Methanol Addition to Dihapto-Coordinated Rhenium Complexes of Furan

Abstract
The complexes [TpRe(CO)(L)(4,5-η2-furan)], present as diastereomeric mixtures (L = tBuNC (1A, 1B), PMe3 (2A, 2B), pyridine (3A, 3B), or 1-methylimidazole (4A, 4B)), undergo acid-catalyzed methanol addition in CH2Cl2 at −40 °C, resulting in the syntheses of dihapto-coordinated 2-methoxy-2,3-dihydrofuran complexes. In all cases, two diastereomers resulted, one in which the oxygen of the dihydrofuran is oriented toward the L ligand (5A, 6A, 7A, and 8A), and one in which the oxygen is oriented away from the L ligand (5B, 6B, 7B, and 8B). In all cases, the methoxy group adds stereoselectively, anti to the metal fragment. In addition, the tBuNC complex 1 yields a dihapto-coordinated vinyl ether (5C) that results from ring opening of the protonated furan ligand. In no case does the diastereomeric ratio of products correlate with that of the starting material.

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