Sandro Gambarotta

The cooperative attack of four (dipyrromethanyl)Sm^II units on dinitrogen resulted in a novel tetranuclear samarium dinitrogen complex (shown schematically). The presence of halogen atoms inhibited reactivity with dinitrogen through the assembly of divalent samarium clusters. dipyrr=diphenylmethyldipyrrolide dianion.

In spite of the short Nb−Nb distance (2.268 Å) and the presumable existence of an Nb≡Nb bond, the paddle-wheel-shaped diniobium(II) complex 1 is paramagnetic. Theoretical calculations indicate that the presence of LiCl moieties on the intermetallic axis lowers the Nb−Nb bond order and is responsible for the observed paramagnetism.

The homoleptic Cr^III amide complexes [(RR′N)₃Cr] [R = R′ = cyclohexyl (1a); R = adamantyl, R′ = 3,5‐Me₂Ph (1 b)] were prepared and characterized. Reactions with elemental sulfur produced the corresponding dinuclear complexes [{(RR′N)₂Cr}₂(μ‐S)₂] (2) through loss of one amide group. These two new dinuclear Cr^IV species are paramagnetic with magnetic moments lower than expected for the d² electronic configuration of Cr^IV. Magnetic measurements and ab initio calculations were carried out to elucidate the nature of magnetic interactions in these dinuclear systems. The molecular structures of 1a and 2a were elucidated by X‐ray crystal structures.

The reactions of (Ph₂N)₃V‐(THF) (1) with [(CH₃)₃Si]N₃ and [(CH₃)₃Si]CHN₂ proceed at room temperature to afford the corresponding derivatives (Ph₂N)₃V[N‐Si(CH₃)₃] (2a) and (Ph₂N)₃V[N₂CHSi(CH₃)₃] (3). Reactions of both 2a and 3 with lithium isopropylamide provide the unprecedented anionic vanadium nitride species [(Ph₂N)₃V(μ‐N)Li(THF)₃]·(THF)_0.5 (4), which displays moderate nucleophilicity. It reacts with (CH₃)₃SiCl and Mel to reform the complex (Ph₂N)₃V(N‐R) [R = Si(CH₃)₃ (2a), Me (2b)]. Reactions with Cp₂ZrCl₂ and CpTiCl₃ lead to the formation of the heterodinuclear bridged nitride complexes [(Ph₂N)₃V(μ‐N)ZrClCp]₂] [Cp = Cp]=Cp (6a), CH₃C₅H₄ (6b)] and [{(Ph₂N)₃V(μ‐N)}₂TiClCp] (8).