RESUMO
The reaction of phenyl azide with (PNP)Ni, where PNP = ( (t)Bu 2PCH 2SiMe 2) 2N (-), promptly evolves N 2 and forms a P=N bond in the product (PNP=NPh)Ni (I). A similar reaction with (PNP)FeCl proceeds to form a P=N bond but without N 2 evolution, to furnish (PNP=N-N=NPh)FeCl. An analogous reaction with (PNP)RuCl occurs with a more dramatic redox change at the metal (and N 2 evolution), to give the salt composed of (PNP)Ru(NPh) (+) and (PNP)RuCl 3 (-), together with equimolar (PNP)Ru(NPh). The contrast among these results is used to deduce what conditions favor N 2 loss and oxidative incorporation of the NPh fragment from PhN 3 into a metal complex.
RESUMO
Reduction of (PNP)MCl [PNP = ((t)Bu(2)PCH(2)SiMe(2))(2)N] with Mg gives three-coordinate, T-shaped (PNP)M for M = Fe(S = 3/2) and Ni. Their reactivity was tested toward CO; Ni binds one CO, but only reversibly (i.e., CO is completely lost in vacuum), and has a CO stretching frequency showing effective back-donation by NiI. The structure of (PNP)Ni(CO) is intermediate between planar and tetrahedral, in contrast to the planar d8 analogue, (PNP)Co(CO). This structural reorganization on carbonylation changes the singly occupied molecular orbital from having negligible phosphorus character [no P hyperfine structure in the electron paramagnetic resonance (EPR) spectrum of (PNP)Ni] to having enough P character to have a triplet structure in the EPR spectrum of the CO. The presence of one fewer electron in (PNP)Fe (vs the Co analogue) leads to binding of two CO, and (PNP)Fe(CO)(2) is characterized as a spin doublet with square-pyramidal structure. Density functional theory calculations strengthen the understanding of the structural and spectroscopic changes along this dn series (n = 7-9).