Triosmium clusters derived from benzylamine and benzyl alcohol: formation of a µ3-o-phenylene complex in the conversion of benzyl alcohol into benzene

Abstract

Benzylamine reacts (125 °C) with [Os3(CO)12] to give mainly the µ-carbamoyl complex [Os3(CO)10H{µ-OCN-(CH2Ph)H}] together with small amounts of [Os3(CO)10H{µ-N(CH2Ph)H}] which may also be obtained by decarbonylation of the first product. The complex [Os3(CO)10(C8H14)2] gives (60–70 °C) the same products, but with the benzylamido-complex predominating. It is probable, but not established, that these derivatives are involved in the [Os3(CO)12]-catalysed carbonylation of benzylamine to (PhCH2NH)2CO. The analogue of only one of these, [Os3(CO)10H(µ-OCH2Ph)], is formed from benzyl alcohol, and thermolysis of nonane solutions of this derivative at 146 °C in sealed glass tubes gives C6H6, PhCHO, [Os3(CO)12], and [Os4(CO)12H4] only; related products are obtained from the 4-methyl-substituted analogue, while [Os3(CO)10H(µ-OCMePhH)] gives only PhCOMe as an organic product. A possible scheme for these degradations is discussed in terms of the intermediates [Os3(CO)9H2(µ-OCH2C6H4)] and [Os3(CO)9H2(µ3-C6H4) which have been isolated from reaction solutions flushed with N2. The complex [Os3(CO)9H2(µ3-C6H3Me-4)] is formed from both isomers [Os3(CO)10H(OCH2C6H4Me-2 or -4)]. Interconversions and structures (based on spectroscopic evidence) of the above complexes are described.