Pendant Alkyl and Aryl Groups on Tin Control Complex Geometry and Reactivity with H2/D2 in Pt(SnR3)2(CNBut)2 (R = But, Pri, Ph, Mesityl)
datasetposted on 2015-01-14, 00:00 authored by Anjaneyulu Koppaka, Lei Zhu, Veeranna Yempally, Derek Isrow, Perry J. Pellechia, Burjor Captain
The complex Pt(SnBut3)2(CNBut)2(H)2, 1, was obtained from the reaction of Pt(COD)2 and But3SnH, followed by addition of CNBut. The two hydride ligands in 1 can be eliminated, both in solution and in the solid state, to yield Pt(SnBut3)2(CNBut)2, 2. Addition of hydrogen to 2 at room temperature in solution and in the solid state regenerates 1. Complex 2 catalyzes H2−D2 exchange in solution to give HD. The proposed mechanism of exchange involves reductive elimination of But3SnH from 1 to afford vacant sites on the Pt center, thus facilitating the exchange process. This is supported by isolation and characterization of Pt(SnMes3)(SnBut3)(CNBut)2, 3, when the addition of H2 to 2 was carried out in the presence of free ligand Mes3SnH (Mes = 2,4,6-Me3C6H2). Complex Pt(SnMes3)2(CNBut)2, 5, can be prepared from the reaction of Pt(COD)2 with Mes3SnH and CNBut. The exchange reaction of 2 with Ph3SnH gave Pt(SnPh3)3(CNBut)2(H), 6, wherein both SnBut3 ligands are replaced by SnPh3. Complex 6 decomposes in air to form square planar Pt(SnPh3)2(CNBut)2, 7. The complex Pt(SnPri3)2(CNBut)2, 8, was also prepared. Out of the four analogous complexes Pt(SnR3)2(CNBut)2 (R = But, Mes, Ph, or Pri), only the But analogue does both H2 activation and H2−D2 exchange. This is due to steric effects imparted by the bulky But groups that distort the geometry of the complex considerably from planarity. The reaction of Pt(COD)2 with But3SnH and CO gas afforded trans-Pt(SnBut3)2(CO)2, 9. Compound 9 can be converted to 2 by replacement of the CO ligands with CNBut via the intermediate Pt(SnBut3)2(CNBut)2(CO), 10.