First observation of metal-mediated nitrile-imine coupling giving ligated 1,3-diaza-1,3-dienes

Article abstract of DOI:10.1039/b008154j

Coupling between benzophenone imine and coordinated organonitriles in the platinum(IV) complexes [PtCl₄-(RCN)₂] (R = Me or Et) proceeded rapidly under mild conditions to afford the 1,3-diaza-l,3-diene compounds [PtCl₄ {NH=C(R)N=CPh₂} ₂] in good yield and this reaction is the first observation of metal-assisted nucleophilic addition of an imine to a ligated nitrile. [PtCl₄{NH=C(R)N=CPh₂}₂] were reduced to the corresponding platinum(II) complexes [PtCl₂{NH=C(R)N=CPh₂}₂] by the carbonyl-stabilized phosphorus ylide Ph₃P=CHCO₂Me. The [PtCl₂{NH=C(Me)N=CPh₂}₂] complex was also detected in a mixture formed in the reaction between the platinum(II) nitrile complex [PtCl₂(MeCN)₂] and Ph₂C=NH, but the selectivity of the platinum(II)-mediated nitrileimine coupling was enhanced by employing for the reaction with benzophenone imine the phenyl cyanide complex [PtCl₂(PhCN)₂] to give [PtCl₂(NH=CPh₂){NH=C(Ph)N=CPh₂}]. Liberation of 1,3-diaza-l,3-dienes was exemplified by the reaction of [PtCl₂ {NH=C(Et)N=CPh₂}₂] with two equivalents of 1,2-bis(diphenylphosphino)ethane in CHCl₃ to give, along with free NH=C(Et)N=CPh₂ retained in solution, the solid complex [Pt(dppe)₂]Cl₂. All isolated metal complexes were characterized by elemental analyses, FAB mass spectrometry, IR, ¹H, ¹³C-{¹H} and ¹⁹⁵Pt NMR spectroscopies and cis-[PtCl₄{Z-NH=C(Et)N=CPh₂}₂] also by X-ray single-crystal diffraction.

Full text of DOI:10.1039/b008154j

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First observation of metal-mediated nitrile–imine coupling giving
ligated 1,3-diaza-1,3-dienes
Dmitrii A. Garnovskii,a Vadim Yu. Kukushkin,*b Matti Haukka,c Gabriele Wagnera and
Armando J. L. Pombeiro*a
a Centro de Química Estrutural, Complexo I, Instituto Superior Técnico, Av. Rovisco Pais,
1049–001 Lisbon, Portugal. E-mail: pombeiro@ist.utl.pt
b Department of Chemistry, St. Petersburg State University, 198904 Stary Petergof,
Russian Federation. E-mail: kukushkin@VK2100.spb.edu
c Department of Chemistry, PO Box 111, FIN-80101, Joensuu, Finland.
E-mail: Matti.Haukka@Joensuu.Fi
Received 10th October 2000, Accepted 20th December 2000
First published as an Advance Article on the web 16th February 2001
Coupling between benzophenone imine and coordinated organonitriles in the platinum() complexes [PtCl4-
(RCN)2] (R = Me or Et) proceeded rapidly under mild conditions to afford the 1,3-diaza-1,3-diene compounds
[PtCl {NH᎐C(R)N᎐CPh } ] in good yield and this reaction is the first observation of metal-assisted nucleophilic
᎐
᎐
4
2 2
addition of an imine to a ligated nitrile. [PtCl {NH᎐C(R)N᎐CPh } ] were reduced to the corresponding
᎐
᎐
4
2 2
platinum() complexes [PtCl {NH᎐C(R)N᎐CPh } ] by the carbonyl-stabilized phosphorus ylide Ph P᎐CHCO Me.
᎐
᎐
᎐
3
2
2
2
2
The [PtCl {NH᎐C(Me)N᎐CPh } ] complex was also detected in a mixture formed in the reaction between the
᎐
᎐
2
2 2
platinum() nitrile complex [PtCl (MeCN) ] and Ph C᎐NH, but the selectivity of the platinum()-mediated nitrile–
᎐
2
2
2
imine coupling was enhanced by employing for the reaction with benzophenone imine the phenyl cyanide complex
[PtCl (PhCN) ] to give [PtCl (NH᎐CPh ){NH᎐C(Ph)N᎐CPh }]. Liberation of 1,3-diaza-1,3-dienes was exemplified
᎐
᎐
᎐
2
2
2
2
2
by the reaction of [PtCl {NH᎐C(Et)N᎐CPh } ] with two equivalents of 1,2-bis(diphenylphosphino)ethane in CHCl
᎐
᎐
2
2
2
3
to give, along with free NH᎐C(Et)N᎐CPh retained in solution, the solid complex [Pt(dppe) ]Cl . All isolated metal
᎐
᎐
2
2
2
complexes were characterized by elemental analyses, FAB mass spectrometry, IR, 1H, 13C-{1H} and 195Pt NMR
spectroscopies and cis-[PtCl {Z-NH᎐C(Et)N᎐CPh } ] also by X-ray single-crystal diffraction.
᎐
᎐
4
2 2
to acetonitrile ligand in the platinum() complex [PtCl2-
Introduction
(MeCN)2] to give [PtCl(Ph S᎐NH){S,N-Ph S᎐NC(Me)᎐
᎐
᎐
2
᎐
2
In organic chemistry organonitriles RCN serve as synthons of
great versatility for the formation of new C–O and C–N bonds
due to nucleophilic addition of O- or N-donors, respectively, to
the nitrile carbon.1 The well recognized susceptibility of the C
atom towards nucleophilic attack can be utilized by the appli-
cation of organonitriles with a strong acceptor radical R. When
activation by this way is insufficient another route to activate
the nitriles can be applied, i.e. their coordination to a metal
center, preferably in a rather high oxidation state, that promotes
addition of nucleophiles to give new C–O,2,3 C–N,2,3 C–C,4
C–P5 or C–S2,3 bonds. Many of these metal-promoted reac-
tions were summarized in reviews on the subject2,3 including the
recent one by Michelin et al.2
NH}]Cl.
Owing to our interest in nucleophilic addition to metal-
bound nitriles13–16 and its application for organic synthesis17 we
have continued the search for new reagents for additions to
ligated RCN molecules and focused our efforts on reactions
with benzophenone imine, Ph C᎐NH. We report herein the first
᎐
2
observation of a facile metal-induced nitrile–imine coupling to
give ligated 1,3-diaza-1,3-dienes, although formation of the
latter species as undetected intermediates, via zinc-mediated
nucleophilic addition of imines to nitriles, was anticipated.18
The previously known organic synthetic methods19 for such
diazadienes do not involve a direct reaction between a nitrile
and an imine.
As far as metal-mediated additions to give C–N bonds are
concerned, reports on coupling between coordinated nitriles
and ammonia, primary or secondary amines2,3 became rather
habitual although some new and interesting aspects of these
reactions are still gradually appearing.6 Among less usual and
yet systematically unexplored additions of N-donors, attention
should be drawn to: (i) the reaction between metal-bound7,8
organonitriles and hydrazine or methylhydrazine to give
amidrazone species; (ii) couplings between nitriles and poten-
tially ambidentate N,O-nucleophiles such as alkylhydroxyl-
amines giving, depending on the metal center, addition
products with new C–N9 or C–O10 bonds; (iii) addition of aza-
heterocycles, e.g. pyrazole, containing a N–H bond to give
iminoacylated rings.11 In the context of the addition of
N-donor nucleophiles to coordinated organonitriles a special
case has recently been described by Kelly and Slawin12 who
Results and discussion
Imines are known as good ligands for platinum20 or other tran-
sition metals21 and these species are coordinated either via the
N atom or the C᎐N double bond. In addition, imine ligands
᎐
that contain aromatic groups attached to the imine carbon, e.g.
Ph C᎐NH, can easily undergo orthometallation giving
᎐
2
very stable N,C-chelates.20 Our interest in the exploration of
benzophenone imine as a reagent for the nucleophilic addition
to metal-bound organonitriles to obtain 1,3-diaza-1,3-dienes
was recently sparked by intriguing data of Grøndahl et al.20
who reported on the reaction between the platinum()
complex [PtCl (MeCN) ] and two equivalents of Ph C᎐NH in
᎐
2
2
2
dichloromethane giving the substitution product [PtCl (Ph C᎐
᎐
2
2
discovered the addition, via the N atom, of sulfimide Ph S᎐NH
NH)2] as a solid in 20% yield, while “the mother liquor con-
᎐
2
560
J. Chem. Soc., Dalton Trans., 2001, 560–566
This journal is © The Royal Society of Chemistry 2001
DOI: 10.1039/b008154j

View Article Online
tained yet unidentified complexes”.20 Taking into account our
previous experience of additions to coordinated organonitrile
species,13–16 we decided to try the extension to imines, as the
nucleophiles, of nucleophile–nitrile coupling reactions and,
concurrently, to investigate whether the low yield of [PtCl2-
ing mostly the cis isomer, see above) with the imine pro-
ceeds rather rapidly at room temperature, while for trans-
[PtCl4(EtCN)2] it is fast and selective even at Ϫ15 ЊC (but
gives a broad spectrum of products at 20–25 ЊC). Subsequent
evaporation of the solvent to dryness and treatment of the
(Ph C᎐NH) ] is explained by the occurrence of an addition of
residue formed with Et O allowed isolation of [PtCl {NH᎐
᎐
2 4
᎐
2
2
imine to the coordinated nitriles. To perform the coupling we
employed the same methodology as has previously been
applied13–15,17,18 to increase the selectivity of the addition and to
enhance the reactivity of platinum-bound organonitriles: (i) to
attempt the reaction between the imine and the platinum()
complexes [PtCl4(RCN)2] (the latter proved to be highly reactive
towards the addition of different nucleophiles13,14,17,18); (ii) if
the coupling is successful, to reduce the compounds [PtCl4-
C(R)N᎐CPh } ] in ca. 80% yield (route (a) in Scheme 1). In
᎐
2 2
{NH᎐C(R)N᎐CPh } ] to the corresponding platinum() com-
᎐
᎐
2
2
plexes [PtCl {NH᎐C(R)N᎐CPh } ]; (iii) to try to detect
᎐
᎐
2
2 2
[PtCl {NH᎐C(Me)N᎐CPh } ] in the mother liquor from the
᎐
᎐
2
2 2
synthesis of [PtCl (Ph C᎐NH) ]20 by application of both TLC
᎐
2
2
2
and NMR methods, thus checking for the possible occurrence
of coupling in [PtCl2(MeCN)2]; (iv) to activate nitriles in the
platinum() complexes [PtCl2(RCN)2] by introducing an
acceptor substituent R, e.g. Ph, and to attempt coupling with
benzophenone imine.
Scheme 1
Platinum(IV)-mediated nitrile–imine coupling
the case of the isomeric mixtures as the starting materials
In accord with the plan, we explored the reaction between the
appropriate mixtures of the geometrical isomers of [PtCl4-
platinum() complexes [PtCl4(RCN)2] and two equivalents of
{NH᎐C(R)N᎐CPh } ] were isolated.
᎐ ᎐
2 2
Ph C᎐NH in dichloromethane. We chose as starting materials
Reaction of trans-[PtCl4(EtCN)2] with the imine led
exclusively to trans-[PtCl {NH᎐C(Et)N᎐CPh } ], while treat-
᎐
2
for this part of the study the acetonitrile and propionitrile com-
plexes [PtCl4(RCN)2] (R = Me or Et). The former was prepared
by chlorination of a mixture of cis- and trans-[PtCl2(MeCN)2]
(ca. 5:1 by NMR integration22) and presumably consists of an
isomeric mixture of cis/trans-[PtCl4(MeCN)2]. However, the
poor solubility of this compound does not allow one to confirm
quantitatively this assumption. Isomeric forms of it were
obtained by Cl2 oxidation of (i) a mixture of cis- and trans-
[PtCl2(EtCN)2] (6:1 by NMR integration23) giving a mixture of
cis/trans-[PtCl4(EtCN)2] with almost the same isomeric ratio
and (ii) pure trans-[PtCl2(EtCN)2]23 to give the isomerically
pure trans-[PtCl4(EtCN)2] complex.
᎐
᎐
4
2 2
ment of the cis/trans mixture of [PtCl (EtCN) ] with Ph C᎐NH
᎐
2
4
2
results in the formation of cis/trans-[PtCl {NH᎐C(Et)N᎐
᎐
᎐
4
CPh2}2]. Crystals of cis-[PtCl {NH᎐C(Et)N᎐CPh } ] were
᎐
᎐
4
2 2
separated mechanically from the latter mixture, after slow
evaporation of its CH2Cl2–Et2O solution, and fully character-
ized (see Experimental section). An X-ray single-crystal diffrac-
tion study of cis-[PtCl {NH᎐C(Et)N᎐CPh } ] revealed an
᎐
᎐
4
2 2
octahedral environment around the metal center and overall
cis geometry with the newly formed NH᎐C(Et)N᎐CPh lig-
᎐
᎐
2
ands in the Z configuration (Fig. 1) with bond lengths and
angles (Table 1) of normal values.13,14,25,26 The 1,3-diaza-1,3-
The heterogeneous reaction of cis/trans-[PtCl4(MeCN)2] and
the homogeneous reaction of cis/trans-[PtCl4(EtCN)2] (contain-
diene unit in the NH᎐C(Et)N᎐CPh ligands is not planar but
᎐ ᎐
2
adopts a transoid conformation with torsion angles N᎐C–
᎐
Fig. 1 PLATON24 view of the structure of cis-[PtCl4{Z-NH᎐C(Et)N᎐CPh2}2] with the atomic numbering scheme.
᎐
᎐
J. Chem. Soc., Dalton Trans., 2001, 560–566
561

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Table 1 Bond lengths (Å) and angles (Њ) for [PtCl4{NH᎐C(Et)N᎐
of a variety of platinum() complexes, including the difficult-
to-obtain imine compounds, that involves reduction of the
᎐
᎐
CPh2}2]
corresponding platinum() complexes by carbonyl stabilized
Pt(1)–Cl(1)
Pt(1)–Cl(2)
Pt(1)–Cl(3)
Pt(1)–Cl(4)
Pt(1)–N(1)
Pt(1)–N(3)
N(1)–C(1)
N(2)–C(1)
N(2)–C(7)
N(3)–C(4)
N(4)–C(4)
N(4)–C(20)
C(1)–C(2)
C(2)–C(3)
C(4)–C(5)
C(5)–C(6)
C(7)–C(14)
C(7)–C(8)
C(8)–C(9)
C(8)–C(13)
C(9)–C(10)
C(10)–C(11)
2.3149(7)
2.3192(7)
2.3159(8)
2.3319(8)
2.042(2)
2.025(3)
1.291(4)
1.366(4)
1.285(3)
1.292(4)
1.364(4)
1.282(4)
1.508(4)
1.512(4)
1.502(4)
1.524(4)
1.491(4)
1.483(4)
1.396(4)
1.397(4)
1.390(4)
1.389(4)
C(11)–C(12)
C(12)–C(13)
C(14)–C(19)
C(14)–C(15)
C(15)–C(16)
C(16)–C(17)
C(17)–C(18)
C(18)–C(19)
C(20)–C(21)
C(20)–C(27)
C(21)–C(26)
C(21)–C(22)
C(22)–C(23)
C(23)–C(24)
C(24)–C(25)
C(25)–C(26)
C(27)–C(32)
C(27)–C(28)
C(28)–C(29)
C(29)–C(30)
C(30)–C(31)
C(31)–C(32)
1.385(4)
1.376(4)
1.404(4)
1.398(4)
1.385(4)
1.386(4)
1.387(4)
1.391(4)
1.493(4)
1.486(4)
1.390(4)
1.388(4)
1.390(4)
1.391(5)
1.379(4)
1.394(4)
1.397(4)
1.409(4)
1.381(4)
1.383(6)
1.390(5)
1.384(4)
phosphorus ylides, Ph P᎐CHCO R, in non-aqueous media.
᎐
3
2
The reaction now is extended to (1,3-diaza-1,3-diene)-
platinum() compounds and it is found that, similarly to other
cases,27 the reduction (route (b) in Scheme 1) with Ph P᎐
᎐
3
CHCO2Me proceeds smoothly at room temperature. The prod-
ucts were purified by chromatography on silica gel and isolated
in good yields. The main features of the spectroscopic data for
the (1,3-diaza-1,3-diene)platinum() complexes are similar to
those of the corresponding platinum() complexes. The most
significant difference is in their 195Pt NMR spectra which dis-
play individual signals in a range from δ Ϫ2026 to Ϫ2143,
which is in good argeement with the range found for other
platinum() [PtCl2(imine)2] compounds.27
Platinum(II)-mediated nitrile–imine coupling
A mixture of the geometrical isomers cis/trans-[PtCl {NH᎐
᎐
2
C(Me)N᎐CPh } ] (which were also obtained as indicated above
᎐
2
2
via reduction, by a phosphorus ylide, of the corresponding plat-
inum() species) was reliably detected, by TLC and NMR
monitoring, in the mother liquor from the synthesis of [PtCl2-
Cl(1)–Pt(1)–Cl(2)
Cl(1)–Pt(1)–Cl(3)
Cl(1)–Pt(1)–Cl(4)
Cl(1)–Pt(1)–N(1)
Cl(1)–Pt(1)–N(3)
Cl(2)–Pt(1)–Cl(3)
Cl(2)–Pt(1)–Cl(4)
Cl(2)–Pt(1)–N(1)
Cl(2)–Pt(1)–N(3)
Cl(3)–Pt(1)–Cl(4)
Cl(3)–Pt(1)–N(1)
Cl(3)–Pt(1)–N(3)
Cl(4)–Pt(1)–N(1)
Cl(4)–Pt(1)–N(3)
N(1)–Pt(1)–N(3)
Pt(1)–N(1)–C(1)
C(1)–N(2)–C(7)
Pt(1)–N(3)–C(4)
C(4)–N(4)–C(20)
N(2)–C(1)–C(2)
N(1)–C(1)–N(2)
N(1)–C(1)–C(2)
C(1)–C(2)–C(3)
N(3)–C(4)–C(5)
C(21)–C(22)–C(23)
C(22)–C(23)–C(24)
C(23)–C(24)–C(25)
C(24)–C(25)–C(26)
C(21)–C(26)–C(25)
C(20)–C(27)–C(28)
C(20)–C(27)–C(32)
C(28)–C(27)–C(32)
C(27)–C(28)–C(29)
93.68(2)
90.36(3)
87.22(2)
174.39(7)
87.87(7)
87.48(2)
91.25(2)
89.34(7)
175.92(7)
177.19(2)
85.05(7)
96.29(7)
97.45(7)
85.05(7)
89.43(10)
133.1(2)
125.8(2)
133.3(2)
126.4(3)
114.6(2)
122.7(2)
122.1(3)
116.5(2)
119.5(3)
119.7(3)
120.3(3)
120.1(3)
119.8(3)
120.2(3)
118.3(2)
123.0(2)
118.6(2)
120.7(3)
C(28)–C(29)–C(30)
C(29)–C(30)–C(31)
C(30)–C(31)–C(32)
C(27)–C(32)–C(31)
N(4)–C(4)–C(5)
N(3)–C(4)–N(4)
C(4)–C(5)–C(6)
120.0(3)
120.1(3)
120.4(3)
120.3(3)
117.4(2)
122.2(3)
109.5(2)
117.1(2)
124.9(2)
117.9(2)
120.2(2)
120.2(2)
119.2(3)
120.6(2)
120.3(3)
119.7(3)
119.9(3)
120.6(3)
120.1(3)
122.2(2)
119.5(2)
118.3(2)
120.3(3)
120.2(3)
119.8(3)
120.8(3)
119.3(3)
124.8(2)
118.9(2)
116.3(2)
120.0(2)
120.0(2)
119.9(3)
(HN᎐CPh ) ] recently reported by Grøndahl and et al.20 and
᎐
2
2
reproduced by us (see Experimental section). However, these
two by-products are formed along with two other unidentified
species thus making difficult their isolation, from the reaction
mixture, in an analytically pure form. Thus, the addition of
benzophenone imine to the acetonitrile ligands in [PtCl2-
(MeCN)2] occurs in accord with eqn. (1) but this is only a
N(2)–C(7)–C(8)
N(2)–C(7)–C(14)
C(8)–C(7)–C(14)
C(7)–C(8)–C(13)
C(7)–C(8)–C(13)
C(9)–C(8)–C(13)
C(7)–C(8)–C(9)
[PtCl (MeCN) ] ϩ 2 HN᎐CPh →
᎐
2
2
2
[PtCl {NH᎐C(Me)N᎐CPh } ] (1)
᎐
᎐
2
2 2
C(8)–C(9)–C(10)
C(9)–C(10)–C(11)
C(10)–C(11)–C(12)
C(11)–C(12)–C(13)
C(8)–C(13)–C(12)
C(7)–C(14)–C(19)
C(15)–C(14)–C(19)
C(7)–C(14)–C(15)
C(14)–C(15)–C(16)
C(15)–C(16)–C(17)
C(16)–C(17)–C(18)
C(17)–C(18)–C(19)
C(14)–C(19)–C(18)
N(4)–C(20)–C(27)
C(21)–C(20)–C(27)
N(4)–C(20)–C(21)
C(20)–C(21)–C(22)
C(20)–C(21)–C(26)
C(22)–C(21)–C(26)
side-reaction accompanying the substitution and perhaps some
other processes.
To enhance the selectivity of the nitrile–imine coupling at the
platinum() centre we employed an (organonitrile)platinum()
complex bearing an acceptor substituent attached to the
nitrile group, i.e. cis/trans-[PtCl2(PhCN)2]. The latter is more
reactive18 towards nucleophilic addition than its acetonitrile
analogue. The interaction is rather fast at 20–25 ЊC and gives
two products. The first is a material so insoluble in the most
common solvents that we were unable to obtain either its NMR
(even at significant acquisition time) or FAB-MS spectra. How-
ever, based on elemental analyses and IR spectroscopy data we
tentatively formulate this complex as the polymer [PtCl2-
{µ-N,N-NH᎐C(Ph)N᎐CPh }] . The alternative structure with
᎐
᎐
2
∞
the same empirical formula, i.e. [PtCl (HN᎐CPh )(PhCN)],
᎐
2
2
᎐
also cannot be ruled out but the absence of ν(C᎐N) stretching
᎐
vibrations and the low solubility favour the polymeric com-
pound. The second product isolated from the mixture is
N᎐C of 104.4 and 111.8Њ, indicating a weak conjugation of
the π system.
Spectroscopic data agree well with the proposed structure of
᎐
formulated as [PtCl (NH᎐CPh ){NH᎐C(Ph)N᎐CPh }] which
᎐
᎐
᎐
2
2
2
is derived from both the addition and substitution reactions.
Although we were unable to obtain crystals suitable for X-ray
study, our main arguments confirming the formulation are
based upon: (i) satisfactory elemental anlyses; (ii) observation
of peaks due to the parent ion [M]ϩ in FABϩ-MS; (iii)
the platinum() complexes with 1,3-diaza-1,3-dienes (Scheme
᎐
1). IR spectra show the disappearance of the C᎐N stretching
᎐
vibrations and the appearance of the two strong ν(C᎐N)
᎐
vibrations, a new strong and characteristic band due to δ(C–H)
of the aromatics and appearance of N–H stretching vibrations.
13C-{1H} NMR spectra display, in particular, two signals from
three different signals from carbons of the C᎐N bonds in
᎐
13C-{1H} NMR spectrum, while the 195Pt NMR spectrum
gives only one signal thus indicating isomeric purity of the
compound.
the two different carbons of the C᎐N bond (range δ 166–
᎐
180) and signals in the 195Pt NMR spectra emerge usually in the
range of δ 100–186, which is ca. 300 ppm more positive than the
characteristic values found for platinum() [PtCl4(imine)2]
complexes.13,14,17
Concluding remarks
In conclusion it is worthwhile to mention that (i) the nitrile–
imine coupling is metal-mediated since it was demonstrated
that benzophenone imine does not react with acetonitrile or
propionitrile even under harsh conditions (50 ЊC, CDCl3, 12 h).
Reduction of [PtCl {NH᎐C(R)N᎐CPh } ] complexes
᎐
᎐
4
2 2
Recently some of us suggested a novel method for generation
562 J. Chem. Soc., Dalton Trans., 2001, 560–566

View Article Online
Table 2 Crystallographic data for cis-[PtCl4{NH᎐C(Et)N᎐CPh2}2]
The complexes are presumably formed by nucleophilic attack
of the imine N atom on the electrophilically activated carbon
atom of the organonitrile. (ii) In coordination chemistry, com-
plexes containing the 1,3-diaza-1,3-diene linkage are known,
although scarce, and all four reported examples are azametalla-
᎐
᎐
Empirical formula
M
C32H32Cl4N4Pt
809.50
T/K
Crystal system
Space group
a/Å
b/Å
c/Å
120
Monoclinic
P21/n (no. 14)
8.7930(2)
25.2910(5)
14.1000(3)
93.3360(10)
3130.30(12)
4
4.853
31 459
6453
5796
cycles [M]–NH᎐C(R1)–N᎐C(R2)–NH.28–31 None of these com-
᎐
᎐
plexes was prepared by direct nitrile–imine coupling, being
formed e.g. in an unusual reaction between [Pt(PPh3)4] or
[RuCpCl(PPh3)2] and CF3CN,28,29 by metal-mediated reaction
of cyanoguanidine with such nucleophiles as oximes or alco-
hols30 or by the addition of Li[(NH)2CPh] to [PtCl2(PhCN)2].31
(iii) In organic chemistry 1,3-diaza-1,3-dienes are useful for syn-
theses of six-membered nitrogen containing heterocycles and
their involvement in [4 ϩ 2] cycloadditions to give these systems
was a subject of rapt attention.19,32 The known synthetic path-
ways19 to achieve 1,3-diaza-1,3-dienes do not include direct
interaction between organonitriles and imines. Our results
indicate that, in the case of the platinum() species, liberation
of 1,3-diaza-1,3-dienes can be achieved by the reaction of
(1,3-diaza-1,3-diene)platinum() species and two equivalents of
1,2-bis(diphenylphosphino)ethane (dppe) in CHCl3. This route
[(c) in Scheme 1] was exemplified upon treatment of [PtCl2-
β/Њ
V/Å3
Z
µ(Mo-Kα)/mmϪ1
Collected reflections
Unique reflections
Observed reflections
R1
0.0218
wR2
0.0488
Addition of Ph C᎐NH to organonitriles in [PtCl (RCN) ]
᎐
2
4
2
trans- and cis-[PtCl {NH᎐C(Me)N᎐CPh } ]. Ph C᎐NH (17
᎐
᎐
᎐
2
4
2
2
mg, 0.095 mmol) was added to a suspension of [PtCl4(MeCN)2]
(a mixture of trans and cis isomers; 20 mg, 0.048 mmol) in
CH2Cl2 (5 mL) at 20–25 ЊC and the reaction mixture left to
stand for 2 h until complete homogenization, whereafter the
solvent was evaporated in a flow of N2 to ca. 0.5 mL followed
{NH᎐C(Et)N᎐CPh } ] with dppe to give in a quantitative
᎐
᎐
2
2
reaction, along with free NH᎐C(Et)N᎐CPh retained in solu-
᎐
᎐
2
tion, the solid complex [Pt(dppe)2]Cl2 (see Experimental
section).
by addition of Et O (5 mL) to precipitate [PtCl {NH᎐
᎐
2
4
C(Me)N᎐CPh } ]. Yield 77%. In accord with 1H and 195Pt
᎐
2
2
NMR data, the complex is a mixture of trans and cis isomers in
an approximate ratio 3:2. Calc. for C30H28Cl4N4Pt: C, 46.11; H,
3.61; N, 7.17. Found: C, 46.21; H, 3.71; N, 6.73%. FABϩ-MS:
m/z 803 [M ϩ H ϩ Na]ϩ; 781, [M ϩ H]ϩ, 710, [M Ϫ 2Cl]ϩ; and
638, [M Ϫ 4Cl]ϩ. mp = 196–199 ЊC (decomp.). IR spectrum in
Experimental
Materials and instrumentation
Benzophenone imine (Aldrich), Ph P᎐CHCO Me (Lancaster)
and solvents were obtained from commercial sources and used
as received. The complexes [PtCl (RCN) ] (R ᎐ Me or Et) were
᎐
3
2
KBr, selected bands, cmϪ1: 3274m-w ν(N–H), 1633s and
᎐
4
2
1
prepared as previously described.13 C, H and N elemental
analyses were carried out by the Microanalytical Service of the
Instituto Superior Técnico. Melting points were determined on
a Kofler table. For TLC, Merck UV 254 SiO2 plates have been
used. Positive-ion FAB mass spectra were obtained on a Trio
2000 instrument by bombarding 3-nitrobenzyl alcohol matrices
of the samples with 8 keV (ca. 1.28 × 10Ϫ15 J) Xe atoms. Mass
calibration for data system acquisition was achieved using
CsI. Infrared spectra (4000–400 cmϪ1) were recorded on a
Bio-Rad FTS 3000MX instrument in KBr pellets, 1H, 13C-
{1H}, 31P-{1H} and 195Pt NMR spectra on a Varian UNITY 300
spectrometer at ambient temperature. 195Pt chemical shifts are
given relative to Na2[PtCl6] (by using aqueous K2[PtCl4],
δ Ϫ1630, as a standard), with half height linewidths in
parentheses.
1610s ν(C᎐N), 1597s ν(C᎐C) and 697s δ(C–H). H NMR in
᎐
᎐
DMSO-d6: δ 1.95 (s, 3H, Me of cis isomer), 1.99 (s, 3H, Me of
trans isomer), 7.50 (“t”), 7.57 (m), 7.67 (“d”) and 7.73 (m)(10H
of each isomer, Ph), 9.70 (s, br, JPtH 18, NH of cis isomer) and
9.32 (s, br, JPtH 29 Hz, NH of trans isomer). 13C-{1H} NMR in
DMSO-d6: δ 22.4 (JPtC 33, Me of cis isomer), 22.8 (JPtC 28,
Me of trans isomer), 128.4, 128.5, 128.6, 129.6 and 129.9
(CHortho, meta), 131.2, 131.6 and 132.7 (CHpara), 135.6, 136.0 and
137.0 (Cipso), 168.2 (C᎐N of cis isomer), 175.5 (J 16, C᎐NH
᎐
᎐
PtC
of cis isomer), 166.2 (C᎐N of trans isomer) and 176.5 (J
8
᎐
PtC
Hz, C᎐NH of trans isomer). 195Pt NMR in DMSO-d6: δ ϩ184
᎐
(660)(cis isomer) and ϩ100 (600 Hz)(trans isomer).
trans-[PtCl {NH᎐C(Et)N᎐CPh } ]. Ph C᎐NH (16 mg, 0.089
᎐
᎐
᎐
2
4
2
2
mmol) was added to a solution of trans-[PtCl4(EtCN)2] (20 mg,
0.045 mmol) in CH2Cl2 (3 mL) at Ϫ15 ЊC and the reaction mix-
ture left to stand for 5 h, whereafter the solvent was evaporated
to dryness in a flow of N2, the residue washed with three 5 mL
portions of Et2O and dried in vacuo at room temperature. Yield
79%. Calc. for C32H32Cl4N4Pt: C, 47.48; H, 3.98; N, 6.92.
Found: C, 47.33; H, 3.87; N, 6.47%. FABϩ-MS: m/z 809, [M]ϩ;
738, [M Ϫ 2Cl]ϩ and 703, [M Ϫ 3Cl]ϩ. mp = 197–198 ЊC
(decomp.). IR spectrum in KBr, selected bands, cmϪ1: 3338m-w
ν(N–H), 1651s and 1603s ν(C᎐N), 1587s ν(C᎐C) and 697s
Crystal structure determination of cis-[PtCl {NH᎐C(Et)-
᎐
4
N᎐CPh } ]
᎐
2
2
Yellow blocks of the complex were grown by slow evaporation
of a dichloromethane–diethyl ether mixture. X-Ray diffraction
data were collected with a Nonius KappaCCD diffractometer
using Mo-Kα radiation (λ = 0.71073 Å) and ꢀ-scan data collec-
tion mode with a Collect33 collection program. The Denzo/
Scalepack34 program pakage was used for cell refinements and
data reduction. A multi-scan absorption correction, based on
equivalent reflections (XPREP in SHELXTL v. 5.135), was
applied. The structure was solved by direct methods using SIR
97.36 Structure refinements were carried out with SHELXL
97.37 All non-hydrogen atoms were refined anisotropically.
Aromatic hydrogens and CH2 hydrogens were placed in ideal-
ized positions. Hydrogens in NH groups were refined with fixed
Uiso = 0.05 Å2. Crystallographic data are summarized in Table 2.
CCDC reference number 186/2310.
᎐
᎐
δ(C–H). TLC (eluent chloroform–acetone 30:1): Rf = 0.63.
1H NMR in CDCl3: δ 1.02 (t, J 7.2, 3H) and 2.24 (q, J 7.5,
2H)(Et), 7.46 (t, J 7.5, 4H), 7.53 (t, J 7.2, 2H) and 7.84 (d, J 7.5
Hz, 4H)(Ph); NH was not detected probably due to overlapping
with the intense signals of the Ph groups. 13C-{1H} NMR in
CDCl3: δ 9.8 and 30.8 (Et), 128.6 and 129.7 (CHortho
meta),
and
132.0 (CHpara), 136.2 (Cipso)(Ph), 170.2 (C᎐N) and 179.9
᎐
(C᎐NH). 195Pt NMR in CDCl3: δ ϩ186 (500 Hz).
᎐
cis-[PtCl {NH᎐C(Et)N᎐CPh } ]. Ph C᎐NH (16 mg, 0.089
᎐
᎐
᎐
2
4
2
2
See http://www.rsc.org/suppdata/dt/b0/b008154j/ for crystal-
lographic files in .cif format.
mmol) was added to a solution of [PtCl4(EtCN)2] (a mixture of
cis and trans isomers in ca. 6:1 ratio; 20 mg, 0.045 mmol) in
J. Chem. Soc., Dalton Trans., 2001, 560–566
563

View Article Online
CH2Cl2 (3 mL) at 20–25 ЊC and the reaction mixture left to
stand for 2 h, whereafter the solvent was evaporated to dryness
in a flow of N2, the obtained solid washed with three 5 mL
portions of Et2O and dried in vacuo at room temperature. Yield
δ(C–H). 1H NMR in CDCl3: δ 6.90 (d, J 7.2, 2H), 7.10 (t, J 7.5,
2H), 7.18 (d, J 7.5, 2H), 7.28–7.56 (m, 12H), 7.76 (m, 6H), 8.28
(d, J 7.0 Hz, 2H) and 9.42 (s, br, NH). 13C-{1H} NMR in
CDCl3: δ 128.5, 129.9 (CHortho, meta), 131.9 (CHpara) and 136.2
(Cipso)(CPh2), signals of the other Ph groups in the range 126.4
of [PtCl {NH᎐C(Et)N᎐CPh } ] 81%. Found: C, 48.26; H, 3.92;
᎐
᎐
4
2 2
N, 6.38%. FABϩ-MS: m/z 809, [M]ϩ; 774, [M Ϫ Cl]ϩ; 738,
[M Ϫ 2Cl]ϩ; and 703, [M Ϫ 4Cl]ϩ. TLC (eluent chloroform–
acetone = 30:1) displayed two spots with Rf = 0.45 (dominant
in intensity) and 0.63 (specific for the trans isomer see above).
to 137.7, 172.0, 174.6 and 179.4 (C᎐N). 195Pt NMR in CDCl3:
᎐
δ Ϫ2018 (640 Hz).
Reduction of the (1,3-diaza-1,3-diene)platinum(IV) complexes
Pure cis-[PtCl {NH᎐C(Et)N᎐CPh } ] was obtained by
᎐
᎐
4
2 2
The platinum() complexes [PtCl {NH᎐C(R)N᎐CPh } ]
᎐
᎐
4
2 2
chromatographic separation of cis/trans-[PtCl {NH᎐C(Et)N᎐
᎐
᎐
4
(R = Me or Et) were reduced by one equivalent of the carbonyl-
CPh2}2] on Merck silica gel 60 (70–230 mesh) (eluent: CH2Cl2–
Et2O 5:1, v/v). Found: C, 47.23; H, 3.82; N. 7.29%. FABϩ-MS:
m/z 809, [M]ϩ; 761, [M Ϫ 2Cl ϩ Na]ϩ; 738, [M Ϫ 2Cl]ϩ; and
667, [M Ϫ 4Cl]ϩ. mp = 207–208 ЊC (decomp.). IR spectrum in
KBr, selected bands, cmϪ1: 3327m-w ν(N–H), 1652s and 1604s
stabilized phosphorus ylide Ph P᎐CHCO Me in CH Cl at
᎐
3
2
2
2
20–25 ЊC for ca. 3–4 h in accord with a recently suggested
procedure.27
[PtCl {NH᎐C(Me)N᎐CPh } ]. The complex was prepared
᎐
᎐
2
2 2
ν(C᎐N), 699s δ(C–H). TLC (eluent chloroform–acetone =
᎐
1
from a mixture of cis- and trans-[PtCl {NH᎐C(Me)N᎐CPh } ].
᎐
᎐
4
2 2
30:1): Rf = 0.45. H NMR in CDCl3: δ 0.81 (t, J 7.2, 3H) and
Yield 55%. Calc. for C30H28Cl2N4Pt: C, 50.71; H, 3.97; N, 7.89.
Found: C, 50.88; H, 3.72; N, 7.18%. FABϩ-MS: m/z 733,
[M ϩ Na]ϩ; 710, [M]ϩ; and 638, [M Ϫ 2Cl]ϩ. mp = 199–201 ЊC
(decomp.). IR spectrum in KBr, selected bands, cmϪ1: 3244m-
2.10 (q, J 7.5, 2H)(Et), 7.44 (t, J 7.8, 4H), 7.55 (t, J 6.9, 2H) and
7.71 (d, J 8.4 Hz, 4H)(Ph); NH was not detected probably due
to overlapping with the intense signals of the Ph groups. 13C-
{1H} NMR in CDCl3: δ 9.8 and 30.8 (Et), 128.6 and 130.4
w ν(N–H), 1634s ν(C᎐N), 1598s ν(C᎐C) and 697s δ(C–H).
᎐
᎐
(CHortho
meta), 132.0 (CHpara), 136.2 (Cipso)(Ph), 170.3 (C᎐N)
᎐
᎐
and
and 179.5 (C᎐NH). 195Pt NMR in CDCl3: δ Ϫ56 (600 Hz).
TLC (eluent chloroform–acetone = 20:1) displayed two
spots with Rf = 0.49 (dominant in intensity) and 0.30. NMR
monitoring indicated that the compound is a mixture of two
isomers in the approximate ratio 5:1. Major isomer: 1H NMR
in CDCl3 δ 1.85 (s, 3H, Me), 7.46 (t, J 7.4, 4H), 7.54 (t, J 7.0,
2H), 7.82 (d, J 7.0 Hz, 4H)(Ph), NH not detected probably due
to overlap with intense signals of the Ph groups; 13C-{1H}
Crystals of the cis isomer suitable for X-ray diffraction study
were obtained by evaporation of a dichloromethane–diethyl
ether solution of the isomeric mixture at room temperature.
Reaction of Ph C᎐NH and [PtCl (MeCN) ]
᎐
2
2
2
The previously described reaction20 between Ph C᎐NH and
᎐
2
NMR in CDCl3 δ 24.1 (Me), 128.5 and 129.6 (CHortho
meta),
and
[PtCl2(MeCN)2] (the authors reported the reaction with trans-
[PtCl2(MeCN)2] as the starting material although the complex
is, in fact, a mixture of cis and trans isomers where the trans
form is the minor component, i.e. 16%22) was reproduced. In
our hands complete homogenization of the reaction mixture
was reached after 3 d (10 d in Ref. 20) at 20–25 ЊC. However,
the reaction mixture was stirred for 10 d and then the solvent
was evaporated to dryness and the residue subjected to both
TLC and NMR monitoring that allowed identification of
131.5 (CHpara), 135.9 (Cipso)(Ph), 168.2 (C᎐N) and 175.9
᎐
(C᎐NH); 195Pt NMR in CDCl3 δ Ϫ2119 (580 Hz). Minor iso-
᎐
mer: 1H NMR in CDCl3 δ 1.93 (s, 3H, Me), 7.4–7.55 (6H, signal
overlapped by the one due to the major isomer), 7.68 (d, J 7.5
Hz, 4H)(Ph), NH not detected probably due to overlap with
intense signals of the Ph groups; 13C-{1H} NMR in CDCl3
δ 24.7 (Me), 128.1 and 129.4 (CHortho
meta), 130.8 (CHpara),
and
(Cipso)(Ph), (C᎐N) and (C᎐NH) not detected; 195Pt NMR not
᎐
᎐
detected.
the two isomers of [PtCl {NH᎐C(Me)N᎐CPh } ] obtained in
᎐
᎐
2
2 2
the independent synthesis (see below).
trans-[PtCl {NH᎐C(Et)N᎐CPh } ]. Yield 76%. Calc. for
᎐
᎐
2
2 2
C32H32Cl2N4Pt: C, 52.04; H, 4.37; N, 7.59%. Found: C, 51.80;
H, 4.27; N, 7.59. FABϩ-MS: m/z 761, [M ϩ Na]ϩ; 738, [M]ϩ;
and 667 [M Ϫ 2Cl]ϩ. mp = 207–208 ЊC (decomp.). IR spectrum
Reaction of Ph C᎐NH and [PtCl (PhCN) ]
᎐
2
2
2
Ph C᎐NH (30 mg, 0.170 mmol) was added to a solution of
᎐
2
in KBr, selected bands, cmϪ1
: 3239m-w ν(N–H), 1648s
[PtCl2(PhCN)2] (a mixture of cis and trans isomers;38 40 mg,
0.085 mmol) in CHCl3 (5 mL) at 20–25 ЊC and the reaction
mixture left to stand for 2 h, whereafter the yellow precipitate
(22 mg) formed (complex A) was removed by filtration. The
filtrate was subjected to column chromatography [Merck silica
gel 60 (70–230 mesh), eluent CH2Cl2–Et2O 5:1, v/v] to separate
a rather intensively colored yellow complex B (TLC: Rf = 0.68,
eluent chloroform–acetone 20:1, v/v).
ν(C᎐N), 1596s ν(C᎐C) and 690s δ(C–H). TLC (eluent
᎐
᎐
chloroform–acetone 15:1): Rf = 0.65. 1H NMR in CDCl3:
δ 0.95 (t, J 7.5, 3H) and 2.14 (q., J 7.8, 2H)(Et), 7.28 (t, J 7.8,
4H), 7.40 (t, J 7.2, 2H) and 7.71 (d, J 8.1 Hz, 4H)(Ph), NH not
detected (may be overlapped by intense signals of Ph groups).
13C-{1H} NMR in CDCl3: δ 9.7 and 30.5 (Et), 128.2 and 129.6
(CHortho
᎐
meta), 130.7 (CHpara), 136.0 (Cipso)(Ph), 166.4
and
(C᎐N) and 180.8 (C᎐NH). 195Pt NMR in CDCl3: δ Ϫ2026 (680
Complex A is a highly insoluble material and we were unable
to obtain its FABϩ-MS (3-nitrobenzyl alcohol and glycerol
matrixes) and NMR spectra. However, its elemental analyses
and IR spectrum give certain evidence in favor of the product
᎐
Hz).
cis- and trans-[PtCl {NH᎐C(Et)N᎐CPh } ]. The amount of
᎐
᎐
2
2 2
of monosubstitution, i.e. [PtCl (HN᎐CPh )(PhCN)] or, in view
the isolated platinum() complex cis-[PtCl {NH᎐C(Et)N᎐
᎐ ᎐
4
᎐
2
2
of its insolubility, of the polymeric coupled product [PtCl2-
{µ-N,N-NH᎐C(Ph)N᎐CPh }] [Calc. for C20H16Cl2N2Pt: C,
CPh2}2] was insufficient to perform synthetic experiments.
Therefore the reduction was carried out starting from the cis/
᎐
᎐
2
∞
43.63; H, 2.91; N, 5.10. Found: C, 44.40; H, 2.91; N, 5.10%.
mp = 189–192 ЊC (decomp.). IR spectrum in KBr, selected
bands, cmϪ1: 3225m-w ν(N–H), 1652s ν(C᎐N), 1595s ν(C᎐C)
trans isomeric mixture of [PtCl {NH᎐C(Et)N᎐CPh } ]. Yield is
᎐ ᎐
4 2 2
1
–
72%. Calc. for C32H32Cl2N4Ptؒ CH2Cl2: C, 50.98; H, 4.31; N,
7.37. Found: C, 51.23; H, 4.23;4N, 7.20%. FABϩ-MS: m/z 761,
[M ϩ Na]ϩ; 738 [M]ϩ; and 667, [M Ϫ 2Cl]ϩ. mp = 201–203 ЊC
(decomp.). IR spectrum in KBr, selected bands, cmϪ1: 3246m-w
᎐
᎐
and 695s δ(C–H)].
[PtCl (HN᎐CPh ){NH᎐C(Ph)N᎐CPh }] B. Yield 27%. Calc.
᎐
᎐
᎐
2
2
2
for C33H27Cl2N3Ptؒ¹CH2Cl2: C, 52.04; H, 3.62; N, 5.44. Found:
ν(N–H), 1635s ν(C᎐N) and 699s δ(C–H). TLC (eluent
᎐
¯
²
C, 52.16; H, 3.53; N, 5.58%. FABϩ-MS: m/z 754, [M ϩ Na]ϩ;
chloroform–acetone = 15:1) displayed two spots with Rf = 0.65
and 0.47 (the latter is dominant in intensity). NMR character-
istics of the cis isomer were obtained by comparison of spectra
731, [M]ϩ; 695 [M Ϫ HCl]ϩ; and 661, [M Ϫ 2HCl]ϩ. mp = 169–
171 ЊC (decomp.). IR spectrum in KBr, selected bands, cmϪ1
:
3225m-w ν(N–H), 1624s ν(C᎐N), 1598s ν(C᎐C) and 695s
of cis/trans-[PtCl {NH᎐C(Et)N᎐CPh } ] with those of pure
᎐ ᎐
2 2 2
᎐
᎐
564
J. Chem. Soc., Dalton Trans., 2001, 560–566

View Article Online
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᎐
2
2 2
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272.
ing indicated that the compound is a mixture of two isomers in
an approximate ratio 20:10. cis Isomer (the major isomer): 1H
NMR in CDCl3 δ 0.85 (t, J 7.5, 3H) and 2.10 (q, J 7.2 Hz,
2H)(Et), 7.47 (t, J 7.5, 4H), 7.52 (t, J 7.0, 2H) and 7.86 (d, J 7.8
Hz, 4H)(Ph), NH not detected (may be overlapped by intense
signals of Ph groups); 13C-{1H} NMR in CDCl3 δ 9.5 and 30.0
(Et), 128.5 and 129.7 (CHortho
meta), 131.5 (CHpara), 136.1
and
(Cipso)(Ph), 168.0 (C᎐N) and 179.9 (C᎐NH); 195Pt NMR in
᎐
᎐
CDCl3 δ Ϫ2143 (620 Hz). The minor isomer is trans-
[PtCl {NH᎐C(Et)N᎐CPh } ] (see above).
᎐
᎐
2
2 2
Liberation of the 1,3-diaza-1,3-diene from trans-[PtCl {NH᎐
᎐
2
C(Et)N᎐CPh } ]
᎐
2
2
dppe (9.7 mg, 0.024 mmol) was added at room temperature to a
solution of trans-[PtCl {NH᎐C(Et)N᎐CPh } ] (9.0 mg, 0.012
᎐
᎐
2
2 2
mmol) in chloroform (2 mL). A colorless crystalline precipitate
of [Pt(dppe)2]Cl2 was filtered off after 30 min (11.5 mg, 98%),
the filtrate was evaporated to dryness under a flow of dinitrogen
at 20–25 ЊC, redissolved in CDCl3 and the “free” ligand charac-
1
terized by NMR spectroscopy. H NMR in CDCl3: δ 1.05 (t,
J 7.4, 3H)(Me), 2.16 (q, J 7.3 Hz, 2H)(CH2) and 7.30–7.50 (m,
10H)(Ph). 13C-{1H} NMR in CDCl3: δ 9.9 (CH3), 29.5 (CH2),
126.6–137.0 (phenyl C), 138.3 (Cipso) 165.2 (C᎐N) and 178.3
᎐
(C᎐NH).
᎐
11 A. Romero, A. Vegas and A. Santos, J. Organomet. Chem., 1986,
310, C8; J. Lopez, A. Santos, A. Romero and A. M. Echavarren,
J. Organomet. Chem., 1993, 443, 221; C. J. Jones, J. A. McCleverty
and A. S. Rothim, J. Chem. Soc., Dalton Trans., 1986, 109; M. O.
Albers, S. F. A. Crosby, D. C. Liles, D. J. Robinson, A. Shaver and
E. Singleton, Organometallics, 1987, 6, 2014; M. A. Cinellu,
S. Stoccoro, G. Minghetti, A. L. Bandini, G. Banditelli and
B. Bovio, J. Organomet. Chem., 1989, 372, 311; C. Pearson and
A. L. Beauchamp, Inorg. Chem., 1998, 37, 1242; K. S.-Y. Leung and
W.-T. Wong, J. Chem. Soc., Dalton Trans., 1998, 1939.
1
–
Complex [Pt(dppe)2]Cl2. Calc. for C52H48Cl2P4Ptؒ8CDCl3: C,
58.09; H, 4.46. Found: C, 57.92; H, 4.36%. IR spectrum in KBr,
selected bands, cmϪ1: 1481m-w ν(P–CPh), 1435s ν(P–CH2),
1
695 and 701s δ(C–HPh). H NMR in CDCl3: δ 3.38 (t, 6.90
Hz, 4H)(CH2) and 7.30–7.70 (m, 20H)(Ph). 31P-{1H} NMR in
CDCl3 (relative to H3PO4): δ 47.7 (2364 Hz) [lit.39 31P NMR
spectrum in CDCl3: δ 47.0 (2360 Hz)].
12 P. F. Kelly and A. M. Z. Slawin, J. Chem. Soc., Chem. Commun.,
1999, 1081.
Acknowledgements
13 V. Yu. Kukushkin, T. B. Pakhomova, Yu. N. Kukushkin, R.
Herrmann, G. Wagner and A. J. L. Pombeiro, Inorg. Chem., 1998,
37, 6511.
14 V. Yu. Kukushkin, T. B. Pakhomova, N. A. Bokach, G. Wagner, M.
L. Kuznetsov, M. Galanski and A. J. L. Pombeiro, Inorg. Chem.,
2000, 39, 216.
15 G. Wagner, A. J. L. Pombeiro, N. A. Bokach and V. Yu. Kukushkin,
J. Chem. Soc., Dalton Trans., 1999, 4083; V. Yu. Kukushkin, I. V.
Ilichev, G. Wagner, J. J. R. Fraústo da Silva and A. J. L. Pombeiro,
J. Chem. Soc., Dalton Trans., 1999, 3047; V. Yu. Kukushkin, I. V.
Ilichev, M. A. Zhdanova, G. Wagner and A. J. L. Pombeiro,
J. Chem. Soc., Dalton Trans., 2000, 1567.
16 V. Yu. Kukushkin, T. Nishioka, S. Nakamura, I. Kinoshita and K.
Isobe, Chem. Lett., 1997, 189; Yu. N. Kukushkin, N. P. Kiseleva, E.
Zangrando and V. Yu. Kukushkin, Inorg. Chim. Acta, 1999, 285,
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Soc., Chem. Commun., 1988, 1052; A. J. L. Pombeiro, New J. Chem.,
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A. J. L. Pombeiro, J. Chem. Soc., Dalton Trans., 1994, 3299; M. F. C.
Guedes da Silva, J. J. R. Fraústo da Silva, A. J. L. Pombeiro,
C. Amatore and J.-N. Verpeaux, Organometallics, 1994, 13, 3943;
M. F. C. Guedes da Silva, J. J. R. Fraústo da Silva, A. J. L.
Pombeiro, C. Amatore and J.-N. Verpeaux, Inorg. Chem., 1998, 37,
2344; L. M. D. R. S. Martins, M. T. Duarte, A. M.
Galvão, C. Resende, A. J. L. Pombeiro, R. A. Henderson and
D. J. Evans, J. Chem. Soc., Dalton Trans., 1998, 3311; V. Yu.
Kukushkin, I. V. Ilichev, G. Wagner, M. D. Revenco, V. H. Kravtsov
and K. Suwinska, Eur. J. Inorg. Chem., 2000, 1315.
D. G. and G. W. are grateful to the PRAXIS XXI program for
fellowships (BPD16368/98 and BPD11779/97). V. Yu. K. is very
much obliged to INTAS (grant 97-0166) and the PRAXIS XXI
program (grant BCC16428/98) for financial support of this
study. V. Yu. K. and M. H. thank the Nordic Council of
Ministers for a grant. A. J. L. P. thanks the FCT (Foundation
for Science and Tecnology) and the PRAXIS XXI program
(Portugal) for financial support. The authors thank Dr Irina A.
Balova for valuable comments on the manuscript, Dr M. F. C.
Guedes da Silva, Dr M. N. Kopylovich and Mrs N. A. Bokach
for experimental assistance.
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