Trigonal-Bipyramidal Tin(IV) Complexes Containing Tetradentate Tripodal Tristhiolatophosphine Ligands: Synthesis, Characterization, Crystal Structure, and Transmetalation Reactions

The reactions of the lithium salts of the proligands P(C6H4-2-SH)3 (P(HSH)3), P(C6H3-3-SiMe3-2-SH)3 (P(TMSSH)3),
and P(C6H3-5-Me-2-SH)3 (P(MeSH)3) with RSnCl3 (R = Ph, Me, n-Bu), in THF at 0 °C, produced a series of
trigonal-bipyramidal complexes of the type RSn(PS3). The crystal structures of PhSn(PHS3), PhSn(PTMSS3), and
PhSn(PMeS3) reveal considerable distortion from local C3v symmetry for the Sn(PS3) group. Unique to PhSn(PMeS3)
is the presence of intramolecular hydrogen bonding between one sulfur atom and an ortho H atom of the Ph
group, creating a plane that includes this S atom and the corresponding C6H3 ring, a phosphorus atom, and the
PhSn group. An analysis of the 1H, 13C, and 31P NMR data from a combination of HMQC, HMBC, 2-D COSY, and
1H{31P} NMR studies reveals that in solution the Sn(PS3) groups exhibit local C3v symmetry, even at low temperature.
Byproducts frequently found in the synthesis of the proligands and tin complexes, and subsequent reactions, result
from the oxidation of the trianionic tristhiolatophosphine ligand. The crystal structure of one of these, [OP(HS3)]2,
shows that the molecule contains two ligands joined by a S−S bond. Within each original ligand the remaining two
sulfur atoms form a S−S bond, and each phosphorus atom is oxidized. PhSn(PTMSS3) reacted with 2 equiv of FeCl3
in CH2Cl2 to produce the iron(IV) complex FeCl(PTMSS3). FeCl(PTMSS3) decomposed in the presence of excess
FeCl3. Similar transmetalation reactions with FeCl2 or [Fe2OCl6]2- required the addition of ferrocenium ion to complete
the oxidation of iron to 4+. RuCl(PTMSS3) was prepared by the reaction between PhSn(PTMSS3) and RuCl2(DMSO)4
without the addition of an external oxidizing agent.