Isolation, structure and reactivity of a scandium boryl oxycarbene complex

A well-defined scandium boryl oxycarbene complex undergoes coupling with CO, C–H activation of lutidine, and cyclopropanation with ethylene.


Supporting Information
Isolation, structure and reactivity of a scandium boryl oxycarbene complex Baoli Wang, a  Synthesis and Characterization of Scandium Cyclopropyl Complex (7) 6) S7 Figure S2. 13 C NMR spectrum of 2 S8 Figure S3. 13 C NMR spectrum of 2-13 C S8 Figure S4. 13 C NMR spectrum of 3 S8 Figure S5. 13 C NMR spectrum of 3-13 C 2 S9 Table S1. Crystal data and structure refinement for complex 5 S10 Table S2. Atomic coordinates and equivalent isotropic displacement parameters for complex 5 S11 Table S3. Bond lengths and angles for complex 5 S13 Electronic Supplementary Material (ESI) for Chemical Science. This journal is © The Royal Society of Chemistry 2015 S2   Table S4. Anisotropic displacement parameters for complex 5 S27 Computational Section S30 Figure S7. Optimized structure of complex 2 S30 Table S5. Structural comparison between X-ray structure and DFT optimized structure of complex 2 S30 Table S6. Selected calculated and experimental IR data for 2 and 2-13 C S31 Figure S8. Computational IR spectrum of 2 S31 Figure S9. Computational IR spectrum of 2-13 C S31 Table S7. Second order perturbation theory analysis for 2 S32 References S33 Ar * (1) Ar = 2,6-( i Pr) 2 C 6 H 3 , * C = 13 C Scheme S1 Synthesis of 13 C labeled complex 2 (C*: 13 C)

Synthesis and Characterization of Phenylamido Enolate Complex (3)
A benzene/THF solution (5 mL/1 mL) of 2 (0.329 g, 0.410 mmol) in a 10-mL Schlenk tube was frozen in liquid nitrogen, evacuated under vacuum and then backfilled with carbon monoxide (1 atm). The reaction solution was slowly warmed to room temperature and stirred for 3 min. Then CO and solvent was removed under reduced pressure, and the residue was extracted with hexane. Yellow crystals of 3 (0.300 g, 81%) were grown from a concentrated hexane solution at -30 °C. 1

C-Labeled Experiments for Complex 3
Complex 2 reacted with 13 C-enriched CO to give complex 3-13 C (Eq. 2). In the 13 C NMR spectrum, a sharp peak at δ 136.7 was observed. On the other hand, the reaction of 13 C labeled complex 2-13 C with CO produced another complex 3-13 C'. 13 C NMR spectrum showed a broad peak at δ 134.7, suggesting that the 13 C atom linked to the boryl unit because of 13 C-11 B coupling. The 13 C NMR spectrum of 3-13 C 2 showed two doublets at δ 134.7 and 136.7, suggesting the presence of a 13 C= 13 C unit, and both C atoms in the OCCO unit originate from external CO molecules.

Synthesis and Characterization of Scandium Alkoxide Complex (4)
A benzene solution (5 mL) of 2 (0.570 g, 0.711 mmol) in a 10-mL Schlenk tube was heated at 100 °C for 2 days. Solvent was removed under reduced pressure, and the residue was extracted with hexane. Colourless crystals of 4 (0.239 g, 42%) were grown from a concentrated hexane solution at -30 °C. 1

Synthesis and Characterization of Scandium Pyridyl Complex (5)
A hexane solution (5 mL) of pyridine (0.013 g, 0.16 mmol) was added into a benzene solution (5 mL) of 2 (0.066 g, 0.082 mmol) at room temperature and the mixture was stirred for 0.5 hour. After solvent removal under reduced pressure, the residue was extracted with hexane. The filtrate was further concentrated to afford colourless crystals of 5 (0.056 g, 76%) at -30 ˚C.

Synthesis and Characterization of Scandium Methyl-Pyridyl Complex (6)
A hexane solution (5 mL) of 2-methylpyridine (0.011 g, 0.12 mmol) was added to a benzene solution (5 mL) of 2 (0.095 g, 0.12 mmol) at room temperature and the mixture was stirred for 26 hour. After solvent removal under reduced pressure, the residue was dissolved with hexane and keep at -30 ˚C to give colourless crystals of 6 (0.059 g, 61%) at -30 ˚C. 1

Computational Section
The complexes 2 ( Figure S7) and 2-13 C were optimized by the DFT method of M06 6 , which was implanted in Gaussian 09 program. 7 In these calculations, the 6-31G* basis set was used for C, H, O, N, and B atoms, and the Sc and Si atoms were treated by the Stuttgart/Dresden effective core potential (ECP) and the associated basis sets. 8 In the Stuttgart/Dresden ECP used in this study, the most inner 10 electrons of Si and Sc are included in the core. The 4 valence electrons of Si atom and 11 valence electrons of Sc were treated by the optimized basis sets, viz. (4s4p)/[2s2p] for Si and (8s7p6d1f)/[6s5p3d1f] for Sc, respectively. The basis set for Sc atom contains one fpolarization function with exponent of 0.27. One d-polarization function (exponent of 0.28) was augmented for Si atom. The optimized structures were analyzed by harmonic vibrational frequencies obtained at the same level and characterized as a minimum (N imag = 0). The recommended scale factors for frequencies in M06/6-31+G** level is 0.950. 9 The second order perturbation theory analysis was performed with the basis set 6-31+G** for C, H, O, N, and B atoms and the basis sets for Sc and Si are same as those in geometry optimizations. The calculated structure showed excellent agreement with the crystallographic structure (Table S5).  Table S5. Structural comparison between X-ray structure and DFT optimized structure of complex 2 (bond distance in Å and angle in degree)

Parameters
DFT optimized structure X-ray structure It was found that the calculated stretching frequency is close to that of experiment data (Table  S6). The bond stretch of the C1-O1 unit in complex 2 could not be identified in the S31 experimentally recorded IR spectrum because of an overlap with those of the Cp and boryl moieties. The DFT analyses were therefore performed, showing the C1-O1 stretching frequency of complex 2 at 1450cm -1 and of complex 2-13 C at 1417 cm -1 . Figures S8, S9)×0.95} Table S6. Selected calculated and experimental IR data for 2 and 2-13 C.