The manuscript by Mitzel and coworkers describes the synthesis of a neutral antimony compound (C2F5)2SbCH2P(tBu)2. The reactivity of this compound is demonstrated with CS2, SO2, PHNCO, PhNCS, and (R3P)AuCl. The compounds are well-characterized by NMR spectroscopy and X-ray crystallographic studies. DFT calculations further support the experimental evidence. The manuscript is recommended for publication after the authors address the following points:
1. The compound (C2F5)2SbCH2P(tBu)2 belongs to the general class of the organoantimony compounds of the type R3Sb. However, in the present case, two R=groups are electron withdrawing -C2F5 and another ligand consisting of a pendant bearing a P(III)-donor functionality. More than “frustration”, the reviewer believes that the low Lewis acidity at antimony prevents the effective interaction of the phosphorus center with the antimony atom. Have the authors performed standard Lewis acidity tests to explore the electronic nature of the antimony center?
2. Can the substrates CS2, SO2, PHNCO, and PhNCS react with phosphines in the absence of the antimony center? If so, what benefit does antimony offer?
3. Are the long Sb-E (E=S, O, and N) interactions in the solid state also seen in the solution?
4. On page 3, “Although both reactions have positive values for the differences in……” should be rephrased appropriately

Mitzel and co-workers have addressed the reviewer's concerns. The manuscript is recommended for publication in Chemical Science. They have studied the Lewis acidity of the antimony center by performing the Gutmann Test. While FIA calculations indicate mild Lewis acidity, a more convincing conclusion can be drawn only by experiments.
The authors have provided convincing experimental evidence on the role of the phosphorus center by performing control reactions MeP(tBu)2 with CS2, SO2, PHNCO, and PhNCS.
The reviewer did not expect the authors to determine bond distances in solution but was curious to know if the long Sb-E (E=S, O, and N) contacts can be detected as weak interaction in solution state by NMR spectroscopy.