Poverenov, E., Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, 76100, Israel
Gandelman, M., Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, 76100, Israel
Shimon, L.J.W., Unit of Chemical Research Support, Weizmann Institute of Science, Rehovot, 76100, Israel
Rozenberg, H., Unit of Chemical Research Support, Weizmann Institute of Science, Rehovot, 76100, Israel
Ben-David, Y., Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, 76100, Israel
Milstein, D., Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, 76100, Israel

The reactivity of the "long arm" PCN-type pincer ligand C 6H4[CH2P(tBu)2](CH2) 2N(CH3)2 (1), which forms complexes bearing a six-member ed amine chelate and a five-membered phosphine chelate, was compared with that of the new "normal" PCN ligand C6H 4[CH2P-(tBu)2](CH2)N(CH 2CH3)2 (2), which leads to formation of complexes bearing two five-membered chelates. The chloride complexes (PCN)PtCl (3, 4) and the unsaturated cationic complexes [(PCN)Pt]+X- (X = BF4, OTf) (5,6,7), based on both PCN ligands, were prepared and reacted with different reagents to give aqua, [(PCN-1)Pt(H2O)] +BF4 - (10); hydroxo, (PCN-1)Pt(OH) (11); carbonyl [(PCN)Pt(CO)]+BF4 - (8, 9); and hydride, (PCN-1)PtH (16) complexes. The structures of complexes 4, 6, 8, 10, 11, and 12 were determined by X-ray crystallography. When both carbonyl complexes were treated with hydrogen gas, the "long arm" PCN-1-based complex 8 led to formation of a trimeric cluster, [C6H6[CH 2P(tBu)2]-(CH2)2N(CH 3)2Pt(CO)]3 (12), while the "normal" PCN-based complex 9 remained unchanged under the same conditions. This observation clearly demonstrates the very significant effect of the amine arm length (five- vs six-membered chelate) on the hemilability of the ligand and the reactivity of the corresponding complexes. © 2005 American Chemical Society.