Side-on coordination of boryl and borylene complexes to cationic coinage metal fragments

The M-(η2-BMn) complex [(η5-C5H5)(OC)2Mn{μ-B(Cl)(tBu)Au(PPh3)}] (2) can be functionalized via halide substitution reactions to afford isostructural complexes [(η5-C5H5)(OC)2Mn{μ-B(R)(tBu)Au(PPh3)}] (R = Ph, CCPh and NCS).


Preparation of [{( 5 -C 5 H 5 )(OC) 2 Mn} 2 {-BtBu} 2 Au][BAr x 4 ], Ar x = 3,5-C 6 H 3 Cl 2 ([8][BAr Cl 4 ]) and 3,5-C 6 H 3 (CF 3 ) 2 ([8][BAr F 4 ])
In a glovebox charged with an Ar atmosphere, a solid mixture of the gold borylene complex 2 (5 mg, 0.007 mmol) and a stoichiometric amount of Na[BAr x 4 ] (Ar x = C 6 H 4 Cl 2 , 4 mg, 0.007 mmol; Ar x = C 6 H 4 (CF 3 ) 2 , 5 mg, 0.007 mmol) was dissolved in ca. 1.5 mL of toluene. The reaction mixture was shaken by hand for three minutes and the resulting intense orange solution was filtered immediately through a cotton plug. The bright orange filtrate was collected in a small vial, to which ca. 1.5 mL of n-pentane was added. The solution mixture S3 was stored at −30 C for 5 days. X-ray quality crystals of [8][BAr Cl 4 ] formed in satisfactory yield (4 mg, 40%), which are sparingly soluble in n-hexane, benzene, toluene, and soluble in DCM. When Na[C 6 H 4 (CF 3 ) 2 ] was used, the reaction mixtures afforded a mixture of crystals in low yields. An analytically pure sample of [8]   The resulting cream-colored slurry was shaken by hand for 5 minutes resulting in a light orange cloudy solution, which was filtered immediately through a cotton plug. The clear orange filtrate was collected in a small vial and stored at -30 C overnight, to which added toluene and pentane (0.5 mL each). This mixture was stored at -30 C for another two days. [(η 5 -C 5 H 5 ) 2 (OC) 4

X-ray Crystallographic Determination
The crystal data of 5a-5c and 12 were collected on a BRUKER X8-APEX 2 (APEX 2 CCDdetector, NONIUS FR-591 rotating anode generator) and those of 8-11 on a BRUKER D8-QUEST (PHOTON CMOS-detector, INCOATEC IS microfocus source) diffractometer with multi-layer mirror monochromated Mo K radiation. The structures were solved using the intrinsic phasing method (SHELXT), expanded using Fourier techniques and refined with the SHELXL software package (see CIF files for detail on software versions). 4 All non-hydrogen atoms were refined anisotropically. Hydrogen atoms were assigned to idealized geometric positions and included in structure factor calculations. Additional details on refinement can be found in CIF files (_refine_special_details section). The SHELXL was interfaced with SHELXLE GUI for most of refinement steps. 5 The pictures of molecules were prepared using POV-RAY 3.6.2. 6 Crystallographic data can be obtained from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif It should be mentioned that because of extensive use of residues in SHELXL refinement, the labels of atoms in the paper are differs from those in CIF files.
Crystal data for 5a:

S6
Crystal data for 8: The quality of the crystals of compound 8 was relatively low. The reflections were diffused and at higher resolutions (0.95-0.8 Å) smudging led to lower completeness (e.g. 5-10% of reflections were not integrated due to exceeding of the image queue). As observed in the case of a few earlier cymantrene-tert-butylborylene derivatives, because of similar volume, the BtBu and cymantrene moieties can exchange their positions. The second cation in the structure was affected by this kind of disorder (see Fig. 1). This led to high residual density near the gold atom. From the remaining residual peaks only manganese and oxygen atoms could be easily localized. The bulk of the light atoms give rise to a random, diffused pattern around the borylene moiety. For this reason the minor disordered part was fitted as a rigid fragment using coordinates from the non-disordered first molecule and all its atoms, apart from the gold atom, were refined isotropically with common U eq parameter. The refinement of this disorder gave an occupancy of 4% for the minor fragment. Crystal data for 11: The metal framework shows two identical moieties [Cu(-BtBu){Mn(η 5 -C 5 H 5 )(CO) 2 }] connected to an extra manganese fragment, with only one borate as a counteranion. To the best of our chemical knowledge, it seems plausible (in terms of charge and electron counting) that a hydride should be present in the structure, which makes 11 a paramagnetic compound (and hence the absence of the NMR signals). The highest Q peak of the structure is located next to one copper atom, which has been attributed to the previously observed

General considerations
The gas-phase geometry pre-optimizations were performed using TURBOMOLE 6.5. 8 The final optimizations and the preparation of wave-function files were performed using the GAUSSIAN 09 program 9 or the ADF 2013 package. 10,11 The B3LYP hybrid functional and respectively Def2-SVP 12 or TZ2P basis set were used for all these computations. 13 We ensured that the calculated geometries are respectively minima on the potential energy pictures of fragment orbitals (SFOs) were prepared using ADF-GUI. 17 The topology of  2  (Atoms in Molecules) based on Def2-SVP basis was calculated with AIMALL program (ver. 13.11.04). 18 Quantitatively equivalent results for the TZ2P basis were obtained with ADF package.

Natural Bond Orbital Analysis (NBO) for cation [10] +
The manganese AOs (sd 2.4 hybrid) contribute 40% of the two-center Mn-B bond (BD), while boron AOs (sp 1.24 hybrid) account for the remaining 60%. This orbital was found in second order perturbation theory analysis to interact with low-populated lone vacant orbital (LV) of the copper atom (E int = 145.1 kcal·mol -1 ). The graphic interpretation of this dative interaction is presented in Figure S2. As expected for a molecule with C 2 symmetry, two of this kind of interaction could be found. The back-bonding from copper to borylene moieties, shown in Figure S4, is ten-fold weaker (E int = 9.7 kcal·mol -1 ) than the bonding of borylene to Cu + . This interaction is described by

Electron Localization Function (ELF) Topology for cation [10] +
The ELF topology of the CuMnB rings is determined by three synaptic basins that have population of ~2.4 ē. Adjacent to these basins along B-Mn bonds, outside of the rings, are located smaller basins with populations of ~0.8 ē (see Figure S5).

Charges [8] + -[10] +
The following tables list the charges obtained from different types of analyses.  Figure S7), and it supports the hypothesis that the interaction between borylene and coinage metal has three-center bond character, i.e. it comes from interaction of manganeseborylne moiety with coinage-metal (-Mn=B → Cu) rather than from covalent interaction B-Cu.

ETS-NOCV analysis of [10] +
The following figures 8 and 9 and table illustrate the fragment orbitals used for the most significant ETS-NOCV interaction.

Calculated and experimental IR-spectra of [11] +
We have computed the structure of [11] + using def-SV(P)/B3LYP level of theory. The additional hydrogen was initially placed at the position used in X-Ray refinement. The optimized geometry has retained this hydrogen at its original localization ( Figure 11).
Simulated, non-scaled IR-Spectrum of [11] + is shown at Figure 12. The vibration of hydrogen was predicted to be at 1237.6 cm -1 with relative intensity of 4% to the highest peak in spectrum. The strong CO-stretches are calculated in range of 2097-1993 cm -1 as compared to observed in IR-spectrum from solid sample of 1980-1840 cm -1 ( Figure S13). Applying these strong vibrations for calculation of scaling factor (0.938), moves the H-vibration to 1160.9 cm -1 . The experimental 1151.3 cm -1 band is very close to this value, however, as this peak is too close to the baseline noise, it cannot be unambiguous proof for presence of this hydrogen.