Structural studies of organo group 15 derivatives of RuOs3 clusters

Abstract

ABSTRACTA high yield route, via lightly stabilized Ru(CO)4(C2H4), to a stable tetranuclear dihydrido heteronuclear cluster, RuOs3(i?--H)2(CO)13 1, has been developed. The unique Ru vertex directs the reactivity of 1, causing preferential substitution to occur there. Only mild conditions are required to effect the synthesis of a series of monosubstituted and disubstituted ER3 clusters (ER3 = PPh3, AsPh3, SbPh3, P(C6F5)3, PMe3, P(n-Bu)3, P(t-Bu)3, PCy3, PCy2Ph ). The number and type of isomers detected depends on the nature of the ligand attached to 1. An attempt has been made to deduce the solution structures of the isomers, as well as the pathways for the intramolecular and intermolecular hydride exchange processes using COSY, HMBC, VT NMR and EXSY experiments for both 1H and 31P nuclei. Through the simulation of the 1H and 31P VT spectra, the kinetic and thermodynamic parameters for the two main exchange processes occurring in RuOs3(i?--H)2(CO)13(ER3) (E = P, As, Sb) have been extracted; of particular interest is migration of the ER3 ligand between the Ru and Os vertices. The PCy2Ph ligand has been found to display unusual broadening in the 1H VT spectra of its derivatives as the temperature is lowered. For the ligands with smallest cone angles, PMe3 and P(n-Bu)3, structures disubstituted at the Ru vertex have been isolated or implied. The similarity of the Ru and Os atoms in the cluster results in disorder in many of the disubstituted crystal structures. The reaction of 1 with PPh2H led to a series of phosphido-bridged clusters via Pi?-H bond cleavage: RuOs3(i?-a??H)3(CO)11(i?-a??PPh2) 20, RuOs3(i?-a??H)2(CO)9(i?-a??CO) (i?-a??PPh2)2, RuOs3(i?-a??H)4(CO)9(i?-a??PPh2)2 and the a??butterflya?? structure RuOs3(i?-a??H)3(CO)11(i?-a??PPh2)(PPh2H). Cluster 20 was also reacted with PPh3 to form RuOs3(ma??H)3(CO)10(ma??PPh2)(PPh3) and the a??butterflya?? structure RuOs3(ma??H)3(CO)11(ma??PPh2)(PPh3). Initial studies show that reacting 20 with P(n-Bu)3 and SbPh3 lead to similarly substituted clusters.