Preparation of η2-acetylene- and η1-vinylidene-manganese complexes from p-diethynylbenzene and cymantrene. X-ray crystal and molecular structure of Cp(OC)2MnCCHC6H4CBrCH2

Cp(OC)₂Mn(THF) reacts with p-diethynylbenzene (Deb), yielding Cp(OC)₂Mn(Deb) (I) and [Cp(OC)₂Mn]₂(Deb) (II) with the η²-acetylene coordination of Deb (to both Mn atoms in II). Under the action of PhLi, I and II are isomerized into Cp(OC)₂MnCCHC₆H₄CCH (III) and [Cp(OC)₂MnCCH]₂C₆H₄ (VI). Treatment of I with PhLi, LiBr and an excess of HCl in ether, as well as direct interaction of III with LiBr and HCl/Et₂O, gives Cp(OC)₂MnCCHC₆H₄CBrCH₂ (IV), which has been characterized by an X-ray single-crystal diffraction study. III adds PPh₃, yielding a zwitterionic complex, Cp(OC)₂Mn⁻C(P⁺Ph₃)CHC₆H₄CCH (V).     

Theoretical studies of the radical reaction H2CSiH2 + H

Ab initio molecular orbital calculations on the transition states and barrier heights for the addition of atomic hydrogen to silaethylene are carried out. The activation energy for the addition to the silicon site is lower than that to the carbon site, while the exothermicity is smaller.     

Charakterisierung und photochemie von (dihalogenmethylen)sulfoxiden,XYCSO

Dihalogenomethylene sulfoxides (dihalogenosulfines) 2a–c were generated by flash vacuum pyrolysis of 2,2,4,4-tetrahalogeno-1,3-dithietane 1,3-dioxides 1a–c and trapping the pyrolysis products in argon at 10 K. At room temperature unstable difluorosulfine (2a) and chlorofluorosulfine (2b) were identified by i.r. spectroscopy, and the photochemistry of the sulfines was investigated. Chlorofluorosulfine (2b) exists in two geometrical isomers. Photolysis of 2a leads to fragmentation to give CF₂ and SO, photolysis of the chlorine containing sulfines 2b and 2c to rearrangement to give the sulfenyl chlorides 6 and 8. This is explained by different migratory tendencies of fluorine and chlorine and the stability of the CF bond.     

Intermediacy of nitrene in the curtius-type rearrangement of phosphinic azides. Insights from Ab initio study of the H2P(O)N⇌HP(O)NH interconversion

Ab initio calculations on the model phosphinic nitrene H₂P(O)N⇌oxoiminophosphorane HP(O)NH interconversion in both lower-lying singlet and triplet states at the UMP4SDQ/6-31 ++ G^* level using the HF/3-21 G^*-optimized geometries are reported. The results support the proposition that the Curtius-type rearrangement of phosphinic azide (azidophosphine oxide) occurs via a non-nitrene mechanism in its singlet ground state. However, if the starting material could be sensitized photochemically into its triplet excited state, then the nitrene could be formed and the Curtius-type rearrangement would not be observed.     

Übergangsmetall-heteroallen-komplexe: XIII. Reaktionen der cobalt-thioketen-komplexe [Co(R2CCS)(C5H5)] mit elektrophilen

Reaction of the η²(C,S)-coordinated thioketene cobalt complex [Co(C₁₁H₁₈S)-(PMe₃(C₅H₅)] (2a) with the electrophils [Mn(CO)₂(THF)(C₅H₅] and [Cr(CO)₅(THF)] gives the dinuclear thioketene complexes (4) with two different metal atoms in the molecule. The structure of the cobalt manganese compound was determined by X-ray diffraction. Protonation of the mononuclear thioketene complexes 2 give novel cationic η²-bonded thioacyl compounds [Co(η²-RCS)-(PMe₃(C₅H₅)]⁺ (9), as confirmed by X-ray analysis.     

Substituted derivatives of tris(butadiene)-molybdenum and -tungsten; the molecular structures of (CH2CMeCMeCH2)3M (M = Mo,W)

Tris(substituted butadiene) complexes of molybdenum and tungsten have been prepared by the reduction of the metal halides with anthracene-activated magnesium in the presence of the appropriate diene. An X-ray diffraction study has shown tris(2,3-dimethylbutadiene)molybdenum and its tungsten analogue to be isomorphous, with each diene unit displaying a long—short—long bond alternation, and having short metal to terminal carbon atom distances, in marked contrast to the unsubstituted complexes.     

Ungesättigte silicium- und germaniumverbindungen: XVI. Stabilisierung des labilen silaethens Me2SiC(SiMe3)2 durch adduktbildung mit donoren. Reaktivität von Me2SiMe3)2 · NME3

Silaethene Me₂SiC(SiMe₃)₃ (1), unstable at −100°C with regard to dimerization, forms an adduct Me₂SiC(SiMe₃)₂ · NMe₃ (1 and NME, and can, therefore, serve as a source of 1. With 1 as an intermediate, the adduct 3 reacts with butadiene, cyclopentadiene, 2,3-dimethylbutadine, Ph₂CNSiMe₃, ^tBuN₃, isobutene or acetone giving either cycloadducts or ene reaction products. Adduct 3 reacts with ROH (R = H, Me, ^tBu, Ph) to yield insertion products, probably by way of a proton adduct of 3, but not via 1. Other donors (D) of which NMe₃ is an example form adducts 1 · D, producing a new class of silicon compounds. As the Lewis basicity of D, relative to 1, decreases (F⁻ ρ NMe₃ ρ NEt₃ ρ Br⁻ ρ THF), the resistance to decomposition of the adducts 1 · D to the dimer of 1 and D also decreases.     

Insertion reactions of [Pt(PPh3)2] fragments into the four-membered ring complex [W(CO)5PPhC(OEt)CPhCHPh]. Crystal and molecular structures of [Pt(dppe)PPh(W(CO)5)C(OEt)CPhCHPh] and [Pt(PPh3)2((W(CO)5)PhPC(OEt)CPhCHPh)(η2-PC))]

Insertion of platinum bis(phosphane) fragments into a 1,2-dihydrophosphete ring lead to complexes derived from a 1-phosphabuta-1,3-diene species.     

The synthesis of and nuclear magnetic resonance strudies on bimetallic chromium(0), or molybdenum(0) carbonyl complexes containing bridging trans-Ph2PCHCHPPh2 ligands: Crystal structure of [Mo2(CO)8(μ-trans-PH2PCHCHPPh2)2]

The trans-PH₂PCH=CHPPh₂ (t-dppe)-bridged bimetallic 10-membered ring complexes [M₂(CO)₈(μ-t0dppe)₂] (M = Cr or MO) have been synthesized by treatment of the metal hexacarbonyl with one equivalent of t-dppe at elevated temperature. the fluxional process in the Mo(μ-t-dppe) Mo ring has been studied by variable temperature ¹³P-{¹H} NMR spectroscopy and is characterised by a change from an A₄ spin system at +20°C to an AA′BB′ system at −100°C. The bimetallic complex [Mo₂(CO)₆(μ-tdppe)₃] has been prepared and ¹³P-{¹H} NMR studies indicate that in solution all four phosphorus nuclei are equivalent, even at −115°C. Attempts to prepare related heterobimetallic complexes are also described. Crystals of [Mo₂(CO)₈(μ-trans-Ph₂PCH=CHPPh₂)₂] are monoclinic, space group P2₁/a, with a 2020.2(5), b 1423.1(5), c 2145.1(5) pm, β 113.95(2)°, and Z = 4; final R factor 0.0465 for 5668 observed reflections. The structure shows two [Mo(CO)₄] moieties linked by two trans-dppe bridges to give a 10-membered Mo₂P₄C₄ ring.     

Different modes of hydrogen migration in reactions of diphosphaallene,ArPCPAr (Ar = 2,4,6-But3C6H2) with [W(CO)5(THF)] and [Fe3(CO)12]. Crystal and molecular structure of [Fe2(CO)6(ArPCHPCH2(CMe2)C6H2But2)]

Rearrangement of ArPCPAr (Ar = 2,4,6-Bu^t₃C₆H₂) involving hydrogen migration from carbon to phosphorus occurs on heating with [W(CO)₅(THF)], but with [Fe₃(CO)₁₂] an unusual carbon to carbon hydrogen migration results.     

The stereoselective reaction of sodium cyanide with the cationic ruthenium vinylidene complex [(η5-C5H5)(PMe3)2RuCC(Me)Ph]+

The reaction of sodium cyanide with [(η⁵-C₅H₅)(PMe₃)₂RuCC(Me)Ph]PF₆ (1) proceeds with high stereoselectivity (> 95 : 5) to give (Z)-(η⁵-C₅H₅)(PMe₃)₂RuC(CN)C(Me)Ph, which under acid conditions isomerises (< 5 : 95) to the E isomer.     

The reaction of Sn[CH(SiMe3)2]2 with ethyne: formation of (HCC)Sn[CH(SiMe3)2]2(μ-trans-CHCH)Sn[CH-(SiMe3)2]2(CHCH2)

The reaction of Sn[CH(SiMe₃)₂]₂ and ethyne at ambient temperature affords a mixture of products, from which the title compound has been separated and identified by IR, ¹H, and ¹³C NMR spectroscopy.     

The synthesis of thionitrosodimethylamine (Me2NNS) complexes of ruthenium,osmium, and iridium

Neutral hydrido complexes [ML]ClH(PPh₃)₃ ([ML] = Ru(CO), Os(CO) and Ir(Cl)] react with thionitrosodimethylamine, Me₂NNS, to give [ML]ClH-(SNNMe₂)(PPh₃)₂ with H trans to Me₂NNS, while the hydrido cations cis,trans-[[ML]H(SNNMe₂)₂(PPh₃)₂]⁺ are obtained from Me₂NNS and [Ru(NCMe)₂(CO)-(PPh₃)₂]⁺, [OsH(OH₂)(CO)(PPh₃)₃]⁺ and [IrClH(NCMe)₂(PPh₃)₂]⁺, respectively. The coordinatively unsaturated aryl complexes [ML′]Cl(p-tolyl)(PPh₃)₂ ([ML′]Ru(CO), Os(CO) and Os(CS)) coordinate one molecule of Me₂NNS to give [ML′]Cl(p-tolyl)(SNNMe₂)(PPh₃)₂, the chloride ligands of which are labile. Spectroscopic data suggest that in all these complexes the Me₂NNS ligand adopts a η¹(S) coordination mode.