Tricyanovinylalkynyl-metal complexes: Synthesis and some reactions

Article abstract of DOI:10.1039/b810720c

Reactions of Group 8 metal ethynyls with tetracyanoethene afford tricyanovinylethynyl-metal derivatives, M{CCC(CN)C(CN)₂}(PP)Cp′ [2; M = Ru, Os; PP = (PPh₃)₂, dppe; Cp′ = Cp, Cp*; not all combinations]; a similar reaction

Full text of DOI:10.1039/b810720c

View Article Online / Journal Homepage / Table of Contents for this issue
COMMUNICATION
www.rsc.org/dalton | Dalton Transactions
Tricyanovinylalkynyl–metal complexes: synthesis and some reactions†
Michael I. Bruce,*a Ale´xandre Burgun,a Kathy A. Kramarczuk,a Brian K. Nicholson,b Christian R. Parker,a
Brian W. Skelton,c Allan H. Whitec and Natasha N. Zaitsevaa
Received 24th June 2008, Accepted 30th October 2008
First published as an Advance Article on the web 13th November 2008
DOI: 10.1039/b810720c
Reactions of Group 8 metal ethynyls with tetracyano-
selected cases, further displacement of a labile ligand on the metal
3
centre gives h -butadienyl complex C.3
∫
ethene afford tricyanovinylethynyl–metal derivatives, M{C
=
For the metal complexes, these reactions are encouraged by the
electron-richness of the alkynyl Cb atom, a property shared with
the related vinylidene complexes. Similar reactions between tcne
and several electron-rich organic molecules have been described
more recently.4
CC(CN) C(CN)2}(PP)Cp¢ [2; M = Ru, Os; PP = (PPh3)2,
dppe; Cp¢ = Cp, Cp*; not all combinations]; a similar reaction
= =
occurs with the vinylidene RuCl( C CHPh)(PPh3)Cp. Fur-
ther replacement of a CN group in 2 occurs with nucleophiles,
while homo- and hetero-metallic derivatives are obtained by
coordination of one of the remaining CN groups to other
metal–ligand fragments.
Seeking to extend this chemistry to the parent ethynyl com-
∫
plexes, we found that reactions of tcne with M(C CH)(PP)Cp¢
[M = Ru, Os; PP = (PPh3)2, dppe; Cp¢ = Cp, Cp*; not all com-
binations] afford mixtures of the tetracyanobutadienyls
=
=
M{C[ C(CN)2]CH C(CN)2}(PP)Cp¢ 1,‡ together with deep
Introduction
∫
=
purple tricyanovinylethynyls M{C CC(CN) C(CN)2}(PP)Cp¢ 2
[M = Ru, Os, (PP)Cp¢ = (PPh3)2Cp; M = Ru, (PP)Cp¢ =
(dppe)Cp*] (Scheme 2).
Major aspects of the chemistry of tetracyanoethene, (NC)2-
=
C C(CN)2 (tcne), include substitution of one or more CN
∫
Thus, the reaction between Os(C CH)(PPh3)2Cp and tcne,
groups by nucleophiles (such as alkoxide, amine, thiolate) and
its interaction with electron-rich molecules, often with formation
of highly coloured charge-transfer complexes.1 The formal [2 +
2]-cycloaddition of tcne to s-alkynyl–metal complexes was first
described in 19792 and this reaction has been shown to proceed via
an initial radical intermediate to give cyclobutenyl A (Scheme 1),
=
carried out in thf at r.t. over 30 min, afforded Os{C[ C-
=
∫
=
(CN)2]CH C(CN)2}(PPh3)2Cp 1b (30%) and Os{C CC(CN)
C(CN)2}(PPh3)2Cp 2b (22%) as shown by their single-crystal XRD
structures (Fig. 1, 2).§
The most significant bond parameters for 2b are Os–C(1)
[at 1.924(2) A] and the C(1)–C(2) separation [1.234(3) A] [cf .
Os–C(1) 2.016(9), C(1)–C(2) 1.16(1) A in Os(C CH)(dppe)Cp].
Spectroscopic data (1H, 13C, 31P NMR, IR, ES-MS) are in accord
˚
˚
1
which undergoes facile ring-opening to give h -butadienyl B. In
˚
∫
∫
with the solid-state structure. The electron-rich Cp¢(PP)MC C
aSchool of Chemistry
& Physics, University of Adelaide, Adelaide,
and electron-poor C(CN)2 substituents have combined to form
a highly polar olefin, the “push–pull” nature of the complex
being shown by the delocalisation of electron density towards the
vinylidene formulation D.
South Australia, 5005, Australia. E-mail: michael.bruce@adelaide.edu.au;
Fax: + 61 8 8303 4358
bDepartment of Chemistry, University of Waikato, Hamilton, New Zealand
cChemistry M313, SBBCS, University of Western Australia, Crawley,
Western Australia, 6009, Australia
† CCDC reference numbers 687736–687740. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/b810720c
Similar substitution of CN in tcne occurs in its reac-
= =
tion with the neutral vinylidene RuCl( C CHPh)(PPh3)Cp*,
Scheme 1
Scheme 2 M = Ru(PPh3)2Cp a; Os(PPh3)2Cp b; Ru(dppe)Cp* c.
The Royal Society of Chemistry 2009
This journal is
Dalton Trans., 2009, 33–36 | 33
©

View Article Online
Scheme 3
S2, . . .) in the presence of NaOMe which give the analogous alkynyl
5
∫
complexes Ru(C CPh)(L)(PPh3)Cp*. The single-crystal XRD
structural study of 3 (Fig. 3)¶ confirms the structural assignment.
=
=
Fig. 1 Plot of a molecule of Os{C[ C(CN)2]CH C(CN)2}(PPh3)2Cp
˚
1b·C6H6 (solvate C6H6 omitted). Selected bond lengths (A): Os–C(2)
2.067(2), C(1)–C(2) 1.388(2), C(2)–C(3) 1.467(2), C(3)–C(4) 1.358(2).
Selected angles (◦): Os–C(2)–C(1) 129.8(1), Os–C(2)–C(3) 117.1(1),
C(2)–C(3)–C(4) 123.8(1).
=
=
=
Fig. 3 Plot of a molecule of RuCl{ C CPh[C(CN) C(CN)2]}(PPh3)Cp*
in 3·0.5CH2Cl2 (solvate CH2Cl2 omitted). Selected bond lengths
˚
(A): Ru–C(1) 1.770(1), C(1)–C(2) 1.377(2), C(2)–C(3) 1.415(2),
C(2)–C(21) 1.500(2), C(3)–C(4) 1.389(2), C(3)–C(31) 1.444(3), C(4)–C(41,
42) 1.431, 1.425(3). Selected angles (◦): Ru–C(1)–C(2) 174.7(1),
C(1)–C(2)–C(3) 117.6(2), C(1)–C(2)–C(21) 119.8(1), C(2)–C(3)–C(4)
128.4(2), C(2)–C(3)–C(31) 117.3(2), C(41)–C(4)–C(42) 114.6(2).
˚
=
=
The extremely short Ru C(1) [1.770(1) A] and long C(1) C(2)
˚
[1.377(2) A] distances are noteworthy and are consistent with 3
tending towards the carbyne formulation E as a result of the
=
presence of the strongly electron-withdrawing C(CN) C(CN)2
group. Spectroscopic data also support the solid-state structure,
with an ES-MS obtained with solutions containing AgNO3
containing [M + Ag]+ at m/z 846, as well as the anticipated
[M - Cl]+ ion at m/z 702.
The formation of the tricyanovinylethynyl complexes 2 and tri-
cyanovinylvinylidene 3 probably results from the steric constraints
of the bulky ligands on the metal centre preventing the usual
[2 + 2]-cyclisation occurring during attack of the tcne upon the
ethynyl ligand. Instead, the electron-rich Cb of the latter attacks
tcne to displace CN (as HCN—CARE!) with formation of the
∫
=
Fig. 2 Plot of a molecule of Os{C CC(CN) C(CN)2}(PPh3)2Cp 2b. Se-
˚
lected bond lengths (A): Os–C(1) 1.924(2), C(1)–C(2) 1.234(3), C(2)–C(3)
1.380(3), C(3)–C(4) 1.388(3), C(3)–C(31) 1.451(3), C(4)–C(41, 42) 1.423,
1.431(3). Selected angles (◦): Os–C(1)–C(2) 170.6(2), C(1)–C(2)–C(3)
170.4(2), C(2)–C(3)–C(4) 125.0(2).
∫
new C–C bond. For Ru(C CH)(dppe)Cp*, 2c is the only product
(93%) and we have carried out studies of the chemistry of the new
cyanocarbon ligand with this complex.
= =
to give the neutral tricyanovinylvinylidene RuCl{ C CPhC-
Addition of RuCl(dppe)Cp* and [NH4]PF6 to 2b in MeOH
afforded the dark blue binuclear derivative [{Cp*(dppe)Ru}{m-
=
(CN) C(CN)2}(PPh3)Cp* 3 (Scheme 3). Complex 3 is formed in
∫
=
a reaction that does not require base, in contrast to previously
described reactions of this complex with ligands L (PR3, O2,
(C C)C(CN) C(CN)CN}{Ru(dppe)Cp*}]PF6
4 (Scheme 4)
(68%) in a reaction similar to many others described by Kaim and
34 | Dalton Trans., 2009, 33–36
This journal is The Royal Society of Chemistry 2009
©

View Article Online
Scheme 4 Reagents: (i) RuCl(dppe)Cp*/[NH4]PF6; (ii) NaOMe. [Ru*] =
Ru(dppe)Cp*
co-workers for tcne and tcnq,6 for example. The XRD structure
∫
Fig. 5 Plot of molecule 1 (molecule 2 is similar) of Ru{C CC-
˚
=
(Fig. 4)ꢀ shows half the phenyl groups to be disordered within the
(OMe) C(CN)2}(dppe)Cp* 5. Selected bond lengths (A): Ru(1)–C(11)
1.950(2), C(11)–C(12) 1.237(3), C(12)–C(13) 1.391(3), C(13)–C(14)
1.388(3), C(13)–O(13) 1.349(3). Selected angles (◦): Ru(1)–C(11)–C(12)
173.0(2), C(11)–C(12)–C(13) 168.8(3), C(12)–C(13)–C(14) 124.7(2),
C(12)–C(13)–O(13) 121.2(2).
∫
∫
lattice, consistent with nearly identical C C and C N structural
parameters.
In conclusion, we have shown that selected neutral ethyl
and vinylidene complexes react with tcne not by the formal
[2 + 2]-cycloaddition reaction commonly encountered, but by
substitution of one of the CN groups. The resulting complexes are
highly reactive, leading to a range of novel chemistry, including
an extensive substitution chemistry and entry into nitrogen
heterocycles, which will be described elsewhere.
Acknowledgements
We thank the ARC for support of this work and Johnson
Matthey plc, Reading, for a generous loan of RuCl3·nH2O and
K2[Os2(OH)4].
∫
=
Fig. 4 Plot of the cation in [{Cp*(dppe)Ru}2{m-C CC(CN) C(CN)-
˚
CN}]PF6 4. Selected bond lengths (A): Ru–C/N(1) 1.976(2), C/N(1)–C(2)
1.192(3), C(2)–C(3) 1.400(4), C(3)–C(31) 1.459(4), C(3)–C(3¢) 1.376(6). Se-
lected angles (◦): Ru–C/N(1)–C(2) 173.4(2), C/N(1)–C(2)–C(3) 174.6(3),
C(2)–C(3)–C(3¢) 123.2(3), C(2)–C(3)–C(31) 118.5(2).
Notes and references
=
‡ Selected spectroscopic data: 1b IR n(CN) 2228 w, 2204 m, n(C C) 1605
w, 1480 m, 1435 s, 1414 w cm-1; 1H NMR (CDCl3): d 4.98 (s, 5H, Cp), 5.82
The formulation is confirmed by microanalysis and ES-MS,
which contains M+ at m/z 1396. Electrochemical studies show
that there is very little change in the first two redox potentials upon
coordinating the second Ru fragment [E1, E2 -1.06, +0.91 V for
2c, -1.00, +0.85 V for 4], although a third non-reversible process
occurs at E3 = +1.24 V for 4.** This suggests that communication
between the two metal centres is minimal.
(s, 1H, CH), 7.05–7.45 (m, 30H, Ph); 13C NMR (CDCl3): d 76.26, 92.82
=
(2 ¥ C), 84.69 (Cp), 113.23, 113.65, 118.46, 122.05 (4 ¥ s, CN), 128.86–
135.24 (Ph), 169.57 [d, J(CP) = 4.8 Hz, CH], 192.42 (dd, OsC); 31P NMR
(CDCl3): d -0.1, -5.2 [2 ¥ d, J(PP) 17 Hz]; HR ES-MS (MeOH/NaOMe,
m/z): 935.206 (calcd 935.211), [M + H]+; 957.189 (calcd 957.193), [M +
Na]+. Anal. found (calcd): C 63.08 (63.14); H 3.89 (3.75); N 6.00 (5.87%).
∫
=
2b IR n(CN) 2210 w; n(C C) 1986 (sh), 1975 vs; n(C C) 1481 w, 1457 m,
1
1435 w cm-1; H NMR (CDCl3): d 4.78 (s, 5H, Cp), 7.14–7.28 (m, 30H,
Ph); 13C NMR (CDCl3): d 65.46, 111.87, 140.21 (3 ¥ s, C), 116.03, 116.89,
117.59 (3 ¥ s, CN), 128.12–137.0 (Ph); 31P NMR (CDCl3): d 2.8; ES-MS
(MeOH/NaOMe, m/z): 840, [M + Na]+. Anal. found (calcd): C 63.65
˚
The long C(3)–C(31) distance in 2b [1.451(3) A; cf . C(4)–
C(41,42) 1.423, 1.431(3) A] suggests that CN(31) might be
˚
displaced by other nucleophiles. Thus, reactions between the ruthe-
nium analogue 2c and alkyllithiums, alkoxides or amines occur
readily to give the appropriately substituted dicyanovinylethynyl
derivatives, formed by displacement of CN(31) by R, OR
or NR2, respectively. For example, NaOMe affords yellow
Ru{C CC(OMe) C(CN)2}(dppe)Cp* 5 (Scheme 4) (36%), char-
acterised by IR, NMR (1H, 13C, 31P) and [M + H]+ in the ES-MS
at m/z 767. The XRD structure of 5 is shown in Fig. 5;†† the
structural parameters closely resemble those of 2b.
=
(63.12); H, 3.89 (3.76); N 4.64 (4.60%). 3 IR n(CN) 2210 m; n(C C) 1664
m, 1349 m, 1093 w cm-1; 1H NMR (CDCl3): d 1.61 [d, J(HP) 1.6 Hz, 15H,
Cp*], 6.16–8.00 (m, 20H, Ph); 31P NMR (CDCl3): d 42.8 (s, PPh3); ES-MS
(MeOH + AgNO3, m/z): 846, [M + Ag]+; 702, [M - Cl]+. Anal. found
(calcd): C 64.77 (63.92); H 4.78 (4.62); N 5.38 (5.39%) (for 0.5CH2Cl2
∫
=
solvate). 4 IR n(CN) 2209 w, n(C C) 1963 s, n(C C) 1604 w, 1448 s,
1436 s cm-1; 1H NMR (CDCl3): d 1.46, 1.55 (2 ¥ s, 15H, Cp*), 2.24–2.52
∫
=
(br m, 3 ¥ CH2, dppe), 2.71–2.79 (m, CH2, dppe), 7.09–7.50 (m, Ph); 13
C
∫
NMR (CDCl3): d 9.82, 93.51 [Cp*-Ru(NC)], 10.10, 98.71 [Cp*-Ru(C C)],
28.2–30.0 (m, CH2), 102.61, 124.23, 152.34 (3 ¥ C), 113.51, 113.92, 115.22
(3 ¥ s, CN), 128.22–136.01 (m, Ph); 31P NMR (CDCl3): d 79.8 [s, 2P,
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 33–36 | 35
©

View Article Online
∫
(dppe)-Ru(C C)], 75.0 [s, 2P, dppe-Ru(NC)], -142.9 [sept, J(PF) 711 Hz,
** Electrochemistry: 0.001 M solutions in CH2Cl2 containing 0.1 M
[NBu4]PF6 as supporting electrolyte; Pt-mesh working, Pt wire counter
and pseudo-reference electrodes, scan rate 100 mV s-1, internal reference
FeCp2/[FeCp2]+ = +0.46 V.
PF6]; ES-MS (MeOH, m/z): 1396, M+; 635, [Ru(dppe)Cp*]+. Anal. found
(calcd): C 61.36 (61.59); H 5.17 (5.10); N 2.72 (2.73%). 5 IR n(CN) 2212 w,
-1
1
∫
=
2199 w; n(C C) 1994 vs, n(C C) 1605 w, 1487 m cm ; H NMR (CDCl3):
d 1.56 (s, 15H, Cp*), 2.30, 2.78 (2 ¥ m, 2 ¥ 2H, dppe), 3.17 (s, 3H, OMe),
7.17–7.59 (m, Ph); 13C NMR (CDCl3): d 10.25, 95.58 (Cp*), 29.62–30.54
(m, CH2), 57.37 (s, OMe), 108.05, 159.98 (2 ¥ s, C), 116.44, 117.50 (2 ¥ s,
CN), 128.01–137.89 (m, Ph), 192.26 (m, Ru-C); 31P NMR (CDCl3): d 82.3
(s, dppe); ES-MS (MeOH, m/z): 767, [M + H]+; 635, [Ru(dppe)Cp*]+.
Anal. found (calcd): C 67.40 (67.44); H 5.57 (5.53); N 3.70 (3.66%).
∫
=
†† 5 Ru{C CC(OMe) C(CN)2}(dppe)Cp* ∫ C43H42N2ORuP2, M = 765.8.
˚
Monoclinic, P21/c, a = 23.8872(8), b = 15.8051(4), c = 21.3047(6) A, b =
◦
3
-3
˚
113.464(4) , V = 7378 A , Z = 8, rc = 1.379 g cm , T = 150 K. Crystal:
0.32 ¥ 0.15 ¥ 0.14 mm, mMo = 0.55 mm-1, Tmin/max = 0.94. 2qmax = 69◦, N =
29943 (Rint = 0.064), No = 13457, R1 = 0.043, wR2 = 0.090.
=
=
§ 1b Os{C[ C(CN)2]CH C(CN)2}(PPh3)2Cp·C6H6 ∫ C49H36N4OsP2·C6H6,
1 (a) E. Ciganek, W. J. Linn and O. W. Webster, in The Chemistry of
the Cyano Group, ed. Z. Rappoport, Interscience, London, 1970, ch. 9,
p. 423; (b) A. J. Fatiadi, Synthesis 1986, 249; (c) A. J. Fatiadi, Synthesis,
1987, 959.
2 A. Davison and J. P. Solar, J. Organomet. Chem., 1979, 166,
C13.
3 (a) M. I. Bruce, J. R. Rodgers, M. R. Snow and A. G. Swincer,
J. Chem. Soc., Chem. Commun., 1981, 271; (b) M. I. Bruce, T. W.
Hambley, M. R. Snow and A. G. Swincer, Organometallics, 1985, 4,
494; (c) M. I. Bruce, T. W. Hambley, M. R. Snow and A. G. Swincer,
Organometallics, 1985, 4, 501; (d) M. I. Bruce, T. W. Hambley, M. J.
Liddell, A. G. Swincer and E. R. T. Tiekink, Organometallics, 1990, 9,
2886.
4 (a) H. Hopf, M. Kreutzer and P. G. Jones, Angew. Chem., 1991, 103,
1148, (Angew. Chem., Int. Ed. Engl., 1991, 30, 1127); (b) N. R. Spreiter,
C. Bosshard, G. Knopfle, P. Gunter, R. R. Tykwinski, M. Schreiber and
F. Dierderich, J. Phys. Chem. B, 1998, 102, 29.
¯
˚
M = 1011.07. Triclinic, P1, a = 9.8081(7), b =◦10.9462(8), c = 21.134(2) A,
3
˚
a = 95.985(2), b = 90.544(2), g = 102.438(2) , V = 2203 A , Z = 2, rc =
1.525 g cm-3. Crystal: 0.44 ¥ 0.26 ¥ 0.08 mm, mMo = 3.0 mm-1, Tmin/max
=
0.64 (multiscan correction). 2qmax = 75◦, N = 22647 [merged sphere of
CCD diffractometer data, (w-scans), T = ca. 150 K, Rint = 0.033], No
=
19652, R1 (full matrix refinement on F2) = 0.027, wR2 = 0.061 (SHELXL
∫
=
97). 2b Os{C CC(CN) C(CN)2}(dppe)Cp* ∫ C48H35N3OsP2, M = 905.93.
˚
Monoclinic, P21/n, a = 11.4883(9), b = 17.556(2), c = 19.604(2) A, b =
◦
3
-3
˚
100.126(2) , V = 3892 A , Z = 4, rc = 1.546 g cm , T = ca. 150 K. Crystal:
0.22 ¥ 0.18 ¥ 0.12 mm, mMo = 3.4 mm-1, Tmin/max = 0.73. 2qmax = 75◦, N =
20385 (Rint = 0.048), No = 13379, R1 = 0.030, wR2 = 0.059.
=
=
=
¶ 3 RuCl{ C CPh[C(CN) C(CN)2]}(PPh3)Cp*·0.5CH2Cl2
∫ C41H35-
ClN3RuP·0.5CH2Cl2, M = 779.67. Monoclinic, ◦P21/n, a = 19.8831(6),
3
˚
˚
b = 8.7254(3), c = 24.0230(8) A, b = 114.101(1) , V = 3804 A , Z = 4,
rc = 1.361 g cm-3, T = 150 K. Crystal: 0.55 ¥ 0.10 ¥ 0.10 mm, mMo
0.63 mm-1, Tmin/max = 0.91. 2qmax = 75◦, N = 19967 (Rint = 0.086), No
9825, R1 = 0.046, wR2 = 0.106.
=
=
5 M. I. Bruce, B. C. Hall, N. N. Zaitseva, B. W. Skelton and A. H. White,
J. Chem. Soc., Dalton Trans., 1998, 1793.
∫
=
ꢀ 4 [{Cp*(dppe)Ru}2{m-C CC(CN) C(CN)CN}]PF6 ∫ C79H78N3P4Ru2·
6 (a) W. Kaim and M. Moscherosch, Coord. Chem. Rev., 1994, 129, 157;
(b) H. Hartmann, W. Kaim, M. Wanner, A. Klein, S. Franz, C. Duboc-
Toia, J. Fiedler and S. Za´lis, Inorg. Chem., 2003, 42, 7018; (c) A. N. Maity,
B. Schwederski, B. Sarkar, S. Za´lis, J. Fiedler, S. Kar, G. K. Lahiri, C.
Doboc, M. Gru¨nert, P. Gutlich and W. Kaim, Inorg. Chem., 2007, 46,
7312.
F6P, M = 1540.51. Monoclinic, C2/c, a = 21.0362(10), b = 14.8998(7),
◦
3
-3
˚
˚
c = 23.7530(10) A, b = 100.380(4) , V = 7323 A , Z = 4, rc = 1.397 g cm ,
T = ca. 100 K. Crystal: 0.34 ¥ 0.13 ¥ 0.13 mm, mMo = 0.58 mm-1, Tmin/max
=
0.89. 2qmax = 63◦, N = 11139 (Rint = 0.031), No = 8177, R1 = 0.045, wR2 =
0.110. Disorder is present in the anion F atoms and some phenyl groups
(see Fig. 4).
36 | Dalton Trans., 2009, 33–36
This journal is
The Royal Society of Chemistry 2009
©