Synthesis and Characterisation of Molecular Polarised-Covalent Thorium-Rhenium and -Ruthenium Bonds

Separate reactions of [Th{N(CH2CH2NSiMe2But)2(CH2CH2NSi(Me)(But)(μ-CH2)]2 (1) with [Re(η5-C5H5)2(H)] (2) or [Ru(η5-C5H5)(H)(CO)2] (3) produced, by alkane elimination, [Th(TrenDMBS)Re(η5-C5H5)2] (ThRe, TrenDMBS = {N(CH2CH2NSiMe2But)3}3-), and [Th(TrenDMBS)Ru(η5-C5H5)(CO)2] (ThRu), which were isolated in crystalline yields of 71% and 62%, respectively. Complex ThRe is the first example of a molecular Th-Re bond to be structurally characterised, and ThRu is only the second example of a structurally authenticated Th-Ru bond. By comparison to isostructural U-analogues, quantum chemical calculations, which are validated by IR and Raman spectroscopic data, suggest that the Th-Re and Th-Ru bonds reported here are more ionic than the corresponding U-Re and U-Ru bonds.

Synthesis and Characterisation of Two Lithium Tetramethylberyllate Salts and a Series of β-Diketiminato Beryllium Alkyl Complexes

A safer route than that previously published for the synthesis of [BeI2(OEt2)2] has been developed. Reactions of beryllium dihalide complexes [BeX2(OEt2)2] (X=Br or I) with either LiMe or LiBun lead to mixtures of products, which have been shown to act as sources of ‘BeR2’ (R=Me or Bun) in previous synthetic studies. Here, a titration method has been developed to determine the quantity of metal alkyl residues in these ‘BeR2’ mixtures that are available for subsequent alkane elimination reactions. Treating ‘BeMe2’ mixtures with N,N,N′,N′-tetramethylethylenediamine (tmeda) gave two lithium tetramethylberyllate compounds, [{(tmeda)Li}2(μ-BeMe4)] and [{[(tmeda)Li](BeMe4)(μ-Li)}∞], which were crystallographically characterised. Treatment of insitu-generated ‘BeR2’ solutions with several β-diketimines (HC{C(Me)=NR}{=C(Me)N(H)R}, NacnacH, R=aryl or alkyl) yielded a series of β-diketiminato beryllium alkyl complexes, [(Nacnac)BeR], including the first chiral example of such a compound. Crystallographic studies of these reveal them to be monomeric, with planar three-coordinate beryllium centres.

1,8-Bis(silylamido)naphthalene complexes of magnesium and zinc synthesised through alkane elimination reactions

Alkane elimination reactions afford magnesium and zinc 1,8-bis(triorganosilyl)diamidonaphthalene complexes, where the tuning of the reaction conditions and steric bulk allows manipulation of the coordination environment.

Unexpected alkane elimination from cationic group 13 dialkyls in a reaction with a macrocyclic polyamine

A macrocyclic polyamine 1,4,7-trimethyl-1,4,7,10-tetraazacyclododecane, (Me3TACD)H formed thermally stable adducts with MR3 (M = Al, In) but released RH from reactions with [MR2]+.

Ligand influence on intramolecular cyclometalation in bis(phosphinimine) rare earth alkyl complexes

The synthesis and reactivity of two new bis(phosphinimine)carbazole ligands (PippN=PMe2)2DMC (HLA, 3) and (PippN=P(C4H8))2DMC (HLB, 10), where Pipp = para-isopropylphenyl and DMC = 3,6-dimethylcarbazole, are reported. Dialkyl lutetium complexes of 3 and 10 were prepared in the presence of DMAP and THF by reaction of the proteo ligands with the new trialkyl reagent, Lu(CH2SiMe3)3(DMAP)2 (4) as well as Lu(CH2SiMe3)3(THF)2. For both ligands 3 and 10, the resulting lutetium complexes were prone to intramolecular cyclometalative alkane elimination reactions whereby the location of cyclometalation was influenced by the identity of the ancillary ligand coordinated to the metal. For ligand 3, cyclometalation of two PMe2 groups generated the complex (LA-κ3N,κ2C)Lu(DMAP)2 (5), whereas ligand 10 resulted in the single ortho-metalation of a para-isopropylphenyl ring to afford (LB-κ3N,κC)Lu(CH2SiMe3) (12). When complexed with scandium, ligand 10 behaved differently; double cyclometalation of two phospholane moieties resulted in the species (LB-κ3N,κ2C)Sc (15). The nature of the cyclometalation reactivity of ligands 3 and 10 is supported by X-ray crystallography and kinetic analysis, respectively.

Synthesis of Sterically Demanding Bis(phosphinimine) Dibenzofuran Ligands and Subsequent Zinc Metalation

In light of previous success surrounding the use of bis(phosphinimine)dibenzofuran ligands for zinc-mediated lactide polymerization, a series of sterically demanding P=N pincer compounds have been prepared with important steric and electronic modifications at both P- and N-sites (L, 3a–d). These systems are highly crystalline and have been extensively characterized using multinuclear NMR spectroscopy, elemental analysis, and X-ray diffraction. The ligands can be transformed into their protonated analogues [HL][BArF4] (4a–d, [BArF4] = [B(m-(CF3)2-C6H3)4]) by reaction with Brookhart’s acid, and subsequently coordinated to zinc via an alkane elimination reaction with [ZnEt2] at ambient temperature to afford the corresponding [LZnEt][BArF4] cationic complexes 5a–d. In addition, an unusual chloridozinc species [LZnCl][BArF4] (5c′) has been isolated and structurally characterized, providing comparisons to previously established ligand sets with similar geometries.

Protonolysis and thermolysis reactions of functionalised NHC–carbene boranes and borates

β-ketoimidazol(in)ium salts show contrasting reactivity with MHBEt3 due to subtle electronic and steric differences. Thermolysis of the chiral β-borate imidazolium salts formed from these reactions results in alkane elimination in the first example of organic borates functioning as Brønsted bases.