Hemilabile orthometallated acetals: Synthesis, spectroscopic characterization and crystal and molecular structures of [RuCl{η2-C,O-C6H4-2-CH(O2C2H4)}(CO)(PPh3)2] and [HgBr{η2-C,O-C6H4-2-CH(O2C2H4)}]

Treatment of [RuHCl(CO)(PPh3)2] with [Hg{C6H4-2-H(O2C2H4)}2] (1) in refluxing toluene affords [RuCl{η2-C,O-C6H4-2-CH(O2C2H4)}(CO)(PPh3)2] (2a). Compound 2a reacts with Ag[BF4] followed by NaX (X = Br, I, F) to give [RuX{η2-C,O-C6H4-2-CH(O2C2H4)}(CO)(PPh3)2] (2b–d). All compounds have been characterized by elemental analysis (C and H), IR, 1H, 13C–{1H} and 31P–{1H} NMR spectroscopy. A crystallographic study of 2a shows the presence one pair of enantiomers and one pair of diastereoisomers in the asymmetric unit. Theoretical calculations (B3LYP using the LanL2DZ basis set) on the model compounds [RuCl(CH3)(EH2)(CO)(PH3)2] (E = O, S) (3a,b) show that for 3a a planar geometry at the OH2 ligand and for 3b a pyramidal structure at SH2 is favoured. The calculated electrostatic potentials for EH2 and the acetals CH2E2C2H4 (E = O, S) are used to comment on the nature of the lone pairs at the chalcogen atoms and the coordination geometries of ether and thioether ligands. The X-ray crystallographically determined molecular structure of [BrHg(η2-C,O-C6H4-2-CHO2C2H4)] (4) is also described and model compounds studied theoretically.