Oligonuclear Tricarbonylchromium- and Tricarbonyltungsten Derivatives of Tris(l-cyclohepta-2,4,6-trienyl)phosphane, P(C7H7)3 , and Related Ligands

Z. Naturforsch. 54 b, 63-72 (1999); received August 3, 1998 Halfsandwich Compounds, Cycloheptatrienyl Complexes, Chromium, Tungsten, X-Ray Data A series of trinuclear carbonylmetal complexes of tri(l-cyclohepta-2,4,6-trienyl)phosphane, P(C? 1̂ 7)3 (1), has been prepared by the reaction of P(SiMe3)3 with ^-tropylium halfsand­ wich salts, [(7/7-C7H7)M(CO)3]BF4, (M = Cr, Mo, W). While phosphorus remains uncoor­ dinated in the chromium complex P[(?/6-C7Hv)Cr(CO)3]3 (2a), the molybdenum and tung­ sten analogues, P[(//4-C7H7)M(CO)3][(??6-C7H7)M(CO)3]2 (M = Mo (2b), W (2c)), contain a coordinated phosphorus atom together with a //4-norcaradienyl substituent. Reaction of 2a with pentacarbonylmetal fragments, [M(CO)s], leads to trinuclear products, P[(/;2-C7H7)M(CO)4][(>7/6-C7H7)M(CO)3]2 (M = Cr (5a), W (5c)), in which phosphorus is coordinated next to an //'-cycloheptatrienyl substituent. Several alkyland arylphosphanes containing [(^6C7H7)Cr(CO)3] substituents (X), e. g. Ph2P(X) (6a), RP(X )2 (R = Me (7a), CH2Ph (8a), Ph (9a)) and (X)2P(R')P(X)2 (R' = methylene (10a) or o-phenylene (11a)), have also been synthesized. The chromium complexes 6a 11a contain an uncoordinated phosphorus center, but in contrast to 9a, the corresponding tungsten compound PhP[(?;4-C7H7)W(CO)3][(?/6-C7H7)W(CO)3]2 (9c) has again a structure similar to 2c. The arsenic complexes, As[(?/6-C7H7)M(CO)3]3 (M = Cr (12a), W (12c)) both contain an uncoordinated arsenic center, analogous to 2a. The molecular structures of all new complexes in solution at room temperature were deduced from a consistent set of 'H, l,C and 31P NMR data, and X-ray structure determinations were carried out for 2a and 5c.