Reactions of Complex Ligands. Part 107 Densely Substituted Hydroquinoid Phenanthrene and Triphenylene Cr(CO)3 Complexes: Chromium‐Templated Synthesis and Molecular Structure

Abstract

AbstractDensely substituted hydroquinoid phenanthrene (10–18), acephenanthrene (19), and triphenylene chromium tricarbonyl complexes (20–22) have been prepared via benzannulation of naphthalenyl (1–7), acenaphthenyl (8) and phenanthrenyl carbene complexes (9), respectively. The naphthalenyl, acenaphthenyl and phenanthrenyl carbene complexes 1–9 were obtained in 52–88 % yield starting from commercially available bromoarenes by dehalolithiation, addition of hexacarbonyl chromium to the lithioarene and O‐alkylation of the resulting acyl chromates with trimethyloxonium tetrafluoroborate (Fischer route). The benzannulation of the aryl carbene complexes (either with 3‐hexyne / (t‐butyl)dimethylsilyl chloride or with (t‐butyl)dimethylsilylethyne) allowed the regiospecific synthesis of the oligocyclic hydroquinoid arene tricarbonyl chromium complexes 10–22 in 44–94 % yield thus providing a two‐step synthesis with overall yields of 18 ‐ 80 %. Under the kinetic reaction conditions used the metal atom is exclusively coordinated to the persubstituted terminal hydroquinoid ring. The molecular structures of phenanthrene complexes 10, 12–14, and 16, acephenanthrene complex 19, and triphenylene complexes 20 and 21 in the solid state have been determined by X‐ray crystallography. The carbonyl ligands either adopt an eclipsed (10, 12, 14, 16, 19, 20) or staggered (13, 21) exo‐conformation pointing away from the center of the phenanthrene, acephenanthrene and triphenylene ligands, respectively. The coordination of the metal atom to the hydroquinoid ring is unsymmetric with the largest metal‐carbon distances found between the chromium atom and one bridgehead carbon and the ring carbon atom bearing the bulky (t‐butyl)dimethylsilyloxy (TBDMSO) substituent.