η³-Propargyl/Allenyl Complexes of Platinum and Palladium of the Type [(PPh₃)₂M(η³-CH₂CCR)]⁺

Abstract

A study is reported on the synthesis, spectroscopic properties, molecular structure, and reaction chemistry of η3-propargyl/allenyl complexes of platinum and palladium of the type [(PPh3)2M(η3-CH2CCR)]+ (M = Pt, R = Ph (1a), Me (1b); M = Pd, R = Ph (2a), Me (2b)). Complexes 1a,b were obtained by each of the following methods: (i) reaction of trans-(PPh3)2PtBr(η1-CH2C⋮CPh) with AgO3SCF3; (ii) treatment of (PPh3)2Pt(η2-PhC⋮CCH2OMe) with BF3·OEt2; (iii) addition of RC⋮CCH2OS(O)2C6H4Me-p to (PPh3)2Pt(η2-C2H4) in solution. Complexes 2a,b resulted upon (i) abstraction of Br- from trans-(PPh3)2PdBr(η1-CH2C⋮CR)/trans-(PPh3)2PdBr(η1-C(R)CCH2) with AgBF4 and (ii) treatment of Pd2(dba)3·CHCl3 with PPh3 and RC⋮CCH2OS(O)2C6H4Me-p. The structures of 1a(OTf)·CH2Cl2 (Tf = O2SCF3) and 2a(BF4) were determined by X-ray diffraction techniques. Both cationic metal complexes show remarkably similar structures, the salient features being the attachment to the metal of all three propargyl/allenyl carbon atoms of the nonlinear C3 fragment (C(1)−C(2)−C(3) bond angles: 152.2(9)° for 1a, 154.7(5)° for 2a) and the essentially coplanar arrangement of the three carbon, two phosphorus, and platinum or palladium atoms. 1a,b react readily with MeOH and Et2NH to afford the corresponding complexes [(PPh3)2Pt(η3-CH2C(X)CHR)]+ (X = OMe, NEt2); 2a,b behave analogously, except that the reaction with MeOH requires trace amounts of NaOMe or NEt3. 1H and 13C NMR spectroscopic data suggest that the reaction products are best formulated as resonance hybrids of η3-allyl and metallacyclic structures.

Palladium‐Catalyzed Annulation of Aryl‐1,2‐diols and Propargylic Carbonates. Theoretical Study of the Observed Regioselectivities

“…The same kind of structure has been obtained for propargyl/ allenyl complexes of other metals such as Pt [36] and Re. [28] A molecular orbital description with FenskeϪHall and DFT Such allenyl/propargyl complexes are easily attacked by nucleophiles, including alcohols, amines, carbanions, etc.…”

“…In some cases, the transfer of the proton from the nucleophile NuH to the terminal carbon atom has been found to be stereospecific, the syn or anti conformation of the final η 3 -allylic complex depending on the nature of the nucleophile (amine or alcohol). [36] Our case is different, since the proton adds to the nonsubstituted carbon atom C 1 , whereas in the literature this carbon atom carries a substituent instead of a hydrogen atom. A question therefore arises: in which relative position, cis or anti, are the methyl group carried by C 3 and the catecholate part fixed on C 2 ?…”

3-(o-Trifluoroacetamidoaryl)-1-propargylic esters: common intermediates for the palladium-catalyzed synthesis of 2-aminomethyl-, 2-vinylic, and 2-alkylindoles

“…2-Aminomethylindoles were purified by flash chromatography, using basic Al 2 O 3 Brockmann activity II (Fluka) as stationary phase, eluting with n-hexane/AcOEt mixtures. 1 H NMR (400.13 MHz) and 13 C NMR (100.6 MHz) and 19 F NMR (376.5 MHz) spectra were recorded with a Brü ker Avance 400 spectrometer. Infrared (IR) spectra were recorded on a JASCO FT/IR-430 spectrophotometer.…”

η3-Propargyl complexes of molybdenum, tungsten, and rhenium

“…A DRL-125 immersion lamp was used for UV irradiation. IR spectra were recorded in solutions on a Specord IR-75 spectrophotometer (r!3-2-Hydroxyallyl)dicarbonylO16-hexametbylbenzene) -molybdenum tetrafluoroborate (9). A mixture of compounds 8e and 9 (0.08 g) was obtained similarly from tricarbonyl(TI6-hexamethylbenzene)molybdenum (0,15 g, 0.44 mmol), propargyl alcohol (0.2t mL, 0.2 g, 3.5 mmol), and 48% aqueous HBF 4 (0.13 g, 1.76 mmol, d = 1.3 gcm -3) in ether (170 mL), the ratio 8c : 9 = 73 : 27 (according to the IH NMR spectra).…”