| Abstrakt: |
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 C3 symmetric species. Attempts to prepare Mo(CO) through reduction of MoCl with Na/Hg in THF under carbon monoxide yielded [Mo(CO)]Na, in which the sodium ion is believed to be bound within the HIPT aryl system. Addition of a variety of acids such as [Et3NH]BAr4 to [Mo(CO)]Na led to formation of the carbonyl hydride, Mo(CO)H, which also could be prepared by treating MoH with CO. Reactions between MoH and ethylene, 1-hexene, or 1-octene in benzene yield paramagnetic, red Mo(CH2R) complexes (CH2R = ethyl, hexyl, or octyl). MoMe could be prepared by treating MoCl with AlMe3 at room temperature over a period of 2 days. Treatment of MoH with acetylene affords yellow diamagnetic Mo(η2-CHCH2) plus polyacetylene. The MoCH2R complexes decompose at ~150 °C to yield the alkylidyne complexes, Mo&tbd1;CR, quantitatively. No change was observed upon heating a toluene solution of MoCH3 to 160 °C for 24 h. However, Mo&tbd1;CH could be prepared from a mixture of MoCl, 3 equiv of dichloromethane, and a large excess of magnesium powder in THF under argon at 90 °C. Although we have seen no evidence of thermal rearrangement of Mo(η2-CHCH2) to Mo&tbd1;CCH3, that rearrangement is readily catalyzed by [2,6-LutH]BAr4. Attempts to prepare Mo-C&tbd1;CH from [Mo(NH3)]BAr4 and NaC&tbd1;CH led to formation of a yellow crystalline compound that was shown in an X-ray study to be one in which the acetylide had 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]BAr4 in PhF at room temperature revealed reversible couples for Mo(C2H4)+/0 and Mo(C2H2)+/0 at −0.42 and −0.94 V, respectively, while Mo(CN) exhibits two redox processes at −0.27 and −1.61 V that we assign to the Mo(CN)+/0 and Mo(CN)0/- redox couples, respectively. Addition of [Cp2Fe]BAr4 to a solution of Mo(η2-C2H2) in C6D6 produces diamagnetic [Mo(η2-C2H2)]BAr4, while addition of [Cp2Fe]BAr4 to a C6D6 solution of Mo(η2-C2H4) led to formation of diamagnetic [Mo(C2H4)]BAr4. Structures of Mo(C2H4), [Mo(C2H4)]BAr4, Mo(CH2CH3), and Mo(C&tbd1;CH) were determined through X-ray studies. |
