The phototransient ReH5P2 (P = PMe2Ph), formed by photolysis of ReH5P3, reacts with cyclooctatetraene to give first (η4-C8H10)ReH3P2 as a stereochemically rigid complex of cyclooctatriene. This undergoes a thermal reaction at 25°C to give (η5-C8H11)ReH2P2, shown to be a 1-5-η5-cyclooctadienyl complex by NMR spectroscopy and X-ray diffraction. This complex has a piano stool form with a diag-ReH2P2 unit forming the base. The two hydride ligands lie in a mirror plane of the open pentadienyl ligand, and these hydrides are thus inequivalent; the spectral data show that this complex is stereochemically rigid. Analogous η4-diene complexes are made from 1,5-cyclooctadiene and ReH5P3 (photochemically) and from ReH7P2 (thermally). Deuterium labeling experiments (employing ReD5P3 and C8H8) reveal that the transfer of three hydrides from metal to ring in the production of (η5-C8H11)ReH2P2 is regiospecific (i.e., no scrambling) and is wholly endo, consistent with an intramolecular mechanism. Crystallographic data (at -160°C): orthorhombic, Pbca with Z = 8 and a = 12.391 (4) Å, b = 17.882 (6) Å, and c = 20.441 (8) Å.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry