Transition metal complexes of cyanoisocyanoarenes as building blocks for one-, two-, and three-dimensional molecular solids

Article abstract of DOI:10.1021/ic950580e

The complexes trans-[MI₂(CNC₆H₄-CN-4)₂]< (M = Pd and Ft), trans-[FeI₂L₄] (L = CNC₆H₄-CN-4 and CNC₆H₂-Me_2-2.6-CN-4), and [Mn(CNC₆H₄-CN-4)₆][SO₃CF ₃] were prepared. The compounds are thermally stable up to 230 °C or higher. The molecular structure of trans-[FeI₂(CNC₆H₄-CN-4)₄] was determined by X-ray crystallography: monoclinic, space group P2₁/n, a = 11.570(2) A?, b = 10.1052(8) A?, c = 28.138(7) A?, β= 92.034(9)°, Z = 4, 3464 unique reflections, R = 0.074, R_w = 0.089. The complexes contain the peripheral cyano groups in linear, planar, and octahedral dispositions, respectively. Solids were obtained by combining solutions of [PdI₂(CNC₆H₄-CN-4)₂] and [Cu(hfacac)₂], [FeI₂CNC₆H₄-CN-4₄)] and AgSO₃CF₃, [FeI₂(CNC₆H₂-Me₂-2,6-CN-4) ₄] and [Rh₂(O₂CCF₃)₄], and [Mn(CNC₆H₄-CN-4)₆][SO₃CF ₃] and [Rh₂(O₂CCF₃)₄]. [PdI₂(CNC₆H₄-CN-4)₂] and [Cu(hfacac)₂] in a ratio of 1:2 form a crystalline, one-dimensional solid: monoclinic, space group P2₁/c, a = 8.317(2) A?, b = 13.541(1) A?, c = 22.568(5) A? β= 100.45(1)°, Z = 2, 3279 unique reflections, R = 0.037, R_w = 0.047.

Full text of DOI:10.1021/ic950580e

Inorg. Chem. 1996, 35, 3183-3187
3183
Transition Metal Complexes of Cyanoisocyanoarenes as Building Blocks for One-, Two-,
and Three-Dimensional Molecular Solids
Li-Feng Mao and Andreas Mayr*,1
Departments of Chemistry, State University of New York at Stony Brook,
Stony Brook, New York 11794-3400, and The University of Hong Kong,
Pokfulam Road, Hong Kong
ReceiVed May 12, 1995X
The complexes trans-[MI2(CNC6H4-CN-4)2], (M ) Pd and Pt), trans-[FeI2L4] (L ) CNC6H4-CN-4 and CNC6H2-
Me2-2,6-CN-4), and [Mn(CNC6H4-CN-4)6][SO3CF3] were prepared. The compounds are thermally stable up to
230 °C or higher. The molecular structure of trans-[FeI2(CNC6H4-CN-4)4] was determined by X-ray
crystallography: monoclinic, space group P21/n, a ) 11.570(2) Å, b ) 10.1052(8) Å, c ) 28.138(7) Å, â )
92.034(9)°, Z ) 4, 3464 unique reflections, R ) 0.074, Rw ) 0.089. The complexes contain the peripheral cyano
groups in linear, planar, and octahedral dispositions, respectively. Solids were obtained by combining solutions
of [PdI2(CNC6H4-CN-4)2] and [Cu(hfacac)2], [FeI2(CNC6H4-CN-4)4] and AgSO3CF3, [FeI2(CNC6H2-Me2-2,6-
CN-4)4] and [Rh2(O2CCF3)4], and [Mn(CNC6H4-CN-4)6][SO3CF3] and [Rh2(O2CCF3)4]. [PdI2(CNC6H4-CN-4)2]
and [Cu(hfacac)2] in a ratio of 1:2 form a crystalline, one-dimensional solid: monoclinic, space group P21/c, a
) 8.317(2) Å, b ) 13.541(1) Å, c ) 22.568(5) Å, â ) 100.45(1)°, Z ) 2, 3279 unique reflections, R ) 0.037,
Rw ) 0.047.
Introduction
be functionalized in ways to promote self-assembly. In this
work, we are exploring the potential of transition metal
The formation of extended solids by the self-assembly of
molecular components is a powerful method in the design of
new materials.2,3 In such systems, the molecular units are
typically held together by weak coordinative bonds2,4 or
hydrogen bonds.3,5 Weak interactions allow the self-assembly
processes to proceed under reversible conditions, thus favoring
the formation of regular structures. Transition metal complexes
of functionalized isocyanides6 lend themselves as building
blocks for molecular materials for several reasons. Isocyanides
are strong ligands, giving rise to stable metal complexes.
Isocyanide ligands are also sterically undemanding in the
immediate vicinity of the metal centers, accommodating most
coordination geometries.7 Furthermore, isocyanide ligands can
isocyanide complexes carrying cyano groups in peripheral sites
as building blocks for molecular materials. The expectation
that such systems will undergo controlled self-assembly in
combination with suitable metal ions or metal complexes is
based on the well-known fact that nitriles are weak ligands8
and the observation that organic polynitriles can serve as
bridging ligands in molecular or extended structures.9 Here we
report the synthesis of transition metal complexes of isocyano-
benzonitriles with linear, square-planar, and octahedral disposi-
tions of the peripheral nitrile groups. These molecular building
blocks are designed to combine with suitable metal ions or
complexes to form one-, two-, and three-dimensional structures.
The viability of the new approach is demonstrated by the
formation of a crystalline one-dimensional solid from linear
metal diisocyanide building blocks and unsaturated metal
complex linking units.
X Abstract published in AdVance ACS Abstracts, April 15, 1996.
(1) On leave at The University of Hong Kong.
(2) (a) Iwamoto, T. In Inclusion Compounds; Vol. 5, Atwood, J. L.,
Davies, J. E. D., MacNicol, D. D., Eds.; Oxford University Press:
Oxford, U.K., 1991; Vol. 5, p 177. (b) Robson, R.; Abrahams, B. F.;
Batten, S. R.; Gable, R. W.; Hoskins, B. F.; Liu, J. In Supramolecular
Architecture; Bein, T., Ed.; ACS Symposium Series 499; American
Chemical Society: Washington, DC, 1992. (c) Lehn, J.-M. In
PerspectiVes in Coordination Chemistry; Williams, A. F., Floriani,
C., Merbach, A. S., Eds.; VCH: Weinheim, Germany, 1992; p 447.
(3) (a) Lehn, J.-M. Supramolecular Chemistry; VCH: Weinheim, Ger-
many, 1995. (b) Etter, M. C. Acc. Chem. Res. 1990, 23, 120. (c)
MacDonald, J. C.; Whitesides, G. M. Chem. ReV. 1994, 94, 2383.
(4) (a) De Munno, G.; Julve, M.; Nicolo’, F.; Lloret, F.; Faus, J.; Ruiz,
R.; Sinn, E. Angew. Chem. 1993, 105, 588; Angew. Chem., Int. Ed.
Engl. 1993, 32, 613. (b) Otieno, T.; Rettig, S. J.; Thompson, R. C.;
Trotter, J. Inorg. Chem. 1993, 32, 4384. (c) Tamaki, H.; Zhong, Z. J.;
Matsumoto, N.; Kida, S.; Koikawa, N.; Hashimoto, Y.; Okawa, H. J.
Am. Chem. Soc. 1992, 114, 6974. (d) Stumpf, H. O.; Pei, Y.; Kahn,
O.; Sletten, J.; Renard, J. P. J. Am. Chem. Soc. 1993, 115, 6738. (e)
Jung, O.-S.; Pierpont, C. G. J. Am. Chem. Soc. 1994, 116, 2229. (f)
Pollagi, T. P.; Geib, S. J.; Hopkins, M. D. J. Am. Chem. Soc. 1994,
116, 6051.
(5) (a) Copp, S. B.; Subramanian, S.; Zaworotko, M. J. J. Am. Chem.
Soc. 1992, 114, 8719. (b) Chang, Y.-L.; West, M.-A.; Fowler, F. W.;
Lauher, J. W. J. Am. Chem. Soc. 1993, 115, 5991. (c) Geib, S. J.;
Vicent, C.; Fan, E.; Hamilton, A. D. Angew. Chem. 1993, 105, 83;
Angew. Chem., Int. Ed. Engl. 1993, 32, 119. (d) Wang, X.; Simard,
M.; Wuest, J. D. J. Am. Chem. Soc. 1994, 116, 12119.
(6) (a) Fehlhammer, W. P.; Fritz, M. Chem. ReV. 1993, 93, 1243. (b) Hahn,
F. E. Angew. Chem. 1993, 105, 681; Angew. Chem., Int. Ed. Engl.
1993, 32, 650.
Results and Discussion
The cyanoisocyanobenzene 1a reacts with suspensions of
[PdI2] and [PtI2] in THF to afford the complexes 2 and 3,
respectively (eq 1). Compound 2 forms orange crystals from
THF/hexane; compound 3 precipitates as a yellow solid from
the same solvent mixture. Treatment of [FeI2‚4H2O] with the
cyanoisocyanobenzenes 1a and 1b in THF gives the complexes
4a and 4b, respectively (eq 2). Both 4a and 4b form dark green
(7) (a) Singleton, E.; Oosthuizen, H. E. AdV. Organomet. Chem. 1983,
22, 209. (b) Yamamoto, Y. Coord. Chem. ReV. 1980, 32, 193. (c)
Treichel, P. M. AdV. Organomet. Chem. 1973, 11, 21.
(8) Dunbar, K. R. Comments Inorg. Chem. 1992, 13, 313.
(9) (a) Konnert, J.; Britton, D. Inorg. Chem. 1966, 5, 1191. (b) Batten, S.
R.; Hoskins, B. F.; Robson, R. J. Chem. Soc., Chem. Commun. 1991,
445. (c) Bartley, S. L.; Dunbar, K. R. Angew. Chem. 1991, 103, 447;
Angew. Chem., Int. Ed. Engl. 1991, 30, 448. (d) Miller, J. S.; Calabrese,
J. C.; McLean, R. W.; Epstein, A. J. AdV. Mater. 1992, 4, 498. (e)
Bunn, A. G.; Caroll, P. J.; Wayland, B. B. Inorg. Chem. 1992, 31,
1297. (f) Cotton, F. A.; Kim, Y. J. Am. Chem. Soc. 1993, 115, 8511.
(g) Kaim, W.; Moscherosch, M. Coord. Chem. ReV. 1994, 129, 157.
(h) Abrahams, B. F.; Hoskins, B. F.; Michail, D. M.; Robson, R.
Nature 1994, 369, 727. (i) Gardner, G. B.; Ventakaraman, D.; Moore,
J. S.; Lee, S. Nature 1995, 374, 792.
S0020-1669(95)00580-5 CCC: $12.00 © 1996 American Chemical Society

3184 Inorganic Chemistry, Vol. 35, No. 11, 1996
Mao and Mayr
Table 1. Crystallographic Data for 4a and 6
crystals from methylene chloride/ether. The manganese com-
plex 5 is obtained by heating a mixture of [MnBr(CO)5] and
excess 1a in THF to reflux for 2 days, followed by metathesis
with NH4SO3CF3 in acetone (eq 3). Complex 5 forms orange-
yellow crystals from acetone/hexane. The isocyanide complexes
2-5 are thermally very stable. Complexes 2, 3, 4b, and 5 show
no signs of decomposition up to 230 °C. Complex 4a begins
to melt and decompose at 230 °C.
4a
6
formula
fw
C32H16FeI2N8
822.19
C36H12Cu2F24I2N4O8Pd
1571.80
P21/c (No. 14)
8.317(2)
13.541(1)
22.568(5)
100.45(1)
2499.5(8)
2
space group
a, Å
b, Å
c, Å
P21/n (No. 14)
11.570(2)
10.1052(8)
28.138(7)
92.034(9)
3280.5(1)
4
â, deg
V, Å3
Z
T, °C
25
25
λ, Å
0.710 73
23.543
0.074
0.710 73
25.568
0.037
linear abs coeff, cm-1
Ra
b
Rw
0.089
0.047
goodness of fit
2.067
2.067
a R ) ∑||Fo| - |Fc||/∑|Fo| (quantity minimized (∑w(|Fo| -|Fc|)2);
2
2
weight w ) 1/(σ(Fo) + 0.0016Fo )]. b Rw ) [∑w(|Fo| - |Fc|)2/∑wFo ]1/2
.
Complexes 2 and 3 exist as the trans isomers. The IR spectra
exhibit only a single sharp absorption for the isocyanide groups
at 2199 and 2191 cm-1 (CH2Cl2 solution), respectively. Weak
signals at 2236 and 2231 cm-1 are observed for the nitrile
groups. The meridional arrangement of the four isocyanide
ligands in 4a and 4b is evident from the IR and NMR data.
The isocyanide groups of complexes 4a and 4b in methylene
chloride solution give rise to absorptions at 2119 and 2117 cm-1,
respectively. The nitrile stretching frequencies of 4a and 4b
are found at 2234 and 2230 cm-1. The 1H and 13C NMR spectra
of 4a and 4b show only single sets of signals for the isocyanide
ligands. The IR spectrum of a CH2Cl2 solution of 5 exhibits a
strong signal at 2089 cm-1 with a shoulder at 2120 cm-1 and
a weak peak at 2037 cm-1 for the isocyanide groups, and a
1
weak absorption at 2233 cm-1 for the nitrile groups. The H
and 13C NMR spectra of 5 show only single sets of signals for
the six isocyanide ligands, indicating a regular octahedral
coordination geometry.
The structure of 4a was determined by X-ray crystallography.
The crystal data are collected in Table 1; selected bond distances
and bond angles are listed in Table 2. Figure 1 shows the
structure of one of two independent molecules in the unit cell.
The two iodide ligands are mutually trans, and the four
isocyanide ligands are in meridional arrangement. The bond
distances and angles are within the expected range, except for
one symmetry-related pair of bent nitrile groups in the second
independent molecule (not shown in Figure 1).
Complexes of the types [MX2(CNR)2] (M ) Pd, Pt; X )
halogen) and [MX2(CNR)4] (M ) Fe, Co; X ) halogen) are
well established.7 They exist as cis and trans isomers. With
the heavier halogens the trans isomers are preferred. Octahedral
complexes of the type [M(CNR)6]+ (M ) Mn, Tc, Re) have
been studied intensively in recent years, primarily because of
the use of technetium complexes as radioimaging agents.10
Isocyanobenzonitriles have received attention as components
in nonlinear optical devices.11
On the basis of the spectroscopic and structural studies, the
peripheral nitrile groups of complexes 2/3, 4, and 5 are in linear,
square-planar, and octahedral dispositions, respectively. If these
nitrile groups are connected in an oriented fashion, e.g. by
coordination to suitable metal centers, then one-, two-, and three-
(10) (a) Treichel, P. M.; Dirreen, G. E.; Mueh, H. J. J. Organomet. Chem.
1972, 44, 339. (b) Abrams, M. J.; Davison, A.; Jones, A. G.; Costello,
C. E.; Pang, H. Inorg. Chem. 1983, 22, 2798.
(11) Ohashi, T.; Kojima, T.; Toda, H.; Itsubo, A. Jpn. Patent JP 02228636
[90156229], 1990; Chem. Abstr. 1991, 114, 132733y.

Transition Metal Complexes of Cyanoisocyanoarenes
Inorganic Chemistry, Vol. 35, No. 11, 1996 3185
Table 2. Selected Bond Lengths (Å) and Angles (deg) for
Complex 4a
Table 3. (a) Selected Bond Lengths (Å) and Angles (deg) for Solid
6
molecule 1
molecule 2
Pd component
Cu component
(a) Bond Lengths
2.619(1) Fe(2)-I(2)
Bond Lengths
2.5795(6) Cu-O(1)
Fe(1)-I(1)
2.637(1)
1.86(2)
1.91(2)
1.16(2)
1.38(2)
1.10(2)
1.11(2)
1.35(2)
1.20(4)
1.51(3)
1.45(4)
Pd-I(1)
1.933(3)
1.921(4)
1.933(4)
1.944(3)
2.669(6)
3.1929(9)
1.253(6)
1.247(7)
1.263(6)
1.253(6)
1.378(8)
1.392(9)
1.369(7)
1.368(8)
Fe(1)-C(1)
Fe(1)-C(9)
N(1)-C(1)
N(1)-C(2)
N(2)-C(8)
N(3)-C(9)
N(3)-C(10)
N(4)-C(16)
C(5)-C(8)
C(13)-C(16)
1.92(1)
1.84(2)
1.13(2)
1.35(2)
1.15(2)
1.18(2)
1.38(2)
1.11(2)
1.43(2)
1.49(2)
Fe(2)-C(17)
Pd-C(11)
1.944(6)
1.147(7)
1.403(7)
1.131(7)
1.360(8)
1.385(8)
1.372(8)
1.364(8)
1.385(8)
1.441(8)
1.373(8)
Cu-O(2)
Cu-O(3)
Cu-O(4)
Cu-N(2)
Cu-I(1)
O(1)-C(1)
O(2)-C(3)
O(3)-C(6)
O(4)-C(8)
C(1)-C(2)
C(2)-C(3)
C(6)-C(7)
C(7)-C(8)
Fe(2)-C(25)
N(5)-C(17)
N(5)-C(18)
N(6)-C(24)
N(7)-C(25)
N(7)-C(26)
N(8)-C(32)
C(21)-C(24)
C(29)-C(32)
N(1)-C(11)
N(1)-C(12)
N(2)-C(18)
C(12)-C(13)
C(12)-C(17)
C(13)-C(14)
C(14)-C(15)
C(15)-C(16)
C(15)-C(18)
C(16)-C(17)
(b) Bond Angles
I(1)-Fe(1)-I(1A)
I(1)-Fe(1)-C(1)
I(1)-Fe(1)-C(9)
180.00
88.6(4)
92.7(4)
I(2)-Fe(2)-I(2A)
I(2)-Fe(1)-C(17)
I(2)-Fe(2)-C(25)
C(17)-Fe(2)-C(17A) 180.00
C(17)-Fe(2)-C(25) 88.5(7)
C(25)-Fe(2)-C(25A) 180.00
180.00
93.8(5)
92.3(4)
(b) Bond Angles
C(1)-Fe(1)-C(1A) 180.00
C(1)-Fe(1)-C(9) 91.1(6)
C(9)-Fe(1)-C(9A) 180.00
I(1)-Pd-I(1A)
I(1)-Pd-C(11)
C(11)-Pd-C(11A)
Pd-C(11)-N(1)
C(11)-N(1)-C(12)
N(1)-C(12)-C(13)
180.00
88.4(2)
180.00
177.2(5)
175.5(6)
118.4(5)
O(1)-Cu-O(2)
92.3(2)
87.3(1)
179.7(2)
177.3(2)
87.9(2)
O(1)-Cu-O(3)
O(1)-Cu-O(4)
O(2)-Cu-O(3)
O(2)-Cu-O(4)
O(3)-Cu-O(4)
Cu-N(2)-C(18)
Cu-I(1)-Pd
Fe(1)-C(1)-N(1)
Fe(1)-C(9)-N(3)
N(1)-C(2)-C(3)
N(2)-C(8)-C(5)
176(1)
178(1)
120(1)
178(2)
Fe(2)-C(17)-N(5)
Fe(2)-C(25)-N(7)
N(5)-C(18)-C(19)
N(6)-C(24)-C(21)
N(7)-C(26)-C(27)
N(8)-C(32)-C(29)
C(17)-N(5)-C(18)
C(25)-N(7)-C(26)
177(1)
177(2)
119(2)
177(3)
121(2)
155(6)
177(2)
168(2)
92.5(1)
C(13)-C(12)-C(17) 122.9(5)
C(12)-C(13)-C(14) 119.0(5)
C(12)-C(17)-C(16) 117.1(5)
C(13)-C(14)-C(15) 119.8(5)
C(14)-C(15)-C(16) 120.5(5)
C(14)-C(15)-C(18) 119.7(5)
C(15)-C(16)-C(17) 120.6(5)
108.4(5)
99.81(2)
124.6(4)
125.3(4)
124.5(3)
124.1(3)
N(3)-C(10)-C(11) 121(2)
N(4)-C(16)-C(13) 177(3)
Cu-O(1)-C(1)
Cu-O(2)-C(3)
Cu-O(3)-C(6)
Cu-O(4)-C(8)
O(1)-C(1)-C(2) 128.2(5)
O(2)-C(3)-C(2) 127.3(5)
O(3)-C(6)-C(7) 127.7(5)
O(4)-C(8)-C(7) 127.5(5)
C(1)-C(2)-C(3) 121.2(5)
C(6)-C(7)-C(8) 122.7(5)
C(1)-N(1)-C(2)
C(9)-N(3)-C(10)
175(1)
172(1)
Figure 1. ORTEP drawing of 4a. Only one of the two independent
molecules is shown. The thermal ellipsoids are shown at the 35%
probability level.
dimensional extended structures should result. To test the
feasibility of this approach, solutions of the complexes 2-5 were
treated with several metal reagents which are known to link
organic nitriles or metal cyanide complexes, e.g. [Cu(hfacac)2]
(hfacac ) hexafluoroacetylacetonate), Ag(I), and [Rh2(O2-
CCF3)4].8,9c,e When a solution of equimolar amounts of 2 and
[Cu(hfacac)2] in CH2Cl2 is slowly evaporated to dryness, a
mixture of solids results. One of the components is the starting
material 2. However, when the palladium building block and
the copper linker are combined in the same manner in a 1:2
ratio, a residue of apparently homogeneous green crystals, solid
6, is obtained. Large dark green crystals of 6 form when the
solvent is allowed to evaporate very slowly. Attempts to obtain
solids from 3 with [Cu(hfacac)2] or other linking units have
not yet given satisfactory results, presumably due to the low
solubility of the platinum complex. Addition of [AgSO3CF3]
to a THF solution of 4a affords solid 7. It contains the
components in a ratio close to 1:2. When benzene solutions of
4b and [Rh2(O2CCF3)4] are combined, solid 8 forms with a
relative ratio of about 1:2.6 of the components. Solid 9, which
results by combining THF solutions of 5 and [Rh2(O2CCF3)4],
contains the manganese building block and the rhodium linker
Figure 2. ORTEP drawing of the molecular components [PdI2-
(CNC6H4-CN-4)2] and [Cu(hfacac)2] of solid 6. The thermal ellipsoids
are shown at the 35% probability level.
in a ratio of about 1:2. This ratio suggests that only four
isocyanide ligands per manganese complex are involved in the
formation of the extended framework.
The crystal structure of solid 6 was determined by X-ray
crystallography. The crystal data are collected in Table 1;
selected bond distances and bond angles are listed in Table 3.
An ORTEP drawing of the molecular components is shown in
Figure 2. The [PdI2(CNC6H4-CN-4)2] building blocks and the
[Cu(hfacac)2] linker units are arranged to form one-dimensional
chains. A short section of a single chain is shown in Figure 3.
Each copper atom achieves an octahedral coordination geometry
by interacting with one nitrile group and one iodine atom of

3186 Inorganic Chemistry, Vol. 35, No. 11, 1996
Mao and Mayr
solid-state chemistry based on cyano-substituted isocyanide
complexes as building blocks can be expected to be quite
extensive.
Experimental Section
Standard inert-atmosphere techniques were used in the execution of
the experiments. The solvents methylene chloride (CaH2), tetrahydro-
furan, ether (Na/benzophenone), and hexane (CaH2) were dried and
distilled prior to use. 1a15 and 1b,15,16 [MnBr(CO)5],17 and [Rh2(O2-
CCF3)4]18 were prepared on the basis of literature procedures.
[FeI2‚4H2O] and [PtI2] were obtained from commercial sources. The
Figure 3. Portion of a chain of [PdI2(CNC6H4-CN-4)2] building blocks
linked by [Cu(hfacac)2] units in solid 6.
1
NMR spectra were measured at 250 or 300 MHz (for H NMR) in
complex 2. Thus, two copper linkers are accomodated per
palladium building block. The nitrile groups are coordinated
to the copper atoms in a bent fashion (Cu-N(2)-C(18),
108.4(5)°). The Cu-N(2) distance of 2.669(6) Å is longer by
about 0.1 Å than in the “linear” links of the one-dimensional
solid [Cu(hfacac)2][TCNE] (Cu-N-C, 164.7(3)°; Cu-N,
2.563(3) Å; TCNE ) tetracyanoethylene). Apparently, a π
orbital of the CN triple bond acts as the donor site rather than
the lone pair of the nitrile group.
CDCl3 at room temperature unless otherwise noted. Solvent peaks were
used as internal reference; the chemical shifts are reported in δ relative
to TMS.
Synthesis of [PdI2(CN-C6H4-CN)2] (2). Black [PdI2] (100 mg,
0.277 mmol) is suspended in CH2Cl2 (20 mL), and CN-C6H4-CN-4
(78 mg, 0.61 mmol) in 10 mL of CH2Cl2 is added. An orange solution
forms immediately. After the mixture is stirred for 1 h at room
temperature, the solvent is removed under vacuum and the residue is
washed with ether to remove excess ligand. The residue is recrystallized
from CH2Cl2 to give orange crystals (0.111 g, 65%), mp >230 °C. 1H
NMR (CD2Cl2): δ 7.70 (d, 2H, J ) 8.7 Hz, C6H4), 7.84 (d, 2 H, J )
8.4 Hz, C6H4). IR (CH2Cl2, cm-1): ν(-CtN) 2236 m, ν(-NtC) 2199
s. Anal. Calcd for C16H8I2N4Pd: C, 31.17; H, 1.31; N, 9.09; I, 41.17.
Found: C, 30.98; H, 1.17; N, 8.86; I, 41.39.
Synthesis of [PtI2(CN-C6H4-CN)2] (3). Black [PtI]2 (200 mg, 0.446
mmol) is suspended in THF (25 mL), and CN-C6H4-CN-4 (114 mg,
0.89 mmol) is added. A green-brown solution forms immediately. The
solution is filtered, and the solvent is removed under vacuum. The
residue is washed with ether and reprecipitated from THF/hexane to
give a yellow noncrystalline solid (0.172 g, 55%), mp >230 °C. 1H
NMR (d8-THF): δ 7.87 (d, 2H, J ) 8.51 Hz, C6H4), 7.99 (d, 2 H, J )
8.52 Hz, C6H4). 13C{1H} NMR (d8-THF): δ 134.8, 128.7, 117.7, 116.2
(C6H4). IR (THF, cm-1): ν(-CtN) 2231 m, ν(-NtC) 2191 s. Anal.
Calcd for C16H8I2N4Pt: C, 27.25; H, 1.14; N, 7.95. Found: C, 27.48;
H, 1.21; N, 7.99.
Synthesis of [FeI2(CN-C6H4-CN)4] (4a). [FeI2‚4H2O] (1.0 g, 2.6
mmol) is first dried under vacuum for 1 h at room temperature and
then dissolved in THF (200 mL) to give a dark purple solution. Upon
addition of CN-C6H4-CN-4 (1.34 g, 10.47 mmol), the solution turns
greenish brown immediately. After the mixture is stirred for 2 h at
room temperature, the solvent is removed under vacuum, and the residue
is washed with ether to remove excess ligand. Recrystallization from
CH2Cl2/ether gives a dark green crystalline solid (0.90 g, 39%).
Crystals suitable for X-ray crystallography were grown by diffusion
of pentane into a CH2Cl2 solution of 4a, mp 230-270 °C dec. 1H
NMR (CDCl3): δ 7.63 (d, 2H, J ) 8.50 Hz, C6H4), 7.78 (d, 2H, J )
8.50 Hz, C6H4). 13C{1H} NMR (CDCl3): δ 176.1 (FesCN), 133.5,
131.3, 127.4, 117.2, 113.4 (C6H4, -CN). IR (CH2Cl2, cm-1): ν(-
CtN) 2234 w, ν(-NtC) 2119 vs, 2039 vw. Anal. Calcd for
C32H16FeI2N8: C, 46.75; H, 1.96; N, 13.63. Found: C, 46.55; H, 1.95;
N, 13.45.
The results demonstrate that metal complexes of 4-cyano-1-
isocyanobenzenes can serve as building blocks for the assembly
of extended molecular solids. An interesting fact, which hints
at electronic communication between the linked metal centers
across the 4-cyano-1-isocyanoarenes, is the observation that the
colors of some solids differ significantly from those of the
building blocks and linking groups. For example, solid 8,
formed from deep green 3b and blue [Rh2(O2CCF3)4], is brown
and solid 9, formed from yellow 5 and blue [Rh2(O2CCF3)4], is
dark yellow. We therefore expect that solids containing metal
complexes of cyanoisocyanoarenes as structural components will
exhibit novel materials properties.
1,4-Diisocyanobenzene, an isomer of 1a, and other diisocy-
anobenzenes have previously been used as bridging ligands in
organometallic polymers.12 Extended solids have also been
obtained with 1,4-dicyanobenzene.3b Electronic communication
between metal centers across the 1,4-diisocyanobenzene ligand
has been studied.13 The linear 4-cyanoisocyanoarenes may also
be considered as elongated neutral analogues of the cyanide
ion. Cyanide forms stable mononuclear complexes by coordi-
nation to metal centers via the carbon atom and polynuclear
assemblies or extended solids upon further coordination of the
nitrogen atom.6a,14 The solids obtained from the new building
blocks 2-5 may thus be viewed as expanded analogues of metal
cyanides. Considering the large number of possible cyanoiso-
cyanoarenes, the rich coordination chemistry of isocyanides and
nitriles, and the formal analogy between metal complexes of
cyanoisocyanoarenes and cyanometal complexes, the molecular
Synthesis of [FeI2(CN-C8H8-Me2-2,6-CN-4)4] (4b). The procedure
for the synthesis of 4a was followed. Reaction of FeI2‚4H2O (200 mg,
0.524 mmol) and 2 (327 mg, 2.10 mmol) in THF and recrystallization
from CH2Cl2/ether gives dark green crystals (202 mg, 41%), mp >230
°C. 1H NMR (CDCl3): δ 7.42 (s, 2 H, C6H2), 2.61 (s, 6 H, CH3).
13C{1H} NMR (CDCl3): 178.1 (FesCN), 137.5, 131.7, 131.0, 117.5,
112.3 (C6H2, -CN), 19.0 (CH3). IR (CH2Cl2, cm-1): ν(-CtN) 2230
m, ν(-NtC) 2117 vs. Anal. Calcd for C40H32FeI2N8: C, 51.42; H,
3.45; N, 11.99. Found: C, 50.74; H, 4.20; N, 11.41. On the basis of
1H NMR, the crystals include a small amount of ether.
(12) (a) Feinstein-Jaffe, I.; Frolow, F.; Wackerle, L.; Goldman, A.; Efraty,
A. J. Chem. Soc. Dalton Trans. 1988, 469. (b) Hanack, M.; Deger,
S.; Lange, A. Coord. Chem. ReV. 1988, 83, 115. (c) Tannenbaum, R.
Chem. Mater. 1994, 6, 550. (d) Bradford, A. M.; Kristof, E.; Rashidi,
M.; Yang, D.-S.; Payne, N. C.; Puddephatt, R. J. Inorg. Chem. 1994,
33, 2355.
(13) Grubisha, D. S.; Rommel, J. S.; Lane, T. M.; Tysoe, W. T.; Bennett,
D. W. Inorg. Chem. 1992, 31, 5022.
(14) (a) Sharpe, A. G. The Chemistry of Cyano Complexes of the Transition
Metals; Academic Press: London, 1976. (b) Park, K.-M.; Kuroda,
R.; Iwamoto, T. Angew. Chem. 1993, 105, 939; Angew. Chem. Int.
Ed. Engl. 1993, 32, 884. (c) Brimah, A. K.; Siebel, E.; Fischer, R. D.;
Davies, N. A.; Apperley, D. C.; Harris, R. K. J. Organomet. Chem.
1994, 475, 85. (d) Abrahams, B. F.; Hardie, M. J.; Hoskins, B. F.;
Robson, R.; Sutherland, E. E. J. Chem. Soc., Chem. Commun. 1994,
1049. (e) Kimizuka, N.; Handa, T.; Ichinose, I.; Kunitake, T. Angew.
Chem. 1994, 106, 2576; Angew. Chem., Int. Ed. Engl. 1994, 33, 2483.
(f) Ohba, M.; Okawa, H.; Ito, T.; Ohto, A. J. Chem. Soc., Chem.
Commun. 1995, 1545. (g) Zhou, M.; Pfennig, B. W.; Steiger, J. L.;
Van Engen, D.; Bocarsly, A. B. Inorg. Chem. 1990, 29, 2456.
(15) (a) Huffman, C. W. J. Org. Chem. 1958, 23, 727. (b) Ugi, I.; Fetzer,
U.; Eholzer, U.; Knupfer, H.; Offermann, K. Angew. Chem. 1965,
77, 492.
(16) (a) Petrini, M.; Ballini, R.; Rosini, G. Synthesis 1987, 713. (b) Dunn,
A. D.; Miles, M. J.; Henry, W. Org. Prep. Proced. Int. 1982, 14, 396.
(17) Abel, E. W.; Wilkinson, G. J. Chem. Soc. 1959, 1501.
(18) Johnson, S. A.; Hunt, H. R.; Neumann, H. M. Inorg. Chem. 1963, 2,
960.

Transition Metal Complexes of Cyanoisocyanoarenes
Inorganic Chemistry, Vol. 35, No. 11, 1996 3187
Synthesis of [Mn(CN-C6H4-CN)6]SO3CF3 (5). A mixture of
[Mn(CO)5Br] (1.50 g, 5.5 mmol) and CN-C6H4-CN-4 (5.59 g, 43.7
mmol) in THF (150 mL) is refluxed for 2 days. During this time the
solution turns from orange to dark red and an orange precipitate forms,
which is collected by filtration and washed with ether. The solid is
transferred into a flask and treated with acetone and NH4SO3CF3. The
resulting suspension is stirred at room temperature for 1 h to give an
orange-yellow solution and a pale yellow precipitate, which is removed
by filtration. The solvent is removed from the filtered solution to give
an orange yellow solid. The solid is redissolved in CH2Cl2, the resulting
solution is filtered, and the solvent is removed again under vacuum.
The product is recrystallized from acetone/hexane to give orange yellow
microcrystals (2.16 g, 40%), mp >230 °C. 1H NMR (CD2Cl2): δ 7.63
(d, 2H, J ) 7.15 Hz, C6H4), 7.76 (d, 2H, J ) 7.16 Hz, C6H4). 13C{1H}
NMR (CD2Cl2): δ 134.4, 131.8, 128.0, 118.0, 113.4 (C6H4 and -CN,
isocyanide signal not found). IR (CH2Cl2, cm-1): ν(-CtN) 2233 w,
ν(-NtC) 2120 sh, 2088 vs, 2037 m. Anal. Calcd for C49H24F3MnN12-
SO3: C, 60.50; H, 2.49; N, 17.28. Found: C, 59.91; H, 2.12; N, 17.37.
Formation of Solid 6 from 2 and [Cu(hfacac)2]. A green solution
of [Cu(hfacac)2] (15 mg, 0.031 mmol) in 0.5 mL of CH2Cl2 is slowly
added to an orange solution of [PdI2(CN-C6H4-CN)2] (10 mg, 0.016
mmol) in 1 mL of CH2Cl2. Green crystals form when the solvent slowly
evaporates. IR (KBr, cm-1): ν(-CtN) 2228 m, ν(-NtC) 2213 s.
Anal. Calcd for [PdI2(CN-C6H4-CN)2] + 2[Cu(hfacac)2]: C, 27.46;
H, 0.80; N, 3.55. Found: C:27.51; H, 0.77; N, 3.56.
Formation of Solid 7 from 4a and AgSO3CF3. A solution of
[AgSO3CF3] (31 mg, 0.12 mmol) in 1 mL of THF is added to a solution
of 4a (50 mg, 0.061 mmol) in 8 mL of THF. A lime green precipitate
forms immediately. The solid is separated from the light yellow
solution by centrifugation. After removal of the supernatant, the
precipitate is washed with THF and dried under vacuum. IR (KBr,
cm-1): ν(-CtN) 2244 w, 2233 w, ν(-NtC) 2182 sh, 2145 s. Anal.
Found: C, 30.03; H, 1.35; N, 8.02; Ag, 17.08. Calcd for 4a +
2.24AgSO3CF3: C, 29.43; H, 1.15; N, 8.02; Ag, 17.29. Calcd for 1Fe
+ 2Ag: C, 30.58; H, 1.21; N, 8.39; Ag, 16.15.
Formation of Solid 9 from 5 and Rh2(O2CCF3)4]. A blue solution
of [Rh2(O2CCF3)4] (50 mg, 0.076 mmol) in CH2Cl2 is added to a yellow
solution of 5 (25 mg, 0.026 mmol) in CH2Cl2. A dark yellow precipitate
forms immediately. It is allowed to stand for 2 days and then separated
by filtration. The solid is washed with CH2Cl2 and dried under vacuum.
IR (KBr, cm-1): ν(-CtN) 2260 w, 2234 w, ν(-NtC) 2120 sh, 2083
s, 2042 m, 1667 s. Anal. Found: C, 34.14; H, 1.17; N, 7.31; F, 22.93.
Calcd for 5 + 2[Rh2(O2CCF3)4]: C, 34.11; H, 1.06; N, 7.34; F, 22.41.
X-ray Structure Determination. The general procedures for unit
cell determination, data collection, and structure solution have been
previously described in detail.19 All intensity measurements were made
on an Enraf-Nonius CAD4A automated diffractometer, using a variable-
rate, ω-2θ scan technique. Empirical absorption corrections (DIFABS)
were applied. All calculations were performed using the TEXRAY
programs. The structures were solved by direct methods and difference
Fourier methods. The positions of the hydrogen atoms were calculated
and used in the least-squares calculations but were not refined. Selected
crystallographic data are listed in Table 1.
The asymmetric unit of compound 4a contains two centrosymmetric
molecules. The terminal CN group (C(32), N(8)) of one ligand in
molecule 4a(2) shows very large thermal parameters. The entire C6
ring also shows large thermal parameters. All attempts to refine models
with a disordered CN group or with a disordered C6 ring and CN group
were unsuccessful. The final model has unrealistic metrical parameters
concerning these fragments. The high values of R (Rw) reflect the
unresolved disorder.
The CF3 groups in compound 6 show significant disorder. An
acceptable refinement was achieved using a model in which the fluorine
atoms of each CF3 group were 2-fold disordered. The structural
diagram in Figure 2 shows only one set of fluorine atoms for each CF3
group.
Acknowledgment. We thank Prof. Stephen A. Koch, David
Nellis, and Hua-Fen Hsu for determining the crystal structures
of 4a and 6. Support for this work by the National Science
Foundation is gratefully acknowledged.
Formation of Solid 8 from 4b and [Rh2(O2CCF3)4]. A blue
solution of [Rh2(O2CCF3)4] (14 mg, 0.021 mmol) in 0.5 mL of benzene
is slowly added to a green solution of 4b (10 mg, 0.011 mmol) in 5
mL of benzene. A brown precipitate forms immediately. The mixture
is stirred for several minutes and then allowed to stand overnight. The
nearly colorless supernatant is decanted; the precipitate is washed with
ether and then dried under vacuum. IR (KBr, cm-1): ν(-NtC) 2124
sh, 2117 s, 2110 sh. Anal. Found: C, 27.82; H, 1.09; N, 4.23. Calcd
for 4b + 2.61[Rh2(O2CCF3)4]: C, 27.58; H, 1.22; N, 4.23.
Supporting Information Available: Tables of crystallographic
data, positional parameters, U values, bond lengths, and bond angles
4a and of crystallographic data, positional parameters, U values, bond
lengths, bond angles, and intermolecular distances for 6 (16 pages).
Ordering information is given on any current masthead page.
IC950580E
(19) Lincoln, S.; Koch, S. A. Inorg. Chem. 1986, 25, 1594.