Crystal‐Packing‐Induced Antiferromagnetic Interactions of Metallocenes: Cyanonickelocenes, ‐cobaltocenes, and ‐ferrocenes

Abstract

The cyano-substituted metallocenes [M(C5H4CN)2] (M=Fe, 1; Co, 2; Ni 3) and [M(C5Me5)(C5H4CN)] (M=Fe, 4; Co, 5; Ni, 6) were synthesized in yields up to 58 % by treating K(C5H4CN) or Tl(C5H4CN) with suitable transition-metal precursors. Cyclic voltammetry indicated that the oxidation and reduction potentials of all the cyanometallocenes were shifted to positive values by up to 0.8 V. Single-crystal X-ray structure analysis showed that 1 had eclipsed ligands, formed planes in the lattice, and--unlike usual metallocenes--lined up in stacks perpendicular to these planes. Powder X-ray studies established that 1 and 2 are isotypic. The 1H and 13C NMR spectra were recorded for all the new compounds. Signal shifts of up to delta=1500 ppm were recorded for the paramagnetic molecules 2 and 3 and were, at a given temperature, strikingly different for solution and solid-state spectra. These results pointed to antiferromagnetic interactions as a consequence of molecular ordering in the lattice, as confirmed by magnetic measurements. The temperature-dependent susceptibilities were reproduced by Heisenberg spin-chain models (H=-J sum n- 1 i=1 SiSi+1), thus yielding J=-28.3 and -10.3 cm(-1) for 2 and 3, respectively, whereas J=-11.8 cm(-1) was obtained for 3 from the Ising spin-chain model. In accordance with molecular orbital (MO) considerations, much spin density was found to be delocalized not only on the cyclopentadienyl ligand but also the cyano substituents. The magnetic interaction was interpreted as a Heitler-London spin exchange and was analyzed based on how the interaction depends on the singly occupied MOs and the shift of parallel metallocenes relative to each other.

Crystal structure of ruthenocenecarbonitrile

“…However, the Ru II atom is slightly shifted from the centre of the C 5 ring to the nitrile-bonded C2 atom, which can be explained best by the significantly different Ru-C bond lengths (Table 1) and also the Ru-D-C angles, which should ideally be 90 (Table 1). This is in accordance with the shift in the ferrocenedicarbonitrile structure (Altmannshofer et al, 2008). The C N substituent itself is bent away from the metal atom in (I), with a maximum shift for N1 [0.047 (4) Å ].…”

“…Comparison of the C-C [1.431 (3) Å ] and the C N distances [1.148 (3) Å ] with the respective ferrocene carbonitrile derivatives (C N = 1.133-1.150; C-C = 1.428-1.433 Å ; Altmannshofer et al, 2008;Dayaker et al, 2010;Bell et al, 1996;Nemykin et al, 2007;Erben et al, 2007) The molecular structure of (I), with displacement ellipsoids drawn at the 50% probability level. All H atoms have been omitted for clarity.…”

1,1′‐Diaryl‐Substituted Ferrocenes: Up to Three Hinges in Oligophenyleneethynylene‐Type Molecular Wires

“…However, the structure reflects the conformation in the solid state and thus packing effects should also be considered in addition to an attractive π-π interaction between the two thiophenyl substituents. Other [31] 1,1Ј-dicyanoferrocene, [32] and a triferrocenyldialkyne. [33] The importance of the eclipsed conformations of 1,1Ј-disubstituted ferrocenes is, however, documented by the facile formation of [4]ferrocenophanes from 1,1Ј-dialkynylferrocenes.…”

Crystal structure of paddle-wheel sandwich-type [Cu2{(CH3)2CO}{μ-Fe(η5-C5H4C[triple-bond]N)2}3](BF4)2·(CH3)2CO

“…Since the first synthesis of 1,1 0 -dicyanoferrocene (Osgerby & Pauson, 1961), only one example of a crystal structure has been reported, that of the molecule itself (Altmannshofer et al, 2008) which exhibits a similar synperiplanar torsion (-2.2 ) of the cyclopentadienyl rings to that in (I). Further molecules bearing one nitrilo substituent at the ferrocenyl backbone include a pentacarbonyl tungsten complex with the second nitrilo functionality involved in a 2,3-dihydro-1,2,3-azadiphosphete (Helten et al, 2010) and recently published square-planar cis-and trans-platinum(II) complexes of cyanoferrocene (Strehler et al, 2014).…”