PARAMAGNETIC TETRAHEDRAL DINITROSYLIRON COMPLEXES CONTAINING REDOX-ACTIVE CYANOMANGANESE LIGANDS

The redox-active cyanomanganese ligands trans-[Mn(CN)(CO)(2){P(OEt)(3) }(dppm)] (dppm=Ph(2)PCH(2)PPh(2)), cis-[Mn(CN(CO)(2)(PEt(3))(dppe)] (d ppe=Ph(2)PCH(2)CH(2)PPh(2)) and trans-[Mn(CN)(CO)(dppm)(2)] reacted wi th [{Fe(mu-I)(NO)(2)}(2)] in CH2Cl2 to give the heterobinuclear comple xes [FeI{(mu-NC)MnL(x)}(NO)(2)] {L(x)= trans-(CO)(2)[P(OEt)(3)](dppm) 1, cis-(CO)(2)(PEt(3))(dppe) 2 and trans-(CO)(dppm)(2) 3}; the molecul ar structure of 3 is consistent with a tetrahedral iron(-I) centre bou nd to octahedral manganese(I) by a near linear Mn-CN-Fe bridge. The ES R spectra of complexes 1-3 are very similar to those of the tetrahedra l Fe--I complex [FeI2(NO)(2)](-). Complexes 1-3 reacted with PPh(3) in the presence of TIPF6 to give [Fe(PPh(3))-{(mu-NC)MnL(x)}(NO)(2)][PF6 ] {L(x)=trans-(CO)(2)[P(OEt)(3)](dppm) 5(+), cis-(CO)(2)(PEt(3))(dppe) 6(+) and trans-(CO)(dppm)(2) 7(+)} which were also prepared from [Fe( PPh(3))(2)(NO)(2)][PF6] and the appropriate, cyanomanganese ligand in a 1:1 ratio; the related cation [Fe(PPh(3)){(mu-NC)MnL(x))(NO)(2)](+) {L(x)= trans-(CO)(2)[P(OPh)(3)](dppm) 8(+)} was generated in solution. The ESR spectra of complexes 6(+)-8(+) showed hyperfine coupling to N (O), P, N(C) and Mn, suggesting a structure similar to that of [Fe(PPh (3))(OPPh(3))(NO)(2)](+) with some delocalisation through the cyanide bridge to manganese. Treatment of 2 equivalents of trans-[Mn(CN)(CO)(2 ) {P(OEt)(3)}(dppm)] or cis-[Mn(CN)(CO)(2)(PEt(3))(dppe)] with [Fe(PPh (3))(2)(NO)(2)][PF6] gave the heterotrinuclear complexes [Fe{(mu-NC)Mn L(x)}(2)(NO)(2)][PF6] {L(x)=trans-(CO)(2)[P(OEt)(3)](dppm) 9(+) and ci s-(CO)(2)(PEt(3))(dppe) 10(+)} which may also be prepared from the rea ction of 1 with trans-[Mn(CN)(CO)(2)(P(OEt)(3)}(dppm)] or 2 with cis-[ Mn(CN)(CO)(2)(PEt(3))(dppe)] in the presence of TIPF6. Complexes 1-10( +), which contain diamagnetic Mn-I and paramagnetic Fe--I centres, und ergo oxidation and reduction at a platinum electrode in CH2Cl2. The Mn -II derivatives 3(+) and 7(2+) and the Fe--II complex 7 have been gene rated in solution by ferrocenium ion oxidation or cobaltocene reductio n respectively.