The free energies of reaction calculated in Gaussian (1 atm standard state concentration) were converted to 1 M standard state values in order to calculate the equilibrium data in Figure 3. The concentration at 1 atm, [1 atm], at each temperature is given by PV/RT, from which the entropy correction, S corr , is given by -Rln(1/[1 atm]). Applying this correction to each of the reactants leads to the corrected ∆G react values given in Table S1. Supporting InformationRadkiewicz-Poutsma and co-workers 4 , raised the concern that B3LYP geometry optimization, as implemented in the CBS-QB3 scheme, may lead to a poor geometry for the borane-olefin π-complex, and as such the energetics from CBS-QB3 may be incorrect for the weak R 2 BH-olefin complexes studied herein. This could also have an influence on the free energy barrier for olefin dissociation in these cases. In addressing this, we first discuss the findings of Gilbert and Radkiewicz-Poutsma, and then evaluate the effect of different methods on our results.Gilbert 3 evaluated various DFT methods as well as MP2 for predicting both the geometry and dissociation energy of amineborane dative bonds. It was found that B3LYP predicts B-N bond dissociation energies (BDEs) that are lower than found experimentally, and also predicts B-N bond distances that are too long. Radkiewicz-Poutsma and co-workers 4 extended the study of amine-borane dative bonds. They found that the poor performance of B3LYP in calculating the B-N BDE is due to how this method calculates the energy of the dative bond, rather than being due to the geometry resulting from optimization with the B3LYP method. Bond energies resulting from high level single point calculations on B3LYP geometries were found to be reliable, and CCSD(T) calculations were relatively insensitive to whether an MP2 or B3LYP geometry was used, despite MP2 leading to a tighter B-N bond. This is consistent with the PES corresponding to the dative bond B-N distance being very flat. Both authors found that the MP2 method leads to more reliable B-N bond distances, and MP2 BDEs were closer to experimental or CCSD(T) values. We note that our work has not employed B3LYP energies (apart from thermal corrections to Gibbs free energy); in all cases higher level composite energies on B3LYP geometries have been obtained. We also note that while validating theoretical studies of propene hydroboration (more directly analogous to our work), Singleton 1 found B3LYP to be reliable for energy calculations.We have investigated the effect of MP2 geometry optimization by studying elimination and re-addition of propene from B i Pr 3 , as shown in Figure 5(a) of the main article. CBS-QB3 optimisation in this case led to the loosest post-elimination borane-olefin complex encountered in this work, presumably for steric reasons. The B-C α distance in the i Pr 2 BH••••propene complex is 4.5 Å in this case. The transition structures (elimination and re-addition), π-complex and separated products (propene and i Pr 2 BH) have been re-optimized at the MP2/6-31+G(...

The insertion, elimination and isomerisation of octenes with di-n-octylaluminium hydride [HAl(Oct)2], tri-n-octylaluminium [Al(Oct)3] and sec-octylaluminium species have been studied as individual steps in a putative aluminium based contrathermodynamic olefin isomerisation process. While elimination of 1-octene from [Al(Oct)3] is energetically unfavourable, the process is driven by high temperature vacuum distillation, leading to very high selectivity to 1-octene (>97%). At high conversions the [HAl(Oct)2] so obtained exists predominately as hydride-bridged cyclic oligomers, whereas at low conversion the mixed alkyl/hydride-bridged dimer [(Oct)2Al(μ-H)(μ-Oct)Al(Oct)2] is the major species. Di-n-octylaluminium hydride recovered after olefin elimination may be recycled and is active toward re-insertion of octenes. Internal octenes (cis- and trans-2-, 3- and 4-octene) only partially insert however, and even after prolonged heating there is no significant secondary to primary alkyl isomerisation evident.

Formation of 2-platinaoxetane 2 from oxo complex 1 and norbornene (NB) is mediated by hydroxo complex 5. The facile reaction of 5 with NB to give protonated 2-platinaoxetane 7 supports the involvement of such reactions in Wacker alkene oxidation.

The insertion of internal olefins (hydroalumination) and chain walking isomerisation at di-n-octylaluminium hydride [Al(Oct)2H], promoted by zirconocene dichloride [Cp2ZrCl2] has been studied. The reaction between [Cp2ZrCl2] and [Al(Oct)2H] in non-polar solvents leads to clusters containing bridging hydride ligands between Zr and Al. This system promotes hydroalumination of 1-octene but is largely ineffective for internal octenes (2-, 3-, 4-octene). In tetrahydrofuran the Zr-Al hydride clusters formed are more reactive and catalyse insertion and isomerisation of internal olefins to primary metal-alkyls, although this is accompanied by catalyst deactivation. Elimination and removal of 1-octene from the system post insertion/isomerisation was attempted, but it was found that the presence of the Zr catalyst leads to back-isomerisation to internal octenes, along with further decomposition with n-octane formation. Some possible pathways of catalyst decomposition, involving reduction of Zr and alkane elimination, have been studied theoretically.

The insertion of α- and internal octenes (hydroalumination) and chain walking isomerisation at di-n-octylaluminium hydride [Al(Oct)2H], catalysed by bis(imino)pyridine-Co complexes has been investigated by NMR spectroscopy. The Co-based catalysts promote efficient hydroalumination of 1-octene. Internal olefins are partially hydroaluminated, with isomerisation to the primary alkyls, but the catalyst responsible appears to deactivate rapidly. The reaction between the Co precatalysts and [Al(Oct)2H] generates a Co-hydride species, likely to be a hydride bridged dinuclear Co and Al complex. This species is reactive towards α-olefins but inert towards internal olefins. In contrast to hydroalumination, the catalysts promote efficient hydroboration, where insertion and isomerisation of internal octenes goes to completion. The differences between the systems may be partially ascribed to formation of an active mononuclear Co catalyst in the borane system versus a less active Co/Al dinuclear complex in hydroalumination.