Pyrazolyl-bridged iridium dimers. 5. Crystal and molecular structures of bis(cycloocta-1,5-diene)bis(.mu.-pyrazolyl)diiridium(I), its dirhodium(I) isomorph, and two bis(cycloocta-1,5-diene)diiridium(I) analogs incorporating 3,5-disubstituted .mu.-pyrazolyl ligands