Distortions in six-co-ordinate complexes of molybdenum(II) and tungsten(II). Crystal structures of mer-[Mo(SC6H2Pri3-2,4,6)2(CO)3(PMePh2)], cis,cis,cis-[W(SC6H2Me3-2,4,6)2(CO)2-(PMe2Ph)2] and [W(SeC6H3Pri2-2,6)2(CO)2(PMe2Ph)2]

Abstract

The red, diamagnetic complexes mer-[Mo(SC₆H₂ Prⁱ₃-2,4,6)₂(CO)₃(PMePh₂)]1 and [Mo(SC₆H₂Prⁱ₃-2,4,6)₂(CO)₂(PMePh₂)₂]2 have been prepared by reaction of [MoH(SC₆H₂Prⁱ₃-2,4,6)₃(PMePh₂)] with CO in tetrahydrofuran. The crystal structure of 1 shows it to have a distorted octahedral geometry with mer-CO ligands [d(Mo–S) 2.380(1) and 2.366(1); d(Mo–C) 2.030(5), 2.026(4) and 2.066(5); d(Mo–P) 2.561(1)Å; large S–Mo–S angle of 116.0°]. Reaction of CO with [WH(SC₆H₂Me₃-2,4,6)₃(PMe₂Ph)₂] in toluene gives green, distorted octahedral cis,cis,cis-[W(SC₆H₂Me₃-2,4,6)₂(CO)₂(PMe₂Ph)₂]3[d(W–S) 2.379(2) and 2.385(2); d(W–C) 1.967(7) and 1.991(8); d(W–P) 2.556(2) and 2.507(2)Å]. Reaction with [WH(SeC₆H₃Prⁱ₂-2,6)₃(PMe₂Ph)₂] gives burgundy, trigonal prismatic [W(SeC₆H₃Prⁱ₂-2,6)₂(CO)₂(PMe₂Ph)₂]4[d(W–Se) 2.506(1) and 2.583(1); d(W–C) 1.942(8) and 1.943(8); d(W–P) 2.467(2) and 2.471(2)Å]. The physical properties of 1–4 and the structures of 1, 3 and 4 are discussed in terms of their distortions from regular octahedral or trigonal-prismatic geometries. A method of classifying such structures is proposed.