Reaction of cationic cyclobutadineruthenium complexes with hydride anion donors; evidence for the formation of η4(5e) butadienyl species and fragmentation of the cyclobutadiene ring: crystal structure of [RuC(Ph)–η3-{C(Ph)·CH(Ph)·CH(Ph)}-(η-C5H5)] and [Ru2(µ-CO){µ-(Z)-C(Ph)CH(Ph)}(CO)2(η4-C4Ph4)(η-C