A series of doubly bridged dinuclear titanium and zirconium complexes (Me2C)(Me2E)(C5H3)2(Cp'MCI2)2 [E=Si,Cp'=C5H5, M=Ti (1), Zr (2); E=Ge, Cp'=C5H5, M=Ti (3), Zr (4); Cp'=C5Me4H, M=Zr, E=Si (5), Ge (6)] and (Me2SiOSiMe2)2(C5H3)2(Cp'MCI2)2[Cp'=C5H5, M=Ti (7), Zr (8); Cp=C5Me4H, M=Zr (9)] were synthesized by the reaction of the lithium compounds of the corresponding doubly bridged cyclopentadienyl ligands with CpTiCl3, CpZrCl3(THF)2 or C5Me4HZrCl3, respectively. These complexes were characterized by 1H-NMR, MS and elemental analysis. The crystal structure of 4 was determined by the X-ray diffraction. Their catalytic properties for ethylene polymerization were also studied in the presence of MAO.

Treatment of (Me2SiSiMe2)[η5-C5H3R1)Fe(CO)]2(u-CO)2(R1=H(1), R1=t-Bu(5)) with R2NC(R2=C6H11, t=Bu) in benzene afforded isocyanide-substituted complexes [(η5:η5-C5H3R1-Me2SiMe2C5H3R1)Fe2(CO)(CNR2)(u-CO)2] (R1=H, R2=t-Bu(4); R1=R2=t-Bu(6)). Turther investigations indicated that the cis substrate 5c afforded only the cis product (6c), while the trans substrate 5t afforded only the trans product (6t). When 3 and 4 were heated respectively in xylene, three different rearranged products (6t). When 3 and 4 were heated respectively in xylene, three different rearranged products [{(Me2Si)(η5-C5H4)-Fe(CO)L1}{(Me2Si)(η5-C5H4)-Fe(CO)L2}](L1=L2=CO(2); L1=C6H11NC, L2=CO(7), L2=C6H11NC(9); L1=t-BuNC, L2=CO(8), L2=t-BuNC(10)) were obtained. Similarly, thermal treatment of 6t afforded three different cls rearranged products, 11c, 12c, and 13c, while treatment of 6c afforded three different cis rearranged products, 11t, 12t, and 13t, This indicated that the rearrangement still follows the reaction mechanism proposed previously on the basis of the intramolecular nature of this reaction mechanism proposed previously on the basis of the intramolecular nature of this reaction if we only take into accunt the configuration of two tert-buty1 groups on the Cp rings. To explain the formation of three different products, an alternative mechanism involving free ligand exchange to from three different iron-centerde radical intermediater is proposed as a supplement to the previous mechanism. The complex stereochemistry in the moecules of 12 and 13 is discussed. Molecular structures of 8,9t, 12t, and 13c have benn determined by single-crystal X-ray diffraction.

Complexes (Me2GeGeMe2)[η5-C5R4)Fe(CO)]2(u-CO)2(R=H, 1; Me, 3) 1 and 3, prepared by the reaction of C5R4HMe2GeGeMe2C5R4H with Fe(CO)5 in refluxing xylene, underwent a novel thermal reaction between their Ge-Ge and Fe-Fe bonds, forming corresponding rearrangement products with new cyclic structures, [Me2Ge(η5-C5R4)Fe(CO)2]2(R=H, 2; Me 4). Compared with the case of silicon, the weaker Ge-Ge bond resulted in an easier rearrangement reaction. Reactions of 1 with indine and sodium amalgam were examined. Molecular structures of 1, 2, 3, and 4 were determined by X-ray diffraction.

When the doubly bridged bis(cyclopentadiene) ligand (Me2C)(Me2Si)(C5H4)2 (1) reacted with Fe(CO)5 in refluxing toluene, the unusual product [(C5H6)(Me2C)(Me2Si)(η5-C5H3)Fe(CO)]2-(μ-CO)2 (2) with a hydrogenated double bond in one of the cyclopentadiene ligands, the diiron complex (Me2C)(Me2Si)[(η5-C5H3)Fe(CO)2]2 (3), and the desilylation product 4 were obtained. When the reaction was performed in refluxing xylene, the novel complex (Me2C)(η5-C5H3)-(η5:η1-C5H3)[(Me2Si)Fe(CO)2][Fe(CO)2] (5) with and Fe-Si bond, which should be accompanied by the cleavage of a C-Si bond in the ligand, was isolated in addition to the complees 2～4. When bis(cyclopentadienyl) ligands bridged with R2C (R2C=Me2C, (CH2)5C)AND Me2E(E=Si, Ge) groups were used instead of 1, the similar novel complexes (R2C)(η5-C5H3)(η5:η1-C5H3)[(Me2E)Fe(CO)2] (R2C=Me2C, E=Ge (7); R2C=(CH2)5C, E=Si(17), Ge (21)) with and Fe-E bond were obtained in addition to the diiron complexes (R2C)(Me2E)-[(η5-C5H3)Fe(CO)]2[Fe(CO)2](R2C=Me2C, E=Ge (8); R2C=(CH2)5C,E=Si (18), Ge (22)) and the desilylation or degermylation products. When a tert-butyl group was introduced into the cyclopentadienyl rings, or two phenyl groups were introduced at the bridging silicon atom instead of two methyl groups in 1, only the diiron complexes (Me2C)(Me2E)[η5-t-BuC5H2]Fe(CO)2]2 (E=Si(10), Ge (13)) and (Me2C)(Ph2Si)[(η5-C5H3)Fe(CO)2]2 (15) were obtained, in addition to the desilylatin or degermylation products. Whem a methylene bridge was used instead of an isopropylene bridge in 1 and 6, the partially hydrogenated complexes (Me2E)(η3-CHC5H6)(η5-C5H3)Fe(CO)3Fe(CO)2(E=Si(24),Ge (28)), the diiron complexes (CH2)(Me2E)[(η5-C5H3)Fe(CO)]2(μ-CO)2(E=Si (25), Ge (29)), and the desilylation or degermylation products were obtained. The molecular structures of 2, 3, 5, 7, 8, 10, 11t, 15, 17, 18, 21, 24, 25, 28, and 29 were determinde by X-ray diffraction.