One-pot synthesis of CpRe(CO)2H2 and trans-CpRe(CO)2(SnPh3)2 from cis- and trans-CpRe(CO)2Br2 and Ph3SnH. Involvement of a radical-chain sequence in the formation of CpRe(CO)2H2
“…As expected, the OC−Re−CO angle in trans - 1 (99.8°) is larger than in cis - 1 (82.3°). The value of 99.8° for trans - 1 is quite similar to that observed in several other dicarbonyl rhenium complexes possessing the same stereochemistry: ( trans -CpRe(CO) 2 (C 6 HF 4 )Br, 99.7°; trans -CpRe(CO) 2 (SnPh 3 ) 2 , 100.5°; trans -(η 5 -C 5 Me 4 CH 2 Br)Re(CO) 2 (C 6 F 5 )Br, 100.5° 13 ). On the other hand, the carbonyl interbond angle of 82.3° found for cis - 1 can be compared to that determined for cis -Cp*Re(CO) 2 I 2 (78.5°), to our knowledge, the only other complex of this type studied by X-ray crystallography …”
Photochemical reaction of (η 5 -C 5 R 5 )Re(CO) 3 (R ) H, Me) with pentachlorobenzene (λ ) 350 nm, hexane solution) yields trans-(η 5 -C 5 R 5 )Re(CO) 2 (2,3,4,5-C 6 HCl 4 )Cl (trans-1, R ) Me; 2, R ) H) formed by insertion of the fragment (η 5 -C 5 R 5 )Re(CO) 2 into the C-Cl bond of C 6 -HCl 5 . Complex trans-1 converts to cis-(η 5 -C 5 Me 5 )Re(CO) 2 (2,3,4,5-C 6 HCl 4 )Cl (cis-1) in MeCN. The stereochemistry of both isomers has been assigned from examination of ν(CO) IR intensities and is supported by an X-ray structure determination of both complexes. A pure sample of either trans-1 or cis-1 dissolved in organic solvents produces an equilibrium mixture. In nonpolar solvents trans-1 is favored, whereas cis-1 is more stable in polar solvents. A mixture of cis-1 and trans-1 in CH 2 Cl 2 solution reacts on silica gel to produce the new tetramethylfulvene complex (η 6 -C 5 Me 4 CH 2 )Re(CO) 2 (2,3,4,5-C 6 HCl 4 ), 3. Supporting Information Available: Tables of coordinates and displacement coefficients for the non-hydrogen atoms, all bond lengths and interbond angles, anisotropic displacement coefficients, and H atom coordinates and isotropic displacement coefficients for cis-1 and trans-1. This material is available free of charge via the Internet at http://pubs.acs.org. OM000032V
“…As expected, the OC−Re−CO angle in trans - 1 (99.8°) is larger than in cis - 1 (82.3°). The value of 99.8° for trans - 1 is quite similar to that observed in several other dicarbonyl rhenium complexes possessing the same stereochemistry: ( trans -CpRe(CO) 2 (C 6 HF 4 )Br, 99.7°; trans -CpRe(CO) 2 (SnPh 3 ) 2 , 100.5°; trans -(η 5 -C 5 Me 4 CH 2 Br)Re(CO) 2 (C 6 F 5 )Br, 100.5° 13 ). On the other hand, the carbonyl interbond angle of 82.3° found for cis - 1 can be compared to that determined for cis -Cp*Re(CO) 2 I 2 (78.5°), to our knowledge, the only other complex of this type studied by X-ray crystallography …”
Photochemical reaction of (η 5 -C 5 R 5 )Re(CO) 3 (R ) H, Me) with pentachlorobenzene (λ ) 350 nm, hexane solution) yields trans-(η 5 -C 5 R 5 )Re(CO) 2 (2,3,4,5-C 6 HCl 4 )Cl (trans-1, R ) Me; 2, R ) H) formed by insertion of the fragment (η 5 -C 5 R 5 )Re(CO) 2 into the C-Cl bond of C 6 -HCl 5 . Complex trans-1 converts to cis-(η 5 -C 5 Me 5 )Re(CO) 2 (2,3,4,5-C 6 HCl 4 )Cl (cis-1) in MeCN. The stereochemistry of both isomers has been assigned from examination of ν(CO) IR intensities and is supported by an X-ray structure determination of both complexes. A pure sample of either trans-1 or cis-1 dissolved in organic solvents produces an equilibrium mixture. In nonpolar solvents trans-1 is favored, whereas cis-1 is more stable in polar solvents. A mixture of cis-1 and trans-1 in CH 2 Cl 2 solution reacts on silica gel to produce the new tetramethylfulvene complex (η 6 -C 5 Me 4 CH 2 )Re(CO) 2 (2,3,4,5-C 6 HCl 4 ), 3. Supporting Information Available: Tables of coordinates and displacement coefficients for the non-hydrogen atoms, all bond lengths and interbond angles, anisotropic displacement coefficients, and H atom coordinates and isotropic displacement coefficients for cis-1 and trans-1. This material is available free of charge via the Internet at http://pubs.acs.org. OM000032V
“…From the data for the carbonyl signals, an activation barrier of Δ G ⧧ = 7.4 ± 1.2 kcal/mol can be estimated for motion A in Figure . This value is in good agreement with the rotational barriers of other σ-donor/π-acceptor ligands on CpM(CO) 2 fragments such as substituted and unsubstituted olefins and acetylenes; in these cases the rotational barriers are 8−10 kcal/mol. − 11 Intramolecular motions in complex 1 .…”
The late transition metal borane complexes (MeCp)Mn(CO) 2 (HBR 2 ) (R ) alkyl, alkoxy) and Cp*Re-(CO) 2 (HBpin) (HBpin ) pinacolborane, Cp* ) pentamethylcyclopentadienyl) have been synthesized and isolated. All complexes were characterized spectroscopically, and X-ray crystal structure analyses were performed for (MeCp)Mn(CO) 2 (HBpin), (MeCp)Mn(CO) 2 (HBcat) (HBcat ) catecholborane) and (MeCp)Mn(CO) 2 (HBCy 2 ) (Cy ) cyclohexyl). These data show that the complexes contain a borane ligand with a weakened but intact B-H bond. The borane ligand in (MeCp)Mn(CO) 2 (HBcat) is replaced by PhCCPh, Ph 3 SnH, Ph 2 MeSiH, CO, and excess HBpin in ligand substitution reactions. The mechanism of substitution by PhCCPh was investigated. Kinetic studies showed that the reaction is first-order in complex and that borane and PhCCPh react competitively with the 16-electron intermediate, (MeCp)Mn(CO) 2 . The ∆H q value for borane dissociation was 24 ( 3 kcal/ mol for (MeCp)Mn(CO) 2 (HBcat) and 21 ( 1 kcal/mol for (MeCp)Mn(CO) 2 (HBCy 2 ), which provided an upper limit on the metal-borane binding energies. Dynamic NMR spectroscopy of (MeCp)Mn(CO) 2 (HBcat) revealed two types of rotations of the borane ligand.
“…The solid‐state structure of this complex (Figure ) reveals the terminal disposition of the SnPh 3 group at the Re fragment, trans to the phosphanyl ligand ( δ P = 217 ppm, J P,Sn = 183 Hz), with a conventional Re–Sn single‐bond length of 2.7369(5) Å (ca. 2.73 Å in [ReCp(SnPh 3 ) 2 (CO) 2 ]) . The coordination sphere of the Re center is completed with three CO ligands arranged in a meridional disposition (retained in solution, as judged from the IR spectrum), and by a tightly bound acetonitrile ligand [ d Re–N = 2.152(5) Å].…”
An efficient synthetic route for the preparation of the title anions was implemented, and it involved two-electron reduction of iodide-bridged [MMoCp(μ-I)(μ-PR 2 )(CO) 5 ] (Cp = cyclopentadienyl) complexes by using Na(Hg). Reaction of these anions with (NH 4 )PF 6 (in THF) and ClSnPh 3 (in MeCN) gave [MMoCp(μ-H)(μ-PR 2 )(CO) 5 (NH 3 )] and [MoReCp(μ-PCy 2 )(SnPh 3 )-(CO) 5 (NCMe)] (Cy = cyclohexyl), respectively, with incorporation [a]
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