Inorganic Chemistry, Vol.37, No.4, 619-623, 1998
Monomeric and dimeric tetrahydrofuran complexes of barium bis[bis(dimethyl-tert-butylsilyl)arsanide]
The metathesis reaction of (dme)LiAsH2 with (ClSiMe2Bu)-Bu-t allows the isolation of bis(dimethyl-tert-butylsilyl)-arsane 1 in a rather poor yield. The inversion barrier of 64 kJ.mol(-1) for 1 can be deduced from dynamic H-1 and C-13{H-1} NMR experiments. The metalation of 1 by bis(tetrahydrofuran)barium bis[bis(trimethylsilyl)amide] in tetrahydrofuran leads to the formation of tetrakis(tetrahydrofuran)barium bis[bis(dimethyl-tert-butylsilyl)arsanide] 2. The coordination sphere of the metal center is best described as a pentagonal bipyramid with the arsanide ligands in apical positions; however, one equatorial position remains unoccupied due to the steric shielding by the demanding trialkylsilyl groups. Recrystallization of 1 from toluene leads to the loss of tetrahydrofuran coligands and the formation of dimeric (tetrahydrofuran)barium bis[bis(dimethyl-tert-butylsilyl)arsanide] 3. The barium atom shows the small coordination number of 4, and therefore, extremely short terminal Ba-As bonds of 319 pm are observed. Crystallographic data : 2, monoclinic, C2/c, a = 1981.8(7) pm, b = 1137.4(3) pm, c = 2445.9(7) pm, beta = 93.71(4)degrees, Z = 4, wR2 = 0.1193; 3, monoclinic, P2(1)/c, a = 3077.91(1) pm, b = 1165.53(1) pm, c = 2611.67(1) pm, beta = 93.58(1)degrees, Z = 4, wR2 = 0.1358.
Keywords:ALKALINE-EARTH DIHALIDES;MX2 M =;MOLECULAR-STRUCTURE;CRYSTAL-STRUCTURE;SPECTROSCOPIC CHARACTERIZATION;TRIMETHYLSILYL DERIVATIVES;ELECTRONIC-STRUCTURES;TOLUENE SOLUTION;VB-ELEMENTS;STRONTIUM