SYNTHESES AND FLUXIONAL BEHAVIOR OF YTTRIUM COMPLEXES CONTAINING THE BULKY ARYLSILOXIDE OSI(T)BUAR(2) [AR=O-C6H4(CH(2)NME(2))] AND THE X-RAY CRYSTAL-STRUCTURE OF Y[OSI(T)BUAR(2)][N(SIME(3))(2)](2)

The silanol ligand HOSi(t)BuAr(2) (1; Ar = 0-C6H4(CH(2)NMe(2))) was pr epared from (t)BuSiCl(3) and 2 equiv of LiAr followed by aqueous worku p. Reaction of 1 with Y[N(SiMe(3))(2)](3) provided the monosiloxide co mplex Y[OSi(t)BuAr(2)]-[N(SiMe(3))(2)](2) (2). A single crystal X-ray diffraction study of 2 revealed a highly distorted tetrahedral geometr y at Y. Only one of the two 2-(N,N-dimethylaminomethyl)phenyl arms of the siloxide is coordinated. [Crystal data: monoclinic space group I2/ a, a = 20.709(3) Angstrom, b = 9.511(1) Angstrom, c = 46.579(6) Angstr om, beta = 98.04(1)degrees, V = 9084.6 Angstrom(3), Z = 8, R = 0.078 a nd R(W) = 0.101]. Reaction of 2 with 2 equiv of HOC(6)H(3)(t)Bu(2)-2,6 afforded Y[OSi(t)BuAr(2)][OC(6)H(3)(t)Bu(2)-2,6](2) (3) in good yield . Complexes 2 and 3 exhibit very similar fluxional behavior in solutio n. Two separate fluxional processes were distinguished by H-1 NMR: a l ower temperature process involving restricted rotation of the silylami de (2, Delta G(rotation) = 53 +/- 1 kJ/mol) or phenoxide (3, Delta G* (rotation) = 57 +/- 1 kJ/mol) groups and a higher temperature process involving exchange of free and coordinated 2-(N,N-dimethylamino-methyl )phenyl arms (2, Delta G(arm exchange) = 72 +/- 1 kJ/mol; 3, Delta G* (arm exchange) = 75 +/- 1 kJ/mol). Complex 3 reacts with 2 equiv of Li CH(2)SiMe(3) to give Ar(2)][OC(6)H(3)(t)Bu(2)-2,6][CH(2)SiMe(3)](2)}(- ) (4). Attempts to prepare a neutral dialkyl by elimination of the rem aining LiOC(6)H(3)(t)Bu(2)-2,6 were not successful. Complex 4 exhibits complex fluxional behavior in solution by H-1 NMR.