Conversion of Benzaldehyde Imines into Isocyanides at a Low-Valent Molybdenum Center. Preparation and Reactivities of Isocyanide−Dinitrogen Complexes trans-[Mo(RNC)(N₂)(Ph₂PCH₂CH₂PPh₂)₂] (R = Aryl, Alkyl)¹

The molybdenum dinitrogen complex trans -[Mo(N 2 ) 2 (dppe) 2 ] ( 1; dppe = Ph 2 PCH 2 CH 2 PPh 2 ) reacts with benzaldehyde imines PhCH NR (R = Ph, C 6 H 4 Me- p, C 6 H 4 OMe- p, C 6 H 4 F- p, C 6 H 4 NMe 2 - p, Bu n, Pr i, CH 2 Ph) 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 -MeOC 6 H 4 CN results in the replacement of the coordinated N 2 by these ligands, affording trans -[Mo(RNC)(L)(dppe) 2 ] (L = CO ( 9 ), p -MeOC 6 H 4 CN ( 10 )). The complex containing two different isocyanides trans -[Mo(PhNC)(Bu t NC)(dppe) 2 ] was obtained analogously from 7a and Bu t NC. On the other hand, when benzene or toluene solutions of 7a and 7e (R = C 6 H 4 NMe 2 - p ) were first heated under Ar up to 80−90 °C for a short period to dissociate the coordinated N 2 and then treated with H 2 at room temperature, dihydrogen complexes trans -[Mo(RNC)(η 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 = C 6 H 4 NMe 2 - p ) along with the bis(isocyanide) complex trans -[Mo(PhNC) 2 (dppe) 2 ].