Abstract
The [FeCo2(CO)9(EtC2Et)] cluster represents the prototype of heterotrimetallic complexes having a nido-octahedral structure or in other words a µ3-(η2-∥) alkyne co-ordination mode. The cluster exhibits a symmetrical (MM∥CC) geometry in the solid state; since fluxionality of the alkyne is observed in solution and therefore the rotamers are characterized by subtile energy differences, we have attempted to understand the factors affecting the alkyne orientation over the metallic triangle. The spectroscopic and structural data of the parent cluster have been compared with those of its mono derivatives [FeCo2(CO)8L(EtC2Et)][L = PEt3, PPh3, P(OMe)3, P(OPh)3, or CNCH2Ph]. The structure of [FeCo2(CO)8(PPh3)(EtC2Et)] has been determined by X-ray methods. It crystallizes in the triclinic space group P, with Z= 2 in a unit cell of dimensions a= 10.690(4), b= 16.267(8), c= 9.457(5)A, α= 95.01(3), β= 107.55(3), and γ= 89.23(2)°. The structure has been solved from diffractometer data by direct and Fourier methods and refined by full-matrix least squares to R= 0.0563 and 4 165 observed reflections. The structure consists of an isosceles triangle of one Fe and two Co atoms. Of the eight carbonyls, seven are terminally bound to the metal atoms [three to Fe, three to the unsubstituted Co(2), one to the Co(1) atom having the phosphine ligand] and one asymmetrically bridges the Fe–Co(1) edge. The EtC2Et ligand interacts with all three metals, being σ bonded to Fe and Co(2) and π bonded to Co(1) through the triple bond which is disposed nearly parallel to the Fe–Co(2) edge of the cluster. Thus the substitution of a CO for PPh3 has caused the reorientation of the alkyne moiety in the ground state. Finally, dimers of formula [{FeCo2(CO)8(-EtC2Et)}2{Ph2P(CH2)nPPh2}](n= 2–4) have been characterized by means of multinuclear n.m.r. spectroscopy.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
