Zusammenfassung
The pnictogen-centered nucleophiles LIE(SiMe3)(2) (E = N, P, or As) substitute a cyclopentadienide ligand of chromocene (Cp2Cr), with elimination of lithium cyclopentadienide, to give the series of pnictogen-bridged compounds [(mu:eta(2):eta(5)-Cp)Cr{mu-N(SiMe3)(2)}(2)Li] (1) and [(eta(5)-Cp)Cr{mu-E(SiMe3)(2)}](2), with E = P (2) or E = As (3). Whereas 1 is a heterobimetallic coordination ...
Zusammenfassung
The pnictogen-centered nucleophiles LIE(SiMe3)(2) (E = N, P, or As) substitute a cyclopentadienide ligand of chromocene (Cp2Cr), with elimination of lithium cyclopentadienide, to give the series of pnictogen-bridged compounds [(mu:eta(2):eta(5)-Cp)Cr{mu-N(SiMe3)(2)}(2)Li] (1) and [(eta(5)-Cp)Cr{mu-E(SiMe3)(2)}](2), with E = P (2) or E = As (3). Whereas 1 is a heterobimetallic coordination polymer, 2 and 3 are homometallic dimers, with the differences being due to a structure-directing influence of the hard or soft character of the bridging group 15 atoms. For compound 1, the experimental magnetic susceptibility data were accurately reproduced by a single-ion model based on high-spin chromium(II) (S = 2), which gave a g-value of 1.93 and an axial zero-field splitting parameter of D = 1.83 cm(-1). Determinations of phosphorus- and arsenic-mediated magnetic exchange coupling constants, J, are rare: in the dimers 2 and 3, variable-temperature magnetic susceptibility measurements identified strong antiferromagnetic exchange between the chromium(II) centers, which was modeled using the spin Hamiltonian H = -2J (S-Cra.S-CrB), and produced large coupling constants of J = -166 cm(-1) for 2 and -77.5 cm(-1) for 3.
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