Hydridotetrylene [Ar*EH] (E = Ge, Sn, Pb) coordination at tantalum, tungsten, and zirconium. Issue 14 (23rd March 2022) - Widemann, Max
Abstract : Low valent cations of tin and lead were used to form hydridotetrylene coordination compounds. The mobility of the hydrogen substituent was investigated in deprotonation equilibria as well as in 1, 2-H-shift reactions. Abstract : In a reaction of tantalocene trihydride with the low valent aryl tin cation [Ar*Sn(C6 H6 )][Al(OC{CF3 }3 )4 ] (1a ) the hydridostannylene complex [Cp2 TaH2 –Sn(H)Ar*][Al(OC{CF3 }3 )4 ] (2 ) was synthesized. Hydride bridged adducts [Cp2 WH2 EAr*][Al(OC{CF3 }3 )4 ] (E = Sn 3a, Pb 3b ) were isolated as products of the reaction between Cp2 WH2 and cations [Ar*E(C6 H6 )][Al(OC{CF3 }3 )4 ] (E = Sn 1a, Pb 1b ). The tin adduct 3a exhibits a proton migration to give the hydridostannylene complex [Cp2 W(H)Sn(H)Ar*][Al(OC{CF3 }3 )4 ] 4a . The cationic complex 4a is deprotonated at the tin atom in reaction with base Me NHC at 80 °C to give a hydrido-tungstenostannylene [Cp2 W(H)SnAr*] 5a . Reprotonation of metallostannylene 5a with acid [H(Et2 O)2 ][BAr F ] provides an alternative route to hydridotetrylene coordination. Complex 4a adds hydride to give the dihydrostannyl complex [Cp2 W(H)–SnH2 Ar*] (7 ). With styrene 4a shows formation of a hydrostannylation product [Cp2 W(H)Sn(CH2 CH2 Ph)Ar*][Al(OC{CF3 }3 )4 ] (8 ). The lead adduct 3b was deprotonated with Me NHC to give plumbylene 5b [Cp2 W(H)PbAr*]. Protonation of 5b with [H(Et2 O)2 ][Al(OC{CF3 }3 )4 ] at −40 °C followed by low temperature NMR spectroscopy indicates a hydridoplumbylene intermediate [Cp2 W(H)Pb(H)Ar*] + (4b ). Hydrido-tungstenotetrylenes of elements Ge (5c ), Sn (5a ) and Pb (5b ) were also synthesized reacting the salt [Cp2 W(H)Li]4 with organotetrylene halides. The metallogermylene [Cp2 W(H)GeAr*] (5c ) shows an isomerization via 1, 2-H-migration to give the hydridogermylene [Cp2 WGe(H)Ar*] (9 ), which is accelerated by addition of AIBN. 9 is at rt photochemically transferred back to 5c under light of a mercury vapor lamp. Zirconocene dihydride [Cp2 ZrH2 ]2 reacts with tin cation 1a to give the trinuclear hydridostannylene adduct 10 [({Cp2 Zr}2 {μ-H})(μ-H)2 μ-Sn(H)Ar*][Al(OC{CF3 }3 )4 ]. Deprotonation of 10 was carried out using benzyl potassium to give neutral [({Cp2 Zr}2 {μ-H})(μ-H)μ-Sn(H)Ar*] (11 ). 11 was also obtained from the reaction of low valent tin hydride [Ar*SnH]2 with two equivalents of [Cp2 ZrH2 ]2 . The trihydride Ar*SnH3 reacts with half of an equivalent of [Cp2 ZrH2 ]2 under evolution of hydrogen and formation of a dihydrostannyl complex 13 [Cp2 Zr(μ-H)SnH2 Ar*]2 and with further equivalents of Ar*SnH3 to give bis(hydridostannylene) complex [Cp2 Zr{Sn(H)Ar*}2 ].