Reaction of the geminal PAl ligand [Mes2PC(═CHPh)AltBu2] (1) with [Pt(PPh3)2(ethylene)] affords the T-shape Pt complex [(1)Pt(PPh3)] (2). X-ray diffraction analysis and DFT calculations reveal the presence of a significant Pt→Al interaction in 2, despite the strain associated with the four-membered cyclic structure. The Pt···Al distance is short [2.561(1) Å], the Al center is in a pyramidal environment [Σ(C-Al-C) = 346.6°], and the PCAl framework is strongly bent (98.3°). Release of the ring strain and formation of X→Al interactions (X = O, S, H) impart rich reactivity. Complex 2 reacts with CO2 to give the T-shape adduct 3 stabilized by an O→Al interaction, which is a rare example of a CO2 adduct of a group 10 metal and actually the first with η(1)-CO2 coordination. Reaction of 2 with CS2 affords the crystalline complex 4, in which the PPtP framework is bent, the CS2 molecule is η(2)-coordinated to Pt, and one S atom interacts with Al. The Pt complex 2 also smoothly reacts with H2 and benzamide PhCONH2 via oxidative addition of H-H and H-N bonds, respectively. The ensuing complexes 5 and 7 are stabilized by Pt-H→Al and Pt-NH-C(Ph) = O→Al bridging interactions, resulting in 5- and 7-membered metallacycles, respectively. DFT calculations have been performed in parallel with the experimental work. In particular, the mechanism of reaction of 2 with H2 has been thoroughly analyzed, and the role of the Lewis acid moiety has been delineated. These results generalize the concept of constrained geometry TM→LA interactions and demonstrate the ability of Al-based ambiphilic ligands to participate in TM/LA cooperative reactivity. They extend the scope of small molecule substrates prone to such cooperative activation and contribute to improve our knowledge of the underlying factors.

Ambiphilic phosphine−borane derivatives 1-B(OR) 2 -2-PR′ 2 −C 6 H 4 (R′ = Ph (1), iPr (2); (OR) 2 = (OMe) 2 (1a, 2a); catechol (1b, 2b) pinacol (1c, 2c), −OCH 2 C-(CH 3 ) 2 CH 2 O− (1d)) were tested as catalysts for the hydroboration of CO 2 using HBcat or BH 3 ·SMe 2 to generate methoxyboranes. It was shown that the most active species were the catechol derivatives 1b and 2b. In the presence of HBcat, without CO 2 , ambiphilic species 1a, 1c, and 1d were shown to transform to 1b, whereas 2a and 2c were shown to transform to 2b. The formaldehyde adducts 1b·CH 2 O and 2b· CH 2 O are postulated to be the active catalysts in the reduction of CO 2 rather than being simple resting states. Isotope labeling experiments and density functional theory (DFT) studies show that once the formaldehyde adduct is generated, the CH 2 O moiety remains on the ambiphilic system through catalysis. Species 2b·CH 2 O was shown to exhibit turnover frequencies for the CO 2 reduction using BH 3 ·SMe 2 up to 228 h −1 at ambient temperature and up to 873 h −1 at 70°C, mirroring the catalytic activity of 1b.