Heterometallic Cubes DOI: 10.1002/anie.200604677 AdditionofTerminalAlkynestoaMolecularTitanium–ZincNitride** JorgeJ.Carbó,AvelinoMartín,MiguelMena,*AdriµnPØrez-Redondo,Josep-M.Poblet,and Carlos YØlamos DedicatedtoProfessorGerhardErkerontheoccasionofhis60thbirthday Transition-metal nitrido complexes have been studied exten- sively in the past few decades. [1,2] While nitrido complexes of Group 6–8 metals usually bear the nitrido ligands as a terminal functionality, M  N, [3] the analogous derivatives of early transition metals exhibit polynuclear structures, with m n - nitrido ligands bridging two or more metal centers. [2,4,5] The reactivity of terminal nitrido ligands has received increasing attention because of their potential to show either nucleo- philic or electrophilic character. [1,3,6] The net result of the latter is usually a two-electron reduction of the metal center and a reduced bond order between the metal and the nitrogen atom [Eq. (1)]. Recently a similar behavior has been pro- ½M nþ NDþ DNu !½M ðn2Þþ ðNNuÞ ðNu ¼ PR 3 ,S 8 ,R  , etc:Þ ð1Þ posed for the nucleophilic attack of a phosphine to a bridging dinitride species; in that case the reduction leads to a complex with a metal–metal bond. [7] Over the last few years we have been studying the reactivity of the trinuclear imido–nitrido titanium derivative [{Ti(h 5 -C 5 Me 5 )(m-NH)} 3 (m 3 -N)] [8] (1) towards metal com- plexes and have reported the coordination of 1 to these metals through the imido groups to give the cube-type adducts [1·ML n ]. [9] The elimination of organic molecules and the formation of nitrido groups that bridge the metal centers occur if the NH bonds of the organometallic ligand 1 are activated by metal–imido, metal–amido, or metal–alkyl linkages. [10] However, none of those processes involves the triply bridging apical nitrido ligand of 1. Herein we present the first example of a reaction at this nitrido ligand, which leads to an alkynylimido ligand by C  N bond formation. We have studied this “apparent” nucleophilic attack of an acetylide at the apical nitrido ligand by density functional calculations and propose a plausible reaction mechanism. Our synthetic route is outlined in Scheme 1. Treatment of the amido zinc derivative 2 [11] with one equivalent of terminal alkyne RCCH in toluene gives the expected zinc acetylides [{(RCC)Zn}(m 3 -N)(m 3 -NH) 2 {Ti(h 5 -C 5 Me 5 )} 3 (m 3 -N)], with R = SiMe 3 (3), CMe 3 (4), or Ph (5), as brown or red solids in good yields (71–87%). Because of the light sensitivity of 2 in solution, the reactions were performed in amber-stained glassware. Complexes 3 and 4 were obtained at room temperature, while 5 had to be prepared at 90 8C to obtain a pure sample. Reaction of 2 with two equivalents of Me 3 SiCCH led to a complex which was shown by X-ray diffraction to be the zinc acetylide [{(RCC)Zn}(m 3 -NH) 3 {Ti- (h 5 -C 5 Me 5 )} 3 (m 3 -NCCR)], with R = SiMe 3 (6). The analogous reaction with PhCCH gave the complex with R = Ph(7). Both 6 and 7 were obtained as black solids in good yields (81 and 91%, respectively). In contrast, the reaction of 2 with more than two equivalents of tert-butylacetylene at a variety of temperatures only produced a mixture of 4 and the unreacted alkyne. [D 6 ]Benzene solutions of 6 are stable at different temperatures, whereas complex 7 decomposes partially at room temperature and completely at 90 8C to give 5 and PhCCH, as determined by NMR spectroscopy. [12] Complexes 3–7 are stable to ambient light and were characterized by spectroscopic and analytical techniques, as well as by an X-ray crystal structure determination in the case of 6. The 1 H and 13 C{ 1 H} NMR spectra of 3–5 show signals for Scheme 1. Synthesis of the alkynyl complexes 3–7. [Ti] = Ti(h 5 -C 5 Me 5 ). [*] Dr. A. Martín, Dr. M. Mena, A. PØrez-Redondo, Dr. C. YØlamos Departamento de Química Inorgµnica Universidad de Alcalµ Campus Universitario, 28871 Alcalµ de Henares, Madrid (Spain) Fax: (+ 34)91885-4683 E-mail: miguel.mena@uah.es Dr. J. J. Carbó, Prof. J.-M. Poblet Department de Química Física i Inorgµnica Universitat Rovira i Virgili Marcel·lí Domingo s/n, 43007 Tarragona (Spain) [**] This work was supported by the Spanish MCYT (CTQ2005-00238 and CTQ2005-06909-C02-01), the Comunidad de Madrid and the Universidad de Alcalµ (CAM-UAH2005/062), the Factoría de Cristalización (CONSOLIDER-INGENIO 2010 CSD2006-00015), and the CIRIT of the Generalitat de Catalunya (2005SGR00104). Supporting information for this article is available on the WWW under http://www.angewandte.org or from the author. Angewandte Chemie 3095 Angew. Chem. Int. Ed. 2007, 46, 3095–3098 # 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim