Synthetic, structural and theoretical studies on the new 2,3-dihydro-1,2,4-thia-, selena- and tellura-diphospholes, P2EC2But2(H)Me, (E=S, Se, Te) and their [M(CO)5] complexes (M=Cr, Mo, W)

Methylation of the 1,2,4-thia-, selena- and tellura-diphospholes P2EC2But2 (E=S, Se, Te) with MeLi, followed by protonation with HCl, affords the new 2,3-dihydro-1,2,4-thia-, selena- and tellura-diphospholes. Further treatment with [M(CO)5(THF)] (M=Cr, Mo, W) yields the corresponding η1-metal pentacarbonyl complexes, of which [M(CO)5{η1-P2EC2But2(H)Me}], (E=S, M=W; E=Se, M=Cr, M=Mo, M=W) have been structurally characterised by single crystal X-ray diffraction studies. Theoretical calculations carried out on the different isomers of the 2,3-dihydro-1,2,4-thia-, selena- and tellura-diphospholes, and the 2,3-dihydro-1H-1,2,4-triphosphole are also presented and discussed.