Reactions of α-lithio (aminocarbene)tungsten anions with diiodoalkanes: Synthesis of (μ-bis(aminocarbene))ditungsten complexes

Abstract Treatment of (CO) 5 W[C(N(CH 3 ) 2 )CH 3 ] ( 1 ) with n BuLi followed by 5–10 equiv. of a diiodoalkane (diiodomethane, 1,2-diiodoethane, 1,3-diiodopropane, 1,4-diiodobutane, or 1,5-diiodopentane) gave the respective (iodoalkylaminocarbene)tungsten complexes (CO) 5 W[C(N(CH 3 ) 2 )CH 2 (CH 2 ) n I] ( n =1–5) ( 2 ). For the reaction of the α-lithio anion of 1 with diiodomethane, only a 5% yield of the corresponding complex 2a ( n = 1) was obtained. Moreover, the reaction of the α-lithio anion of 1 with 1,2-diiodoethane gave no product 2b ( n = 2). On the other hand, good to excellent yields (69–93%) of complexes 2c–e (n = 3–5) were obtained using 1,3-diiodopropane, 1,4-diiodobutane, or 1,5-diiodopentane. Complexes 2c–e were further treated with the α-lithio anion of 1 to afford the new (μ-bis(aminocarbene))ditungsten complexes (CO) 5 W[C(N(CH 3 ) 2 )CH 2 (CH 2 ) n CH 2 C(N(CH 3 ) 2 )]W(CO) 5 ( n =3–5) ( 3c–e ) in yields ranging from 52 to 61%.