Linkage isomerism of the sulfate ion in ditoluenesulfinato-bis(2,2′-bipyridyl) complexes of iron(II), cobalt(II), and nickel(II)

Abstract

Linkage isomers involving the O- and S-bonded unidentate sulfinate ions were prepared. The isomers are of the type [M(bipy) 2(RSO 2) 2] where R = p-toluene and the metal = Fe II, Co II, and Ni II. In the iron(II) compounds, S-bonded sulfinate effects spin-pairing. Thus, Mössbauer spectra of the iron(II) O-bonded (Ia) and S-Bonded (Ib) isomers show, at 259°K, quadrupole splittings ΔE Q = 2.65 and 0.31 mm/sec and isomer shifts δ IS = +0.99 and +0.31 mm/sec, for Ia and Ib, serially. These values are characteristic for 5T 2 and 1A 1 ground states in iron(II) consistent with the magnetic moments, at 292°K, of μ eff = 5.27 and 0.95 BM in Ia and Ib, respectively. From the electronic dd spectra of nickel(II) O-bonded (IIa) and S-bonded (IIb) isomers, the average values 10Dq = 10,200 and 11,600 cm −1 as well as β 35 = 1.03 and 0.97 were obtained for IIa and IIb, serially. In the O-bonded cobalt(II) isomer (IIIa), 10Dq = 11,025 cm −1 and β 35 = 0.84, whereas only the a 4T 1→ 4T 2 transition has been observed in the S-bonded isomer (IIIb) giving the estimate 10Dq∼12,300 cm −1. The magnetism of IIa,b and IIIa,b is consistent with six-coordinated nickel(II) and cobalt(II), respectively. The consequences with regard to the position of the unidentate O- and S-bonded sulfinate ion in the spectrochemical and nephelauxetic series are discussed.