Crystal and Molecular Structures of the Functional Lithium Cyclopentadienides [Li(tmeda)][R2PCMe2C5H4], R = Ph, Me

Abstract

The crystal and molecular structures of the phosphinomethyl-substituted lithium cyclopentadienides [Li(tmeda)][R2PCMe2C5H4], R = Ph (1), Me (2) (tmeda = N,N,N',N'-tetramethylethylenediamine) were determined as their tmeda adducts on the basis of low temperature single crystal X-ray diffraction. (Crystal data: 1: monoclinic, space group P21/n, a = 8.511(5), b = 11.936(2), c = 24.20(1) Å, β = 90.02(3)°, Z = 4.2: monoclinic, space group P21/n, a = 10.887(2), b = 13.326(2), c = 13.131(2) Å, β= 92.872(6)°, Z = 4). In both compounds lithium has a slightly distorted 17 coordination to the cyclopentadienide (Cp) ring. There are no interactions between lithium and the phosphine donors in the solid state as the phosphinomethyl substituents are oriented to the other side of the Cp ring for steric reasons. The isopropene-substituted lithium cyclopentadienide, which is formed as a by-product in the synthesis of phosphinomethyl cyclopentadienides containing a CMe2 bridge, was also structurally characterized as its tmeda adduct [Li(tmeda)][H2C=CMeC5H4] (3). (Crystal data: monoclinic, P21/c, a = 8.00(2), b = 16.701(2), c = 11.942(6) Å, β= 112.68(7)°, Z = 4). As in 1 and 2, lithium is η5 -coordinated to the Cp ring, and there is no interaction of the functional group (isopropene) with lithium.