Deprotonation of μ3-methylidyne groups on a Ti3O3 support:: A way to build oxotitanocubanes containing alkali and alkaline-earth metals

The mu(3)-methylidyne group of the complex [{TiCp*(mu-O)}(3)(mu(3)-CH)] (1) (CP* = eta(5)-C5Me5) was deprotonated by amides of the group 1 elements, [MN(SiMe3)(2)] (M = Li, Na, K, Rb, Cs) to form the oxoheterometallocubane complexes [M(mu(3)-O)(3){Ti3CP3*(mu(3)-C)}] [M = Li (3), Na (4), K (5), Rb (6), Cs (7)]. Similar treatments of I with the alkaline-earth amides [M{N(SiMe3)(2)}(2)(thf)(2)] (M = Mg, Ca, Sr) afforded the heterometallocubane derivatives [{(thf)(x)(Me3Si)(2)NM}(mu(3)- O)(3)(Ti3CP3*(mu(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 (C5H6) or pentamethylcyclopentadiene (C5Me5H) to the compounds 3-7 allowed recovery of the mu(3)- methylidyne oxocomplex 1. The analogous reaction of 8-10 with C5H6 caused the displacement of the amide fragment to give the heterometallocubanes [(CpM)(mu(3)-O)(3)(Ti3CP3*(mu(3)- C)}] [M = Mg (11), Ca (12), Sr (13)], while C5Me5H reacts only with 9 and 10 to give the compounds [((CPM)-M-*)(mu(3)-O)(3)(Ti3CP3*(mu(3)-C)}] [M = Ca (14), Sr (15)], Furthermore, heating of the species 8-10 in the presence of the starting complex I produced amine elimination and afforded the cornershared mu(3)-O [M = Mg (16), Ca (17), Sr (18)]. Treatment of 1 with the amide [Ba{N(SiMe3)(2)}(2)(thf)(2)] or dialkyl derivatives of magnesium [MgR2(thf)(2)] (R = CH2Ph, tBu) and barium [Ba(CH2Ph)(2)] Provided the corner-shared metallodicubanes [M{(mu(3)-O)(3)Ti3Cp3*- (mu(3)-C)}(2)] [M = Mg(16), Ba(19)]. The molecular structures of complexes 9, 16, 17 and 18 have been established by singlecrystal X-ray analyses. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)