Syntheses and properties of NCN-bridged tri- and tetranuclear complexes of cobalt and rhodium

The reaction of [Cp∗CoI2]2 (1b) with 2 equiv of NaNCNH affords the 16-membered macrocyclic NCNH-bridged tetracobalt(III) complex [Cp∗CoI(μ2-NCNH-N,N′)]4 (2b), while that with 2 equiv of Na2NCN yields the C3-elongated cubane-like NCN-bridged tetracobalt(III) complex [Cp∗Co(μ3-NCN-N,N,N′)3(CoCp∗)3(μ3-NCN-N,N,N)] (4b). Treatment of [Cp∗RhCl2]2 (1c) with 2 equiv of NaNCNH gives the C3-elongated cubane-like tetrarhodium(III) complex [Cp∗Rh(μ3-NCN-N,N,N′)3(RhCp∗)3(μ3-NCN-N,N,N)] (4c) via the macrocyclic complex [Cp∗RhCl(μ2-NCNH-N,N′)]4 (2c). On the other hand, the reaction of [Cp∗CoCl]2 (7) with Na2NCN affords the anionic bis(NCN)-capped tricobalt(II) complex Na[(Cp∗Co)3(μ3-NCN-N,N,N)2] (6). The molecular structures of complexes 2b · CH2Cl2 and 4c · 2C6H6 have been confirmed by X-ray analyses. The electrochemical properties of these types of NCN-bridged group 9 metal complexes have also been examined.

The 16-membered macrocyclic NCNH-bridged tetracobalt(III) complex [Cp∗CoI(μ2-NCNH-N,N′)]4, the C3-elongated cubane-like NCN-bridged tetracobalt(III) and tetrarhodium(III) complexes [Cp∗M(μ3-NCN-N,N,N′)3(CoCp∗)3(μ3-NCN-N,N,N)] (M = Co, Rh), and the anionic bis(NCN)-capped tricobalt(II) complex Na[(Cp∗Co)3(μ3-NCN-N,N,N)2] have been newly synthesized, the last of which is shown to undergo one quasi-reversible reduction and two quasi-reversible oxidations.Figure optionsDownload as PowerPoint slide