Crown thioether chemistry: homoleptic hexakis(thioether) complexes of nickel(II)

Metal binding studies with macrocyclic hexathioethers: Transition metal complexes of 22S6 and 20S6

“…(2) with Ni(II), Cd(II), Ru(II), and Cu(II) are also presented in this report. The magnetic moments for the Ni(II) complexes were in the range of 2.95-3.05 B.M., similar to previously reported values of hexakis(thioether) nickel(II) complexes and consistent with two unpaired electrons per nickel [9,51,61,62]. Magnetic susceptibility measurements on the 22S6 complexes of Fe(II) and Co(II) complexes show that both are low-spin complexes, and their absorption spectra (see below) are also consistent with low-spin systems.…”

Preparations for 1,4,7,11,14,17-hexa-thiacycloeicosane, 1,4,7-trithiecan-9-ol, 1,11 -dioxa-4,8,14,18-tetrathia-cycloeicosane, 1 -oxa-4,8-dithiacyclo-decane, and some complexes of iron, cobalt, nickel, and palladium

“…In their compound, the unit cell contains only one enantiomer whereas in ours there are four cations per unit cell, two of which are the d form and two of which are the 1 form so that the sample overall is racemic. Coordination of L1 to produce gauche placement of its sixmembered chelate rings by use of meridional looping is in contrast to that found for 18S6 (18S6 = 1,4,7,10,13, 16-hexathiacyclooctadecane) in [Ni(18s6)l2+ in which all loops are facial but is similar to that for 2436 in [Ni(24s6)l2+ (2436 = 1,5,9,13,17,2 1-hexathiacyclotetracosane) (43). In [Ni(L1)12+ (L1 = 20S6), there are two meridional loops involving the six-membered chelate rings whereas in [Ni(18s6)l2+, which has only five-membered chelate rings, coordination is always facial.…”

“…The electronic spectra (see Experimental) of violet [Ni(Ll)][C104]2 and of purple [Ni(L2)2:I[C104], in nitromethane are similar to spectraof other nickel species with pseudo-octahedral thioether coordination spheres (43). Of the three d-d bands expected, only the first two are observed, while the highest energy band is obscured by a charge transfer band that extends from about 400 nm into the ultraviolet as is usual for such compounds (16,43).…”

“…Of the three d-d bands expected, only the first two are observed, while the highest energy band is obscured by a charge transfer band that extends from about 400 nm into the ultraviolet as is usual for such compounds (16,43). The Racah parameter, B, the nephelauxetic ratio, P, and the ligand field parameter, Ad, for the compounds reported in this study are given in Table 8 together with those of some related compounds for compari- strength and a much larger nephelauxetic effect for the thioethers than for the N-donors.…”

Pentadentate thioether-oxime macrocyclic and quasi-macrocyclic complexes of copper(II) and nickel(II)

“…With donor atoms from row-3 and beyond, the Ni(II) spectra become less straightforward to interpret. Generally, it is known that only two d-d transitions are observed when thioether donors are present, the highest energy band ( 3 T 1g (P) 3 A 2g ) becoming obscured by the charge-transfer processes ( 400 nm) [35]. Two other problems are often encountered in Ni(II) thioether and nitrogen containing systems which are interrelated: (a) The mathematical relation-ships involving spectral transitions and the ligand field parameters break down if there are row-3 donors in the coordination sphere [36]; (b) the lowest energy band ( 3 T 2g 3 A 2g ) often exhibits a double-humped shape due to mixing with a close-lying spin-forbidden transition ( 1 E g 3 A 2g ) through spin-orbit coupling [37,38].…”