Aseries of hafnium complexes with areduced arene of the general formula [K(L)][Hf(Xy-N 3 N)(arene)] (Xy-N 3 N = {(3,5-Me 2 C 6 H 3 )NCH 2 CH 2 } 3 N 3À ,L= THF,1 8-crown-6; arene = C 10 H 8 2À ,C 14 H 10 2À)m imic the chemistry of hafnium in its formal oxidation state + II. All compounds were obtained upon reduction of the chlorido complex [HfCl(Xy-N 3 N)(thf)] with two equivalents of potassium naphthalenide or anthracenide.T he reducing nature and the basicity of the reduced anthracene ligand were explored in the reaction of benzonitrile and azobenzene,a nd by deprotonation of tert-butylacetylene, respectively.T he reduction of benzonitrile provides an initial double nitrile insertion product under kinetic control that rearranges after extrusion of one of the inserted nitriles to ahafnium imido complex as the thermodynamic product. The reduction of azobenzeneresulted in adiphenylhydrazido(2À) complex. Treatment of terminal alkynes with the anthracene or diphenylhydrazido(2À)c omplex led to the selective protonation of the corresponding dianionic ligand.

A mononuclear hafnium hydride supported by an aryl-substituted triamidoamine ligand [HfH(thf)(Xy-N3N)] (Xy-N3N = {(3,5-Me2C6H3)NCH2CH2}3N3–) was synthesized by either hydrogenolysis of the hydrocarbyl complex [Hf(R)(thf)(Xy-N3N)] (R = Me, CH2SiMe3, η3-C3H5, CH2Ph) in tetrahydrofuran (THF) or, more conveniently, by salt metathesis of the chloro precursor [HfCl(thf)(Xy-N3N)] with NaBEt3H in methylcyclohexane. The structure of a terminal hydride with a distorted capped trigonal bipyramidal geometry was characterized by single crystal X-ray diffraction (d(Hf–H): 1.83(3) Å) and by 1H NMR spectroscopy. The unusually low field shifted 1H chemical shift for the hydride ligand was detected at δ 18.28 ppm. Dehydrogenative thermolysis of the hydride complex at 25 °C in benzene or toluene resulted in deprotonation of the α-hydrogen of one of the three XyNCH2CH2 groups in the ligand by the hydride, followed by the combination of this deprotonated anionic complex with cationic complex [Hf(Xy-N3N)]+ to give an unsymmetric dinuclear complex bridged by μ-H, μ-NXy, and μ,κN,κC-XyNCHCH2 groups. This decomposition product was characterized by single crystal X-ray diffraction and by 1H and 13C NMR spectroscopy and analyzed by density functional theory (DFT) calculations. Hydrogenation in THF at 25 °C reformed the hydride complex over a period of 48 h. The hydride complex reacted with olefins RHCCH2 (R = H, Et, nHex, cHex, Ph) to give the corresponding anti-Markovnikov insertion products [Hf(CH2CH2R)(thf)n(Xy-N3N)]. Catalytic hydrogenation of olefins was achieved with 5 mol % of the hydride complex at 70 °C in THF or benzene.

Hafniumkomplexe mit reduzierten Arenen der Formel [K(L)][Hf(Xy‐N3N)(Aren)] (Xy‐N3N={(3,5‐Me2C6H3)NCH2CH2}3N3−, L=THF, 18‐Krone‐6; Ar=C10H82−, C14H102−) ahmen die Chemie von Hafnium in seiner formalen Oxidationsstufe +II nach. Alle Verbindungen wurden nach Reduktion des Chloridokomplexes [HfCl(Xy‐N3N)(THF)] mit zwei Äquivalenten Kaliumnaphthalinid oder ‐anthracenid erhalten. Die reduzierende Natur und die Basizität des reduzierten Anthracenliganden wurden bei der Reaktion von Benzonitril und Azobenzol bzw. durch Deprotonierung von tert‐Butylacetylen untersucht. Die Reduktion von Benzonitril liefert ein anfängliches doppeltes Insertionsprodukt zweier Nitrile unter kinetischer Kontrolle, das nach Abgabe eines der inserierten Nitrile zu einem Hafniumimidokomplex als thermodynamisches Produkt umlagert. Die Reduktion von Azobenzol führte zu einem Diphenylhydrazido(2−)‐Komplex. Die Umsetzung von terminalen Alkinen mit dem Anthracen‐ oder Diphenylhydrazido(2−)‐Komplex führte zur selektiven Protonierung des entsprechenden dianionischen Liganden.