The reactions of alkyltrimethylphosphinenickel complexes with isocyanides and alkynes

t-Butylisocyanide reacts with NiRCl(PMe₃)₂ (R  CH₃, Ia; R  CH₂SiMe₃, Ib) to give, successively, the products of mono- and di-insertion into the nickelcarbon bonds; with more than two equivalents of isocyanide, trimethylphosphine ligands are displaced. In contrast to related palladium reactions, cyclohexyl isocyanide gives mono-insertion products only, while benzyl isocyanide is polymerised. The reactions of diphenylacetylene with Ia and Ib in methanol give (Z) vinylnickel complexes, trans-Ni{C(Ph)C(Ph)R}Cl(PMe₃)₂, while from reaction in diethyl ether a precursor complex [NiMeCl(PMe₃)₂ · (PhCCPh)_0.5] can be isolated. On heating the (Z)-vinyl complexes come into thermodynamic equilibrium with their (E)-isomers. The vinyl complexes are stereochemically rigid and resistant to further insertion.     

Insertion of isocyanides into the palladium-(2-pyridyl) bond

The reaction of the pyridyl-bridged binuclear complex [PdBr(μ-2-C₅H₄N)(PPh₃)]₂ with isocyynides CNR (R  p-C₆H₄OMe, Me, C₆H₁₁) yields the complex $\text{PdBr}${(&2.dbnd;NR)C(&2.dbnd;NR) (2-C₅H₄N)}(PPh₃)] containing a C,N-chelated 1,2-bis(imino)-2-(2-pyridyl)ethyl group, which results from successive insertions of two isocyanides molecules into the palladium2-pyridyl bond. The mononuclear compound trans-[PdBr(2-C₅H₄N)(PMePh₂)₂] readily reacts with various CNR ligands (R  p-C₆H₄OMe, Me, C₆H₁₁, CMe₃) to give the imino(2-pyridyl)methylpalladium(II) derivatives, trans-[Pdbr{C(=NR)(2-C₅H₄N)} (PMePh₂)₂].     

Insertion reactions of isocyanides with platinumcarbon σ-bonded complexes

[Pt(C₁₀H₁₂OCH₃)(PPh₃)Cl] reacts readily with isocyanides by displacement of the coordinated olefinic end of the organic moiety followed by insertion of the isocyanide into the metalcarbon σ-bond. The reaction between the methoxydienyl complex [Pt(C₁₀H₁₂OCH₃)Cl]₂ and cyclohexyl isocyanide involves chloride bridge-splitting to give [Pt(C₁₀H₁₂OCH₃)(C₆H₁₁NC)Cl], followed by olefin displacement and finally isocyanide insertion. The imino derivative produced in this latter reaction has a trans-isocyanide configuration.The chemical properties of these new isocyanide complexes are discussed in terms of relative trans influences, coordinating abilities, and electrophilic characters in comparison with the CO analogues.     

Insertion of terminal alkynes into the phosphirene ring

In the presence of catalytic amounts of Pd(PPh₃)₄, terminal alkynes readily insert into the ring of phosphirene P-W(CO)₅complexes to give the corresponding phosphole complexes.     

The insertion of the dioxides of carbon and sulphur into the palladium-carbon bond

Bis ( η¹, η²-allyl) palladium phosphine complexes react with carbon dioxide and sulphur dioxide by insertion into the palladium-carbon σ-bond to give η³-allylpalladium-carboxylate and -S-sulphinate complexes.     

Stereochemistry of the insertion of disubstituted alkynes into the metal aminocarbyne bond in diiron complexes

Terminal alkynes (HCCR^′) (R^′=COOMe, CH₂OH) insert into the metal-carbyne bond of the diiron complexes [Fe₂{μ-CN(Me)(R)}(μ-CO)(CO)(NCMe)(Cp)₂][SO₃CF₃] (R=Xyl, 1a; CH₂Ph, 1b; Me, 1c; Xyl=2,6-Me₂C₆H₃), affording the corresponding μ-vinyliminium complexes [Fe₂{μ-σ:η³-C(R^′)CHCN(Me)(R)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (R=Xyl, R^′=COOMe, 2; R=CH₂Ph, R^′=COOMe, 3; R=Me, R^′=COOMe, 4; R=Xyl, R^′=CH₂OH, 5; R=Me, R^′=CH₂OH, 6). The insertion is regiospecific and C-C bond formation selectively occurs between the carbyne carbon and the CH moiety of the alkyne. Disubstituted alkynes (R^′CCR^′) also insert into the metal-carbyne bond leading to the formation of [Fe₂{μ-σ:η³-C(R^′)C(R^′)CN(Me)(R)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (R^′=Me, R=Xyl, 8; R^′=Et, R=Xyl, 9; R^′=COOMe, R=Xyl, 10; R^′=COOMe, R=CH₂Ph, 11; R^′=COOMe, R=Me, 12). Complexes 2, 3, 5, 8, 9 and 11, in which the iminium nitrogen is unsymmetrically substituted, give rise to E and/or Z isomers. When iminium substituents are Me and Xyl, the NMR and structural investigations (X-ray structure analysis of 2 and 8) indicate that complexes obtained from terminal alkynes preferentially adopt the E configuration, whereas those derived from internal alkynes are exclusively Z. In complexes 8 and 9, trans and cis isomers have been observed, by NMR spectroscopy, and the structures of trans-8 and cis-8 have been determined by X-ray diffraction studies. Trans to cis isomerization occurs upon heating in THF at reflux temperature. In contrast to the case of HCCR^′, the insertion of 2-hexyne is not regiospecific: both [Fe₂{μ-σ:η³-C(CH₂CH₂CH₃)C(Me)CN(Me)(R)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (R=Xyl, 13; R=Me, 15) and [Fe₂{μ-σ:η³-C(Me)C(CH₂CH₂CH₃)CN(Me)(R)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (R=Xyl, 14, R=Me, 16) are obtained and these compounds are present in solution as a mixture of cis and trans isomers, with predominance of the former.     

Insertion of alkynes into the Pt-Si bond of silylplatinum complexes leading to the formation of 4-sila-3-platinacyclobutenes and 5-sila-2-platina-1,4-cyclohexadienes

The reaction of dimethyl acetylenedicarboxylate (DMAD) with [Pt(SiHPh(2))(2)(PMe(3))(2)] produces cis-[Pt(CZ=CZ-SiHPh(2))(SiHPh(2))(PMe(3))(2)] (cis-1, Z = COOMe) and [Pt(CZ=CZ-SiPh(2))(PMe(3))(2)] (2) depending on the reaction conditions. cis-1 and 2 are equilibrated in solution at room temperature, and they are isolated by recrystallization of the mixtures. cis-1 is converted slowly in solution into trans-[Pt(CZ=CZ-SiHPh(2))(SiHPh(2))(PMe(3))(2)] (trans-1) via intermediate 2 followed by reaction with H(2)SiPh(2). DMAD also reacts with [Pt(SiHPh(2))(2)(dmpe)] (dmpe = 1,2-bis(dimethylphosphino)ethane) to afford [Pt(CZ=CZ-SiHPh(2))(SiHPh(2))(dmpe)] (3). Conversion of 3 into 4-sila-3-platinacyclobutene [Pt(CZ=CZ-SiPh(2))(dmpe)] (4) takes place, accompanied by formation of H(2)SiPh(2), to give an equilibrated mixture of the two complexes. Crystallographic and spectroscopic data of cis-1, trans-1, and 3 suggest the presence of an intramolecular interaction between the Si-H group of the 3-sila-1-propenyl ligand and Pt via an Si-H-Pt three-center-four-electron bond in the solid state and in solution. DMAD reacts with 2 to give 5-sila-2-platina-1,4-cyclohexadiene with pi-coordinated DMAD, [Pt(CZ=CZ-SiPh(2)-CZ=CZ)(DMAD)(PMe(3))(2)] (5), which is also obtained from the reaction of excess DMAD with [Pt(SiHPh(2))(2)(PMe(3))(2)]. Unsymmetrical six-membered silaplatinacycles without pi-coordinated alkyne, [Pt(CZ=CZ-SiPh(2)-CH=CX)(PMe(3))(2)] (6: X = COOMe; 7: X = Ph), are prepared analogously from the respective reactions of phenyl acetylene and of methyl acetylene carboxylate with 2. Methyl 2-butynolate reacts with 2 at 50 degrees C to form a mixture of the regioisomers [Pt(CZ=CZ-SiPh(2)-CMe=CZ)(PMe(3))(2)] (8) and [Pt(CZ=CZ-SiPh(2)-CZ=CMe)(PMe(3))(2)] (9).     

Direct mono-insertion of isocyanides into terminal alkynes catalyzed by rare-earth silylamides

Rare-earth silylamide complexes, Ln[N(SiMe3)2]3 (Ln = Y, La, Sm, Yb), effectively catalyzed the coupling reaction of isocyanides with both aliphatic and aromatic terminal alkynes under mild conditions.     

Uncatalyzed insertion reaction of isocyanides into a carbon-sulfur bond

Tert-butylisocyanide and tert-octylisocyanide insert into the carbone-sulfur bond of activated sulfides 2 yielding thioimidates 5 which rearrange to enamines 6.     

Gold metal-catalyzed reactions of isocyanides with primary amines and oxygen: analogies with reactions of isocyanides in transition metal complexes

Despite its generally poor catalytic properties, bulk gold metal is observed to catalyze reactions of isocyanides (CN-R) with primary amines (H2N-R') and O2 to give carbodiimides (R-N=C=N-R') at room temperature and above. Detailed infrared reflection absorption spectroscopic (IRRAS) and kinetic studies show that the reaction occurs by initial eta1-adsorption of the isocyanide on the Au surface, which activates the isocyanide to attack by the amine. This attack is the rate-determining step in the catalytic cycle and has characteristics very similar to those of amine reactions with coordinated isocyanides in transition metal complexes. However, the metallic Au surface provides a pathway involving O2 to give the carbodiimide product whereas homogeneous metal ion catalysts give formamidines [HC(=NR)(NHR')].     

Hydridocyanoalkyl complexes of platinum(II). Insertion of olefins into the PtH bond

The preparation and spectroscopic properties are described of some platinum(II) complexes having a hydride ligand cis or trans to an sp³ carbon, viz. trans-PtH(YCN)(PPh₃)₂ and cis-PtH(YCN)(LL) with YCN = C₂H₄CN, n-C₃H₆CN, o-CH₂C₆H₄CN and LL = bis(diphenylphosphino)-ethene or -ethane. The complexes trans-PtH(YCN)(PPh₃)₂ can add a fifth ligand in solution; the resulting five-coordinate complex was observed by ³¹P NMR in the case of PtH(C₃H₆CN)(PPh₃)₃. Insertion of olefin (ethen, 1-cyanoethene, norbornadiene, allen) into the PtH bond of the trans-hydrido complexes occurs to give cis-dialkyl complexes, but the cis-hydrido complexes are unreactive. The mechanism of insertion is discussed in terms of the kinetics and the geometries of reactants and products.     

Insertion of chloral into P-Br bond of phosphoranes

Chloral inserts into the P-Br bond of pyrocatechintribromophosphorane with the formation of stable mono-, di- and tri(1-bromo-2,2,2-trichloroethoxy) phosphoranes and, also, into the P-Br bond of bis (pyrocatechin) bromophosphorane with the formation of 1-bromo-2,2,2-trichloroethoxybis (pyrocatechin) phosphorane.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2819–2823, December, 1989.     

Insertion reactions of heterocumulene into metal-ligand bonds

Published and authors’ own data on the typical examples of behavior of organic iso(thio)cyanates and other unsaturated substrates in reactions with metal-heteroatom bonds-M-O, M-N, M-P, and M-Hal-are reviewed. A possibility of multiple insertion of heterocumulenes into the same M-L bond and their ability to undergo-sphere condensation with other ligands upon heteromolecular insertion as well as the cocyclization of inserted ligands upon complex will be discussed in this review. Factors that affect the direction of iso(thio)cyanate addition to upon metal-heteroatom bond as well as the possibility of different kinds of their combination for the formation of heterocyclic ligands or compounds are also. Most of the findings are based on the results of IR and NMR spectroscopical, as well as X-ray structural studies.     

Insertion of unsaturated organic electrophiles into molybdenumbond-alkoxide and rheniumbond-alkoxide bonds of neutral,stable carbonyl complexes

Alkoxo complexes [Re(OR)(CO)(3)(N-N)] (R=Me, Et, tBu; N-N=2,2'-bipyridine (bipy), 4,4'-dimethyl-2,2'bipyridine (bipy'), 1,10-phenanthroline (phen)) and [M(OMe)(eta(3)-allyl)(CO)(2)(phen)] (M=Mo, W) have been synthesized in good yields and using mild conditions by the reaction of sodium alkoxides with [Re(OTf)(CO)(3)(N-N)] and [MCl(eta(3)-allyl)(CO)(2)(phen)] precursors. These have been characterized by IR and NMR spectroscopy as well as by X-ray diffraction for [W(OMe)(eta(3)-allyl)(CO)(2)(phen)] (10). The reactions of the molybdenum and rhenium alkoxo complexes with isocyanates, R'NCO, yield [L(n)M[N(R')C(O)OR]] complexes; the carbamate ligand, which results from an R'NCO insertion into the Mbond;OR bond, is monodentate through the nitrogen atom. The solid-state structures of Mo and Re examples have been determined by X-ray diffraction. The geometry around the carbamate nitrogen of these compounds is planar, and the distances indicate delocalization of the nitrogen lone pair involving mainly the carbonyl groups. Experiments carried out with the Re complexes showed that aryl isocyanates are more reactive than their alkyl counterparts, and that bulky R' groups led to slow rates of insertion. Insertion reactions were also observed with isothiocyanates, although here it is the Sbond;C bond that inserts into the Mbond;OR bond, and the resulting ligand is bound to the metal by sulfur. Competition experiments with the Re compounds indicate that isocyanates are more reactive than isothiocyanates towards the Rebond;OR bonds. Tetracyanoethylene inserts into the Rebond;OMe bond of [Re(OMe)(CO)(3)(bipy')], forming a complex with a 2-methoxytetracyanoethyl ligand; the structure of which was determined by X-ray diffraction. The formation of the xanthato complex [Re(SC(S)OtBu)(CO)(3)(bipy)] (20) by reaction of [Re(OTf)(CO)(3)(bipy)] with CS(2) and NaOtBu, but not by the reaction of CS(2) and [Re(OtBu)(CO)(3)(bipy)] (5 a), suggests that the insertion reactions do not take place by ionization of the alkoxo complexes to give the free alkoxide ion.     

Thermal and photochemical reactions of Fischer carbene complexes with trialkylsilyl-substituted alkynes

Thermal reaction of Fischer carbene complexes with triisopropylsilyl (TIPS) substituted alkynes in benzene afforded TIPS-substituted vinylketenes or 2-TIPS-substituted cyclobutenones as major products while photochemical reaction of Fischer carbene complexes with trimethylsilyl (TMS) substituted alkynes in acetonitrile afforded 3-TMS-substituted cyclobutenones.     

Trapping reactions of an intermediate containing a tungsten-phosphorus triple bond with alkynes

The thermolysis of the phosphinidene complex [Cp*P[W(CO)5]2] (1) in toluene in the presence of tBuC(triple bond)CMe leads to the four-membered ring complexes [[[eta2-C(Me)C(tBu)]Cp*(CO)W(mu3-P)[W(CO)3]][eta4:eta1:eta1-P[W(CO)5]WCp*(CO)C(Me)C(tBu)]] (4) as the major product and [[W[Cp*(CO)2]W(CO)2WCp*(CO)[eta1:eta1-C(Me)C(tBu)]](mu,eta3:eta2:eta1-P2[W(CO)5]] (5). The reaction of 1 with PhC(triple bond)CPh leads to [[W(Co)2[eta2-C(Ph)C(Ph)]][(eta4:eta1-P(W(CO)5]W[Cp*(CO)2)C(Ph)C(Ph)]] (6). The products 4 and 6 can be regarded as the formal cycloaddition products of the phosphido complex intermediate [Cp*(CO)2W(triple bond)P --> W(CO)5] (B), formed by Cp* migration within the phosphinidene complex 1. Furthermore, the reaction of 1 with PhC(triple bond)CPh gives the minor product [[[eta2:eta1-C(Ph)C(Ph)]2[W(CO)4]2][mu,eta1:eta1-P[C(Me)[C(Me)]3C(Me)][C(Ph)](C(Ph)]] (7) as a result of a 1,3-dipolaric cycloaddition of the alkyne into a phosphaallylic subunit of the Cp*P moiety of 1. Compounds 4-7 have been characterized by means of their spectroscopic data as well as by single-crystal X-ray structure analysis.     

Insertion of ketenes into lanthanocene n-butylamide and imidazolate complexes

Reaction of Cp₂LnNHⁿBu with 1 equiv. of Ph₂CCO in toluene affords dimeric complexes [Cp₂Ln(OC(CHPh₂)NⁿBu)]₂ [Ln = Yb (1), Dy (2)], derived from a formal insertion of the CC bond of the ketene into the N–H bond. Treatment of CpErCl₂ with 2 equiv. of LiNHⁿBu followed by reacting with Ph₂CCO affords a rearrangement product [Cp₂Er(OC(CHPh₂)NⁿBu)]₂ (3). Treatment of [Cp₂Ln(μ-Im)]₃ (Im = imidazolate) with PhRCCO gives [Cp₂Ln(μ-OC(Im)CPhR)]₂ [R = Et, Ln = Yb (4); R = Ph, Ln = Yb (5), Er (6)]. In contrast to the previous observations that [Cp₂ErNⁱPr₂]₂ and [Cp₂ErNHEt]₂ react with ketenes to give di-insertion products, in the present cases the presence of excess of ketenes has no influence on the final product even with prolonged heating and only monoinsertion products are isolated. All these complexes were characterized by elemental analysis, IR and mass spectroscopies. The structures of complexes 1 and 3–6 were also determined through X-ray single crystal diffraction analysis.     

Dinuclear palladium-azido complexes containing thiophene derivatives: reactivity toward organic isocyanides and isothiocyanates

Cyclopalladated tetranuclear Pd(II) complexes, [Pd2(micro-Cl)2(Y)]2 (Y = L1 or L2; H2L1 = di(2-pyridyl)-2,2'-bithiophene; H2L2 = 5,5'-di(2-pyridyl)-2,2':5',2'-terthiophene), containing two pyridyl-alpha, alpha'-disubstituted derivatives of thiophene were prepared. Treating these products with PR3 and subsequently with NaN3 produced the dinuclear Pd-azido complexes [(PR3)2(N3)Pd-Y-Pd(N3)(PR3)2] (Y = L1 or L2) or a cyclometallated complex [(PR3)(N3)Pd-Y'-Pd(N3)(PR3)] (Y' = C,N-L2). Reactions of these Pd-azido complexes with CN-Ar (Ar = 2,6-Me(2)C(6)H(3), 2,6-i-Pr(2)C(6)H(3)) or R-NCS (R = i-Pr, Et, allyl) led to the complexes containing end-on carbodiimido groups [(PMe3)2(N[double bond]C[double bond]N-Ar)Pd-Y-Pd(N[double bond]C[double bond]N-Ar)(PMe3)2] or S-coordinated tetrazole-thiolato groups {(PMe3)2[CN4(R)]S-Pd-Y-Pd-S[CN4)(R)](PMe3)2}. Interestingly, when treated with elemental sulfur, the carbodiimido complexes transformed into the cyclometallated derivatives, [(PMe3)(N[double bond]C[double bond]N-Ar)Pd-Y'-Pd(N[double bond]C[double bond]N-Ar)(PMe3)] (Y' = C,N-L1, C,N-L2). We also report the preparation of linear, thienylene-bridged dinuclear Pd complexes [L2(N3)Pd-X(or X')-Pd(N3)L2] (L = PMe3 or PMe2Ph; H2X = 2,2'-bithiophene or H2X' = 2,2':5',2'-terthiophene) and their reactivity toward organic isocyanide and isothiocyanates.