Cyclopentadienylruthenium and -osmium chemistry. 33. Cyclobutenyl-nitrile complexes. X-ray structure of Ru[C:CPhC(CF3)2C(CN)2](NCMe)(PPh3)(.eta.-C5H5) and [Ru[C:CPhC(CF3)2C(CN)2](PPh3)(.eta.-C5H5)]2[.mu.-(NC)2C:C(CF3)2]