| Abstract: | Multiple bonds between boron and transition metals are known in many borylene (:BR) complexes via metal dπ→BR back‐donation, despite the electron deficiency of boron. An electron‐precise metal–boron triple bond was first observed in BiB2O? Bi≡B?B≡O]? in which both boron atoms can be viewed as sp‐hybridized and the B?BO]? fragment is isoelectronic to a carbyne (CR). To search for the first electron‐precise transition‐metal‐boron triple‐bond species, we have produced IrB2O? and ReB2O? and investigated them by photoelectron spectroscopy and quantum‐chemical calculations. The results allow to elucidate the structures and bonding in the two clusters. We find IrB2O? has a closed‐shell bent structure (Cs, 1A′) with BO? coordinated to an Ir≡B unit, (?OB)Ir≡B, whereas ReB2O? is linear (C∞v, 3Σ?) with an electron‐precise Re≡B triple bond, Re≡B?B≡O]?. The results suggest the intriguing possibility of synthesizing compounds with electron‐precise M≡B triple bonds analogous to classical carbyne systems. |
