Synthesis of cis- and trans-[M(CN)2(1-CH3-C6H10-NC)4] (M = Fe, Ru) and crystal structure of trans-[Ru(CN)2(1′-CH3-C6H10-NC)4]

Article abstract of DOI:10.1016/j.inoche.2009.10.035

The reaction of the metal carbonyls Fe₂(CO)₉ or Ru₃(CO)₁₂ with 1-isocyano-1-methyl-cyclohexane produces the octahedral metal(II) cyano complexes [M(CN)₂(1-CH₃-C₆H₁₀-NC)₄] in good yields. The cis-isomer is not isolated as a pure compound due to rearrangement processes that yield the sterically less crowded trans-isomer. The molecular structure of the trans-isomer of the ruthenium complex shows the expected almost ideal octahedral coordination of the central ruthenium ion with two cyanide and four isocyanide ligands. This reaction again indicates that isocyanides exhibiting quarternary carbon atoms in α-position with respect to the isocyano substituent in general react with di- or trinuclear metal carbonyls to yield cyano complexes with oxidized metal centres and concomitant reductive cleavage of the respective isocyanide.

Full text of DOI:10.1016/j.inoche.2009.10.035

Inorganic Chemistry Communications 13 (2010) 119–122
Contents lists available at ScienceDirect
Inorganic Chemistry Communications
journal homepage: www.elsevier.com/locate/inoche
Synthesis of cis- and trans-[M(CN)2(1-CH3-C6H10-NC)4] (M = Fe, Ru) and crystal
structure of trans-[Ru(CN)2(10-CH3-C6H10-NC)4]
*
Anke Sterzik, Markus Schwierz, Helmar Görls, Wolfgang Imhof
Institute of Inorganic and Analytical Chemistry, Friedrich-Schiller-University, August-Bebel-Str. 2, 07743 Jena, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
The reaction of the metal carbonyls Fe2(CO)9 or Ru3(CO)12 with 1-isocyano-1-methyl-cyclohexane pro-
duces the octahedral metal(II) cyano complexes [M(CN)2(1-CH3-C6H10-NC)4] in good yields. The cis-iso-
mer is not isolated as a pure compound due to rearrangement processes that yield the sterically less
crowded trans-isomer. The molecular structure of the trans-isomer of the ruthenium complex shows
the expected almost ideal octahedral coordination of the central ruthenium ion with two cyanide and
four isocyanide ligands. This reaction again indicates that isocyanides exhibiting quarternary carbon
atoms in a-position with respect to the isocyano substituent in general react with di- or trinuclear metal
carbonyls to yield cyano complexes with oxidized metal centres and concomitant reductive cleavage of
the respective isocyanide.
Received 7 August 2009
Accepted 27 October 2009
Available online 30 October 2009
Keywords:
Iron
Ruthenium
Cyanide
Isocyanide
X-ray
Ó 2009 Elsevier B.V. All rights reserved.
Transition metal cyanide complexes with a limited number of
cyanide ligands in a well-defined stereochemistry have attracted
increasing interest due to the enhanced predictability of heteronu-
clear coordination polymers in which cyanides act as bridging li-
gands compared to related compounds derived from homoleptic
metallocyanates [1]. The cyanide ligand is one of the most widely
used bifunctional ligands. This is due to the fact that linear
M–CN–M0 bridges may be formed from the reaction of cyanide
complexes M–CN with additional transition metal fragments. In
addition, effective communication between the bridged metal cen-
The synthetic procedure for the preparation of the iron and
ruthenium complexes is depicted in Scheme 1. 1-Isocyano-1-
methyl-cyclohexane, 1, has been produced following a literature
procedure [5] and has been identified by IR spectroscopy and mass
spectrometry [6]. The reaction of 1 with Fe2(CO)9 or Ru3(CO)12
,
respectively, leads to the formation of the octahedral complexes
2a, b and 3a, b [7]. As it has been pointed out before the reaction
with ruthenium carbonyl only proceeds under CO pressure. Most
probably this is due to the fact that after cleavage of the trinuclear
cluster core a mononuclear ruthenium carbonyl species has to be
stabilized for some time. Since Fe(CO)5 is much more stable than
Ru(CO)5 the analogous reaction with iron carbonyl works without
additional CO pressure. The presence of cis- and trans-isomers is
clearly shown by their different IR spectra. It is also possible to sep-
arate the isomers by column chromatography. Nevertheless, dur-
ing recrystallization procedures of the cis-isomer it slowly
interconverts to give the sterically less crowded trans-isomer.
The latter isomer is therefore the only compound that is isolable
in pure form from the reaction mixtures. The same rearrangement
reactions of cis-configurated complexes has been observed if iOcNC
was used as the isocyanide [3b,4d]
All MS spectra show the respective molar peak as well as suc-
cessive fragmentation of cyanide ligands or formation of coordi-
nated hydroisocyanic acid by elimination of cyclohexene from
metal bound 1. IR spectra are highly related to those of derivatives
of compounds of type 2 and 3 with the less symmetrical cis-isomer
presenting an enhanced number of signals with regard to the trans-
isomers [3]. 1H NMR spectra are not very significant due to
unstructured multiplets representing the cyclohexyl as well as
tres may be established because of the
p-system of cyanide itself
[2]. Therefore, some of us in the last years have developed a syn-
thetic methodology of preparing octahedral metal(II) or metal(I)
cyanide complexes of the general formulae [M(CN)2(RNC)4]
(M = Fe, Ru; R = tBu, iOc) and [M(CN)(CO)(RNC)4] (M = Mn,
i
R = tBu, Oc) from the reaction of isocyanides with the respective
metal carbonyls [3]. These reactions obviously follow a complex
redox reaction mechanism and seem to be limited to tertiary isocy-
anides. The latter fact has been attributed by us to the enhanced
stability of tertiary carbenium ions compared to secondary or pri-
mary ones. These ions are most probably produced during the reac-
tion by heterolytic cleavage of isocyanides into a cyanide anion and
a carbenium ion. In addition, we produced several cyanide bridged
coordination oligomers or polymers showing that the cis- or trans-
stereochemistry of these complexes significantly influences the
communication between the bridged metal centres [4].
* Corresponding author. Tel.: +49 3641 948185; fax: +49 3641 948102.
E-mail address: Wolfgang.Imhof@uni-jena.de (W. Imhof).
1387-7003/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2009.10.035

120
A. Sterzik et al. / Inorganic Chemistry Communications 13 (2010) 119–122
Scheme 1.
trans-position to each other. The metal carbon bond length of the
cyanide ligands is slightly longer than the respective bond lengths
of the isocyanide ligands (206.8(5) pm vs. 199.6(5) pm in average).
The latter are in the same range as it has already been reported for
[Ru(C6H11NC)6][BF4]2 [9]. As it is expected bond angles at the coor-
dinated carbon atoms C1 and C2 are almost linear. The angle at the
isocyanide nitrogen atom N2 is slightly bent out of linearity. The
coordination of the other isocyanide ligand most probably due to
steric reasons shows higher deviations from linearity as it can be
seen from the angles at C10 and N3, respectively. The crystal struc-
ture of 2b is presented in Fig. 2. Molecules of this complex are
linked to give an infinite 2D network by establishing hydrogen
bonds of the C–Hꢀ ꢀ ꢀN type [10] between one of the protons of a
methyl substituent (C9) towards the cyanide nitrogen atom (N1).
In summary, another example for a synthetic procedure yield-
ing cis- and trans-[M(CN)2(RNC)4] in a one-pot reaction from the
isocyanide and the respective metal carbonyl is presented herein.
The assumption that the stability of intermediate carbenium ions
limits the scope of this reaction prior to steric requirements of
the isocyanide has again been demonstrated. Therefore, the steri-
cally more demanding 1-isocyano-1-methyl-cyclohexane is
smoothly converted to the respective octahedral complexes
whereas 1-isocyano-cyclohexane does not give any comparable
result.
Fig. 1. Molecular structure of [Ru(CN)2(MeCyNC)4], 2a, thermal ellipsoids are
depicted at the 35% probability level.
methyl protons. Nevertheless, 13C spectra again reflect the differ-
ent symmetry of the cis- and trans-isomers.
Recrystallization of crude 2b after chromatographic workup
from acetone yielded colorless crystals of 2b that were suitable
for X-ray diffraction [8]. The molecular structure of 2b is depicted
in Fig. 1, most important bond lengths and angles are summarized
in Table 1. The central ruthenium atom is situated on a crystallo-
graphic centre of inversion. The coordination sphere around ruthe-
nium is almost perfectly octahedral with the cyanide ligands in
Supplementary material
CCDC 738730 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via http://www.ccdc.ca-
m.ac.uk/data_request/cif.
Table 1
Selected bond lengths [pm] and angles [°] of 2b.
Ru1–C1
C1–N1
N2–C3
206.8(5)
113.9(6)
147.0(6)
Ru1–C2
C2–N2
N3–C11
200.5(5)
114.3(6)
147.2(7)
Ru1–C10
C10–N3
198.6(5)
114.6(6)
C1–Ru1–C2
Ru1–C1–N1
Ru1–C10–N3
89.2(2)
177.3(5)
173.3(5)
C1–Ru1–C10
Ru1–C2–N2
C10–N3–C11
94.3(2)
177.7(5)
164.0(6)
C2–Ru1–C10
C2–N2–C3
90.8(2)
174.1(5)
Hydrogen bond
C9–H9Cꢀ ꢀ ꢀN1
DH [pm]a
98
HA [pm]a
259
DA [pm]a
350(2)
DHA [°]a
154.0
a
D = hydrogen bond donor site; A = hydrogen bond acceptor site.

A. Sterzik et al. / Inorganic Chemistry Communications 13 (2010) 119–122
121
Fig. 2. Supramolecular structure of 2a.
(i) T.-F. Liu, D. Fu, S. Gao, Y.-Z. Zhang, H.-L. Sun, G. Su, Y.-J. Liu, J. Am. Chem.
Soc. 125 (2003) 13976;
Acknowledgments
(k) T. Kajiwara, M. Nakano, Y. Kaneko, S. Takaishi, T. Ito, M. Yamashita, A.
Igashira-Kamiyama, H. Nojiri, Y. Ono, N. Kojima, J. Am. Chem. Soc. 127 (2005)
10150;
(l) R. Lescouëzec, J. Vaissermann, C. Ruiz-Pérez, F. Lloret, R. Carrasco, M. Julve,
M. Verdaguer, Y. Dromzee, D. Gatteschi, W. Wernsdorfer, Angew. Chem. 115
(2003) 1521.
The authors gratefully acknowledge financial support by the
Deutsche Forschungs-gemeinschaft (IM 22/6-2).
References
[3] (a) D. Dönnecke, W. Imhof, J. Chem. Soc., Dalton Trans. (2003) 2737;
(b) W. Imhof, K. Halbauer, Acta Crystallogr. Sect. E 62 (2006) m1514;
(c) K. Halbauer, D. Dönnecke, H. Görls, W. Imhof, Z. Anorg. Allg. Chem. 632
(2006) 1477;
(d) K. Halbauer, H. Görls, T. Fidler, W. Imhof, J. Organomet. Chem. 692 (2007)
1898.
[4] (a) W. Imhof, K. Halbauer, H. Görls, Acta Crystallogr. Sect. E 61 (2005) m2130;
(b) K. Halbauer, G. Leibeling, W. Imhof, Z. Anorg. Allg. Chem. 632 (2006) 264;
(c) K. Halbauer, A. Göbel, A. Sterzik, H. Görls, S. Rau, W. Imhof, Eur. J. Inorg.
Chem. (2007) 1508;
[1] (a) For typical examples see: S.K. Dutta, U. Beckmann, E. Bill, T. Weyhermüller,
K. Wieghardt, Inorg. Chem. 39 (2000) 3355;
(b) M. Ray, R. Mukherjee, J.F. Richardson, R.M. Buchanan, J. Chem. Soc., Dalton
Trans. (1993) 2451;
(c) C.-F. Chow, M.H.W. Lam, W.-Y. Wong, Inorg. Chem. 43 (2004) 8387;
(d) H.-R. Wen, C.-F. Wang, J.-L. Zuo, Y. Song, X.-R. Zeng, X.-Z. You, Inorg. Chem.
45 (2006) 582;
(e) D. Li, S. Parkin, R. Clérac, S.M. Holmes, Inorg. Chem. 45 (2006) 7569;
(f) D. Li, S. Parkin, G. Wang, G.T. Yee, R. Clérac, W. Wernsdorfer, S.M. Holmes, J.
Am. Chem. Soc. 128 (2006) 4214;
(g) J.-N. Rebilly, L. Catala, G. Charron, G. Rogez, E. Rivière, R. Guillot, P. Thuéry,
A.-L. Barra, T. Mallah, Dalton Trans. (2006) 2818;
(h) R. Lescouëzec, L.M. Toma, J. Vaissermann, M. Verdaguer, F.S. Delgado, C.
Ruiz-Pérez, F. Lloret, M. Julve, Coord. Chem. Rev. 249 (2005) 2691;
(i) L.M. Toma, F.S. Delgado, C. Ruiz-Pérez, R. Carrasco, J. Cano, F. Lloret, M.
Julve, Dalton Trans. (2004) 2836;
(j) L. Toma, L.M. Toma, R. Lescouëzec, D. Armentano, G. De Munno, M. Andruh,
J. Cano, F. Lloret, M. Julve, Dalton Trans. (2005) 1357;
(k) J.-N. Rebilly, L. Catala, E. Rivière, R. Guillot, W. Wernsdorfer, T. Mallah,
Inorg. Chem. 44 (2005) 8194;
(l) H.-R. Wen, C.-F. Wang, Y. Song, S. Gao, J.-L. Zuo, X.-Z. You, Inorg. Chem. 45
(2006) 8942;
(m) Z.-G. Gu, Q.-F. Yang, W. Liu, Y. Song, Y.-Z. Li, J.-L. Zuo, X.-Z. You, Inorg.
Chem. 45 (2006) 8895;
(n) S. Wang, M. Ferbinteanu, M. Yamashita, Inorg. Chem. 46 (2007) 610;
(o) L. Jiang, X.-L. Feng, T.-B. Lu, S. Gao, Inorg. Chem. 45 (2006) 5018;
(p) W. Liu, C.-F. Wang, Y.-Z. Li, J.-L. Zuo, X.-Z. You, Inorg. Chem. 45 (2006)
0058;
(q) J. Kim, S. Han, K.I. Pokhodnya, J.M. Migliori, J.S. Miller, Inorg. Chem. 44
(2005) 6983;
(r) C.-F. Wang, J.-L. Zuo, B.M. Bartlett, Y. Song, J.R. Long, X.-Z. You, J. Am. Chem.
Soc. 128 (2006) 7162;
(s) E.J. Schelter, A.V. Prosvirin, K.R. Dunbar, J. Am. Chem. Soc. 126 (2004)
15004;
(d) K. Halbauer, H. Görls, T. Fidler, W. Imhof, Z. Anorg. Allg. Chem. 634 (2008)
1921.
[5] Y. Kitano, K. Chiba, M. Tada, Tetrahedron Lett. 39 (1998) 1911.
[6] IR (KBr pellet) [cmꢁ1]: 2960 (
mas CH3), 2938 (mas CH2), 2864 (ms CH2, CH3), 2127
(
m
NC), 1450 (das CH3), 1380 (ds CH3); MS (EI) [m/z (%)]: 122 (M+ꢁH, 9), 106
(C7H7N+, 13), 97 (C7H1þ0, 17), 81 (C6H9þ, 100), 67 (C5Hþ7 , 16), 54 (C4Hþ6 , 38), 41
(C3Hþ5 , 40).
[7] Synthesis and analytical data for 2a and 3a.
A 23 mg sample of Fe2(CO)9
(0.063 mmol) together with an excess of 1-isocyano-1-methyl-cyclohexane, 1,
(150 mg, 1.24 mmol) in 5 mL of anhydrous toluene are placed inside a stainless
steel autoclave and heated to 130 °C for 24 h. After the autoclave has cooled
down to room temperature the resulting solution was evaporated to dryness in
vacuo. The reaction mixture was then separated by column chromatography
using acetone (elution of 2a) and methanol (elution of 3a). Yields: 32 mg 2a
(0.053 mmol, 42%), 27 mg 3a (immediately after chromatographic workup,
0.045 mmol, 36%). IR (KBr pellets) [cmꢁ1]: 2a: 2935 (
CH2), 2151 ( CN), 2098 ( CN), 1450 (das CH3), 1383 (ds CH3); 3a: 2932 (
CH2), 2860 ( s CH3, CH2), 2160 ( CN), 2112 ( CN), 1462 (ds CH2), 1450 (das CH3),
m
as CH3, CH2), 2860 (
m
s CH3,
m
m
mas CH3,
m
m
m
1381 (ds CH3); MS (FAB) [m/z, (%)], mass spectra show the same fragmentation
scheme albeit different relative intensities of the ions (normal font style 2a,
italics 3a): 601 (M++H, 100, 32), 574 (M+ꢁCN, 8, 0), 548 (M+ꢁ2 CN, 12, 10), 505
([Fe(CN)(HNC)2(MeCyNC)3]+, 28, 9), 451 ([Fe(CN)(MeCyNC)3]+, 46, 31), 425
([Fe(MeCyNC)3]+, 51, 33), 409 ([Fe(CN)(HNC)3(MeCyNC)2]+, 27, 10), 355
([Fe(CN)(HNC)(MeCyNC)2]+, 20, 9), 328 ([Fe(CN)(MeCyNC)2]+, 48, 46), 313
([Fe(CN)(HNC)4(MeCyNC)]+, 31, 19), 302 ([Fe(MeCyNC)2]+, 48, 50), 232
([Fe(CN)(HNC)(MeCyNC)]+, 54, 91), 217 ([Fe(CN)(HNC)5]+, 27, 30), 205
([Fe(CN)(MeCyNC)]+, 58, 100); Elemental analysis of 2a, C34H52N6Fe
(t) J.I. Kim, H.Y. Kwak, J.H. Yoon, D.W. Ryu, I.Y. Yoo, N. Yang, B.K. Cho, J.-G. Park,
H. Lee, C.S. Hong, Inorg. Chem. 48 (2009) 2956.
(600.672 g molꢁ1
(13.99). Synthesis and analytical data for 2b and 3b.
)
[%, (calcd.)]:
C
67.62 (67.99);
H
8.40 (8.73);
N 13.90
[2] (a) D. Gatteschi, Adv. Mater. 6 (1994) 9;
A
28 mg sample of
(b) R. Sessoli, D. Gatteschi, Angew. Chem. 115 (2003) 278;
(c) W. Schmitt, C.E. Anson, W. Wernsdorfer, A.K. Powell, Chem. Commun.
(2005) 2098;
(d) A. Mishra, W. Wernsdorfer, S. Parsons, G. Christoua, E.K. Brechin, Chem.
Commun. (2005) 2086;
(e) R.T.W. Scott, S. Parsons, M. Murugesu, W. Wernsdorfer, G. Christoub, E.K.
Brechin, Chem. Commun. (2005) 2083;
(f) D. Li, S. Parkin, G. Wang, G.T. Yee, A.V. Prosvirin, S.M. Holmes, Inorg. Chem.
44 (2005) 4903;
(g) E.M. Rumberger, S.J. Shah, C.C. Beedle, L.N. Zakharov, A.L. Rheingold, D.
Hendrickson, Inorg. Chem. 44 (2005) 2742;
(h) R. Clérac, H. Miyasaka, M. Yamashita, C. Coulon, J. Am. Chem. Soc. 124
(2002) 12837;
Ru3(CO)12 (0.044 mmol) together with an excess of 1-isocyano-1-methyl-
cyclohexane, 1, (160 mg, 1.30 mmol) in 5 mL of anhydrous toluene are placed
inside a stainless steel autoclave. The autoclave is pressurized with 10 bar of
carbon monoxide and heated to 130 °C for 17 h. After the autoclave has cooled
down to room temperature the resulting solution was evaporated to dryness in
vacuo. The reaction mixture was then separated by column chromatography
using acetone (elution of 2b) and methanol (elution of 3b). Yields: 28 mg 2b
(0.043 mmol, 33%), 21 mg 3b (immediately after chromatographic workup,
0.033 mmol, 25%). IR (KBr pellets) [cmꢁ1]: 2b: 2935 (
CH2), 2154 ( CN), 2105 ( CN), 1450 (das CH3), 1384 (ds CH3); 3b: 2933 (
CH2), 2861 ( s CH3, CH2), 2207 ( CN), 2156 ( CN), 2118 ( CN), 2004 (
1449 (das CH3), 1382 (ds CH3); MS (FAB) [m/z, (%)], mass spectra show the same
m
as CH3, CH2), 2862 (
m
s CH3,
as CH3,
CN),
m
m
m
m
m
m
m
m

122
A. Sterzik et al. / Inorganic Chemistry Communications 13 (2010) 119–122
fragmentation scheme albeit different relative intensities of the ions (normal
[8] Crystal data for 2b: [Ru(CN)2(MeCyNC)4], monoclinic, space group P21/n,
a = 1112.31(5) pm, b = 1257.73(7) pm, c = 1271.98(7) pm, b = 101.902(3)°,
font style 2b, italics 3b): 646 (M++H, 14, 34), 550 ([Ru(CN)(HNC)2(MeCyNC)3]+, 9,
17), 454 ([Ru(CN)(HNC)3(MeCyNC)2]+, 11, 20), 427 ([Ru(CN)(HNC)2(MeCyNC)2]+,
8, 16), 400 ([Ru(CN)(HNC)(MeCyNC)2]+, 11, 10), 358 ([Ru(CN)(HNC)4(MeCyNC)]+,
22, 31), 331 ([Ru(CN)(HNC)3(MeCyNC)]+, 18, 25), 302 ([Ru(CN)3(MeCyNC)]+, 14,
16), 262 ([Ru(CN)(HNC)5]+, 48, 60), 235 ([Ru(CN)(HNC)4]+, 76, 100), 208
([Ru(CN)(HNC)3]+, 100, 63); 1H NMR 3b (CDCl3, 298 K) [ppm]: 0.96–1.48 (m,
7 H, CH3, CH2), 1.48–1.82 (m, 4 H, CH2), 1.82–2.06 (m, 2 H, CH2); 13C NMR 3b
(CDCl3, 298 K) [ppm]: 22.0 (CH2), 24.9 (CH3), 29.4 (CH2), 38.6 (CH2), 60.9 (C),
135.8 (CN), 144.3 (RNC); Elemental analysis of 2b, C34H52N6Ru
(645.925 g molꢁ1) [%, (calcd.)]: C 62.81 (63.22); H 7.89 (8.11); N 12.95 (13.01).
V = 1.7412(1) nm3,
(Mo K
Z = 2,
Dc = 1.232 g cmꢁ3
,
F(0 0 0) = 648,
k
a
) = 0.71073 Å, T = 183 K, Rint = 0.080, structure solution and
refinement based on 2842 independent reflections with I > 2
parameters gave R1 = 0.0645, wR2 = 0.1731, GOF = 1.080.
r (I) and 185
[9] F.A. Cotton, A. Yokochi, Inorg. Chim. Acta 557 (1998) 275–276.
[10] G.R. Desiraju, T. Steiner, The Weak Hydrogen Bond, Oxford Science
Publications, 1999.