C.J. Elsevier

Insertion reactions involving palladium complexes with nitrogen ligands I. Reactivity towards carbon monoxide of methylpalladium(II) complexes containing bidentate α-diimine ligands: crystal structures of four methylpalladium(II) and acylpalladium(II) complexes

Abstract Neutral compounds of the type (2,2′-bipyridine)Pd(CH3)(Cl) and 6-R′C5H3N-2-C(H)=NR)Pd(CH3)(Cl) ( R = i Pr ; R ′ = H : i Pr  PyCa ) ( R = t Bu ; R ′ = H : t Bu-PyCa ) ( R = i Pr ; R ′ = CH 3 : i Pr -6- Me  PyCa ) (R = CH2CH2C6H5;R′ = H: PhePyCa) ( R = t Bu ; R ′ = CH 3 : t Bu -6- Me  PyCa ) ( R = i Pr ; R′ = C ( H ) O : i Pr  IPA ) have been synthesized starting from (1,5-cyclooctadiene)Pd(CH3)(Cl) and ionic compounds of the type [(N-N)Pd(CH3)]BF4 (NN = bipy, iPrPyCa, tBuPyCa or iPr-6-MePyCa) by treatment of the methyl(chloro)palladium compounds with silver tetrafluoroborate. All products have been characterized by spectroscopic methods. Reaction of the compounds with carbon monoxide gives that neutral acyl compounds (NN)Pd(C(O)CH3)(Cl) and ionic acyl compounds [(NN)Pd(C(O)CH3)]BF4 (NN = bipy, iPrPyca, tBuPyCa, iPr-6-MePyCa or PhePyCa). The crystal structures of (iPr-6-MePyCa)Pd(CH3)(Cl), (iPrIPA)Pd(CH3)(Cl), (bipy)Pd(C(O)CH3)(Cl) and (iPrPyCa)Pd(C(O)CH3(Cl), have been determined. Comparison of data for the PdNCC5H4N moieties of the complexes concerned show that the geometries are almost identical, the largest r.m.s. deviation (between (iPr-6-MePyCa)Pd(CH3)(Cl) and (bipy)Pd(C(O)CH3)(Cl)) being 0.2 A. The PdC bond distances in the two acetylpalladium complexes are 0.05 A shorter than those in the two methylpalladium complexes. The PdN bond distances for the nitrogen atoms situated trans to the organic group are shorter by 0.11 A in the case of acetyl ligands. An unprecedented influence of the steric properties of the ligands on the half-life for the CO insertion is observed; substituents adjacent to the nitrogen donor atoms cause strongly acceleration.

Reactions of bis(iminophosphoranes) with palladium(II) dichloride: Metal-induced tautomerization orthopalladation and unexpected platinum-assisted [2 + 2] cycloaddition of an aryl-nitrile with a phosphinimine moiety

Reactions of bis(iminophosphoranyl)methane, CH 2 (PPh 2  N-aryl) 2 , (BIPM; 1a,b ) or 1,1-bis(iminophosphoranyl)ethane (1,1-BIPE; 1e ) with Pd- and Pt-dichlorides containing weakly coordinating ligands (L) such as nitriles or cyclo-octadiene, afforded several products depending on the reaction time, type of ligand ( 1a-c ) or nature of the metal. The first reaction observed is a metal-assisted tautomerization of BIPM to aryl-NPPh 2 CHPPh 2 NH-aryl. When BIPM reacts with PdCl 2 (L) 2 , exclusive formation of the C , N -chelate PdCl 2 {CH(PPh 2  N-aryl)(PPh 2 NHaryl)} ( 2a,b ) is observed, whereas with 1,1-BIPE ( 1c ) a product mixture consisting of C , N -chelate ( 2c ) and an N , N ′-chelate ( 3 ) is found. Orthometallation of the four-membered palladacycle ( 2 ) took place upon heating. giving the five-membered palladacycle [PdCl 2 {2-C 6 H 4 -PPh(NH[-pTol)-C′H-PPh 2 (NH-pTol)})- C , C ′] ( 4 ). The molecular structure of 4 has been determined by X-ray crystallography. Reactions of BIPM ( 1a,b ) with PtCl 2 (RCN) 2 (Rphenyl, p -tolyl) affored entirely different products: the six-membered platinacycles [PtCl(RCN)(arylN(R)NPPl 2 CHPPb 2 NHaryl)- C , N ]Cl ( 5 ) and [PtCl 2 (arylNC(R)NPPh 2 NHaryl]- C , N ] ( 6 ), due to an unexpected 2 + 2 cycloaddition of a nitrile with a PN group.

Preparation and crystal structure of [Rh(COD)(p-tolyl-NPPh2CHPPh2NH-p-tolyl)]-[Rh(COD)Cl2]. A rhodium(I) complex containing a new σ-N,σ-C-chelating iminophosphoranylmethanide ligand

Reaction of the bis(iminophosphoranyl)methane [(p-tolyl-NPPh2)2CH2] with [RhL2Cl]2 (L = CO or L2 = COD) yields two different types of compounds. In one of these the bis(iminophosphoranyl)methane ligand is coordinated in a σ-N,σ-N′-chelating mode to form a six-membered metallaheterocycle, whereas in the other the ligand is coordinated in a σ-N,σ-C-chelating mode to form a novel four-membered ring. The solid state structure of [Rh(COD)(p-tolyl-NPPh2CHPPh2NH-p-tolyl)]-[Rh(COD)Cl2] has been determined by an X-ray diffraction study. The lithiated derivative [(p-tolyl-NPPh2)2CHLi] yields an organorhodium compound in which the bis(iminophosphoranyl)methanide ligand coordinates in a σ-N,σ-C-coordination mode towards rhodium(I).

Stable palladium(0) and palladium(II) complexes containing a new, multifunctional and semi-labile phosphorus–bisnitrogen ligand

The new, multifunctional, semi-labile phosphorus–bisnitrogen ligand N-(2-diphenylphosphinobenzylidene)-2-(2-pyridyl)ethylamine, PNN, stabilises methyl(chloro)-, η1-ally(chloro)-, dichloro- and bis(tetrafluoroborate)-palladium(II) PNN complexes in a terdentate coordination fashion, resulting in ionic palladium complexes, as well as an unprecedented palladium(0) PNN complex as is evidenced from 1H, 13C, 31P and 15N NMR spectra and an X-ray structural analysis of [(PNN)PdMe]+[Cl]–.

Iminophosphorane complexes of rhodium(I) and X-ray crystal structure of [Rh(COD)Cl(Et3PN-p-tolyl)]

New rhodium(I)-iminophosphorane complexes [RhL 2 Cl(R 3 P=NR′)], in which the iminophosphorane ligand is coordinating as a two electron donor, have been prepared by bridge splitting reactions in benzene or chloroform between [RhL 2 Cl] 2 (L=CO, L 2 =COD) and the parent iminophosphoranes R 3 P=NR′ ( 1 ). In solution an equilibrium is established between the product [RhL 2 Cl(R 3 P=NR′)] and its constituting compounds. This equilibrium lies completely to the product side for L=CO, whereas for L 2 =COD it is dependent on the substituents on N and P, the temperature and the molar ratio Rh:R 3 P=NR′. The molecular structure of [Rh(COD)Cl(Et 3 P=N- p -tolyl)] ( 3a ) has been determined by means of X-ray crystallography. Complex 3a crystallizes in space group P 2 1 / a with a =23.134(4), b =10.946(2), c =8.686(2) A and β=90.12(2)° , and the structure was refined to R =0.036 by using 6363 independent reflections. The structure of 3a consists of a square planar rhodium complex in which the iminophosphorane is coordinated via the lone pair on nitrogen. Important dimensions are d (RhN)=2.142(3) A, d (NP)=1.608(3) A and <(RhNP)=121.0°.

103Rh-NMR spectroscopy of some hydridorhodiumbis(carbonyl)diphosphine compounds

Abstract The 103 Rh chemical shifts of a series of hydridorhodiumbis(carbonyl)diphosphine compounds 1 – 17 and one phosphine–phosphite analogue 18 , containing chelating bidentate P-ligands, have been obtained by inverse HMQC detection sequences 1 H-{ 103 Rh} and 31 P-{ 103 Rh, 1 H}. These active hydroformylation catalysts are stable only under pressure of H 2 /CO (synthesis gas) and hence 1 H-, 31 P- and 103 Rh-NMR spectra have been recorded in a sapphire high-pressure NMR tube. The compounds HRh(CO) 2 (PP) exist as a mixture of equatorial–equatorial and equatorial–axial five-coordinate isomers for 1 – 17 , which are in a dynamic equilibrium that could not be brought into the slow exchange regime on the proton, the phosphorus or the rhodium NMR time scales. A correlation ( R =0.980) was found between δ ( 103 Rh) and the Hammett σ p -constant of the para -substituents Y of the P(C 6 H 4 Y- p ) 2 groups in the thixantphos ligand for the series of compounds 4 , 8 – 13 (lower δ ( 103 Rh) for electron withdrawing substituents). Correlation of δ ( 103 Rh) with Tolman basicity parameters (higher δ ( 103 Rh) with higher basicity) also gave a good fit ( R =0.955). The finding that correlations exist for this series between the ligand basicity, the ratio of equatorial–equatorial/equatorial–axial trigonal bipyramidal isomers and the δ ( 103 Rh) indicates that small structural and electronic changes in the ligands in the vicinity of transition metal nuclei have a small but significant influence on δ ( 103 Rh). This, together with other knowledge, may in the future serve to use Rh-NMR as an analytical tool in coordination chemistry.

Monoazadienes ruthenium carbonyl chemistry

Abstract In this paper out recent research in the area of coordination and organometallic chemistry of monoazadienes (MAD) is reviewed. Emphasis is on the coordination of MAD to and activation by low-valent ruthenium carbonyl complexes and the reactivity and interconversions of the resulting oligonuclear azametallacycles.

The synthesis and properties of Pt2→M (M=Ag(I), Hg(II)) adducts of Pt2{o-C6H4P(Ph)(CH2)3PPh2}2 with Ag(O2CCF3), HgCl2 and Hg(O2CCF3)2. X-ray crystal structure of [Pt2{o-C6H4P(Ph) (CH2)3PPh2}2Hg(O2CCF3)2]

Abstract During the attempted synthesis of (dppp)Pt(C 2 H 4 ) (dppp =1,3-bis(diphenylphosphino)propane) a Pt(I)Pt(I) dimer, Pt 2 { o -C 6 H 4 P(Ph)(CH 2 ) 3 PPh 2 } 2 , was formed in approximately 5–10% yield. In this dimer the dppp ligand coordinates with two phosphorus atoms to one Pt centre, while one of the phenyl groups of the ligand is ortho -metallated to the second Pt centre. The reaction of this Pt(I)Pt(I) dimer with Ag(O 2 CCF 3 ), HgCl 2 and Hg(O 2 CCF 3 ) 2 resulted in the formation of Pt 2 -to-M donor adducts [Pt 2 { o -C 6 H 4 P(Ph)(CH 2 ) 3 PPh 2 } 2 Z] (Z=Ag(O 2 CCF 3 ), HgCl 2 and Hg(O 2 CCF 3 ) 2 ) in which the PtPt bond, although weakened, remained intact. The 31 p{ 1 H} NMR spectra showed, with increasing electronegativity of Z, an increase in coupling constant 1 J (PtP1) and a decrease in coupling constant 1 J (Pt′P1) for the approximately linear P1PtPt′P1′ unit, indicating a weaker PtPt bond and a stronger Pt 2 →M bond in the order M=Hg(II)>;Ag(I). An X-ray structure of the red-brown crystals of [Pt 2 { o -C 6 H 4 P(Ph)(CH 2 ) 3 PPh 2 } 2 Hg(O 2 CCF 3 ) 2 ] has been determined (space group Cc2a , a =14.392(2), b =19.950(1), c =19.427(1) A, V =5577.9(9) A 3 , Z =4, R =0.038, R w =0.061). The structure shows a PtHgPt triangle with bond lengths PtPt=2.7608(7) and PtHg=2.6690(10) A.

{1,2-Bis[N-(4-methylphenyl)imino-N]acenaph-thene}(η2-maleic anhydride)palladium(0)

The title compound, [Pd(C 26 H 20 N 2 )(C 4 H 2 O 3 )], displays trigonal coordination of palladium by both N atoms and the double bond of maleic anhydride. The spatial arrangement of the N-aryl groups in the title compound, compared with a more sterically congested analogue, explains satisfactorily its enhanced reactivity towards organic substrates. The crystal packing involves weak C-H...O and C-H...π interactions.

Unambiguous determination of the stereochemistry of methylcopper and lithium tetranydridoaluminate-induced allene formation in the steroid series. A revision of literature data

The structure of the allene obtained from mestranol methane sulphinate and methlycopper has been determinde by X-ray analysis; the allene turns out to be the 21α-Me compound, and not the erroneously reported 21β-Me epimer.