Complex [OsHCl(≡CPh)(IPr)(P i Pr 3 )]OTf (1; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolylidene, OTf = CF 3 SO 3 ) replaces the chloride ligand by a hydroxo group to give [OsH(OH)(≡CPh)(IPr)(P i Pr 3 )]OTf (2), which undergoes hydroboration and hydrogenation of its metal-carbon triple bond. The hydroboration products depend upon the used reagent. Treatment of 2 with Na [BH 4 ] leads to the bis-σ-borane complex OsH 2 (η 2 , η 2 -H 2 BCH 2 Ph)(IPr)(P i Pr 3 ) (3), whereas pinacolborane (HBPin) affords the arene compound [Os(η 6 -C 6 H 5 CH 2 Bpin)H(IPr)(P i Pr 3 )]OTf (4). The hydrogenation of the triple bond of 2 occurs under 4 atm of H 2 and yields the toluene derivative [Os(η 6 -C 6 H 5 CH 3 )H(IPr)(P i Pr 3 )]OTf (5).Isolobality 1 often relates organometallics to organic functionalities. Hydroboration 2 and related processes, such as hydrogenation, 3 of carbon-carbon multiple bonds are powerful tools in organic synthesis. Analogous reactions with the organometallics counterparts, where a unit of the multiple carbon-carbon bond has been replaced by a transition metal and its associated ligands, are also known and represent a relevant group of transformations with exceptional possibilities in organometallic chemistry. However, in contrast to the purely organic processes, they have received scarce attention. 4 This is due in a part to their high complexity which is associated not only with the variety of transition metal and metal ions but also with the wide range of known co-ligands. These Lewis bases subtly govern the electron density of the metal center. Thus, they determine the behavior of a particular complex, 5 although they do not participate directly in its reactions.It is well established that the first step for the cleavage of a σ-bond is its coordination to an unsaturated transition metal compound to form a σ-complex. Thus, σ-B-H species are considered the key intermediates in the metal promoted B-H bond cleavage and have been therefore prepared by direct coordination to the metal center. 6 In contrast to the large number of dihydrogen derivatives and silane compounds, which have been studied, few examples of B-H complexes have been isolated and characterized, in particular those having most electrophilic B-alkyl moieties 7 and third row metals such as osmium. 8 In this communication, we demonstrate that σ-derivatives of the type Os(η 2 ,η 2 -H 2 Balkyl) can be prepared by hydroboration of Os-alkylidene complexes, when the coligands of the starting compound and the hydroboration reagent are appropriately selected.Hydride ligands of cationic complexes show protic character. 9 Thus, they generally undergo deprotonation. 10 In agreement with this, the hydride-alkylidyne cations [Os(η 5 -C 5 H 5 )H(≡CPh)(PR 3 )] + react with Brønsted bases to afford the corresponding neutral derivatives Os(η 5 -C 5 H 5 )(≡CPh)(PR 3 ) (PR 3 = P i Pr 3 , 11 P i Pr 2 [C(CH 3 )=CH 2 ] 12 ). The five-coordinate hydride-alkylidyne derivative [OsHCl(≡CPh)(IPr)(P i Pr 3 )]OTf (1; IPr = 1,3-bis(2,6-diisopropylphenyl)...
