The tetrahydroborate OsH(eta(2)-H2BH2)(CO)-((PPr3)-Pr-i)(2) (1) reacts with aniline and p-toluidine to give the amino-boryl derivatives Os{B(NHC6H4R)NHCCHCHC(R)CHC}- (CO)((PPr3)-Pr-i)(2) (R = H (2), CH3 (3)) and four H-2 molecules. Treatment of 2 and 3 with phenylacetylene gives Os{B-(NHC6H4R)(2)}(C CPh)(CO)((PPr3)-Pr-i)(2) (R=H (4), CH3 (5)), which react with HBF4 to afford the amino(fluoro)boryl species Os{BF(NHC6H4R)}(C CPh)(CO)((PPr3)-Pr-i)(2) (R= H (6), CH3 (7)). In contrast to HBF4, the addition of acetic acid to 4 and 5 induces the release of phenylacetylene and the formation of the six-coordinate derivatives Os{B(NHC6H4R)(2)}(k(2)-O2CCH3)(CO)((PPr3)-Pr-i)(2) (R = H (8), CH3 (9)). The coordination number six for 4 and 5 can be also achieved by addition of CO. Under this gas Os{B(NHC6H4R)(2)}(C-CPh)(CO)(2)((PPr3)-Pr-i)(2) (R = H (10), CH3 (11)) are formed. In toluene, these alkynyl-aminoboryl compounds evolve into the aminoborylvinylidenes Os{=C=C(Ph)B(NHC6H4R)(2)}-(CO)(2)((PPr3)-Pr-i)(2)-(R = H (12), CH3 (13)) via a unimolecular 1,3-boryl migration from the metal to the C-beta atom of the allcynyl ligand. Similarly to 4 and 5, complexes 6 and 7 coordinate CO to give Os{BF(NHC6H4R)}(C CPh)(CO)(2)((PPr3)-Pr-i)(2) (R = H (1S), CH3 (16)), which evolve to Os{=C=C(Ph)BF(NHC6H4R)}(CO)(2)((PPr3)-Pr-i)(2) (R = H (17), CH3 (18)).