Xiuzhong Zhou

Synthesis, structures and catalytic properties of Group 4 metallocenes based upon [Me2E(C5H4)(C5Me4)]2 (E=Si, Ge) supporting coordination

The ansa -metallocene complexes Me 2 Si(η 5 -C 5 H 4 )(η 5 -C 5 Me 4 )MCl 2 [M=Ti ( 1 ), Zr ( 2 ), Hf ( 3 )] were prepared by the reaction of [Me 2 Si(η 5 -C 5 H 4 )(η 5 -C 5 Me 4 )]Li 2 with MCl 4 ·2THF. Complexes Me 2 Ge(η 5 -C 5 H 4 )(η 5 -C 5 Me 4 )MCl 2 [M=Ti ( 4 ), Zr ( 5 )] were synthesized using similar method from the germyl-bridged ligand. The molecular structures of 1 – 3 and 5 have been determined by X-ray diffraction. Complexes 1 – 3 and 5 in combination with MAO were studied as catalysts for ethylene polymerization and it was found that zirconocene catalysts show much higher activities than the titanocene and hafnocene and the activities reach the maximum at high temperature. This indicates that the zirconocene system based upon [Me 2 E(C 5 H 5 )(C 5 Me 4 )] 2 (E=Si, Ge) supporting coordination is a highly stable ethylene polymerization catalyst system. The relationship between structures and catalytic properties of catalysts is discussed.

Siloxy-substituted tetramethylcyclopentadienyl and indenyl trichlorotitanium complexes for syndiospecific polymerization of styrene

Abstract ( η 5 -trimethylsiloxytetramethylcyclopentadienyl)- and ( η 5 -2- trimethylsiloxyindenyl)trichloro titanium have been synthesized and characterized. Their catalytic behavior for the polymerization of styrene was studied in the presence of methylaluminoxane (MAO) as a cocatalyst. They show only low activity for styrene polymerization.

The first sila-bridged dicyclopentadienyl diruthenium complex: synthesis and X-ray structure of (Me2Si)[(η5-C5H4)Ru(CO)]2(μ-CO)2

Abstract Thermal treatment of a solution of Ru 3 (CO) 12 and C 5 H 5 Me 2 SiC 5 H 5 in heptane gives (Me 2 Si)[(η 5 -C 5 H 4 )Ru(CO)] 2 (μ-CO) 2 ( 1 ) in good yield. An investigation on the infrared spectra of 1 in KBr disc and CH 2 Cl 2 solution reveals the coexistence of two isomers 1a (bridging form) and 1b (non-bridging form), with the former dominant. The molecular structure of 1a has been determined by X-ray diffraction.

Synthesis, structures and polymerization catalytic properties of germyl-bridged bis(cyclopentadienyl) metallocenes

Abstract The ansa-metallocene complexes Me2Ge(η5-C5Me4)2MCl2 [M=Ti (1), Zr (2)], Me2Ge(η5-C5H3Bu-t)2ZrCl2 (3) and Me2Ge(η5-C5H4)(η5-C5H3R)ZrCl2 [R=Me (4), t-Bu (5)] were prepared by the reaction of the corresponding ligands with n-BuLi and MCl4·2THF, respectively. The molecular structures of 1 and 2 have been determined by the X-ray diffraction method. Complexes 2–5 in combination with MAO were studied as catalysts for ethylene polymerization and all the germyl-bridged zirconocene catalysts show high activities at relative high temperatures. This indicates that the germyl-bridged zirconocene systems show thermally stable catalyst systems for polymerization of ethylene.

Thermal rearrangement reaction of disilyl-bridged bis(tetramethyl cyclopentadienyl) tetracarbonyl diiron The molecular structures of (Me2SiSiMe2)[(η5-C5Me4)Fe(CO)]2(μ-CO)2 and [(Me2Si) (η5-C5Me4) Fe(CO) 2]2

Abstract Binuclear iron complex (Me 2 SiSiMe 2 )[( η 5 -C 5 Me 4 )Fe(CO)] 2 ( μ -CO) 2 ( 2 ) have been prepared in good yield by thermal treatment of Me 4 HC 5 (Me 2 SiSiMe 2 )C 5 HMe 4 with Fe(CO) 5 . Its thermal rearrangement reaction exhibits greater difficulty in comparison with the parent complex (Me 2 SiSiMe 2 )[( η 5 -C 5 H 4 )Fe(CO)] 2 ( μ -CO) 2 ( 1 ). Even when the reaction time was prolonged to 24 h, the rearrangement product [(Me 2 Si)( η 5 -C 5 Me 4 )Fe(CO) 2 ] 2 ( 3 ) was isolated in 3% yield. The molecular structures of 2 and 3 have been determined by X-ray diffraction. Crystals of 2 are orthorohomic, space group P2 1 2 1 2 1 , with a = 11.015(5) A, b = 11.020(4) A, c = 11.173(4) A, V = 1355(2) A 3 , Z = 2, D x = 1.423 g cm −3 , R ( R w ) = 0.056 (0.064). Crystals of 3 are triclinic, space group P-1, with a = 8.297(1) A, b = 9.988(2) A, c = 10.290(2) A, α = 60.70(1)°, β = 63.79(2)°, γ = 77.41(2)°, V = 667.1(2) A 3 , Z =1, D x = 1.46 g cm −3 , R ( R w ) = 0.044 (0.031).

Crystal structures and polymerization catalytic properties of 1,1,2,2-tetramethyldisilane-bis(3-t-butyl-η5-cyclopentadienyl) titanium and zirconium dichlorides

Abstract The title complexes Me 4 Si 2 (1-C 5 H 3 -3- t Bu) 2 MCl 2 (M=Ti, 1 ; M=Zr, 2 ) have been prepared by reaction of Li 2 Me 4 Si 2 (C 5 H 3 -3- t Bu) 2 with MCl 4 ·2THF in refluxing THF. Rac / meso ratio of about 2/3 was obtained for the titanocene complex 1 . But for the zirconocene 2 , only meso isomer was obtained. The crystal structures of meso - 1 and meso - 2 were determined. Their catalytic properties for ethylene polymerization have also been studied with MAO as a cocatalyst.

Thermal rearrangement of digermyl-bridged bis(1-indenyl) diiron complexes (Me2GeGeMe2)[(η5-1-indenyl)Fe(CO)]2(μ-CO)2

Abstract Reaction of IndMe2GeGeMe2Ind with Fe(CO)5 in refluxing xylene yields complex (Me2GeGeMe2)[(η5-1-indenyl)Fe(CO)]2(μ-CO)2(2). 2 undergoes a novel thermal rearrangement reaction between its Ge–Ge and Fe–Fe bonds, forming two isomeric rearrangement products with new cyclic structures, [Me2Ge(η5-1-indenyl)Fe(CO)2]2 (3). The crystal structures of the cis isomer 3c and the trans isomer 3t were determined by X-ray diffraction.

Synthesis and structures of cycloalkylidene-bridged biscyclopentadienyl-tetracarbonyldiiron complexes C(CH2) n [( η 5-C5H4)Fe(CO)]2( μ-CO)2(n = 4, 5 and 6)

A series of cycloalkylidene-bridged biscyclopentadienyldiiron complexes, C(CH2)n[(η5-C5H4)Fe(CO)]2(μ-CO)2 (n = 4, 5 and 6) have been synthesized by the reacting C(CH2) nCp2 (Cp = C5H5) with Fe(CO)5 in refluxing xylene. The molecular structures of C(CH2)5[(η5-C5H4)Fe(CO)]2(μ-CO)2(2) and trans-C(CH2)4[(η5-t-BuC5H3)Fe(CO)]2(μ-CO)2(4t) have been determined by X-ray diffraction. The Fe—Fe bond distance [2.466 Å], in (2) is the shortest reported to date for bridged biscyclopentadienyldiiron complexes.

Organopolysilane oligomers bearing transition metal moieties: synthesis and UV absorption properties of (η6-Me3SiSiMe2C6H5)M(CO)3 (M = Cr, Mo, W)

Abstract The reaction of Me3SiSiMe2C6H5 with M(CO)6 under thermal conditions afforded (η6-Me3SiSiMe2C6H5)M(CO)3 [M=Cr (1), Mo (2) and W (3)] with retention of the silicon–silicon bond. UV absorption properties of 1–3 were recorded and discussed with emphasis on the σ–π conjugation between the SiSi bond and the phenyl group.

Synthesis and structures of bridged diruthenium complexes (E)[η5-C5H4)Ru(CO)]2(μ-CO)2 (E = Me2Ge, Me2SiOSiMe2, Me2SiOSiMe2OSiMe2)

A series of bridged diruthenium complexes (E)[(η5-C5H4)Ru(CO)]2(μ-CO)2 (E = Me2Ge (2); Me2SiOSiMe2 (3); Me2SiOSiMe2OSiMe2 (4)) has been prepared by reacting Ru3(CO)12 with Cp2E in refluxing heptane. The molecular structures of (2) and (4) have been determined by X-ray diffraction.