, 33, 1374.
Synthesis, ed. B. M. Trost, Pergamon Press, Oxford, U.K.,
1991, ch. 3, vol. 8, p. 12; (b) B. Marciniec, in Comprehensive
Handbook on Hydrosilylation, Pergamon Press, Oxford, U.K.,
1992; (c) I. Ojima, Z. Li and J. Zhu, in Chemistry of Organic
Silicon Compounds, ed. Z. Rappoport and Y. Apeloig, Wiley,
Chichester, U.K., 1998, vol. 2, p. 1687; (d) B. Marcinies,
in Applied Homogenous Catalysis with Organometallic
26 (a) M. Wiecko, D. Girnt, M. Rastätter, T. K. Panda and
P. W. Roesky, Dalton Trans., 2005, 2147; (b) K. Naktode,
R. K. Kottalanka and T. K. Panda, New J. Chem., 2012, 36,
2280.
27 Review: (a) H. Schumann, J. A. Meese-Marktscheffel and
L. Esser, Chem. Rev., 1995, 95, 865; (b) C. J. Schaverien, Adv.
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 14876–14888 | 14887

View Article Online
Paper
Dalton Transactions
Compounds, ed. B. Cornils and W. A. Herrmann,
P. W. Roesky, Organometallics, 2008, 27, 1207;
(e) A. Trambitas, T. K. Panda, J. Jenter, P. Roesky,
C.-G. Daniliuc, C. Hrib, P. G. Jones and M. Tamm, Inorg.
Chem., 2010, 49, 2435.
Wiley, Weinheim, Germany, 2002, vol. 1, p. 491;
(e) F. T. Edelmann, in Comprehensive Organometallic
Chemistry II, Pergamon Press, Oxford, U.K., 1995, vol. 4,
pp. 11–210.
40 (a) K. Takaki, K. Sonoda, T. Kousaka, G. Koshoji,
T. Shishido and K. Takehira, Tetrahedron Lett., 2001, 42,
9211; (b) D. V. Gribkov, F. Hampel and K. C. Hultzsch,
Eur. J. Inorg. Chem., 2004, 4091; (c) M. Konkol,
M. Kondracka, P. Voth, T. P. Spaniol and J. Okuda, Organo-
metallics, 2008, 27, 3774.
37 (a) G. A. Molander and J. A. C. Romero, Chem. Rev., 2002,
102, 2161; (b) P.-F. Fu, L. Brard, Y. Li and T. J. Marks, J. Am.
Chem. Soc., 2002, 117, 7157; (c) I. Castillo and T. D. Tilley,
Organometallics, 2000, 19, 4733; (d) G. A. Molander and
J. Winterfeld, J. Organomet. Chem., 1996, 524, 275.
38 (a) Z. Hou, Y. Zhang, O. Tardif and Y. Wakatsuki, J. Am. 41 (a) H. Schumann, M. R. Keitsch, J. Winterfeld, S. Muhle
Chem. Soc., 2001, 123, 9216; (b) A. Z. Voskoboynikov,
A. K. Shestakova and I. P. Beletskaya, Organometallics, 2001,
20, 2794; (c) O. Tardif, M. Nishiura and Z. Hou, Tetra-
and G. A. Molander, J. Organomet. Chem., 1998, 559, 181;
(b) Y. Horino and T. Livinghouse, Organometallics, 2004, 23,
12.
hedron, 2003, 59, 10525; (d) D. Robert, A. A. Trifonov, 42 R. Chen and K. Tatsumi, J. Coord. Chem., 2002, 55, 1219.
P. Voth and J. Okuda, J. Organomet. Chem., 2006, 691, 4393. 43 G. D. Vaughn, K. A. Krein and J. A. Gladysz, Organometal-
39 (a) M. R. Bürgstein, H. Berberich and P. W. Roesky, Chem. –
Eur. J., 2001, 7, 3078; (b) P. W. Roesky and T. E. Müller, 44 M. Sheldrick, SHELXS-97, Program of Crystal Structure Solu-
Angew. Chem., Int. Ed., 2003, 42, 2708; (c) T. K. Panda, tion, University of Göttingen, Germany, 1997.
A. Zulys, M. T. Gamer and P. W. Roesky, J. Organomet. 45 G. M. Sheldrick, SHELXL-97, Program of Crystal Structure
lics, 1986, 5, 936.
Chem., 2005, 690, 5078; (d) S. Datta, M. T. Gamer and
Refinement, University of Göttingen, Germany, 1997.
14888 | Dalton Trans., 2014, 43, 14876–14888
This journal is © The Royal Society of Chemistry 2014