Pentakis(methoxycarbonyl)cyclopentadiene chemistry. Part 6. Some first-row transition-metal derivatives: crystal and molecular structures of [Fe{C5(CO2Me)5}2(MeOH)2], [Co{C5(CO2Me)5}2(OH2)2], and [Cu{C5(CO2Me)5}2(MeOH)2]