Keliang Pang

Palladium complexes with Pd→B dative bonds: Analysis of the bonding in the palladaboratrane compound [κ4-B(mimBut)3]Pd(PMe3)

The dinuclear complex {[mu-kappa(1),kappa(3)-B(mim(Bu(t)))(3)]Pd}(2), which features a Pd-->B dative bond, may be obtained by the reaction of [Tm(Bu(t))]K with Pd(OAc)(2); treatment of {[mu-kappa(1),kappa(3)-B(mim(Bu(t)))(3)]Pd}(2) with PMe(3) affords the mononuclear boratrane derivative [kappa(4)-B(mim(Bu(t)))(3)]Pd(PMe(3)), for which a molecular orbital analysis indicates that the palladium center possesses a d(8) configuration.

New Modes for Coordination of Aromatic Heterocyclic Nitrogen Compounds to Molybdenum: Catalytic Hydrogenation of Quinoline, Isoquinoline, and Quinoxaline by Mo(PMe3)4H4

The heterocyclic nitrogen compounds isoquinoline (iQH), quinoxaline (QoxH) and quinazoline (QazH), abbreviated generally as NHetH, react with Mo(PMe3)6 to give (η2-NHet)Mo(PMe3)4H as a result of cleavage of the C−H bond adjacent to the nitrogen atom. The C−H bond cleavage is reversible. For example, in the case of isoquinoline and quinoxaline, treatment of (η2-NHet)Mo(PMe3)4H with PMe3 regenerates Mo(PMe3)6 and NHetH. Furthermore, at elevated temperatures (η2-NHet)Mo(PMe3)4H converts sequentially to isomers of (η6-NHetH)Mo(PMe3)3 in which the N-heteroaromatic ligand coordinates via either the heterocyclic or carbocyclic rings. Isomers of (η6-NHetH)Mo(PMe3)3 in which the heterocyclic ring coordinated to molybdenum may be hydrogenated. Thus, (η6-C5N-iQH)Mo(PMe3)3 and (η6-C4N2-QoxH)Mo(PMe3)3 react with H2 at 90 °C to give Mo(PMe3)4H4 and release 1,2,3,4-tetrahydroisoquinoline and 1,2,3,4-tetrahydroquinoxaline, respectively. Furthermore, Mo(PMe3)4H4 serves as a catalyst precursor for the hydrogenation of quin...

Synthesis and Structural Characterization of Tris(2-seleno-1-mesitylimidazolyl)hydroborato Complexes: A New Type of Strongly Electron Donating Tripodal Selenium Ligand

A new tripodal ligand that features three selenium donors, namely the tris(2-seleno-1-mesitylimidazolyl)hydroborato ligand, [Tse(Mes)], has been constructed via the reaction of KBH(4) with 1-mesitylimidazole-2-selone; comparison of the IR spectroscopic data of [Tse(Mes)]Re(CO)(3) with those of a variety of related LRe(CO)(3) complexes demonstrates that the [Tse(Mes)] ligand is more strongly electron donating than Cp, Cp*, [Tp], [Tp(Me(2))] and [Tm(Mes)] ligands.

Silicon–Carbon bond cleavage reactions of Ansa tungstenocene compounds: The [Me2Si] bridge as a site for metallocene functionalization

[Me2Si(CpMe2)2]W(H)Cl is obtained via reaction of WCl6 with a mixture of [Me2Si(CpMe2)2]Li2 and NaBH4, from which the dichloride [Me2Si(CpMe2)2]WCl2 is obtained via treatment with CHCl3. [Me2Si(CpMe2)2]WCl2 provides a means to access other ansa tungstenocene compounds, such as [Me2Si(CpMe2)2]WH2, [Me2Si(CpMe2)2]WMe2, and [Me2Si(CpMe2)2]WCO. Of most interest, the reactions of [Me2Si(CpMe2)2]W(H)Cl with organolithium reagents do not yield simple ansa tungstenocene derivatives. Specifically, the reactions of [Me2Si(CpMe2)2]W(H)Cl with MeLi, BunLi, or PhLi result in the formation of mixed-ring tungstenocene compounds resulting from C–Si cleavage and functionalization of the ansa bridge, namely (CpMe2)(η5,κ1–C5H2Me2SiMe2CH2)WH, (CpMe2)[η5,κ1–C5H2Me2Si(Me)(Bun)CH2]WH, and (CpMe2)[η5,κ1–C5H2Me2SiMe2(C6H4)]WH, respectively. In contrast to the C–Si cleavage achieved by MeLi, BunLi, and PhLi, the ansa bridge of [Me2Si(CpMe2)2]W(H)Cl is inert to ButLi and the product obtained is the fulvene (“tuck-in”) complex [Me2Si(CpMe2)(η6–C5MeH2CH2)]WH derived from dehydrohalogenation.