Trisubstituted Group 6 metal carbonyl complexes with di-2-pyridylamine ligands. Crystal structures of (2,2′-bipyridyl-N,N′) tricarbonyl(di-2-pyridylamine-N′)-molybdenum(0) and -tungsten(0)

Abstract

Reactions of [M(CO)₄(bipy)](M = Mo or W; bipy = 2,2′-bipyridyl) with di-2-pyridylamine, (C₅H₄N)₂NH (dipyam), yield the isostructural mixed-ligand complexes [M(CO)₃(bipy)(dipyam)]. Both complexes crystallise in the monoclinic space group P2₁/c with, Mo [W], a= 10.620(15)[1 0.564(6)], b= 12.915(12)[12.925(6)],c= 16.524(26)[16.508(12)]Å,β= 107.81(11)[107.83(6)]°, and Z= 4. The complexes have fac-octahedral structures with bidentate 2,2′bipyridyl and monodentate di-2-pyridylamine ligands. Substitution of monodentate heterocyclic amines, L, in [M(CO)₄(dipyam)](M = Cr,Mo, or W) yields the mixed-ligand complexes [M(CO)₃(dipyam)L] which have three well resolved v(CO) stretching absorptions in their i.r. spectra. This contrasts with the two v(CO) bands characteristically observed in the analogous fac-[M(CO)₃(bipy)L] or fac-[M(CO)₃(phen)L](phen = 1, 1 0-phenanthroline) complexes and raises the possibility that the [M(CO)₃(dipyam) L] complexes may have the relatively unusual mer-octahedral geometry. Binuclear di-2-pyridylamine-bridged complexes are readily obtained from the reactions of [M(CO)₄(dipyam)] with di-2-pyridylamine.