1993 Fiscal Year Final Research Report Summary
ACTIVATION OF H-H,C-H,Si-H,AND C-C BONDS BY MEANS OF COORDINATIVELY UNSATURATED METAL SPECIES
| Project/Area Number |
03453098
|
|---|
| Research Category |
Grant-in-Aid for General Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Research Field |
Synthetic chemistry
|
|---|
| Research Institution | THE UNIVERSITY OF TOKYO |
|---|
Principal Investigator |
SABURI Masahiko THE UNIVERSITY OF TOKYO,FACULTY OF ENGINEERING,ASSOCIATE PROFESSOR, 工学部, 助教授 (90011022)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
TAKAHASI Tamotsu INSTITUTE FOR MOLECULAR SCIENCE,COORDINATION CHEMISTRY LABORATORIES,ASSOCIATE PR, 錯体化学研究施設, 助教授 (30163273)
|
|---|
| Project Period (FY) |
1991 – 1993
|
| Keywords | Ruthenium Complex / Five-Coordinate Complex / Molecular Hydrogen Complex / Agostic Interaction / Hydrogen Exchange Reaction / Activation of C-H Bond / Silane |
|---|
| Research Abstract |
(1)A series of molecular hydrogen complexes [RuH (eta^2-H_2) (diphosphine)_2] PF_6 was prepared by reactions of dihydrogen gas with coordinatively unsaturated ruthenium (II) complexes [RuH (diphosphine)_2] PF_6 in solution. The solution behaviors of the dihydrogen complexes were examined by NMR spectroscopy to reveal that the intramolecular hydrogen exchange in these complexes is affected by the rigidity of diphosphine chelate ring. Thus, the hydrogen exchange in dpbp complex, the chelate of which is flexible, is much faster than in binap complex, in which the chelate ring is entirely rigid.
(2)It was confirmed by variable temperature NMR measurements that the five-coordinate complex with dppb and diop exhibit agostic interaction between the C-H moiety of chelate methylene group and ruthenium center. Further, the occurrence of unprecedented hydrogen exchange between the agostic C-H and Ru-H was established by spin-saturation transfer technique at lower temperatures. The rate of exchange were determined and the kinetics parameters were obtained for dppb complex. This indicates agostic interaction is a mode of C-H bond activation at unsaturated metal center.
(3)Reactions of five-coordinate complex [RuH (dppp)_2]^+ with silane H-SiR_3 were examined. It was recognized by ^1H NMR measurements that a fairly reactive eta^2-H-Si species [RuH (eta^2-H-SiR_3) (dppp)_2]^+ in the initial stage of the reaction. The eta^2-H-Si species is considerably reactive toward nucleophiles such as H_2O and ROH to give rise to dihydrogen complex [RuH (eta^2-H_2)-(dppp)_2]^+ and siloxane (R_3SiOSiR_3) or silyl ether (R_3SiOR), suggesting that the five coordinate complex is effective in the activation of Si-H bond. Detailed mechanism of this reaction was studied by the use of deuterated silane (DSiR_3) or MeOD.It was clarified that the dihydrogen was generated from both silane and alcohol.
|
