N-Bonding complexes

Reaction of the bis(salicylidenimine)palladium(II) complexes with mineral acids yields N-bonded complexes tranr-[PdX2(LH)2] (X = Cl, Br, I, SCN LH = HOC6H4CHNPh).243... 

When aqueous solutions of the complexes [Co(NH3)5(N=CR)]3+ (R=Me or Ph) are treated with an excess of NaN3 at pH 5-6 (to prevent base hydrolysis to the amido complex) tetrazole complexes are formed (Scheme 17).32 The formation of 5-methyltetrazoIe from sodium azide and acetonitrile requires a reaction time of 25 h at 150 °C323 compared with only 2 h at ambient temperature for coordinated acetonitrile. The subsequent conversion of the N -bonded complex to an N2-bonded complex has been confirmed as the latter complex has been prepared and its crystal structure determined.324... 

Other N-bonded complexes are (CODjCIRh ONQH A-Me and Pd1 Cl2(ONPh)2 compounds with O-bonding and with 7V,0-bridged bonding are known.198... 

For the C2H4 n-bonded complexes the Av values with respect to C2H4 gas are indicated in parentheses. 

A single sharp band at 480 cm has been assigned to the bending mode in an N-bonded complex, in contrast to the several, low-intensity bands near 420 cm observed in jS-thiocyanates (489, 639). 

An attempt has been made to extend the intensity criterion to insoluble materials, using KBr disks. Satisfactory results have been obtained enabling N-bonded complexes to be distinguished from S-bonded [i81). This technique has been further extended by using a suitable internal standard 60) the C—0 stretching band in salicylic acid (1654 cm ) has been used, and the ratio of the intensity of vcn to the intensity of this band has been suggested as a satisfactory criterion to distinguish N- and S-bonded complexes, provided that known complexes are used for calibration. 

Opening of the three-center bond affords the carbenium ion of greatest stability according to the well-known Markovnikov rule. It should be pointed out that except in extremely crowded cases such as adamantylideneadaman-tane, there is no direct evidence that the three-center n-bonded complex is an intermediate, and thus it is only a depiction of the transition state or high-lying intermediate of the addition reaction. 

The S(NCSe) of N-bonded complexes are above 400cm", whereas Se-bonded complexes show at least one component of 6(NCSe) below 400 cm". ... 

As discussed in Sec. 111-15, the mode of coordination of the pseudohalide ion can be determined by vibrational spectroscopy. Burmeister et al. " found that all NCS and NCSe groups are N-bonded in M(Cp) X2-type compounds, where M is Ti, Zr, Hf, or V, and X is NCS or NCSe. In the case of analogous NCO complexes, Ti, Zr, and Hf form O-bonded complexes, whereas V forms an N-bonded complex. Later, Jensen et al suggested the N-bonded structure for the titanium complex. 

Fully N-bonded complexes have been isolated for most transition metal ions forming stable M—N bonds Co", " RuUi 770.77, Rh", - Ir", Cu", Ni", Pd", Pt" and... 

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