Elaine M. Armstrong

X-ray crystal structure and 13C NMR spectra of [WI2(CO)3(NCMe)2]

Abstract The X-ray crystal structure of [WI 2 (CO) 3 (NCMe) 2 ] ( 1 ) was determined and the crystals are orthorhombic with a = 12.405(8), b = 7.590(8), c = 13.844(12) A. X-ray data for 911 independent reflections above background were collected on a diffractometer and the structure determined by Fourier methods and refined to R = 0.074. The tungsten geometry is capped octahedral with a carbonyl ligand in the unique capping position. The iodide ligands are trans to each other with the two acetonitrile and octahedral carbonyl ligands cis to each other. The low temperature (−70°C, CD 2 Cl 2 ) 13 C NMR spectrum of ( 1 ) showed carbonyl resonances at δ = 202.36 and 228.48 ppm with an intensity ratio of 2 : 1. The resonance at lower field can be ascribed to the carbonyl ligand in the unique capping position. However, the room temperature 13 C NMR spectrum of ( 1 ) shows a single carbonyl resonance at δ = 219.65 ppm.

Reactions of [WI2(CO)(NCMe)(η2-RC2R)2] (R = Me or Ph) with carbon monoxide to give either [WI2(CO)2(η2-MeC2Me)2] or [W(-I) I(CO) (η2-PhC2Ph)2]2. Crystal structure of [WI2(CO) 2( η2-MeC2Me)2]

Abstract The complexes [WI 2 (CO)(NCMe)(η2)-RC 2 R) 2 ] (R = Me and Ph) react in CH 2 Cl 2 with an excess of carbon monoxide to give initially the acetonitrile substituted products [WI 2 (CO) 2 (η 2 -RC 2 R) 2 ]. For R= Me, the complex [WI 2 (CO) 2 (η 2 - MeC 2 Me) 2 ] (1) was isolated and its structure determined by X-ray crystallography. However, for R = Ph, dimerisation occurs to give the iodide-bridged compound [W(μ-I)I(CO)(η 2 -PhC 2 Ph) 2 ] 2 (2) with loss of carbon monoxide. These reactions are reversible as 1 and 2 react with acetonitrile to give [WI 2 (CO)(NCMe)(η 2 -RC 2 R) 2 ]. The 13 C NMR spectra of I and 2 indicate that the two alkyne ligands donate a total of six electrons to the tungsten in these complexes.

Solid state structures and 13C NMR spectra of the seven-coordinate complexes [WI2(CO)3(NCR)2] (R Me or Et)

Abstract The X-ray crystal structures of the two seven-coordinate complexes [WI 2 (CO) 3 (NCR) 2 ] {R  Me ( 1 ) or Et ( 2 )} have been determined. In both structures, the molecules have crystallographic m symmetry. The geometries of the metal coordination spheres are very similar, conforming reasonably well to distorted capped octahedra. The 13 C NMR spectra of 1 and 2 are also described, and for the case of complex 1 can be correlated with the crystallographically aobserved geometry.

Reactions of the bis(alkyne) complexes [Wi2(CO)(NCMe)(η2-RC2R)2](R = Me or Ph) with mono- and bi-dentate phosphine-donor ligands and the X-ray crystal structure of [Wl2(CO){Ph2P(CH2)PPh2}(η2-MeC2Me)]

Reaction of the complexes [Wl2(CO)(NCMe)(η2-RC2R)2](R = Me or Ph) either with 2 equivalents of L{L = PMe3, PEt3, PBun3, PMe2Ph, PMePh2, PEt2Ph, PEtPh2, PPh2(CH2CHCH2)[(PPh3) and PPh2(C6H11) for R = Me only]} or 1 equivalent of L2{L2= Ph2P(CH2)nPPh2(n= 1,2,3,4, or 6) or [Fe(η5-C5H4PPh2)2] for R = Me only} in CH2Cl2, at room temperature affords good yields of the compounds [Wl2(CO)L2(η2-RC2R)](1)–(24) by successive substitutions of acetonitrile and an alkyne ligand. X-Ray crystallographic studies were carried out on the complex [Wi2(CO){Ph2P(CH2)PPh2}(η2-MeC2Me)](19). Crystals of (19) are monoclinic, space group P21/n with a= 12.208(4), b= 13.395(2), c= 20.820(6)A, and β= 104.31(2)°. The structure was refined to R= 0.052 (R′= 0.060) for 2 860 reflections with Fo < 3σ(Fo). The tungsten co-ordination may be described in terms of a pseudo-octahedral structure. The bidentate phosphine ligand, but-2-yne, and an iodide ligand occupy the four equatorial sites, and the carbonyl and iodide ligands the two axial sites. The but-2-yne ligand is oriented so that it is approximately coplanar with the axial ligands. Phosphorus-31 n.m.r. and i.r. spectral studies are interpreted to suggest the likely structures for the other [Wl2(CO)L2(η2-RC2R)] complexes. The barrier to but-2-yne rotation of a number of complexes has been determined by variable-temperature 1H n.m.r. spectroscopy. These results are discussed in terms of the electronic and steric effects of the phosphorus-donor ligands and also the di-iodo complexes are compared with the analogous dibromo and dichloro complexes reported by other workers. The 13C n.m.r. chemical shifts of the alkyne contact carbons suggest that the alkyne ligand is acting as a four-electron donor in these complexes.

Mono- and dinuclear phosphine coordinated 1,4-bis(diphenylphosphino)ethyne seven-coordinate complexes of molybdenum(II) and tungsten(II)

Abstract Equimolar quantities of the seven-coordinate compounds [MI 2 (CO) 3 (NCMe) 2 ] (M = Mo and W) and Ph 2 PCCPPh 2 react in CH 2 Cl 2 at room temperature to afford the Ph 2 PCCPPh 2 phosphine coordinated bridged complexes [M 2 I 4 (CO) 6 (μ-Ph 2 PCCPPh 2 ) 2 ] in good yield. Reaction of [MI 2 (CO) 3 (NCMe) 2 ] with two equivalents of Ph 2 PCCPPh 2 in CH 2 Cl 2 at room temperature gives the mononuclear compounds [MI 2 (CO) 3 (Ph 2 PCCPPh 2 ) 2 ]. 31 P NMR studies show the Ph 2 PCCPPh 2 ligand in [MI 2 (CO) 3 (Ph 2 PCCPPh 2 ) 2 ] to have monodentate phosphine coordination.

Reactions of the complexes [WI2(CO)(NCMe)(η2-RC2R)2](R = Me or Ph) with dithiocarbamates and related ligands, and the X-ray crystal structure of [WI(CO)(S2CNC4H8)(η,2-MEC2Me)2]

The complexes [WI2(CO)(NCMe)(η2-RC2R)2](R = Me or Ph) react with 1 equivalent of S2CX–[X = NMe2, NEt2, N(CH2Ph)2, OEt, NC4H8, or NC5H10] in CH2Cl2 or Et2O at room temperature eventually to give the new bis(alkyne) complexes [WI(CO)(S2CX)(η2-RC2R)2]. Infrared spectral studies of the reaction of [WI2(CO)(NCMe)(η2-MeC2Me)2] with 1 equivalent of Na[S2CNEt2]·3H2O in CH2Cl2 suggest the formation of several intermediates including those with monodentate dithiocarbamate attached to tungsten. X-Ray single-crystal studies wen carried out on the compound [WI(CO)(S2CNC4H8)(η2-MeC2Me)2](9). Crystals of (9) are monoclinic, space group P21/n, in a unit cell of dimensions a= 9.256(8), b= 17.685(14), c= 10.962(11)A, and β 90.5(1)°. The structure was refined to R= 0.061 for 2 097 reflections above background. The co-ordination geometry around the tungsten is octahedral with the two parallel cis-but-2-yne ligands trans to a sulphur and an iodide with the other sulphur of the dithiocarbamate and the carbonyl ligand occupying the axial sites. Variable-temperature 1H n.m.r. studies show complex (9) to he fluxional in solution. The complexes [WI2(CO)(NCMe)(η2-RC2R)2] also react with 2 equivalents of S2CX–[R = Me, X = NMe2, NEt2, N(CH2Ph)2, OEt, NC4H8, or NC5H10; R = Ph, X = NEt2 or OEt] to give the monoalkyne complexes [W(CO)(S2CX)2(η2-RC2R)]. 13C N.m.r. spectroscopy shows that the alkyne ligands in the bis(alkyne) complexes [WI(CO)(S2CX)(η2-RC2R)2] are donating an average of three electrons each to the metal, whereas the alkyne ligand in [W(CO)(S2CX)2(η2-RC2R)] is donating four electrons to the tungsten.

1,4-Diphenylbutadiyne complexes of tungsten(II)

Equimolar quantities of [WI2(CO)3(NCMe)2] and 1,4-diphenylbutadiyne (PhC2C2Ph) react in CH2Cl2 at room temperature to eventually give the iodo-bridged dimer [W(μ-I)I(CO)(NCMe)(η2PhC2C2Ph)]2 (1). Reaction of [W2(CO)3(NCMe)2] with two equivalents of PhC2C2Ph eventually afforded [WI2(CO)(NCMe)(η2-PhC2C2Ph)2] (2). The bimetallic 1,4-diphenylbutadiyne complex [W2I4(CO)2(NCMe)2(μ2,μ2′-η2,η2′-PhC2C2Ph)2] (3) was synthesized by reaction of equimolar quantities of 2 and [WI2(CO)3(NCMe)2]. The reactions of 1 and 2 with mono- and bidentate neutral donor ligands are also described.

Reactions of [WI2(CO)(NCMe)(η2-RC2R)2] (R Me or Ph) with t-butylisonitrile

Abstract The complexes [WI2(CO)(NCMe)(η2-RC2R)2] (R  Me or Ph) react with one, two, three, four, or five equivalents of CNtBu in CH2Cl2 at room temperature to give [WI2(CO)(CNtBu)(η2-RC2R)2] (1 and 2), [WI2(CO)(CNtBu)2(η2-RC2R)] (3 and 4), [WI2(CNtBu)3(η2-RC2R)] (5 and 6), [WI(CNtBu)4(η2-RC2R)]I (7 and 8), [W(CNtBu)5(η2-RC2R)]2I (9 and 10) respectively. The 1H NMR data are used to indicate the likely stereochemistry of 1–10, and the 13C NMR spectra to indicate the number of electrons donated by the alkyne ligands to the tungsten in selected compounds.

Tungsten(II) alkyne complexes containing monodentate neutral oxygen and sulphur donor ligands

Abstract The compounds [WI 2 (CO)(NCMe)(η 2 -RC 2 R) 2 ] (R = Me or Ph) react with one equivalent of L (L = OC(NH 2 ) 2 or SC(NH 2 )Me) at room temperature (for R = Me, L = OC(NH 2 ) 2 in acetone—methanol; R = Me, L = SC(NH 2 )Me in methanol; R = Ph, L = OC(NH 2 ) 2 , SC(NH 2 )Me in acetone) to give good yields of the acetonitrile substituted products [WI 2 (CO)L(η 2 -RC 2 R) 2 ]. 13 C NMR spectroscopy indicates that the alkyne ligands in these complexes are donating a total of six electrons to the metal. Reaction of [WI 2 (CO)(NCMe)(η 2 -PhC 2 Ph) 2 ] with one equivalent of L [L = SC(NH 2 ) 2 (tu) and SC(NMe 2 ) 2 (tmtu)] in acetone at various temperatures gave a mixture of products. However, reaction of [WI 2 (CO)(NCMe)(η 2 -MeC 2 Me) 2 ] with two equivalents of L (L = tu or tmtu) in acetone at room temperature gave the monobut-2-yne products [WI 2 (CO)L 2 (η 2 -MeC 2 Me)], whereas reaction of [WI 2 (CO)(NCMe)(η 2 -PhC 2 Ph) 2 ] with two equivalents of tu in dichloro-methane—methanol gave the non-carbonyl containing bisdiphenylacetylene complex [WI 2 (tu) 2 (η 2 -PhC 2 Ph) 2 ]. Reaction of [WI 2 (CO)(NCMe)(η 2 -PhC 2 Ph) 2 ] with two equivalents of tmtu in acetone eventually gave the unusual iodide-bridged dimer [W(μ-I)I(CO)(tmtu)(η 2 -PhC 2 Ph)] 2 ·tmtu. 13 C NMR spectroscopy suggests that the alkyne ligands in [WI 2 (tu) 2 (η 2 -PhC 2 Ph) 2 ] are donating six electrons to the metal and each alkyne in the dimer [W(μ-I)I(CO)(tmtu)(η 2 -PhC 2 Ph)] 2 is donating four electrons to the tungsten.

Reactions of [WI2(CO)(NCMe)(η2-RC2R)2] (R = Me or Ph) with 1,4-diaza-1,3-butadienes

Abstract Reaction of [WI 2 (CO)(NCMe)(η 2 -RC 2 R) 2 ] (R = Me or Ph) in CH 2 Cl 2 at room temperature with an equimolar quantity of R′N: CHCH: NR′ (R′ = Cy, i Pr, Ph, p -MePh or p -MeOPh) gave high yields of the new cationic bisalkyne complexes [WI(CO)(R′N: CHCH: NR′)(η 2 -RC 2 R) 2 ]I via successive displacement of acetonitrile and an iodide ligand. The cationic compounds [WI(CO)(CyN: CHCH: NCy)(η 2 -RC 2 R) 2 ][BPh 4 ] were also prepared by reaction of [WI 2 (CO)(NCMe)(η 2 -RC 2 R) 2 ] with CyN: CHCH: NCy in the presence of Na[BPh 4 ] in order to confirm the ionic nature of these complexes. 13 C NMR spectroscopy indicated that the two alkyne ligands are donating a total of six electrons to the metal in these complexes.