Reactions of Sodium Bis(N-aryliminophosphoranyl)alkanides with Halide-Bridged Platinum(II) and Palladium(II) Phosphine Dimers Affording Four-Membered M−N−P−C Metallacycles and Orthometalated Platinum(II) and Palladium(II) Complexes

• Published in: Organometallics 1996-04, Vol.15 (9), p.2376-2392
• Main Authors: Avis, Mandy W, Vrieze, Kees, Ernsting, Jan M, Elsevier, Cornelis J, Veldman, Nora, Spek, Anthony L, Katti, Kattesh V, Barnes, Charles L
• Format: Article
• Language: English
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om950635k

Reaction of the sodium bis(iminophosphoranyl)alkanide compounds Na[CR‘‘(PPh2NC6H4R‘-4)2] (1a, R‘‘ = H, R‘ = CH3; 1b, R‘‘ = H, R‘ = OCH3; 1c, R‘‘ = CH3, R‘ = CH3) with M2X4(PR3)2 (M = Pt, Pd; X = Cl, Br; PR3 = PEt3, PMe2Ph) yields the four-membered metallacycles MX(PR3){CR‘‘(PPh2NC6H4R‘-4)2} (2a−f, M = Pt; 3a−c, M = Pd), containing the bis(iminophosphoranyl)alkanide ligand coordinated in a σ-C,σ-N chelating fashion. The molecular structure of 2e (X = Cl, PR3 = PMe2Ph, R‘‘ = CH3, R‘ = CH3) has been determined by X-ray crystallography. The 1,1-bis(iminophosphoranyl)ethanide ligand (1c) in 2e is σ-C,σ-N-chelated toward the square-planar-surrounded Pt, with N coordinated trans to PMe2Ph (Pt−N = 2.132(4) Å) and C trans to Cl (Pt−C = 2.116(4) Å), resulting in a puckered M−N−P−C metallacycle and one noncoordinated phosphinimine moiety. In solution the complexes 2 and 3 undergo a dynamic process, involving an intermediate (for 2) or fast (for 3) N,N‘ exchange of coordinated and noncoordinated PN groups. Heating (to 60−80 °C) or prolonged stirring of solutions of the kinetically obtained four-membered metallacycles 2 and 3 gives the orthometalated complexes PtX(PR3){2-C6H4PPh(NHC6H4R‘-4)CHPPh2 NC6H4R‘-4} (4a−d,f) and PdCl(PR3){2-C6H4PPh(NC6H4Me-4)CHPPh2NHC6H4Me-4} (5a,c). The X-ray crystal structure of 4a (X = Cl, PR3 = PEt3, R‘ = CH3) has been determined. The new mononuclear orthometalated Pt complexes 4 contain a σ-C,σ-C‘ coordinated [2-C6H4PPh(NHC6H4R-4‘)CR‘‘PPh2NC6H4R‘-4]- ligand, in which the ortho-H (Ph) has shifted to a bridge position between the two noncoordinating nitrogen atoms. The four-membered platinacycles 2a,b and the orthometalated platinacycles 4a,b react with 1 equiv of HBF4 or CF3COOH to give 6a,b and 7a,b, respectively, by protonation of the noncoordinated PNC6H4R‘-4 groups only. Addition of CO2 to 2a,d and 4c,f results in an aza-Wittig reaction, giving PtCl(PR3){CH(PPh2NC6H4R‘-4)(PPh2O)} (8a,d) and PtX(PR3){2-C6H4PPh(O)CHPPh2NHC6H4R‘-4} (9c,f), respectively, together with aryl isocyanate and bis(aryl)carbodiimide.