metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
(Tro®menko et al., 1962). Unfortunately, structures in which
the cdm anion bridges transition metal centers are yet
unknown. Single-crystal X-ray diffraction studies have
revealed that Ni (Shi et al., 2001), Co (Shi, Yin et al., 2002) and
Mn (Schlueter et al., 2003) form isomorphous mononuclear
complexes, [M(cdm)2(H2O)4]Á2H2O, in which the metal atom
is octahedrally coordinated by the nitrile N atoms of two cdm
anions and the O atoms of four water molecules. In this study,
the crystal structure of Kcdm was examined in an attempt to
understand why tcm has a tendency to form polymeric
networks while cdm preferentially forms molecular species.
ISSN 0108-2701
Potassium carbamoyldicyano-
methanide
John A. Schlueter* and Urs Geiser
Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue,
Argonne, IL 60439, USA
Correspondence e-mail: jaschlueter@anl.gov
Received 14 November 2003
Accepted 18 November 2003
Online 6 December 2003
The crystal structure of the title compound, K[(CN)2-
CC(O)NH2)] or K+ÁC4H2N3O , conventionally abbreviated
as Kcdm, where cdm is carbamoyldicyanomethanide, is
described. The bond lengths and angles of the cdm cation
are comparable to those reported previously for
[M(cdm)2(H2O)4]Á2H2O (M = Ni, Mn and Co). The K atoms
are coordinated to four nitrile N atoms and two carbonyl O
atoms in a distorted trigonal prismatic fashion, with two
further N atoms semicoordinated through the centers of two
prism side faces. This coordination leads to the formation of
mixed anion±cation sheets parallel to the ab plane, which are
joined together via hydrogen-bonding interactions. The cdm
anion is potentially useful for the formation of transition metal
coordination polymers, in which magnetic superexchange
could occur through a bidentate cdm bridge. Kcdm provides a
model compound by which the molecular geometry of the cdm
anion can be analyzed.
The geometry of the cdm anion in the Kcdm salt is essen-
tially identical to that found in [M(cdm)2(H2O)4]Á2H2O. The
Ê
anion is very nearly planar (the r.m.s. deviation is 0.009 A), the
Ê
greatest deviation from planarity being 0.017 (1) A for
methanide atom C3 (Fig. 1). As expected, the CÐCÐC angles
about the methanide C atom [117.6 (1), 120.2 (1) and
122.2 (1)ꢀ] sum to 360.0ꢀ, indicating nearly complete sp2
hybridization. A distorted trigonal prismatic inner coordina-
tion sphere exists about the potassium cation, consisting of
two carbonyl O atoms and four nitrile N atoms of six different
cdm anions. The outer coordination sphere of potassium
contains one amide and one nitrile N atom whose KÐN
Ê
distances are about 0.4 A longer than the inner-sphere KÐN
bond lengths.
The plane of the cdm ligand lies at an angle of 26.79 (2)ꢀ
with respect to the ac plane. The angle between cdm molecular
planes related by the screw axis is twice as large. The potas-
sium coordination links the cdm anions into bi-bridged sheets
parallel to the ab plane (Fig. 2). Intersheet hydrogen bonding
is observed between amine atom H3A and the carbonyl O
atoms. The second amine H atom, H3B, has a signi®cantly
Comment
The structural and magnetic properties of coordination poly-
mers containing cyano-based anions have received increased
attention over the past decade. The dicyanamide (dca) anion,
N(CN)2 , has been shown to be an effective magnetic super-
exchange ligand, with Ni(dca)2 exhibiting ferromagnetism at
21 K (Kurmoo & Kepert, 1998). A logical extension of this
research is to include cyanocarbon anions as molecular
building blocks for the construction of magnetic solids. Tri-
cyanomethanide (tcm), C(CN)3 , is one of the simplest
cyanocarbon anions that is capable of forming polymeric
structures. The M(tcm)2 (M = Cu, Mn and Zn) crystal struc-
tures are characterized by the interpenetration of two iden-
tical rutile-like lattices, in which the tcm anion is ꢀ3-bonded to
three MII ions (Batten et al., 1991; Manson et al., 1998;
Hoshino et al., 1999). The carbamoyldicyanomethanide (cdm)
anion, (CN)2CC(O)NH2 , is a derivative of tcm in which one
nitrile group is replaced with C(O)NH2. The cdm anion is
therefore a candidate for forming coordination polymers
Figure 1
A view of the molecular structure of Kcdm, showing the atom-numbering
scheme. Displacement ellipsoids are drawn at the 50% probability level,
and H atoms are shown as small spheres of arbitrary radii.
m10 # 2004 International Union of Crystallography
DOI: 10.1107/S0108270103026568
Acta Cryst. (2004). C60, m10±m12
Schlueter, John A.
