Charge Effects on Oxygen Atom Transfer

Abstract

The rhenium(V) complex [(HCpz3)ReOCl2]+ ([1]+), the tris(pyrazolyl)methane analogue of the known tris(pyrazolyl)borate complex (HBpz3)ReOCl2 (2), has been prepared. The two complexes are strikingly similar, as are the phosphine oxide adducts [(HCpz3)ReCl2(OPPh3)]Cl ([3]Cl) and (HBpz3)ReCl2(OPPh3) (4), which have been characterized by X-ray crystallography. Comparison of the bimolecular reduction of [1]BF4 and 2 by triarylphosphines reveals a pronounced charge effect, with the cationic species being reduced by PPh3 about 1,000 times faster than its neutral analogue in CH2Cl2 at room temperature. Ligand substitution of the adducts [3]+ and 4 is dissociative, with the cationic complex dissociating phosphine oxide about 56 times more slowly than the neutral compound. The relative impact of charge on ground and transition states in atom transfer reactions is discussed.

Oxygen Atom Transfer

“…66 The cationic monooxorhenium(V) complex [(HCpz 3 )ReOCl 2 ] þ (HCpz 3 ¼ tris(pyrazolyl)methane) was compared with the neutral complex [(HBpz 3 )Re(O)Cl 2 ] (HBpz 3 ¼ tris(pyrazolyl)borate) (Figure 3.25). The reaction of each with PPh 3 to give the corresponding Re III (OPPh 3 ) complexes was studied.…”

Phosphine‐Promoted Conversion of Oxo(dithiolato)rhenium(V) into Thio(thiolatoalkyl)rhenium(V) Compounds

“…The first step comprises nucleophilic attack on the oxo group of 1 a, a process which is reasonable given the formal charges, Re À O + ; moreover, attack of phosphine at a terminal oxo group has precedent. [10] The resulting intermediate is assisted to the product by the Re …”

Influence of the Crystallization Solvent on Molecular and Supramolecular Structures of Silver(I) Tris(3‐Phenylpyrazolyl)methane Complexes

“…The greater shifts in acetone are likely due to hydrogen bonding of the acetone with the acidic methine hydrogen, an effect that has been observed previously. [29,30] Electrospray mass spectroscopy (ES/MS) has emerged as a technique for investigating solution aggregation of covalent and noncovalent species. In the case of coordination polymers, ES/MS was used to probe the aggregation between the ligands and silver() salts in solution, aggregates that might be related to the building blocks and subsequently to the final supramolecular structure of the coordination polymers.…”