Isocarbonyl complexes of divalent samarium and ytterbium. The molecular structures of [{Ln(Tp(tBu,Me))(THF)(mu-CO)(2)Mo-(eta-C5H4Me)(CO)}(2)] (Ln = Sm, Yb)

The reaction of [Ln(Tp(tBu,Me))I(THF)] (1a Ln = Sm, 1b Ln = Yb) with Na[Mo( eta-C5H4Me)(CO)(3)] gives good yields of [{Ln(Tp(tBu,Me))(THF)(mu-CO)(2)Mo( eta-C5H4Me)(CO)(3)}(2)], 2a (Ln = Sm), 2b (Ln = Yb). The low temperature X- ray crystal structures of 2a and 2b have been determined. The structures co ntain a 12-membered ring of samarium/ytterbium and molybdenum atoms with is ocarbonyl groups linking the metal centres. 2a represents the first example of an isocarbonyl bound to samarium(II). Addition of pyridine results in t he breakup of the tetramer to give [{Ln(Tp(tBu,Me))(py)(n)(mu-CO)Mo(eta-C5H 4Me)(CO)(2)}(2)].