Towards co-operative reactivity in conjoint classical-organometallic heterometallic complexes: The co-ordination chemistry of novel ligands with triphenylphosphine and bis(pyridylethyl)amine or triazacyclononane domains

Article abstract of DOI:10.1039/b201720m

With a view towards later studies of co-operativity in heteronuclear complexes with hard classical (oxygen-activating) and soft organometallic (organic-substrate binding) metal centres, four novel ditopic N₃P-donor ligands (L¹-L⁴), each comprising triphenylphosphine tethered to an N,N′-bis(2-pyridyl-2-ethyl)amine (bpea) or a 1,4-diisopropyl-1,4,7-triazacyclononane (tacn*) N₃-donor group, have been designed and prepared by reductive aminations of ortho- and meta-(diphenylphosphino)benzaldehydes with bpea (for L¹ and L³) and tacn* (for L² and L⁴). A range of κN_n, κP-chelate mononuclear complexes have been isolated from the reactions of the ortho-substituted ligands, L¹ and L², with Cu(I), Zn(II) and Pt(II) sources, and the X-ray crystal structures of [Cu(L¹)][PF₆], [Cu(L²)][PF₆] (communicated in: S. E. Watkins, D. C. Craig and S. B. Colbran, J. Chem. Soc., Dalton Trans., 1999, 1539) and [PtCl(L¹)][PF₆] have been determined. Six complexes with the phosphine of L¹-L⁴ co-ordinated to a softer [Pt(II), Ir(I) or W(O)] metal centre and with dangling, metal-free N₃-donor domains have been prepared: for the ortho-substituted ligands L¹ and L², it was necessary to protect the hard, more basic N₃-donor domains by protonation (pH control) to prevent formation of κN_n, κP-chelate mononuclear complexes; for the meta-substituted ligands L³ and L⁴, pH control was unnecessary as the phosphine group selectively binds to the softer metal ions. The complex trans-[IrCl(CO)(L³)₂] reversibly forms a dioxygen adduct. An Ir(III)Cu(II)₂ and four Pt(II)Cu(II)₂ heterometallic complexes were prepared by adding hard Cu(II) ions to the Ir(I) and Pt(II) complexes with metal-free N₃-donor domains, and the full characterisation of these is described. The tungsten(O) carbonyl complex [W(CO)₅(L³)], with a metal-free N₃-bpea domain, was prepared for a study of metal ion recognition. No perturbation of the carbonyl region of the IR spectrum was observed when metal ions were added. The effect of submolar quantities of heterometallic complexes, obtained by adding a first d-series metal(II) ion (2 equivalents) to [IrCl(CO)(L³)₂], on the oxidation of styrene by oxygen in methylethyl ketone has been assayed: inhibition of the oxidation is observed with the %conversion and the product selectivity dependant on the metal(II) ion.

Full text of DOI:10.1039/b201720m

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Towards co-operative reactivity in conjoint classical-organometallic
heterometallic complexes: the co-ordination chemistry of novel
ligands with triphenylphosphine and bis(pyridylethyl)amine or
triazacyclononane domains†
Scott E. Watkins, Donald C. Craig and Stephen B. Colbran*
School of Chemical Sciences, The University of New South Wales, Sydney, NSW 2052,
Australia. E-mail: s.colbran@unsw.edu.au
Received 15th February 2002, Accepted 15th April 2002
First published as an Advance Article on the web 15th May 2002
With a view towards later studies of co-operativity in heteronuclear complexes with hard classical (oxygen-activating)
and soft organometallic (organic-substrate binding) metal centres, four novel ditopic N3P-donor ligands (L1–L4),
each comprising triphenylphosphine tethered to an N,NЈ-bis(2-pyridyl-2-ethyl)amine (bpea) or a 1,4-diisopropyl-
1,4,7-triazacyclononane (tacn*) N3-donor group, have been designed and prepared by reductive aminations of
ortho- and meta-(diphenylphosphino)benzaldehydes with bpea (for L1 and L3) and tacn* (for L2 and L4). A range
of κNn,κP-chelate mononuclear complexes have been isolated from the reactions of the ortho-substituted ligands,
L1 and L2, with Cu(), Zn() and Pt() sources, and the X-ray crystal structures of [Cu(L1)][PF6], [Cu(L2)][PF6]
(communicated in: S. E. Watkins, D. C. Craig and S. B. Colbran, J. Chem. Soc., Dalton Trans., 1999, 1539) and
[PtCl(L1)][PF6] have been determined. Six complexes with the phosphine of L1–L4 co-ordinated to a softer [Pt(), Ir()
or W()] metal centre and with dangling, metal-free N3-donor domains have been prepared: for the ortho-substituted
ligands L1 and L2, it was necessary to protect the hard, more basic N3-donor domains by protonation (pH control) to
prevent formation of κNn,κP-chelate mononuclear complexes; for the meta-substituted ligands L3 and L4, pH control
was unnecessary as the phosphine group selectively binds to the softer metal ions. The complex trans-[IrCl(CO)(L3)2]
reversibly forms a dioxygen adduct. An Ir()Cu()2 and four Pt()Cu()2 heterometallic complexes were prepared
by adding hard Cu() ions to the Ir() and Pt() complexes with metal-free N3-donor domains, and the full
characterisation of these is described. The tungsten() carbonyl complex [W(CO)5(L3)], with a metal-free N3-bpea
domain, was prepared for a study of metal ion recognition. No perturbation of the carbonyl region of the IR
spectrum was observed when metal ions were added. The effect of submolar quantities of heterometallic complexes,
obtained by adding a first d-series metal() ion (2 equivalents) to [IrCl(CO)(L3)2], on the oxidation of styrene by
oxygen in methylethyl ketone has been assayed: inhibition of the oxidation is observed with the %conversion and the
product selectivity dependant on the metal() ion.
advances have been made in our understanding of the struc-
Introduction
tures and function of biological oxygen-activating centres.2–5
Heterometallic systems offer prospects for advantageous syn-
ergistic effects where the reactivity of the whole is greater than
Modelling studies have greatly contributed to this knowledge.
For example, simple copper() complexes of ligands with N,NЈ-
the sum of the parts. The goal of the research described in this
bis(2-pyridyl-2-ethyl)amine (bpea) or 1,4-diisopropyl-1,4,7-
paper was to design, synthesise and characterise heterometallic
triazacyclononane (tacn*) N3-donor groups are able to bind
complexes comprised of two different types of reactive metal
oxygen to afford Cu()2(µ-peroxo) ↔ Cu()2(µ-oxo)2 dimeric
centres linked by a ditopic ligand to provide the means for the
species, which closely model the active sites in oxygen-binding
study of such co-operative bimetallic reactivity.1 One possible
proteins with dicopper active sites such as hemocyanin, tyrosin-
combination of reactive metal centres, and the one which pro-
sase and catechol oxidase, and are able to hydroxylate appro-
vided the main impetus for this work, is to couple an oxygen
priately situated arene or alkyl groups within the ligands and
binding and activating, classical centre, akin to those found in
to oxidise exogenous hydrocarbon substrates.2–5 We there-
oxygen-activating proteins, to an organometallic centre known
fore chose to incorporate the bpea and tacn* groups into the
to bind and activate organic substrates. The combination of
these two types of centres offers the possibility of afford-
ing artificial oxidases or oxygenases, complexes which employ
the clean and abundant oxidant, oxygen, in the co-operative
targeted ditopic ligands. Following a similar line of thought,
Nolte has prepared a diphenylglycouril receptor substituted by
two (bpea)Cu centres for use as a catechol oxidase mimic—to
date, however, oxidation of exogenous substrates has not been
oxidations or oxygenations of organic substrates.
observed using this particular system.5
The ditopic ligands, L1–L4, were targeted for this study for
Second, triphenylphosphine is one of the more commonly
the following reasons. First, over the last decade or so major
used ligands in inorganic chemistry and is one of the most
common ligands found in homogeneous transition metal
† Electronic supplementary information (ESI) available: NMR and
catalysts for the binding and transformations of organic sub-
FTIR spectra; table of ES-MS and NMR spectral data for the mono-
strates.6 For this reason, the triphenylphosphine group was
nuclear complexes; table of analytical and EPR and electronic spectral
chosen as the second metal-binding domain in the targeted
ditopic ligands. Moreover, we anticipated that use of ditopic
ligands with P- and N3-donors would provide a useful degree of
data for heteronuclear complexes; table of FTIR spectral data for
[W(CO)5(L3)] solutions in thf following addition of transition metal
salts. See http://www.rsc.org/suppdata/dt/b2/b201720m/
DOI: 10.1039/b201720m
J. Chem. Soc., Dalton Trans., 2002, 2423–2436
This journal is © The Royal Society of Chemistry 2002
2423

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derivatives, L1–L4. The 2- and 3-isomers of diphenylphos-
phinobenzaldehyde were required. The Hoot–Rauchfuss
modification32 of Schiemenz and Kaack’s original synthesis33
of the 2-isomer proceeded as reported. However, in our hands
the yellow oil(s) repeatedly obtained following Schiemenz and
Kaack’s procedure to the 3-isomer,33 contained at best 45% of
1
phosphinobenzaldehyde product (as ascertained from H and
31P NMR spectra; it is perhaps noteworthy that the only charac-
terisation data for this product in the original report33 is
1
from a 60 MHz H NMR spectrum). Although the yellow oil
could be further purified by chromatography [silica support;
petroleum ether–ethyl acetate (2 : 1) eluent] to afford 3-isomer
that was pure by 1H and 31P NMR spectroscopy, consider-
able material was always lost leading to an overall yield (from
3-bromobenzaldehyde) less than 20%.
selectivity when constructing the targeted heteronuclear metal
complexes—phosphines are soft donors and should preferen-
tially bind to soft metal ions whereas the harder bpea and tacn*
donors should prefer hard metal ions.7 At the outset of
this work and presently, Schiff-base (imine) derivatives of
2-diphenylphosphinobenzaldehyde are the most common Nn,P-
donor ligands.8–13 We discounted use of Schiff-base ligands in
our work because these are susceptible to hydrolysis (imine
formation is reversible). Other ligands with Nn- and P-donor
domains14–25 have either long or not readily adaptable
preparations,17–19,21,22 or alkyl “linkers” that would be too flex-
ible for our purposes (see below);14–16,19,20,22 and only a handful
have macrocyclic Nn-sets.14–16,18,20,23,24 These problems are over-
come in L1–L4 which we thought should be readily available
from reductive aminations24–26 of the corresponding diphenyl-
phosphinobenzaldehydes; moreover, this methodology had the
attraction of potentially being applicable to the preparations of
a wide variety of phosphinoamine derivatives.
Third, it was important that the metal centres in the hetero-
nuclear ensemble should retain their individual reactivities.
Here, we were particularly mindful of Bosnich and co-workers’
extensive studies of a series of hetero-bimetallic species, which
revealed the oxidation of one metal centre to invariably cause
deactivation of the other.1 The deactivation followed from
ligand designs that allowed (mechanical, electronic or electro-
static) coupling between the metal centres. We thought that the
meta-benzyl “linker” in ligands L3 and L4 should keep the metal
centres sufficiently apart for these to maintain their individual
reactivities but at the same time should allow an organic sub-
strate bound and activated at the organometallic centre to
approach close to the oxygen-binding classical centre. Con-
siderably more interactions between metal centres are expected
in heterometallic species bridged by the ortho-benzyl substi-
tuted ligands L1 and L2, which would provide interesting
comparisons.
For the organometallic centres, analogues of [PtCl2(PPh3)2]
and [Ir(CO)Cl(PPh3)2], Vaska’s complex,27–29 were targeted in
this preliminary study. Such complexes are relatively easily pre-
pared, have diamagnetic, square-planar d8 metal centres that
facilitate their NMR characterisation, and most importantly,
exhibit extensive organometallic chemistries.30 Also targeted
were [W(CO)5(κP–L)] (L = L1, L3), analogues of [W(CO)5-
(PPh3)] with a dangling bpea group, because any changes to the
carbonyl IR bands upon binding of a second metal ion would
provide a useful measure of inter-metal centre interactions.
Moreover, if the carbonyl IR bands were perturbed by the
addition of a second metal, then the [W(CO)5(L)] complexes
could be considered to be “IR metal ion sensors”,31 with the
dangling bpea group acting as the recognition centre and
the tungsten() carbonyl moiety acting as the IR signal
transducer.
As anticipated, the reductive aminations26 of 2- and
3-phosphinobenzaldehydes
with
bis(2-pyridylethyl)amine
(bpea) and 1,4-diisopropyl-1,4,7-triazacyclononane (tacn*)
using sodium triacetoxyborohydride (1.6 equivalents) in
1,2-dichloroethane afforded the four new N3,P-donor ligands,
L1–L4, as thick yellow–orange oils. The crude products
obtained following neutralisation, extraction into dichloro-
methane and evaporation of this solvent were generally quite
clean by NMR spectroscopy and were used in subsequent
reactions. Although giving “purer” ligands, column chromato-
graphy [silica support; petroleum ether–ethyl acetate (2 : 1)
eluent] resulted in considerable losses and is not recommended.
The “purer” ligands tenaciously retain traces of solvent and, as
a result, elemental analyses were not acquired. However,
ES-MS and NMR spectroscopic data (see Experimental) are
entirely consistent for the ligands, and the subsequent success-
ful syntheses of metal complexes (see below) further attest to
their successful preparations. Ligands L3 and L4 are the first
derivatives of 3-diphenylphosphinobenzaldehyde to be
reported, a fact perhaps explained by the difficulties in purifica-
tions of these compounds and the starting aldehyde.
Protonation of bis(2-pyridylethyl)amine and 1,4,7-triaza-
cyclononane derivatives, which are most often oils, may give
tractable solids.34 Accordingly, the crude products from
the preparations of L1 and L2 (see above) were dissolved in
methanol and treated with excess ammonium hexafluoro-
phosphate to afford white precipitates of the monoprotonated
derivatives, [HL][PF6] (L = L1, L2), in 55 and 60% yield (overall
from 2-phosphinobenzaldehyde). NMR spectra of the proton-
ated derivatives show relatively large shifts in δH for the proton
peaks of the N3-domains and relatively small shifts in δP for
the phosphine (for data, see Experimental) suggesting that
protonation occurs at only the more basic N3-domains and not
at the phosphine group. Notable in the 1H NMR spectra of L2
and [HL2]ϩ are the methyl resonances of the isopropyl groups
which appear as a doublet for L2 and two sharp doublets for
[HL2]ϩ, indicating that monoprotonation is sufficient to lock
the macrocyclic ring and prevent ring inversion within the
NMR timescale. In an attempt to obtain a more highly proton-
ated derivative of L1, 70% perchloric acid was added to L1 in
methanol; a white precipitate formed, which shows 31P{1H}
NMR peaks at δP Ϫ16.87 (relative integrated intensity: 1.00)
typical of a “free” phosphine and at δP 34.8 (0.08), 35.5 (0.08)
and 40.7 (0.07) typical of phosphine oxide species. The peak at
δP 40.7 grows upon standing and attempted recrystallisations of
the original white precipitate afforded this species, a colour-
less crystalline solid which analyses as the triprotonated or
tris(hydronium ion) complex of the phosphine oxide, [H3L1O]-
(ClO4)3ؒ3H2O or (L1O)[H3O]3(ClO4)3 respectively. The positive-
ion ES-MS spectrum of the original white precipitate shows
a single strong peak at m/z 502.0 corresponding to the [HL1]ϩ
ion and products from reactions with metal ions suggest it is
principally tris-protonated ligand, [H3L1](ClO4)3, in which the
phosphine group is unprotonated (see below). It is noteworthy
that oxidation of [HnL1]nϩ to phosphine oxide-containing
Results and discussion
Ligands
Our proposal that direct reductive amination of phosphino-
benzaldehydes is a simple route to phosphinoamine ligands was
tested by the syntheses of the targeted triphenylphosphine-
2424
J. Chem. Soc., Dalton Trans., 2002, 2423–2436

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Table 1 Selected bond lengths (Å) and angles (Њ) for [Cu(L1)][PF6]
species was only observed when (oxidising) perchlorate was the
counter-anion.
Cu–P
2.197(1)
2.034(4)
2.055(4)
2.159(4)
P–Cu–N(1)
P–Cu–N(2)
P–Cu–N(3)
N(1)–Cu–N(2)
N(1)–Cu–N(3)
N(2)–Cu–N(3)
125.6(1)
122.5(1)
97.7(1)
105.2(2)
97.9(2)
Cu–N(1) (pyridyl)
Cu–N(2) (pyridyl)
Cu–N(3) (amine)
Mononuclear Nn,P-chelated complexes of L1 and L2
For the ortho-substituted triphenylphosphine derivatives, L1
and L2, it seemed likely that the P- and N3-ligand domains
could simultaneously bind to the same metal. To explore this
possibility, reactions of these ligands with sources of copper(),
zinc() and platinum() ions were investigated.
100.4(2)
[Cu(L2)]ϩ is more distorted due to the dual constraints of the
ortho-phosphino-benzylamine linkage [P–Cu–N(benzylamine):
100.6(1)Њ] and the macrocyclic ring which prevents the two
remaining amine donors from splaying outward toward
the phosphorus atom [P–Cu–N(iso-propylamine): 133.6(1),
138.9(1)Њ].24 Comparable Cu–P bond lengths are found in
[Cu(L1)]ϩ [2.197(1) Å] and [Cu(L2)]ϩ [2.141(1) Å].24 The two
Cu–N(pyridyl) bonds in [Cu(L1)]ϩ average 2.045 Å, significantly
shorter than the Cu–N(amine) bond [2.159(4) Å], which is con-
sistent with copper() ions forming stronger bonds with the
softer, pyridyl nitrogens. These Cu–N(pyridyl), Cu–N(amine)
and Cu–P bond lengths are similar to those reported for Cu()
complexes of bpea-based ligands with triphenylphosphine as a
co-ligand.36
The electrochemistries of the copper() complexes and the
ligands L1 and L2 were examined by cyclic voltammetry
experiments. Cyclic voltammograms (CVs) of L1 and L2 show
an anodic peak for an irreversible oxidation at ≈ϩ1.1 V vs.
ferrocenium–ferrocene (Fcϩ–Fc) couple; the number of
electrons transferred in the processes were not ascertained by
coulometry. CVs of [Cu(L1)][PF6], Fig. 2, exhibit an electro-
Copper(I) complexes. Reactions of [Cu(MeCN)4][PF6] with L
(L = L1 or L2) or [HL][PF6] in dichloromethane afforded the
corresponding copper() complex, [CuL][PF6], which are air
stable. ES-MS spectra, see Table 1 of the ESI,† show prominent
peaks for the [CuL]ϩ molecular ions at m/z 564 (L = L1) and 551
(L = L2) respectively. NMR spectra are presented in Fig. 1 and 2
1
of the ESI.† Marked changes are observed between the H
NMR spectra of the free or protonated ligand and the corre-
sponding copper() complex characteristic for co-ordination to
copper, and 31P{1H} NMR spectra in (CD3)2CO show a broad
peak centred at δP ≈ Ϫ10 (fwhh ≈ 1600 Hz) for [CuL1]ϩ and at
δP ≈ Ϫ0.3 (fwhh ≈ 700 Hz) for [CuL2]ϩ as well as the distinctive
sharp peaks of the hexafluorophosphate septet (δP Ϫ142.0, JPF
707 Hz). The 31P NMR peaks are broad due to quadrupolar
relaxation [63,65Cu, I = 3/2] and are indicative of the asymmetric
charge distributions about copper.35
Recrystallisation of both copper() complexes from aceto-
nitrile–diethyl ether gave clear, colourless crystals suitable for
X-ray crystallography. The crystal structure of [Cu(L2)][PF6] is
reported in a communication.24 In the crystal structures of
[CuL][PF6] (L = L1, L2) there are no significant interion inter-
actions. The structure determinations confirm the copper() ion
in both complexes is κ3N,κP-bound by the ligand, e.g. Fig. 1 and
Fig. 1 View of the cation from the crystal structure of [Cu(L1)][PF6]
(10% thermal ellipsoids).
Fig. 2 Cyclic voltammograms of [Cu(L1)][PF6] (a, b) and [Cu(L2)]-
[PF6] (c, d). Conditions: 0.1 M [NBu4][PF6]-acetonitrile; 295 K; 1 mm
ref. 24. The co-ordination geometry for the copper() ion is best
described as distorted tetrahedral for both complexes; the sum
of the six bond angles about the copper() ion is 649Њ for
[Cu(L1)]ϩ (Table 1) and 631Њ for [Cu(L2)]ϩ 24 compared to 657Њ
for a perfect tetrahedron.
diameter Pt disk electrode; scan rate = 100 mV sϪ1
.
chemically quasireversible Cu()–Cu() couple at ϩ0.40 V [ipc/
ipa ≈ 0.85 and ∆Ep = 110 mV at scan rate (ν) = 100 mV sϪ1 cf.
∆Ep(Fcϩ–Fc) = 65 mV; ∆Ep increases with ν], suggesting that
rate-limiting structural changes accompany the forward and
reverse electron transfer processes. Coulometry at ϩ0.60 V
confirmed that the ϩ0.4 V couple is a one-electron process. In
For [Cu(L1)]ϩ, the ligand design constrains the N(3)–Cu–P
bond angle to 97.7(1)Њ (compared to 107.5Њ for a perfect tetra-
hedron), whilst the P–Cu–N(pyridyl) bond angles are greater
than 120Њ (Table 1), which minimises the steric interactions
between the pyridyl and phenyl rings. The geometry about
J. Chem. Soc., Dalton Trans., 2002, 2423–2436
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CVs of [Cu(L2)][PF6] the Cu()–Cu() couple is less electro-
chemically reversible with an anodic peak at ϩ0.48 V for oxid-
ation of the Cu() complex that gives rise to a cathodic peak in
the reverse sweep at ϩ0.22 V for reduction of the thus-
produced Cu() species. In the CVs of both complexes at more
positive potential an irreversible oxidation is observed, at ϩ1.36
V for [Cu(L1)][PF6] and at ϩ1.27 V for [Cu(L2)][PF6], which on
the basis of relative peak currents is a two-electron process. For
[Cu(L2)][PF6], the irreversible oxidation at ϩ1.27 V gives rise to
“daughter” cathodic peaks at Ϫ0.12 and Ϫ0.41 V in the reverse
negative sweep. The irreversible two-electron oxidations are ten-
tatively attributed to a phosphine-centred oxidation process,
possibly to the corresponding phosphine oxide, with the two-
electron nature of the process somewhat unexpected as, despite
some controversies, it has been established that triphenyl-
phosphine undergoes a one-electron oxidation above ϩ1.0 V.37
One possibility is that the copper centres assist in the two-
electron oxidation of the phosphine. The low affinity of
copper() for phosphine donors19,38 suggests that the phosphine
should dissociate in the copper() species and oxidation of
the dangling, dissociated phosphine group is consistent with
the loss of chemical reversibility for the Cu()–Cu() redox
couples after the two-electron oxidation is traversed in the CVs.
The low affinity of copper() for phosphine ligands19,38 also
accounts for the relatively high Cu()–Cu() couples for these
complexes [as recently discussed by Rorabacher et al.,39 Cu()–
Cu() couples are determined largely by the stabilities of the
copper() complexes, with the stabilities of the copper()
congeners being relatively invariant and having little effect].
co-ordination chemistry is not extensive and assignments of
genuine zinc-phosphine complexes are considered somewhat
controversial41 with only a handful of crystallographically
characterised examples reported to date.20
Platinum(II) complexes. Pale yellow crystalline [PtCl(L1)]-
[PF6] was obtained in 43% yield from the reaction of
[PtCl2(PhCN)2] with [HL1][PF6] and excess triethylamine in
1,2-dichloroethane at reflux, followed by recrystallisation from
MeCN–Et2O.
The positive-ion ES-MS mass spectrum of [PtCl(L1)][PF6]
shows only peaks for the [PtCl(L1)]ϩ ion centred at m/z 732.0
1
(see Table 1 of the ESI†). The H NMR spectrum exhibits
extremely broad peaks suggestive for fluxional behaviour in
solution, and the large downfield shift of the pyridyl H6 peak
from δ 8.22 [(CD3)2CO] for [HL2] to δ 8.67 [(CD3)2CO] (see ESI
Table 1 and ESI Fig. 3†) is indicative for one of the pyridyl
groups binding to platinum. Although not pursued further, it is
likely that exchange of the metal-free, dangling and the bound
pyridyl groups (see below) on the NMR timescale is the under-
lying process leading to the broad peaks; the bound pyridyl is
expected to be labile as it lies opposite the phosphine (see
below) which exerts a strong trans effect. The 31P{1H} NMR
spectrum [in (CD3)2CO; see inset to Fig. 3 of the ESI†] exhibits
the hexafluorophosphate septet (δP Ϫ142.0, JPF 707 Hz) and a
“triplet” at δP 0.78 (JPPt 3624 Hz) due to coupling to 195Pt (195Pt:
I = 1/2, 33% natural abundance) for the phosphine group
bonded to platinum.35
A zinc(II) complex. Each of the ligands was treated with
anhydrous zinc() chloride in ethanol, followed by excess
ammonium hexafluorophosphate: for L1 the monoprotonated
ligand, [HL1][PF6], precipitated (see above), and for L2 an off-
white precipitate formed. This was recrystallised but crystals of
quality sufficient for X-ray crystallography could not be
obtained. A partial elemental analysis of the precipitate is con-
sistent with the formulation “ZnCl(H2O)(L2)(PF6)”. The ES-
MS spectrum exhibits a single strong peak at m/z 588 for the
[ZnCl(L2)]ϩ ion (see Table 1 of the ESI†), consistent with this
being the molecular ion. An electrical conductivity measure-
ment reveals the complex is a 1 : 1 electrolyte in dichloro-
methane also consistent with chloride binding to the zinc()
ion. The 1H NMR spectrum of the zinc complex (see Table 1 of
the ESI†) shows significant differences to those of L2 and
[HL2]ϩ: for example, the benzyl peak shifts downfield from
δ(CDCl3) 3.97 for [HL2]ϩ to δ(CDCl3) 4.14, the macrocyclic
alkyl proton resonances are more spread, and the characteristic
iso-propyl C–H septet shifts from δ(CDCl3) 3.11 for [HL2]ϩ to
δ(CDCl3) 3.51. These data provide compelling evidence for the
co-ordination of the zinc() ion to the N3-donor set. The
31P{1H} NMR spectrum shows the expected hexafluoro-
phosphate septet and a phosphine singlet at δP (CDCl3) Ϫ17.72
only slightly upfield of [HL2]ϩ [δP (CDCl3): Ϫ14.22]. In the
The X-ray structure of [PtCl(L1)][PF6] confirms that in
the cation the platinum() ion is bound by the phosphine, the
amine and one pyridyl of L1, and by a chloride co-ligand in
the position trans to the amine, Fig. 3. A dangling pyridyl lies
complex cation [Zn2(κ3N,κP-L5)2Cl3]ϩ [L5
=
N-(diphenyl-
phosphinopropyl)-1,4,7-triazacyclononane,
a ligand closely
related to L2], one zinc is N3PCl2-pseudo-octahedral and the
other is formally five (N3PCl-) co-ordinate but with a weak
interaction (2.91 Å) to one of the two chlorides of the pseudo-
octahedral zinc centre.20 The change in 31P chemical shift upon
co-ordination of L5 to zinc is small (∆δP = Ϫ3.2),20 typical for
other examples of phosphine co-ordination to zinc() ion.20,40
Thus the 31P data for “ZnCl(H2O)(L2)(PF6)” are consistent with
structures for the cation in which the phosphine binds zinc such
as [ZnCl(κN3,κP-L2)]ϩ (A). However, the 31P data are also con-
sistent with structures having a dangling phosphine group such
as in [ZnCl(H2O)(κN3-L2)]ϩ (B), in which case the proximate
zinc() centre could cause δP to shift upfield from that of
L2. Overall the present data highlight the difficulties in assign-
ing authentic zinc() phosphine complexes; zinc-phosphine
Fig. 3 View of the cation from the crystal structure of [PtCl(L1)][PF6]
(10% thermal ellipsoids).
orientated away from the platinum centre. Perhaps most
remarkable about the structure is that it is entirely undistorted
compared to related phosphine and pyridyl platinum() com-
plexes: the co-ordination geometry about the platinum()
centre is square planar (the sum of the eight bond angles about
the metal centre is 713Њ, close to the value of 720Њ expected for a
2426
J. Chem. Soc., Dalton Trans., 2002, 2423–2436

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Table 2 Selected bond lengths (Å) and angles (Њ) for [PtCl(L1)][PF6]
predominant product always being [PtCl(κ3N,κP-L1)][PF6].
Monoprotonation of L1 apparently leaves the amine and one
pyridyl donor “free” for complex formation and is therefore
insufficient to prevent the N3-domain from binding to platinum.
For L1, however, triple protonation served to protect the
N3-domain; thus reaction of [PtCl2(PhCN)2] and [H3L1](ClO4)3
(2 equivalents) in acetonitrile cleanly afforded the complex
trans-[PtCl2(H3L1)2](ClO4)6 with dangling triply-protonated
bpea domains. The meta-substitution of the triphenyl-
phosphine moiety in L3 and L4 prevents the phosphine and
N3-domains from simultaneously binding to a metal and, in this
case, protonation of the ligand to protect the N3-domain is
unnecessary. Thus, the direct reactions of L3 (2 equivalents)
with [PtCl2(PhCN)2] in dichloromethane and cis-[IrCl(CO)2-
(4-NH2C6H4CH3)] in tetrahydrofuran gave cis-[PtCl2(L3)2] and
trans-[IrCl(CO)(L3)2], respectively, also with dangling bpea
domains.
Pt–P
Pt–Cl
Pt–N(1)
Pt–N(3)
2.234(1)
2.285(1)
2.105(3)
2.120(3)
Cl–Pt–P
91.9(1)
89.2(1)
174.0(1)
178.7(1)
93.3(1)
85.6(1)
Cl–Pt–N(1)
Cl–Pt–N(3)
P–Pt–N(1)
P–Pt–N(3)
N(1)–Pt–N(3)
perfect square planar structure), the Pt–N and Pt–Cl bond
lengths (Table 2) are in the ranges established for similar
platinum() complexes, and the Pt–P [2.234(1) Å] bond length
is typical of those reported for other platinum() compounds
with transoid phosphine and pyridyl groups.42–44 Likewise the
P–Pt–N(3) bond angle [93.3(1)Њ] is only slightly greater than the
90Њ expected for a perfect square planar structure. Clearly L1
can comfortably accommodate tetrahedral and square planar
co-ordination geometries.
To test for interactions between the metal centres in dimers,
tungsten() carbonyl complexes of L1 and L3 were also sought.
Reactions of [W(CO)5(thf )] with L1 or L3 always produced mix-
tures, the 31P{1H} NMR spectra of which showed many sing-
lets, all with no discernable satellites from 183W coupling (183W:
I = 1/2, 14.4% natural abundance), suggestive for multiple
products in which the phosphine is not bound to tungsten. As
an alternative route to the targeted complexes, the complexes
[W(CO)5(L)] (L = 2- and 3-diphenylphosphinobenzaldehyde)
were prepared and reductive aminations with bpea using tri-
acetoxyborohydride in 1,2-dichloroethane attempted. The reac-
tions of [W(CO)5(2-Ph2PC6H4CHO)],48 including using forcing
conditions such as heating or addition of excess acetic acid, all
failed with the starting complex recovered, presumably because
of steric protection of the aldehyde group by the bulky W(CO)5
moiety. Reductive amination of [W(CO)5(3-Ph2PC6H4CHO)]
with bpea using triacetoxyborohydride in 1,2-dichloroethane,
however, proceeded as expected and afforded [W(CO)5(L3)],
isolated as a thick yellow–orange oil in 37% yield after purifica-
tion by flash chromatography (silica support; eluent: ethyl
acetate).
Noteworthily, [PtCl(L1)][PF6] is completely air stable and
survives heating in ethanol solution at 60 ЊC under oxygen.
Under the latter conditions cis-[PtCl2(κ2N-tacn)] is rapidly
oxidised to the peroxo-bridged platinum() dimer, [Pt2Cl2-
(κ3N-tacn)2(µ-O2)2], a reaction proposed to be facilitated by the
binding of the non-co-ordinated N-donor group of the tacn to
platinum.45 The failure of [PtCl(L1)][PF6], which has a similarly
placed dangling pyridyl arm, to react with oxygen highlights
the importance of the ligand(s) influence upon the electronic
properties of the metal centre.
Although reaction of [PtCl2(PhCN)2] with [HL2][PF6] and
excess triethylamine in 1,2-dichloroethane heated at reflux
afforded a yellow solid, this unfortunately could not be further
purified—attempted recrystallisations and chromatography
always lead to oily product containing trace solvent. The
positive-ion ES-MS mass spectrum of the solid is remarkably
simple exhibiting only a peak for the [PtCl(L2)]ϩ ion (m/z 717.0;
calc. m/z 717.25), and the 31P{1H} NMR spectrum shows a
“triplet” at δP Ϫ0.71 (JPPt 3752 Hz), values remarkably similar
to those for [PtCl(L1)]ϩ, and the hexafluorophosphate septet.
These data are consistent with [PtCl(L2)][PF6] having formed.
Of these six complexes, only [PtCl2(H3L1)2](ClO4)6 and [PtCl2-
(HL2)2][PF6]2 with protonated N3-donor domains were solids
and partial elemental analyses of these were consistent with
the formulations. The remaining four complexes could not be
obtained free from trace solvent(s) and were viscous oils or
solids that tended to oil upon attempts to recrystallise them. As
a result, elemental analyses were not measured. However, the
ES-MS and MALDI-MS, NMR and IR data (see Table 1 of the
ESI†) along with their subsequent reactions (see below) provide
compelling evidence for their suggested structures. All of the
positive-ion ES-MS spectra show only peaks for ions that are
consistent for the proposed metal centre, having the correct
(number of ) co-ligands and N3,P-ligands, and with protonation
of one or two of the dangling N3-domains. MALDI-MS
spectra were also recorded for [W(CO)5(L3)] (observed: m/z
826.50; calc. m/z 826.99 for [W(CO)5(HL3)]ϩ) and [IrCl-
(CO)(L3)2] (observed: m/z 1259.86, 1223.43; calc. m/z 1259.89,
1223.32 for [IrCl(CO){H(L3)2}]ϩ and [Ir(CO)(L3)2]ϩ, respect-
ively). The CO bands in infrared spectra of [W(CO)5(L3)] and
[IrCl(CO)(L3)2] (see footnotes, Table 1 of the ESI†) are within
5 cmϪ1 of those for the corresponding triphenylphosphine
complex.27,49
1
However the H NMR spectrum (see Table 1 of the ESI†) is
complicated with more than the expected number of sharp
peaks—there was no evidence for fluxional behaviour—and
could not be fully assigned.
Heteronuclear complexes
We reasoned that pH control should allow selective prepar-
ations of heteronuclear complexes from ligands, L1–L4. Reac-
tions of the protonated ligands, in which the N3-domains are
effectively “tied-up” and unavailable for metal binding, with
sources of softer metal ions in solvents with little or no Brøn-
sted basicity should allow mononuclear phosphine complexes
with dangling, metal-free N3-donor domains, so-called “com-
plex ligands”,46,47 to be prepared. If they could be made, these
would be useful precursors to heteronuclear complexes—
deprotonation of the dangling N3-domain followed by addition
of harder metal ions could be used to selectively prepare hard–
soft heteronuclear trimeric complexes. For the reasons outlined
in the Introduction, these ideas were tested using platinum()
and iridium() as softer metal centres and copper() as a harder
metal centre.
1
The H NMR spectra of these six complexes exhibit large
Mononuclear precursors with dangling, metal-free N3-
domains. Six such complexes were isolated. The platinum()
examples with dangling monoprotonated tacn-based domains,
trans-[PtCl2(HL)2][PF6]2 (L = L2, L4), were obtained from
reactions of [PtCl2(PhCN)2] with [HL][PF6] (2 equivalents)
in dichloromethane. Attempts to prepare the analogous
platinum() complex using [HL1][PF6], which has a bpea-
domain, always resulted in a mixture of products (as judged by
the 31P{1H} NMR spectra of the reaction mixtures) with the
co-ordination shifts for the benzylic resonances and shifts and
changes in the phenyl peaks, while the peaks for the bpea or
tacn* groups (depending on the ligand) are little changed from
those in the spectrum of the ligand (L) or protonated ligand
salt {[HnL]nϩ} (as appropriate). These observations are consist-
ent with phosphine co-ordination and dangling, metal-free
1
N3-donor domains. Fig. 4 and 5 of the ESI† reproduce the H
and 31P{1H} NMR spectra for trans-[PtCl2(κP–HL2)2][PF6]2
and [W(CO)5(κP–L3)], which show the same general features as
J. Chem. Soc., Dalton Trans., 2002, 2423–2436
2427

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those of the other κP–L complexes. The 31P{1H} NMR spec-
trum of each of the six complexes exhibits only one phosphine
resonance (and, when expected, a hexafluorophosphate septet)
consistent in each case with a single phosphine-containing
species in solution. For [W(CO)5(L3)] the phosphine peak
at δP (CDCl3) 21.49 is flanked by a satellite doublet due to
31P–183W coupling (JPW 243 Hz); these data compare with δP
(CH2Cl2) 26.6 (JPW 280 Hz) for [W(CO)5(PPh3)].49 Likewise the
phosphine resonances of the platinum() complexes appear as
“triplets” because of 31P–195Pt couplings, which are character-
istic for cis- or trans-co-ordination geometries (trans-[PtCl2-
(PR3)2]: JPPt < 2800 Hz; cis-[PtCl2(PR3)2]: JPPt > 3200 Hz).35
Interestingly 31P{1H} NMR spectra acquired early during syn-
theses of [PtCl2(L3)2] reveal a “triplet” at δ 21.61 (JPPt 2632 Hz)
for the trans-isomer which is only slowly replaced on standing
in solution overnight by the “triplet” at δ 15.03 (JPPt 3674 Hz)
for the cis-isomer. This reproducible, thermodynamic prefer-
ence for cis over trans co-ordination geometry is typical for
[PtCl2P2] (P = non-bulky phosphine) complexes, and the isom-
erisation from trans kinetic product to cis thermodynamic
product can be catalysed by extra ligand in the solution such as
free halide or phosphine.50 The fact that the three other trans-
platinum() complexes did not isomerise may be attributable to
the bulk of the ortho-substituted triphenylphosphines L1 and L2
and to the protonation of the N3-donor domains rendering
these unavailable to catalyse isomerisation.
differing spectra. Constable et al. likewise report that they could
not obtain reproducible ES-MS spectra of heteronuclear com-
plexes based on a similar N3,P-ditopic phosphinoterpyridine
ligand.21
The EPR and electronic absorption spectra of the PtCu2 and
IrCu2 complexes are characteristic for a single type of copper()
centre in each complex. In each case the electronic absorption
and EPR spectra of the complex are markedly different from
the spectra of the corresponding copper() source {[Cu2(OAc)4-
(H2O)2] or CuCl2ؒ2H2O} in the same solvent,38 which is
evidence for co-ordination of copper() ions by the dangling
N3-domains of the mononuclear Pt or Ir precursor. The EPR
spectra are all axial and no half-field transitions are observed
[which would have indicated exchange-coupled copper()
centres38], Fig. 4 (data are in Table 2 of the ESI†). For the
Heteronuclear Ir(I)–Cu(II)2 and Pt(II)–Cu(II)2 trimers. Treat-
ing the mononuclear complexes trans-[PtCl2(H3L1)2]6ϩ and
trans-[PtCl2(HL)2]2ϩ (L = L2, L4), which have dangling proton-
ated N3-domains, with [Cu2(OAc)4(H2O)2] in the presence of
excess triethylamine as base in acetonitrile afforded the corre-
sponding [PtCl2{(L)Cu(OAc)}2]2ϩ complex (isolated in 55–80%
yield). Addition of CuCl2ؒ2H2O (2 equivalents) to thf solu-
tions of cis-[PtCl2(L3)2] or trans-[IrCl(CO)(L3)2], in which the
dangling N3-domains are unprotonated, caused immediate pre-
cipitation of [PtCl2{(L3)CuCl2}2] (78% yield) and mer-[IrCl3-
(CO){(L3)CuCl2}2] (47% yield) respectively. The yield of the
latter complex (less than 50%) is consistent with the stoichio-
metry shown in eqn. 1, but was not increased by adding CuCl2ؒ
2H2O (4 equivalents) to trans-[IrCl(CO)(L3)2]. Vaska’s complex,
trans-[IrCl(CO)(PPh3)2], is likewise oxidised by CuCl2 to afford
mer-[IrCl3(CO)(PPh3)2].51 The PtCu2 complexes of L1 and L2,
the ortho-substituted triphenylphosphine ligands, decomposed
on prolonged standing in solution during attempted recrystal-
lisations; e.g. over several weeks a mixture of colourless crystals
of [Cu(L2)][PF6] and green “flowers” of an unidentified
species52 grew from trans-[PtCl2{(L2)Cu(OAc)}2][PF6]2 in
MeCN–Et2O. In distinct contrast, the IrCu2 and two PtCu2 tri-
mers from the meta-substituted triphenylphosphine ligands L3
and L4 were indefinitely stable in solution. Unfortunately the
crystals of these complexes obtained from recrystallisations
were of insufficient quality for X-ray crystallography.
Fig. 4 X-Band EPR spectra (at ν = 9.52 GHz) of heteronuclear
complexes at 77 K: (a) [PtCl2{(L1)Cu(OAc)}2](ClO4)2, (b) [PtCl2-
{(L2)Cu(OAc)}2][PF6]2, (c) PtCl2{(L4)Cu(OAc)}2][PF6]2, (d ) [PtCl2-
{(L3)CuCl2}2], (e) [IrCl(CO){(L3)CuCl2}2]; frozen acetonitrile solution
for spectra (a)–(c) and frozen chloroform solution for (d ), (e).
[PtCl2{(L)Cu(OAc)}2]2ϩ (L = L1, L2, L4) complexes: g|| (≈ 2.25–
2.26) > g⊥ (≈ 2.06–2.07) and A|| ≈ 160–166 G, parameters
indicative for square pyramidal or tetragonally-distorted
trans-[IrCl(CO)(L3)2] ϩ 4CuCl2
mer-[IrCl3(CO){(L3)CuCl2}2] ϩ 2CuCl (1)
octahedral copper() complexes with a dx Ϫy ground-state.34,38
The parameters for [PtCl2{(L3)CuCl2}2] and mer-[IrCl3(CO)-
{(L3)CuCl2}2], g|| (= 2.23) > g⊥ (= 2.10) and a lower A|| value
(121 G and 125 G), are identical within experimental error to
those for [Cu(Bzbpea)Cl2] [Bzbpea = benzylbis(2-pyridylethyl)-
amine)] (see Experimental),34 which we prepared for compar-
ative purposes. The observation of axial EPR spectra and
the absence of half-field transitions argue against structures
containing exchange-coupled dicopper() centres, e.g. with
bridging acetato, hydroxo or chloro ligands.38
2
2
Partial elemental analyses (for C, H and N) and elemental
ratios for Cu, P and Pt calculated from ICP-AES analyses are
presented in Table 2 of the ESI.† The carbon contents of the
CuCl2-containing complexes are low which is consistent with
lattice waters as is often found for Cu–Cl containing species.34,53
ICP-AES analyses were not obtained for mer-[IrCl3(CO)-
{(L3)CuCl2}2] because all attempted digestions of this complex
(e.g. with hot 20% nitric acid or hot aqua regia) produced insol-
uble iridium-containing precipitates. Frustratingly, the ES-MS
spectra of these heteronuclear complexes show only peaks for
the protonated ligands, ligand fragments and fragment ions
containing Pt or Ir or Cu but never the molecular ions, and with
poor reproducibility—repeat acquisitions sometimes produced
The electronic absorption spectra of the five heteronuclear
complexes show intense ligand-centred absorptions below 340
nm (ε > 3000 dm3 molϪ1 cmϪ1) and characteristic, weak d–d
2428
J. Chem. Soc., Dalton Trans., 2002, 2423–2436

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Probable structures for [PtCl2{(L3)Cu(OAc)}2]2ϩ and mer-
[IrCl3(CO){(L3)CuCl2}2] deduced from the geometry of the
mononuclear Pt or Ir precursor, from the stoichiometry estab-
lished by analyses, and from the EPR, Vis/NIR and IR spectro-
scopic properties are drawn below. The copper centres are
representative of those in the other trimers. Given the limited
stabilities of the trimers spanned by the ortho-substituted
triphenylphosphines L1 and L2, which may be related to the
ability of these ligands to form mononuclear chelate complexes,
our subsequent studies were concentrated on the more stable
heteronuclear complexes of L3, which is much the more eco-
nomically made (in terms of both money and time spent)
meta-substituted triphenylphosphine ligand.
Inter-metal centre interaction. Two results point to the near
independence of the Ir and Cu centres in mer-[IrCl3(CO)-
{(L3)CuCl2}2]: 1. The EPR and Vis-NIR spectroscopic proper-
ties of mer-[IrCl3(CO){(L3)CuCl2}2], which characterise the
Cu() centres, are identical to those of [CuCl2(Bzbpea)] (see
Table 2 of the ESI†). 2. The νCO band energies of mer-
[IrCl3(CO){(L3)CuCl2}2] and mer-[IrCl3(CO)(PPh3)2] are near
identical (see above) indicating that meta-substitution of the
triphenylphosphine ligands in the latter complex by Cu(bpea)
centres to give the former complex does not perturb the elec-
tronic properties of the Ir centre. Likewise, the CO bands in the
IR spectrum of [W(CO)5(L3)] in thf were not perturbed upon
addition of a 10-fold molar excess of M(ClO4)2ؒ6H2O (M =
Mn, Fe, Co, Ni, Cu, Zn), see ESI Fig. 6 and ESI Table 3.†
Clearly “meta-substituted” [W(CO)5(L3)] does not act as an IR-
metal ion sensor of the type proposed in the Introduction;
greater inter-metal ion interactions are expected in metal com-
plexes of “ortho-substituted” [W(CO)5(L1)], but this complex
could not be prepared (see above) to test for these.
Vaska’s complex, trans-[IrCl(CO)(PPh3)2], cleanly and
reversibly forms a dioxygen adduct.28 Substitutions to afford
analogues of Vaska’s complex critically affect the oxygen
reactivity; for example, alkylphosphine and Rh() analogues are
unreactive and [Ir(CO)I(PPh3)2] is irreversibly oxidised by oxy-
gen.57,58 Since the oxidation of trans-[IrCl(CO)(L3)2] by CuCl2
prevented the preparation and study of an Ir() complex with
pendant (bpea)Cu() centres, the reaction of trans-[IrCl(CO)-
(L3)2] with oxygen was investigated. Fig. 6 shows IR spectra
collected as oxygen was bubbled through a solution of trans-
[IrCl(CO)(L3)2]. The spectra show a quantitative conversion to
the dioxygen adduct trans-[IrCl(CO)(L3)2(O2)] (νCO: 2006 cmϪ1),
that is cleanly reversed by heating the solution at reflux (inset
to Fig. 6).59 The conversion was also clean by 31P{1H} NMR
spectroscopy [δP (adduct): 5.2] and the ES-MS spectrum of
the adduct shows a strong peak at m/z 1291.0 (calc. 1291.0) for
the [IrCl(CO){H(L3)}2(O2)]ϩ ion. The meta-substitution of the
triphenylphosphine ligands in trans-[IrCl(CO)(L3)2] has little
affected the reactivity with oxygen compared to Vaska’s
complex.
Fig.
5
Vis-NIR spectra of the heteronuclear complexes:
(a) [PtCl2{(L1)Cu(OAc)}2](ClO4)2 (——), [PtCl2{(L2)Cu(OAc)}2][PF6]2
( ؒ ؒ ؒ ؒ ؒ ؒ ) and PtCl2{(L4)Cu(OAc)}2][PF6]2 (– – –) in acetonitrile
solution; (b) [PtCl2{(L3)CuCl2}2] (——) and [IrCl(CO){(L3)CuCl2}2]
( ؒ ؒ ؒ ؒ ؒ ؒ ) along with [Cu(Bzbpea)Cl2] (– – –) in chloroform solution.
bands in the 500–1200 nm region, Fig. 5 and ESI† Table 2.
Briefly, [PtCl2{(L1)Cu(OAc)}2](ClO4)2 with (bpea)Cu(OAc)
centres shows a band at 664 nm (ε = 300 MϪ1 cmϪ1) with a
prominent low energy tail, whilst [PtCl2{(L)Cu(OAc)}2][PF6]2
(L = L2, L4) with (tacn*)Cu(OAc) centres exhibit almost identi-
cal spectra—distinct Cu() d–d bands at ≈650 nm (ε ≈ 70 MϪ1
cmϪ1) and ≈1080 nm (ε ≈ 30 MϪ1 cmϪ1). These data are similar
to those reported for comparable square pyramidal Cu()
complexes bound by a N3-donor ligand and a chelating (κ2O–)-
acetate co-ligand such as [Cu(κ3N-dpt)(κ2O–OAc)](ClO4) [dpt =
dipropylenetriamine; λmax (solid): 641 nm],54 [Cu(κ3N–Pri3tacn)-
(κ2O–OAc)](CF3SO3) [λmax (MeOH): 672 nm (the spectrum
above 680 nm was not recorded)],55 and [Cu(κ3N–L)(κ2O–
OAc)](ClO4) [L
=
2,4,4Ј-trimethyl-1,5,9-triazacyclododec-
1-ene; λmax (acetone): 694 nm (ε = 99 MϪ1 cmϪ1), 1150 nm
(ε = 99 MϪ1 cmϪ1)].56 Spectra of [PtCl2{(L3)CuCl2}2] and
mer-[IrCl3(CO){(L3)CuCl2}2] with (bpea)CuCl2 centres reveal a
band at ≈775 nm and high energy shoulder at ≈990 nm, d–d
bands typical of a square pyramidal N3Cl2–Cu() centre34,38
and identical to those of [CuCl2(Bzbpea)] but with double the
extinction coefficient as is expected for two copper centres in
each trimer. Finally the infrared spectrum of mer-[IrCl3(CO)-
{(L3)CuCl2}2] shows a single strong carbonyl band at νCO
(CHCl3) = 2074 cmϪ1, which compares with νCO (CHCl3) = 2075
cmϪ1 for mer-[IrCl3(CO)(PPh3)2].29
A preliminary “catalysis” study: styrene oxidation. The oxid-
ation of styrene by oxygen is catalysed by Vaska’s complex and
close Ir-analogues, and affords acetophenone, benzaldehyde or
J. Chem. Soc., Dalton Trans., 2002, 2423–2436
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Table 3 Oxidation of styrene by oxygen in MEK. Reagents and conditions: solutions were prepared containing styrene (500 mM), the iridium
complex (1 mM) and the added metal ion as the perchlorate salt, [M(ClO4)2ؒ6H2O] [2 mM (two equiv./Ir)]. The solutions were bubbled with oxygen
whilst heated at 80 ЊC for 16 h and then analysed directly by gas chromatography. The %conversion refers to the number of moles of products relative
to the number of moles of styrene added and was determined by comparison of the gas chromatograms of reaction mixtures with calibration curves
for authentic samples of the products
Iridium complex
Added metal ion
Products
%Conversion
trans-[IrCl(CO)(PPh3)2]
trans-[IrCl(CO)(L3)2]
trans-[IrCl(CO)(L3)2]
trans-[IrCl(CO)(L3)2]
trans-[IrCl(CO)(L3)2]
trans-[IrCl(CO)(L3)2]
trans-[IrCl(CO)(L3)2]
trans-[IrCl(CO)(L3)2]
—
—
—
benzaldehyde (54%), styrene oxide (42%), acetophenone (4%) 6.1
no products
benzaldehyde
no products
0
2.3
0
Mn()
Fe()
Co()
Ni()
Cu()
Zn()
—
benzaldehyde
benzaldehyde
benzaldehyde
benzaldehyde
<0.2
0.9
5.3
24
benzaldehyde (90%), styrene oxide (10%)
19
constant rate under the identical conditions employed in the
parallel reactions, the order of inhibition of styrene oxidation
is: trans-[IrCl(CO)(L3)2] ≈ ϩFe() ≈ ϩCo() (complete inhib-
ition) ≥ ϩNi() > ϩMn() > ϩCu() ≈ [IrCl(CO)(PPh3)2] ӷ
ϩZn() (no inhibition; at least the same %conversion as with
no metal) {where ϩ (metal ion) indicates the metal ion added to
trans-[IrCl(CO)(L3)2]}. The complete inhibition of styrene
oxidation by trans-[IrCl(CO)(L3)2] may represent the ability of
the N3-donor domain in this complex to scavenge trace metal
ion (e.g. Fe2ϩ) from glassware. At present we have no explan-
ation for the distinct and interesting differences in %conversion
and selectivity when [IrCl(CO)(PPh3)2] or [IrCl(CO)(L3)2] ϩ
2Zn2ϩ are employed.
Summary and conclusions
Towards our goal of demonstrating co-operativity between
metal centres in conjoint classical-organometallic hetero-
metallic complexes we have prepared the new ligands L1–L4
with triphenylphosphine and bis(2-pyridylethyl)amine or tri-
azacyclononane N3-donor domains, and have undertaken pre-
liminary studies of their co-ordination chemistry. We believe
the research demonstrates the following:
1. Reductive amination is a convenient method for linking a
phosphinobenzaldehyde and a secondary amine substituted
with metal co-ordinating groups; it should prove to be a power-
ful, general route to a wide range of ditopic ligands with soft
phosphine and hard Nn-metal-binding donor domains, includ-
ing asymmetric examples from chiral amines. The major dif-
ficulty may be the synthesis of the appropriate phosphino-
benzaldehyde.
Fig. 6 FTIR spectra recorded at approx. 3 h intervals as a tetra-
hydrofuran solution of trans-[IrCl(CO)(L3)2] was bubbled with oxygen
at 295 K showing conversion to trans-[IrCl(CO)(L3)2(O2)]. Inset: the
FTIR spectrum of the same solution after heating at reflux under
nitrogen to regenerate trans-[IrCl(CO)(L3)2].
2. The Nn-donor domains can be selectively protonated,
which may facilitate purification and handling of the ligands.
3. Ligands with an ortho-benzyl “linker” such as L1 and L2
can act as κNn,κP-chelate ligands supporting tetrahedral and
square planar metal centres. Although not tested in this work,
there are no geometrical constraints to these ligands forming
square pyramidal and octahedral metal complexes. A rich
κNn,κP-chelate co-ordination chemistry is predicted.
styrene oxide in proportions that depend on the exact
conditions.60–63 It has been shown that the reactions proceed by
a radical process with the role of the Ir centre not to activate
oxygen but to decompose organic peroxides and thereby initiate
radical formation.61,63 Since either trans-[IrCl(CO)(L3)2] or its
metal adducts [formed in situ by adding M(ClO4)2ؒ6H2O
(2 equivalents)] were not soluble in the solvents such as toluene,
ethanol, acetic acid and dioxane that had been previously used
for Ir-catalysed oxidations of styrene, we chose methylethyl
ketone (MEK) as the solvent for its ability to keep all of the
metal species used in this work in solution and because it is
readily oxidised in air to the peroxide (MEKP), which is a
reason for the extensive use of this solvent in radical-initiated
polymerisations.64 Reagents, reaction conditions and our results
are summarised in Table 3. Despite the previous claims of
solvent independence in Ir-catalysed styrene oxidations,60–63
it is clear that this is not so65 and that MEK is a solvent par
excellence for this reaction and, moreover, that in MEK the
metal complexes are inhibitors of the reaction. Perhaps most
astonishing is the dependence of the inhibition on the metal
ion added to trans-[IrCl(CO)(L3)2]. Since MEKP will form at
4. The meta-benzyl “linker” (in L3 and L4) is sufficiently
rigid to prevent the Nn- and P-domains from binding to the
same metal ion. This control over co-ordination is not
matched in those previous Nn,P-ligands with flexible alkyl
“linkers”.14–16,18,19,20,23
5. Mononuclear complexes in which the phosphine group is
selectively bound to a soft metal leaving the Nn-donor domain
dangling and metal-free are directly available by addition of
a meta-substituted ligand such as L3 or L4 to a source of a
softer metal ion. For the ortho-substituted ligands, L1 and L2,
protonation (pH control) protects the Nn-donor domain, pre-
venting κNn,κP-chelate monomers from forming, and thereby
enables the selective binding of the phosphine group to soft
metals. The physical characteristics of these mononuclear com-
plexes reflect those of their dangling N3-donor domains: those
2430
J. Chem. Soc., Dalton Trans., 2002, 2423–2436

View Article Online
with the unprotonated N3-donor domains tend to be oils and
protonation may lead to more tractable compounds.
EE008) but filled with the same electrolyte solution as used in
the experiment [rather than saturated AgCl in 3 M KCl(aq)
solution], a freshly polished platinum disk (1 mm diameter)
working electrode and a platinum wire as the auxiliary elec-
trode. Solutions of the compounds were 1.0 mM in anhydrous
acetonitrile (Aldrich, used as received) with 0.1 M [NBun4][PF6].
Solutions were de-oxygenated by bubbling with high purity
nitrogen (pre-saturated with solvent) and then blanketed with a
cover of nitrogen for the duration of the experiment. Data are
reported from cyclic voltammograms recorded at a scan rate of
100 mV sϪ1. The electrochemical potentials quoted are relative
to the ferrocene–ferrocenium (Fcϩ–Fc) couple measured under
the same experimental conditions (same concentrations, sol-
vent, support electrolyte, electrodes, temperature and scan rate).
Controlled-potential electrolysis (coulometry) of [Cu(L1)][PF6]
was carried out in a conventional three-compartment “H”-cell
adapted so that it could be loaded and sealed under an inert
atmosphere (high purity nitrogen). An acetonitrile-filled Ag/
AgCl quasi-reference electrode (the same as used in CV experi-
ments) was placed in the working compartment along with the
Pt gauze (5 × 2 cm2) working electrode. The counter electrode
was a Pt gauze (4 × 2 cm2) and was separated from working
compartment by two fine-porosity glass frits. During the elec-
trolysis the potential of the working electrode was fixed at
ϩ0.60 V and the solution in the working compartment was
6. Addition of hard metal ions to the mononuclear com-
plexes with dangling, metal-free N3-donor domains (when these
are protonated, with a weakly co-ordinating Brønsted base also
added) affords the targeted hard-soft heteronuclear complexes.
The heteronuclear complexes of the meta-substituted ligands,
L3 and L4, were more stable than those of their analogues from
the ortho-substituted ligands, L1 and L2, perhaps because
decomposition pathways leading to κNn,κP-chelate mono-
mers are unavailable to the former heteronuclear complexes.
The protection/deprotection of the Nn-donor domain by
protonation/deprotonation under pH control route appears
well suited to the combinatorial syntheses of libraries of
heteronuclear complexes.
7. The available evidence for the heteronuclear complexes of
meta-substituted L3 and L4 suggests that the hard and soft
metal centres retain their individual reactivities and only weakly
perturb each other’s spectroscopic properties. That is not to say
co-operative behaviour will not lead to new reactivitity beyond
that for the individual metal centres: for example, the results for
styrene oxidation, particularly those with [IrCl(CO)(PPh3)2]
added compared to [IrCl(CO)(L3)2] ϩ 2Zn2ϩ added, are
intriguing in this regard. However, it remains to be definitely
demonstrated that co-operativity between the metal centres in
these or similar heteronuclear systems can result in new and
advantageous reactivity for the complex as whole.
stirred magnetically with
a Teflon-coated stirring bar.
Anhydrous acetonitrile (Aldrich) was used as the solvent, and
the concentration of [Cu(L1)][PF6] was 2.0 mM and the support
electrolyte was 0.2 M [NBun ][PF6].
4
Experimental
Gas chromatographic analyses employed a Shimadzu GC-
17A gas chromatograph equipped with a hydrogen flame
ionisation detector interfaced to a Macintosh computer. The
column used was an Alltech Econocap carbowax column,
#19654, 30 m × 0.32 mm ID, FSOT, 0.25 micron. The carrier
gas was nitrogen. The gas chromatograph settings used are
given below.
Physical measurements
Elemental analyses for C, H and N were determined by the
Australian National University Microanalytical Unit. Elem-
ental ratios for Cu, Fe and S are calculated from inductively-
coupled plasma-atomic emission spectroanalysis (ICP–AES )
data. Samples for ICP–AES were prepared by digestion of the
complex with 10% nitric acid overnight; the individual concen-
trations of P, Cu and/or Pt, in the samples were then simul-
taneously determined (to 10%) using a GBC Integra ICP-AES
instrument fitted with a 22-channel polychromator. Electro-
spray mass spectra (ES-MS) were acquired on a VG Quattro
mass spectrometer with a capillary voltage of 4 kV and a cone
voltage of 30 V. The solvent system was 50 : 50 acetonitrile–
water with 1% acetic acid. MALDI-MS spectra were obtained
at the Biomedical Mass Spectroscopy Centre, UNSW, using a
Voyager DE-STR MALDI-time-of-flight mass spectrometer
and samples in an α-cyano-4-hydroxycinnamic acid matrix. 1H
and 31P NMR spectra were recorded on a Bruker AC 300F (300
MHz) or Bruker DPX (300 MHz) spectrometer. Molar con-
ductivity measurements were made on ≈1 mM solutions of the
complexes in MeCN or CH2Cl2 at 25 ЊC. The molar conductiv-
ity of the 1 : 1 electrolyte tetra-n-butylammonium hexafluoro-
phosphate was determined to be 157 S cm2 molϪ1 in MeCN and
28 S cm2 molϪ1 in CH2Cl2 under these conditions. Electronic
spectra of complexes were recorded between 200 and 1400 nm
on a CARY 5 spectrometer in the dual beam mode (1 nm reso-
lution); solution spectra were recorded in sealed 1 cm quartz
cuvettes. EPR spectra of frozen solutions (at 77 K; liquid
nitrogen dewar) were recorded using a Bruker EMX 10 EPR
spectrometer (ν ≈ 9.52 GHz). Infrared spectra were recorded
in the quoted solvents in a solution cell with CaF2 windows
using a Mattson Genesis FTIR spectrometer ( 1.0 cmϪ1
resolution).
Syntheses
Reactions were routinely carried out under an atmosphere of
dry nitrogen using standard Schlenk and cannula techniques.
Dry solvents were obtained by routine distillations from the
appropriate drying agent under nitrogen immediately prior to
use: methanol and ethanol from magnesium turnings activated
with iodine; thf, diethyl ether and toluene from sodium benzo-
phenone ketyl; MeCN, CH2Cl2 and 1,2-dichloroethane from
CaH2; chloroform from P2O5; triethylamine from BaO; and
dimethylformamide under reduced pressure from CaH2.
Styrene was purified before use by passage through a neutral
alumina (Brockmann I) column (eluent: dichloromethane) and
the solvent removed under vacuum. Flash chromatography was
carried out using Merck silica gel 7730 60GF254. Columns were
packed with dry gel; solvent was applied to the column before a
concentrated solution of the sample in the appropriate solvent.
Table 1 of the ESI† presents ES-MS, NMR and IR data for the
monomeric (diamagnetic) complexes. Partial elemental analy-
ses, elemental ratios from ICP-AES, and EPR and electronic
spectral data for the heteronuclear (paramagnetic) complexes
are given in Table 2 of the ESI.†
The following substances were prepared according to
methods in the literature: 2-(diphenylphosphino)benzalde-
hyde,31 N,N-bis(2-pyridyl-2-ethyl)amine (bpea),66 1,4-diisopro-
pyl-1,4,7-triazacyclononane
(tacn*),67
bis(benzonitrile)-
platinum() dichloride,68 cis-dicarbonylchloro(p-toluidine)-
iridium(),69 pentacarbonyl(phenyl-2-carbaldehyde diphenyl-
phosphine-κP)tungsten48 and tetrakis(acetonitrile)copper()
hexafluorophosphate.70
Electrochemical measurements were recorded using a Pine
Instrument Co. AFCBP1 Bipotentiostat interfaced to and con-
trolled by a Pentium computer. For cyclic voltammetry meas-
urements, a standard three electrode configuration was used
with a quasi-reference electrode comprised of a commercial
Ag–AgCl mini-reference electrode (Cyprus Systems, Inc.
Warning: Although no problems were encountered in this
work, perchlorate salts of metal complexes are potentially
explosive and should be treated with due care.
J. Chem. Soc., Dalton Trans., 2002, 2423–2436
2431

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[2-(Diphenylphosphino)benzyl]-N,N-bis(2-pyridyl-2-ethyl)-
amine, L1. A solution of bpea (1.49 g, 6.56 mmol) and
2-diphenylphosphinobenzaldehyde (1.92 g, 6.56 mmol) in
1,2-dichloroethane (40 cm3) was treated with solid sodium
triacetoxyborohydride (2.21 g, 10.4 mmol). The mixture
was stirred under nitrogen at room temperature for 18 h
and then neutralised with a saturated aqueous solution of
sodium hydrogen carbonate (20 cm3). The organic phase was
separated and the aqueous phase extracted with dichloro-
methane (2 × 20 cm3). The combined organic extracts were
dried with magnesium sulfate and concentrated to give crude
L1 as a thick orange oil (2.86 g), δP[(CD3)2CO] Ϫ14.23;
δH[(CD3)2CO] 8.42 (2 H, d), 7.70–7.00 (18 H, m), 6.87 (2 H,
t), 3.93 (2 H, d), 2.90–2.70 (8 H, m); m/z (ES-MS) 502
([HL1]ϩ).
(4 H, s), 2.90 (8 H, s), 1.13 (12 H, d); m/z (ES-MS) 488
{[HL2]ϩ}.
Protonation of L2: [HL2][PF6]. A solution of L2 (0.60 g, 1.2
mmol) in methanol (15 cm3) was treated with a solution of
ammonium hexafluorophosphate (2.0 g, 12 mmol) in methanol
(10 cm3). The solution was stirred at room temperature for 1 h
and the white precipitate collected by filtration. Further prod-
uct was obtained by concentration of the filtrate. The product
was recrystallised from MeCN–diethyl ether to give a white
powder (0.55 g, 72%), (Found: C, 57.91; H, 6.47; N, 6.60.
C31H43F6N3P2ؒ0.5H2O requires C, 57.94; H, 6.90; N, 6.54%);
δP(CDCl3) Ϫ14.22 (s), Ϫ143.78 [sept, J(PF) 707 Hz]; δH(CDCl3)
7.37–7.32 (8 H, m), 7.24–7.17 (5 H, m); 6.90–6.85 (1 H, m), 3.97
(2 H, d), 3.11 (2 H, sept), 3.00–2.93 (4 H, m), 2.79 (8 H, br s),
1.21 (6 H, d), 1.14 (6 H, d); m/z (ES-MS) 488 {[HL2]ϩ}.
Protonation of L1: [HL1][PF6]. A solution of crude L1 (0.83 g,
1.7 mmol) was dissolved in methanol (10 cm3) and treated
with an excess of ammonium hexafluorophosphate (4.2 g) in
methanol (20 cm3). The solution was stirred at room temper-
ature for 5 h and the volume reduced to 25 cm3 whereupon
scratching of the flask resulted in immediate precipitation. The
solution was cooled in a Ϫ15 ЊC freezer for 2 h to complete
precipitation followed by filtration of the yellow powder
(0.94 g, 87%). An analytically pure sample was obtained by
recrystallisation from dichloromethane–diethyl ether, (Found:
C, 59.58; H, 5.12; N, 6.36. C33H33F6N3P2ؒH2O requires C, 59.55;
H, 5.30; N, 6.31%); δP[(CD3)2CO] Ϫ15.38 (s), Ϫ142.02 [sept,
J(PF) 708 Hz]; δP(CDCl3) Ϫ16.46 (s), Ϫ143.42 [sept, J(PF)
713 Hz]; δH[(CD3)2CO] 8.22 (2 H, d), 7.90–7.10 (19 H, m), 7.07
(1 H, t), 4.97 (2 H, s), 3.98 (4 H, t), 3.47 (4 H, t); δH(CDCl3) 8.04
(2 H, d), 7.70–7.60 (3 H, m), 7.50–7.30 (8 H, m), 7.20 (2 H, d),
7.10 (6 H, m), 6.99 (1 H, m), 4.63 (2 H, s), 3.80 (4 H, t), 3.28
(4 H, t); m/z (ES-MS) 502 {[HL1]ϩ}.
Preparation of 3-(diphenylphosphino)benzaldehyde. (a) 2-(3-
Bromophenyl)-1,3-dioxolane.
A solution of 3-bromobenz-
aldehyde (25.1 g, 0.136 mol), ethylene glycol (11.5 cm3, 0.206
mol) and p-toluenesulfonic acid (0.14 g, 0.74 mmol) in toluene
(150 cm3) was heated at reflux for 45 h with the water produced
by the reaction collected through the use of a Dean–Stark con-
denser. The solution was cooled and washed with a saturated
aqueous solution of sodium hydrogen carbonate (50 cm3) and
then a saturated aqueous solution of sodium chloride (50 cm3).
The combined organic layers were dried with potassium
carbonate, concentrated and distilled at 94–99 ЊC at 0.4 mmHg
to give a yellow oil (25.1 g, 80%), δH(CDCl3) 7.65 (1 H, s), 7.49
(1 H, d), 7.39 (1 H, d), 7.24 (1 H, t), 5.77 (1 H, s), 4.04 (4 H, m).
(b) [3-(1,3-Dioxolan-2-yl)phenyl]diphenylphosphine. A mix-
ture of magnesium turnings (2.8 g, 0.12 mol) in thf (160 cm3)
was prepared in a 250 cm3 flask equipped with a condenser and
a dropping funnel under nitrogen. A crystal of iodine was
added and the mixture was then slowly treated with a solution
of 2-(3-bromophenyl)-1,3-dioxolane (25.0 g, 0.11 mol) in thf
(30 cm3) via the dropping funnel. The grey mixture was heated
at reflux for 0.5 h and then cooled to room temperature (little
magnesium remained). The mixture was then cooled in an ice
bath and treated with a solution of chlorodiphenylphosphine
(19.1 cm3, 0.11 mmol) in thf (40 cm3) via the dropping funnel
over about 2 h with the temperature maintained below 5 ЊC.
The solution was warmed to room temperature, heated at 40 ЊC
for 3 h and then stirred under nitrogen for a further 11 h.
The solution was then cooled to Ϫ10 ЊC and treated with a
40% aqueous solution of ammonium chloride. The organic
layer was separated and the aqueous phase washed with diethyl
ether (100 cm3). The combined organic layers were dried with
sodium sulfate and the solvent removed in vacuo to give a thick
yellow oil (22.1 g, 61%), δP(CDCl3) Ϫ4.44 (s); δH(CDCl3)
7.90–7.40 (4 H, m), 7.40–7.00 (10 H, m), 5.75 (1 H, s), 4.04
(4 H, m).
Protonation of L1 with perchloric acid. A solution of L1
(1.31 g, 2.61 mmol) in methanol (40 cm3) was treated with per-
chloric acid (70%, 12 cm3). The solution was stirred at room
temperature for 2 h and then diluted with water (5 cm3) until
just cloudy. The solution was then cooled in a Ϫ15 ЊC freezer
overnight and the white precipitate was collected by filtration,
washed with diethyl ether and dried under vacuum (1.48 g),
δP[(CD3)2CO] Ϫ16.87 (s); δH[(CD3)2CO] 9.00 (2 H, d), 8.73 (2 H,
t), 8.18 (4 H, m), 7.92 (1 H, t), 7.70–7.50 (2 H, m), 7.39 (6 H, m),
7.27 (4 H, m), 7.16 (1 H, m), 5.18 (2 H, s), 4.21–4.09 (8 H, m);
m/z (ES-MS) 502 {[HL1]ϩ}. Subsequent reactions (see below)
are consistent with the solid being [HnL1](ClO4)n with n ≈ 3.
Recrystallisation of a small sample of [HnL1](ClO4)n from
methanol in air over a period of days gave colourless crystals of
a phosphine oxide derivative, [H3L1O](ClO4)3ؒ3H2O, (Found: C,
45.60; H, 3.95; N, 4.84. C33H35Cl3N3O13Pؒ3H2O requires C,
45.40; H, 4.73; N, 4.81%); δP[(CD3)2CO] 40.74 (s); δH[(CD3)2-
CO] 9.00 (2 H, d), 8.68 (2 H, t), 8.21 (2 H, d), 8.13 (2 H, t), 8.04
(1 H, m), 7.87 (1 H, t), 7.78–67 (11 H, m), 7.32 (1 H, m), 4.82
(2 H, s), 4.11 (4 H, m), 3.92 (4 H, m); m/z (ES-MS) 518
{[HL1O]ϩ}.
(c) 3-(Diphenylphosphino)benzaldehyde.
A solution of
[3-(1,3-dioxolan-2-yl)phenyl]-diphenylphosphine (11.06 g, 33.1
mmol) and p-toluenesulfonic acid (0.5 g, 2.6 mmol) in toluene
(250 cm3) was heated at reflux for 16 h. The hot solution was
diluted with water (50 cm3) and allowed to cool. The organic
layer was separated and the aqueous phase extracted with ben-
zene (2 × 50 cm3). The combined organic layers were dried
with sodium sulfate and the solvent removed in vacuo to give a
thick yellow oil (10.11 g), δP 31.99 (0.22), 31.64 (0.13), 29.90
(0.10), 28.76 (0.23), Ϫ4.36 (0.28), Ϫ4.47 (0.23), Ϫ4.79 (1.00).
The oil was judged to be about 45% pure by 31P NMR and
was used “as is” in subsequent reactions. However, further
purification of 2.00 g of the crude oil was achieved by flash
chromatography [eluent: 60–80 ЊC petroleum ether–ethyl
acetate (2 : 1)] to afford the product, a pale yellow oil (0.74 g),
δP(CDCl3) Ϫ4.80; δH(CDCl3) 9.94 (1 H, s), 7.85 (1 H, d), 7.80
(1 H, d), 7.49 (2 H, m), 7.35 (10 H, m); m/z (ES-MS) 292
{[H(3-Ph2PC6H4CHO)]ϩ}.
1-[2-(Diphenylphosphino)benzyl]-4,7-diisopropyl-1,4,7-tri-
azacyclononane, L2. Solid sodium triacetoxyborohydride
(4.61 g, 21.8 mmol) was added to a stirred solution of tacn*
(2.90 g, 13.6 mmol) and 2-diphenylphosphinobenzaldehyde
(3.95 g, 13.6 mmol) in 1,2-dichloroethane (60 cm3). The mixture
was stirred under nitrogen for 24 h, and then neutralised with a
saturated aqueous solution of sodium hydrogen carbonate
(20 cm3). The organic phase was separated and the aqueous
phase further extracted with dichloromethane (2 × 40 cm3). The
combined organic extracts were dried with magnesium sulfate
and the solvent removed to yield crude L2 as a thick orange oil
(5.32 g), δP(CDCl3) Ϫ14.66 (s); δH(CDCl3) 7.48 (1 H, m), 7.35–
7.19 (8 H, m), 6.88 (1 H, m), 3.94 (2 H, d), 3.09 (2 H, t), 3.00
2432
J. Chem. Soc., Dalton Trans., 2002, 2423–2436

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[3-(Diphenylphosphino)benzyl]-N,N-bis(2-pyridyl-2-ethyl)-
amine, L3. A solution of bpea (1.66 g, 7.27 mmol) and crude
3-diphenylphosphinobenzaldehyde (2.32 g, 8.00 mmol) in
1,2-dichloroethane (30 cm3) was treated with solid sodium
triacetoxyborohydride (2.47 g, 11.6 mmol). The mixture was
stirred under nitrogen at room temperature for 19 h and then
neutralised with a saturated aqueous solution of sodium
hydrogen carbonate (20 cm3). The organic phase was separ-
ated and the aqueous phase extracted with dichloromethane
(2 × 20 cm3). The combined organic extracts were dried with
magnesium sulfate and concentrated to give crude L3 as a thick
orange oil. The crude oil was further purified by flash chrom-
atography (eluent: ethyl acetate) giving L3 as an orange oil
(1.14 g, 31%), δP(CDCl3) Ϫ4.50; δH(CDCl3) 8.46 (2 H, d), 7.48
(2 H, t), 7.30–7.00 (16 H, m), 6.97 (2 H, d), 3.67 (2 H, s), 2.88
(8 H, s); m/z (ES-MS) 502 {[HL1]ϩ}.
allowed to slowly evaporate overnight (to 1 cm3) yielding yellow
microcrystals which were collected by filtration (0.046 g, 49%),
(Found: C, 55.25; H, 4.89; N, 5.80. C33H32CuF6N3P2ؒ0.5H2O
requires C, 55.16; H, 4.56; N, 5.85%). A small portion of the
sample was recrystallised from MeCN–diethyl ether to yield
colourless crystals suitable for X-ray analysis.
[Cu(L2)][PF6]. A solution of [HL2][PF6] (0.287 g, 0.454
mmol) and [Cu(CH3CN)4][PF6] (0.169 g, 0.454 mmol) in
dichloromethane (20 cm3) were stirred under nitrogen for 16 h.
The light yellow solution was concentrated to 10 cm3 and pre-
cipitated with diethyl ether to give a white powder (0.270 g,
86%), (Found: C, 52.62; H, 6.41; N, 6.10. C31H42CuF6N3P2ؒ
0.5H2O requires C, 52.80; H, 6.15; N, 5.96%). A small portion
of the sample was recrystallised from MeCN–diethyl ether to
yield colourless crystals suitable for X-ray analysis.24
1-[3-(Diphenylphosphino)benzyl]-4,7-diisopropyl-1,4,7-triaza-
cyclononane, L4. Solid sodium triacetoxyborohydride (3.00 g,
14.1 mmol) was added to a stirred solution of tacn* (2.16 g,
10.1 mmol) and crude 3-diphenylphosphinobenzaldehyde
(2.94 g, 10.1 mmol) in 1,2-dichloroethane (50 cm3). The mixture
was stirred under nitrogen for 17 h, and then neutralised with
a saturated aqueous solution of sodium hydrogen carbonate
(40 cm3). The organic phase was separated and the aqueous
phase further extracted with dichloromethane (6 × 20 cm3). The
combined organic extracts were dried with magnesium sulfate
and the solvent removed to yield crude L4 as a thick brown–red
oil (4.70 g), δP(CDCl3) Ϫ32.11 (0.19), Ϫ28.98 (0.12), Ϫ4.44
(0.33), Ϫ4.47 (0.33), Ϫ4.87 (1.00); δH(CDCl3) 7.90–7.30 (4 H,
m), 7.30–7.10 (9 H, m), 7.14 (1 H, t), 3.73 (2 H, s), 3.20–2.70
(14 H, m), 1.07 (12 H, t); m/z (ES-MS) 488 {[HL4]ϩ}.
[ZnCl(L2)][PF6]. Solid zinc dichloride was added to a stirred
solution of crude L2 (0.155 g, 0.318 mmol) in ethanol (25 cm3).
The solution was warmed gently to get all of the reactants
into solution following which solid ammonium hexafluoro-
phosphate (0.207 g, 1.27 mmol) was added and the solution
allowed to stir at room temperature for 3 h. The solution was
cooled in a Ϫ15 ЊC freezer and the off white precipitate that
formed collected by filtration (0.163 g, 70%), (Found: C, 49.86;
H, 6.32; N, 5.78. C31H42ClF6N3P2ZnؒH2O requires C, 49.54; H,
5.90; N, 5.59%).
[PtCl(L1)][PF6]. A solution of [PtCl2(PhCN)2] (0.095 g, 0.20
mmol) in 1,2-dichloroethane (10 cm3) was treated dropwise
with a solution of [HL1][PF6] (0.130 g, 0.20 mmol) and triethyl-
amine (0.020 g, 0.20 mmol) in 1,2-dichloroethane (10 cm3). The
solution was heated at reflux for 3 h, then cooled and a yellow
powder precipitated by the addition of diethyl ether. The
powder was recrystallised from MeCN–diethyl ether to give
yellow microcrystals, (0.076 g, 43%), (Found: C, 45.38; H, 3.41
N; 4.68. C33H32ClF6N3PPt requires C, 45.19; H, 3.68; N,
4.79%). A second recrystallisation of a small portion of the
sample from MeCN–diethyl ether yielded colourless crystals
suitable for X-ray analysis.
Protonation of L4: [HL4][PF6]. A solution of ammonium
hexafluorophosphate (1.8 g, 11 mmol) in methanol (10 cm3) was
added to a stirred solution of L4 (0.50 g, 1.0 mmol) in methanol
(10 cm3). After stirring for 2 h at room temperature, water
(2 cm3) was added and the solution cooled in a Ϫ15 ЊC freezer
overnight. The orange solid was collected by filtration and
washed with a small amount of diethyl ether, (0.40 g),
δP(CDCl3) Ϫ4.86 (s), Ϫ143.59 [sept, J(PF) 712 Hz]; δH(CDCl3)
7.50–7.20 (13 H, m), 7.16 (1 H, t), 3.74 (2 H, s), 3.10–2.80 (6 H,
m), 2.80–2.60 (6 H, m), 1.08 (12 H, t); m/z (ES-MS) 488
{[HL4]ϩ}. Subsequent reactions (see below) are consistent with
the solid being [HL4][PF6].
[PtCl(L2)][PF6]. A solution of [PtCl2(PhCN)2] (0.048 g,
0.10 mmol) in 1,2-dichloroethane (5 cm3) was treated with a
solution of [HL2][PF6] (0.064 g, 0.10 mmol) in 1,2-dichloro-
ethane (5 cm3) and triethylamine (0.014 cm3, 0.10 mmol). The
solution was heated at reflux for 2 h. The solvent was removed
under vacuum and redissolved in dichloromethane. Layering of
the solution with n-pentane gave a sticky yellow solid (0.110 g).
Benzyl{N,N-bis(2-pyridyl-2-ethyl)amine} (Bzbpea). The syn-
thesis of this ligand has previously been reported by Karlin et
al.71 In this work, an alternative synthetic method was adopted.
A solution of bpea (0.121 g, 0.533 mmol), benzaldehyde (0.057
g, 0.53 mmol) and glacial acetic acid (0.048 g, 0.80 mmol) in
1,2-dichloroethane (10 cm3) was treated with solid sodium
triacetoxyborohydride (0.181 g, 0.850 mmol). The mixture was
stirred at room temperature for 19 h and then neutralised with a
saturated aqueous solution of sodium hydrogen carbonate (10
cm3). The organic phase was separated and the aqueous phase
extracted with dichloromethane (2 × 20 cm3). The combined
organic extracts were dried with magnesium sulfate and concen-
trated to give a thick orange oil (0.145 g, 86%), δH(CDCl3) 8.46
(2 H, d), 7.51 (2 H, t), 7.40–6.90 (9 H, m), 3.70 (2 H, s), 2.93
(8 H, s); m/z (ES-MS) 318 {[HL5]ϩ}. Lit.:71 δH(CDCl3) 8.35
(2 H, br d), 7.40–6.70 (11 H, br m), 3.60 (2 H, br s), 2.85 (8 H,
br s).
trans-[PtCl2(H3L1)2][ClO4]6.
A
solution of [HnL1][ClO4]n
(0.706 g, 0.880 mmol if n = 3) in MeCN (20 cm3) was treated
with a solution of [PtCl2(PhCN)2] (0.238 g, 0.503 mmol) in
MeCN (40 cm3) and stirred at room temperature for 4.5 h. The
solvent was removed in vacuo and the crude oil dissolved in a
solution of MeCN (5 cm3), methanol (30 cm3) and diethyl ether
(5 cm3) which was cooled in a Ϫ15 ЊC freezer overnight to give
[PtCl2(H3L1)2][ClO4]6 as a yellow microcrystalline solid (0.800 g,
85% based on Pt). An analytically pure sample was obtained by
recrystallisation from acetone–dichloromethane, (Found: C,
42.21; H, 3.89; N, 4.19. C66H70Cl8N6O24P2Ptؒ4H2O requires C,
42.12; H, 4.18; N, 4.47%).
trans-[PtCl2(HL2)2][PF6]2. A solution of [PtCl2(PhCN)2]
(0.30 g, 0.63 mmol) in dichloromethane (25 cm3) was added to a
solution of [HL2][PF6] (0.80 g, 1.3 mmol) in dichloromethane
(25 cm3). The solution was stirred at room temperature for 3 h,
concentrated to 25 cm3, layered with diethyl ether (10 cm3) and
allowed to stand in a Ϫ15 ЊC freezer overnight. The yellow
microcrystalline solid was collected by filtration and washed
with diethyl ether, (0.84 g, 87%), (Found: C, 48.07; H, 5.33; N,
[Cu(L1)][PF6]. A solution of [HL1][PF6] (0.086 g, 0.13 mmol)
in dichloromethane (5 cm3) was added to a solution of [Cu-
(MeCN)4][PF6] (0.050 g, 0.13 mmol) in dichloromethane
(5 cm3). The solution immediately turned cloudy and stirring
was continued for 4 h. The solvent was removed and the crude
yellow–green powder was dissolved in MeCN (5 cm3) which was
J. Chem. Soc., Dalton Trans., 2002, 2423–2436
2433

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5.13. C62H86Cl2F12N6P4PtؒH2O requires C, 48.06; H, 5.72; N,
5.42%).
by flash chromatography (eluent: ethyl acetate) to give an
orange oil (0.213 g, 37%); m/z (MALDI-MS) for C38H32N3O5-
PW (MHϩ), calc. 826.50, found 826.99.
cis-[PtCl2(L3)2]. A solution of L3 (0.270 g, 0.539 mmol)
in dichloromethane (20 cm3) was treated with a solution of
[PtCl2(PhCN)2] (0.121 g, 0.257 mmol) in dichloromethane
(10 cm3) and stirred at room temperature overnight by which
time the trans-isomer [δP(dichloromethane) 21.61 {s, J(PPt)
2632 Hz}] had all been converted to the cis-isomer as evidenced
by 31P{1H} NMR. Addition of diethyl ether to the cooled solu-
tion gave a sticky yellow powder which was washed with diethyl
ether and dried under vacuum (0.182 g, 56%).
[CuCl2(Bzbpea)]. A solution of Bzbpea (0.027 g, 0.085 mmol)
in methanol (5 cm3) was treated with a solution of CuCl2ؒ2H2O
in methanol (2 cm3) and the dark green solution was stirred for
2 h. Addition of diethyl ether (15 cm3) and cooling in a Ϫ15 ЊC
freezer overnight resulted in the formation of blue–green
needles which were collected by filtration, washed with diethyl
ether and dried under vacuum (0.023 g, 60%), (Found: C, 53.27;
H, 5.56; N, 8.45. C21H23Cl2CuN3ؒH2O requires C, 53.68; H,
5.36; N, 8.94%); λmax/nm (ε/MϪ1 cmϪ1) (chloroform) 778 (68),
987 (52); EPR (chloroform, 77 K): g|| 2.22 (A|| 127 G), g⊥ 2.12;
m/z (ES-MS) 439 {[Cu(OAc)(Bzbpea)]2ϩ} (Note: the acetate
anion observed in the ES mass spectrum is due to exchange
between the chloride ligand of the complex and acetic acid in
the feed solvent used).
trans-[PtCl2(HL4)2][PF6]2. A solution of [PtCl2(PhCN)2]
(0.049 g, 0.10 mmol) in dichloromethane (5 cm3) was added to a
solution of [HL4][PF6] (0.130 g, 0.21 mmol) in dichloromethane
(10 cm3). The solution was stirred at room temperature for 2 h
and the solvent removed under vacuum. The resultant orange
oil was washed with n-pentane and then dried in vacuo to give a
sticky yellow solid (0.130 g). Although clearly contaminated by
excess benzonitrile (≈20%), no additional resonances were
observed in the 31P{1H} NMR spectrum and the product was of
sufficient purity for further reactions.
[PtCl2{(L1)Cu(OAc)}2][ClO4]2. A solution of trans-[PtCl2-
(H3L1)2](ClO4)6 (0.0528 g, 0.028 mmol) in MeCN (10 cm3) was
treated with triethylamine (0.017 g, 0.17 mmol) and then stirred
at room temperature for 40 min by which time a cloudy precipi-
tate had formed. The mixture was then diluted with MeCN
(5 cm3) and ethanol (5 cm3). The cloudy solution was then
treated with a solution of [Cu2(OAc)4(H2O)2] (0.0112 g, 0.028
mmol) in MeCN (5 cm3). After 6 h stirring at room temperature
the solution remained slightly cloudy and stirring was therefore
continued overnight resulting in a clear, light green solution.
The solution was then concentrated to 8 cm3 and diluted with
diethyl ether (2 cm3) until just cloudy. This cloudy solution was
then warmed gently to give a clear, green solution which upon
standing in a Ϫ15 ЊC freezer overnight resulted in light green
microcrystals which were collected by filtration, (0.030 g, 62%).
trans-[IrCl(CO)(L3)2]. A solution of cis-[IrCl(CO)2(p-tolu-
idine)] (0.187 g, 0.506 mmol) in deoxygenated thf (10 cm3) was
added to a stirred solution of L3 (0.533 g, 1.06 mmol) in
deoxygenated thf (10 cm3). The red–brown solution was stirred
under nitrogen for 2 h whereupon its IR spectrum revealed the
complete disappearance of carbonyl peaks for the starting
complex: νCO/cmϪ1 1967s, 1928s (thf ); δP(thf ) 25.19 (0.01, s),
21.78 (1.00, br), 4.86 (0.01, s). The solvent was removed
in vacuo. In order to remove the p-toluidine (bp 200 ЊC at
760 mmHg), the oil was redissolved in thf (10 cm3) and the
solvent again removed under high vacuum (0.01 mmHg) to give
a thick orange oil (0.626 g, 98%), which contained only a trace
amount of p-toluidine (≈ 0.2%) as judged by the 1H NMR
spectrum; m/z (MALDI-MS) for C67H65ClIrN6OP2 (MH)ϩ,
calc. 1259.89, found 1259.86; for C67H64IrN6OP2 (M–Cl)ϩ, calc.
1223.43, found 1223.32.
[PtCl2{(L2)Cu(OAc)}2][PF6]2. A solution of [Cu2(OAc)4-
(H2O)2] (0.095 g, 0.24 mmol) in MeCN (20 cm3) was added to a
stirred solution of trans-[PtCl2(HL2)2][PF6]2 (0.37 g, 0.24 mmol)
and triethylamine (0.066 cm3, 0.48 mmol) in MeCN (20 cm3).
The green solution was allowed to stir at room temperature for
24 h and a green powder was precipitated by the addition of
diethyl ether. The powder was recrystallised from MeCN–
diethyl ether to give a light green powder, (0.24 g, 56%); m/z
(ES-MS) 743 {[PtCl2{(L2)Cu(OAc)}2]2ϩ}.
Pentacarbonyl(phenyl-3-carbaldehyde
diphenylphosphine-
ꢀP)tungsten. A solution of tungsten hexacarbonyl (1.99 g,
5.67 mmol) in thf (160 cm3) was stirred at room temperature in
a flask fitted with a quartz cased mercury UV lamp. The solu-
tion was photolysed for 2 h whilst being bubbled with nitrogen.
This solution was then added via a cannula to a solution of
crude 3-diphenylphosphinobenzaldehyde (1.83 g) in thf (50
cm3) and the yellow solution stirred under nitrogen overnight.
The solvent was removed under vacuum and the resultant yel-
low oil purified twice by flash chromatography [eluent: 60–80 ЊC
petroleum ether–dichloromethane (3 : 7) then 60–80 ЊC petrol-
eum ether–dichloromethane (6 : 4)] to give a thick orange oil
(1.07 g, 31% based on W), νCO/cmϪ1 2072m, 1984w, 1941vs
(chloroform); δP(CDCl3) 22.16 [s, J(PW) 246 Hz]; δH(CDCl3)
9.98 (1 H, s), 7.94 (2 H, m), 7.72 (1 H, m), 7.63 (1 H, m), 7.47
(10 H, m); m/z (EI-MS) 614 (Mϩ), 586 (M Ϫ CO), 558
(M Ϫ 2CO), 530 (M Ϫ 3CO), 502 (M Ϫ 4CO), 474 (M Ϫ 5CO).
[PtCl2{(L3)CuCl2}2]. A warm solution of cis-[PtCl2(L3)2]
(0.048 g, 0.038 mmol) in thf (30 cm3) was treated with a solu-
tion of CuCl2ؒ2H2O (0.012 g, 0.072 mmol) in thf (4 cm3). This
resulted in the immediate formation of a precipitate and stir-
ring was continued for a further 1 h. The light green precipitate
was collected by filtration and washed with diethyl ether (0.043
g, 78% based on Cu).
[PtCl2{(L4)Cu(OAc)}2][PF6]2. A solution of trans-[PtCl2-
(HL4)2][PF6]2 (0.130 g, 0.085 mmol) in MeCN (10 cm3) was
treated with triethylamine (0.024 cm3, 0.09 mmol) and a solu-
tion of [Cu2(OAc)4(H2O)2] (0.034 g, 0.085 mmol) in MeCN (20
cm3). The solution was stirred at room temperature for 1.5 h
and the solvent was removed in vacuo. The remaining green oil
was dissolved in dichloromethane (5 cm3). The solution was
layered with diethyl ether and allowed to stand resulting in the
formation of a brown–green precipitate which was collected by
filtration (0.083 g, 55%). An analytically pure sample was
obtained by slow evaporation of a methanol–ethanol solution.
[W0(CO)5(L3)]. Solid sodium triacetoxyborohydride (0.238 g,
1.12 mmol) was added to a stirred solution of bpea (0.159 g,
0.700mmol)andpentacarbonyl(phenyl-3-carbaldehydediphenyl-
phosphine-κP)tungsten (0.430 g, 0.700 mmol) in 1,2-dichloro-
ethane (15 cm3). The mixture was stirred under nitrogen for
22 h and then neutralised with a saturated aqueous solution of
sodium hydrogen carbonate (10 cm3). The organic phase was
separated and the aqueous phase extracted with dichloro-
methane (3 × 10 cm3). The combined organic extracts were
dried with magnesium sulfate, filtered and the solvent removed
in vacuo to give an orange oil. The crude product was purified
mer-[IrCl3(CO){(L3)CuCl2}2]. A solution of CuCl2ؒ2H2O
(0.016 g, 0.095 mmol) in deoxygenated thf (10 cm3) was added
via a cannula to a solution of [IrCl(CO)(L3)2] (0.066 g, 0.053
mmol) in deoxygenated thf (15 cm3). The solution was stirred
under nitrogen and began to turn cloudy within 5 min. Stirring
2434
J. Chem. Soc., Dalton Trans., 2002, 2423–2436

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Table 4 Numerical crystal and refinement data for the X-ray crystal structures
Complex
[Cu(L1)][PF6]
[PtCl(L1)][PF6]
Formula (sum)
M
Crystal system
C33H32CuF6N3P2
710.1
C33H32ClF6N3P2Pt
877.1
Monoclinic
P21/c
Triclinic
¯
Space group
P1
a/Å
b/Å
c/Å
α/Њ
10.979(7)
11.717(7)
13.848(11)
71.18(6)
78.57(5)
70.04(6)
1577(2)
2
18.910(3)
10.098(1)
19.429(3)
90
118.93(1)
90
3247.1(8)
4
104.7
β/Њ
γ/Њ
V/Å3
Z
µ/cmϪ1 (Cu-Kα)
24.98
Reflections collected
Rmerge (no. of equiv. reflections)
Observed reflections [I/σ(I ) > 3]
No. of parameters
4680
0.039 (3)
2879
298
9.7
0.042, 0.057
1.85
0.74, Ϫ0.80
6341
0.020 (192)
5250
288
18.3
0.027, 0.043
1.64
1.58, Ϫ0.93
Observed reflections/no. parameters
Final R, Rw [I/σ(I ) > 3]
Goodness-of-fit
Max., min. peaks in final difference map/e ÅϪ3
was continued for 2 h and the cloudy mixture was left in a
Ϫ15 ЊC freezer overnight. The green–brown powder was
collected by filtration. Additional product (which gave identical
IR and electronic spectra) was obtained by concentration of the
filtrate and layering with diethyl ether (0.038 g, 47%); νCO/cmϪ1
2074s (chloroform).
conditions the following retention times were observed for
authentic samples: thf (2.5 min), MEK (2.5 min), toluene
(2.6 min), MeCN (2.6 min), styrene (3.0 min,), o-dichloro-
benzene (4.3 min), benzaldehyde (4.8 min,), styrene oxide
(5.9 min), acetophenone (6.7 min). The results of the styrene
oxidation reactions are summarised in Table 3.
[IrCl(CO)(O2)(L3)2]. A solution of trans-[IrCl(CO)(L3)2]
(0.048 g, 0.038 mmol) in thf (10 cm3) was bubbled with oxygen
and the IR spectrum recorded at various intervals over a 24 h
period. After 24 h almost the entire product had been converted
to the dioxygen adduct, [IrCl(CO)(O2)(L3)2], as judged by IR
and 31P{1H} NMR spectroscopy: νCO/cmϪ1 2006s (thf ); δP(thf )
27.38 (0.04, s), 25.72 (0.06, s), 25.65 (0.03, s), 25.36 (0.03, s),
4.96 (1.00, s); m/z (ES-MS) 1291.0 ([IrCl(CO)(O2)(HL3)2]2ϩ).
The solution was then heated at reflux under nitrogen for 2.5 h
to cleanly regenerate the starting complex as judged by IR and
31P{1H} NMR spectroscopy.
X-Ray crystallography
Relevant crystal and refinement data are collected in Table 4.
CCDC reference numbers 179667 and 179668.
See http://www.rsc.org/suppdata/dt/b2/b201720m/ for crys-
tallographic data in CIF or other electronic format.
Acknowledgements
1,4-Diisopropyl-1,4,7-triazacyclononane was prepared by
Dr Xinhao Yang. We are grateful for research support from
UNSW and for an Australian Postgraduate Award (to S. E. W.).
Metal ion sensing experiment with [W0(CO)5(L3)]
Separate aliquots (0.15 cm3 each) of a 1.00 mM solution of
[W0(CO)5(L3)] (0.0207 g, 0.0251 mmol) in thf (25.0 cm3) were
treated with an approximately 10 fold molar excess of solid
M(ClO4)2ؒ6H2O (M = Mn, Fe, Co, Ni, Cu, Zn). The IR spectra
of the solutions before and after the addition of the metal ions
were recorded and the results are summarised in ESI Table 3
and ESI Fig. 6.†
References and notes
1 B. Bosnich, Inorg. Chem., 1999, 38, 2554.
2 K. D. Karlin, S. Kaderli and A. D. Zuberbuhler, Acc. Chem. Res.,
1997, 30, 139.
3 H. V. Obias, Y. Lin, N. N. Murthy, E. Pidcock, E. I. Solomon,
M. Ralle, N. J. Blackburn, Y. M. Neuhold, A. D. Zuberbuhler and
K. D. Karlin, J. Am. Chem. Soc., 1998, 120, 12960.
4 W. B. Tolman, Acc. Chem. Res., 1997, 30, 227.
5 R. Gebbink, C. F. Martens, P. J. A. Kenis, R. J. Jansen, H. F.
Nolting, V. A. Sole, M. C. Feiters, K. D. Karlin and R. J. M. Nolte,
Inorg. Chem., 1999, 38, 5755.
6 A Scifinder search found 145,000 triphenylphosphine compounds
in 34,500 papers of which 12,738 (or 37%) are also closely associated
with the terms “catalyst” or “catalysis”.
7 R. G. Pearson, Chem. Rev., 1985, 85, 41.
8 J. C. Jeffery, T. B. Rauchfuss and P. A. Tucker, Inorg. Chem., 1980,
19, 3306.
9 J. X. Gao, T. Ikariya and R. Noyori, Organometallics, 1996, 15,
1087.
10 R. E. Rulke, V. E. Kaasjager, P. Wehman, C. J. Elsevier,
P. Vanleeuwen, K. Vrieze, J. Fraanje, K. Goubitz and A. L. Spek,
Organometallics, 1996, 15, 3022.
11 S. E. Watkins, D. C. Craig and S. B. Colbran, Inorg. Chim. Acta,
2000, 307, 134.
12 X. M. Liu, K. F. Mok and P. H. Leung, Organometallics, 2001, 20,
3918.
13 K. R. Reddy, K. Surekha, G. H. Lee, S. M. Peng and S. T. Liu,
Organometallics, 2001, 20, 5557.
14 H. Hope, M. Viggiano, B. Moezzi and P. P. Power, Inorg. Chem.,
1984, 23, 2550.
Styrene oxidations
In a typical reaction, a measured aliquot (≈150 × 10Ϫ3 cmϪ3) of
freshly purified styrene was added to a solution of trans-
[IrCl(CO)(L3)2] in the solvent (2 cm3) and the solution was
bubbled with oxygen using a glass pipette whilst being heated at
80 ЊC for 16 h. The solution was sampled at various time inter-
vals and an aliquot (1 × 10Ϫ3 cm3) injected directly into the
gas chromatograph. Reactions with heterometallic catalysts
involved the addition of a solution (2 cm3) containing two
molar equivalents (with respect to the iridium complex) of the
added metal ions [as the perchlorate salt {M(ClO4)2ؒ6H2O}].
For some reactions o-dichlorobenzene (50 × 10Ϫ3 cm3) was
added after the completion of the reaction as an internal
standard.
The following gas chromatograph settings were used: column
temperature: 115 ЊC, injector temperature: 200 ЊC, detector
temperature: 200 ЊC, column inlet pressure: 42 kPa, total flow
rate: 42 cm3 minϪ1, split ratio: (1 :) 43, range: 0. Under these
J. Chem. Soc., Dalton Trans., 2002, 2423–2436
2435

View Article Online
15 A. Carroy, C. R. Langick, J.-M. Lehn, K. E. Matthes and D. Parker,
Helv. Chim. Acta, 1986, 69, 580.
16 S. J. McLain, Inorg. Chem., 1986, 25, 3124.
17 R. Ziessel, Tetrahedron Lett., 1989, 30, 463.
18 E. Kimura, Y. Kodama, M. Shionoya and T. Koike, Inorg. Chim.
Acta, 1996, 246, 151.
44 A. J. Jircitano, W. G. Rohly and K. B. Mertes, J. Am. Chem. Soc.,
1981, 103, 4879.
45 M. S. Davies and T. W. Hambley, Inorg. Chem., 1998, 37, 5408.
46 V. Balzani, A. Juris, M. Venturi, S. Campagna and S. Serroni, Chem.
Rev., 1996, 96, 759.
47 E. C. Constable, Chem. Commun., 1997, 1073.
48 E. W. Ainscough, A. M. Brodie, S. L. Ingham and J. M. Waters,
Inorg. Chim. Acta, 1995, 234, 163.
19 G. Pilloni, G. Bandoli, F. Tisato and B. Corain, Chem. Commun.,
1996, 433.
20 D. Ellis, L. J. Farrugia, D. T. Hickman, P. A. Lovatt and R. D.
Peacock, Chem. Commun., 1996, 1817.
21 E. C. Constable, C. E. Housecroft, M. Neuburger, A. G. Schneider,
B. Springler and M. Zehnder, Inorg. Chim. Acta, 2000, 300, 49.
22 G. Pickaert, M. Cesario, L. Douce and R. Ziessel, Chem. Commun.,
2000, 1125.
23 D. Ellis, L. J. Farrugia, P. A. Lovatt and R. D. Peacock, Eur. J. Inorg.
Chem., 2000, 1489.
24 S. E. Watkins, X. Yang, D. C. Craig and S. B. Colbran, J. Chem.
Soc., Dalton Trans., 1999, 1539.
25 M. Karlson, M. Johansson and C. Andersson, J. Chem. Soc., Dalton
Trans., 1999, 4187.
26 A. F. Abdel-Magid, K. G. Carson, B. D. Harris, C. A. Maryanoff
and R. D. Shah, J. Org. Chem., 1996, 61, 3849.
27 L. Vaska and J. W. DiLuzio, J. Am. Chem. Soc., 1962, 84, 679.
28 L. Vaska, Science, 1963, 140, 809.
49 S. O. Grim, D. A. Wheatland and W. McFarlane, J. Am. Chem. Soc.,
1967, 89, 5573.
50 J. A. Rahn, M. S. Holt and J. H. Nelson, Polyhedron, 1989, 8, 897.
51 J. Vecernik, J. Masek and A. A. Vlcek, Inorg. Chim. Acta, 1977, 21,
271.
52 The product is possibly a copper complex of the phosphine oxide of
L2 (ES-MS: m/z 556.0 {556.0 calc. for [Cu(L2O)]ϩ}).
53 G. Murphy, P. Nagle, B. Murphy and B. Hathaway, J. Chem. Soc.,
Dalton Trans., 1997, 2645.
54 B. W. Skelton, T. N. Waters and N. F. Curtis, J. Chem. Soc., Dalton
Trans., 1972, 2133.
55 J. L. Schneider, V. G. Young and W. B. Tolman, Inorg. Chem., 1996,
35, 5410.
56 J. W. L. Martin, J. H. Johnston and N. F. Curtis, J. Chem. Soc.,
Dalton Trans., 1978, 68.
57 L. Vaska, Phosphorus, Sulfur Silicon Relat. Elem., 1990, 49/50,
29 L. Vaska, Acc. Chem. Res., 1968, 1, 335.
30 C. Elschenbroich and A. Salzer, Organometallics:
Introduction, VCH, Weinheim, 1989.
437.
A
Concise
58 A. A. Bowden and J. D. Atwood, J. Coord. Chem., 1998, 46, 203.
59 The reaction of CuCl2 with the dioxygen adduct was briefly
investigated: addition of CuCl2 (2 equivalents) to [IrCl(CO)(L3)2-
(O2)] (νCO/cmϪ1: 2006) in oxygen-saturated thf caused immediate
precipitation of a green powder. The green solid was soluble in
dichloromethane and the IR spectrum showed a strong νCO band at
31 A. Perez-Ponce and B. Lendl, Appl. Spectrosc., 2000, 54, 676.
32 J. E. Hoots, T. B. Rauchfuss and D. A. Wrobleski, Inorg. Synth.,
1982, 21, 175.
33 G. P. Schiemenz and H. Kaack, Liebigs Ann. Chem., 1973, 1480.
34 A. J. Evans, S. E. Watkins, D. C. Craig and S. B. Colbran, J. Chem.
Soc., Dalton Trans., 2002, 983.
2012 cmϪ1
,
possibly for [IrCl(CO)(O2){(L3)CuCl2}2], that was
replaced over several hours by a νCO band at 2052 cmϪ1 for an
unidentified species.
35 J. G. Verkade and J. A. Mosbo, Stereospecificity in 31P-Element
Couplings: One-bond Couplings to Other Non-metals and to
Metals, in Phosphorus-31 NMR Spectroscopy in Stereochemical
Analysis, ed. J. G. Verkade and L. D. Quin, VCH Publishers,
Deerfield Beach, FL, 1987.
60 K. Takao, Y. Fujiwara, T. Imanaka and S. Teranishi, Bull. Chem.
Soc. Jpn., 1970, 43, 1153.
61 A. Fusi, R. Ugo, F. Fox, A. Pasini and S. Cenini, J. Organomet.
Chem., 1971, 26, 417.
36 N. Wei, N. N. Murthy, Q. Chen, J. Zubieta and K. D. Karlin, Inorg.
Chem., 1994, 33, 1953.
62 J. E. Lyons and J. O. Turner, Tetrahedron Lett., 1972, 2903.
63 S. Muto and Y. Kamiya, J. Catal., 1976, 41, 148.
64 J. Sheppard, Peroxy Compounds, in Encyclopedia of Polymer Science
and Engineering, Wiley, New York, 1988, vol. 11, pp. 1–21.
65 We also found that no reaction occurs when styrene and
[IrCl(CO)(PPh3)2] are treated with pure oxygen in acetonitrile or in
chlorobenzene.
37 J. A. Caram and E. J. Vasini, Electrochim. Acta, 1994, 39, 2395.
38 B. J. Hathaway, Copper, in Comprehensive Co-ordination Chemistry,
ed. G. Wilkinson, Pergamon Press, Oxford, 1987, vol. 5, p. 533.
39 E. A. Ambundo, M. V. Deydier, A. J. Grall, N. Aguera-Vega,
L. T. Dressel, T. H. Cooper, M. J. Heeg, L. A. Ochrymowycz and
D. B. Rorabacher, Inorg. Chem., 1999, 38, 4233.
40 R. G. Goel, W. P. Henry and N. K. Jha, Inorg. Chem., 1982, 21, 2551.
41 R. H. Prince, Zinc and Cadmium, in Comprehensive Co-ordination
Chemistry, ed. G. Wilkinson, Pergamon Press, Oxford, 1987, vol. 5,
p. 959.
42 A. Albinati, F. Lianza, B. Muller and P. S. Pregosin, Inorg. Chim.
Acta, 1993, 208, 119.
43 B. Schmid, L. M. Venanzi, A. Albinati and F. Mathey, Inorg. Chem.,
1991, 30, 4693.
66 L. E. Brady, M. Freifelder and G. R. Stone, J. Org. Chem., 1961, 26,
4757.
67 J. A. Halfen and W. B. Tolman, Inorg. Synth., 1998, 32, 75.
68 G. K. Anderson and M. Lin, Inorg. Synth., 1990, 28, 60.
69 U. Klabunde, Inorg. Synth., 1974, 15, 82.
70 G. J. Kubas, Inorg. Synth., 1990, 28, 68.
71 I. Sanyal, M. Mahroof-Tahir, M. S. Nasir, P. Ghosh, B. I. Cohen,
Y. Gultneh, R. W. Cruse, A. Farooq, K. D. Karlin, L. Shuncheng
and J. Zubieta, Inorg. Chem., 1992, 31, 4322.
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J. Chem. Soc., Dalton Trans., 2002, 2423–2436