Margaret M. Meehan

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.

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) .

Tripodal triphos {MeC(CH2PPh2)3} complexes of molybdenum(II) and tungsten(II). Reactions of [MI2(CO)3{MeC(CH2PPh2)3P,P′}] (M=Mo or W) with molybdenum(II) and tungsten(II) complexes

Abstract Equimolar quantities of [MI 2 (CO) 3 (NCMe) 2 ] (M=Mo or W) and tripodal triphos {MeC(CH 2 PPh 2 ) 3 } react in CH 2 Cl 2 at room temperature for 5 min to give [MI 2 (CO) 3 {MeC(CH 2 PPh 2 ) 3  P , P ′}] ( 1 and 2 ) which contain one uncomplexed phosphorus donor atom capable of further coordination. Complexes 1 and 2 react in refluxing CHCl 3 for 15 h (M=Mo) or 72 h (M=W) to give the complexes [MI 2 (CO) 2 {MeC(CH 2 PPh 2 ) 3  P , P ′, P ″}] ( 3 and 4 ). The complexes [MI 2 (CO) 3 (NCMe) 2 ] (M=Mo or W) react with two equivalents of 1 (L Mo ) and 2 (L W ) to yield the trimetallic complexes [MI 2 (CO) 3 (L Mo or L W ) 2 ] ( 5 – 8 ). A series of mixed-ligand seven-coordinate bimetallic complexes of the type [MI 2 (CO) 3 L(L Mo or L W )] {M=Mo or W; L=PPh 3 , AsPh 3 , SbPh 3 ; for M=W, P(OR) 3 (R=Me, Et, Ph)} ( 9 – 17 ) have been prepared by reaction of [MI 2 (CO) 3 (NCMe) 2 ] with one equivalent of L to give [MI 2 (CO) 3 (NCMe)L], followed by an in situ reaction with L Mo or L W . Similarly, reactions of [MI 2 (CO) 3 {Ph 2 P(CH 2 ) n PPh 2 }] { n =1 or 2} (prepared in situ) with equimolar amounts of L Mo or L W affords the cationic complexes, [MI(CO) 3 (L Mo or L W ){Ph 2 P(CH 2 ) n PPh 2 }]I ( 18 – 21 ). Reaction of equimolar quantities of [MI 2 (CO)(NCMe)(η 2 -EtC 2 Et) 2 ] and L Mo (for M=Mo) or L W (for M=W) affords the acetonitrile displaced products, [MI 2 (CO)(L Mo or L W )(η 2 -EtC 2 Et) 2 ] ( 22 ) and ( 23 ). Treatment of [MI 2 (CO)(NCMe)(η 2 -EtC 2 Et) 2 ] with two equivalents of L Mo (for M=Mo) or L W (for M=W) gives the mono(3-hexyne) trimetallic complexes [MI 2 (CO)(L Mo or L W ) 2 (η 2 -EtC 2 Et)] ( 24 ) and ( 25 ). All the new complexes described in this paper have been characterised by elemental analysis, IR, 1 H- and 31 P-NMR spectroscopy.

Multimetallic complexes of molybdenum(II) and tungsten(II) derived from [WI2(CO){PhP(CH2CH2PPh2)2-P,P′}(η2-RC2R)](R = Me or Ph). Crystal structures of [WI2(CO){PhP(CH2CH2PPh2)2-P,P′}(η2-MeC2R)](R = Me or Ph)

Equimolar quantities of [WI2(CO)(NCMe)(η2-RC2R′)2](R = R′= Me or Ph; R = Me, R′= Ph) and PhP(CH2CH2PPh2)2(L) reacted in CH2Cl2 at room temperature to give the mono(alkyne) complexes [WI2(CO)(L-P,P′)(η2-RC2R′)] in high yield. The molecular structures of [WI2(CO)(L-P,P′)(η2-MeC2R)](R = Me or Ph) have been crystallographically determined. There are two independent molecules in the asymmetric unit which are diastereoisomers. The co-ordination pattern about the metal atom in [WI2(CO)(L-P,P′)(η2-MeC2Me)]·0.75CH2Cl21 is a distorted octahedron with two adjacent phosphorus atoms of the triphosphine, a carbonyl and an iodide ligand in the equatorial plane and an iodide and the but-2-yne ligand occupying axial sites. The complex [WI2(CO)(L-P,P′)(η2-MeC2Ph)] is also a distorted octahedron, with identical co-ordination to that of 1, except in that the but-2-yne ligand is substituted by the 1-phenylprop-1-yne ligand. In 1 there is a pendant arm of the triphosphine ligand free to co-ordinate with other species. The reactions of the complexes [WI2(CO)(L-P,P′)(η2-RC2R)](R = Me or Ph) as monodentate phosphine ligands with the molybdenum(II) and tungsten(II) complexes [MI2(CO)3(NCMe)2], [MI2(CO)3(NCMe)L′](L′= PPh3, AsPh3 or SbPh3), [MoCl(GeCl3)(CO)2(NCMe)2(PPh3)] and [WI2(CO)(NCMe)(η2-RC2R)2](R = Me or Ph) were found to give a range of bi- and tri-metallic complexes which have all been characterised.

Molecular structure and iodine oxidative-thermal decarbonylation of the seven-coordinate complex [MoI2(CO)3(NCMe)2] to give the crystallographically characterised complex mer-[MoI3(NCMe)3]

The X-ray crystal structure of the seven-coordinate complex [MoI2(CO)3(NCMe)2] (1) has been determined and shows discrete molecules. The geometry of the metal coordination sphere conforms to a distorted capped octahedron with a carbonyl group in the unique capping position. The capped face contains two carbonyl ligands and an iodo group, the uncapped face two MeCN ligands and an iodo group. The low temperature 13C n.m.r. spectrum (−70 °C, CD2Cl2) shows a single band at δ = 222.8 ppm, which suggests that the complex is rearranging more rapidly than the n.m.r. timescale at this temperature. Refluxing a 2:1 mixture of [MoI2 (CO)3(NCMe)2] and I2 in MeCN for 2h gives the crystallographically characterised molybdenum(III) complex mer-[MoI3(NCMe)3] (2) in quantitative yield.

2,2′:6′,2″-Terpyridine complexes of molybdenum(II) and tungsten(II). X-ray crystal structures of [MoI(CO)(terpy)(η2-PhC2Ph)]I and [WI(terpy)(η2-PhC2Ph)2]I·CDCl3

Abstract Equimolar quantities of [MI 2 (CO) 3 (NCMe) 2 ] (M=Mo or W) and terpy (terpy=2,2′:6′,2″-terpyridine) react in CH 2 Cl 2 at room temperature to give the cationic complexes [MI(CO) 3 (terpy)]I ( 1 and 2) in high yield. Treatment of [MoCl(GeCl 3 )(CO) 3 (NCMe)(PPh 3 )] with one equivalent of terpy affords [Mo(GeCl 3 )(CO) 2 (PPh 3 )(terpy)]Cl ( 3 ) in good yield. Reaction of [MI 2 (CO)(NCMe)(η 2 -RC 2 R) 2 ](M=Mo, W; R=Ph; for M=W only, R=Me) with an equimolar quantity of terpy in CH 2 Cl 2 at room temperature gives the cationic complexes [MI(CO)(terpy)(η 2 -RC 2 R)]I ( 4 and 5) or the crystallographically characterised cationic complex [WI(terpy)(η 2 -PhC 2 Ph) 2 ]I ( 6 ). Equimolar quantities of [WI(CO)(terpy)(η 2 -MeC 2 Me)]I( 5 ) and Na[BPh 4 ] react to give the anion-exchanged product, [WI(CO)(terpy)(η 2 -MeC 2 Me)][BPh 4 ] ( 7 ). The X-ray crystal structure of [MoI(CO)(terpy)(η 2 -PhC 2 Ph)]I shows the three nitrogen atoms of the terpy bonded in the equatorial plane of an octahedron together with the carbonyl group. The iodo and diphenylacetylene ligands are mutually trans - to each other in the axial positions. The structure of [WI(terpy)(η 2 -PhC 2 Ph) 2 ]I·CDCl 3 ( 6 ) has a distorted octahedral geometry, with the three nitrogen atoms of the terpy ligand in a mer -configuration, with two cis -and parallel diphenylacetylene ligands and an iodo group occupying the other three mer -sites.

The first iodine induced halide abstraction reaction: synthesis and molecular structure of fac-[Re(CO)3(NCMe)3]·BrI2

Abstract Equimolar quantities of [ReBr(CO)5] and I2 react in refluxing acetonitrile for 5 h to give the cationic tris(acetonitrile) complex fac-[Re(CO)3(NCMe)3]·BrI2 (1) in a quantitative yield, via the first iodine promoted halide abstraction reaction. The structure of 1 has, as expected, a facial arrangement of carbonyl and acetonitrile ligands, with the linear anion, BrI2 as the counter ion.

Synthesis and characterisation of the bidentately attached linear triphos complexes [MXY(CO)(L-P,P′)(η2-RC2R)] {M=Mo, W; X, Y=Cl, Br, I; L=PhP(CH2CH2PPh2)2; R=Me, Ph}. X-ray crystal structures of [WX2(CO)(L-P,P′)(η2-PhC2Ph)] (X=Br and I) and [MoI2(O){Ph2P(CH2)2PPh(CH2)2POPh2-P,P′,O}]

Abstract Reaction of equimolar quantities of [MXY(CO)(NCMe)(η 2 -RC 2 R) 2 ] and L {L=PhP(CH 2 CH 2 PPh 2 ) 2 } in CH 2 Cl 2 at room temperature gives the bidentately coordinated triphos complexes [MXY(CO)(L- P , P ′)(η 2 -RC 2 R)] (M=Mo, X=Y=I, R=Me or Ph; M=W, X=Y=Br, R=Me or Ph; M=W, X=Br, Cl, Y=I, R=Me or Ph) ( 1–8 ) in high yield. The molecular structures of [WX 2 (CO)(L- P , P ′)(η 2 -PhC 2 Ph)] (X=Br, I) have been determined crystallographically and are equivalent. The coordination geometry about the tungsten atom in both complexes is distorted octahedral with two adjacent phosphorus atoms in the triphos ligand, a halide and a carbonyl ligand occupying the equatorial plane, with the diphenylacetylene and the other halide atom occupying the axial positions. The 13 C-NMR spectrum of WBr 2 (CO)(L- P,P ′)η 2 -PhC 2 Ph ( 4 ) shows the diphenylacetylene ligand is donating four electrons to the metal. Refluxing a slightly wet acetonitrile solution of [MoI 2 (CO)(L- P , P ′)(η 2 -MeC 2 Me)] for 24 h affords the unusual crystallographically characterised molybdenum(IV) oxidised triphos complex [MoI 2 (O){Ph 2 P(CH 2 ) 2 PPh(CH 2 ) 2 POPh 2 - P , P ′, O }] ( 9 ).

Synthesis and spectroscopic properties of some new bi-, tri- and tetrametallic complexes of the type [M(CO)5L], [M(CO)4L2] and [M(CO)3L3] {M = Cr, Mo, W; L = [Ph(CH2)2PPh2-P, P′}(η2-RC2R′)] (R = R′ = Me, Ph; R = Me, R′ = Ph)}

Abstract Reaction of L {L = [ Ph(CH 2 ) 2 PPh 2 - P, P′ }(η 2 -RC 2 R′)] (R = R′ = Me, Ph; R = Me, R′ = Ph)} with an equimolar quantity of [M(CO) 5 (NCMe)] (M = Cr, Mo, W) (prepared in situ) gives high yields of the bimetallic complexes [M(CO) 5 L] {L = [ Ph(CH 2 ) 2 PPh 2 - P, P′ )(η 2 -RC 2 R′)] (M = Cr, W, R = R′ = Me; M = Cr, Mo, R = Me, R′ = Ph; M = Mo, W; R = R′ = Ph)} ( 1 → 6 ). Treatment of cis -[M(CO) 4 (piperidine) 2 ] (M = Mo, W) with two equivalents of L (as above) in refluxing CH 2 Cl 2 affords the trimetallic complexes [M(CO) 4 L 2 ] {L = [ Ph(CH 2 ) 2 PPh 2 - PP′ }(η 2 -RC 2 R′)] (M = Mo, W, R = R′ = Me; M = W, R = Me, R′ = Ph)} ( 7 → 9 ). The cis—trans isomerism of complexes 7 and 8 has been investigated by infrared spectroscopy. Reaction of fac -[Mo(CO) 3 (NCMe) 3 ] (prepared in situ) with three equivalents of L in refluxing acetonitrile yields the tetrametallic complexes [Mo(CO) 3 L 3 ] {L = [ Ph(CH 2 ) 2 PPh 2 - P, P′ }(η 2 -RC 2 R′)] (R = R′ = Me, Ph; R = Me, R′ = Ph)} ( 10 → 12 ). All the new complexes have been characterised by elemental analysis (C, H and N), infrared, 1 H NMR spectroscopy and in selected cases by 31 P NMR spectroscopy.

High yield synthesis, molecular structure and n.m.r. studies of the seven-coordinate complex [WI2(CO)3(PEt3)2]

The reaction of [WI2(CO)3(NCMe)2] with two equivalents of PEt3 in Et2O/CH2Cl2 gives the MeCN-displaced product [WI2(CO)3(PEt3)2] (1) in high yield. The crystallographically determined solid state structure of (1) shows the complex to be capped octahedral with a carbonyl ligand capping an octahedral face containing the two octahedral carbonyls and one PEt3 group. The other face contains the two iodo ligands trans to carbonyl groups, and the second PEt3 ligand trans to the first PEt3 group. The low temperature (-30°C) 13C-{1H}-n.m.r. spectrum of (1) correlates with the solid state structure, and the fluxional properties of (1) have been investigated by VT 31P-{1H}-n.m.r.spectroscopy.