Bis(allenylidene) Complexes of Palladium and Platinum

Abstract

trans-Bis(alkynyl)palladium complexes, trans-[(PEt 3) 2 Pd(-CtCC{dO}NR 2) 2 ] (NR 2 = NMe 2 (2a), N(CH 2) 4 (2b)), were synthesized by two different methods: (a) by copper-catalyzed reaction of HCtCC(dO)NR 2 with [PdCl 2 (PEt 3) 2 ] under basic conditions and (b) by treating HCtCC(dO)NR 2 with AgNO 3 followed by transmetalation of the alkynyl ligand from silver to [PdCl 2 (PEt 3) 2 ]. The reaction of AgCtCC(dO)NMe 2 (3a) with trans-[Br(P i Pr 3) 2 PdCtCC(dO)N(CH 2) 4 ] (5) affords a complex containing two different alkynyl ligands, trans-[(P i Pr 3) 2 Pd{-CtCC(dO)NMe 2 }{-CtCC-(dO)N(CH 2) 4 }] (6). Methylation of 2a,b and 6 with MeOTf or [Me 3 O]BF 4 yields dicationic bisallenylidene complexes of palladium, trans-[(PEt 3) 2 Pd{dCdCdC(OMe)NR 2 } 2 ] 2þ 2X (X = OTf, BF 4 ; NR 2 = NMe 2 , N(CH 2) 4) and trans-[(PEt 3) 2 Pd{dCdCdC(OMe)NMe 2 }{dCdCdC-(OMe)N(CH 2) 4 }] 2þ 2OTf (7-OTf). In contrast to the reaction of 3a with [PdCl 2 (PEt 3) 2 ], that of 3a with the platinum complex [PtCl 2 (PPh 3) 2 ] gives cisand trans-[(PPh 3) 2 Pt(-CtCC{dO}NMe 2) 2 ] (8a (cis) and 9a (trans)), depending on the reaction conditions and, upon subsequent alkylation with MeOTf, the cis and trans isomers of the first allenylidene platinum complexes, cisand trans-[(PPh 3) 2 Pt{dCdCdC(OMe)NMe 2 } 2 ] 2þ 2OTf .

Synthesis, characterization and palladium complex formation of pyridinium- and quinolinium-3-acetylides: mesomeric betaines or betaine-stabilized carbenes?

“…39 In addition, a triplet of the C^CePd (d¼108.1 ppm) carbon atom is visible in the 13 C NMR spectra of 18 (J PC ¼3.85 Hz) which confirms that the two phosphine ligands are mutually trans. 48,49 This value is in agreement with literature known trans-[bis(3-(pentamethyleneamino)-3-methoxy-1,2-propadienylidene)bis (triethylphoshine)palladium(II)] alkynyl complexes (d¼104.3 ppm 46 ), and is shifted downfield in comparison to their corresponding allenylidene complexes (d¼97.3 ppm 46 ). In the IR spectra one band of the C^C-stretching vibration is detected at 2104 cm À1 , and the anion hexafluorophosphate can be seen by a signal at d¼À144.5 ppm in the 31 P NMR spectrum.…”

“…It is literature-known that the 13 C NMR detection in related complexes is difficult or impossible. 39,47,49 …”

Isolation of cationic and neutral (allenylidene)(carbene) and bis(allenylidene)gold complexes

“…To our delight, this complex undergoes a dismutation reaction, affording bis(triphenylphosphine)gold( i ) along with the bis(allenylidene)gold( i ) complex 8 , which was isolated in 11% yield as a moisture and air stable solid ( Scheme 2 ). So far, only bis(allenylidene) complexes of Ag, 6 Pd, 6 , 18 Pt, 18 and Ru 16 have been isolated. 1 H and 13 C NMR spectroscopy of 8 clearly shows a symmetrical structure.…”

Molecular and Crystal Structure of Chlorido[2-(N,N,N',N'- tetramethylamidinio)ethynido]silver

“…Conductivity measurements gave similar results as those reported above. We therefore assume that analogous equilibria exist in both cases; however, while in our study the 1 : 1 complex 3 was found in the solid state, (4). Symmetry transformation used to generate equivalent atoms (Cl , Ag ): −x + 1, −y + 2, −z + 1. a 2 : 2 ion-pair complex analogous to 2B was obtained in the reported case [26].…”

“…In another related study, Fischer and coworkers [4] have prepared Pd(II) complexes 7 with two 3-alkoxy-3-dialkylaminoallenylidene ligands (or zwitterions − C≡C-C + (OR)(NR 2 ), depending on the point of view). Based on certain NMR and IR data, these authors have emphasized the strong contribution of the alkynyl-type resonance form to the bonding in these so-called bis(allenylidene) complexes.…”