Syntheses and reactivity of pentachlorophenylpalladium(I) derivatives. Molecular structure of Pd2(μ-dppm)2(C6Cl5)2 (original) (raw)
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Structural and reactivity comparison of analogous organometallic Pd(iii) and Pd(iv) complexes
Dalton Transactions, 2012
All operations were performed under a nitrogen atmosphere using standard Schlenk and glove box techniques if not indicated otherwise. All reagents for which the syntheses are not given were purchased from Sigma-Aldrich, Acros, STREM, or Pressure Chemical and were used as received without further purification. Solvents were purified prior to use by passing through a column of activated alumina using an MBRAUN SPS. 2,11diaza[3,3](2,6)pyridinophane (H N4), 1 N,N'-methyl-2,11-diaza[3,3](2,6)pyridinophane (Me N4), 1 (PhCN)Pd II Cl 2 , 2 (COD)Pd II Cl 2 , 3 (COD)Pd II MeCl, 4 and (Me 2 S) 2 Pd II Cl 2 5 were prepared according to literature procedures. The synthesis and characterization of complexes (tBu N4)PdMeCl, (tBu N4)PdMe 2 , [(tBu N4)Pd III MeCl] + , and [(tBu N4)Pd III Me 2 ] + were reported previously. 6 NMR spectra were obtained on a Varian Mercury-300 spectrometer (300.121 MHz) or a Varian Unity Inova-600 spectrometer (599.746 MHz). Chemical shifts are reported in parts per million (ppm) with residual solvent resonance peaks as internal references. 7 Abbreviations for the multiplicity of NMR signals are singlet (s), doublet (d), triplet (t), quartet (q), septet (sep), multiplet (m), broad resonance (br). Solution magnetic susceptibility measurements for Pd III complexes were obtained at 293 K by the Evans method 8 using coaxial NMR tubes and CD 3 CN as solvents, and the corresponding diamagnetic corrections were included. 9 UV-visible spectra were recorded on a Varian Cary 50 Bio spectrophotometer and are reported as max , nm (, M-1 *cm-1). EPR spectra were recorded on a JEOL JES-FA X-band (9.2 GHz) EPR spectrometer in PrCN-MeCN (3:1) at 77 K. ESI-MS experiments were performed using a linear quadrupole ion trap Fourier transform ion cyclotron resonance mass spectrometer (LTQ-FTMS, Thermo, San Jose, CA) or a Bruker Maxis Q-TOF mass spectrometer with an electrospray ionization source. ESI mass-spectrometry was provided by the Washington University Mass Spectrometry Resource. Elemental analyses were carried out by the Columbia Analytical Services Tucson Laboratory. Electrochemical measurements Cyclic voltammetry (CV) studies were performed with a BASi EC Epsilon electrochemical workstation or CHI Electrochemical Analyzer 660D. Electrochemical grade Bu 4 NClO 4 , Bu 4 NPF 6 , or Bu 4 NBF 4 from Fluka were used as the supporting electrolytes. The electrochemical measurements were performed under a blanket of nitrogen, and the analyzed solutions were deaerated by purging with nitrogen. A glassy carbon disk electrode (GCE) was used as the working electrode, and a Pt wire as the auxiliary electrode. The non-aqueous Ag-wire reference electrode assembly was filled with 0.01 M AgNO 3 /0.1 M Bu 4 NClO 4 /MeCN solution. The reference electrodes were calibrated against ferrocene at the end of each CV measurement.
Organometallics, 1992
A series of complexes of unusually stable alkylpalladium complexes of the formula (Me2NCS2)Pd-(PR&alkyl) (R = Me, Et) have been prepared from the reaction of (Me2NCSJPd(PFtJC1 and the appropriate alkyllithium or Grignard reagent. The substituted complexes (Me2NCS2)Pd(PEt3) (CH2CH2CF3) and (Me2NCS2)Pd(PEt3) (CH2CH2CN) were prepared in similar reactions, and the isomer of the latter, (Me2NCS2)Pd(PEt3)(CH(CN)CH3), was prepared from the low-temperature, in situ reaction of (Me2NCS2)Pd(PEt3)H and CH2CHCN. The reaction of (Me2NCS2)Pd(PEt3)Cl with Li[C(CH3),]CuCN gives a color change indicative of the formation of the alkylpalladium complex, but this tert-butyl compound decomposes above -40 OC with the formation of its isomer, (Me2NCS2)Pd(PEt3)(CH2CH(CH3)2). With this one exception, all of these complexes are extremely stable, especially the substituted alkyl complexes, which can be heated over 100 O C in solution for extended periods without noticeable decomposition. Heating the unsubstituted isomers at 75 OC in solution leads to isomerization of the alkyl ligand. For example, heating either (Me2NCS2)Pd(PEt3)(CH2CH2CH3) or (Me2NCS2)Pd(PEt3)(CH(CH3),) leads to a 1O:l.O equilibrium mixture, respectively, of the two. An equilibrium mixture of 101.0 is found for the other alkyl ligands studied. This 1.6 kcal/mol difference between the isomers is proposed to be the difference in energy between secondary versus primary alkylmetal complexes in the absence of steric constraints imposed by other ligands in the coordination sphere. At 120 OC, the primary isomer (Me2NCS2)Pd isomerizes completely to the secondary isomer (Me2NCS2)Pd(PEt3)(CH(CN)CH3), whereas (Me2NCS2)-Pd(PE&J(CH2CH2CF3) isomerizes to a 1:l mixture with its secondary isomer. The alkyl ligand in (Me2NCS2)Pd(PEt3)(CH(CH3)2) exchanges with 1-hexene to yield an isomeric mixture of all three (Me2NCS2)Pd(PEt&hexyl) isomers. This reaction is only successful for monosubstituted alkenes. Kinetic studies of the alkyl isomerization reaction show that it is first order and that Lewis bases, especially added PEt3, substantially slow the reaction. It has also been shown that the free and complexed PEt, exchange rapidly. The structure of ((CH2),NCS2)Pd(PEt,)(CH(CN)CH3) has been determined by X-ray crystallography. Crystal data: triclinic, PI, a = 11.865 3) A, b = 16.003 (5) A, c = 10.060 (3) A, a = 93.45 (3)O, fl = 91.27 (3)O, y = 101.08 (3)O, V = 1870 A3, 2 = 4, RF = 4.1%, and RwF = 5.8%. There are no obvious structural features in the standard square planar geometry of this compound that indicate why the cyanide substituent stabilizes this branched isomer in favor of the linear isomer.
Organometallic Complexes of Palladium(II) Derived from 2,6-Diacetylpyridine Dimethylketal
Organometallics, 2010
PdCl 2 reacts with 2,6-diacetylpyridine (dap) (1:1) in refluxing MeOH to give the pincer complex [Pd(O 1 ,N 1 ,C 1 -L)Cl] (1) and (QH) 2 [{PdCl 2 ( μ-Cl)}] 2 (2), where L is the monoanionic ligand resulting from deprotonation of the acetyl methyl group of the monoketal of dap and QH is C 5 H 3 NH{C-(OMe) 2 Me} 2 -2,6, the diketal of Hdap þ . Reaction of 2 with NEt 3 (1:2) in MeOH affords Q = C 5 H 3 N{C(OMe) 2 Me} 2 -2,6 (3). Complex 1 reacts with 2 equiv of RNC at 0°C to give trans-[Pd(C 1 -L)Cl(CNR) 2 ] (R = Xy = 2,6-dimethylphenyl (4a), t Bu (4b)) but at room temperature affords [Pd(O 2 , C 2 -L R )Cl(CNR)] (R = Xy (5a), t Bu (5b)). The ligand L R results from the insertion of one isocyanide into the Pd-C bond plus a tautomerization process from β-ketoimine to β-ketoenamine and coordinates in 5 through the carbonyl oxygen atom (O 2 ) and the inserted isocyanide carbon atom (C 2 ). The reaction of 1 with 1 equiv of RNC at 0°C leads to a mixture of [Pd(N 1 ,C 1 -L)Cl(CNR)] (R = Xy (6a), t Bu (6b); 85-90%), 1, and 4, but at room temperature gives the pincer complex [Pd(O 1 ,N 1 ,C 2 -L R )Cl] (R = Xy (7a), t Bu (7b)), resulting from insertion/tautomerization processes similar to that leading to 5. Complex 7 reacts at 0°C (1) with 2 equiv of RNC to give trans-[Pd(C 2 -L R )Cl(CNXy) 2 ] (R = Xy (8a), t Bu (8b)) or (2) with 1 equiv of t BuNC to afford 5b. The reaction of 1 (1) with [Tl(acac)] gives [Pd(N 1 ,C 1 -L)(acac)] (9); (2) with chelating ligands N ∧ N affords [Pd(C 1 -L)Cl(N ∧ N)] (N ∧ N = 2,2 0bipyridine = bpy (10), 4,4 0 -di-tert-butyl-2,2 0 -bipyridine = dbbpy (11)); (3) with 1 equiv of PPh 3 gives, in the same way as with isocyanides, an equilibrium mixture of [Pd(N 1 ,C 1 -L)Cl(PPh 3 )] (12), 1, and trans-[Pd(C 1 -L)Cl(PPh 3 ) 2 ] (13), which is the only product when 2 equiv of PPh 3 is added to the reaction mixture; and with excess PPh 3 affords the monoketal of dap, C 5 H 3 N{C(O)Me-2}{C(OMe) 2 Me-6} (14), and [Pd(PPh 3 ) 4 ]. The crystal structures of complexes 1, 2, 5b, 6a, and 7a have been determined. *Corresponding authors. E-mail: jvs1@um.es (J.V.); aurelia@um.es (A.A.). Web: http://www.um.es/gqo/.
Inorganica Chimica Acta, 1983
The complex [PdC13(PPh3)]-[Ph$'(CH2CH2CO-CH,)J+ (I) was prepared by reacting trans-[Pd&-(PPhJJ with CH,COCH,CH,Cl in boiling ethanol. The i.r. spectrum of (I) shows a band of strong intensity at 1717 cm-' for v(~,~, and bands attributable to v(pd__Cl) at 343(s), 301(w) and 277(m) cm-? bonded to the palladium atom but to a phosphorus atom to form the cation [Ph3P(CHZCH2COCHs)]+ which is the counter ion of the anionic complex of palladium(H) [PdCls(PPh,)]-. We present here the X-ray diffraction study of the resulting complex. The crystal and molecular structure of complex (I) has been determined from three-dimensional X-ray diffractometer data. The complex crystallizes in the monoclinic space group P2Jn. Cell parameters are as follows: a = 18.849(9), b = 21.301(9), c = 9.156(7) A, 0 = 92.8(l)=', Z = 4. Full-matrix least-squares refinement converged at R = 0.063 (R W = 0.055). The anion [PdC13(PPh3)]-has approximately square planar geometry. The cation [Ph fl(CH,CH,CO-CH-JJ+ shows the usual angular distortions from the tetrahedral value at the phosphorus atom. Experimental Solvents were purged before use. Trans-[PdCl,-(PPh,),] and [PdCl,(PPhs)] Z were prepared following the procedure reported in the literature [2]. Infrared spectra were recorded with a Perkin-Elmer spectrophotometer Mod. 683 using CsI windows, in nujol mulls.
Journal of Organometallic Chemistry, 2000
The reaction of [Pd(C 6 H 4-2-PPh 2 C(H)COCH 2 PPh 3)(m-Cl)] 2 (ClO 4) 2 (1) with the deprotonating reagent NBu 4 OH (1:2.5 molar ratio, room temperature (r.t.)) and subsequently with monodentate ligands L (1:4 molar ratio) or bidentate ligands L-L (1:2 molar ratio) gives the cationic complexes [Pd(C 6 H 4-2-PPh 2 C(H)COCH PPh 3)(L) 2 ](ClO 4) (L= PPh 3 (2), H 2 NCH 2 CH CH 2 (3)) or [Pd(C 6 H 4-2-PPh 2 C(H)COCH PPh 3)(L L)](ClO 4) (L L=dppm (4), Ph 2 PCH 2 PPh 2 C(H)COPh (5), NC 5 H 4-2-CO N PPh 3 (6)). In complexes 2-6 the orthometallated-ylide ligand is coordinated through the arylic carbon and through one ylidic carbon, and contains a free ylide fragment C(H) PPh 3. The reaction of 1 with NBu 4 OH (1:2.5 molar ratio, r.t.) and with [PPh 2 CH 2 PPh 2 CH 2 COMe]ClO 4 (1:2 molar ratio) gives [Pd(PPh 2 CH 2 PPh 2 CHC(O)Me) 2 ](ClO 4) 2 (7) and the ylide-phosphonium salt [Ph 3 P C(H)COCH 2 PPh 3 ]ClO 4. The reaction seems to occur through protonation of the orthometallated-ylide ligand by the acid protons of the phosphonium unit. All complexes were characterized on the basis of their spectroscopic data.
Inorganica Chimica Acta, 2002
The synthesis of palladacyclopentadiene derivatives with the mixed-donor bidentate ligands o-Ph 2 PC 6 H 4 CH NR (N P) has been achieved. The new complexes of general formula [Pd{C 4 (COOMe) 4 }(o-Ph 2 PC 6 H 4 CH NR)] [R=Me (1), Et (2), i Pr (3), t Bu (4), NH Me (5)] have been prepared by reaction between the precursor [Pd{C 4 (COOMe) 4 }] n and the corresponding iminophosphine. The polymer complex [Pd{C 4 (COOMe) 4 }] n also reacts with pyridazine (C 4 H 4 N 2) to give the insoluble dinuclear complex [Pd{C 4 (COOMe) 4 }(m-C 4 H 4 N 2)] 2 (6), which has been successfully employed as precursor in the synthesis of pyridazine-based palladacyclopentadiene complexes. The reaction of 6 with tertiary phosphines yielded complexes containing an N,P-donor setting of formula [Pd{C 4 (COOMe) 4 }(C 4 H 4 N 2)(L)] (L =PPh 3 (7), PPh 2 Me (8), P(p-MeOC 6 H 4) 3 (9), P(p-FC 6 H 4) 3 (10)). The new complexes were characterized by partial elemental analyses and spectroscopic methods (IR, 1 H, 19 F and 31 P NMR). The molecular structure of complex 3 has been determined by a single-crystal diffraction study, showing that the iminophosphine acts as chelating ligand with coordination around the palladium atom slightly distorted from the square-planar geometry.
Journal of Organometallic Chemistry, 1985
The preparations of the complexes truns-[Pd{C(C,F,)=N(Ri)}C1(CNR2)2] and [Pd{C(C,F,)=N(Ri)}(CNR2),]X (R' = Me, p-Tol; R2 = Me, p-Tol, Bu'; X = ClO, or BPh,) from [Pd,{ ~-C(C6F5)N(Ri)}2C12(CNR2)2] are described. The splitting of the imidoyl bridges is accompanied by an isomerization of the imidoyl group from the syn to the anti conformation as shown by a single crystal X-ray diffraction study of truns-[Pd{C(C,F,)=N(Me)}Cl(CNMe),]. Attempted preparations of [Pd{C-(C,F,)=N(R')}Cl(PPh,),] from [Pd,{ ~-C(C6F5)=N(R)}2C12(PPh,)2] led to elimination of CNR and formation of truns-[Pd(C,F,)Cl(PPh,),]; this is the first example of isonitrile elimination in palladium chemistry. * Further crystallographic details (structure factors, H atom coordinates, temperature factors) can be ordered from the Fachinformationszentrum Energie Physik Mathematik, D-7514 Eggenstein-Leopoldshafen 2, F.R.G. Please quote reference number CSD/51200 and the full literature citation.