Structural effects of the co-ordination of quadridentate Schiff bases to transition-metal atoms. Structure of NN′-(o-phenylene)bis(salicylideneamine) and of its cobalt(II) complex

Abstract

Structural Effects of the Co-ordination of Quadridentate Schiff Bases t o Transition-metal Atoms. Structure of NN'-(o-phenylene)bis(salicylideneamine) and of its Cobalt(i1) Complex

Schiff-base complexes of calcium: crystal structure analysis of dinitrato[N,N'-propane-1,3-diylbis(salicylideneimine)]calcium(II) and the spectroscopic properties of some related complexes

“…Here N(I)-H(20) is 0.95 (5)/i, and O(1)... H(20) is 1.83 (5) A with the remainder of the ligand bond lengths similar to those found in Co(salphen) (Pahor et al, 1976) and the salen complexes (Calligaris, Nardin & Randaccio, 1971). As N(1)-C(8) at 1.466 /i, is close to the expected bond length of 1.47 A for N(sp2)-C(sp3), writing (lc) as a major contribution is justified, but the bond lengths within the acyl rings and the shortening of C(1)--O(1) and C(6)--C(7) require a contribution from (Ib).…”

“…Comparisons with previously determined structures ( Table 6) Throughout this section the numbering scheme shown in the left-hand side of Fig. 1 will be used: where there are differences in bond lengths and angles for the two halves of any molecule mean values will be given so that, for instance, C(I)-O(1) refers to the mean of C ( 1)--O(1) and C (13)--O(2) for C a(H 2salpd)(NO 3)2" For HEsalphen (Pahor et al, 1976), the enol-imine tautomer (la) predominates over the keto-enamine form (lb) since H(20) and H(21) are located close to the O atoms; C(7)-N(1) is much shorter than C(6)-C(7), and C (1) Bond lengths in the o-phenylene ring connecting N(I) and N(2) will not be considered here. On removal of the phenolic protons and formation of a Co n complex of salphen the bond-length differences in the acyl rings persist although C ( 1)-C (2), C ( 1 )-C (6), and C(5)-C(6) are not much different, with C(7)-C(6) shortening and C(7)-N(1) lengthening on coordination of the O and N atoms.…”

Bis(N-2-propylsalicylideneamino-N,O)cobalt(II)

“…The coordination geometry is very similar to that found for corresponding complexes in which the isopropyl groups are replaced by either n-butyl or tert-butyl groups, these complexes retaining the distorted tetrahedral coordination (Bahron, Larkworthy, Marecaux, Povey & Smith, 1994); the mean Co----O and Co-N distances in the present structure are 1.906 (5) and 1.992 (8),~, respectivel)~, with corresponding values of 1.894 (4) and 1.968 (4) A for the averages of the n-butyl and tert-butyl structures. In contrast, linking the two ligands by a two-carbon bridge between the N atoms forces an approximate square-planar coordination geometry in which the Co---O bonds are shorter by about 0.06 and the CoN bonds are drastically shortened by about 0.13 ,~, (Pahor et al, 1976;Hiller, Nishinaga, Tsutsui & Rieker, 1993). Octahedral coordination of Co "I by three similar salicylideneamino ligands gives mean Co----O. and Co--N bond lengths of 1.893 (3) and 1.948 (4)A, respectively, the smaller intrinsic size of the Co I" ion being largely compensated for, as is generally observed, by an increase in the effective size with a larger coordination number (Elerman, Kabak, Svoboda & Geselle, 1994).…”

“…Molecular graphics: ORTEPII . Software used to prepare material for publication: KAPPA (Macf~ek, unpublished). lic derivatives (Pahor, Calligaris, Delise, Dodic, Nardin & Randaccio, 1976); metal complexes of Schiff bases in general have been extensively studied (Calligaris, Nardin & Randaccio, 1972). We describe here the structure of the bis(N-isopropylsalicylideneamino)cobalt(II), (I), complex and compare it with related compounds having different substituents.…”

[N,N'-1,3-Propylenebis(salicylaldimine)]bis(pyridine)cobalt(III) Tetraphenylborate Pyridine Solvate

“…Recently, some crystal structures have been determined for the free quadridentate ligands (Elerman, Svoboda & Fuess, 1991;Pahor et al, 1976) and their cobalt(II) derivatives in order to obtain insight into the bonding between cobalt and macrocyclic ligands. Since some Co" complexes are air-sensitive, we selected Co m systems for our studies.…”