Foreword for the Special Issue “Hydrocarbon Chemistry: Activation and Beyond”. Responsible or Irresponsible Use of Hydrocarbons? You Be the Judge!

Abstract

I n the process of choosing contributors for this special issue in Organometallics entitled "Hydrocarbon Chemistry: Activation and Beyond", we focused our attention on science that interfaced with the frontier areas of organometallic chemistry. Our target was to place special emphasis on organometallic applications that implicated novel transformations and catalysis with, but not limited to, hydrocarbons. This special issue highlights different approaches and synthetic strategies to target unique organometallic reagents as well as to understand C−X bond-activation or bond-making reactions that interface with energy-related transformations, especially those that hold promise in industry. This issue also interfaces homogeneous, heterogeneous, and theoretical communities, all sharing common interests in catalysis and the understanding of reaction mechanisms. As a result, this special issue captures some of the best content in organometallic chemistry involving the "responsible usage" of hydrocarbons. The meaning of the term "responsible" relates to the exploration of noncombustible processes that can better take advantage of the energy stored in these natural resources. We try to emphasize the importance of controlled C−H bond activation and functionalization in our cover art for this issue, as an alternative to the more detrimental (but simpler) process of combustion.With Guest Editors Christophe Copeŕet and Alan Goldman, we are privileged to showcase some of the most entertaining reactions involving M−C bonds, hydrocarbon activation, and hydrocarbon functionalization, as well as catalytic processes leading to their functionalization and/or coupling. It is notable to mention that early, mid, and late transition metals, in addition to main-group and lanthanide (and rare-earth) examples, are integral parts of this special issue with solid-, solution-, and gas-phase reactions being included.A well established pillar of organometallic chemistry has been the preparation of reactive metal−carbon bonds (or multiple bonds) that promote C−H activation reactions of hydrocarbons. 1−4 In this vein, is a series of papers involving the highly electropositive transition and lanthanide metal ions. Legzdins and co-workers 5,6 publish back-to-back manuscripts that describe the use of well-defined tungsten complexes that can activate and subsequently functionalize hydrocarbons (including methane). 7 Speaking of methane, one major impediment to utilization of this valuable resource is the limited understanding of its reactivity in the gas phase. Schwarz and co-workers 8 address this challenge in their combined experimental and theoretical study of the thermal gas-phase chemistry of CH 4 . By moving diagonally from tungsten to niobium compounds with strained organometallic ligands, Etienne and co-workers 9 report stereospecific C−H bond splitting reactions via a 1,3-CH addition process. 10 Cundari and Parveen 11 compliment some of the early-transition-metal chemistry by "theoretically" tuning Ta(III) systems that can undergo oxidation...

Observation and Characterization of CH3CH2–MH, (CH2)2–MH2, and CH3–C≡MH3 Prepared in Reactions of Ethane with Laser-Ablated Group 6 Metal Atoms

“…Parallel to the Mo case described above, the product absorptions are marked with i , m , and y depending the intensity variation on photolysis and annealing. The y absorptions are the strongest in the W spectra (even in the original deposition spectra) and the i absorptions are weaker, consistent with the general trend that the higher oxidation-state product of a heavier metal in a family group is more favored …”

“…A weak product absorption at 501.0 cm –1 is tentatively assigned to the C–Cr stretching mode. Similarly, the insertion complexes were the single primary products in matrix and gas phase reactions of the first row transition metals with small alkanes with the exception of the Sc and Ti cases, where both the insertion and methylidenes were observed. , …”

“…The stability of this W methylidyne reconfirms the tendency that the higher oxidation-state product becomes more favored with moving down the group column. HCWH 3 and HCWH 2 X are also the most stable products in the formerly studied reactions of W with methane and methyl halides, and the W methylidyne products are the only products observed in reactions with di-, tri-, and tetrahalomethanes …”

“…The previous studies of transition-metal reactions with methane and methyl halides have shown that the first-produced insertion complexes (CH 3 –MZ, Z = H or halogen) convert to the methylidene product (CH 2 MHz) via H-migration from C to M by photon energy . Matrix reactions of group 4 metals and actinides with ethane have revealed that metallacyclopropanes [(CH 2 ) 2 –MH 2 ] were produced from CH 3 CH 2 –MH via β-H-migration and cyclization instead of α-H-migration. , α-H-migration would have generated CH 3 CHMH 2 , which is energetically higher than the metallacyclopropane [e.g., CH 3 –CHTiH 2 is 88 kJ/mol higher in energy than (CH 2 ) 2 –TiH 2 ] .…”

“…The journal Organometallics opened this year with a special issue on hydrocarbon chemistry. The introductory articles focused on the dramatic impact on the earth of burning hydrocarbons and the importance of C–H bond activation chemistry to mitigate hydrocarbons …”