72-76 Valence electron clusters. An extension of the 16-18 electron rule. Synthesis, crystal structure, and solution dynamics of the trigonal-bipyramidal pentanuclear clusters [PtIr4(CO)9(.mu.-CO)5]2- and [PtIr4(CO)9(.mu.-CO)3]2-
72-76 Valence electron clusters. An extension of the 16-18 electron rule. Synthesis, crystal structure, and solution dynamics of the trigonal-bipyramidal pentanuclear clusters [PtIr4(CO)9(.mu.-CO)5]2- and [PtIr4(CO)9(.mu.-CO)3]2-