Bridge-splitting reactions of Pt2&(PR3)2 (X = C1, Br; PR3 = PEt3, PMezPh) with bis(iminophosphorany1)methanes CH2(PPh2=NC6H4-4-R')2 (BIPM: la, R' = Me; lb, R' = OMe) produced Pt(I1) complexes, in which the BIPM ligand is N,C-coordinated: [P~X(PR~)(CH-(PP~~=N-C~H~-~-R')(PP~Z-NH-C~~-~-R')}]+Y-(2a-f, R' = CH3, OCH3, Y = C1, Br, BF4, CF3CO2; 2g, R' = CH3, PR3 = PEt3, Y = PtCl3PEt3). In the N,C-coordinated BIPM, a net 1,3-H-shift from the bridging methylene group to the noncoordinated N-atom has taken place. NMR studies have revealed a monodentate a-N-coordinated species P~X~(PR~)(N(C~H~-~-R')=PP~ZCH~PP~~=NC~~ A, as the first intermediate in the formation of 2. The complex formation is strongly dependent on the metal to ligand ratio, M:L. For M:L = 2: 1, compound 2gi was formed, a N,N'-coordinated six-membered platinacycle, followed by conversion into the N,C chelate 2g, whereas at M:L = 1:2 two new products were obtained; a deprotonated Pt(I1) complex with N,C-coordinated BIPM, [P~X(PR~){CH(PP~Z=NC~I&-~-R')~] (3; X = C1, PR3 = PEt3, R' = CH3), and the HCl salt of the ligand [HC(PPh2NHC&-4-R')2]+Cl-(4). The molecular structures of [PtCl(PMe2Ph)(CH(PPh2=NC6H4-4-CH3)(PPh2N~C~-~CH3)~]+(Cl)-(2d) and [PtCl(PEt3){CH(PPhz=NC&-4-CH,)(PPh2N'HC6I&-4-CH3)}]+(PtC13PEt3)-(2g) have been determined by X-ray crystallography. Crystal data for 2d: trigonal, space group Pi, with a = 14.3852(11) A, b = 15.4886(9) A, c = 20.190(2) 8, a = 100.580(7)", p = 92.223(8)", y = 99.508(6)", V = 4350.1(6) A3, and Z = 4. Crystal data for 2g: trigonal, space group Pi, with a = 10.1970(8) A, b = 14.5045(9) A, c = 20.5471(19) A, a = 96.154(7)", p = 103.993 (7)", y = 107.548(6)", V = 2757.8(4) A3, and Z = 2. The structure refinement converged to R, = 0.0432, R = 0.0436 for 2d and wR2 = 0.1247, R1 = 0.501 for 2g. The structure of the cationic parts of 2d and 2g comprises a distorted square planar Pt(I1) environment, the coordination sites taken by PR3, C1, and the N and C atoms of the BIPM ligand. The structure of the anionic part of 2g, PtCL,(PEt3), is almost perfectly square-planar and is linked with the cationic part via a NH.. C1 hydrogen bond.

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.

The new ligand, 1,1-bis((N-p-tolylimino)diphenylphosphoranyl)ethane (1,1-BIPE), 1, has been synthesized by means of a Staudinger reaction of 1,1-bis(diphenylphosphino)ethane (1,1-dppe) with 2 equiv of p-tolylazide. Bridge-splitting reactions of Pt2Cl4(PR3)2 with 1 readily afforded σ-N monodentate complexes, [PtCl2(PR3){1,1-BIPE-σN}] (2a, PR3 = PEt3; 2b, PR3 = PMe2Ph). Conversion of 2 into the six-membered platinacycle [PtCl(PR3){1,1-BIPE-σN,σN‘}]+[X]- (3) (X = Cl, PtCl3(PR3), BF4) took place after prolonged stirring, its reaction rate being strongly dependent on the type of phosphine (>5 days for 2a in the presence of NaBF4, 1 h for 2b) and the metal-to-ligand ratio. The compounds 1, 2, and 3 have been fully characterized by 1H, 31P{1H}, and 13C{1H} NMR and IR spectroscopy, elemental analysis, or FAB mass spectroscopy. The molecular structures of CHCH3(PPh2NC6H4-4-CH3)2 (1) and [PtCl(PMe2Ph){(N(pTol)PPh2)2CHCH3}]+[Cl]- (3b) have been determined by X-ray crystallography. Crystal data for 1:  space group P21 /c with a = 8.9591(5) Å, b = 19.1961(12) Å, c = 21.9740(9) Å, β = 105.069(4)°, V = 3649.1(3) Å3, and Z = 4. The structure refinement converged to R = 0.080 and R w = 0.109. Crystal data for 3b:  monoclinic, space group P21 /c with a = 12.4021(7) Å, b = 16.9705(11) Å, c = 23.760(2) Å, β = 109.544(5)°, V = 4712.7(5) Å3, and Z = 4. The structure refinement converged to R1 = 0.057, wR2 = 0.122. Variable temperature NMR spectroscopy has revealed that complexes 3 exclusively adopt a twisted boat conformation with the methyl group in equatorial position at low temperature, in agreement with the solid state structure of 3b as determined by X-ray crystallography. Boat-to-boat inversion is assumed to take place at temperatures above 293 K. Furthermore, for 3, hindered rotation of one of the p-tolyl substituents on nitrogen has been established at low temperatures.

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