Difluorenyl[2]borametallocenophanes of Group 4 Metals: Synthesis and Structure

Abstract

We report the synthesis of difluorenyl[2]borametallocenophanes of Zr and Hf. The ligand precursor has been synthesized starting from 1,2‐dibromo‐1,2‐bis(dimethylamino)diborane(4) upon reaction with Li[C13H9]. All compounds have been fully characterized by multinuclear NMR spectroscopy and, in addition, selected examples by X‐ray analysis. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Winheim, Germany, 2009)

Diboron(4) Compounds: From Structural Curiosity to Synthetic Workhorse

“…Braunschweig and co-workers subsequently developed a synthesis for the bis-cyclopentadienyl-diboron ligand, allowing for the preparation of other transition-metal complexes . Related sandwich complexes containing B–B bonds as bridging atoms were prepared either through anionic diboryl species − or via deprotonation of the transition-metal precursor and subsequent addition of dichlorodiborons. , For example, the reaction of 2 equiv of lithioferrocene with B 2 Cl 2 (NMe 2 ) 2 generated the diboron-bridged bis-ferrocene complex Fc­(NMe 2 )­BB­(NMe 2 )­Fc. ,, …”

Catalytic Activity of [2]Borametallocenophanes

“…Polymerization catalysts were prepared according to literature procedures: [(Me 2 N) 2 B 2 (η 5 ‐C 5 H 4 ) 2 M Cl 2 ] [ M = Ti ( 1 ), Zr ( 2 ), Hf ( 3 )],21 [(Me 2 N) 2 B 2 (η 5 ‐C 5 H 4 )(η 5 ‐C 13 H 8 ) M Cl 2 ] [ M = Zr ( 4 ), Hf ( 5 )],22 [(Me 2 N) 2 B 2 (η 5 ‐C 5 H 4 )(η 5 ‐C 29 H 36 ) M Cl 2 ] [ M = Zr ( 6 ), Hf ( 7 )],24 [(Me 2 N) 2 B 2 (η 5 ‐C 13 H 8 ) 2 M Cl 2 ] [ M = Zr ( 8 ), Hf ( 9 )],23 [(Me 2 N) 2 B 2 (η 5 ‐C 29 H 36 ) 2 ZrCl 2 ] ( 10 ) 24. MAO, ethylene, and 1‐hexene were obtained commercially and used without further purification.…”

Boron, aluminium, gallium, indium and thallium

“…Photo-degradation of the metallocenes results in the formation of the 1,3-diboretane system [(C 13 H 8 ) 2 {m-BNMe 2 } 2 ]. 103 In related studies reaction of the {B 2 (NMe 2 ) 2 } linked ferrocene systems [(Me 2 N) 2 B 2 (Z 5 -C 3 H 4 ) 2 Fe] with the diboranes B 2 (Pin) 2 or B 2 (Cat) 2 have been shown to result in exchange between the -BNMe 2 -BNMe 2bridge and diborane, with the concomitant formation of 1,1 0 -borylated ferrocenes. 104 The synthesis and X-ray crystal structures of the diborane isomers 1,1-B 2 {1,2-(NH) 2 C 6 H 4 } 2 and 1,2-B 2 {1,2-(NH) 2 C 6 H 4 } 2 have been described, together with the results of quantum chemical calculations which shed light on their relative stabilities and degree of aromaticity.…”