Cycloheptatrienyl complexes preparation

Three zirconium/cycloheptadienyne complexes (231a-c) have been prepared by /3-hydrogen elimination from a mixture of cycloheptatrienyl complexes 269-271 (Scheme 33) and have been used as intermediates for the preparation of a zirconaazulene.87 The alkyne complexes are formed to the exclusion of the allene isomer 268. This is believed to be due to the proximity of the /3-vinyl hydrogen that is a result of both the shorter double bond and its forced coplanarity with the metal. Allene formation from 269 might be induced by blocking the vinyl position (see Sections IV,B and IV,C), but this has not been tested. 

Although Able et al. (2, 8) had originally set out to prepare 7r-cyclo-heptatrienyl complexes of metals, the cycloheptatriene complexes they actually obtained served as key intermediates in forming the former complexes. In 1958 Dauben and Honnen (61) reported that cycloheptatriene-molybdenum tricarbonyl reacted with triphenylmethyl tetrafluoroborate in methylene chloride solution with abstraction of hydride ion from the molybdenum complex. The reaction products, obtained in nearly quantitative yields, were triphenylmethane and the 7r-cycloheptatrienyl complex [(7r-C7H7)Mo(CO)3]+BF4 . 

The preparation of jr-cycloheptatrienyl complexes by ring expansion reactions is discussed in section A (c), (i). 

Reduction of ZrCl4 with Na/Hg at < -10 °C in the presence of cycloheptatriene gives Zr(i76-C7H8)2 it exhibits a non-parallel arrangement of the cycloheptatrienyl ligands (18-A-VIII) and can be used to prepare a series of zero- and monovalent 16-e zirconium complexes such as Zr(rf-CjH-,)(rf-CjH,)(PMe3), Zi(rf-0,H7)-(tmeda)Cl, and others.72... 

The mixed cyclopentadienyl-cycloheptatrienyl ( 5-7 ) titanium complex Cp( -C7H7)Ti has been prepared in 33 -40% yield by the reduction of CpTiCb with isopropylmag-nesium bromide or Mg in the presence of cycloheptatriene. Reduction of Cp TiCb in THF with Mg in the presence of cycloheptatriene gives Cp ( -C7H7)Ti in 68% yield. Titanium 5-7 complexes exhibit sandwich structures see Sandwich Compound) with the five-membered and seven-membered rings nearly parallel to each other. 

Initial attempts to prepare 7r-cycloheptatrienyl-iron tricarbonyl complexes were not successful—the products often being 7r-cycloheptadienyl-iron tricarbonyl derivatives (60). In 1964 Mahler, Jones, and Pettit (162) reported the synthesis of a complex [(C7H7)Fe(CO)3] BF4 by the following route ... 

Bisalkynylplatinate complexes with the 6, A-chelating benzo[ ]-quinolinate ligand 683 have been prepared by transmetallation of the lithium acetylides with dichloroplatinate. " " The absorption peaks at 392-405 nm are attributed to ligand (acetylide) to ligand (benzoquinolinate) transition. Tris(cycloheptatrienyl)phosphine and diphenyl-phosphine oxide form complexes with two alkynyl ligands at m-positions 684 and 685. " " ... 

Ferrocenyl-containing Complexes. - A collection of compounds derived from ferrocenyl-substituted acetylide Ti-based tweezer molecules have been prepared and characterised." The crystal structure of the cyclohexadienyl-containing complex 168 has been reported." A series of multimetallic complexes have been prepared by addition of enolates of bis-(ferrocenyl)-1,3-diketones to a range of p -ethene-, riCcydohexatriene-, p -cycloheptatrienyl- and pCcyclo-heptatrienyl-containing complexes." The crystal structure of 169 has been described." Compounds 170 and 171 were obtained from the reaction between... 

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