The reaction of cis-[Mo2(O2C-Fc)2(NCCH3)4][BF4]2 (cis-1) with three electronically different N,N'-diarylformamidinate (DArF) ligands [DArF = N,N'-diphenylformamidinate (DPhF), N,N'-di(p-trifluoromethylphenyl)formamidinate (DTfmpF), and N,N'-di(p-anisyl)formamidinate (DAniF)] results in products of the general composition [Mo2(O2C-Fc)2(DArF)2]. Even though the trans-[Mo2(O2C-Fc)2(DArF)2] isomers were originally expected to be the sole products, the corresponding cis-[Mo2(O2C-Fc)2(DArF)2] complexes were isolated as well via crystallization and verified unambiguously by X-ray crystallography. All novel complexes, namely, cis-[Mo2(O2C-Fc)2(DPhF)2] (cis-2a), cis-[Mo2(O2C-Fc)2(DTfmpF)2] (cis-2b), and trans-[Mo2(O2C-Fc)2(DAniF)2] (trans-2c), were studied regarding their electrochemical properties with respect to electrolyte, solvent, and ligand. The electron-donating ligand DArF(-) enables the oxidation of the [Mo2](4+) unit prior to that of Fc, while the oxidation sequence is reversed when acetonitrile or diphosphine ligands are coordinated instead of formamidinate. In the case of trans-[Mo2(O2C-Fc)2(DAniF)2], interactions were found between the two redox-active ferrocenecarboxylate ligands, with a clear ΔE1/2 value originating from the peak-to-peak separation in DPV of around 100 mV with CH2Cl2 as solvent. Furthermore, the second oxidation of the Mo2-handle [Mo2](5+)/[Mo2](6+) was exclusively observed with DAniF(-) as the ligand. Similar absorption patterns in UV-vis spectra were found within the series 2a-2c, corresponding to similar structural and electronic features of the complexes.

The use of ruthenium complexes in transvinylation catalysis has been well established since the 1980s. However, the reaction mechanism and the active catalyst species, which is presumed to contain ruthenium carbonyl carboxylate entities, have so far remained elusive. In this work the synthesis and characterization of three novel ruthenium complexes comprising ruthenium carbonyl carboxylate structural motifs including two single crystal structures as well as the crystal structures of two known ruthenium complexes are reported. These new complexes and four known ruthenium complexes with appropriate structural motifs were applied in transvinylation catalysis. Mechanistic studies including identification and characterization of the active species, isotope labeling experiments and examination of the regio‐ and stereoselectivity of the transvinylation reaction are presented, resulting in the proposal of a probable reaction mechanism, which is supported by DFT calculations on the B3LYP/6‐31G* level of theory.magnified image

No abstract

No abstract

The direct synthesis of the first μ(2)-η(2),η(2)-allyl-bridged diiridium complex ([2](+)), bearing the uncommon counterion [IrCl2(COD)](-) ([3](-)), is described. Both bridging moieties in [2](+), namely, allyl and acetate, are introduced in a single reaction step from [{IrCl(COD)}2] (1) and allyl acetate. A combination of X-ray crystallography and density functional theory calculations reveals pronounced metal-allyl π-back-bonding.