metal-organic compounds
interaction between these chains is a ꢁ±ꢁ interaction between
the C24±C29 ring and its symmetry equivalent by inversion
under (1 x, y, 1 z); the rings are necessarily parallel, the
We have observed similar patterns in the geometry of Cu
ions in cryptand hosts derived from tren and trpn [see, for
example, Farrar et al. (1995) and Nelson et al. (1998)],
supporting the suggestion that steric constraints mean that the
larger podand has more dif®culty accommodating bonding
between the CuI ion and all four donors than the smaller
analogue. These results also go some way to explaining the
initially counterintuitive ®nding that, in the dinuclear imino-
cryptate series, the shortest internuclear distances between
cationic guests are found for the larger hosts (Drew et al., 2000;
Farrar et al., 1995; Nelson et al., 1998). In the case of the
cryptand ligands, the twist imposed on each strand by the
coordination of the imine donors shortens the distance
between the two metal binding sites.
Ê
interplanar distance is 3.393 (4) A and centroid-to-centroid
Ê
distance is 3.710 (4) A.
Complex (VI), namely {tris[(2-nitrobenzylidene)amino-
propyl]amine}copper(I) perchlorate, is analogous to complex
(II), except that the longer tripodal amine tris(amino-
propyl)amine (trpn) is used in place of tren. As for (II), the Cu
ion is stabliized in the +1 state and has trigonal±pyramidal
geometry (Fig. 4 and Table 4). However, the CuI ion is
Ê
displaced from the imine plane by 0.167 (1) A towards the
bridgehead [i.e. in the opposite sense from complex (II)]. As
observed for complex (II), the requirement to coordinate the
CuI ion to all four N-atom donors results in tilting of the CÐ
N
C planes relative to the plane of the three sp2-hybridized
imine donors. In complex (VI), however, this effect is much
more pronounced [interplanar angles 34.9 (2), 36.3 (2) and
39.4 (2)ꢀ for atoms N11, N21 and N31, respectively].
Experimental
For the preparation of [CuI(I)]ClO4Á2CH3CN, (II), tris[(2-nitro-
The three-dimensional `podand bite' in the two CuI
complexes, (II) and (VI), can be compared by considering the
dimensions of the trigonal pyramid formed by the four N-atom
donors, with the tertiary amine (N1) at the apex and the imine
atoms N11, N21 and N31 in the basal plane. As mentioned
above, the CuI ion is outside the pyramid in complex (II) and
inside for (VI). However, the CuÐN1 distances are identical
benzylidene)aminoethyl]amine, (I) (0.93 g, 1.7 mmol), was dissolved
in dry deoxygenated acetonitrile (30 ml) and
a solution of
Cu(CH3CN)4ClO4 (0.55 g, 1.7 mmol) in deoxygenated acetonitrile
(20 ml) was added slowly with stirring. The red±brown solution was
stirred for 30 min at 313 K and then cooled, during which time an
orange crystalline product precipitated. This was ®ltered off and
dried under nitrogen, losing the acetonitrile solvent in the process
(yield 0.70 g, 52%). Analytical results (available in the archived CIF)
are consistent with the stated composition for all compounds
reported here.
Ê
[2.196 (2) A] and the CuÐN(imine) bonds are only marginally
Ê
Ê
different [mean values 2.003 (2) A for (II) and 2.018 (2) A for
(VI)]. The mean imine±imine distances in the basal plane are
The amine podand tris[(2-nitrobenzyl)aminoethyl]amine, (III),
was prepared by reduction of the imine analogue (Liu et al., 1992).
The imine (I) (2.15 g, 3.9 mmol) was dissolved in methanol (60 ml).
Na2B4O7 (0.81 g, 4.0 mmol) was added, followed by NaBH4 (0.65 g,
17.2 mmol) in small portions over a period of 30 min. The solution
was stirred for 2 h and then the solvent was removed on a rotary
evaporator. NH4Cl (4 g, 76 mmol) in water (40 ml) was added and the
mixture was extracted with CHCl3 (3 Â 60 ml). The CHCl3 solution
was washed with water, dried over MgSO4 and ®ltered. Finally, the
solvent was removed under reduced pressure to yield the amine as a
pale-yellow oil (yield ca 88%). The IR spectrum of the oil con®rmed
that the ligand had been successfully reduced. The imine stretch at ca
Ê
similar [3.456 and 3.483 A for (II) and (VI), respectively], but
the mean base±apex edges are signi®cantly different
Ê
[2.842 (2) A for (II) and 3.103 (2) for (VI)]. An indication of
steric strain in complex (VI) is given by the NÐCÐC and CÐ
CÐC angles in the saturated chain between N1 and the imine
N atoms; the average angle is 114.4 (3)ꢀ, compared with
110.5 (2)ꢀ for complex (II).
1
1630 cm was no longer present, but symmetric and antisymmetric
stretches of the nitro group at 1347 and 1526 cm 1, respectively,
con®rmed that the substituent remained unchanged. The amine was
used in the next step without further puri®cation.
For the preparation of [CuII(III)Cl]ClÁC2H5OH, (IV), the amine
ligand (III) (0.05 g, 0.09 mmol) was dissolved in ethanol (1.5 ml),
forming a pale-orange solution. On addition of a solution containing
CuCl2 (0.013 g, 0.09 mmol) in ethanol (1 ml), a turquoise solution was
formed. Green crystals of (IV) were obtained on allowing the solu-
tion to stand (yield 0.03 g, 48%).
Ligand (V) was prepared by the dropwise addition of tris(3-
aminoisopropyl)amine (0.32 g, 1.7 mmol) in methanol (20 ml) with
stirring to nitrobenzaldehyde (0.77 g, 5.1 mmol) in methanol (20 ml).
The resulting solution was stirred at 313 K for 30 min and the volume
was then reduced to yield a yellow oil, viz. (V). The oil was dissolved
in deoxygenated acetonitrile (30 ml) and Cu(CH3CN)4ÁClO4 (0.55 g,
1.7 mmol) was added. A brown solution formed and dark-red crystals
of [CuI(V)]ClO4, (VI), were obtained on allowing the solution to
stand (yield 0.69 g, 54%).
Figure 4
The structure of complex (VI), showing the atom-numbering scheme.
Displacement ellipsoids are drawn at the 40% probability level and H
atoms have been omitted for clarity.
m474 Coyle et al. [Cu(C27H27N7O6)]+, [Cu(C30H33N7O6)]+ and [Cu(C27H33N7O6)Cl]+
Acta Cryst. (2006). C62, m472±m476
ꢁ