Derivatives of Borole, XVII1). – {η5‐[1‐(Diisopropylamino)borole]}metal Complexes: Syntheses, Protonation, Internal RotationNew complexes M(CO)4L (M = Cr, W),cis‐M(CO)2L2[M = Mo, W (not isolated)], and (COD)NiL have been prepared from the Diels‐Alder dimer L2, where L is 1‐(diisopropylamino)borole, C4H4BNiPr2. Complexes of L can be protonated at the nitrogen atom to give stable salts such as [Cr(CO)4(LH)]BF4, [Fe(CO)3(LH)]BF4, [(C6Me6)Ru(LH)]BF4, and [CpCo(LH)]BF4; B — N bond dissociation is not observed. Barriers to internal rotation have been determined by variable temperature NMR spectroscopy for Cr(CO)4L, (COD)NiL, and NiL2. Three processes have been identified: rotation of the NiPr2group around the B — N bond, gear‐mesh rotation of the isopropyl groups around the C — N bonds, and rotation of L with respect to