Synthesis and Reactivity of Triangular Heterometallic Complexes Containing Zn-Zn Bond.

This work provides a facile access to a series of triangular [Zn2M] (M = group 10 and 11 metals) clusters. Treatment of Zn-Zn-bonded compounds [LZn-ZnL] (L = CH3C(2,6-iPr2C6H3N)CHC(CH3)(NCH2CH2PR2); R = Ph, iPr) with zero-valent transition-metal reagents selectively afforded the corresponding triangular clusters [Zn2M], where M = Ni(0), Pd(0), and Pt(0). Notably, the isoelectronic triangular clusters [Zn2M]+, where M = Ag(I) and Cu(I), could also be obtained by reactions of [LZn-ZnL] with AgOTf and CuOTf, respectively. The [Zn2Ag]+ complex containing elusive Zn-Ag bonds was investigated by density functional theory analysis, showing a 3c-2e bonding feature in the metallic ring. The electrochemical behaviors of [Zn2M] complexes were examined and revealed the donation of electron density from the Zn-Zn σ-bond to the metal centers. Reaction of the [Zn2Ni] complex with isocyanide gave heterometallic species by coordination of isocyanide to the nickel center, keeping the trimetallic ring core structure intact. In contrast, the Zn-Zn bond was rapidly cleaved upon treatment of the [Zn2Ni] complex with dihydrogen or phenyl acetylene, generating the hydride- or acetylide-bridged heterotrimetallic complex.