SYNTHESIS AND REACTIONS OF ETA-CYCLOHEPTATRIENYL DERIVATIVES OF MOLYBDENUM

An improved route to [Mo(eta-C7H7)(eta-C7H9)] 2 has been found which i nvolves the reduction of MoCl5 with sodium amalgam in the presence of cycloheptatriene followed by thermolysis. Compound 2 can be oxidised w ith a half equivalent of iodine or tetrafluoroboric acid forming the c orresponding cation [Mo(eta-C7H7) (eta-C7H9)]+ 3, which reacts with et hanol or an excess of iodine to yield the binuclear cations [(eta-C7H7 )Mo(mu-X)3 Mo(eta-C7H7)]+ (X = O Et 4 or 15 respectively). Treatment o f 2 with 1 equivalent of iodine, bromine or an excess of PhlCl2 in the presence of a weak co-ordinating solvent or sigma-donor affords the 1 7-electron compounds [Mo(eta-C7H7)LX2] [L = tetrahydrofuran (thf), MeC N, PPh3, PMe3 or Et2S; X = Cl, Br or 1). Treatment of [Mo(eta-C7H7)(Me CN)I2] 11 with [NBu4]I gives [NBu4][Mo(eta-C7H7)I3] 18 and reduction o f 11 with sodium amalgam in the presence of 1,2-bis(dimethylphosphino) ethane (dmpe), 1,2-bis(diphenylphosphino)ethane (dppe) or PMe3 gives [ Mo(eta-C7H7)(dmpe)I] 19, [Mo(eta-C7H7)(dppe)I] 20 or [Mo(eta-C7H7) (PM e3)2I] 13, respectively. Compound 11 also reacts with Na(C5H4R) (R = H or Me) or lithium indenide to yield the mixed-sandwich compounds [Mo( eta-C7H7)(eta-C5H4R)] (R = H 21 or Me 22) or [Mo(eta-C7H7)(eta-C9H7)] 23. The crystal structures of [NBu4][Mo(eta-C7H7)I3] 18 and [Mo(eta-C7 H7)(eta-C5H4Me)] 22 have been determined. Compound 22 reacts with 1 eq uivalent of tetracyanoethene (tcne) to give the electron-transfer comp lex [Mo(eta-C7H7)(eta-C5H4Me)][tcne] 24 while compound 21 reacts with 1 equivalent of 7,7,8,8-tetracyanoquinodimethane (tcnq) to yield [Mo(e ta-C7H7)(eta-C5H5)]2[tcnq] 25.