The chemical behavior of the azido group bonded to copper(I): synthesis and reactivity of thiothiatriazolato and alkynyl complexes

The copper(I) azido-derivatives, (PPh3)(phen)CuN3 (Ia) and (PPh3)(TMP)CuN3 (Ib) (phen = 1,10-phenanthroline; TMP = 3,4,7,8-tetramethyl-1,10-phenanthroline), obtained from [(PPh3)2CuN3]2 and the bidentate ligand (biL), react with CS2 to give the thiothiatriazolato-copper(I) complexes, (PPh3)(phen)Cu (IIa) and (PPh3)(TMP)Cu (IIb). The preparation of IIa and IIb occurs only when free triphenylphosphine is present in the reaction medium. The isothiocyanate complexes, (PPh3)(biL)Cu(NCS) (biL = phen, IIIa; biL = TMP, IIIb) are formed, instead of IIa and IIb, when free PPh3 is not added to the reaction medium. The complexes IIIa and IIIb are also obtained when CH2Cl2 solutions of IIa and IIb are stirred for 15 h in the absence of light; if longer reaction times are used, the dimeric isothiocyanato complexes [(biL)Cu(NCS)]2 are formed. Compounds IIa and IIb react with PhCOCl to give (PPh3)(biL)CuCl and 4-benzoyl-1,2,3,4-thiatriazole-5-thione, PhCO. Treatment of Ia and Ib, or [(PPh3)2CuN3]2, with COS did not lead to isolation of characterizable products. An unsaturated molecule such as ethyl propriolate, EtO2CCCH, does not behave as a 1,3-dipolarophile in its reactions with Ia and Ib, the alkynyl derivatives [(biL)Cu2(CCCO2Et)2]n (n is probably 2; biL = phen, IVa; biL = TMP, IVb), being obtained. Similarly the azido-complex [(PPh3)2CuN3]2 reacts with ethyl propiolate to give the asymmetric binuclear alkynyl derivative, (PPh3)3Cu2(CCCO2Et)2 (V). The reaction of V with hydrogen chloride gives EtO2CCCH and the known complex (PPh3)3Cu2Cl2, confirming the above formulation. The reactions of V with neutral ligands such as TMP, phen and CyNC have also been studied, leading to the isolation of new copper(I) alkynyl-derivatives.