Heterobimetallic Bisphosphonate Titanium Complexes: Carbene‐Like Carbanions?

Abstract

A new class of carbene-like titanium complexes is easily accessible by means of a dilithiation-transmetallation sequence of a bisphosphonate. The X-ray structure of the dimeric, organometallic compound 3 reveals a nano-sized, multi-layer aggregate with titanium-metallated, trigonal planar carbon centers being devoid of Li contacts. DFT calculations show that the metallated carbon is a carbanion with only a slight carbene portion (10 %); the carbene character can be easily

Carbene Complexes Based on Dilithium Methandiides

“…This reactivity is in contrast to that of the BIPM TMS and BTPM ligands, which both formed monocarbene complexes such as 2 upon treatment with [ZrCl 4 (THF) 2 ] 9,42. However, phosphonate ligand 21 has so far only been used in the synthesis of carbene complexes with zirconium 43…”

Phosphinoalkylidene and -alkylidyne Complexes of Titanium: Intermolecular C–H Bond Activation and Dehydrogenation Reactions

“…High-oxidation-state metal complexes having a phosphinoalkylidene (L n MCR′PR 2 ) are a relatively unexplored ligand class in which the phosphine group is attached to the alkylidene carbon, whereas the capped P­(V) analogues, L n MCR′P­(X)­R 2 (X = O, S, NR), have been more widely studied . Examples of the phosphinoalkylidene ligand with high-valent early transition metals are somewhat common for Ta, Mo, and W, and this scaffold can sometimes chelate via the pendant phosphino group .…”

Phosphorus stabilized carbene complexes: bisphosphonate dianion synthesis, reactivity and DFT studies of O∼C∼O zirconium(iv) complexes

“…In the recently reported mixed Ti 2 -Li 6 cluster, obtained from the reaction of a neutral bisphosphonate with an excess of n-BuLi followed by the addition of the Ti(IV) precursor [Ti(O i Pr) 3 Cl], an analogous trigonal planar geometry is observed at the carbon center. 26 As mentioned above, the presence of a singlet in the 31 P NMR spectrum is not consistent with the solid state structure, which contains two different phosphorus centers. A variable temperature NMR experiment was therefore carried out but lowering the temperature down to -80 • C in dichloromethane did not lead to any appreciable modification of the spectrum.…”

“…A large body of data is now available for Zr complexes of ligands 1 23, 24 and 2, 25 and the most recent work by Mueller et al showed that a mixed Ti-Li cluster species could be obtained from mixtures of BuLi, neutral bis-phosphonate and a Ti(IV) precursor. 26 We wish to present here the unexpected results of the chemistry of the O~C~O dianionic system 3 towards Zr(IV), which point to strong differences between ligands 1 and 2. In particular, the first example of a triscarbene dianionic Zr fragment is reported.…”