Research in nickel-catalyzed olefin oligomerization and polymerization continues to progress at an accelerating pace. [1] With the synthesis of new Ni II catalysts that are highly tolerant towards polar substrates and are less oxophilic, [2] we are now able to target specific functional products. This advancement has brought along a host of new ligands, catalysts, [3] and mechanistic data. [4] It has also spilled over into scientific breakthroughs in new nickel chemistry, among which the recent isolation of low-valent coordinatively unsaturated Ni I is particularly noteworthy. [5, 6] This immediately gave rise to some pertinent questions, such as how Ni I compares to the classical Ni II and the sensitive Ni 0 in catalytic performance or whether a coordinatively and electronically unsaturated Ni I center might exhibit enhanced activity.
To address some of these questions, we need to design, prepare, and isolate close counterparts for direct structural and catalytic comparisons. We herein report our preliminary findings in using a ferrocenediyl iminophosphane supporting ligand. The flexibility of the ferrocenyl backbone, [7,8] coupled with the hemilability of the donors, [9] allows the metal to "pick and choose" its donors, and tune its receptivity to the substrates. It also raises our chances of isolating catalytically important intermediates for structural verification. The use of iminophosphanes as ligands for late transition metals for olefin polymerization has been demonstrated. [10] NiCl 2 (DME) (DME = dimethoxyethane) reacts with [{h-C 5 H 4 CH=N(C 6 H 5 )}Fe{h-C 5 H 4 P(tBu) 2 }] to give the Ni II
] (2; Scheme 1), with no evidence of methylnickel(i/ii) products similar to the result from bis(imino)pyridylcobalt(ii) with methylaluminoxane (MAO). [11] Ligand replacement of [Ni(cod) 2 ] (cod = 1,5cyclooctadiene) with [{h-C 5 H 4 CH=N(C 6 H 5 )}Fe{h-[