Preparation and properties of molybdenum and tungsten dinitrogen complexes. 64. Conversion of benzaldehyde imines into isocyanides at a low-valent molybdenum center. Preparation and reactivities of isocyanide-dinitrogen complexes trans-[Mo(RNC)(N-2)(Ph2PCH2CH2PPh2)(2)] (R = aryl, alkyl)

The molybdenum dinitrogen complex trans-[Mo(N-2)(2)(dppe)(2)] (1; dppe = Ph 2PCH2CH2PPh2) reacts with benzaldehyde imines PhCH=NR (R = Ph, C6H4Me-p, C6 H4OMe-p, C6H4F-p, C6H4- NMe2-p, Bu-n, Pr-i, CH2Ph) in benzene at reflux to give a series of isocyanide-dinitrogen complexes trans-[Mo(RNC)(N-2)(dppe)( 2)] (7) with the concurrent formation of benzene. The structure of 7a (R = Ph) has been determined by X-ray crystallography. Treatment of 7a and 7f (R = Bu-n) with CO (1 atm) or p-MeOC6H4CN results in the replacement of the c oordinated N-2 by these ligands, affording trans-[Mo(RNC)(L)(dppe)(2)] (L = CO (9), p-MeOC6H4CN (10)). The complex containing two different isocyanide s trans-[Mo(PhNC)((BuNC)-N-t)(dppe)(2)] was obtained analogously from 7a an d ButNC. On the other hand, when benzene or toluene solutions of 7a and 7e (R = C6H4NMe2-p) were first heated under Ar up to 80-90 degrees C for a sho rt period to dissociate the coordinated N-2 and then treated with H-2 at ro om temperature, dihydrogen complexes trans-[Mo(RNC)(eta(2)-H-2)(dppe)(2)] ( 13) were produced. The X-ray analyses have revealed the detailed structures for 9a (R = Ph), 10a (R = Ph), and 13e (R = C6H4NMe2-p) along with the bis (isocyanide) complex trans-[Mo(PhNC)(2)(dppe)(2)].