Advanced
Study of Hydroboration of (μ-H)<sub>2</sub>Os<sub>3</sub>(CO)<sub>10</sub> with Various Borane Complexes(BH<sub>3</sub>·L: L
Study of Hydroboration of (μ-H)2Os3(CO)10 with Various Borane Complexes(BH3·L: L
Journal of the Korean Chemical Society. 2003. Dec, 47(6): 675-678
Copyright © 2003, The Korean Chemical Society
  • Received : September 28, 2003
  • Published : December 20, 2003
Download
PDF
e-PUB
PubReader
PPT
Export by style
Article
Author
Metrics
Cited by
TagCloud
About the Authors
장훈 정

Abstract
Keywords
EXPERIMENTAL SECTION
- General data
All reactions were prerformed under inert-atmosphere conditions. Standard vacuum line and inert-atmosphere techniques were employed. 5 Os 3 (CO) 12 (Strem) was used as received. (μ-H) 2 Os 3 (CO) 10 was prepared according to the literature method. 6 Diborane was prepared by literature methods and stored at -196℃ in a glass tube. 7 O(CH 3 ) 2 (Matheson Scientific Products) was dried and stored over Na at -78℃. BH 3 .L (L=N(CH 3 ) 3 , N(C 2 H 5 ) 3 , Pyridine, THF, S(CH 3 ) 2 , P(C 4 H 9 ) 3 , PPh 3 ) (Aldrich) was stroed in a glovebox refrigerator and used as received. Solvents were dried with P 2 O 5 or Na, distilled and stored in a sealed flask. Thin-layer chromatography plates (J.T.Baker, 250 m) were activated at 45 ℃ for 24 hours before use. 1 H and 11 B NMR chemical shifts are referenced to Si(CH 3 ) 4 ( 1 H, δ=0.00 ppm) and BF 3 .OEt 2 ( 11 B, δ=0.00 ppm).
- Reaction of (-H)2Os3(CO)10with BH3.S(CH3)2
In the glovebox, (μ-H) 2 Os 3 (CO) 10 (200 mg, 0.235 mmol) was weighed into a 50 mL long-neck flask equipped with a Kontes vacuum line adaptor. Borane complex. BH 3 .S(CH 3 ) 2 (9.38 mmol) was added to the flask and 25 mL volume of CH 2 CL 2 was condensed into the flask at -78℃. After being warmed to room tmeperature, the solution was stirred for 7 days during which time yellow solution formed. The solvent and excess BH 3 .L was removed by means of dynamic high vacuum leaving a yellow solid. An extractor and receiver flask were attached to the flask including the yellow solid in glovebox. A 20 mL volume of hexane was vacuum trans-ferred into the flask and the solution was srirred at room temperature for 1 hour. The solution was flitered to give a yellow filtrate. The solid left on the frit was then washed a couple of times with hexane. The solvent was removed by means of dynamic high vacuum leaving a light yellow solid and then the solid was recrystallyzed in CH 3 CI. This yellow product was identified as (μ-H) 2 Os 3 (CO) 9 (μ-H) 2 BH by 1 H & 11 B NMR spectroscopies. The yield of product is 86.5 mg (0.013 mmol). a 44.0% yield based on (μ-H) 2 Os 3 (CO) 10 . (μ-H) 2 Os 3 (CO) 9 (μ-H) 2 BH: 1 H NMR (CDCI 3 , 30C) δ 4.7(br, 1 B-H), -13.6 (br, 2 B-H-Os), -20.5 (q, 2 Os-H-Os) ppm; 11 B NMR (CDCl 3 , 30C) δ 18.5 (br) ppm.
- Reactions of (μ-H)2Os3(CO)10with BH3.L (L=N (CH3)3, N(C2H5)3, Pyridine, THF, P(C4H9)3, PPh3)
(μ-H) 2 Os 3 (CO) 10 (200 mg, 0.235 mmol) was weighed into a 50 mL long-neck flask equipped with a Kontes vacuum line adaptor. Borane complex BH 3 .L (9.38 mmol; (L=N (CH 3 ) 3 , N(C 2 H 5 ) 3 , Pyridine, THF, P(C 4 H 9 ) 3 , PPh 3 ) was added to the flask in the glovebox and 25 mL volume of CH 2 CL 2 was condensed into the flask at -78 ℃. After being warmed to room temperature, the solution was stirred for 7 days. The volatile components were removed by means of dynamic high vacum leaving brown residue. The products were separated by preparative TLC on 2 mm silica using a mixed solvent toluene/hexane as an eluent. A light yellow band was identified from its NMR spectrum, as reported above, as (μ-H) 2 Os 3 (CO) 9 (μ-H) 2 BH.
- Reactions of (μ-H)2Os3(CO)10with BH3.L (L=O (CH3)2, O(C2H5)2
(μ-H) 2 Os 3 (CO) 10 (200 mg, 0.235 mmol) was weighed into a 50 mL long-neck flask. The flask was topped with a Kontes vacuum line adaptor and evacuated. 25 mL volume of CH 2 CL 2 was condensed into the flask at -78 ℃. Lewis base (0.235 mmol: O(CH 3 ) 2 , O(C 2 H 5 ) 2 ) and B 2 H 6 (0.118 mmol) was measured in a calibrated bulb and condensed into the flask. The solution was stirred at room temperature for 7 days. The volatile components were removed leaving a light yellow residue. The yellow product was recrystallized from CH 2 Cl 2 . The product was identified as (μ-H) 3 Os 3 (CO) 9 ( 3 μ-BCO) by 1 H & 11 B NMR spectroscopies. (μ-H) 3 Os 3 (CO) 9 3 -BCO): 1 H NMR (CDCl 3 , 30C) δ - 19.8 (q, 3 Os-H-Os) ppm; 11 B NMR (CDCl 3 , 30C) δ 18.5 ppm.
REULTS AND DISCUSSIONS
The hydroboration reactions of the unsaturated cluster (μ-H) 2 Os 3 (CO) 10 with various borane complexes BH 3 .L (L=O (CH 3 ) 2 , O(C 2 H 5 ) 2 , THF, N(CH 3 ) 3 , N(C 2 H 5 ) 3 , Pyridine, S(CH 3 ) 2 , P(C 4 H 9 ) 3 , PPh 3 ) were investigated.
PPT Slide
Lager Image
As shown in 1 , (μ-H) 2 Os 3 (CO) 9 (μ-H) 2 BH was produced in 44.0% yield from the reaction of (μ-H) 2 Os 3 (CO) 10 with BH 3 .S(CH 3 ) 2 . Meanwhile, the cluster was produced in yield of less than 1% from thr reactions of (μ-H) 2 Os 3 (CO) 10 with BH 3 .L (L=N (CH 3 ) 3 , N(C 2 H 5 ) 3 , Pyridine, P(C 4 H 9 ) 3 , PPh 3 ) and not from thr reactions of (μ-H) 2 Os 3 (CO) 10 with BH 3 .L (L=O(CH 3 ) 2 , O(C 2 H 5 ) 2 , THF).
Although thr reactions wrer followed by means of NMR spectroscopy, it was not successful to observe intermediates in the reactions of (μ-H) 2 Os 3 (CO) 10 with various borane complexes. However, on the basis of the known chemistry of boranes and thr products obtained, the reaction pathways for the formation of (μ-H) 2 Os 3 (CO) 9 (μ-H) 2 BH in 1 can be proposed. BH 3 .L functions as an electron pair donor through a B-H bond, adding to the unsaturated cluster (μ-H) 2 Os 3 (CO) 10 by forming two hydrogen bridged Os-H-B bonds of Ib. The ability of the borane complexes BH 3 .L to add to transition metals through the formation of metal-H-B bonds is well-konwn. 8 For the formation of (μ-H) 2 Os 3 (CO) 9 (μ-H) 2 BH, a
Yield of (μ-H)2Os3(CO)9(μ-H)2BH in the reaction of H2Os3(CO)10with Borane complexes
PPT Slide
Lager Image
Yield of (μ-H)2Os3(CO)9(μ-H)2BH in the reaction of H2Os3(CO)10 with Borane complexes
PPT Slide
Lager Image
Proposed reaction pathways for the formation of (μ-H)2Os3(CO)9(μ-H)2BH.
CO of Os(CO) 4 unit of the intermaediate Ib should be eliminated to form Os(CO) 3 . The CO shifts to an electronically unsaturated neighboring Os atom to form a CO bridged Os-CO-Os bond and two terminal hydrogens do to neighboring Os atoms to form H bridged Os-H-Os bonds of Ic. The intermediate Ic was not observed but Fe analogue of Ic including the CO bridged Os-CO-Os bond was prepared by Fehlner. 9 The formations of the bridge bonds are followed by elimination of CO from Os-CO-Os bond, thereby inducing formation of another Os-B bond due to the electron deficiency of the osmium atom. As shown in final step of the proposed pathways, B atom shifts to the Os atom and thus BH 3 .L unit is incorporated into Os 3 triangle by formation of a Os-B bond. Finally, release of L from the adduct produces the (μ-H) 2 Os 3 (CO) 9 (μ-H) 2 BH.
A key step in the formation of the cluster is release of Lewis base from the adduct. In the scheme of the reaction pathways, release of Lewis base from thr adducth occurs in the last step. However, Shore reported that for the formation of another tri-osmium borylidyne carbonyl cluster (μ-H) 3 Os 3 (CO) 9 3 -BCO) containing Os 3 B core in the hydroboratin reaction of (μ-H) 2 Os 3 (CO) 10 with B 2 H 6 in presence of O(CH 3 ) 2 , release of lewis base O(CH 3 ) 2 from the adduct occurred in the early step of the reaction pathways, inducing migration of a CO of Os(CO) 4 to B atom to form BCO unit capping Os 3 core. 3 , 10 The distinct difference between the pathways for the formation of (μ-H) 2 Os 3 (CO) 9 (μ-H) 2 BH and (μ-H) 3 Os 3 (CO) 9 3 -BCO) is when the release of Lewis base L from the adduct of BH 3 .L occurs. The results of the reactions in 1 can be rationaled by the proposed reaction pathways and the hard-soft acid-base principle. 11 , 12 The bond strength in donor-acceptor complexes such as BH 3 .L (L=Lewis base) can be interpretated on the basis of the theory of hard and soft acids and bases suggested by Pearson. 13 , 14 The reaction of (μ-H) 2 Os 3 (CO) 10 with BH 3 .S(CH 3 ) 2 , produces the cluster in the largest yield of 44%. According to the theory, soft acid BH 3 combines with soft base S(CH 3 ) 2 to form very stable borane complexes BH 3 .S(CH 3 ) 2 and thus the base S(CH 3 ) 2 hardly dissociate from the complex until the final step of the reaction pathway so that migration of CO to B atom for the formation of (μ-H) 3 Os 3 (CO) 9 3 -BCO) is inhibited. Instead, the large stability of the complex induces decarbonylation to form (μ-H) 2 Os 3 (CO) 9 (μ-H) 2 BH. That is why BH 3 .S(CH 3 ) 2 reacts with (μ-H) 2 Os 3 (CO) 10 to produce (μ-H) 2 Os 3 (CO) 9 (μ-H) 2 BH in the largest yield.
Soft bases P(C 4 H 9 ) 3 and PPh 3 strongly combime with soft acid BH 3 . However, the reactions of the (μ-H) 2 Os 3 (CO) 10 with the borane complexes produce little (μ-H) 2 Os 3 (CO) 9 (μ-H) 2 BH, because the borane complexes hardly add to the cluster due to the steric hindrance of bulky phosphins. In the reactions of (μ-H) 2 Os 3 (CO) 10 with BH 3 .L (L=O(CH 3 ) 2 , O(C 2 H 5 ) 2 , THF), (μ-H) 2 Os 3 (CO) 9 (μ-H) 2 BH is not produced because O(CH 3 ) 2 , O(C 2 H 5 ) 2 , and THF are typical hard bases and thus the relaease of Lewis bases easily occurs in the early step of the reaction pathways due to weak combination of BH 3 with the Lewis bases. Although N(CH 3 ) 3 , N(C 2 H 5 ) 3 . and Pyrdine are a little bit softer than ether, those are hard bases and thus the borane complexes easily dissociate in the early step of the reaction pathways. Therefore, the reactions of (μ-H) 2 Os 3 (CO) 10 with BH 3 .L (L=N(CH 3 ) 3 , N(C 2 H 5 ) 3 , Pyridine) produce little (μ-H) 2 Os 3 (CO) 9 (μ-H) 2 BH.
In summary, the proposed reaction pathways for the formation of (μ-H) 2 Os 3 (CO) 9 (μ-H) 2 BH on basis of the hard-soft acid-base princlple is consistent with the results of the hydroboration reactions of (μ-H) 2 Os 3 (CO) 10 with various borane complexes. The yield of the cluster in the hydroboration reaction depends on the stability of the borane complexes.
Acknowledgements
This work was supported by grant No. 2001-2-12200-001-2 from the Basic Research Program of the Korea Science & Engineering Foundation.
References
Shore S.G. , Jan D.-Y. , Hsu L.-Y. , Kennedy S. , Hoffman J.C. , Wang T.-C. , Marshall A.G. 1984 J. Chem. Soc., Chem, Commun 392 -    DOI : 10.1039/c39840000392
Orpen A. G. , Rivera A. V. , Bryan E. G. , Pippard D. , Sheldric G.M. 1978 J. Chem. Soc., Chem. Commun 723 -    DOI : 10.1039/c39780000723
Shore S.G. , Jan D.-Y. , Hsu L.-Y. , Hsu W.-L. 1983 J. Am. Chem. Soc. 105 5924 -    DOI : 10.1021/ja00356a040
Chung J.-H. , Boyd E. P. , Liu j. , Shore S. G. 1997 Inog. Chem. 36 4778 -    DOI : 10.1021/ic970683s
Shriver D.F. , Drezdzon M.A. The Manipulation of Air Sensitive Compounds 2nd ed. John Wiely & Sons New York 1986 -
Knox S. A. R. , Koepke J.W. , Andrews M.A. , Kaesz H.D. 1975 J. Am. Chem. Soc. 97 3942 -    DOI : 10.1021/ja00847a013
Taft M.A. , Leach J.B. , Himpsl F.L. , Shore S.G. 1982 Inorg. Chem. 21 1592 -
Gilbert K. B , Boocock S.K. , Shore S.G. 1982 in Comprehensive Organometallic Chemistry 7 897 -
Vites J. C. , Housecroft C.E. , Jacobsen G. B. , Fehlner T.P. 1984 Organometallics 3 1591 -    DOI : 10.1021/om00088a025
Jan D.-Y. , Workman D.P. , Hsu L.-Y. , Krause J.A. , Shore S.G. 1992 Inorg. Chem. 31 5123 -    DOI : 10.1021/ic00050a036
Anane H. , Jarid A. , Boutalib A. , Nebot-Gil I. , Tomas F. 1998 J. Mol. Struct (Theochem) 455 51 -    DOI : 10.1016/S0166-1280(98)00241-3
Williams R.J.P. , Hale J.D. 1996 Structrue and Bonding, Jorgenson, Ed. 1 Springer-Verlag Berlin 255 -
Huheey J. E. , Evans R. S. 1970 J. Inorg. Nucl. Chem. 32 383 -    DOI : 10.1016/0022-1902(70)80245-7
Pearson R.G. 1963 J. Am. Chem. Soc. 85 3553 -    DOI : 10.1021/ja00905a005