Six new auraferraboranes of the general formula [Fe4(CO)12Au2LL'BH] (L = L' = P(c-C6H11)3, P(p-MeC6H4)3, PMePh2, PMe2Ph, PMe3; L = PMePh2, L' = PMe2Ph) have been prepared. Two structural types are represented, one in which the endo-hydrogen atom bridges an Fe-B edge (structure I) and one in which it bridges an Fe-Fe edge (structure II). The change in hydrogen atom location is accompanied by a rearrangement of the gold(I) phosphine moieties and a reorientation of one iron tricarbonyl unit, while essentially retaining a constant Fe4B framework. The crystal structures of two compounds, [Fe4-(CO)12Au2(P(p-C6H4)3)2BH]*CH2Cl2(1) and [HFe4(CO)12Au2(PEt3)2B] (2), are reported, the former being representative of structure I and the latter of structure II. 1: monoclinic, P21/n; a = 20.891 (6), b = 13.367 (4), c = 23.441 (7) Å; β = 110.82 (3)°; V = 6118 (4) Å 3; Z = 4; R(F) = 6.39%. 2: monoclinic, I2/a; a = 17.783 (5), b = 11.277 (3), c = 18.084 (7) Å; β = 106.26 (3)°; V = 3481.3 (17) Å3; Z = 4; R(F) = 4.75%. The structure of 1 is similar to that of the related cluster [Fe4(CO)12Au2(PPh3)2BH] (3). In solution, a ligand-dependent equilibrium exists between structures I and II for the clusters [Fe4(CO)12Au2LL'BH]. The factors that control the dominance of structure I or II for a particular phosphine ligand have been investigated, and the interplay of steric and electronic effects has been assessed. Electronic factors appear to drive the gold(I) phosphine groups to interact with Fe-B rather than Fe-Fe edges of the cluster, while steric factors dictate the actual Fe4Au2B core geometry.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry