Intramolecular CH insertion reactions of (pentamethylcyclopentadienyl)Rhenium alkynylcarbene complexes

Thermolysis of the alkynylcarbene complex CP*(CO)(2)Re=C(Ph)C-13 drop (13)C Tol (5) at 120 degreesC resulted in rapid equilibration (t(1/2) = 33 min) t o a 1:1 mixture of 5 and CP*(CO)(2)Re=C-13- (Tol)C-13=CPh (7) via a [1,3]-r henium shift. Extended thermolysis of this mixture provided the CH insertio n products {eta (5):eta (2)-[C-5(CH3)(4)(CH2CH)-C-13(Tol)C-13 drop CPh]}Re( CO)(2) (8) and {eta (5):eta (2)-[C-5(CH3)(4)CH2CH(Ph)C-13 drop (13)CTol] }R e(CO)(2) (9). Thermolysis of the symmetrically substituted alkynylcarbene c omplex CP*(CO)(2)Re=C(Ph)C drop CPh (6) produced the CH insertion product { eta (5):eta (2)-[C-5(CH3)(4)CH2CH(Ph)C drop CPh]}Re(CO)(2) (10). The CH ins ertion of CP*(CO)(2)Re=C(Ph)C drop CC6D5 (6-HD) was monitored at low conver sion before complete equilibration with CP*(CO)(2)Re=C(C6D5)C drop CPh (6-D H) occurred. An excess of {eta (5):eta (2)-[C-5(CH3)(4)CH2CH(C6D5)C drop CP h]}Re(CO)(2) (13-HD) over {eta (5):eta (2)-[C-5(CH3)(4)CH2CH(Ph)C drop CC6D 5]}Re(CO)(2) (13-DH) provides evidence for site-selective CH insertion of t he remote alkyne carbon into the CH bond of a Cp* methyl group.