Title full: Synthesis and characterization of a series of trans-[Mo(CO)5(R2PNHCH2CH2NC HC6H4-o-O)]2M (R2 Ph2, OCH2CMe2CH2O; M Co, Ni, Cu) complexes and the crystal structure of trans-[Mo(CO)5(Ph2PNHCH2-CH2 -NCHC6H4-o-O)]2Ni · 2Et2O. A series of heterotrinuclear complexes of the type trans-[Mo(CO)5(R2PNHCH2CH2NC HC6H4-o-O)]2M (R2 Ph2, OCH2CMe2CH2O; M Co, Ni, Cu) have been synthesized and characterized by multinuclear NMR, IR and VIS-NIR spectroscopy and by measurement of solution magnetic susceptibilities. These studies indicate that the coordination environment of the high spin Co2+ ion is octahedral while that of the diamagnetic Ni2+ ion is square planar. Coordination of the Ni2+ ion to the mononuclear Mo(CO)5(R2PNHCH2CH2NCHC 6H4-o-OH) complexes causes quite different effects in the spectra of the diphenylphosphino and dioxaphosphorinane complexes. These differences appear to be due to differences in the intramolecular interactions between the P substituents and bis(salicyladiminato)M groups. The molecular structure of trans-[Mo(CO)5(R2PNHCH2CH2NC HC6H4-o-O)]2Ni · 2Et2O has been determined. The complex cystallizes from an HOAc/THF/Et2O mixture in the monoclinic space group C2/c (crystal data: a 37.71(1), b 9.822(1), c 17.91(1) Å; α = γ = 90.00(0)°, β 105.45(6)°; Z = 4). The Ni2+ ion is coordinated to two salicylaldiminato groups in a non-tetrahedrally distorted square planar geometry while the Mo is coordinated to five COs and a P in a slightly distorted octahedral geometry. An interesting feature of the structure is the nearly planar stacking of a phenyl ring on each P with the bis(salicylaldiminato)Ni group. © 1988.