1-Aminoboratabenzene Complexes of Scandium Group Metals

Abstract

The syntheses of the new lithium boratabenzenes Li(3,5-Me 2 C 5 H 3 BNiPr 2 ), Li(3), and Li 2 [(3,5-Me 2 C 5 H 3 BNMe) 2 -(CH 2 ) 2 ], Li 2 (5), via the dicarbanion route are described. Lithium 1-aminoboratabenzenes react with metal trihalides in toluene (110°C, 3 d) to give the stepped ladder dimers [(3,5-31 cleavage product Y(acac)(3,5-Me 2 C 5 H 3 BNMe 2 ) 2 (14) is obtained from 12 and Na(acac) in toluene at ambient temperature. The complexes 12, 14, 16, 18·PhMe, 19·PhMe, 20 (as two polymorphs α-20 and β-20), 21, and 24 (as the rac-stereomer) are characterized by single-crystal structure determinations. In all structures except those of the mononuclear complexes 18 and 19, the ring-ring rotational positions are close to 180°, cf. e.g. 14, or to 60°, cf. e.g. 20; these conformations minimize transannular ligand-ligand repulsions. The internal coordination of a B-NMe 2 sidearm, which is unprecedented, is found in the structures of the stepped ladder dimers 12 and 13, and in the mononuclear complexes 15 and 16. According to solution NMR spectroscopy, all complexes are dynamic with respect to ring-ring rotation and, in the cases with internal coordination, they are dynamic with respect to the interchange between free and coordinated B-NMe 2 sidearms.ZieglerϪNatta olefin polymerization processes that are derived from CpZr and CpTi complexes. Some of the catalyst systems so obtained are rather similar to those derived from ZrCl 2 Cp 2 , [8m] and others display considerably modified properties, [5,8fϪ8l] thus widening the range of the potential applications of these complexes. A similar parallel between cyclopentadienyl and boratabenzene complexes may be expected for catalysts of the scandium group metals, [9] providing a further incentive to explore the chemistry of boratabenzene complexes of the Sc group metals.The goal of the present paper is to report on the syntheses and structures of Sc, Y, Sm, and Lu bis(boratabenzene) complexes that bear a B-amino group. It will be seen that the presence of a B-amino group provides a remarkably rich structural chemistry to this class of complexes.

Recent developments in the non-cyclopentadienyl organometallic and related chemistry of scandium

“…Another class of arene ligand that has recently received much attention is the boratabenzene ligands. The group of Herberich has shown 29,30 that the lithium salts of a number of boratabenzene derivatives react with ScCl 3 in refluxing toluene to afford a range of scandium chloride complexes, the nature of which is heavily influenced by the steric requirements of the boratabenzene B-substituent (see 9-11 in Chart 1). The methylsubstituted ligand 9 and the dimethylamide-substituted ligand 10 react to form dinuclear products [Sc 2 (h 6 -C 5 H 5 BR) 4 (m-Cl) 2 ] with bridging chloride ligands.…”

Organometallic building blocks with amino-substituted cyclopentadienyl and boratabenzene ligands for the synthesis of heterometallic complexes and clusters

“…Concentration of the filtrate gave a viscous residue which was triturated with pentane to form a yellow suspension. The yellow solid was collected on a frit, washed with pentane (2 × 5 mL) and recrystallized from toluene to afford 10 (0.89 g, 87%); mp 171-172 • C. Synthesis of [Hg{Mo(g 5 -3,5-Me 2 C 5 H 3 BNi-Pr 2 )(CO) 3 }Cl] (Hg-Mo) (11). Solid HgCl 2 (0.50 g, 1.84 mmol) was added to a suspension of Li•6•2DME (0.95 g, 1.66 mmol) in toluene (40 mL).…”

“…MHz;11 B, 160.4 MHz; 31 P, 202.4 MHz), a Varian VXR 300 or Bruker Avance 300 ( 1 H, 300 MHz; 13 C, 75.47 MHz; 31 P, 121.49 MHz) or a Varian Mercury 200 ( 1 H, 200 MHz) spectrometer. Chemical shifts (in ppm) were measured at ambient temperature and are referenced to internal TMS for 1 H and 13 C and to external BF 3 •OEt 2 for 11 B, and external H 3 PO 4 (84%) for…”