Ferrocenyl(trihydro)borates: building blocks for the synthesis of heterooligonuclear metallocene complexes

Abstract

The reaction of [Cp(2)ZrCl(2)] with the lithium salt Li[FcBH(3)] in stoichiometric ratios of 1.5 : 1 or 0.4 : 1 furnishes the mixed-metallocene complexes [Cp(2)(Cl)Zr(H(3)BFc)] (1) and [Cp(2)Zr(H(3)BFc)(2)] (3), respectively (Cp = cyclopentadienyl; Fc = ferrocenyl). When the two reagents are combined in a ratio of 0.6 : 1, complex 1 is formed together with the zirconium hydride species [Cp(2)(H)Zr(H(3)BFc)] (2). Compound 2 can be obtained in pure form from [Cp(2)Zr(H)Cl] and Li[FcBH(3)]. Treatment of the half-sandwich complexes [(C(5)R(5))ZrCl(3)] with 3 equivalents of Li[FcBH(3)] leads to the heterotetranuclear aggregates [(C(5)R(5))Zr(H(3)BFc)(3)] (4: R = H; 5: R = CH(3)). Li(2)[fc(BH(3))(2)] and 3 equivalents of [Cp(2)ZrCl(2)] give the heterotrinuclear compound [fc(BH(3)Zr(Cl)Cp(2))(2)] (6) with bridging ferrocenylene core (fc = 1,1'-ferrocenylene). According to X-ray crystallography, the trihydroborate ions are coordinated in a [Zr(μ-H)(2)B(H)-] fashion in 1, 2, 3 and 6, whereas 4 and 5 are carrying tridentate trihydroborate ligands.

Synthesis and Reactivity of o-Phosphane Oxide Substituted Aryl(hydro)borates and Aryl(hydro)boranes

“…The result would be an anionic pincer ligand possessing an unusual dihydroborate moiety instead of a classical Lewis basic atom at the central donor site. The ability of hydroborates to coordinate (transition) metal ions has ample precedence in the literature , and also becomes evident from an inspection of the crystal structures of (Li[ 3 ]) 2 ·C 6 H 6 , Mg(Et 2 O)[ 5 ] 2 ·Et 2 O, and Mg[ 7 ] 2 ·2C 6 H 6 .…”

[μ-3,3′-Bis(trihydroboryl)[3]ferrocenophane]bis(chloridozirconocene)

“…Zr show a H•••Zr distance of 3.14 (7) Å and 3.13 (8) Å. Since the two cyclopentadienyl rings of the ferrocene unit are connected by an ansa bridge, the two Zr centres approach each other to a distance of 6.485 (1) Å compared to 7.128 (1) Å in the compound without an ansa bridge (Reichert et al, 2013a). The crystal packing is stabilized by C-H•••Cl interactions.…”

“…For ZrÁ Á ÁB distances, see: Edelstein (1981). For information about the coordination behaviour of mono-and ditopic ferrocenylhydroborates toward [Cp 2 ZrCl] À , see: Reichert et al (2013a). For synthetic details, see: Reichert (2013); Reichert et al (2013b).…”

Diborylated Magnesium Anthracene as Precursor for B2H5−‐Bridged 9,10‐Dihydroanthracene

“…2) The tetrahydroborate ion can establish BÀHÀMt wo-electron three-center bonds towardavariety of metal atoms and thereby act as monodentate, bidentate, or tridentate ligand. [28][29][30] Chelating coordination modes as well as coordination polymers have been observed with ditopic hydroborates such as 1,2-bis(trihydroborato)benzene. [31][32][33] Am ore balanced rigidity of the ligand framework, as provided by the DHA backbone in ligands[ H ] 2 À (Scheme 2), is expectedt of urther broaden the range of accessible metal complexes.…”

“…Diborylated DHAs such as compounds G (Scheme ) should nicely complement the existing selection of potential boron catalysts as they contain a less rigid, but still structurally well‐defined molecular backbone. 2) The tetrahydroborate ion can establish BHM two‐electron three‐center bonds toward a variety of metal atoms and thereby act as monodentate, bidentate, or tridentate ligand 28–30. Chelating coordination modes as well as coordination polymers have been observed with ditopic hydroborates such as 1,2‐bis(trihydroborato)benzene 31–33.…”