The rhodium-catalyzed hydroformylation of alkyl acrylates with different P–N diphosphine ligands is investigated here. Under mild conditions (syngas pressure: 2 MPa, 20 °C), 2,2′-bis(dipyrrolylphosphinooxy)-1,1′-(±)-binaphthyl (L1) rhodium catalyst could give good conversion of ethyl acrylate (82.9%) in 12 h and exclusive branched aldehyde selectivity of >99.0%. More importantly, on elevating the temperature to 90 °C, this Rh system could preferentially afford the linear aldehyde with 96.1% regioselectivity, and the TOF could reach up to 9000 h−1. Deuterioformylation was conducted to explore the mechanism of regioselectivity reversal, and the results established that the reversible rhodium hydride addition to form the Rh-alkyl species might play a vital role in this reversal. The β-hydride elimination of branched Rh-alkyl species was comparatively stronger than that of linear ones under increased temperature, probably because L1 could cause comparatively larger steric repulsion in branched Rh-alkyl species under high temperature, due to its bulky and rigid binaphthyl backbone characteristics. In turn, the linear Rh-alkyl species progress to linear aldehyde was facilitated.

Rhodium catalyzed hydroformylation of α-methylstyrene was investigated in the presence of monodentate phosphine ligands L1–L6. We found that the phosphine with good π-acceptability could efficiently improve the activity of the α-methylstyrene hydroformylation. The big steric hindrance of α-C in α-methylstyrene enhanced the regioselectivity towards the linear aldehyde, which resulted in 3-phenylbutanal as the predominant product (>99.0%). When tris(N-pyrrolyl)phosphine (L1) modified Rh(acac)(CO)2 was employed as the catalyst, the TOF could reach up to 5786 h−1 in the α-methylstyrene hydroformylation at relatively mild conditions (110 °C, 6 MPa).The tris(1-pyrrolyl)phosphane ligand (L) modified Rh-catalyzed hydroformylation of α-methylstyrene could make a satisfactory activity (TOF: 5786 h−1) under mild conditions, and the regioselectivity for linear aldehyde is above 99%, which offers an efficient way to produce 3-phenylbutanal with an excellent regioselectivity.

•The NH3 content would impact the dehydrogenation property of Li(NH3)nBH4.•Li(NH3)2BH4 dehydrogenate at lower temperatures in a much improved reaction rate.•Fairly high H-purity (99.99%) can be released in the Co-catalyzed Li(NH3)BH4 sample.•The dehydrogenation process of Li(NH3)nBH4 was studied by XRD, FTIR and Raman.Due to the coordinative nature of NH3 in the LiBH4 ammines, NH3 desorbs predominantly at temperatures below 180 °C under an open flow mode. Interestingly, the emission of NH3 can be effectively suppressed in conjunction with improved hydrogen desorption properties by introducing a cobalt catalyst (Co-catalyst) and heating the amines in a small closed vessel. Under such condition, Li(NH3)nBH4, where n = 1, 4/3, 2, releases ca. 15.3 wt%, 17.8 wt%, 14.3 wt% hydrogen at 250 °C, respectively. Fairly high H-purity (99.99%) can be achieved in the Co-catalyzed Li(NH3)BH4 sample upon releasing over 15 wt% H2 below 250 °C. As for the Co-catalyzed Li(NH3)2BH4 sample approximately 14.3 wt% of H2 (H-purity: 97.60%) can be desorbed in a much improved reaction rate.As compared to Co–Li(NH3)4/3BH4 (17.8 wt% H2), the Co–Li(NH3)2BH4 dehydrogenates at lower temperatures with faster rate but at the expense of the H2 capacity (14.3 wt%). In the case of Co–Li(NH3)BH4, fairly pure H2 (99.99%) with comparative amount of H2 (15.3 wt%) can be obtained.