Synthesis of the cationic bis(but-2-yne) complex [W(CO)(NCMe)(S2CNC4H8)-(η2-MeC2Me)2]BF4 and its reactions with neutral bidentate donor ligands (L–L) to give [W(CO)(S2CNC4H8)(L–L)(η2-MeC2Me)]BF4: X-ray crystal structure determination of [W(CO)(S2CNC4H8)(Ph2PCH2PPh2)(η2-MeC2Me)]BF4
Abstract
Silver tetrafluoroborate reacts with an equimolar quantity of [WI(CO)(S2CNC4H8)(η2-MeC2Me)2] in acetonitrile at room temperature to give the cationic mono(acetonitrile) compound [W(CO)(NCMe)(S2CNC4H8)(η2-MeC2Me)2]BF4(1) in good yield. Equimolar quantities of (1) and L–L [L–L = Ph2P(CH2)nPPh2(n= 1 or 2), Ph2P(CH2)2PPh(CH2)2PPh2, 2,2′-bipyridine, 1,10-phenanthroline, 5,6-dimethyl-1,10-phenanthroline, or S2CP(C6H11)3] react in CH2Cl2 at room temperature to give the highly coloured mono(but-2-yne) complexes [W(CO)(S2CNC4H8)-(L–L)(η2-MeC2Me)]BF4(2)–(8) in high yield. The structure of [W(CO)(S2CNC4H8)(Ph2PCH2PPh2)-(η2-MeC2Me)]BF4(2) was determined by X-ray crystallography. Crystals of (2) are monoclinic, space group P21/c with a= 11.638(1), b= 12.400(2), c= 25.165(3)Å, and β= 90.40(1)°. The structure was refined to R= 0.069 (R′= 0.094) for 2 031 reflections with Fo > 5σ(Fo). The geometry about the tungsten atom in (2) can be described as pseudo-octahedral, with the but-2-yne ligand trans to one of the phosphorus atoms of the Ph2PCH2PPh2 ligand. The other phosphorus atom, the two sulphur atoms of the dithiocarbamate ligand, and the carbon monoxide ligand all lie approximately in the equatorial plane. The barrier to rotation of the but-2-yne ligand in complexes (2)–(6) was determined by variable-temperature 1H n.m.r. spectroscopy. The results are discussed in terms of the steric and electronic effects of the bidentate donor ligands in (2)–(6). Carbon-13 n.m.r. spectroscopy suggests that the two but-2-yne ligands in (1) are donating a total of six electrons to the metal whereas the but-2-yne ligand in (2)–(8) acts as a four-electron donor to the metal centre.