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In a recent full-paper (Dalton Trans. 2009, 5612 - 5626; "Hot Article") we reported on synthetically valuable precursor compounds as well as the synthesis and some reactivity studies of a novel ambidentate tris(pyrazolyl)silanide (^MeTpsd). This silicon-containing Janus-head ligand can either separately or simultaneously act as κ¹Si- or κ³N-coordinating ligand (see inside front cover of issue 29)

A straight forward synthetic access towards cationic germanium / nitrogen cages of the general formula [Ge(m₂-R₂pz)₃Ge]⁺[OTf]^- has been described recently (see Dalton Trans. 2009, 5335 – 5347). Additionally, detailed NMR investigations, DFT calculations and molecular structures of these Janus-head molecules have been provided.

Tripodal Ligands

a) Zwitterionic “sandwiches”: Combined preparative, spectroscopic and theoretical studies on the syntheses, structures and electronic properties of zwitterionic iron(II) and cobalt(II) sandwich complexes [M(^MeTpmd)₂] containing κ³N-coordinated tris(pyrazolyl)methanide ligands (^MeTpmd; see picture) have been published recently.

b) A straight forward synthetic access towards novel ruthenium(II) mixed-sandwich complexes comprising tris(pyrazolyl)methane and cyclopentadienyl ligands has been described recently. Detailed NMR investigations, molecular structures and the electrochemical properties of these complexes have been presented as illustrated.

NMR Methods

In a recent collaborative work with the group of Ignacio Fernández a straightforward natural abundance 2D HMQC NMR experiment between lithium-7 and nitrogen-15 has been reported. This fast, reliable and routinely implementable method represents a powerful spectroscopic tool to study complex structures or intermediate species in solution, in particular those containing nitrogen-lithium bonds.

Metallapropellanes

Detailed studies on the synthesis, structure, redox chemistry and bonding properties of pentagerma[1.1.1]propellane (1) have been published and spotlighted recently (see section "Publications"). Fundamental aspects of the interactions between the bridgehead germanium atoms in 1 were examined using density functional theory and CASSCF calculations. The latter have been performed in close collaboration with Prof. Wim Klopper (Uni KA).

Scorpionates to Janus-heads: multidentate ligands


In a recent Dalton Perspective we reviewed the area of multidentate ligands ranging from scorpionates to Janus-head types, concentrating, in particular, on C₃-symmetric tripodal ligands (see Dalton Trans. 2008, 5836 - 5865).

Multifunctional ligands with podand topology provide intrinsically well-defined coordination geometries. Several subgroups of multidentate ligand systems comprising dual functionality have been developed so far. Recent advances made in this research area nicely reflect its topicality. Work on metal complexes of ambiphilic ligands consisting of Lewis-acidic Group 13 element bridgehead atoms and additional donor functionalities is in the current focus of interest. The intrinsic topology of tetradentate ligands may introduce a fascinating reactivity and interesting electronic properties of the metal complexes. Janus-head type ligands are very promising candidates for the preparation of multimetallic complexes.