Synthesis and Structures of d10–d10 M2(μ‐dppm)2 Complexes with Sensitive Metal–Metal Distances in Response to the Binding of Sigma Donors

Diphosphine‐bridged dicopper(I) acetate complexes [Cu₂(μ‐dppm)₂(μ‐OAc)]X ( 2 X; X^? = , ) and [Cu₂(μ‐dppm)₂(μ‐OAc)(MeCN)]X ( 4 X) were prepared and the structures of 2 (PF₆ ) and 4 (PF₆ ) determined by X‐ray crystallography. The ground‐state geometries of [Cu₂(μ‐dppm)₂(μ‐OAc)]⁺ and [Cu₂(μ‐dppm)₂(μ‐OAc)(L)]⁺ (L = py, MeCN, THF, acetone, MeOH) were also obtained using density functional theory (DFT). The increased Cu – Cu distances found experimentally and theoretically by comparing the structures of cation [Cu₂(μ‐dppm)₂(μ‐OAc)]⁺ and its derivatives [Cu₂(μ‐dppm)₂(μ‐OAc)(L)]⁺ reflect the binding of various sigma donors (L). When using [Cu₂(μ‐dppm)₂(μ‐OAc)]⁺ as a structure sensor, the electron‐donating strength of a sigma donor can be quantitatively expressed as a DFT‐calculated Cu – Cu distance with the relative strength in the order py > MeCN > THF > acetone > MeOH, as determined.     

Metal–Metal Interactions in Heterobimetallic Complexes with Dinucleating Redox‐Active Ligands

The tuning of metal–metal interactions in multinuclear assemblies is a challenge. Selective P coordination of a redox‐active PNO ligand to Au^I followed by homoleptic metalation of the NO pocket with Ni^II affords a unique trinuclear Au–Ni–Au complex. This species features two antiferromagnetically coupled ligand‐centered radicals and a double intramolecular d⁸–d¹⁰ interaction, as supported by spectroscopic, single‐crystal X‐ray diffraction, and computational data. A corresponding cationic dinuclear Au–Ni analogue with a stronger d⁸–d¹⁰ interaction is also reported. Although both heterobimetallic structures display rich electrochemistry, only the trinuclear Au–Ni–Au complex facilitates electrocatalytic C?X bond activation of alkyl halides in its doubly reduced state. Hence, the presence of a redox‐active ligand framework, an available coordination site at gold, and the nature of the nickel–gold interaction appear to be essential for this reactivity.     

Conformational Tuning of Magnetic Interactions in Metal–DNA Complexes

The alignment of Cu ²⁺ ions along a modified DNA helix is studied with either hydroxypyridone (H) or bis(salicylaldehyde)ethylenediamine (S‐en) metalated base pairs (MBPs). The conformational motion of H‐MBP leads to the interlinking of the H‐MBPs by an extended Cu‐O network that is ferromagnetic, whereas the conformational freezing of the S‐en‐MBP leads to an ordered pairwise‐stacked arrangement that is weakly antoferrimagnetic.

     

Metal—-Metal “Communication” of Rh or Pd with Nd in Novel Heterobinuclear Complexes

The reaction of a neodymium “ate” complex and an electron-rich transition metal chloride by salt elimination is an efficient method for synthesizing heterobinuclear compounds which contain a lanthanide and a Group 9 or 10 metal [Eq. (1), H₂Ap=2-amino-4-methylpyridine]. The use of bisaminopyridinato ligands allows extremely short distances between Rh or Pd and Nd.     

Metal–Metal Distances at the Limit: Cr–Cr 1.73 Å – the Importance of the Ligand and its Fine Tuning

The synthesis and structure of a homobimetallic chromium complex is reported. The ligand used to stabilise the quintuply bonded metals is a sterically fine‐tuned guanidinate. A chromium–chromium bond length of 1.7293(12) Å was observed. It is the shortest metal–metal distance reported for a stable compound yet.     

Secondary Interactions in Phosphane‐Functionalized Group 4 Cycloheptatrienyl–Cyclopentadienyl Sandwich Complexes

Twice as reactive : The coordination chemistry of phosphane‐functionalized Zr and Hf cycloheptatrienyl–cyclopentadienyl complexes gives rise to unusual secondary interactions associated with the presence of Lewis acidic 16‐electron sandwich moieties. These structures can develop weak dative bonds as exemplified by the noncovalent Pd→Zr interaction in the heterobimetallic {Zr₂Pd} complex (see picture).

     

Methods for the Synthesis of μ-Hydrocarbon Transition Metal Complexes without Metal–Metal Bonds

Transition metal complexes in which hydrocarbons serve as σ,σ-, σ,π- or π,π-bound bridging ligands are currently of great interest. This review presents efficient and directed syntheses for such compounds, which often have very aesthetic structures. These reactions are among the most important reaction types in modern organometallic chemistry. They can be a useful aid for the synthesis of tailor-made compounds, for example, for models of catalytic processes and, specifically, for the construction of heterometallic compounds. We will discuss reactions of electrophilic complexes with nucleophilic ones, numerous transformations of (functionalized) hydrocarbons with metal complexes, the currently very topical complexes with bridging acetylide and carbide ligands, and organometallic polymers, which can be expected to have interesting and novel materials properties. Chisholm

1 M. H. Chisholm, Polyhedron 1988 , 7, 757–1077.

has described the importance of these complexes as follows: “Central to the development of polynuclear and cluster chemistry are bridging ligands and central to organometallic chemistry are metal–carbon bonds. Thus bridging ligands hold a pivotal role ins the development of Binuclear and polynuclear organometallic chemistry”.     

Direct X‐Ray Scattering Evidence for Metal–Metal Interactions in Solution at the Molecular Level

The study of the aggregation of small molecules in solution induced by metallophilic interactions has been traditionally performed by spectroscopic methods through identification of chemical changes in the system. Herein we demonstrate the use of SAXS (small‐angle X‐ray scattering) to identify structures in solution, taking advantage of the excellent scattering intensity of heavy metals which have undergone association by metallophilic interactions. An analysis of the close relationship between solid‐state and solution arrangements of a dynamic [Ag₂(bisNHC)₂]²⁺ (NHC=N‐heterocyclic carbene) system, and how they are complementary to each other, is reported.     

Dichlorodinickel(I) Complexes with μ2-CO or μ2-CS Bridges and Trimethylphosphane Ligands: Homologous Composition,but Different Frameworks

High ligand mobility is shown by the coordinatively unsaturated nickel(I ) compound 1 with a short Ni–Ni distance and an asymmetric CO bridge. The thio homologue 2 contains the novel (thiocarbonyl)trimethylphosphorane bridging ligand, which sits like a “stork's nest” on top of the roof-shaped dinuclear complex. In contrast to 1 , complex 2 does not show fluctional behavior and can be methylated without decomposition. X=Cl, Me.     

Barrierless Single‐Electron‐Induced cis–trans Isomerization

Lowering the activation energy of a chemical reaction is an essential part in controlling chemical reactions. By attaching a single electron, a barrierless path for the cis–trans isomerization of maleonitrile on the anionic surface is formed. The anionic activation can be applied in both reaction directions, yielding the desired isomer. We identify the microscopic mechanism that leads to the formation of the barrierless route for the electron‐induced isomerization. The generalization to other chemical reactions is discussed.     

Synthesis and Structures of Dinuclear Copper(I) and Silver(I) 1, 3‐Bis[(2‐chloro)benzene]triazenide Complexes

In the presence of Et₃N, the reaction of 1, 3‐bis[(2‐chloro)benzene]triazene (HL) with CuCl or AgNO₃ gives the triazenide complexes {Cu₂(L)₂} ( 1 ) and {Ag₂(L)₂} ( 2 ), respectively. The X‐ray crystal structures of both complexes were obtained. The metal–metal distances (Cu ··· Cu and Ag ··· Ag) are 2.4974(5) and 2.7208(5) Å, respectively.     

[B(O–C6H4–CN)4]– based Silver and Copper Coordination Polymers

A series of new coordination polymers bearing the [B(O–C₆H₄–CN)₄]^– anion was synthesized. Two new, one dimensional coordination frameworks of the type M[B(O–C₆H₄–CN)₄] (M = Ag, Cu) were obtained by salt metathesis. The reactivity towards organic Lewis‐bases was studied. The reaction with bidentate ligands yielded two dimensional networks with the general formula [M(L)][B(O–C₆H₄–CN)₄] {L = 2,2′‐bipyridine, 4,4′‐bipyridine, 1,2‐bis(pyridyl)ethane, 1,4‐diazabicyclo[2.2.2]octane}. The synthesis, properties and single crystal structure are reported.     

Thermally Stable Heterobinuclear Bivalent Group 14 Metal Complexes Ar2M−Sn[1,8-(NR)2C10H6] (M=Ge,Sn; Ar=2,6-(Me2N)2C6H3; R=CH2tBu)

The first thermally robust Ge ^II −Sn ^II compound 1 and the structurally characterized Sn^II-Sn^II analogue 2 , which maintain their structural integrity in solution, were obtained by treating MAr₂ (M=Ge, Sn; Ar=2,6-(Me₂N)₂C₆H₃) with Sn[1,8-(NR₂)₂C₁₀H₆] (R=CH₂tBu). On the basis of structural and spectroscopic data, the M−Sn bond is regarded as the interaction of a MAr₂ donor with an Sn[1,8-(NR₂)₂C₁₀H₆] acceptor.