Synthesis and X-ray structures of some metal carbonyl complexes containing dipyridylformamidine ligands

Five metal carbonyl complexes of N,N′-di(2-pyridyl)formamidine (HDpyF) and N,N′-di(6-methyl-2-pyridyl)formamidine (HDMepyF) are reported. Complexes of the type ReBr(CO)3L (L=HDpyF, 1; L=HDMepyF, 2) were prepared by the reactions of ReBr(CO)5 with HDpyF and HDMepyF in THF, respectively, while the complexes M(CO)4(L) (M=Mo, L=HDpyF, 3; M=Mo, L=HDMepyF, 4; M=W, L=HDMepyF, 5) were prepared by the reactions of HDpyF or HDMepyF with corresponding Group 6 metal hexacarbonyls. The neutral dipyridylformamidine ligands in 1 and 2 adopt the s-cis-syn-s-cis and s-trans-anti-s-trans conformations, respectively, while those in complexes 3–5 adopt the s-trans-anti-s-cis conformation.