Alexander D. Hopkins

Phosphinidine complexes of p block metals; new routes to cyclic ligands and Zintl phases

Abstract In contrast to the reactions of E(NMe 2 ) 3 (E=As, Sb, Bi) with [RNHM] (M=Li–Cs) which generate stable Group 15 imido anions (such as the dianions [E 2 (NR) 4 ] 2− and trianions [E(NR) 3 ] 3− ), the phosphide analogues formed in the analogous reactions using [RPHM] decompose readily to give Zintl compounds. This process is accompanied by the formation of [RP] n rings, indicating that the alloy-forming reaction is driven thermodynamically by the bond energy of P–P bonds. The apparent intermediates in this reaction are heterocyclic anions of the type [(RP) n E] – ( n =3 or 4). The latter are interesting new ligands for a range of metals, with the potential ability to behave as sources of metal atoms (E). The anions exhibit unusual reactivity with transition metal metallocenes, adding to the cyclopentadienyl rings in preference to the attack of metal–halogen bonds. In addition, the reactions of the cyclic anions with electrophiles (R′X) furnish a simple selective route to neutral oligophosphine ligands of the type [(RP) n R′ 2 ].

Synthesis and structure of [{Sn(μ‒PCy)}3(Na·PMDETA)2], containing an electron-deficient [{Sn(μ‒PCy)}3]2- dianion

The reaction of CyPHNa with Sn(NMe2)2 in the presence of PMDETA (= {Me2NCH2CH2}2NMe) gives the title compound [{Sn(μ–PCy)}3(Na·PMDETA)2] (1), containing an electron-deficient [(Sn(μ–PCy)}]32− dianion with a novel two-electron, three centre (2e–3c) bonding arrangement.

The first example of a Si-bridged tris(pyridyl) ligand; synthesis and structure of [MeSi(2-C5H4N)3LiX](X = 0.2Br, 0.8Cl)

The low-temperature reaction of MeSiCl3 with 2-Li-C5H4N (1:3 equivalents) in thf gives [MeSi(2-C5H4N)3LiX](X = 0.2Br, 0.8Cl), containing the first example of a Si-bridged tris(pyridyl) ligand.

Sterically induced cis isomerism in an Sb(III) imido dimer; synthesis, structure and solution dynamics of [(Me2N)Sb(μ-NDipp)]2 (Dipp = 2,6-Pr2iC6H3)

Abstract The reaction of [Sb(NMe2)3] with the sterically bulky amine [DippNH2] gives the unusual cis dimer [(Me2N)Sb(μ-NDipp)]2 1, containing a puckered Sb2N2 core. 1H NMR studies show that the cis conformation is retained in solution.

Stoichiometric assembly of [Sb(PCy)3]2Li6·6HNMe2·2C6H5Me; a highly fluxional antimony(III) phosphinidine complex containing Me2NH ligation of lithium†

All of the Me2NH produced by the reaction of [Sb(NMe2)3] with CyP(H)Li (Cy = C6H11) coordinates the Li+ cations of the product [Sb(PCy)3]2Li6·6HNMe2·2C6H5Me 1; the complex contains the first example of a group 15 metal phosphinidine anion {[Sb(PR)3]3–}.

Pyridyl 'ring-flipping' in the dimers [Me2E(2-py)]2 (E=B, Al, Ga; 2-py=2-pyridyl).

The boron and aluminium dimers [Me2E(micro-py)]2 [E=B (1); Al (2)] are formed as mixtures of two isomers in which the group 13 centres are coordinated by the bridging 2-py ligands in a cis or trans manner, however, in contrast to previous studies, we find that simply heating the mixtures of these isomers of and gives the more thermodynamically stable (synthetically useful) trans isomers exclusively (the trans isomer being the only product in the case of the gallium analogue ).

The First Bismuth Phosphide Complex: [Li(thf)4]+[{(tBuP)3}2Bi]−

Thermally unstable crystals of the title compound-the first bismuth phosphide complex to be structurally characterized (see picture)-are obtained by the reaction of [Bi(NMe(2))(3)] with [tBuPHLi] (1:3) in THF/hexane. Berry pseudorotation of the pseudo-trigonal-bipyramidal [{(tBuP)(3)}(2)Bi](-) ion is prevented for steric reasons.

Reductive-elimination of phosphide units; the basis of a general approach to a range of alloys and materials

Heterometallic alkali metal/Group 15 (E = As–Bi) phosphinidene cage compounds (containing RP2− groups) are thermally unstable, decomposing via the formation of thermodynamically stable P–P single bonds into Zintl compounds containing E73− or E42− anions. This approach provides access to photoactive alkali metal antimonates and a potentially general route to a range of new and existing alloys. This short review aims to highlight the mechanism of the phosphide-coupling reaction involved and the scope of this strategy in future materials synthesis.

A one-pot synthesis to [(Me3Si)3SiSb]4; a potential precursor for Sb42−

The reaction of (Me(3)Si)(3)SiK[middle dot]18-crown-6 with SbCl(3)(3 : 1 equiv.) provides a simple route to the title complex [(Me(3)Si)(3)SiSb](4). The potassium base initially acts as a nucleophile and then as a coupling agent, forming Sb-Sb bonds.

Synthesis, structures and coordination behaviour of [As(NR)3]3− trianions

Re-examination of the X-ray structure of the imido As(III) complex previously formulated as [{As(NtBu)3}2Li6]·benzene (1·benzene) indicates that the disorder within the [{As(NtBu)3}2Li6] cage can be better explained by the molecular formulae [{As(NtBu)3}2Li6]·[LiNHtBu]6 or [{As(NtBu)3}Li3·(tBuNHLi)3]. The syntheses and X-ray structures of the new complexes [{As(N(2-MeO-C6H4)3)}2Li6·2TMEDA] (3) and [As{N(2-py)}3·LiN(2-py)·3thf]2·2thf (4·2thf), containing [As(NR)3]3− anions, are reported. Attempts to prepare the heteroleptic trianion [As(NCy)2(NCH2Ph)]3−via reaction of the arsazane dimer [CyNHAs(μ-NCy)]2 (5) with PhCH2NHLi (1 ∶ 6 equivalents) led to the unexpected formation of Zintl compounds containing the As73− anion. The X-ray structure of [As7Li3·3(CyNH2)·3thf] 6 is also reported.