Paul K. Baker

The synthesis and spectral properties of some highly reactive new seven-coordinate molybdenum(II) and tungsten(II) bisacetonitrile dihalogenotricarbonyl complexes

Abstract The complexes [M(CO) 3 (NCMe) 3 ] (M = Mo and W) react with X 2 (X = Br and I) in NCMe to afford high yields of the new seven-coordinate complexes [MX 2 (CO) 3 (NCMe) 2 ].

Oxidation of [Mo(CO)3(NCMe)3] with SnCl4 to give the seven-coordinate compound [MoCl(SnCl3)(CO)3(NCMe)2]. Reactions of [MoCl(SnCl3)(CO)3(NCMe)2] with phosphine donor ligands

Abstract The trisacetonitrile complex [Mo(CO) 3 (NCMe) 3 ] reacts in situ with an equimolar quantity of SnCl 4 to give a quantitative yield of the new seven-coordinate complex [MoCl(SnCl 3 )(CO) 3 (NCMe) 2 ]. This reacts with two equivalents of Ph 3 in acetone at room temperature to give a good yield of the stable complex [MoCl(SnCl 3 )(CO) 3 (PPh 3 ) 2 ]. Reaction of [MoCl(SnCl 3 )(CO) 3 (NCMe) 2 ] with one equivalent of PPh 2 (CH 2 ) n PPh 2 ( n = 1–3, 6) in acetone at room temperature gives the expected seven-coordinate species [MoCl(SnCl 3 )(CO) 3 PPh 2 (CH 2 ) n PPh 2 ].

The reactions of [MI2(CO)3(NCMe)2] (M = Mo or W) with one equivalent of L(L = phosphorus, arsenic and antimony donor ligands) to afford [MI2(CO)3(NCMe)L] and [M(μ−I)I(CO)3L]2

SummaryThe complexes [MI2(CO)3(NCMe)2] (M=Mo or W) react with one molar equivalent of L in CH2Cl2 at room temperature initially to afford the mononuclear sevencoordinate complexes [MI2(CO)3(NCMe)L] which have been isolated for L-PPh3, AsPh3, SbPh3, PPh2Cy or P(OPh3)3. Many of these complexes dimerise to give the iodide bridged compounds [{M(μ−I)I(CO)3L}2]via displacement of acetonitrile. When L=PPhCy2, PCy3, PEt3 or P(OMe)3 only the dimeric complexes have been isolated. The ease of dimerisation of the mononuclear complexes [MI2(CO)3(NCMe)L] is discussed in terms of the electronic and steric effects of the ligands, L. Low temperature13C n.m.r. spectroscopy of the mononuclear [Wl2(CO)3(NCMe)(EPh3)](E=P or As) complexes are interpreted as suggesting the likely stereochemistry of these seven-coordinate complexes.

Reactions of co-ordinated ligands. Part 27. Formation of η3-allyl and σ-vinyl complexes by nucleophilic attack on cationic molybdenum monoacetylene complexes. Molecular structures of [Mo(CO)(PEt3)(η3-anti-1-MeC3H4)(η5-C9H7)] and [Mo{P(OMe)3}3{σ-(E)-CHCHBut}(η-C5H5)]

Reaction of [MoLL1(η-MeC2R)A][BF4][R = Me, Et, or Pri; L = L1= P(OMe)3; LL1= Ph2PCHCHPPh2; L = PEt3, L1= CO; A =η-C5H5 or η5-C9H7] with NaBH4 or K[BHBus3] in tetrahydrofuran affords the anti-substituted η3-allyl complexes [MoLL1(η3-CH2CHCHR)A]. The structure of the complex [Mo(CO)(PEt3)(η3-anti-1-MeC3H4)(η5-C9H7)] was established by single-crystal X-ray crystallography. Crystals are monoclinic, space group P21/n with a= 10.038(2), b= 17.291(4), c= 11.346(3)A, β= 95.000(18)°, and Z= 4. Using 3 887 reflections measured on a four-circle diffractometer at room temperature, the structure has been refined to R 0.0344, R′ 0.0459. The molecule adopts an exo-conformation with the methyl substituent of the allyl ligand in an anti-position cis to the carbonyl ligand. Treatment of the complex [Mo{P(OMe)3}2(η-HC2But)(η-C5H5)][BF4] with NaBH4 or K[BHBus3] in the presence of excess P(OMe)3 gives the σ-vinyl complex [Mo{P(OMe)3}3{σ-(E)–CHCHBut}(η-C5H5)], structurally identified by n.m.r, spectroscopy and X-ray crystallography. Crystals are monoclinic, space group P21/c with a= 11.731(3), b= 12.796(3), c= 18.827(4)A, β= 92.33(2)°, and Z= 4. Using 7 437 intensity data, measured at 195 K on a four-circle diffractometer, the structure has been refined to residuals R= 0.026, R′= 0.026. The molecule shows typical four-legged ‘piano-stool’ geometry with the vinyl group adopting E stereochemistry, σ-bonded to the molybdenum atom. In contrast, the reaction of K[BHBus3] with [Mo{P(OMe)3}2(η-HC2Pri)(η-C5H5)][BF4] in tetrahydrofuran at low temperature affords the allyl complex [Mo{P(OMe)3}2(η3-1,1-Me2C3H3)(η-C5H5)]. The n.m.r. spectra and mechanism of formation of these compounds are discussed.

Reactions of co-ordinated ligands. Part 24. The reaction of bis-(but-2-yne)carbonyl(η-cyclopentadienyl or η5-indenyl)molybdenum tetrafluoroborate with acetonitrile and phosphines; crystal structures of but-2-ynecarbonyl(η5-indenyl)(triethylphosphine)molybdenum tetrafluoroborate and but-2-yne(η5-indenyl)bis(trimethylphosphine)molybdenum tetrafluoroborate

Reaction of the compounds [Mo(CO)(RC2R1)2(η-C5H5 or η5-C9H7)][BF4] with refluxing acetonitrile in the presence of the respective acetylene affords the compounds [Mo(NCMe)(RC2R1)2(η-C5H5 or η5-C9H7)][BF4] where R = R1= Me; R = But, R1= H; R = Ph, R1= Me; R = Pr1, R1= H. Treatment of [Mo(CO)(RC2R1)2(η-C5H5 or η5-C9H7)][BF4] at room temperature in methylene chloride with PEt3, PPh3, or P(C6H11)3 gives the monoacetylene compounds [Mo(CO)L(RC2R1)(η-C5H5 or η5-C9H7)][BF4][L = PEt3, PPh3, P(C6H11)3; R = R1= Me; R = But, R1= H; R = Pri, R1= H; R = Ph, R1= Me; or R = R1= C6H4Me-4]. Reaction of the acetonitrile complexes with the phosphines PEt3, PMe3, PMePh2, Ph2PCHCHPPh2, (Ph2PCH2)2, or (Me2PCH2)2 results in the displacement of both the acetonitrile and one acetylene ligand to form complexes of the type [MoL2(RC2R1)-(η-C5H5 or η-5-C9H7)][BF4]. X-Ray single-crystal crystallographic studies were carried out on the compounds [Mo(CO)(PEt3)(MeC2Me)(η5-C9H7)][BF4] and [Mo(PMe3)2(MeC2Me)(η5-C9H7)][BF4]. Crystals of the former are monoclinic, space group P21/c, Z= 4, in a unit cell of dimensions a= 9.158(2), b= 14.726(2), c= 16.581(3)A, and β= 94.12(2)°. Crystals of the latter complex are also monoclinic, space group P21, Z= 2, in a unit cell of dimensions a= 8.661 (2), b= 10.293(2), c= 13.580(2)A, and β= 106.42(2)°. The structures have been refined to R 0.041 (R′ 0.045) and R 0.039 (R′ 0.048) for 4 329 and 2 052 respective reflections with I > 3σ(I). The molybdenum co-ordination in each cation may be described in terms of a pseudo-octahedral structure. The but-2-yne ligand adopts a similar conformation in both complexes lying approximately coplanar with either the Mo–CO or Mo–PMe3 bond. Variable-temperature 1H and 13C n.m.r. data are interpreted in terms of rotation of the acetylene. Examination of the 13C chemical shifts of the acetylene contact carbons suggests that in these complexes the acetylene ligand can act as a four-electron donor.

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.

Use of the seven-coordinate complexes [MXY(CO) 3(NCMe)2] (M = Mo or W; X, Y = halide) and their derivatives in homogeneous catalysis

Abstract The seven-coordinate halocarbonyl complexes, [MXY(CO) 3 (NCMe) 2 ] (M=Mo or W; X, Y=halide) and their derivatives have been investigated in several types of homogeneous catalytic reactions. These include, the alkene metathesis polymerisation of norbornadiene using either, [MX 2 (CO) 3 (NCMe) 2 ] (M=Mo or W;X=Br or I), [MI 2 (CO) 3 (L′- P , P ′)] {M=Mo or W; L′=MeC(CH 2 PPh 2 ) 3 } or [MXY(CO)(L or L′- P, P ′)(η 2 -RC 2 R′)] {X,Y=Cl, Br or I; L=PhP(CH 2 CH 2 PPh 2 ) 2 ; R,R′=Me, Ph}. The isolation and characterisation of a key intermediate, [WI 2 (CO) 2 (η 4 -nbd)] ( 1 ) (nbd=norbornadiene) is also described. The development of water soluble polymerisation catalysts using water-solubilising pyridine ligands, and the biphasic polymerisation of styrene using [WI 2 (CO) 3 (NC 5 H 4 CO 2 Na-4) 2 ], ZrCl 4 , sodium lauryl sulphate and sodium hydrogen phosphate is also discussed. The room temperature polymerisation of phenylacetylene using [WX 2 (CO) 3 (NCMe) 2 ] (X=Cl, I), [WI 2 (CO) 3 (NCMe)L] (L=PPh 3 , AsPh 3 ) or [WBr 2 (CO)(NCMe)(η 2 -HC 2 Ph) 2 ] ( 4 ) is also described, and a mechanism is proposed for these polymerisation reactions.

Seven-co-ordinate dibromo complexes of molybdenum(II) and tungsten(II) derived from [MBr2(CO)3(NCMe)2]. Crystal structures of the isostructural complexes [WX2(CO)3(NCMe)(SBPh3)]·Ch2Cl2(X = Br or I)

Reaction of the complexes fac-[M(CO)3(NCMe)3](M = Mo or W)(prepared in situ) with an equimolar quantity of Br2 at –78 °C afforded high yields of the seven-co-ordinate complexes [MBr2(CO)3(NCMe)2]. The reaction of these complexes with an equimolar amount of L (L = PPh3, AsPh3 or SbPh3) in CH2Cl2 at room temperature gave the new mixed-ligand complexes [MBr2(CO)3(NCMe)L]. The molecular structure of [WBr2(CO)3(NCMe)(SbPh3)]·CH2Cl2 and its diiodo analogue [WI2(CO)3(NCMe)(SbPh3)]·CH2Cl2 have been crystallographically determined. Crystals of the former are monoclinic of space group P21/c, a= 8.302(3), b= 26.199(3), c= 13.020(4)A, β= 97.53(2)°, Z= 4. Crystals of the latter are also monoclinic of space group P21/c, a= 8.450(2), b= 25.941 (6), c= 13.042(4)A, β= 96.47(2)°, Z= 4. The two complexes are isostructural and can best be described as distorted capped trigonal prismatic with one triangular face having three carbonyl ligands and the other triangular face having X(2), Sb and N. The X(1 ) atom caps the rectangular face defined by C(1), X(2), N and C(3). The low-temperature (–6O °C, CDCl3)13C NMR spectrum of [WI2(CO)3(NCMe)(SbPh3)]·CH2Cl2 was obtained and correlated with the solid-state structure. Reaction of [WBr2(CO)3(NCMe)2] with 2 equivalents of AsPh3 in CH2Cl2 at room temperature gave [WBr2(CO)3(AsPh3)2].

Halocarbonyl alkyne complexes of molybdenum (II) : crystal structures of [MoI2 (CO) (NCMe) (η2-RC2R) 2] (R=Me and Ph) and [MoI2 (CO) (5,6-Me2-1,10-phen) (η2-PhC2Ph) ]

Abstract Reaction of [MoXX′ (CO) 3 (NCMe) 2] with RC2R′ in CH2Cl2 at room temperature gave the bis (alkyne) complexes [MoXX′ (CO) (NCMe) (η2-RC2R′) 2] (X=X′=I, R=R′=Me; X=X′=Br, R=R′=Me, Ph; X′=I, X=Cl, Br, R=R′=Me, Ph) (1→7) in high yield. The molecular structures of [MoI2 (CO) (NCMe) (η2-RC2R) 2] (R=Me, Ph) have been determined by X-ray crystallography. The two structures are very similar, with the two alkyne ligands cis- and parallel to each other and trans- to the two iodo ligands. The carbon monoxide and acetonitrile ligands occupy the two axial sites. Treatment of [MoI2 (CO) (NCMe) (η2-RC2Ph) 2] with an equimolar amount of L∩L {for R=Ph, L∩L=5,6-Me2-1,10-phen, Ph2P (CH2) 2PPh2; for R=Me, L∩L=2,2′-bipy, Ph2P (CH2) nPPh2, n=1, 3, 4} yielded the mono (alkyne) complexes [MoI2 (CO) (L∩L) (η2-RC2Ph) ] (8→13) , which for L∩L=5,6-Me2-1,10-phen, R=Ph (8) was crystallogaphically characterised. The geometry around the molybdenum centre is essentially octahedral, with the phenanthroline ligand trans- to a carbonyl and an iodide ligand, with the alkyne and other iodide group in the axial sites. Reaction of [MoI2 (CO) (NCMe) (η2-MeC2Ph) 2] with two equivalents of NaS2CNMe2 in CH2Cl2 gave [Mo (CO) (S2CNMe2) 2 (η2-MeC2Ph) ] (14) .