Some Organometallic Chemistry of Molybdenum Complexes that Contain the [HIPTN3N]3- Triamidoamine Ligand, {[3,5-(2,4,6-i-Pr3C6H2)2C6H3NCH2CH2]3N}3-

Reactions between [HIPTN 3 N]Mo(N 2 ) and ethylene, acetylene, or CO yield Mo (η 2 -C 2 H 4 ), Mo (η 2 -C 2 H 2 ), and Mo (CO), respectively ([HIPTN 3 N] 3 - = [3,5-(2,4,6- i -Pr 3 C 6 H 2 ) 2 C 6 H 3 NCH 2 CH 2 ] 3 N 3 -; HIPT = hexaisopropylterphenyl; [HIPTN 3 N]Mo = Mo ). All are paramagnetic C 3 symmetric species. Attempts to prepare Mo (CO) through reduction of Mo Cl 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 [Et 3 NH]BAr‘ 4 to [ Mo (CO)]Na led to formation of the carbonyl hydride, Mo (CO)H, which also could be prepared by treating Mo H with CO. Reactions between Mo H and ethylene, 1-hexene, or 1-octene in benzene yield paramagnetic, red Mo (CH 2 R) complexes (CH 2 R = ethyl, hexyl, or octyl). Mo Me could be prepared by treating Mo Cl with AlMe 3 at room temperature over a period of 2 days. Treatment of Mo H with acetylene affords yellow diamagnetic Mo (η 2 -CHCH 2 ) plus polyacetylene. The Mo CH 2 R complexes decompose at ∼150 °C to yield the alkylidyne complexes, Mo ⋮CR, quantitatively. No change was observed upon heating a toluene solution of Mo CH 3 to 160 °C for 24 h. However, Mo ⋮CH could be prepared from a mixture of Mo Cl, 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 (η 2 -CHCH 2 ) to Mo ⋮CCH 3, that rearrangement is readily catalyzed by [2,6-LutH]BAr‘ 4 . Attempts to prepare Mo -C⋮CH from [ Mo (NH 3 )]BAr‘ 4 and NaC⋮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 Mo CN can be isolated in good yield from the reaction between [ Mo (NH 3 )]BPh 4 and [Bu 4 N]CN in fluorobenzene. Electrochemical studies in 0.1 M [Bu 4 N]BAr‘ 4 in PhF at room temperature revealed reversible couples for Mo (C 2 H 4 ) +/0 and Mo (C 2 H 2 ) +/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 [Cp 2 Fe]BAr‘ 4 to a solution of Mo (η 2 -C 2 H 2 ) in C 6 D 6 produces diamagnetic [ Mo (η 2 -C 2 H 2 )]BAr‘ 4, while addition of [Cp 2 Fe]BAr‘ 4 to a C 6 D 6 solution of Mo (η 2 -C 2 H 4 ) led to formation of diamagnetic [ Mo (C 2 H 4 )]BAr‘ 4 . Structures of Mo (C 2 H 4 ), [ Mo (C 2 H 4 )]BAr‘ 4, Mo (CH 2 CH 3 ), and “ Mo (C⋮CH)” were determined through X-ray studies.