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An analysis of the literature data indicates a wide front of research and development in the field of the use of methane–hydrogen mixtures as a promising environmentally friendly low-carbon fuel. The conclusion of most works shows that the use of methane–hydrogen mixtures in internal combustion engines improves their performance and emission characteristics. The most important aspect is the concentration of hydrogen in the fuel mixture, which affects the combustion process of the fuel and determines the optimal operating conditions of the engine. When using methane–hydrogen mixtures with low hydrogen content, the safety measures and risks are similar to those that exist when working with natural gas. Serious logistical problems are associated with the difficulties of using the existing gas distribution infrastructure for transporting methane–hydrogen mixtures. It is possible that, despite the need for huge investments, it will be necessary to create a new infrastructure for the production, storage and transportation of hydrogen and its mixtures with natural gas. Further research is needed on the compatibility of pipeline materials with hydrogen and methane–hydrogen mixtures, safety conditions for the operation of equipment operating with hydrogen or methane–hydrogen mixtures, as well as the economic and environmental feasibility of using these energy carriers.

We elaborated a synthetic approach to a new family of PNP ligands that involves assembling sequential molecules based on the rigid 5,6-dihydrodibenzo­[c,e]­[1,2]­azaphosphinine backbone (−Z−). This approach allowed us to obtain PNP-type ligands of the general formula Ar2P–Z–Ar′ (Ar, Ar′ = Ph, o-MeOC6H4) with high yields and without the formation of PPN byproducts. Ar2P–Z–Ar′/Cr­(acac)3 (acac = acetylacetonate) adducts activated by modified methylalumoxane (MMAO-12) effectively catalyzed ethylene oligomerization; the number of ortho-methoxyphenyl fragments n controls the direction of the process, from slow polymerization (n = 0) to rapid oligomerization (n = 3), thereby producing a mixture of 1-hexene and 1-octene in ∼2:1 ratio with very low formation of polyethylene (∼0.6%).

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