Intramolecular CH insertion reactions of (pentamethylcyclopentadienyl)Rhenium alkynylcarbene complexes

Thermolysis of the alkynylcarbene complex CP*(CO)(2)Re=C(Ph)C-13 drop (13)CTol (5) at 120 degreesC resulted in rapid equilibration (t(1/2) = 33 min) to a 1:1 mixture of 5 and CP*(CO)(2)Re=C-13- (Tol)C-13=CPh (7) via a [1,3]-rhenium shift. Extended thermolysis of this mixture provided the CH insertion 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] }Re(CO)(2) (9). Thermolysis of the symmetrically substituted alkynylcarbene complex 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 insertion of CP*(CO)(2)Re=C(Ph)C drop CC6D5 (6-HD) was monitored at low conversion before complete equilibration with CP*(CO)(2)Re=C(C6D5)C drop CPh (6-DH) occurred. An excess of {eta (5):eta (2)-[C-5(CH3)(4)CH2CH(C6D5)C drop CPh]}Re(CO)(2) (13-HD) over {eta (5):eta (2)-[C-5(CH3)(4)CH2CH(Ph)C drop CC6D5]}Re(CO)(2) (13-DH) provides evidence for site-selective CH insertion of the remote alkyne carbon into the CH bond of a Cp* methyl group.