Metallocenes of the alkaline earth metals and their carbene complexes

Novel alkaline earth metallocenes with various cyclopentadienyl ligands and their carbene adducts with 1,3-di-iso -propyl-4,5-dimethylimidazol-2-ylide ne (iPr-carbene) are described. The syntheses of the magnesocenes (C4Me4H)( 2)Mg (1), (C(5)Me(4)tBu)(2)Mg (2), and (C5H3-1-(SiMe3)-3-tBu)(2)Mg (3) were carried out by reaction of the corresponding cyclopentadiene with dibutylm agnesium. The calcocenes (C5Me4H)(2)(NH3)(2)Ca (6), (C5Me4H)(2)(NH3)(THF)Ca (7) and the barocene (C(5)Me(4)tBu)(2)(THF)(2)Ba (13) were prepaired by re action of calcium and barium, respectively, with the corresponding cyclopen tadienes. Refluxing 7 in THF-toluene yielded the ammonia-free complex (C5Me 4H)(2)(THF)Ca (8). Metathesis reaction of (C(5)Me(4)iPr)Na with CaI2 gave t he calcocene (C(5)Me(4)iPr)(2)(THF)Ca (9). (C(5)Me(4)tBu)(2)(py)(2)Ba (14) results from dissolving 13 in pyridine. 1,3-Di-iso-propyl-4,5-dimethylimida zol-2-ylidene reacted with 1, 3, 7, 8, 13, and (C5Me5)(2)(THF)(2)Sr in tolu ene or THF to give the air- and moisture-sensitive adducts (C5Me4H)(2)(iPr- carbene)Mg (4), (C5H3-1-(SiMe3)-3-tBu),(iPr-carbene)Mg (5), (C5Me4H)(2)(iPr -carbene)Ca (10), (C(5)Me(4)iPr)(2)(iPr-carbene)Ca (11), (C5Me5)(2)(iPr-car bene) Sr (12), and (C(5)Me(4)tBu)(2)(iPr-carbene)Ba (15). The novel compoun ds 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). (C) 2001 Elsevier Scie nce B.V. All rights reserved.