Steric Effects in the Formation of Copper and Cobalt Complexes with the Epimeric Salicylidenementhylamines
IN a previous communication1, it was reported that cobaltous ions do not react readily with salicylidene-aniline bases bearing ortho substituents on the aniline ring. In the present communication are reported some further attempts to prepare similar complexes of cobalt and copper, using as the amine components of the salicylidene bases four epimeric forms of menthylamine which, with bulky isopropyl substituents and nonplanar ring forms, may be expected to exert considerable steric resistance to a tetrahedral grouping of ligands about cobalt ions. The complexes were prepared by mixing aqueous solutions of the metal acetates with an alcoholic solution of the salicylidene base2. The results of this work are indicated in Table 1, the complexes isolated being of the form bis (salicylidenementhylamine) cobalt (copper).
Structure of Cobalt Complexes with Salicylideneanilines
THE structures of cobalt inner complexes with salicylideneanilines have not been determined, whereas the planar form of copper complexes of this type has been established beyond doubt by the isolation of cis and trans isomers1 and by X-ray investigation2. A difference in reactivity has now been observed between copper and cobalt ions with various salicylideneaniline bases which suggests a tetrahedral structure for the cobalt complexes. Attempts have been made to prepare complexes of the type bis-(salicylideneaniline)cobalt with bases containing aromatic amines bearing substituents in the ortho, meta and para positions. The compounds prepared are tabulated below together with the corresponding copper complexes previously prepared3.
Röntgenographische Untersuchungen an inneren Kupferkomplexsalzen
Es wird der Molekel- und Kristallbau einer Reihe innerer Kupferkomplexsalze mit koordinativ vierwertigem Kupfer an Einkristallen rontgenographisch untersucht. Es ergab sich in allen Fallen, in denen eine diesbezugkiche Bestimmung moglich war, eine ebene Transanordnung der vier am Kupferatom gebundenen Atome – mit Ausnahme der Falle, bei denen durch eine Verknupfung zweier Liganden zwangsmasig die cis-Konfiguration festgelegt ist. – Auch dann, wenn eine Verbindung in mehreren verschiedenen Formen auftrat, handelte es sich stets nur um polymorph verschiedenartige Zusammenlagerung gleichartig gebauter Molekeln. – Falls keine sterische Hinderung dem entgegensteht, erwiesen sich (soweit feststellbar) die ganzen Molekeln als eben. – Die Art der Zusammenlagerung der Molekeln zum Kristall last sich weitgehend aus der Form der Molekeln verstehen.