Teresa Szymańska-Buzar

Photochemical reaction of W(CO)6 with SnCl4 I. Synthesis and X-ray structure of tri-μ-chloro-trichlorostannate-heptacarbonylditungsten(II) [(CO)4W(μ-Cl)3W(SnCl3)(CO)3]

The crystal structure of [(CO)4W(μ-Cl)3W(SnCl3)(CO)3] (1) formed in the photochemical reaction of W(CO)6 with SnCl4 was determined by the single-crystal X-ray diffraction method. The crystals are orthorhombic, of space group Pbca, a = 12.706(3) A, b = 16.655(4) A, c = 18.669(3) A, V = 3951(2) A3 and Z = 8. The structure solved by the heavy-atom method has been refined to R = 0.0299 for 2187 observed reflections. The tungsten atoms in the molecule are both seven-coordinate, each being bonded to three bridging chlorines, to four CO groups on one end and three CO groups and a SnCl3 group on the other. For each tungsten, there is a 4-3 geometry of ligand. Nuclear magnetic resonance, IR and electronic absorption spectroscopies were used to examine the litle compound. Compound 1 is a unique example of the halo carbonyls of Group 6 metals with an MSn bond.

The initiation of ring-opening metathesis polymerisation of norbornadiene by seven-coordinate molybdenum(II) compounds. X-ray crystal structure of [Mo(μ-Cl)(SnCl3)(CO)3(η4-NBD)]

Abstract The new heterobimetallic complex [Mo(μ-Cl)(SnCl 3 )(CO) 3 (η 4 -NBD)] ( 1 ) has been prepared by reaction of [(CO) 4 Mo(μ-Cl) 3 Mo(SnCl 3 )(CO) 3 ] with norbornadiene (NBD) at room temperature. The structure of complex 1 was established by X-ray crystallography. The IR, 1 H- and 13 C-NMR spectra of 1 are also described and can be correlated with the crystallographically observed geometry. In the presence of an excess of NBD compound 1 initiates the ring-opening metathesis polymerisation (ROMP). The initiation mechanism of ROMP by seven-coordinate molybdenum(II) compounds have been discussed. The microstructure of polynorbornadiene formed was determined by 1 H- and 13 C-NMR spectroscopy.

Ring-opening metathesis polymerization of norbornene and norbornadiene by tungsten(II) and molybdenum(II) complexes

Abstract The reaction of norbornene (NBE) and norbornadiene (NBD) in the presence of seven-coordinate tungsten(II) and molybdenum(II) complexes of the [(CO) 4 M(μ-Cl) 3 M(SnCl 3 )(CO) 3 ] and [MCl(M′Cl 3 )(CO) 3 (NCMe) 2 ] (M=W, Mo; M′=Sn, Ge) types leads to ring-opening metathesis polymerization (ROMP) and to the formation of high molecular weight polymers. The geometric structure of these polymers was determined by means of 1 H - and 13 C -NMR spectroscopy. The monitoring of the reaction between cyclic olefins and the metal complex by means of 1 H -NMR spectroscopy allowed us to observe the coordination of NBD to metal atoms in the initiation step of the polymerization process. Compounds of the [MCl(SnCl 3 )(CO) 3 (η 4 -NBD)] type prepared directly from [(CO) 4 M(μ-Cl) 3 M(SnCl 3 )(CO) 3 ] or [MCl(M′Cl 3 )(CO) 3 (NCMe) 2 ] (M=W, Mo) in the presence of an excess of NBD initiate the ROMP reaction immediately. The detection of the first-formed products in the reaction between the metal complex and cyclic olefins provides valuable information concerning the nature of the initiating species.

PHOTOCHEMICAL SYNTHESIS, SPECTROSCOPIC PROPERTIES AND BARRIERS TO ALKENE ROTATION IN THE NOVEL BIS(ALKENE) TETRACARBONYL COMPLEXES OF TUNGSTEN

Abstract Photolysis of W(CO) 6 in the presence of twentyfold alkene excess (1-pentene, 1-hexene, 2-hexene, 3-hexene, 1-heptene, 1-octene, 1-decene, cyclopentene, cyclohexene cycloheptene and cyclooctene) in n -hexane leads to the formation of the corresponding bis(alkene)tetracarbonyl complexes of tungsten via the less stable [( ν 2 -alkene)W(CO) 5 ] complexes; the products have been isolated and characterized by their IR, UV-visible and NMR spectra. Bis(alkene)tetracarbonyl complexes of tungsten exhibit fluxional behaviour on the NMR time scale due to rotation of the alkene ligands around the axis defined by the metal and the midpoint of the C 2 linkage. The barriers to alkene rotation, which reflects the energy difference between the ortogonal and the parallel arrangement of the two C=C units, of a number of bis(alkene) complexes, have been determined using variable-temperature 13 C NMR spectroscopy.

The structure of oxotricobalt acetate

Abstract The product of the oxidation reaction of cobalt(II) acetate in anhydrous acetic acid solution has been investigated. The IR, UV and visible spectra as well as magnetic susceptibility measurements on cobalt complex are discussed. According to those and polarographic and conductometric studies, the complex investigated has been reformulated as Co3O(OAc)6(HOAc)3.

Synthesis and reactivity of Mo–Sn compounds: X-ray crystal structure of a novel [Mo(SnCl3)2(CO)2(NCEt)3]

[Mo(CO) 4 (NCMe) 2 ] reacts with SnCl 4 in CH 2 Cl 2 to produce a mixture of compounds which can be regarded as the results of oxidative addition with the elimination of CO and the formation of a Mo–Sn bond. The compound [MoCl(SnCl 3 )(CO) 3 (NCMe) 2 ] 1 is the main product but others containing Mo–Sn bond compounds can be formed also in variable amounts, as was shown by IR and NMR investigation of the reaction mixture. The structure of a novel [Mo(SnCl 3 ) 2 (CO) 2 (NCEt) 3 ] 4 was established by X-ray crystallography. This is the first structurally characterized molybdenum(II) carbonyl complex containing two anionic SnCl 3 ligands and the very rare example of the 4:3 piano stool seven-coordinate geometry. In the reaction of 1 with alkynes, complexes were isolated in which CO and/or acetonitrile ligands were replaced by alkyne ligands. The alkyne molybdenum(II) complexes formed were characterized structurally by IR and NMR spectroscopy. However, the reaction of 1 with phenylacetylene leads to the catalytic coupling of alkyne molecules and the formation of cycloligomers and polymers. The possible mechanisms for the formation of molybdenum(II) complexes and their role in the catalytic process are discussed.

Reactions of W(CCMe3) (OCMe3)3 with terminal alkynes: metathesis and polymerization

Catalytic metathesis of terminal alkynes RCCH (R = alkyl, phenyl) is performed with the carbyne complex WCCMe3 (OCCMe3)3 1. This reaction is rapidly masked by a polymerization reaction, which is the only process occurring at low temperature. The production of deprotiometallacyclic complexes WC3R2(OCCMe3)2 2 by loss of tert-butyl alcohol from the metallacyclobutadiene intermediates is shown to be responsible for the deactivation in metathesis. Compounds of type 2 are extremely reactive in phenylacetylene polymerization.

Synthesis, structure and reactivity of novel W–Ge chlorocarbonyl compounds. X-ray crystal structure of [WCl(GeCl3)(CO)3(NCEt)2]

Abstract The reaction of GeCl4 with tungsten(0) compounds yielded heterobimetallic W–Ge complexes. The novel dinuclear complex [(CO)4W(μ-Cl)3W(GeCl3)(CO)3] 1 was obtained together with [W(CO)5(GeCl2)] 2 in a photochemical reaction of W(CO)6 with GeCl4. The mononuclear seven-coordinate complex [WCl(GeCl3)(CO)3(NCMe)2] 3 was formed in a reaction of complex 1 with acetonitrile or in a reaction of [W(CO)4(NCMe)2] with GeCl4 in dichloromethane. A single-crystal X-ray diffraction study of the complex [WCl(GeCl3)(CO)3(NCEt)2] 4 showed that the environment of the tungsten atom is a distorted capped octahedron with the GeCl3 anionic ligand occupying the unique capping position above an octahedral face defined by the three carbonyl groups. The position of the GeCl3 ligand is approximately trans to the W–Cl bond. The dinuclear complex 1 and the mononuclear complex 3 show similar behavior in reaction with alkynes. Complexes were isolated in which CO or/and acetonitrile ligands were replaced by alkyne ligands. The alkyne tungsten(II) complexes 7–13 formed were structurally characterized by IR and NMR spectroscopy. However, the reaction of 1 and 3 with phenylacetylene (PA) leads to polymerization and formation of a high molecular weight polyphenylacetylene (PPA). The structures and mechanisms of the formation of various new types of complexes and their role in the catalytic process are discussed.

SEVEN-COORDINATE COMPLEXES OF MOLYBDENUM(II) CONTAINING A TRICHLOROGERMYL LIGAND : X-RAY CRYSTAL STRUCTURE OF A NOVEL MO(GECL3)2(CO)2(NCET)3

The oxidative–addition of GeCl 4 to [Mo(CO) 4 (NCMe) 2 ] in CH 2 Cl 2 provides a high-yield and fast route to the trichlorogermyl complex [MoCl(GeCl 3 )(CO) 3 (NCMe) 2 ] ( 1 ). Beside 1 , other compounds containing a Mo–Ge bond are formed, as was shown by IR and NMR investigation of the reaction mixture. These compounds react further with an excess of propionitrile giving among others, a novel, crystallographically characterized [Mo(GeCl 3 ) 2 (CO) 2 (NCEt) 3 ] ( 3 ). Compound 3 is the first structurally characterized molybdenum(II) carbonyl complex, containing two trichlorogermyl ligands. Reaction of 1 or 3 with an alkyne (PhCCPh, PhCCMe, PhCCH) affords compounds in which CO and/or nitrile ligands were replaced by alkyne ligands. The alkyne molybdenum(II) complexes formed were characterized structurally by IR and NMR spectroscopy. However, the reaction of 1 with phenylacetylene (PA) leads to the catalytic coupling of alkyne molecules and the formation of cyclotrimers and polymers. The possible mechanisms for the formation of molybdenum(II) complexes and their role in the catalytic process are discussed.

Spectroscopic properties, structure and reactivity of [WCl(SnCl3)(CO)3(NCMe)2]

Abstract A series of seven-coordinate tungsten(II) nitrile complexes of the type [WCl(SnCl3)(CO)3(NCR)2](1–4), R=Me, Et, n-Bu, Ph, has been synthesized. These new complexes have been characterized by IR, NMR and UV-vis spectroscopy. In addition single-crystal X-ray diffraction was used to structurally characterize [WCl(SnCl3)(CO)3(NCMe)2](1). The most prominent feature of complex 1 is the facility by which acetonitrile and carbonyl ligands can be replaced by other ligands. Complexes were isolated in which CO and acetonitrile ligands were substituted by alkyne ligands. The alkyne tungsten(II) complexes 5–8 formed were structurally characterized by IR and NMR spectroscopy. The complex 1 has been found to be an active catalyst for the polymerization of phenylacetylene. The structures and mechanisms of the formation of various new types of complexes and their role in the catalytic process are discussed.