Reaction of Re(CO)3(PPh3)2Cl with MeC(CH2PPh2)3 (triphos) gives (triphos)Re(CO)2Cl (1) which is converted to the hydride (triphos)Re(CO)2H (2) by treatment with LiAlH4. An X-ray diffraction analysis of 2 shows that the rhenium atom is octahedrally coordinated by triphos, which occupies a triangular face of the coordination polyhedron, by two carbonyl groups and by a terminal hydride ligand. Treatment of 2 with Me3OBF4 results in the evolution of methane and formation of the unsaturated complex [(triphos)Re(CO)2]BF4(4) which is stabilized by an agostic interaction between the rhenium center and a phenyl C-H bond of triphos. The η2-H2 complex [(triphos)Re(CO)2(H2)]BF4(3) is obtained either by protonation of 2 or by addition of H2 to the agostic complex 4. The presence of an intact dihydrogen ligand in 3 is unambiguosly shown by 1H NMR spectroscopy [T1min= 8.6 ms (CD2Cl2, 300 MHz, -58 °C); Jhdof 30.8 Hz for the monodeuteriated isotopomer [(triphos)Re(CO)2(HD)]- BF4(3-d1)]. Vinylidene derivatives of the formula [(triphos)Re(CO)2({C=C(H)R}]BPh4(R = Ph, 8; CO2Et, 9; C6H13, 10) are obtained by reaction of either the η2-H2 complex 3 or the agostic complex 4 with terminal alkynes in the presence of NaBPh4. The preference for the coordination of neutral groups at rhenium in the [(triphos)Re(CO)2]+ fragment follows the order N2 < C-H(agostic) < H2 < HC≡CR < CH3CN < CO. All the reactions described have been carried out in tetrahydrofuran or dichloromethane. © 1995, American Chemical Society. All rights reserved.
Reactions of the Rhenium(I) Fragment [{MeC(CH2PPh2)3}Re(CO)2]+. Synthesis and Characterization of a Stable Cationic η2-H2Complex of Rhenium
MARCHI, Andrea;MARVELLI, Lorenza;ROSSI, Roberto;
1995
Abstract
Reaction of Re(CO)3(PPh3)2Cl with MeC(CH2PPh2)3 (triphos) gives (triphos)Re(CO)2Cl (1) which is converted to the hydride (triphos)Re(CO)2H (2) by treatment with LiAlH4. An X-ray diffraction analysis of 2 shows that the rhenium atom is octahedrally coordinated by triphos, which occupies a triangular face of the coordination polyhedron, by two carbonyl groups and by a terminal hydride ligand. Treatment of 2 with Me3OBF4 results in the evolution of methane and formation of the unsaturated complex [(triphos)Re(CO)2]BF4(4) which is stabilized by an agostic interaction between the rhenium center and a phenyl C-H bond of triphos. The η2-H2 complex [(triphos)Re(CO)2(H2)]BF4(3) is obtained either by protonation of 2 or by addition of H2 to the agostic complex 4. The presence of an intact dihydrogen ligand in 3 is unambiguosly shown by 1H NMR spectroscopy [T1min= 8.6 ms (CD2Cl2, 300 MHz, -58 °C); Jhdof 30.8 Hz for the monodeuteriated isotopomer [(triphos)Re(CO)2(HD)]- BF4(3-d1)]. Vinylidene derivatives of the formula [(triphos)Re(CO)2({C=C(H)R}]BPh4(R = Ph, 8; CO2Et, 9; C6H13, 10) are obtained by reaction of either the η2-H2 complex 3 or the agostic complex 4 with terminal alkynes in the presence of NaBPh4. The preference for the coordination of neutral groups at rhenium in the [(triphos)Re(CO)2]+ fragment follows the order N2 < C-H(agostic) < H2 < HC≡CR < CH3CN < CO. All the reactions described have been carried out in tetrahydrofuran or dichloromethane. © 1995, American Chemical Society. All rights reserved.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
