Protonation of (Ph 3 P) 2 Pt[η 2 -HC≡CC(CH 3 ) CH 2 ] (2a) with excess HBF 4 Et 2 O produced the π-allyl complex (Ph 3 P) 2 Pt[η 3 -H 2 C CC(CH 3 ) CH 2 ] + BF - 4 (3a-BF 4 ) instead of a π-propargyl complex. Reaction of excess CF 3 CO 2 H with 2a initially produced the analogous π-allyl complex 3a-CF 3 CO 2 which then added CF 3 CO 2 H across the vinylidene unit of 3a-CF 3 CO 2 to give the π-allyl complex (Ph 3 P) 2 Pt[η 3 -CH 3 C(CF 3 CO 2 )C(CH 3 )CH 2 ] + CF 3 CO 2 - (5a). Protonation of the platinum diyne complex [(p-CH 3 -C 6 H 4 ) 3 P] 2 Pt(η 2 -CH 3 C≡CC≡ CCH 3 ) (7b) with HBF 4 Et 2 O at -73°C initially produced the platinum hydride complex trans-[(p-CH 3 -C 6 H 4 ) 3 P] 2 - PtH(η 2 -CH 3 C≡CC≡CCH 3 ) + BF - 4 (9), which rearranged to the platinum π-propargyl complex [(p-CH 3 -C 6 H 4 ) 3 P] 2 Pt[η 3 -(CH 3 CH )- CC≡CCH 3 ] + BF 4 - (11) at -28°C.