Deprotonation of μ 3 ‐Methylidyne Groups on a Ti 3 O 3 Support: A Way to Build Oxotitanocubanes Containing Alkali and Alkaline‐Earth Metals

The μ 3 ‐methylidyne group of the complex [{TiCp*(µ‐O)} 3 (µ 3 ‐CH)] ( 1 ) (Cp* = η 5 ‐C 5 Me 5 ) was deprotonated by amides of the group 1 elements, [MN(SiMe 3 ) 2 ] (M = Li, Na, K, Rb, Cs) to form the oxoheterometallocubane complexes [M(μ 3 ‐O) 3 {Ti 3 Cp* 3 (μ 3 ‐C)}] [M = Li ( 3 ), Na ( 4 ), K ( 5 ), Rb ( 6 ), Cs ( 7 )]. Similar treatments of 1 with the alkaline‐earth amides [M{N(SiMe 3 ) 2 } 2 (thf) 2 ] (M = Mg, Ca, Sr) afforded the heterometallocubane derivatives [{(thf) x (Me 3 Si) 2 NM}(μ 3 ‐O) 3 {Ti 3 Cp* 3 (μ 3 ‐C)}] [M = Mg, x = 0, ( 8 ); Ca, x = 1, ( 9 ); Sr, x = 1, ( 10 )] in high yields. The addition of ligands such as cyclopentadiene (C 5 H 6 ) or pentamethylcyclopentadiene (C 5 Me 5 H) to the compounds 3 − 7 allowed recovery of the μ 3 ‐methylidyne oxocomplex 1 . The analogous reaction of 8 − 10 with C 5 H 6 caused the displacement of the amide fragment to give the heterometallocubanes [(CpM)(μ 3 ‐O) 3 {Ti 3 Cp* 3 (μ 3 ‐C)}] [M = Mg ( 11 ), Ca ( 12 ), Sr ( 13 )], while C 5 Me 5 H reacts only with 9 and 10 to give the compounds [(Cp*M)(μ 3 ‐O) 3 {Ti 3 Cp* 3 (μ 3 ‐C)}] [M = Ca ( 14 ), Sr ( 15 )]. Furthermore, heating of the species 8 − 10 in the presence of the starting complex 1 produced amine elimination and afforded the corner‐shared heterometallodicubanes [M{(μ 3 ‐O) 3 Ti 3 Cp* 3 (μ 3 ‐C)} 2 ] [M = Mg ( 16 ), Ca ( 17 ), Sr ( 18 )]. Treatment of 1 with the amide [Ba{N(SiMe 3 ) 2 } 2 (thf) 2 ] or dialkyl derivatives of magnesium [MgR 2 (thf) 2 ] (R = CH 2 Ph, t Bu) and barium [Ba(CH 2 Ph) 2 ] provided the corner‐shared metallodicubanes [M{(μ 3 ‐O) 3 Ti 3 Cp* 3 (μ 3 ‐C)} 2 ] [M = Mg( 16 ), Ba( 19 )]. The molecular structures of complexes 9 , 16 , 17 and 18 have been established by single‐crystal X‐ray analyses. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)