Reactions of the Unsaturated Hydroxo Complex [W2Cp2(OH)(μ-PPh2)2(CO)]BF4 with Mono- and Bidentate Ligands Having E–H bonds (E = O, S, N)

The title compound reacted with CO at room temperature in the presence of excess HBF4·OEt2 to yield a mixture of the electron-precise complexes [W2Cp2(μ-PPh2)2(CO)4]­(BF4)2 and [W2Cp2(μ-PPh2)2(CO)3(OH2)]­(BF4)2, with the aquo ligand in the latter complex being easily displaced by simple donors such as acetonitrile. Reaction of the title complex with simple acidic molecules such as HSPh or HBr took place rapidly with elimination of H2O to give the 32-electron cations [W2Cp2(Z)­(μ-PPh2)2(CO)]+ [Z = Br, SPh (W–W = 2.8076(9) Å)], which were reversibly carbonylated to give the electron-precise derivatives [W2Cp2(μ-Z)­(μ-PPh2)2(CO)2]+. Reaction with hydrogen sulfide likely proceeded analogously, but also involved fast cleavage of the second S–H bond to give the sulfido hydride cation [W2Cp2(μ-H)­(μ-PPh2)2(S)­(CO)]+. Deprotonation of the latter cation with 1,8-diazabicycloundec-7-ene (DBU) in the presence of excess H2S gave a mixture of the corresponding sulfido and disulfido complexes [W2Cp2(μ-PPh2)2(S)­(CO)] and [W2Cp2(κ2-S2)­(μ-PPh2)2(CO)]. Reactions of [W2Cp2(OH)­(μ-PPh2)2(CO)]­BF4 with several bidentate ligands (L2H) having weakly acidic H atoms (L2 = SC5H4N, SC6H4NH2, NHC­(S)­Ph) gave the unsaturated chelate derivatives [W2Cp2(κ2-L2)­(μ-PPh2)2(CO)]­BF4. The N–H bonds in the latter cations could be further deprotonated with strong bases (DBU or NaOH) to give neutral derivatives displaying either chelate (N,S-SC6H4NH) or imido-like terminal ligands (N-NC­(S)­Ph), respectively. The related chelate complex [W2Cp2(O,O′-OC6H4O)­(μ-PPh2)2(CO)] (W–W = 2.836(1) Å) was obtained in high yield from the reaction of the thiolato complex [W2Cp2(SPh)­(μ-PPh2)2(CO)]­BF4 with catechol in the presence of DBU.