Organmetallic Selenolates, IV . Reactions of MSeW(CO) 3 cp (M=Li, Na) with Organodi‐ and ‐tetrahalides – X‐ray Crystal Structures of C 6 H 5 CH 2 W(CO) 3 (η 5 ‐C 5 H 5 ), μ‐[ m ‐C 6 H 4 {CH 2 SeW(CO) 3 (η 5 ‐C 5 H 5 )} 2 ], μ‐[ p ‐C 6 H 4 {CH 2 SeW(CO) 3‐ (η 5 ‐C 5 H 5 )} 2 ], and C 6 H 5 CH[SeW(CO) 3 (η 5 ‐C 5 H 5 )] 2

Organotungsten‐selenolato complexes were prepared in moderate yields by insertion of selenium into the alkali metaltungsten bonds of MSeW(CO) 3 cp (M = Li, Na) and subsequent reactions with the organohalides o ‐, m ‐, and p ‐ C 6 H 4 (CH 2 Br) 2 , C 6 H 5 CHBr 2 , m ‐C 6 H 4 (CHBr 2 ) 2 and C 6 H 5 CCl 3 . The 77 Se‐NMR data of the new complexes are discussed and compared with those of related complexes derived from organomonohalides. Moreover, the X‐ray crystal structures of C 6 H 5 CH 2 W(CO) 3 cp ( 1 ), μ‐[ m ‐C 6 H 4 {CH 2 SeW(CO) 3 cp} 2 ] ( 3 ), μ‐[ p ‐C 6 H 4 {CH 2 SeW(CO) 3 cp} 2 ] ( 4 ), and C 6 H 5 CH[SeW‐(CO) 3 cp] 2 ( 5 ) were determined. In complex ( 1 ), the W–CH 2 bond length is 2.374 Å; the W–Se bond lengths in the complexes 3, 4 and 5 are all in the range 2.625–2.655 Å, corresponding to W–Se single bonds.