Synthesis and Structural Characterization of M(PMe₃)₃(O₂CR)₂(OH₂)H₂ (M = Mo, W):  Aqua−Hydride Complexes of Molybdenum and Tungsten

Mo(PMe₃)₆ and W(PMe₃)₄(η²-CH₂PMe₂)H undergo oxidative addition of the O−H bond of RCO₂H to yield sequentially M(PMe₃)₄(η²-O₂CR)H and M(PMe₃)₃(η²-O₂CR)(η¹-O₂CR)H₂ (M = Mo and R = Ph, Bu^t; M = W and R = Bu^t). One of the oxygen donors of the bidentate carboxylate ligand may be displaced by H₂O to give rare examples of aqua−dihydride complexes, M(PMe₃)₃(η¹-O₂CR)₂(OH₂)H₂, in which the coordinated water molecule is hydrogen-bonded to both carboxylate ligands.