Interaction of dodecacarbonyltetra-.mu.-hydridotetraruthenium with diphosphines in the presence of trimethylamine N-oxide. X-ray crystal structure analyses of (.mu.-H)4Ru4(CO)10(.mu.-{Ph2P(CH2)nPPh2}) (n = 1, 3, 4), (.mu.-H)4Ru4(CO)10(.mu.-{Ph2PCH2CH(CH3)PPh2}), and (.mu.-H)4Ru4(CO)10({Ph2PCH2CH(CH3)PPh2})