Ian Cragg-Hine

Dilithiated salen complexes: chiral [(salen)Li2·hmpa]2 and deliberate partial hydrolysis to give [(salen)Li2]3·Li2O·2tmen·H2O [H2salen =N,N′-ethylenebis(salicylideneimine); hmpa = hexamethylphosphoramide; tmen = tetramethylethylenediamine]

Chiral [(salen)Li2·hmpa]2 has a Li4O4 cubane-type core in the solid but low-temperature NMR spectroscopy reveals a racemisation equilibrium in solution; deliberate addition of H2O to [(salen)Li2]n in the presence of tmen produces a species having two Li4O4 cubes sharing a common oxygen and containing tmen ligands acting in a hitherto unobserved monofunctional mode.

The first structurally characterised early main-group metal diazallyl complex; synthesis and crystal structure of LiCPh(NPh)2·NMe[(CH2)2NMe2]2

n-Butyllithium reacts with a solution of PhNC(Ph)NHPh (N,N′-diphenylbenzamidine) and NMe[(CH2)2NMe2]2(pmdeta) to give the complex LiCPh(NPh)2·pmdeta, which is monomeric in the solid state with a five-co-ordinate litium cation bound to a tridentate pmdeta ligand and a bidentate amidinide anion (diazaallyl system, chelating), in which the two N–C bond lengths of 1.336(4) and 1.335(4)A suggest almost uniform delocalisation along the NCN unit.

The first structurally characterised sodium primary amide complex; synthesis and crystal structure of 2-PhOC6H4NHNa·NMe[(CH2)2NMe2]2

The compound 2-PhOC6H4NHNa·NMe[(CH2)2NMe2]2has been synthesised by a 1 : 1 reaction of sodium hydride with 2-phenoxyaniline in toluene in the presence of N,N,N′,N″,N″-pentamethyldiethylene-triamine (pmdien); X-ray crystallography revealed a solid-state structure comprising a near-symmetrical Na2N2 ring dimer with each sodium cation chelated by a tridentate pmdien ligand in an unprecedented near-planar conformation.

Self-assembly in the metallation of bis(aminoaryl) ethers

Abstract The dilithiation of 2,2′-bis(2-methoxyethylamino)diphenyl ether ( 4 ) and 2,2′-bis( N , N -dimethylethylenediamino)diphenyl ether ( 7 ) in the absence of any Lewis base donor resulted in the formation of dimeric complexes 8 and 9 , respectively, containing the unprecedented Li 4 O 2 N 4 “adamantanoid” metal core as a consequence of the self-recognition and self-assembly involving the two metallated subunits. In contrast, on monometallation using particular conditions, e.g. sodium hydride in the presence of Lewis base donor, the same ligands undergo a Smiles-type rearrangement, providing the first example of such a reaction involving an amine and a deactivated aromatic system. The conditions needed to promote this rearrangement have been investigated.

Monometallation of a di(aminoaryl) ether induces a Smiles rearrangement leading to a sodium aryloxide complex: the synthesis and crystal structure of [(MeOCH2CH2)(C6H4NHCH2CH2OMe)NC6H4O·Na]2

The title compound was synthesised by 1 : 1 reaction of sodium hydride with a di(aminoaryl) ether ligand in toluene–hexamethylphosphoramide (HMPA) solution; X-ray crystallography revealed that an in situ Smiles rearrangement of the ligand had taken place to give a dimeric aryloxide sodium complex, which is in stark contrast to previous results obtained by 2 : 1 reaction of BunLi with the ligand in the absence of HMPA.

The isolation and structure of a highly stable, metallation-resistant and multiply hydrogen-bonded sulfonylamide–phosphine oxide adduct, PhSO2CH2C(O)NH2·OP(NMe2)3, PSA·HMPA (PSA = phenylsulfonylacetamide, HMPA = hexamethylphosphoramide)

Attempted metallations of the expectedly acidic sulfonylamide (PSA) in the presence of the phosphine oxide HMPA all fail, giving instead the very stable 1:1 adduct PSA·HMPA; its solid-state structure consists of layers of PSA molecules linked by intercalated HMPA molecules, such aggregation resulting in particular from a large number of significant C–H ⋯ O hydrogen-bonding interactions per PSA·HMPA unit.

The mechanisms of dilithiation reactions in organic syntheses: a case study based on the syntheses of ketene dithioacetals

An investigation of the lithiation and Cs2-insertion reactions of R1R2CH2 precursors (reactions used in the syntheses of ketene dithioacetals) leads to the crystal structure determination of the monolithiated complexes R1R2CHCS2Li·TMEDA, 3(R1= Ph, R2= pyridyl) and 4 (R1= H, R2= 2-methylpyrazine); attempted second lithiation of 3 fails to give the R1R2CCS2Li2 species anticipated in the mechanism of reactions of this type, but synthetic and 1H NMR spectroscopic evidence indicates that 4 can be lithiated further.