ENTHALPIES OF REACTION OF (ETA-5-C5H5)RU(CYCLOOCTADIENE)CL WITH TERTIARY PHOSPHINE-LIGANDS - LIGAND SUBSTITUTION AS A GAUGE FOR METAL BASICITY AND A LINEAR CORRELATION OF BOND-LENGTH AND BOND ENTHALPY

The enthalpies of reaction of CpRu(COD)Cl (1) (Cp = eta(5)-C5H5; COD = cyclooctadiene) with a series of monodentate ligands, leading to the formation of CpRu(ER(3))(2)Cl (E = P, As), have been measured by anaer obic solution calorimetry in THF at 30.0 degrees C. These reactions ar e rapid and quantitatively lead to the formation of the corresponding CpRu(ER(3))(2)Cl complexes. The overall relative order of stability es tablished for the preceding complexes is as follows: AsEt(3) < PPh(3) < PPh(2)Me < P(OPh)(3) < PEt(3) < P(n)Bu(3) < PPhMe(2) < PMe(3) < P(OM e)(3). Comparisons with other organometallic systems providing insight s into factors influencing the Ru-L bond disruption enthalpies and met al basicity are discussed. Structural studies of two of these CpRu(ER( 3))(2)Cl complexes (ER(3) = AsEt(3) (2) and PEt(3) (3)) have also been performed. Data for 2: monoclinic, C2/c; a = 30.549(5); b =. 10.523(2 ); c = 13.503(3) Angstrom; alpha gamma = 90 degrees; beta = 103.71(2)d egrees; V = 4217.1 Angstrom(3); Z = 8; d(calcd) 2 = 1.656g cm(-1);n(ob sd) 5328; R = 0.032. Data for 3: monoclinic, P2(1)/c; a 13.553(1); b = 8.283(2); c = 19.359(3) Angstrom; beta = 109.74(1)degrees; V = 2045.5 Angstrom 3; Z = 4; dcalcd = 1.422 g cm(-1); n(obsd) = 5152; R = 0.030 . A relationship between bond distances and relative bond energies is made possible by the present data. This correlation is good and repres ents a rare example of such a relationship.