| Abstract
| - A variety of organometallic complexes of molybdenum that contain the [HIPTN3N]3- ligand ([HIPTN3N]3- = [3,5-(2,4,6-i-Pr3C6H2)2C6H3NCH2CH2]3N3-) have been found to be much more thermally robust than previous examples that contain related triamidoamine supporting ligands. For example, the [HIPTN3N]MoCH2CH3 complex shown is stable up to ∼150 °C, where it decomposes to yield [HIPTN3N]Mo⋮CCH3 quantitatively.
- Reactions between [HIPTN3N]Mo(N2) and ethylene, acetylene, or CO yield Mo(η2-C2H4),Mo(η2-C2H2), and Mo(CO), respectively ([HIPTN3N]3- = [3,5-(2,4,6-i-Pr3C6H2)2C6H3NCH2CH2]3N3-; HIPT = hexaisopropylterphenyl; [HIPTN3N]Mo = Mo). All are paramagnetic C3symmetric species. Attempts to prepare Mo(CO) through reduction of MoCl with Na/Hg inTHF under carbon monoxide yielded [Mo(CO)]Na, in which the sodium ion is believed to bebound within the HIPT aryl system. Addition of a variety of acids such as [Et3NH]BAr‘4 to[Mo(CO)]Na led to formation of the carbonyl hydride, Mo(CO)H, which also could be preparedby treating MoH with CO. Reactions between MoH and ethylene, 1-hexene, or 1-octene inbenzene yield paramagnetic, red Mo(CH2R) complexes (CH2R = ethyl, hexyl, or octyl). MoMecould be prepared by treating MoCl with AlMe3 at room temperature over a period of 2days. Treatment of MoH with acetylene affords yellow diamagnetic Mo(η2-CHCH2) pluspolyacetylene. The MoCH2R complexes decompose at ∼150 °C to yield the alkylidynecomplexes, Mo⋮CR, quantitatively. No change was observed upon heating a toluene solutionof MoCH3 to 160 °C for 24 h. However, Mo⋮CH could be prepared from a mixture of MoCl,3 equiv of dichloromethane, and a large excess of magnesium powder in THF under argonat 90 °C. Although we have seen no evidence of thermal rearrangement of Mo(η2-CHCH2)to Mo⋮CCH3, that rearrangement is readily catalyzed by [2,6-LutH]BAr‘4. Attempts toprepare Mo-C⋮CH from [Mo(NH3)]BAr‘4 and NaC⋮CH led to formation of a yellowcrystalline compound that was shown in an X-ray study to be one in which the acetylidehad “inserted” into an ortho C−H bond in the phenyl ring attached to the amido nitrogen.Orange paramagnetic MoCN can be isolated in good yield from the reaction between[Mo(NH3)]BPh4 and [Bu4N]CN in fluorobenzene. Electrochemical studies in 0.1 M [Bu4N]BAr‘4 in PhF at room temperature revealed reversible couples for Mo(C2H4)+/0 andMo(C2H2)+/0 at −0.42 and −0.94 V, respectively, while Mo(CN) exhibits two redox processesat −0.27 and −1.61 V that we assign to the Mo(CN)+/0 and Mo(CN)0/- redox couples,respectively. Addition of [Cp2Fe]BAr‘4 to a solution of Mo(η2-C2H2) in C6D6 producesdiamagnetic [Mo(η2-C2H2)]BAr‘4, while addition of [Cp2Fe]BAr‘4 to a C6D6 solution of Mo(η2-C2H4) led to formation of diamagnetic [Mo(C2H4)]BAr‘4. Structures of Mo(C2H4), [Mo(C2H4)]BAr‘4, Mo(CH2CH3), and “Mo(C⋮CH)” were determined through X-ray studies.
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