Heterodinuclear Transition‐Metal Complexes: Fundamentals, Synthesis, and Applications

Abstract

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.

Towards clustered carbonyl cations [M3(CO)14]2+ (M = Ru, Os): the need for innocent deelectronation

“…41 While zero valent and pentacoordinated group 8 complexes are known for having Lewis-basic behaviour and silver cations are known to be Lewis acidic, their heterodinuclear complexes are scarce. 41,42 In contrast to the previously known cationic group 8 → group 11 MOLPs, the primary interaction in [ 3a ] + and [ 3b ] + is the donation of electron density from a metal–metal σ-bond instead of a single metal donor orbital. This donation leads to an elongation of the tangential metal–metal bond by 0.13 Å, 43 while the other metal does not experience significant shifts.…”

Investigations into the AuI and PtII Coordination Chemistry of Bidentate “cis‐Spanning” Ligands

“…The platinum atom in [L PN (Pt{CNC})] ( 19) is coordinated in a distorted squareplanar fashion by the phosphorous atom of L PN and the tridentate CNC pincer-ligand. The protons of the two phenyl rings of the CNC ligand are chemically equivalent as indicated by 1 H-NMR spectroscopy (SI 42). The 31 P{ 1 H}-NMR spectrum of isolated crystals of 19 in CD 2 Cl 2 exhibits a singlet centered at 24.0 ppm featuring 195 Pt satellites ( 1 J PÀ Pt = 4040 Hz, SI 43).…”

“…Heterodinuclear transition-metal complexes are of fundamental interest in catalysis research due to the possibility to tune the catalyst's properties not only by ligand modifications but also by the selective exchange of one of the metal atoms. [1,2] The combination of two or even more metals causes a significant increase of the number of possible complexes when compared with their mononuclear congeners. Moreover, a precise adjustment of the properties of these complexes might become possible by selective metal-atom exchange.…”

“…[3][4][5] In catalysis, for example, heterodinuclear complexes might exhibit an increased affinity for substrate binding due to the polarity of the metal-metal bond. [1] Thus, the catalytic activity might be improved when compared with analogous homometallic complexes of the same nuclearity. [3-5,6a-d,7] Within the last decade, several concepts have been developed for the systematic assembly of two different transition-metal atoms within one complex, and particularly metal-metal-bonded systems form their own body of research within this field.…”

Structurally Precise Two-Transition-Metal Water Oxidation Catalysts: Quantifying Adjacent 3d Metals by Synchrotron X-Radiation Anomalous Dispersion Scattering

“…This information is needed for a quantitative comparison of the WOC and other properties of Co 2 Ni 2 P 2 versus Co 4 P 2 . There are organometallics, − coordination compounds, − nanomaterials, , and POMs − that contain two different metals. For some of these compounds, there is a sufficient separation distance and/or a difference in metal Z value (electron density) in which conventional fixed-wavelength X-ray crystallography can distinguish the two metals reasonably well.…”