Molybdänkomplexe mit hochalkylierten Cyclopentadienyl‐Liganden

Molybdenum Complexes with Highly Alkylated Cyclopentadienyl Ligands Reaction of hexacarbonylmolybdenum with 1,2,3,4‐tetraisopropylcyclopentadiene gives [(η5‐C5iPr4H)Mo(CO)3H] (1), which on treatment with 2,5‐norbornadiene is dehydrogenated to [{(η5‐C5iPr4H)Mo(CO)2}2](Mo  Mo) (2). The mixed‐substituted dimolybdenum complex [(η5‐C5Me5)(CO)2Mo  Mo(CO)2(η5‐C5iPr4H)] (6) is accessible, e.g., from [(η5‐C5Me5)Mo(CO)3Cl] and [(η5‐C5iPr4H)Mo(CO)3]Na (3). Complex 3 yields [(η5‐C5iPr4H)Mo(CO)3Cl] (4) with CuCl2 and [(η5‐C5iPr4H)Mo(CO)3‐SiHMe2] (5) with Me2HSiCl. Low‐temperature 1H‐NMR spectra of [(η5‐C5iPr5)Mo(CO)3CH3] (7), synthesized from [(η5‐C5iPr5)Mo(CO)3]Na and MeI, show the signals of two isomers with different orientation of the isopropyl groups about the five‐membered ring. ΔG‡ of isopropyl rotation has been calculated to be 55.6 ± 4 kJ/mol. [(η5‐C5H2tBu3‐1,2,4)Mo(CO)3]Na reacts with MeI to form [(η5‐C5H2tBu3 ‐1,2,4)Mo(CO)3CH3] (8).