BIS(DITHIOSQUARAMIDE) LIGANDS AND THEIR COMPLEXES WITH DIVALENT NICKEL: THERMOCHROMIC BEHAVIOUR AND UNANTICIPATED FORMATION OF 2:2 SPECIES

Abstract

Abstract Reaction of two equivalents of N-mono- or di-substituted 3-amino-4-(n-butoxy)-3-cyclobutene-1,2-diones with a 1,2-diaminoethane gave N-mono- or di-substituted 1,2-bis((2-amino-1-cyclobutene-3,4-dione)amino)-ethane derivatives (bis(squaramides)). Reaction of the bis(squaramides) with excess P4S10 gave the analogous tetrathio derivatives (bis(dithiosquaramides), LH2) of formula (NR1R2)C4S2(NHCH2CH2NH)-C4S2(NR1R2) (R1=n-Bu, R2=H; R1=R2=Et, n-Bu). The new bis(dithiosquaramide) ligands were characterized by elemental analysis, IR, 1H NMR, 13C NMR, electronic, and mass spectroscopic methods. The complexes of these ligands with nickel(II) were prepared, isolated and characterized. The isolated complexes are neutral 2:2 species of formula Ni2L2, as evidenced by results from mass spectrometry, and they exhibit thermochromic behaviour in pyridine solution. Additional spectroscopic data (IR, NMR) are consistent with the ligands being coordinated only through sulfur donor atoms and a structure for the comple...