Synthesis and reactivity of (η6-arene)(phosphino enolato)ruthenium(II) complexes, their coupling reaction with phenylacetylene, and thermal rearrangement to a phosphametallacyclopropane. X-ray crystal structures of {Ru[η3-CH=C(Ph)CH(PPh2)C(But)=O](p-cymene)}(PF6), of {Ru[η3-CH=C(Ph)C(Me)(PPh2)C(Et)=