Dinitrogen molecule

The Ge—N—N—W chain found in the complexes lrans- WI(NNGcR3 )(PR3 L]52 (4) results from the novel coupling reaction of a coordinated dinitrogen molecule with R3GeCl... 

Figure I. Possible coordination modes of the dinitrogen molecule in the mono- and dinuclear complexes...

Because the N2 molecule in the complex is still expected to have partial multiple bond character, the d-type functions could be needed. Therefore, d-type function have been added to nitrogen atoms (using a Gaussian exponent of 0.8) of the dinitrogen molecule. Our preliminary test of the effect of phosphorus atom d-type functions on the calculated Zr-PH3 bond lengths of model complexes A1 and A7 showed that the influence of d-type functions on the P atom is insignificant. Therefore, here we will not include d-type of functions for P-atoms. 

Interest in metal complexes able to bind molecular dinitrogen is mainly due to a desire to understand and reproduce in the laboratory the so-called nitrogen fixation reaction. This process, which in nature is catalysed by the metalloprotein nitrogenases, reduces the inert dinitrogen molecule to the metabolically useful NH3 ... 

Amongst the model compounds able to coordinate dinitrogen, some can coordinate one dinitrogen and some two dinitrogen molecules. The following coordination modes have been identified for such complexes. 

Metal Complexes with Terminal Coordination to One Dinitrogen Molecule... 

The N-N distance of the linearly coordinated dinitrogen molecule (1.12 A) is slightly longer than that of the nitrogen molecule in the gaseous state (1.10 A). 

Each ruthenium atom is octahedrally coordinated and the dinitrogen molecule is positioned in between the two metal centres. 

The dinitrogen molecule bridges the two tungsten atoms, each of which assumes a four-legged piano stool geometry. 

Fig. 5.18 (a) Total electron density contours for the carbon monoxide molecule. The carbon atom is on the left (b) Total electron density contours for the dinitrogen molecule. [From Bader, R. F. W. Bandrauk, A. D. J. Chem. Phys. 1968,49, 1653. Reproduced with permission.]... 

The suggestion for the catalytic cycle is presented in Scheme 4.18. Initially, an unsaturated iron complex is formed by expulsion of both dinitrogen molecules. Next, coordination of the alkene takes place, which is preferred since activation of hydrogen is also feasible. After alkene coordination, oxidative addition of hydrogen yields a formally 18-electron complex. Insertion of the alkene gave an alkyl complex, which recreated the starting complex via reductive elimination. Notably, the alkene complex also supports an isomerization of the double bond, hence an extension of possible intermediates is conceivable. 

Ab initio calculations on Ru(NH3)5(N2)l2 [Mo(N2)2(PH3)4], and other species suggest that the polarization of the dinitrogen molecule changes from species to species, being, in the examples cited, in the... 

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