 The low coordination number of the iron complex is largely due to the steric effects of the bulky bis(trimethylsilyl)amide, however the complex will bind THF to give the adduct, {(THF)Fe[N(SiMe3)2]2}.Similar behavior can be seen in Mn(hmds)2 and Co(hmds)2, which are monomeric in the gas phase and dimeric in the crystalline phase.Group 11 complexes are especially prone to oligomerization, forming tetramers in the solid phase.