HOMOLEPTIC AND HETEROLEPTIC ZINC ARSANIDE S - SYNTHESES AND STRUCTURE

Bis(trimethylsilyl)arsane reacts with dialkylzinc ZnR(2) (R = Me, Et, CH(2)SiMe(3))(1)) in the stoichiometric ratio of 1:1 in hydrocarbons t o the heteroleptic alkyl zink bis(trimethylsilyl)arsanides. The steric demand of the alkyl substituent enforces the oligomerisation degree o f two or three. Diethylzinc and two equivalents of HAs(SiMe(3))(2) yie ld dimeric zinc bis[bis(trimethylsilyl)arsanide] . Methyl zinc bis(tri methylsilyl)arsanide crystallizes as a trimer with a six-membered Zn3A s3-cycle in the twist-boat conformation {orthorhombic, P2(1)2(1)2(1), a = 1015.3(1), b = 1887.6(4), c = 2272.9(4) pm, Z = 4}. The molecule o f ethyl zinc bis(trimethylsilyl)arsanide is built similar in the solid state (monoclinic, P2(1)/n, a = 1220.2(4), b = 1889.0(6), c = 1968.5( 6) pm, beta = 90.24(1)degrees, Z = 4). However, zinc bis[bis(trimethyl silyl)arsanide] separates due to the steric demand of the terminal (Me (3)Si)(2)As-ligand as a dimer in the triclinic space group P (1) over bar (a = 967.8(2), b = 1088.5(2), c = 1238.1(2)pm, alpha = 92.41(1), b eta = 105.20(1), gamma = 105.05(1)degrees, Z = 2). The endocyclic zinc -arsenic distances vary only slightly around 248 pm, but the exocyclic one is with a value of 238 pm drastically shorter. The Zn-Cbond lengt hs with values around 197 pm lie in the characteristic region for zinc with the coordination number of three.