Scandium-catalysed intermolecular hydroaminoalkylation of olefins with aliphatic tertiary amines.

A homoleptic scandium trialkyl complex in combination with a borate compound served as an excellent catalyst for the C-H addition of aliphatic tertiary amines to olefins. This highly regiospecific, 100% atom efficient C-H bond alkylation reaction was applicable to a wide variety of tertiary amines and olefins, including functionalised styrenes and unactivated α-olefins. This work represents the first example of rare-earth catalysed olefin hydroaminoalkylation and also the first example of catalytic C-H addition of aliphatic tertiary amines to olefins with any catalyst.

Bis(σ-B-H) complexes of copper(i): precursors to a heterogeneous amine-borane dehydrogenation catalyst.

A series of bis(σ-B-H) complexes of copper(i) have been prepared by displacement of arene solvent from a ß-diketiminate copper(i) complex by four-coordinate boranes, H3B-L (L = NMe3, lutidine). In the presence of the same copper arene complex, the secondary amine-borane H3B-NMe2H undergoes dehydrogenation. We provide evidence for formation of a heterogengous catalyst from decomposition of the solution species.

Yttrium-catalysed dehydrocoupling of alanes with amines.

We report [Y{N(SiMe3)2}3] as a precatalyst for the dehydrocoupling of sterically demanding amines with ß-diketiminate stabilised aluminium dihydrides. While simple fluorinated anilines readily undergo Al-H/N-H dehydrocoupling under thermal conditions, catalytic methods are required to achieve reasonable rates of reaction for ortho-substituted anilines or hindered aliphatic amines.

Mechanistic and cytotoxicity studies of group IV ß-diketonate complexes.

Group IV metal complexes have previously shown promise as novel anticancer agents. Here, we discuss the mechanistic and cytotoxic nature of a series of group IV ß-diketonate coordination complexes. Clear evidence that the ligands are exchangeable on the metal centre and that the ß-diketonate ligands can act as potential drug delivery vehicles of the group IV metal ions was obtained. When evaluated for the cytotoxicity against human colon adenocarcinoma (HT-29) and human breast adenocarcinoma (MCF-7) cell lines, a general trend of decreasing potency down the group IV metals was observed. The most promising results obtained were for the hafnium complexes, with the tris diphenyl ß-diketonate hafnium complex exhibiting IC50 values of 4.9 ± 0.9 µM and 3.2 ± 0.3 µM against HT-29 and MCF-7, respectively, which are comparable with the activity of cisplatin against the same cell lines. This tri ß-diketonate hafnium complex is the first to show potent in vitro cytotoxic activity. The results reported show that ligand design has a significant effect on the cytotoxic potential of the complexes, and that these group IV complexes warrant further evaluation as novel metal-containing anticancer agents.

Preparation and properties of a series of structurally diverse aluminium hydrides supported by ß-diketiminate and bis(amide) ligands.

The synthesis of a diverse series of hydride complexes of aluminium coordinated by N,N'-chelating ligands is reported. Reaction of [{2,6-(i)Pr2C6H3}NC(Me)CHC(Me)N(H)CH2CH2NMe2] with either LiAlH4 or Me3N·AlH3 allows isolation of the corresponding five-coordinate aluminium dihydride [κ(3)-{(2,6-(i)Pr2C6H3)NC(Me)CHC(Me)NCH2CH2NMe2}AlH2] (2). The latter complex demonstrates trigonal bipyramidal geometry in the solid-state. Correlation of solid and n-hexane solution infrared spectroscopy data reveals that this coordination is retained in solution. To evaluate the observed coordination geometry, the dissociation of the pendant ligand of 2 was investigated by DFT methods conducted with the M06-2X functional and a hybrid 6,31G+(d,p)/Lanl2DZ basis-set. Reaction of Me3N·AlH3 with both N,N'-bis(di-iso-propylphenyl)ethylenediamine and N,N'-bis(mesityl)ethylenediamine gave [{κ(2)-(ArNCH2)2}AlH(NMe3)] (Ar = Mes, 3a; Ar = 2,6-di-iso-propylphenyl, 3b) in moderate yields. Removal of NMe3 from 3b by heating under dynamic vacuum allowed the isolation of cis-[AlH{µ-N(Ar)CH2CH2N(Ar)}] (Ar = 2,6-di-iso-propylphenyl, cis-4b2) as a single diastereomer following crystallization. DFT studies in combination with infrared and NMR spectroscopy and single crystal X-ray diffraction data provide a weight of evidence consistent with the robust dimeric structure of cis-4b2 remaining intact in solution. An unusual reaction in which the aluminium dihydride, [κ(2)-{(2,6-Me2C6H3NHCH2)2CH}AlH2], promotes the P-C bond cleavage of Ph3PCH2 is also reported.