om000359w_si_001.pdf (1.2 MB)
Synthesis and Bonding in the Diamagnetic Dinuclear Tantalum(IV) Hydride Species ([P2N2]Ta)2(μ-H)4 and the Paramagnetic Cationic Dinuclear Hydride Species {([P2N2]Ta)2(μ-H)4}+I- ([P2N2] = PhP(CH2SiMe2NSiMe2CH2)2PPh): The Reducing Ability of a Metal−Metal Bond
journal contribution
posted on 2000-08-24, 00:00 authored by Michael D. Fryzuk, Samuel A. Johnson, Steven J. RettigThe controlled reaction of the Ta(V) trimethyl species [P2N2]TaMe3, where [P2N2] =
PhP(CH2SiMe2NSiMe2CH2)2PPh, under 0.5 atm of hydrogen gas produces a partially
hydrogenated Ta(V) species, ([P2N2]TaMe2(H), of unknown structure. Under 4 atm of
hydrogen gas, further hydrogenation does not produce the complex [P2N2]TaH3; instead,
reduction of the tantalum center occurs to yield the dinuclear Ta(IV) hydride ([P2N2]Ta)2(μ-H)4. This diamagnetic tetrahydride fails to react with many reagents, including ethylene
and carbon monoxide; however, upon addition of iodomethane, {([P2N2]Ta)2(μ-H)4}+I- is
produced as a paramagnetic green crystalline solid. The number of hydrides in this reaction
product was confirmed by a deuterium labeling study. The results of a variable-temperature
magnetic susceptibility study of this tetrahydride cation can be partially modeled with the
Curie−Weiss law and a large correction for temperature-independent magnetism. Ab initio
calculations using density functional theory were performed in an attempt to further
understand the influence of the macrocyclic ligand in the bonding in these complexes.