N2 Functionalization at Iron Metallaboratranes

The reactivity of the anionic dinitrogen complex [(TPB)Fe(N2)]− (TPB = tris[2-(diisopropylphosphino)phenyl]borane) toward silicon electrophiles has been examined. [(TPB)Fe(N2)]− reacts with trimethylsilyl chloride to yield the silyldiazenido complex (TPB)Fe(NNSiMe3), which is reduced by Na/Hg in THF to yield the corresponding sodium-bound anion [(TPB)Fe(NNSiMe3)]Na(THF). The use of 1,2-bis(chlorodimethylsilyl)ethane in the presence of excess Na/Hg results in the disilylation of the bound N2 molecule to yield the disilylhydrazido(2−) complex (TPB)FeNR (R = 2,2,5,5-tetramethyl-1-aza-2,5-disilacyclopentyl). One of the phosphine arms of TPB in (TPB)FeNR can be substituted by CO or tBuNC to yield crystalline adducts (TPB)(L)FeNR (L = CO, tBuNC). The N–N bond in (TPB)(tBuNC)FeNR is cleaved upon standing at room temperature to yield a phosphoraniminato/disilylamido iron(II) complex. The flexibility of the Fe–B linkage is thought to play a key role in these transformations of Fe-bound dinitrogen.本研究考察了阴离子二氮配合物[(TPB)Fe(N₂)]⁻（其中TPB为三[2-(二异丙基膦基)苯基]硼烷（tris[2-(diisopropylphosphino)phenyl]borane））与亲电硅试剂的反应活性。[(TPB)Fe(N₂)]⁻可与三甲基氯硅烷反应，生成硅基重氮亚胺配合物(TPB)Fe(NNSiMe₃)；该产物经钠汞齐（Na/Hg）在四氢呋喃（THF）中还原，得到相应的配位钠离子型阴离子[(TPB)Fe(NNSiMe₃)]Na(THF)。当以过量钠汞齐为还原剂并加入1,2-双(氯二甲基硅基)乙烷时，配位氮分子会发生二硅基化反应，生成二硅基肼基(2−)配合物(TPB)Fe≡NR（R = 2,2,5,5-四甲基-1-氮杂-2,5-二硅杂环戊基）。配合物(TPB)Fe≡NR中的一个TPB膦配体臂可被CO或叔丁基异腈（tBuNC）取代，得到结晶加合物(TPB)(L)Fe≡NR（L = CO, tBuNC）。配合物(TPB)(tBuNC)Fe≡NR中的N–N键在室温静置条件下会发生断裂，生成磷亚胺基/二硅基氨基铁(II)配合物。研究表明，铁-硼键的柔性在该系列铁配位二氮的转化过程中发挥了关键作用。