Photoreaktion von (μ‐η] 2:2 ‐Acetylen)tetracarbonylbis(η 5 ‐cyclopentadienyl)‐dimolybdän und ‐wolfram mit Acetylen und 1,3‐Butadien

Photoreaktion von (μ‐η] 2:2 ‐Acetylen)tetracarbonylbis(η 5 ‐cyclopentadienyl)‐dimolybdenum and ‐tungsten with Acetylene and 1,3‐Butadiene [Mo 2 (η 5 ‐C 5 H 5 ) 2 (CO) 4 (μ‐η 2:2 ‐C 2 H 2 )] ( 1 ) and [W 2 (η 5 ‐C 5 H 5 ) 2 (CO) 4 ‐(μ‐η 2:2 ‐C 2 H 2 )] ( 2 ) react upon UV irradiation with acetylene, 1,3‐butadiene, and isoprene. Main products of the reactions with acetylene are the fly‐over complexes [M 2 (η 5 ‐C 5 H 5 ) 2 (CO) 2 (η 1:3:3:1 ‐1,3,5‐hexatriene‐1,6‐diyl)] ( 8 : M = Mo; 9 : M = W). There is some IR evidence for the formation of [Mo 2 (η 5 ‐C 5 H 5 ) 2 (CO)(η 5 η 1:4:1 ‐1,3‐butadiene‐1,4‐diyl)] ( 10 ). In addition [Mo 3 (η 5 ‐C 5 H 5 ) 6 (μ‐η 1:2 ‐ethynyl)] ( 12 ) is obtained. 1 reacts with 1,3‐butadiene with C—C bond formation to give [Mo 2 (η 5 ‐C 5 H 5 ) 2 >(CO)(μ‐η 1:2 ‐CO)(μ‐η 1:2:3 ‐1,5‐hexadiene‐1,4‐diyl)] ( 15 ) and [Mo 2 (η 5 ‐C 5 H 5 ) 2 (CO) 4 [μ‐η 1:3 ‐ E,Z ‐2,4‐hexadiene‐1‐ylidene)] ( 18 ). With isoprene [Mo 2 (η 5 ‐C 5 H 5 ) 2 (CO) 4 [μ‐η 1:3 ‐ E,Z ‐5‐methyl‐2,4‐hexadiene‐1‐ylidene)] ( 18a ) is obtained. The reaction of 2 with 1,3‐butadiene yields six complexes. Beside thermolabile [W 2 [W 2 (η 5 ‐C 5 H 5 ) 2 (CO) (μ‐η 1:2:1 ‐3‐oxo‐1‐propene‐1, 3‐diyl)(η 4 ‐1,3‐butadiene)] ( 21 ), (η 5 ‐C 5 H 5 ) 2 (CO) (μ‐η 1:4 ‐3‐methylene‐1,4‐pentadiene‐1‐yl)] ( 20 ), the tungsten homologue of 15 , [W 2 (η 5 ‐C 5 H 5 ) 2 (CO) (μ‐η 1:2:3 ‐1,5‐hexadiene‐1,4‐diyl)] ( 16 ), its isomer [W 2 (η 5 ‐C 5 H 5 ) 2 (CO) 2 (μ‐η 1:2:3 ‐1,5‐hexadiene‐1,4‐diyl)] ( 23 ) with a W—W double bond, and [W 2 (η 5 ‐C 5 H 5 ) 2 (CO) 2 (μ‐η 1:2:1 ‐1,4‐hexadiene‐1,6‐diyl)] ( 17 ) are isolated. Furthermore, [W 2 (η 5 ‐C 5 H 5 ) 2 (CO) 2 (μ‐η 1:2 ‐vinylidene)] ( 11 ) is obtained. In solution 21 rearranges to 23 . The crystal and molecular structures were determined for 15 and 18 . The constitutions of the other products were deduced from the IR and 1 H‐NMR spectra.