www.elsevier.nl/locate/ica Inorganica Chimica Acta 312 (2001) 7–14 Metallic carbonyl complexes containing heterocycles nitrogen ligands  Part VI. Re(I), Mn(I), Mo(0), and W(0) compounds with 4%-phenyl-2,2%:6%,2ƒ-terpyridine Sergio A. Moya a, *, Rube´n Pastene a , Hubert Le Bozec b , Pablo J. Baricelli c , Alvaro J. Pardey d , Jose´ Gimeno e a Departamento de Quı ´mica Aplicada, Facultad de Quı ´mica y Biologı ´a, Uni6ersidad de Santiago de Chile, Santiago, Chile b UMR 6509, CNRS -Uni6ersite´ de Rennes 1, Organome´talliques et Catalyse, Campus de Beaulieu, 35042 Rennes Cedex, France c Centro de In6estigaciones Quı ´micas, Facultad de Ingenierı ´a, Uni6ersidad de Carabobo, Valencia, Venezuela d Escuela de Quı ´mica, Facultad de Ciencias, Uni6ersidad Central de Venezuela, Caracas, Venezuela e Departamento de Quı ´mica Orga´nica e Ino´rganica, Instituto de Quı ´mica Organometa´lica ‘Enrique Moles’(CSIC), Facultad de Quı ´mica, Uni6ersidad de O6iedo, O6iedo, Spain Received 27 August 1999; accepted 28 August 2000 Abstract The synthesis and spectroscopic characterization of new transition metal complexes containing the heterocyclic nitrogen ligand 4%-phenyl-2,2%:6%,2ƒ-terpyridine are reported. Complexes of the [XM(CO) 3 (L)] type (M=Re(I), Mn(I), Mo(0), or W(0); X =Br or CO; and L =4%-phenyl-2,2%:6%,2ƒ-terpyridine) were prepared by photosubstitution or by thermolytic reactions. Aspects of the IR, UV – Vis, proton NMR spectra and electrochemistry of the complexes are discussed. Special attention is given to the fact that the heterocyclic nitrogen ligand ph-tpy acts as a bidentate or terdentate chelate in complexes of this type and shows the fluxionality in the coordination. Correlations between redox potentials and spectroscopic measurements indicate the various interactions of the ligand and the metal center, and allow the evaluation of the metal – ligand back-donation. © 2001 Elsevier Science B.V. All rights reserved. Keywords: Metal carbonyl complexes; Rhenium(I); Manganese(I); Molybdenum(0) and Tungsten(0); Heterocyclic nitrogen ligand 1. Introduction A few examples of transition metal complexes with 2,2%:6%,2ƒ-terpyridine ligand (tpy) coordinated in a bidentate arrangement, leaving off one external pyridyl ring uncoordinated, are known [2]. If the meridional coordination site is available the most current binding mode of this ligand to metals is the terdentate array [3]. The spectroscopic characterization of this type of bidentate species is of interest since they have been postulated to have an important participation as prod- ucts of photolysis of tridentate terpyridine transition metal complexes [4]. Moreover, the remarkable photo- physical and photochemical properties of these com- plexes are especially convenient for studying the structural modifications of heterocyclic nitrogen ligands with the purpose of causing variations on the electronic properties of these species. Furthermore, systems such as [XRe I (CO) 3 (L)] type (X =halide and L =2,2%- bipyridine, 2,2%-biquinoline or their derivatives) have been found to be efficient catalysts for the reduction of CO 2 to CO both photochemically [5] and electrochemi- cally [6]. Only scarce examples with the 4%-phenyl- 2,2%:6%,2ƒ-terpyridine ligand coordinated to iron(III), ruthenium(II), cobalt(II), and platinum(II) centers are known [7], therefore we have selected this ligand as a  For Parts I–V, see Ref. [1]. * Corresponding author. Fax: +56-2-681 2108. E-mail address: smoya@lauca.usach.cl (S.A. Moya). 0020-1693/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved. PII:S0020-1693(00)00292-9