Rigid Bidentate Nitrogen Ligands in Organometallic Chemistry and Homogeneous Catalysis. 6. Zerovalent Palladium and Platinum Complexes Containing Rigid Bidentate Nitrogen Ligands and Alkenes: Synthesis, Characterization, Alkene Rotation and Substitution Reactions. X-ray Crystal Structure of [Bis((2,6-diisopropylphenyl)imino)acenaphthene](maleic anhydride)palladium(0)

Abstract

Zerovalent palladium and platinum complexes containing rigid bidentate nitrogen ligands and alkenes: synthesis, characterization, alkene rotation and substitution reactions. X-ray crystal structure of [Bis((2,6-diisopropylphenyl)imino)acenaphthene](maleic van Asselt, R.; Elsevier, C.J.; Smeets, W.J.J.; Spek, A.L. Published in: Inorganic Chemistry DOI: 10.1021/ic00085a050Link to publication Citation for published version (APA):van Asselt, R., Elsevier, C. J., Smeets, W. J. J., & Spek, A. L. (1994). Zerovalent palladium and platinum complexes containing rigid bidentate nitrogen ligands and alkenes: synthesis, characterization, alkene rotation and substitution reactions. X-ray crystal structure of [Bis((2, General rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. A number of zerovalent palladium and platinum M(NN)(alkene) complexes, containing the rigid bidentate nitrogen ligands bis(ary1imino)acenaphthene (Ar-BIAN) and bis(pheny1imino)camphane (Ph-BIC) have been synthesized and characterized. Stable complexes were obtained with electron poor alkenes, such as dimethyl fumarate, fumaronitrile, maleic anhydride, and tetracyanoethylene. Complexes bearing asymmetric Ar-BIAN or Ph-BIC ligands occurred as mixtures of isomers. From IR, UV, and 'H and 13C NMR spectroscopy and from substitution reactions it was concluded that the back-donation of electron density from the metal to the alkene is the major factor determining the stability of the complexes. Some of the complexes show fluxional behavior on the NMR time scale, which was explained by rotation of the alkene around the metal-alkene bond. The estimated rotation barriers of 50-69 kJ/mol for Pd and >72 kJ/mol for Pt are high as compared to reported values for other palladium and platinum alkene complexes. IntroductionThere has been considerable interest in the chemistry of palladium and platinum complexes containing *-coordinated unsaturated ligands,*J which may, apart from the interesting structure of and bonding in this type of complexes, be ascribed to the fascinating catalytic reactions involving platinum and palladium $-alkene and +alkyne comple~es.~ In most cases, the active species are divalent complexes, and as a consequence

Combined Low Temperature Rapid Scan and1H NMR Mechanistic Study of the Protonation and Subsequent Benzene Elimination from a (Diimine)platinum(II) Diphenyl Complex Relevant to Arene C−H Activation

“…[177][178][179][180][181][182][183][184] In the case of substitution reactions at Pt(II)(η 2 -C 6 H 6 ), we have already mentioned for Ar-DAB complexes that this reaction proceeds associatively. 137 In the current study, we also characterized the associative character of the benzene substitution for the Ar-BIAN complex 4b.…”

Qualitative and quantitative discrimination of fake and true alkene rotation processes in pd(η2-olefin) complexes. A new bimolecular mechanism

“…the propeller-like olefin rotation. This is the earliest and most frequently proposed mechanism [1-5]; 2. olefin-metal dissociation followed by recombination; [3] [3,5]; 4. metal-L or metal-L 0 bond dissociation, followed by rotation of the ancillary ligand and recombination [4]; 5. intermolecular exchange with the free ancillary ligand L-L 0 . In this case, a mechanism has been proposed which involves an olefin-metal dissociation step [3].…”

“…This is the earliest and most frequently proposed mechanism [1-5]; 2. olefin-metal dissociation followed by recombination; [3] [3,5]; 4. metal-L or metal-L 0 bond dissociation, followed by rotation of the ancillary ligand and recombination [4]; 5. intermolecular exchange with the free ancillary ligand L-L 0 . In this case, a mechanism has been proposed which involves an olefin-metal dissociation step [3]. During our investigation [6] of the fluxional behaviour in CD 2 Cl 2 of the complex [Pd(g 2 -tmetc)(N-SMe)] (1) (tmetc = tetramethylethylenetetracarboxylate, N-SMe = 2-methylthiomethylpyridine), we discovered a concentration dependent scrambling of the olefin resonances, which could be rationalized only by invoking one further mechanism: 6. bimolecular process through a dimeric complex (see Chart 1).…”

A novel oxidative addition product from [Pt2(dba)3]: synthesis and spectroscopic characterization of a bimetallic Pt-eta2-tetracyanoethylene complex containing 2,3,5,6-tetrakis(alpha-pyridyl)pyrazine

“…[Pt 2 (dba) 3 ] or [Pt(1,5-cyclooctadiene) 2 ]}, an olefin with electron withdrawing groups, such as tetracyanoethylene (TCNE), and the N,N donor ligand. [22][23] Usually, the isolated products have the general formula [Pt(η 2 -alkene)(N,N)] and the bonding at the Pt-η 2 -alkene moiety is described according to the metalacyclopropane model. 24 Indeed, in olefin complexes of platinum, the bonding at the Pt-η 2 -alkene moiety can be understood in terms of either the classical Dewar-Chatt-Duncanson model 24,25 or the metalacyclopropane model.…”

“…24 Spectroscopic methods and single-crystal X-ray diffraction studies have been used to distinguish between these two bonding possibilities in Pt-η 2 -alkene structures. [22][23][24][25][26] In this work we have employed the aforementioned strategy to prepare a bimetallic Pt-η 2 -TCNE complex containing TPP as a bis-bidentate ligand, namely [{Pt(η 2 -TCNE)} 2 (μ-TPP)} (1). Solid-state 13 C (CP/ MAS) NMR spectroscopy has been used to examine the bonding at the Pt-η 2 -TCNE moieties as well as the mode adopted by TPP upon coordination to the metallic centers.…”