A percyanovinylidene-ruthenium complex, Ru{=C=C5(CN) 3[=C(CN)2]2}(dppe)Cp*

Article abstract of DOI:10.1021/om1010885

The reaction between Ru(C=CC=CAg)(dppe)Cp* and tcne affords a novel percyanovinylidene complex by an unusual decyano-dimerization reaction of the cyanocarbon with the diynyl fragment. This complex is also obtained from tcne and Ru{C=CC=C[Au(PPh₃)]}(dppe)Cp*, together with Ru{C=CC[=C(CN)₂]C[Au(PPh₃)]=C(CN)₂}(dppe)Cp *, formed by the anticipated [2 + 2] cycloaddition and subsequent ring-opening reactions.

Full text of DOI:10.1021/om1010885

Organometallics 2011, 30, 653–656 653
DOI: 10.1021/om1010885
A Percyanovinylidene-Ruthenium Complex,
Ru{dCdC5(CN)3[dC(CN)2]2}(dppe)Cp*
Michael I. Bruce,*,† Jonathan C. Morris,‡ Brian K. Nicholson,§ Brian W. Skelton,
Allan H. White, and Natasha N. Zaitseva†
†School of Chemistry & Physics, University of Adelaide, South Australia 5005, Australia,
‡School of Chemistry, University of New South Wales, Sydney, New South Wales 2052, Australia,
§Department of Chemistry, University of Waikato, Hamilton, New Zealand, and Chemistry M313, SBBCS,
The University of Western Australia, Crawley, Western Australia 6009, Australia
Received November 18, 2010
Summary: The reaction between Ru(CtCCtCAg)(dppe)Cp*
and tcne affords a novel percyanovinylidene complex by an
unusual decyano-dimerization reaction of the cyanocarbon
with the diynyl fragment. This complex is also obtained from
tcne and Ru{CtCCtC[Au(PPh3)]}(dppe)Cp*, together with
Ru{CtCC[dC(CN)2]C[Au(PPh3)]dC(CN)2}(dppe)Cp*, formed
by the anticipated [2 þ 2] cycloaddition and subsequent ring-
opening reactions.
afford the cyanoethynyl complexes directly with concomitant
loss of phenol (or phenoxide).4 Recently, we have described the
nucleophilic displacement of CN from tcne by Ru(CtCH)-
(dppe)Cp* to give Ru{CtCC(CN)dC(CN)2}(dppe)Cp*,
together with some of its chemistry.5 [2 þ 2] cycloaddition of
tcne to Ru(CtCCN)(dppe)Cp afforded the pentacyanobuta-
dienyl complex Ru{C[dC(CN)2]C(CN)dC(CN)2}(dppe)Cp.4b
Approaches to cyanovinylidene ligands using reactions of the
N-cyano(dimethylamino)pyridinium cation, [Me2NC5H4N-
(CN)]þ, with Ru(CtCH)(dppe)Cp* allow both preparation of
the cyanoethynyl complex and also subsequent addition of CN
to give the dicyanovinylidene ligand in [Ru{dCdC(CN)2}-
(dppe)Cp*]BF4.6 This note describes related reactions of group
11 derivatives of Ru(CtCCtCH)(dppe)Cp*.
For several years, we have studied the reactions of tetra-
cyanoethene, C2(CN)4 (tcne), with alkynyl- and polyynyl-
transition-metal complexes.1 Characteristic of these is the
[2 þ 2] cycloaddition to the alkynyl complex A to give tetra-
cyanocyclobutenyl derivatives B, which undergo a more or
less ready ring opening (retro-cycloaddition) to form the
η1-tetracyanobuta-1,3-dienyl complexes C (Scheme 1). A
further reaction occurs if weakly bound ligands are present
on the metal center, with formation of the analogous η3-tetra-
cyanobutadienyl complexes D. An interesting structural
feature of D is the presence of a short Ru-C bond, consistent
with some degree of multiple-bonding character. This feature
has been examined in more detail using DFT calculations.2
The chemistry of cyanoethynyl complexes has recently
attracted some attention, with early studies being dependent
upon the reactions of cyanoethyne, a reactive and not easily
accessible alkyne. Improved yields were obtained from cyano-
ethynyltrimethylsilane,3 although this too requires prior
synthesis of HCtCCN. More convenient are the sequential
reactions of Ru(CtCH)(PPh3)2Cp or [Ru(dCdCH2)-
(dppe)Cp*]þ with LiBu followed by phenyl cyanate, which
Results and Discussion
Reaction between tcne and Ru(CtCCtCAg)(dppe)Cp*.
We recently described the reaction of AgNO3 with Ru(Ct
CCtCH)(dppe)Cp* to give a yellow solid with elemental
analyses consistent with its formulation as the ligand-free
silver(I) derivative Ru(CtCCtCAg)(dppe)Cp* (1).7 The
structure of this interesting derivative is presently unknown,
neither the electrospray mass spectrum nor X-ray-quality
single crystals yet having been obtained. In the course of
trying to characterize this material, however, its reaction
with tcne was examined. In a one-pot synthesis, during which
the silver complex 1 was not separated, two products, blue (2)
and red (3), were isolated. The IR spectrum of 2 in MeCN
contains ν(CN) at 2208, 2185 cm-1 and ν(CtC) at 1932 cm-1
;
in CH2Cl2, ν(CN) occurs at 2213, 2184 cm-1 and ν(CtC) at
1934 cm-1. The 1H NMR spectrum contains peaks characteristic
of the Ru(dppe)Cp* group, while the 31P NMR spectrum con-
tains only one signal for dppe at δ 80.9. The ES-MS contains
*To whom correspondence should be addresssed. Fax: þ 61 8 8303 4358.
E-mail: michael.bruce@adelaide.edu.au.
M
[Ru{C8(CN)7}(dppe)Cp*]þ) and 936, respectively, although
during the measurement, the solution changed color to red,
þ and [M þ Na]þ at m/z 913 (corresponding to M =
(1) (a) Bruce, M. I.; Rodgers, J. R.; Snow, M. R.; Swincer, A. G.
J. Chem. Soc., Chem. Commun. 1981, 271. (b) Bruce, M. I.; Hambley, T. W.;
Snow, M. R.; Swincer, A. G. Organometallics 1985, 4, 501. (c) Bruce, M. I.;
Cifuentes, M. P.; Snow, M. R.; Tiekink, E. R. T. J. Organomet. Chem. 1989,
359, 379. (d) Bruce, M. I.; Hall, B. C.; Low, P. J.; Skelton, B. W.; White, A. H.
J. Organomet. Chem. 1999, 592, 74. (e) Bruce, M. I.; Skelton, B. W.; White,
A. H.; Zaitseva, N. N. Dalton Trans. 2001, 3627. (f) Bruce, M. I.; Skelton,
B. W.; White, A. H.; Zaitseva, N. N. J. Organomet. Chem. 2002, 650, 141.
(g) Bruce, M. I.; Low, P. J.; Hartl, F.; Humphrey, P. A.; de Montigny, F.; Jevric,
M.; Lapinte, C.; Perkins, G. J.; Roberts, R. L.; Skelton, B. W.; White, A. H.
Organometallics 2005, 24, 5241. (h) Bruce, M. I.; Jevric, M.; Perkins, G. J.;
Skelton, B. W.; White, A. H. J. Organomet. Chem. 2007, 692, 1757.
(2) Bruce, M. I.; Fox, M. A.; Low, P. J.; Skelton, B. W.; Zaitseva,
N. N. Dalton Trans. 2010, 39, 3759.
(4) (a) Cordiner, R. L.; Corcoran, D.; Yufit, D. S.; Goeta, A. E.;
Howard, J. A. K.; Low, P. J. Dalton Trans. 2003, 3541. (b) Cordiner, R. L.;
ꢀ
Smith, M. E.; Batsanov, A. S.; Albesa-Jove, D.; Hartl, F.; Howard, J. A. K.;
Low, P. J. Inorg. Chim. Acta 2006, 359, 946.
(5) Bruce, M. I.; Burgun, A.; Kramarczuk, K. A.; Nicholson, B. K.;
Parker, C. R.; Skelton, B. W.; White, A. H.; Zaitseva, N. N. Dalton
Trans. 2009, 33.
(6) Brown, N. J.; Eckert, P. K.; Fox, M. A.; Yufit, D. S.; Howard,
J. A. K.; Low, P. J. Dalton Trans. 2008, 433.
(3) Zhou, Y.; Arif, A. M.; Miller, J. S. J. Chem. Soc., Chem. Commun.
1996, 1881.
(7) Bruce, M. I.; Low, P. J.; Nicholson, B. K.; Skelton, B. W.;
Zaitseva, N. N.; Zhao, X.-L. J. Organomet. Chem. 2010, 695, 1569.
r
2011 American Chemical Society
Published on Web 01/19/2011
pubs.acs.org/Organometallics

654 Organometallics, Vol. 30, No. 3, 2011
Scheme 1. [2 þ 2] Cycloaddition of tcne to Alkynyl-Metal Complexes
Bruce et al.
so that we cannot be certain that these data refer to the initial
product 2.
A molecule of 3 MeCN is depicted in Figure 1, selected
3
bond parameters being included in the caption; more ex-
tensive details, together with those of the different solvate
phase, which are slightly less precise but independent and
generally in agreement, are given in Table S1 in the Support-
ing Information. The Ru(dppe)Cp* group is unexceptional
Compound 2 is very unstable, solutions in common
solvents readily precipitating red crystals of 3 (see below).
The red complex 3 also has a composition corresponding to
addition of two molecules of tcne with loss of AgCN: i.e., a
heptacyano compound. The IR spectrum contains ν(CN)
bands between 2227 and 2181 cm-1 but no ν(CtC) absorp-
tion. The ES-MS (from a solution containing NaOMe)
contains ions at m/z 936 and 952, assigned to [M þ Na]þ
and [M þ K]þ, respectively, for the X-ray-determined for-
mulation: i.e., the same as found for 2. The molecular ion is
present in only very low concentration, possibly because of
the high affinity of Naþ or Kþ (also present in the spectro-
meter) for the CN groups. Complex 3 has extremely low
solubility in all organic solvents, including MeCN and
DMSO, so that it has not been possible to record any
NMR spectra. However, the decomposition/isomerization
of 2 afforded red crystals of 3 as the MeCN solvate, allowing
its molecular structure to be established as the unusual cyclic
vinylidene by a single-crystal XRD study. Elemental ana-
lyses of the former agree with the solid-state formulation.
The same product 3, obtained as a different phase, is formed
from Ru{CtCCtC[Au(PPh3)]}(dppe)Cp* and tcne, to-
gether with the known Ru{CtCC[dC(CN)2]C[Au(PPh3)]d
C(CN)2}(dppe)Cp* (4), the product of the anticipated [2 þ 2]
cycloaddition of the cyanocarbon to the diynyl-ruthenium
complex, followed by a ring-opening reaction.8 However,
attempts to obtain 3 from the reaction between 4 and another
1 equiv of tcne (in refluxing thf or benzene for 24 h) were
unsuccessful.
˚
with Ru-C(cp) (average 2.305 A) and Ru-P(1,2) distances
(2.3315, 2.3511(10) A) and the near-octahedral geometry for
˚
the Ru center (P(1)-Ru-P(2) = 80.72(4)°, P(1,2)-Ru-
C(1) = 84.7, 97.7(1)°) being within the ranges previously
observed. The cyanocarbon ligand consists of an Rud
˚
C(1)dC(2) vinylidene (Ru-C(1) = 1.825(3) A, C(1)-C(2) =
1.330(4) A), with atom C(2) being part of the five-membered
˚
ring C(2-6). There are two CN groups on C(3) and one on
C(4), while C(5) and C(6) are both parts of CdC(CN)2 groups.
Around the ring, C(2)-C(3) and C(3)-C(4) are long, at
˚
1.545(5) and 1.539(5) A, respectively, with C(4)-C(5) being
˚
short at 1.386(5) A but C(2)-C(6) and C(5)-C(6) longer, at
˚
1.469(5) and 1.491(5) A, respectively. The C(5)-C(7) and
˚
C(6)-C(8) separations (1.392(5) and 1.349(5) A, respectively)
are CdC double bonds linking the C(CN)2 groups to the C5
ring. Angles within the C5 ring are between 100.3(3) and
111.4(3)°, while Ru-C(1)-C(2) is close to linear (168.7(3)°).
These structural data can be accommodated by the un-
precedented zwitterionic formulation shown, where the Ru-
(dppe)Cp* center carries a positive charge, with negative
charge being delocalized around C(4)-C(5)-C(6) and the
two attached dicyanomethylene groups. The presence of the
highly cyanated ligand results in exceptional back-bonding
from the metal, and the RudC(1) and C(1)-C(2) bonds
are respectively somewhat shorter and longer than normal
˚
(cf. e.g., values of 1.848(2) and 1.305(4) A found in [Ru(dCd
CH2)(dppm)Cp*]PF6 ).
9
A plausible route to 3 is shown in Scheme 2 and involves
[2 þ 2] cycloaddition of tcne to the outer CtC triple bond of
Ru(CtCCtCAg)(dppe)Cp* (1 )followed by ring opening to
give the silver derivative of the tetracyanobutadienyl com-
plex A. Reaction of A with a second molecule of tcne would
give intermediate B, which then undergoes intramolecular
5-exo-trig cyclization by attack of the dicyanomethylene anion
(8) Bruce, M. I.; Jevric, M.; Parker, C. R.; Patalinghug, W.; Skelton,
B. W.; White, A. H.; Zaitseva, N. N. J. Organomet. Chem. 2008, 693,
2915.
(9) Bruce, M. I.; Ellis, B. G.; Low, P. J.; Skelton, B. W.; White, A. H.
Organometallics 2003, 22, 3184.

Note
Organometallics, Vol. 30, No. 3, 2011 655
Scheme 2. Suggested Mechanism for the Reaction of tcne with
Ru(CtCCtCAg)(dppe)Cp*
Figure 1. Projection of a molecule of Ru{dCdC5(CN)3-
[dC(CN)2]2}(dppe)Cp* (3) in the MeCN solvate; H atoms are
˚
omitted for clarity. Selected bond parameters (distances in A
and angles in deg): Ru-C(1) = 1.825(3), C(1)-C(2) = 1.330(4),
C(2)-C(3,6) = 1.545, 1.469(5), C(3)-C(4) = 1.539(5), C(4)-
C(5) = 1.386(5), C(5)-C(6,7) = 1.491(5), 1.392(5), C(6)-C(8) =
1.349(5); Ru-C(1)-C(2) = 168.7(3), C(1)-C(2)-C(3,6) =
129.1(3), 126.9(3), C(2)-C(3)-C(4) = 100.3(3), C(3)-C(4)-
C(5) = 111.4(3), C(4)-C(5)-C(6) =105.5(3),C(2)-C(6)-C(5) =
105.8(4).
2181 m; other bands at 1595 m, 1571 m, 1526 m. ES-MS (MeOH þ
NaOMe, m/z): 936.171 (calcd 936.169), [M þ Na]þ; 952.142 (calcd
952.143), [M þ K]þ; 887, [M - CN]þ.
Conversion of blue to red isomers occurs spontaneously, a
blue solution of 2 in MeCN slowly depositing red crystals of 3
over a period of several hours.
on Cβ to give C. Elimination of AgCN from C then affords 3.
While we have not yet characterized the blue compound 2, the
presence of ν(CN) and ν(CtC) bands in its IR spectrum, the
latter disappearing upon conversion to red 3, suggests that its
structure is closely related to those depicted for B and C.
Reaction between tcne and Ru{CtCCtC[Au(PPh3)]}(dppe)Cp*.
A solution of Ru{CtCCtC[Au(PPh3)]}(dppe)Cp* (35 mg, 0.031
mmol) and tcne (8 mg, 0.62 mmol) in benzene (6 mL) was stirred
overnight at room temperature, after which time it was burgundy
red with a red-orange precipitate. The precipitate was filtered off and
washed with benzene, and the combined solutions were evaporated.
Preparative tlc of a CH2Cl2 extract of the residue (3/7 acetone/
hexane) afforded Ru{CtCC[dC(CN)2]C[Au(PPh3)]dC(CN)2}-
(dppe)Cp* (4; 15.9 mg, 41%), obtained as red crystals (CH2Cl2/
hexane). The red-orange precipitate was crystallized (CH2Cl2) to
give Ru{dCdC5(CN)3[dC(CN)2]2}(dppe)Cp* (3; 6.4 mg, 23%).
Structure Determinations. Full spheres of diffraction data
were measured using a Bruker AXS CCD area-detector instru-
ment. All data were measured using monochromatic Mo
Experimental Section
The general reaction conditions and instrumentation used are
similar to those described earlier.9 Ru(CtCCtCH)(dppe)Cp*
was obtained from RuCl(dppe)Cp* and HCtCCtCSiMe3;10
tcne was a commercial product (Aldrich).
Reaction of tcne with Ru(CtCCtCAg)(dppe)Cp*. Solid
AgNO3 (12.5 mg, 0.073 mmol) was added to a solution of Ru(Ct
CCtCH)(dppe)Cp* (50 mg, 0.073 mmol) in thf (8 mL), and
the mixture was stirred in the dark. After 1 h, tcne (18.7 mg,
0.146 mmol) was added, upon which the yellow solution immedi-
ately turned blue. After a further 1 h of stirring, most of the solvent
was removed and the residue was separated by preparative tlc
(silica, 1/2 acetone/hexane). One major band (2, turquoise blue, Rf
= 0.50) separated and was collected. A dark blue solid (22.4 mg,
41%) was obtained from a MeCN extract. IR (MeCN, cm-1):
ν(CN) 2208 w, 2185 w; ν(CtC) 1932 w (br); other bands at 1597 w
(br), 1573 w, 1528 m (br). IR (CH2Cl2, cm-1): ν(CN) 2213 w, 2184
w; ν(CtC) 1934 m (br); other bands at 1593 w, 1524 s. 1H NMR
(CDCl3): δ 1.50 (s, 15H, Cp*), 2.54, 3.08 (2 m, 4H, CH2),
7.18-7.52 (m, 20H, Ph). 31P NMR (CDCl3): δ 80.9 (s, dppe).
ES-MS (MeCN, MeOH þ NaOMe, m/z): 936, [M þ Na]þ; 913,
Mþ. The red baseline was extracted with acetone to give red solid 3
(27.3 mg, 41%), which gave X-ray-quality crystals of the MeCN
solvate from CH2Cl2/MeCN/EtOH. The solid material so ob-
tained proved to be resistant to redissolution. Anal. Found: C,
67.20; H, 4.39; N, 10.69. Calcd for C51H39N7P2Ru: C, 67.10; H.
4.31; N, 10.74; M, 914. IR (Nujol, cm-1): ν(CN) 2227 w, 2202 w,
˚
KR radiation (λ = 0.710 73 A). Ntotal reflections were merged to
Nunique (Rint cited) after “empirical”/multiscan absorption correc-
tion (proprietary software) and used in the full-matrix least-
squares refinements on F2, No with F > 4σ(F) being considered
“observed”. Anisotropic displacement parameter forms were re-
fined for the non-hydrogen atoms, hydrogen atom treatment
following a riding model (weights: (σ2(Fo)2 þ (aP)2 (þ bP))-1
,
2
with P = (Fo þ 2Fc2)/3). Neutral atom complex scattering factors
were used; computation used the SHELXL 97 program.11 Perti-
nent results are given in Figure 1 (which shows non-hydrogen
atoms with 50% probability amplitude displacement ellipsoids;
hydrogen atoms have been omitted for clarity) and its caption.
Crystal data and refinement details for 3 MeCN (=Ru-
{dCdC5(CN)3[dC(CN)2]2}(dppe)Cp*.MeCN ꢀ C51H39N7P2Ru
3
3
C2H3N): M = 953.96, orthorhombic, space group P212121, a =
3
˚
˚
˚
˚
9.485(2) A, b = 20.908(5) A, c = 23.495(6) A, V = 4659(2) A ,
Fc = 1.360 g cm-3, Z = 4, μ(Mo KR) = 0.45 mm-1, crystal 0.28 ꢁ
0.20 ꢁ 0.20 mm, Tmin/max = 0.83, 2θmax = 58°, Nt = 30 225, N =
11 517 (Rint = 0.076), No = 9033, R1 = 0.045, wR2 = 0.105 (a =
0.055, b = 0.79), xabs = 0.23(2), T = 150 K.
(10) Bruce, M. I.; Ellis, B. G.; Gaudio, M.; Lapinte, C.; Merlino, G.;
Paul, F.; Skelton, B. W.; Smith, M. E.; Toupet, L.; White, A. H. Dalton
Trans. 2004, 1601.
(11) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112.

656 Organometallics, Vol. 30, No. 3, 2011
Bruce et al.
Crystal data and refinement details for 3 2.5S (=Ru{dCd
3
Acknowledgment. We thank the Australian Research
Council for support of this work and Johnson Matthey plc,
Reading, U.K., for a generous loan of RuCl3 nH2O.
C5(CN)3[dC(CN)2]2}(dppe)Cp* 2.5S ꢀ C51H39N7P2Ru 2.5S):
3
3
M = 912.9 (þ 2.5S), monoclinic, space group P21/n, a =
3
˚
˚
˚
17.2203(6) A, b = 12.527(2) A, c = 22.520(2) A, β = 101.908(5)°,
V = 4753.4(9) A , Fc = 1.276 g cm-3, Z = 4. μ(Mo KR) =
3
˚
Supporting Information Available: Table S1, giving selected
bond parameters for both forms of 2, and CIF files giving
crystallographic data for 3 MeCN and 3 2.5S. This material
0.44 mm-1, crystal 0.19 ꢁ 0.16 ꢁ 0.08 mm, Tmin/max =0.75, 2θmax
=
56°, Nt = 72 949, N = 10 184 (Rint = 0.092), No = 6773, R1 =
0.059, wR2 = 0.149 (a = 0.0815), T = 100 K.
3
3
is available free of charge via the Internet at http://pubs.acs.org.
Full cif depositions have also been deposited with the Cam-
bridge Crystallographic Data Centre as CCDC 793948 and
793949. Copies of this information may be obtained free of
charge from The Director, CCDC, 12 Union Road, Cambridge
CB2 1EZ, U.K. (fax, þ 44 1223 336 033; e-mail, deposit@ccdc.
cam.ac.uk; web, http://www.ccdc.cam.ac.uk).
Minor difference map residues were insusceptible to sensible
modeling and were suppressed using “SQUEEZE”.12 The Cp*
was modeled as disordered over two sets of sites, occupancies
refining to 0.644(11) and complement.
(12) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7.