Isonitrile Complexes Research Articles

Rhodium(I) and platinum(II) complexes with chelating bidentate isonitrile ligands

Rhodium(I) complexes, [Rh(DiNC) 2]A, where A −  Cl −, BF 4 −, or BPh 4 −, and [Rh(t-BuDiNC) 2]A, where A −  Cl −, BPh 4 −, or PF 6 −, were prepared by reaction of [Rh(COD)Cl] 2 with the bidentate chelating isonitrile ligands, DiNC and t-BuDiNC. The solid compounds are variously colored yellow, green, blue or violet. In dilute (∼10 −5 M) solutions, the compounds are yellow, but as the concentrations of the solutions are increased, the colors become green or blue. Ultraviolet-visible spectroscopic studies suggest, as found previously for monodentate isonitrile rhodium(I) complexes, that the [Rh(DiNC) 2] + cation exists as a monomer in dilute solutions, but dimers, trimers, and tetramers are found at higher concentrations. For [Rh(t-BuDiNC) 2] +, only monomers and dimers are observed; presumably the bulky t-butyl groups prevent the formation of higher oligomers in this case. Equilibrium constants for the dimerizations of [Rh(DiNC) 2] + and [Rh(t-BuDiNC) 2] + were determined. When exposed to room light, blue solutions of the oligomers [Rh(DiNC) 2] x x+ fade to the yellow color of the monomer; 1H NMR spectra of the solutions confirm the photodissociation of the oligomers. The reaction of [Rh(DiNC) 2] + with I 2 yields the binuclear [Rh 2(DiNC) 4I 2] 2+ presumed to have a structure with a RhRh bond and terminal I − ligands. Under the same conditions, monodentate isonitrile complexes [Rh(CNAr) 4] + yield mononuclear [Rh(CNAr) 4I 2] + upon reaction with I 2. The greater stability of the dimeric structure for DiNC may be due to the smaller steric bulk of the DiNC ligand as a consequence of its near planarity as compared with monodentate CNAr ligands in which the Ar groups may rotate. Additional evidence for dimer stabilization by DiNC is the high temperature (70°C) required for RhRh bond cleavage as observed in 1H NMR studies of [Rh 2(DiNC) 4I 2] 2+. The yellow platinum(II) complex [Pt(DiNC) 2]PtCl 4 is isolated from the reaction of (Et 4N) 2PtCl 4 with DiNC. The reaction of K 2PtCl 4 with t-BuDiNC yields white cis-PtCl 2(t-BuDiNC). Complexes reported herein are characterized by their UV-visible, IR, and 1H and 13C NMR spectra.

Proton nuclear magnetic resonance studies of isonitrile-heme protein complexes.

Steric interactions between bound ligand molecules and the valine E11 methyl groups of human hemoglobin and sperm whale myoglobin have been examined directly by high resolution NMR techniques. The methyl proton resonances of this amino acid are shifted markedly upfield and away from the bulk of the protein resonances by the shielding effect of circulating pi electrons in the porphyrin ring. We have monitored the valine resonance in the presence of CO and a series of isonitriles and found considerable shifts in its position, both between the various protein complexes and among the different liganded states. The ring current shifts of the gamma 1-methyl group of Val E11 in the CO forms of isolated alpha and beta chains and myoglobin are -2.70, -2.91, and -3.30 ppm, respectively. In all the proteins, these positions show little change in going from bound CO to bound methyl and ethyl isocyanide. In alpha subunits and myoglobin, n-propyl and n-butyl isocyanide binding produces marked decreases in the magnitude of these shifts, indicating that the valine residue has been forced away from the center of ring by the presence of these large ligand molecules. In the case of beta subunits, however, only tert-butyl isocyanide produces a marked decrease (from -2.91 to -1.99 ppm) in the ring current shift of the valine methyl protons. New peaks were observed in the isonitrile-protein spectra and identified as ligand proton resonances by comparing the spectra of normal and totally deuterated isonitrile complexes. The magnitudes of the ring current shifts for the terminal methyl protons of ethyl isocyanide suggest a linear geometry for the Fe equal to C equal to N - C bonds in beta chains and a bent geometry for alpha chains. The bent geometry in alpha subunits appears to be dictated by the position of the Val E11 methyl group which is located further up from the heme plane but closer to the heme center than the corresponding position of the beta subunit residue. The free energy changes for ethyl isocyanide binding to the two chains are nearly identical, suggesting that the linear and bent geometries are energetically equivalent. Myoglobin ethyl isocyanide complexes exhibit ligand ring current shifts intermediate to those observed for the hemoglobin subunits. Assignment of resonances and positions to the alkyl protons of the longer isonitriles is more difficult.

Über neue Cyano-nitrosylmanganate und Isonitril-nitrosyl-Komplexe des Mangans/On New Cyano Nitrosyl Manganates and Isonitrile Nitrosyl Complexes of Manganese

Abstract The anionic cyano nitrosyl manganates [Mn(NO)(CO)3CN] - and [Mn(NO)3CN]- are formed by the reactions of Mn(NO)(CO)4 and Mn(NO)3CO with NaN(SiMe3)2. The alkylation of these anions with [R3O]BF4 (R = Me, Et) leads to the corresponding isonitrile complexes Mn(NO)(CO)3CNR and Mn(NO)3CNR. IR, mass and 13C NMR spectra indicate trigonal-bipyramidal coordination for nitrosyl tricarbonyl derivatives, with three CO ligands in facial positions and NO in the equatorial plane. Based on the temperature dependent 13C NMR spectra of Mn(NO)(CO)3CNR and Mn(NO)(CO)4 the fluctional behaviour of these compounds could be demonstrated with ⊿G+ values of 48 kJ/mol or less for the CO exchange.

Angriff eines lithiierten Aminofluorsilans auf die C-O-Bindung des Cr(CO)6; Bildung von Isonitrilkomplexen/Attack by a Lithiated Aminofluorosilane on the C - O Bond of Cr(CO)6; Formation of Isonitrile Complexes

Abstract The photochemical reaction of a lithiated aminofluorosilane with Cr(CO)6 leads to substitution of one or two carbonyl oxygen atoms and formation of isonitrile complexes. The crystal structure of the disubstituted product, cis-di(tert-butylisonitrile) tetracarbonylchromium, has been determined.

Cationic pentafluorophenyl isonitrile complexes of palladium and their conversion to carbene and imidoyl complexes

The preparation of fourteen complexes of the type [Pd(C6F5)L2(CNR)]ClO4 (L2=2PR′3, bipy, tmen or diphos; R=But, Cy orp-Tol) is described. Their reactivity with alcohols or amines is much lower than that of similar haloderivatives. Only the complexes with L2=chelating ligand react with YH to form the corresponding carbene complexes [Pd(C6F5)(chelate){C(NHTol)Y}]ClO4 (YH=p-TolNH2, BzNH2, ButNH2, MeOH or EtOH), which can be deprotonated with KOH in alcohol, rendering the first imidoylorganopalladium complexes [Pd(C6F5){C(=NTol)Y}(bipy)].

Electrophilic and nucleophilic attacks on alkyl, nitrile, and isonitrile complexes of Pd(II) and Pt(II)

Abstract

Oxide promoted isomerisation of an isonitrile complex, H 2Os 3(CO) 10[CN(CH 2) 3Si(OEt) 3

The isomerisation of H 2Os 3(CO) 10[CN(CH 2) 3Si(OEt) 3] to HOs 3(CO) 10-[CN(H)(CH 2) 3Si(OEt) 3] is accelerated by interaction with some oxides; both complexes afford HOs 3(CO) 10[CN(H)(CH 2) 3Si(OEt) 3it-x(O) x] as oxide supported clusters.

An investigation of the reaction between [{Fe(η5–C5H5)(CO)2}2] and aryl isonitriles

The direct reaction between [{Fe(η5-C5H4X)(CO)2}2](X = H, Me, or COOMe) and aryl isonitriles RNC (R = 2,6-Me2C6H3 or C6H5) in refluxing toluene readily yields the tetrasubstituted derivatives [{Fe(η5-C5H4X)(RNC)2}2]. The intermediate derivatives [Fe2(η5-C5H5)2(CO)4–n(RNC)n](n= 1 or 2) can be prepared by the exchange reaction between [{Fe(η5-C5H5)(RNC)2}2] and [{Fe(η5-C5H5)(CO)2}2]. Reaction rates for the substitution of [{Fe(η5= C5H5X)(CO)2}2] by RNC are dependent on both the nature of R and X, and increase with both the nucleophilicity of R and the electron-withdrawing power of X. An alternative route to [Fe2(η5-C5H5)2(CO)4–n(RNC)n](n= 1 or 2) is via the reaction between Na[Fe(η5-C5H5)(CO)2] and 2,6-Me2C6H3NC in the presence of C7H7+BF4–. The isonitrile complexes have been characterized by i.r. and n.m.r. spectroscopy.

Substitution and isomerisation reactions at platinum(II) involving halide, tertiary phosphine, carbonyl, and lsonitrile ligands

Carbon monoxide catalyses trans to cis isomerisations of [PtCl2L2](L = tertiary phosphine) in chloroform solution. The process involves formation of five-co-ordinate intermediates from which halide or tertiary phosphine can be eliminated, giving trans-[PtCl(CO)L2]+ or cis-[ PtCl2(CO)L] respectively. Structure changes appear to be by pseudo-rotations rather than by consecutive displacements. A number of isonitrile complexes undergo similar reactions. Halide-bridged cations [Pt2(µ-Cl)2L4]2+ formed by halide extraction from cis-[PtCl2L2] by Ag+ enter rapid (n.m.r. time-scale) exchange processes with the latter complexes at ambient temperatures. Halide elimination from cis-[PtCl2L2] by solvent chloroform appears to initiate the process. The trans isomers do not participate in the exchange.

Synthesis and structure of neutral and cationic pentahaloarylpalladium(II) isonitrile complexes

Complexes of the types (a) trans- and cis-[Pd(C 6X 5) 2 (CNR) 2], (b) trans- [Pd(C 6X 5)Cl(CNR) 2] and (c) [Pd(C 6X 5)(CNR) 3]ClO 4 (X = F or Cl;R = Bu t cyclohexyl or p-tolyl) have been made by replacement of the tetrahydrothiophen or Cl groups of appropriate precursors by isonitrile. Their structures have been assigned on the basis of their IR and 1H NMR spectra.

The catalytic substitution of metal carbonyls and substituted metal carbonyls by isonitriles in the presence of rhodium(I) and polymer-supported rhodium(I) complexes

Metal carbonyls and substituted metal carbonyls, under relatively mild reaction conditions, in the presence of isonitriles, undergo catalytic CO substitution by rhodium(I) and polymer-supported rhodium(I) complexes. The reaction provides a facile route to the synthesis of transition metal isonitrile metal isonitrile complexes.

Basische metalle: XXVIII. Zur reaktivität von isothiocyanaten gegenüber C 5H 5Co(PMe 3) 2- Synthese und eigenschaften von C 5H 5Co(PMe 3)cnr und cobaltaheterocyclen C 5H 5(PMe 3)C [formula omitted](NR)

The reaction of C 5H 5Co(PMe 3) 2 with isothiocyanates SCNR (R = Me, Ph) leads to the isonitrile complexes C 5H 5Co(PMe 3)CNR; in addition,the cobaltaheterocycles C 5H 5(PMe 3)C oSC(NR)SC (NR) are obtained in low yields. The compounds C 5H 5Co(PMe 3)CNR (R = Me, t-Bu, Ph), also formed from C 5H 5Co(PMe 3) 2 and CNR, react with MeI and MeCOCl by addition of the methyl and the acetyl group to the metal. In pentane as solvent, the primary products [C 5H 5CoCH 3(PMe 3)CNR]I can be isolated; in acetone solution, the reaction of C 5H 5Co(PMe 3)CNPh with MeI yields the neutral acylimino complex C 5H 5CoI(PMe 3) [η 1-C(CH 3)NPh] whereas from C 5H 5Co(PMe 3)CN-t-Bu and MeI the salt [C 5H 5Co(PMe 3){η 2-C(CH 3)N-t-Bu}]I is obtained. The acetyl complexes [C 5H 5CoCOCH 3(PMe 3)CNR]PF 6(R = Me, t-Bu, Ph) are also produced from [C 5H 5CoCH 3(PMe 3)CO]PF 6 and CNR. Like the corresponding rhodium compounds [C 5H 5RhCOCH 3(PMe 3CNR]PF 6 (R = Me, t-Bu), the cobalt complexes react with NaH by reductive elimination to yield C 5H 5M(PMe 3)CNR and/or C 5H 5M(PMe 3)CO; the composition of the product depends both on Mand R.

13C-NMR-spektren und dynamisches verhalten von olefin- sonitril-eisendicarbonyl-komplexen.

The 13C NMR spectra of the isonitrile complexes olen fe(CO) 2CNR (R = Me, EMe 3; E = Si, Ge, Sn) with butadiene, penta- 1,3-diene, cyclohexa-1,3-diene, 2,3-dimethylbutadiene, cyclohepta-1,3-diene as olefiinic ligands indicate the fluctional behavior of these compounds in solution. At low temperature there is a conformative preference in all cases so that one CO group occupies the apical position of a square pyramid whereas the isonitrile ligand together with a CO and the olefin part are in the basal positions. Depending on te various olefin ligands and the CNR groups the pseudorotation process is dicussed on the basis of /gD G/DG values for the CO/CNR ligand exchange.

Massenspektroskopishce untersuchungen an olefin-isonitril-eisendicarbonyl-komplexen

The mass spectra of the isonitrile complexes oleneFe(CO) 2CNL (olene, see Table 1, L = Me, Et, SiMe 3, SnMe 3) are summarized and a comparative discussion is given. Whilst the successive loss of CO and the elimination of the intact isonitrile or olefin ligands are similar processes for all compounds, there are important differences in the fragmentations of the complexes olefin ligands, which are therefore noteworthy.

ESR evidence for tight ion-pairs solvent effects in electron transfer reduction of nitroso compounds by copper(0)-isonitrile complexes

Persistent radicals are observed by ESR in electron transfer reduction of nitroso compounds by copper(0)-isonitrile complexes. ESR spectra exhibit hyperfine splitting to one nitrogen nucleus, one copper nucleus and eventually hydrogen nucleus. The results obtained from different aromatic nitroso are consistent with the formation or nitroxide-like or anilino-like radicals. But the ESR study of solvent and temperature effects on these species, agree with the formation of nitroso radical anion-complexed copper cation tight pairs. For example ▪ The interaction between nitroso radical anion and copper counterion is very sensitive to solvent effect and sometimes in an unexpected manner which will be discussed.

Preparation of polymer-supported isonitrile complexes

The preparation of isonitrile ligands bound to polystyrene and silica supports is reported; these ligands react with [Rh(CO)2Cl]2 to yield [Rh(CO)2Cl(pol–NC)] complexes (pol = polymeric support).

The reactions of isonitrile complexes of molybdenum(0) and tungsten(0) with alkylating agents to give carbyne (aminomethyne) complexes

Treatment of the complexes trans-[M(CNMe) 2(dppe) 2] (A, M = Mo or W; dppe = Ph 2PCH 2CH 2PPh 2) with MeFSO 3, Me 2SO 4 or [Et 3O] BF 4 in benzene gives the complexes trans-[M(CNRMe)(dppe) 2]X (B, R = Me or Et; X = FSO 3, MeSO 4 or BF 4). Dialkylated compounds were not observed. The compounds B isomerise in CH 2Cl 2 solution to give cis-[M(CNRMe)(dppe) 2]X. Spectroscopic data are reported for the complexes and are used to deduce their structures.

A carbyne complex of rhenium(V) by protonation at nitrogen of an isonitrile complex of rhenium(I)

The complexes trans-[ReCl(CNR)(dppe) 2] (I, R = Me or t-Bu) have been prepared by displacement of dinitrogen from trans-[ReCl(N 2)(dppe) 2]. I(R = Me) reacts with HBF 4 to give the carbyne-type complex trans-[ReCl{CNH(Me)}(dppe) 2]BF 4.

Reduction monoelectronique par les complexes du cuivre metallique I - halogenures d'alkyle et complexe Cu(0)-isonitrile

Alkyl halides can be dimerized in excellent yield by the Cu(0)-isonitrile complex. This reaction is related to the mono-electronic reducing character of the complex.

Reduction monoelectronique par les complexes du cuivre metallique II - Gem-dibromocyclopropanes et complexe Cu(0)-isonitrile : voie d'acces aux composes alleniques

Gem-dibromocyclopropanes give selectively the corresponding allenes by treatment with the Cu(0)-isonitrile complex.