Synthesis and application of diphenylbis(3,5-dimethylpyrazol-1-yl)methane to form η2-arene complexes of molybdenum

Article abstract of DOI:10.1016/0022-328X(93)83147-N

The neutral nitrogen-bidentate ligand, diphenylbis(3,5-dimethylpyrazol-1-yl)methane, Ph2CPz'2, can readily be obtained by the reaction of Ph2CCl2 with excess HPz' in a mixed-solvent system of toluene and triethylamine.It reacts with in 1,2-dimethoxyethane to give the η²-arene complex, (1).This η²-ligation appears to stabilize the coordination of Ph2CPz'2 in forming (2) and (3) from the reaction of 1 with the appropriate diazonium salt but the stabilization seems not strong enough when 3(CO)3> is formed from the reaction of 1 with P(OMe)3.The solid-state structures of 1 and 3 have been determined by X-ray crystallography: 1-CH2Cl2, monoclinic, P2₁/n, a=11.814(3), b=11.7929(12), c=19.460(6) Angstroem, β=95.605(24)^o, V=2698.2(11) Angstroem³, Z=4, D_calc=1.530 g/cm³, R=0.044, R_w=0.036 based on 3218 reflections with I > 2?(I); 2 (3)-1/2 hexane-1/2 CH3OH-1/2 H2O-1 CH2Cl2, monoclinic, C2/c, a=41.766(10), b=20.518(4), c=16.784(3) Angstroem, β=101.871(18)^o, V=14076(5) Angstroem³, Z=8, D_calc=1.457 g/cm³, R=0.064, R_w=0.059 based on 5865 reflections with I > 2?(I).Two independent cations were found in the asymmetric unit of the crystals of 3.The average distance between the Mo and the two η²-ligated carbon atoms is 2.574 Angstroem in 1 and 2.581 and 2.608 Angstroem in 3.The average distance between the Mo and the two η²-ligated carbon atoms is 2.574 Angstroem in 1 and 2.581 and 2.608 Angstroem in 3.The unfavourable disposition of the η²-phenyl group with respect to the metal centre in 3 and the rigidity of the η²-arene ligation excludes the possibility of any appreciable agostic C-H -> Mo interaction.