Open AccessStereochemical Control of Valence and Its Application to the Reduction of Coordinated NO and N 2
Author(s) -
John H. Enemark,
Robert D. Feltham
Publication year - 1972
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.69.12.3534
Subject(s) - valence (chemistry) , chemistry , crystallography , ligand (biochemistry) , metal , bite angle , trigonal bipyramidal molecular geometry , valence electron , bent molecular geometry , stereochemistry , protonation , transition metal , electron , crystal structure , physics , ion , catalysis , biochemistry , receptor , organic chemistry , quantum mechanics , denticity
The electronic structures of transition metal complexes of NO are controlled by the stereochemistry about the metal atom (stereochemical control of valence). The six-coordinate complex, trans-[CoNO(NCS)-(C(6)H(4) [As(CH(3))(2)](2))(2)](+), consists of [Co(III)-(N=O(-))](2+) (angle(Co-N-O) = 135 degrees ), while the pentacoordinate trigonal bipyramidal complex, [CoNO(C(6)H(4)[As(CH(3))(2)](2))(2)] (2+), is best formulated as [Co(I)-(N identical withO(+)](2+) (angle(Co-N-O) = 179 degrees ). Evidence indicates that complexes of (NO)(+) and N(2) are electronically similar. Hence, the principles of stereochemical control of valence may be applied to metal complexes of N(2). In a linearly coordinated M(n) m(N identical withN) complex, valence electrons can be transferred from the metal to the N(2) ligand producing a bent, protonated, and/or metallated M(n+2)-(N=N(2-)) complex. This reduction of N(2) can be effected by the addition of an appropriate ligand to M or by a change in the coordination geometry about M. Stereo-chemical control of valence leads to the rejection of one of the previously proposed mechanisms for reduction by nitrogenase.