Complex Formation and Rearrangement Reactions of the Phosphine Hydride Anions [OsH₃(PPh₃)₃]^- and [IrH₂(PPh₃)₃]^-

[OsH₄(PPh₃)₃] (1) reacts with KH in THF in the presence of 18-crown-6 to form [K(THF)(18-crown-6)][OsH₃(PPh₃)₃] (2), characterized by NMR spectroscopy and X-ray crystallography; cation−anion contact is achieved through three Os−H···K moieties. In contrast, [IrH₃(PPh₃)₃] (6) reacts with KH and 18-crown-6 in THF with redistribution of ligands to produce the known bis-phosphine complex [K(18-crown-6)][IrH₄(PPh₃)₂] (7). This reaction has been followed by NMR spectroscopy, and [IrH₂(PPh₃)₃]^- has been identified as a likely intermediate. K[OsH₃(PPh₃)₃] (3) reacts with Buⁿ₃SnCl to form the tin-osmium complex [OsH₃(SnBuⁿ₃)(PPh₃)₃] (8), characterized by NMR spectroscopy and X-ray crystallography. The molecule contains a seven-coordinate osmium center, which can be described approximately as a distorted fac-[OsH₃(PPh₃)] arrangement, with the SnBuⁿ₃ moiety capping the OsH₃ face.