Density functional calculations and Raman spectroscopic data were correlated with the unique catalytic epoxidation activity of peroxomolybdenum complexes [MoO(O 2 ) 2 (O-ER 3 )] (E N, P, As; R n-dodecyl) in a biphasic chloroform ± 1-octene/aqueous hydrogen peroxide system. Crystal structure determinations on [MoO(O 2 ) 2 (OPtBu 3 )(OCMe 2 )] and two complexes containing chelating hemilabile ether ± phosphane oxide and ether ± arsane oxide ligands [MoO(O 2 ) 2 -{iPr 2 E(O)CH 2 CH 2 OCH 3 }] (E P, As) are reported. A mechanistic study with these model complexes reveals the importance of free coordination sites for peroxide activation. Calculations and Raman spectroscopic data indicate the tendency of coordinatively unsaturated species [MoO(O 2 ) 2 (L)] to dimerize in noncoordinating solvents. The catalytic activity in the presence of water as competing ligand could be correlated with the calculated proton affinity of the ligands OER 3 (R N, P, As). Elucidation of the vibrational behavior of the structurally characterized peroxo complexes was supported by normal-coordinate analyses.

Keywords: Ligand design / N ligands / Tripodal ligands / Coordination chemistry / Manganese / Iron / Zinc / MolybdenumThe synthesis of the novel tripod ligand N[CH 2 CH 2 N= C(NMe 2 ) 2 ] 3 , based on the tris(2-ethylamino)amine (tren) backbone and having a set of three superbasic tetramethylguanidine (TMG) donor atoms instead of the primary amine functionalities, is described. This ligand has been prepared by treating tren with the Vilsmeyer salt [(Me 2 N) 2 CCl]Cl in

The focus of the current report lies on recent developments of synthetic methods applied to the synthesis of some high‐valent complexes containing the nitrido functionality [N]3— as a link between a group 4, 5 or 6 transition metal and a main group element E (E = B, Si, Ge, P, S). Emphasis is put on results, that have been obtained within the “Schwerpunktprogramm “Nitridobrücken” funded by the Deutsche Forschungsgemeinschaft. The synthetic methods include condensation reactions of reactive chloro and oxo complexes (M = V, Nb, Ta, Cr, Mo, W) with silylamines, sulfonylamides, with N‐silyl and N‐lithio iminophosphoranes, furthermore methatesis reactions of oxo complexes with N‐sulfonyl sulfinyl amides (M = V, Cr, Mo, W), the oxidative addition of element azides to d2 metal centers (M = V, W), and finally transamination reactions of N‐H iminophosphoranes with amido complexes (M = Ti, Sm).

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Keywords: Niobium / Tantalum / N ligands / Cyclopentadienyl ligands / Rearrangements Convenient strategies towards the synthesis of silylimido niobium and -tantalum complexes of the metallocene and half-sandwich type are reported. Bent metallocenes [(η 5 -C 5 H 5 ) 2 M(NSiMe 3 )Cl] (M = Nb: 1a; Ta: 1b) and [(η 5 -C 5 H 5 ) 2 M(NSiMe 3 )(η 1 -C 5 H 5 )] (M = Nb: 2a; Ta: 2b) are synthesized by reaction of [M(NSiMe 3 )Cl 3 (py) 2 ] with 2 or 3 equiv. NaCp, respectively. Half-sandwich type silylimido complexes [(η 5 -C 5 Me 5 )M(NSiMe 3 )Cl 2 ] (M = Nb: 3a; Ta: 3b) cannot selectively be obtained from the (pyridine)(silylimido) precursor complexes. However, their synthesis is accomplished by reaction of [(η 5 -C 5 Me 5 )MCl 4 ] with LiN(SiMe 3 ) 2 . On the other hand pyridine silylimido complexes are perfect