Reactions of Group 4 Metallocene Complexes with Mono‐ and Diphenylacetonitrile: Formation of Unusual Four‐ and Six‐Membered Metallacycles

Abstract

Reactions of Group 4 metallocene alkyne complexes [Cp'2M(η(2)-Me3SiC2SiMe3)] (1: M = Zr, Cp' = Cp* = η(5)-pentamethylcyclopentadienyl; 2 a: M = Ti, Cp' = Cp*, and 2 b: M = Ti, Cp'2 = rac-(ebthi) = rac-1,2-ethylene-1,1'-bis(η(5)-tetrahydroindenyl)) with diphenylacetonitrile (Ph2CHCN) and of the seven-membered zirconacyclocumulene 3 with phenylacetonitrile (PhCH2CN) were investigated. Different compounds were obtained depending on the metal, the cyclopentadienyl ligand and the reaction temperature. In the first step, Ph2CHCN coordinated to 1 to form [Cp*2Zr(η(2)-Me3SiC2SiMe3)(NCCHPh2)] (4). Higher temperatures led to elimination of the alkyne, coordination of a second Ph2CHCN and transformation of the nitriles to a keteniminate and an imine ligand in [Cp*2Zr(NC2Ph2)(NCHCHPh2)] (5). The conversion of 4 to 5 was monitored by using (1)H NMR spectroscopy. The analogue titanocene complex 2 a eliminated the alkyne first, which led directly to [Cp*2Ti(NC2Ph2)2] (6) with two keteniminate ligands. In contrast, the reaction of 2 b with diphenylacetonitrile involved a formal coupling of the nitriles to obtain the unusual four-membered titanacycle 7. An unexpected six-membered fused zirconaheterocycle (8) resulted from the reaction of 3 with PhCH2CN. The molecular structures of complexes 4, 5, 6, 7 and 8 were determined by X-ray crystallography.

Reactions of Group 4 Metallocenes with N,N′‐Diphenylformamidine – Hydrogen Generation versus Oxidative Addition

“…[10] It seems worth to mention that analogous compounds like Cp 2 Ti[κ 2 -N,NЈ-RN=C=NR] without substituents at ring C atom do not exist and are stabilized depending on R by different reactions. [11] The question was if complex 2 is stable or shows any further reaction at the C-H bond.…”

Reactions of rac‐(ebthi)M(η2‐Me3SiC2SiMe3) (M=Ti, Zr) with Aryl Nitriles

“…Recently, we investigated the reactions of Ph 2 CHCN with Group 4 metallocene alkyne complexes 8. A nitrile–nitrile NC coupling took place in the reaction of rac ‐(ebthi)Ti(η 2 ‐Me 3 SiC 2 SiMe 3 ) ( 1 a ; rac ‐(ebthi)= rac ‐1,2‐ethylene‐1,1′‐bis(η 5 ‐tetrahydroindenyl)) with this nitrile to afford the four‐membered cycle E .…”

Nitril‐Nitril‐C‐C‐Kupplungen an Gruppe‐4‐Metallocenen zu 1‐Metalla‐2,5‐diazacyclopenta‐2,4‐dienen und deren Reaktionen

“…Der Ringschluss wird meist durch eine daraus resultierende Stabilisierung oder eine Wechselwirkung mit einem Zusatzliganden begünstigt. Nach unserer Kenntnis wurden bisher nur zwei viergliedrige Ringe (D), einer für Yttrium [14] und einer für Titan, [15] durch eine N-C-Kupplung von Nitrilen erhalten.…”