268206-22-0Relevant academic research and scientific papers
Synthetic, reactivity, and structural studies on borylcyclopentadienyl complexes of titanium: New CpB titanocene complexes with C-B-Cl, C-B-O, and C-B-N bridges (CpB = η5-C5H4B(C6F5) 2)
Lancaster, Simon J.,Al-Benna, Sarah,Thornton-Pett, Mark,Bochmann, Manfred
, p. 1599 - 1608 (2000)
The (borylcyclopentadienyl)titanium complex (CpB)TiCl3 (1; CpB = η5-C5H4B(C6F5) 2) reacts with LiC5H5 (LiCp), LiC5H4SiMe3 (LiCp′), and LiC9H7 (LiInd) to give the titanocene complexes (CpB)CpTiCl2 (2), (CpB)Cp′TiCl2 (3), and (CpB)(Ind)TiCl2 (4), respectively. In contrast to 1, which possesses piano stool geometry with an uncoordinated, trigonal-planar boryl moiety, the -B(C6F5)2 substituents in 2-4 act as intramolecular Lewis acids by coordinating to chloride ligands, with formation of B-Cl-Ti bridges that have relatively short B-Cl and elongated Ti-Cl bonds. The compounds are fluxional, with the -B(C6F5)2 moiety switching rapidly from one chloride ligand to the other (2: ΔG? = 37 kJ mol-1 (200 K)). Recrystallization of 2 in the presence of traces of moisture afforded (CpB)CpTi(μ-OH)Cl (5), with a rigid B-O-Ti chelate arrangement. Treatment of 1 with 1 or 2 equiv of LiHNCMe3 gives the binuclear titanium imido complexes [(CpB)TiCl(μ-NCMe3)]2 (7) and [(CpB)TiCl(μ-NCMe3)·H2NCMe 3]2 (8), respectively. These complexes are based on Ti2N2 rings but show no boron-imide interactions. In contrast, the reaction of 2 with LiNHCMe3 affords (CpB)CpTi(μ-NHCMe3)Cl (9), which exhibits a constrained-geometry type Cp-B-N arrangement. The crystal structures of 4, 5, 8, and 9 have been determined.
