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

Reaction of the sodium bis(iminophosphoranyl)alkanide compounds Na[CR‘‘(PPh 2 NC 6 H 4 R‘-4) 2 ] ( 1a, R‘‘ = H, R‘ = CH 3; 1b, R‘‘ = H, R‘ = OCH 3; 1c, R‘‘ = CH 3, R‘ = CH 3 ) with M 2 X 4 (PR 3 ) 2 (M = Pt, Pd; X = Cl, Br; PR 3 = PEt 3, PMe 2 Ph) yields the four-membered metallacycles MX(PR 3 ){CR‘‘(PPh 2 NC 6 H 4 R‘-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, PR 3 = PMe 2 Ph, R‘‘ = CH 3, R‘ = CH 3 ) 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 PMe 2 Ph (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(PR 3 ){2-C 6 H 4 PPh(NHC 6 H 4 R‘-4)CHPPh 2 NC 6 H 4 R‘-4} ( 4a−d,f ) and PdCl(PR 3 ){2-C 6 H 4 PPh( NC 6 H 4 Me-4)CHPPh 2 NHC 6 H 4 Me-4} ( 5a,c ). The X-ray crystal structure of 4a (X = Cl, PR 3 = PEt 3, R‘ = CH 3 ) has been determined. The new mononuclear orthometalated Pt complexes 4 contain a σ-C,σ-C‘ coordinated [2-C 6 H 4 PPh(NHC 6 H 4 R-4‘)CR‘‘PPh 2 NC 6 H 4 R‘-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 HBF 4 or CF 3 COOH to give 6a,b and 7a,b, respectively, by protonation of the noncoordinated P NC 6 H 4 R‘-4 groups only. Addition of CO 2 to 2a,d and 4c,f results in an aza-Wittig reaction, giving PtCl(PR 3 ){CH(PPh 2 NC 6 H 4 R‘-4)(PPh 2 O)} ( 8a,d ) and PtX(PR 3 ){2-C 6 H 4 PPh( O)CHPPh 2 NHC 6 H 4 R‘-4} ( 9c,f ), respectively, together with aryl isocyanate and bis(aryl)carbodiimide.