Molybdenum-mediated imido group transfer: Stoichiometric and catalytic reactions and structures

Article abstract of DOI:10.1021/ja00157a030

The isoelectronic relationship O² = RN^2- implies imido group transfer chemistry related to oxygen atom transfer reactivity, which is extensive for certain elements. This has subjected to its first systematic examination, using the N,N-diethyldithiocarbamate (Ei₂dtc) complexes of molybdenum and the N-tosylimido (NTs) group. The imido group transfer reactions to Mo, MoO(Et₂dtc)₂ + XNR and Mo(CO)₂(Et₂dtc)₂ + XNR, afford MoO(NTs) (Et₂dtc)₂ and Mo(NTs)₂(Et₂dtc)₂, respectively, in yield with the imido group transfer reagents XNR = C₅H₅NNTs, PhMeSNTs, Ph₃SbNTs, PhINTs, nd TsN₃, MoO(NTs) (Et₂dtc)₂·¹/2Ph Me crystallizes crystallizes in triclinic space PI with a = 9.212 (2) A?, b = 12,080 (4) A?, c = 14.310 (4) A?, α = 115,02 (2)°, β = 95.51 (2)°, γ = 100.34 (2)°, and Z = 2; the structure was refined to R = 4.8%. Mo(NTs)₂(Et₂dtc)₂ was obtained in monoclinic space group,P2₁/n with a = 10.632 (2) A?, b = 16.307 (3) A?, c = 19.023 (5) A?, β = 101.29 (2)°, Z = 4; the structure was refined to R = 4.0%. The two compounds have a distorted octahedral structure with the multiply bonded group O and NTs in cis positions. Comparison of structures with that of MoO₂(Et₂dtc)₂ reveals that the NTs group is a nearly isostructural replacement for oxo. The imido transfer reactions from Mo, MoO(NTs)(Et₂dtc)₂ + R₃P, proceed but with the more basic phosphines favoring imido (R₃PNTs) rattier than oxo (R₃PO) transfer. Imido transfer to and from Mo involve the purple intermediates Mo₂O₂(NTs)(Et₂dtc)₄ and MoO(NTs)₂(Etjdtc)4, respectively, which are in presumed equilibrium with Mo(IV,VI) complexes. The complex Mo(NTs)(Et₂dtc)₂, resulting from imido group transfer, was too unstable to be isolated. Group transfers to and from Mo were coupled to form the catalytic XNTs + R₃P → X + R₃PNTs, which did not proceed at a measurable rate in the absence of Mo(NTs)₂(Et₂dtc)₂. The system based on PhMeSNTs + Ph₂MeP 28 turnovers in 7.5 h in chloroform at 35 °C. The PhMeSNTs + 2PMSH → PhSMe + PhSSPh + TsNH₂, in which benzenethiot acts as an electron donor, was also catalyzed by Mo(NTs)₂(Et₂dtc)₂. All known imidometal group are tabulated, and oxo and imido transfer reactions of Mo are schematically summarized. rized.