Preparation of Mo and W complexes containing a new linear tetradentate phosphine ligand meso-o-C6H4(PPhCH2CH2PPh2)(2) from dinitrogen complexes trans-[M(N-2)(2)(Ph2PCN2CH2PPh2)(2)] (M = Mo, W)

A benzene solution of trans-[Mo(N-2)(2)(dppe)(2)] (1a; dppe = Ph2PCH2CH2PPh 2) and an equimolar amount of dppe was heated at reflux for 2 h under Ar to give [Mo(P-4)(dppe)] (2a; P-4 = meso-o-C6H4(PPhCH2CH2PPh2)(2)), where the new linear tetraphosphine P-4 is presumed to form through condensation of t wo dppe ligands in the coordination sphere of Mo. The W complex [W(P-4)(dpp e)] (2b) and its dppm analogue [W(P-4)(dppm)] (dppm = Ph2PCH2PPh2) were als o prepared from the reactions of trans[W(N-2)(2)(dppe)(2)] with one equiv o f dppe or dppm in toluene at reflux for 2 h under Ar. Detailed structures o f 2a and 2b were determined by X-ray crystallography. In contrast, when the reaction mixtures obtained by treatment of 1a with excess PR3 (R = Bu-n, E T) in place of dppe were cooled down to room temperature under N-2, novel d initrogen complexes containing the P-4 ligand [Mo(N-2)(P-4)(PR3)] formed; t hese were characterized spectroscopically anc l by elemental analysts.