Implications of the Methylene Bridge

Similar conclusions emphasizing the importance of M—H bonding have been drawn for the related methylidyne (CH) species from ultrahigh-vacuum spectroscopic studies (241) and from theoretical work (239), according to which structure 111, found in a plethora of well-characterized clusters, is less stable for chemisorbed CH units. Once again, hydrogen 

The other example to be discussed in this context comes from Pettit s group. Simultaneous treatment of the iron complex (/u.-CH2)[Fe(CO)4]2 (35) with hydrogen and ethylene gives both methane (66%) and propylene (6%), the expected products from the two separate reactions. In addition, ethane (—600%) is formed, with the actual hydrogenation catalyst still to be determined (72). Because simple diazoalkanes provide the cleanest method to metal-attached alkylidenes, and with the expectation that dissociative chemisorption of diazomethane to absorbed CH2 and free N2 would occur, the reactions of CH2N2 with and without H2 over various transition metals were examined in a careful study with regard to the product ratio (73). It was found, that gas-phase decomposition of the parent diazoalkane upon passage over active Ni, Pd, Fe, Co, Ru, or Cu- 

---