Quadruply bonded complexes containing η2- or η3-tridentate phosphine ligands; syntheses, structures and 31P{ 1H} NMR spectra of Mo 2Cl 4( η3-etp)(L) and Mo 2Cl 4( η2-etp) 2 (L = CH 3OH, PMe 3 and PEt 3; etp = Ph 2PCH 2CH 2P(Ph)CH 2CH 2PPh 2)

Abstract

The reactive complex Mo 2Cl 4( η 3-etp)(CH 3OH) (etp = Ph 2PCH 2CH 2P(Ph)CH 2CH 2PPh 2) ( 1) was synthesized by reacting (NH 4) 5Mo 2Cl 9 with 1 equiv. of etp in CH 3OH. Reactions of 1 with PMe 3 and PEt 3 in THF gave Mo 2Cl 4( η 3-etp)(PMe 3) ( 2) and Mo 2Cl 4( η 3-etp)(PEt 3) ( 3) respectively. The complex α-Mo 2Cl 4( η 2-etp) 2 ( 4) was synthesized by refluxing Mo 2Cl 4( η 3-etp)(CH 3OH) with 1 equiv. of etp in CH 3OH, where η 3-etp is transformed to η 2-etp. Complex 4 can also be prepared by reacting (NH 4) 5Mo 2Cl 9 with 2 equiv. of etp in refluxing CH 3OH. Their UV-Vis and 31P NMR spectra were recorded and the structures of 3 and 4 were determined. Crystal data for 3·C 7H 8: space group P2 1/n, a = 11.846(2), b = 29.349(3), c = 15.429(3) A ̊ , β = 112.52(1)°, V = 4955(2) A ̊ 3, Z = 4 , with final residuals R = 0.0797 and R w = 0.0811. Crystal data for 4·2C 7H 8: space group P2 1/c, a = 14.555(2), b = 14.988(2), c = 20.220(3) A ̊ , β = 106.80(1)°, V = 4222(1) A ̊ 3, Z = 2 , with final residuals R = 0.0882 and R w = 0.0893. The etp ligands in 1–3 are coordinated to the Mo centers in tridentate fashion with chelating/bridging bonding modes. The etp ligands in 4 are chelated to the Mo centers in bidentate fashion through the central phosphorus atom and one terminal phosphorus atom. Complex 4 appears to be the first binuclear biligate complex chelated by linear tridentate ligands. Study of the 31P{ 1H} NMR spectrum of 3 leads to the conclusion that the through metal-metal quadruple bonding coupling | 4 J PMoMoP| is in the range from 18.18 to 24.28 Hz for complexes of the type Mo 2Cl 4( η 3-etp)(L) (L = monodentate ligand).