Metallaheteroborane chemistry. Part 7. Synthesis, crystal structure, and characterisation of two dinuclear rhodatelluraboranes, [{(PPh3)2RhTeB10H10}2] and [(PPh3)(CO)Rh2Te2B20H20

Abstract

The dinuclear rhodatelluraborane closo-[(PPh3)(CO)Rh2Te2B20H20](2) was obtained from the reaction between either [Os3H2(CO)10] and closo-[2,2-(PPh3)-2-H-1,2-TeRhB10H10](1) in dichloromethane solvent, or [Rh(cod)(PPh3)Cl](cod = cyclo-octa-1,5-diene) and Cs[TeB10H11] in ethanol. The reaction between [Mo(CO)6] and closo-[2,2-(PPh3)2-2-H-1,2-TeRhB10H10] in tetrahydrofuran afforded [{closo-(PPh3)RhTeB10H10}2], (3). X-Ray crystallographic analysis of compound (2) shows it to crystallise with a monoclinic space group (P21/c), containing four molecules in a unit cell of dimensions a= 16.213(4), b= 13.082(4), c= 17.048(3)A, and β= 95.29(2)°, The final R factor was 0.028 for 5 992 observed reflections. X-Ray analysis of the CH2Cl2 solvate of (3) shows the crystal to be monoclinic, space group P21/a with four molecules in a unit cell that measures a= 16.384(5), b= 16.197(6), c= 19.879(5)A, and β= 70.84(2)°. The final R factor was 0.039 for 3 973 observed reflections. Both (2) and (3) contain two {RhTeB10} cages bonded by Rh–Rh′, Rh–B′, Rh′–B, Rh–H′–B′, and Rh′–H–B′, interactions. Principal interatomic distances are Rh–Rh′ 2.737 1 (3), Rh–B′ 2.380(4), Rh′–B 2.329(4), Rh–Te 2.565 3(3), Rh′–Te′ 2.581 7(3)A in (2) with the corresponding distances in (3), 2.834 4(12), 2.354(12), 2.341(13), 2.604 7(12), and 2.581 1 (10)A respectively. The exo-cage ligands (PPh3 or CO) in both (2) and (3) adopt cis configurations about the central Rh–Rh′ portions of the molecules. The 1H, 11B, and 31P n.m.r. data for (2) and (3) show close similarities with those of (1).