Metallocenes of the alkaline earth metals and their carbene complexes

Abstract Novel alkaline earth metallocenes with various cyclopentadienyl ligands and their carbene adducts with 1,3-di- iso -propyl-4,5-dimethylimidazol-2-ylidene ( i Pr-carbene) are described. The syntheses of the magnesocenes (C 5 Me 4 H) 2 Mg ( 1 ), (C 5 Me 4 t Bu) 2 Mg ( 2 ), and (C 5 H 3 -1-(SiMe 3 )-3- t Bu) 2 Mg ( 3 ) were carried out by reaction of the corresponding cyclopentadiene with dibutylmagnesium. The calcocenes (C 5 Me 4 H) 2 (NH 3 ) 2 Ca ( 6 ), (C 5 Me 4 H) 2 (NH 3 )(THF)Ca ( 7 ) and the barocene (C 5 Me 4 t Bu) 2 (THF) 2 Ba ( 13 ) were prepaired by reaction of calcium and barium, respectively, with the corresponding cyclopentadienes. Refluxing 7 in THF–toluene yielded the ammonia-free complex (C 5 Me 4 H) 2 (THF)Ca ( 8 ). Metathesis reaction of (C 5 Me 4 i Pr)Na with CaI 2 gave the calcocene (C 5 Me 4 i Pr) 2 (THF)Ca ( 9 ). (C 5 Me 4 t Bu) 2 (py) 2 Ba ( 14 ) results from dissolving 13 in pyridine. 1,3-Di- iso -propyl-4,5-dimethylimidazol-2-ylidene reacted with 1 , 3 , 7 , 8 , 13 , and (C 5 Me 5 ) 2 (THF) 2 Sr in toluene or THF to give the air- and moisture-sensitive adducts (C 5 Me 4 H) 2 ( i Pr-carbene)Mg ( 4 ), (C 5 H 3 -1-(SiMe 3 )-3- t Bu) 2 ( i Pr-carbene)Mg ( 5 ), (C 5 Me 4 H) 2 ( i Pr-carbene)Ca ( 10 ), (C 5 Me 4 i Pr) 2 ( i Pr-carbene)Ca ( 11 ), (C 5 Me 5 ) 2 ( i Pr-carbene)Sr ( 12 ), and (C 5 Me 4 t Bu) 2 ( i Pr-carbene)Ba ( 15 ). The novel compounds have been characterized by elemental analysis, mass spectrometry and NMR spectroscopy as well as the X-ray structures of the metallocenes ( 1 , 2 , 6 , 9 , 13 ) and the carbene adducts ( 4 , 10 , 11 , 12 , 15 ).