Observation and Characterization of CH₃CH₂–MH, (CH₂)₂–MH₂, CH₂═CH–MH₃, and CH₃–C≡MH₃^– Produced by Reactions of Group 5 Metal Atoms with Ethane

Abstract

The primary products in reactions of laser-ablated group 5 metal atoms with ethane were identified in argon matrix IR spectra and characterized via density functional theory computations. The second- and third-row transition metals Nb and Ta produced insertion, metallacyclopropane, vinyl trihydrido, and anionic ethylidyne complexes (CHCH-MH, (CH)-MH, CH═CH-MH, and CHC≡MH), while the first-row transition metal V yielded only the insertion and metallacyclopropane products. The energetically higher ethylidenes and neutral ethylidynes (CHCH═MH and CHC[Formula: see text]MH) were not detected. The unique anionic ethylidynes are the most stable anionic species in the Nb and Ta systems. Evidently back-donation from the metal center to the C-C π* orbital is stronger than that in the group 6 metal analogue but weaker than that in the corresponding group 4 metal complex. The C-M bond for the Nb and Ta ethylidyne anions is a true triple bond.

Reactions of Laser-Ablated Aluminum Atoms with Cyanogen: Matrix Infrared Spectra and Electronic Structure Calculations for Aluminum Isocyanides Al(NC)1,2,3 and Their Novel Dimers

“…30 For example, laser-ablated Nb and Ta provide electrons for capture and lead to the formation of HCMH 3 − and CH 3 CMH 3 − in experiments with methane and ethane. 42,43 Numerous transition metal carbonyl cations and anions have also been observed. 44 Similar laser ablation of aluminum produced a plasma plume with optical emissions from both Al and Al + , which looks like our plume to the naked eye.…”

Matrix Infrared Spectra of Insertion and Metallacyclopropane Complexes [CH3CH2–MH and (CH2)2–MH2] Prepared in Reactions of Laser-Ablated Group 3 Metal Atoms with Ethane

“…16 Similarly, the C−M bonds of these ethylidenes (2.143, 2.317, and 2.427 Å for Sc, Y, and La) are evidently too long for effective electron donation from the C− H bond to the metal center. The relatively short C−Sc bond, which is still considerably longer than those of the Ti and V analogues (1.814 and 1.797 Å), 20,21 reflects the smallest covalent radius of Sc (1.44, 1.62, and 1.69 Å for Sc, Y, and La). 49 The C−C bond insertion products have C 2v structures with computed C−M−C bond angles of 115.9, 111.6, and 108.8°, respectively.…”

“…19−28 Another H-migration from C to M and ring opening result in formation of the vinyl trihydrido complex (CH 2 CH−MH 3 ), which has been previously observed in group 4 and 5 metal reactions. 19,20 Following H-migration from α to β carbon makes ethylidyne (CH 3 CMH 3 ), reaction 1. 20,21,23,25,28 The H-migration from α-C to M of CH 3 CH 2 − MH would produce the ethylidene, reaction 2, and C−C bond insertion of ethane would lead to (CH 3 ) 2 −M, reaction 3.…”

“…Anion and fragmented products have also been observed. 20,22 The previous studies of ethane reactions have shown that the observed products, which are usually the most stable constituents in the reaction path, are largely dependent on the reacting transition metal. 7,8,19−28 The preference for the higher oxidation-state complexes (e.g., ethylidynes, CH 3 C MH 3 ) observed in heavier metal systems in the middle of the dblock of the periodic table gradually fades away with moving to its right and left sides.…”

“…The primary products of a group 4 metal are (CH 3 ) 2 −MH 2 and CH 2 CH− MH 3 ; those of heavy group 6−8 metals are CH 3 CMH 3 , and a group 5 metal forms the insertion product as well as the anionic ethylidyne (CH 3 CMH 3 − ). [19][20][21]23,25 The early actinides are chemically similar to the group 4 metals. 28 In this study we performed group 3 metal reactions with ethane and identified the products in the matrix IR spectra on the basis of deuterium shifts, theoretical predictions, and related previous results.…”