Nickel(II) and Palladium(II) Bis-Aminophosphine Pincer Complexes

The aminophosphine ligands CH2(CH2NHPtBu2)2 (1), (CH2NHPtBu2)2 (2), and (CH2NMePtBu2)2 (3) were prepared from the corresponding amines and ClPtBu2. The ligand 1 reacts with PdI2 to give the pincer complex (κ3P,C,P-CH(CH2NHPtBu2)2)PdI (4). The analogous reaction of 1 with NiCl2(dme) gave a the purple product (κ3P,N,P-tBu2PNH(CH2)3NPtBu2)NiCl (5), which contains a strained three-membered P–N–Ni ring. Subsequent reaction of 5 with B(C6F5)3 resulted in conversion to (κ3P,C,P-CH(CH2NHPtBu2)2)NiCl (6). The related reaction of the aminophosphine ligand 2 with PdI2 and with NiCl2(dme) led, in both cases, to the complexes (κ3P,N,P-tBu2PNH(CH2)2NPtBu2)MX (MX = PdI (7), NiCl (8)), respectively, whereas the reaction of 3 with PdX2 gave (κ3P,C,P-tBu2PN(Me)CHCH2N(Me)PtBu2)PdX (X = I (9), Br (10), Cl (11)). The analogous reaction of 3 with NiCl2(dme) afforded [(tBu2PH)(NMe)(CH2)2(NMe)(tBu2P)NiCl3], (12), which upon treatment with B(C6F5)3 afforded the species (κ3P,C,P-tBu2PN(Me)CHCH2N(Me)PtBu2)NiCl (13). Crystallographic studies of 4–6, 8, 9, 11, and 12 are reported. The implications of these results are considered.