Reactions of transition-metal .sigma.-acetylide complexes. 14. Cyclobutenyl, butadienyl, and allyl complexes of ruthenium derived from 1,1-dicyano-2,2-bis(trifluoromethyl)ethene. X-ray structures of [cyclic] Ru[C:CPhC(CF3)2C(CN)2](CO)(PPh3)(.eta.-C5H5), Ru[C(:C(CN)2)CX:C(CF3)2](CO)(PPh3)(.eta.-C5H5)