Chlorosilyl-Substituted Monocyclopentadienyl Niobium Chloro, Imido Chloro, and Benzyl Complexes. X-ray Molecular Structure of [{(NbCl₂)₂(μ-O)(μ-Cl)₂}{(η⁵-C₅H₄)₂(Me₂SiOSiMe₂)}]

Abstract

We report the synthesis of 1-(chloromethylphenylsilyl)cyclopentadiene. The reaction of a toluene/CH 2 Cl 2 suspension of NbCl 5 with 1-(SiClMeX)-1-(SiMe 3 )C 5 H 4 (X ) Me, Ph) leads to the monocyclopentadienyl derivatives [M{η 5 -C 5 H 4 (SiClMeX)}Cl 4 ] (X ) Me, Ph) in 90 and 78% yields, respectively. Reaction of 1 equiv of water with [M{η 5 -C 5 H 4 (SiClMe 2 )}Cl 4 ] in toluene takes place with elimination of HCl, resulting in formation of the dinuclear niobium oxo derivative [{(NbCl 2 ) 2 (µ-O)(µ-Cl) 2 }{(η 5 -C 5 H 4 ) 2 (Me 2 SiOSiMe 2 )}]. Reaction of the complexes [M{η 5 -C 5 H 4 (SiClMeX)}Cl 4 ] with LiNH t Bu and NEt 3 in toluene leads to the half-sandwich imido complexes [Nb{η 5 -C 5 H 4 (SiClMeX)}Cl 2 (N t Bu)] (X ) Me, Ph), which react at room temperature with 1 equiv of Mg(CH 2 Ph) 2 (THF) 2 to give the imido dibenzyl complexes [Nb-{η 5 -C 5 H 4 (SiClMeX)}(CH 2 Ph) 2 (N t Bu)] (X ) Me, Ph). The reaction of the chloro imido complexes [Nb{η 5 -C 5 H 4 (SiClMeX)}Cl 2 (N t Bu)] with excess Mg(CH 2 Ph) 2 (THF) 2 on heating for 2-3 days to 80-90 and 50-60 °C, respectively, takes place, affording the totally alkylated complexes [Nb{η 5 -C 5 H 4 [Si(CH 2 Ph)MeX]}(CH 2 Ph) 2 (N t Bu)] (X ) Me, Ph). The chloro benzyl derivative [Nb{η 5 -C 5 H 4 (SiClMe 2 )}(CH 2 Ph)Cl(N t Bu)], which could not be prepared by addition of the stoichiometric amount of the alkylating agent, was isolated in quantitative yield by heating a mixture of the dichloro and dibenzyl complexes in toluene at 120 °C for 4 h. The 18-electron imido η 2 -iminoacyl derivatives [Nb{(η 5 -C 5 H 4 (SiMeXY)}R(N t Bu){η 2 -C(CH 2 Ph)dN-(2,6-Me 2 C 6 H 3 )}] (R ) CH 2 Ph, X ) Cl, Y ) Me, Ph; R ) CH 2 Ph, X ) CH 2 Ph, Y ) Me, Ph; R ) Cl, X ) Cl, Y ) Me) are formed when the isocyanide CN(2,6-Me 2 C 6 H 3 ) is added to a hexane solution of the benzylimido complexes. The molecular structure of the oxo complex [{(NbCl 2 ) 2 -(µ-O)(µ-Cl) 2 }{(η 5 -C 5 H 4 ) 2 (Me 2 SiOSiMe 2 )}] has been determined by X-ray diffraction methods.

Aryl-imido niobium complexes with chloro-silyl and aryl-η-amidosilyl cyclopentadienyl ligands: X-ray structure of the constrained-geometry compound [Nb(η5-C5H4SiMe2-η1-NAr)(NAr)Cl] (Ar=2,6-Me2C6H3)

“…The selective hydrolysis of the Si-Cl bond with formation of a Si-O-Si bridge was the expected behaviour for this type of niobium compound [11,27]. In contrast, it was observed [6,[30][31][32][33] that the hydrolysis reactions of related monocyclopentadienyl group 4 metal complexes with Scheme 1. the chloro-silylcyclopentadienyl ligand afforded Si-O-M bridges.…”

“…It has been suggested that aryl-imido ligands provide more crystalline solids [26]. Consequently, we decided to extend our research on Si-Cl functionalized monocyclopentadienyl niobium complexes [11,27,28] to isolate new aryl-imido derivatives using the organomagnesium compounds [Mg(NAr)-(THF)] 6 (Ar = 2,6-Me 2 C 6 H 3 , 1a; Ph, 1b) as imido transfer reagents. This method was first published by Power and co-workers [29] to obtain titanium and zirconium imido compounds.…”

Synthesis and Reactivity of Oxametallacyclic Niobium Compounds by Using α,β‐Unsaturated Carbonyl Ligands

“…Complexes 1-3 present three nucleophilic centers that can react with protic acids: the Nb-Cl, [21][22][23][24] the Nb-C [24] , and the oxametallacyclic Nb-O [19] bonds. It would be reasonable to expect that the Nb-C bond should be the most reactive one toward protonolysis due to its lower bond energy, the higher energy of the resulting C-H bond, and the higher nucleophilic character of the niobium-bonded alkyl carbon atom.…”

Synthesis and reactivity of imido niobium complexes containing the functionalized (dichloromethylsilyl)cyclopentadienyl ligand

“…We focused our research interest on studies related to cyclopentadienyl group 4-6 metal complexes supporting modified cyclopentadienyl rings [2][3][4][5][6][7][8][18][19][20][21][22][23][24], and reported the synthesis of silyl-g-amido cyclopentadienyl group 4 and 5 metal complexes using the related (chlorodimethylsilyl)cyclopentadienyl metal derivatives [2][3][4][5][6][7][8]24]. Hydrolysis of these compounds also led to the isolation of dinuclear derivatives with Si-O-Si bridges for Nb [8,21,25], Mo and W [24] and Si-O-M bridges for Nb [25] and group 4 metals [2,26,27].…”

“…Hydrolysis of these compounds also led to the isolation of dinuclear derivatives with Si-O-Si bridges for Nb [8,21,25], Mo and W [24] and Si-O-M bridges for Nb [25] and group 4 metals [2,26,27].…”