Half-sandwich complexes of molybdenum-(III), -(IV) and -(V) with P-O and P-N bifunctional ligands Ph2PCH2X (X=2-oxazolinyl, or C(O)NPh2)

The reaction of the ligands Ph2PCH2X (X=2-oxazolinyl, I; or C(O)NPh2, II) w ith the half-sandwich molybdenum(III) precursors [Mo(eta-C5R5)(mu-Cl)(2)](2 ) (R=H or Me) has been investigated. Ligand I reacts with both complexes to form the corresponding adducts [Mo(eta-C5R5)Cl-2(Ph2PCH2C3H4NO)] (R=H, 1; or Me, 2). The reaction between I and [MoCp*Cl-4] (Cp*=eta-C5Me5) affords [ MoCp*Cl-4(Ph2PCH2C3H4NO-kappa(1)P)] as a kinetic isomer, which then transfo rms quantitatively to [MoCp*Cl-3(Ph2PCH2C3H4NO-kappa(2)P,N)]Cl-+(-), 3. Lig and II reacts with [MoCp(mu-Cl)(2)](2) (Cp=eta-C5H5) to afford the adduct [ CpMoCl2{Ph2PCH2C(O)NPh2-kappa(2)P,O}], 4, as an equilibrium mixture of two isomers. Longer reaction times in CH2Cl2 lead to the molybdenum(IV) by-prod uct [MoCpCl3{Ph2PCH2C(O)NPh2-kappa(2)P,O}], 5. While ligand II does not rea ct with [MoCp*(mu-Cl)(2)](2), it does so in the presence of 1 equivalent of AgBF4 to afford [MoCp*Cl-2{Ph2PCH2C(O)NPh2-kappa(2)P,O}][BF4], 6. Further reaction with CH2Cl2 leads to [MoCp*Cl-3{Ph2PCH2C(O)NPh2-kappa(2)P,O}] [BF4 ], 7. The direct reaction between [MoCp*Cl-4] and ligand II affords [MoCp*C l-4{Ph2PCH2C(O)NPh2-kappa(1)P}] 8 as a kinetic isomer which then slowly est ablishes a solvent-dependent equilibrium with the ionic isomer [MoCp*Cl-3{P h2PCH2C(O)NPh2-kappa(2)P,O}](+) Cl-. The solid state structure of compounds 5 and 7 has been determined by single crystal X-ray diffraction. The chemi cal, spectroscopic, and electrochemical data indicate that ligand II has a greater hemilabile character than ligand I.