LANTHANIDE COMPLEXES OF BULKY SILOXIDE LIGANDS INCORPORATING PENDANT AMINE DONORS - SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF A VOLATILETRIS(SILOXIDE) COMPLEX OF YTTRIUM(III) AND A NOVEL ZWITTERIONIC TETRAKIS(SILOXIDE) OF YTTERBIUM(III)
Pc. Shao et al., LANTHANIDE COMPLEXES OF BULKY SILOXIDE LIGANDS INCORPORATING PENDANT AMINE DONORS - SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF A VOLATILETRIS(SILOXIDE) COMPLEX OF YTTRIUM(III) AND A NOVEL ZWITTERIONIC TETRAKIS(SILOXIDE) OF YTTERBIUM(III), Inorganic chemistry, 33(16), 1994, pp. 3452-3458
The silanol ligands HOSi(t-Bu)3-n[(CH2)3NMe2]n(3,n = 2;4, n = 1), were
prepared from the appropriate chlorosilanes, HSi(t-Bu)3-nCln, in two
steps. Reaction of 3 equiv of 3 or 4 with Ln[N(SiMe3)2]3 allowed isola
tion of the tris(siloxide) complexes Ln{OSi(t-Bu)3-n[(CH2)3NMe2]n}3 (5
, Ln = Y, n = 2; 6, Ln = Y, n =1; 7, Ln = Ce, n = 1). Complexes 6 and
7 sublimed unchanged at 115 and 135-degrees-C at 10(-4) Torr, respecti
vely. A single-crystal X-ray diffraction study of 6 revealed a trigona
l bipyramidal geometry with the equatorial sites occupied by three sil
oxide O and the axial sites occupied by two NMe2 groups. The third dim
ethylaminopropyl arm is not coordinated. [Crystal data: triclinic spac
e group P1BAR, a = 13.738(2) angstrom, b = 15.940(3) angstrom, c = 13.
363(2) angstrom, alpha = 93.80(1)-degrees, beta = 116.77(1)-degrees, g
amma = 74.55(1)-degrees, V = 2513.5 angstrom3, Z = 2, R = 0.0839, and
R(W) = 0.1081.] Complex 6 is fluxional in solution to -80-degrees-C; e
xchange of coordinated and dangling (dimethylamino)propyl arms is sugg
ested as a possible mechanism. Reaction of 4 equiv of 4 with Ln(N(SiMe
3)2]3 produced novel zwitterionic tetrakis(siloxide) complexes, Ln[OSi
-(t-Bu)2(CH2)3NMe2]3[OSi(t-Bu)2(CH2)3NMe2H) (8, Ln = Y; 9, Ln = Yb). A
n X-ray crystallographic study of 9 revealed a tetrahedral arrangement
of siloxide O about Yb. One of the four dangling NMe2 groups is proto
nated and hydrogen-bonded to a second NMe2 unit. [Crystal data: monocl
inic space group P2(1)/n, a = 13.266(3) angstrom, b = 23.337(5) angstr
om, c = 21.914(3) angstrom, beta = 93.94(1)-degrees, V = 6768.0 angstr
om3, Z = 4, R = 0.0684, and R(W) = 0.0929.] Complex 8 partially dissoc
iates into 4 and 6 in toluene solution. A variable-temperature H-1 NMR
study yielded DELTAH-degrees = 40 +/- 4 kJ mol-1 and DELTAS-degrees =
124 +/- 10 J mol-1 K-1 for this equilibrium. Reaction of 8 with LiCH2
SiMe3 produced Li+{Y[OSi(t-BU)2(CH2)3NMe2]4}- (10) in good yield.