Izabela Czeluśniak

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.

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.

Polymerization of tert-butylacetylene by seven-coordinate heterobimetallic tungsten(II) and molybdenum(II) compounds

Abstract The reaction of tert -butylacetylene ( t -BA) in the presence of seven-coordinate tungsten(II) and molybdenum(II) compounds [MCl(M′Cl 3 )(CO) 3 (NCR) 2 ] (M=Mo, W; M′=Sn, Ge; R=Me, Et) leads to the catalytic coupling of t -BA molecules and the formation of high-molecular-weight ( M n >10 5 ) soluble polymers. The geometric structure of poly( tert -butylacetylene) (P- t -BA) was determined by means of 1 H- and 13 C-NMR spectroscopy. The monitoring of the reaction between t -BA and the metal complex by means of 1 H-NMR spectroscopy provided further insight into the initiation step of this polymerization process. The reaction of a heterobimetallic compound with a stoichiometric amount of t -BA yields compounds in which CO and/or nitrile ligands have been replaced by a t -BA ligand. The alkyne molybdenum(II) and tungsten(II) complexes formed were characterized structurally by means of IR and NMR spectroscopy. The possible mechanisms for the formation of very reactive intermediate compounds and their role in the catalytic process are discussed.

Reactivity of [Mo(μ-Cl)(SnCl3)(CO)3(NCMe)2] towards norbornadiene.: X-ray crystal structure of [Mo(μ-Cl)(SnCl3)(CO)2(η4-C7H8)(NCMe)]

Reaction of [Mo(μ-Cl)(SnCl 3 )(CO) 3 (NCMe) 2 ] ( 1 ) with bicyclo[2.2.1]hepta-2,5-diene (norbornadiene) at room temperature in dichloromethane solution affords a mixture of compounds containing norbornadiene ligands. The formation of [Mo(μ-Cl)(SnCl 3 )(CO) 3 (η 4 -C 7 H 8 )] ( 2 ) is observed from the beginning of the reaction, but other compounds, such as [Mo(μ-Cl)(SnCl 3 )(CO) 2 (η 4 -C 7 H 8 )(NCMe)] ( 3 ), [Mo(SnCl 3 ) 2 (CO)(η 4 -C 7 H 8 )(NCMe) 2 ] ( 4 ) and [MoCl 2 (CO)(η 4 -C 7 H 8 )(NCMe) 2 ] ( 5 ), are also formed in variable amounts, as shown by IR and NMR investigation of the reaction mixture. The structure of a novel compound 3 was established by the single-crystal X-ray diffraction method. The environment of the molybdenum atom in 3 can be described as a distorted pentagonal bipyramid. Two carbonyl ligands are mutually cis . The IR, 1 H and 13 C NMR spectra of new molybdenum complexes containing norbornadiene ligands are also described and correlate with the crystallographically observed geometry. Reaction of 3 with an excess of norbornadiene is accompanied by the ring-opening metathesis polymerisation and the formation of polynorbornadiene. The initiation mechanism of this catalytic reaction by seven-coordinate molybdenum(II) compounds is proposed.

A novel Mo–Sn chlorocarbonyl compound. X-ray crystal structure of [(CO)4Mo(μ-Cl)3Mo(SnCl3)(CO)3] and [MoCl(SnCl3)(CO)3(NCEt)2]

Abstract The new heterobimetallic complex [(CO)4Mo(μ-Cl)3Mo(SnCl3)(CO)3] (1) has been prepared by photochemical reaction of Mo(CO)6 with SnCl4. The structure of complex 1 was established by X-ray crystallography. The basic structural units of 1 are two seven-coordinate molybdenum atoms, which are linked by three chlorine atoms occupying a bridging position between the molybdenum atoms. The mononuclear seven-coordinate complex [MoCl(SnCl3)(CO)3(NCMe)2] (2) is formed by reaction of [(CO)4Mo(μ-Cl)3Mo(SnCl3)(CO)3] with acetonitrile. Treatment of compound 2 with propionitrile affords [MoCl(SnCl3)(CO)3(NCEt)2] (3). A single-crystal X-ray diffraction study of the complex [MoCl(SnCl3)(CO)3(NCEt)2] (3) showed that the environment of the molybdenum atom is a distorted capped octahedron with the SnCl3 anionic ligand occupying the unique capping position above an octahedral face defined by the bridging chlorine and two carbonyl groups.

The oxidative addition of SnCl4 to [W(CO)4(NCMe)(PPh3)]. The X-ray crystal structure of [WH(CO)3(NCMe)(PPh3)2][SnCl5·MeOH]

Abstract The oxidative addition reaction of SnCl4 with [W(CO)4(NCMe)(PPh3)] in acetonitrile gives a mixture of seven-coordinate tungsten(II) compounds: [WCl(SnCl3)(CO)3(NCMe)(PPh3)] (1), [WCl2(CO)3(NCMe)(PPh3)] (2), [WCl(SnCl3)(CO)2(NCMe)2(PPh3)] (3), and [WCl2(CO)2(NCMe)2(PPh3)] (4) identified by IR and NMR (1H, 13C{1H}, and 31P{1H}) studies. Treatment of [W(CO)4(NCMe)(PPh3)] with 1 equiv. of SnCl4 in CH2Cl2 solution besides compounds 1 and 2 also gives ionic species such as [HPPh3]+ and [SnCl6]2− and cationic tungsten(II) complexes. The crystal structure of one of these, [WH(CO)3(NCMe)(PPh3)2][SnCl5·MeOH] (5), has been established by single-crystal X-ray diffraction. The IR, 1H, 13C{1H} and 31P{1H} spectra of 5 are also described and can be correlated with the crystallographically observed geometry. A notable feature of 5 is the presence of an agostic interaction of the hydride ligand with one of the carbonyl ligands.

A novel heterobimetallic W–Ge compound. X-ray crystal structure of [W(μ-Cl)(GeCl 3 )(CO) 3 (η 4 -C 7 H 8 )]

Abstract The new heterobimetallic complex [W(μ-Cl)(GeCl3)(CO)3(η4-C7H8)] (1) has been prepared by photochemical reaction of W(CO)6 with bicyclo[2.2.1]hepta-2,5-diene (NBD) and GeCl4. The structure of compound 1 was established by X-ray crystallography. The IR, 1 H and 13 C NMR spectra are also described and correlated with the crystallographically observed geometry. Compound 1 is noteworthy since it is the first alkene complex of tungsten isolated in W(CO)6 – Lewis acid photocatalytic system.

Reactivity of [WCl(SnCl3)(CO)3(NCMe)2] towards tBuCCH.: X-ray crystal structure of [WCl(CO)(tBuCCH)(NCMe)(PPh3)2]2[SnCl6]

In the reaction of [WCl(SnCl 3 )(CO) 3 (NCMe) 2 ] with tert -butylacetylene the very labile bis(alkyne) complex [WCl(SnCl 3 )(CO)( t BuCCH) 2 (NCMe)] has been observed as the major product by means of IR and NMR spectroscopy. The latter compound in reaction with two equivalents of PPh 3 in CH 2 Cl 2 solution gives very poorly soluble purple crystals of the tungsten(II) cationic complex. The crystal structure of this compound consists of the discrete [SnCl 6 ] 2− anion, two independent [WCl(CO)( t BuCCH)(NCMe)(PPh 3 ) 2 ] + cations and four MeCN (solvent) molecules. This is the first crystallographically characterized cationic chlorocarbonyl complex of tungsten(II) containing a terminal alkyne as ligand.

Reaction of [(CO)4Mo(μ-Cl)3Mo(SnCl3)(CO)3] with PhCCPh. X-ray crystal structure of [Mo3(μ3-O)(μ3-Cl)(μ2-Cl)(μ2-OH)2(O)(η2-PhCCPh)5]

Abstract Reaction of [(CO4Mo(μ-Cl)3Mo(SnCl3)(CO)3] 1 with PhCCPh in inert atmosphere affords the mixture of alkyne halocarbonyl compounds, which after exposure to moist air rearranges to give the complex [Mo3(μ3-O)(μ3-Cl)(μ2-Cl)(μ2-OH)2(O)(η2-PhCCPh5)] 2. The structure of complex 2 was established by X-ray crystallography. The molecule consists of a nearly isosceles triangle of Mo atoms joined by triply bridging oxygen and chlorine atoms. Compound 2 is noteworthy since it is the first trinuclear complex of molybdenum in which a mixed-valence Mo2IIMoIV core has been established.