Abstract: The intramolecular acetylene insertion reactions of C1L, PdCO2 (CH2), C= CCH3 (la, L= Ph3P, n= 2; lb, L= p-tol, P, n= 2; 2, L= Ph3P, n= 3) and the intramolecular olefin insertion reaction of CIL2PdC02CH2CH2CH= CH2 (3, L= Ph3P) have been investigated. The acetylene insertion reactions give stable vinyl complexes 5a, 5b, and 6; the olefin insertion reaction gives an unsaturated lactone by@ hydrogen elimination from the initially ...