Transition-metal-promoted cyclization reactions of isocyanide ligands. Synthesis of cyclic aminooxycarbene complexes of platinum(II) and x-ray structure of trans-[(PPh3)2Pt[CN(C6H4Me-p)CH2CH2O]Br]BF4

Redox-Transmetalation Reactions: Easy Access to Homo- and Heterodimetallic d8,d10 Complexes

The ability of the imine PyCH═N-CH2Py (Py = 2-pyridyl, bpi) to behave as a heteroditopic ligand, which is suitable for creating two separate compartments to host metals in different oxidation states, has been developed by studying the reactions of the mixed-valence complexes [(cod)M-Ι(μ-bpi)MΙ(cod)] (M = Rh, Ir) with [M'(Cl)2(PPh3)2] (M' = Pd, Ni). The results depend on the molar ratio of the reagents used (1:1 or 1:2) to give the heterometallic complexes {d10-M',d8-M}-[(PPh3)(Cl)M'0(μ-bpi)MΙ(cod)] (Pd,Rh, 4; Pd,Ir, 5; Ni,Rh, 8; Ni,Ir, 9) and the two-electron mixed-valent compounds [(PPh3)(Cl)M'0(μ-bpi)M'ΙΙ(Cl)] (M' = Ni, 10; Pd, 11), respectively. A redox process occurs in the replacement of the low-valent [(cod)M-I] fragment, whereas the exchange of the [(cod)MI] fragment is redox-neutral. The metal with a d8 configuration in the products exhibits a square-planar geometry coordinated to two (Rh/Ir) or three (Ni/Pd) nitrogen atoms of the bridging bpi ligand. Conversely, the metal with a d10 configuration adopts trigonal-planar geometries, π-bonded to the imine C═N bond. The isolated complexes 4/5 and 10/11, along with the hypothetical heterometallic Pd,Ni compound (12), were studied by DFT methods. Additionally, the T-shaped moiety 'M'ΙΙ(PPh3)(Cl)(η1-CH-N(bpi))', stabilized by a secondary γ-agostic interaction, and the 'M'II(Cl)(κ3N-bpi)' fragment was found to be accessible redoxomers of complexes 10 and 11 by DFT calculations.

Synthesis of Ester- and Phosphonate-Functionalized AuI -Imidazolylidene Chlorides through the Isonitrile Route

Starting from DMSAuCl, isonitriles and functionalized propargylammonium salts in the presence of simple trimethylamine as auxiliary base, unsymmetrically substituted ester- and phosphonate-functionalized Au^I -imidazolylidene complexes were synthesized in an easy-to-use modular one-pot template synthesis. In the course of the reaction, after the initial nucleophilic addition of the amine to the gold(I)-activated isonitrile, a Michael addition closes the N-heterocyclic carbene (NHC) ring. Then the remaining double bond migrates into the NHC ring, evidently a more stable position than the initial exocyclic double bond. These functional groups attached to the back bone of the NHC ligands represent ideal handles for a further modification of the system, for example an attachment to larger assemblies or heterogenization by an attachment to surfaces are conceivable.

Diversity of reactivity modes upon interplay between Au(iii)-bound isocyanides and cyclic nitrones: a theoretical consideration

Metal-bound isocyanides demonstrate a very rich chemistry towards 1,3-dipoles of the allyl anion type such as nitrones. Depending on the metal centre, dipole nature and substituent in isocyanides, cycloadducts, imine + isocyanates or metallacycles may be formed. In this work, the reasons for such diversity, intimate details of the reaction mechanism and main factors determining the chemoselectivity in the reaction between Au(iii)-bound isocyanides ([AuCl₃(C[triple bond, length as m-dash]NR)]) and cyclic nitrones ^-O-N[combining low line]⁺[double bond, length as m-dash]C(H)XXX[combining low line] (XXX = CH₂CH₂CMe₂, CH₂CH₂CH₂, OCH₂CMe₂, CH₂OCMe₂ and CH₂CH₂O) are analysed in detail by theoretical (DFT) methods. The formation of cycloadducts is controlled by the LUMO_{π*(C[triple bond, length as m-dash]N)} of isocyanides and it occurs in a stepwise manner via the initial nucleophilic addition of nitrone at the C atom of C[triple bond, length as m-dash]NR (except for nitronate ^-O-N[combining low line]⁺[double bond, length as m-dash]C(H)CH₂CH₂O[combining low line]). The imine + isocyanate products are formed upon oxygen transfer from nitrones to isocyanides, and N-O bond cleavage is the main factor determining this process. A metallacycle is formed upon decomposition of the cycloadduct, and this process includes deprotonation of the oxadiazoline CH group/N-O bond cleavage and Cl^- elimination/cyclization. The main factor controlling the metallacycle formation is the acidity of the endocyclic CH group in the cycloadduct. Effects of the substituent R in C[triple bond, length as m-dash]NR and the nitrone nature on the reactivity are analysed.

PdII-mediated integration of isocyanides and azide ions might proceed via formal 1,3-dipolar cycloaddition between RNC ligands and uncomplexed azide

The generation of (tetrazolate)Pd^II complexes via the integration of (isocyanide)Pd^II precursors with uncomplexed azides and the verification of plausible reaction mechanisms.

Simple Synthesis of New Mixed Isocyanide-NHC-Platinum(II) Complexes and Their Catalytic Activity

Using the new modular and convergent approach to isocyanide-N-hetrocyclic carbene-platinum(ii) complexes, eight new compounds have been synthesised. For three of these, detailed structural data could be obtained by X-ray crystal structure analyses. This new family of organoplatinum complexes is catalytically active for hydrosilylation reactions; styrene and phenylacetylene could be used as substrates; triethylsilane and 1,1,1,3,5,5,5-heptamethyltrisiloxane could be used as reagents. With some of the new platinum pre-catalysts, excellent regioselectivities of up to 98 : 2 could be obtained, and turnover numbers up to 840 were achieved.

cis-Dichloridobis(2-isocyano-phenyl 4-meth-oxy-benzoate)palladium(II) chloro-form monosolvate

In the title compound, [PdCl2(C15H11NO3)2]·CHCl3, the Pd(II) atom adopts a slightly distorted square-planar coordination geometry composed of two Cl atoms in cis positions and two C atoms from isocyano-phenyl ligands. The mol-ecular conformation is stabilized by π-π stacking inter-actions [shortest centroid-centroid distance = 3.600 (1) Å] between substituted benzene rings of different ligands. The crystal packing is characterized by C-H⋯O and C-H⋯Cl inter-actions involving the chloro-form solvent mol-ecules.

Metal complexes from 1,1′-di(pyrazinyl)ferrocene: coordination polymers and bridged diferrocenes

Ferrocene-based ligands 1,1'-di(pyrazinyl)ferrocene (L1) and 1,1'-di(2-pyrimidinyl)ferrocene (L2) were synthesized and copper and silver complexes were obtained from L1. Coordination polymers [{Cu(2)(PhCOO)(4)}(L1)](n) (1), [{Cu(2)(C(5)H(11)COO)(4)}(L1)](n) (2), and [{Cu(2)(OAc)(4)}(L1)](n).0.5n[Cu(2)(OAc)(4)(H(2)O)(2)].1.5nCH(3)CN (3) resulted from the reaction with the corresponding copper carboxylates. In all three complexes, L1 links the dinuclear copper carboxylate units to form one-dimensional step-like chains. In 2, these chains are further linked by [Cu(2)(OAc)(4)(H(2)O)(2)] dinuclear units via hydrogen bonding to form sheet structures. The reaction of L1 with copper(I) iodide resulted in a multinuclear complex [(CuI)(4)(L1)(2)].(L1) (4), which contains a [(CuI)(4)(L1)(2)] diferrocene unit with a step-like (CuI)(4) core. Reactions of L1 with silver(I) salts resulted in silver-bridged diferrocenes [Ag(2)(L1)(2)]X(2) (X = ClO(4) (5a, b), NO(3) (6a-c) and PF(6) (7)), some of which incorporate aromatic solvents into their crystal lattices. The intramolecular Ag...Ag separations in these metallamacrocycles (3.211-3.430 A) depended upon the counter-anions and on the coordination mode of the silver ions. In all of these coordination complexes, L1adopts a synperiplanar eclipsed conformation and acts as a bidentate ligand, with only the 5-nitrogen of each pyrazine ring involved in coordination.