Iron ß-diiminate complexes with As2-, As4- and As8-ligands.

Different substituents at the ß-diiminato ligand in low-valent [LFe(tol)] (L = ß-diiminato) complexes fundamentally change their reactivity towards yellow arsenic. By using dmp (2,6-dimethylphenyl) as flanking groups, the tetranuclear complexes [(LFe)4As8] (L = L1 (1), L2 (2)) are isolated. For dipp (2,6-diisopropylphenyl) substituted ligands, dinuclear complexes [(LFe)2(cyclo-As4)] (L = L3 (3a), L4 (4a)) are obtained. Not only the choice of the ligand impacts the product formation, but also the temperature of the crystallization can shift their ratio in the solid state.

The Influence of ß-diiminato Ligands on As4 Activation by Cobalt Complexes.

In a systematic study of the activation of As4 , three [LCo(tol)] (L=ß-diiminato) complexes have revealed different steric and electronic influences. 2,6-Diisopropylphenyl (Dipp) and 2,6-dimethylphenyl (dmp) flanking groups were used, one of the ligands with H backbone substituents (ß-dialdiminate L0 ) and two with Me substituents (ß-diketiminates L3 and L1 ). In the reaction with As4 , different dinuclear products [(LCo)2 As4 ] (LM=L0 (1), L1 (2), L3 (3)) were isolated, with all showing differently shaped [Co2 As4 ] cores in the solid state: octahedral in 1, prismatic in 2, and asterane-like in 3. Thermal treatment of 3 leads to the abstraction of one arsenic atom to yield [(L3 Co)2 As3 ] (4). All products were comprehensively characterized by single-crystal X-ray diffraction, FD-MS, and 1 H NMR spectroscopy. A rational explanation for the different reactivity is also proposed and DFT calculations shed light on the nature of the highly flexible [Co2 As4 ] cores.

Nacnac-Cobalt-Mediated P4 Transformations.

A comparison of P4 activations mediated by low-valent ß-diketiminato (L) cobalt complexes is presented. The formal Co0 source [K2 (L3 Co)2 (µ2 :η1 ,η1 -N2 )] (1) reacts with P4 to form a mixture of the monoanionic complexes [K(thf)6 ][(L3 Co)2 (µ2 :η4 ,η4 -P4 )] (2) and [K(thf)6 ][(L3 Co)2 (µ2 :η3 ,η3 -P3 )] (3). The analogue CoI precursor [L3 Co(tol)] (4 a), however, selectively yields the corresponding neutral derivative [(L3 Co)2 (µ2 :η4 ,η4 -P4 )] (5 a). Compound 5 a undergoes thermal P atom loss to form the unprecedented complex [(L3 Co)2 (µ2 :η3 ,η3 -P3 )] (6). The products 2 and 3 can be obtained selectively by an one-electron reduction of their neutral precursors 5 a and 6, respectively. The electrochemical behaviour of 2, 3, 5 a, and 6 is monitored by cyclic voltammetry and their magnetism is examined by SQUID measurements and the Evans method. The initial CoI -mediated P4 activation is not influenced by applying the structurally different ligands L1 and L2 , which is proven by the formation of the isostructural products [(LCo)2 (µ2 :η4 ,η4 -P4 )] [L=L3 (5 a), L1 (5 b), L2 (5 c)].

{[CuSn5 Sb3 ](2-) }2 : A Dimer of Inhomogeneous Superatoms.

Reaction of the binary Zintl anion (Sn2 Sb2 )(2-) with the ß-diketiminato complex [LCu(NCMe)] (L=nacnac=[(N(C6 H3 (i) Pr2 -2,6)C(Me))2 CH](-) ) in ethylenediamine or DMF affords the ternary cluster dimer {[CuSn5 Sb3 ](2-) }2 (1) as its [K(crypt-222)](+) salt. The chemical formulation of 1 is supported by energy-dispersive X-ray spectroscopy (EDX) and quantum chemical calculations. Each monomeric part of the dimer represents a trimetallic "[CuSn5 Sb3 ](2-) " cluster, with an architecture in between a tricapped trigonal prism and a capped square antiprism. As shown by quantum chemical investigations, the presence of Sb atoms and, in particular, of Cu atoms in the cluster skeleton makes the monomeric unit behave like an inhomogeneous superatom, which clearly prefers to dimerize, thereby producing a relatively short, yet virtually non-bonding Cu⋅⋅⋅Cu distance.

Influence of the nacnac Ligand in Iron(I)-Mediated P4 Transformations.

A study of P4 transformations at low-valent iron is presented using ß-diketiminato (L) Fe(I) complexes [LFe(tol)] (tol=toluene; L=L(1) (1 a), L(2) (1 b), L(3) (1 c)) with different combinations of aromatic and backbone substituents at the ligand. The products [(LFe)4 (µ4 -η(2) :η(2) :η(2) :η(2) -P8 )] (L=L(1) (2 a), L(2) (2 b)) containing a P8 core were obtained by the reaction of 1 a,b with P4 in toluene at room temperature. Using a slightly more sterically encumbered ligand in 1 c results in the formation of [(L(3) Fe)2 (µ-η(4) :η(4) -P4 )] (2 c), possessing a cyclo-P4 moiety. Compounds 2 a-c were comprehensively characterized and their electronic structures investigated by SQUID magnetization and (57) Fe Mössbauer spectroscopy as well as by DFT methods.

Fixation and release of intact E4 tetrahedra (E=P, As).

By the reaction of [NacnacCuCH3CN] with white phosphorus (P4) and yellow arsenic (As4), the stabilization and enclosure of the intact E4 tetrahedra are realized and the disubstituted complexes [(NacnacCu)2(µ,η(2:2)-E4)] (1 a: E=P, 1 b: E=As) are formed. The mono-substituted complex [NacnacCu(η(2)-P4)] (2), was detected by the exchange reaction of 1 a with P4 and was only isolated using low-temperature work-up. All products were comprehensively spectroscopically and crystallographically characterized. The bonding situation in the products as intact E4 units (E=P, As) was confirmed by theory and was experimentally proven by the pyridine promoted release of the bridging E4 tetrahedra in 1.