Monomeric versus dimeric arrangement in the solid-state structures of pyridine adducts of lithium derivatives of two primary phosphanes

The syntheses and X-ray crystal structure determinations of tBu3C6H2P(H)Li(py)3 (1) and [DmpP(H)Li(py)]2 (2) (Dmp=2,6-dimesitylphenyl) are reported. Complex 1 crystallizes in the monoclinic space group P21/c. Crystal data for 1 at 243 K: a=10.574(3); b=16.652(5); c=18.340(13) Å; β=98.62(3)°; V=3193(3) Å3; Z=4; Dcalc=1.085 g cm−3; RF=5.34%. Complex 2 crystallizes in the triclinic space group Crystal data for 2 at 198 K: a=8.7750(4); b=11.3889(5); c=14.3840(7) Å; α=70.8878(12); β=75.9487(8); γ=68.7190(9)°; V=1253.0(2) Å3; Z=1; Dcalc=1.144 g cm−3; RF=9.72%. The molecular structure of monomeric 1 shows a four-coordinate lithium cation in a distorted tetrahedral coordination environment, while the molecular structure of dimeric 2 features formally three-coordinate lithium cations in virtually trigonal-planar coordination environments.