Abstract
Photolysis of cis-Ru(dmpm)2H2 (dmpm = Me2PCH2PMe2) generates the four-coordinate species Ru(dmpm)2, which has been studied by laser flash photolysis and matrix isolation techniques. Ru(dmpm)2 displays weak bands in the visible region of the spectrum. Comparison with analogues containing diphosphines with a CH2CH2 bridge demonstrates the sensitivity of the spectrum to variation of the bite angle, P-Ru-P, of the ring formed by the metal and the diphosphine ligands. The rate constants for the reaction of Ru(dmpm)2 with H2, CO, C2H4, and Et3SiH have been measured. All of the rate constants lie in the range from 2.8 × 108 to 4.9 × 108 dm3 mol-1 s-1 at 295 K, showing that Ru(dmpm)2 is very unselective. Ru(dmpm)2 reacts with benzene with complex kinetics, which can be interpreted in terms of a rapid equilibrium between Ru(dmpm)2 and the benzene complex Ru(dmpm)2-(η2-C6H6). The latter forms the phenyl hydride complex Ru(dmpm)2(Ph)H relatively slowly (rate constant 3.5 × 103 s-1, kinetic isotope effect k(C6H6)/k(C6D6) = 1.8). A single-crystal X-ray structure of cis-Ru(dmprn)2H2 shows that the Ru-P bonds trans to hydrogen (mean length 2.304(2) Å) are longer than the remaining two Ru-P bonds (mean length 2.282(2) Å). The mean bite angle P-Ru-P of the bridged phosphorus atoms is 72.0°. The unbridged, P-Ru-P angles are 108.0° and 179.2°.
| Original language | English |
|---|---|
| Pages (from-to) | 1410-1417 |
| Number of pages | 8 |
| Journal | Organometallics |
| Volume | 16 |
| Issue number | 7 |
| Publication status | Published - 1 Apr 1997 |