Some reactions of an η3-tetracyanobutadienyl-ruthenium complex

Article abstract of DOI:10.1039/b921324d

In the η³-butadienyl complex Ru{η³-C(CN) ₂CPhCC(CN)₂}(PPh₃)Cp 1, which is formed from Ru(CCPh)(PPh₃)₂Cp and tcne, a CN group reacts with MeO^- to give the methoxy-amide Ru{NHC(OMe)C(CN)CCPhC(CN) ₂}(PPh₃)Cp 2, in which the NH has displaced the CC from the Ru centre with formation of a RuC₃N ring. Click addition of azide to a CN group in 1 gives the oligomeric tetrazolato complex Ru{N₃N[Na(OEt₂)]CC(CN)CCPhC(CN) ₂}(PPh₃)Cp 3, also containing a RuC₃N ring. Salt-elimination reactions of 3 with MeOTf, FeCl(dppe)Cp, RuCl(dppe)Cp* and trans-PtCl₂{P(tol)₃}₂ result in selective substitution at one nitrogen atom of the RuC₃N ring. Geometries of 1 and the anion in 3 were computed by DFT methods. Preferences for CN groups attacked in the nucleophilic and cycloaddition reactions of 1 are supported by NBO calculations. Alkylation of 1 in reactions with 1,2-dimethoxyethane gave two isomers of Ru{N₃[CH(CH₂OMe)(OMe)]NCC(CN)CCPhC(CN) ₂}(PPh₃)Cp 8 and 9, differing in the sites of attachment of the alkyl group, likely by radical processes. The molecular structures of eight complexes are reported, including a re-determination of 1. Computed NMR chemical shifts are used to reassign the butadienyl carbon resonances in the ¹³C NMR spectrum of 1.

Full text of DOI:10.1039/b921324d

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PAPER
www.rsc.org/dalton | Dalton Transactions
Some reactions of an g3-tetracyanobutadienyl-ruthenium complex†
Michael I. Bruce,*a Mark A. Fox,b Paul J. Low,b Brian W. Skeltonc and Natasha N. Zaitsevaa
Received 12th October 2009, Accepted 29th January 2010
First published as an Advance Article on the web 11th March 2010
DOI: 10.1039/b921324d
3
3
=
In the h -butadienyl complex Ru{h -C(CN)2CPhC C(CN)2}(PPh3)Cp 1, which is formed from
-
≡
Ru(C CPh)(PPh3)2Cp and tcne, a CN group reacts with MeO to give the methoxy-amide
=
=
=
=
Ru{NH C(OMe)C(CN) CCPh C(CN)2}(PPh3)Cp 2, in which the NH has displaced the C C from
the Ru centre with formation of a RuC3N ring. “Click addition” of azide to a CN group in 1 gives the
=
=
=
oligomeric tetrazolato complex Ru{N3N[Na(OEt2)] CC(CN) CCPh C(CN)2}(PPh3)Cp 3, also
containing a RuC3N ring. Salt-elimination reactions of 3 with MeOTf, FeCl(dppe)Cp, RuCl(dppe)Cp*
and trans-PtCl2{P(tol)3}2 result in selective substitution at one nitrogen atom of the RuC3N ring.
Geometries of 1 and the anion in 3 were computed by DFT methods. Preferences for CN groups
attacked in the nucleophilic and cycloaddition reactions of 1 are supported by NBO calculations.
Alkylation of 1 in reactions with 1,2-dimethoxyethane gave two isomers of Ru{N3[CH(CH2OMe)-
=
=
=
(OMe)]N CC(CN) CCPh C(CN)2}(PPh3)Cp 8 and 9, differing in the sites of attachment of the alkyl
group, likely by radical processes. The molecular structures of eight complexes are reported, including a
re-determination of 1. Computed NMR chemical shifts are used to reassign the butadienyl carbon
resonances in the 13C NMR spectrum of 1.
≡
The reaction between tcne and Ru(C CPh)(PPh3)2Cp affords
directly the h -butadienyl 1 (complex C in Scheme 1) in high
Introduction
3
yield (Scheme 3).11 In this paper we describe an investigation into
some chemistry of 1 with a view to discover further examples of
cyclic complexes. We have re-determined the structure of 1 using
a polymorph which does not exhibit the disorder found initially
and have carried out DFT studies on complex 1 and some of its
reaction products.
After the initial report of the addition of the electron-poor olefin
tetracyanoethene, C2(CN)4 (tcne), to alkynyl-iron complexes,1
extensive studies with other transition metal alkynyl complexes
showed that this reaction proceeds via an initial intensely-coloured
radical species (presently structurally unidentified) to form the
[2 + 2]-cycloadduct A, which then undergoes a more or less
1
rapid ring-opening reaction to form an h -butadienyl complex B
(Scheme 1).2-10 If weakly bonded ligands are present on the metal
centre, then displacement of one of these and chelation to give
3
an h -butadienyl C may occur.2,3,8,9,11-14 This type of reaction also
Results
15,16
=
occurs with related cyanoethenes such as (CF3)2C C(CN)2,
The extensive chemistry of tcne includes many examples of the
characteristic nucleophilic displacement of one or two CN groups
by alcohols, thiols, amines and similar reagents.21-23 Consequently,
our first foray into the chemistry of 1 involved astudyofits reaction
with sodium methoxide. The reaction between 1 and NaOMe, car-
ried out in a MeOH–thf mixture, resulted in a slow colour change
from yellow to red-brown over a period of 48 h at r.t. Conventional
work-up afforded dark red crystals of the cyclic amido derivative
CH(CO2Me) C(CO2Me)CN and PhCH C(CN)2.18,19 As far as
we are aware, the only reactions which have been reported for
ruthenium complexes of type C are the addition of a ligand L¢ to
17
=
=
1
give the h -butadienyl D.3,11,19
However, serendipitous hydrolysis or methanolysis of one
of the CN groups has also been found to occur with the
=
=
related complexes W{C(CY CX2) C(CN)2}(CO)3Cp (X =
CF3, Ph or CN, Fc) of type
to give the five-membered metallacyclic complexes of type
Y
=
X
=
Y
=
B
=
=
Ru{NHC(OMe)C(CN) CCPh C(CN)2}(PPh3)Cp 2 (Scheme 3)
in 72% yield. This compound was characterised by a single-crystal
X-ray structural determination while the elemental microanalysis
and spectroscopic properties were in accord with the solid-state
structure.
=
=
=
W{NH C(OR)C(CN) C(CY CX2)}(CO)2Cp (R
=
H or
Me; Scheme 2).7,15 Similar cyclic complexes M{NH C(OH)-
=
=
C(CN) CH}(CO)2Cp (M = Mo, W) have been obtained from
20
=
hydrolysis of M{CCl C(CN)2}(CO)3Cp.
The IR spectrum of 2 contained n(CN) bands at 2203 and
2226 cm-1, accompanied by several weak to medium intensity
absorptions between 1520 and 1733 cm-1. The 1H NMR spectrum
contained resonances at d 3.62 (OMe), 4.46 (Cp), 6.53 (NH)
and between 6.67 and 7.53 (Ph), while the 31P NMR spectrum
contains a singlet at d 46.9. The extremely low solubility of 2
rendered attempts to obtain the 13C NMR spectrum fruitless. In the
electrospray mass spectrum (ES-MS) from a solution containing
NaOMe, an ion at m/z 713 is assigned to [M + Na]+.
aSchool of Chemistry & Physics, University of Adelaide, Adelaide, South
Australia, 5005. E-mail: michael.bruce@adelaide,edu.au; Fax: + 61 8 8303
4358
bDepartment of Chemistry, Durham University, South Road, Durham, UK
DH1 3LE
cChemistry M313, School of Biomedical, Biomolecular and Chemical
Sciences, University of Western Australia, Crawley, Western Australia, 6009
† CCDC reference numbers 730741–730749. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/b921324d
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The Royal Society of Chemistry 2010
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Scheme 1 The reaction of tcne with an alkynyl metal complex to afford a [2 + 2]-cycloadduct, and subsequent transformations.
were assigned to the five C(1–5) atoms in the bicyclic ligand. In
the ES-MS, ions at m/z 724 and 746 correspond to [anion +
(H + Na)]+ and [anion + 2Na]+, respectively, where the anion
is [Ru{N4CC(CN)CCPhC(CN)2}(PPh3)Cp]-. In the negative-ion
mode, the ion at m/z 700 corresponds to [M - Na(OEt2)]-.
A
minor product from the reaction affording
3 was
crystallographically identified as the binuclear complex Ru{N2N-
=
=
=
[Ru(PPh3)2Cp]N CC(CN) CCPh C(CN)2}(PPh3)Cp 4, in
which the Na(OEt2) fragment has been replaced by Ru(PPh3)2Cp.
This reaction requires migration of PPh3 from part of the reactant,
but the reaction between 3 and RuCl(PPh3)2Cp afforded this
complex in 91% yield, demonstrating that 3 could be a source
of binuclear systems containing the tetrazolate bridging group.
Accordingly, similar reactions between 3 and FeCl(dppe)Cp and
trans-PtCl2{P(tol)3}2 afforded the heterometallic compounds Ru-
Scheme 2 The hydrolysis and methanolysis of a CN group in W
complexes of type B.
The “click” reaction24,25 between 1 and NaN3 was carried
out in refluxing 1,2-dimethoxyethane (dme) for 24 h, a dark
red-purple colour developing over this period. Preparative t.l.c.
enabled the separation of the bicyclic tetrazolate as the sodium
=
=
=
salt Ru{N3N[Na(OEt2)] CC(CN) CCPh C(CN)2}(PPh3)Cp 3
in 88% yield. Spectroscopic data are consistent with the solid-
state structure, with n(CN) bands at 2194 and 2220 cm-1 in the
IR spectrum, and resonances for the Cp [dH 4.33, dC 79.8 (d,
J(CP) = 2 Hz)] and Ph groups (dH 7.09–7.50, dC 127.9–134.0)
being accompanied by signals for the coordinated Et2O. The CN
groups gave three resonances (dC 115.6–116.7) and various signals
found at dC 72.3, 100.1, 168.3, 188.5 and 221.0 [d, J(CP) = 11 Hz]
=
=
=
{N2N[Fe(dppe)Cp]N CC(CN) CCPh C(CN)2}(PPh3)Cp
5
= =
Ru{N3N[cis-PtCl{P(tol)3}2] CC(CN) CCPh
=
(76%)
and
C(CN)2}(PPh3)Cp 6 (74%) respectively. Both were characterised
by single-crystal X-ray structure determinations and elemental
microanalyses. In the IR spectra, there are two n(CN) bands
between 2198 and 2222 cm-1, while the 1H and 31P NMR spectra
contain resonances arising from the Cp and tertiary phosphine
Scheme 3 The formation of 1 and subsequent reactions.
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ligands. 195Pt satellites were present on the P(tol)3 signals at dP
3.98 and 14.3 [J(PP) = 19 Hz, J(PPt) = 3322 Hz], consistent
with the cis stereochemistry. Again, for solubility reasons, a 13C
NMR spectrum could be obtained only for 6 and, in addition to
resonances for the Me (d 21.4), Cp (d 79.8) and aromatic carbons
(d 125.9–135.2) three CN signals (d 114.4, 114.9, 116.3) and
three carbons of the tetrazolate ligand (d 71.6, 97.2, 185.9) were
present. The ES-MS contained [M + H + Na]+ (for 4) or [M +
Na]+ (for 5 and 6) ion clusters.
=
Treatment of 3 with MeOTf afforded red Ru{N3NMe CC-
=
=
(CN) CCPh C(CN)2}(PPh3)Cp 7, for which the presence of the
1
NMe group was indicated by a H NMR signal at dH 3.89. In
the ES-MS, major ions include [2M + Na]+ and [M + Na]+
at m/z 1453 and 738, respectively. The molecular structure was
confirmed by a single-crystal X-ray structure determination. A
related complex was obtained serendipitously from the reaction
between 3 and cis-RuCl2(dppe)2 carried out in dme. The red-
brown product was not the expected diruthenium derivative,
but identified by an X-ray diffraction study as being formed
by alkylation of the N(5) atom by the solvent dme, namely
=
=
=
Ru{N2N[CH(CH2OMe)(OMe)]N CC(CN) CCPh C(CN)2}-
(PPh3)Cp 8. Identification of this complex was also confirmed by
the ES-MS, which contains [2M + Na]+, [M + Na]+ and M+ ions
at m/z 1603, 812 and 790, respectively. In a separate experiment
it was established that prolonged heating of 3 in dme at reflux
point, in the absence of any other reagents, resulted in formation
of 8 (21%) together with its isomer 9 (12%), the latter also being
identified by a single-crystal X-ray structure determination. We
did not find any evidence for a tautomeric equilibrium between
these two compounds.
=
=
Fig. 2 Plot of a molecule of Ru{NHC(OMe)C(CN) CCPh C(CN)2}-
(PPh3)Cp 2.
Molecular structures
The structures of all complexes 1–9 have been determined by crys-
tallographic methods, single molecules of each being illustrated in
Fig. 1–8, significant structural parameters for all new complexes
being collected in the caption to Fig. 1 (for 1) and in Table 1 (2–9).
Fig. 3 Plot of a fragment of the polymeric structure of Ru{N3N-
=
=
=
[Na(OEt2)] CC(CN) CCPh C(CN)2}(PPh3)Cp 3.
3
=
The molecular structure of complex Ru{h -C(CN)2CPhC C-
(CN)2}(PPh3)Cp 1 was reported in our first communication.11
Some disorder was present in the crystal, resulting in less than
precise bond parameters being determined, of which the most
interesting is the interaction between C(3) and the Ru centre.
˚
The Ru–C(3) distance [1.919(5) A] was found to be shorter than
˚
the other two Ru–C separations [2.231, 2.135(4) A], suggesting
3
=
Fig. 1 Plot of a molecule of Ru{h -C(CN)2CPhC C(CN)2}(PPh3)Cp
some degree of multiple-bond character. The present structure
determination of 1 (Fig. 1), from a crystal obtained from MeCN–
Et2O, refined satisfactorily with no signs of anisotropy in C(3)
and has yielded bond parameters (see caption to Fig. 1) which are
more precise that those obtained in the earlier determination. In
particular, the coordination of the Ru centre by the cyanocarbon
1. Bond lengths: Ru(1)–P(1) 2.3734(8), Ru(1)–C(cp) 2.203–2.264(3), av.
2.224, Ru(1)–C(1) 2.182(3), Ru(1)–C(2) 2.130(3), Ru(1)–C(3) 1.979(3),
C(1)–C(2) 1.469(4), C(2)–C(3) 1.426(5), C(3)–C(4) 1.354(5) A. Bond
angles: P(1)–Ru(1)–C(1,2) 93.99(9), 115.29(9), P(1)–Ru(1)–C(3) 95.16(9),
C(1)–Ru(1)–C(3) 71.4(1), C(1)–C(2)–C(3) 114.4(3), C(2)–C(3)–C(4)
134.8(3)◦.
˚
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Table 1 Selected structural data for complexes 2–9
Complex
2
3
4
5
6
7
8
9
˚
Bond distances/A
Ru(1)–P(1)
Ru(1)–C(cp)
(av.)
2.3152(3)
2.2965(8)
2.3127(6)
2.301(2)
2.306(2)
2.3262(6)
2.3242(5)
2.3211(5)
2.189–2.245(1) 2.191–2.224(4) 2.176–2.231(2) 2.155–2.185(12) 2.184–2.227(9) 2.208–2.239(2) 2.194–2.226(2) 2.195–2.247(2)
2.215
2.208
2.200
2.170
2.207
2.221
2.210
2.218
Ru(1)–C(3)
Ru(1)–N(52)
C(1)–C(2)
C(2)–C(3)
C(3)–C(4)
2.043(1)
2.106(1)
1.370(2)
1.457(2)
1.377(2)
1.441(2)
1.295(2)
2.047(3)
2.076(3)
1.379(5)
1.464(4)
1.369(5)
1.442(4)
1.348(4)
1.331(4)
1.346(4)
1.309(4)
1.365(4)
2.050(2)
2.095(2)
1.364(3)
1.462(3)
1.366(3)
1.450(3)
1.345(2)
1.330(3)
1.341(2)
1.330(2)
1.350(2)
2.055(9)
2.057(8)
1.39(1)
1.46(1)
1.36(1)
1.43(1)
1.35(1)
1.33(1)
1.33(1)
1.33(1)
1.37(1)
2.038(7)
2.059(7)
1.36(1)
1.48(1)
1.36(1)
1.44(1)
1.352(9)
1.32(1)
1.351(9)
1.323(9)
1.347(8)
1.47, 1.45(1)
1.48(1)
2.035(2)
2.082(2)
1.361(2)
1.470(3)
1.376(3)
1.436(3)
1.335(3)
1.341(3)
1.363(2)
1.300(3)
1.360(3)
2.052(2)
2.057(2)
1.364(3)
1.466(3)
1.370(3)
1.436(3)
1.364(3)
1.320(3)
1.326(2)
1.318(3)
1.336(3)
2.033(2)
2.057(2)
1.362(3)
1.463(3)
1.392(2)
1.437(2)
1.337(2)
1.348(2)
1.366(2)
1.290(2)
1.366(2)
C(4)–C(51)
C(51)–N(52)
C(51)–N(55)
N(52)–N(53)
N(53)–N(54)
N(54)–N(55)
C(1)–C(11,12)
C(2)–C(21)
1.439, 1.432(2) 1.441, 1.431(5) 1.445, 1.447(3) 1.43, 1.42(2)
1.486(2)
1.432(2)
1.448, 1.441(3) 1.443, 1.439(3) 1.445, 1.435(3)
1.491(3)
1.437(3)
1.482(5)
1.435(5)
1.483(3)
1.432(3)
1.49(2)
1.42(2)
1.485(3)
1.437(3)
1.485(3)
1.431(3)
C(4)–C(41)
1.46(1)
Bond angles/◦
P(1)–Ru(1)–C(3)
P(1)–Ru(1)–N(52)
C(3)–Ru(1)–N(52)
Ru(1)–C(3)–C(2)
Ru(1)–C(3)–C(4)
97.98(3)
91.28(3)
76.82(4)
124.75(8)
116.08(8)
95.49(9)
90.84(8)
75.8(1)
97.71(6)
86.98(5)
76.41(7)
121.6(2)
118.4(2)
116.6(1)
136.4(1)
120.6(2)
119.4(2)
113.3(2)
115.2(2)
133.0(2)
106.9(2)
103.0(2)
106.0(2)
112.4(2)
111.7(2)
96.7(3)
90.1(2)
75.7(3)
95.9(2)
80.9(2)
76.2(3)
94.87(6)
86.78(5)
76.27(8)
122.6(2)
118.6(2)
116.7(2)
136.1(2)
120.8(2)
118.6(2)
112.4(2)
115.8(2)
136.7(2)
107.0(2)
108.6(2)
109.8(2)
107.0(2)
107.6(2)
97.85(5)
87.74(5)
76.52(7)
120.7(1)
118.0(1)
117.7(1)
135.0(1)
121.2(2)
120.7(2)
113.6(2)
114.2(2)
134.2(2)
107.3(2)
94.87(5)
89.73(5)
76.48(7)
121.5(1)
118.0(1)
117.5(1)
134.8(1)
119.2(2)
119.7(2)
112.0(2)
115.3(2)
137.6(2)
107.6(2)
108.3(2)
109.45(2)
107.6(2)
107.0(2)
122.5(2)
118.1(2)
118.1(2)
135.9(2)
116.7(3)
118.8(3)
113.8(3)
113.5(3)
119.2(7)
118.4(7)
117.9(7)
135.8(6)
119.4(1)
122.1(9)
113.4(9)
114.5(9)
133.6(9)
105.7(8)
104.1(7)
108.8(8)
109.7(8)
111.7(9)
121.2(6)
118.7(6)
117.5(5)
135.7(5)
121.2(8)
119.5(7)
112.8(7)
114.5(7)
136.9(7)
106.8(6)
107.9(6)
108.3(6)
108.3(6)
108.5(7)
Ru(1)–N(52)–C(51) 116.74(8)
Ru(1)–N(52)–N(53)
C(1)–C(2)–C(3)
119.0(1)
118.8(1)
114.8(1)
115.6(1)
C(2)–C(3)–C(4)
C(3)–C(4)–C(51)
C(4)–C(51)–N(52)
C(4)–C(51)–N(55)
C(51)–N(52)–N(53)
C(51)–N(55)–N(54)
N(52)–N(53)–N(54)
N(53)–N(54)–N(55)
N(52)–C(51)–N(55)
105.9(3)
104.0(3)
108.2(3)
110.7(3)
111.3(3)
104.4(2)
115.2(2)
111.5(2)
◦
˚
For 2: C(51)–O(5) 1.336(1), C(5)–O(5) 1.433(2) A; C(4)–C(51)–O(5) 115.9(1), C(5)–O(5)–C(51) 118.5(1) . For 3: Na(1)–N(41¢) 2.403(3), Na(1)–N(53¢¢)
˚
2.427(3), Na(1)–N(54¢¢) 2.585(3), Na(1)–N(55) 2.367(3), Na(1)–O(03) 2.438(4) A; N(41¢)–Na(1)–N(53¢¢) 108.6(1), N(41¢)–N(1)–N(54¢¢) 134.7(1), N(41¢)–
Na(1)–N(55) 94.2(1), N(41¢)–Na(1)–O(03) 98.1(1), N(53¢¢)–Na(1)–N(54¢¢) 30.07(9), N(53¢¢)–Na(1)–N(55) 137.7(1), N(53¢¢)–Na(1)–O(03) 102.1(1), N(54¢¢)–
Na(1)–N(55) 111.4(1), N(54¢¢)–Na(1)–O(03) 106.9(1), N(55)–Na(1)–O(03) 109.5(1)◦, where ¢ and ¢¢ refer to the atoms at -x, 1/2 + y, 1/2 - z and -x, y - 1/2,
˚
1/2 - z, respectively. For 4: Ru(2)–P(2,3) 2.3393(6), 2.3228(6), Ru(2)–C(cp) 2.216–2.231(2), (av.) 2.220, Ru(2)–N(54) 2.085(2) A; P(2)–Ru(2)–P(3) 99.63(2),
P(2,3)–Ru(2)–N(54) 92.33(5), 88.35(5), Ru(2)–N(54)–N(53, 55) 121.7(1), 125.9(1)◦. For 5: Fe(2)–P(2,3) 2.220(4), 2.187(3), Fe(2)–C(cp) 2.06–2.11(1), (av.)
◦
˚
2.08, Fe(2)–N(54) 2.008(9) A; P(2)–Fe(2)–P(3) 83.6(1), P(2, 3)–Fe(2)–N(54) 92.2(2), 95.1(3), Fe(2)–N(54)–N(53, 55) 124.0(7), 125.2(6) . For 6: Pt(1)–Cl(1)
2.336(2), Pt(1)–N(55) 2.058(6), Pt(1)–P(2, 3) 2.254(2), 2.268(2) A; Cl(1)–Pt(1)–N(55) 87.3(2), Cl(1)–Pt(1)–P(2, 3) 86.61(7), 175.68(8), N(55)–Pt(1)–P(2,
˚
◦
˚
3) 89.9(2), 172.5(2), P(2)–Pt(1)–P(3) 96.47(7), Pt(1)–N(55)–C(51) 133.3(5), Pt(1)–N(55)–N(54) 118.2(5) . For 7: N(55)–C(55) 1.465(3) A; C(51)–N(55)–
C(55) 130.6(2), C(51)–N(55)–N(54) 108.6(2), C(55)–N(55)–N(54) 120.8(2)◦. For 8: C(03)–N(54) 1.503(3), C(03)–O(02) 1.326(4), C(03)–C(04) 1.532(4),
˚
C(01)–O(02) 1.429(5), C(04)–O(05) 1.377(3), C(06)–O(05) 1.439(4) A; C(03)–N(54)–N(53, 55) 121.4(2), 122.1(2), N(54)–C(03)–O(02) 111.3(3), N(54)–
C(03)–C(04) 109.8(2), C(01)–O(02)–C(03) 115.1(3), C(03)–C(04)–O(05) 107.0(2), C(04)–O(05)–C(06) 112.1(2), N(52)–C(51)–C(4) 114.2(2), O(02)–C(03)–
C(04) 112.9(2)◦. For 9: C(03)–N(55) 1.481(2), C(03)–O(02) 1.383(3), C(03)–C(04) 1.539(3), C(01)–O(02) 1.432(3), C(04)–O(05) 1.425(3), C(06)–O(05)
˚
1.417(3) A; C(03)–N(55)–N(54) 119.3(2), N(55)–C(03)–O(02) 111.7(2), N(55)–C(03)–C(04) 107.4(2), C(01)–O(02)–C(03) 113.4(2), C(03)–C(04)–O(05)
107.3(2), C(04)–O(05)–C(06) 114.6(2), N(52)–C(51)–C(4) 115.2(2), O(02)–C(03)–C(04) 109.1(2)◦.
ligand is more accurately determined. The presently determined
Common features of the structures of 2–9 include the
Ru(PPh3)Cp group chelated by a C3N fragment which carries
the 1,1-dicyano-2-phenylvinyl substituent on C(3) that forms part
of the h -dienyl ligand present in 1, now displaced by N(5)
of the new ligand. The ruthenium atom is pseudo-octahedrally
˚
values for Ru–C(1, 2, 3) are 2.182(3), 2.130(3), 1.979(3) A,
respectively. These values are similar to those reported for the
Cp* analogue of 1.13 Along the C4 chain, C–C separations
3
˚
are 1.469(4), 1.426(5) and 1.354(5) A for C(1)–C(2), C(2)–C(3)
˚
and C(3)–C(4) bonds, respectively. The C(1)–C(2) and C(2)–C(3)
coordinated by the Cp [Ru–C(cp) (av.) 2.17–2.22 A] and PPh3
˚
˚
separations [1.469(4), 1.426(5) A, respectively] are consistent with
ligands [Ru–P 2.2965(8)–2.3262(6) A] and C(3) and N(5) of the
an allylic group coordinated to a metal. The C(3)–C(4) separation
chelating ligand [Ru–C(3) 2.033(2)–2.055(9), Ru–N(52) 2.057(2)–
˚
˚
[1.354(5) A] resembles those found for other cyano-olefins. The
2.106(1) A]. Around the RuC3N ring, C(3)–C(4) and C(4)–C(51)
˚
˚
Ru–P(1) [2.3734(8) A] and Ru–C(cp) distances [2.203–2.264(3), av.
[1.36(1)–1.392(2), 1.43(1)–1.450(3) A, respectively] are consistent
˚
=
2.224 A] fall within the usual ranges found for related Ru(PPh3)Cp
with their being C C double and C–C single bonds, while in 3–
8 C(51)–N(52) [1.345(2)–1.364(3) A] has double bond character.
˚
complexes.
3762 | Dalton Trans., 2010, 39, 3759–3770
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=
=
Fig. 4 Plot of a molecule of Ru{N2N[Ru(PPh3)2Cp]N CC(CN)
=
CCPh C(CN)2}(PPh3)Cp 4.
=
=
Fig. 6 Plot of a molecule of Ru{N3N[PtCl{P(tol)3}2-cis] CC(CN)
=
CCPh C(CN)2}(PPh3)Cp 6.
= =
molecule of Ru{N2N[Fe(dppe)Cp]N CC(CN)
Fig.
5
=
Plot of
a
CCPh C(CN)2}(PPh3)Cp 5.
=
Within the CPh C(CN)2 fragment, there are no unusual features
requiring comment, while the OMe substituent in 2 [C(51)–O(51)
˚
1.433(2) A] is also conventional.
=
=
=
Fig. 7 Plot of a molecule of Ru{N3NMe CC(CN) CCPh C(CN)2}-
Cycloaddition of azide to CN(5) in 1 has given the tetrazolato
group in 3–9 which comprises atoms C(51)N(52–55), attached
to Ru by N(52) [2.057(2)–2.095(2) A]. Around the ring, C(51)–
N(55) ranges between 1.320(3) and 1.348(2) A, while the N–N
distances range between 1.290(2) and 1.366(2) A. Shorter N(53)–
(PPh3)Cp 7.
˚
for the Fe and Ru fragments, while the Pt centre is distorted
square-planar [P(2)–Pt–P(3) 96.47(7)◦, other angles at Pt 86.61(7)–
89.8(2)◦], with the larger angle at Pt caused by steric repulsion
between the two large mutually cis P(tol)3 ligands.
Similar disparity in sites of attachment is found for 7–9, where
the Me group in 7 is bonded to N(55), whereas the dme-derived
groups in 8 and 9 are attached to N(54) and N(55), respectively. The
C–C, C–O and C–N bond parameters have no unusual features,
the different sites of attachment resulting in localisation of the
˚
˚
˚
N(54) distances are found for 3, 7 and 8 [1.300(3)–1.318(3) A].
In 3, the [Na(OEt2)]+ cation is attached to the complex anion
via coordination to N(55) and also to N(53, 54) and N(41)
from two other anions related by crystallographic 21 screw axes.
˚
The separation N(53)–N(54) [1.309(4) A] corresponds to an
=
=
N N double bond, so that the Na–N N interaction is properly
described as a p bond, similar to those found in related pyrazolate
salts containing Group 11 or 12 metal cations.26,27
=
=
C N and N N double bonds.
Replacement of the Na(OEt2) cation by transition metal frag-
ments Ru(PPh3)2Cp (in 4), Fe(dppe)Cp (in 5) or cis-PtCl{P(tol)3}2
(in 6) results in the Group 8 metals being attached to N(54) [Ru–
Computations
Molecular structures determined for several transition metal
complexes containing the h -tetracyanobutadienyl ligand such as
1 all show that the M–C(3) bond is substantially shorter than the
3
˚
N(54) 2.085(2), Fe–N(54) 2.008(9) A] while Pt is bonded to N(55)
˚
[2.058(6) A]. The usual pseudo-octahedral geometries are found
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bond orders and natural charges have been computed on the X-
ray geometry of 1 and these are summarised in Fig. 9. Good
3
quality data for the X-ray geometry of an h -allyl complex
3
Ru{h -CH2CMeCHC(O)Me}(PPh3)Cp* 10 are also included for
comparison.33 Most notably, the nucleophilic attack at the carbon
atom C(5) in 1 by the methoxide anion is consistent with the
highest positive charge of 0.29 calculated on C(5) of the butadienyl
ligand. The azide anion appears to attack selectively one of four
CN groups present in 1 to form the anion found in 3. It is likely
that the most polar CN group, at CN(5), as shown by calculated
charges, is preferred for the dipolar [3 + 2] cycloaddition process.
3
The bond order of 0.68 for Ru–C(3) in the h -butadienyl
3
complex 1 is almost double that found in the h -allyl complex
10 (0.36) although the charges at Ru are comparable (1, +0.49;
10, +0.45). The C(3)–C(4) bond order of 1.57 in 1 is somewhat
less than expected for a double bond and the substantial negative
charge of -0.34 at C(4) supports the description of complexes
3
containing the h -tetracyanobutadienyl ligand as intermediate
between C and the zwitterion geometry E (Scheme 1). Natural
bond orbital (NBO) analysis of the orbitals involved in the
bonding of 1 reveals that both the sp2 and p orbitals at C(3)
(19% s, 81% p) are involved in the Ru–C(3) bond, whereas only
=
the p-orbitals of C(1) C(2) (5% s, 95% p) contribute to the Ru–
C(1) and Ru–C(2) bonds respectively.
The Ru–C(3) bond length depends on the substituents at
C(4). For example, the contraction of the Ru–C(3) bond length
relative to the Ru–C(1) and Ru–C(2) bonds is not so obvious in
3
structures of ruthenium h -butadienyl complexes with less strongly
electron-withdrawing groups.30,34,35 Since ruthenium complexes
with electron-donating substituents at C(4) are not known exper-
imentally, the DFT-optimised geometry of the model compound
11 derived from compound 1 by substitution of the CN moieties
at C(4) by methyl groups was calculated. The Ru–C(3) bond in
˚
11 is elongated by 0.1 A compared to 1, with little change in the
Ru–C(1) and Ru–C(2) bond lengths. Nevertheless, the Ru–C(3)
bond is still shorter than the other two Ru–C bonds by 0.05–
˚
0.10 A. Natural bond order (NBO) analysis of the orbitals in the
bonding of 11 reveals very similar compositions to those of the
analogous orbitals in 1. It therefore appears that the “short” M–
C(3) bond length is a general feature for all neutral transition
=
Fig. 8 Plots of molecules of Ru{N2N[CH(CH2OMe)(OMe)]N CC-
3
metal h -butadienyl complexes.29,31,32,36
=
=
(CN) CCPh C(CN)2}(PPh3)Cp 8 (lower) and Ru{N3N[CH(CH2OMe)-
=
=
=
Whilst the charges on the metal for the optimised geometries of
1 and 11 are essentially identical (+0.49 and +0.47, respectively),
greater variation is found in the charges on the C(3) and C(4) atoms
(Fig. 9). The changes in calculated bond order in 1 compared to
11 are chemically sensible and clearly support the notion that
the electron-withdrawing groups at C(4) stabilise the zwitterionic
form E.
(OMe)] CC(CN) CCPh C(CN)2}(PPh3)Cp 9 (upper).
M–C(2) and M–C(1) bonds whereas the C(1)–C(2) and C(2)–C(3)
bonds are nearly equivalent.2,6,9,12-14 These characteristics are also
3
evident in experimental structures of related h -cyanobutadienyl
ligands.16,17,19 Indeed, crystallographically determined structures
3
of complexes with h -butadienyl ligands generally show a trend
for the M–C(3) bond to be shorter than the M–C(2) and M–C(1)
bonds. This contraction becomes quite obvious in cases where
strong electron-withdrawing groups such as CN and CF3 are
present at C(4) and is accompanied by elongation of the C(3)–
C(4) bond.28 This pattern of bond lengths is often interpreted as
evidence for contribution to the structure of these compounds
from a zwitterionic form E (Scheme 1),9,13,16,29-32 noting that the
orientation of the substituents at C(4) rules out p-conjugation
between C(4) and the allyl p-orbitals.29,32
Molecular orbital (MO) calculations on 1 showed the LUMO to
be mainly on the metal-h -tetracyanobutadienyl moiety whereas
3
the HOMO is located on the metal and the Cp ring (Fig. 10,
Table 2). MO calculations on the optimised geometry of 11 reveal
similar frontier orbitals but the HOMO and LUMO energies are
0.74 and 0.97 eV higher in energy when compared to 1. Computed
3
MO data obtained from the h -allyl complex 10 show the HOMO
to be similar to those found for 1 and 11 but the LUMO is
3
located on the PPh3 moiety rather than on the h -allyl ligand. The
In order to understand the bonding and reactivity patterns
low LUMO and HOMO energies in 1 are in agreement with the
oxidation and reduction waves observed elsewhere for derivatives
3
in complexes containing the h -cyanobutadienyl ligand, Wiberg
3764 | Dalton Trans., 2010, 39, 3759–3770
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Table 2 Molecular orbital energies and compositions for 1, 10 and 11
1
eV
Ru
Cp
PPh3
C(1)
C(2)
C(3)
(CN)2
Ph
C(CN)2
169
168
167
166
L + 1
-1.88
-2.43
-6.29
-6.38
44
22
44
20
25
8
22
13
21
3
6
0
17
5
1
14
0
0
13
3
3
7
9
1
2
8
0
22
2
8
10
1
LUMO
HOMO
H - 1
16
20
5
2
10
eV
Ru
Cp*
PPh3
C(1)
C(2)
C(3)
H2
Me
CO2MeH
157
156
155
154
L + 1
-0.45
-0.64
-4.65
-4.95
10
3
43
80
5
3
27
8
79
94
9
1
0
6
2
0
0
0
3
1
0
9
1
0
0
0
0
0
0
0
0
4
0
5
4
LUMO
HOMO
H - 1
2
11
eV
Ru
Cp
PPh3
C(1)
C(2)
C(3)
(CN)2
Ph
CMe2
165
164
163
162
L + 1
-1.30
-1.46
-5.55
-5.71
39
27
46
27
21
10
14
15
32
4
7
1
9
7
4
1
15
0
0
1
7
10
2
11
6
3
17
0
0
4
12
18
LUMO
HOMO
H - 1
8
3
3
12
Fig. 9 Wiberg bond indices (italics) and natural charges (square brackets) for 1, 10 and 11.
This suggests that the Na ◊ ◊ ◊ N interactions are weak and the anion
in 3 is likely to be discrete in solution.
Fig. 11 shows the frontier orbitals for the anion in 3 where the
HOMO involves the Ru atom and the N4C ring and the HOMO
energy is relatively high as expected for an anion. The LUMO
=
in the anion of 3 is mainly the p* orbital on the C C double
bond of the CPh C(CN)2 group. Charge calculations on both
=
Fig. 10 Frontier orbitals for 1. Contour values are plotted at 0.04
(e/bohr3)1/2
.
related to 1.6 The reductions of 1 and related derivatives are likely
3
to take place at the metal-h -tetracyanobutadienyl moieties.
The anion in 3 was shown to react with electrophiles to form
compounds with substituents at one of two nitrogen atoms of the
tetrazolato ring, N(4) or N(5). Comparison between the optimised
and experimental geometries for the anion in 3 reveals little
differences in the tetrazolato cycle despite the Na ◊ ◊ ◊ N interactions
between the anion and cation found in the solid state geometry.
Fig. 11 Frontier orbitals for anion in 3. Contour values are plotted at
0.04 (e/bohr3)1/2
.
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optimised and experimental geometries of the anion show the
N(5) atom to have the highest negative charge (-0.33) of the three
unsaturated nitrogen atoms [-0.13 for N(4) and -0.15 for N(3)] in
the N4C ring. This is in accord with formation of the 5-substituted
products 6 and 7 from the reactions of 3 with trans-PtCl2{P(tol)3}2
and MeOTf, respectively.
the Ru centre and is converted to 2 during work-up. Protonation
of the nitrogen by MeOH solvent occurring concomitantly with
addition of OMe at the carbon atom cannot, however, be ruled
out. Structural parameters of 2 are similar to those of the related
tungsten complexes mentioned above.7,15
Current interest in “click chemistry” encouraged us to ex-
amine the reaction between 1 and sodium azide.24,25 There is
precedent in the “reverse” reaction between Ru(N3)(PP)Cp and
nitriles or isonitriles, which afforded the tetrazolato complexes
Ru(N4C)(PP)Cp.40-43 The product from the reaction of 1 with NaN3
was determined to be the sodium salt of the anionic tetrazolate
3, in which each Na+ cation interacts with three anions to give a
polymeric array. The bicyclic ligand incorporates the Ru centre,
with a Na(OEt2) fragment interacting with two nitrogen atoms of
one molecule [N(53,54)], a third [N(55¢)] from a second molecule,
and a CN group [N(41¢¢)] from a third anion, together with an
Et2O molecule (Fig. 3). The interaction between the sodium and
In contrast, the formation of the 4-substituted products, 4 and
5, rather than the 5-substituted analogues may be attributed
to the steric effects of the electrophiles [Ru(PPh3)2Cp]+ and
[Fe(dppe)Cp]+, which prevent formation of M–N bonds with
the more negative N(5) and N(3) atoms. Optimisations of two
geometries of 5 where the Fe(dppe)Cp fragment is at the 4- or 5-
position revealed the 4-substituted isomer to be more stable than
the 5-substituted isomer by 5.6 kcal mol-1. The steric effect of the
Fe(dppe)Cp fragment is obvious in the 5-substituted isomer where
the Fe–N–N angle is 109.6◦ whereas in the 4-substituted isomer
the Fe–N–N angle is 122.9◦ suggesting little steric effect in the
latter. The latter value is close to the angle of 125.2(6)◦ observed
experimentally for 5. The formation of both 4- and 5-substituted
products 8 and 9 in low yields from 3 in refluxing dme is likely
to be a radical process rather than an electrophilic process where
only product 9 would be expected. According to the energies of
the optimised geometries for products 8 and 9, the 5-substituted
isomer 9 is 6.9 kcal mol-1 more stable than isomer 8.
2
2
N(53)–N(54) is properly described as h (or k ).26,27 It is likely that
a [3 + 2]-cycloaddition of the CN(5) group in 1 to azide anion takes
place to form the tetrazolato anion, which then interacts with the
Ru centre with conversion to anion 3.
Reactions between 3 and several metal halide complexes proceed
by salt elimination to give the binuclear Ru2, Ru–Fe and Ru–Pt
complexes 4–6. In 4 and 5, the M(PP)Cp¢ fragment is s-bonded
to N(4), whereas in 6, the Pt is attached to N(5) (Scheme 3). In 7,
formed by methylation of 3 with MeOTf, the Me group is bonded
to N(5). Computations show the N(5) atom to have the highest
negative charge of the three unsaturated nitrogen atoms N(3), N(4)
and N(5). Thus electrophilic attack would be expected to occur at
N(5) as observed in the formation of 6 and 7. It is likely that the
site of attachment N(4) observed for 4 and 5 is a function of the
steric demands of the MLn groups. This assumption is supported
by the observed rearrangement of the trans to cis conformation at
the Pt centre to reduce steric effects and to allow Pt–N(55) bond
formation in 6 which is not possible for the more bulky Fe and Ru
fragments.
NMR spectra
The 13C NMR shifts for the butadienyl carbons in 1 were tenta-
tively assigned in the earlier study.3 The order of the resonances
on going from low to high field was assigned to C(3), C(1), C(4)
and C(2). This contrasts with the order of resonances at C(3),
C(4), C(2) and C(1) found for other neutral transition metal
3
h -butadienyl complexes in more recent literature.36-40 Calculated
NMR shifts obtained from the geometry of 1 reveal the order to
be C(3), C(4), C(2) and C(1) and thus the experimental 13C NMR
data for 1 are reassigned here (see Experimental). Calculated 13
C
NMR shifts for the anion in 3 and for the platinum complex 6 were
also used to aid assignments of their experimental 13C data. The
optimised geometry for a model of 6, in which the tolyl groups
have been substituted by phenyl rings, features a large P–Pt–P
angle (98.5◦) which is in accord with the experimental geometry
[96.47(7)◦].
The products 8 and 9, formed in low yields from reactions of 3
with the solvent dme, contain the alkyl group MeOCH2CH(OMe)
attached to either N(4) or N(5). From the low and non-selective
yields of products, it is believed that radical rather than elec-
trophilic processes are taking place in these reactions. The two
isomers are formed in similar amounts, reflecting the usual lack
of site preference found in reactions of pyrazoles and similar five-
membered N-heterocycles. There is no evidence for any tautomeric
equilibrium between 8 and 9. Compound 9 would be expected to
be the sole (or major) isomer in any equilibrium according to the
relative stabilities of 8 and 9.
Discussion
3
Ligand displacement reactions of complexes containing h -
tetracyanobutadienyl ligands are reported to form complexes
1
containing h -tetracyanobutadienyl ligands, suggesting that the
2
3,11
=
Ru–C(3) bond is stronger than the Ru-(h -C C) attachment.
Conclusions
Similarly, attack on one of the CN groups by nucleophiles to gen-
erate amido groups may give chelating ligands with concomitant
displacement of the coordinated dicyanovinyl group, as observed
previously with tungsten complexes (Scheme 2).7,15
Complex 1 is obtained in high yield from the reaction between
≡
tcne and Ru(C CPh)(PPh3)2Cp. One of the CN groups in the
h -tetracyanobutadienyl ligand has proved to be susceptible to
3
In the present study, the reaction between 1 and NaOMe
nucleophilic attack. Reaction of 1 with methoxide has given
the methoxy(amido) compound 2, in which a chelating ligand
containing a RuC3N cycle is present. Addition of azide to a CN
group affords the bicyclic anion found in 3 with RuC3N and
N4C rings, which can be further derivatised with metal–ligand
fragments via salt-elimination reactions. The dimetallic products
2
affords complex 2 containing a methoxy(amido) ligand, the h -
=
CPh C(CN)2 group being displaced from the Ru centre. The
methoxide acts as a nucleophile attacking at C(5), which is the
most positively charged carbon based on computed charges on
the geometry of 1. The resulting C(OMe)N- group interacts with
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show that electrophilic attack at one of the three unsaturated
nitrogen atoms of the N4C ring takes place selectively and the
site of attack depends on the size of the electrophile. Natural
charge calculations show that the cyanide group involved in the
reactions of 1 with methoxide and azide has a greater positive
chargeat C anda greater negative charge atNthan those calculated
for the other three cyanide groups present in 1. In all of the
products, the dicyano(phenyl)vinyl substituent no longer interacts
with the Ru centre, in contrast to the situation in precursor 1.
DFT computations show that the short Ru–C(3) bond length
compared to Ru–C(1) and Ru–C(2) in 1 largely results from the
presence of the strongly electron-withdrawing CN groups at C(4),
(s, Cp), 111.2 [d, J(CP) = 3 Hz], 115.8 [d, J(CP) = 3 Hz], 118.8
[d, J(CP) = 7 Hz], 118.9 [d, J(CP) = 1 Hz] (4 ¥ CN), 128.6–134.5
(m, Ph), 218.7 [d, J(CP) = 15 Hz, C(3)]. 31P NMR: d 43.7 (s,
PPh3). Calculated 13C NMR data for 1: 17.3 [C(1)], 71.3 [C(2)],
81.6 [C(4)], 85.1 (Cp), 98.1 [C(6)N], 101.8 [CN at C(1) near Ru],
105.1 [CN at C(1) away from Ru], 105.4 [C(5)N], 111.5 (meta C,
PPh3), 112.3 [meta C at C(2)Ph], 113.3 [para C at C(2)Ph], 113.7
(para C, PPh3), 114.2 [ortho C at C(2)Ph], 117.7 (ipso C, PPh3),
118.1 (ortho C, PPh3), 119.7 [ipso C at C(2)Ph], 208.9 [C(3)].
3
=
Reactions of Ru{g -C(CN)2CPhC C(CN)2}(PPh3)Cp 1
3
3
and contrasts with related complexes containing a h -butadienyl
ligand with less electron-withdrawing substituents at C(4).
(a) With NaOMe.
A
1
solution of Ru{h -C(CN)2-
=
CPhC C(CN)2}(PPh3)Cp
(60 mg, 0.09 mmol) in thf–
MeOH (5 : 1, 12 ml) was treated with NaOMe [from Na (0.11 mg)
in MeOH (1 ml)] and the reaction mixture was stirred at r.t.
for 48 h, during which time the colour changed from yellow
to red-brown. After removal of solvent, a dichloromethane
extract of the residue was separated by preparative t.l.c.
(acetone–hexane, 3/7). A brown band (Rf 0.24) contained
Experimental
General
All reactions were carried out under dry nitrogen, although
normally no special precautions to exclude air were taken during
subsequent work-up. Common solvents were dried, distilled under
nitrogen and degassed before use. Separations were carried out
by preparative thin-layer chromatography on glass plates (20 ¥
20 cm2) coated with silica gel (Merck, 0.5 mm thick).
=
=
Ru{NHC(OMe)C(CN) CCPh C(CN)2}(PPh3)Cp 2 (46 mg,
72%), obtained as dark red crystals following recrystallisation
from MeCN–Et2O. Anal. Found: C, 65.80; H, 4.24; N, 8.15. Calcd
(C38H29N4OPRu): C, 66.88; H, 4.24; N, 8.12; M, 690. IR (cm-1):
n(CN) 2203 s, 2226 m; other bands at 1733 w (br), 1714 vw, 1607
1
m, 1579 s, 1520 m. H NMR: d 3.62 (s, 3H, OMe), 4.46 (s, 5H,
Instruments
Cp), 6.53 (s, 1H, NH), 6.67–7.53 (m, 20H, Ph). 31P NMR: d 46.9
(s, PPh3). ES-MS (m/z): 713, [M + Na]+.
IR spectra were obtained using a Bruker IFS28 FT-IR spec-
trometer. Spectra of CH2Cl2 solutions were obtained using a
0.5 mm path-length solution cell with NaCl windows. NMR
spectra were recorded on a Varian Gemini 2000 instrument (1H
at 300.14 MHz, 13C at 75.48 MHz, 31P at 121.50 MHz). Unless
otherwise stated, samples were dissolved in CDCl3 contained in
5 mm sample tubes. Chemical shifts are given in ppm relative to
internal tetramethylsilane for 1H and 13C NMR spectra, external
H3PO4 for 31P NMR spectra. Electrospray mass spectra (ES-MS)
were obtained from samples dissolved in MeOH which, unless
otherwise stated, contained NaOMe as an aid to ionisation.44
Solutions were injected into a Varian Platform II spectrometer
via a 10 ml injection loop. Nitrogen was used as the drying
and nebulising gas. Peaks listed are the most intense of the
isotopic clusters. Elemental analyses were by Campbell Microan-
alytical Laboratory, Chemistry Department, University of Otago,
Dunedin, New Zealand.
(b) With NaN3. A suspension of 1 (100 mg, 0.15 mmol)
and NaN3 (20 mg, 0.3 mmol) in dme (50 ml) was heated
under reflux for 24 h. Solvent was removed from the now
dark red-purple solution and an acetone extract of the
residue was purified by preparative t.l.c. (acetone–hexane,
2/1). The major red-purple band (Rf 0.20) contained
=
=
=
Ru{N3N[Na(OEt2)] CC(CN) CCPh C(CN)2}(PPh3)Cp
3
(107 mg, 88%), obtained as very dark red crystals after
recrystallisation from MeCN–Et2O. Anal. Found: C, 62.03; H,
4.36; N, 11.88. Calcd (C41H35N7NaOPRu): C, 61.81; H, 4.40; N,
12.31; M, 757. IR (cm-1): n(CN) 2194 m, 2220 m; other bands at
1515 m (br), 1459 m (br), 1434 m, 1377 w. 1H NMR (acetone-d6):
d 1.12 (t, J = 7 Hz, 6H, 2 ¥ Me), 3.42 (q, J = 7 Hz, 4H, 2 ¥ CH2),
4.33 (s, 5H, Cp), 7.09–7.50 (m, 20H, Ph). 13C NMR (acetone-d6):
d 15.0 (s, Me), 65.7 (s, CH2), 72.3 [s, C(1)], 79.8 [d, J(CP) = 2 Hz,
Cp], 100.1 [s, C(4)], 115.6, 115.6, 116.7 (3 ¥ s, CN), 127.9–134.0
(m, Ph), 168.3 [s, C(5)], 188.5 [s, C(2)], 221.0 [d, J(CP) = 11 Hz,
C(3)]. Calculated 13C NMR data for anion of 3: 64.5 [C(1)], 77.9
(Cp), 91.8 [C(4)], 102.3 [CN at C(1) near Ru], 103.3 [CN at C(4)],
104.5 [CN at C(1) away from Ru], 109.9 (meta C, PPh3), 110.3
(para C, PPh3), 110.5 [meta C at C(2)Ph], 110.9 [para C at C(2)Ph],
114.2 [ortho C at C(2)Ph], 118.1 (ortho C, PPh3), 123.5 (ipso C,
PPh3), 123.6 [ipso C at C(2)Ph], 150.9 [C(5)], 160.1 [C(2)], 214.3
[C(3)]. 31P NMR (acetone-d6): d 51.4 (s, PPh3). ES-MS (negative
ion, MeOH, m/z): 700, [M - Na(OEt2)]-; (positive ion, MeOH +
NaOMe): 746 [anion + 2Na]+; 724, [anion + (H + Na)]+. Both
ions are weak, but the former increases in intensity upon addition
of more NaOMe.
Reagents
The compounds FeCl(dppe)Cp,45 RuCl(PPh3)2Cp,46 Ru(C
≡
47
48
CPh)(PPh3)2Cp,46 cis-RuCl2(dppe)2 and trans-PtCl2{P(tol)3}2
were all prepared by the cited literature procedures. All other
reagents were obtained from Sigma-Aldrich or Fluka and used
as received without further purification.
3
=
The compound Ru{h -C(CN)2CPhC C(CN)2}(PPh3)Cp
1
was made as previously described from tcne and
11
≡
Ru(C CPh)(PPh3)2Cp. Crystals suitable for the X-ray study
were obtained from MeCN–Et2O. IR (Nujol cm-1): n(CN) 2217
m; (CH2Cl2/cm-1): n(CN) 2223 s. H NMR: d 4.80 (s, 5H, Cp),
1
7.30–7.55 (m, 20H, Ph). 13C NMR: d 7.9 [d, J(CP) = 5 Hz, C(1)],
66.7 [d, J(CP) = 2 Hz, C(2)], 84.9 [d, J(CP) = 8 Hz, C(4)], 92.4
Three minor bands were also resolved, one of which afforded
complex 4 (6 mg) (see below).
This journal is
The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 3759–3770 | 3767
©

View Article Online
=
=
=
=
=
=
Reactions of Ru{N3N[Na(OEt2)] CC(CN) CCPh C(CN)2}-
t.l.c. afforded Ru{N3NMe CC(CN) CCPh C(CN)2}(PPh3)Cp
7 (4 mg, 24%) as red crystals from CHCl3–MeOH. Anal. Found:
C, 63.11; H, 3.97; N, 13.56. Calcd (C38H28N7PRu): C, 63.86; H,
3.95; N, 13.72; M, 715. IR (cm-1): n(CN) 2199 m, 2224 m; other
bands at 1556 m, 1520 m, 1462 w, 1401 w. 1H NMR: d 3.89 (s, 3H,
Me), 4.75 (s, 5H, Cp), 7.15–7.36 (m, 20H, Ph). 31P NMR: d 49.5 (s,
PPh3). ES-MS (positive ion, MeOH + NaOMe, m/z): 1453, [2M +
Na]+; 738, [M + Na]+.
(PPh3)Cp 3
(a) With RuCl(PPh3)2Cp. A mixture of 3 (20 mg, 0.025 mmol)
and RuCl(PPh3)2Cp (18.1 mg, 0.025 mmol) was heated in
refluxing dme (8 ml) for 30 min. Removal of solvent and
purification of the residue by preparative t.l.c. (acetone–hexane,
1/2) gave a major purple band (Rf 0.30) which contained
Ru{N2N[Ru(PPh3)2Cp]N CC(CN)=CCPh C(CN)2}(PPh3)Cp
4 (32 mg, 91%), which formed dark red-brown crystals from
CH2Cl2. Anal. Found: C, 67.01; H, 4.89; N, 6.62. Calcd
(C78H60N7P3Ru2): C, 67.38; H, 4.35; N, 7.05; M, 1391. IR (cm-1):
n(CN) 2203 m, 2221m; other bands at 1729 w (br), 1516 m, 1501
m, 1482 m. 1H NMR: d 3.95 (s, 5H, Cp), 4.05 (s, 5H, Cp), 6.89–7.32
(m, 50H, Ph). 31P NMR: d 45.0 [d, J(PP) = 4 Hz, 2P, PPh3], 47.4
(s, 1P, PPh3). ES-MS (m/z): 1415, [M + H + Na]+; 1392, [M + H]+.
=
=
(e) With cis-RuCl2(dppe)2. A reaction between 3 (20 mg,
0.025 mmol) and cis-RuCl2(dppe)2 (12.1 mg, 0.0125 mmol) was
carried out in refluxing dme (20 ml) for 14 h. The usual
work-up (acetone–hexane 3/7) afforded recovered 3 (7 mg,
35%) together with an orange band (Rf 0.14) from which
Ru{N2N[CH(CH2OMe)(OMe)]N CC(CN) CCPh C(CN)2}-
(PPh3)Cp 8 (3.4 mg, 17%) was obtained as red-brown crystals from
CH2Cl2–MeOH. Anal. Found: C, 62.17; H, 4.23; N, 12.69. Calcd
(C41H34N7O2PRu): C, 62.43; H, 4.34; N, 12.43; M, 790. IR (cm-1):
n(CN) 2197 m, 2223 m; other bands at 1728 w (br), 1533 m, 1515
m, 1478 m, 1354 m, 1195 m. ES-MS (m/z): 1603, [2M + Na]+; 812,
[M + Na]+; 790, M+.
=
=
=
(b) With FeCl(dppe)Cp.
A similar experiment used 3
(20 mg, 0.025 mmol), FeCl(dppe)Cp (14 mg, 0.025 mmol)
in dme (8 ml), heating for 1.5 h. Preparative t.l.c. (acetone–
hexane, 3/7) gave
a purple band (Rf 0.19) containing
=
=
=
Ru{N2N[Fe(dppe)Cp]N CC(CN) CCPh C(CN)2}(PPh3)Cp 5
(23 mg, 76%) as dark red crystals after recrystallisation from
CH2Cl2–MeOH. Anal. Found: C, 66.75; H, 4.45; N, 7.90. Calcd
(C68H54FeN7P3Ru): C, 67.00; H, 4.45; N, 8.04; M, 1219. IR (cm-1):
n(CN) 2198 m, 2221 m; other bands at 1514 m, 1481 m, 1311 w.
1H NMR: d 2.33, 2.82 (2 ¥ m, 2 ¥ CH2, dppe), 3.97 (s, 5H, Cp-Ru),
4.27 [s (br), 5H, Cp-Fe], 6.64–7.45 (m, 40H, Ph). 31P NMR: d 42.2
(s, 1P, PPh3), 108.0 [s (br), 2P, dppe]. ES-MS (m/z): 1242, [M +
Na]+; 1219, M+.
(f) Independent preparation of 8 and its isomer 9. A solution
of 3 (10.5 mg, 0.013 mmol) in dme (5 ml) was heated at reflux
point for 48 h, the colour of the solution gradually changing from
purple to brown-red. The filtered solution was evaporated under
vacuum and the residue was dissolved in acetone and separated by
preparative t.l.c. (acetone–hexane, 3/7) to give two bands. The first
orange band (Rf 0.16) contained 9 (1 mg, 13%), obtained as red
crystals from CH2Cl2–EtOH. The second orange band (Rf 0.14)
afforded 8 (2 mg, 21%) as brown-red crystals after recrystallisation
from CH2Cl2–EtOH.
(c) With trans-PtCl2{P(tol)3}2. A mixture of 3 (32 mg,
0.4 mmol) and trans-PtCl2{P(tol)3}2 (35 mg, 0.04 mmol)
was heated in refluxing dme (25 ml) for 6 h. After re-
moval of solvent, an acetone extract of the residue was
purified by preparative t.l.c. (acetone–hexane, 1/2) to give
a major purple-red band (Rf 0.48) containing Ru{N3N[cis-
Structure determinations
The crystal data for 1–9 are summarised in Table 3 with the
structures depicted in Fig. 1–8, where ellipsoids have been drawn
at the 50% probability level (20% for 5) and hydrogen atoms have
=
=
=
PtCl{P(tol)3}2] CC(CN) CCPh C(CN)2}(PPh3)Cp 6 (45 mg,
74%), isolated as red-brown crystals after recrystallisation from
CH2Cl2–MeOH. Anal. Found: C, 60.93; H, 4.39; N, 6.25. Calcd
(C79H67ClN7P3PtRu): C, 61.66; H, 4.39; N, 6.37; M (unsolvated),
1539. IR (cm-1): n(CN) 2199 w, 2222 w; other bands at 1520 m,
˚
arbitrary radii of 0.1 A. Selected coordination geometries for 2–9
are given in Table 1. Crystallographic data for the structures were
collected at low temperature (T/K quoted) on Oxford Diffraction
Gemini (for 1, 5, 6, 9) or Xcalibur diffractometers (for 2–4, 7, 8)
1
1464 m, 1437 m, 1379 w. H NMR: d 2.32 (s, 18H, Me), 4.10 (s,
˚
fitted with monochromated Mo Ka (l = 0.71073 A; 2–4, 7–9) or
5H, Cp), 5.31 (s, 2H, CH2Cl2), 6.96–7.21 (m, 44H, Ph + C6H4). 13
C
˚
Cu Ka radiation (l = 1.54178 A; 1, 5, 6) yielding Ntot reflections,
NMR: d 21.4 (s, Me), 71.6 [C(1)], 79.8 (s, Cp), 97.2 [C(4)], 114.4,
114. 9, 116.3 (3 ¥ s, CN), 125.2–135.2 (m, Ph + C6H4), 185.9 [C(2)],
C(3) and C(5) peaks are not observed. Calculated 13C NMR data
for 6: 17.3–17.5 (Me), 77.4 (Cp), 87.2 [C(4)], 101.4 [CN at C(1)
near Ru], 103.1 [CN at C(1) away from Ru], 106.5 [CN at C(4)],
108.8–129.2 (aromatic Cs), 147.3 [C(5)], 158.9 [C(2)], 239.4 [C(3)].
31P NMR: d 4.0 [d, J(PP) = 19 Hz, J(PPt) = 3322 Hz, 2P, P(tol)3],
14.3 [d, J(PP) = 19 Hz, J(PPt) = 3322 Hz, P(tol)3], 39.9 (s, PPh3).
ES-MS (m/z): 1562, [M + Na]+.
merging to N unique after multi-scan (2–5, 9) or face-indexed (1,
6–8) absorption corrections (Rint cited), with No reflections having
I > 2s(I). The structures were refined against F2 with full-matrix
least-squares using the program SHELXL-97.49a In general, all H
atoms were added at calculated positions and refined by use of a
riding model with isotropic displacement parameters based on the
isotropic displacement parameter of the parent atom. Exceptions
were in 2 where H(52) was refined without restraints. Anisotropic
displacement parameters, except where stated, were employed
for all non-hydrogen atoms. For 6, the occupancy factor for the
CH2Cl2 solvent molecule refined to 0.160(8), this being reflected
in the large mosaic spread and weak diffraction. The solvent C
atom was refined with an isotropic displacement parameter only.
For 7, the water molecule H geometries were restrained to ideal
values. For 8, one MeO group of the coordinated dme ligand
was modelled as being disordered over two sites with refined site
(d) With MeOTf. A suspension of 3 (20 mg, 0.025 mmol)
in thf (7 ml) was treated with MeOTf (4 mg, 0.025 mmol)
dissolved in thf (1 ml). After keeping at r.t. for 1 h, solvent was
removed and an acetone extract of the residue was separated by
preparative t.l.c. (acetone–hexane 2/3). The red-purple baseline
contained unreacted 3 (13 mg, 67%) and an orange band (Rf 0.70)
which afforded an oil. Purification of this oil multiple times by
3768 | Dalton Trans., 2010, 39, 3759–3770
This journal is
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©

View Article Online
Table 3 Crystal data and refinement details
Complex
Formula
1
2
3
4
5
6
7
8
9
C37H25N4PRu C38H29N4-
OPRu
657.65
C41H35N7-
NaOPRu
796.79
C78H60N7-
P3Ru2
1390.38
C68H54FeN7- C79H67ClN7-
P3Ru
1219.01
C38H28N7-
C41H34N7O2- C41H34N7-
P3PtRu·0.16CH2Cl2 PRu·H2O
PRu·0.3CH4O O2PRu
MW
689.69
1552.5 732.73
798.4
788.79
Crystal
Monoclinic Monoclinic Monoclinic Triclinic
Monoclinic Monoclinic
Monoclinic Triclinic
Monoclinic
system
¯
¯
Space group P21/c
P21/c
10.1827(1) 19.5078(8) 12.6767(4) 11.8912(3) 17.9190(3)
19.0790(2) 9.6382(2) 15.6939(5) 32.4015(10) 18.4210(3)
P21/c
P1
P21/c
P21/n
P21/n
P1
P21/n
˚
a/A
8.7167(1)
17.6764(2)
19.8463(2)
13.5236(3)
13.7074(3)
17.8548(3)
12.5756(4)
13.0641(6)
13.7818(5)
64.569(4)
69.109(3)
66.706(4)
1829.9
12.3947(2)
17.7047(3)
17.1249(3)
˚
b/A
˚
c/A
16.4900(1) 22.4454(9) 18.7018(7) 15.3484(4) 22.6747(4)
102.871(3)
104.380(1) 115.464(5) 104.493(3) 99.774(3)
90.705(3)
a/◦
b/◦
g /◦
99.231(1)
105.141(2)
98.452(2)
97.322(2)
3
˚
V/A
rc
3018.3
1.447
4
3103.2
1.476
4
3810.2
1.389
4
3502.6
1.318
2
5827.8
1.389
4
7224.8
1.427
4
3273.9
1.487
4
3727.3
1.406
4
1.449
Z
2
◦
2qmax
/
134 (0.60)
82 (0.92)
58 (0.68)
68 (0.79)
136 (0.60)
134 (0.60)
69 (0.80)
72 (0.83)
65 (0.76)
(sinq/lmax
m/mm-1
Tmin/max
)
4.96
0.67/0.83
0.60
0.84/0.91
0.51
0.72/1.0
0.55
0.98/1.0
5.25
0.35/1.0
6.71
0.53/0.83
0.57
0.86/0.96
0.52
0.85/0.99
0.51
0.87/0.95
Crystal
0.11 ¥ 0.11 ¥ 0.31 ¥ 0.23 ¥ 0.21 ¥ 0.15 ¥ 0.14 ¥ 0.13 ¥ 0.22 ¥ 0.17 ¥ 0.14 ¥ 0.11 ¥ 0.03
0.40 ¥ 0.32 ¥ 0.66 ¥ 0.13 ¥ 0.22 ¥ 0.14 ¥
dimensions/ 0.05
0.15
0.05
0.08
0.04
0.09
0.02
0.10
mm-3
Ntot
30 233
85 683
5340 (0.078) 20 107
(0.044)
47 404
10 103
(0.063)
6251
0.050
0.122
100
74 235
27 609
(0.053)
14 417
0.042
0.082
100
73 154
10 360
(0.12)
5010
0.085
0.278
200
81 172
12 778
(0.093)
7969
0.054
0.162
100
52 868
13 247
(0.063)
8224
0.045
0.100
100
40 379
16 687
(0.041)
10 462
0.045
0.117
100
42 565
12 675
(0.068)
7571
0.037
0.073
100
N (Rint
)
No
R1
wR2
T/K
4429
0.037
0.097
100
11 897
0.033
0.095
150
occupancy factors of 0.628(5) and 1–0.628(5). Two close atoms
were modelled as being the C and O atoms of a solvent MeOH
molecule with site occupancy refining to 0.298(6). Solvent H atoms
were not included in the model. Atoms of the minor component
of the disordered dme and of the solvent molecule were refined
with isotropic displacement parameters.
Both 4 and 6 contain voids. Those in 4 are large but, as recorded
in the cif, no significant e-density was located. Use of the program
SQUEEZE did significantly decrease the R-factor. For 6, the voids
are small and program SQUEEZE was not used.
basis set 3-21G* or the larger mixed basis set LANL2DZ/6-
31G* (LANL2DZ for Ru, 6-31G* for other atoms) revealed no
imaginary frequencies. Geometrical differences were insignificant
between these model geometries at both basis sets indicating the 3-
21G* basis set to be appropriate for computations on compounds
1, 3, 5, 6 and 8–11 discussed here. The 3-21G* basis set was also
found to be suitable for related ruthenium complexes discussed
elsewhere.59-62 Calculated charges at NBO 3.1 on these model
geometries were found to be basis set-independent on going from
3-21G* to LANL2DZ/6-31G* with only the positive charge at the
ruthenium atom being significantly smaller with the LANL2DZ
basis set.
The Table of Contents graphic was generated from the molecu-
lar structure of 1 using the OLEX2 suite of programs.49b
Acknowledgements
Computational section
All DFT computations were carried out with the Gaussian 03
package.50 The geometries of 1, 3, 5, 6, 10 and 11 discussed here
were optimised at the B3LYP 51,52/3-21G* 53 (LANL2DZ 54 for Pt
in 6) level of theory with no symmetry constraints. Wiberg bond
indices, atomic bond orbitals and natural charges were computed
with the NBO 3.1 version. Electronic structure calculations were
also carried out at the B3LYP/3-21G* level of theory. The MO
diagrams and orbital contributions were generated with the aid
of Gabedit55 and GaussSum56 packages respectively. Theoretical
13C NMR chemical shifts obtained at the GIAO57,58-B3LYP/3-
21G*//B3LYP/3-21G* level on the optimised geometries were
referenced to TMS: d(13C) = 200 - s(13C). Computed NMR values
reported here for phenyl, methyl and Cp groups are averaged.
Frequency calculations on the optimised model geometries
of 1 and 3 with Ph groups replaced by H atoms with the
We thank the Australian Research Council for support of
this work and Johnson Matthey plc for a generous loan
of RuCl3·nH2O. Mass spectra were obtained by Professor
B. K. Nicholson (Department of Chemistry, Waikato University).
We thank Durham University for access to the High Performance
Computing Cluster.
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3770 | Dalton Trans., 2010, 39, 3759–3770
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