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' = CH3; 1b, R '' = H, R' = OCH3; 1c, R '' = CH3, R' = CH3) 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 sigma-C,sigma-N chelating fashion. The molecular structure of 2e (X = Cl, PR(3) = PMe(2)Ph, R '' = CH3, R' = CH3) has been determined by X-ray crystallography. The 1,1-bis(iminophosphoranyl)ethanide ligand (1c) in 2e is sigma-C,sigma-N-chelated toward the square-planar-surrounded Pt, with N coordinated trans to PMe(2)Ph (Pt-N = 2.132(4) Angstrom) and C trans to Cl (Pt-C = 2.116(4) Angstrom), 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 degrees 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' = CH3) has been determined. The new mononuclear orthometalated Pt complexes 4 contain a sigma-C,sigma-C' coordinated [2-C6H4-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 HER or CF3COOH to give 6a,b and 7a,b, respectively, by protonation of the noncoordinated P=NC(6)H(4)R'-4 groups only. Addition of CO2 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.