Studies of ansa-bis(cyclopentadienyl)tungsten derivatives

Abstract

The new compounds [W{(η-C 5 H 4 )X(η-C 5 H 4 )}Cl 2 ] 1, [W{(η-C 5 H 4 )X(η-C 5 H 4 )}Me 2 ] 2, [W{(η-C , where X = SiMe 2 , SiEt 2 or CMe 2 CMe 2 , and Y = BF 4 or Cl, have been prepared. The crystal structures of [W{(η-C 5 H 4 )X(η-C 5 H 4 )}Me 2 ] (X = SiMe 2 or CMe 2 CMe 2 ) have been determined.Recently we have described ansa-metallocenes of tungsten and molybdenum and shown that their properties are significantly different from non-ansa analogues. 1,2 In particular we noted that the complex [W{(η-C 5 H 4 )CMe 2 (η-C 5 H 4 )}H 3 ] ϩ PF 6 Ϫ displays exceptional highly temperature variable 1 H NMR spectroscopic data with 2 J(HH) of ca. 16 000 Hz at Ϫ70 ЊC attributed to quantum mechanical exchange coupling. By comparison, [W(η-C 5 H 5 ) 2 H 3 ] ϩ BF 4 Ϫ shows very different temperature independent behaviour. 3 We have prepared a number of related ansa-tungstenocene complexes to investigate the effect that changes in the bridging ring substituents have upon their properties.Compound and analysis a 1a [W{(η-C 5 H 4 )SiMe 2 (η-C 5 H 4 )}Cl 2 ] Green C, 28.7 (28.7); H, 3.7 (3.3) Spectroscopic data b 1 H: c 6.12 (4 H, m, C 5 H 4 ), 5.81 (4 H, m, C 5 H 4 ), 0.09 (6 H, s, Me 2 Si) 13 C-{ 1 H}: c 125.9 (s, C 5 H 4 ), 78.7 (s, C 5 H 4 ), 66.0 (s, C 5 H 4 , C ipso ), Ϫ5.9 (s, SiMe 2 ) Mass (FAB): m/z 442 (M ϩ ), 405 (M ϩ Ϫ Cl) 1b [W{(η-C 5 H 4 )SiEt 2 (η-C 5 H 4 )}Cl 2 ] Green 1

Strained Metallocenophanes and Related Organometallic Rings Containing π‐Hydrocarbon Ligands and Transition‐Metal Centers

“…materials with identical elemental composition on standing at room temperature. [148] In 1999 Heinekey and Radzewich reported the synthesis and the structure of the rhenium(III) d 4 = 41.18, b = 08).…”

Silicon–Carbon bond cleavage reactions of Ansa tungstenocene compounds: The [Me 2 Si] bridge as a site for metallocene functionalization

“…Previous studies of ansa tungstenocene complexes that incorporate [Me 2 Si] bridges have focused on ligands that feature a rather limited number of substitution patterns, namely [Me 2 Si(Cp) 2 ]WX 2 (11,12) (3,4). However, ansa tungstenocene compounds that possess only two alkyl substituents on each ring have not been reported.…”

Photoinduced FeCp Bond Cleavage and Insertion Reactions of Strained Silicon‐ and Sulphur‐Bridged [1]Ferrocenophanes in the Presence of Transition‐Metal Carbonyls

“…Photolysis of 1 with [Co 2 (CO) 8 ] afforded the remarkable tetrametallic dimer [(CO) 2 2 ] 2 (13). The corresponding photochemical reaction of 8 with [Co 2 (CO) 8 ] gave a trimetallic insertion product in high conversion,…”

“…[37] These results have been explained in terms of a decreased HOMO-LUMO gap and increased ligand character for the LUMO on increasing a. [20,37] The inherent ring-strain in ferrocenophanes also renders these species highly susceptible to ringAbstract: The photochemical reactions of the moderately strained sila [1] (10) and [Fe 2 (CO) 2 …”

“…Since the discovery of the first example, sila [1]ferrocenophane 1 in 1975 by Osborne and co-workers, [1] strained [1]ferrocenophanes 2 have attracted considerable attention and have inspired growing interest in a range of related species containing various metals, [2][3][4][5][6][7][8][9][10][11] bridging elements [12][13][14][15][16][17][18][19][20][21][22][23][24][25] and even p-hydrocarbon ligands. [26][27][28][29][30][31][32][33][34][35] The angle created by the planes of the two Cp rings in a ferrocenophane, generally denoted as a, serves as a convenient qualitative measure of the degree of strain present.…”