A Bis(thiophosphinoyl)methanediide Palladium Complex: Coordinated Dianion or Nucleophilic Carbene Complex?

Abstract

A question of identity: A palladium complex featuring a carbenic S,C,S‐based pincer ligand is reported (see scheme). DFT calculations show that, unlike classical carbene complexes, coordination occurs through donation from a d orbital at the metal into the empty np orbital of the carbene fragment, with the nσ orbital essentially acting as a nonbonding orbital. The complex is shown to have nucleophilic character.

Octahedral Tin(IV) Complexes of the Chalcogen‐Centered Ligands [EC(PPh2S)2]2– (E = S, Se)

“…Leung and co-workers have shown that the reaction of SnCl 4 with the magnesium reagent MgC(PPh 2 S) 2 (THF) 2 produces the tin(IV) complex Sn[C(PPh 2 S) 2 ] 2 , in which the ligand is bonded in a tridentate (S,C,S) fashion to tin. [10] Interestingly, in this work we isolated small amounts of complex 1b from the reaction of the dilithium reagent Li 2 2 ] (EЈ = S, Se) via chalcogen insertion into Pb-C bonds has been reported previously by Leung et al [11] The 31 P NMR spectra of 1b and 1c in CD 2 Cl 2 show a single resonance at δ = 54.9 and 57.6 ppm, respectively, cf. δ = 61.6 for 1a in CD 2 Cl 2 .…”

“…Although heteroleptic complexes with In III [5] and Te IV , [6] as well as monomeric Pb II derivatives, [11] were previously known, the Sn IV examples 1b and 1c represent the first homoleptic complexes of these interesting ligands with p-block metals or metalloids. However, the low isolated yields and detection of the diselenide [{Li(tmeda)}{SeC(PPh 2 S) 2 2-(EЈ = S, Se) with CuCl 2 . [7,8,9] Experimental Section General Procedures: All reactions and manipulations were carried out in an argon atmosphere by using standard Schlenk techniques.…”

“…Three years ago we reported synthesis and X-ray crystal structure of the octahedral tin(IV) complex Sn[SeC(PPh 2 Se) 2 ] 2 (1a), which was obtained unexpectedly from the reaction of SnCl 2 and TMEDA.Li[(H)C(PPh 2 Se) 2 ] via a process that involves selenium-proton exchange as well as a redox transformation. [1] The dianion [SeC(PPh 2 Se) 2 ] 2-in this complex represents a new class of trichalcogenido-centered PCP-bridged ligand.…”

“…[3] To date the synthesis of the all-selenium analogue Li 2 [SeC(PPh 2 Se) 2 ] has proved to be elusive because the generation of the selenium derivative of the Le Floch reagent, i.e. Li 2 [C(PPh 2 Se) 2 ], via double deprotonation of H 2 C(PPh 2 Se) 2 with organolithium reagents is accompanied by P-Se bond cleavage. [4] Preliminary investigations of the metathetical reactions of the new reagents Li 2 [EЈC(PPh 2 S) 2 ] (EЈ = S, Se) with main group metal or metalloid halides have produced heteroleptic complexes of indium(III) and tellurium(IV), [5,6] which have been structurally characterized.…”

“…The potentially wide scope of these tridentate ligands in the coordination chemistry of both main group and transition metals led us to the development of the direct synthesis of the dilithium derivatives of analogous all-sulfur and mixed sulfur/ selenium reagents Li 2 [EЈC(PPh 2 S) 2 ] (EЈ = S, Se) by the reaction of the well-known Le Floch reagent Li 2 [C(PPh 2 S) 2 ] [2] with the appropriate chalcogen. [3] To date the synthesis of the all-selenium analogue Li 2 [SeC(PPh 2 Se) 2 ] has proved to be elusive because the generation of the selenium derivative of the Le Floch reagent, i.e. Li 2 [C(PPh 2 Se) 2 ], via double deprotonation of H 2 C(PPh 2 Se) 2 with organolithium reagents is accompanied by P-Se bond cleavage.…”