Inorganic Chemistry, Vol.41, No.8, 2260-2265, 2002
Stabilization of the P(CF3)(2)(-) ion as a reversible CS2 adduct, [P(CF3)(2)CS2](-), and its potential use as a nucleophilic P(CF3)(2)(-) source: Synthesis and structure of [18-Crown-6-K][P(C6F5)(2)CS2]
The bis(trifluoromethyl)phosphanide ion, P(CF3)(2-), decomposes slowly above -30 degreesC in CH2Cl2 and THF solution, An increase of the thermal stability of the P(CF3)(2) moiety is observed if excess CS2 is added. The P(CF3)(2)-moiety is stabilized because of the formation of the bis(trifluoromethyl)phosphanodithioformate anion. Solutions of a [P(CF3)(2)CS2](-) salt still act as a source of P(CF3)(2-), even in the presence of excess Of CS2. The stable compound [18-crown-6-K][P(CF3)(2)CS2] was characterized by multinuclear NMR spectroscopy, elemental analysis, and vibrational spectroscopy in combination with quantum chemical calculations. The thermally unstable P(C6F5)(2) ion decomposes even at -78 degreesC in solution giving polymeric material. The intermediate formation of the bis(pentafluorophenyl)phosphanide anion in the presence of excess Of CS2 allows the isolation of [18-crown-6-K][P(C6F5)(2)CS2]. The novel compound crystallizes with one solvent molecule CH2Cl2 in the monoclinic space group P2(1)/n with a = 1151.8(1) pm, b = 1498.1(2) pm, c = 2018.2(2) pm, beta = 102.58(1)degrees, and Z = 4. Optimized geometric parameters of the [P(C6F5)(2)CS2](-) ion at the B3PW91/6-311G(d) level of theory are in excellent agreement with the experimental values.