Aminomethylene complexes of molybdenum(IV) and tungsten(IV) bearing 1,2-dithiolato ligands

The syntheses, spectroscopic data and the structures of molybdenum(IV) and tungsten(IV) aminomethylene complexes bearing 1,2-dithiolato ligands are presented. Oxidative decarbonylation of Cp*(CO)2MCNEt2 (1a,b) (a: M=Mo; b: M=W; Cp*=pentamethylcyclopentadienyl) with PhICl2 affords the aminocarbyne complexes cis-Cp*(Cl)2(CO)MCNEt2 (2a,b), which react with the 1,2-dithiolates Na2(mnt)×DMF, (mnt2−=1,2-dicyanoethene-1,2-dithiolate), Li2(bdt) (bdt2−=1,2-benzenedithiolate) and Li2(Mebdt) (Mebdt2−=4-methyl-1,2-benzenedithiolate) to afford the substitution products Cp*(mnt)(CO)MCNEt2 (3a,b), Cp*(bdt)(CO)MCNEt2 (4a,b) and Cp*(Mebdt)(CO)WCNEt2 (5b), respectively. Treatment of 3b with HCl yields, after elimination of CO, the 16-electron aminomethylene complex Cp*(Cl)(mnt)WC(H)NEt2 (6b). Addition of HCl to the MC triple bond of complexes 4a,b and 5b affords the 18-electron aminomethylene complexes Cp*(Cl)(bdt)(CO)MC(H)NEt2 (7a,b) and Cp*(Cl)(Mebdt)(CO)WC(H)NEt2 (8b), which upon heating lose carbon monoxide to afford the 16-electron aminomethylene complexes Cp*(Cl)(bdt)MC(H)NEt2 (9a,b) and Cp*(Cl)(Mebdt)WC(H)NEt2 (10b), respectively. An alternative approach to 9b offers the nucleophilic substitution reaction of Cp*(Cl)3WC(H)NEt2 with Li2(bdt). Complexes 2a–10b have been fully characterized and the crystal structures of the complexes 3b, 6b and 9b are discussed.