To a cooled inixture (approx. 0 C under an argon atmosphere) containing IiBuBi-(2 mmolj, hexamethyldisilazane (4 mmol). and TMEDA (4 mmol) in 2 mL of pentane was added nBuLi (6 mmol, from a Z M solution in pentanej. The mixture was stirred for five minutes. after which pinacolone (2 mmol) was added over a period of one minute. The opaque solution &as warmed to 20 C and concentrated to half volume in vacuo. After gentle heating. the clear colorless solution was kept at -20 .C. Upon standing for several w8eeks. a small crop of crystalline 1 was deposited. Although the yield of these crystals varied with the crystallization conditions. it was reproducible and not insignificant.

Überraschend gut strukturiert sind Gele, die aus faserbildenden Molekülen wie denen der Titelverbindung 1 gebildet werden. Dies ließ sich jetzt anhand von Pulverdiagrammen zeigen und auch, wie sich die Struktur der Gele in Abhängigkeit vom Lösungsmittel ändert.

The reaction of [ Fe(salen)CI] [H,salen = N,N'-bis(salicy1idene)ethane-1.2-diamine] with an excess of L [imidazole (Him), 1 -, 2-or 4-methylimidazole (1 -, 2-or 4-mim)I in acetone resulted in the isolation of heterobisadducts, [ Fe(salen) L( Cl)] (L = Him, 1 -or 2-mim) and a homobisadduct, [ Fe(salen) &] CI (L = 4-mim). The structures of [ Fe(salen) (1 -mim)CI] and [ Fe(salen) (4-mim),]CI were determined by single-crystal X-ray diffraction: [Fe(salen)(l -mim)CI], monoclinic, space group P2,/c, Z = 4, a = 9.8510(10), b = 15.9830(10), c = 12.8350(10) A, p = 107.610(10)"; [Fe(salen)(4-mirn),]CI,orthorhombic, space group Fdd2, Z = 8, a = 21.7650(10), b = 12.5040(10), c = 18.508(2) A. The structures were refined by full-matrix least-squares methods on F Z to R = 0.0537 and 0.0338 for 2609 and 1207 reflections, respectively. A significant difference between the two structures is that the dihedral angle between the two phenyl rings of the salen ligand is 17.5" for [Fe(salen)(lmim)CI] and 4.4" for [Fe(salen) (4-mim),]CI. All of the complexes were characterized by variabletemperature magnetic susceptibility and Mossbauer spectroscopy. The heterobisadducts, which have a N,O,CI donor set, exhibit an admixed electronic ground state whereas the homobisadduct is high spin. Another N, O, CI donor set molecule has been found to exhibit a temperature-dependent spin equilibrium, 2T c 6A, as evidenced by variable-temperature magnetic susceptibility, ESR and Mossbauer spectroscopies.We recently reported the first heterodinuclear spin-crossover complexes which were prepared by the reaction of tetra-or penta-dentate Schiff-base complex of Fe"' with a nickel imidazolate chelate to give, in the case of the tetradentate ligand N,N'-bis(salicylidene)ethane-1,2-diamine (H,salen), a N302Cl donor set A and, in the case of the pentadentate ligands a N402 donor set B.' It has been reported previously that the N402 donor set produces an overall ligand field close to the crossover point for Fe"' in salen Schiff-base complexes.2 Whether or not a complex with this donor set exhibits the crossover phenomenon was found to depend on the counter ion, substituents on the salen ligand, structural features of the axial ligand, and intermolecular effects in the solid state. Therefore, the observation of spin crossover in the solid state in complexes derived from pentadentate Schiff-base ligands was not unexpected. However, the observation of spin crossover in the complex derived from [Fe(salen)Cl] and the nickel imidazolate chelate is the first example reported for Fe"' in a N302CI donor set. The objective of the present work was the synthesis of other examples of iron(r1r) complexes containing the N30,Cl donor set which might show unusual electronic and structural properties. The compounds prepared were derived from [Fe-(sa1en)Cl-J or [Fe(SMeO-salen)Cl] and an imidazole donor to give an unsymmetrical heterobisadduct of the iron(1rr) Schiff base in which the imidazole donor occupies one axial site and chloride ion occupies the other. These complexes are a...

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