Reactions of [(eta(6)-arene)RuCl2](2) 1 (arene = p-cymene (a), 1,2,3,4-Me(4)C(6)H(2) (b), 1,2,3-Me(3)C(6)H(2) (c)) with tris-(2,6-dimethoxyphenyl)phosphine (TDMPP) led to loss of two molecules of CH3Cl to give (eta(6)-arene)Ru[{2-O-C6H3-6-OMe}(2){C6H3(OMe)(2)-2,6}], 2a-c, which contains a trihapto ligand (eta(3)-P,O,O) derived from TDMPP, whereas the 1,3,5-Me(3)C(6)H(3) (1d), 1,2,3,5-Me(4)C(6)H(2) (1e), and C(6)Me(6) (1f) complexes did not react with TDMPP. The structures of 2a and 2b were confirmed by X-ray analyses : for 2a, a = 11.691(2) Angstrom, b = 15.228(2) Angstrom, c = 10.320(1) Angstrom, alpha = 95.93(1)degrees, beta = 113.783(9)degrees, gamma = 83.86(1)degrees, triclinic, , Z = 2, R = 0.051; for 2b, a = 17.79(2) Angstrom, b = 15.43(1) Angstrom, c = 20.93(1) Angstrom, beta = 91.25(8)degrees, monoclinic, P2(1)/n, Z = 8, R = 0.056.Bis(2,6-dimethoxyphenyl)phenylphosphine (BDMPP) reacted with 1a, 1b, and 1d at room temperature to give (eta(6)-arene)-RuCl[PPh(2-O-C6H3-6-OMe){C6H3(OMe)(2)-2,6}], 3a,b,d, which contains a dihapto (eta(2)-P,O) ligand derived from BDMPP by an X-ray analysis of 3a: a = 12.33(1) Angstrom, b = 14.246(8) Angstrom, c = 11.236(9) Angstrom, alpha = 91.47(8)degrees, beta = 117.28(6)degrees, gamma = 111.70(6)degrees, triclinic, , Z = 2, R = 0.040. A similar reaction with 1f recovered the starting materials, but that in refluxing MeCN produced [(eta(6)-C(6)Me(6))Ru[PPh(2-O-C6H3-6-OMe}2], 4f, containing a trihapto (eta(3)-P,O,O) ligand derived from BDMPP. Complex 1d reacted with BDMPP at reflux in MeCN/CH2Cl2 and resulted in a loss of an arene ring to give a five-coordinate complex, Ru[eta(2)-P,O-PPh(2-O-C6H3-6-OMe){C6H3(OMe)(2)-2,6}[(2)(MeCN), 5. Treatment of (2,6-dimethoxyphenyl)diphenylphosphine (MDMPP) with 1f gave (eta(6)-C(6)Me(6))RuCl[eta(2)-P,O-PPh(2)(2-O-C6H3-6-OMe)], 6f, and that with 1b gave (eta(6)-1,2,3,4-Me(4)C(6)H(2))RuCl[eta(2)-P,O-PPh(2)(2-O-C6H3-6-OMe}], 6b, and (eta(6)-1,2,3,4-Me(4)C(6)H(2))RuCl2[eta(1)-P-PPh(2){C6H3(OMe)(2)-2,6}], 7b. The phosphine ligand of 6b acted as a bidentate ligand derived from MDMPP: a = 8.074(4) Angstrom, b = 16.816(3) Angstrom, 18.916(4) Angstrom, beta = 94.05(3)degrees, monoclinic, P2(1)/n, Z = 4, R = 0.051. Transformation of 7b to 6b readily occurred accompanying an elimination of MeCl. Reaction of 1a with MDMPP eliminated an arene ring to give the octahedral compound RuCl2[eta(2)-P,OMe-PPh(2)(C6H3(MeO)(2)-2,6)](2), 8. An X-ray analysis of 8 showed that two MDMPP ligands were in a cis-position: a = 10.596(14) Angstrom, b = 27.586(12) Angstrom, c = 13.036(8) Angstrom, beta = 108.17(7)degrees, monoclinic, P2(1)/n, Z = 4, R = 0.035.