The reactivity of group 15 Zintl ions, E₇^3– (E = P, As), towards a number of transition and post-transition metal reagents has been studied. The synthesis and characterisation of the resulting novel cluster anions are described herein. The reactions of E₇^3– with [Cu₅(mes)₅], MPh₂ (M = Zn, Cd) and InPh₃ yielded the Cu–Cu bridged species [Cu₂(E₇)₂]^4– (E = P, As), the group 12 bridged cluster anions [M(E₇)₂]^4– (M = Zn: E = P, As; M= Cd: E = P), and the In-functionalised Zintl ions [E₇InPh<sub>2<sub>]^2–, respectively. P₇^3– and As₇^3– have been found to react with a number of metal salts, namely [M(nbe)₃][SbF₆] and MCl (M = Ag, Au), InCl₃, TlCl and MI₂ (M = Sn, Pb). These reactions formed the Ag–Ag and Au–Au bridged complexes [M₂(HP₇)₂]^2– (M = Ag, Au), the In-bridged species [In(E₇)₂]^3– (E = P, As), the Tl-derivatised Zintl ions [TlE₇]^2– (E = P, As), and the sixteen vertex cluster anions [ME₁₅]^3– (M = Sn, Pb; E = P, As). The reactivity of P₇^3– towards a series of group 8 compounds has also been studied. The reactions of P₇^3– with FeCl₂ and [Ru(PPh₃)₃Cl₂] produced [M(HP₇)₂]^2- (M = Fe, Ru). NMR studies showed that these species can be deprotonated to form [M(P₇)₂]^4– (M = Fe, Ru). These Fe and Ru complexes are isoelectronic with ferrocene. In addition, P₇^3– reacts with [Ru(COD)(η³-CH₂C(CH₃)CH₂)₂] to form [(C₄H₇)P₇Ru(COD)]^2–. Both P₇^3– and As₇^3– undergo transition metal mediated activation reactions in the presence of [Co(PEt₂Ph₂)(mes)₂], yielding [Co(η⁵-P₅){η²-HP₂(mes)}]^2– and [Co([η³-As₃){η⁴-As₄(mes)₂}]^2–, respectively.

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This thesis presents electronic structure calculations on problems related to the bonding in inorganic coordination compounds and clusters. A wide range of molecules with the ability to exist in different structural forms or electronic states has been selected and density functional theory is systematically applied in order to gain detailed insight into their characteristics and reactivity at the electronic level. First, we address the question of redox non-innocent behaviour of bipyridine in a series of 1st row transition metal complexes. Complexes of the type [M(2,2'-bipyridine)(mes)₂]⁰ (M = Cr, Mn, Fe, Co, Ni; mes = 2,4,6-Me₃C6H₂) and their one-electron reduced forms have been explored. The results clearly show that the anions are best described as complexes of the monoanionic bipyridine radical (S_bpy = 1/2), giving a rationale for the observed structural changes within the ligand. Likewise, we have identified dianionic bipyridine in both the complexes [Zn2(4,4'-bpy)(mes)₄]²⁻ and [Fe(2,2'-bpy)₂]²⁻. In no case have we found evidence for significant metal-to-ligand backbonding. The subject of redox-noninnocence is further revisited in a comparative study of the two complexes [M(o-Clpap)₃] (M = Cr, Mo; o-Clpap = 2-[(2-chloro-phenyl)azo]-pyridine), and their associated electron transfer series. The results indicate that all electron transfer processes are primarily ligand-based, although in the case of the Mo analogue these are coupled to substantial electron density changes at the metal. The ability of pap to form radical anions finds a contrasting case in the di- nuclear Rh complex [Rh₂(μ-p-Clpap)₂ (cod)Cl₂], where the two ligand bridges act as acceptors of strong dπ∗ backbonding from a formally Rh^–I centre. We then direct our attention to the endohedral Zintl clusters [Fe@Ge₁₀]³⁻ and [Mn@Pb₁₂]³⁻, which reveal peculiar topologies. We have probed the electronic factors that influence their geometric preferences, and propose a model based on the shift of electron density from the endo- hedral metal to the cage to account for the observed geometries. Subsequently, we reassess the electronic structure of the xenophilic clusters Mn₂(thf)₄(Fe(CO)₄)₂ and [Mn(Mn(thf)₂)₃(Mn(CO)₄)₃]^–. We conclude that these are best viewed as exchange coupled Mn^II centres bridged by closed- shell carbonylate fragments. In the closing chapter the reduction of NO₂^– to NO by the complex [Cu(tct)(NO₂)]⁺ (tct = cis,cis-1,3,5-tris(cinnamylideneamino)cyclohexane) is studied, a process that mimics the enzyme-catalysed reaction. Two viable pathways for the reaction have been traced and key inter-mediates identified. Both direct release of NO or via decomposition of a Cu-NO complex are kinetically and thermodynamically feasible.

NR 20140805

This thesis describes the reactivity of Zintl ions of groups 14 [E₉]^4– (E = Ge and Sn)and 15 [E'₇]^3– (E' = P and As) towards a number or transition, post-transition and main group reagents. The synthesis and characterisation of the resulting novel cluster anions is described herein. Coordination compounds of group 14 Zintl ions were synthesised when K₄Ge₉ was reacted with Zn[N(SiMe₃)₂]₂ to give the simple coordination compound [Ge₉ZnN(SiMe₃)₂]^3–. The heavier analogue K₄Sn₉ reacts with the same metal precursor to give the paramagnetic species [Sn₉ZnNSiMe₃]^3– where a trimethylsilyl group has been lost. K₄Ge₉ reacts with [Ru(COD)(&eta;³-CH₂C(CH₃)CH₂)₂] to form the paramagnetic endohedral compound [Ru@Ge₁₂]^3– and with [Co(PEt₂Ph)₂(mes)₂] to form the prolate endohedral compound [Co₂@Ge₁₆]^4–, which has two metal centres encapsulated inside the sixteen atom germanium cage. Regarding group 15 Zintl ion reactivity, the reactions between pyridine solutions of [HP₇]^2– and E[N(SiMe₃)₂]₂ (E = Ge, Sn and Pb) have been found to yield coordination compounds of the type [P7E(N(SiMe3)2]2–. The germanium containing species [P₇GeN(SiMe₃)₂]^2– quickly decomposes at room temperature to give rise to the thermodynamic product [(P₇)₂Ge₂N(SiMe₃)₂]^3–, a process that involves the loss of an amide moiety. Activation products were also synthesised from the reaction of [E'₇]^3– with varying stoichiometries of VCp₂. The reaction with 0.7 equivalents of VCp₂ yields the sandwich complexes [CpV(&eta;⁵-E'₅)]^n– (E' = P: n = 1; E' = As, n = 1 and 2) whereas with 2.5 equivalents the products are the triple-decker sandwich complexes [(CpV)₂(&eta;^x-E'_x)]– (E' = P: x = 6; E' = As: x = 5).