Stuart G. Fraser

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.

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.

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.

Synthesis and spectroscopic properties of the ‘mixed’ seven-co-ordinate complexes [MI2(CO)3L(L′)][M = Mo or W; L,L′= PPh3, PPh2(C6H11), PPh(C6H11)2, AsPh3, or SbPh3] and rearrangement of selected [MI2(CO)3L(L′)] to [HL][MI3(CO)3L′]. X-Ray crystal structure of [PPh2(C6H11)H][WI3(CO)3(SbPh3)]·Et2O

Reaction of the complexes [MI2(CO)3(NCMe)2](M = Mo or W) with 1 equivalent of L(L = PPh3, AsPh3, or SbPh3) in CH2Cl2 at room temperature followed by 1 equivalent of L′[L′= PPh3, PPh2(C6H11), PPh(C6H11)2, AsPh3, or SbPh3]in situ affords the ‘mixed’ seven-co-ordinate compounds [MI2(CO)3L(L′)]. Low-temperature (-70 °C, CD2Cl2)13C n.m.r. spectra of the triphenylantimony complexes [MI2(CO)3L(SbPh3)][L = PPh3, PPh2(C6H11), or PPh(C6H11)2] showed two carbonyl resonances. This indicated capped octahedral geometry with a carbonyl ligand in the unique capping position. Some of the neutral seven-co-ordinate complexes [MI2(CO)3L(L′)] containing phosphines disproportionated in CH2Cl2 to give the salts [HL][MI3(CO)3L′]. 31P N.m.r. spectroscopy and negative ion mass spectrometry confirmed that the more electron-rich phosphine is protonated in [HL][MI3(CO)3(PPh3)][L = PPh2(C6H11) or PPh(C6H11)2]. The structure of the complex [PPh2(C6H11)H][WI3(CO)3(SbPh3)]·Et2O was determined by X-ray analysis. The co-ordination geometry about the tungsten is capped octahedral with a carbonyl ligand in the unique capping position. The capped face contains two carbonyl groups and the triphenylantimony ligand, with the three iodide ligands occupying the uncapping face. The low-temperature (-70 °C, CD2Cl2) spectrum of the related complex [NBun4][WI3(CO)3(SbPh3)] prepared by treating [WI2(CO)3(NCMe)(SbPh3)]in situ with 1 equivalent of [NBun4]I in CH2Cl2showed two carbonyl resonances at δ= 209.68 and 235.50 p.p.m. with an intensity ratio of 2 : 1. The lower-field resonance can be ascribed to the unique capping carbonyl ligand and the higher-field resonance to the two equivalent carbonyl ligands on the octahedron. The low-temperature 13C n.m.r. spectrum of [NBun4][MoI3(CO)3(PPh3)] shows a single resonance at δ= 222.20 p.p.m. which suggests a different capped octahedral structure with the triphenylphosphine ligand capping the three carbonyl ligands.

New synthesis of seven-coordinate complexes of molybdenum(II) and tungsten(II) containing bidentate phosphorus ligands, [MI2(CO)3{Ph2P(CH2)nPPh2}] (n = 1–6)

Abstract A new high yielding synthesis of the seven-coordinate complexes [MI 2 (CO) 3 {Ph 2 P(CH 2 ) n PPh 2 }] (M = Mo and W; n = 1–6) is described. The procedure involves reacting the complexes [MI 2 (CO) 3 (NCMe) 2 ] in CH 2 Cl 2 with an equimolar amount of the bidentate phosphorus ligand. The low temperature (−70 °C) 13 C NMR spectra of the complexes [Wl 2 (CO) 3 {Ph 2 P(CH 2 ) n PPh 2 }] ( n = 3 and 5) indicates that the geometry is capped octahedral with a carbonyl ligand in the unique capping position.

Synthesis of some mixed seven-coordinate complexes of the type [MI2(CO)3LL′] (M = Mo or W;L = pyridine or substituted pyridines; L′ = PPh3, AsPh3 or SbPh3)

Abstract The seven-coordinate bisacetonitrile complexes [MI 2 (CO) 3 (NCMe) 2 ] (M = Mo or W) react with L′ (L′ = PPh 3 , AsPh 3 or SbPh 3 ) in CH 2 Cl 2 at room temperature to give [MI 2 (CO) 3 (NCMe)L′] which when reacted in situ with L (L = pyridine or substituted pyridines) affords good yields of 28 mixed seven-coordinate complexes [MI 2 (CO) 3 LL′]. It is likely these reactions occur via successive dissociative displacements of two acetonitrile ligands.

The reactions of [MI2(CO)3(NCMe)2] (M = Mo or W) with one equivalent of L (L = pyridine or substituted pyridines) to give [WI2(CO)3(NCMe)L] and [M(μ-I)I(CO)3L]2

Abstract The complexes [MI 2 (CO) 3 (NCMe) 2 ] (M = Mo or W) react with one equivalent of L in CH 2 Cl 2 at room temperature to give initially the mononuclear seven-coordinate complexes [MI 2 (CO) 3 (NCMe)L] which have been isolated for M = W; L = 3Cl-py, 3Br-py, 4Cl-py and 4Br-py. These compounds dimerise to give the iodidebridged dimers [M(μ-I)I(CO) 3 L] 2 by displacement of acetonitrile. When M = Mo; L = 3Cl-py, 3Br-py, 4Cl-py and 4Br-py, and when M = Mo and W; L = py, 2Me-py (for M = W only), 4Me-py, 3,5-Me 2 -py, 2Cl-py and 2Br-py, only the dimeric complexes have been isolated. The ease of dimerisation of [MI 2 (CO) 3 (NCMe)L] is discussed in terms of the steric and electronic effects of the substituted pyridines.

Synthesis, spectral properties and reactions of the novel acetonitrile diiodotricarbonyltriphenyl phosphine, arsine and antimony complexes of molybdenum(II) and tungsten(II)

Abstract The bisacetonitrile complexes [MI2(CO)3(NCMe)2] (M = Mo or W) react with L (L = PPh3, AsPh3 or SbPh3) to give the novel compounds [MI2(CO)3(NCMe)L], which undergo acetonitrile displacement reactions to afford a variety of new mixed complexes.

1, 1′-Bis(diphenylphosphino)ferrocene complexes of molybdenum(II) and tungsten(II)

Synthese des nouveaux complexes [MI 2 (CO) x (Ph 2 PFePPh 2 )] et de [MoCl 2 (CO) 2 (Ph 2 PFePPh 2 ) 2 ]

Triphenylbismuth seven-coordinate complexes of molybdenum(II) and tungsten(II)

Abstract The seven-coordinate complexes [MI 2 (CO) 3 (NCMe) 2 ] (M = Mo and W) react with one equivalent of BiPh 3 in CH 2 Cl 2 at room temperature to give the monoacetonitrile complexes [MI 2 (CO) 3 (NCMe)(BiPh 3 )]. The molybdenum complex [MoI 2 (CO) 3 (NCMe)(BiPh 3 )] after stirring in CH 2 Cl 2 at room temperature for 5 h affords the iodide-bridged dimer [Mo(μ-I)I(CO) 3 (BiPh 3 )] 2 , whereas the tungsten complex [WI 2 (CO) 3 (NCMe)(BiPh 3 )] does not appear to dimerise even after stirring for 48 h in CH 2 Cl 2 at room temperature. Reaction of [MI 2 (CO) 3 (NCMe) 2 ] with two equivalents of BiPh 3 gives the bistriphenylbismuth compounds [MI 2 (CO) 3 (BiPh 3 ) 2 ] in good yield. The new mixed ligand complexes [MI 2 (CO) 3 L(BiPh 3 )] were prepared either by reaction of [MI 2 (CO) 3 (NCMe)(BiPh 3 )] in situ with one equivalent of L(L = P(OPh) 3 ), or an in situ reaction of [MI 2 (CO) 3 (NCMe)L] (L = PPh 3 and SbPh 3 ; and L = AsPh 3 and PPh 2 Cy (for M = Mo only) with an equimolar quantity of BiPh 3 . Reaction of [MoI 2 (CO) 3 (NCMe)(BiPh 3 )] with one equivalent of 2,2′-bipyridyl (bipy) in CH 2 Cl 2 at room temperature afforded the cationic complexes [MoI(CO) 3 (bipy)(BiPh 3 )]I in good yield. The complex [WI 2 (CO) 3 (NCMe)(BiPh 3 )] (prepared in situ ) reacts with two equivalents of NaS 2 CNMe 2 ·2H 2 O to eventually give the non-triphenylbismuth containing product [W(CO) 3 (S 2 CNMe 2 ) 2 ] in high yield.