New chemistry of 1,2-closo-P2B10H10 and 1,2-closo-As2B10H10; in silico and gas electron diffraction structures, and new metalladiphospha- and metalladiarsaboranes
The molecular structures of 1,2-closo-P 2 B 10 H 10 (1) and 1,2-closo-As 2 B 10 H 10 (2) have been determined by gas electron diffraction and the results obtained compared with those from computation at the MP2/6-31G** level of theory. The level of agreement is good for 2 (root-mean-square [rms] misfit for As and B atoms 0.0297 Å ) and very good for 1 (rms misfit for P and B atoms 0.0082 Å ). In comparing the structures of 1 and 2 with that of 1,2-closo-C 2 B 10 H 12 (I) it is evident that
... s evident that expansion of the polyhedron from I to 1 to 2 is restricted only to the heteroatom vertices and the B 6 face to which these are bound. Following deboronation (at B3) and subsequent metallation, compounds 1 and 2 have been converted into the new metalladiheteroboranes 3-(h-C 9 H 7 )-3,1,2-closo-CoAs 2 B 9 H 9 (4), 3-(h-C 10 H 14 )-3,1,2-closo-RuAs 2 B 9 H 9 (5), 3-(h-C 5 H 5 )-3,1,2-closo-CoP 2 B 9 H 9 (6), 3-(h-C 9 H 7 )-3,1,2-closo-CoP 2 B 9 H 9 (7) and 3-(h-C 10 H 14 )-3,1,2-closo-RuP 2 B 9 H 9 (8), the last three constituting the first examples of metalladiphosphaboranes. Together with the known compound 3-(h-C 5 H 5 )-3,1,2-closo-CoAs 2 B 9 H 9 (3), compounds 4-8 have been analysed by NMR spectroscopy and (except for 8) single-crystal X-ray diffraction. The 11 B NMR spectra of analogous pairs of metalladiphosphaborane and metalladiarsaborane (6 and 3, 7 and 4, 8 and 5 ) reveal a consistently narrower (9-10 ppm) chemical shift range for the metalladiarsaboranes, the combined result of a deshielding of the lowest frequency resonance (B6) and an increased shielding of the highest frequency resonance (B8) via an antipodal effect. In crystallographic studies, compounds 3 and 5B (one of two crystallographically-independent molecules) suffer As/B disorder, but in both cases it was possible to refine distinct, ordered, components of the disorder, the first time this has been reported for metalladiarsaboranes. Moreover, whilst the Cp compounds 6 and 3 are disordered, their indenyl analogues 7 and 4 are either ordered or significantly less disordered, a consequence of both the reduced symmetry of an indenyl ligand compared to a Cp ligand and the preference of the former for a distinct conformation relative to the cage heteroatoms. Unexpectedly, whilst this conformation in the cobaltadiphosphaborane 7 is cis-staggered (similar to that previously established for the analogous cobaltadicarborane), in the cobaltadiarsaborane 4 the conformation is close to cis-eclipsed. ; Fax: +64 3 364 2110; Tel: +64 3 364 2456 † Electronic supplementary information (ESI) available: Tables S1-S16; final refined parameters, dependent parameters and SARACEN restraints, amplitudes of vibration and SARACEN restraints, correlation matrices, final GED coordinates and computational coordinates at BP86/SDD/6-31G**, BP86/6-31G**, B3LYP/6-31G** and MP2/6-31G** levels of theory for 1 and 2 followed by a description of the models used in the GED refinement. Fig. S1 -S2; molecular scattering intensity curves for 1 and 2.