Cymantrenecarboxylate complexes of nickel(II) and cobalt(II)

Abstract

Reactions of cymantrenecarboxylic acid (CO)3MnC5H4COOH (CymCOOH) with Ni(II) and Co(II) pivalates in boiling THF followed by extraction of the products with diethyl ether or benzene and treatment with triphenylphosphine gave the binuclear complexes LM(CymCOO)4ML (M = Ni (I) and Co (II); L = PPh3). Treatment of the benzene extract of the intermediate cobalt cymantrenecarboxylate with 2,6-lutidine (L’) yielded the trinuclear complex L’Co(CymCOO)3Co(CymCOO)3CoL’ (III). Complex I is antiferromagnetic; μeff decreases from 3.7 to 0.9 μB in a temperature range from 300 to 2 K. Structures I-III were identified using X-ray diffraction. The frameworks of complexes I and II are like Chinese lanterns, having four carboxylate bridges and axial ligands L (Ni-P, 2.358(1) A; Co-P, 2.412(2) A). The metal atoms are not bonded to each other (Ni…Ni, 2.7583(9) A; Co…Co, 2808 (2) A). In complex III, either terminal Co atom is coordinated to one ligand L’ (Co-N, 2.059(2) A). The Co atoms form a linear chain showing no M-M bonds (Co…Co, 3.346(1) A), in which either terminal Co atom is linked with the central Co atom by three carboxylate bridges (on average, Cocentr-O, 2.164 A; COterm-O, 2.094 A). In one of three carboxylate groups, only one carboxylate O atom serves as a bridge, while the other is bonded to the terminal Co atom only (Coterm-O, 2.094 and 2.389 A); so this carboxylate group is a bridging and chelating ligand.