Heterodinuclear transition‐metal complexes, that is coordination compounds comprising two different transition‐metal atoms, witness growing interest. This development is driven by the incentive to find complexes, which outperform their mononuclear competitors in reactivity and selectivity. It is particularly the close proximity of the two transition‐metal atoms, which promises to promote these favorable interactions denoted as “cooperative”. Therefore, mainly dinuclear complexes with direct metal–metal bonds are discussed in this article. Since the very first report of a heterodinuclear transition‐metal complex in 1960, a repertoire of methodologies for the targeted synthesis has been established. Besides the description of this progress, the focus of the present article is on the discussion of appropriate characterization methods. Typical questions concern the nature of the metal–metal bond as well as the elucidation of mechanistic details of reactions involving the polar metal–metal bonds present in heterodinuclear complexes. Several applications are detailed, in which heterodinuclear complexes either surpass the limitations of mononuclear complexes or even exhibit so far unknown reactivity. So‐called “early–late” complexes represent the most dominant branch in this context, while also “late–late” complexes show fruitful reactivity. Herein, the focus is on transition‐metal‐containing complexes, thus ignoring main‐group elements completely.
The PPh 3 ligands in the heterodinuclear AuPt complex [(Ph 3 P)AuPt(PPh 3 ) 3 ][BAr 4 F ] (BAr 4 F = tetrakis[3,5bis(trifluoromethyl)phenyl]borate) exhibit a high fluxionality on the AuPt core. Fast intramolecular and slow intermolecular processes for the reversible exchange of the PPh 3 ligands have been identified. When [(Ph 3 P)AuPt(PPh 3 ) 3 ][BAr 4F ] is heated in solution, the formation of benzene is observed, and a trinuclear, cationic AuPt 2 complex is generated. This process is preceded by reversible phenyl-group exchange between the PPh 3 ligands present in the reaction mixture as elucidated by deuterium-labeling studies. Both the elimination of benzene and the preceding reversible phenyl-group exchange have originally been observed in massspectrometry-based CID experiments (CID = Collision-Induced Dissociation). While CID of mass-selected [Au,Pt,(PPh 3 ) 4 ] + results exclusively in the loss of PPh 3 , the resulting cation [Au,Pt,(PPh 3 ) 3 ] + selectively eliminates C 6 H 6 . Thus, the dissociation of a PPh 3 ligand from [Au,Pt,(PPh 3 ) 3 ] + is energetically not able to compete with processes which result in C−H-and C−P-bond cleavage. In both media, the heterobimetallic nature of the employed complexes is the key for the observed reactivity. Only the intimate interplay of the gas-phase investigations, studies in solution, and thorough DFT computations allowed for the elucidation of the mechanistic details of the reactivity of [(Ph 3 P)AuPt(PPh 3 ) 3 ][BAr 4 F ].
Due to the weakly bound alkene ligands, [(Ph3P)AuPt(nbe)3][BAr4F] can serve as a precursor for the synthesis of formal Au+IPt0 complexes.
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