The preparation, structure, and reactions of the mononuclear thiolate–hydride complexes [MoH(SR)(dppe)2](R = bulky alkyl or aryl group, dppe = Ph2PCH2CH2PPh2); X-ray structure determination of cis-[MoH(SC6H2Pri3-2,4,6)(dppe)2]

Abstract

Reaction of trans-[Mo(N₂)₂(dppe)₂](dppe = Ph₂PCH₂CH₂PPh₂) with the bulky thiols RSH (R = Prⁱ, Bu^t, C₆H₂Me₃-2,4,6, C₆H₂Prⁱ₃-2,4,6, or C₆H₂BrPrⁱ₂-4,2,6) at reflux in tetrahydrofuran (thf) gives the green hydride complexes [MoH(SR)(dppe)₂]. The complex cis-[MoH(SC₆H₂Prⁱ₃-2,4,6)(dppe)₂]·0.5C₆H₅Me has a distorted octahedral structure, with distances: Mo–S 2.402(2), Mo–H 1.61(9), Mo–P 2.380(2)–2.465(2)Å. The ¹H hydride resonances of these compounds occur in the range –3.98 to –4.98 p.p.m. (relative to SiMe₄) and show fluxionality at room temperature with respect to the phosphorus atoms except for R = C₆H₂BrPrⁱ₂-4,2,6. Other spectroscopic properties of the compounds are used as a basis to discuss the mechanism of their formation. The complex [MoH(SC₆H₂Prⁱ₃-2,4,6)(dppe)₂] reacts at 20 °C with CO or Bu^tNC to give the known compounds [Mo(CO)₂(dppe)₂] and [Mo(Bu^tNC)₂(dppe)₂], and with PhSH to give trans-[Mo(SPh)₂(dppe)₂].