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Planar-chiral ferrocenylphosphine-borane complexes featuring agostic-type B-H E (E = Hg, Sn) interactionsElectronic supplementary information (ESI) available: Details for the synthesis and characterization of FcPPh2·BH3, NMR and mass spectra of all new compounds (PDF), FT-IR spectral data, computational details. CCDC 1523540-1523543. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c6dt04791b
The synthesis of ferrocenylphosphine-borane adducts 1,2-fc(E)(PPh 2 ·BH 3 ) (E = SnR 2 R′, HgX; 1,2-fc = 1,2-ferrocenediyl) that are substituted with organotin or organomercury Lewis acid moieties in ortho -position is presented. Several compounds that feature two ferrocenylphosphine-borane moieties...
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| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Online Access: | Get full text |
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| Summary: | The synthesis of ferrocenylphosphine-borane adducts 1,2-fc(E)(PPh
2
·BH
3
) (E = SnR
2
R′, HgX; 1,2-fc = 1,2-ferrocenediyl) that are substituted with organotin or organomercury Lewis acid moieties in
ortho
-position is presented. Several compounds that feature two ferrocenylphosphine-borane moieties bridged by Sn or Hg are also introduced. The products are fully characterized by multinuclear NMR spectroscopy, high-resolution MALDI-TOF mass spectrometry and elemental analysis. The attachment of the Lewis acid substituent to the same Cp ring of the ferrocene results in planar-chirality and the close proximity between the boron hydride group and the Lewis acid is expected to allow for agostic-type B-H E (E = Sn, Hg) interactions. Structural investigations by X-ray diffraction reveal a short B-H Sn contact of 2.755(4) Å for 1,2-fc(SnMe
2
Cl)(PPh
2
·BH
3
), which is only the second reported example of such a short agostic-type contact involving a coordinatively saturated tin(
iv
) center. In contrast, for the tetraorganotin derivatives 1,2-fc(SnMe
3
)(PPh
2
·BH
3
) and [1,2-fc(PPh
2
)](μ-SnMe
2
)[1,2-fc(PPh
2
·BH
3
)], in which the Lewis acidity of the tin atom is weaker than in 1,2-fc(SnMe
2
Cl)(PPh
2
·BH
3
), the B-H Sn distances are much longer but still within the sum of the van der Waals radii of Sn and H (
∑
vdW
= 3.27 Å). The chloromercury-substituted ferrocenylphosphine-borane 1,2-fc(HgCl)(PPh
2
·BH
3
) shows a similarly short B-H Hg contact of 2.615(5) Å (
∑
vdW
= 3.15 Å). Inspection of the extended structure of 1,2-fc(HgCl)(PPh
2
·BH
3
) reveals that the Lewis acidic mercury atom is also involved in intermolecular Hg Cl interactions with a neighboring molecule. An analysis of
31
P and
11
B NMR data reveals a correlation between the chemical shifts and the Lewis acidity of the adjacent organotin/mercury substituent. Structure optimization of 1,2-fc(SnMe
3
)(PPh
2
·BH
3
) and 1,2-fc(SnMe
2
Cl)(PPh
2
·BH
3
) by density functional theory (DFT) indicates B-H Sn contacts respectively of 3.129 and 2.631 Å that are close to the experimental values. Natural bond orbitals (NBO) and atom in molecules (AIM) analyses reveals a B-H→Sn donor-acceptor interaction energy of 5.46 kcal mol
−1
and a B-H Sn bond path for the chlorodimethyltin-substituted derivative with a modest electron density
ρ
(
r
) of 0.0082 a.u. and a positive Laplacian at the bond critical point.
Ferrocenylphosphine-borane adducts with Lewis acidic organotin and organomercury substituents in
ortho |
|---|---|
| ISSN: | 1477-9226 1477-9234 |
| DOI: | 10.1039/c6dt04791b |