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 (Bu3C6H2P)-Bu-t (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 P2(1)/c. Cr ystal data for 1 at 243 K: a = 10.574(3); b = 16.652(5); c = 18.340(13) Ang strom; beta = 98.62(3)degrees; V = 3193(3) Angstrom (3); Z = 4; D-calc= 1.0 85 g cm (- 3); R-F = 5.34%. Complex 2 crystallizes in the triclinic space g roup P (1) over bar. Crystal data for 2 at 198 K: a = 8.7750(4); b = 11.388 9(5); c = 14.3840(7) Angstrom; alpha = 70.8878(12); beta = 75.9487(8); gamm a = 68.7190(9)degrees; V = 1253.0(2) Angstrom (3); Z = 1; D-calc = 1.144 g cm(-3); R-F = 9.72%. The molecular structure of monomeric 1 shows a four-co ordinate lithium cation in a distorted tetrahedral coordination environment , while the molecular structure of dimeric 2 features formally three-coordi nate lithium cations in virtually trigonal-planar coordination environments . (C) 2001 Elsevier Science B.V. All rights reserved.