Hydration of Nitrosylruthenium Bis(alkynyl) Complexes with Hydrotris(pyrazolyl)borate:  Insertion/Hydration and Double Hydration Products

Hydration of nitrosylruthenium bis(alkynyl) complex TpRu(C⋮CPh)₂(NO) (1) (Tp = BH(pyrazol-1-yl)₃) was carried out in the presence of HBF₄·Et₂O in distilled MeOH and afforded the metallacycle TpRu{CHC(Ph)C(O)CH(Ph)}(NO) (2) (39%) and the bis(ketonyl) TpRu(CH₂C(O)Ph)₂(NO) (3) (37%). While double hydration of 1 gave 3, 2 was produced through a combination of insertion and hydration processes. On the other hand, a similar reaction performed in THF instead of MeOH afforded 2 (52%), the acyl-ketonyl complex TpRu(C(O)CH₂Ph)(CH₂C(O)Ph)(NO) (4) (8.9%), and trace amounts of 3 and TpRu(C⋮CPh)(CH₂C(O)Ph)(NO) (5). Moreover, the 1/HBF₄·Et₂O/H₂O reaction system in distilled MeOH at 0 °C gave rise to 5 exclusively (79%). Treatment of THF solution of isolated 5 with water in the presence of protic acid furnished 3 and 4, revealing that 5 is the intermediate in their formation.