Reactions of [Os3(µ-H)2(CO)10] with organic azides: structural characterization of [Os3(µ-H)(CO)10(µ-HN3Ph)] and [Os3(µ-H)2(CO)9(µ3-NPh)

Abstract

The unsaturated cluster [Os3(µ-H)2(CO)10] reacts with azides N3R [R = Ph (1), Bun(2), CH2Ph (3), cyclo-C6H11(4), or CPhCH2(5)] to give complexes with the general formula [Os3(µ-H)(CO)10(HN3R)]. The structure of complex (1) has been established by an X-ray analysis, and shown to contain an equilateral Os3 triangle one edge of which is bridged by the HN3Ph group. This complex crystallises in the monoclinic space group P21/c with a= 9.665(3), b= 8.823(4), c= 25.571(14)A, β= 100.17(4)°, and Z= 4. This structure was solved by a combination of direct methods and Fourier-difference techniques and refined by blocked-cascade least squares to R= 0.042 for 3 155 observed intensities. At 85 °C in 1,2-dimethoxyethane the complexes (1)–(4) liberate a N2 and a CO molecule to give complexes with the general formula [Os3(µ-H)2(CO)9(µ3-NR)][R = Ph (6), Bun(7), CH2Ph (8), or cyclo-C6H11(9)]. The structure of complex (6) contains an isosceles triangle of Os atoms which is capped by the N atom of the NPh group. This complex also crystallises in space group P21/c with a= 11.630(4), b= 9.217(4), c= 18.527(7)A, β= 99.71(2)°, and Z= 4. The structure was solved and refined, by the same techniques as for complex (1), to R= 0.033 for 2 861 observed intensities. Thermolysis of the azido-1 -phenylethene adduct (5) under the same conditions, however, gave [Os3(µ-H)(CO)10(µ-NCMePh)](10) presumably by rapid tautomerism after loss of N2. Azides with an electron-withdrawing substituent adjacent to the azido-function evolved N2 when reacted with [Os3(µ-H)2(CO)10] to give clusters of the type [Os3(µ-H)(CO)10(µ-NHR)][R = PO(OPh)2(11) or 2-(6-CINC5H3)(12)] or products which are, apparently, formed by rearrangement of this system, i.e.[Os3(µ-H)(CO)10(NHCOPh)](14)(from phenacyl azide) and [Os3(µ-H)(CO)10(2-NHCN2HC6H4)](15)(from 2-azidobenzimidazole).