The synthesis of ring-substituted cycloheptatrienyl complexes 7-C7H6R)>+ (M = Cr, Mo or W; R = Me, tBu, C6H4-F-p or CCPh)

Article abstract of DOI:10.1016/0022-328X(93)80465-N

The relative merits of various routes to ring-substituted cycloheptatrienyl complexes 7-C7H6R)>⁺ (M = Cr, Mo or W) have been explored.Substitution at a metal coordinated C7H7 ring is effected via addition, thermal rearrangement and subsequent H^- abstraction.Thus reaction of 7-C7H7)>⁺ with NaOMe gives 6-(7-exo-OMe)C7H7>>, which affords substituted cycloheptatriene complexes 6-(7-exo-R)C7H7>> tBu (2); C6H4-F-p (3)> by reaction with RMgX; direct addition of C<*>CPh to 7-C7H7)>⁺ to give6-(7-exo-C<*>CPh)C7H7>> is brought about by reaction with alkynyl cuprate reagents.Thermolysis of 1-4 gives isomeric mixtures of rearranged cycloheptatriene complexes 6-(n-R)C7H7>> (n = 1, 2 or 3), which contain a CH2 ring carbon with an exo hydrogen accessible to H^- abstraction by Ph3C⁺ to yield the ring-substituted cycloheptatrienyl complexes 7-C7H6R)>⁺ tBu (8); C6H4-F-p (9); M = Cr, R = C<*>CPh (10)>.Alternatively, substituted cycloheptatrienes C7H7R and cycloheptatrienyl ions C7H6R⁺ may be coordinated directly to .Reaction of 7-Me-C7H7 with (M = Cr, Mo or W) in THF affords 6-(7-Me)C7H7>> as a (metal dependent) exo/endo isomeric mixture at C(7).The reaction of the cycloheptatrienyl ions C7H6R⁺ (R = Me, ^tBu, C6H4-F-p, C<*>CPh) with (M = Mo, R' = Me; M = W, R' = ⁿPr) proceeds at room temperature in THF or CH2Cl2 and provides convenient syntheses of 7, 8, 9, 7-C7H6(C<*>CPh)>⁺ (11) and 7-C7H6R)>⁺ .Complexes 7, 8, 9, 12and 13 are useful starting materials for investigation of the chemistry of ring-substituted cycloheptatrienyl complexes, as exemplified by the syntheses of 7-C7H6Me)> and the sandwich complex 6-toluene)(η⁷-C7H6Me)>⁺ (16).