DINUCLEAR METAL-CARBONYLS BRIDGED BY PYRIDYL LIGANDS INCORPORATING AN ALKYNE ENTITY

New pyridyl ligands, 1,4-bis(4'-pyridylethynyl)benzene (1,BPEB), ferrocenyl-4-pyridylacetylene (12, FPA), and (4-nitrophenyl)-4'-pyridylacetylene (17, NPPA), which contain an alkyne entity in the backbone, are synthesized. Ligation of these compounds as well as 4,4'-dipyridylbutadiyne (DPB) provides [(OC)(4)(L)W](2)(mu-DPB) (2, L = CO; 3, L = PEt(3); 4, L PPh(3); 5, L = P(OEt)(3); 6, L P(OPh)(3)), [(OC)(4)(L)W](2)(mu-BPEB) (7, L = CO; 8; L = PMe(3); 9, L = PPh(3); 10, L = P(OMe)(3); 11, L = P(OEt)(3)), W(CO)(4)(L)(FPA) (13, L = CO; 14, L = PEt(3): 15 L = PPh(3); 16, L = P(OEt)(3)), and W(CO)(4)(L)(NPPA) (18, L = CO; 19, L = PEt(3); 20, L = PPh(3); 21, L = P(OEt)(3)). The energy of the metal to pyridyl pi(*) charge-transfer (MLCT) is dependent on both the pyridyl ligand and the ancillary ligand, L. X-ray structural analyses for 6, 10, 16, and 19 were carried out: 6, C58H38N2O14P2W2, orthorhombic, Pcba, Z = 4, a = 13.636(3) Angstrom, b = 19.442(5) Angstrom, c = 20.299(7) Angstrom, R = 0.031, R(w) = 0.029; 10, C34H30N2O14P2W2, triclinic, P (1) over bar, Z = 1, a = 8.428(3) Angstrom,b = 10.996(4) Angstrom, c = 11.894(4) Angstrom, alpha = 110.68(3)degrees, beta = 90.28(3)degrees, gamma = 105.88(3)degrees, R = 0.031 degrees, R(w) = 0.035; 16, C27H28FeNO7PW, orthorhombic, P2(1)2(1)2(1), Z = 4, a = 9.903(1) Angstrom, b = 14.536(3) Angstrom, c = 20.059(3) Angstrom, R = 0.041, R(w) = 0.041; 19, C23H23N2O6PW, orthorhombic, Pcba, Z = 8, a = 14.178(2) Angstrom, b = 15.007(2) Angstrom, c = 23.878(2) Angstrom, R = 0.033, R(w) = 0.034.