Investigation of Isomer Formation of Triorganotin(IV) Complexes Involving Diorganophosphino-N-Phenyl(Thioformamide) Ligands: The Crystal and Molecular-Structure of [Diphenylphosphino-N-Phenyl(Thioformamido)]Triphenyltin, Ph₃Sn[Ph₂PC(S) NPh ]

Abstract

The isomer of Ph₃Sn[Ph₂PC(S) NPh] formed depends on the method of preparation. The crystal and molecular structure of the tin(IV) complex Ph₃Sn[Ph₂PC(S) NPh ] has been established by single-crystal X-ray diffraction techniques. The crystals are monolinic, space group P2₁/n, a 12.620(2), b 10.541(2), c 24.292(4)Ǻ, β 96.90(1) with Z 4; R and Rw were 0.031 and 0.034 respectively for 5632 unique reflections with I > 3σ(I). The crystals consist of discrete Ph₃Sn[Ph₂PC(S) NPh ] molecules. There is a tetrahedral environment about the tin atom formed by the three phenylic carbons and a sulfur atom of the [Ph₂PC(S) NPh ]^- ligand . Comparisons are made with the structurally similar compound Ph₃Sn[(c-C₆H₁₁)₂PC(S) NPh ]. On the basis of these comparisons and on earlier n.m.r . data, a favoured four-centered mechanism for insertion of dipolar PhNCS into the tin-phosphorus bond of Ph₃SnPPh₂ is inferred. Differences in reactivity of Ph₂PC(S)N(H)Ph and (c-C₆H₁₁)₂PC(S)N(H)Ph appear to result from electronic rather than steric effects.