Paul Schooler

Group 12 and heavier Group 13 alkali metal 'ate complexes

Abstract Heterobimetallic complexes in which a Group 1 metal centre counteracts the negative charge placed on a Group 12 or higher Group 13 metal have been known for some years. Their usefulness in chemical transformations is discussed in the context of the regiospecificity with which they effect reaction and the manner in which it differs to that resulting from the use of homometallic alkali metal reagents. Their structural properties are reported both in solution and in the solid state. Theoretical studies are presented where appropriate.

Synthesis and Solid‐State Structure of (Li4Am3)+·{Li[(μ‐Me)2Al(Me)tBu]2}− {Am = [PhNC(Ph)NPh]−}: A Polymeric Species Incorporating a Lithium‐Nitrogen Cluster Cation

The sequential reaction of PhN(H)C(Ph)NPh (AmH) with AlMe3 and tBuLi leads to the isolation of both the cluster (Li4Am3)+·{Li[(μ-Me)2Al(Me)tBu]2}−(5) and the aluminium tris(amidinate) AlAm3(6). In the solid state, 5 has a polymeric structure based on tetranuclear Li4-cluster cations and lithium bis(aluminate) anions which associate by the formation of weak Li···MeAl bonds.

Ligand Effects in the Syntheses of Molecular Main Group Metal Species Containing Interstitial Hydride

In seeking to investigate whether structures of the type observed for {[Me3Al(TMP)]Li}∞ (TMP = 2,2,6,6-tetramethylpiperidide) can be oligomerised by the use of polyfunctional N-centred ligands, we report lithium aluminates incorporating RN−C(H)−NR residues. For PhN−C(Ph)−NPh = Am cluster cation-containg (Li4Am3)+·{Li[(μ-Me)2Al(Me)But]2}− is afforded. However, the empolyment of PhN(H)(2-pyr) (pyr = pyridyl) instead affords both {Li8(H)[N(2-pyr)Ph]6}+·[Li(Me2AlBut 2)2]− and Li7(H)[N(2-pyr)Ph]6: the first molecular Main Group clusters to incorporate interstial hydride. Results indicate that β-elimination from ButLi represents the source of H− in these reactions.

Synthesis and characterisation of pendant-arm alcohol derivatives of [9]aneN2S and complexation with CuII ([9]aneN2S = 1-thia-4,7-diazacyclononane)†

An improved detosylation of 4,7-bis(tolyl-p-sulfonyl)-1-thia-4,7-diazacyclononane to give the free amine [9]aneN2S has been accomplished using Li/NH3 or HBr/acetic acid. Reaction of [9]aneN2S with ethylene oxide, 1,1-dimethylethylene oxide and methylenecyclohexane oxide in alcoholic solution affords the potentially pentadentate ligands 4,7-bis(hydroxyethyl)-1-thia-4,7-diazacyclononane (H2L1), 4,7-bis(2-hydroxy-2-methylpropyl)-1-thia-4,7-diazacyclononane (H2L2) and 4,7-bis(2-cyclohexyl-2-hydroxymethyl)-1-thia-4,7-diazacyclononane (H2L3) respectively. The copper(II) complexes of these ligands have been prepared and reveal that increasing the steric bulk on the pendant arm has a marked effect upon the resultant co-ordination chemistry. Thus, the complex of H2L1 shows a dimeric structure [Cu2(HL1)2][PF6]2 1 in which one of the hydroxy groups has been deprotonated. With H2L2 two complexes can be isolated: the dimer [Cu2(HL2)2][PF6]2 2 and the monomer [Cu(HL2)][PF6] 3. In contrast, with H2L3 only the monomer [Cu(HL3)][PF6] 4 could be isolated. Single crystal structures of 1 and 3 have been determined. Magnetochemistry of 1 indicates that the two copper(II) centres are essentially non-coupled.

Variations in the solid-state, solution and theoretical structures of a laterally deprotonated aromatic tertiary amideElectronic supplementary information (ESI) available: synthetic and analytical data for (4)3thf and computed structures I, (IIa?d)?(Va?d). See http://www.rsc.org/suppdata/cc/b3/b302283h/

Reaction of 2-ethyl-N,N-diisopropyl-1-naphthamide 3 with ButLi in tetrahydrofuran (thf) affords a laterally metallated derivative which exists as a tris(thf) solvated monomer with no Li–C interaction and an sp2 hybridised carbanionic centre in the solid-state; NMR spectroscopy suggests that this structure is viable in solution but that Li–C bonded atropisomers are also possible and calculations corroborate these data.

The crystallographic observation of molecular lithium oxide: synthesis and solid-state structure of [Me2AlN(2-C5H4N)Ph]2(O)Li2·2THF

The reaction of Me2Al[N(2-C5H4N)Ph], 1, with 1 equiv. (Me3Si)2NLi affords the lithium aluminate Me2Al[N(SiMe3)2][N(2-C5H4N)Ph]Li, 2, which exhibits solvent dependent reactivity towards oxygen. In toluene 2 appears to resist oxygenation but in the presence of THF it reacts to afford the new complex [Me2AlN(2-C5H4N)Ph]2(O)Li2·2THF, 3. X-Ray diffraction data reveal that 3 has a butterfly-type Al2Li2 bimetallic core with two equivalents of reformed 1 stabilising discrete, molecular lithium oxide. The structures of 1–3 are probed theoretically.

Synthesis and characterisation of amino and bromo ring substituted derivatives of [Ru6C(CO)14L] (L = [2.2]paracyclophane)

The synthesis, isolation and characterisation of two new cluster complexes [Ru6C(CO)14(C16H15NH2)] 1 and [Ru6C(CO)14(C16H15Br)] 2 are reported. An X-ray crystallographic study has shown that the 4-amino[2.2]paracyclophane ligand in the former compound is coordinated via its aniline ring in the novel µ3-η1∶η2∶η2 mode. In contrast, correlation 1H NMR shows that the 4-bromo[2.2]paracyclophane ligand in the latter compound is coordinated via the unsubstituted ring. These observations are consistent with the relative activating and deactivating effects of the substituents.

Linked arene clusters

The synthesis, isolation and characterisation of a number of [2n]cyclophane transition metal clusters with nuclearities ranging from four to twelve atoms is described. The primary objective of this work has been to prepare molecules composed of alternating cyclophane and cluster subunits which may be considered as precursors to novel organometallic polymer chains and networks. This aim has been achieved to a certain degree using the [2.2.2]paracyclophane ligand, which has been shown to interact with metal clusters (e.g. tetracobalt nonacarbonyl) via all three of its aromatic rings. Also, the dimerisation of a hexa- ruthenium-[2.2.2]paracyclophane complex has yielded a remarkable dodecanuclear bis-arene cluster which may form the basis for a novel linear polymeric chain containing only metal atoms in the backbone. We have also been able to demonstrate that the coordinated [2.2.2]paracyclophane unit is able to embrace metal ions such as GaI and AgI giving rise to a concomitant change in the observed IR spectrum of the attached cluster. This perspective highlights these areas of research and also examines the factors controlling coordination mode preferences of the [2n]cyclophane ligand and the central cluster nuclearity and geometry.

Selective Oxygen Capture in Lithium Zincate Chemistry

Sequential reaction of N=C-N-containing ligands with ZnMe2, tBuLi, pre-dried (P2O5) air and tetrahydrofuran affords crystalline species which demonstrate differing modes of oxo-capture. Whereas oxo-insertion into a metal-carbon bond is implicated for L = (2-Pyr)N(H)Ph (Pyr = pyridyl) and PhNC(Ph)N(H)Ph, when L = (2-Pyr)N(H)Bz (Bz = benzyl) tBuOLi co-crystallises with the tetrahedral oxo-encapsulation complex, (μ4-O)Zn4[(2-Pyr)NBz]6 2. For L = (2-Pyr)N(H)Me the only isolable product of reaction is the novel octahedral complex tBu(μ3-O)Li3(μ6 -O)Zn3[(2-Pyr)NMe]6, 3, which demonstrates both encapsulation of oxygen and insertion into metal-carbon bonds.

SYNTHESIS AND CHARACTERISATION OF RU6C(CO)14 CLUSTER COMPLEXES OF SOME 2.2- AND 2.2.2-CYCLOPHANE LIGANDS

Some [Ru6C(CO)14] cluster complexes bearing the [2.2]ortho-, anti-[2.2]meta- and [2.2.2]para-cyclophane ligands have been prepared, isolated and characterised. The molecular structure of two new compounds [Ru6C(CO)14(meta-C16H16)] 2 and [Ru6C(CO)14(para-C24H24)] 4 have been established by X-ray diffraction studies which show that the cyclophane ligands are bound in an apical η6 mode in both cases. This is at variance with the face-capping µ3-η2∶η2∶η2 mode observed in the previously reported structure of [Ru6C(CO)14(para-C16H16)] 1. Spectroscopic evidence obtained for [Ru6C(CO)14(ortho-C16H16)] 3 suggests that the cyclophane ligand is bound in an apical η6 mode too. The synthesis of 1 via the redox coupling of [Ru5C(CO)14]2– with [Ru(η6-C16H16)(NCMe)3]2+ is presented as an alternative to the thermolysis of [Ru3(CO)12] with [2.2]paracyclophane in heptane.