Early-late, mixed-metal compounds supported by amidophosphine ligands

Article abstract of DOI:10.1039/b402409e

A series of discrete early-late mixed-metal compounds supported by amidophosphine ligands were studied. Their sequential synthesis, structure and the reaction profiles were also investigated. X-ray crystal structure analysis and cyclic voltammetry were carried out for the studies. The compounds were found to be inert to transamination and protonolysis reactions with Ti amides and alkyls. The catalyst activity of the complexes were also discussed.

Full text of DOI:10.1039/b402409e

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Early–late, mixed-metal compounds supported by amidophosphine
ligands†
Q. Folashade Mokuolu,a Paul A. Duckmanton,a Peter B. Hitchcock,b Claire Wilson,a
Alexander J. Blake,a Lena Shuklab and Jason B. Love*a
a School of Chemistry, University of Nottingham, University Park, Nottingham, UK NG7 2RD.
E-mail: jason.love@nottingham.ac.uk; Fax: ϩ44 115 9513563; Tel: ϩ44 115 8467167
b Department of Chemistry, University of Sussex, Falmer, Brighton, UK BN1 9QJ
Received 17th February 2004, Accepted 21st April 2004
First published as an Advance Article on the web 27th April 2004
The sequential syntheses, structural characterisation and reactivity studies of a series of discrete early–late
mixed-metal complexes supported by the unique amidophosphine ligand m-(But2CH)N(C6H4)PPh2 L1 are described.
This ligand was synthesised using a Schiff-base/ButLi protocol and the resultant lithium salt LiL1 found to adopt a
tetrameric structure in the solid state in which both two-coordinate N–Li–N and η6:η6-arylLi metallocene bonding
motifs are present. Reaction between HL1 and labile Pt() and Pd() chlorides formed MCl2(HL1)2 complexes 4
(M = Pt) and 5 (M = Pd) in which a weak N–H ؒ ؒ ؒ π(aryl) hydrogen bonding interaction was identified in the
solid-state structure of 4. These compounds were found to be inert to transamination and protonolysis reactions
with Ti amides and alkyls; instead, stepwise alkyl transfer from Ti to Pt, resulting in Pt(CH2SiMe3)2(HL1)2 6 was
observed. Access to mixed-metal complexes was achieved using an early-metal-first approach. Reaction between the
metalloligand TiCl2(L1)2 and labile Group 10 and group 9 compounds resulted in the formation of TiCl2(µ-L1)2PtCl2
8, TiCl2(µ-L1)2PtMe2 9, TiCl2(µ-L1)2PdCl2 10, TiCl2(µ-L1)2NiBr2 11, and {TiCl2(µ-L1)2RhCl(CO)}2 12. In the
solid state, the Group 4/10 compounds 8, 9 and 10 adopt similar structures that exhibit both intramolecular
But2C–H ؒ ؒ ؒ Cl–Ti hydrogen bonding and arylNP π-stacking interactions; this hydrogen-bonding interaction is
conserved in solution. Unlike the above Group 4/10 complexes, the Ti–Rh complex 12 adopts a tetranuclear
structure in the solid state that is stabilised by similar hydrogen-bonding and π-stacking interactions. The Group
4/10 complexes were assessed as catalysts for olefin polymerisation and cross-coupling reactions. In combination with
MAO, the mixed-metal complexes 8 and 10 were poor ethylene polymerisation catalysts and resulted in polymers of
both high molecular weight and polydispersity. The Ti–Ni complex 11 formed oligomeric material only, while the
mononuclear Ti metalloligand TiCl2(L1)2 gave the best results, showing low activity (6.14 kg molϪ1 barϪ1 hϪ1) and
moderate polydispersity (12). The Ti–Pd complex 10 was assessed in arylamination and Suzuki–Miyaura reactions.
While little or no catalytic activity was observed in arylamination reactions, 10 was found to effect Suzuki coupling
between activated aryl bromides and phenylboronic acid at 80 ЊC. Unlike with TiCl2(L1)2, reactions between 8 and
the reducing agents C8K or Mg led to intractable mixtures. However, the cyclic voltammetry of both compounds
indicated that a reversible one-electron reduction process occurs at a similar potential (ca. Ϫ0.7 V) and was assigned
to the formation of the monohalides TiCl(L1)2 and TiCl(µ-L1)2PtCl2. The reactivity of the metallocage TiCl(µ-L3)3Pt
was also investigated. While reduction reactions were unsuccessful, the metallocage reacted with CO to form the
Ti–Pt carbonyl, TiCl(µ-L3)3Pt(CO) 13. The X-ray crystal structure of 13 revealed that accommodation of CO
at the Pt centre has caused the cage expansion and loss of agostic aryl-H ؒ ؒ ؒ Pt interactions. Furthermore,
reaction of TiCl(µ-L3)3Pt with excess MeI resulted in the formation of the Ti()–Pt() complex
trans-TiCl2(µ-L3)2(κ1-L3MeI)Pt(Me)I.
mixtures of well-defined, early and late metal alkene poly-
Introduction
merisation catalysts have been shown to promote the formation
The need for more efficient and straightforward chemical
of branched polyalkenes using a single monomer source.9
processes has encouraged the development and exploitation of
One strategy towards tandem catalysis that has yet to be
metal complexes that can act as multifunctional catalysts for
significantly exploited is to develop mixed-metal complexes
mechanistically-different chemical reactions. This tandem
in which each discrete and distinctly different metal centre can
catalysis methodology is becoming increasingly incorporated
potentially interact with different substrates and so promote
intramolecular reactions between the activated species. Ideal
into organic and bioorganic synthesis,1 with one-pot, single-
catalyst tandem cyclisations,2 cascade reactions,3 metathesis–
candidates that would facilitate these reactions would result
hydrogenation or isomerisation, oxo-Mannich,4 hydroamin-
from combinations of metals from the antipodes of the trans-
ation-hydrosilylation,5 and hydroaminomethylation6 reactions
all recently reported. Furthermore, dual-function catalysis is
ition metal series (i.e. early–late), as they have the potential
to promote unusual reactivity that is not available from
also becoming prevalent in polymerisation chemistry, with the
either metal alone.10 However, the reaction profiles of early–late
development of ROMP-hydrogenation7 and ROMP-ATRP
heterobimetallic (ELHB) complexes are disappointing and
often demonstrate no improvement when compared to
procedures.8 Polyalkene synthesis has also benefited from
a variation of the single-catalyst, one-pot approach, in that
mononuclear counterparts. Even so, ELHB complexes have
been shown to be active as hydroformylation,11 hydrosilylation,
hydrogenation12 and alkene polymerisation catalysts,13 although
† Electronic supplementary information (ESI) available: Tables of crys-
tal data and selected bond lengths and angles, plus Ortep diagrams of
complexes 9 and 10. See http://www.rsc.org/suppdata/dt/b4/b402409e/
it is rare that both metal centres are both involved in the
catalytic cycle.10
D a l t o n T r a n s . , 2 0 0 4 , 1 9 6 0 – 1 9 7 0
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 4
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Usually, early–late heterobimetallic (ELHB) complexes are
designed so that metallic proximity is promoted, either through
the formation of direct metal–metal bonds or by the inclusion
of bridging donor groups.10,14 However, such interactions often
result in steric and electronic saturation of the early metal
moiety which can endanger resultant reactivity. We reasoned
that it would be desirable to separate the metallic sites in order
to limit metal–metal bonding and inadvertent bridging inter-
actions, so developed an amidophosphine ligand L in which the
N and P-donors are rigidly spaced by a m-substituted aryl ring.
The construction of ELHB complexes is often aided by the use
of mixed-donor ligands that selectively bind to distinct metals;
classically, mixed-donor ligands such as cyclopentadienyl-
and alkoxy-phosphines have been employed to generate well-
defined mixed-metal complexes.10,15 However, amidophosphine
ligands have been poorly utilised in the synthesis of ELHB
complexes, which is surprising given the recent renaissance
of the amido ligand in early transition metal and f-element
chemistry.16 We recently communicated that the N-silyl-substi-
tuted amidophosphine ligand L3 facilitates the sequential
assembly of the anisotropic TiIV/Pt0 metallocage ClTi(µ-L3)3Pt
in which the metals are well-separated and each metal moiety
structurally resembles their mononuclear analogues.17 Further-
more, we also reported that the more bulky, N-But2CH-substi-
tuted analogue L1 facilitates the formation of the disubstituted
metalloligand TiCl2(L1)2, and that reduction of this compound
by magnesium results in the formation of an unusual TiIIIMg2
hydride.18 We report here the syntheses and structures of new,
amidophosphine-based Ti/Pt, Ti/Pd, Ti/Ni and Ti/Rh mixed-
metal complexes that stem from the titanium metalloligand
TiCl2(L1)2 and the reactivity of these mixed-metal complexes
and the metallocage ClTi(µ-L3)3Pt.
isolated yield. The 1H NMR spectrum of 2a reveals the
resonance characteristic of the imine proton at 7.68 ppm. It has
been shown that the addition of MeLi across the N᎐C imine
᎐
bond derived from anilines and (CD ) C᎐O is successful as the
᎐
3
2
usual α-deprotonation reaction is isotopically inhibited.21 In
contrast, the imines 2a and 2b contain no acidic α-protons, and
so they undergo clean addition reactions with RLi reagents; the
addition of ButLi to 2a and 2b results in the clean formation of
the lithium amides LiL1 and LiL2, respectively, in high yields.
In the case of the phosphine-substituted aniline, it was found
synthetically simpler to quench the lithium salt LiL1 in water,
isolate the But2CH-substituted aniline HL1 and react this with
BunLi in a separate step to reform LiL1 as a yellow, crystalline
solid. The 1H NMR spectrum of HL1 shows resonances
characteristic of NH and CH protons as doublets at 3.80 and
2.90 ppm, respectively. The X-ray crystal structure of LiL1 was
determined (Fig. 1), and reveals that aggregation in the solid
state has occurred to form a tetrameric complex (ESI†). This
aggregation has been promoted by the presence of two different
lithium coordination environments.
Results and discussion
Ligand synthesis and characterisation
In order to effectively control the coordination number at
titanium and avoid possibly detrimental side-reactions
involving the cleavage of the SiMe3 substituents in L3, we
sought a new route to bulky alkylanilides from the readily
available precursor 3-diphenylphosphinoaniline, 1a.19 N-tert-
butylanilides have been synthesised in a variety of ways,
including reaction of ButNH2 with benzynes, and Pd-catalysed
arylamination of ButNH2.20,21 We reasoned that benzyne
formation from the PPh2-substituted aniline, 1a would be
non-regiospecific, and found that the presence of the PPh2
group hindered the Pd-catalysed methodology, so we instead
turned our attention to classic Schiff-base functionalisation
(Scheme 1).
Fig. 1 Solid-state structure of LiL1 (50% ellipsoids). For clarity, all
hydrogens and pentane solvent molecules are omitted.
In a classical manner, Li1 is symmetrically bound solely to
two amido-nitrogens N1 [Li1–N1 1.937(9) Å] and N2 [Li1–N2
1.936(8) Å].22 As with other low-coordinate lithium amides, the
coordinative unsaturation of the lithium atom is satisfied both
by weak interactions with, and the steric protection provided
by the hydrocarbon ligand framework;23 close contacts are
observed between Li1 and the But carbons C26 (2.815 Å) and
C52 (2.700 Å), respectively. More unusually, the second lithium,
Li2 is sandwiched between two aryl rings that form the bridge
between the N and P donor atoms. Although η6-coordination
of an aryl ring to lithium is increasingly well known,24 the above
η6:η6-metallocene ligation for lithium is more rare, with only
five crystallographically characterised examples reported,25
and is unique in solid-state amidolithium chemistry. The
metallocene aryl rings C1–C6 and C28–C33 are coplanar
(dihedral angle 0.7 Њ) and staggered, with Li2 centrally disposed
[Li2–cent = 2.049(9) and 2.025(8) Å] and linear [cent–Li2–centЈ
= 174.0(5)Њ]. However, the Li2–C(aryl) distances vary consider-
ably [2.707(9)–2.325(9) Å], with the longest distance associated
with the amido carbon C3. This asymmetry is reflected in the
N1–C3 bond [1.345(5) Å] and the C–C bonds of the aryl ring
itself [1.379(6)–1.440(6) Å], which are compatible with a reson-
ance form in which the N–C bond possesses a significant degree
of double bond character. Structural comparison between LiL1
and HL1 was not possible as the free-base is an oil, so the
phosphine oxide, 3 was synthesised by peroxide oxidation of
HL1 in ethanol (Scheme 1) and the X-ray crystal structure
determined (Fig. 2), ESI.†
Scheme 1 Synthetic route to the bulky anilides, LiL1 and LiL2.
As such, the reaction between anilines 1a or 1b and tri-
methylacetaldehyde in benzene in conjunction with azeotropic
water removal yields the imines 2a and 2b, respectively, in good,
D a l t o n T r a n s . , 2 0 0 4 , 1 9 6 0 – 1 9 7 0
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Group 10 monometallic complexes
The reaction between the free-base HL1 and labile Pt() and
Pd() complexes cleanly results in high yields of the phosphine
halides, cis-PtCl2(HL1)2 4 and cis-PdCl2(HL1)2 5 (Scheme 2).
NMR and microanalytical data fully support the proposed
formulation.
Fig. 2 Solid-state structure of the aminophosphine oxide 3 (50%
ellipsoids). All hydrogens except on N and C19 are removed for clarity.
A comparison of the bond lengths of the aryl ring bridging
the N and P donors of LiL1 and 3 is made in Fig. 3, and is
consistent with the adoption of the resonance form A. Here, the
Scheme 2 Synthesis of Group 10 aminophosphine complexes and
attempted protonolysis reactions.
The cis-ligation in solution was confirmed by 31P{1H} NMR
spectroscopy using both chemical shift and Pt–P coupling
constant information; both 4 and 5 show similar data to the
structurally characterised Pd and Pt triphenylphosphine
analogues. The solid-state structure of 4 was confirmed by
X-ray diffraction studies; colourless crystals of 4 were grown
from benzene and the solid-state structure is shown in Fig. 4
(ESI†).
N1–C3 bond is shortened and similar to reported N᎐C(sp2)
᎐
bond lengths, in conjunction with an elongation of the C2–C3
and C3–C4 bonds.
Fig. 3 Comparison between structural parameters of LiL1 and 3.
An investigation into the solution structure of LiL1 by NMR
spectroscopy was undertaken to see if the tetrameric, solid-state
structure was retained. 1H, 31P{1H} and 7Li{1H} variable-
temperature NMR spectra were recorded, and showed that
a dynamic process was occurring in solution; unfortunately,
no straightforward assignment of the solution structure could
be made. At 298 K, each ligand resonance is doubled, with, for
example two resonances at 3.15 and 2.71 ppm seen for the
CHBut2 protons. On warming to 70 ЊC, these resonances
coalesce and then decoalesce at 100 ЊC to a broad singlet at 2.90
7
ppm. Both 31P{1H} and Li{1H} NMR spectra display broad,
single resonances at 298 K that sharpen on warming. It is clear
from these data that at high temperature a single species is
present in solution, and that on cooling aggregation occurs,
presumably to form an equilibrium mixture. In an attempt to
clarify the nature of the solution species at 298 K, the molecular
weight of LiL1 was determined by cryoscopic freezing point
depression in cyclohexane, and at 690 u was found to lie
approximately in between that of a monomer (409.47) and
dimer (818.94), and cannot be assigned to that of the tetramer
as seen in the solid state. It therefore appears that a monomer–
dimer equilibrium operates at 298 K, and that facile
dissociation of the tetramer occurs in solution.
Fig. 4 The solid-state structure of 4 (50% ellipsoids). All hydrogens
except those on N1 and N2 are removed for clarity.
As expected for a d8 metal, a square-planar ligand arrange-
ment is seen at Pt (Σ angles = 360.13Њ), and the phosphines
adopt a cis-configuration; the P–Pt–P bite angle at 97.17(8)Њ
is almost identical to that of cis-PtCl2(PPh3)2 (97.79Њ).26 The
C(aryl)–N bond length of 1.384(10) Å is comparable to that
found in the phosphine oxide 3 and is a value intermediate
between a C–N single and double bond distance. Interestingly,
the N1–H bond points towards the centre of the N,P-substi-
tuted aryl ring of the other aminophosphine ligand and so
engages in a N–H ؒ ؒ ؒ π-aryl hydrogen bonding interaction.
This type of interaction has been surveyed using crystallo-
graphic and theoretical data, and it has been observed that the
preferred X–H ؒ ؒ ؒ π geometry involves the direct interaction of
the X–H bond with the carbon atoms of the aryl ring, and that
the H ؒ ؒ ؒ π distance is moderated by the X–H acidity.27 In 4,
close contacts between N1H and the aryl carbons C44 (3.091
Å) and C45 (3.077 Å) are seen, with a NH ؒ ؒ ؒ π-centroid
distance of 3.339 Å. However, this interaction is not conserved
Synthetic approaches to mixed-metal complexes
Two routes involving the sequential ligation of either early or
late transition metals by L1 in order to systematically form
the desired mixed-metal complexes were assessed. Initially, late-
metal ligation was attempted, as the resultant monometallic
complexes would be air- and moisture-stable and require little
specialist handling. Incorporation of the early metal could
then be achieved via standard transamination or protonolysis
reactions.
1
in solution as the N–H resonance in the H NMR spectrum
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appears at 3.84 ppm, a value that is comparable to that of the
free-base HL1. Transamination and protonolysis NMR tube
reactions between the Pt aminophosphine complex 4 and
Ti(NMe2)4, Zr(NEt2)4 and Ti(CH2SiMe3)4 were carried out.
Unfortunately, no transamination reactions were observed,
even at elevated temperatures (80 ЊC). However, metathesis
reactions did occur, although these did not result in the form-
ation of the desired mixed-metal complex but in the formation
of Pt() alkyl complexes with presumably concurrent TiCl4
production. Monitoring the reaction between 4 and Ti(CH2-
SiMe3)4 in C6D6 at room temperature by 31P{1H} NMR
spectroscopy clearly shows the immediate formation of the
asymmetric Pt complex, cis-PtCl(CH2SiMe3)(HL1)2 6 (Scheme
2); associated doublets (JPP 14.1 Hz) are seen at δ 25.8 ppm with
PtP coupling constants of 1672 and 4432 Hz that are consistent
with P trans to alkyl and chloride, respectively.28 After 24 h, this
complex has been completely converted into the cis-bis(alkyl)
complex, 7, with PtP coupling of 2016 Hz commensurate with
this isomer.29 The lack of titanium ligation is confirmed in the
1H NMR spectrum of 7, in which the N–H proton remains as
a doublet at 3.90 ppm. It is therefore evident that the acidity
of the amino group in HL1 is too low for transamination or
protonolysis to occur, presumably as a consequence of the
extreme steric protection offered by the But2CH substituents.30
The problems associated with this metallation route led us to
investigate the alternate early-metal-first protocol.
Fig. 5 Solid-state structure of the Ti–Pt complex, 8 (50% ellipsoids).
All hydrogens and benzene solvate molecules have been removed for
clarity.
bond lengths are similar to previously reported values.31,32 Fur-
thermore, the Pt() centre is square planar (Σ angles = 362.59Њ)
and reveals Pt–P and Pt–Cl bond lengths similar to those of cis-
PtCl2(PPh3)2.26 As with the metalloligand precursor TiCl2(L1)2,
the N-substituent CH protons are oriented towards the chloride
atoms, and engage in an overall C2-symmetric, hydrogen-
bonding motif (av. H ؒ ؒ ؒ Cl 2.94 Å, av. C–H ؒ ؒ ؒ Cl 127Њ).
While agostic interactions of the methine proton of Pri sub-
stituents with an early transition metal centre is becoming
increasingly reported,33,34 hydrogen-bonding interactions
between the methine proton and ligated halide are more rare.35
Octahedral, Pri-substituted diazadiene Ti chlorides display two
C–H ؒ ؒ ؒ Cl interactions that result in significant elongation of
the Ti–N and Ti–Cl bond distances;36 on the contrary, no
significant bond elongation is seen in 8. Furthermore, the N–Pri
substituents of Arduengo carbenes (L) interact strongly with
chloride in the adducts ZrCl4L2; DFT calculations suggest that
this interaction has a significant effect on rotation about
the Zr–carbene vector.37 The hydrogen bonding interaction
Ti–Group 10 mixed-metal compounds
We have recently reported the synthesis and reduction reactions
of titanium() complexes that incorporate L1 and L2.18
Synthesis of these complexes by salt elimination methodology
is surprisingly straightforward and leads to bis(ligand) com-
plexes TiCl2(L)2 in which incorporation of neither donor
solvent nor eliminated halide are seen. The X-ray crystal struc-
ture of TiCl2(L2)2 showed that a distorted tetrahedral geometry
was adopted at titanium and that the aryl rings π-stack. A
preliminary X-ray structure of the amidophosphine analogue
TiCl2(L1)2 shows a similar connectivity and π-stacking of the
aryl rings to TiCl2(L2)2 and indicates that this complex will act
as a chelating metalloligand; the poor quality X-ray data meant
that only the general connectivity of this complex was deter-
mined. Reaction between this metalloligand and labile Group
10 complexes results in the formation of discrete binuclear
mixed-metal complexes (Scheme 3).
1
observed in the solid state is reflected in solution. In the H
NMR spectrum of 8, two But resonances are seen at δ 0.70 and
0.90 ppm, and are a consequence of C2-symmetry imposed by
both the asymmetric π-stacking of the bridging aryl groups and
the hydrogen bonding interaction. Significantly, the resonance
attributed to the methine proton appears at 5.23 ppm, and
represents a considerable shift to low field as compared to
LiL1 (δCH 2.71) in which no strong hydrogen bonding inter-
actions are observed. Similar downfield shifts have been
observed in complexes that contain either agostic C–H ؒ ؒ ؒ M
or C–H ؒ ؒ ؒ Cl interactions and are consistent with a weakening
of the C–H bond.34,36,37 The 31P{1H} NMR spectrum indicates a
symmetrical ligand disposition and cis-ligation at platinum,
with JPtP 3686 Hz consistent with P trans to Cl. These data are
similar to those for cis-PtCl2(PPh3)2 and also for the platinum-
only complex, 4, and implies that no gross structural or elec-
tronic reorganisation has occurred upon incorporation of the
second metal (this is also reflected in the metrical data seen at
the Ti centre). It is therefore evident that the conjoined metal
moieties should realistically behave as independent fragments.
In a similar manner to the synthesis of 8 by labile ligand
substitution, the dimethyl complex TiCl2(µ-L1)2PtMe2, 9 was
prepared in moderate yield as a red, crystalline material
(Scheme 3). The X-ray crystal structure of 9 was determined
(ESI†) and was found to be isostructural to 8, although the
higher trans-influence of the Me groups as compared to
chloride in 8 is reflected in the slightly longer Pt–P distances in 9
Scheme 3 Synthesis of Ti–Group 10 mixed-metal complexes.
The reaction between TiCl2(L1)2 and PtCl2(hexadiene) results
in the clean formation of the early–late dinuclear metallo-
macrocycle TiCl2(µ-L1)2PtCl2, 8 as a red, crystalline material;
the X-ray crystal structure was determined and is shown in
Fig. 5 (ESI†).
The solid-state structure confirms the binuclear nature of 8,
and shows that the two metals are bridged by two amido-
phosphine ligands which rigidly enforce a large M ؒ ؒ ؒ MЈ
separation (7.662 Å). The titanium() centre is distorted
tetrahedral, with the large N1–Ti1–N2 angle of 117.3(2)Њ
attributable to the bulky nature of the N-substituents. Similarly
obtuse N–Ti–N angles have been reported for titanium amido
complexes that incorporate bulky N-substituents, e.g. Ti(CH2-
Ph)2{N(SiMe3)2}2 [120.6(1)Њ] and TiCl2(L2)2 [117.74(6)]. Chel-
ating diamido complexes, however, generally exhibit smaller
bite angles,31 with the exception of ferrocenyl-based diamido
complexes that exhibit angles >130Њ.32 The Ti–N and Ti–Cl
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[2.290(3) and 2.291(2) Å]. Similar Pt–P bond distances are seen
in PtMe2(L2) complexes, where L2 is a chelating diphosphine,
and the Pt–Me bond distances in 9 also correlate well with these
dialkyl complexes. The small thermal ellipsoids observed for the
methyl carbons of 9 may be due to the contamination and
co-crystallisation of 9 with the monoalkyl species TiCl2(µ-L1)2-
PtMeCl. The 31P{1H} NMR spectrum of 9 displays a singlet
that is attributable to the major dialkyl product at 32.9 ppm
(JPtP 1867 Hz), plus a minor product (<5%) with an AAЈBBЈ
coupling pattern (δ 33.66, 30.95, JPtP 4432, 1854, JPP 15 Hz) that
is consistent with monoalkylation at platinum. In the 1H NMR
spectrum of 9, the Pt–Me group resonates at 0.42 ppm
(JPtC 68.4 Hz).
The reaction between the Ti metalloligand and PdCl2-
(PhCN)2 cleanly results in the formation of the dinuclear,
mixed-metal tetrahalide complex TiCl2(µ-L1)2PdCl2, 10 in good
yield as a red, crystalline material (Scheme 3). The X-ray crystal
structure of 10 was determined (ESI†) and was found to be
isostructural to both 8 and 9 with the metric parameters at Pd
similar to those reported for other Pd() phosphine complexes.
The intrametallic M–MЈ separation of 7.702 Å in 10 is similar
to that observed in 8 and 9 (7.662 and 7.680 Å, respectively). In
the 31P{1H} NMR spectrum of 10, two products are observed
in a 3 : 1 ratio. The chemical shift of the major product at 36.4
ppm is similar to that seen for the monometallic Pd complex,
5 and can be assigned to the cis-isomer, whereas the minor
product at 24.4 ppm is attributable to the trans-isomer. It is
evident that the trans-isomer is the kinetic product, as heating
a sample of cis/trans-10 in C6D6 for 48 h results in complete
conversion to cis-10 only.
The formation of mixed Ti/Ni complexes was also explored.
Here, the choice of Ni precursor was key to complex formation,
as no reaction between the Ti metalloligand and the nickel()
chlorides NiCl2, NiCl2(DME), NiCl2(PBu3)2, or NiCl2(MeCN)2
was observed, even at elevated temperature. However, the
reaction between the Ti metalloligand and NiBr2(DME) in
THF at 85 ЊC was successful, and generated TiCl2(µ-L1)2NiBr2,
11 in good yield as a dark green solid. Unfortunately, and
despite exhaustive attempts, no crystalline material suitable for
X-ray diffraction studies was obtained; combustion analyses
confirmed the expected empirical formula. While the mass
spectrum (EI) did not show a molecular ion, a fragment due to
the loss of four methyl groups was seen at 890 u. The isotopic
pattern is consistent with that calculated to include TiCl2NiBr2,
and implies that 11 is dinuclear. NMR spectra showed that 11
is paramagnetic, and so suggests that the Ni() centre has
tetrahedral geometry. The solution magnetic moment of 3.2 µB
was determined by Evan’s method and is consistent with the
presence of the two unpaired electrons expected for tetrahedral
d8 Ni() (µcalc = 2.83 µB).
Fig. 6 Solid-state structure of the Ti–Rh dimer 12 (50% ellipsoids);
But methyl carbons, all hydrogens and CH2Cl2 solvate molecules have
been omitted for clarity.
NMR spectra were recorded on mixing of the Ti and Rh
reagents in CD2Cl2, prior to the precipitation of 12. In the
31P{1H} NMR spectrum, a doublet at 30.2 ppm with associated
Rh–P coupling of 128 Hz is observed, and is consistent with the
adoption of a trans-configuration in solution; some cis-isomer
is also present (<2% δ 31.8 and 28.1 ppm, JRhP 127, JPP 7.0 Hz).
Furthermore, the C–H ؒ ؒ ؒ Cl contact observed in the solid
state is conserved in solution, with the methine H resonating to
low field at 5.35 ppm in the 1H NMR spectrum. It is difficult to
reason why the Ti–Rh complex adopts a tetranuclear structure,
whereas the Ti–Pt/Pd/Ni complexes exhibit dinuclear structural
motifs, but it is probable that both the preference of trans- over
cis-configuration at Rh and the different π-stacking arrange-
ment displayed by 12 are factors involved in the outcome. It is
remarkable that only discrete di- and tetranuclear molecules are
formed, and that no polymeric material is observed in any of
these syntheses.
ꢀ-Stacking interactions
A common feature of all of the crystallographically character-
ised mixed-metal complexes described above is the π-stacking
interaction between the unique bridging arylNP rings. The two
different π-stacking arrangements are shown in Fig. 7 and the
degree of offset, centroid-centroid distances and the dihedral
angles between aryl planes in 8, 9, 10, 12 and TiCl2(L2)2 are
listed in Table 1 for comparison.
The reaction between TiCl2(L1)2 and the rhodium carbonyl
dimer {RhCl(CO)2}2 did not form the expected dinuclear
complex as observed above for the Group 10 metals, but instead
resulted in the formation of the tetrametallic complex {TiCl2-
(µ-L1)2RhCl(CO)}2, 12 as an orange, poorly soluble crystalline
material in good yield; the X-ray crystal structure was deter-
mined and is shown in Fig. 6 (ESI†). As with the dinuclear Ti–Pt
complex 8, the titanium centre in 12 is four-coordinate and
distorted tetrahedral, and displays an obtuse N–Ti–N bond
angle of 114.60(11)Њ. The Rh() centre is square planar (Σ angles
at Rh = 360.21Њ), of trans-configuration, and displays bond
distances and angles similar to trans-RhCl(CO)(PPh3)2.38
C–H ؒ ؒ ؒ Cl hydrogen bonding similar to that seen in 8 is also
observed in 12, although here the methine protons interact
solely with one chloride (Cl1); close C–H ؒ ؒ ؒ Cl contacts
between Cl3 and the central aryl C–H pocket are also evident.
The four metals are well separated by the bridging arylNP rings,
and form a rhombohedral motif (acute Rh–Ti–Rh angle
55.83Њ) in which the Ti ؒ ؒ ؒ Rh separations are 8.057 and 8.487
Å. Although 12 is poorly soluble in common organic solvents,
Aromatic π–π stacking interactions are well documented and
have been observed both in discrete bimetallic and polymetallic
network structures.39 The general aromatic ring arrangement in
bimetallic and network structures is where the two rings are
parallel and offset. This maximises the attractive interaction
between the π-electron cloud and the carbon σ- and/or the
CH-framework and minimises repulsive, electrostatic π–π
interactions. Ring centroid contacts of 3.8 Å and offset angles
of 20Њ represent the average offset π-stacking interaction,
although an increase in the offset angle corresponds to an
increase in the π–σ attraction. It is evident that all of the mixed-
metal complexes exhibit offset π-stacking similar to that
observed in the Ti metalloligand. On addition of the late metal,
the bridging aryl rings are significantly more offset than in the
monometallic complex, and may signify increased π–σ inter-
action. When the late metal is Rh, the π-stacked rings deviate
significantly from parallel and exhibit closer centroid contact.
While it is difficult to draw firm structural conclusions from
these π-stacking effects, it is probable that the formation of
these discrete metallomacrocycles is favoured over polymeric
D a l t o n T r a n s . , 2 0 0 4 , 1 9 6 0 – 1 9 7 0
1964

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Table 1 Analysis of π-stacking interactions
Centroid–centroid/Å
Stacking anglea/Њ
Offset angleb/Њ
TiCl2(L2)2
Ti–PtCl2 8
Ti–PtMe2 9
Ti–Pd 10
3.746
3.772
3.746
3.714
3.512
4.6
1.4
4.2
2.2
10.3
22.3
30.3
29.8
30.3
22.6
Ti–Rh 12
a Parallel aryl rings have a stacking angle of 0Њ. b Angle showing degree of ring slippage, 0Њ for eclipsed rings.
Table 2 Polymerisation data
a
Activityb
Mw
Mn
PDI
TiCl2(L2)2
Ti ؒ ؒ ؒ PtCl2 8
Ti ؒ ؒ ؒ Pd 10
Ti ؒ ؒ ؒ Ni 11
714000
674250
946000
58800
10848
14825
12.1
62.2
63.8
6.14
2.88
1.05
Unidentified oligomeric material
a The GPC was calibrated with polystyrene and a mathematical
procedure involving the use of literature viscosity constants applied
to the calibration to allow for the difference in chemical type between
the sample and the calibrants. b kg molϪ1 barϪ1 hϪ1
.
Fig. 8 GPC of polyethylene produced using Ti and Ti/Pt and Ti/Pd
procatalysts (duplicate experiments shown).
Unfortunately, it is evident that all of these complexes exhibit
low activity as olefin polymerisation catalysts, especially when
compared to the standard Cp2ZrCl2/MAO system that was
evaluated under identical conditions (activity = 29.2 kg molϪ1
hϪ1 barϪ1). Incorporation of Pt or Pd (complexes 8, 10) results
in a two- to three-fold drop in activity and a large increase in
polydispersity over the monometallic system, while no polymer
was observed when incorporating Ni (complex 11). In this latter
case, however, a significant exotherm (ca. 40 ЊC above ambient)
was observed during the polymerisation experiment which may
imply that some oligomerisation reactions have occurred;
unfortunately, we were unable to characterise any oligomeric
material using NMR spectroscopy or mass spectrometry. In all
cases (except Ni), the resultant polyethylene is of high molec-
ular weight and some ultrahigh molecular weight material
was seen to precipitate as a gel from hot chlorobenzene solu-
tions prior to GPC analysis. It therefore appears that the
incorporation of the late metal is having an adverse effect
during catalysis, both by arresting the activity observed for
the Ti-only complex TiCl2(L1)2 and also by providing multiple
sites for propagative and termination steps. Furthermore, it is
possible that the addition of MAO during the activation of
the procatalyst has promoted the reductive decomposition to
inactive TiIII or TiII material. Unlike the above Ti–Pt/Pd/Ni
compounds, zirconocene-based mixed-metal complexes have
been reported to exhibit enhanced activity as alkene poly-
merisation catalysts as compared to their mononuclear
counterparts. However, prior to this work, no discrete Ti-based
mixed-metal complexes have been reported to partake in this
Fig. 7 Illustration of the π-stacking interactions in Ti–Pt, 4 and
Ti–Rh, 12 complexes.
species by the incorporation of both constructive π-stacking
and C–H ؒ ؒ ؒ Cl hydrogen bonding interactions.
Reactivity studies
The general reactivity of the fully characterised, mixed-metal
complexes described above was assessed, initially to determine
if these complexes underwent similar reactions to their
mononuclear counterparts. Therefore, representative catalytic
reactions specific to either the early or late metal were probed,
and the effect of the second, disparate metal centre examined.
Alkene polymerisation
Given the success of early transition metal amides as catalysts
for alkene polymerisation,40 and the efficacy of mixtures of
early and late metal complexes in tandem alkene polymerisation
(see above), the Ti-only and Ti–Group 10 complexes were
evaluated as ethylene polymerisation catalysts. It was antici-
pated that polyethylene with a significant degree of branching
could be synthesised, as oligomers produced at the late metal
could possibly be incorporated into linear polyethylene
produced at the early metal centre. Solutions of these
complexes in toluene were treated with MAO and pressurised
with ethylene at 10 bar for 1 h; the resultant polyethylene was
analysed by high temperature GPC (Fig. 8 and Table 2).
D a l t o n T r a n s . , 2 0 0 4 , 1 9 6 0 – 1 9 7 0
1965

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type of reaction, and our attempts to synthesise analogous
Zr-based mixed-metal complexes have so far been unsuccessful.
led us to probe Suzuki–Miyaura cross-coupling reactions. In
this instance, the reaction between 10, phenylboronic acid and
3,5-dimethoxybromobenzene in dioxane at 80 ЊC using Cs2CO3
as the base was monitored by GCMS, and showed the high
yielding formation of the desired biaryl compound (m/z 214,
90%), plus a quantity of biphenyl (m/z 154, 10%) after 36 h.
A similar reaction using 4-nitrobromobenzene also resulted in
the desired biaryl compound (85%), plus a similar amount of
biphenyl (10%, by GCMS). Both biaryl products were isolated
and their formulation confirmed by NMR spectroscopy and
melting point. Similar reactions were attempted at 25 ЊC and
also using aryl chlorides instead of aryl bromides, but in both
cases no reaction occurred.
Reduction reactions
We recently reported that the reduction of the Ti metalloligand
TiCl2(L1)2 by magnesium metal in THF results in double
o-metallation of L1 combined with Ti reduction to form
the unique TiIIIMg2 hydride {(THF)4Mg2(µ2-Cl)}(µ3-H)2Ti-
{N(CHBut2)2C6H3PPh2-3}2.18 Several attempts at reducing the
Ti–Pt complex 8 were made using a variety of reducing agents.
The use of C8K in THF resulted in substantial decomposition
from which only free ligand resonances were observed by NMR
spectroscopy, and implies that both Ti and Pt centres are by
affected by this reagent. Reduction by magnesium generated
dark brown, paramagnetic solutions that superficially appeared
similar to solutions of the above TiIIIMg2 hydride, but no firm
data could be obtained for this material. As such, analysis of
the reduction process by cyclic voltammetry was undertaken in
Reactions of the metallocage ClTi(ꢁ-L3)3Pt
We previously reported the synthesis and structural character-
isation of the Ti()–Pt(0) metallocage ClTi(L3)3Pt, where L3 is
the silylated analogue of L1, i.e. (Me3Si)N(C6H4PPh2-3).17 Here,
the reduced steric bulk of the SiMe3 N-substituents of L3
as compared to the CHBut2 substituents in L1 results in
trisubstitution at Ti that eventually leads to cage-like hetero-
bimetallic molecules rather than the metallomacrocycles
observed above. Both oxidative addition and donor substi-
tution reactions were probed (Scheme 4).
CH2Cl2 using Bun NBF4 as the electrolyte (see Fig. 9).
4
Scheme 4 Reactions of the metallocage, ClTi(L3)3Pt.
In order to assess the flexibility of this rigid metallocage
molecule towards the addition of donor molecules at Ti or Pt,
the reaction between the metallocage and CO was carried out.
The exposure of a solution of ClTi(µ-L3)3Pt to a CO atmos-
phere immediately generated the desired carbonyl complex
which was isolated in good yield as a yellow, crystalline solid.
The IR spectrum of 13 confirms the presence of one carbonyl
group in the solid state with a single absorption seen at 1918
cmϪ1; no resonance attributable to the carbonyl carbon was
observed in the 13C{1H} NMR spectrum. The 1H, 13C{1H} and
31P{1H} NMR data are consistent with a symmetrical ligand
environment, and show no evidence of agostic interactions
between the unique bridging aryl-H and the Pt(0) centre. This
is unlike the precursor metallocage, in which a weak agostic
interaction was observed both in solution and in the solid state
and implied that the cage adopted a rigid structure. The
magnitude of the PtP coupling constant seen in the 31P{1H}
NMR spectrum (JPtP 3513 Hz) indicates the retention of a Pt(0)
oxidation state. Yellow crystals of 13 suitable for X-ray dif-
fractometry were grown from benzene; the solid-state structure
is shown in Fig. 10 (ESI†).
Fig. 9 Cyclic voltammograms of the reduction of (a) TiCl2(L1)2 and
(b) the Ti–Pt complex, 8.
It is evident that the mixed-metal complex 8 undergoes a
similar reversible, one electron reduction process to the mono-
metallic TiCl2(L1)2, albeit at slightly less negative potential
(Ϫ0.71 and Ϫ0.81 V, respectively). As we previously speculated,
this reversible wave is likely due to the formation of the mono-
halide {TiCl(µ-L1)PtCl2} via one-electron uptake and halide
loss.18,41 Unlike TiCl2(L1)2, the mixed-metal species cannot
reorganise to promote the metallation of the arylNP ring at
titanium as this would involve platinum decomplexation
(as observed using strongly reducing C8K), and so it is likely
that reduction is halted at a TiIIICl stage.
Both the Ti and Pt centres adopt distorted tetrahedral
geometries in which the metric parameters are similar to mono-
nuclear TiCl{N(SiMe3)2}3 and Pt(CO)(PPh3)3 analogues,43 with
both the chloride and carbonyl groups situated within
protective hydrocarbon pockets provided by the three NP-
ligands. The change in geometry at Pt from trigonal planar to
tetrahedral has resulted in a 1 Å increase in the Ti ؒ ؒ ؒ Pt separ-
ation from 5.81 Å in ClTi(µ-L3)3Pt to 6.81 Å in 13. This has also
removed the rigidity of the interlocked bridging aryl groups
which has resulted in the loss of the agostic aryl C–H ؒ ؒ ؒ Pt
interaction described above; the unique aryl H’s undergo
intramolecular, edge-to-face π-stacking interactions with
adjacent bridging aryl groups. It is evident from this reaction
that while the addition of an extra ligand to the platinum centre
has an overall structural effect, the result metal moieties adopt
similar structural arrangements to their mononuclear counter-
parts, which implies that the ligand is effective at conjoining
Palladium-mediated cross-coupling reactions
The reaction profile pertinent to the late metal moiety of
the Ti–Pd complex 10 was probed by observing the catalytic
activity of 10 in arylamination and Suzuki–Miyaura cross-
coupling reactions. Using a protocol developed by Buchwald
and co-workers,42 the arylamination reaction between
4-bromoanisole and aniline catalysed by 10 in toluene with
NaOBut as the added base was investigated. The progress of the
reaction at 80 ЊC was monitored by GCMS, and revealed that
no reaction had occurred at this temperature. Heating at 100 ЊC
resulted in a slow reaction over three days, with some (1% yield)
of the coupled product PhNH(C6H4OMe-4) (m/z 199) observed
by GCMS; the major product of this reaction is tentatively
assigned to PhOBut (m/z 151, 25%), with some biphenyl
(m/z 154, 3%) and free-base HL1 (m/z 358, 1%) also formed.
The lack of catalytic activity of 10 in arylamination reactions
D a l t o n T r a n s . , 2 0 0 4 , 1 9 6 0 – 1 9 7 0
1966

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Experimental
General experimental procedures
Unless otherwise stated, all reactions were carried out in a
Vacuum Atmospheres Omnilab glovebox or using standard
Schlenk techniques under an atmosphere of oxygen free
dinitrogen. Solvents were dried and degassed (hexane, toluene,
diethyl ether and tetrahydrofuran were passed through
activated alumina towers,45 dichloromethane was dried over
CaH2 and distilled), and stored over 4 Å molecular sieves. d2-
Dichloromethane and d5-pyridine were trap-to-trap distilled
from activated Al2O3, and C6D6 was boiled with K under
vacuum and trap-to-trap distilled. The compounds 3-H2NC6-
H4PPh2 (1a),19 Ti(CH2SiMe3)4,46 Zr(NEt2)4,47 PdCl2(PhCN)2,48
PtMe2(hexadiene),49 PtCl2(hexadiene),49 [RhCl(CO)2]2,50 and
C8K,51 were synthesised according to literature procedures;
all other reagents were used as purchased without further
purification. The 1H, 13C{1H}, 31P{1H} and 7Li{1H} NMR
spectra were recorded at 298 K on a Bruker DPX-300
spectrometer operating at 300.36, 75.47, 121.49 and 116.64
1
MHz respectively. H and 13C{1H} NMR spectra were refer-
enced internally while 31P{1H} and 7Li{1H} NMR spectra were
referenced externally to trimethyl phosphite resonating at 142.0
ppm and LiCl, respectively. IR spectra were recorded on a
Nicolet Avatar 360 FTIR spectrometer using Nujol mull
samples. Polymerisation runs were carried out using a purpose-
built rig at the University of Sussex. Cyclic voltammetry and
controlled potential electrolysis were carried out under argon
using an Autolab PGSTAT20 potentiostat on 10Ϫ3 M CH2Cl2
Fig. 10 Solid-state structure of the Ti–Pt carbonyl, 13 (50%
ellipsoids). All hydrogens have been omitted for clarity.
these species but does not ultimately prescribe a defined
geometry at the metal.
Pt(0) complexes are well known to undergo oxidative
addition reactions with alkyl and aryl halides, often as a first
step in a catalytic cycle. We therefore explored the reactivity
of ClTi(µ-L3)3Pt with alkyl halides to see if a metallomacro-
cycle could be prepared that incorporated a (L3)2PtRX motif;
this would necessitate the dissociation of one phosphine from
the Pt centre. Surprisingly, no reaction between ClTi(µ-L3)3Pt
and iodobenzene was observed, even at elevated temperature
(80 ЊC for 48 h). However, reaction with MeI was observed,
although no pure complex could be isolated from the reaction
mixture. Monitoring the reaction between an excess of MeI and
ClTi(µ-L3)3Pt in C6D6 by 31P{1H} NMR spectroscopy revealed
the presence of a new, Pt-containing product at 29.0 ppm with
associated Pt satellites (JPtP 3064 Hz), and is tentatively assigned
to trans-ClTi(µ-L3)2(κ1-L3MeI)Pt(Me)I 14. These data are
directly comparable to that of trans-Pt(Me)I(PPh3)2 (27.7 ppm,
JPtP 3063 Hz) which is afforded on reaction of Pt(PPh3)3 with
MeI.44 Other phosphorus-containing species that are not
associated with Pt are also present at 22.2 and 22.0 are probably
due to both quaternisation of the pendant phosphine (cf. 22.6
ppm for MeP(Br)(PPh3)) allied with some decomposition of the
complex.
n
solutions with 0.4 M Bu4 BF4 supporting electrolyte. Elemental
analyses were carried out by Mr. Stephen Boyer at London
Metropolitan University, and mass spectra were recorded by
Dr. Ali Abdul-Sada of the University of Sussex.
Synthetic procedures
Synthesis of 3-(tert-butylimino)phenyldiphenylphosphine, 2a.
To a mixture of 1a (0.51 g, 1.84 mmol) and trimethylacetal-
dehyde (0.28 g, 3.30 mmol) was added benzene (20 mL). The
mixture was stirred and heated to 100 ЊC under Dean–Stark
conditions for 16 h, after which the solvent was removed under
vacuum to yield 0.54 g, 88% of 2a as a pale yellow oil that
solidified on standing. Analysis. Found: C, 80.12; H, 6.98; N,
3.97. C23H24NP requires: C, 80.00; H, 6.95; N, 4.05%. 1H NMR
(CDCl3): δH 7.68 (s, 1H, imine-H), 7.31 (br s, 10H, aryl-P), 7.07
t
31
(m, 4H, aryl-PN), 1.20 (s, 9H, Bu); P{1H} NMR (CDCl3):
δP Ϫ3.20 (s)
Synthesis of N-tert-butyliminoaniline, 2b. A solution of
aniline (10.8 g, 0.116 mol) and trimethylacetaldehyde (10.0 g,
0.116 mol) in benzene (50 mL) was stirred at reflux temperature
for 24 h in a round bottom flask fitted with Dean–Stark
condenser. The solvent was removed under vacuum, and the
resultant oil purified by distillation at 42 ЊC, 1.1 mbar to yield
Conclusions
We have shown that the addition of very bulky NCHBut2-
substituents to aryl amide ligands facilitates the isolation
of the four-coordinate TiIV diamidochlorides TiCl2(L1)2 and
TiCl2(L2)2. When functionalised by m-phosphine donor groups,
TiCl2(L1)2 acts as a metalloligand and undergoes substitution
reactions with labile Group 9 and 10 complexes. As such, we
have been able to synthesise and, in some cases structurally
characterise new and discrete Ti–Pt, Ti–Pd, Ti–Ni dinuclear
and Ti–Rh tetranuclear complexes. These compounds
adopt rigid structures that maximise both intramolecular Ti–
Cl ؒ ؒ ؒ H–C hydrogen bonding and aryl–aryl π-stacking
interactions, yet maintain coordinative environments that are
similar to their mononuclear counterparts. We have investigated
these complexes as catalysts for alkene polymerisation and
carbon-carbon coupling reactions, and have found that the
incorporation of the second metal has a general negative effect
on overall proficiency in these reactions.
1
6.68 g, 71% of the imine 2b as a colourless oil (bp 212 ЊC). H
NMR (CDCl3): δH 7.69 (s, 1H, N᎐CH), 7.32 (t, 2H, J = 7.8 Hz,
᎐
ArH), 7.16 (t, 1H, J = 7.6 Hz, ArH), 6.99 (d, 2H, J = 7.4 Hz,
ArH), 1.19 (s, 9H, CH3); 13C{1H} NMR (CDCl3): δC 173.6
(s, HC᎐N), 152.6 (s, aryl), 128.8 (s, aryl), 125.0 (s, aryl), 120.5
᎐
(s, aryl), 36.7 (s, CMe3), 26.7 (s, CH3); MS(EI): m/z 161.12021
(Mϩ, 36%).
Synthesis of HL1. To a solution of the imine 2a (0.61 g, 1.75
t
mmol) in diethyl ether (30 mL) was added a solution of BuLi
in pentane (1.5 M, 2.11 mmol) at Ϫ78 ЊC. The reaction was
allowed to warm to room temperature and stirred for a further
16 h, after which the mixture was quenched in iced water and
extracted into diethyl ether (50 mL). The organic extracts were
dried (MgSO4), filtered and the filtrate evaporated under
1
vacuum, yielding 0.37 g, 67% of HL1 as a pale brown oil. H
D a l t o n T r a n s . , 2 0 0 4 , 1 9 6 0 – 1 9 7 0
1967

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NMR (CDCl3): δH 7.39 (br s, 10H, aryl-P), 7.10 (m, 1H, aryl-
PN), 6.54 (m, 3H, aryl-PN), 3.80 (br d, J 10.6 Hz, 1H, NH),
2.90 (d, 1H, J 10.7 Hz, CHBut2), 1.08 (s, 18H, tBu); MS(EI): m/z
403 (Mϩ, 55%), 346 (Mϩ Ϫ tBu, 100%)
Synthesis of PdCl2(HL1)2, 5. To a slurry of PdCl2(PhCN)2
(0.02 g, 0.05 mmol) in toluene (15 mL) was added a solution of
HL1 (0.04 g, 0.10 mmol) in toluene (15 mL) at room temper-
ature. The reaction mixture was stirred at room temperature for
8 h, after which the mixture was filtered and the solvents
removed under reduced pressure, yielding oily yellow solids.
These isolated solids were washed with hexanes (2 × 10 mL)
and dried under vacuum, yielding 0.036 g, 80% of 5 as a yellow
powder. Analysis. Found: C, 65.92; H, 6.89; N, 2.88. C54H68-
N2P2Cl2Pd requires: C, 65.89; H 6.96; N 2.85%. 1H NMR
(C6D6): δH 7.93 (m, 8H, o-arylP), 7.16–6.94 (m, 8H, arylPN),
6.33–6.84 (m, 10H, m/p-arylP), 6.45 (m, 2H, arylPN), 3.75 (d,
2H, J 10.6 Hz, NH), 3.03 (d, 2H, J 10.5 Hz, CH), 1.05 (s, 36H,
But); 31P{1H} NMR (C6D6): δP 35.1 (br s)
Synthesis of LiN(CHBut2)(C6H4PPh2-3), LiL1. To a stirred
solution of HL1 (0.61 g, 1.75 mmol) in diethyl ether (30 mL)
was added dropwise a solution of ButLi (1.40 mL, 1.6 M, 2.18
mmol) in pentane at Ϫ78 ЊC. The mixture was allowed to warm
to room temperature and stirred for a further 4 h, after which
the volatiles were evaporated under vacuum to yield 0.41 g, 67%
of LiL1 as an orange oil that solidified on standing. Slow
cooling a solution of LiL1 in n-pentane to Ϫ30 ЊC resulted in
the formation of orange prisms that were suitable for X-ray
diffraction studies. Analysis. Found: C, 79.18; H, 7.95; N, 3.52.
1
C27H33NPLi requires C, 79.22; H, 8.07: N, 3.42%. H NMR
In-situ synthesis of the platinum alkyls 6 and 7. A solution of
4 (0.03 g, 0.2 mmol) in C6D6 was added to a solution of
Ti(CH2SiMe3)4 (0.01 g, 0.2 mmol) in C6D6. The reaction was
(C6D6): δH 7.32 (m, 4H, o-arylP), 7.10 (m, 4H, o-arylP), 6.89 (m,
6H, m/p-arylP), 6.58 (m, 6H, m/p-arylP), 6.20 (m, 1H, aryl-PN),
6.10 (m, 1H, aryl-PN), 5.54 (m, 3H, aryl-PN), 5.30 (m, 3H,
aryl-PN), 3.15 (s, 1H, CH), 2.71 (s, 1H, CH), 1.08 (s, 18H, But),
0.92 (s, 18H, But); 31P{1H} NMR (C6D6): δP Ϫ3.49 (br s);
7Li{1H} NMR (C6D6): δLi Ϫ0.20 (s)
1
monitored by H and 31P{1H} NMR spectroscopy at regular
intervals.
Immediate. 31P{1H} NMR: δP 25.8 (dd, JPP 14.1, JPtP 1672,
JPtP 4432 Hz).
After 24 h. 31P{1H} NMR (C6D6): δP 27.5 (s, JPtP 2016 Hz).
Synthesis of LiN(CHBut2)(C6H5), LiL2. A stirred solution of
2b (5.0 g, 31.0 mmol) in Et2O (50 mL) was treated dropwise
with a solution of ButLi (20.7 mL, 1.6 M) in pentane at Ϫ78 ЊC.
The mixture was allowed to reach RT and stirred for a further
24 h, after which the volatiles were removed under vacuum. The
resultant solids were washed with hexane (2 × 25 mL) yielding
4.8 g, 69% of LiL2 as a yellow solid. Analysis. Found: C, 79.70;
H, 10.94; N, 6.04. C15H24NLi requires: C, 79.96; H, 10.74; N,
Synthesis of TiCl2(L1)2PtCl2, 8. To a stirred solution of
TiCl2(L1)2 (0.5 g, 0.5 mmol) in dichloromethane (10 mL) was
added dropwise a solution of PtCl2(hexadiene) (0.188 g,
0.5 mmol) in dichloromethane (10 mL) at room temperature.
The reaction mixture was stirred overnight at room temper-
ature, after which the volume was reduced under vacuum to ca.
2 mL and cooled to Ϫ20 ЊC, causing the precipitation of 0.42 g,
71% of 8 as red single crystals. Analysis. Found: C, 54.60; H,
5.62; N, 2.29. C54H66N2P2Cl2PtTi requires: C, 54.50; H, 5.55; N,
1
6.22%. H NMR (d5-pyridine): δH 7.36 (m, 2H, ArH), 7.00 (d,
2H, J 8.6 Hz, ArH), 6.26 (t, 1H, J 6.8 Hz, ArH), 3.61 (br s, 1H,
CH(CH3)3), 1.33 (s, 18H, CH3); 13C{1H} NMR (d5-pyridine):
δC 165.0 (s, ArC), 131.0 (s, ArCH), 130.0 (s, ArCH), 115.0 (s,
ArCH), 71.0 (s, CHBut2), 40.0 (s, CMe3), 31.0 (s, CH3); 7Li{1H}
NMR (d5-pyridine): δLi 3.06 (s)
1
2.35%. H NMR (CD2Cl2): δH 0.70 (s, 18H, But), 0.90 (s, 18H,
But), 5.23 (s, 2H, CH), 6.21 (m, 2H, aryl-PN), 6.93 (m, 2H,
aryl-PN), 7.21 (m, 4H, o-aryl-P), 7.52 (m, 8H, m/p-aryl-P, PN),
7.68 (m, 8H, m/p-aryl-P, PN), 7.83 (m, 4H, o-aryl-P); 31P{1H}
NMR (CD2Cl2): δP 18.7 (s, JPtP 3686 Hz); MS(EI): m/z
Synthesis of HN(CHBut2)(C6H4P(O)Ph2-3), 3. To a solution
of HL1 (0.23 g, 0.57 mmol) in ethanol (20 mL) was added an
excess of H2O2 (30 mL, 28 wt% in H2O). The reaction mixture
was allowed to stir at room temperature for 1 h, after which the
solvent was removed under vacuum, and the resulting solids
washed with diethyl ether (2 × 10 mL), yielding 0.18 g, 78% of
3 as a colourless solid. Crystals suitable for X-ray analysis
were grown by the slow evaporation of an ethanol solution of
3. Analysis. Found: C, 77.52; H, 8.16; N, 3.40. C27H34NPO
requires: C, 77.32; H, 8.11; N, 3.39%. 1H NMR (C6D6): δH 7.70
(m, 4H, o-aryl-P), 7.50–7.39 (m, 6H, aryl-P), 7.11 (m, 1H,
aryl-PN), 7.05 (m, 1H, aryl-PN), 6.52 (d, 1H, aryl-PN), 6.47
(m, 1H, aryl-PN), 3.96 (d, 1H, J 10.9 Hz, NH) 3.03 (d, 1H,
1126 (Mϩ Ϫ (CH3)4, 10), 1070 (Mϩ Ϫ (CH3)4 Ϫ Bu, 25), 979
t
(Mϩ Ϫ (CH3)4 Ϫ tBu Ϫ Ar, 90), 346 (tBuNP, 5%)
Synthesis of TiCl2(L1)2PtMe2, 9. To a stirred solution of
TiCl2(L1)2 (0.205 g, 0.22 mmol) in CH2Cl2 (15 mL) was added a
solution of PtMe2(hexadiene) (0.068 g, 0.22 mmol) in CH2Cl2
(15 mL) at room temperature. The reaction mixture was stirred
for 16 h, after which the volume of the solvent was reduced to
ca 1 mL and the reaction mixture cooled to Ϫ20 ЊC. After two
days, 0.143 g, 55.5% of 9 was deposited as red crystals that were
suitable for X-ray diffraction studies. Analysis. Found: C, 58.39;
H, 6.47; N, 2.29. C56H72N2P2Cl2PtTi requires: C, 58.53; H, 6.27;
1
N, 2.43%. H NMR (CD2Cl2): δH 0.42 (m, 6H, CH3), 0.72 (s,
t
J 10.9 Hz, CHBut2), 1.05 (s, 18H, Bu); 31P{1H} NMR (C6D6):
18H, But), 0.93 (s, 18H, But), 5.26 (s, 2H, CH), 6.29 (m, 2H,
aryl-PN), 6.89 (m, 2H, aryl-PN), 7.24 (m, 4H, o-aryl-P), 7.46
(m, 8H, m/p-aryl-P/PN), 7.58 (m, 8H, m/p-aryl-P/PN), 7.73 (m,
4H, o-aryl-P); 13C{1H} NMR (CD2Cl2): δC 143.5 (s), 138.2 (s),
137.4 (s), 133.7 (s), 129.5 (s) 128.6 (s), 128.5 (s), 117.5 (s), 112.4
(s), 67.9 (s), 29.0 (s), 8.00 (br m); 31P{1H} NMR (CD2Cl2):
δP 18.7 (s, JPtP 3686 Hz); MS(EI): m/z 1133 (Mϩ Ϫ CH3, 15), 346
(NPtBuCH, 75%).
δP 31.5 (br s).
Synthesis of PtCl2(HL1)2, 4. To a slurry of PtCl2(hexadiene)
(0.117 g, 0.33 mmol) in toluene (10 mL) was added a solution
of HL1 (0.27 g, 0.67 mmol) in toluene (10 mL) at room temper-
ature. The resultant pale yellow solution was stirred at room
temperature for 8 h, after which the solvent was removed under
reduced pressure to yield oily cream solids. The solids were
washed with n-pentane (3 × 10 mL) and dried under vacuum,
yielding 0.30 g, 82% of 4 as colourless solids. Analysis. Found:
C, 60.39; H, 6.38; N, 2.57. C54H66N2P2Cl2Pt requires: C, 60.44;
H, 6.34; N, 2.61%. 1H NMR (CDCl3): δH 7.47 (m, 8H, o-arylP),
7.41 (m, 6H, aryl-P), 7.23 (m, 10H, aryl-P/aryl-PN), 6.98 (br m,
2H, aryl-PN), 6.58 (br m, 2H, aryl-PN), 3.84 (d, 2H, J 10.7 Hz,
NH), 2.89 (d, 2H, J 10.4 Hz, CH), 0.98 (s, 36H, But); 13C{1H}
NMR (CDCl3): δC 29.69 (s), 67.9 (s), 106.8 (br s), 127.5 (d),
129.6 (d), 130.2 (d), 135.4 (d); 31P{1H} NMR (CDCl3): δP 16.3
(s, JPtP 3670 Hz)
Synthesis of TiCl2(L1)2PdCl2, 10. To a stirred slurry of
PdCl2(PhCN)2 (0.104 g, 0.27 mmol) in toluene (15 mL) was
added a solution of TiCl2(L1)2 in toluene (15 mL) at room
temperature. The resultant solution was stirred at room
temperature for 8 h, after which the solvent was removed
under vacuum, yielding peachy-orange solids. The solids were
redissolved in dichloromethane (2 mL) and cooled to Ϫ20ЊC for
2 days, after which 0.24 g, 81.0% of 10 were deposited as single
red crystals. Analysis. Found: C, 58.76; H, 5.85; N, 2.53.
1
C54H66N2P2Cl4PdTi requires: C, 58.89, H, 5.99; N, 2.54%. H
D a l t o n T r a n s . , 2 0 0 4 , 1 9 6 0 – 1 9 7 0
1968

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NMR (CD2Cl2): δH 0.70 (s, 18H, But), 0.90 (s, 18H, But), 5.23
(s, 2H, CH), 6.24 (m, 2H, aryl-PN), 6.92 (m, 2H, aryl-PN), 7.21
(m, 4H, o-aryl-P), 7.52 (m, 8H, m/p-aryl-P/PN), 7.68 (m, 8H,
m/p aryl-P/PN), 7.83 (m, 4H, o-aryl-P); 31P{1H} NMR
(CD2Cl2): δP 34.0 (s).
1H NMR (CDCl3): δH 8.31 (d, 2H, J 2.0 Hz), 7.73 (d, 2H,
J 2.0 Hz), 7.61 (m, 2H), 7.49 (m, 3H); 13C{1H} NMR (CDCl3):
δC 147.1 (s, quat), 146.3 (s, quat), 140.4 (s, quat), 129.2 (s), 129.0
(s), 127.9 (s), 127.5 (s), 124.2 (s); mp 99.2–101.5 ЊC.
Synthesis of TiCl(L3)3Pt(CO), 13. A solution of TiCl(L3)3Pt
(0.15 g, 0.1 mmol) in toluene (10 mL) was stirred for 3 h under
an atmosphere of CO (1 atm), causing a change in colour from
bright orange to a pale yellow. The volume of solvent was
reduced to ca. 1 mL and cooled to Ϫ20 ЊC, causing 0.12 g, 78%
of 13 to precipitate as yellow crystals. Analysis. Found: C,
59.02; H, 5.44; N, 3.23. C71H78N3P3Si3ClOTiPt requires: C,
59.06; H, 5.37; N, 2.91%. 1H NMR (CD2Cl2): δH 8.49 (br s, 6H,
o-H aryl-P), 8.13 (br s, 6H, o-H aryl-P), 7.84 (br m, 9H,
m/p-protons aryl-P), 7.53 (br m, 3H, aryl-PN), 7.36 (br m,
9H, m/p-protons aryl-P), 6.82 (br m, 3H, aryl-PN), 5.86 (br s,
3H, aryl-PN), 5.30 (br s, 3H, aryl-PN), 0.79 (s, 27H, Me3Si);
31P{1H} NMR (CD2Cl2): δC 15.3 (s, JPtP 3513 Hz); IR (KBr
disc): ν/cmϪ1 1918 (m); MS(EI): m/z 1323 (Mϩ Ϫ CO, 55), 349
(SiMe3NP, 100%).
Synthesis of TiCl2(L1)2NiBr2, 11. THF (30 mL) was added to
a high-pressure ampoule charged with NiBr2(DME) (0.037 g,
0.12 mmol) and TiCl2(L1)2 (0.11 g, 0.12 mmol). The mixture
was heated to 65 ЊC for 2 h, filtered and the dark green solution
evaporated to dryness, yielding 0.11 g, 71.4% of 11 as a dark
green solid. Analysis. Found: C, 56.86; H, 5.81; N, 2.40.
C54H66N2P2Br2Cl2TiNi requires: C, 56.76; H, 5.78, N, 2.37%.
µeff = 3.2 µB; MS(EI): m/z 890 (Mϩ Ϫ 4(CH(CH3)3), 15), 346
(NPtBuCH, 75%).
Synthesis of {TiCl2(L1)2RhCl(CO)}2 12. To a solution of
{RhCl(CO2)}2 (0.042 g, 0.11 mmol) in CH2Cl2 (15 mL) was
added dropwise a solution of TiCl2(L1)2 (0.20 g, 0.22 mmol) in
CH2Cl2 (15 mL) at room temperature. The mixture was stirred
at room temperature for 4 h, then cooled to Ϫ20 ЊC, causing
0.21 g, 85% of 12 to deposit as orange crystals that were
suitable for X-ray studies. Analysis. Found: C, 54.63; H, 5.52;
N, 1.89. C55H66N2P2Cl3RhTi(CH2Cl2)2 requires: C, 55.05; H,
5.63; N, 2.25%. IR (KBr disc): ν/cmϪ1 1982 (m); 1H NMR
(CD2Cl2): δH 0.86 (br s, 18H, But), 5.35 (br s, 1H, CHBut2), 6.70
(br s, 1H, aryl H), 7.00–8.00 (br m’s, 12H, aryl H), 8.37 (br s,
1H, aryl H); 31P{1H} NMR (CD2Cl2): δP 30.2 (br d, JRhP
125.8 Hz)
Synthesis of trans-ClTi(L3)2(ꢂ1-L3MeI)Pt(Me)I 14. A stirred
solution of TiCl(L3)3Pt (0.043 g, 0.032 mmol) in toluene (3 mL)
was treated with neat MeI (20 µL, 10 eq) at room temperature.
After 24 h, the mixture was evaporated to dryness under
vacuum, yielding 0.039 g, 75% of 14 as pale yellow solids.
Recrystallisation attempts using a variety of solvent mixtures
were unsuccessful.
1H NMR (CD2Cl2): δH 8.00–6.50 (m, 42H, aryl-H), 0.15 (br s,
27H, SiMe3); 31P{1H} NMR (CD2Cl2): δP 29.0 (s, JPtP 3064 Hz),
22.2 (s), 22.0 (s)
Protocol for ethylene polymerisation. A glass autoclave
equipped with an overhead stirrer was charged with the
procatalyst (0.020 g, 0.01 mmol), toluene (100 mL), and MAO
(10 mL, 10 mmol, 10 wt% soln.). The reaction vessel was
pressurised at 20 ЊC with 10 bar of ethylene. Each mixture was
stirred for 1 h with the change in temperature being monitored
throughout, after which acidified methanol (100 mL) was
added to the vessel. The precipitated polyethylene was isolated
on a glass frit, washed with water (3 × 100 mL) and dried in a
vacuum oven at 50 ЊC. The isolated polymer was analysed
by Dr Steven Holding at Rapra Technology using high-
temperature GPC.
Arylamination reactions. A glass, Teflon-tapped ampoule was
charged with the Ti–Pd complex, 10 (0.028 g, 0.025 mmol),
4-bromoanisole (0.40 g, 2.1 mmol), aniline (0.20 g, 2.1 mmol),
NaOBut (0.20 g, 9.00 mmol) and toluene (50 mL), evacuated
and heated to 75 ЊC for 24 h, after which the mixture was
sampled by GCMS. The mixture was then heated to 100 ЊC for
3 days; after each 24 h, the mixture was sampled by GCMS.
GCMS: 7.31 (Mϩ 93.1, 35%, C6H5NH2), 10.3 (188, 33,
BrC6H4OMe-4), 12.9 (154, 3, Ph–Ph), 13.7 (151, 25, PhOBut),
17.5 (358, 1, HL1), 18.7 min (199, 1, PhNH{C6H4OMe-4}).
Suzuki–Miyaura reactions. A glass, Teflon-tapped ampoule
was charged with the Ti–Pd complex, 10 (0.015 g, 0.013 mmol),
2,4-dimethoxybromobenzene (0.10 g, 0.46 mmol), phenyl-
boronic acid (0.084 g, 0.69 mmol), Cs2CO3 (0.30 g, 0.90 mmol)
and dioxane (25 mL) and heated at 80 ЊC for 36 h, after which
the mixture was sampled by GCMS. The cooled mixture was
filtered through a glass sinter, the filtrate evaporated to dryness
under vacuum and the oily residues slurried in diethyl ether
(40 mL). The solids were collected on a frit, washed with
hexanes (2 × 10 mL) and air-dried, yielding 0.95 g, 95% of 3,5-
dimethoxybiphenyl as colourless solids.
Crystallographic details. Crystallographic data for all
structures were collected using graphite-monochromated
Mo-Kα X-radiation (λ = 0.71703 Å). Data for all structures
were collected at 173(2) K using a Kappa CCD diffractometer;
data for compound 12 were collected on a Bruker SMART1000
CCD area detector diffractometer at 150 K. For all structures,
apart from LiL1, data were corrected for absorption using a
multi-scan correction. The structures were solved using direct
methods using SHELXS-9752 or SIR-9253 (compound 12) and
refined using full-matrix least-squares refinement against F 2
using the SHELXL-97 within the WINGX program package.54
Unless otherwise stated all non-hydrogen atoms were refined
with anisotropic atomic displacement parameters (adps)
and hydrogen atoms were placed in geometrically calculated
positions and refined as part of a riding model. LiL1 contained
two molecules of pentane solvate, one of which is in a general
position and the second is disordered across an inversion centre.
In both cases, atoms were refined with isotropic adps and
suitable geometry restraints applied; hydrogen atoms were
omitted. Compound 4 contains two CH2Cl2 solvate molecules,
one of which is poorly defined and the C–Cl bond lengths were
restrained to be equal. Compounds 8 and 13 contain two
deuterated benzene solvate molecules which in both cases were
poorly defined and were included in the model as rigid
bodies. In compound 13, the carbon atoms were given a
common isotropic displacement parameter. Ortep diagrams
were drawn using ORTEP-3.55
CCDC reference numbers 216487–231691.
See http://www.rsc.org/suppdata/dt/b4/b402409e/ for crystal-
lographic data in CIF or other electronic format.
1H NMR (CDCl3): δH 7.52 (d, 2H, J 8.1 Hz), 7.39 (t, 2H, J 7.2
Hz), 7.29 (dd, 4H, J 9.3, 6.0 Hz), 3.86 (s, 3H, OMe), 3.80 (s, 3H,
OMe)
In a similar manner, 10 (0.016 g, 0.014 mmol), phenylboronic
acid (0.10 g, 0.735 mmol), 4-nitrobromobenzene (0.1 g, 0.49
mmol), Cs2CO3 (0.30 g, 0.90 mmol) and dioxane (25 mL)
yielded 0.86 g, 88% of 4-nitrobiphenyl.
Acknowledgements
We thank Prof. Geoff Cloke and Dr Guy Clentsmith at the
University of Sussex for their assistance with polymerisation
studies and the molecular weight determination, Dr Peter
Licence for help with GCMS measurements, Dr Stephen Davies
for the cyclic voltammetry, and the Royal Society (University
D a l t o n T r a n s . , 2 0 0 4 , 1 9 6 0 – 1 9 7 0
1969

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A. R. Kennedy, R. E. Mulvey and R. B. Rowlings, J. Am. Chem.
Soc., 1998, 120, 7816.
24 B. Schiemenz and P. P. Power, Angew. Chem., Int. Ed., 1996, 35,
2150.
Research Fellowship, J. B. L., and Summer Studentship, L. S.),
EPSRC (studentship, Q. S. M.) and the University of
Nottingham for their continued support.
25 D. Vagedes, G. Kehr, D. König, K. Wedeking, R. Fröhlich, G. Erker,
C. Mück-Lichtenfeld and S. Grimme, Eur. J. Inorg. Chem., 2002,
2015; C. Uffing, R. Köppe and H. Schnöckel, Organometallics, 1998,
17, 3512; H. Nöth, H. Sachdev, M. Schmidt and H. Schwenk, Chem.
Ber., 1995, 128, 105; H. Chen, R. A. Bartlett, H. V. R. Dias,
M. M. Olmstead and P. P. Power, Inorg. Chem., 1991, 30, 2487;
D. Bladauski, W. Broser, H.-J. Hecht, D. Rewicki and H. Dietrich,
Chem. Ber., 1979, 112, 1380.
26 G. K. Anderson, H. C. Clark, J. A. Davies, G. Ferguson and
M. Parvez, J. Crystallogr. Spectrosc. Res., 1982, 12, 449.
27 J. F. Malone, C. M. Murray, M. H. Charlton, R. Docherty and
A. J. Lavery, J. Chem. Soc., Faraday Trans., 1997, 93, 3429;
F. H. Allen, J. A. K. Howard, V. J. Hoy, G. R. Desiraju, D. S. Reddy
and C. C. Wilson, J. Am. Chem. Soc., 1996, 118, 4081.
28 A. Pidcock, J. Chem. Soc., A, 1968, 17, 2700.
29 B. Wozniak, J. D. Ruddick and G. Wilkinson, J. Chem. Soc. A, 1971,
20, 311.
30 O. Kühl, S. Blaurock, J. Sieler and E. Hey-Hawkins, Polyhedron,
2001, 20, 111.
31 C. H. Lee, Y.-H. La, S. J. Park and J. W. Park, Organometallics, 1998,
17, 3648; S. Tinkler, R. J. Deeth, D. J. Duncalf and A. McCamley,
Chem. Commun., 1996, 2623.
32 A. Shafir, M. P. Power, G. D. Whitener and J. Arnold,
Organometallics, 2001, 20, 1365.
33 P.-J. Sinnema, L. van der Veen, A. L. Spek, N. Veldman and
J. H. Teuben, Organometallics, 1997, 16, 4245.
References
1 A. E. Sutton, B. A. Seigal, D. F. Finnegan and M. L. Snapper, J. Am.
Chem. Soc., 2002, 124, 13390; J. Louie, C. W. Bielawski and
R. H. Grubbs, J. Am. Chem. Soc., 2001, 123, 11312; G. J. Rowlands,
Tetrahedron, 2001, 57, 1865.
2 A. de Meijere and S. Bräse, J. Organomet. Chem., 1999, 576, 88.
3 R. Grigg and V. Sridharan, J. Organomet. Chem., 1999, 576, 65.
4 R. M. Deshpande, M. M. Diwakar, A. N. Mahajan and
R. V. Chaudhari, J. Mol. Catal. A: Chem., 2004, 211, 49.
5 L. J. Field, B. A. Messerle and S. L. Wren, Organometallics, 2003, 22,
4393.
6 E. Teuma, M. Loy, C. Le Berre, M. Etienne, J.-C. Daran and
P. Kalck, Organometallics, 2003, 22, 5261.
7 D. E. Fogg, D. Amoroso, S. D. Drouin, J. Snelgrove, J. Conrad and
F. Zamanian, J. Mol. Catal. A: Chem., 2002, 190, 177.
8 C. W. Bielawski, J. Louie and R. H. Grubbs, J. Am. Chem. Soc.,
2000, 122, 12872.
9 K. Musikabhumma, T. P. Spaniol and J. Okuda, J. Polym. Sci. A:
Polym. Chem., 2003, 41, 528; O. Sperber and W. Kaminsky,
Macromolecules, 2003, 36, 9014; Z. J. A. Komon, G. M. Diamond,
M. K. Leclerc, V. Murphy, M. Okazaki and G. C. Bazan, J. Am.
Chem. Soc., 2002, 124, 15280; Z. J. A. Komon and G. C. Bazan,
Macrmol. Rapid Commun., 2001, 22, 467.
10 N. Wheatley and P. Kalck, Chem. Rev., 1999, 99, 3379.
11 M. A. F. Hernandez-Gruel, J. J. Pérez-Torrente, M. A. Ciriano,
A. B. Rivas, F. J. Lahoz, I. T. Dobrinovitch and L. A. Oro,
Organometallics, 2003, 22, 1237; B. E. Bosch, I. Brümmer, K. Kunz,
G. Erker, R. Fröhlich and S. Kotila, Organometallics, 2000, 19, 1255;
M. Quirmbach, A. Kless, J. Holz, V. Tararov and A. Börner,
Tetrahedron: Asymmetry, 1999, 10, 1803.
34 R. M. Pupi, J. N. Coalter and J. L. Petersen, J. Organomet. Chem.,
1995, 497, 17.
35 G. Aullón, D. Bellamy, L. Brammer, E. A. Bruton and A. G. Orpen,
Chem. Commun., 1998, 653.
36 T. Spaniel, H. Görls and J. Scholz, Angew. Chem., Int. Ed., 1998, 37,
1862.
37 M. Niehues, G. Kehr, G. Erker, B. Wibbeling, R. Fröhlich,
O. Blacque and H. Berke, J. Organomet. Chem., 2002, 663, 192.
38 K. R. Dunbar and S. C. Haefner, Inorg. Chem., 1992, 31, 3676.
39 C. Janiak, J. Chem. Soc. Dalton Trans., 2000, 3885; H. W. Roesky
and M. Andruh, Coord. Chem. Rev., 2003, 236, 91.
40 G. J. P. Britovsek, V. C. Gibson and D. F. Wass, Angew. Chem. Int.
Ed., 1999, 38, 428.
41 N. El Murr, A. Chaloyard and J. Tirouflet, J. Chem. Soc., Chem.
Commun., 1980, 446; E. Samuel and J. Vedel, Organometallics, 1989,
8, 237; D. W. Stephan, Organometallics, 1992, 11, 996.
42 D. W. Old, J. P. Wolfe and S. L. Buchwald, J. Am. Chem. Soc., 1998,
120, 9722.
12 J. R. Fulton, T. A. Hanna and R. G. Bergman, Organometallics,
2000, 19, 602, and references therein.
13 C. Takayama, Y. Yamaguchi, T. Mise and N. Suzuki, J. Chem. Soc.,
Dalton Trans., 2001, 948; Y. Yamaguchi, N. Suzuki, T. Mise and
Y. Wakatsuki, Organometallics, 1999, 18, 996; M. L. H. Green and
N. H. Popham, J. Chem. Soc., Dalton Trans., 1999, 1049; M. Mitani,
M. Hayakawa, T. Yamada and T. Mukaiyama, Bull. Chem. Soc.
Jpn., 1996, 69, 2967.
14 L. H. Gade, Angew. Chem., Int. Ed., 2000, 39, 2658; P. Braunstein,
X. Morise, M. Bénard, M.-M. Rohmer and R. Welter, Chem.
Commun., 2003, 610.
15 D. W. Stephan, Coord. Chem. Rev., 1989, 95, 41; R. Kempe, H. Noss
and T. Irrgang, J. Organomet. Chem., 2002, 647, 12; T. W. Graham,
A. Llamazares, R. McDonald and M. Cowie, Organometallics, 1999,
18, 3502; T. W. Graham, A. Llamazares, R. McDonald and
M. Cowie, Organometallics, 1999, 18, 3490.
16 R. Kempe, Angew. Chem., Int. Ed., 2000, 39, 468; L. H. Gade, Chem.
Commun., 2000, 173.
17 Q. F. Mokuolu, A. G. Avent, P. B. Hitchcock and J. B. Love,
J. Chem. Soc., Dalton Trans., 2001, 2551.
18 Q. F. Mokuolu, P. A. Duckmanton, A. J. Blake, C. Wilson and
J. B. Love, Organometallics, 2003, 22, 4387.
43 V. Albano, G. M. Basso Ricci and P. L. Bellon, Inorg. Chem., 1969,
8, 2109.
44 B. S. Balaji, Y. Obora, D. Ohara, S. Koide and Y. Tsuji,
Organometallics, 2001, 20, 5342.
45 A. B. Pangborn, M. A. Giardello, R. H. Grubbs, R. K. Rosen and
F. J. Timmers, Organometallics, 1998, 15, 1518.
46 M. R. Collier, M. F. Lappert and R. Pearce, J. Chem. Soc., Dalton
Trans., 1973, 445.
47 G. M. Diamond, R. F. Jordan and J. L. Petersen, Organometallics,
1996, 15, 4030.
48 G. K. Anderson and M. Lin, Inorg. Synth., 1990, 28, 60.
49 J. L. Spencer, personal communication.
50 J. A. McCleverty and G. Wilkinson, Inorg. Synth., 1987, 28, 84.
51 D. E. Berbreiter and J. M. Killough, J. Am. Chem. Soc., 1978, 100,
2126.
19 A. Hessler, O. Stelzer, H. Dibowski, K. Worm and F. Schmidtchen,
J. Org. Chem., 1997, 62, 2362.
20 A. Fürstner, C. Mathes and C. W. Lehmann, Chem. Eur. J., 2001, 7,
5299.
21 A. R. Johnson and C. C. Cummins, Inorg. Synth., 1998, 32, 123.
22 F. Antolini, P. B. Hitchcock, M. F. Lappert and P. Merle, Chem.
Commun., 2000, 1301; K. Gregory, P. von Ragué Schleyer and
R. Snaith, Adv. Inorg. Chem., 1991, 37, 47.
23 M. Veith, A. Koban, K. Fries, P. Spaniol, R. Elsässer, A. Rammo,
V. Huch and U. Kleinsteuber, Organometallics, 1998, 17, 2612;
52 G. M. Sheldrick, in SHELX97 – Programs for Crystal Structure
Analysis, Göttingen, 1998.
53 A. Altomare, G. Cascarano, C. Giacovazzo and A. Guagliardi,
J. Appl. Crystallogr., 1993, 26, 343.
54 L. J. Farrugia, J. Appl. Crystallogr., 1999, 32, 837.
55 L. J. Farrugia, J. Appl. Crystallogr., 1997, 30, 565.
D a l t o n T r a n s . , 2 0 0 4 , 1 9 6 0 – 1 9 7 0
1970