The use of pyrazolylborates as ancillaries for lanthanide complexes

[Sm(Tp(Me,Me))(2)] reacts with dichalcogenides to give a series of isolepti c complexes [Sm(Tp(Me,Me))(2)ER] (E = O, S, Se, Te; R = phenyl) which have been structurally characterized. An unusual distortion of the Tp(Me,Me) for the selenolates is discussed in relation to fluxionality and decomposition mechanisms for these complexes. The fluxional behaviour of [Sm(Tp(Me,Me))( 2)(S2CNR2)] and [Sm(Tp(Me,Me))(2)(S-2-pyr)] is also described. [Sm(Tp(Me,Me ))(2)] reacts with Mn-2(CO)(10) to give [Sm(Tp(Me,Me))(2)]Mn(CO)(5) and sma ll amounts of {[Sm(Tp(Me,Me))(2)](2)(mu-O2CH)}Mn(CO)(5) - effectively the r oom temperature conversion of CO to formate. The corresponding reaction wit h Re-2(CO)(10) yields [Sm(Tp(Me,Me))(2)]Re(CO)(5) and [Sm(Tp(Me,Me))(2)](2) Re-4(CO)(17). (C) 2000 Elsevier Science S.A. All rights reserved.