HETEROLEPTIC DIORGANYLZINC COMPOUNDS WITH A BIS(TRIMETHYLSILYL)PHOSPHIDO SUBSTITUENT

Dialkylzinc ZnR2 (Me, Et, iso-Pr, nBu, tBu, CH2SiMe3) reacts with one equivalent of bis(trimethylsilyl)-phosphine in carbohydrates to the he teroleptic compounds RZnP(SiMe3)2; dependent from the steric demand of the alkyl group R the derivatives are dimeric or trimeric in solution as well as in the solid state. Monomeric thylsilyl)phosphido-tris(tri methylsilyl)methylzinc yields from the reaction of lithium tris(trimet hylsilyl)methanide and lithium bis(trimethylsilyl)phosphide with zinc( II) chloride. Bis(trimethylsilyl)phosphido-methylzinc crystallizes in the orthorhombic space group P2(1)2(1)2(1) with {a = 1007.6(1); b = 18 72.3(3); c = 2231.0(4) pm; Z = 4} as a trimeric molecule with a centra l cyclic Zn3P3 moiety in the twist-boat conformation. Bis(trimethylsil yl)phosphido-n-butylzinc, that crystallizes in the orthorombic space g roup Pbcn with {a = 1261.7(2); b = 2253.0(4); c = 1798.9(2) pm; Z = 4} , shows a simular central Zn3P3 fragment. The stericially more demandi ng trimethylsilylmethyl substituent leads to the formation of a dimeri c molecule of (trimethylsilyl)phosphido-trimethylsilylmethylzinc {mono klin, P2(1)/c; a = 907.2(4); b = 2079.8(8), c = 1070,2(3) pm; beta = 1 03,48(1)-degree; Z = 2}. Bis(trimethylsilyl)phosphido-iso-propylzinc s hows in solution a temperatur-dependent equilibrium of the dimeric and trimeric species; the crystalline state contains a 1:1 mixture of the se two oligomers {orthorhombisch; Pbca; a = 1859.0(3); b = 2470.9(2); c = 3450.7(3) pm; Z = 8}. The Zn-P bond lengths vary in a narrow range around 239 pm, the Zn-C distances were found between 196 and 203 pm.