Reactivity of 2-chalcogenopyridines with palladium–phosphine complexes: isolation of different complexes depending on the nature of chalcogen atom and phosphine ligand

Abstract

Reactions of either Pd(0) phosphine complexes with dipyridyldichalcogenides or [PdCl2(P∩P)] (P∩P = dppe, dppp) with pyridylchalcogenolate ions have been examined and a variety of Pd(II) complexes have been isolated and characterized. Oxidative addition of {SeC5H3(3-R)N}2 (R = H or Me) to [Pd(P∩P)2] (P∩P = dppe, dppp) gave either a mononuclear complex, [Pd{2-Se-C5H3(3-R)N}2(P∩P)] (for P∩P/R: dppe/H or Me; dppp/H) or a cationic binuclear complex, [Pd2{μ-SeC5H3(3-Me)N}2(dppp)2]2+ (4b) (R = Me) whereas reactions involving the tellurium analogue exclusively afforded trinuclear complexes, [Pd3(μ-Te)2(P∩P)3]Cl2 (P∩P = dppe (2) or dppp (6)). The latter was also obtained in the substitution reaction between [PdCl2(P∩P)] and NaTeC5H3(3-R)N. The substitution reactions between [PdCl2(dppe)] and Pb{EC5H3(3-R)N}2 yielded mononuclear complexes, [Pd{2-E-C5H3(3-R)N}2(dppe)] (1a–1e) (E = S, Se or Te) while in the case of [PdCl2(dppp)], the reactions resulted in the formation of mono-, bi- and tri- nuclear complexes depending on the nature of the chalcogen atom (E = S, Se or Te) and the substituent on the pyridyl ring (R = H or Me). Treatment of dipyridyl ditellurides, {TeC5H3(3-R)N}2 (R = H or Me), with [Pd(PPh3)4] gave expected tellurolate complexes, [Pd{2-TeC5H3(3-R)N}2(PPh3)2] (7a, 7b) which on prolonged standing in CDCl3 solution gave green crystals of [PdCl{2-Te(Cl)2C5H3(3-Me)N}(PPh3)] (9). The molecular structures of {TeC5H3(3-Me)N}2, [Pd2{μ-TeC5H3(3-Me)N}2(dppp)2]Cl2·3H2O (5·3H2O), [Pd3(μ-Te)2(dppp)3]Cl2·3CHCl3 (6·3CHCl3) and [PdCl{2-Te(Cl)2C5H3(3-Me)N}(PPh3)] (9) were established by single crystal X-ray diffraction analyses.

Supramolecular Pt and Pd Complexes of 4,4′‐Dipyridylditelluride/Diselenide Ligands through Self‐Assembly

“…All of the six Pd–Te bond lengths are almost equal (2.61 Å) and are comparable with the reported structures. Two of the Pd ··· Pd distances are the same (3.36 Å) as observed in [Pd 3 (µ‐Te) 2 (dppp) 3 ]Cl 2 , but the other distance (Pd1 ··· Pd3: 3.31 Å) is slightly shortened. The Te ··· Te separation (3.52 Å) is greater than that in [Pd 3 (µ‐Te) 2 (dppp) 3 ] 2+ (3.32 Å) and [Pd 2 (µ‐Te) 2 (dppe) 3 ] 2+ (3.32 Å) .…”

“…Two of the Pd ··· Pd distances are the same (3.36 Å) as observed in [Pd 3 (µ‐Te) 2 (dppp) 3 ]Cl 2 , but the other distance (Pd1 ··· Pd3: 3.31 Å) is slightly shortened. The Te ··· Te separation (3.52 Å) is greater than that in [Pd 3 (µ‐Te) 2 (dppp) 3 ] 2+ (3.32 Å) and [Pd 2 (µ‐Te) 2 (dppe) 3 ] 2+ (3.32 Å) . The increased separation may be explained by the shorter Pd–P bond length (2.27 Å), the smaller P–Pd–P angle (ca.…”

“…The structure of trinuclear complex [Pd 3 (µ 3 ‐Te) 2 (dppe) 3 ](OTf) 2 , 10 , looks very similar to other ionic clusters of the type [M 3 (µ 3 ‐E) 2 (P ∩ P) 3 ] 2+ (M = Pd, Pt; E = S, Se, Te; P ∩ P = dppm, dppe,, dppp, ), with respect to its bonding and shape. The structure is comprised of three square‐planar cis ‐“Pd(dppe)” units, bridged by two µ 3 ‐Te 2– ligands, forming a trigonal bipyramidal Pd 3 Te 2 core.…”

“…The same and similar ionic clusters of the types [M 3 E 2 (dppe) 3 ] 2+ (M = Ni, Pd, Pt; E = S, Se, Te) have been isolated from the reaction of [M II (dppe)(solvent)] 2+ with NaEH . The oxidative addition reaction of diaryldichalcogenide Ar 2 E 2 with deliberately taken [M 0 (PPh 3 ) 4 ] or [M 0 (P ∩ P) 2 ] (P ∩ P = dppe, dppp) also yield similar types of cluster products …”

Reactivity of dipyrimidyldiselenides with [M(PPh3)4] and 2-pyrimidylchalcogenolates with [MCl2(diphosphine)] (M = Pd or Pt)

“…Palladium catalyzed addition of EeE bond to alkyne has emerged an important strategy to prepare vinylsulfides/selenides [9] which find numerous applications in organic synthesis, coordination chemistry and electronics [11e14]. The catalytic reaction proceeds with excellent stereoselectivity and is believed to involve mononuclear cis-[Pd(EAr) 2 (PR 3 ) 2 ] (E ¼ S or Se) complexes [15], although binuclear complexes, [Pd 2 (EAr) 2 (m-EAr) 2 2 (Te)(PPh 3 )] contain Te 0 as a ligand [23], and [Pt{PPh 2 C(TeC 5 H 3 (3-R)N)PPh 2 } 2 ] (R ¼ H or Me) [24] as well as metastable species like [Pd(2-TeC 5 H 4 N) 2 (dppp)] which in chlorinated hydrocarbon solvents solution slowly transformed to a trinuclear product [Pd 3 (m-Te) 2 (dppp) 3 ] 2þ via other intermediate complexes [25]. These reactions have prompted us to examine chemistry of ligand systems where chalcogen carbon is indirectly linked to two heteroatoms, e.g.…”