Inorganic Chemistry, Vol.55, No.10, 4746-4756, 2016
Radical and Non-Radical States of the [Os(PIQ)] Core (PIQ=9,10-Phenanthreneiminoquinone): Iminosemiquinone to Iminoquinone Conversion Promoted o-Metalation Reaction
The coordination and redox chemistry of 9,10-phenanthreneiminoquinone (PIQ) with osmium ion authenticating the [Os(II()PIQ(center dot-)], [Os-III(PIQ(center dot-))], [Os-III(C,N-PIQ)], [Os-III(PIQ)], and [Os-III(PIQ(2-))] states of the [Os(PIQ)] core in the complexes of types trans-[Os-II(PI center dot-)(PPh3)(2)(CO)Br] (1), trans-[Os-III(PIQ(center dot-)(PPh3)(2)Br-2] (2), trans-[Os-III(C,N-PIQ)(PPh3)(2)Br-2]center dot 2CH(2)Cl(2) (3 center dot 2CH(2)Cl(2)), trans-[Os-III(C,N-PIQ(Br))(PH3)(2)Br-2]center dot 2CH(2)Cl(2) (4 center dot 2CH(2)Cl(2)), trans-[Osm(III)(C,N-PIQ(Cl2))(PPh3)(2)Br-2] (6), trans-[Os-III(PIQ(center dot-))(PPh3)(2)Br-2](+) 1/2I(3)(-) 1/2Br(-) (1(+)1/2I(3)(-)1/2Br(-)), [OSIII(PIQ)(PPh3)(2)Br-2](+) (2(+)), and [Os-III(PIQ(2-))(PPh3)(2)Br-2](-) (2(-)) are reported (PIQ(center dot-) = 9,10-phenanthreneiminosemiquinonate anion radical; C,N-PIQ = ortho-metalated PIQ C,N-PIQ(Br) = ortho-metalated 4-bromo PIQ, and C,N-PIQ(Cl2) = ottho-metalated 3,4-dichloro PIQ). Reduction of PIQ by [Os-II(PPh3)(3)(H)(CO)Br] affords 1, while the reaction of PIQ with [Os-II(PPh3)(3)Br-2] furnishes 2. Oxidation of 1 with 12 affords 1+1/2I(3)(-)1/2Br(-), while the similar reactions of 2 with X-2 (X = I, Br, Cl) produce the ortho-metalated derivatives 3 center dot 2CH(2)Cl(2), 4 center dot 2CH(2)Cl(2), and 6. PIQ and PIQ(2-) complexes of osmium(III), 2(+) and 2(-) are generated by, constant-potential electrolysis. However, 2(+) ion is unstable in solution and slowly converts to 3 and partially hydrolyzes to trans-[Os-III(PQ(center dot-)(PPh3)(2)Br-2] (2(PQ)), a PQ(center dot-) analogue of 2. Conversion of 2(+) -> 3 in solution excludes the formation of aryl halide as an intermediate for this unique ortho-metalation reaction at 295 K, where PIQ acts as a redox-noninnocent ambidentate ligand. In the complexes; the PIQ(center dot-) state where the atomic spin is mote localized on the nitrogen atom is stable and is more abundant. The reaction of 2(PQ), with I-2 does not promote any ortho-metalation, reaction and yields a PQ complex of type trans-[Os-III(PQ)(PPh3)(2)Br-2]I-+(5)-center dot 2CH(2)Cl(2) (5(+)I(5)(+)center dot 2CH(2)Cl(2)). The molecular and electronic structures of 1-4, 6, 1(+), and 5(+) were established by different spectra, single-crystal X-ray bond parameters, cyclic voltammetry, and DFT calculations.