Chelating phosphines with low coordinated phosphorus atoms Part I. Phosphaalkenes associated with phosphine moieties - X-ray structure of cis-(CO)(4)Mo[ortho-Ph2P-C6H4-CH=P(t-Bu3C6H2)]center dot C7H16

Condensation of ortho-diphenylphosphinobenzaldehyde with 2,4,6-tri-t-butyl- phenylphosphine yields the lambda (2),lambda (3)-diphosphorus chelating age nt 2a with an E-configurated phosphaalkene unit as indicated by the analysi s of the NMR data, On irradiation with UV light Za is transformed to the Z- isomer (2b). E-2a forms stable Mo(0), Pd(II) and Pt(II) chelate complexes ( 3-5). The X-ray structure of the molybdenum complex 3-C7H16 (space group P2 (1)2(1)2(1)) has been determined showing the phosphaalkene moiety to be coo rdinated in a eta (1)-mode to molybdenum within a distorted six-membered ch elate ring. (C) 2001 Elsevier Science B.V. All rights reserved.