The Photochemistry of the (Cycloalkene)(hydro)(trispyrazolylborato)iridium Complexes [Ir(η4-cod)(TpMe2)] and [Ir(η2-coe)H2(TpMe2)]: the Formation of [IrH4(TpMe2)] and [Ir(CO)H2(TpMe2)]

✍ Scribed by Arlen Ferrari; Massimo Merlin; Silvana Sostero; Orazio Traverso; Heinz Rüegger; Luigi M. Venanzi

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: German
• Weight: 192 KB
• Volume: 81
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/(sici)1522-2675(19981111)81:11<2127::aid-hlca2127>3.0.co;2-h

✦ Synopsis

Photolysis of [Ir(h 2 -coe)H 2 (Tp Me2 )] (1; Tp Me2 hydrotris(3,5-dimethylpyrazolyl)borato, coe ( Z )-cyclooctene) in CH 3 OH gives a mixture of [ IrH 4 (Tp Me2 )] ( 4) and [ Ir(CO )H 2 (Tp Me2 )] (5) in a ca. 1 : 1 ratio. Massspectral analysis of the distillate of the reaction mixture at the end of the photolysis shows the presence of coe. When pure CD 3 OD is used as solvent, the deuteride complexes [ IrD 4 (Tp Me2 )] (( D 4 )-4) and [ Ir(CO )D 2 (Tp Me2 )] (( D 2 )-5) are obtained. Also the photolysis of [ Ir(h 4 -cod)( Tp Me2 )] (3) (cod cycloocta-1,5-diene) gives 4 and 5.

A key feature of this photoreaction is the intramolecular dehydrogenation of cod with formation of cycloocta-1,3,5-triene, detected by mass spectroscopy at the end of the photolysis. Labeling experiments using CD 3 OD show that the hydrides in 4 originate from MeOH. When 13 CH 3 OH is used as solvent, [ Ir( 13 CO )H 2 (Tp Me2 )] is formed demonstrating that CH 3 OH is the source of the CO ligand. The observation that the photolysis of both 1 and 3 give the same product mixture is attributed to the formation of a common intermediate, i.e., the coordinatively unsaturated 16e À species {IrH 2 (Tp Me2 )}.