Synthesis, characterization and photochemistry of [Rh2 (diisocyanide)4 Re2 (CO)10] (PF6)2 complexes (diisocyanide 1,3-diisocyanopropane; 2,5-diisocyano-2,5-dimethylhexane; 1,8-diisocyano-p-menthane)

Marlene M. Mixa, Andrew Sykes, K. R. Mann

Research output: Contribution to journalArticlepeer-review

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Abstract

The syntheses, characterization and photochemistry of a series of tetranuclear complexes of the form [Rh2(diisocyanide)4Re2(CO)10]2+ (diisocyanide = 1,3-diisocyanopropane (bridge), 2,5-diisocyano-2,5- dimethylhexane (TM4), or 1,8-diisocyano-p- menthane (dimen)) are reported. The syntheses of Rh2(dimen)4Mn 2(CO)10(PF6)2 and Rh2(bridge)4Mn2(CO)10(BF4)2 were successful, but the complexes could not be purified. The syntheses of similar tetra- nuclear complexes with [MoCp(CO)3]2 (Cp cyclopentadienyl) and [FeCp(CO)2]2 as the terminal metal groups were not successful. All of the complexes exhibit an intense allowed (ε{lunate} > 50000 M-1 cm-1) electronic transition in the visible spectral region attributable to a metal localized transition in the linear tetranuclear core. Shifts in the energy of this transition with changes in the tetranuclear species accord with the predictions of simple Hückel MO theory for a highly delocalized, four orbital, four metal atom system. Photochemical studies of [Rh2(TM4)4Re2(CO)10](PF6)2 that address three types of potential photochemical reactivity are reported: stability in the absence of substrates, terminal metal group radical exchange and ligand substitution. The complex is inert upon σ → σ* excitation in the absence of substrates and does not exhibit radical exchange of the terminal metal groups. Photochemical ligand substitution occurs in the presence of phosphine ligands, but the complex undergoes primary diisocyanide substitution at Rh rather than CO substitution at Re. These results contrast the photochemical behavior of binuclear species (M2(CO)10) that contain a single metalmetal bond.

Original languageEnglish (US)
Pages (from-to)159-165
Number of pages7
JournalInorganica Chimica Acta
Volume160
Issue number2
DOIs
StatePublished - Jun 15 1989

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