Ruthenium metallophosphorus clusters: Ru5(CO)12(.mu.4-PPh)(.mu.3-CCH2CHMe2)(.mu.2-PPh2) and HRu5(CO)10(.mu.4-PPh)2(.mu.3-PPh)(.mu.2-PPh2), face-capped-octahedral and pentagonal-bipyramidal clusters via stepwise reduction of an acetylide