Capturing HBCy2: Using N,O-Chelated Complexes of Rhodium(I) and Iridium(I) for Chemoselective Hydroboration

1,3‐N,O‐chelated complexes of RhI and IrI cooperatively and reversibly stabilized the B−H bond of HBCy2 to afford six‐membered metallaheterocycles (M=Rh (7) or Ir (8)) having a δ‐[M]⋅⋅⋅H‐B agostic interaction. Treatment of these Shimoi‐type borane adducts 7 or 8 with both an aldehyde and an alkene resulted in chemoselective aldehyde hydroboration and reformation of the 1,3‐N,O‐chelated starting material. The observed chemoselectivity is inverted from that of free HBCy2, which is selective for alkene hydroboration. Cooperative activation of HBCy2 provided six‐membered genuine rhoda‐ and iridacycles containing a δ‐[M]⋅⋅⋅H−B agostic interaction. The treatment of these Shimoi‐type borane adducts with an aldehyde and an alkene resulted in chemoselective aldehyde hydroboration and reformation of the 1,3‐N,O‐chelated starting material (see scheme). In contrast, free HBCy2 is selective for alkene hydroboration.