Chemical and electrochemical oxidation of CpRe(PAr3)2H2 complexes to give stable 17-electron radical cations. Disproportionation to diamagnetic species via electron-transfer catalysis

Abstract

Electrochemical oxidations of (I) in both MeCN and CH2Cl2 give stable 17‐electron radical monocations as determined by controlled‐potential thin‐layer coulometry and double‐potential step chronocoulometry.

Stable Paramagnetic Half-Sandwich Mo(V) and W(V) Polyhydride Complexes. Structural, Spectroscopic, Electrochemical, Theoretical, and Decomposition Mechanism Studies of [Cp*MH3(dppe)]+ (M = Mo, W)

“…Since one of the principal decomposition pathways for 17-electron monohydride complexes is deprotonation by virtue of the increased acidity relative to that of the 18-electron precursors, 108 an increased stability may be expected through the use of donor ligands via a buffering effect of this acidity. At the same time, donor ligands render the 18-electron precursor more easily oxidizable, as experimentally verified for several systems, such as the CpRe(PAr3)2H2 (Ar = p-C6H4X; X = H, Me, F, OMe) 63 and Cp*Ru(L2)H (L2 = dppm, dppp, (PPh3)2, (PMePh2)2, (PMe2Ph)2, (PMe3)2) 43 series. A qualitative correlation between oxidation potential and stability is, indeed, typically observed.…”

Electrophilic Addition vs Electron Transfer for the Interaction of Ag+ with Molybdenum(II) Hydrides. 1. Reaction with CpMoH(PMe3)3 and the Mechanism of Decomposition of [CpMoH(PMe3)3]+

“…52 A THF adduct deriving from the oxidation of CpRe(PPh 3 ) 2 H 2 in THF, [CpRe(PPh 3 ) 2 (THF)H] + , has been described. 53 Compound 3 is much more stable than compound 2 and could be recrystallized from MeCN/Et 2 O, yielding analytically pure crystals that were investigated by NMR and X-ray crystallography. The inequivalent phosphine ligands give rise to two resonances in a 2:1 ratio in both the 1 H and the 31 P NMR spectrum, in agreement with the crystallographically determined structure (vide infra).…”

Formation of organometallic hydroxo and oxo complexes by oxidation of transition metal hydrides in the presence of water. X-Ray structures of [CpMo(OH)(PMe3)3][BF4] and [CpMo(O)(PMe3)2][BF4]

“…10) and (11), respectively. Equation (11) involves again an ox/1 ratio of 1 : 1, whereas the formation of 4 in equation (10) requires less than 1 equivalent of oxidant. The observation of the EPR triplet resonance when using a small amount of oxidant (see It is interesting to observe that each oxidation step is followed by the release of a proton, and that each molecule of the oxidizing 1 + generates a molecule of 1 that can capture the proton.…”

“…Data collection and reduction and structure solution were routine. The structure was refined with an initial Flack parameter refining to 0.87 (10) indicating that the structure needed to be inverted. Following inversion and further refinement, one of the three PMe 3 groups was found to be disordered with major : minor contributors of 0.631 : 0.369.…”