Synthesis and reactivity of the TlI salts of [TCNE].- and [TCNE] 2-: The structural determination of TlI[TCNE] and [TDAE][TCNE]2 and evidence for a chelated [TCNE].-

Abstract

Synthons TlI[TCNE].- (1) and TlI2[TCNE]2- (2), for [TCNE].- and [TCNE]2-, respectively, in metathesis reactions have been quantitatively prepared and characterized. The structure of 1 was solved and refined in a monoclinic unit cell at 27°C [C2/c, a=12.6966 (12) Å, b=7.7599 (7) Å, c=15.5041 (15) Å, β=96.610 (5)°, V=1517.4 (2) Å3, Dcalcd=2.911 g cm-3, Z=8, R1= 0.0575, wR2=0.0701] and exhibits vCN absorptions at 2191 (s) and 2162 (s) cm-1 consistent with metal-bound [TCNE].-. The structure of 1 consists of a distorted square antiprismatic octacoordinate TlI bound to six monodentate [TCNE].-s with TlN separations ranging from 2.901 to 3.171 Å averaging 3.020 Å, and one bidentate [TCNE].- with TlN separations averaging 3.279 Å. The TlN bonding is attributed to electrostatic bonding. The [TCNE].-s form dimerized zigzag chains with intra- and interdimer separations of 2.87 and 3.29 Å, respectively. The tight π-[TCNE]22- dimer is diamagnetic and has the shortest intradimer [TCNE].- distance reported. These synthons for [TCNE].- and [TCNE]2- in metathesis reactions lead to the precipitation of, for example, TlIX (X=Cl, Br, OAc). Reaction of 1 with MnIII(porphyrin)X (X=Cl, OAc) forms the molecule-based magnets of [MnIII(porphyrin)]-[TCNE] composition, while the reaction of [CrI(C6H6)2]Br and (Me2N)2CC-(NMe2)2Cl2, [TDAE]Cl2, with 1 forms [CrI(C6H6)2][TCNE] and [TDAE]-[TCNE]2, respectively. The structure of [TDAE][TCNE]2·MeCN was solved and refined in an orthorhombic unit cell at 21°C [I222, a=10.2332(15), b= 13.341(6), c=19.907(8) Å, V=2717.7 Å3, Z=4; Dcalcd=1.216 g cm-3, R=0.083, Rw=0.104] and exhibits vCN absorptions at 2193 (m), 2174 (s), and 2163 (s) cm-1 consistent with isolated [TCNE]22-, in contrast to the aforementioned TlI bound [TCNE]22-. The reaction of 2 with [TDAE]Cl2 forms [TDAE]2+[TCNE]2-.